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Abstracts

Alpha Lipoic Acid : 70 Research Abstracts

NUCLEAR FACTOR KAPPA B –(other NF kappa B are also in other sections)

1. Endocr Rev. 2002 Oct;23(5):599-622.
Oxidative stress and stress-activated signaling pathways: a unifying hypothesis of type 2 diabetes.
Evans JL, Goldfine ID, Maddux BA, Grodsky GM.
University of California at San Francisco, San Francisco, California 94143, USA. jevansphd@earthlink.net

In both type 1 and type 2 diabetes, the late diabetic complications in nerve, vascular endothelium, and kidney arise from chronic elevations of glucose and possibly other metabolites including free fatty acids (FFA). Recent evidence suggests that common stress-activated signaling pathways such as nuclear factor-kappaB, p38 MAPK, and NH2-terminal Jun kinases/stress-activated protein kinases underlie the development of these late diabetic complications. In addition, in type 2 diabetes, there is evidence that the activation of these same stress pathways by glucose and possibly FFA leads to both insulin resistance and impaired insulin secretion. Thus, we propose a unifying hypothesis whereby hyperglycemia and FFA-induced activation of the nuclear factor-kappaB, p38 MAPK, and NH2-terminal Jun kinases/stress-activated protein kinases stress pathways, along with the activation of the advanced glycosy ation end-products/receptor for advanced glycosylation end-products, protein kinase C, and sorbitol stress pathways, plays a key role in causing late complications in type 1 and type 2 diabetes, along with insulin resistance and impaired insulin secretion in type 2 diabetes. Studies with antioxidants such as vitamin E, alpha-lipoic acid, and N-acetylcysteine suggest that new strategies may become available to treat these conditions.

2. Exp Gerontol. 2002 Jan-Mar;37(2-3):401-10.
Alpha-lipoic acid modulates NF-kappaB activity in human monocytic cells by direct interaction with DNA. Lee HA, Hughes DA.
Immunology Group, Nutrition and Consumer Science Division, Institute of Food Research, Norwich Research Park, Colney, Norwich, Norfolk NR4 7UA, UK.

The constitutive activity of the redox-sensitive transcription factor, NF-kappaB, which regulates the production of many inflammatory cytokines and adhesion molecules, appears to be up-regulated in an age-associated manner and it is thought this might contribute to the increased incidence of chronic inflammatory conditions observed with increasing age. As some antioxidants have demonstrated protective effects against rheumatoid arthritis, we are investigating the effects of vitamin E, vitamin C and alpha-lipoic acid (ALA) on NF-kappaB activity and on the expression of intracellular adhesion molecule (ICAM)-1. MonoMac6 cells (a human monocytic cell line) stimulated with tumour necrosis factor-alpha (TNF-alpha) were treated with antioxidants at physiological achievable levels and ICAM-1 mRNA levels investigated. Both vitamin E and vitamin C had no effect on ICAM-1 expression at the doses used, but ALA reduced the TNF-alpha-stimulated ICAM-1 expression in a dose-dependent manner, to levels observed in unstimulated cells. Alpha-lipoic acid also reduced NF-kappaB activity in these cells in a dose-dependent manner. Addition of ALA to the binding reaction of nuclear extract with DNA prior to gel-shift analysis showed that it caused inhibition at this level. These initial results suggest that antioxidant modulation of monocyte activity might have potential benefits in inhibiting the dysregulated activity of redox-sensitive transcription factors that occurs with increasing age.

3. FASEB J. 2001 Nov;15(13):2423-32.
Alpha-lipoic acid inhibits TNF-alpha-induced NF-kappaB activation and adhesion molecule expression in human aortic endothelial cells.
Zhang WJ, Frei B.
Linus Pauling Institute, Oregon State University, Corvallis, Oregon 97331, USA.

Endothelial activation and monocyte adhesion are initiating steps in atherogenesis thought to be caused in part by oxidative stress. The metabolic thiol antioxidant alpha-lipoic acid has been suggested to be of therapeutic value in pathologies associated with redox imbalances. We investigated the role of (R)-alpha-lipoic acid (LA) vs. glutathione and ascorbic acid in tumor necrosis factor alpha (TNF-alpha) -induced adhesion molecule expression and nuclear factor kappaB (NF-kappaB) signaling in human aortic endothelial cells (HAEC). Preincubation of HAEC for 48 h with LA (0.05-1 mmol/l) dose-dependently inhibited TNF-alpha (10 U/ml) -induced adhesion of human monocytic THP-1 cells, as well as mRNA and protein expression of E-selectin, vascular cell adhesion molecule 1 and intercellular adhesion molecule 1. LA also strongly inhibited TNF-alpha-induced mRNA expression of monocyte chemoattractant protein-1 but did not affect expression of TNF-alpha receptor 1. Furthermore, LA dose-dependently inhibited TNF-alpha-induced IkappaB kinase activation, subsequent degradation of IkappaB, the cytoplasmic NF-kappaB inhibitor, and nuclear translocation of NF-kappaB. In contrast, TNF-alpha-induced NF-kappaB activation and adhesion molecule expression were not affected by ascorbic acid or by manipulating cellular glutathione status with l-2-oxo-4-thiazolidinecarboxylic acid, N-acetyl-l-cysteine, or d,l-buthionine-S,R-sulfoximine. Our data show that clinically relevant concentrations of LA, but neither vitamin C nor glutathione, inhibit adhesion molecule expression in HAEC and monocyte adhesion by inhibiting the IkappaB/NF-kappaB signaling pathway at the level, or upstream, of IkappaB kinase.

4. Drug Metab Rev. 1998 May;30(2):245-75.
alpha-Lipoic acid: a metabolic antioxidant which regulates NF-kappa B signal transduction and protects against oxidative injury.
Packer L.
Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.

Although the metabolic role of alpha-lipoic acid has been known for over 40 years, it is only recently that its effects when supplied exogenously have become known. Exogenous alpha-lipoic acid is reduced intracellularly by at least two and possibly three enzymes, and through the actions of its reduced form, it influences a number of cell process. These include direct radical scavenging, recycling of other antioxidants, accelerating GSH synthesis, and modulating transcription factor activity, especially that of NF-kappa B (Fig. 12). These mechanisms may account for the sometimes dramatic effects of alpha-lipoic acid in oxidative stress conditions (e.g., brain ischemia-reperfusion), and point the way toward its therapeutic use.

5. Biochem Biophys Res Commun. 1992 Dec 30;189(3):1709-15.
Alpha-lipoic acid is a potent inhibitor of NF-kappa B activation in human T cells.
Suzuki YJ, Aggarwal BB, Packer L.
Department of Molecular & Cell Biology, University of California, Berkeley 94720.

Acquired immunodeficiency syndrome (AIDS) results from infection with a human immunodeficiency virus (HIV). The long terminal repeat (LTR) region of HIV proviral DNA contains binding sites for nuclear factor kappa B (NF-kappa B), and this transcriptional activator appears to regulate HIV activation. Recent findings suggest an involvement of reactive oxygen species (ROS) in signal transduction pathways leading to NF-kappa B activation. The present study was based on reports that antioxidants which eliminate ROS should block the activation of NF-kappa B and subsequently HIV transcription, and thus antioxidants can be used as therapeutic agents for AIDS. Incubation of Jurkat T cells (1 x 10(6) cells/ml) with a natural thiol antioxidant, alpha-lipoic acid, prior to the stimulation of cells was found to inhibit NF-kappa B activation induced by tumor necrosis factor-alpha (25 ng/ml) or by phorbol 12-myristate 13-acetate (50 ng/ml). The inhibitory action of alpha-lipoic acid was found to be very potent as only 4 mM was needed for a complete inhibition, whereas 20 mM was required for N-acetylcysteine. These results indicate that alpha-lipoic acid may be effective in AIDS therapeutics.

AGING

6. J Alzheimers Dis. 2003 Jun;5(3):229-39.
Protection against amyloid beta peptide and iron/hydrogen peroxide toxicity by alpha lipoic acid.
Lovell MA, Xie C, Xiong S, Markesbery WR.
Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.

Current evidence supports the role of oxidative stress in the pathogenesis of neuron degeneration in Alzheimer's disease (AD). alpha-Lipoic acid (LA), an essential cofactor in mitochondrial dehydrogenase reactions, functions as an antioxidant and reduces oxidative stress in aged animals. Here, we describe the effects of LA and its reduced form, dihydrolipoic acid (DHLA), in neuron cultures treated with amyloid beta-peptide (Abeta 25-35) and iron/hydrogen peroxide (Fe/H_2O_2). Pretreatment of dissociated primary hippocampal cultures with LA significantly protected against Abeta and Fe/H_2O_2toxicity. In contrast, concomitant treatment of cultures with LA and Fe/H_2O_2 significantly potentiated the toxicity. Decreased cell survival in cultures treated concomitantly with LA and Fe/H_2O_2 correlated with increased free radical production measured by dichlorofluorescein fluorescence. Treatment of cortical neurons with DHLA significantly protected glucose-transport against Fe/H_2O_2 or beta-mediated decreases although treatment with LA did not provide protection. These data suggest that DHLA, the reduced form of LA, significantly protects against both Abetaand Fe/H_2O_2 mediated toxicity. The data also suggest that concomitant exposure to LA and Fe/H_2O_2 significantly potentiates the oxidative stress. Overall, these data suggest that the oxidation state of LA is critical to its function and that in the absence of studies of LA/DHLA equilibria in human brain the use of LA as an antioxidant in disorders where there is increased Fe such as AD is of questionable efficacy.

7. Neurosci Lett. 2002 Aug 9;328(2):93-6.
Alpha-lipoic acid prevents ethanol-induced protein oxidation in mouse hippocampal HT22 cells.
Pirlich M, Kiok K, Sandig G, Lochs H, Grune T.
Department of Gastroenterology and Hepatology, University Hospital Charite, Humboldt-University Berlin, Schumannstr. 20/21, 10098, Berlin, Germany.

Oxidative stress is involved in a number of neurological disorders, including the neurotoxic effects of ethanol. Recent studies have described a neuroprotective potential of alpha-lipoic acid (LC) in several models of neuronal cell death related to oxidative stress. We tested the hypothesis that LC could be effective in preventing ethanol-induced neurotoxicity employing the clonal hippocampa cell line HT22. A 24 h incubation with ethanol 100-600 mM caused a dose-dependent loss of cell viability and a significant increase of the overall intracellular protein oxidation. Coincubation with LC 0.1 mM resulted in a significant decrease of ethanol-related neurotoxicity and a complete prevention of the ethanol-induced intracellular protein oxidation. These results indicate that the radical scavenging properties of LC are effective to ameliorate ethanol-induced neurotoxicity.

8. Neurosci Lett. 2002 Mar 15;321(1-2):100-4.
Beneficial effects of alpha-lipoic acid plus vitamin E on neurological deficit, reactive gliosis and neuronal remodeling in the penumbra of the ischemic rat brain.
Gonzalez-Perez O, Gonzalez-Castaneda RE, Huerta M, Luquin S, Gomez-Pinedo U, Sanchez-Almaraz E, Navarro-Ruiz A, Garcia-Estrada J.
Division de Neurociencias, Centro de Investigacion Biomedica de Occidente (CIBO) del Instituto Mexicano del Seguro Social (IMSS), Sierra Mojada 800, Guadalajara Jalisco 44340, Mexico.

During cerebral ischemia-reperfusion, the enhanced production of oxygen-derived free radicals contributes to neuronal death. The antioxidants alpha-lipoic acid and vitamin E have shown synergistic effects against lipid peroxidation by oxidant radicals in several pathological conditions. A thromboembolic stroke model in rats was used to analyze the effects of this mixture under two oral treatments: intensive and prophylactic. Neurological functions, glial reactivity and neuronal remodeling were assessed after experimental infarction. Neurological recovery was only found in the prophylactic group, and both antioxidant schemes produced down-regulation of astrocytic and microglial reactivity, as well as higher neuronal remodeling in the penumbra area, as compared with controls. The beneficial effects of this antioxidant mixture suggest that it may be valuable for the treatment of cerebral ischemia in humans.

9. Free Radic Biol Med. 1997;22(1-2):359-78.
Neuroprotection by the metabolic antioxidant alpha-lipoic acid.
Packer L, Tritschler HJ, Wessel K.
Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.

Reactive oxygen species are thought to be involved in a number of types of acute and chronic pathologic conditions in the brain and neural tissue. The metabolic antioxidant alpha-lipoate (thioctic acid, 1, 2-dithiolane-3-pentanoic acid; 1, 2-dithiolane-3 valeric acid; and 6, 8-dithiooctanoic acid) is a low molecular weight substance that is absorbed from the diet and crosses the blood-brain barrier. alpha-Lipoate is taken up and reduced in cells and tissues to dihydrolipoate, which is also exported to the extracellular medium; hence, protection is afforded to both intracellular and extracellular environments. Both alpha-lipoate and especially dihydrolipoate have been shown to be potent antioxidants, to regenerate through redox cycling other antioxidants like vitamin C and vitamin E, and to raise intracellular glutathione levels. Thus, it would seem an ideal substance in the treatment of oxidative brain and neural disorders involving free radical processes. Examination of current research reveals protective effects of these compounds in cerebral ischemia-reperfusion, excitotoxic amino acid brain injury, mitochondrial dysfunction, diabetes and diabetic neuropathy, inborn errors of metabolism, and other causes of acute or chronic damage to brain or neural tissue. Very few neuropharmacological intervention strategies are currently available for the treatment of stroke and numerous other brain disorders involving free radical injury. We propose that the various metabolic antioxidant properties of alpha-lipoate relate to its possible therapeutic roles in a variety of brain and neuronal tissue pathologies: thiols are central to antioxidant defense in brain and other tissues. The most important thiol antioxidant, glutathione, cannot be directly administered, whereas alpha-lipoic acid can. In vitro, animal, and preliminary human studies indicate that alpha-lipoate may be effective in numerous neurodegenerative disorders.

CATARACT

10. Diabetes Metab Res Rev. 2001 Jan-Feb;17(1):44-50.
Cataract development in diabetic sand rats treated with alpha-lipoic acid and its gamma-linolenic acid conjugate.
Borenshtein D, Ofri R, Werman M, Stark A, Tritschler HJ, Moeller W, Madar Z.
Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

BACKGROUND: Diabetes commonly leads to long-term complications such as cataract. This study investigated the effects of alpha-lipoic acid (LPA) and its gamma-linolenic acid (GLA) conjugate on cataract development in diabetic sand rats. METHODS: Two separate experiments were conducted. In Experiment 1, sand rats were fed a "high-energy" diet (70% starch), an acute model of Type 2 diabetes, and injected with LPA. In Experiment 2, the animals received a "medium-energy" diet (59% starch), a chronic diabetic model, and were intubated with LPA or its GLA conjugate. Throughout the experiments, blood glucose levels and cataract development were measured. At the termination of the experiments, lens aldose reductase (AR) activity and lenticular reduced glutathione (GSH) levels were analyzed. RESULTS: LPA injection significantly inhibited cataract development and reduced blood glucose levels in rats fed the "high-energy" diet. Lens AR activity tended to be lower, while lenticular GSH levels increased. In sand rats fed a "medium-energy" diet (59% starch), LPA intubation had no effect on blood glucose levels and cataract development but GSH levels were increased. In contrast, sand rats intubated with GLA conjugate showed the highest blood glucose levels and accelerated cataract development. The conjugate treatment also decreased lenticular GSH content. CONCLUSIONS: The hypoglycemic effects of LPA are beneficial in the prevention of acute symptoms of Type 2 diabetes. It remains to be shown that the antioxidant activity of LPA is responsible for prevention or inhibition of cataract progression in sand rats. Copyright 2000 John Wiley & Sons, Ltd.

11. Biochem Mol Biol Int. 1998 Oct;46(3):585-95.
Modelling cortical cataractogenesis XX. In vitro effect of alpha-lipoic acid on glutathione concentrations in lens in model diabetic cataractogenesis.
Kilic F, Handelman GJ, Traber K, Tsang K, Packer L, Trevithick JR.
Department of Biochemistry, University of Western Ontario, London, Canada.

In previous studies stereospecific protection against lens opacity was consistent with specific reduction of R-alpha-lipoic acid(R-alpha-LA) in mitochondria of the vulnerable cells at the lens equator where the first globular degeneration is seen in glucose cataract. In this study two further possible explanations of this effect were investigated: (1) increased glucose uptake by the lens, leading to increased glycolysis and release of lactate into the incubation medium and/or (2) maintenance of glutathione levels by the R-alpha-LA. The data did not support 1, but was consistent with 2, after 24 hr incubation. The concentrations of glutathione in normal lenses or lenses incubated with R- or racemic alpha-LA were not significantly different, but the concentration of glutathione in lenses incubated with S-alpha-LA was significantly lower than the R-alpha-LA-incubated lenses.

12. Biochem Biophys Res Commun. 1996 Apr 16;221(2):422-9.
Stereospecific effects of R-lipoic acid on buthionine sulfoximine-induced cataract formation in newborn rats.
Maitra I, Serbinova E, Tritschler HJ, Packer L.
Department of Molecular and Cell Biology, University of California, Berkeley, 94720-3200, USA.

This study revealed a marked stereospecificity in the prevention of buthionine sulfoximine-induced cataract, and in the protection of lens antioxidants, in newborn rats by alpha-lipoate, R- and racemic alpha-lipoate decreased cataract formation from 100% (buthionine sulfoximine only) to 55% (buthionine sulfoximine + R-alpha-lipoic acid) and 40% (buthionine sulfoximine + rac-alpha-lipoic acid) (p<0.05 compared to buthionine sulfoximine only). S-alpha-lipoic acid had no effect on cataract formation induced by buthionine sulfoximine. The lens antioxidants glutathione, ascorbate, and vitamin E were depleted to 45, 62, and 23% of control levels, respectively, by buthionine sulfoximine treatment, but were maintained at 84-97% of control levels when R-alpha-lipoic acid or rac-alpha-lipoic acid were administered with buthionine sulfoximine; S-alpha-lipoic acid administration had no protective effect on lens antioxidants. When enantiomers of alpha-lipoic acid were administered to animals, R-alpha-lipoic acid was taken up by lens and reached concentrations 2- to 7-fold greater than those of S-alpha-lipoic acid, with rac-alpha-lipoic acid reaching levels midway between the R-isomer and racemic form. Reduced lipoic acid, dihydrolipoic acid, reached the highest levels in lens of the rac-alpha-lipoic acid-treated animals and the lowest levels in S-alpha-lipoic acid-treated animals. These results indicate that the protective effects of alpha-lipoic acid against buthionine sulfoximine-induced cataract are probably due to its protective effects on lens antioxidants, and that the stereospecificity exhibited is due to selective uptake and reduction of R-alpha-lipoic acid by lens cells.

13. Biochem Mol Biol Int. 1995 Oct;37(2):361-70.
Modelling cortical cataractogenesis 17: in vitro effect of a-lipoic acid on glucose-induced lens membrane damage, a model of diabetic cataractogenesis.
Kilic F, Handelman GJ, Serbinova E, Packer L, Trevithick JR.
Dept. of Biochemistry, University of Western Ontario, London, Canada.

The effect of R, S, and racemic forms of a-lipoic acid was tested on the formation of opacity in normal rat lenses incubated with 55.6 mM glucose, as a model for in vivo diabetic cataractogenesis. Control lenses, incubated 8 days with 5.56 mM glucose, did not develop opacities. Formation of lens opacities in vitro was correlated with lactate dehydrogenase (LDH) leakage into the incubation medium. Opacity formation and LDH leakage, resulting from incubation in medium containing 55.6 mM glucose to model diabetes, were both suppressed by the addition of 1 mM R-lipoic acid. Addition of 1 mM racemic lipoic acid reduces these damaging effects to the lens by one-half, while S-lipoic acid potentiated LDH leakage, consistent with the hypothesis that R-lipoic acid is the active form. Although HPLC analysis demonstrated that both stereoisomers of lipoic acid were reduced to dihydrolipoate at comparable rates by the intact lens, the mitochondrial lipoamide dehydrogenase system is highly specific for reduction of exogenous R-lipoic to dihydrolipoic acid. Therefore, stereospecific protection against this opacity is consistent with specific reduction of R-lipoic acid in mitochondria of the vulnerable cells at the lens equator where the first globular degeneration is seen in glucose cataract.

DIABETES

14. Vnitr Lek. 2002 Jun;48(6):534-41.
[Autonomic neuropathy in diabetics, treatment possibilities] [Article in Czech]
Lacigova S, Rusavy Z, Cechurova D, Jankovec Z, Zourek M. I.
interni klinika Fakultni nemocnice, Plzen.

Diabetic neuropathy is a chronic complication of diabetes. It involves non-inflammatory damage of the function and structure of peripheral nerves by metabolic vascular pathogenic processes. In case of affection of vegetative nerves (small non-myelinated C fibres) autonomic neuropathy develops. It is a relatively frequent form of neuropathy which remains for a long time without clinical symptoms and therefore is rarely diagnosed and treated. Manifestations of the affection are encountered in all organs which are supplied by vegetative nerves. The presence of this complication of diabetes is signalized by tachycardia at rest, deterioration of gastric evacuation, diabetic diarrhoea or constipation, erectile dysfunction, impaired function of the sweat glans or impaired pupillary reaction. The advanced form involves the danger of latent myocardial ischaemia, serious postural hypotension and sudden death. It increases significantly the mortality of the affected patients. Similarly as the treatment of other complication of diabetes, treatment of autonomic neuropathy is difficult. The objective of the present paper is to review contemporary therapeutic possibilities. An essential prerequisite remain efforts to achieve optimal compensation. The authors draw attention to the effect of alpha-lipoic acid which exerts a positive effect not only on subjective symptoms but also on the objective finding. The other mentioned drugs are used either only experimentally or for purely symptomatic treatment.

15. Diabetes Metab Res Rev. 2002 May-Jun;18(3):176-84.
Oxidative stress and diabetic neuropathy: pathophysiological mechanisms and treatment perspectives.
van Dam PS.
Department of Internal Medicine and Endocrinology, University Medical Center, Utrecht, The Netherlands. P.S.vanDam@digd.azu.nl

Increased oxidative stress is a mechanism that probably plays a major role in the development of diabetic complications, including peripheral neuropathy. This review summarises recent data from in vitro and in vivo studies that have been performed both to understand this aspect of the pathophysiology of diabetic neuropathy and to develop therapeutic modalities for its prevention or treatment. Extensive animal studies have demonstrated that oxidative stress may be a final common pathway in the development of diabetic neuropathy, and that antioxidants can prevent or reverse hyperglycaemia-induced nerve dysfunction. Most probably, the effects of antioxidants are mediated by correction of nutritive blood flow, although direct effects on endoneurial oxidative state are not excluded. In a limited number of clinical studies, antioxidant drugs including alpha-lipoic acid and vitamin E were found to reduce neuropathic symptoms or to correct nerve conduction velocity. These data are promising, and additional larger studies with alpha-lipoic acid are currently being performed. Copyright 2002 John Wiley & Sons, Ltd.

Endocr Pract. 2002 Jan-Feb;8(1):29-35.
Pharmacokinetics, tolerability, and fructosamine-lowering effect of a novel, controlled-release formulation of alpha-lipoic acid.
Evans JL, Heymann CJ, Goldfine ID, Gavin LA.
Northern California Diabetes Institute, Seton Medical Center, Dale City, CA 94015, USA.

OBJECTIVE: To determine the pharmacokinetics, safety, and tolerability of a novel, controlled-release oral formulation of alpha-lipoic acid (LA) and to investigate whether sustaining the concentration of LA in plasma would have a beneficial effect on glycemic control in patients with type 2 diabetes. METHODS: For the pharmacokinetic study, a single, 600-mg dose of either controlled-release LA (CRLA) or quick-release LA (QRLA) was administered orally to 12 normal human subjects. The plasma profile of LA was determined for 24 hours after administration of the dose,and pharmacokinetic analyses were performed. For the safety and tolerability study, 21 patients with type 2 diabetes were given 900 mg of CRLA daily for 6 weeks, followed by 1,200 mg of CRLA daily for an additional 6 weeks. Active treatment was followed by a 3-week washout period. Throughout the study, patients continued to take their prestudy antidiabetic medications, which included metformin (Glucophage), sulfonylureas (Amaryl, glyburide, and Glucotrol), acarbose (Precose), troglitazone (Rezulin), and insulin (either as monotherapy or in combination). CRLA was evaluated for safety and tolerability as well as for effects on glycemic control. RESULTS: The Tmax (time to maximal plasma concentration) of LA administered as CRLA was 1.25 hours and was approximately 2.5-fold longer in comparison with the Tmax for QRLA (Tn,5X = 0.5 hour; P<0.02). No severe side effects or changes in either liver or kidney function or hematologic profiles were noted after the administration of CRLA. In 15 patients, the mean plasma fructosamine concentration was reduced from 313 to 283 micromol/L(P<0.05) after 12 weeks of treatment with CRLA. CONCLUSION: CRLA increased the plasma concentration of LA over time in healthy subjects, and CRLA was safe, well tolerated, and effective in reducing plasma fructosamine in patients with type 2 diabetes.

16. Nutrition. 2001 Oct;17(10):888-95.
Molecular aspects of lipoic acid in the prevention of diabetes complications.
Packer L, Kraemer K, Rimbach G.
Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, 1985 Zonal Avenue, Los Angeles, CA 90098-9121, USA. packerresearch@aol.com

Alpha-lipoic acid (LA) and its reduced form, dihydrolipoic acid, are powerful antioxidants. LA scavenges hydroxyl radicals, hypochlorous acid, peroxynitrite, and singlet oxygen. Dihydrolipoic acid also scavenges superoxide and peroxyl radicals and can regenerate thioredoxin, vitamin C, and glutathione, which in turn can recycle vitamin E. There are several possible sources of oxidative stress in diabetes including glycation reactions, decompartmentalization of transition metals, and a shift in the reduced-oxygen status of the diabetic cells. Diabetics have increased levels of lipid hydroperoxides, DNA adducts, and protein carbonyls. Available data strongly suggest that LA, because of its antioxidant properties, is particularly suited to the prevention and/or treatment of diabetic complications that arise from an overproduction of reactive oxygen and nitrogen species. In addition to its antioxidant properties, LA increases glucose uptake through recruitment of the glucose transporter-4 to plasma membranes, a mechanism that is shared with insulin-stimulated glucose uptake. Further, recent trials have demonstrated that LA improves glucose disposal in patients with type II diabetes. In experimental and clinical studies, LA markedly reduced the symptoms of diabetic pathologies, including cataract formation, vascular damage, and polyneuropathy. To develop a better understanding of the preventative and therapeutic potentials of LA, much of the current interest is focused on elucidating its molecular mechanisms in redox dependent gene expression.

17. J Am Coll Nutr. 2001 Oct;20(5 Suppl):363S-369S; discussion 381S-383S.
Use of antioxidant nutrients in the prevention and treatment of type 2 diabetes.
Ruhe RC, McDonald RB.
Department of Nutrition, University of California, Davis 95616-8669, USA.

Type 2 diabetes, or non-insulin dependent diabetes mellitus (NIDDM), is increasingly common throughout the world. The World Health Organization has predicted that between 1997 and 2025, the number of diabetics will double from 143 million to about 300 million. The incidence of NIDDM is highest in economically developed nations, particularly the U.S., where approximately 6.5% of the population (17 million people) have either diagnosed or undiagnosed diabetes. The two most important factors contributing to the development of NIDDM are obesity and physical inactivity. The leading cause of mortality and morbidity in people with NIDDM is cardiovascular disease caused by macro- and microvascular degeneration. Current therapies for NIDDM focus primarily on weight reduction. Indeed, several investigations indicate that 65% to 75% of cases of diabetes in Caucasians could be avoided if individuals in this subgroup did not exceed their ideal weight. The success of this approach has been, at best, modest. An alternate approach to the control of Type 2 diabetes is to arrest the progress of the pathology until a cure has been found. To this end, some investigators suggest that dietary antioxidants may be of value. Several studies in humans and laboratory animals with NIDDM indicate that vitamin E and lipoic acid supplements lessen the impact of oxidative damage caused by dysregulation of glucose metabolism. In this brief review, we discuss the incidence, etiology, and current therapies for NIDDM and further explore the usefulness of dietary antioxidants in treating this disorder.

18. Metabolism. 2001 Aug;50(8):868-75.
The effects of treatment with alpha-lipoic acid or evening primrose oil on vascular hemostatic and lipid risk factors, blood flow, and peripheral nerve conduction in the streptozotocin-diabetic rat.
Ford I, Cotter MA, Cameron NE, Greaves M.
Departments of Medicine & Therapeutics, University of Aberdeen, Aberdeen, Scotland.

Oxidative stress and defective fatty acid metabolism in diabetes may lead to impaired nerve perfusion and contribute to the development of peripheral neuropathy. We studied the effects of 2-week treatments with evening primrose oil (EPO; n = 16) or the antioxidant alpha-lipoic acid (ALA; n = 16) on endoneurial blood flow, nerve conduction parameters, lipids, coagulation, and endothelial factors, in rats with streptozotocin-induced diabetes. Compared with their nondiabetic littermates, untreated diabetic rats had impaired sciatic motor and saphenous sensory nerve-conduction velocity (NCV; P <.001), reduced endoneurial blood flow (P <.001), and increased serum triglycerides (P <.01), cholesterol (P < 0.01), plasma factor VII (P <.0001), and von Willebrand factor (vWF; P <.0001). Plasma fibrinogen and serum high-density lipoprotein concentrations were not significantly different. Treatment with either ALA or EPO effectively corrected the deficits in NCV and endoneurial blood flow. ALA was associated with marked and statistically significant decreases in fibrinogen, factor VII, vWF, and triglycerides (P <.01, paired t tests before v after treatment). In contrast, EPO was associated with significant (P <.05) increases in fibrinogen, factor VII, vWF, triglycerides, and cholesterol and a significant decrease in high-density lipoprotein. Changes in levels of coagulation factors and lipids, qualitatively similar to those found with EPO, were obtained with a diet containing sunflower oil (to control for calorific and lipid content) or with a normal diet alone. Blood glucose and hematocrit levels were not significantly altered by treatments. These data suggest that although both ALA and EPO improve blood flow and nerve function, their actions on vascular factors differ. The marked effects of ALA in lowering lipid and hemostatic risk factors for cardiovascular disease indicate potential antithrombotic and antiatherosclerotic actions that could be of benefit in human diabetes and merit further study. Copyright 2001 by W.B. Saunders Company

19. Diabetes Technol Ther. 2000 Autumn;2(3):401-13.
Alpha-lipoic acid: a multifunctional antioxidant that improves insulin sensitivity in patients with type 2 diabetes.
Evans JL, Goldfine ID.
Medical Research Institute, San Bruno, California 94066, USA. jevans@lipoic.com

Alpha-Lipoic acid (LA) is a disulfide compound that is produced in small quantities in cells, and functions naturally as a co-enzyme in the pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase mitochondrial enzyme complexes. In pharmacological doses, LA is a multifunctional antioxidant. LA has been used in Germany for over 30 years for the treatment of diabetes-induced neuropathy. In patients with type 2 diabetes, recent studies have reported that intravenous (i.v.) infusion of LA increases insulin-mediated glucose disposal, whereas oral administration of LA has only marginal effects. If the limitations of oral therapy can be overcome, LA could emerge as a safe and effective adjunctive antidiabetic agent with insulin sensitizing activity.

20. Free Radic Biol Med. 2001 Jul 1;31(1):53-61.
Beneficial effects of alpha-lipoic acid and ascorbic acid on endothelium-dependent, nitric oxide-mediated vasodilation in diabetic patients: relation to parameters of oxidative stress.
Heitzer T, Finckh B, Albers S, Krohn K, Kohlschutter A, Meinertz T.
Universitatsklinikum Hamburg-Eppendorf Klinik und Poliklinik fur Innere Medizin, Abteilung Kardiologie, Hamburg, Germany. heitzer@uke.uni-hamburg.de

The impairment of nitric oxide (NO)-mediated vasodilation in diabetes has been attributed to increased vascular oxidative stress. Lipoic acid has been shown to have substantial antioxidative properties. The aim of this study was to assess the effect of lipoic acid on NO-mediated vasodilation in diabetic patients in comparison with the well-recognized effect of ascorbic acid. Using venous occlusion plethysmography, we examined the effects of lipoic acid (0.2 mM) and ascorbic acid (1 and 10 mM) on forearm blood flow responses to acetylcholine, sodium nitroprusside and concomitant infusion of the NO-inhibitor, N(G)-monomethyl-L-arginine, in 39 diabetic patients and 11 control subjects. Plasma levels of antioxidants and parameters of lipid peroxidation were measured and correlated to endothelial function tests. Lipoic acid improved NO-mediated vasodilation in diabetic patients, but not in controls. NO-mediated vasodilation was improved by ascorbic acid at 10 mM, but not 1 mM. Improvements of endothelial function by ascorbic acid and lipoic acid were closely related. The beneficial effects of lipoic acid were positively related to plasma levels of malondialdehyde and inversely related to levels of ubiquinol-10. These findings support the concept that oxidative stress contributes to endothelial dysfunction and suggest a therapeutic potential of lipoic acid particularly in patients with imbalance between increased oxidative stress and depleted antioxidant defense.

21. Diabetes Res Clin Pract. 2001 Jun;52(3):175-83.
Effect of alpha-lipoic acid on the progression of endothelial cell damage and albuminuria in patients with diabetes mellitus: an exploratory study.
Morcos M, Borcea V, Isermann B, Gehrke S, Ehret T, Henkels M, Schiekofer S, Hofmann M, Amiral J, Tritschler H, Ziegler R, Wahl P, Nawroth PP.
Department of Internal Medicine I, University of Heidelberg, Bergheimerstr. 58, 69115 Heidelberg, Germany. michael_morcos@med.uni-heidelberg.de

Oxidative stress plays a central role in the pathogenesis and progression of late microangiopathic complications (diabetic nephropathy) in diabetes mellitus. Previous studies suggested that treatment of diabetic patients with the antioxidant alpha-lipoic acid reduce oxidative stress and urinary albumin excretion. In this prospective, open and non-randomized study, the effect of alpha-lipoic acid on the progression of endothelial cell damage and the course of diabetic nephropathy, as assessed by measurement of plasma thrombomodulin and urinary albumin concentration (UAC), was evaluated in 84 patients with diabetes mellitus over 18 months. Forty-nine patients (34 with Type 1 diabetes, 15 with Type 2 diabetes) had no antioxidant treatment and served as a control group. Thirty-five patients (20 with Type 1 diabetes, 15 with Type 2 diabetes) were treated with 600 mg alpha-lipoic acid per day. Only patients with an urinary albumin concentration <200 mg/l were included into the study. After 18 months of follow up, the plasma thrombomodulin level increased from 35.9+/-9.5 to 39.7+/-9.9 ng/ml (P<0.05) in the control group. In the alpha-lipoic acid treated group the plasma thrombomodulin level decreased from 37.5+/-16.2 to 30.9+/-14.5 ng/ml (P<0.01). The UAC increased in patients without alpha-lipoic acid treatment from 21.2+/-29.5 to 36.9+/-60.6 ng/l (P<0.05), but was unchanged with alpha-lipoic acid. It is postulated that the significant decrease in plasma thrombomodulin and failure of UAC to increase observed in the alpha-lipoic acid treated group is due to antioxidative effects of alpha-lipoic acid, and if so that oxidative stress plays a central role in the pathogenesis of diabetic nephropathy. Furthermore, progression of the disease might be inhibited by antioxidant drugs. A placebo-controlled study is needed.

22. Bull Exp Biol Med. 2000 Oct;130(10):986-90.
The function of endogenous protective systems in patients with insulin-dependent diabetes mellitus and polyneuropathy: effect of antioxidant therapy.
Strokov IA, Manukhina EB, Bakhtina LY, Malyshev IY, Zoloev GK, Kazikhanova SI, Ametov AS.
Department of Endocrinology and Diabetology, Russian Medical Academy of Postgraduate Education, Moscow.

alpha-Lipoic acid is a very efficient antioxidants for the treatment and prevention of diabetic neuropathy. The aim of the present study was to evaluate the function of nitric oxide (NO) and stress proteins (HSP72) in insulin-dependent diabetes complicated by polyneuropathy and possible contribution of these systems to the therapeutic effects of alpha-lipoic acid. Plasma content of nitrites and nitrates in diabetic patients was almost 2-fold below the normal. The treatment with alpha-lipoic acid completely normalized the plasma content of these stable NO metabolites. The majority of patients had also low level of HSP72. Positive clinical effects of alpha-lipoic acid were accompanied by normalization of HSP72 synthesis. Thus, activation of the NO and HSP protective systems is involved in the therapeutic effect of alpha-lipoic acid in diabetic patients (type 1 diabetes mellitus) with polyneuropathy.

23. Free Radic Biol Med. 2000 Dec;29(11):1122-8.
Lipoic acid decreases lipid peroxidation and protein glycosylation and increases (Na(+) + K(+))- and Ca(++)-ATPase activities in high glucose-treated human erythrocytes.
Jain SK, Lim G.
Department of Pediatrics, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA. sjain@lsuhsc.edu

Lipoic acid supplementation has been found to be beneficial in preventing neurovascular abnormalities in diabetic neuropathy. Insufficient (Na(+) + K(+))-ATPase activity has been suggested as a contributing factor in the development of diabetic neuropathy. This study was undertaken to test the hypothesis that lipoic acid reduces lipid peroxidation and glycosylation and can increase the (Na(+) + K(+))- and Ca(++)-ATPase activities in high glucose-exposed red blood cells (RBC). Washed normal human RBC were treated with normal (6 mM) and high glucose concentrations (45 mM) with 0-0.2 mM lipoic acid (mixture of S and R sterioisomers) in a shaking water bath at 37 degrees C for 24 h. There was a significant stimulation of glucose consumption by RBC in the presence of lipoic acid both in normal and high glucose-treated RBC. Lipoic acid significantly lowered the level of glycated hemoglobin (GHb) and lipid peroxidation in RBC exposed to high glucose concentrations. High glucose treatment significantly lowered the activities of (Na(+) + K(+))- and Ca(++)-ATPases of RBC membranes. Lipoic acid addition significantly blocked the reduction in activities of (Na(+) + K(+))- and Ca(++)-ATPases in high glucose-treated RBC. There were no differences in lipid peroxidation, GHb and (Na(+) + K(+))- and Ca(++)-ATPase activity levels in normal glucose-treated RBC with and without lipoic acid. Thus, lipoic acid can lower lipid peroxidation and protein glycosylation, and increase (Na(+) + K(+))- and Ca(++)-ATPase activities in high-glucose exposed RBC, which provides a potential mechanism by which lipoic acid may delay or inhibit the development of neuropathy in diabetes.

24. Med Hypotheses. 2000 Dec;55(6):510-2.
Alpha lipoic acid: a novel treatment for depression.
Salazar MR. Amherst College, Amherst, Massachusetts, USA.

Insulin resistance has been associated with people diagnosed with depression. Conversely, it has also been documented that diabetics have an increased risk of depression. Evidence suggests that insulin activity plays a role in serotonergic activity by increasing the influx of tryptophan into the brain. This increased influx of tryptophan has been shown to result in an increase in serotonin synthesis. In accordance with the serotonin theory of depression, it may be possible to treat depression by increasing insulin activity. The antioxidant alpha lipoic acid has been shown to increase insulin sensitivity and is used to treat people with diabetes. Therefore, the nutrient alpha lipoic acid should be clinically tested as an adjunct treatment for depression. Copyright 2000 Harcourt Publishers Ltd.

25. Wien Klin Wochenschr. 2000 Jul 28;112(14):610-6.
Therapeutic potential of glutathione.
Exner R, Wessner B, Manhart N, Roth E.
Department of Surgery, University of Vienna, Austria.

Reactive oxygen species, formed in various biochemical reactions, are normally scavenged by antioxidants. Glutathione in its reduced form (GSH) is the most powerful intracellular antioxidant, and the ratio of reduced to oxidised glutathione (GSH:GSSG) serves as a representative marker of the antioxidative capacity of the cell. Several clinical conditions are associated with reduced GSH levels which as a consequence can result in a lowered cellular redox potential. GSH and the redox potential of the cell are components of the cell signaling system influencing the translocation of the transcription factor NF kappa B which regulates the synthesis of cytokines and adhesion molecules. Therefore, one possibility to protect cells from damage caused by reactive oxygen species is to restore the intracellular glutathione levels. Cellular GSH concentration can be influenced by exogenous administration of GSH (as intravenous infusion or as aerosol), of glutathione esters or of GSH precursors such as glutamine or cysteine (in form of N-acetyl-L-cysteine, alpha-lipoic acid). The modulation of GSH metabolism might present a useful adjuvant therapy in many pathologies such as intoxication, diabetes, uremia, sepsis, inflammatory lung processes, coronary disease, cancer and immunodeficiency states.

26. Exp Clin Endocrinol Diabetes. 2000;108(3):168-74.
Effects of alpha-lipoic acid on microcirculation in patients with peripheral diabetic neuropathy.
Haak E, Usadel KH, Kusterer K, Amini P, Frommeyer R, Tritschler HJ, Haak T. Medical
Department I, Center of Internal Medicine, University Hospital, Frankfurt, Germany. E.Haak@em.uni-frankfurt.de

Diabetic polyneuropathy is a serious complication in patients with diabetes mellitus. In addition to the maintenance of a sufficient metabolic control, alpha-lipoic acid (ALA) (Thioctacid, Asta Medica) is known to have beneficial effects on diabetic polyneuropathy although the exact mechanism by which ALA exerts its effect is unknown. In order to study the effect of ALA on microcirculation in patients with diabetes mellitus and peripheral neuropathy one group of patients (4 female, 4 male, age 60+/-3 years, diabetes duration 19+/-4 years, BMI 24.8+/-1.3 kg/m2) received 1200 mg ALA orally per day over 6 weeks (trial 1). A second group of patients (5 female, 4 male, age 65+/-3 years, diabetes duration 14+/-4 years, BMI 23.6+/-0.7 kg/m2) was studied before and after they had received 600 mg ALA or placebo intravenously over 15 minutes in order to investigate whether ALA has an acute effect on microcirculation (trial 2). Patients were investigated by nailfold video-capillaroscopy. Capillary blood cell velocity was examined at rest and during postreactive hyperemia (occlusion of the wrist for 2 minutes, 200 mmHg) which is a parameter of the perfusion reserve on demand. The oral therapy with ALA resulted in a significant decrease in the time to peak capillary blood cell velocity (tpCBV) during postocclusive hyperemia (trial 1: 12.6+/-3.1 vs 35.4+/-10.9 s, p<0.05). The infusion of ALA also decreased the tpCBV in patients with diabetic neuropathy (trial 2: before: 20.8+/-4,5, ALA: 11.74+/-4.4, placebo: 21.9-5.0 s, p<0.05 ALA vs both placebo and before infusions) indicating that ALA has an acute effect on microcirculation. Capillary blood cell velocity at rest (rCBV), hemodynamic parameters, hemoglobinA1c and local skin temperature remained unchanged in both studies. These results demonstrate that in patients with diabetic polyneuropathy ALA improves microcirculation as indicated by an increased perfusion reserve on demand. The observed effects are apparently acute effects. With the restriction of the pilot character of this investigation the findings support the assumption that ALA might exert its beneficial effects at least partially by improving microcirculation which is likely to occur also at the level of the vasa nervorum.

27. In Vivo. 2000 Mar-Apr;14(2):327-30.
In vivo effect of lipoic acid on lipid peroxidation in patients with diabetic neuropathy.
Androne L, Gavan NA, Veresiu IA, Orasan R. Diabetes Center & Clinic, Cluj Napoca.

BACKGROUND: The diabetic state, in both humans and experimental animals, is associated with oxidative stress. Lipid peroxidation of nerve membranes has been suggested as a mechanism by which peripheral nerve ischemia and hypoxia could cause neuropathy. Lipoic acid (LA) is a powerful inhibitor of iron-dependent lipid peroxidation and reactive oxygen species. The treatment of diabetic peripheral and cardiac autonomic neuropathy with LA is based on good clinical and experimental evidence. MATERIALS AND METHODS: To investigate the magnitude of the oxidative stress, serum ceruloplasmin (Cp) and lipid peroxide (Lp) levels were measured in 10 patients with diabetic neuropathy, before and 70 days after treatment with single dose of 600 mg LA/day. For other 12 healthy age- and sex-matched control subjects the serum Cp and Lp levels were evaluated. RESULTS: Our results show that hyperglycemia is a factor for an increase in serum ceruloplasmin in patients with diabetic neuropathy compared to healthy subjects (p < 0.0001). High serum ceruloplasmin (Cp) level in patients with diabetes may be related to antioxidant defense. The treatment of diabetic neuropathy with LA does not affect significantly the serum Cp activity. The serum Lp levels after LA administration were significantly lower (p < 0.005) than those before treatment. CONCLUSIONS: The antioxidant therapy with LA improves and may prevent diabetic neuropathy. This improvement is associated with a reduction in the indexes of lipid peroxidation. Oxidative stress appears to be primarily due to the processes of nerve ischemia and hyperglycemia autooxidation.

28. Diabet Med. 1999 Dec;16(12):1040-3.
Effects of 3-week oral treatment with the antioxidant thioctic acid (alpha-lipoic acid) in symptomatic diabetic polyneuropathy.
Ruhnau KJ, Meissner HP, Finn JR, Reljanovic M, Lobisch M, Schutte K, Nehrdich D, Tritschler HJ, Mehnert H, Ziegler D.
Deutsches Diabetes-Forschungsinstitut an der Heinrich-Heine-Universitat, Dusseldorf, Germany.

AIMS: To evaluate the efficacy and safety of short-term oral treatment with the antioxidant thioctic acid (TA) on neuropathic symptoms and deficits in patients with Type 2 diabetes mellitus with symptomatic polyneuropathy. METHODS: Patients were randomly assigned to oral treatment with 600 mg of TA t.i.d. (n = 12) or placebo (n = 12) for 3 weeks. Neuropathic symptoms (pain, burning, paraesthesiae, and numbness) in the feet were scored at weekly intervals and summarized as a Total Symptom Score (TSS). The Hamburg Pain Adjective List (HPAL) and the Neuropathy Disability Score (NDS) were assessed at baseline and day 19. RESULTS: At baseline the TSS, HPAL, and NDS were not significantly different between the groups. The TSS in the foot decreased from baseline to day 19 by -3.75 +/- 1.88 points (-47%) in the TA group and by -1.94 +/- 1.50 points (-24%) in the placebo group (P= 0.021 for TA vs. placebo). The total HPAL score decreased from baseline to day 19 by -2.20 +/- 1.65 points (-60%) in the TA group and by -0.96 +/- 1.32 points (-29%) in the placebo group (P = 0.072 for TA vs. placebo). The NDS decreased by -0.27 +/- 0.47 points in the TA group, whereas it slightly increased by +0.18 +/- 0.4 points in the placebo group (P = 0.025 for TA vs. placebo). No differences between the groups were noted regarding the rates of adverse events. CONCLUSIONS: These preliminary findings indicate that oral treatment with 600 mg of TA t.i.d. for 3 weeks may improve symptoms and deficits resulting from polyneuropathy in Type 2 diabetic patients, without causing significant adverse reactions.

29. Biofactors. 1999;10(2-3):157-67.
The role of oxidative stress and NF-kappaB activation in late diabetic complications.
Mohamed AK, Bierhaus A, Schiekofer S, Tritschler H, Ziegler R, Nawroth PP.
Medizinische Klinik I der Universitat Heidelberg, Germany.

A common endpoint of hyperglycemia dependent cellular changes is the generation of reactive oxygen intermediates (ROIs) and the presence of elevated oxidative stress. Therefore, oxidative stress is supposed to play an important role in the development of late diabetic complications. Formation of advanced glycation end products (AGE's) due to elevated nonenzymatic glycation of proteins, lipids and nucleic acids is accompanied by oxidative, radical-generating reactions and thus represents a major source for oxygen free radicals under hyperglycemic conditions. Once formed, AGE's can influence cellular function by binding to several binding sites including the receptor for AGE's, RAGE. Binding of AGE's (and other ligands) to RAGE results in generation of intracellular oxidative stress and subsequent activation of the redox-sensitive transcription factor NF-kappaB in vitro and in vivo. Consistently, activation of NF-kappaB in diabetic patients correlates with the quality of glycemic control and can be reduced by treatment with the antioxidant alpha-lipoic acid. The development of techniques allowing for a tissue culture independent measurement of NF-kappaB activation in patients with diabetes mellitus gives insights into the molecular mechanisms linking diabetes mellitus and hyperglycemia with formation of advanced glycated endproducts and generation of oxidative stress finally resulting in oxidative stress mediated cellular activation.

30. Exp Clin Endocrinol Diabetes. 1999;107(7):421-30.
Alpha-lipoic acid in the treatment of diabetic polyneuropathy in Germany: current evidence from clinical trials.
Ziegler D, Reljanovic M, Mehnert H, Gries FA.
Diabetes-Forschungsinstitut an der Heinrich-Heine-Universitat, Dusseldorf, Germany. dan.ziegler@dfi.uni-duesseldorf.de

Diabetic neuropathy represents a major health problem, as it is responsible for substantial morbidity, increased mortality, and impaired quality of life. Near-normoglycaemia is now generally accepted as the primary approach to prevention of diabetic neuropathy, but is not achievable in a considerable number of patients. In the past two decades several medical treatments that exert their effects despite hyperglycaemia have been derived from the experimental pathogenetic concepts of diabetic neuropathy. Such compounds have been designed to improve or slow the progression of the neuropathic process and are being evaluated in clinical trials, but with the exception of alpha-lipoic acid (thioctic acid) which is available in Germany, none of these drugs is currently available in clinical practice. Here we review the current evidence from the clinical trials that assessed the therapeutic efficacy and safety of thioctic acid in diabetic polyneuropathy. Thus far, 15 clinical trials have been completed using different study designs, durations of treatment, doses, sample sizes, and patient populations. Within this variety of clinical trials, those with beneficial effects of thioctic acid on either neuropathic symptoms and deficits due to polyneuropathy or reduced heart rate variability resulting from cardiac autonomic neuropathy used doses of at least 600 mg per day. The following conclusions can be drawn from the recent controlled clinical trials. 1.) Short-term treatment for 3 weeks using 600 mg of thioctic acid i.v. per day appears to reduce the chief symptoms of diabetic polyneuropathy. A 3-week pilot study of 1800 mg per day given orally indicates that the therapeutic effect may be independent of the route of administration, but this needs to be confirmed in a larger sample size. 2.) The effect on symptoms is accompanied by an improvement of neuropathic deficits. 3.) Oral treatment for 4-7 months tends to reduce neuropathic deficits and improves cardiac autonomic neuropathy. 4.) Preliminary data over 2 years indicate possible long-term improvement in motor and sensory nerve conduction in the lower limbs. 5.) Clinical and postmarketing surveillance studies have revealed a highly favourable safety profile of the drug. Based on these findings, a pivotal long-term multicenter trial of oral treatment with thioctic acid (NATHAN I Study) is being conducted in North America and Europe aimed at slowing the progression of diabetic polyneuropathy using a clinically meaningful and reliable primary outcome measure that combines clinical and neurophysiological assessment.

31. Free Radic Biol Med. 1999 Aug;27(3-4):309-14.
Oral administration of RAC-alpha-lipoic acid modulates insulin sensitivity in patients with type-2 diabetes mellitus: a placebo-controlled pilot trial.
Jacob S, Ruus P, Hermann R, Tritschler HJ, Maerker E, Renn W, Augustin HJ, Dietze GJ, Rett K.
Hypertension and Diabetes Research Unit, Max Grundig Clinic, Buhl and City Hospital, Baden-Baden, Germany. snjacob@med.uni-tuebingen.de

Alpha-lipoic acid (ALA), a naturally occuring compound and a radical scavenger was shown to enhance glucose transport and utilization in different experimental and animal models. Clinical studies described an increase of insulin sensitivity after acute and short-term (10 d) parenteral administration of ALA. The effects of a 4-week oral treatment with alpha-lipoic acid were evaluated in a placebo-controlled, multicenter pilot study to determine see whether oral treatment also improves insulin sensitivity. Seventy-four patients with type-2 diabetes were randomized to either placebo (n = 19); or active treatment in various doses of 600 mg once daily (n = 19), twice daily (1200 mg; n = 18), or thrice daily (1800 mg; n = 18) alpha-lipoic acid. An isoglycemic glucose-clamp was done on days 0 (pre) and 29 (post). In this explorative study, analysis was done according to the number of subjects showing an improvement of insulin sensitivity after treatment. Furthermore, the effects of active vs. placebo treatment on insulin sensitivity was compared. All four groups were comparable and had a similar degree of hyperglycemia and insulin sensitivity at baseline. When compared to placebo, significantly more subjects had an increase in insulin-stimulated glucose disposal (MCR) after ALA treatment in each group. As there was no dose effect seen in the three different alpha-lipoic acid groups, all subjects receiving ALA were combined in the "active" group and then compared to placebo. This revealed significantly different changes in MCR after treatment (+27% vs. placebo; p < .01). This placebo-controlled explorative study confirms previous observations of an increase of insulin sensitivity in type-2 diabetes after acute and chronic intravenous administration of ALA. The results suggest that oral administration of alpha-lipoic acid can improve insulin sensitivity in patients with type-2 diabetes. The encouraging findings of this pilot trial need to be substantiated by further investigations.

32. Free Radic Biol Med. 1999 Jun;26(11-12):1495-500.
alpha-Lipoic acid decreases oxidative stress even in diabetic patients with poor glycemic control and albuminuria.
Borcea V, Nourooz-Zadeh J, Wolff SP, Klevesath M, Hofmann M, Urich H, Wahl P, Ziegler R, Tritschler H, Halliwell B, Nawroth PP.
Department of Internal Medicine I, University of Heidelberg, Germany.

In the present cross-sectional study, the influence of alpha-lipoic acid on markers of oxidative stress, assessed by measurement of plasma lipid hydroperoxides (ROOHs), and on the balance between oxidative stress and antioxidant defence, determined by the ratio ROOH/(alpha-tocopherol/cholesterol), was examined in 107 patients with diabetes mellitus. Patients receiving alpha-lipoic acid (600 mg/day for > 3 months) had significant lower ROOHs and a lower ROOH/(alpha-tocopherol/cholesterol) ratio than those without alpha-lipoic acid treatment [ROOH: 4.76 +/- 2.49 vs. 7.16 +/- 3.22 mumol/l; p < .0001] and [ROOH/(alpha-tocopherol/cholesterol): 1.37 +/- 0.72 vs. 2.16 +/- 1.17; p < 0.0001]. In addition, the influence of glycemic control and albuminuria on ROOHs and on the ratio of ROOH/(alpha-tocopherol/cholesterol) was examined in the presence and absence of alpha-lipoic acid treatment. Patients were subdivided into three groups based on (1) their HbA1 levels (< 7.5, 7.5-9.5, and > 9.5%) and (2) their urinary albumin concentrations (< 20, 20-200, and > 200 mg/l). Neither poor glycemic control, nor the presence of micro- or macroalbuminuria prevented the antioxidant effect of alpha-lipoic acid. Using stepwise multiple regression analysis, alpha-lipoic acid was found to be the only factor significantly predicting low ROOHs and a low ratio of ROOH/(alpha-tocopherol/cholesterol). These data provide evidence that treatment with alpha-lipoic acid improves significantly the imbalance between increased oxidative stress and depleted antioxidant defence even in patients with poor glycemic control and albuminuria.

33. Microvasc Res. 1999 Jul;58(1):28-34.
The effect of alpha-lipoic acid on the neurovascular reflex arc in patients with diabetic neuropathy assessed by capillary microscopy.
Haak ES, Usadel KH, Kohleisen M, Yilmaz A, Kusterer K, Haak T.
Center of Internal Medicine, Johann Wolfgang Goethe-University, Frankfurt, D-60590, Germany.

Patients with diabetic polyneuropathy are known to have an impaired neurovascular reflex arc compared to healthy controls. This is seen in a delayed decrease in microcirculation of the ipsilateral hand after cooling of the contralateral hand. The aim of this pilot study was to investigate whether intravenous alpha-lipoic acid (ALA) (Thioctacid, Asta Medica) therapy might be able to improve this impaired neurovascular reflex arc in patients with diabetic neuropathy. In addition, clinical effects were evaluated with the aid of the neuropathy symptom score (NSS) and the neuropathy disability score (NDS). Ten patients with diabetes mellitus and polyneuropathy (5 females, 5 males, 2 smokers, 5 IDDM, 5 NIDDM, body mass index 26.1 +/- 1.0 kg/m2, age 58.3 +/- 9.5 years, diabetes duration 15.7 +/- 11.2 years, Hb A1c 6.8 +/- 0.3%) were investigated by nail-fold capillaroscopy after contralateral cooling before and after intravenous therapy with 600 mg alpha-lipoic acid per day over 3 weeks. Cardiac autonomic neuropathy was excluded by beat-to-beat variation analysis. Symptoms of diabetic neuropathy were evaluated before and after therapy with the aid of the NSS and NDS. Capillary blood cell velocity (CBV) of the hand was determined before, during, and for the following 30 min after cooling (3 min at 15 degrees C) of the contralateral hand. Blood pressure, heart rate, and local skin temperature were monitored at 2-min intervals. ALA therapy resulted in a significant improvement of the microcirculatory response to cooling, as seen by an immediate decrease in CBV of 12. 3% (P < 0.02 vs before treatment), which was absent before therapy. Blood pressure, heart rate, and local skin temperature were not different between investigations. There was a significant improvement of the NSS after therapy (5.4 +/- 1.1 vs 8.6 +/- 1.1 points, P < 0.01). These results demonstrate that intravenous therapy with ALA has a positive influence on the impaired neurovascular reflex arc in patients with diabetic neuropathy. Copyright 1999 Academic Press.

34. Diabetes Care. 1999 Feb;22(2):280-7.
alpha-Lipoic acid treatment decreases serum lactate and pyruvate concentrations and improves glucose effectiveness in lean and obese patients with type 2 diabetes.
Konrad T, Vicini P, Kusterer K, Hoflich A, Assadkhani A, Bohles HJ, Sewell A, Tritschler HJ, Cobelli C, Usadel KH.
Department of Internal Medicine, J.W. Goethe-University, Frankfurt, Germany.

OBJECTIVE: We examined the effect of lipoic acid (LA), a cofactor of the pyruvate dehydrogenase complex (PDH), on insulin sensitivity (SI) and glucose effectiveness (SG) and on serum lactate and pyruvate levels after oral glucose tolerance tests (OGTTs) and modified frequently sampled intravenous glucose tolerance tests (FSIGTTs) in lean (n = 10) and obese (n = 10) patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: FSIGTT data were analyzed by minimal modeling technique to determine SI and SG before and after oral treatment (600 mg, twice a day, for 4 weeks). Serum lactate and pyruvate levels of diabetic patients after glucose loading were compared with those of lean (n = 10) and obese (n = 10) healthy control subjects in which SI and SG were also determined from FSIGTT data. RESULTS: Fasting lactate and pyruvate levels were significantly increased in patients with type 2 diabetes. These metabolites did not exceed elevated fasting concentrations after glucose loading in lean patients with type 2 diabetes. However, a twofold increase of lactate and pyruvate levels was measured in obese diabetic patients. LA treatment was associated with increased SG in both diabetic groups (lean 1.28 +/- 0.14 to 1.93 +/- 0.13; obese 1.07 +/- 0.11 to 1.53 +/- 0.08 x 10(-2) min-1, P < 0.05). Higher SI and lower fasting glucose were measured in lean diabetic patients only (P < 0.05). Lactate and pyruvate before and after glucose loading were approximately 45% lower in lean and obese diabetic patients after LA treatment. CONCLUSIONS: Treatment of lean and obese diabetic patients with LA prevents hyperglycemia-induced increments of serum lactate and pyruvate levels and increases SG.

35. Diabetologia. 1999 Feb;42(2):222-32.
Peripheral blood mononuclear cells isolated from patients with diabetic nephropathy show increased activation of the oxidative-stress sensitive transcription factor NF-kappaB.
Hofmann MA, Schiekofer S, Isermann B, Kanitz M, Henkels M, Joswig M, Treusch A, Morcos M, Weiss T, Borcea V, Abdel Khalek AK, Amiral J, Tritschler H, Ritz E, Wahl P, Ziegler R, Bierhaus A, Nawroth PP.
Department of Medicine, University of Heidelberg, Germany.

Increased oxidative stress and subsequent activation of the transcription factor NF-kappaB has been linked to the development of late diabetic complications. To determine whether oxidative stress dependent NF-kappaB activation is evident in patients with diabetic nephropathy we used an Electrophoretic Mobility Shift Assay based semiquantitative detection system which enabled us to determine NF-kappaB activation in ex vivo isolated peripheral blood mononuclear cells. We examined 33 patients with diabetes mellitus (Type I and Type II). Patients with diabetic nephropathy showed higher NF-kappaB binding activity in Electrophoretic Mobility Shift Assays and stronger immunohistological staining for activated NF-kappaBp65 than patients without renal complications. NF-kappaB binding activity correlated with the degree of albuminuria (r = 0.316) and with thrombomodulin plasma concentrations (r = 0.33), indicative for albuminuria associated endothelial dysfunction. In a 3 day intervention study in which 600 mg of the antioxidant thioctic acid (alpha-lipoic acid) per day were given to nine patients with diabetic nephropathy oxidative stress in plasma samples was decreased by 48% and NF-kappaB binding activity in ex vivo isolated peripheral blood mononuclear cells by 38%. In conclusion, activation of the transcription factor NF-kappaB in ex vivo isolated peripheral blood mononuclear cells of patients with diabetes mellitus correlates with the degree of diabetic nephropathy. NF-kappaB activation is at least in part dependent on oxidative stress since thioctic acid (alpha-lipoic acid) reduced NF-kappaB binding activity.

36. Diabetes Metab. 1998 Nov;24 Suppl 3:79-83.
Future prevention and treatment of diabetic neuropathy.
Tomlinson DR.
Department of Pharmacology, Queen Mary and Westfield College, London, UK. d.tomlinson@qmw.ac.uk

This review orders the likely components of the pathogenesis of diabetic neuropathy into vertical (temporal) and horizontal dimensions. It is argued that the effects of hyperglycaemia are transduced to neuronal dysfunction via at least three secondary biochemical disturbances--the sorbitol (polyol) pathway, non-enzymatic glycation of proteins and oxidative stress--and that there are clear interactions between them. Because of these interactions, interference with one of these biochemical transducers could either worsen or attenuate the effects of the others. Examples of these alternatives are given. It is suggested that the prime goal for pharmacological intervention should be a combined attack on all three sources of disturbance. Interventions further on in the sequence of pathogenesis are also considered, and the arguments for the use of neurotrophic factors are persuasive because of their selectivity for different neuronal phenotypes, even though side-effects may be inevitable. Finally, a novel conjugate of gamma-linolenic acid and alpha-lipoic acid is considered as an agent with the potential to correct effects arising from more than one pathway of disorder in experimental diabetic neuropathy. The preliminary results with this agent have been encouraging.

37. Diabetes Care. 1998 Aug;21(8):1310-6.
Insufficient glycemic control increases nuclear factor-kappa B binding activity in peripheral blood mononuclear cells isolated from patients with type 1 diabetes.
Hofmann MA, Schiekofer S, Kanitz M, Klevesath MS, Joswig M, Lee V, Morcos M, Tritschler H, Ziegler R, Wahl P, Bierhaus A, Nawroth PP.
Department of Medicine, University of Heidelberg, Germany.

OBJECTIVE: The redox-sensitive transcription factor nuclear factor-kappa B (NF-kappa B) is believed to contribute to late diabetic complications. It is unknown whether NF-kappa B is influenced by glycemic control. RESEARCH DESIGN AND METHODS: To determine whether NF-kappa B is activated in patients with insufficient glycemic control (HbA1c > 10%), we developed a tissue culture-independent electrophoretic mobility shift assay (EMSA)-based semiquantitative detection system that allowed us to determine NF-kappa B activation in ex vivo-isolated peripheral blood mononuclear cells (PBMCs). We included 43 patients with type 1 diabetes in this cross-sectional study. 10 of those received the antioxidant thioctic acid (600 mg/day p.o.) for 2 weeks. RESULTS: Monocytes of patients with HbA1c levels > 10% demonstrated significantly higher NF-kappa B binding activity in an EMSA and a stronger NF-kappa B staining in immunohistochemistry than monocytes of patients with HbA1c levels of 6-8%. The increase in NF-kappa B activation correlated with an increase in plasmatic markers of lipid peroxidation. Treatment with the antioxidant thioctic acid decreased NF-kappa B binding activity. CONCLUSIONS: Hyperglycemia induces activation of the transcription factor NF-kappa B in ex vivo-isolated PBMCs of patients with type 1 diabetes. NF-kappa B activation is at least partially dependent on oxidative stress, since the antioxidant thioctic acid significantly lowered the extent of NF-kappa B binding activity.

38. Diabetes. 1997 Sep;46(9):1481-90.
Advanced glycation end product-induced activation of NF-kappaB is suppressed by alpha-lipoic acid in cultured endothelial cells.
Bierhaus A, Chevion S, Chevion M, Hofmann M, Quehenberger P, Illmer T, Luther T, Berentshtein E, Tritschler H, Muller M, Wahl P, Ziegler R, Nawroth PP.
Department of Internal Medicine, University of Heidelberg, Germany.

Depletion of cellular antioxidant defense mechanisms and the generation of oxygen free radicals by advanced glycation end products (AGEs) have been proposed to play a major role in the pathogenesis of diabetic vascular complications. Here we demonstrate that incubation of cultured bovine aortic endothelial cells (BAECs) with AGE albumin (500 nmol/l) resulted in the impairment of reduced glutathione (GSH) and ascorbic acid levels. As a consequence, increased cellular oxidative stress led to the activation of the transcription factor NF-kappaB and thus promoted the upregulation of various NF-kappaB-controlled genes, including endothelial tissue factor. Supplementation of the cellular antioxidative defense with the natural occurring antioxidant alpha-lipoic acid before AGE albumin induction completely prevented the AGE albumin-dependent depletion of reduced glutathione and ascorbic acid. Electrophoretic mobility shift assays (EMSAs) revealed that AGE albumin-mediated NF-kappaB activation was also reduced in a time- and dose-dependent manner as long as alpha-lipoic acid was added at least 30 min before AGE albumin stimulation. Inhibition was not due to physical interactions with protein DNA binding, since alpha-lipoic acid, directly included into the binding reaction, did not prevent binding activity of recombinant NF-kappaB. Western blots further demonstrated that alpha-lipoic acid inhibited the release and translocation of NF-kappaB from the cytoplasm into the nucleus. As a consequence, alpha-lipoic acid reduced AGE albumin-induced NF-kappaB mediated transcription and expression of endothelial genes relevant in diabetes, such as tissue factor and endothelin-1. Thus, supplementation of cellular antioxidative defense mechanisms by extracellularly administered alpha-lipoic acid reduces AGE albumin-induced endothelial dysfunction in vitro.

39. Diabetes. 1997 Sep;46 Suppl 2:S62-6.
Alpha-lipoic acid in the treatment of diabetic peripheral and cardiac autonomic neuropathy.
Ziegler D, Gries FA.
Diabetes Research Institute at the Heinrich Heine University, Dusseldorf, Germany.

Antioxidant treatment has been shown to prevent nerve dysfunction in experimental diabetes, providing a rationale for a potential therapeutic value in diabetic patients. The effects of the antioxidant alpha-lipoic acid (thioctic acid) were studied in two multicenter, randomized, double-blind placebo-controlled trials. In the Alpha-Lipoic Acid in Diabetic Neuropathy Study, 328 patients with NIDDM and symptomatic peripheral neuropathy were randomly assigned to treatment with intravenous infusion of alpha-lipoic acid using three doses (ALA 1,200 mg; 600 mg; 100 mg) or placebo (PLAC) over 3 weeks. The total symptom score (TSS) (pain, burning, paresthesia, and numbness) in the feet decreased significantly from baseline to day 19 in ALA 1,200 and ALA 600 vs. PLAC. Each of the four individual symptom scores was significantly lower in ALA 600 than in PLAC after 19 days (all P < 0.05). The total scale of the Hamburg Pain Adjective List (HPAL) was significantly reduced in ALA 1,200 and ALA 600 compared with PLAC after 19 days (both P < 0.05). In the Deutsche Kardiale Autonome Neuropathie Studie, patients with NIDDM and cardiac autonomic neuropathy diagnosed by reduced heart rate variability were randomly assigned to treatment with a daily oral dose of 800 mg alpha-lipoic acid (ALA) (n = 39) or placebo (n = 34) for 4 months. Two out of four parameters of heart rate variability at rest were significantly improved in ALA compared with placebo. A trend toward a favorable effect of ALA was noted for the remaining two indexes. In both studies, no significant adverse events were observed. In conclusion, intravenous treatment with alpha-lipoic acid (600 mg/day) over 3 weeks is safe and effective in reducing symptoms of diabetic peripheral neuropathy, and oral treatment with 800 mg/day for 4 months may improve cardiac autonomic dysfunction in NIDDM.

40. Diabetes. 1997 Sep;46 Suppl 2:S38-42.
The roles of oxidative stress and antioxidant treatment in experimental diabetic neuropathy.
Low PA, Nickander KK, Tritschler HJ.
Department of Neurology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.

Oxidative stress is present in the diabetic state. Our work has focused on its presence in peripheral nerves. Antioxidant enzymes are reduced in peripheral nerves and are further reduced in diabetic nerves. That lipid peroxidation will cause neuropathy is supported by evidence of the development of neuropathy de novo when normal nerves are rendered alpha-tocopherol deficient and by the augmentation of the conduction deficit in diabetic nerves subjected to this insult. Oxidative stress appears to be primarily due to the processes of nerve ischemia and hyperglycemia auto-oxidation. The indexes of oxidative stress include an increase in nerve, dorsal root, and sympathetic ganglia lipid hydroperoxides and conjugated dienes. The most reliable and sensitive index, however, is a reduction in reduced glutathione. Experimental diabetic neuropathy results in myelinopathy of dorsal roots and a vacuolar neuropathy of dorsal root ganglion. The vacuoles are mitochondrial; we posit that lipid peroxidation causes mitochondrial DNA mutations that increase reduced oxygen species, causing further damage to mitochondrial respiratory chain and function and resulting in a sensory neuropathy. Alpha-lipoic acid is a potent antioxidant that prevents lipid peroxidation in vitro and in vivo. We evaluated the efficacy of the drug in doses of 20, 50, and 100 mg/kg administered intraperitoneally in preventing the biochemical, electrophysiological, and nerve blood flow deficits in the peripheral nerves of experimental diabetic neuropathy. Alpha-lipoic acid dose- and time-dependently prevented the deficits in nerve conduction and nerve blood flow and biochemical abnormalities (reductions in reduced glutathione and lipid peroxidation). The nerve blood flow deficit was 50% (P < 0.001). Supplementation dose-dependently prevented the deficit; at the highest concentration, nerve blood flow was not different from that of control nerves. Digital nerve conduction underwent a dose-dependent improvement at 1 month (P < 0.05). By 3 months, all treated groups had lost their deficit. The antioxidant drug is potentially efficacious for human diabetic sensory neuropathy.

41. Metabolism. 1997 Jul;46(7):763-8.
Lipoic acid reduces glycemia and increases muscle GLUT4 content in streptozotocin-diabetic rats.
Khamaisi M, Potashnik R, Tirosh A, Demshchak E, Rudich A, Tritschler H, Wessel K, Bashan N.
Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.

Alpha lipoic acid (lipoate [LA]), a cofactor of alpha-ketodehydrogenase, exhibits unique antioxidant properties. Recent studies suggest a direct effect of LA on glucose metabolism in both human and experimental diabetes. This study examines the possibility that LA positively affects glucose homeostasis in streptozotocin (STZ)-induced diabetic rats by altering skeletal muscle glucose utilization. Blood glucose concentration in STZ-diabetic rats following 10 days of intraperitoneal (i.p.) injection of LA 30 mg/kg was reduced compared with that in vehicle-treated diabetic rats (495 +/- 131 v 641 +/- 125 mg/dL in fed state, P = .003, and 189 +/- 48 v 341 +/- 36 mg/dL after 12-hour fast, P = .001). No effect of LA on plasma insulin was observed. Gastrocnemius muscle crude membrane GLUT4 protein was elevated both in control and in diabetic rats treated with LA by 1.5- and 2.8-fold, respectively, without significant changes in GLUT4 mRNA levels. Gastrocnemius lactic acid was increased in diabetic rats (19.9 +/- 5.5 v 10.4 +/- 2.8 mumol/g muscle, P < .05 v nondiabetic rats), and was normal in LA-treated diabetic rats (9.1 +/- 5.0 mumol/g muscle). Insulin-stimulated 2-deoxyglucose (2 DG) uptake into isolated soleus muscle was reduced in diabetic rats compared with the control group (474 +/- 15 v 568 +/- 52 pmol/mg muscle 30 min, respectively, P = .05). LA treatment prevented this reduction, resulting in insulin-stimulated glucose uptake comparable to that of nondiabetic animals. These results suggest that daily LA treatment may reduce blood glucose concentrations in STZ-diabetic rats by enhancing muscle GLUT4 protein content and by increasing muscle glucose utilization.

42. Diabetes Care. 1997 Mar;20(3):369-73. Comment in: Diabetes Care. 1997 Dec;20(12):1918-20.
Effects of treatment with the antioxidant alpha-lipoic acid on cardiac autonomic neuropathy in NIDDM patients. A 4-month randomized controlled multicenter trial (DEKAN Study). Deutsche Kardiale Autonome Neuropathie.
Ziegler D, Schatz H, Conrad F, Gries FA, Ulrich H, Reichel G.
Diabetes-Forschungsinstitut an der Heinrich-Heine-Universitat, Dusseldorf, Germany.

OBJECTIVE: To evaluate the efficacy and safety of oral treatment with the antioxidant alpha-lipoic acid (ALA) in NIDDM patients with cardiac autonomic neuropathy (CAN), assessed by heart rate variability (HRV). RESEARCH DESIGN AND METHODS: In a randomized, double-blind placebo-controlled multicenter trial (Deutsche Kardiale Autonome Neuropathie [DEKAN] Study), NIDDM patients with reduced HRV were randomly assigned to treatment with daily oral dose of 800 mgALA (n = 39) or placebo (n = 34) for 4 months. Parameters of HRV at rest included the coefficient of variation (CV), root mean square successive difference (RMSSD), and spectral power in the low-frequency (LF; 0.05-0.15 Hz) and high-frequency (HF; 0.15-0.5 Hz) bands. In addition, cardiovascular autonomic symptoms were assessed. RESULTS: Seventeen patients dropped out of the study (ALA n = 10; placebo n = 7). Mean blood pressure and HbA1 levels did not differ between the groups at baseline and during the study, but heart rate at baseline was higher in the group treated with ALA (P < 0.05). RMSSD increased from baseline to 4 months by 1.5 ms (-37.6 to 77.1) [median (minimum-maximum)] in the group given ALA and decreased by -0.1 ms (-19.2 to 32.8) in the placebo group (P < 0.05 for ALA vs. placebo). Power spectrum in the LF band increased by 0.06 bpm2 (-0. 09 to 0.62) in ALA, whereas it declined by -0.01 bpm2 (-0.48 to 1.86) in placebo (P < 0.05 for ALA vs. placebo). Furthermore, there was a trend toward a favorable effect of ALA versus placebo for the CV and HF band power spectrum (P = 0.097 and P = 0.094 for ALA vs. placebo). The changes in cardiovascular autonomic symptoms did not differ significantly between the groups during the period studied. No differences between the groups were noted regarding the rates of adverse events. CONCLUSIONS: These findings suggest that treatment with ALA using a well-tolerated oral dose of 800 mg/day for 4 months may slightly improve CAN in NIDDM patients.

43. Biochem Pharmacol. 1997 Feb 7;53(3):393-9.
Modulation of cellular reducing equivalent homeostasis by alpha-lipoic acid. Mechanisms and implications for diabetes and ischemic injury.
Roy S, Sen CK, Tritschler HJ, Packer L.
Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, U.S.A. sashwati@violet.berkeley.edu

The therapeutic potential of alpha-lipoic acid (thioctic acid) was evaluated with respect to its influence on cellular reducing equivalent homeostasis. The requirement of NADH and NADPH as cofactors in the cellular reduction of alpha-lipoic acid to dihydrolipoate has been reported in various cells and tissues. However, there is no direct evidence describing the influence of such reduction of alpha-lipoate on the levels of cellular reducing equivalents and homeostasis of the NAD(P)H/NAD(P) ratio. Treatment of the human Wurzburg T-cell line with 0.5 mM alpha-lipoate for 24 hr resulted in a 30% decrease in cellular NADH levels. alpha-Lipoate treatment also decreased cellular NADPH, but this effect was relatively less and slower compared with that of NADH. A concentration-dependent increase in glucose uptake was observed in Wurzburg cells treated with alpha-lipoate. Parallel decreases (30%) in cellular NADH/NAD+ and in lactate/pyruvate ratios were observed in alpha-lipoate-treated cells. Such a decrease in the NADH/NAD+ ratio following treatment with alpha-lipoate may have direct implications in diabetes, ischemia-reperfusion injury, and other pathologies where reductive (high NADH/NAD+ ratio) and oxidant (excess reactive oxygen species) imbalances are considered as major factors contributing to metabolic disorders. Under conditions of reductive stress, alpha-lipoate decreases high NADH levels in the cell by utilizing it as a co-factor for its own reduction process, whereas in oxidative stress both alpha-lipoate and its reduced form, dihydrolipoate, may protect by direct scavenging of free radicals and recycling other antioxidants from their oxidized forms.

44, Free Radic Biol Med. 1997;22(1-2):359-78.
Neuroprotection by the metabolic antioxidant alpha-lipoic acid.
Packer L, Tritschler HJ, Wessel K.
Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.

Reactive oxygen species are thought to be involved in a number of types of acute and chronic pathologic conditions in the brain and neural tissue. The metabolic antioxidant alpha-lipoate (thioctic acid, 1, 2-dithiolane-3-pentanoic acid; 1, 2-dithiolane-3 valeric acid; and 6, 8-dithiooctanoic acid) is a low molecular weight substance that is absorbed from the diet and crosses the blood-brain barrier. alpha-Lipoate is taken up and reduced in cells and tissues to dihydrolipoate, which is also exported to the extracellular medium; hence, protection is afforded to both intracellular and extracellular environments. Both alpha-lipoate and especially dihydrolipoate have been shown to be potent antioxidants, to regenerate through redox cycling other antioxidants like vitamin C and vitamin E, and to raise intracellular glutathione levels. Thus, it would seem an ideal substance in the treatment of oxidative brain and neural disorders involving free radical processes. Examination of current research reveals protective effects of these compounds in cerebral ischemia-reperfusion, excitotoxic amino acid brain injury, mitochondrial dysfunction, diabetes and diabetic neuropathy, inborn errors of metabolism, and other causes of acute or chronic damage to brain or neural tissue. Very few neuropharmacological intervention strategies are currently available for the treatment of stroke and numerous other brain disorders involving free radical injury. We propose that the various metabolic antioxidant properties of alpha-lipoate relate to its possible therapeutic roles in a variety of brain and neuronal tissue pathologies: thiols are central to antioxidant defense in brain and other tissues. The most important thiol antioxidant, glutathione, cannot be directly administered, whereas alpha-lipoic acid can. In vitro, animal, and preliminary human studies indicate that alpha-lipoate may be effective in numerous neurodegenerative disorders.

45. Exp Clin Endocrinol Diabetes. 1996;104(3):284-8.
Improvement of insulin-stimulated glucose-disposal in type 2 diabetes after repeated parenteral administration of thioctic acid.
Jacob S, Henriksen EJ, Tritschler HJ, Augustin HJ, Dietze GJ.
Hypertension and Diabetes Research Unit, Max Grundig Clinic, Buhl, Germany.

Insulin resistance of skeletal muscle glucose uptake is a prominent feature of Type II diabetes (NIDDM); therefore, pharmacological intervention should aim to improve insulin sensitivity. Thioctic acid (TA), a naturally occurring compound, was shown to enhance glucose utilization in various experimental models after acute and chronic administration. It also increased insulin-stimulated glucose disposal in patients with NIDDM after acute administration. This pilot study was initiated to see whether this compound also augments glucose disposal in humans after repeated treatment. Twenty patients with NIDDM received TA (500 mg/ 500 ml NaCl, 0.9%) as daily infusions over a period of ten days. A hyperinsulinaemic, isoglycaemic glucose-clamp was done on day 0 and day 11. Parenteral administration of TA resulted in a significant increase of insulin-stimulated glucose-disposal by about 30% (metabolic clearance rate for glucose, 2.5 +/- 0.3 vs. 3.2 +/- 0.4 ml/kg/min and insulin-sensitivity-index: 3.5 +/- 0.5 vs. 4.7 +/- 0.4 mg/kg/microU/ml; p < 0.05, Wilcoxon-Rank-Sum-Test). There were no changes in fasting plasma levels for glucose or insulin; this can be explained, however, by the short period of treatment and observation. This is the first clinical study to show that a ten day administration of TA is able to improve resistance of insulin-stimulated glucose disposal in NIDDM. Experimental data suggest several mechanisms in the mode of action. As the present investigation was an uncontrolled pilot trial, the encouraging results call for controlled studies to further elucidate the clinical relevance of the findings and the mode of action of this compound.

46. Diabetologia. 1995 Dec;38(12):1425-33.
Treatment of symptomatic diabetic peripheral neuropathy with the anti-oxidant alpha-lipoic acid. A 3-week multicentre randomized controlled trial (ALADIN Study).
Ziegler D, Hanefeld M, Ruhnau KJ, Meissner HP, Lobisch M, Schutte K, Gries FA.
Diabetes-Forschungsinstitut an der Heinrich-Heine-Universitat, Dusseldorf, Germany.

Anti-oxidant treatment has been shown to prevent nerve dysfunction in experimental diabetes mellitus, thus providing a rationale of potential therapeutic value for diabetic patients. The effects of the anti-oxidant alpha-lipoic acid (thioctic acid) were studied in a 3-week multicentre, randomized, double-blind placebo-controlled trial (Alpha-Lipoic Acid in Diabetic Neuropathy; ALADIN) in 328 non-insulin-dependent diabetic patients with symptomatic peripheral neuropathy who were randomly assigned to treatment with intravenous infusion of alpha-lipoic acid using three doses (1200, 600, or 100 mg ALA) or placebo (PLAC). Neuropathic symptoms (pain, burning, paraesthesiae, and numbness) were scored at baseline and at each visit (days 2-5, 8-12, and 15-19) prior to infusion. In addition, the Hamburg Pain Adjective List, a multidimensional specific pain questionnaire, and the Neuropathy Symptom and Disability Scores were assessed at baseline and day 19. According to the protocol 260 (65/63/66/66) patients completed the study. The total symptom score in the feet decreased from baseline to day 19 by -4.5 +/- 3.7 (-58.6%) points (mean +/- SD) in ALA 1200, -5.0 +/- 4.1 (-63.5%) points in ALA 600, -3.3 +/- 2.8 (-43.2%) points in ALA 100, and -2.6 +/- 3.2 (-38.4%) points in PLAC (ALA 1200 vs PLAC: p = 0.003; ALA 600 vs PLAC: p < 0.001). The response rates after 19 days, defined as an improvement in the total symptom score of at least 30%, were 70.8% in ALA 1200, 82.5% in ALA 600, 65.2% in ALA 100, and 57.6% in PLAC (ALA 600 vs PLAC; p = 0.002). The total scale of the Pain Adjective List was significantly reduced in ALA 1200 and ALA 600 as compared with PLAC after 19 days (both p < 0.01). The rates of adverse events were 32.6% in ALA 1200, 18.2% in ALA 600, 13.6% in ALA 100, and 20.7% in PLAC. These findings substantiate that intravenous treatment with alpha-lipoic acid using a dose of 600 mg/day over 3 weeks is superior to placebo in reducing symptoms of diabetic peripheral neuropathy, without causing significant adverse reactions.

47. Arzneimittelforschung. 1995 Aug;45(8):872-4.
Enhancement of glucose disposal in patients with type 2 diabetes by alpha-lipoic acid.
Jacob S, Henriksen EJ, Schiemann AL, Simon I, Clancy DE, Tritschler HJ, Jung WI, Augustin HJ, Dietze GJ.
Department of Internal Medicine, City Hospital, Baden-Baden, Germany.

Insulin resistance of skeletal muscle glucose uptake is a prominent feature of Type II diabetes (NIDDM); therefore pharmacological interventions should aim to improve insulin sensitivity. Alpha-lipoic acid (CAS 62-46-4, thioctic acid, ALA), a natural occurring compound frequently used for treatment of diabetic polyneuropathy, enhances glucose utilization in various experimental models. To see whether this compound also augments insulin mediated glucose disposal in NIDDM, 13 patients received either ALA (1000 mg/Thioctacid/500 ml NaCl, n = 7) or vehicle only (500 ml NaCl, n = 6) during a glucose-clamp study. Both groups were comparable in age, body-mass index and duration of diabetes and had a similar degree of insulin resistance at baseline. Acute parenteral administration of ALA resulted in a significant increase of insulin-stimulated glucose disposal; metabolic clearance rate (MCR) for glucose rose by about 50% (3.76 ml/kg/min = pre vs. 5.82 ml/kg/min = post, p < 0.05), whereas the control group did not show any significant change (3.57 ml/kg/min = pre vs. 3.91 ml/kg/min = post). This is the first clinical study to show that alpha-lipoic acid increases insulin stimulated glucose disposal in NIDDM. The mode of action of ALA and its potential use as an antihyperglycemic agent require further investigation.

AGE-RELATED

48. Eur Neuropsychopharmacol. 2003 Aug;13(4):241-7.
Effect of alpha lipoic acid on intracerebroventricular streptozotocin model of cognitive impairment in rats.
Sharma M, Gupta YK.
Neuropharmacology Laboratory, Department of Pharmacology, All India Institute of Medical Sciences, New Delhi 110029, India.

In the present study, the effect of alpha lipoic acid, a potent free radical scavenger, was investigated against the intracerebroventricular streptozotocin model of cognitive impairment in rats, which is characterized by a progressive deterioration of memory, cerebral glucose and energy metabolism, and oxidative stress. Wistar rats were injected with intracerebroventricular streptozotocin bilaterally. The rats were treated chronically with alpha lipoic acid (50, 100 and 200 mg/kg) orally for 21 days starting from day 1 of streptozotocin injection in separate groups. The learning and memory behavior was evaluated and the rats were sacrificed for estimation of oxidative stress. The intracerebroventricular streptozotocin rats treated with alpha lipoic acid (200 mg/kg, p.o.) showed significantly less cognitive impairment as compared to the vehicle treated rats. There was also an insignificant increase in oxidative stress in the alpha lipoic acid treated groups. The study demonstrated the effectiveness of alpha lipoic acid in preventing cognitive impairment and oxidative stress induced by intracerebroventricular streptozotocin and its potential in dementia associated with age and age related neurodegenerative disorders where oxidative stress is involved such as Alzheimer's disease.

49. J Neurochem. 2003 Mar;84(5):1173-83.
The antioxidants alpha-lipoic acid and N-acetylcysteine reverse memory impairment and brain oxidative stress in aged SAMP8 mice.
Farr SA, Poon HF, Dogrukol-Ak D, Drake J, Banks WA, Eyerman E, Butterfield DA, Morley JE.
Geriatric Research Education and Clinical Center (GRECC), VA Medical Center (151/JC), 915 N. Grand Boulevard, St. Louis, MO 63109, USA. farrsa52@aol.com

Oxidative stress may play a crucial role in age-related neurodegenerative disorders. Here, we examined the ability of two antioxidants, alpha-lipoic acid (LA) and N-acetylcysteine (NAC), to reverse the cognitive deficits found in the SAMP8 mouse. By 12 months of age, this strain develops elevated levels of Abeta and severe deficits in learning and memory. We found that 12-month-old SAMP8 mice, in comparison with 4-month-old mice, had increased levels of protein carbonyls (an index of protein oxidation), increased TBARS (an index of lipid peroxidation) and a decrease in the weakly immobilized/strongly immobilized (W/S) ratio of the protein-specific spin label MAL-6 (an index of oxidation-induced conformational changes in synaptosomal membrane proteins). Chronic administration of either LA or NAC improved cognition of 12-month-old SAMP8 mice in both the T-maze footshock avoidance paradigm and the lever press appetitive task without inducing non-specific effects on motor activity, motivation to avoid shock, or body weight. These effects probably occurred directly within the brain, as NAC crossed the blood-brain barrier and accumulated in the brain. Furthermore, treatment of 12-month-old SAMP8 mice with LA reversed all three indexes of oxidative stress. These results support the hypothesis that oxidative stress can lead to cognitive dysfunction and provide evidence for a therapeutic role for antioxidants.

50. Exp Gerontol. 2002 Dec;37(12):1489-94.
Neurochemical changes related to ageing in the rat brain and the effect of DL-alpha-lipoic acid.
Arivazhagan P, Panneerselvam C.
Department of Medical Biochemistry, Dr AL Mudaliar Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai 600 113, India.

Age-related impairments of cognitive and motor function have been linked to a number of deleterious morphological and functional changes involving different areas of the brain. Loss of neurotransmitters, their receptors and responsiveness to neurotransmitters are key manifestations of neurological ageing and age-related disorders. In the present investigation we have evaluated the effect of DL-alpha-lipoic acid on neurotransmitters in discrete brain regions of young and aged rats. The levels of neurotransmitters were found to be lowered in aged rats. Moreover, DL-alpha-lipoic acid treated aged rats showed a increase in the status of dopamine, serotonin and norepinephrine. The results of this study provide evidence that DL-alpha-lipoic acid (a potent antioxidant) treatment can improve neurotransmitters during ageing. Hence, it can be concluded that DL-alpha-lipoic acid act as a potent neuromodulator in the brain of aged rats.

51. Ann N Y Acad Sci. 2002 Apr;959:508-16.
Can antioxidant diet supplementation protect against age-related mitochondrial damage?
Miquel J.
Department of Biotechnology, University of Alicante, E-03080 Alicante, Spain.

Harman's free radical theory of aging and our electron-microscopic finding of an age-related mitochondrial degeneration in the somatic tissues of the insect Drosophila melanogaster as well as in the fixed postmitotic Leydig and Sertoli cells of the mouse testis led us to propose a mitochondrial theory of aging, according to which metazoan senescence may be linked to oxygen stress-injury to the genome and membranes of the mitochondria of somatic differentiated cells. These concepts attract a great deal of attention, since, according to recent work, the mitochondrial damage caused by reactive oxygen species (ROS) and concomitant decline in ATP synthesis seem to play a key role not only in aging, but also in the fundamental cellular process of apoptosis. Although diet supplementation with antioxidants has not been able to increase consistently the species-characteristic maximum life span, it results in significant extension of the mean life span of laboratory animals. Moreover, diets containing high levels of antioxidants such as vitamins C and E seem able to reduce the risk of suffering age-related immune dysfunctions and arteriosclerosis. Presently, the focus of age-related antioxidant research is on compounds, such as deprenyl, coenzyme Q10, alpha-lipoic acid, and the glutathione-precursors thioproline and N-acetylcysteine, which may be able to neutralize the ROS at their sites of production in the mitochondria. Diet supplementation with these antioxidants may protect the mitochondria against respiration-linked oxygen stress, with preservation of the genomic and structural integrity of these energy-producing organelles and concomitant increase in functional life span.

52. Ann N Y Acad Sci. 2002 Apr;959:491-507.
Mitochondrial decay in the aging rat heart: evidence for improvement by dietary supplementation with acetyl-L-carnitine and/or lipoic acid.
Hagen TM, Moreau R, Suh JH, Visioli F.
Department of Biochemistry and Biophysics, Linus Pauling Institute, Oregon State University, Corvallis, Oregon 97331, USA. tory.hagen@orst.edu

Mitochondrial decay has been postulated to be a significant underlying part of the aging process. Decline in mitochondrial function may lead to cellular energy deficits, especially in times of greater energy demand, and compromise vital ATP-dependent cellular operations, including detoxification, repair systems, DNA replication, and osmotic balance. Mitochondrial decay may also lead to enhanced oxidant production and thus render the cell more prone to oxidative insult. In particular, the heart may be especially susceptible to mitochondrial dysfunction due to myocardial dependency on beta-oxidation of fatty acids for energy and the postmitotic nature of cardiac myocytes, which would allow for greater accumulation of mitochondrial mutations and deletions. Thus, maintenance of mitochondrial function may be important to maintain overall myocardial function. Herein, we review the major age-related changes that occur to mitochondria in the aging heart and the evidence that two such supplements, acetyl-l-carnitine (ALCAR) and (R)-alpha-lipoic acid, may improve myocardial bioenergetics and lower the increased oxidative stress associated with aging. We and others have shown that feeding old rats ALCAR reverses the age-related decline in carnitine levels and improves mitochondrial beta-oxidation in a number of tissues studied. However, ALCAR supplementation does not appear to reverse the age-related decline in cardiac antioxidant status and thus may not substantially alter indices of oxidative stress. Lipoic acid, a potent thiol antioxidant and mitochondrial metabolite, appears to increase low molecular weight antioxidant status and thereby decreases age-associated oxidative insult. Thus, ALCAR along with lipoic acid may be effective supplemental regimens to maintain myocardial function.

53. Proc Natl Acad Sci U S A. 2002 Feb 19;99(4):1876-81. Erratum in: Proc Natl Acad Sci U S A 2002 May 14;99(10):7184.
Age-associated mitochondrial oxidative decay: improvement of carnitine acetyltransferase substrate-binding affinity and activity in brain by feeding old rats acetyl-L- carnitine and/or R-alpha -lipoic acid.
Liu J, Killilea DW, Ames BN.
Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720, USA.

We test whether the dysfunction with age of carnitine acetyltransferase (CAT), a key mitochondrial enzyme for fuel utilization, is due to decreased binding affinity for substrate and whether this substrate, fed to old rats, restores CAT activity. The kinetics of CAT were analyzed by using the brains of young and old rats and of old rats supplemented for 7 weeks with the CAT substrate acetyl-l-carnitine (ALCAR) and/or the mitochondrial antioxidant precursor R-alpha-lipoic acid (LA). Old rats, compared with young rats, showed a decrease in CAT activity and in CAT-binding affinity for both substrates, ALCAR and CoA. Feeding ALCAR or ALCAR plus LA to old rats significantly restored CAT-binding affinity for ALCAR and CoA, and CAT activity. To explore the underlying mechanism, lipid peroxidation and total iron and copper levels were assayed; all increased in old rats. Feeding old rats LA or LA plus ALCAR inhibited lipid peroxidation but did not decrease iron and copper levels. Ex vivo oxidation of young-rat brain with Fe(II) caused loss of CAT activity and binding affinity. In vitro oxidation of purified CAT with Fe(II) inactivated the enzyme but did not alter binding affinity. However, in vitro treatment of CAT with the lipid peroxidation products malondialdehyde or 4-hydroxy-nonenal caused a decrease in CAT-binding affinity and activity, thus mimicking age-related change. Preincubation of CAT with ALCAR or CoA prevented malondialdehyde-induced dysfunction. Thus, feeding old rats high levels of key mitochondrial metabolites can ameliorate oxidative damage, enzyme activity, substrate-binding affinity, and mitochondrial dysfunction.

54. Proc Natl Acad Sci U S A. 2002 Feb 19;99(4):1870-5. Erratum in: Proc Natl Acad Sci U S A 2002 May 14;99(10):7184.
Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress.
Hagen TM, Liu J, Lykkesfeldt J, Wehr CM, Ingersoll RT, Vinarsky V, Bartholomew JC, Ames BN.
Department of Biochemistry and Biophysics, Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA.

Mitochondrial-supported bioenergetics decline and oxidative stress increases during aging. To address whether the dietary addition of acetyl-l-carnitine [ALCAR, 1.5% (wt/vol) in the drinking water] and/or (R)-alpha-lipoic acid [LA, 0.5% (wt/wt) in the chow] improved these endpoints, young (2-4 mo) and old (24-28 mo) F344 rats were supplemented for up to 1 mo before death and hepatocyte isolation. ALCAR+LA partially reversed the age-related decline in average mitochondrial membrane potential and significantly increased (P = 0.02) hepatocellular O(2) consumption, indicating that mitochondrial-supported cellular metabolism was markedly improved by this feeding regimen. ALCAR+LA also increased ambulatory activity in both young and old rats; moreover, the improvement was significantly greater (P = 0.03) in old versus young animals and also greater when compared with old rats fed ALCAR or LA alone. To determine whether ALCAR+LA also affected indices of oxidative stress, ascorbic acid and markers of lipid peroxidation (malondialdehyde) were monitored. The hepatocellular ascorbate level markedly declined with age (P = 0.003) but was restored to the level seen in young rats when ALCAR+LA was given. The level of malondialdehyde, which was significantly higher (P = 0.0001) in old versus young rats, also declined after ALCAR+LA supplementation and was not significantly different from that of young unsupplemented rats. Feeding ALCAR in combination with LA increased metabolism and lowered oxidative stress more than either compound alone.

55. Exp Gerontol. 2001 Dec;37(1):81-7.
Effect of DL-alpha-lipoic acid on glutathione metabolic enzymes in aged rats.
Arivazhagan P, Ramanathan K, Panneerselvam C.
Department of Medical Biochemistry, Dr AL Mudaliar Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, 600 113, Chennai, India. palaniarivu@yahoo.com

Ageing is characterized by a failure to maintain homeostasis under conditions of physiological stress, with an increasing susceptibility to disease and death. The accumulation of errors committed by faulty biochemical reactions over a vast period generates the cumulative effect observed during ageing. The most notable among the effects of ageing are the age-related disorders where free radicals are the major cause. When the level of free radicals increases because of diet, lifestyle, environment or other influences, it results in subsequent reduction of antioxidants. Reduced glutathione is one of the most fascinating molecules virtually present in all animal cells in often quite higher concentrations. An essential mechanism that accounts for most of the metabolic and cell regulatory properties of glutathione is the thiol disulfide exchange equilibria. We evaluated the age-associated alterations in glutathione dependent enzymes, glutathione and hydroxyl radicals in young and aged rats with respect to lipoate supplementation. In aged rats, activities of glutathione peroxidase, glutathione reductase, glutathione-S-transferase and glucose-6-phosphate dehydrogenase and the level of glutathione were low, whereas the level of hydroxyl radical was higher than in the young ones. Administration of DL-alpha-lipoic acid, a thiol antioxidant intraperitoneally to the aged rats, led to a time-dependent reduction in hydroxyl radicals and elevation in the activities/level of glutathione systems. Hence it can be suggested that lipoate, a dithiol prevents the oxidation of reduced glutathione and protects its related enzymes from peroxidative damage.

56. FASEB J. 2001 Mar;15(3):700-6.
Oxidative stress in the aging rat heart is reversed by dietary supplementation with (R)-(alpha)-lipoic acid.
Suh JH, Shigeno ET, Morrow JD, Cox B, Rocha AE, Frei B, Hagen TM.
Linus Pauling Institute, Department of Biochemistry, Oregon State University, Corvallis, Oregon 97331, USA.

Oxidative stress has been implicated as a causal factor in the aging process of the heart and other tissues. To determine the extent of age-related myocardial oxidative stress, oxidant production, antioxidant status, and oxidative DNA damage were measured in hearts of young (2 months) and old (28 months) male Fischer 344 rats. Cardiac myocytes isolated from old rats showed a nearly threefold increase in the rate of oxidant production compared to young rats, as measured by the rates of 2,7-dichlorofluorescin diacetate oxidation. Determination of myocardial antioxidant status revealed a significant twofold decline in the levels of ascorbic acid (P = 0.03), but not alpha-tocopherol. A significant age-related increase (P = 0.05) in steady-state levels of oxidative DNA damage was observed, as monitored by 8-oxo-2'-deoxyguanosine levels. To investigate whether dietary supplementation with (R)-alpha-lipoic acid (LA) was effective at reducing oxidative stress, young and old rats were fed an AIN-93M diet with or without 0.2% (w/w) LA for 2 wk before death. Cardiac myocytes from old, LA-supplemented rats exhibited a markedly lower rate of oxidant production that was no longer significantly different from that in cells from unsupplemented, young rats. Lipoic acid supplementation also restored myocardial ascorbic acid levels and reduced oxidative DNA damage. Our data indicate that the aging rat heart is under increased mitochondrial-induced oxidative stress, which is significantly attenuated by lipoic acid supplementation.

57. Antioxid Redox Signal. 2000 Fall;2(3):473-83.
(R)-alpha-lipoic acid reverses the age-associated increase in susceptibility of hepatocytes to tert-butylhydroperoxide both in vitro and in vivo.
Hagen TM, Vinarsky V, Wehr CM, Ames BN.
Department of Molecular and Cell Biology, University of California at Berkeley 94720, USA.

Hepatocytes were isolated from young (3-5 months) and old (24-28 months) rats and incubated with various concentrations of tert-butylhydroperoxide (t-BuOOH). The t-BuOOH concentration that killed 50% of cells (LC50) in 2 hr declined nearly two-fold from 721 +/- 32 microM in cells from young rats to 391 +/- 31 microM in cells from old rats. This increased sensitivity of hepatocytes from old rats may be due, in part, to changes in glutathione (GSH) levels, because total cellular and mitochondrial GSH were 37.7% and 58.3% lower, respectively, compared to cells from young rats. Cells from old animals were incubated with either (R)- or (S)-lipoic acid (100 microM) for 30 min prior to the addition of 300 microM t-BuOOH. The physiologically relevant (R)-form, a coenzyme in mitochondria, as opposed to the (S)-form significantly protected hepatocytes against t-BuOOH toxicity. Dietary supplementation of (R)-lipoic acid [0.5% (wt/wt)] for 2 weeks also completely reversed the age-related decline in hepatocellular GSH levels and the increased vulnerability to t-BuOOH as well. An identical supplemental diet fed to young rats did not enhance the resistance to t-BuOOH, indicating that antioxidant protection was already optimal in young rats. Thus, this study shows that cells from old animals are more susceptible to oxidant insult and (R)-lipoic acid, after reduction to an antioxidant in the mitochondria, effectively reverses this age-related increase in oxidant vulnerability.

58. Am J Otol. 2000 Mar;21(2):161-7.
Biologic activity of mitochondrial metabolites on aging and age-related hearing loss.
Seidman MD, Khan MJ, Bai U, Shirwany N, Quirk WS.
Department of Otolaryngology Head & Neck Surgery, Henry Ford Health System, Detroit, Michigan 48323, USA.

HYPOTHESIS: Compounds that upregulate mitochondrial function in an aging model will improve hearing and reduce some of the effects of aging. BACKGROUND: Reactive oxygen metabolites (ROM) are known products of oxidative metabolism and are continuously generated in vivo. More than 100 human clinical conditions have been associated with ROM, including atherosclerosis, arthritis, autoimmune diseases, cancers, heart disease, cerebrovascular accidents, and aging. The ROM are extremely reactive and cause extensive DNA, cellular, and tissue damage. Specific deletions within the mitochondrial DNA (mtDNA) occur with increasing frequency in age and presbyacusis. These deletions are the result of chronic exposure to ROM. When enough mtDNA damage accrues, the cell becomes bioenergetically deficient. This mechanism is the basis of the mitochondrial clock theory of aging, also known as the membrane hypothesis of aging. Nutritional compounds have been identified that enhance mitochondrial function and reverse several age-related processes. It is the purpose of this article to describe the effects of two mitochondrial metabolites, alpha-lipoic acid and acetyl L-carnitine, on the preservation of age-related hearing loss. METHODS: Twenty-one Fischer rats, aged 24 months, were divided into three groups: acetyl-1-carnitine, alpha-lipoic acid, and control. The subjects were orally supplemented with either a placebo or one of the two nutritional compounds for 6 weeks. Auditory brainstem response testing was used to obtain baseline and posttreatment hearing thresholds. Cochlear, brain, and skeletal muscle tissues were obtained to assess for mtDNA mutations. RESULTS: The control group demonstrated an expected age-associated threshold deterioration of 3 to 7 dB in the 6-week study. The treated subjects experienced a delay in progression of hearing loss. Acetyl-1-carnitine improved auditory thresholds during the same time period (p<0.05). The mtDNA deletions associated with aging and presbyacusis were reduced in the treated groups in comparison with controls. CONCLUSIONS:These results indicate that in the proposed decline in mitochondrial function with age, senescence may be delayed by treatment with mitochondrial metabolites. Acetyl-1-carnitine and alpha-lipoic acid reduce age-associated deterioration in auditory sensitivity and improve cochlear function. This effect appears to be related to the mitochondrial metabolite ability to protect and repair age-induced cochlear mtDNA damage, thereby upregulating mitochondrial function and improving energy-producing capabilities.

59. Neurobiol Aging. 1999 Nov-Dec;20(6):655-64.
Age-related changes in LTP and antioxidant defenses are reversed by an alpha-lipoic acid-enriched diet.
McGahon BM, Martin DS, Horrobin DF, Lynch MA.
Department of Physiology, Trinity College, Dublin, Ireland.

Among the age-related changes identified in rat hippocampus are impairments in LTP and glutamate release. These deficits have been coupled with decreased arachidonic acid concentration. In this study we compared LTP and glutamate release in groups of aged and young rats fed for 8 weeks on a control diet or on a diet enriched in alpha-lipoic acid. Dietary supplementation in aged rats restored hippocampal arachidonic acid concentration to levels observed in tissue prepared from young rats. We observed that aged rats that received the experimental diet sustained LTP in perforant path-granule cell synapses in a manner indistinguishable from young rats whereas the age-related impairment in glutamate release was reversed in synaptosomes prepared from dentate gyrus obtained from these rats. The evidence presented supports the hypothesis that the alpha-lipoic acid-enriched diet has antioxidant properties, because the age-related increase in superoxide dismutase activity and decrease in alpha-tocopherol concentration were reversed. The finding that the age-related increase in interleukin-1 (IL-1)beta concentration was also reversed suggests a possible role for this cytokine in ageing.

60. FASEB J. 1999 Feb;13(2):411-8.
(R)-alpha-lipoic acid-supplemented old rats have improved mitochondrial function, decreased oxidative damage, and increased metabolic rate.
Hagen TM, Ingersoll RT, Lykkesfeldt J, Liu J, Wehr CM, Vinarsky V, Bartholomew JC, Ames AB.
Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.

A diet supplemented with (R)-lipoic acid, a mitochondrial coenzyme, was fed to old rats to determine its efficacy in reversing the decline in metabolism seen with age. Young (3 to 5 months) and old (24 to 26 months) rats were fed an AIN-93M diet with or without (R)-lipoic acid (0.5% w/w) for 2 wk, killed, and their liver parenchymal cells were isolated. Hepatocytes from untreated old rats vs. young controls had significantly lower oxygen consumption (P<0. 03) and mitochondrial membrane potential. (R)-Lipoic acid supplementation reversed the age-related decline in O2 consumption and increased (P<0.03) mitochondrial membrane potential. Ambulatory activity, a measure of general metabolic activity, was almost threefold lower in untreated old rats vs. controls, but this decline was reversed (P<0.005) in old rats fed (R)-lipoic acid. The increase of oxidants with age, as measured by the fluorescence produced on oxidizing 2',7'-dichlorofluorescin, was significantly lowered in (R)-lipoic acid supplemented old rats (P<0.01). Malondialdehyde (MDA) levels, an indicator of lipid peroxidation, were increased fivefold with age in cells from unsupplemented rats. Feeding rats the (R)-lipoic acid diet reduced MDA levels markedly (P<0.01). Both glutathione and ascorbic acid levels declined in hepatocytes with age, but their loss was completely reversed with (R)-lipoic acid supplementation. Thus, (R)-lipoic acid supplementation improves indices of metabolic activity as well as lowers oxidative stress and damage evident in aging.

61. Pharmacol Biochem Behav. 1993 Dec;46(4):799-805.
The potent free radical scavenger alpha-lipoic acid improves memory in aged mice: putative relationship to NMDA receptor deficits.
Stoll S, Hartmann H, Cohen SA, Muller WE.
Central Institute for Mental Health, Department of Psychopharmacology, Mannheim, Germany.

alpha-Lipoic acid (alpha-LA) improved longer-term memory of aged female NMRI mice in the habituation in the open field test at a dose of 100 mg/kg body weight for 15 days. In a separate experiment, no such effect could be found for young mice. alpha-LA alleviated age-related NMDA receptor deficits (Bmax) without changing muscarinic, benzodiazepine, and alpha 2-adrenergic receptor deficits in aged mice. The carbachol-stimulated accumulation of inositol monophosphates was not changed by the treatment with alpha-LA. These results give tentative support to the hypothesis that alpha-LA improves memory in aged mice, probably by a partial compensation of NMDA receptor deficits. Possible modes of action of alpha-LA based on its free radical scavenger properties are discussed in relation to the membrane hypothesis of aging.

62. Arzneimittelforschung 1995 Aug;45(8):872-4
Enhancement of glucose disposal in patients with type 2 diabetes by alpha-lipoic acid.
Jacob S, Henriksen EJ, Schiemann AL, Simon I, Clancy DE, Tritschler HJ, Jung WI, Augustin HJ, Dietze GJ.
Department of Internal Medicine, City Hospital, Baden-Baden, Germany.

Insulin resistance of skeletal muscle glucose uptake is a prominent feature of Type II diabetes (NIDDM); therefore pharmacological interventions should aim to improve insulin sensitivity. Alpha-lipoic acid (CAS 62-46-4, thioctic acid, ALA), a natural occurring compound frequently used for treatment of diabetic polyneuropathy, enhances glucose utilization in various experimental models. To see whether this compound also augments insulin mediated glucose disposal in NIDDM, 13 patients received either ALA (1000 mg/Thioctacid/500 ml NaCl, n = 7) or vehicle only (500 ml NaCl, n = 6) during a glucose-clamp study. Both groups were comparable in age, body-mass index and duration of diabetes and had a similar degree of insulin resistance at baseline. Acute parenteral administration of ALA resulted in a significant increase of insulin-stimulated glucose disposal; metabolic clearance rate (MCR) for glucose rose by about 50% (3.76 ml/kg/min = pre vs. 5.82 ml/kg/min = post, p < 0.05), whereas the control group did not show any significant change (3.57 ml/kg/min = pre vs. 3.91 ml/kg/min = post). This is the first clinical study to show that alpha-lipoic acid increases insulin stimulated glucose disposal in NIDDM. The mode of action of ALA and its potential use as an antihyperglycemic agent require further investigation.

63. Diabetes 1996 Aug;45(8):1024-9
The antioxidant alpha-lipoic acid enhances insulin-stimulated glucose metabolism in insulin-resistant rat skeletal muscle.
Jacob S, Streeper RS, Fogt DL, Hokama JY, Tritschler HJ, Dietze GJ, Henriksen EJ.
Department of Physiology, University of Arizona College of Medicine, Tucson, USA.

Insulin resistance of muscle glucose metabolism is a hallmark of NIDDM. The obese Zucker (fa/fa) rat--an animal model of muscle insulin resistance--was used to test whether acute (100 mg/kg body wt for 1 h) and chronic (5-100 mg/kg for 10 days) parenteral treatments with a racemic mixture of the antioxidant alpha-lipoic acid (ALA) could improve glucose metabolism in insulin-resistant skeletal muscle. Glucose transport activity (assessed by net 2-deoxyglucose [2-DG] uptake), net glycogen synthesis, and glucose oxidation were determined in the isolated epitrochlearis muscles in the absence or presence of insulin (13.3 nmol/l). Severe insulin resistance of 2-DG uptake, glycogen synthesis, and glucose oxidation was observed in muscle from the vehicle-treated obese rats compared with muscle from vehicle-treated lean (Fa/-) rats. Acute and chronic treatments (30 mg.kg-1.day-1, a maximally effective dose) with ALA significantly (P < 0.05) improved insulin-mediated 2-DG uptake in epitrochlearis muscles from the obese rats by 62 and 64%, respectively. Chronic ALA treatment increased both insulin-stimulated glucose oxidation (33%) and glycogen synthesis (38%) and was associated with a significantly greater (21%) in vivo muscle glycogen concentration. These adaptive responses after chronic ALA administration were also associated with significantly lower (15-17%) plasma levels of insulin and free fatty acids. No significant effects on glucose transporter (GLUT4) protein level or on the activities of hexokinase and citrate synthase were observed. Collectively, these findings indicate that parenteral administration of the antioxidant ALA significantly enhances the capacity of the insulin-stimulatable glucose transport system and of both oxidative and nonoxidative pathways of glucose metabolism in insulin-resistant rat skeletal muscle.

64. Am J Physiol 1997 Jul;273(1 Pt 1):E185-91
Differential effects of lipoic acid stereoisomers on glucose metabolism in insulin-resistant skeletal muscle.
Streeper RS, Henriksen EJ, Jacob S, Hokama JY, Fogt DL, Tritschler HJ.
Department of Physiology, University of Arizona, Tucson 85721-0093, USA.

The racemic mixture of the antioxidant alpha-lipoic acid (ALA) enhances insulin-stimulated glucose metabolism in insulin-resistant humans and animals. We determined the individual effects of the pure R-(+) and S-(-) enantiomers of ALA on glucose metabolism in skeletal muscle of an animal model of insulin resistance, hyperinsulinemia, and dyslipidemia: the obese Zucker (fa/fa) rat. Obese rats were treated intraperitoneally acutely (100 mg/kg body wt for 1 h) or chronically [10 days with 30 mg/kg of R-(+)-ALA or 50 mg/kg of S-(-)-ALA]. Glucose transport [2-deoxyglucose (2-DG) uptake], glycogen synthesis, and glucose oxidation were determined in the epitrochlearis muscles in the absence or presence of insulin (13.3 nM). Acutely, R-(+)-ALA increased insulin-mediated 2-DG-uptake by 64% (P < 0.05), whereas S-(-)-ALA had no significant effect. Although chronic R-(+)-ALA treatment significantly reduced plasma insulin (17%) and free fatty acids (FFA; 35%) relative to vehicle-treated obese animals, S-(-)-ALA treatment further increased insulin (15%) and had no effect on FFA. Insulin-stimulated 2-DG uptake was increased by 65% by chronic R-(+)-ALA treatment, whereas S-(-)-ALA administration resulted in only a 29% improvement. Chronic R-(+)-ALA treatment elicited a 26% increase in insulin-stimulated glycogen synthesis and a 33% enhancement of insulin-stimulated glucose oxidation. No significant increase in these parameters was observed after S-(-)-ALA treatment. Glucose transporter (GLUT-4) protein was unchanged after chronic R-(+)-ALA treatment but was reduced to 81 +/- 6% of obese control with S-(-)-ALA treatment. Therefore, chronic parenteral treatment with the antioxidant ALA enhances insulin-stimulated glucose transport and non-oxidative and oxidative glucose metabolism in insulin-resistant rat skeletal muscle, with the R-(+) enantiomer being much more effective than the S-(-) enantiomer.

65. Free Radic Biol Med 2000 Dec;29(11):1122-8
Lipoic acid decreases lipid peroxidation and protein glycosylation and increases (Na(+) + K(+))- and Ca(++)-ATPase activities in high glucose-treated human erythrocytes.
Jain SK, Lim G.
Department of Pediatrics, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA. sjain@lsuhsc.edu

Lipoic acid supplementation has been found to be beneficial in preventing neurovascular abnormalities in diabetic neuropathy. Insufficient (Na(+) + K(+))-ATPase activity has been suggested as a contributing factor in the development of diabetic neuropathy. This study was undertaken to test the hypothesis that lipoic acid reduces lipid peroxidation and glycosylation and can increase the (Na(+) + K(+))- and Ca(++)-ATPase activities in high glucose-exposed red blood cells (RBC). Washed normal human RBC were treated with normal (6 mM) and high glucose concentrations (45 mM) with 0-0.2 mM lipoic acid (mixture of S and R sterioisomers) in a shaking water bath at 37 degrees C for 24 h. There was a significant stimulation of glucose consumption by RBC in the presence of lipoic acid both in normal and high glucose-treated RBC. Lipoic acid significantly lowered the level of glycated hemoglobin (GHb) and lipid peroxidation in RBC exposed to high glucose concentrations. High glucose treatment significantly lowered the activities of (Na(+) + K(+))- and Ca(++)-ATPases of RBC membranes. Lipoic acid addition significantly blocked the reduction in activities of (Na(+) + K(+))- and Ca(++)-ATPases in high glucose- treated RBC. There were no differences in lipid peroxidation, GHb and (Na(+) + K(+))- and Ca(++)-ATPase activity levels in normal glucose-treated RBC with and without lipoic acid. Thus, lipoic acid can lower lipid peroxidation and protein glycosylation, and increase (Na(+) + K(+))- and Ca(++)-ATPase activities in high-glucose exposed RBC, which provides a potential mechanism by which lipoic acid may delay or inhibit the development of neuropathy in diabetes.

66. Free Radic Biol Med 1999 Aug;27(3-4):309-14
Oral administration of RAC-alpha-lipoic acid modulates insulin sensitivity in patients with type-2 diabetes mellitus: a placebo-controlled pilot trial.
Jacob S, Ruus P, Hermann R, Tritschler HJ, Maerker E, Renn W, Augustin HJ, Dietze GJ, Rett K.
Hypertension and Diabetes Research Unit, Max Grundig Clinic, Buhl and City Hospital, Baden-Baden, Germany. snjacob@med.uni-tuebingen.de

Alpha-lipoic acid (ALA), a naturally occuring compound and a radical scavenger was shown to enhance glucose transport and utilization in different experimental and animal models. Clinical studies described an increase of insulin sensitivity after acute and short-term (10 d) parenteral administration of ALA. The effects of a 4-week oral treatment with alpha-lipoic acid were evaluated in a placebo-controlled, multicenter pilot study to determine see whether oral treatment also improves insulin sensitivity. Seventy-four patients with type-2 diabetes were randomized to either placebo (n = 19); or active treatment in various doses of 600 mg once daily (n = 19), twice daily (1200 mg; n = 18), or thrice daily (1800 mg; n = 18) alpha-lipoic acid. An isoglycemic glucose-clamp was done on days 0 (pre) and 29 (post). In this explorative study, analysis was done according to the number of subjects showing an improvement of insulin sensitivity after treatment. Furthermore, the effects of active vs. placebo treatment on insulin sensitivity was compared. All four groups were comparable and had a similar degree of hyperglycemia and insulin sensitivity at baseline. When compared to placebo, significantly more subjects had an increase in insulin-stimulated glucose disposal (MCR) after ALA treatment in each group. As there was no dose effect seen in the three different alpha-lipoic acid groups, all subjects receiving ALA were combined in the "active" group and then compared to placebo. This revealed significantly different changes in MCR after treatment (+27% vs. placebo; p < .01). This placebo-controlled explorative study confirms previous observations of an increase of insulin sensitivity in type-2 diabetes after acute and chronic intravenous administration of ALA. The results suggest that oral administration of alpha-lipoic acid can improve insulin sensitivity in patients with type-2 diabetes. The encouraging findings of this pilot trial need to be substantiated by further investigations.

67. Diabetes Care 1999 Feb;22(2):280-7
alpha-Lipoic acid treatment decreases serum lactate and pyruvate concentrations and improves glucose effectiveness in lean and obese patients with type 2 diabetes.
Konrad T, Vicini P, Kusterer K, Hoflich A, Assadkhani A, Bohles HJ, Sewell A, Tritschler HJ, Cobelli C, Usadel KH.
Department of Internal Medicine, J.W. Goethe-University, Frankfurt, Germany.

OBJECTIVE: We examined the effect of lipoic acid (LA), a cofactor of the pyruvate dehydrogenase complex (PDH), on insulin sensitivity (SI) and glucose effectiveness (SG) and on serum lactate and pyruvate levels after oral glucose tolerance tests (OGTTs) and modified frequently sampled intravenous glucose tolerance tests (FSIGTTs) in lean (n = 10) and obese (n = 10) patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: FSIGTT data were analyzed by minimal modeling technique to determine SI and SG before and after oral treatment (600 mg, twice a day, for 4 weeks). Serum lactate and pyruvate levels of diabetic patients after glucose loading were compared with those of lean (n = 10) and obese (n = 10) healthy control subjects in which SI and SG were also determined from FSIGTT data. RESULTS: Fasting lactate and pyruvate levels were significantly increased in patients with type 2 diabetes. These metabolites did not exceed elevated fasting concentrations after glucose loading in lean patients with type 2 diabetes. However, a twofold increase of lactate and pyruvate levels was measured in obese diabetic patients. LA treatment was associated with increased SG in both diabetic groups (lean 1.28 +/- 0.14 to 1.93 +/- 0.13; obese 1.07 +/- 0.11 to 1.53 +/- 0.08 x 10(-2) min-1, P < 0.05). Higher SI and lower fasting glucose were measured in lean diabetic patients only (P < 0.05). Lactate and pyruvate before and after glucose loading were approximately 45% lower in lean and obese diabetic patients after LA treatment. CONCLUSIONS: Treatment of lean and obese diabetic patients with LA prevents hyperglycemia-induced increments of serum lactate and pyruvate levels and increases SG.

68. Exp Clin Endocrinol Diabetes 1996;104(3):284-8
Improvement of insulin-stimulated glucose-disposal in type 2 diabetes after repeated parenteral administration of thioctic acid.
Jacob S, Henriksen EJ, Tritschler HJ, Augustin HJ, Dietze GJ.
Hypertension and Diabetes Research Unit, Max Grundig Clinic, Buhl, Germany.

Insulin resistance of skeletal muscle glucose uptake is a prominent feature of Type II diabetes (NIDDM); therefore, pharmacological intervention should aim to improve insulin sensitivity. Thioctic acid (TA), a naturally occurring compound, was shown to enhance glucose utilization in various experimental models after acute and chronic administration. It also increased insulin-stimulated glucose disposal in patients with NIDDM after acute administration. This pilot study was initiated to see whether this compound also augments glucose disposal in humans after repeated treatment. Twenty patients with NIDDM received TA (500 mg/ 500 ml NaCl, 0.9%) as daily infusions over a period of ten days. A hyperinsulinaemic, isoglycaemic glucose-clamp was done on day 0 and day 11. Parenteral administration of TA resulted in a significant increase of insulin-stimulated glucose-disposal by about 30% (metabolic clearance rate for glucose, 2.5 +/- 0.3 vs. 3.2 +/- 0.4 ml/kg/min and insulin-sensitivity-index: 3.5 +/- 0.5 vs. 4.7 +/- 0.4 mg/kg/microU/ml; p < 0.05, Wilcoxon-Rank-Sum-Test). There were no changes in fasting plasma levels for glucose or insulin; this can be explained, however, by the short period of treatment and observation. This is the first clinical study to show that a ten day administration of TA is able to improve resistance of insulin-stimulated glucose disposal in NIDDM. Experimental data suggest several mechanisms in the mode of action. As the present investigation was an uncontrolled pilot trial, the encouraging results call for controlled studies to further elucidate the clinical relevance of the findings and the mode of action of this compound.

69. Protection against oxidative stress-induced insulin resistance in rat L6 muscle cells by mircomolar concentrations of alpha-lipoic acid.
Maddux BA, See W, Lawrence JC Jr, Goldfine AL, Goldfine ID, Evans JL.
Diabetes Research Laboratory, Mount Zion Hospital, San Francisco, California 94143-1616, USA. bmaddux@itsa.ucsf.edu
Diabetes. 2001 Feb;50(2):404-10. Free Full Text Article Here http://diabetes.diabetesjournals.org/cgi/content/full/50/2/404

In diabetic patients, alpha-lipoic acid (LA) improves skeletal muscle glucose transport, resulting in increased glucose disposal; however, the molecular mechanism of action of LA is presently unknown. We studied the effects of LA on basal and insulin-stimulated glucose transport in cultured rat L6 muscle cells that overexpress GLUT4. When 2-deoxy-D-glucose uptake was measured in these cells, they were more sensitive and responsive to insulin than wild-type L6 cells. LA, at concentrations < or = 1 mmol/l, had only small effects on glucose transport in cells not exposed to oxidative stress. When cells were exposed to glucose oxidase and glucose to generate H2O2 and cause oxidative stress, there was a marked decrease in insulin-stimulated glucose transport. Pretreatment with LA over the concentration range of 10-1,000 pmol/l protected the insulin effect from inhibition by H2O2. Both the R and S isomers of LA were equally effective. In addition, oxidative stress caused a significant decrease (approximately 50%) in reduced glutathione concentration, along with the rapid activation of the stress-sensitive p38 mitogen-activated protein kinase. Pretreatment with LA prevented both of these events, coincident with protecting insulin action. These studies indicate that in muscle, the major site of insulin-stimulated glucose disposal, one important effect of LA on the insulin-signaling cascade is to protect cells from oxidative stress-induced insulin resistance.

70. Cataract development in diabetic sand rats treated with alpha-lipoic acid and its gamma-linolenic acid conjugate.
Borenshtein D, Ofri R, Werman M, Stark A, Tritschler HJ, Moeller W, Madar Z.
Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Diabetes Metab Res Rev. 2001 Jan-Feb;17(1):44-50.

BACKGROUND: Diabetes commonly leads to long-term complications such as cataract. This study investigated the effects of alpha-lipoic acid (LPA) and its gamma-linolenic acid (GLA) conjugate on cataract development in diabetic sand rats. METHODS: Two separate experiments were conducted. In Experiment 1, sand rats were fed a "high-energy" diet (70% starch), an acute model of Type 2 diabetes, and injected with LPA. In Experiment 2, the animals received a "medium-energy" diet (59% starch), a chronic diabetic model, and were intubated with LPA or its GLA conjugate. Throughout the experiments, blood glucose levels and cataract development were measured. At the termination of the experiments, lens aldose reductase (AR) activity and lenticular reduced glutathione (GSH) levels were analyzed. RESULTS: LPA injection significantly inhibited cataract development and reduced blood glucose levels in rats fed the "high-energy" diet. Lens AR activity tended to be lower, while lenticular GSH levels increased. In sand rats fed a "medium-energy" diet (59% starch), LPA intubation had no effect on blood glucose levels and cataract development but GSH levels were increased. In contrast, sand rats intubated with GLA conjugate showed the highest blood glucose levels and accelerated cataract development. The conjugate treatment also decreased lenticular GSH content. CONCLUSIONS: The hypoglycemic effects of LPA are beneficial in the prevention of acute symptoms of Type 2 diabetes. It remains to be shown that the antioxidant activity of LPA is responsible for prevention or inhibition of cataract progression in sand rats. Copyright 2000 John Wiley & Sons, Ltd.