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Background: Elevated blood homocysteine is a risk factor for cardiovascular disease. A 5-Rmol/L increase is associated with an approximately 70% increase in relative risk of cardiovascular disease in adults. For patients with established risk factors, this risk is likely even greater. Objective: Effects of increased dietary folate and recommended intakes of vitamins B-12 and B-6 on serum total homocysteine (tHcy) were assessed in individuals at high risk of cardiovascular disease. Design: This trial was conducted at 10 medical research centers in the United States and Canada and included 491 adults with hypertension, dyslipidemia, type 2 diabetes, or a combination thereof. Participants were randomly assigned to follow a prepared meal plan (PMP; n = 244) or a self-selected diet (SSD; ii = 247) for 10 wk, which were matched for macronutrient content. The PMP was fortified to provide >/= 100% of the recommended dietary allowances for 23 micronutrients, including folate. Results: Mean folate intakes at 10 wk were 601 +/= 143 mu g/d with the PMP and 270 +/= 107 mu g/d with the SSD. With the PMP, serum tHcy concentrations fell from 10.8 +/= 5.8 to 9.3 +/= 4.9 mu mol/L (P < 0.0001) between weeks 0 and 10 and the change was associated with increased intakes of folate, vitamin B-12, and vitamin B-6 and with increased serum and red blood cell folate and serum vitamin B-12 concentrations. tHcy concentrations did not change significantly with the SSD. Conclusions: The PMP resulted in increased intakes and serum concentrations of folate and vitamin B-12. These changes were associated with reduced serum tHcy concentrations in persons at high risk of cardiovascular disease. Copyright (c) 1999 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]

BACKGROUND: Premenopausal black women have a greater rate of coronary artery disease (CAD) than do premenopausal white women. Plasma total homocysteine concentrations, a risk factor for CAD, have not been reported in premenopausal black women. OBJECTIVE: The purpose of this study was to compare plasma total homocysteine, folate, and vitamin B-12 concentrations in premenopausal black and white women. DESIGN: Eighty-nine black and 90 white, healthy, premenopausal women living in Portland, OR, were recruited. Dietary histories were obtained by using the Diet Habit Survey, a 40-item eating-behavior questionnaire. Plasma concentrations of total homocysteine, folate, and vitamin B-12 were measured. RESULTS: Black women had higher plasma total homocysteine (8.32 compared with 7.60 micromol/L;P = 0. 013), lower plasma folate (6.62 compared with 9.88 nmol/L;P < 0. 0001), and higher vitamin B-12 (355 compared with 283 pmol/L;P < 0. 001) concentrations than white women. White women had a greater rate of daily multivitamin supplement use (42.4% compared with 24.7%;P = 0.019) and ate more ready-to-eat cereal than did black women. After adjustment for multivitamin use and intake of ready-to-eat cereal, plasma total homocysteine concentrations did not differ significantly, but plasma folate remained significantly lower in the black women. None of the black women but 12.3% of the white women (P = 0.013) were homozygous for the cytosine to thymidine mutation at nucleotide 677 in the methylenetetrahydrofolate reductase gene. CONCLUSIONS: Black women had higher plasma total homocysteine and lower plasma folate concentrations than white women, largely because of lifestyle factors, which may contribute to the greater rate of CAD in premenopausal black than in white women. Copyright (c) 1999 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]

Purpose: To determine whether homocyst(e)ine (H(e)) is related to hemostatic factors in a population-based sample without evidence of cardiovascular disease.Methods: A subsample of 660 participants--67 African-American women, 53 African-American men, 201 white women, and 339 white men--was selected from the Atherosclerosis Risk in Communities Study baseline cohort. This was based on carotid intimal-medial wall thickness above the 90th percentile or below the 75th percentile of the population distribution, assessed by B-mode ultrasonography. Unadjusted and multivariable-adjusted associations between fasting plasma H(e) and the hemostatic factors fibrinogen, factor VII:c, factor VIII:c, protein C antigen, hematocrit, platelet count, beta-thromboglobulin (beta-TG), tissue plasminogen activator (tPA), PAI-1, D-dimer, and lipoprotein[a] were examined.Results: Mean age-adjusted H(e) was positively, albeit weakly, correlated with beta-TG, tPA, hematocrit, D-dimer and PAI-1; inversely correlated with protein C; and was higher in smokers, men and African-Americans. In multivariable regression, beta-TG, tPA, and factor VII:c were positively associated with H(e), as well as age, black race, male sex, and current cigarette smoking.Conclusions: These cross-sectional data for a biracial group of middle-aged individuals suggest that H(e) levels falling below values consistent with homocyst(e)inemia are associated with several prothrombotic factors after adjustment for sociodemographic factors. If H(e) change is antecedent to altered hemostasis, FDA-mandated fortification of grain products with folic acid for prevention of fetal neural tube defects may lead to both reduced plasma H(e) levels and improved hemostatic profiles. [ABSTRACT FROM AUTHOR]

Premenopausal black women have a 2- to 3-fold greater rate of coronary heart disease (CHD) than premenopausal white women. The purpose of this study was to provide greater insight into the reasons for this difference, which are currently unclear. We compared CHD risk factors in 99 black and 100 white, healthy premenopausal women, aged 18 to 45 years, and of relatively advantaged socioeconomic status. Compared with white women, black women had a higher body mass index (32.0 +/- 9.2 vs 29.0 +/- 9.4 kg/m2, p = 0.021), and higher systolic (124 +/- 17 vs 115 +/- 14 mm Hg, p <0.0001) and diastolic (79 +/- 14 vs 75 +/- 11 mm Hg, p = 0.048) blood pressures. The mean plasma lipoprotein(a) concentration was markedly higher in the black women (40.2 +/- 31.3 mg/dl) than in the white women (19.2 +/- 23.7 mg/dl, p <0.0001). The plasma total homocysteine level was also higher in the black women (8.80 +/- 3.38 vs 7.81 +/- 2.58 micromol/L, p = 0.013). The black women, however, had lower plasma triglyceride levels (0.91 +/- 0.46 vs 1.22 +/- 0.60 mmol/L, p <0.0001), and a trend toward higher high-density lipoprotein (HDL) cholesterol levels (1.37 +/- 0.34 vs 1.29 +/- 0.31 mmol/L, p = 0.064) than the white women. Plasma total and low-density lipoprotein (LDL) cholesterol levels were similar, despite a greater consumption of saturated fat and cholesterol by the black women. Rates of cigarette smoking and alcohol intake were low and similar between the races. In summary, premenopausal black women had a higher mean body mass index, blood pressure, lipoprotein(a), and plasma total homocysteine level, and a greater consumption of saturated fat and cholesterol than white women. These differences in coronary risk factors may place the black women in our study at increased risk for CHD compared with the white women. [ABSTRACT FROM AUTHOR]

The present study was designed to examine the relationship between homocyst(e)ine (H[e]) levels and muscle mass. Two experimental groups each of 24 Caucasian males, one consisting of higher-muscle mass subjects (HMM) and the other of lower-muscle mass subjects (LMM) participated in this study. Muscle mass was estimated from 24-hour urine collections of creatinine (Crt). Muscle mass was 40.3 ± 15.9 kg in HMM and 37.2 ± 11.4 kg in LMM (P= 0.002). Mean plasma H(e) levels in HMM were 10.29 ± 2.9 nmol/mL, and in LMM were 10.02 ± 2.4 nmol/L (Not significant, [NS]). Urinary H(e) levels (UH[e]) were 9.95 ± 4.3 nmol/mL and 9.22 ± 2.9 nmol/mL for HMM and LMM, respectively (NS). Plasma H(e) levels correlated well with UH(e) (HMM: r= 0.58, P= 0.009; LMM: r= 0.66, P= 0.004). Muscle mass and was not correlated to either plasma H(e) or UH(e). However, in HMM trends were identified for body mass to be correlated with UH(e) (r= 0.39, P= 0.10) and UCrt (r= 0.41, P= 0.08). Surprisingly, in HMM plasma and UCrt were only weakly correlated (r= 0.44, P= 0.06). Our results do not support a causal relationship between the amount of muscle mass and H(e) levels in plasma or urine.

Background: We examined the relationship of maternal plasma concentrations of soluble vascular cell adhesion molecule-1 (sVCAM-1), a specific marker of endothelial dysfunction, and risk of preeclampsia. We also evaluated the relationship in the presence and absence of maternal hypertriglyceridemia and hyperhomocystein(e)mia., Methods: A total of 170 women with preeclampsia and 184 control subjects were included in this case-control study analysis. Maternal postdiagnosis plasma sVCAM-1 concentrations were determined using immunoassays. Total plasma homocysteine (tHcy) was measured using high-performance liquid chromatography with electrochemical detection procedures; and triglyceride concentrations were determined using standard enzymatic procedures. Logistic regression procedures were used to estimate odds ratios (OR) and 95% confidence intervals (CI) adjusted for confounders., Results: The relative risk of preeclampsia (as estimated by the OR) was increased 3.6-fold for women with sVCAM-1 concentrations >/=842 ng/mL compared with women who had lower concentrations (OR = 3.6; 95% CI 1.8 to 7.4). Of the three biological markers investigated, elevated sVCAM-1 concentrations was most strongly related to preeclampsia risk (OR = 4.6, 95% CI 1.6 to 13.5), followed by hyperhomocysten(e)mia (OR = 2.4, 95% CI 0.8 to 7.4) and hypertriglyceridemia (OR = 2.1, 95% CI 0.9 to 5.0). Compared with women who did not have any of the three risk factors, those with all three risk factors had an extremely high risk of preeclampsia (OR = 26.4; 95% CI 8.5 to 81.9)., Conclusions: These findings suggest that elevated sVCAM-1 concentrations are associated with an increased risk of preeclampsia. Our findings extend the literature by documenting progressively increased risk with increasing numbers of biological markers of dyslipidemia and endothelial dysfunction.

Hyperhomocyst(e)inemia (HH) is an established independent risk factor for coronary, cerebral and peripheral vascular diseases. Recent studies have indicated that certain cardiovascular risk factors, including diabetes and hypercholesterolemia, impair expression of vascular endothelial growth factor (VEGF) and endogenous angiogenesis. In this study, we investigate the impact of moderate HH on angiogenesis and VEGF pathway in a mouse model of hindlimb ischemia. Upon induction of unilateral hindlimb ischemia, endogenous angiogenesis, expression of VEGF, and phosphorylation of the VEGF receptor Flk-1 were evaluated in mice heterozygous for a deletion of the cystathionine beta-synthase gene (CBS) and compared with those observed in CBS+/+ mice. CBS+/- mice exhibit moderate HH, as demonstrated by measuring plasma total homocyst(e)ine (tHcy) levels, which were significantly higher in these animals compared with CBS+/+ mice (4.77 +/- 0.82 vs 2.10 +/- 0.28, p < 0.01). Twenty-eight days after induction of ischemia, hindlimb blood flow was significantly reduced in CBS+/- mice compared with CBS+/+ animals (0.49 +/- 0.03, n = 12 vs 0.71 +/- 0.09, n = 10; p < 0.05). In addition, there was a significant negative correlation between plasma homocyst(e)ine levels and the laser Doppler perfusion ratio in CBS+/- mice (p = 0.0087, r = -0.7171). While VEGF expression and Flk-1 phosphorylation were not impaired in the ischemic muscles of CBS+/- mice, phosphorylation of the endothelial cell survival factor Akt was significantly inhibited by homocyst(e)ine in a dose-dependent manner in human umbilical vein endothelial cell (HUVECs) in vitro. In conclusion, our findings demonstrate that endogenous angiogenesis is inversely related to plasma levels of homocyst(e)ine in genetically engineered, heterozygous mice with moderate HH. This impairment, however, is not dependent on reduced expression of VEGF or impaired phosphorylation of its receptor Flk-1. In contrast, our data suggest that impaired Akt phosphorylation mediates the impairment of angiogenesis associated with HH.

Context: In observational studies, elevated plasma total homocysteine levels have been positively associated with ischemic stroke risk. However the utility of homocysteine-lowering therapy to reduce that risk has not been confirmed by randomized trials., Objective: To determine whether high doses of folic acid, pyridoxine (vitamin B6), and cobalamin (vitamin B12), given to lower total homocysteine levels, reduce the risk of recurrent stroke over a 2-year period compared with low doses of these vitamins., Design: Double-blind randomized controlled trial (September 1996-May 2003)., Setting and Participants: 3680 adults with nondisabling cerebral infarction at 56 university-affiliated hospitals, community hospitals, private neurology practices, and Veterans Affairs medical centers across the United States, Canada, and Scotland., Interventions: All participants received best medical and surgical care plus a daily multivitamin containing the US Food and Drug Administration's reference daily intakes of other vitamins; patients were randomly assigned to receive once-daily doses of the high-dose formulation (n = 1827), containing 25 mg of pyridoxine, 0.4 mg of cobalamin, and 2.5 mg of folic acid; or the low-dose formulation (n = 1853), containing 200 microg of pyridoxine, 6 microg of cobalamin and 20 microg of folic acid., Main Outcome Measures: Recurrent cerebral infarction (primary outcome); coronary heart disease (CHD) events and death (secondary outcomes)., Results: Mean reduction of total homocysteine was 2 micromol/L greater in the high-dose group than in the low-dose group, but there was no treatment effect on any end point. The unadjusted risk ratio for any stroke, CHD event, or death was 1.0 (95% confidence interval [CI], 0.8-1.1), with chances of an event within 2 years of 18.0% in the high-dose group and 18.6% in the low-dose group. The risk of ischemic stroke within 2 years was 9.2% for the high-dose and 8.8% for the low-dose groups (risk ratio, 1.0; 95% CI, 0.8-1.3) (P =.80 by log-rank test of the primary hypothesis of difference in ischemic stroke between treatment groups). There was a persistent and graded association between baseline total homocysteine level and outcomes. A 3- micromol/L lower total homocysteine level was associated with a 10% lower risk of stroke (P =.05), a 26% lower risk of CHD events (P<.001), and a 16% lower risk of death (P =.001) in the low-dose group and a nonsignificantly lower risk in the high-dose group by 2% for stroke, 7% for CHD events, and 7% for death., Conclusions: In this trial, moderate reduction of total homocysteine after nondisabling cerebral infarction had no effect on vascular outcomes during the 2 years of follow-up. However, the consistent findings of an association of total homocysteine with vascular risk suggests that further exploration of the hypothesis is warranted and longer trials in different populations with elevated total homocysteine may be necessary.

Background: An elevated plasma total homocysteine (tHcy) level is associated with an increased risk of vascular disease. Some studies have shown associations between tHcy level and small-vessel disease of the brain on magnetic resonance imaging (MRI)., Design: In the Cardiovascular Health Study, 622 elderly participants without a history of transient ischemic attack or stroke had results for tHcy level and cranial MRI. We sought associations between tHcy level and MRI findings of ventricular grade, sulcal grade, white matter grade, and infarcts. We controlled for other factors, including levels of creatinine, folate, and vitamins B(6) and B(12) and methylenetetrahydrofolate reductase genotype., Results: After controlling for age and sex, tHcy level was not associated with the individual MRI findings. Further adjustments for other factors and other blood tests had little effect on these findings. The only significant finding was a linear trend across quintiles of tHcy level and a pattern of MRI findings combining infarcts and high white matter grade. The linear trend remained significant after controlling for other risk factors and atherosclerotic markers (top quintile vs bottom quintile odds ratio, 3.3; 95% confidence interval, 0.96-11.20; P =.04 for linear trend) but was slightly diminished after further controlling for creatinine, folate, and vitamins B(6) and B(12) (odds ratio, 3.2; 95% confidence interval, 0.81-13.10; P =.07 for linear trend)., Conclusion: We were unable to confirm the results of previous studies with respect to tHcy level and individual MRI findings, although an association was seen for an MRI pattern combining infarcts and high white matter grade.

Hyperhomocyst(e)inemia (HHcy) is a risk factor of endothelial dysfunction and preeclampsia. Soluble vascular cell adhesion molecule-1 (sVCAM-1), a specific marker of endothelial dysfunction, is elevated in preeclampsia. Few have assessed the joint contribution of these biomarkers in predicting preeclampsia. We assessed the extent to which HHcy and elevated sVCAM-1 are independently and jointly associated with preeclampsia. We conducted a case-control analysis of 100 preeclampsia cases and 100 controls to test our study hypothesis. Maternal plasma was collected before labor onset. Total plasma homocysteine (tHcy) was measured using high-performance liquid chromatography with electrochemical detection procedures. Plasma sVCAM-1 was determined using ELISA. Using the distribution of each analyte among controls, elevated tHcy was defined as plasma tHcy >6.6 micromol/l and elevated sVCAM-1 was defined as plasma concentrations >845 ng/ml (i.e., values above the median). Odds ratios (OR) and 95% confidence intervals (CIs) were calculated. Compared with women without elevated tHcy and without elevated sVCAM-1 (the referent group), those with elevated sVCAM-1 alone had a 4.1-fold increased risk of preeclampsia (95% CI 1.2-13.8). The OR for women with elevated tHcy alone was 2.2 (95% CI 0.6-7.9). The OR for women with elevated tHcy and sVCAM-1 was 13.2 (95% CI 4.1-42.2). Elevated tHcy and sVCAM-1 together were strongly associated with an increased risk of preeclampsia. Larger, prospective studies are needed to confirm these findings and to determine the extent to which elevated tHcy and sVCAM-1 together in early pregnancy are predictive of preeclampsia risk., (Copyright (c) 2004 S. Karger AG, Basel.)

Objectives: To explore plasma total homocysteine (tHcy) as a predictor of long-term prognosis after premature myocardial infarction (MI)., Design: Prospective cohort study., Settings: Akershus University Hospital., Subjects: A total of 247 patients (193 men and 54 women) in stable clinical phase after premature MI (males: first MI at age < or =55; females < or =60)., Main Outcome Measures: The primary end-point was total mortality and the secondary end-point was cardiac death. The third end-point was major cardiac events: a combination of cardiac death, MI and cardiac arrest., Results: After 10 years, 44 patients had died, 36 from cardiac causes. Major cardiac event occurred in 70 patients. The relative risk for death of all causes increased 1.43 (95% CI, 1.08-1.88) per tHcy quartile (P for trend = 0.01), and was only modestly reduced after adjustment for age, ejection fraction, total cholesterol, C-reactive protein, fibrinogen, smoking and hypertension to 1.37 (95% CI, 1.04-1.80) (P for trend = 0.03). Similar results were observed when cardiac death was used as the end-point, but we observed no association between tHcy and the end-point major cardiac event., Conclusions: Total homocysteine was an independent predictor of total and cardiac mortality in stable patients following premature MI. tHcy had no effect on major cardiac event in contrast to most other risk factors in this study. Thus, the mechanism(s) underlying the effects of homocysteine on coronary heart disease may differ from other risk factors.

Hyperhomocysteinemia has been proposed to inhibit the protein C anticoagulant system through 2 mechanisms: decreased generation of activated protein C (APC) by thrombin, and resistance to APC caused by decreased inactivation of factor Va (FVa). We tested the hypotheses that generation of APC by thrombin is impaired in hyperhomocysteinemia in monkeys and that hyperhomocysteinemia produces resistance to APC in monkeys, mice, and humans. In a randomized crossover study, cynomolgus monkeys were fed either a control diet or a hyperhomocysteinemic diet for 4 weeks. Plasma total homocysteine (tHcy) was approximately 2-fold higher when monkeys were on the hyperhomocysteinemic diet than when they were on the control diet (9.8 +/- 2.0 microM versus 5.6 +/- 1.0 microM; P <.05). After infusion of human thrombin (25 microg/kg of body weight), the peak level of plasma APC was 136 +/- 16 U/mL in monkeys fed the control diet and 127 +/- 13 U/mL in monkeys fed the hyperhomocysteinemic diet (P >.05). The activated partial thromboplastin time was prolonged to a similar extent by infusion of thrombin in monkeys fed the control diet and in those fed the hyperhomocysteinemic diet. The sensitivity of plasma FV to human APC was identical in monkeys on control diet and those on hyperhomocysteinemic diet. We also did not detect resistance of plasma FV to APC in hyperhomocysteinemic mice deficient in cystathionine beta-synthase (plasma tHcy, 93 +/- 16 microM) or in human volunteers with acute hyperhomocysteinemia (plasma tHcy, 45 +/- 6 microM). Our findings indicate that activation of protein C by thrombin and inactivation of plasma FVa by APC are not impaired during moderate hyperhomocysteinemia in vivo.

Chronic rejection (CR) and transplant vascular sclerosis (TVS) cause the majority of graft failures in cardiac transplantation. Hyperhomocyst(e)inemia [hH(e)] is associated with human TVS without a proven causal relationship. This study investigated the effect of hH(e) on graft survival and TVS in allogeneic and syngeneic rat cardiac transplants. Lewis recipients of heterotopic F344 heart allografts, received normal or hH(e)-inducing (folate, methionine) diets [controls: syngeneic transplanted [+/- hH(e), + CsA] and nontransplanted rats [+/- hH(e), +/- CsA]]. Serial plasma homocyst(e)ine [H(e)] levels were measured. TVS was assessed in clinically rejected grafts and a subset of pre-rejection normal diet allografts (day 64) (neointimal index, NI). The hH(e) diet elevated plasma H(e) levels. When compared with normal diet controls (n = 9), hH(e) diet allografts (n = 9) had decreased time to onset of CR (40 +/- 9 vs. 72 +/- 10d, p = 0.02), and graft failure (64 +/- 10 vs. 107 +/- 12d, p = 0.009). hH(e) diet allografts at rejection (n = 9, 64d) had more severe TVS (NI = 68 +/- 2) than both time-matched normal diet allografts (NI = 49 +/- 6, n = 8, 64d, p <0.001) and normal diet allografts at rejection (NI = 58 +/- 5, n = 9, 107d, p = 0.007). hH(e) induced TVS in syngeneic grafts (NI=50 +/- 3, n = 10 vs. NI = 5 +/- 3, n = 10, 130d, p <0.001). hH(e) accelerated rejection and increased the severity of TVS in allogeneic cardiac transplants, and induced TVS in syngeneic cardiac transplants.

Purpose: Hyperhomocyst(e)inemia (hH[e]) is a risk factor for atherosclerosis. Neointimal hyperplasia (NH) after vessel injury can contribute to atherosclerosis. In this study, we investigated the effects of hH(e) on NH formation after arterial balloon injury in rats., Methods: Lewis rats that were given a hH(e)-inducing (high methionine, low folate) or normal diet for 150 days underwent common carotid artery (CCA) balloon injury. Two and 4 weeks after injury, CCAs were formalin perfusion-fixed, sectioned, and stained for elastin. Neointimal index (NI, percent lumen occlusion) and neointima (N) and media (M) area were measured by using computer-interfaced microscopy., Results: Plasma homocyst(e)ine (H[e]) levels were elevated in rats given the study diet compared with rats given the normal diet at days 40 and 90 (69 +/- 8 and 73 +/- 9 micromol/L vs 4 +/- 0.4 and 4 +/- 0.6 micromol/L, P <.001). After balloon injury, the CCA NI and N/M ratio, but not the M area, were increased by hH(e) compared with normal plasma H(e) (2 weeks [n = 6,7]: NI = 7.3 +/- 1.7 vs 2.9 +/- 0.7, P =.002, and N/M = 0.31 +/- 0.08 vs 0.08 +/- 0.02, P <.001; 4 weeks [n = 4,7]: NI = 13.1 +/- 2.2 vs 6.3 +/- 1.3, P =.002, and N/M = 0.36 +/- 0.08 vs 0.17 +/- 0.03, P <.001)., Conclusion: hH(e) accelerates NH in a rat CCA balloon-injury model. The effect of hH(e) on NH may contribute to increased atherosclerosis in humans with hH(e).

Hyperhomocysteinemia is associated with increased risk for cardiovascular events, but it is not certain whether it is a mediator of vascular dysfunction or a marker for another risk factor. Homocysteine levels are regulated by folate bioavailability and also by the methyl donor S-adenosylmethionine (SAM) and its metabolite S-adenosylhomocysteine (SAH). We tested the hypotheses that endothelial dysfunction occurs in hyperhomocysteinemic mice in the absence of folate deficiency and that levels of SAM and SAH are altered in mice with dysfunction. Heterozygous cystathionine beta-synthase-deficient (CBS(+/-)) and wild-type (CBS(+/+)) mice were fed a folate-replete, methionine-enriched diet. Plasma levels of total homocysteine were elevated in CBS(+/-) mice compared with CBS(+/+) mice after 7 weeks (27.1+/-5.2 versus 8.8+/-1.1 micromol/L; P<0.001) and 15 weeks (23.9+/-3.0 versus 13.0+/-2.3 micromol/L; P<0.01). After 15 weeks, but not 7 weeks, relaxation of aortic rings to acetylcholine was selectively impaired by 35% (P<0.05) and thrombomodulin anticoagulant activity was decreased by 20% (P<0.05) in CBS(+/-) mice. Plasma levels of folate did not differ between groups. Levels of SAH were elevated approximately 2-fold in liver and brain of CBS(+/-) mice, and correlations were observed between plasma total homocysteine and SAH in liver (r=0.54; P<0.001) and brain (r=0.67; P<0.001). These results indicate that endothelial dysfunction occurs in hyperhomocysteinemic mice even in the absence of folate deficiency. Endothelial dysfunction in CBS(+/-) mice was associated with increased tissue levels of SAH, which suggests that altered SAM-dependent methylation may contribute to vascular dysfunction in hyperhomocysteinemia.

Hepatic steatosis is common in patients having severe hyperhomocysteinemia due to deficiency for cystathionine beta-synthase. However, the mechanism by which homocysteine promotes the development and progression of hepatic steatosis is unknown. We report here that homocysteine-induced endoplasmic reticulum (ER) stress activates both the unfolded protein response and the sterol regulatory element-binding proteins (SREBPs) in cultured human hepatocytes as well as vascular endothelial and aortic smooth muscle cells. Activation of the SREBPs is associated with increased expression of genes responsible for cholesterol/triglyceride biosynthesis and uptake and with intracellular accumulation of cholesterol. Homocysteine-induced gene expression was inhibited by overexpression of the ER chaperone, GRP78/BiP, thus demonstrating a direct role of ER stress in the activation of cholesterol/triglyceride biosynthesis. Consistent with these in vitro findings, cholesterol and triglycerides were significantly elevated in the livers, but not plasmas, of mice having diet-induced hyperhomocysteinemia. This effect was not due to impaired hepatic export of lipids because secretion of VLDL-triglyceride was increased in hyperhomocysteinemic mice. These findings suggest a mechanism by which homocysteine-induced ER stress causes dysregulation of the endogenous sterol response pathway, leading to increased hepatic biosynthesis and uptake of cholesterol and triglycerides. Furthermore, this mechanism likely explains the development and progression of hepatic steatosis and possibly atherosclerotic lesions observed in hyperhomocysteinemia.

Background: Hyperhomocysteinemia is associated with increased risk of atherosclerotic and thrombotic vascular disease. In many patients, hyperhomocysteinemia can be treated or prevented by dietary supplementation with B vitamins, but the clinical benefit of B vitamins for the prevention of vascular disease has not been proven., Methods and Results: Using an atherogenic diet that produces both hyperhomocysteinemia and hypercholesterolemia, we tested the hypothesis that dietary supplementation with B vitamins (folic acid, vitamin B(12), and vitamin B(6)) would prevent hyperhomocysteinemia, vascular dysfunction, and atherosclerotic lesions in monkeys. After 17 months, plasma total homocysteine increased from 3.6+/-0.3 to 11.8+/-1.7 micromol/L in monkeys fed an unsupplemented atherogenic diet (P<0.01) but did not increase in monkeys fed an atherogenic diet supplemented with B vitamins (3.8+/-0.3 micromol/L). Serum cholesterol increased from 122+/-7 to 550+/-59 mg/dL in the unsupplemented group (P<0.001) and from 118+/-5 to 492+/-55 mg/dL in the supplemented group (P<0.001). Responses to endothelium-dependent vasodilators, both in resistance vessels in vivo and in the carotid artery ex vivo, were impaired to a similar extent in groups that did and did not receive vitamin supplements. Anticoagulant responses to the infusion of thrombin were also impaired to a similar extent in both groups. Vitamin supplementation failed to prevent intimal thickening in the carotid or iliac arteries., Conclusions: These findings demonstrate that supplementation with B vitamins prevents hyperhomocysteinemia but is not sufficient to prevent the development of vascular dysfunction or atherosclerotic lesions in monkeys with marked hypercholesterolemia, even in the absence of preexisting atherosclerosis.

Methionine synthase (MS) encodes an enzyme that catalyzes the remethylation of homocysteine to methionine using a methyl group donated by 5-methyltetrahydrofolate, which is the major circulating form of folate in the body. Functional genetic variants of the MS may alter total homocysteine (tHcy) as well as folate levels which are independent risk factors for vascular disease. The influence of a common genetic polymorphism (2756A-->G, D919G) of the MS gene on plasma tHcy and folate levels and its relation to the risk of myocardial infarction (MI) in a prospective study of male physicians in the US was investigated. A nested case-control study was conducted within the Physicians' Health Study which was originally designed as a double-blind trial of aspirin and beta-carotene among 22071 US male physicians, aged 40-84 years in 1982. Sixty-eight percent of participants also donated a blood sample. The study included 387 incident MI case and 767 controls matched on age, smoking status, and time from randomization in 6-month intervals. Individuals with GG genotype had a non-significant reduction of MI risk (RR 0.51, 95% CI 0.17-1.16) compared to individuals with DD genotype after adjusting for MI risk factors. The MS polymorphism was associated with decreased tHcy (10.55, 9.87 and 9.57 nmol/ml for DD, DG and GG genotypes, respectively) and increased folate levels (3.95, 3.78, 7.31 ng/ml for DD, DG and GG genotypes, respectively) only among controls but not cases. It was concluded that influence of the MS (D919G) polymorphism on the plasma tHcy and folate levels is at most moderate, but should be further investigated in other large prospective studies.

Elevated plasma levels of homocyst(e)ine [H(e)] are surprisingly common and strongly associated with endothelial dysfunction and a marked increase in vascular risk. Treatment with a combination of folic acid, pyridoxine (vitamin B6) and cobalamin (vitamin B12) reduces plasma H(e) levels in most cases, restores endothelial function, and regresses carotid plaque, but there is no evidence that such treatment will reduce clinical events. The Vitamin Intervention for Stroke Prevention (VISP) study is a double-masked, randomized, multicenter clinical trial designed to determine if, in addition to best medical/surgical management, high-dose folic acid, vitamin B6, and vitamin B12 supplements will reduce recurrent stroke compared to lower doses of these vitamins. Patients at least 35 years old with a nondisabling ischemic stroke within 120 days, and screening plasma H(e) > the 25th percentile of benchmark population data are eligible. Secondary endpoints are myocardial infarction or fatal coronary heart disease. This paper describes the design and rationale of the study.

Folic acid is presently the mainstay of treatment for most subjects with elevated plasma homocyst(e)ine concentrations [Plasma or serum homocyst(e)ine, or total homocysteine, refers to the sum of the sulfhydryl amino acid homocysteine and the homocysteinyl moieties of the disulfides homocystine and homocystein-cysteine, whether free or bound to plasma proteins.] Changes in homocyst(e)ine in response to folic acid supplementation are characterized by considerable interindividual variation. The purpose of this study was to identify factors that contribute to heterogeneity in short-term responses to folic acid supplementation. The effects of folic acid supplementation (1 or 2 mg per day) for 3 wk on plasma homocyst(e)ine concentrations were assessed in 304 men and women. Overall, folic acid supplementation increased mean plasma folate 31.5 +/- 98.0 nmol/L and decreased mean plasma homocyst(e)ine concentrations 1.2 +/- 2.4 micromol/L. There was evidence of substantial interindividual variation in the homocyst(e)ine response from -18.5 to +7.1 micromol/L, including an increase in homocyst(e)ine in 20% of subjects (mean increase 1.5 +/- 1.4 micromol/L). Basal homocyst(e)ine, age, male gender, cigarette smoking, use of multivitamins, methylene tetrahydrofolate reductase, and cystathionine beta-synthase polymorphisms accounted for 47.6% of the interindividual variability in the change in homocyst(e)ine after folic acid supplementation, but about 50% of variability in response to folic acid was not explained by the variables we studied.

Hyperhomocysteinemia is a risk factor for stroke, myocardial infarction, and venous thrombosis. Moderate hyperhomocysteinemia is associated with impaired endothelial function, but the mechanisms responsible for endothelial dysfunction in hyperhomocysteinemia are poorly understood. We have used genetic and dietary approaches to produce hyperhomocysteinemia in mice. Heterozygous cystathionine beta-synthase-deficient mice (CBS +/-), which have a selective defect in homocysteine transsulfuration, and wild-type (CBS +/+) littermates were fed either a control diet or a diet that is relatively deficient in folic acid for 6 wk. Plasma total homocysteine was 5.3 +/- 0.7 microM in CBS +/+ mice and 6.4 +/- 0.6 microM in CBS +/- mice (P = 0.3) given the control diet. Plasma total homocysteine was 11.6 +/- 4.5 microM in CBS +/+ mice and 25.1 +/- 3.2 microM in CBS +/- mice (P = 0.004) given a low-folate diet. In mice fed the control diet, relaxation of aortic rings in response to the endothelium-dependent vasodilator acetylcholine did not differ significantly between CBS +/+ mice and CBS +/- mice. In contrast, in mice fed a low-folate diet, maximal relaxation to acetylcholine was markedly impaired in CBS +/- mice (58 +/- 9%) compared with CBS +/+ mice (84 +/- 4%) (P = 0.01). No differences in relaxation to the endothelium-independent vasodilator sodium nitroprusside were observed among the four groups of mice. These data indicate that CBS-deficient mice are predisposed to hyperhomocysteinemia during dietary folate deficiency, and moderate hyperhomocysteinemia is associated with marked impairment of endothelial function in mice.

Objective: We tested the hypothesis that cessation of habitual ingestion of breakfast cereals would be associated with elevated plasma homocyst(e)ine concentrations. We anticipated that those subjects who reported consuming breakfast cereals containing 100 to 400 ,microg of folic acid per serving before entering the study would achieve higher plasma homocyst(e)ine concentrations if, in addition to their regular diet, they began ingesting a daily serving of breakfast cereal that contained less than 10 microg of folic acid per serving., Design: Seventy-nine subjects consumed a daily serving of breakfast cereal containing either < 10 microg or folic acid per serving (placebo) or breakfast cereal containing 200 microg of folic acid per serving (folic acid fortified)., Results: Cessation of intake of commercially available breakfast cereal was associated with homocyst(e)ine elevation. Breakfast cereal containing 200 microg folic acid per day was sufficient to maintain the homocyst(e)ine lowering effects of commercial cereals., Conclusions: Habitual consumption of commercially available fortified breakfast cereals, usually containing 100 to 400 microg folic acid per serving, had significant homocyst(e)ine lowering effects as shown by the homocyst(e)ine increase after cessation of habitual intake of commercial breakfast cereal. Substitution of breakfast cereal containing only 200 microg folic acid per day was sufficient to maintain the homocyst(e)inelowering effects of commercial cereals.

Premenopausal black women have a two to threefold greater rate of coronary heart disease than premenopausal white women. This study was designed to provide greater insight into the reasons for this difference which is currently unclear. Coronary heart disease risk factors were compared in 100 black and 100 white, healthy premenopausal women, ages 18-45 years, and of relatively advantaged socioeconomic status. Compared to white women, black women had a higher body mass index (32.0±9.2 vs. 29.0±9.4 kg/m2, p=0.021), and higher systolic (124±17 vs. 115±14 mm Hg, p<0.0001) and diastolic (79±14 vs. 75±11 mm Hg, p=0.048) blood pressures. The mean plasma lipoprotein(a) concentration was markedly higher in the black women (40.2±31.3 mg/dL) than in the white women (19.2±23.7 mg/dL, p<0.0001). The plasma total homocysteine level was also higher in the black women (8.80±3.38 vs. 7.81±2.58 mmol/L, p=0.013). The black women, however, had lower plasma triglyceride levels (0.91±0.46 vs. 1.22±0.60 mmol/L, p<0.0001) and a trend toward higher high-density lipoprotein cholesterol levels (1.37±0.34 vs. 1.29±0.31 mmol/L, p=0.064) than the white women. Plasma total and low-density lipoprotein cholesterol levels were similar. Black women consumed more saturated fat and cholesterol. Rates of cigarette smoking and alcohol intake were low and similar between the races. In summary, compared to white women, black women had a higher mean body mass index, higher blood pressures, higher lipoprotein(a) and plasma total homocysteine levels, and greater consumption of saturated fat and cholesterol. The differences in coronary risk factors between these two premenopausal groups may explain the higher incidence of coronary heart disease in black women. (c) 2000 by CHF, Inc.

Elevated total plasma homocysteine (tHcy) is an established risk factor for the development of vascular disease and neural tube defects. Total homocysteine levels can be lowered by folic acid supplements but individual response is highly variable. In this case-control study, involving 142 coronary artery disease (CAD) patients and 102 controls, we have typed six genetic polymorphisms in three homocysteine metabolizing genes and examined their relationship to the incidence of CAD, tHcy levels, and lowering of tHcy levels in response to folic acid supplementation. We found that two single nucleotide polymorphisms in the cystathionine beta synthase (CBS) gene, 699C --> T and 1080T --> C, are associated with decreased risk of CAD and increased responsiveness to the tHcy lowering effects of folic acid. Individuals homozygous for 699T were significantly underrepresented in CAD patients as compared to controls (4.9% vs 17.3%, P = 0.0015), as were individuals homozygous for the 1080C (29.6% vs 44.2%, P = 0.018). Additionally, 699T and 1080C homozygous individuals were the most responsive to folate supplementation. 699T homozygotes lowered tHcy levels 13.6% on average, compared to 4.8% lowering in 699C homozygotes (P = 0.009), while 1080C homozygotes lowered 12.9% compared to just 2.7% for 1080T homozygotes (P = 0.005). The two polymorphisms in CBS are third codon changes and would not be predicted to affect the underlying protein. However, there is strong linkage disequilibrium between these two positions, suggesting that they may also be linked to other as yet unidentified polymorphisms within the CBS gene. These observations suggest that specific CBS alleles are a risk factor for the development of vascular disease and that genetic information could be predictive of individual response to folic acid supplementation., (Copyright 2000 Academic Press.)

We conducted a case control study at Harare Maternity Hospital, Zimbabwe. We genotyped a total of 171 cases with preeclampsia or eclampsia and 185 normotensive control subjects for the methylenetetrahydrofolate reductase (MTHFR) 677 C --> T genotype. The wild-type allele frequency among cases and controls was 91.2 and 91.3%, respectively. Only one subject (0.3%) was homozygous for the 677 C --> T MTHFR genotype and this subject had preeclampsia. After adjustment for confounding factors, there was statistically no significant association between maternal MTHFR genotype and risk of preeclampsia (adjusted odds ratio = 1.0; 95% CI, 0.5-1.9). In addition, plasma homocyst(e)ine, vitamin B(12), and folate concentrations were not statistically different between normotensive control subjects with wild-type genotype as compared with normotensive subjects who were heterozygous for the mutant allele. Conversely, there was a strong graded association between maternal plasma folate concentration and risk of preeclampsia. Women with plasma folate concentrations less than 5.7 nmol/L experienced a 10. 4-fold increase in risk of preeclampsia. There was no clear pattern of preeclampsia risk and vitamin B(12) concentrations., (Copyright 2000 Academic Press.)

Plasma total homocysteine (tHcy) has been identified as an independent risk factor for cardiovascular diseases (CVD). The difference in tHcy between the sexes has most often been related to the sex hormones, but also to a higher muscle mass in men. The purpose of this study was to assess the effects of acute exercise, brief exhaustive training, and menstrual cycle phase on circulating plasma tHcy concentrations. Fifteen untrained eumenorrheic women (mean age [+/-SD]: 18.7+/-0.4 yr, body fat: 25.8+/-3.4%, VO2max: 43.8+/-2.3 ml x kg(-1) x min(-1)) volunteered for the present study, which covered two menstrual cycles. During the second cycle the subjects participated in two exhaustive 5-day training programs on a cycle ergometer: one in the follicular (FPh) and one in the luteal phase (LPh). Pre- and posttraining plasma tHcy and total estrogen (E) responses were determined in blood samples obtained immediately before, during and immediately after incremental exercise to exhaustion. tHcy levels showed a large between-subject variation, but differences between FPh and LPh levels were consistent (P=0.063). Mean tHcy levels at rest were 9.44+/-1.65 micromol/L and 8.93+/-1.71 micromol/L during the FPh and LPh, respectively. Brief exhaustive training did not elicit any changes in plasma tHcy concentrations, although posttraining LPh E levels were lower (P<0.01). Overall, the differences between FPh and LPh values for tHcy and E were attenuated by training. Acute exercise increased plasma tHcy concentrations (P<0.001). At exhaustion, tHcy levels increased by 17% and 16% during the FPh and LPh, respectively. This was also significantly above tHcy levels at submaximal exercise (P=0.044). After a short period of training tHcy levels did not increase as much during acute exercise as they did before training; however, the increments were still significant (P=0.048). In conclusion, acute exercise in women produces significant increases in plasma tHcy concentrations, whereas brief exhaustive training does not significantly alter plasma tHcy levels. Our findings also suggest that plasma tHcy concentrations are menstrual cycle phase-dependent and that there is a close association between estrogen status and tHcy levels.

Objective: To examine the relationship between plasma homocyst(e)ine and risk of eclampsia and preeclampsia among sub-Saharan African women who delivered at Harare Maternity Hospital in Zimbabwe., Methods: We ran a hospital-based, case-control study at Harare Maternity Hospital, University of Zimbabwe, Harare, Zimbabwe comprising 33 pregnant women with eclampsia and 138 with preeclampsia. Controls were 185 normotensive pregnant women. Plasma was collected postpartum and homocyst(e)ine levels were measured by high-performance liquid chromatography and electrochemical detection., Results: Women with eclampsia or preeclampsia had significantly higher mean homocyst(e)ine levels than normotensive controls (12.54 or 12.77 micromol/L versus 9.93 micromol/L, respectively, P<.001). The odds ratio (OR) for eclampsia was 6.03 among women in the highest quartile of the control homocyst(e)ine distribution (median 13.9 micromol/L) compared with women in the lowest quartile (median 6.2 micromol/L). The corresponding OR for preeclampsia was 4.57. Nulliparas with elevated homocyst(e)ine had a 12.90 times higher risk of preeclampsia compared with multiparas without elevated homocyst(e)ine., Conclusion: Postpartum plasma homocyst(e)ine concentrations are higher among Zimbabwean women with eclampsia and preeclampsia compared with normotensive women.