Peculiarities of the endocrine time structure in noninsulin-dependent adult-onset (type II) diabetes mellitus.

Sackett-Lundeen L, Nicolau GY, Lakatua DJ, Bogdan C, Petrescu E, Jachimowicz A, Haus E
Prog Clin Biol Res 1987;227A:467-82

Twenty noninsulin-dependent elderly diabetic patients, ten of whom were treated by oral hypoglycemic agents and ten of whom were regulated by diet alone, and 20 clinically healthy subjects matched for age, sex, height, and weight were examined with six blood and six urine samples at 4-hr intervals over a 24-hr span. Plasma ACTH, cortisol, aldosterone, and dehydroepiandrosterone-sulfate (DHEA-S) were determined by radioimmunoassay (RIA); epinephrine, norepinephrine, and dopamine in urine were determined by high-pressure liquid chromatography (HPLC); and magnesium in urine was determined colorimetrically on a DuPont ACA. There were a number of changes in some of these functions in type II diabetic patients with and without oral hypoglycemic agents that appear to be of interest. The circadian mean in plasma ACTH concentration in diabetic patients with and without oral hypoglycemic agents is significantly higher than in matched nondiabetic controls. The plasma aldosterone concentration is similar in type II diabetics treated by diet only and in matched controls but is statistically significantly elevated in patients on oral hypoglycemic agents. Correspondingly, the urinary excretion of sodium in type II diabetic patients on oral hypoglycemic agents is lower than in matched controls. The plasma cortisol concentration is unchanged in type II diabetic patients treated by diet alone but shows a slight increase in patients on oral hypoglycemic agents. The circadian means of plasma DHEA-S concentration is slightly higher in diabetic patients with and without oral hypoglycemic agents than in matched controls. This elevation, however, does not quite reach the 95% level of statistical significance. Urinary norepinephrine excretion in type II diabetic patients is similar to that in matched controls. The urinary epinephrine excretion in diabetics with and without oral hypoglycemic agents, however, was lower than in controls, and the urinary excretion of dopamine was higher in the diabetics. The urinary magnesium excretion in type II diabetic patients was lower than in matched controls.

Antiobesity effects of etiocholanolones in diabetes (db), viable yellow (Avy), and normal mice.

Coleman DL
Endocrinology 1985 Dec;117(6):2279-83

Two metabolites of the adrenal steroid dehydroepiandrosterone (DHEA), 3alpha-hydroxyetiocholanolone and 3 beta-hydroxyetiocholanolone, were found to have antiobesity properties with respect to both prevention of the development of obesity as well as weight reduction after obesity was established. All of the obesity types studied responded to metabolite therapy to a greater or lesser extent. The more natural obesity seen in certain strains of mice with aging responded most rapidly to the feeding of either metabolite. The effective dosage (0.1%) fed in the diet was only one quarter the dosage required for DHEA to produce the same effect in preventing diabetes symptoms in C57BL/Ks diabetic (db) mutant mice. Unlike DHEA, neither metabolite produced any undesirable estrogenic or androgenic side-effects. 3 alpha-hydroxyethiocholanolone and 3 beta-hydroxyetiocholanolone, formerly considered only as inert end products of steroid metabolism, have beneficial actions in mice with various diabetes-obesity conditions and may be metabolic effectors in their own right.

Circadian time structure of endocrine and biochemical parameters in adult onset (type II) diabetic patients.

Nicolau GY, Haus E, Lakatua D, Bogdan C, Petrescu E, Robu E, Sackett-Lundeen L, Swoyer J, Adderley J
Endocrinologie 1984 Oct-Dec;22(4):227-43

Forty-one endocrine and biochemical serum parameters were studied over a 24-hour span with 6 samples at 4-hour intervals in 20 non-insulin dependent (Type II) diabetics and in 20 non-diabetic subjects matched for sex, age, height and weight. Circadian rhythms were verified by cosinor analysis. Group-synchronized circadian rhythms were detected in diabetic and non-diabetic subjects with no statistically significant difference in any of the rhythm parameters (rhythm adjusted mean, amplitude and acrophase) in: Aldosterone, cortisol, insulin, 17-OH progesterone, prolactin, testosterone, TSH, and in serum albumin, creatine phosphokinase (CPK), serum iron, inorganic phosphate and total protein. Statistically significant (p less than .05) circadian rhythms in both groups with a difference in some parameters between the diabetic and the non-diabetic subjects, which were verified by the Bingham Test (p less than .05) were found with a difference in the mesor in cholesterol, glucose, urea nitrogen (BUN), in the amplitude in C-peptide and in the acrophase in triglycerides, globulin and reverse T3 (rT3). Statistically significant circadian rhythms were detected as a group phenomenon for the diabetics only in progesterone, free and total T4, chloride, calcium, bilirubin and LDH and in the non-diabetic subjects only in ACTH, LH, total T3, alkaline phosphatase, uric acid and potassium. In the remainder of the functions studied, acircadian rhythm was detectable with statistical significance by cosinor analysis as a group phenomenon neither in the diabetics nor in the matched non-diabetic controls (DHEA-S, estradiol, FSH, GH, glucagon, free T3, sodium, GOT and gamma GT). In the absence of a detectable circadian rhythmas group phenomenon, the circadian mean was different between the diabetics and the non-diabetic subjects in sodium, chloride and calcium which were higher in the diabetic patients and serum LDH which was lower. In a comparison of endocrine determinations in the two groups, the circadian mean or mesor in T3 was lower in the diabetics and ACTH higher, without corresponding changes in TSH or in corticosteroids. The circadian time structure of Type II diabetic patients thus seems to be very similar to that seen in non-diabetic subjects of the same sex, age, weight and height.The minor differences found in some rhythm parameters will have to be confirmed or excluded in larger numbers of subjects. The higher circadian mean ACTH concentrations without change in steroid rhythm parameters observed in this group is interesting but will also require confirmation. (ABSTRACT TRUNCATED AT 400 WORDS)

Effect of genetic background on the therapeutic effects of dehydroepiandrosterone (DHEA) in diabetes-obesity mutants and in aged normal mice.

Coleman DL, Schwizer RW, Leiter EH
Diabetes 1984 Jan;33(1):26-32

Dehydroepiandrosterone (DHEA) was fed at 0.1-0.4% in the diet to genetically diabetic (db/db) or obese (ob/ob) C57BL/KsJ (BL/Ks) or C57BL/6J (BL/6) mice. Treatment of BL/Ks-db/db or ob/ob mice with 0.4% DHEA prevented hyperglycemia, islet atrophy, and severe diabetes associated with this inbred background, but did not affect weight gain and food consumption. Homozygous obese (ob) or diabetes (db) mice on the BL/6 background were more sensitive to DHEA, and the mild, transient hyperglycemia associated with ob or db gene expression on the BL/6 inbred background could be prevented by 0.1% DHEA. Both body weight and food consumption were decreased in BL/6 mutants maintained on 0.1% DHEA whereas this effect was not seen in BL/Ks mutants fed up to 0.4% DHEA. Early therapy with 0.4% DHEA, initiated at 2 wk of age, prevented the developmentof most diabetes symptoms and decreased the rate of weight gain in pups of all genotypes. In addition to therapeutic effects on both obese mutants, DHEA effected significant changes in an aging study using normal BL/6 female mice. Four weeks of DHEA treatment initiated at 2 yr of age improved glucose tolerance and at the same time reduced plasma insulin to a "younger" level. This suggests that DHEA may act in insulin-resistant mutant mice and in aging normal mice to increase the sensitivity to insulin.

Amniotic fluid beta-endorphin and beta-lipotropin concentrations during the second and third trimesters.

Petrucha RA, Goebelsmann U, Hung TT, Haase HR, Lobo RA
Am J Obstet Gynecol 1983 Jul 15;146(6):644-51

Amniotic fluid beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) were measured by radioimmunoassay after silicic acid extraction and gelchromatographic separation of the two peptides in uncomplicatedsecond-trimester and term pregnancies, in diabetic patients at term, and inpregnancies complicated by Rh-isoimmunization, premature labor, and intrauterine growth retardation. Furthermore, the lecithin/sphingomyelin (L/S) ratios as well as the dehydroepiandrosterone sulfate (DHEA-S) and cortisol levels were determined in most of the amniotic fluid specimens. Both the mean (+/- SE) beta-EP (65.3 +/- 9.1 fmol/ml) and beta-LPH (150 +/-15.8 fmol/ml) concentrations were significantly higher in the 20 patients with normal pregnancies of 16 to 21 weeks' duration than those found in 21 patients with uncomplicated term pregnancies of 38 weeks' gestation, averaging 42.6 +/- 6.0 and 80.1 +/- 10.7 fmol/ml, respectively. The mean amniotic fluid beta-EP and beta-LPH concentrations measured in the latter subjects were similar to those observed in 23 diabetic patients with otherwise uncomplicated term pregnancies. The mean amniotic fluid beta-EP and beta-LPH levels found in the limited number of patients with Rh-isoimmunization (N = 9), premature labor (n = 8), and intrauterine growth retardation (n = 5) with pregnancies of 24 to 36, 24 to 36, and 34 to 38 weeks' gestation, respectively, were not significantly different from the mean amniotic fluid beta-EP and beta-LPH concentrations of uncomplicated term pregnancies. In all patients but those with Rh-isoimmunization, beta-EP concentrations exhibited a positive correlation with beta-LPH levels. However, the molar beta-LPH:beta-EP ratio was significantly lower at term than during the early second trimester. Neither beta-EP nor beta-LPH correlated with the amniotic fluid L/S ratio and only beta-LPH exhibited a significant inverse correlation with amniotic fluid DHEA-S. The latter was significantly higher in uncomplicated term than second-trimester pregnancies. These results confirm that immunoassayable beta-EP is present in amniotic fluid and declines toward term. These data demonstrate that immunoassayable beta-LPH is present in amniotic fluid and show a more pronounced decrease toward the end of pregnancy than beta-EP. Neither peptide, at least on account of the amniotic fluid levels, appears to be associated with fetal maturation. The physiologic significance of amniotic fluid beta-EP and beta-LPH and their possible role as markers of fetal response to stress remain to be elucidated.

Therapeutic effects of dehydroepiandrosterone (DHEA) in diabetic mice.

Coleman DL, Leiter EH, Schwizer RW
Diabetes 1982 Sep;31(9):830-3

Dehydroepiandrosterone (DHEA), a major adrenal secretory steroid in humans, was therapeutic when fed in a concentration of 0.4% to C57BL/KsJ mice with either non-insulin-dependent or insulin-dependent diabetes. Genetically diabetic (db/db) mice of both sexes develop obesity and aglucose intolerance and hyperglycemia associated with insulin resistance by 2 mo of age, and exhibit beta-cell necrosis and islet atrophy by 4 mo. In contrast, DHEA feeding initiated between 1 and 4 mo of age, while only moderately effective in preventing obesity, did prevent the other pathogenic changes and effected a rapid remission of hyperglycemia, a preservation of beta-cell structure and function, and an increased insulin sensitivity as measured by glucose tolerance tests. DHEA feeding was also therapeutic to normal C57BL/KsJ male mice made diabetic by multiple low doses of streptozotocin (SZ). While DHEA treatments did not block either the direct cytotoxic action of SZ on beta-cells or the development of insulitis, the steroid significantly moderated the severity of the ensuing diabetes (reduced hyperglycemia and water consumption, and increased plasma insulin and numbers of residual, granulated beta-cells.

Plasma androgen concentrations in diabetic women.

Szpunar WE, Blair AJ Jr, McCann DS
Diabetes 1977 Dec;26(12):1125-9

Plasma androgen levels were determined in women assigned to the following groups: idiopathically hirsute, diabetic, both idiopathically hirsute and diabetic, and normal. The androgens examined were androstenedione (AD), dihydrotestosterone (DHT), testosterone (T), and dehydroepiandrosterone (DHEA). We find statistical differences between young (less than 38 years) and older (larger than or equal to 38 years) controls at confidence levels of p less than or equal to 0.01 for AD, DHT, and T and of p less than or equal to 0.05 for DHEA. The results indicate that peak circulating androgen levels occur prior to age 30-35 years for women. There are no significant differences between the young controls and young idiopathically hirsute subjects, but a statistical difference exists between older hirsute and older controls for all four androgens (p less than or equal to 0.05). When a comparison is made among the diabetic, hirsute diabetic, and older control groups (all groups larger than or equal to 38 years), the diabetic group is significantly higher than the control in plasma AD (p less than or equal to 0.01) and DHEA (p less than or equal to 0.05). These same two steroids are also higher in the diabetic group than in the hirsute diabetic group (p less than or equal to 0.05), while the latter differs from controls only in testosterone levels (p less than or equal to 0.05). DHT levels are similar for all three groups.

Conversion of DHEA-sulfate to estrogens as a test of placental function.

Lauritzen C
Horm Metab Res 1969 Mar;1(2):96

No abstract.

[Evaluation of placenta function using DHEA-S tolerance test; comparison with cardiotocography and placental histology]

Crabben H van der, Hammacher K, Werner C, Kaiser E
Geburtshilfe Frauenheilkd 1970 Jan;30(1):71-84

No abstract.

Interaction of alpha-lipoic acid enantiomers and homologues with the enzyme components of the mammalian pyruvate dehydrogenase complex.

Loffelhardt S, Bonaventura C, Locher M, Borbe HO, Bisswanger H
Physiologisch-Chemisches Institut, University of Tubingen, Germany.
Biochem Pharmacol 1995 Aug 25;50(5):637-46

Lipoic acid (alpha-lipoic acid, thioctic acid) is applied as a therapeutic agent in various diseases accompanied by polyneuropathia such as diabetes mellitus. The stereoselectivity and specificity of lipoic acid for the pyruvate dehydrogenase complex and its component enzymes from different sources has been studied. The dihydrolipoamide dehydrogenase component from pig heart has a clear preference for R-lipoic acid, a substrate which reacts 24 times faster than the S-enantiomer. Selectivity is more at the stage of the catalytic reaction than of binding. The Michaelis constants of both enantiomers are comparable (Km = 3.7 and 5.5 mMfor R- and S-lipoic acid, respectively) and the S-enantiomer inhibits the R-lipoic acid dependent reaction with an inhibition constant similar to its Michaelis constant. When three lipoic acid homologues were tested, RS-1,2-dithiolane-3-caproic acid was one carbon atom longer than lipoic acid, while RS-bisnorlipoic acid and RS-tetranorlipoic acid were two and four carbon atoms shorter, respectively. All are poor substrates but bind to and inhibit the enzyme with an affinity similar to that of S-lipoic acid. No essential differences with respect to its reaction with lipoicacid enantiomers and homologues exist between free and complex-bound dihydrolipoamide dehydrogenase. Dihydrolipoamide dehydrogenase from human renal carcinoma has a higher Michaelis constant for R-lipoic acid (Km = 18mM) and does not accept the S-enantiomer as a substrate. Both enantiomers of lipoic acid are inhibitors of the overall reaction of the bovine pyruvate dehydrogenase complex, but stimulate the respective enzyme complexes from rat as well as from Escherichia coli. The S-enantiomer is the stronger inhibitor, the R-enantiomer the better activator. The two enantiomers have no influence on the partial reaction of the bovine pyruvate dehydrogenase component, but do inhibit this enzyme component from rat kidney. The implications of these results are discussed.

alpha-Lipoic acid as a biological antioxidant.

Packer L; Witt EH; Tritschler HJ
Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720 USA
Free Radic Biol Med 1995 Aug;19(2):227-50

alpha-Lipoic acid, which plays an essential role in mitochondrial dehydrogenase reactions, has recently gained considerable attention as an antioxidant. Lipoate, or its reduced form, dihydrolipoate, reacts with reactive oxygen species such as superoxide radicals, hydroxyl radicals, hypochlorous acid, peroxyl radicals, and singlet oxygen. It also protects membranes by interacting with vitamin C and glutathione, which may in turn recycle vitamin E. In addition to its antioxidant activities, dihydrolipoate may exert prooxidant actions through reduction of iron. alpha-Lipoic acid administration has been shown to be beneficial in a number of oxidative stress models such as ischemia-reperfusion injury, diabetes (both alpha-lipoic acid and dihydrolipoic acid exhibit hydrophobic binding to proteins such as albumin, which can prevent glycation reactions), cataract formation, HIV activation, neurodegeneration, and radiation injury. Furthermore, lipoate can function as a redox regulator of proteins such as myoglobin, prolactin, thioredoxin and NF-kappa B transcription factor. We review the properties of lipoate in terms of

(1) reactions with reactive oxygen species;
(2) interactions with other antioxidants;
(3) beneficial effects in oxidative stress models or clinical conditions. (153 Refs.)

[Diabetes mellitus--a free radical-associated disease. Results of adjuvant antioxidant supplementation]

Kahler W, Kuklinski B, Ruhlmann C, Plotz C
Klinik fur Innere Medizin, Klinikums Rostock-Sudstadt.
Z Gesamte Inn Med 1993 May;48(5):223-32

Our investigations carried out in patients with diabetes mellitus revealed oxidative stress loads. The study presented here was to clarify whether a therapy with antioxidants can contribute to an improvement of prognosis. 80 patients affected with a long term diabetic late syndrome were randomised and arranged to 4 groups of n = 20 each. In contrast to a control group these patients received 600 mg of alpha lipoic acid or 100 micrograms of selenium (sodium selenite) daily or 1200 IE of D-alpha-tocopherol respectively for a time of 3 months. In comparison with the control group all groups treated in an antioxidative way showed significantly diminished serum concentrations of thiobarbituric acid reactive substances and of urinary albumin excretion rates. The symptoms of distal symmetric neuropathy measured according to the thermo- and vibration sensitivity also improved in a highly significant manner. The results prove that oxidative stress plays a promoting role in developing of long term diabetic late complications and that a therapy with adjuvant antioxidants may lead to a regression of diabetic late complications.

Lipoate prevents glucose-induced protein modifications.

Suzuki YJ, Tsuchiya M, Packer L
Department of Molecular & Cell Biology, University of California, Berkeley 94720.
Free Radic Res Commun 1992;17(3):211-7

Nonenzymatic glycation has been found to increase in a variety of proteins in diabetic patients. The present study examined a possibility of preventing glycation and subsequent structural modifications of proteins by alpha-lipoic acid (thioctic acid) as lipoate, a substance which has gained attention as a potential therapeutic agent for diabetes-induced complications. Incubation of bovine serum albumin (BSA) at 2 mg/ml with glucose (500 mM) in a sterile condition at 37 degrees C for seven days caused glycation and structural modifications of BSA observed by SDS-PAGE, near UV absorption, tryptophan and nontryptophan fluorescence, and fluorescence of an extrinsic probe, TNS (6-(p-toluidinyl) naphthalene-2-sulfonate). When BSA and glucose were incubated in the presence of lipoate (20mM), glycation and structural modifications of BSA were significantly prevented. Glycation and inactivation of lysozyme were also prevented by lipoate. These results suggest a potential for the therapeutic use of lipoic acid against diabetes-induced complications.

Effect of DL-alpha-lipoic acid on the citrate concentration and phosphofructokinase activity of perfused hearts from normal and diabetic rats.

Singh HP, Bowman RH
Biochem Biophys Res Commun 1970 Nov 9;41(3):555-61

No abstract.

Increased anti-Gal activity in diabetic patients transplanted with fetal porcine islet cell clusters.

Galili U, Tibell A, Samuelsson B, Rydberg L, Groth CG
Department of Microbiology and Immunology, Medical College of Pennsylvania, Philadelphia, Pennsylvania 19129, USA.
Transplantation 1995 Jun 15;59(11):1549-56

The natural anti-Gal antibody seems to create a major obstacle for discordant xenotransplantation in humans. Anti-Gal, which is produced in large amounts in humans (1% of circulating IgG), interacts specifically with the carbohydrate structure Gal alpha 1-3Gal beta 1-4Glc-NAc-R (termedthe alpha-galactosyl epitope). This epitope is present in large amounts on porcine cells, as well as on cells of other nonprimate mammals (1 x 10(6)to 35 x 10(6) epitopes/cell). The interaction of anti-Gal with alpha-galactosyl epitopes on the xenograft was found to mediate the immune destruction of discordant xenografts. In the present study, the human immune response to alpha-galactosyl epitopes on xenografts was assessed by measuring changes in anti-Gal titers and affinity in sera of diabetic patients transplanted with fetal porcine islet cell clusters. The activityof this antibody was assessed by a hemagglutination assay with RBC, byELISA with mouse laminin as a solid-phase antigen, and by equilibrium dialysis with the radiolabeled free haptenic form of the alpha-galactosylepitope, i.e. [3H]Gal alpha 1-3Gal beta 1-4GlcNAc. All assays revealed a marked increase in anti-Gal activity after transplantation. The increase in anti-Gal titers ranged between 8- and 64-fold. A similar increase was observed in the binding of free alpha-galactosyl epitopes to anti-Gal, as assayed in equilibrium dialysis. Immunoglobulin concentration did not increase after transplantation, suggesting that the observed increase in anti-Gal activity is the result of a specific immune response against alpha-galactosyl epitopes on the xenograft. The elevation in anti-Gal activity was observed in all three immunoglobulin classes and the highest activity was found within the IgG class. Analysis of IgG binding to fixed porcine endothelial cells suggested that most of the observed increased activity against these cells in transplanted patients may be attributed to the elevation in anti-Gal activity.

Intracellular glutathione influences collagen generation by mesangial cells.

Shan Z, Tan D, Satriano J, Silbiger S, Schlondorff D
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York.
Kidney Int 1994 Aug;46(2):388-95

The cellular redox state is altered in a number of pathological conditions, including various forms of glomerular injury and diabetes. For example, glucose, via the pentose phosphate pathway generates NADPH, which maintains glutathione (GSH) (part of a major intracellular reducing system) in its reduced state. GSH in turn influences the activity of transcription factors on gene expression. We therefore examined whether changes in cellular GSH influence total collagen synthesis and mRNA levels for collagen I, collagen IV and TGF-beta in SV-40 transformed mouse mesangial cells (MC) maintained in either 5 or 25 mM glucose media. Total intracellular GSH was increased by N-acetylcysteine (NAC; 10 mM) or decreased with the GSH synthesis inhibitor buthionine sulfoximine (BSO; 0.2mM) in MC. NAC increased 3H-proline incorporation into collagenase-sensitive protein while BSO decreased it under both glucose conditions. The presence of BSO did not reverse the increased collagen synthesis seen in the NAC stimulated cells. Northern blot analysis showed increased mRNA levels for collagen I, collagen IV and TGF-beta in cells grown in high glucose (25 mM). NAC increased the mRNA for all three compounds while BSO alone had no effect on these mRNA levels. However, BSO reversed the increased mRNA levels for collagen I, IV and TGF-beta seen in the presence of NAC. These findings suggest that the cellular redox state may influence gene transcription in MC, and may have implications in explaining injury-associated alterations of mesangial matrix generation.

[Cholestyramine in the treatment of severe diarrhea and diarrhea of the diabetic patient].

Laudanna AA, Germ:an JC, Gama Rodriques JJ, Mekler M, Gama AH, Bertarello A
Rev Fac Cien Med Univ Nac Cordoba 1985;43(2):3-6
Published erratum appears in Rev Fac Cien Med Univ Nac Cordoba 1986;44(2):preceding 3

No abstract.

Neural dysfunction and metabolic imbalances in diabetic rats. Prevention by acetyl-L-carnitine.

Ido Y, McHowat J, Chang KC, Arrigoni-Martelli E, Orfalian Z, Kilo C, Corr PB, Williamson JR
Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110.
Diabetes 1994 Dec;43(12):1469-77

The rationale for these experiments is that administration of L-carnitine and/or short-chain acylcarnitines attenuates myocardial dysfunction

1) in hearts from diabetic animals (in which L-carnitine levels are decreased);
2) induced by ischemia-reperfusion in hearts from nondiabetic animals; and
3) in nondiabetic humans with ischemic heart disease.

The objective of these studies was to investigate whether imbalances in carnitine metabolism play a role in the pathogenesis of diabetic peripheral neuropathy. The major findings in rats with streptozotocin-induced diabetes of 4-6 weeks duration were that 24-h urinary carnitine excretion was increased approximately twofold and L-carnitine levels were decreased in plasma (46%) and sciatic nerve endoneurium (31%). These changes in carnitine levels/excretion were associated with decreased caudal nerve conduction velocity (10-15%) and sciatic nerve changes in Na(+)-K(+)-ATPase activity (decreased 50%), Mg(2+)-ATPase (decreased 65%), 1,2-diacyl-sn-glycerol (DAG) (decreased 40%), vascular albumin permeation (increased 60%), and blood flow (increased 65%). Treatment with acetyl-L-carnitine normalized plasma and endoneurial L-carnitine levels and prevented all of these metabolic and functional changes except the increased blood flow, which was unaffected, and the reduction in DAG, which decreased another 40%. In conclusion, these observations

1) demonstrate a link between imbalances in carnitine metabolism and several metabolic and functional abnormalities associated with diabetic polyneuropathy and
2) indicate that decreased sciatic nerve endoneurial ATPase activity (ouabain-sensitive and insensitive) in this model of diabetes is associated with decreased DAG.

Serum and urine levels of levocarnitine family components in genetically diabetic rats.

Morabito E, Corsico N, Marzo A, Arrigoni Martelli E
Department of Pharmacology, Sigma-Tau S.p.A., Pomezia, Roma, Italy.
Arzneimittelforschung 1994 Aug;44(8):965-8

Serum concentration and urinary excretion of levocarnitine (L-carnitine, CAS 541-15-1) family components were evaluated in a Wistar derived strain of genetically diabetic rats BB/BB, in comparison with normal Wistar rats, and their control rats BB/WB of both sexes. BB/BB diabetic animals have lower serum concentration of total-L-carnitine (TC), L-carnitine (LC), acetyl-L-carnitine (ALC), and short chain L-carnitine esters (SCLCE) than both the strains of non-diabetic rats, as previously observed in streptozotocin diabetic rats. No or marginal variations between control and diabetic rats were detected in cumulative urinary excretion of L-carnitine family components. A strain difference was observed between Wistar and BB/WB non-diabetic rats, BB/WB showing higher serum concentration and lower cumulative urinary excretion of LC and TC than Wistar animals. Renal clearance of L-carnitine components proved to be markedly higher in BB/BB diabetic rats, as previously shown in streptozotocin rats. The reduction of serum concentration of the carnitines endogenous pool may explain this finding. The lack of an increased urinary excretion of L-carnitine components in diabetic animals despite the high increase of diuresis suggests that the saturable tubular reabsorption of L-carnitine family components also in diabetes is the primary mechanism to preserve the homeostatic equilibria of the L-carnitine family, the variation in serum concentration being attributable to the complex systemic metabolicalterations typical of diabetes. In agreement with previous investigations,male animals of all the strains showed higher serum concentration andurinary excretion of L-carnitine components as compared to females.

Acetyl-L-carnitine corrects electroretinographic deficits in experimental diabetes.

Lowitt S, Malone JI, Salem A, Kozak WM, Orfalian Z
Department of Pediatrics, University of South Florida, Tampa.
Diabetes 1993 Aug;42(8):1115-8

Acetyl-L-carnitine reduces the latencies of electroretinogram oscillatory potentials in healthy humans. The effect of acetyl-L-carnitine (50mg.kg-1.day-1) on the increased electroretinogram latencies found in rats with STZ-induced hyperglycemia of 3-wk duration was evaluated. The aldosereductase inhibitor sorbinil, which has been shown to normalize abnormal electroretinogram tracings associated with STZ-induced diabetes, was used as a positive control. Aldose reductase inhibitors are thought to lower tissue sorbitol while increasing myo-inositol. The electroretinograms of the STZ-induced diabetic rats in this study were abnormal; treatment withacetyl-L-carnitine as well as sorbinil significantly improved electroretinogram b-wave amplitude and decreased the latencies of oscillatory potentials 2 and 3. Acetyl-L-carnitine treatment of STZ-induced diabetic rats did not affect hyperglycemia or erythrocyte polyol pathway activity as reflected by erythrocyte sorbitol levels. In contrast, sorbinil did reduce elevated erythrocyte sorbitol levels. This suggests that the impaired electroretinograms associated with STZ-induced diabetes may not be caused solely by increased polyol pathway activity.

Acetyl-L-carnitine effect on nerve conduction velocity in streptozotocin-diabetic rats.

Morabito E, Serafini S, Corsico N, Martelli EA
Department of Pharmacology, Sigma-Tau S.p.A. Pomezia, Rome, Italy.
Arzneimittelforschung 1993 Mar;43(3):343-6

Measurement of nerve conduction velocity (NCV) is a useful and sensitive tool for evaluating diabetes related neurological dysfunctions. The method used allows to monitor the parameter at different times in the same group of rats, so that it is possible to observe simultaneously the development of the damage in time, and to evaluate the improvement related to the treatment. The repeated oral treatment with acetyl-L-carnitine (ALC, CAS 5080-50-2) 250 mg/kg caused an improvement in NCV of the diabetic rats; the effect was higher when the treatment started early with respect to the diabetes induction. The improvement in NCV was constant in time and comparable from 2 to 6 weeks of the treatment. In conclusion, oral treatment with ALC was able to normalize the impairment of NCV in streptozotocin rats, the effect being constant in time from 2 to 6 weeks of treatment and up to 8 weeks after induction when administration started in early stage of diabetes (2-3 weeks after induction); however, at this time the NCV is already significantly decreased.

Effect of acetyl-L-carnitine treatment on the levels of levocarnitine and its derivatives in streptozotocin-diabetic rats.

Marzo A, Corsico N, Cardace G, Morabito E
Department of Drug Metabolism and Pharmacokinetics, Sigma-Tau S.p.A., Pomezia, Rome, Italy.
Arzneimittelforschung 1993 Mar;43(3):339-42

The effect of diabetes induced by streptozotocin and that of acetyl-L-carnitine (ALC) hydrochloride (CAS 5080-50-2) treatment on the homeostasis of the levocarnitine (L-carnitine) moiety was investigated in Sprague-Dawley rats. The diabetic status was ascertained by measuring blood glucose. L-carnitine (LC), total acid soluble L-carnitine (TC) and ALC were measured in serum, tissues and urine by radioenzymatic methods. Short-chain L-carnitine esters (SCLCE) were obtained by subtracting LC from TC. Serum concentration of L-carnitine moiety was decreased in diabetic when compared to normal rats; whereas ALC oral treatment (50 and 150 mg/kg p.o. for 4 weeks) in diabetic rats increased, dose-dependently, all the components of L-carnitine moiety, SCLCE and ALC being completely restored. In the liverof diabetic rats all the analytes proved to be higher than in normal rats, mainly LC and TC. A similar trend was observed in skeletal muscle, at least with LC and TC, whereas SCLCE and ALC were not affected. The treatment with ALC increased the liver concentration of all the analytes in a dose-related way whereas in skeletal muscle only LC and TC showed an increase with the highest dose of ALC. Myocardium and kidneys showed a decrease of all the analytes in diabetes; the treatment with ALC normalized the situation in kidneys, in a dose-related way, but not in the myocardium. Urinary excretion and renal clearance of L-carnitine moiety increased in diabetes; an additional dose-related increase was observed with the ALC treatment.

Acetyl-L-carnitine prevents substance P loss in the sciatic nerve and lumbar spinal cord of diabetic animals.

Di Giulio AM, Gorio A, Bertelli A, Mantegazza P, Ferraris L, Ramacci MT
Department of Medical Pharmacology, University of Milan, Italy.
Int J Clin Pharmacol Res 1992;12(5-6):243-6

Diabetic neuropathy is a disease of peripheral nerves, characterized by axonal atrophy and degeneration that might be preceded by a marked impairment of axonal transport and by a reduced conduction velocity. Sensory nerves are particularly susceptible to diabetes. In the present report it is shown that experimental diabetes in rats causes a significant reduction of the content of the pain-related neuropeptide substance P insciatic nerve and lumbar spinal cord. Such a loss of substance P is fully prevented by acetyl-L-carnitine treatment. The neuroprotective pharmacological effect is selective and takes place without significant changes of hyperglycaemia and without modifications of the reduced rate of body growth typical of diabetic animals.

Altered neuroexcitability in experimental diabetic neuropathy: effect of acetyl-L-carnitine.

Malone JI, Lowitt S, Corsico N, Orfalian Z
University of South Florida, Tampa.
Int J Clin Pharmacol Res 1992;12(5-6):237-41

Sciatic nerve conduction velocity (NCV) is reduced in rats made hyperglycaemic with streptozotocin (STZ). This neurophysiologicaldys function has been associated with increased nerve sorbitol and reduced nerve inositol. Treatment of STZ diabetic rats with aldose reductase inhibitors (ARIs) which reduce sorbitol and increase inositol in the nerve results in normalization of NCVs. Male Wistar rats were made diabetic with 50 mg/kg of streptozotocin given intraperitoneally. Those animals with blood glucose > 300 mg/dl two weeks later were included in this study. The STZ-diabetic rats were treated with either the ARI sorbinil (40 mg/kg per day), or acetyl-L-carnitine (ALC) (300 mg/kg per day) or sterile 0.15% aqueous NaCl for 16 weeks after 4 or 8 weeks of untreated hyperglycaemia. A control group of non-diabetic rats received no treatment during the interval. Sciatic-nerve sorbitol was elevated (1.08 +/- 0.13 nanomol/mg wet weight vs. 0.19 +/- 0.03 nm/mg wet weight) and inositol was reduced (1.21+/- 0.12 nm/mg ww vs. 2.02 +/- 0.08 nm/mg ww) in the STZ diabetic rats, which were untreated for 4 weeks. Treatment with sorbinil was associated with normalization of the tissue sorbitol (0.10 +/- 0.05 nm/mg ww), while ALC treatment also significantly reduced the nerve sorbitol but only to a level (0.34 +/- 0.08 nm/mg ww) more elevated than the normal level. The nerves of STZ animals treated with sorbinil or ALC had inositol levels no different from untreated diabetic rats. Thus, hyperglycaemic animals treated with either ALC or sorbinil had similar improvements in NCVs as the diabetic, even though the effect on nerve sorbitol was different and nerve inositol was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

[The action of carnitine-series preparations in experimental alloxan diabetes mellitus]

Kim EK, Trevisani C, Trevisani M
Eksp Klin Farmakol 1992 Jul-Aug;55(4):35-6

The study was undertaken to examine the effects of l-carnitine and acetyl-l-carnitine in rats and mice with experimental alloxan diabetes. The findings suggest that acetyl-l-carnitine is more effective against diabetes in increasing glucose tolerance, restoring the impaired response of glucagon to glucose, showing glycogen-sparing action than is l-carnitine.

Aminoguanidine and diabetic neuropathy

Monnier VM
Institute of Pathology, Case Western Reserve University, Cleveland, OH, USA.
Eur J Endocrinol 1996 Apr;134(4):398-400

No abstract.

Evaluation of the mechanism of endothelial dysfunction in the genetically-diabetic BB rat.

Pieper GM, Moore-Hilton G, Roza AM
Department of Transplant Surgery, Medical College of Wisconsin, Froedtert Memorial Lutheran Hospital, Milwaukee, 53226 USA.
Life Sci 1996;58(9):PL147-52

Endothelial dysfunction is known to occur in chemically-induced animal models of diabetes. The BB diabetic rat is a genetic diabetes-prone model which more closely resembles Type I diabetes mellitus. In this study, we examined the role of superoxide anion radical and cyclooxygenase activity on endothelial dysfunction in aorta of the spontaneous diabetic BB rat.Vascular endothelial function was studied in vitro in aortic rings from 8-wk diabetic rats and age-matched nondiabetic littermates. There was no alteration in reactivity to norepinephrine as a result of diabetes. Relaxation to acetylcholine (but not nitroglycerin) was impaired in diabetic rings. Relaxation to acetylcholine was abolished by 100 micro ML-nitroarginine but unaltered by an equimolar concentration of aminoguanidine (an inducible nitric oxide synthase inhibitor) in both control and diabetic rings. Incubation with 10 microM indomethacin did not alter relaxation to acetylcholine in either control or diabetic rings. In contrast, addition of 20 U/ml superoxide dismutase enhanced relaxation to acetylcholine in diabetic rings but had no effect on relaxation to acetylcholine in control rings. Thus, nitric oxide-mediated, endothelium-dependent relaxation is diminished in aortic rings of the genetic diabetic BB rat. Furthermore, superoxide anion radicals but not cyclooxygenase products play an important role in endothelial dysfunction in this genetic diabetic model.

Effect of aminoguanidine on the frequency of neuroaxonal dystrophy in the superior mesenteric sympathetic autonomic ganglia of rats with streptozocin-induced diabetes.

Schmidt RE, Dorsey DA, Beaudet LN, Reiser KM, Williamson JR, Tilton RG
Department of Pathology, Washington University of Medicine, St. Louis, Missouri 63110, USA.
Diabetes 1996 Mar;45(3):284-90

Aminoguanidine, which prevents formation of advanced glycation end products and is a relatively selective potent inhibitor of the inducible (versus constitutive) isoform(s) of nitric oxide synthase, has been reported to ameliorate structural and functional abnormalities in peripheral somatic nerves in rats with streptozocin (STZ)-induced diabetes. In the present studies, the effects of aminoguanidine treatment on ultrastructural changes in the autonomic nervous system of rats with STZ-induced diabetes were examined. The frequency of neuroaxonal dystrophy, the neuropathological hallmark of sympathetic autonomic neuropathy in diabetic rats, increased 9- to 11-fold in the superior mesenteric ganglia of 7- and 10-month STZ-diabetic rats compared with that in age-matched controls. Administration of aminoguanidine continuously from the time of induction of diabetes at a dose equal to or in excess of that providing a salutary effect in the diabetic somatic peripheral nervous system did not alter the severity of diabetes as assessed by plasma glucose level, 24-hurine volume, and levels of glycated hemoglobin. Chronic aminoguanidine therapy did not diminish the frequency or affect the ultrastructural appearance of neuroaxonal dystrophy in diabetic or age-matched control rat sympathetic ganglia after 7 or 10 months of continuous administration. Our findings (under these experimental conditions) do not support a role for aminoguanidine-sensitive processes in the development of sympathetic neuroaxonal dystrophy in diabetic rats. Glycation-linked aminoguanidine-insensitive processes, however, such as the formation of early glucose adducts (Schiff bases and Amadori products) withintra cellular and/or extracellular proteins and amine-containing lipids, superoxide anion generation during subsequent autoxidation of these glucoseadducts, and non-glycative processes, remain potential pathogenetic mechanisms for diabetic autonomic neuropathy.

[The relation between the changes of width and anionic sites of glomerular basement membrane and transferrinuria in rats]

Chen Y, Qian Y
Department of Endocrine, First Hospital, Beijing Medical University.
Chung Hua I Hsueh Tsa Chih 1995 Sep;75(9):537-9, 574

The changes of width and anionic sites of glomerular basement membrane (GBM) are considered early changes of diabetic nephropathy. Recent work suggests that the normal barrier to the penetration of renal glomerular basement membrane by anionic plasma proteins may depend in part on the existence of negatively charged sites within the membrane. We evaluated the relationship between the change of width, anionic sites of GBM and transferrinuria in diabetic rats and normal controls in 1, 3, 6 months after administration by STZ. Diabetic rats revealed a thicken GBM(0.40-0.44 microns) and reduced anionic sites (16-12/1000nm GBM length) compared with control rats (0.22 microns, 20-22/1000 nm GBM lenth). Transferrinuria was also significantly greater in diabetic rats than normals (P < 0.01). The changes in anionic sites and transferrinuria represented defect of GBM charge barrier in early phase of diabetic nephropathy. Aminoguanidine attenuated the rise in transferrinuria and prevented GBM thickness and loss of anionie sites.

Increased endocytosis in retinal vascular endothelial cells grown in high glucose medium is modulated by inhibitors of nonenzymatic glycosylation.

Stitt AW, Chakravarthy U, Archer DB, Gardiner TA
Department of Ophthalmology, Queen's University of Belfast, Northern Ireland.
Diabetologia 1995 Nov;38(11):1271-5

We sought to determine if hyperglycaemia is responsible for increased retinal vascular endothelial-cell (RVEC) endocytosis in diabetes and to assess the role of nonenzymatic glycosylation in mediation of this novel endothelial-cell pathology. RVECs were propagated in media containing either 5 or 25 mmol/l glucose for up to 10 days after which they were exposed to the protein tracer horseradish peroxidase for 30 min. The level of RVEC endocytosis was quantified in intact cell monolayers by electron microscopic stereology, and in cell lysates by a simple spectrophotometric method. The effect of the nonenzymatic glycosylation inhibitors, aminoguanidine and D-lysine, on high-glucose medium induced changes in RVEC endocytosis was tested by inclusion of these agents in the culture medium. RVECs exposed to 25 mmol/l glucose showed a stepwise increase in endocytosis of horseradish peroxidase culminating in a two- to threefold increase after 10 days. Endocytosis returned to normal levels after afurther 10 days in 5 mmol/l glucose medium. The increase in RVEC endocytosis was markedly reduced, but not completely normalised, by aminoguanidine and D-lysine. Exposure of cultured RVECs to 25 mmol/l glucose causes an increase in endocytosis of similar magnitude to that experienced by RVEC in early diabetes, and implicates hyperglycaemia in the latter situation. A significant component of the increase in RVEC endocytosis appears to be mediated by nonenzymatic glycosylation.

In vitro advanced glycation end product formation in rat tail tendon fibers: influence of aminoguanidine.

Troncoso IA, Esteban MM, Ruiz MA, Florez L, Barneo L
Functional Biology Department, University of Oviedo, Spain.
Transplant Proc 1995 Dec;27(6):3345-6

No abstract.

Yorek MA, Conner CE, Spanheimer RG
Department of Internal Medicine, Veterans Affairs Medical Center, Iowa City, IA 52246, USA.
J Cell Physiol 1995 Dec;165(3):658-66

L-fucose is a monosaccharide which is present in low concentrations in normal serum but is increased in diabetes, cancer, and inflammatory diseases. The contribution that abnormal L-fucose levels make to the progression of these disorders is unknown. In a previous study we showed that increased L-fucose concentration reduced proliferation and proteoglycan production by cultured cerebral microvessel endothelial cells. In the present study we show that exposing cerebral microvessel endothelial cells for 2 weeks to medium containing an increased concentration of L-fucose causes a significant decrease in collagen and to a lesser extent noncollagen protein production. The effect of L-fucose on collagen and noncollagen protein production is concentration-dependent: 1 mM L-fucose causes a significant decrease in collagen production but has no effect on noncollagen protein production; a 5 mM L-fucose concentration causes a maximum decrease in both collagen and noncollagen protein production. This defect is unrelated to the reduction in myo-inositol uptake caused by L-fucose and is not prevented by aminoguanidine. Collagen production can be improved by restoring L-fucose-conditioned cells to normal medium. Culturing cells for 2 weeks in medium containing 10 mM L-fucose resulted in a 50% decrease in collagen production, which was restored to 75% of control after cells were transferred to normal medium for 7 days. In contrast, noncollagen protein production was totally restored after 3 days in normal medium. Increasing levels of L-fucose in serum of rats also resulted in a decrease in collagen production. Collagenase digestible in corporation of L-[2,3,4,5-3H]proline into protein of the articular cartilage from rats fed a diet containing 20% L-fucose for 3 weeks was reduced by about 40%compared to rats fed a normal diet. The decrease in collagen production in L-fucose fed rats was less than the reduction that occurred in streptozotocin-induced diabetic rats. These data suggest that changes in L-fucose concentration itself may be a factor in the regulation of collagen production.

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