Combined vitamin B6 plus folic acid therapy in young patients with arteriosclerosis and hyperhomocysteinemia

A Novel Review of Homocysteine and Pregnancy Complications

Homocysteine (Hct) is a substance produced in the metabolism of methionine. It is an essential type of amino acid gained from the daily diet. Methylenetetrahydrofolate reductase (MTHFR) gene mutation is related to elevated total homocysteine (tHct) expressions, in particular, among women with low folate intake. Hyperhomocysteinemia (HHct) is caused by numerous factors, such as genetic defects, lack of folic acid, vitamin B₆ and B₁₂ deficiency, hypothyroidism, drugs, aging, and renal dysfunction. Increased Hct in peripheral blood may lead to vascular illnesses, coronary artery dysfunction, atherosclerotic changes, and embolic diseases. Compared to nonpregnant women, the Hct level is lower in normal pregnancies. Recent studies have reported that HHct was associated with numerous pregnancy complications, including recurrent pregnancy loss (RPL), preeclampsia (PE), preterm delivery, placental abruption, fetal growth restriction (FGR), and gestational diabetes mellitus (GDM). Besides, it was discovered that neonatal birth weight and maternal Hct levels were negatively correlated. However, a number of these findings lack consistency. In this review, we summarized the metabolic process of Hct in the human body, the levels of Hct in different stages of normal pregnancy reported in previous studies, and the relationship between Hct and pregnancy complications. The work done is helpful for obstetricians to improve the likelihood of a positive outcome during pregnancy complications. Reducing the Hct level with a high dosage of folic acid supplements during the next pregnancy could be helpful for females who have suffered pregnancy complications due to HHct.

Effect of Folic Acid therapy on Homocysteine Level in patients with Atherosclerosis or Buerger's Disease and in Healthy individuals: A clinical trial

Background

Hyperhomocysteinemia is considered a risk factor for atherosclerosis and some other vascular diseases such as Buerger’s disease.

Objective

The aim of this study was to measure the Homocysteine levels in 3 different groups of participants (Buerger’s disease, atherosclerosis patients, and healthy cases) and determine the therapeutic effect of folic acid therapy on homocysteine levels for these three groups

Methods

This nonrandomized clinical trial study was conducted in the vascular and endovascular surgery research center of Mashhad University of Medical Sciences in Mashhad, Iran. This interventional study consisted of 44 participants of which 22 patients had Buerger’s disease and a control group of 22 healthy individuals, all of which were enrolled in this study. All of the study’s participants had their serum homocysteine levels measured both before and after 12 weeks of folic acid (5mg/day) therapy. The data analysis used fo data analysis was a Chi square and t-test or their non-parametrical equivalents for data analysis by means of Statistical Package for the Social Sciences (SPSS) version 16

Results

The homocysteine levels were found to be significantly higher in patients with Buerger’s disease as compared to other groups before treatment with folic acid (Buerger = 21.8 ± 8.5 Mm/L, atherosclerosis = 17.3 ± 6.9, healthy = 13.8 ± 3.1; p < 0.001). After treatment with folic acid at 5 mg/daily for 12 weeks, the new plasma homocysteine levels did not show any significant difference (p = 0.38) between the Buerger’s disease group (14.6 ± 4.5 Mm/L) and atherosclerosis group (13.9 ± 4.7), but it was found to besignificantly higher in both groups when compared to the healthy group (10.7 ± 3.9, p<0.05). The plasma homocysteine level was reduced significantly when compared to its initial level in all 3 groups. The comparison of differences among three groups was found not to be significant (p=0.41)

Conclusions

It seems that supplementary therapy with folic acid at a dose of 5 mg daily may reduce the serum homocysteine levels significantly and may have a role in the development of vascular diseases such as Buerger’s disease. We suggest that folic acid should be considered as a routine agent in the Buerger’s disease therapeutic regime

Clinical trial registration

The trial was registered at the Thai Clinical Trials Registry (http://www.clinicaltrials.in.th) with the ID: TCTR20160601003.

Funding

This study was not funded by any organization.

Management of hyperhomocysteinemia

Hyperhomocysteinemia is an established risk factor for cardiovascular disease. The modification of traditional cardiovascular risk factors has resulted in better morbidity and mortality outcomes, so the treatment of hyperhomocysteinemia is explored for a similar benefit. Vitamin B(6), vitamin B(12) and folate, as co-factors in the metabolism of homosyteine, are used in the treatment of hyperhomocysteinemia. Betaine, a methyl-donor in a separate homocysteine metabolism pathway, is also used to treat hyperhomocysteinemia. These supplements have been used in various doses and combinations for different periods of time, with favorable outcomes. There is still no concensus whether hyperhomocysteinemia can be treated with folic acid alone, or in combination with vitamin B(6) and vitamin B(12). The dose of the supplements required to normalize fasting homocysteine remains to be determined, especially in diabetic nephropathy, hemodialysis and renal transplant patients. The benefits from lowering homocysteine levels have mainly been demonstrated in surrogate cardiovascular outcomes. The treatment of hyperhomocysteinemia cannot be firmly advocated until there are trials that demonstrate a beneficial clinical endpoint. In patients who have cardiovascular disease in the absence of more established risk factors, investigation and treatment of hyperhomocysteinemia should be considered.

Differences in nutrition status by body mass index in patients with peripheral artery disease

Peripheral Arterial Disease (PAD) is most prevalent in the elderly and associated with increased cardio vascular disease (CVD) morbidity and mortality. Treatment focuses on improving functional capacity and reducing CVD risk factors. To date, little is understood about dietary habits and weight in this patient population. Nutritional and weight recommendations are based on heart health, and little is known about the unique needs of elderly PAD patients with multiple comorbidities. This prospective study compared 1) the dietary intake of nonobese PAD patients in comparison with those who were obese and; 2) dietary intake of those patients with the Estimated Average Requirement (EAR) based on age, gender and BMI. Nutritional intake was assessed with the Block 98 Food Frequency Questionnaire. Body mass index (BMI) was calculated in accordance with the National Heart, Lung, and Blood Institute (NHLBI) guidelines.The study population was divided into obese (BMI ≥ 30) and nonobese (NO) groups. Comparisons between groups were performed using the Mann-Whitney U test for continuous variables and the Chi-square test for ordinal variables. All tests were two-tailed and P < 0.05 was considered significant. The Estimated Average Requirement (EAR) cut-point method was used to compare nutritional variables with Dietary Reference Intakes (DRI). The study population included 189 NO (BMI < 30) and 111 obese (BMI > 30) individuals. Obese participants reported greater intake of foods containing cholesterol and trans-fatty acids and more frequent intake of B vitamins in comparison with the NO BMI group. Additionally, the nutrient intake of all participants by age, gender and BMI was lower than the EAR for magnesium, folate, and Vitamin E. These results suggest that the nutritional intake of PAD patients differs based on gender and BMI. Additionally, EAR was lower for specific nutrients than recommended. Further investigation is needed to examine the association between nutritional intake and nutrition-related deficits.

Nutrition impacts the prevalence of peripheral arterial disease in the United States

OBJECTIVE

Traditional recommendations for peripheral arterial disease (PAD) risk factor reduction include smoking cessation, low-fat/low-salt diet, exercise, and optimal medical management of chronic disease. Little attention has been paid to the role of dietary supplementation of specific nutrients in the prevention of PAD.

METHODS

This cross-sectional study used the National Health and Nutrition Examination Survey (NHANES) to determine specific nutrients that are associated with prevalent PAD in the United States (US) population. NHANES data include nationwide sampling of the US population, using physical examination, questionnaire, and laboratory testing. PAD status was defined by an ankle-brachial index (ABI) of <0.9. Nutritional information was collected by 24-hour dietary recall using the US Department of Agriculture dietary collection instrument. Data were linked to a database of foods and their nutrient composition. Univariate and multivariate logistic regression analyses were performed to evaluate associations between specific nutrient intake and the presence of PAD. Multivariate models adjusted for the effects of age, gender, hypertension, coronary vascular disease, diabetes, and smoking.

RESULTS

NHANES data for 1999 to 2004 included 7203 lower extremity examinations, of which 422 individuals had prevalent PAD (5.9%). Examinees with PAD had significantly higher rates of hypertension, coronary artery disease, diabetes, and smoking than those without PAD. Univariate analysis revealed that consumption of all nutrients considered were associated with lower odds of PAD, including antioxidants (vitamins A, C, and E), folate, other B vitamins (B(6), B(12)), fiber, and polyunsaturated and saturated fatty acids. After adjustment for traditional risk factors, nutrients associated with reduced prevalence of PAD were vitamin A (odds ratio [OR], 0.79; P = .036), vitamin C (OR, 0.84; P < .001), vitamin E (OR, 0.78; P = .011), vitamin B(6) (OR, 0.71; P = .023), fiber (OR, 0.65; P < .001), folate (OR, 0.67; P = .006), and omega-3 (alpha-linolenic) fatty acid (OR, 0.79; P = .028).

CONCLUSIONS

Improved nutrition is associated with a reduced prevalence of PAD in the US population. Higher consumption of specific nutrients, including antioxidants (vitamin A, C, and E), vitamin B(6), fiber, folate, and omega-3 fatty acids have a significant protective effect, irrespective of traditional cardiovascular risk factors. These findings suggest specific dietary supplementation may afford additional protection, above traditional risk factor modification, for the prevention of PAD.

Does nutrition have a role in peripheral vascular disease?

Peripheral vascular disease (PVD) is a manifestation of systemic atherosclerosis in the lower limbs, and PVD patients have a 3- to 5-fold increased risk of cardiovascular mortality compared with age-matched controls. Nevertheless, recent reports show how PVD patients are undertreated with regard to CVD risk-factor reduction and the use of lipid-lowering or antiplatelet drugs. There is appreciable evidence that demonstrates the beneficial effects of certain nutrients and dietary habits in the prevention of CVD, but there has been little attention paid to the role of nutrients in PVD. The purpose of the present review is to provide an overview of our understanding of how foods could possibly benefit PVD. In the last few decades, several nutrients have arisen as potentially health-promoting in PVD. While nutritional interventions in PVD show positive clinical effects for fish oil, carnitine or vitamin E, others such as olive oil or vitamin C seem to interact only at a biochemical level by decreasing risk factors. Moreover, only epidemiological associations exist for the potential role of fibre, folates or vitamin B6 in this disease. In all cases, the limited data available provide no clear-cut evidence in favour of the clinical benefit of nutritional interventions aimed at reducing risk factors and ameliorating symptoms in PVD patients. No practical recommendations can be given at this stage, and further studies are clearly needed.

Vitamin Intervention for Stroke Prevention Trial

Background and Purpose— The Vitamin Intervention for Stroke Prevention trial (VISP) intention-to-treat analysis did not show efficacy of combined vitamin therapy for recurrent vascular events in patients with nondisabling stroke. Reasons for lack of efficacy may have included folate fortification of grain products, inclusion of the recommended daily intake for B 12 in the low-dose arm, treatment with parenteral B 12 in patients with low B 12 levels in both study arms, a dose of B 12 too low for patients with malabsorption, supplementation with nonstudy vitamins, and failure of patients with significant renal impairment to respond to vitamin therapy. We conducted an efficacy analysis limited to patients most likely to benefit from the treatment, based on hypotheses arising from evidence developed since VISP was initiated. The criteria for this subgroup were defined before any data analysis.

Methods— For this analysis, we excluded patients with low and very high B 12 levels at baseline (<250 and >637 pmol/L, representing the 25th and 95th percentiles), to exclude those likely to have B 12 malabsorption or to be taking B 12 supplements outside the study and patients with significant renal impairment (glomerular filtration rate <46.18; the 10th percentile).

Results— This subgroup represents 2155 patients (37% female), with a mean age of 66±10.7 years. For the combined end point of ischemic stroke, coronary disease, or death, there was a 21% reduction in the risk of events in the high-dose group compared with the low-dose group (unadjusted P =0.049; adjusted for age, sex, blood pressure, smoking, and B 12 level P =0.056). In Kaplan–Meier survival analysis comparing 4 groups, patients with a baseline B 12 level at the median or higher randomized to high-dose vitamin had the best overall outcome, and those with B 12 less than the median assigned to low-dose vitamin had the worst ( P =0.02 for combined stroke, death, and coronary events; P =0.03 for stroke and coronary events).

Conclusions— In the era of folate fortification, B 12 plays a key role in vitamin therapy for total homocysteine. Higher doses of B 12 , and other treatments to lower total homocysteine may be needed for some patients.

Place of drug therapy in the treatment of carotid stenosis

Carotid stenosis is an important cause of transient ischaemic attacks and stroke. The cause of carotid stenosis is most often atherosclerosis; contributing to the pathogenesis of the lesion are endothelial injury, inflammation, lipid deposition, plaque formation, fibrin, platelets and thrombin. Carotid stenosis accounts for 10-20% of cases of brain infarction, depending on the population studied. Despite successful treatment of selected patients who have had an acute ischaemic stroke with tissue plasminogen activator and the promise of other experimental therapies, prevention remains the best approach to reducing the impact of ischaemic stroke. High-risk or stroke-prone patients can be identified and targeted for specific interventions. At this juncture, treatment of carotid stenosis is a well established therapeutic target and a pillar of stroke prevention. There are two main strategies for the treatment of carotid stenosis. The first approach is to stabilise or halt the progression of the carotid plaque through risk factor modification and medication. Hypertension, diabetes mellitus, smoking, obesity and high cholesterol levels are closely associated with carotid stenosis and stroke; control of these factors may decrease the risk of plaque formation and progression. The second approach is to eliminate or reduce carotid stenosis through carotid endarterectomy or carotid angioplasty and stenting. Carotid endarterectomy, which is the mainstay of therapy for severe carotid stenosis, is beyond the scope of this review. Anticoagulants seem to play little role (if any) in the medical (i.e. non-surgical) treatment of carotid stenosis. Adoption of a healthy lifestyle combined with the reduction of risk factors has been shown to lead to a reduction in the extent of carotid stenosis. The medical treatment of carotid stenosis should be based on the triad of the reduction of risk factors, patient education, and use of antiplatelet agents.

Folic acid supplements in pregnancy and birth outcome: re-analysis of a large randomised controlled trial and update of Cochrane review

Periconceptual folic acid prevents neural tube defects. The effect of folic acid taken throughout pregnancy is unclear, however. We re-analysed data from a large randomised controlled trial performed between 1966 and 1967 and combined the results with those from trials included in a Cochrane review. A total of 2928 women were randomised: 1977 were allocated to placebo, 466 to folic acid 200 microg/day and 485 to folic acid 5 mg/day. Folic acid supplementation was not associated with any difference in mean birthweight, placental weight or gestational age. When combined with trials in the Cochrane review folic acid at high doses was associated with reduced risk of low birthweight (pooled relative risk 0.73 [95% CI 0.53, 0.99]). We found no conclusive evidence of benefit for folic acid supplementation in pregnant women given from time of booking onwards.

Effect of homocysteine-lowering treatment with folic acid plus vitamin B on cerebrovascular atherosclerosis and white matter abnormalities as determined by MRA and MRI: a placebo-controlled, randomized trial

BACKGROUND

A high plasma homocysteine concentration is an independent risk factor for large and possibly small vessel disease. We investigated the effects of homocysteine-lowering treatment with folic acid plus vitamin B(6) on markers of cerebrovascular atherosclerosis and cerebral microangiopathy.

MATERIALS AND METHODS

Using 158 healthy siblings (mean age 46.0 +/- 7.6 years) of patients with premature atherosclerotic disease, we performed a randomized, placebo-controlled trial using 5 mg of folic acid plus 250 mg of vitamin B(6) daily (n = 78) or placebo medication (n = 80). Participants were followed for 2 years with magnetic resonance angiography (MRA) (carotid stenosis; carotid and/or vertebral elongation) and magnetic resonance imaging (MRI) (white matter abnormalities; cerebral atrophy).

RESULTS

Seventeen (10.8%) subjects refused MRA/MRI owing to claustrophobia and were excluded. From the remaining 141 participants, 68 received vitamin and 73 received placebo medication [42 (61.8%) and 48 (65.8%) had postmethionine hyperhomocysteinaemia, respectively]. Twenty-four participants (15.2%; 10 in the treatment and 14 in the placebo group) did not complete both years of the trial. Vitamin treatment was associated with an increase in plasma folate (13-fold vs. placebo; P < 0.001) and vitamin B(6) (8.8-fold; P < 0.001). Fasting and postmethionine total homocysteine concentrations decreased 38.7% (95% CI, 27.4-50.0) and 29.1% (95% CI, 19.2-39.0) vs. placebo (all P < 0.001). During follow up six individuals in the vitamin-treated and 11 in the placebo-treated group deteriorated in their outcome measurements. Vitamin treatment, as compared with placebo, was associated with nonsignificantly improved outcomes on both MRA and MRI outcome measurements (odds ratio 0.48; 95% CI 0.17-1.41; P = 0.18 and 0.48; CI 0.14-1.60; P = 0.23, respectively).

CONCLUSIONS

These results could indicate a possible favourable effect of homocysteine-lowering treatment on cerebrovascular atherosclerosis and cerebral microangiopathy among healthy siblings of patients with premature atherosclerotic disease, but larger trials are required to establish this with certainty.

Dietary folate and vitamin b6 are independent predictors of peripheral arterial occlusive disease

BACKGROUND

It has been suggested that hyperhomocysteinemia (HHcy) is an independent risk factor for peripheral arterial occlusive disease (PAOD). However, the relationship between dietary folate and vitamin B6, cofactors in the metabolism of homocysteine (Hcy), and PAOD is unclear.

AIMS

To study the relationship between dietary folate and B6 and PAOD.

METHODS

Case-control population based study of 392 men older than 50 years living in Huntingdon, United Kingdom. PAOD, defined as an ankle-brachial pressure index (ABPI) < 0.9, was present in 86 (22%) of subjects. Folate, vitamin B6, and vitamin B12 intakes were calculated by means of the EPIC (European Prospective Investigation into Cancer) food frequency questionnaire.

RESULTS

Daily folate intake was significantly lower in case subjects (mean, 288; 95% confidence interval [CI], 266-309 microg) than in control subjects (324; 95% CI, 313-335 microg). Daily vitamin B6 intake was also lower in case subjects (2.05; 95% CI, 1.92-2.19 mg versus 2.26; 95% CI, 2.19-2.33 mg). Daily folate and vitamin B6 intakes were independent predictors of PAOD after adjusting for age, blood pressure, cholesterol levels, diabetes, and smoking status in a logistic regression model. This model suggests that increasing daily folate intake by 1 standard deviation decreased the risk of PAOD by 46%. A similar increase in daily vitamin B6 intake decreased the risk of PAOD by 29%.

CONCLUSION

In men older than 50 years, dietary folate and B6 intakes are independent predictors of PAOD. Longitudinal studies are required to determine whether dietary modification can reduce the incidence of PAOD in the population.

Folate, homocysteine levels, methylenetetrahydrofolate reductase (MTHFR) 677C --> T variant, and the risk of myocardial infarction in young women: effect of female hormones on homocysteine levels

In young women data are limited about the association between myocardial infarction (MI) and hyperhomocysteinemia, low folate or methylenetetrahydrofolate reductase (MTHFR) genotypes. The effect of oral contraceptive (OC) use on plasma homocysteine levels is not clear. We assessed the association between hyperhomocysteinemia, low folate, MTHFR 677TT mutation and risk of MI, and we investigated the effect of OC use on homocysteine levels in controls. In 181 patients with a first MI and 601 controls 18-49 years of age from a population-based case-control study, non-fasting blood samples were available. The homozygote mutant allele (TT) was detected in 12% of the patients and in 10% of controls. The odds ratio (OR) for MI in TT patients compared with the wild-type (CC) controls was 1.3 [95% confidence interval (CI) 0.8, 2.3]. For all MTHFR genotypes combined, the OR for MI in the lowest quartile of folate (<5.4 nmol L-1) compared with the highest quartile (>10.4 nmol L-1) was 3.0 (95% CI 1.7, 5.1). A 2-fold increased risk of MI was found in women with the TT genotype who had folate levels below the median of 7.4 nmol L-1 compared with CC genotype and folate levels above the median (OR = 2.0; 95% CI 1.0, 3.7). Mean homocysteine levels were 12.2 micromol L-1 in OC users and 12.3 micromol L-1 in non-users. Only at the 97.5 percentile (cut-off 21.0 micromol L-1) was the adjusted OR for higher vs. lower homocysteine levels increased by 2.8-fold (95% CI 1.2, 6.8). Low folate is a risk factor for MI, particularly in women with the MTHFR 677TT genotype. Homocysteine levels were not influenced by OC use.

Effects of the interaction between the C677T 5,10-methylenetetrahydrofolate reductase polymorphism and serum B vitamins on homocysteine levels in pregnant women

OBJECTIVE

The purpose of this study was to investigate the effect of the interaction between the C677T mutation in the 5,10-methylenetetrahydrofolate reductase (MTHFR) genotypes and serum levels of B vitamins on serum homocysteine levels in pregnant women.

DESIGN

A cross-sectional study.

SETTING

Ewha Womans University Hospital, Seoul, Korea.

SUBJECTS

A total of 177 normal pregnant women, 24.6+/-1.1 weeks of gestation, in a 6-month period during 2001-2002.

INTERVENTIONS

Serum vitamin B2, vitamin B6, and homocysteine analyses were conducted using high-performance liquid chromatography methods. Serum folate and vitamin B12 concentrations were determined using a radioimmunoassay kit. MTHFR gene mutation was investigated by the polymerase chain reaction of a genomic DNA fragment.

RESULTS

Serum homocysteine was higher in women with the T/T genotype than those with the C/T or C/C genotype of the MTHFR gene (P<0.05). Serum homocysteine was negatively correlated with serum folate in all MTHFR genotypes (P<0.001), and the correlation between the two serum levels was the strongest in the T/T genotype. Serum homocysteine was higher in the subjects with the T/T MTHFR genotype only when the serum folate was below the median level. Explanatory power of B vitamin status as predictors of serum homocysteine levels was more pronounced in the T/T genotypes (68.5%) compared with the C/T (37.9%) or C/C genotypes (20.6%).

CONCLUSIONS

Serum homocysteine levels in pregnant women varied significantly with MTHFR genotype and the serum B vitamin status. Higher serum folate, vitamin B2, and vitamin B12 concentrations may lessen the MTHFR genotypic effect on serum homocysteine levels.

Meta-analysis of plasma homocysteine, serum folate, serum vitamin B12, and thermolabile MTHFR genotype as risk factors for retinal vascular occlusive disease

PURPOSE

To assess the role of plasma total homocysteine (tHcy) levels, serum folate and vitamin B(12)levels, and homozygosity for the thermolabile methylenetetrahydrofolate reductase genotype (TT) as risk factors for retinal vascular occlusive disease.

DESIGN

Meta-analysis of literature.

METHODS

A MEDLINE search was performed to identify all published case-control studies of plasma tHcy levels, serum folate and vitamin B(12) levels, and TT genotype in persons with retinal vascular occlusive disease. Main outcome measures included calculation of plasma tHcy, serum folate, and serum vitamin B(12) standard differences and odds ratios (OR) of TT genotype between cases and controls.

RESULTS

In total, 614 patients with all types of retinal vein occlusion had higher plasma tHcy levels than 762 control subjects (standard difference, 0.867; 95% confidence interval [CI] = 0.735, 0.999; P <.001). Plasma tHcy levels were also higher in 154 patients with retinal artery occlusion compared with 358 control subjects (standard difference 1.174; 95% CI = 0.947, 1.402; P <.001). Serum folates, but not vitamin B(12) levels, were lower in 287 patients with retinal vascular occlusion than in the same number of control subjects (standard difference, 0.508; 95% CI = 0.340, 0.675; P <.001; and -0.060; 95% CI = -0.024, 0.104; P =.474, respectively). Similar proportions of 690 patients with retinal vein occlusion and 2754 control subjects demonstrated the TT genotype (OR = 1.332; 95% CI = 0.995, 1.783; P =.054) as did 152 patients with retinal artery occlusions and 435 control subjects (OR = 1.716; 95% CI = 0.977, 3.014; P =.060).

CONCLUSIONS

Retinal vascular occlusion is associated with elevated plasma tHcy levels and low serum folate levels, but not serum vitamin B(12) levels and TT genotype. Until a prospective multicenter trial is undertaken, plasma tHcy levels and serum folate levels should be determined in patients with retinal vascular occlusions, and dietary supplementation with low doses of folate and vitamin B(12) should be considered for affected persons.

[Hyperhomocysteinemia: an independent risk factor or a simple marker of vascular disease? 1. Basic data]

Recent epidemiological studies have suggested that hyperhomocysteinemia is associated with increased risk of vascular disease. Homocysteine is a sulphur-containing amino acid whose metabolism stands at the intersection of two pathways: remethylation to methionine, which requires folate and vitamin B12 (or betaine in an alternative reaction); and transsulfuration to cystathionine which requires vitamin B6. The two pathways are coordinated by S-adenosylmethionine which acts as an allosteric inhibitor of the methylenetetrahydrofolate reductase (MTHFR) and as an activator of cystathionine beta-synthase (CBS). Hyperhomocysteinemia arises from disrupted homocysteine metabolism. Severe hyperhomocysteinemia is due to rare genetic defects resulting in deficiencies in CBS, MTHFR, or in enzymes involved in methyl cobalamine synthesis and homocysteine methylation. Mild hyperhomocysteinemia seen in fasting condition is due to mild impairment in the methylation pathway (i.e. folate or B12 deficiencies or MTHFR thermolability). Post-methionine-load hyperhomocysteinaemia may be due to heterozygous cystathionine-beta-synthase defect or B6 deficiency. Patients with homocystinuria and severe hyperhomocysteinemia develop arterial thrombotic events, venous thromboembolism, and more seldom premature arteriosclerosis. Experimental evidence suggests that an increased concentration of homocysteine may result in vascular changes through several mechanisms. High levels of homocysteine induce sustained injury of arterial endothelial cells, proliferation of arterial smooth muscle cells and enhance expression/activity of key participants in vascular inflammation, atherogenesis, and vulnerability of the established atherosclerotic plaque. These effects are supposed to be mediated through its oxidation and the concomitant production of reactive oxygen species. Other effects of homocysteine include: impaired generation and decreased bioavailability of endothelium-derived relaxing factor/nitric oxide; interference with many transcription factors and signal transduction; oxidation of low-density lipoproteins; lowering of endothelium-dependent vasodilatation. In fact, the effect of elevated homocysteine appears multifactorial affecting both the vascular wall structure and the blood coagulation system.

Postmethionine-load homocysteine determination for the diagnosis hyperhomocysteinaemia and efficacy of homocysteine lowering treatment regimens

Substantial epidemiological evidence supports the vision that moderate hyperhomocysteinaemia is a graded and independent cardiovascular risk factor. The additional value of the methionine loading test for the assessment of hyperhomocysteinaemia continues to be disputed. This overview presents the historical background for the rationale of the methionine loading test and describes determinants and variability of the postmethionine-load homocysteine concentration. The association of postmethionine-load homocysteine concentrations and the risk of cardiovascular events is discussed. Furthermore, the results of homocysteine lowering treatment on postmethionine-load homocysteine are given. Up to 50% of subjects with hyperhomocysteinaemia can only be detected after performing a methionine loading test; these subjects have a normal fasting homocysteine. Both fasting and postmethionine-load homocysteine concentrations are influenced by serum folate and creatinine concentrations and by the methylenetetrahydrofolate reductase genotype, and may be subject to a wide intra-individual variability (approximately 20%). Cross-sectional studies suggest that cardiovascular risk may increase gradually from postmethionine-load homocysteine concentrations above 38 micromol/l. Supplementation with folic acid 0.5 mg daily adequately reduces postmethionine-load homocysteine; addition of pyridoxine appears to have no further homocysteine lowering effect. Prospective studies supporting the clinical significance of the methionine loading test for individual patient counselling are lacking; it seems, therefore, prudent to restrict this test for research purposes.

Hyperhomocysteinaemia in patients with peripheral arterial occlusive disease

In the Western world, cardiovascular disease is still the most common cause of death. Over the past decade it has become clear that apart from common risk factors, high concentrations of total homocysteine are relavant to the process of atherosclerosis, especially in the development of premature vascular disease. Hyperhomocysteinaemia (HHC) can be found in 25-32% of the patients with premature peripheral arterial occlusive disease (PAD). Retrospective and prospective studies, evaluating the clinical course of patients with PAD, showed significant associations between high concentrations of total homocysteine and the severity of atherosclerosis and with a more rapid disease progression and mortality rates. HHC can be treated with vitamin B6 and folic acid. Although there may be indications that there is a protective effect of treatment, prospective randomized clinical trials are urgently needed to unravel the role of HHC and its treatment in patients with premature PAD.

Diagnosis and treatment of hyperhomocysteinemia

Hyperhomocysteinemia has emerged as an important risk factor for cardiovascular disease. However, its place in clinical practice is somewhat unclear, due to the lack of clinical trials documenting the benefit of treatment on reducing cardiovascular events. Vitamin therapy, particularly with folic acid, reduces plasma homocysteine significantly and improves other surrogate markers of cardiovascular risk such as endothelial function. Although a consensus is lacking on the right approach to diagnosis and treatment of this risk factor, we have suggested an algorithm based on data from clinical studies. We are optimistic that such an approach will be helpful for the clinician until clinical trials, with cardiovascular events as endpoints, are completed.

Patients with atherosclerotic vascular disease: how low should plasma homocyst(e)ine levels go?

Plasma homocyst(e)ine level is a strong independent risk factor for vascular disease. The spelling of homocyst(e)ine reflects that what is measured, and what constitutes the risk factor; it includes homocysteine, homocystine (the dimer of homocysteine) and mixed cysteine-homocysteine disulfide. Homocyst(e)ine levels above 10.2 micro mol/L are associated with a doubling of coronary risk, and levels above 20 micro mol/L are associated with a 9.9-fold increase in risk compared with levels below 9 micro mol/L. The mechanisms by which homocyst(e)ine promotes vascular disease include increased thrombosis, consumption of nitric oxide, endothelial injury, and reduced thrombolysis. Homocyst(e)ine is an independent predictor of carotid atherosclerosis. Vitamin therapy with folate, pyridoxine (vitamin B(6)), and cyanocobalamin (vitamin B(12)) reduces blood levels of homocyst(e)ine, improves endothelial function, reduces levels of fibrinogen and lipoprotein(a), improves thrombolysis, and in uncontrolled clinical observation, leads to regression of carotid plaque. These lines of evidence support a causal relationship between homocyst(e)ine and atherosclerosis, and suggest that in patients with vascular disease, an appropriate target level for therapy may be below 9 or 10 micro mol/L. Randomized controlled studies are under way to determine whether vitamin therapy is effective in secondary prevention of myocardial infarction and stroke.

Hyperhomocysteinemia and pregnancy--review of our present understanding and therapeutic implications

Homocysteine results from the transmethylation of methionine. Its metabolism depends primarily on three enzymes and several vitamin cofactors. Genetic abnormality in these enzymes or deficiency of these vitamins lead to hyperhomocysteinemia (HHCh). HHCh is usually biologically defined by a fasting value >15 micromol/l. HHCh belongs among the congenital hypercoagulable states and is a long-known vascular disease risk factor. The discovery that HHCh may also be responsible for several pregnancy complications has only recently been made. Studies in this area are still scarce and report on limited numbers of patients. It nevertheless appears clear that HHCh is associated with the syndromes of repeated miscarriage, pre-eclampsia, placenta abruptio, thromboembolic events, neural tube defects, and perhaps with fetal death-in-utero and intra-uterine growth retardation. Supplementation with vitamin B9 can reduce plasma HC levels, and is thus recommended in patients with HHCh. The prevention of thromboembolic events during pregnancy by anticoagulant treatment is also desirable in these patients.

Hyperhomocysteinemia in type 2 diabetes mellitus: cardiovascular risk factors and effect of treatment with folic acid and pyridoxine

OBJECTIVE

To determine whether hyperhomocysteinemia (HH) exacerbates other cardiovascular risk factors and markers of coagulation and hemostasis in patients with type 2 diabetes mellitus (DM) and whether treatment of HH with vitamins will alter these risk factors.

METHODS

We measured several cardiovascular risk factors and markers of coagulation and hemostasis in patients with type 2 DM with and without HH. We also treated patients with type 2 DM and coexistent HH with high doses of folic acid and pyridoxine to determine whether this treatment would lower plasma total homocysteine concentrations as well as correct other associated cardiovascular risk factors in this population.

RESULTS

Plasma levels of plasminogen activator inhibitor type 1 and fibrinogen were significantly higher in all patients with DM in comparison with control subjects (P<0.01), whether they had HH or not. No significant difference was noted between the two groups of patients with DM. The presence of hypertension and microalbuminuria did not lead to a higher plasma total homocysteine. After treatment with folic acid, 15 mg daily, and pyridoxine, 600 mg daily, fasting (basal) plasma total homocysteine declined significantly in patients with DM from 12.3 +/- 2.9 micromol/L to 9.1 +/- 1.1 micromol/L (P<0.01). The peak post-methionine load plasma total homocysteine in the patients with DM decreased from 39.9 +/- 11.4 micromol/L to 30.4 +/- 6.5 micromol/L (P<0.05). Neither fasting nor peak plasma total homocysteine changed in normal subjects. None of the cardiovascular risk factors measured changed significantly with the vitamin treatment.

CONCLUSION

The coexistence of type 2 DM and HH does not lead to an exacerbation of abnormalities in the measured variables of coagulation and hemostasis. Treatment with high doses of folic acid and pyridoxine lowers the plasma total homocysteine significantly but does not improve any of the associated cardiovascular risk factors that we measured. Long-term clinical trials should be conducted to determine whether high-dose vitamin treatment will diminish the increased morbidity and mortality associated with cardiovascular disease in patients with type 2 DM.

The effect of different treatment regimens in reducing fasting and postmethionine-load homocysteine concentrations

OBJECTIVES

To determine the homocysteine-lowering effect of different treatment regimens on both fasting and postmethionine-load plasma total homocysteine (tHcy) concentrations.

DESIGN

Descriptive study of consecutive hyperhomocysteinaemic subjects per treatment regimen. Homocysteine was measured in the fasting state and 6 h after methionine loading, both before and after 8 weeks of vitamin therapy. Hyperhomocysteinaemia was defined as a fasting tHcy and/or increase in tHcy (postmethionine-load minus fasting tHcy concentration) exceeding the 95th percentile of local controls.

SETTING

Outpatient clinic of internal medicine of a large non-academic teaching hospital.

SUBJECTS

One hundred and seventeen hyperhomocysteinaemic subjects (vascular patients and first-degree relatives).

INTERVENTIONS

There were four regimens: pyridoxine, 200 mg; folic acid, 5 mg; combination of folic acid 0.5 mg and pyridoxine 100 mg; and folic acid, 0.5 mg daily.

RESULTS

All regimens, except pyridoxine 200 mg, significantly reduced fasting tHcy without differences in the percentage reduction (32-38%). All regimens produced a significant reduction in the increase in tHcy and postmethionine-load tHcy. The reduction in postmethionine-load tHcy was smaller for pyridoxine 200 mg than for combination therapy. No differences were found in the percentage reduction (for both increase in tHcy and postmethionine-load tHcy) between folic acid 5 mg and folic acid 0.5 mg.

CONCLUSIONS

Monotherapy folic acid (0.5 mg daily) is the lowest effective therapy for reducing both fasting and postmethionine-load tHcy concentrations, with the same results as high-dose folic acid (5 mg daily). Pyridoxine has no additional value.

Clinical relevance of hyperhomocysteinaemia in atherothrombotic disease

High fasting plasma homocysteine levels (> 12 to 15 mumol/L) are commonly encountered in clinical practice and are associated with increased risk of atherothrombotic disease. Treatment with folic acid (1 to 5 mg/day) is inexpensive and effective in normalising plasma homocysteine levels. High plasma homocysteine levels after methionine loading (> 40 to 50 mumol/L) are also common and can be treated with pyridoxine-based regimens (50 to 250 mg/day). As compared with fasting plasma homocysteine levels, the association between high postmethionine loading plasma homocysteine levels and atherothrombotic disease has been less extensively studied. There is reasonable, but not clearly definitive, evidence that high plasma homocysteine levels are causally related to atherothrombotic disease. Results of randomised trials of homocysteine-lowering treatment with clinical end-points will be available in 4 to 6 years. At present, a reasonable policy for the practising clinician would be to consider homocysteine-lowering treatment in individuals at very high risk of atherothrombotic disease, such as patients with clinically manifest atherothrombotic disease with onset before 55 years of age, patients with end stage renal disease, and healthy subjects with a strong family history of early-onset atherothrombotic disease. Such a policy should be reassessed as the results of randomised trials become available.

Effect of homocysteine-lowering treatment with folic acid plus vitamin B6 on progression of subclinical atherosclerosis: a randomised, placebo-controlled trial

BACKGROUND

A high plasma homocysteine concentration is associated with increased risk of atherothrombotic disease. We investigated the effects of homocysteine-lowering treatment (folic acid plus vitamin B6) on markers of subclinical atherosclerosis among healthy siblings of patients with premature atherothrombotic disease.

METHODS

We did a randomised, placebo-controlled trial among 158 healthy siblings of 167 patients with premature atherothrombotic disease. 80 were assigned placebo and 78 were assigned 5 mg folic acid and 250 mg vitamin B6 daily for 2 years. The primary endpoint was the development or progression of subclinical atherosclerosis as estimated from exercise electrocardiography, the ankle-brachial pressure index, and carotid and femoral ultrasonography.

FINDINGS

Ten participants in the treatment group, and 14 in the placebo group dropped out. Vitamin treatment, compared with placebo, was associated with a decrease in fasting homocysteine concentration (from 14.7 to 7.4 micromol/L vs from 14.7 to 12.0 micromol/L), and in postmethionine homocysteine concentration (from 64.9 to 34.9 micromol/L vs from 64.8 to 50.3 micromol/L). It was also associated with a decreased rate of abnormal exercise electrocardiography tests (odds ratio 0.40 [0.17-0.93]; p=0.035). There was no apparent effect of vitamin treatment on ankle-brachial pressure indices (0.87 [0.56-1.33]), or on carotid and peripheral-arterial outcome variables (1.02 [0.26-4.05] and 0.86 [0.47-1.59], respectively).

INTERPRETATION

Homocysteine-lowering treatment with folic acid plus vitamin B6 in healthy siblings of patients with premature atherothrombotic disease is associated with a decreased occurrence of abnormal exercise electrocardiography tests, which is consistent with a decreased risk of atherosclerotic coronary events.

[Lowering high levels of fasting total homocysteine with folic acid and vitamins B in patients with venous thromboembolism: relationship between response and the C677T methylenetetrahydrofolate reductase (MTHRF) genotype]

BACKGROUND

High levels of plasma total homocysteine (tHcy) are involved in arterial or venous occlusive diseases. It essentially depends on the nutritional status of folic acid (FA) and vitamins B12 or B6, but also on the methylenetetrahydrofolate reductase (MTHFR) enzymatic activity. We aim to evaluate the response of the hyperhomocysteinemia (HHcy) to a standard schedule of vitamin supplementation, according with the MTHFR genotype.

PATIENTS AND METHODS

227 patients, diagnosed with venous thromboembolism (VTE) were analysed for tHcy (in fasting conditions), and for the MTHFR-C677T gene polymorphism. When the tHcy exceeded the cut-off point (men = 16, women = 15 mumol/l), the patients were supplemented with a dose equivalent to 1 mg FA, 0.2 mg B12 and 100 mg of B6, daily by 6 weeks. Afterwards they were reanalysed and the reduction was stratified by MTHFR genotype, looking for any difference in the response.

RESULTS

The mean fasting tHcy was 12.3 mumol/l (SD = 8). The 51 hyperhomocysteinemic patients (22%) were older (65.1 y) than the normal ones (55.0 y) (p = 0.0001). The treatment was carried out properly in 46 patients (90%). The pre-treatment mean Hcy was 23.2 (SD = 10.5) mumol/l, and it was reduced to 13.0 (SD = 5.9) (p = 0.0001) (mean reduction = 42.1%). By genotype, the C/C reduced from 21.0 to 13.2 mumol/l (37%) (n = 18), the C/T from 25.0 to 12.6 mumol/l (46%) (n = 24), and the abnormal homozygotes T/T from 22.7 to 14.5 mumol/l (39%) (n = 4), although no statistical significant differences were found. In 80% of cases (37/46), tHcy values normalised. A negative correlation (r = -0.471) (p = 0.005) was observed between age and response.

CONCLUSIONS

The FA/B6/B12 based therapy reduces in a simple, quick and effective way (> 40% in 6 weeks) the pathologic tHcy levels on a VTE population and this is not influenced by the MTHFR genotype. As HHcy seems related with recurrences of venous thrombosis, we could speculate if it would be useful to analyse routinely the tHcy, attempting reduction in selected cases.

Total homocysteine and cardiovascular disease

Recent data have shown that an elevated plasma level of the amino acid homocysteine (Hcy) is a common, independent, easily modifiable and possibly causal risk factor for cardiovascular disease (CVD) which may be of equal importance to hypercholesterolemia, hypertension and smoking. This paper reviews the biochemical, clinical, epidemiological and experimental data underlying this conclusion and is critically questioning whether elevated tHcy is a causal factor.

Homocysteine metabolism

Homocysteine is a sulfur amino acid whose metabolism stands at the intersection of two pathways: remethylation to methionine, which requires folate and vitamin B12 (or betaine in an alternative reaction); and transsulfuration to cystathionine, which requires pyridoxal-5'-phosphate. The two pathways are coordinated by S-adenosylmethionine, which acts as an allosteric inhibitor of the methylenetetrahydrofolate reductase reaction and as an activator of cystathionine beta-synthase. Hyperhomocysteinemia, a condition that recent epidemiological studies have shown to be associated with increased risk of vascular disease, arises from disrupted homocysteine metabolism. Severe hyperhomocysteinemia is due to rare genetic defects resulting in deficiencies in cystathionine beta synthase, methylenetetrahydrofolate reductase, or in enzymes involved in methyl-B12 synthesis and homocysteine methylation. Mild hyperhomocysteinemia seen in fasting conditions is due to mild impairment in the methylation pathway (i.e. folate or B12 deficiencies or methylenetetrahydrofolate reductase thermolability). Post-methionine-load hyperhomocysteinemia may be due to heterozygous cystathionine beta-synthase defect or B6 deficiency. Early studies with nonphysiological high homocysteine levels showed a variety of deleterious effects on endothelial or smooth muscle cells in culture. More recent studies with human beings and animals with mild hyperhomocysteinemia provided encouraging results in the attempt to understand the mechanism that underlies this relationship between mild elevations of plasma homocysteine and vascular disease. The studies with animal models indicated the possibility that the effect of elevated homocysteine is multifactorial, affecting both the vascular wall structure and the blood coagulation system.

Normohomocysteinaemia and vitamin-treated hyperhomocysteinaemia are associated with similar risks of cardiovascular events in patients with premature peripheral arterial occlusive disease. A prospective cohort study

OBJECTIVES

Mild hyperhomocysteinaemia (HHC), fasting or after methionine loading, is associated with an increased risk and severity of atherosclerotic vascular disease. Post-methionine and fasting HHC are responsive to treatment with vitamin B, and folic acid. We performed a prospective cohort study amongst normohomocysteinaemic and vitamin-treated (vitamin B6, 250 mg plus folic acid, 5 mg daily) hyperhomocysteinaemic patients with premature peripheral arterial occlusive disease and assessed the incidence of cardiovascular events.

DESIGN

We studied 273 consecutive patients with clinically manifest peripheral arterial occlusive disease with onset before the age of 56, 79 (28.9%) of whom had postmethionine HHC. Follow-up was obtained in 232 (85'%o) patients. At baseline, 70 (30')/) were hyperhomocysteinaemic after methionine loading and started treatment with vitamin B, and folic acid; 162 (70%) were normohomocysteinaemic (reference group).

RESULTS

During the follow-up period (median 20, range 1-63 months), 48 (29.6%) and 23 (32.9%) of the normo- and the hyperhomocysteinaemic patients, respectively, had a new cardiovascular event. Most (75%) involved the peripheral arterial system. The crude incidence rate for any cardiovascular event was 0.16 (95% CI, 0.12-0.21) per person per year in the normohomocysteinaemic and 0.16 (95% CI, 0.09-0.22) per person per year in the hyperhomocysteinaemic group. Multivariate Cox regression analyses showed that higher plasma homocysteine levels were associated with an increased risk of new cardiovascular events in the normohomocysteinaemic patients (relative risk [RR] per 1 micromol L(-1), 1.17 [CI, 1.05-1.30] for fasting and 1.06 [CI, 1.01-1.12] for postmethionine levels), but not in the hyperhomocysteinaemic (vitamin-treated) patients. The adjusted RR for new cardiovascular events in the hyper- as compared to the normohomocysteinaemic patients was 0.76 (CI, 0.33-1.74).

CONCLUSIONS

These data are consistent with a protective effect of treatment with vitamin B6 and folic acid in patients with premature peripheral arterial occlusive disease and postmethionine HHC. Double-blind randomized trials are necessary to confirm this.

Plasma homocysteine levels and folate status in children with sickle cell anemia

PURPOSE

A sensitive inverse relationship between plasma homocysteine concentration and folate status has been demonstrated. Although children with sickle cell anemia (SCA) are at potential risk for folate deficiency, plasma homocysteine levels have not been reported in such patients. Therefore, a study was designed to assess plasma homocysteine levels as a marker of folate status.

DESIGN

Plasma homocysteine concentrations were measured in 120 children with SCA (102 in steady state and 18 during an acute complication) who had never received supplemental folic acid. Folate status was directly assessed in 34 of these patients.

RESULTS

Plasma homocysteine levels in the patients with SCA and control subjects were similar. The mean value +/- 1 SD was 5.8+/-2.5 micromol/L (range, 1.6 to 14.1 micromol/L) in the patients with SCA and 6.1+/-2.7 micromol/L (range, 1.7 to 15.3 micromol/L) in 73 pediatric control subjects. In a subpopulation of the study group (34 children), simultaneous serum folate, red cell folate, and total homocysteine concentrations were also measured. Their serum folate and red cell folate concentrations were normal: 12.4+/-10.0 nmol/L (range, 1 to 42 nmol/L) and 604+/-374.7 nmol/L (range, 205 to 1741 nmol/L), respectively. There was no correlation of plasma homocysteine concentration with various clinical or laboratory measures or with red cell folate concentration.

CONCLUSION

Folate stores in children with SCA not receiving folic acid supplements are adequate despite an underlying hemolytic anemia.

Determinants of fasting and post-methionine homocysteine levels in families predisposed to hyperhomocysteinemia and premature vascular disease

Elevated plasma total homocysteine (tHcy) levels, either measured in the fasting state or after oral methionine loading, are associated with an increased risk of atherothrombotic disease. Fasting and post-methionine hyperhomocysteinemia (HHC) overlap to a limited extent; both can occur as familial traits. We investigated determinants of fasting, postmethionine and delta (ie, post-methionine minus fasting levels) tHcy levels in 510 subjects of 192 HHC-prone families including 161 patients with clinical vascular disease and 349 without vascular disease. We focused on tHcy levels in relation to levels of vitamin B12, B6 and folate and the methylenetetrahydrofolate reductase (MTHFR) C677T mutation. Multivariate linear analyses adjusted for the presence of vascular disease showed that fasting tHcy was significantly related to folate and vitamin B12, and the presence of the MTHFR TT genotype and the T allele, and to age, smoking habits, and serum levels of creatinine. Both post-methionine and delta tHcy levels were related to serum folate levels, and the presence of the MTHFR TT genotype and the T allele, and to postmenopausal status, and body mass index. An interaction was found between MTHFR TT genotype and serum folate levels for both fasting and post-methionine tHcy, ie, for a given decrease in serum folate, homocysteine levels increased more in subjects with the TT genotype than in those with the CC genotype. Fasting, post-methionine and delta tHcy were higher in patients with vascular disease than in their healthy siblings, but these levels were less dependent on serum folate levels (P<0.05), whereas the effect of MTHFR genotype was stronger (P=0.01). This study found evidence that post-methionine and delta tHcy levels are not only influenced by factors affecting homocysteine transsulfuration but also by factors that affect remethylation. The explained variances of fasting, post-methionine and delta tHcy were 49%, 62%, and 78%, respectively. We also found evidence, in patients with premature vascular disease but not in their healthy siblings, for a factor that increases tHcy levels but weakens the normal inverse relation between folate and tHcy and amplifies the effect of the MTHFR genotype.

Risk factors for premature atherosclerosis

OBJECTIVES

to investigate the prevalence of risk factors in patients with premature atherosclerosis.

DESIGN

retrospective controlled study.

MATERIALS

135 consecutive patients with premature atherosclerosis </= 55 years (group I) were investigated. A control group comprised 107 consecutive patients >/= 65 years (group II) with atherosclerosis. Statistical analysis was performed with Chi-squared test and logistic regression analysis.

RESULTS

group I versus group II: diabetes 11% vs. 27% (p=0.001), smoking 84% vs. 67% (p=0.002), hypertension 36% vs. 58% (p=0.001), hypercholesterolaemia 47% vs. 34% (p=0.04), family history of cardiovascular disease 53% vs. 42% (p=0.08). In group I hyperhomocysteinaemia was present in 24 of the 108 patients tested, anticardiolipin antibodies were present in four of the 34 tested and coagulation abnormalities were found in four of the 22 patients tested.

CONCLUSION

the difference in the prevalence of the different risk factors between the two groups suggests that either certain risk factors are more likely to cause premature atherosclerosis, or that other risk factors must be present in addition to the known risk factors in order to induce premature atherosclerosis.

Combination of low-dose folic acid and pyridoxine for treatment of hyperhomocysteinaemia in patients with premature arterial disease and their relatives

Hyperhomocysteinaemia is an independent risk factor for atherosclerotic disease and venous thrombosis. The optimal homocysteine-lowering vitamin dose and target total homocysteine (tHcy) concentration are currently unknown. We prospectively studied the homocysteine-lowering effect after 8 weeks low-dose combination of folic acid (0.5 mg) and pyridoxine (100 mg) in 49 hyperhomocysteinaemic persons (33 patients with documented premature arterial disease and 16 of their first-degree relatives). Hyperhomocysteinaemia was in both sexes defined as fasting tHcy concentration > 12 micromol/l and/or post-methionine load tHcy concentration > 38 micromol/l. Low-dose vitamin therapy significantly reduced fasting tHcy concentration (median 13.9 to 9.3 micromol/l, reduction 32% (95% CI: 27-37%)) and post-load tHcy concentration (median 55.2 to 36.5 micromol/l, reduction 30% (95% CI: 25-35%)). Fasting tHcy reduction was similar in women and men, as well as in patients and relatives. Post-load tHcy reduction was significantly less in men compared to women (P = 0.04) and in relatives compared to patients (P = 0.03). Although low-dose combination of folic acid and pyridoxine results in a substantial reduction of tHcy concentrations (30-32%) in subjects with hyperhomocysteinaemia, the normalisation percentage to predefined criteria was less impressive (49%).

Effect of folic acid and betaine on fasting and postmethionine-loading plasma homocysteine and methionine levels in chronic haemodialysis patients

OBJECTIVES

To study fasting and postmethionine-loading (increment and decrement) plasma homocysteine levels in end-stage renal disease (ESRD) patients in relation to B-vitamin status and after folic acid treatment without or with betaine.

DESIGN

Plasma total homocysteine (tHcy) and methionine levels were measured in chronic haemodialysis patients after an overnight fast, and 6 and 24 h after an oral methionine load (0.1 g kg-1). The patients were subsequently randomized to treatment with folic acid 5 mg daily with or without betaine 4 g daily, and the loading test was repeated after 12 weeks. The patients were then re-randomized to treatment with 1 or 5 mg folic acid daily for 40 weeks, after which a third loading test was performed.

SETTING

Haemodialysis unit of university hospital and centre for haemodialysis.

SUBJECTS

Twenty-nine consecutive maintenance (> 3 months) haemodialysis patients, not on folic acid supplementation, 26 of whom completed the study.

RESULTS

At baseline, the mean fasting, the 6 h postload and the 6 h postload increment plasma tHcy levels were increased as compared with those in healthy controls (46.8 +/- 6.9 (SEM), 92.8 +/- 9.1 and 46.0 +/- 4.2 mumol L-1, respectively) and correlated with serum folate (r = -0.42, P = 0.02; r = -0.61, P = 0.001 and r = -0.54, P = 0.003, respectively), but not with vitamin B6 or vitamin B12. At week 12, these variables had all decreased significantly. Betaine did not have additional homocysteine-lowering effects. At week 52, fasting and postload tHcy levels did not differ significantly between patients on 1 or 5 mg folic acid daily. Plasma tHcy half-life and plasma methionine levels after methionine loading were not altered by folic acid treatment.

CONCLUSIONS

In chronic haemodialysis patients, fasting as well as postmethionine-loading plasma tHcy levels depend on folate status and decrease after folic acid therapy. Increased postload homocysteine levels in these patients therefore do not necessarily indicate an impaired transsulphuration capacity only; alternatively, folate may indirectly influence transsulphuration. The elucidation of the complex pathogenesis of hyperhomocysteinaemia in chronic renal failure requires further investigation.

Homocysteine, a Risk Factor for Cardiovascular Disease

Fasting hyperhomocysteinemia is an independent risk factor for coronary artery disease, stroke, peripheral vascular atherosclerosis, and for arterial and venous thromboembolism. The risk for cardiovascular disease with homocysteine is similar to conventional risk factors. The interaction of hyperhomocysteinemia with hypertension and smoking is strong and the combined effect is more than multiplicative. The combined effect of homocysteine and cholesterol is additive. Homocysteine produces atherosclerosis, thromboembolism, and vascular endothelial cell injury. Vascular dysfunction produced by homocysteine may be due to endothelial cell damage. Homocysteinemia-induced atherosclerosis is probably due to various factors including endothelial cell injury, inability to sustain S-nitroso-homocysteine formation because of imbalance between production of nitric oxide by dysfunctional endothelium and homocysteine, smooth muscle cell proliferation, and thromboembolism. There is strong evidence that endothelial cell injury is associated with oxidative stress produced by homocysteine. Hyperhomocysteinemia is associated with numerous conditions, including coronary disease, stroke, peripheral vascular disease (carotid artery and cerebrovascular atherosclerosis), venous thrombosis, renal disease, diabetes mellitus, and organ transplant. Folic acid, vitamin B12 and B6 have been shown to be beneficial in reducing plasma homocysteine levels. Folic acid is specifically very effective, safe and inexpensive.

Carotid and femoral artery wall thickness and stiffness in patients at risk for cardiovascular disease, with special emphasis on hyperhomocysteinemia

Recent developments in ultrasound technology enable the noninvasive measurement of structural and functional vessel wall changes. Until now, the effect of homocysteine on the arterial wall has remained unclear: reports on intima-media thickness (IMT) yield conflicting results, whereas data on vessel wall stiffness are lacking. Because several cardiovascular risk factors result in an increased IMT or stiffness, different groups at risk for atherosclerotic disease, with special emphasis on hyperhomocysteinemia, were studied. Nineteen patients homozygous and 14 subjects heterozygous for cystathionine beta-synthase (CBS) deficiency, 21 patients with familial hypercholesterolemia (FH), 15 patients with essential hypertension, 20 smokers, and 28 control subjects were studied. The IMT values (both right and left) of the common carotid artery (CCA), bulb (BUL), internal carotid artery (ICA), and common femoral artery (CFA) were measured in millimeters by high-resolution ultrasound (Biosound). The distensibility (DC, in 10(-3). kPa-1) and compliance (CC in mm2. kPa-1) coefficients of the CCA (right and left) and CFA (right) were determined by a wall track system (Pie Medical). The mean IMT of the posterior wall in the CCA was 0.70+/-0.09 mm in healthy controls. For patients with vascular disease, FH, and hypertension and in smokers, the mean CCA IMT was larger, whereas no major differences in IMT were observed in patients either homozygous or heterozygous for CBS deficiency. The DC and CC in the right CCA were 23.5+/-6.9 (10(-3). kPa-1) and 0.9+/-0.3 (mm2. kPa-1) in healthy subjects, slightly lower in patients homozygous for CBS deficiency, and clearly lower in patients with vascular disease, FH, and hypertension. No positive correlation was found between plasma homocysteine level and either IMT, CC, or DC. Because smoking was a confounder in each risk group, a stepwise regression analysis was carried out to assess the contribution of each risk factor on IMT and arterial wall stiffness. Age explained most of the variation in IMT of the CCA (coefficient of determination R2 of 0.34), whereas R2 values for serum low density lipoprotein cholesterol, smoking (pack-years), and systolic blood pressure were 0.08, 0.07, and 0.06, respectively. Homocysteine did not contribute to variation in IMT in both the CCA and CFA. Age and smoking contributed to the variation in IMT in the CFA. The variation in DC and CC in the right CCA and right CFA could in part be explained by age, low density lipoprotein cholesterol, and blood pressure. Plasma homocysteine concentration explained only a small proportion of the variation in DC in the CCA (R2=0.02) and in CC in the CFA (R2=0.04). In this study, no relationship was found between homocysteine level and the thickness of the arterial wall, with only a marginal influence on stiffness.

Folate administration reduces circulating homocysteine levels in NIDDM patients on long-term metformin treatment

OBJECTIVES

Metformin treatment increases circulating homocysteine levels. We studied whether administration of folate reduces serum total homocysteine levels in patients on long-term metformin treatment.

DESIGN

A prospective, randomized, double-blind, placebo-controlled study lasting for 12 weeks and taking place in a university hospital setting.

SUBJECTS

Thirty patients treated with a metformin dose of at least 1000 mg day-1 for a minimum of 1 year were included. At baseline serum total homocysteine levels were within the reference range. One patient who withdrew and one who died were excluded from the statistical evaluation. Twenty-six of the remaining patients suffered from NIDDM, the other two from hyperlipidaemia.

INTERVENTION

Patients were randomized into two groups at week 0. The folate group received 0.25 mg day-1 of folate in addition to 60 mg day-1 of Fe2+, while the placebo group received only 60 mg day-1 of Fe2+.

MAIN OUTCOME MEASURES

Fasting homocysteine, cysteine, cysteinylglycine, vitamin B12 and folate were measured at week 0, 4 and 12. Changes from week 0 to week 4 and from week 0 to week 12 were calculated.

RESULTS

Folate administration reduced serum levels of total homocysteine in the folate group as compared with the placebo group by 13.9% (P < 0.01) and 21.7% (P < 0.001) at week 4 and 12, respectively. In the folate group versus the placebo group serum levels of vitamin B12 increased by 9.9% (P = 0.010) and 9.6% (P = 0.043) while folate levels increased by 96.9 and 89.9% at week 4 and 12, respectively.

CONCLUSION

The present study indicates that the homocysteine-increasing effect of metformin can be counteracted by folate administration.

Relationship between homocysteine and thrombotic disease

Hyperhomocysteinemia is a condition which, in the absence of kidney disease, indicates a disrupted sulfur amino acid metabolism, either because of vitamin deficiency (folate, B12 and B6) or a genetic defect. Epidemiologic evidence suggests that mild hyperhomocysteinemia is associated with increased risk of arteriosclerotic disease and stroke. The relationship between hyperhomocysteinemia and thrombosis has been investigated in 10 studies involving a total of 1200 patients and 1200 controls. Eight of these studies demonstrated positive association with odds ratios that ranged from two to 13. This association was enhanced by including a methionine loading test. There is some evidence which suggests that hyperhomocysteinemia and activated protein C resistance have synergistic effect on the onset of thrombotic disease. Recent studies with animal models for mild hyperhomocysteinemia provided encouraging results in the understanding of the mechanism that underlies this relationship between mild elevations of plasma homocysteine and vascular disease. These animal models pointed to the possibility that the effect of elevated homocysteine is multifactorial, affecting both the vascular wall structure and the blood coagulation system.

Effects of folic acid and vitamin B6 supplementation on women with hyperhomocysteinemia and a history of preeclampsia or fetal growth restriction

OBJECTIVE

Our purpose was to assess the incidence of hyperhomocysteinemia in patients with a history of preeclampsia or fetal growth restriction, to evaluate the effects of vitamin supplementation on the methionine loading test, and to study the course of subsequent pregnancies in women with hyperhomocysteinemia and a history of preeclampsia or fetal growth restriction.

STUDY DESIGN

A total of 207 consecutive patients with a history of preeclampsia or fetal growth restriction was tested for hyperhomocysteinemia. Thirty-seven were found to be positive and were treated with folic acid and vitamin B6, and 27 had a second methionine loading test after vitamin supplementation. Fourteen patients became pregnant again while receiving vitamins and aspirin.

RESULTS

All patients who underwent a methionine loading test after vitamin supplementation had a completely normalized methionine loading test. Of the 14 pregnancies in women receiving vitamins and aspirin, 7 were complicated by preeclampsia. Birth weights were 2867 +/- 648 g compared with 1088 +/- 570 g in the previous pregnancies.

CONCLUSIONS

Vitamin B6 and folic acid correct the methionine loading test in patients with hyperhomocysteinemia. Perinatal outcome in patients with a history of preeclampsia or fetal growth restriction and hyperhomocysteinemia appears to be favorable.

[A young patient with multiple arterial occlusions]

BACKGROUND

Mild hyperhomocysteinemia due to genetic causes and nutrition factors is well known as an independent strong risk factor for premature arterial occlusive disease.

CASE REPORT

A 27-year-old female with a history of two episodes of small bowel ileus due to vascular causes presented with subacute pain in the left lower extremity. Angiography revealed a short segmental occlusion in the P III segment of the popliteal artery with small vessel collateralization and proximal occlusion of the superior mesenteric artery und the coeliac trunk. Vascular risk factors in this patient included smoking over a duration of 10 years, use of oral contraceptives (estrogen and gestagen combination) and elevated levels of homocysteine in the fasting state and after methionin loading. The patient was treated conservatively with intravenous application of prostaglandins, additionally she underwent training to improve her walking capability. After 4 weeks of the fasting state as well as after methionin loading were normalized by an oral substitution with folate and B vitamins. So far it was not possible to prove a genetic defect of the enzymes participating in the metabolism of homocysteine.

CONCLUSION

This clinical conference of a young female patient with occlusion of several arteries illustrates the differential diagnosis of premature occlusive vascular disease with special regard to mild hyperhomocysteinemia as an independent risk factor.

Homocysteine and cardiovascular disease

An elevated level of total homocysteine (tHcy) in blood, denoted hyperhomocysteinemia, is emerging as a prevalent and strong risk factor for atherosclerotic vascular disease in the coronary, cerebral, and peripheral vessels, and for arterial and venous thromboembolism. The basis for these conclusions is data from about 80 clinical and epidemiological studies including more than 10,000 patients. Elevated tHcy confers a graded risk with no threshold, is independent of but may enhance the effect of the conventional risk factors, and seems to be a particularly strong predictor of cardiovascular mortality. Hyperhomocysteinemia is attributed to commonly occurring genetic and acquired factors including deficiencies of folate and vitamin B12. Supplementation with B-vitamins, in particular with folic acid, is an efficient, safe, and inexpensive means to reduce an elevated tHcy level. Studies are now in progress to establish whether such therapy will reduce cardiovascular risk.

Lowering blood homocysteine with folic acid based supplements: meta-analysis of randomised trials. Homocysteine Lowering Trialists' Collaboration

OBJECTIVE

To determine the size of reduction in homocysteine concentrations produced by dietary supplementation with folic acid and with vitamins B-12 or B-6.

DESIGN

Meta-analysis of randomised controlled trials that assessed the effects of folic acid based supplements on blood homocysteine concentrations. Multivariate regression analysis was used to determine the effects on homocysteine concentrations of different doses of folic acid and of the addition of vitamin B-12 or B-6.

SUBJECTS

Individual data on 1114 people included in 12 trials.

FINDINGS

The proportional and absolute reductions in blood homocysteine produced by folic acid supplements were greater at higher pretreatment blood homocysteine concentrations (P < 0.001) and at lower pretreatment blood folate concentrations (P < 0.001). After standardisation to pretreatment blood concentrations of homocysteine of 12 mumol/l and of folate of 12 nmol/l (approximate average concentrations for Western populations), dietary folic acid reduced blood homocysteine concentrations by 25% (95% confidence interval 23% to 28%; P < 0.001), with similar effects in the range of 0.5-5 mg folic acid daily. Vitamin B-12 (mean 0.5 mg daily) produced an additional 7% (3% to 10%) reduction in blood homocysteine. Vitamin B-6 (mean 16.5 mg daily) did not have a significant additional effect.

CONCLUSIONS

Typically in Western populations, daily supplementation with both 0.5-5 mg folic acid and about 0.5 mg vitamin B-12 would be expected to reduce blood homocysteine concentrations by about a quarter to a third (for example, from about 12 mumol/l to 8-9 mumol/l). Large scale randomised trials of such regimens in high risk populations are now needed to determine whether lowering blood homocysteine concentrations reduces the risk of vascular disease.

Vitamin supplementation reduces blood homocysteine levels: a controlled trial in patients with venous thrombosis and healthy volunteers

Hyperhomocysteinemia is a risk factor for atherosclerosis and thrombosis and is inversely related to plasma folate and vitamin B12 levels. We assessed the effects of vitamin supplementation on plasma homocysteine levels in 89 patients with a history of recurrent venous thrombosis and 227 healthy volunteers. Patients and hyperhomocysteinemic (homocysteine level >16 micromol/L) volunteers were randomized to placebo or high-dose multivitamin supplements containing 5 mg folic acid, 0.4 mg hydroxycobalamin, and 50 mg pyridoxine. A subgroup of volunteers without hyperhomocysteinemia was also randomized into three additional regimens of 5 mg folic acid, 0.5 mg folic acid, or 0.4 mg hydroxycobalamin. Before and after the intervention period, blood samples were taken for measurements of homocysteine, folate, cobalamin, and pyridoxal-5'-phosphate levels. Supplementation with high-dose multivitamin preparations normalized plasma homocysteine levels (< or = 16 micromol/L) in 26 of 30 individuals compared with 7 of 30 in the placebo group. Also in normohomocysteinemic subjects, multivitamin supplementation strongly reduced homocysteine levels (median reduction, 30%; range, -22% to 55%). In this subgroup the effect of folic acid alone was similar to that of multivitamin: median reduction, 26%; range, -2% to 52% for 5 mg folic acid and 25%; range, -54% to 40% for 0.5 mg folic acid. Cobalamin supplementation had only a slight effect on homocysteine lowering (median reduction, 10%; range, -21% to 41%). Our study shows that combined vitamin supplementation reduces homocysteine levels effectively in patients with venous thrombosis and in healthy volunteers, either with or without hyperhomocysteinemia. Even supplementation with 0.5 mg of folic acid led to a substantial reduction of blood homocysteine levels.

Hyperhomocysteinaemia and protein S deficiency in complicated pregnancies

OBJECTIVE

The aim of our study was to investigate whether women with placental abruption, intrauterine fetal death or small for gestational age infants have metabolic and/or haemostatic abnormalities which are known to be risk factors for intravascular thrombosis.

DESIGN

For two years blood tests were performed at > 10 weeks after delivery on all women without hypertensive disorders either before or during pregnancy, who had been consecutively admitted to our hospital with placental abruption, intrauterine fetal death and small for gestational age.

SAMPLE

A total of 62 women who had placental abruption (n = 31), intrauterine fetal death (n = 18) and a small for gestational age infant (n = 13).

SETTING

Obstetric outpatient clinic in a university hospital (Free University Hospital, Amsterdam).

METHODS

Presence of hyperhomocysteinaemia, various coagulation abnormalities and anticardiolipins was investigated.

RESULTS

Abnormalities were found in 20 women in the placental abruption group (20/31, 65%), in 10 women in the intrauterine fetal death group (10/18, 56%) and in 11 women in the small for gestational age group (11/13, 85%). Eight out of these 31 women had more than one abnormality. In the group of 62 women protein S deficiency was demonstrated in 26%, hyperhomocysteinaemia in 24%, Protein C deficiency in 6%, anticardiolipin IgG in 11%, anticardiolipin IgM in 5%, Lupus anticoagulant in 2%. An antithrombin III deficiency was not found. Thirty-three women were tested for activated protein C resistance (9% positive) and factor V Leiden mutation (6% positive). Hyperhomocysteinaemia was treated with a daily oral dose of 250 mg pyridoxine and 5 mg folic acid. After six weeks of vitamin supplementation homocysteine levels were tested again. At that time a mean reduction of fasting homocysteine value of 68% (95% CI 57-79) was found and of post-load value of 65% (95% CI 55-76).

CONCLUSIONS

Based on the results of our study, it can be concluded that women whose pregnancies are complicated by either placental abruption, intrauterine fetal death or small for gestational age, even if there is no history of thrombo-embolic disorders or hypertension during pregnancy, should be advised to undergo an examination for metabolic and/or haemostatic abnormalities.