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.

Plasma homocysteine levels and mortality in patients with coronary artery disease

BACKGROUND

Elevated plasma homocysteine levels are a risk factor for coronary heart disease, but the prognostic value of homocysteine levels in patients with established coronary artery disease has not been defined.

METHODS

We prospectively investigated the relation between plasma total homocysteine levels and mortality among 587 patients with angiographically confirmed coronary artery disease. At the time of angiography in 1991 or 1992, risk factors for coronary disease, including homocysteine levels, were evaluated. The majority of the patients subsequently underwent coronary-artery bypass grafting (318 patients) or percutaneous transluminal coronary angioplasty (120 patients); the remaining 149 were treated medically.

RESULTS

After a median follow-up of 4.6 years, 64 patients (10.9 percent) had died. We found a strong, graded relation between plasma homocysteine levels and overall mortality. After four years, 3.8 percent of patients with homocysteine levels below 9 micromol per liter had died, as compared with 24.7 percent of those with homocysteine levels of 15 micromol per liter or higher. Homocysteine levels were only weakly related to the extent of coronary artery disease but were strongly related to the history with respect to myocardial infarction, the left ventricular ejection fraction, and the serum creatinine level. The relation of homocysteine levels to mortality remained strong after adjustment for these and other potential confounders. In an analysis in which the patients with homocysteine levels below 9 micromol per liter were used as the reference group, the mortality ratios were 1.9 for patients with homocysteine levels of 9.0 to 14.9 micromol per liter, 2.8 for those with levels of 15.0 to 19.9 micromol per liter, and 4.5 for those with levels of 20.0 micromol per liter or higher (P for trend=0.02). When death due to cardiovascular disease (which occurred in 50 patients) was used as the end point in the analysis, the relation between homocysteine levels and mortality was slightly strengthened.

CONCLUSIONS

Plasma total homocysteine levels are a strong predictor of mortality in patients with angiographically confirmed coronary artery disease.

Folate, vitamin B12, and serum total homocysteine levels in confirmed Alzheimer disease

BACKGROUND

Recent studies suggest that vascular disease may contribute to the cause of Alzheimer disease (AD). Since elevated plasma total homocysteine (tHcy) level is a risk factor for vascular disease, it may also be relevant to AD.

OBJECTIVE

To examine the association of AD with blood levels of tHcy, and its biological determinants folate and vitamin B12.

DESIGN

Case-control study of 164 patients, aged 55 years or older, with a clinical diagnosis of dementia of Alzheimer type (DAT), including 76 patients with histologically confirmed AD and 108 control subjects.

SETTING

Referral population to a hospital clinic between July 1988 and April 1996.

MAIN OUTCOME MEASURES

Serum tHcy, folate, and vitamin B12 levels in patients and controls at entry; the odds ratio of DAT or confirmed AD with elevated tHcy or low vitamin levels; and the rate of disease progression in relation to tHcy levels at entry.

RESULTS

Serum tHcy levels were significantly higher and serum folate and vitamin B12 levels were lower in patients with DAT and patients with histologically confirmed AD than in controls. The odds ratio of confirmed AD associated with a tHcy level in the top third (> or = 14 micromol/L) compared with the bottom third (< or = 11 micromol/L) of the control distribution was 4.5 (95% confidence interval, 2.2-9.2), after adjustment for age, sex, social class, cigarette smoking, and apolipoprotein E epsilon4. The corresponding odds ratio for the lower third compared with the upper third of serum folate distribution was 3.3 (95% confidence interval, 1.8-6.3) and of vitamin B12 distribution was 4.3 (95% confidence interval, 2.1-8.8). The mean tHcy levels were unaltered by duration of symptoms before enrollment and were stable for several years afterward. In a 3-year follow-up of patients with DAT, radiological evidence of disease progression was greater among those with higher tHcy levels at entry.

CONCLUSIONS

Low blood levels of folate and vitamin B12, and elevated tHcy levels were associated with AD. The stability of tHcy levels over time and lack of relationship with duration of symptoms argue against these findings being a consequence of disease and warrant further studies to assess the clinical relevance of these associations for AD.

Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion

Background: Measurement of plasma total homocysteine has become common as new methods have been introduced. A wide range of disorders are associated with increased concentrations of total homocysteine. The purpose of this review is to provide an international expert opinion on the practical aspects of total homocysteine determinations in clinical practice and in the research setting and on the relevance of total homocysteine measurements as diagnostic or screening tests in several target populations.

Methods: Published data available on Medline were used as the basis for the recommendations. Drafts of the recommendations were critically discussed at meetings over a period of 3 years.

Outcome: This review is divided into two sections: (a) determination of homocysteine (methods and their performance, sample collection and handling, biological determinants, reference intervals, within-person variability, and methionine loading test); and (b) risk assessment and disease diagnosis (homocystinuria, folate and cobalamin deficiencies, cardiovascular disease, renal failure, psychiatric disorders and cognitive impairment, pregnancy complications and birth defects, and screening of elderly and newborns). Each of these subsections concludes with a separate series of recommendations to assist the clinician and the research scientist in making informed decisions. The review concludes with a list of unresolved questions.

Total homocysteine in plasma or serum: methods and clinical applications

Total homocysteine is defined as the sum of all homocysteine species in plasma/serum, including free and protein-bound forms. In the present review, we compare and evaluate several techniques for the determination of total homocysteine. Because these assays include the conversion of all forms into a single species by reduction, the redistribution between free and protein-bound homocysteine through disulfide interchange does not affect the results, and total homocysteine can be measured in stored samples. Total homocysteine in whole blood increases at room temperature because of a continuous production and release of homocysteine from blood cells, but artificial increase is low if the blood sample is centrifuged within 1 h of collection or placed on ice. Different methods correlate well, and values between 5 and 15 mumol/L in fasting subjects are considered normal. Total homocysteine in serum/plasma is increased markedly in patients with cobalamin or folate deficiency, and decreases only when they are treated with the deficient vitamin. Total homocysteine is therefore of value for the diagnosis and follow-up of these deficiency states and may compensate for weaknesses of the traditional laboratory tests. In addition, total homocysteine is an independent risk factor for premature cardiovascular diseases. These disorders justify introduction of the total homocysteine assay in the routine clinical chemistry laboratory.

Prospective study of serum total homocysteine concentration and risk of stroke in middle-aged British men

Moderate hyperhomocysteinaemia is common in the general population and has been linked with cardiovascular disease. However, there are no data from prospective, population-based studies. We examined the association between serum total homocysteine (tHcy) concentration and stroke in a nested case-control study within the British Regional Heart Study cohort. Between 1978 and 1980 serum was saved from 5661 men, aged 40-59 years, randomly selected from the population of one general practice in each of 18 towns in the UK. During follow-up to December, 1991, there were 141 incident cases of stroke among men with no history of stroke at screening. Serum tHcy was measured in 107 cases and 118 control men (matched for age-group and town, without a history of stroke at screening, who did not develop a stroke or myocardial infarction during follow-up). tHcy concentrations were significantly higher in cases than controls (geometric mean 13.7 [95% CI 12.7-14.8] vs 11.9 [11.3-12.6] mumol/L; p = 0.004). There was a graded increase in the relative risk of stroke in the second, third, and fourth quarters of the tHcy distribution (odds ratios 1.3, 1.9, 2.8; trend p = 0.005) relative to the first. Adjustment for age-group, town, social class, body-mass index, hypertensive status, cigarette smoking, forced expiratory volume, packed-cell volume, alcohol intake, diabetes, high-density-lipoprotein cholesterol, and serum creatinine did not attenuate the association. These findings suggest that tHcy is a strong and independent risk factor for stroke.

Total plasma homocysteine and cardiovascular risk profile. The Hordaland Homocysteine Study

OBJECTIVE

To estimate the relations between established cardiovascular risk factors and total homocysteine (tHcy) in plasma.

DESIGN

Health examination survey by the Norwegian Health Screening Service in 1992 and 1993.

SETTING

General community, Hordaland County of Western Norway.

PARTICIPANTS

A total of 7591 men and 8585 women, 40 to 67 years of age, with no history of hypertension, diabetes, coronary heart disease, or cerebrovascular disease were included.

MAIN OUTCOME MEASURE

Plasma tHcy level.

RESULTS

The level of plasma tHcy was higher in men than in women and increased with age. In subjects 40 to 42 years old, geometric means were 10.8 mumol/L for 5918 men and 9.1 mumol/L for 6348 women. At age 65 to 67 years, the corresponding tHcy values were 12.3 mumol/L (1386 men) and 11.0 mumol/L (1932 women). Plasma tHcy level increased markedly with the daily number of cigarettes smoked in all age groups. Its relation to smoking was particularly strong in women. The combined effect of age, sex, and smoking was striking. Heavy-smoking men aged 65 to 67 years had a mean tHcy level 4.8 mumol/L higher than never-smoking women aged 40 to 42 years. Plasma tHcy level also was positively related to total cholesterol level, blood pressure, and heart rate and inversely related to physical activity. The relations were not substantially changed by multivariate adjustment, including intake of vitamin supplements, fruits, and vegetables.

CONCLUSIONS

Elevated plasma tHcy level was associated with major components of the cardiovascular risk profile, ie, male sex, old age, smoking, high blood pressure, elevated cholesterol level, and lack of exercise. These findings should influence future studies on the etiology and pathogenesis of cardiovascular disease.

Vitamin B12 and folate concentrations during pregnancy and insulin resistance in the offspring: the Pune Maternal Nutrition Study

AIMS/HYPOTHESIS

Raised maternal plasma total homocysteine (tHcy) concentrations predict small size at birth, which is a risk factor for type 2 diabetes mellitus. We studied the association between maternal vitamin B12, folate and tHcy status during pregnancy, and offspring adiposity and insulin resistance at 6 years.

METHODS

In the Pune Maternal Nutrition Study we studied 700 consecutive eligible pregnant women in six villages. We measured maternal nutritional intake and circulating concentrations of folate, vitamin B12, tHcy and methylmalonic acid (MMA) at 18 and 28 weeks of gestation. These were correlated with offspring anthropometry, body composition (dual-energy X-ray absorptiometry scan) and insulin resistance (homeostatic model assessment of insulin resistance [HOMA-R]) at 6 years.

RESULTS

Two-thirds of mothers had low vitamin B12 (<150 pmol/l), 90% had high MMA (>0.26 micromol/l) and 30% had raised tHcy concentrations (>10 micromol/l); only one had a low erythrocyte folate concentration. Although short and thin (BMI), the 6-year-old children were relatively adipose compared with the UK standards (skinfold thicknesses). Higher maternal erythrocyte folate concentrations at 28 weeks predicted higher offspring adiposity and higher HOMA-R (both p < 0.01). Low maternal vitamin B12 (18 weeks; p = 0.03) predicted higher HOMA-R in the children. The offspring of mothers with a combination of high folate and low vitamin B12 concentrations were the most insulin resistant.

CONCLUSIONS/INTERPRETATION

Low maternal vitamin B12 and high folate status may contribute to the epidemic of adiposity and type 2 diabetes in India.

Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial

Background

An increased rate of brain atrophy is often observed in older subjects, in particular those who suffer from cognitive decline. Homocysteine is a risk factor for brain atrophy, cognitive impairment and dementia. Plasma concentrations of homocysteine can be lowered by dietary administration of B vitamins.

Objective

To determine whether supplementation with B vitamins that lower levels of plasma total homocysteine can slow the rate of brain atrophy in subjects with mild cognitive impairment in a randomised controlled trial (VITACOG, ISRCTN 94410159).

Methods and Findings

Single-center, randomized, double-blind controlled trial of high-dose folic acid, vitamins B₆ and B₁₂ in 271 individuals (of 646 screened) over 70 y old with mild cognitive impairment. A subset (187) volunteered to have cranial MRI scans at the start and finish of the study. Participants were randomly assigned to two groups of equal size, one treated with folic acid (0.8 mg/d), vitamin B₁₂ (0.5 mg/d) and vitamin B₆ (20 mg/d), the other with placebo; treatment was for 24 months. The main outcome measure was the change in the rate of atrophy of the whole brain assessed by serial volumetric MRI scans.

Results

A total of 168 participants (85 in active treatment group; 83 receiving placebo) completed the MRI section of the trial. The mean rate of brain atrophy per year was 0.76% [95% CI, 0.63–0.90] in the active treatment group and 1.08% [0.94–1.22] in the placebo group (P = 0.001). The treatment response was related to baseline homocysteine levels: the rate of atrophy in participants with homocysteine >13 µmol/L was 53% lower in the active treatment group (P = 0.001). A greater rate of atrophy was associated with a lower final cognitive test scores. There was no difference in serious adverse events according to treatment category.

Conclusions and Significance

The accelerated rate of brain atrophy in elderly with mild cognitive impairment can be slowed by treatment with homocysteine-lowering B vitamins. Sixteen percent of those over 70 y old have mild cognitive impairment and half of these develop Alzheimer's disease. Since accelerated brain atrophy is a characteristic of subjects with mild cognitive impairment who convert to Alzheimer's disease, trials are needed to see if the same treatment will delay the development of Alzheimer's disease.

Trial Registration

Controlled-Trials.com ISRCTN94410159

Serum total homocysteine and coronary heart disease

BACKGROUND

Several studies have observed high plasma levels of homocysteine among patients with coronary heart disease (CHD). The only prospective study was based on US physicians, and concluded that homocysteine was associated with subsequent myocardial infarction (MI). However, the association was limited to those above a threshold level of homocysteine.

METHODS

We conducted a nested case-control study among the 21,826 subjects, aged 12-61 years, who were surveyed in the municipality of Tromsø, Norway. Among those free from MI at the screening, 123 later developed CHD. Four controls were selected for each case.

RESULTS

Level of homocysteine was higher in cases than in controls (12.7 +/- 4.7 versus 11.3 +/- 3.7 mumol/l (mean +/- SD); P = 0.002). The relative risk for a 4 mumol/l increase in serum homocysteine was 1.41 (95% confidence interval (CI): 1.16-1.71). Adjusting for possible confounders reduced the relative risk to 1.32 (95% CI: 1.05-1.65). There was no threshold level above which serum homocysteine is associated with CHD events.

CONCLUSIONS

In the general population serum total homocysteine is an independent risk factor for CHD with no threshold level.

Plasma total homocysteine, pregnancy complications, and adverse pregnancy outcomes: the Hordaland Homocysteine study

BACKGROUND

Total homocysteine (tHcy) measured in serum or plasma is a marker of folate status and a risk factor for cardiovascular disease.

OBJECTIVE

Our objective was to investigate associations between tHcy and complications and adverse outcomes of pregnancy.

DESIGN

Plasma tHcy values measured in 1992-1993 in 5883 women aged 40-42 y were compared with outcomes and complications of 14492 pregnancies in the same women that were reported to the Medical Birth Registry of Norway from 1967 to 1996.

RESULTS

When we compared the upper with the lower quartile of plasma tHcy, the adjusted risk for preeclampsia was 32% higher [odds ratio (OR): 1. 32; 95% CI: 0.98, 1.77; P for trend = 0.02], that for prematurity was 38% higher (OR: 1.38; 95% CI: 1.09, 1.75; P for trend = 0.005), and that for very low birth weight was 101% higher (OR: 2.01; 95% CI: 1.23, 3.27; P for trend = 0.003). These associations were stronger during the years closest to the tHcy determination (1980-1996), when there was also a significant relation between tHcy concentration and stillbirth (OR: 2.03; 95% CI: 0.98, 4.21; P for trend = 0.02). Neural tube defects and clubfoot had significant associations with plasma tHcy. Placental abruption had no relation with tHcy quartile, but the adjusted OR when tHcy concentrations >15 micromol/L were compared with lower values was 3.13 (95% CI: 1.63, 6. 03; P = 0.001).

CONCLUSION

Elevated tHcy concentration is associated with common pregnancy complications and adverse pregnancy outcomes.

Is folic acid good for everyone?

Fortification of food with folic acid to reduce the number of neural tube defects was introduced 10 y ago in North America. Many countries are considering whether to adopt this policy. When fortification is introduced, several hundred thousand people are exposed to an increased intake of folic acid for each neural tube defect pregnancy that is prevented. Are the benefits to the few outweighed by possible harm to some of the many exposed? In animals, a folic acid-rich diet can influence DNA and histone methylation, which leads to phenotypic changes in subsequent generations. In humans, increased folic acid intake leads to elevated blood concentrations of naturally occurring folates and of unmetabolized folic acid. High blood concentrations of folic acid may be related to decreased natural killer cell cytotoxicity, and high folate status may reduce the response to antifolate drugs used against malaria, rheumatoid arthritis, psoriasis, and cancer. In the elderly, a combination of high folate levels and low vitamin B-12 status may be associated with an increased risk of cognitive impairment and anemia and, in pregnant women, with an increased risk of insulin resistance and obesity in their children. Folate has a dual effect on cancer, protecting against cancer initiation but facilitating progression and growth of preneoplastic cells and subclinical cancers, which are common in the population. Thus, a high folic acid intake may be harmful for some people. Nations considering fortification should be cautious and stimulate further research to identify the effects, good and bad, caused by a high intake of folic acid from fortified food or dietary supplements. Only then can authorities develop the right strategies for the population as a whole.

Biological and clinical implications of the MTHFR C677T polymorphism

The enzyme methylenetetrahydrofolate reductase (MTHFR) directs folate species either to DNA synthesis or to homocysteine (Hcy) remethylation. The common MTHFR C677T polymorphism affects the activity of the enzyme and hence folate distribution. Under conditions of impaired folate status, the homozygous TT genotype has been regarded as harmful because it is associated with a high concentration of plasma total Hcy, increased risk of neural tube defects and colorectal neoplasias, and can also predispose individuals to adverse effects from drugs with antifolate effects. The MTHFR C677T polymorphism shows no consistent correlation with cardiovascular risk and longevity but, in combination with positive folate balance, the TT genotype is associated with decreased risk of colorectal neoplasias. Because of the high prevalence of this polymorphism in most populations, the TT variant might represent an ancestral genetic adaptation to living constraints (tissue injury or unbalanced vitamin intake) that has become a determinant of disease profiles in modern times.

The Hordaland Homocysteine Study: a community-based study of homocysteine, its determinants, and associations with disease

The Hordaland Homocysteine Study (HHS) is a population-based study of more than 18,000 men and women in the county of Hordaland in Western Norway. The first investigation (HHS-I) took place in 1992-93, when the subjects were aged 40-67 y. In 1997-99, a follow-up study (HHS-II) of 7,053 subjects was carried out. In this large population, plasma levels of total homocysteine (tHcy) are associated with several physiologic and lifestyle factors and common diseases. Increasing age, male sex, smoking, coffee consumption, high blood pressure, unfavorable lipid profile, high creatinine, and the MTHFR 677C > T polymorphism are among the factors associated with increased tHcy levels; physical activity, moderate alcohol consumption, and a good folate or vitamin B-12 status are associated with lower tHcy levels. Subjects with raised tHcy levels have increased risk of cardiovascular morbidity, cardiovascular and noncardiovascular mortality, and are more likely to suffer from depression and from cognitive deficit (elderly). Among women, raised tHcy levels are associated with decreased bone mineral density and increased risk of osteoporosis. Women with raised tHcy levels also have an increased risk of having suffered from pregnancy complications and an adverse pregnancy outcome. Significant associations between tHcy and clinical outcomes are usually observed for tHcy levels > 15 micromol/L, but for most conditions, there is a continuous concentration-response relation with no apparent threshold concentration. Overall, the findings from HHS indicate that a raised tHcy level is associated with multiple clinical conditions, whereas a low tHcy level is associated with better physical and mental health.

Homocysteine and other thiols in plasma and urine: automated determination and sample stability

We have developed a modified version of our fully automated column-switching HPLC method for determining total plasma homocysteine based on single-column (reversed-phase) separation. Homocysteine, cysteine, and cysteinylglycine in plasma (total concentrations), acid-precipitated plasma (non-protein-bound concentrations), and urine can be determined. The derivatization and chromatography were performed automatically by a sample processor. The successful separation of all thiol species (within 15 min) was accomplished by accurate adjustment of the pH of the mobile phase to 3.65 (plasma) or 3.50 (acid-precipitated plasma, urine). Maximal fluorescence yield of cysteine, cysteinylglycine, and, to a lesser degree, homocysteine was dependent on optimal concentrations of EDTA and dithioerythritol during reduction (with NaBH4) and derivatization (with monobromobimane). The method is sensitive (detection limit approximately 0.05 pmol) and has a high degree of precision (CV &lt; 5%). The sample output is approximately 70 samples in 24 h. Serum and heparin plasma can also be analyzed. Hemolysis up to approximately 2.0 g/L of hemoglobin did not interfere with the analytical recovery of homocysteine or cysteine. Collection of blood, separation of plasma from whole blood, and acid precipitation must be standardized to obtain reproducible thiol results. Our modifications and the standardization of blood-sampling procedures have substantially improved the method and broadened its applications.

The controversy over homocysteine and cardiovascular risk

Elevated plasma total homocysteine (tHcy) is a risk factor for occlusive cardiovascular disease (CVD). This concept is based on the observations of premature vascular disease in patients with homocystinuria, the relation between tHcy and both clinical CVD as well as preclinical atherosclerotic disease, the relation between tHcy in children and CVD in their parents or relatives, and reduction in CVD or surrogate endpoints after tHcy-lowering intervention with B vitamins. Plausible mechanisms include the in vivo interference with nitric oxide-dependent reactive vasodilatation. Some observations have raised questions about tHcy as a risk factor. 1) Some prospective studies showed a weak relation or no relation between tHcy and CVD. 2) Several traditional risk factors are associated with tHcy and may confound the relation between tHcy and CVD. 3) tHcy is related to renal function, and hyperhomocysteinemia may reflect early nephrosclerosis. 4) The C677T transition of the methylenetetrahydrofolate reductase gene causes a moderate increase in tHcy but no or only minor increased CVD risk. However, the strength of some of these arguments can be questioned because there is increasing evidence that tHcy is a proximate risk factor provoking the acute event, it strongly interacts with traditional risk factors, and it may predict CVD or death in patients with chronic renal failure. Furthermore, the studies of the C677T polymorphism lack statistical power, and the TT genotype may even modulate CVD risk independently of homocysteine. Thus, only placebo-controlled intervention studies with tHcy-lowering B vitamins and clinical endpoints can provide additional valid arguments for the debate over whether tHcy is a causal CVD risk factor.

Low circulating folate and vitamin B6 concentrations: risk factors for stroke, peripheral vascular disease, and coronary artery disease. European COMAC Group

BACKGROUND

A high plasma homocysteine concentration is a risk factor for atherosclerosis, and circulating concentrations of homocysteine are related to levels of folate and vitamin B6. This study was performed to explore the interrelationships between homocysteine, B vitamins, and vascular diseases and to evaluate the role of these vitamins as risk factors for atherosclerosis.

METHODS

In a multicenter case-control study in Europe, 750 patients with documented vascular disease and 800 control subjects frequency-matched for age and sex were compared. Plasma levels of total homocysteine (before and after methionine loading) were determined, as were those of red cell folate, vitamin B12, and vitamin B6.

RESULTS

In a conditional logistic regression model, homocysteine concentrations greater than the 80th percentile for control subjects either fasting (12.1 micromol/L) or after a methionine load (38.0 micromol/L) were associated with an elevated risk of vascular disease independent of all traditional risk factors. In addition, concentrations of red cell folate below the lowest 10th percentile (<513 nmol/L) and concentrations of vitamin B6 below the lowest 20th percentile (<23.3 nmol/L) for control subjects were also associated with increased risk. This risk was independent of conventional risk factors and for folate was explained in part by increased homocysteine levels. In contrast, the relationship between vitamin B6 and atherosclerosis was independent of homocysteine levels both before and after methionine loading.

CONCLUSIONS

Lower levels of folate and vitamin B6 confer an increased risk of atherosclerosis. Clinical trials are now required to evaluate the effect of treatment with these vitamins in the primary and secondary prevention of vascular diseases.

Mortality and cardiovascular events in patients treated with homocysteine-lowering B vitamins after coronary angiography: a randomized controlled trial

CONTEXT

Observational studies have reported associations between circulating total homocysteine concentration and risk of cardiovascular disease. Oral administration of folic acid and vitamin B(12) can lower plasma total homocysteine levels.

OBJECTIVE

To assess the effect of treatment with folic acid and vitamin B(12) and the effect of treatment with vitamin B(6) as secondary prevention in patients with coronary artery disease or aortic valve stenosis.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, double-blind controlled trial conducted in the 2 university hospitals in western Norway in 1999-2006. A total of 3096 adult participants undergoing coronary angiography (20.5% female; mean age, 61.7 years) were randomized. At baseline, 59.3% had double- or triple-vessel disease, 83.7% had stable angina pectoris, and 14.9% had acute coronary syndromes.

INTERVENTIONS

Using a 2 x 2 factorial design, participants were randomly assigned to 1 of 4 groups receiving daily oral treatment with folic acid, 0.8 mg, plus vitamin B(12), 0.4 mg, plus vitamin B(6), 40 mg (n = 772); folic acid plus vitamin B(12) (n = 772); vitamin B(6) alone (n = 772); or placebo (n = 780).

MAIN OUTCOME MEASURES

The primary end point was a composite of all-cause death, nonfatal acute myocardial infarction, acute hospitalization for unstable angina pectoris, and nonfatal thromboembolic stroke.

RESULTS

Mean plasma total homocysteine concentration was reduced by 30% after 1 year of treatment in the groups receiving folic acid and vitamin B(12). The trial was terminated early because of concern among participants due to preliminary results from a contemporaneous Norwegian trial suggesting adverse effects from the intervention. During a median 38 months of follow-up, the primary end point was experienced by a total of 422 participants (13.7%): 219 participants (14.2%) receiving folic acid/vitamin B(12) vs 203 (13.1%) not receiving such treatment (hazard ratio, 1.09; 95% confidence interval, 0.90-1.32; P = .36) and 200 participants (13.0%) receiving vitamin B(6) vs 222 (14.3%) not receiving vitamin B(6) (hazard ratio, 0.90; 95% confidence interval, 0.74-1.09; P = .28).

CONCLUSIONS

This trial did not find an effect of treatment with folic acid/vitamin B(12) or vitamin B(6) on total mortality or cardiovascular events. Our findings do not support the use of B vitamins as secondary prevention in patients with coronary artery disease.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00354081.

Major lifestyle determinants of plasma total homocysteine distribution: the Hordaland Homocysteine Study

We report on the location and skewness of the distribution of plasma total homocysteine (tHcy) according to lifestyle indexes in 11,941 apparently healthy participants of the Hordaland Homocysteine Study. Most subjects were in two age groups: 9165 subjects were aged 40-42 y and 2351 subjects were aged 65-67 y. The remaining 425 subjects were of intermediate ages. In multivariate analysis, sex, age, folate intake, smoking status, and coffee consumption were the strongest determinants of tHcy concentration. The combined effect of the three modifiable factors was larger than the effect from each factor alone. A lifestyle profile characterized by low folate intakes, smoking, and coffee consumption was associated with a high median tHcy concentration and a pronounced skewness toward high tHcy values. In subjects characterized by a contrasting lifestyle profile [high folate intakes, nonsmoking status, and low coffee consumption (< 1 cup/d)], tHcy values were almost normally distributed and the median concentration was 3.0-4.8 micromol/L lower. Among all 40-42-y-old subjects, the 95% reference ranges based on geometric mean tHcy concentrations were 5.1-16.5 micromol/L for women and 6.2-18.7 micromol/L for men. The corresponding ranges for subjects characterized by high folate intakes, nonsmoking status, and low or moderate coffee consumption (< 5 cups/d) were 4.8-12.8 micromol/L and 6.2-14.7 micromol/L. These findings are relevant for establishing adequate reference ranges for tHcy and emphasize folate intake, smoking status, and coffee consumption as major acquired determinants of tHcy concentration in this general population.

Cognitive and clinical outcomes of homocysteine-lowering B-vitamin treatment in mild cognitive impairment: a randomized controlled trial

BACKGROUND

Homocysteine is a risk factor for Alzheimer's disease. In the first report on the VITACOG trial, we showed that homocysteine-lowering treatment with B vitamins slows the rate of brain atrophy in mild cognitive impairment (MCI). Here we report the effect of B vitamins on cognitive and clinical decline (secondary outcomes) in the same study.

METHODS

This was a double-blind, single-centre study, which included participants with MCI, aged ≥ 70 y, randomly assigned to receive a daily dose of 0.8 mg folic acid, 0.5 mg vitamin B(12) and 20 mg vitamin B(6) (133 participants) or placebo (133 participants) for 2 y. Changes in cognitive or clinical function were analysed by generalized linear models or mixed-effects models.

RESULTS

The mean plasma total homocysteine was 30% lower in those treated with B vitamins relative to placebo. B vitamins stabilized executive function (CLOX) relative to placebo (P = 0.015). There was significant benefit of B-vitamin treatment among participants with baseline homocysteine above the median (11.3 µmol/L) in global cognition (Mini Mental State Examination, P < 0.001), episodic memory (Hopkins Verbal Learning Test-delayed recall, P = 0.001) and semantic memory (category fluency, P = 0.037). Clinical benefit occurred in the B-vitamin group for those in the upper quartile of homocysteine at baseline in global clinical dementia rating score (P = 0.02) and IQCODE score (P = 0.01).

CONCLUSION

In this small intervention trial, B vitamins appear to slow cognitive and clinical decline in people with MCI, in particular in those with elevated homocysteine. Further trials are needed to see if this treatment will slow or prevent conversion from MCI to dementia.

Cancer incidence and mortality after treatment with folic acid and vitamin B12

CONTEXT

Recently, concern has been raised about the safety of folic acid, particularly in relation to cancer risk.

OBJECTIVE

To evaluate effects of treatment with B vitamins on cancer outcomes and all-cause mortality in 2 randomized controlled trials.

DESIGN, SETTING, AND PARTICIPANTS

Combined analysis and extended follow-up of participants from 2 randomized, double-blind, placebo-controlled clinical trials (Norwegian Vitamin Trial and Western Norway B Vitamin Intervention Trial). A total of 6837 patients with ischemic heart disease were treated with B vitamins or placebo between 1998 and 2005, and were followed up through December 31, 2007.

INTERVENTIONS

Oral treatment with folic acid (0.8 mg/d) plus vitamin B(12) (0.4 mg/d) and vitamin B(6) (40 mg/d) (n = 1708); folic acid (0.8 mg/d) plus vitamin B(12) (0.4 mg/d) (n = 1703); vitamin B(6) alone (40 mg/d) (n = 1705); or placebo (n = 1721).

MAIN OUTCOME MEASURES

Cancer incidence, cancer mortality, and all-cause mortality.

RESULTS

During study treatment, median serum folate concentration increased more than 6-fold among participants given folic acid. After a median 39 months of treatment and an additional 38 months of posttrial observational follow-up, 341 participants (10.0%) who received folic acid plus vitamin B(12) vs 288 participants (8.4%) who did not receive such treatment were diagnosed with cancer (hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.03-1.41; P = .02). A total of 136 (4.0%) who received folic acid plus vitamin B(12) vs 100 (2.9%) who did not receive such treatment died from cancer (HR, 1.38; 95% CI, 1.07-1.79; P = .01). A total of 548 patients (16.1%) who received folic acid plus vitamin B(12) vs 473 (13.8%) who did not receive such treatment died from any cause (HR, 1.18; 95% CI, 1.04-1.33; P = .01). Results were mainly driven by increased lung cancer incidence in participants who received folic acid plus vitamin B(12). Vitamin B(6) treatment was not associated with any significant effects.

CONCLUSION

Treatment with folic acid plus vitamin B(12) was associated with increased cancer outcomes and all-cause mortality in patients with ischemic heart disease in Norway, where there is no folic acid fortification of foods.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00671346.

5-methyltetrahydrofolate rapidly improves endothelial function and decreases superoxide production in human vessels: effects on vascular tetrahydrobiopterin availability and endothelial nitric oxide synthase coupling

BACKGROUND

The circulating form of folic acid, 5-methyltetrahydrofolate (5-MTHF), may have beneficial effects on endothelial function; however, its mechanisms of action remain uncertain. Decreased nitric oxide (NO) bioavailability and increased vascular superoxide production in vascular disease states are due in part to endothelial NO synthase (eNOS) uncoupling related to deficiency of the eNOS cofactor tetrahydrobiopterin (BH4), but whether this mechanism is important in human atherosclerosis and represents a rational therapeutic target remains unclear. We hypothesized that 5-MTHF would improve endothelial function by decreasing superoxide and peroxynitrite production and by improving eNOS coupling, mediated by BH4 availability.

METHODS AND RESULTS

Vascular superoxide/peroxynitrite production and vasomotor responses to acetylcholine and bradykinin were determined in saphenous veins and internal mammary arteries from 117 patients undergoing CABG. The effects of 5-MTHF were examined ex vivo (n = 61) by incubating vessels with 5-MTHF (1 to 100 micromol/L) and in vivo by intravenous infusion of 5-MTHF or placebo before vessel harvest (n = 56). 5-MTHF improved NO-mediated endothelium-dependent vasomotor responses and reduced vascular superoxide, both ex vivo and in vivo. These changes were not explained by direct superoxide scavenging by 5-MTHF in vitro or by changes in plasma total homocysteine in vivo. Rather, 5-MTHF was a strong peroxynitrite scavenger and increased vascular BH4 and the BH4/total biopterin ratio. Furthermore, 5-MTHF reversed eNOS uncoupling, as assessed by NG-nitro-l-arginine methyl ester-inhibitable superoxide production, increased the eNOS dimer:monomer ratio, and enhanced eNOS activity.

CONCLUSIONS

5-MTHF has beneficial effects on endothelial function and vascular superoxide production in human atherosclerosis, by preventing peroxynitrite-mediated BH4 oxidation and improving eNOS coupling.

Folate, vitamin B12, homocysteine, and the MTHFR 677C->T polymorphism in anxiety and depression: the Hordaland Homocysteine Study

BACKGROUND

An association between depression and folate status has been demonstrated in clinical studies, whereas data are sparse on the relationship between depression and other components of 1-carbon metabolism such as vitamin B12, homocysteine, and the methylenetetrahydrofolate reductase 677C-->T polymorphism. The relationship between anxiety and these components is less well known. This study examined the associations between folate, total homocysteine, vitamin B12, and the methylenetetrahydrofolate reductase 677C-->T polymorphism, and anxiety and depression in a large population-based study.

METHODS

Anxiety and depression, measured by the Hospital Anxiety and Depression Scale, were assessed in 5948 subjects aged 46 to 49 years (mean, 47.4 years) and 70 to 74 years (mean, 71.9 years) from the Hordaland Homocysteine Study cohort. By means of logistic regression models, anxiety and depression scores were examined in relation to the factors listed above.

RESULTS

Overall, hyperhomocysteinemia (plasma total homocysteine level > or =15.0 micro mol/L [> or =2.02 mg/dL]) (odds ratio, 1.90; 95% confidence interval, 1.11-3.25) and T/T methylenetetrahydrofolate reductase genotype (odds ratio, 1.69; 95% confidence interval, 1.09-2.62), but not low plasma folate or vitamin B12 levels, were significantly related to depression without comorbid anxiety disorder. Plasma folate level was inversely associated with depression only in the subgroup of middle-aged women. None of the investigated parameters showed a significant relationship to anxiety.

CONCLUSION

Our results provide further evidence of a role of impaired 1-carbon metabolism in depression.

Hyperhomocysteinemia and elevated methylmalonic acid indicate a high prevalence of cobalamin deficiency in Asian Indians

BACKGROUND

In India, most people adhere to a vegetarian diet, which may lead to cobalamin deficiency.

OBJECTIVE

The objective was to examine indicators of cobalamin status in Asian Indians.

DESIGN

The study population included 204 men and women aged 27-55 y from Pune, Maharashtra, India, categorized into 4 groups: patients with cardiovascular disease (CVD) and diabetes, patients with CVD but no diabetes, patients with diabetes but no CVD, and healthy subjects. Data on medical history, lifestyle, and diet were obtained by interviews and questionnaires. Blood samples were collected for measurement of serum or plasma total cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA), and total homocysteine (tHcy) and hemetologic indexes.

RESULTS

MMA, tHcy, total cobalamin, and holoTC did not differ significantly among the 4 groups; therefore, the data were pooled. Total cobalamin showed a strong inverse correlation with tHcy (r = -0.59) and MMA (r = -0.54). Forty-seven percent of the subjects had cobalamin deficiency (total cobalamin <150 pmol/L), 73% had low holoTC (<35 pmol/L), 77% had hyperhomocysteinemia (tHcy >15 micromol/L), and 73% had elevated serum MMA (>0.26 micromol/L). These indicators of impaired cobalamin status were observed in both vegetarians and nonvegetarians. Folate deficiency was rare and only 2.5% of the subjects were homozygous for the MTHFR 677C-->T polymorphism.

CONCLUSIONS

About 75% of the subjects had metabolic signs of cobalamin deficiency, which was only partly explained by the vegetarian diet. If impaired cobalamin status is confirmed in other parts of India, it may have important health implications.