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LE Magazine October 1999

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Featured:
Monitoring Homocysteine Levels
CLA and Prostate Cancer
Care For Arthritis
Indole3C: The Natural Antioxidant


Arterial occlusive disease
Homocysteine and arterial occlusive disease: a concise review
Cardiologia 1999 Apr;44(4):341-5

Many cross-sectional and prospective studies have shown that raised serum/plasma levels of total homocysteine increase the risk of coronary, cerebral, and peripheral artery disease. The risk associated with hyperhomocysteinemia appears to be concentration-dependent and not attributable to traditional risk factors. The odds ratio for ischemic heart disease has been estimated to be 1.4 for every 5 mumol/l increase of total plasma homocysteine. Median fasting total plasma homocysteine in adult males is approximately 10 mumol/l. Mild hyperhomocysteinemia is estimated to occur in 5-10% of the general population. Plasma concentrations are increased as a result of age, male gender, impaired renal function, low vitamin B intake, and genetically-determined defects of the enzymes involved in homocysteine metabolism. Folate supplements can reduce total homocysteine levels by approximately 25%. Studies in vitro and in vivo indicate that homocysteine can impair endothelial function. Despite increasing recognition of hyperhomocysteinemia as a risk factor for arterial occlusive disease, irrefutable proof that mild hyperhomocysteinemia contributes directly to the pathogenesis of atherothrombosis will come if interventions to lower total homocysteine reduce cardiovascular events. Family studies may also provide evidence of causality if genetic causes of hyperhomocysteinemia are found to segregate with disease.


Cardiovascular disease in the elderly
Homocysteine and short-term risk of myocardial infarction and stroke in the elderly: the Rotterdam Study
Arch Intern Med 1999 Jan 11;159(1):38-44

BACKGROUND: Elevated homocysteine level increases vascular disease risk. Most data are based on subjects younger than 60 years; data for the elderly are more limited. We examined the relationship of homocysteine level to incident myocardial infarction and stroke among older subjects in a nested case-control study. METHODS: Subjects were participants in the Rotterdam Study, a cohort study among 7983 subjects residing in the Ommoord district of Rotterdam, the Netherlands. Baseline examinations were performed from March 1, 1990, to July 31, 1993. The analysis is restricted to myocardial infarction and stroke that occurred before December 31, 1994. One hundred four patients with a myocardial infarction and 120 with a stroke were identified with complete data. Control subjects consisted of a sample of 533 subjects drawn from the study base, free of myocardial infarction and stroke. Nonfasting total homocysteine levels were measured. RESULTS: Results were adjusted for age and sex. The risk of stroke and myocardial infarction increased directly with total homocysteine. The linear coefficient suggested a risk increase by 6% to 7% for every 1-micromol/L increase in total homocysteine. The risk by quintiles of total homocysteine level was significantly increased only in the group with levels above 18.6 micromol/L (upper quintile): odds ratios were 2.43 (95% confidence interval, 1.11-5.35) for myocardial infarction and 2.53 (95% confidence interval, 1.19-5.35) for stroke. Associations were more pronounced among those with hypertension. CONCLUSIONS: The present study, based on a relatively short follow-up period, provides evidence that among elderly subjects an elevated homocysteine level is associated with an increased risk of cardiovascular disease.


Vitamin supplements and homocysteine
Vitamin intake: a possible determinant of plasma homocysteine among middle-aged adults
Ann Epidemiol 1997 May;7(4):285-93

PURPOSE: Many epidemiologic studies have identified elevated plasma homocyst(e)ine as a risk factor for atherosclerosis and thromboembolic disease. To examined the relationship between vitamin intakes and plasma homocyst(e)ine, we analyzed dietary intake data from a case-control study of 322 middle-aged individuals with atherosclerosis in the carotid artery and 318 control subjects without evidence of this disease. METHODS: All of these individuals were selected from a probability sample of 15,800 men and women who participated in the Atherosclerosis Risk in Communities (ARIC) Study. RESULTS: Plasma homocyst(e)ine was inversely associated with intakes of folate, vitamin B6, and vitamin B12 (controls only for this vitamin)--the three key vitamins in homocyst(e)ine metabolism. Among nonusers of vitamin supplement products, on average each tertile increase in intake of these vitamins was associated with 0.4 to 0.7 mumol/L decrease in plasma homocyst(e)ine. An inverse association of plasma homocyst(e)ine was also found with thiamin, riboflavin, calcium, phosphorus, and iron. Methionine and protein intake did not show any significant association with plasma homocyst(e)ine. CONCLUSIONS: In almost all analyses, cases and controls showed similar associations between dietary variables and plasma homocyst(e)ine. Plasma homocyst(e)ine among users of vitamin supplement products was 1.5 mumol/L lower than that among nonusers. Further studies to examine possible causal relationships among vitamin intake, plasma homocyst(e)ine, and cardiovascular disease are needed.


Folate's impact on homocysteine
Dietary intake pattern relates to plasma folate and homocysteine concentrations in the Framingham Heart Study
J Nutr 1996 Dec;126(12):3025-31

We examined the relationship between intake of food group (and supplement) sources of folate and plasma folate and homocysteine concentrations among 885 elderly subjects in the Framingham Heart Study. Dietary data were collected by food-frequency questionnaire, and blood samples analyzed for folate and homocysteine concentrations. Top contributors to total folate intake were ranked. Mean folate intake, plasma folate and homocysteine concentrations were estimated for users vs. non-users of supplements, and key foods--those which both contribute to total folate intake and are known to be good sources of folate--and examined statistically with adjustment for age, gender and total energy intake. Plasma folate and homocysteine concentrations were also determined by quintile of intake frequency for breakfast cereals and for fruits and vegetables. Plasma folate was significantly greater and homocysteine lower in women than in men. Despite somewhat greater plasma folate concentrations with age, homocysteine was significantly higher in those over 80 y of age than in younger subjects. Major contributors to folate intake were cold breakfast cereals (13.3%), multivitamins (12.8%) and orange juice (12.4%). Users of supplements, breakfast cereals, or green leafy vegetables had significantly greater plasma folate and lower homocysteine levels than non-users. Plasma folate concentration was also greater in those who drank orange juice. We identified clear dose-response relationships for both plasma folate and homocysteine with increased quintile of breakfast cereal and of fruit and vegetable use. Frequent consumption of these foods is associated with higher folate and lower homocysteine concentrations.


CLA's effects on prostatic cancer
Opposite effects of linoleic acid and conjugated linoleic acid on human prostatic cancer in SCID mice
CLA's effects on prostatic cancer

Opposite effects of linoleic acid and conjugated linoleic acid on human prostatic cancer in SCID miceAnticancer Res 1998 May-Jun;18(3A):1429-34 The relationship between dietary fat intake (level and type) and cancer development is a matter of concern in Western society. The purpose of this study was to determine the effect of three different diets on the local growth and metastatic properties of DU-145 human prostatic carcinoma cells in severe combined immunodeficient (SCID) mice. Animals were fed a standard diet or diets supplemented with 1% LA or 1% CLA for 2 weeks prior to subcutaneous (s.c.) inoculation of DU-145 cells and throughout the study (total of 14 weeks). Mice receiving LA-supplemented diet displayed significantly higher body weight, lower food intake and increased local tumor load as compared to the other two groups of mice. Mice fed the CLA-supplemented diet displayed not only smaller local tumors than the regular diet-fed group, but also a drastic reduction in lung metastases. These results support the view that dietary polyunsaturated fatty acids may influence the prognosis of prostatic cancer patients, thus opening the possibility of new therapeutic options.


Antirheumatic agents
Nuclear factor kappaB (NF-kappaB) pathway as a therapeutic target in rheumatoid arthritis
J Korean Med Sci 1999 Jun;14(3):231-8

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by persistent joint swelling and progressive destruction of cartilage and bone. Current RA treatments are largely empirical in origin and their precise mechanism of action is uncertain. Increasing evidence shows that chronic inflammatory diseases such as RA are caused by prolonged production of proinflammatory cytokines including tumor necrosis factor (TNF) and interleukin 1 (IL-1). The nuclear factor kappaB (NF-kappaB) plays an essential role in transcriptional activation of TNF and IL-1. NF-kappaB is induced by many stimuli including TNF and IL-1, forming a positive regulatory cycle that may amplify and maintain RA disease process. NF-kappaB and enzymes involved in its activation can be a target for anti-inflammatory treatment. Aspirin and sodium salicylate inhibit activation of NF-KB by blocking IkappaB kinase, a key enzyme in NF-kappaB activation. Glucocorticoids suppress expression of inflammatory genes by binding glucocorticoid receptor with NF-kappaB, and increasing expression of inhibitory protein of NF-kappaB, IkappaBalpha. Sulfasalazine and gold compounds also inhibit NF-kappaB activation. Continuing advances in our understanding of action mechanism of antirheumatic agents will benefit the future development of RA regimens with greater efficacy and less toxicity.


Cytokine expression and inflammatory
disease

Role of cytokines in rheumatoid arthritis
Annu Rev Immunol 1996;14:397-440

Analysis of cytokine mRNA and protein in rheumatoid arthritis tissue revealed that many proinflammatory cytokines such as TNF alpha, IL-1, IL-6, GM-CSF, and chemokines such as IL-8 are abundant in all patients regardless of therapy. This is compensated to some degree by the increased production of anti-inflammatory cytokines such as IL-10 and TGF beta and cytokine inhibitors such as IL-1ra and soluble TNF-R. However, this upregulation in homeostatic regulatory mechanisms is not sufficient as these are unable to neutralize all the TNF alpha and IL-1 produced. In rheumatoid joint cell cultures that spontaneously produce IL-1, TNF alpha was the major dominant regulator of IL-1. Subsequently, other proinflammatory cytokines were also inhibited if TNF alpha was neutralized, leading to the new concept that the proinflammatory cytokines were linked in a network with TNF alpha at its apex. This led to the hypothesis that TNF alpha was of major importance in rheumatoid arthritis and was a therapeutic target. This hypothesis has been successfully tested in animal models, of, for example, collagen-induced arthritis, and these studies have provided the rationale for clinical trials of anti-TNF alpha therapy in patients with long-standing rheumatoid arthritis. Several clinical trials using a chimeric anti-TNF alpha antibody have shown marked clinical benefit, verifying the hypothesis that TNF alpha is of major importance in rheumatoid arthritis. Retreatment studies have also shown benefit in repeated relapses, indicating that the disease remains TNF alpha dependent. Overall these studies demonstrate that analysis of cytokine expression and regulation may yield effective therapeutic targets in inflammatory disease.


N-3 fats and RA
Dietary n-3 fatty acids and therapy for rheumatoid arthritis
Semin Arthritis Rheum 1997 Oct;27(2):85-97

OBJECTIVE: To examine the potential for dietary n-3 fats to be component of therapy for rheumatoid arthritis (RA). METHODS: Studies of encapsulated fish oil use in RA were reviewed and critiqued, and possible biochemical mechanisms for fish oil effects were examined. The potential for use of n-3 fats was evaluated within a dietary framework rather than a quasi-pharmaceutical framework. RESULTS: There is consistent evidence from double-blind, placebo-controlled clinical trials that dietary n-3 fats, supplied as fish oil, can have beneficial effects in RA. The beneficial effects appear modest, but their size and extent may have been moderated by common trial design factors such as high n-6 polyunsaturated fat diets and concurrent antiinflammatory drug use. Mechanisms for the clinical effects of n-3 fats in RA may involve their ability to suppress production of inflammatory mediators, including n-6 eicosanoids and proinflammatory cytokines. Suppression of n-6 eicosanoid and cytokine production will be possible using foodstuffs that are rich in n-3 fats and poor in n-6 fats. CONCLUSIONS: There are many overlapping biochemical effects of n-3 fatty acids and antiinflammatory pharmaceuticals that could explain the clinical actions of n-3 fats in RA. They suggest that there is the potential for complementarity between drug therapy and dietary choices that increase intake of n-3 fats and decrease intake of n-6 fats. In particular, there is the potential for drug-sparing effects. Future studies with n-3 fats in RA need to address the fat composition of the background diet and the issue of concurrent drug use.


Suppressive effect of I3C
Chemoprevention of aflatoxin B1-induced carcinogenesis by indole-3-carbinol in rat liver-predicting the outcome using early biomarkers
Carcinogenesis 1998 Oct;19(10):1829-36

Indole-3-carbinol (I3C) was examined for its ability to inhibit aflatoxin B1 (AFB1)-induced hepatocarcinogenesis in male Fischer rats when administered either before or after the carcinogen. After 13 weeks, animals pretreated with I3C (0.5% in the diet) for 2 weeks prior to administration of AFB1 and with continuing treatment during exposure to the carcinogen were protected from development of preneoplastic lesions, as determined by the classical markers gamma-glutamyltranspeptidase (GGT) and glutathione S-transferase (GST) P. In animals receiving AFB1 for 6 weeks before treatment with I3C, there was no obvious protective effect at 13 weeks compared with animals receiving only AFB1. Using cytokeratin 18 expression as a marker, animals fed AFB1 alone had a small number of positive foci at 13 weeks. However, no cytokeratin-positive foci were visible in the majority of livers from either group receiving I3C in combination with AFB1 and after 43 weeks all animals in these groups were protected from liver tumour formation. These results suggest that expression of cytokeratin 18, a later phenotypic change in foci than induction of GST-P and GGT, correlates more closely with tumour outcome in this model. I3C appeared to retard progression of AFB1-induced carcinogenesis at both the initiation and promotion stages. Continuous treatment with I3C for 13 weeks caused significant induction of CYP1A1, 1A2, 3A and 2B1/2, GST Yc2, aflatoxin B1 aldehyde reductase and quinone reductase. Such alteration of the drug metabolizing capacity of the liver by I3C contributes to blocking of initiation, while the observed inhibition of ornithine decarboxylase, a rate limiting enzyme in polyamine biosynthesis, and of tyrosine kinase activity may contribute to the suppressive effect of I3C.


Chemoprevention of breast cancer
Chemoprevention of chemically-induced mammary carcinogenesis by indole-3-carbinol
Anticancer Res 1995 May-Jun;15(3):709-16

Indole-3-carbinol, a component of cruciferous vegetables, was evaluated for it efficacy in the prevention of chemically-induced mammary tumors using three different protocols. Because this compound was unstable, it was administered by gavage rather than in the diet. A preliminary dose range study revealed that dose levels of 100 and 50 mg/day, 5x/week, were not toxic to female Sprague-Dawley rats. Initial studies in the DMBA model showed that administering indole-3-carbinol during the initiation and promotion phases were highly effective chemopreventive methods (91-96% reduction in cancer multiplicity). Subsequent studies showed that the administration of indole-3-carbinol only during the initiation phase (7 days prior to until 7 days post DMBA) was also highly effective as a chemopreventive agent. Determination of enzyme levels in the livers of animals treated long-term with indole-3-carbinol showed high levels of induction of various phase I and phase II drug metabolizing enzymes. Finally, indole-3-carbinol when administered both prior to and after MNU (a direct acting carcinogen) caused a significant decrease (65%) in mammary tumor multiplicity. These results support previous studies that indole-3-carbinol can prevent mammary carcinogenesis by direct and indirect acting carcinogens. Therefore, indole-3-carbinol might be a good candidate for chemoprevention of breast cancer in women.


Lower mammary tumor incidence
Effects of dietary indole-3-carbinol on estradiol metabolism and spontaneous mammary tumors in mice
Carcinogenesis 1991 Sep;12(9):1571-4

Indole-3-carbinol (I3C) is a potent inducer of cytochrome P450 enzymes in many species, including humans. We therefore studied alterations in the cytochrome P450-dependent metabolism of estradiol in different strains of mice consuming I3C in semisynthetic powdered diets at doses ranging from 250 to 5000 p.p.m. (34-700 mg/kg/day) for different periods of time. In short-term metabolic studies (3 weeks), wet liver weight increased in SW and C3H/OuJ mice in a dose-responsive manner. Dietary I3C increased the cytochrome P450 content measured in hepatic microsomes, as well as the extent of estradiol 2-hydroxylation, up to 5-fold. In a long-term feeding experiment (8 months), female C3H/OuJ mice consumed synthetic diets containing I3C at 0, 500 or 2000 p.p.m. Mammary tumor incidence and multiplicity were significantly lower at both doses of I3C, and tumor latency was prolonged in the high-dose group. We conclude that I3C is an inducer of hepatic P450-dependent estrogen metabolism in mice, and that it is chemopreventive in the C3H/OuJ mouse mammary tumor model. This protective effect may be mediated in part by the increased 2-hydroxylation and consequent inactivation of endogenous estrogens.


Reducing cancer risk
Altered estrogen metabolism and excretion in humans following consumption of indole-3-carbinol
Nutr Cancer 1991;16(1):59-66

Research studies have demonstrated a strong association between estrogen metabolism and the incidence of breast cancer, and we have therefore sought pharmacological means of favorably altering both metabolism and subsequent risk. Indole-3-carbinol (I3C), obtained from cruciferous vegetables (e.g., cabbage, broccoli, etc.), is a known inducer of oxidative P-450 metabolism in animals. We investigated the effects in humans of short-term oral exposure to this compound (6-7 mg/kg/day over 7 days). We used an in vivo radiometric test, which provided a highly specific and reproducible measure of estradiol 2-hydroxylation before and after exposure to I3C. In a group of 12 healthy volunteers, the average extent of reaction increased by approximately 50% during this short exposure (p less than 0.01), affecting men and women equally. We also measured the urinary excretion of two key estrogen metabolites, 2-hydroxyestrone (2OHE1) and estriol (E3). We found that the excretion of 2OHE1 relative to that of E3 was significantly increased by I3C, further confirming the ongoing induction of 2-hydroxylation. These results indicate that I3C predictably alters endogenous estrogen metabolism toward increased catechol estrogen production and may thereby provide a novel "dietary" means for reducing cancer risk.


I3C, a natural antioxidant
Intervention in free radical mediated hepatotoxicity and lipid peroxidation by indole-3-carbinol
Biochem Pharmacol 1988 Jan 15;37(2):333-8

The cytoprotective effect of the natural dietary constituent indole-3-carbinol (I-3-C) on carbon tetrachloride (CCl4) mediated hepatotoxicity in mice was examined. I-3-C pretreatment by gavage 1 hr prior to intraperitoneal injection of CCl4 produced a 63% decrease in CCl4-mediated centrolobular necrosis and a related 60% decrease in plasma alanine aminotransferase activity (a marker of liver necrosis). Since the toxicological effects of CCl4 are mediated by radical species generated during reductive metabolism by cytochrome P-450, we examined the potential ability of I-3-C to scavenge reactive radicals. Three systems were used to evaluate the ability of I-3-C to intervene in free radical mediated lipid peroxidation. These systems consisted of the following: (1) phospholipid dissolved in chlorobenzene, with peroxidation initiated by the thermal and photo decomposition of azobisisobutyronitrile (AIBN); (2) sonicated phospholipid vesicles in phosphate buffer (pH 7.4), with peroxidation initiated by ferrous/ascorbate; and (3) mouse liver microsomes containing an NADPH-regenerating system, with peroxidation initiated with CCl4. Lipid peroxidation was measured in these three systems as thiobarbiturate-reacting material. In the AIBN and ferrous/ascorbate systems, I-3-C inhibited lipid peroxidation, with greater inhibition under conditions of low rates of free radical generation. I-3-C was not as effective an antioxidant as butylated hydroxytoluene (BHT) or tocopherol, but it inhibited peroxidation in a dose-response manner. I-3-C was most effective as a radical scavenger in the microsomal CCl4-initiated system by inhibiting lipid peroxidation in a dose-dependent fashion, with 50% inhibition at 35-40 microM I-3-C. This concentration is about one-third of the concentration of I-3-C achieved in liver after treatment of mice by gavage with 50 mg I-3-C/kg body weight. These data suggest that I-3-C may be a natural antioxidant in the human diet and, as such, may intervene in toxicological or carcinogenic processes that are mediated by radical mechanisms.



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