Plasma folate, vitamin B(12), and total homocysteine and homozygosity for the C677T mutation of the 5,10-methylene tetrahydrofolate reductase gene in patients with Alzheimer's dementia. A case-control study.

BACKGROUND: Elevated total plasma homocysteine (tHcy) levels are considered a risk factor for cerebrovascular disease and may also play an important role in the pathogenesis of Alzheimer's disease (AD). High values of plasma tHcy and low levels of vitamin B(12) and folate are frequently present in AD patients. Moreover, the homozygous mutation (C677T) of the methylene tetrahydrofolate reductase (MTHFR) gene, related to a thermolabile type of the encoded enzyme, causes hyperhomocysteinemia by reducing the 5-methyltetrahydrofolate availability. OBJECTIVE: The aim of the study was to investigate plasma levels of folate, vitamin B(12) and tHcy in patients with AD. These values were also related to the severity and the duration of the disease and to the possible role of the MTHFR genotype (C677T). METHOD: Plasma tHcy levels, homozygosity for the C677T mutation of the MTHFR gene, and folate and vitamin B(12) plasma levels were evaluated in 74 patients with AD (45 men, 29 women, mean age 68 years) and in 74 healthy matched controls (42 men, 32 women, mean age 68 years). RESULTS: AD patients had higher mean (+/- SD) plasma levels of tHcy (20.9 +/- 15 micromol/l compared to 11.8 +/- 5 micromol/l, p < 0.001) and lower mean plasma folate (5.7 +/- 2.1 ng/ml compared to 8.5 +/- 3.2 ng/ml, p < 0.001) and vitamin B(12) (491 +/- 144 pmol/l compared to 780 +/- 211 pmol/l, p < 0.001) concentrations. Homozygosity for the C677T mutation of the MTHFR gene had a similar prevalence among controls (18%) and AD patients (20%). Homozygous AD patients (n = 15) had higher plasma tHcy values than nonhomozygotes, in spite of similar mean plasma folate and vitamin B(12) levels. This difference in plasma tHcy levels was not observed in controls. Patients with levels of plasma tHcy above and of plasma folate below the normal limits were more frequent in the homozygous AD group. The duration of the disease correlated with plasma levels of tHcy (r = +0.832, p < 0.001), plasma folate (r = -0.580, p < 0.05), and vitamin B(12) (r = -0.460, p < 0.05). However, when all the data were corrected for age, serum creatinine levels, and duration of the disease, mean plasma tHcy, folate, and vitamin B(12) levels were not statistically different between controls and AD patients. CONCLUSIONS: Our data suggest that rather than a risk factor for AD, hyperhomocysteinemia is related to its progression and increasing severity. This might be particularly relevant in homozygotes for the C677T mutation of the MTHFR gene and supports the possible need for continuous supplements in this setting.     

Glomerular filtration rate as measured by serum cystatin C is an important determinant of plasma homocysteine and serum methylmalonic acid in the elderly

OBJECTIVES: To explore the dependence of glomerular filtration rate (GFR) on plasma total homocysteine (tHcy) and serum methylmalonic acid (MMA), as well as the consequences for the diagnosis of cobalamin and/or folic acid deficiency in an elderly community-dwelling population. DESIGN AND SETTING: Population-based study of 209 community-dwelling subjects, mean age 76 years. INTERVENTIONS: Four months' treatment study with oral vitamin B(12), folic acid and B(6) or placebo. MAIN OUTCOME MEASURES: Determinants of tHcy and MMA: cystatin C as a marker of GFR and serum/plasma concentrations of vitamin B(12) and folate, age and sex. RESULTS: Elevated cystatin C (>1.55 mg L(-1)) was found in 31.3% (men) and 13.0% (women). Elevated tHcy (> or = 16 micromol L(-1)) occurred in 53% and elevated MMA (> or = 0.34 micromol L(-1)) in 11% of all subjects. When GFR was taken into consideration, the proportion of elevated tHcy was reduced to 10% (20/209), whilst the proportion of elevated MMA was unchanged. Cystatin C was correlated with tHcy (r = 0.45, P < 0.001) and with MMA (r =0.28, P < 0.001), independently of vitamin B(12)- and folate status. According to multiple regression, independent predictors for tHcy were plasma folate (15%), cystatin C (11%) and vitamin B(12) (4%), and for MMA, cystatin C (8%) and vitamin B(12) (2%). CONCLUSIONS: The prevalence of elevated tHcy may be overestimated in elderly populations unless GFR is taken into account. Nomograms for evaluation of tHcy and MMA in relation to both cystatin C and serum creatinine are presented.     

Hyperhomocysteinemia and endothelial function in young subjects: effects of vitamin supplementation

BACKGROUND: The relationship between hyperhomocysteinemia and cardiovascular disease has not been totally elucidated. HYPOTHESIS: The study aimed to verify the association between hyperhomocysteinemia and endothelial dysfunction before and after modification of total homocysteine (tHcy) serum levels with vitamin supplementation in young male subjects devoid of any other cardiovascular risk factor. METHODS: Twenty hyperhomocysteinemic (tHcy > 15 [micromol/l) male volunteers (< or = 40 years) and 20 age-matched subjects with normal tHcy levels (tHcy < 13 micromol/l) were included. Exclusion criteria were smoking, hypertension, diabetes, vitamin ingestion, obesity, hypercholesterolemia, renal failure, and positive antiphospholipid antibodies. Serum tHcy, folate, vitamin B12 levels, activated protein C and S, protein C resistance, fibrinogen, prothrombin, thrombin, antithrombin III, and in vitro oxidation of low-density lipoprotein (LDL) particles were measured. Noninvasive ultrasound measurements of endothelium-dependent (EDD) and -independent dilatation (EID) of the brachial artery were performed. Each pair was then randomly assigned to receive a vitamin capsule (0.6 mg folic acid, 0.8 mg B12. and 2.0 mg B6) oran identical placebo during 8 weeks, in a double-blind study design. After the treatment phase, blood samples and vascular reactivity were repeated. RESULTS: Nine pairs of volunteers received vitamins and 11 received placebo. Hyperhomocysteinemic subjects had lower baseline serum levels of vitamin B12. Serum folate levels, antithrombotic function, in vitro LDL oxidation, and EDD were similar in all groups. After the vitamin supplementation, serum folic acid levels increased significantly both in normo- and hyperhomocysteinemic subjects, unlike vitamin B12, which increased only in the hyperhomocysteinemic individuals. Plasma tHcy decreased significantly in the supplemented groups. Treatment with vitamins was not associated with improvement in EDD or antithrombotic function. CONCLUSIONS: Mild hyperhomocysteinemia is not associated with endothelial dysfunction in young male subjects with no additional cardiovascular risk factors, and reduction of tHcy by vitamin supplementation does not modify EDD in this age group. In this sample, tHcy was more related to vitamin B12 than to folic acid status.     

Plasma homocysteine levels in acute coronary syndromes

Hyperhomocysteinemia is currently regarded as an independent and modifiable risk factor for ischemic vascular diseases and thrombosis. We measured fasting plasma total homocysteine levels by HPLC with fluorescence detection in 30 patients presenting with acute coronary syndromes and 30 age and sex-matched control subjects. Demographic data, classical risk factors (systolic blood pressure, diabetes mellitus, smoking, ethanol intake, family history of ischaemic heart disease) and life-style habits were recorded. Lipid fractions including total cholesterol, triglycerides, HDL-cholesterol, total cholesterol/HDL-cholesterol ratio, serum creatinine, LDL-cholesterol and vitamins involved in the metabolism of homocysteine, folic acid and vitamin B12 were also assessed. Total fasting homocysteine concentrations were significantly higher in the patient group (12.2 +/- 1.01 micromol/l) than in the control subjects (7.05 +/- 0.36 micromol/l; p < 0.0001). Homocysteine correlated positively with age (r = 0.617; p < 0.01) and serum creatinine (r = 0.457; p < 0.01) in the patient group. Hyperhomocysteinemia was not associated with vitamin B12 or folate deficiency states. Vitamin B12 concentration was 273 +/- 16.4 ng/l in the control group and 284.3 +/- 32.2 ng/l in the patient group (p = NS). Serum folate concentration also was not significantly different between controls and patients; 7.57 +/- 0.58 microg/l and 8.05 +/- 0.72 microg/l, respectively. Since no significant difference was observed in the lipid parameters between patients and controls, the hyperhomocysteinemia in the patient group supports the view that homocysteine is an independent risk factor for cardiovascular diseases. Our results strongly suggest that elevated homocysteine levels are among the interacting factors in the complex, multifactorial pathophysiology of ischemic heart disease.     

The relation between plasma cysteine, plasma homocysteine and coronary atherosclerosis

Several studies have reported that elevated plasma levels of total homocysteine (tHcy) are related to an increased risk of cardiovascular disease. Only a few studies have looked at the effect of cysteine, another amino thiol, on cardiovascular disease risk. Therefore, in the present case-control study we compared plasma total cysteine (tCys) levels and plasma tHcy levels among subjects with severe coronary atherosclerosis (cases, n=131), subjects without severe coronary atherosclerosis (coronary controls, n=88) and healthy subjects (population-based controls, n=101). Cases were defined as those having > or =90% occlusion in one and > or =40% occlusion in a second coronary artery, while coronary controls had a maximum of 50% occlusion in only one coronary artery. Both males and females, aged 26--64 years were studied. We have previously reported that plasma tHcy is an independent risk factor for coronary atherosclerosis in this study population. In the present analysis, we found that cases had statistically significant higher mean plasma tCys levels than coronary controls and population-based controls (295.8+/-40.2, 279.0+/-35.5 and 282.6+/-32.4 micromol/l, respectively). The odds ratio (OR) of coronary atherosclerosis for the upper tertile of tCys compared with the bottom tertile was 2.5 (95% confidence interval (CI), 1.4--4.3). However, the association between tCys and coronary atherosclerosis was confounded to a great extent by risk factors (OR, 1.0; 95% CI, 0.5--2.0). The multivariate adjusted OR of coronary atherosclerosis per 1 S.D. increase in plasma tCys was 1.0 (95% CI, 0.8--1.3). The corresponding OR per 1 S.D. increase in plasma tHcy was 1.4 (95% CI, 1.1--1.8). We conclude that plasma tCys, unlike plasma tHcy, is not an independent risk factor for atherosclerosis.     

Association of low red blood cell folate concentrations with coronary artery disease in Iranians: a matched case-control study

BACKGROUND: It is not fully established whether the increasing risk of coronary artery disease (CAD) is associated with high plasma homocysteine levels or components of the homocysteine remethylation pathway, e.g. vitamin B(12) or 5-methyltetrahydrofolate (5-MTHF) in plasma and red blood cells (RBC). In this study, we tested the hypothesis that 5-MTHF in RBC, which represents the long-term folate status of individuals, may be a more reliable marker of homocysteine remethylation pathway disturbances, and its deficiency may be associated with CAD in Iranians. METHODS: Plasma total homocysteine (tHcy), vitamin B(12), and plasma and RBC 5-MTHF were measured in 200 angiographically documented patients and 200 controls matched for sex and age. RESULTS: In the plasma, tHcy levels were significantly higher in cases compared to controls (geometric mean 12.9 +/- 6.5 vs. 10.6 +/- 5.6 micromol/l, p = 0.04). However, RBC 5-MTHF (527.2 +/- 185.9 vs. 461.3 +/- 117.9 nmol/l, p = 0.007) and vitamin B(12) (254.2 +/- 132.8 vs. 182.2 +/- 110.4 pmol/l, p = 0.04) were significantly higher in controls than patients. RBC 5-MTHF was a strong and independent predictor of plasma tHcy (beta = -0.01, p = 0.003, r(2) = 0.19). Subjects in the lowest quartile of red-cell 5-MTHF had a 2.5-fold increased prevalence of CAD compared to subjects in the highest quartile. The association of CAD in the first quartile with red-cell 5-MTHF remained significant when adjusted for plasma tHcy, vitamin B(12), hypertension and hypercholesterolemia (odds ratio, OR 2.3, confidence interval: 1.1-3.9, p = 0.01). However, the association between CAD in the highest quartile and plasma tHcy decreased and became insignificant when adjusted for red-cell 5-MTHF, vitamin B(12), hypertension and hypercholesterolemia (OR 1.27, confidence interval: 0.96-1.69, p = 0.11). CONCLUSION: In this study, the association between CAD and low RBC 5-MTHF was stronger than with plasma 5-MTHF and plasma tHcy levels, indicating that RBC 5-MTHF may be a more stable parameter to study disturbances in the homocysteine remethylation pathway in Iranians.     

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%).     

Gonadotropin treatment increases homocysteine levels in idiopathic hypogonadotropic hypogonadism: an indirect effect mediated by changes in body composition

The main objective of the present study was to examine the alterations in plasma total homocysteine (tHcy) concentrations during a testosterone-deficient state and after gonadotropin treatment for 6 Months in patients with idiopathic hypogonadotropic hypogonadism (IHH). Thirty-five newly diagnosed male patients with IHH (mean age 21.34+/-1.53 years) and 29 age- and body mass index-matched healthy males (mean age 21.52+/-1.77 years) were recruited into the study. Pretreatment levels of free testosterone (1.51+/-0.66 pg/ml), estradiol (21.37+/- 4.37 pg/ml), FSH (0.91+/-0.24 IU/l) and LH (1.25+/- 0.53 IU/l) were lower than controls (25.17+/-3.06 pg/ml, 31.00+/-4.96 pg/ml, 3.14+/-1.62 IU/l and 4.83+/-1.65 IU/l respectively) (P<0.001). They increased significantly after treatment (18.18+/-1.59 pg/ml, 27.97+/- 4.25 pg/ml, 2.41+/-0.27 IU/l and 2.79+/-0.19 IU/l respectively) (P<0.001). Patients with IHH had lower tHcy levels than controls (10.14+/-1.34 and 12.58+/- 2.29 micro mol/l respectively) (P<0.001). Plasma tHcy concentrations increased significantly (12.63+/-1.44 micromol/l) after 6 months of treatment (P<0.001). As compared with the controls, pretreatment levels of serum creatinine (63.54+/-13.01 vs 82.84+/-16.69 micromol/l), hemoglobin (12.98+/-0.56 vs 13.83+/-0.71 g/dl) and hematocrit (39.29+/-2.01 vs 41.38+/-1.95%) were significantly lower (P<0.001), and they increased significantly following treatment (80.24+/-11.93 micromol/l, 13.75+/-0.49 g/dl and 41.26+/-1.78% respectively) (P<0.001). The pretreatment folic acid and vitamin B(12) levels were significantly higher in patients when compared with controls (14.87+/-5.68 vs 12.52+/-4.98 nmol/l, P=0.034 and 289.75+/-92.34 vs 237.59+/-108.17 pmol/l, P=0.002 respectively). They decreased significantly after treatment (11.29+/-3.31 nmol/l and 228.51+/-54.33 pmol/l respectively) (P<0.001). The univariate and multivariate regression analysis results showed that only changes in creatinine, creatinine clearance, vitamin B12 and folic acid were independently associated with changes in tHcy levels in patients with IHH. In conclusion, the increase in plasma tHcy concentrations following gonadotropin treatment seems to be largely independent of changes in androgen levels.     

Influence of training volume and acute physical exercise on the homocysteine levels in endurance-trained men: interactions with plasma folate and vitamin B12

The interrelation between physical exercise and plasma levels of homocysteine (Hcy), vitamin B(12), and folic acid has not been examined. Therefore, we investigated the influence of extensive endurance training and acute intense exercise on plasma concentrations of total Hcy, vitamin B(12), and folic acid in 42 well-trained male triathletes. Examinations and blood sampling took place before and after a 30-day endurance training period as well as before and 1 and 24 h after a competitive exercise (sprint triathlon). Following the training period, no significant change in Hcy levels could be detected for the whole group. Subgroup analysis in quartiles of training volume revealed that - as compared with the lowest quartile (low-training group: 9.1 h training/week) - athletes in the highest training quartile (high-training group: 14.9 h training/week) exhibited a significant decrease in Hcy levels (from 12.7 +/- 2.3 to 11.7 +/- 2.4 micromol/l as compared with levels of 12.5 +/- 1.5 and 12.86 +/- 1.5 micromol/l in the low-training group; p < 0.05). The plasma folate levels were significantly higher in the high-training group at all points of examination (p < 0.05). 1 h and 24 h after competition, the Hcy concentration increased in all athletes independent of the previous training volume (24 h: 12.3 +/- 1.8 vs. 13.5 +/- 2.6 micromol/l; p < 0.001), although the increase was decisively stronger in the low-training group. 1 h after competition, the plasma folate concentration increased (7.03 +/- 2.1 vs. 8.33 +/- 2.1 ng/ml; p < 0.05) in all athletes. Multivariate analysis showed that the exercise-induced increase in the Hcy levels was dependent on baselines levels of folate and training volume, but not on the vitamin B(12) levels. In conclusion, although intense exercise acutely increased the Hcy levels, chronic endurance exercise was not associated with higher Hcy concentrations. Moreover, athletes with the highest training volume, exhibiting also the highest plasma folate levels, showed a decrease in Hcy levels following the training period as well as a much lower increase of the Hcy concentration after acute intense exercise. The combined effect of training and higher plasma folate levels to reduce Hcy should be investigated in future studies.     

Enhanced reduction of fasting total homocysteine levels with supraphysiological versus standard multivitamin dose folic acid supplementation in renal transplant recipients

The mild fasting hyperhomocysteinemia commonly observed in chronic (ie, >/=6 months posttransplantation) renal transplant recipients (RTRs) can be effectively treated with combined B-vitamin supplementation featuring supraphysiological doses of folic acid. There are no controlled data evaluating the comparative efficacy of supraphysiological versus standard multivitamin dose folic acid supplementation in reducing fasting total homocysteine (tHcy) levels among RTRs. We block-randomized 60 chronic, stable RTRs on the basis of their screening fasting tHcy level to 3 groups of 20 subjects treated for 12 weeks with folic acid at either 2.4 (group 1), 0.4 (ie, standard multivitamin dose) (group 2), or 0.0 (group 3) mg/d. All 60 study participants also received 50 mg/d vitamin B(6) and 0.4 mg/d vitamin B(12). The mean percent reductions (+/-SEM) in fasting tHcy were as follows: group 1, 32.3+/-2.4%; group 2, 23.4+/-2.3%; and group 3, 19.1+/-2.3%. ANCOVA accounting for the pretreatment matching and adjusted for pretreatment levels of fasting tHcy, folate, and albumin; change in creatinine during the study; and cyclosporine A use revealed significant overall group differences (P=0.005) and significant differences between groups 1 and 2 (P=0. 038) and groups 1 and 3 (P=0.001), but not between groups 2 and 3 (P=0.153). Moreover, a chi(2) analysis of participants with pretreatment tHcy levels >/=15 micromol/L (n=29) indicated that a significantly greater proportion of those in group 1 achieved posttreatment levels <12 micromol/L: group 1, 5 of 10 (50%); group 2, 1 of 11 (9%); and group 3, 0 of 8 (0%) (P=0.016; test of trend P=0. 007). We conclude that a supraphysiological dose of folic acid is superior to standard multivitamin dosing for the reduction of fasting tHcy levels in chronic RTRs.     

Endothelial function in healthy younger and older hyperhomocysteinemic subjects

OBJECTIVES: To compare endothelium-dependent vasomotor response in healthy younger and older subjects without classic cardiovascular risk factors, with high and normal fasting homocysteine (tHcy) levels. DESIGN: We compared endothelium-dependent vasodilatation, using ultrasound, in healthy younger (aged 18-40) and older (> or =70) people with normal (<13 micromol/L) and high (>15 micromol/L) tHcy levels. Exclusion criteria were smoking, personal history of cardiovascular disease, hypertension, chronic diseases, vitamin intake, obesity, abnormal serum lipids levels, and creatinine higher than 130 micromol/L. SETTING: Research laboratory. MEASUREMENTS: In addition to tHcy levels, serum folate and vitamin B12 levels were measured. RESULTS: We studied 17 younger and 12 older hyperhomocysteinemic subjects and respective aged-matched normohocysteinemic subjects. Endothelium-dependent vasodilatation was lower in the hyperhomocysteinemic older people (P <.01) than in all younger subjects and in normohomocysteinemic older people. Serum vitamin B12 levels were higher in younger and older normal controls. Folic acid levels were higher in younger controls and in both older groups. CONCLUSIONS: This study shows an effect of high circulating tHcy on vascular reactivity in older people. Because serum levels of tHcy are associated with nutritional status of vitamin B12 and folic acid, prospective studies are necessary to demonstrate the effects of a long-term nutritional supplementation with vitamins on vascular function and global cardiovascular risk.     

Hyperhomocysteinemia in children with juvenile idiopathic arthritis is not influenced by methotrexate treatment and folic acid supplementation: a pilot study

OBJECTIVE: Our first objective was to compare plasma total homocysteine (tHcy) concentrations in juvenile idiopathic arthritis (JIA) patients requiring methotrexate (MTX) treatment and healthy children. Our second aim was to evaluate the influence of low-dose (10-15 mg/m2/week) MTX treatment combined with folic acid supplementation (1 mg/d) or placebo on tHcy concentrations in JIA patients. METHODS: In 17 JIA patients and 17 age- and sex-matched healthy children, baseline tHcy concentrations were measured. When MTX treatment was initiated, JIA patients were randomly assigned to folic acid 1 mg/d/p.o. followed by placebo (8 weeks each) or vice versa. Blood samples for measurement of tHcy, vitamin B6, B12 and folate were taken after 4 weeks, 12 weeks and 20 weeks of treatment. RESULTS: 1) In the healthy children the mean tHcy concentration was 6.3 +/- 1.68 mumol/l as compared to 9.99 +/- 5.17 mumol/l in JIA patients (p < 0.04). At baseline, 5/17 JIA patients had tHcy concentrations > 10.5 mumol/l, the 99th percentile for teenagers. 3/5 patients even exceeded the upper normal level for adults (tHcy > or = 15 mumol/l). MTX treatment did not result in a significant increase of tHcy and folic acid supplementation had no significant impact on tHcy levels. CONCLUSION: This pilot study shows that patients with JIA requiring MTX treatment have significantly elevated baseline plasma tHcy concentrations compared to age- and sex-matched healthy controls. No significant impact of MTX and folate supplementation on tHcy concentration was found.     

High prevalences of vitamin B12 and folic acid deficiency in elderly subjects in Israel

The prevalences of vitamin B12 and folic acid deficiency in the general Israeli population of elders has not been assessed. We measured plasma cobalamin and folic acid concentrations in 418 subjects from four institutions for the aged, 749 subjects attending 19 geriatric day centres and 104 healthy controls. Methylmalonic acid (MMA) and/or homocysteine concentrations were determined in subjects who had a cobalamin concentration <221 pmol/l or folic acid concentration <11 nmol/l respectively. The prevalences of vitamin B12 deficiency (cobalamin <147 pmol/l and MMA > or =0.24 micromol/l), and folic acid deficiency (folic acid <11 nmol/l and homocysteine of >15 micromol/l) in subjects from day centres were 12.6% and 16.4% respectively, and in subjects from institutions 1.2% and 2.2% respectively (P < 0.001). Multiple logistic regression analysis indicated that the relative risk of living at home versus institutions for the aged was highly significant, with odds ratios (OR) of 6.8 [95% confidence interval (CI) 2.6-18.0] for vitamin B12 deficiency and 6.6 (95% CI 2.9-13.1) for folic acid deficiency. Analysis of data for day centre patients showed that folic acid deficiency was a significant risk factor of vitamin B12 deficiency (adjusted OR 3.68, 95% CI 2.27-5.98), and vitamin B12 deficiency was a significant risk of folic acid deficiency (adjusted OR 3.69, 95% CI 2.27-6.01). These data suggest that malnutrition is a major cause of the highly prevalent deficiencies of vitamin B12 and/or folic acid in elderly Israeli subjects dwelling at home.     

Hyper-homocysteinemia is not a main feature of juvenile uncomplicated type 1 diabetes

Total plasma homocysteine (tHcy) was measured by high pressure liquid chromatography (HPLC) method in 28 patients (12 females and 16 males) at the onset of type 1 diabetes mellitus (T1DM), 4 females during diabetes ketoacidosis (DKA) and 154 (68 females and 86 males) during follow-up. Serum folate, pyridoxal 5' phosphate (PLP) and Vitamin B12 (Vit B12) were also measured. Plasma tHcy levels were not found significantly different in T1DM patients known to have diabetes (males 9.2 +/- 7.7 and females 7.0 +/- 2.8 micromol/l) and in those who were newly diagnosed (males 9.7 +/- 4.8 and females 7.16 +/- 2.8 micromol/l) than in healthy controls (males 8.7 +/- 3.5 and females 7.8 +/- 2.55 micromol/l). Only a significant difference for sex was observed in known diabetes (p = 0.0281). Serum folate, PLP and Vit B12 were normal (12.6 +/- 3.6 ng/ml, 20.11 +/- 0.8 ng/ml and 416.7 +/- 41.9 pg/ml) in all T1DM patients. Age significantly correlated with plasma tHcy. Only in 4 patients, studied during DKA, plasma tHcy was significantly lower (2.76 +/- 1.33 micromol/l, p < 0.001) than the healthy controls.     

Homocysteine-lowering therapy does not affect inflammatory markers of atherosclerosis in patients with stable coronary artery disease

OBJECTIVES: A high level of total homocysteine (tHcy) is a risk marker for cardiovascular disease (CVD), and is related to inflammation. We wanted to test the effect of homocysteine-lowering B-vitamin therapy, as used in the Western Norway B-vitamin Intervention Trial (WENBIT), on inflammatory markers associated with atherosclerosis. DESIGN: Single centre, prospective double-blind clinical interventional study, randomised in a 2 x 2 factorial design. SUBJECTS AND METHODS: Ninety patients (21 female) with suspected coronary artery disease (CAD), aged 38-80 years, were blindly randomised into one of four groups of daily oral treatment with (A) folic acid (0.8 mg)/vitamin B12 (0.4 mg)/vitamin B6 (40 mg), (B) folic acid/vitamin B12, (C) vitamin B6 alone or (D) placebo. Blood samples were collected before and after 6 months of treatment. RESULTS: Before intervention, median levels of the analytes were: tHcy 11.0 micromol L(-1), neopterin 8.1 nmol L(-1), soluble CD40 ligand (sCD40L) 3.9 ng mL(-1), interleukin (IL)-6 1.9 pg mL(-1), C-reactive protein (CRP) 1.9 mg L(-1) and low-density lipoprotein (LDL) cholesterol 3.3 mmol L(-1). tHcy was significantly associated with neopterin (r = 0.49, P < 0.001) and with IL-6 (r = 0.29, P = 0.01), but not with CRP or sCD40L. Neither treatment with folic acid/B12 nor with B6 induced significant changes in any of these inflammatory biomarkers (P >or= 0.14). In patients receiving folic acid/B12 (groups A and B), tHcy was reduced with 33% (P < 0.001). CONCLUSIONS: In patients with stable CAD, homocysteine-lowering therapy with B-vitamins does not affect levels of inflammatory markers associated with atherogenesis. Failure to reverse inflammatory processes, may partly explain the negative results in clinical secondary B-vitamin intervention trials.     

Fat metabolism during high-intensity exercise in endurance-trained and untrained men

To determine whether trained individuals rely more on fat than untrained persons during high-intensity exercise, six endurance-trained men and six untrained men were studied during 30 minutes of exercise at 75% to 80% maximal oxygen consumption (VO2max). The rates of appearance (Ra) and disappearance (Rd) of glycerol and free fatty acids (FFAs) were determined using [1,1,2,3,3-2H]glycerol and [1-13C]palmitate, respectively, whereas the overall rate of fatty acid oxidation was determined using indirect calorimetry. During exercise, the whole-body rate of lipolysis (ie, glycerol Ra) was higher in the trained group (7.1 +/- 1.2 v 4.5 +/- 0.7 micromol x min(-1) x kg(-1), P < .05), as was the Ra (approximately Rd) of FFA (9.0 +/- 0.9 v 5.0 +/- 1.0 micromol x min(-1) x kg(-1), P < .001). FFA utilization was higher in trained subjects even when expressed as a percentage of total energy expenditure (10% +/- 1% v 7% +/- 1%, P < .05). However, this difference in plasma FFA flux could not account for all of the difference in fatty acid oxidation between trained and untrained subjects (20.8 +/- 3.3 v 7.9 +/- 1.6 micromol x min(-1) x kg(-1), or 23% +/- 3% v 13% +/- 2% of total energy expenditure, both P < .05). Thus, the oxidation of fatty acids derived from some other source also must have been greater in the trained men. We conclude that trained athletes use more fat than untrained individuals even during intense exercise performed at the same percentage of VO2max. The additional fatty acids appear to be derived from both adipose tissue and, presumably, intramuscular triglyceride stores.     

Heavy alcohol intake, homocysteine and Type 2 diabetes.

Although moderate alcohol intake is associated with reduced risk of atherosclerotic disease in both the general population and in diabetic patients, a recent report suggests that heavy alcohol intake facilitates the development of atherosclerosis exclusively in diabetic individuals. We studied cross-sectionally the effects of the interaction between ethanol consumption category and the prevalence of diabetes on plasma total homocysteine (tHcy), a risk factor for atherosclerotic disease, in middle-aged men. Heavy drinking was associated with elevated tHcy levels only in diabetic subjects but not in non-diabetic subjects. Plasma tHcy of heavy drinkers (average ethanol consumption > 30 ml/day) was higher than that of abstainers in the diabetic subgroup (10.25 +/- 3.39 vs. 8.88 +/- 1.94 micromol/l, P < 0.05), whereas tHcy levels in heavy drinkers were comparable with that of abstainers in the non-diabetic subgroup (9.36 +/- 2.52 vs. 9.12 +/- 2.10 micromol/l, NS). In a two-factor anova, significant interaction was observed on the effects of ethanol consumption category and diabetes prevalence on tHcy levels (P < 0.01). Confounding factors including folate, vitamin B(12), creatinine, age or cigarette smoking did not contribute to the interaction. These findings may partly explain the reported association between heavy drinking and atherosclerosis in diabetic subjects.     

Reduction of homocysteine levels in coronary artery disease by low-dose folic acid combined with vitamins B6 and B12

An increased plasma homocysteine concentration is a risk factor for atherosclerosis. Folic acid lowers homocysteine but the optimal dose in patients with coronary artery disease (CAD) is unclear. This placebo-controlled, single-blind, dose-ranging study evaluates the effect of low-dose folic acid on homocysteine levels in 95 patients aged 61 +/- 11 years (mean +/- SD) with documented CAD. Patients in each group were given either placebo or 1 of 3 daily supplements of folic acid (400 microg, 1 mg, or 5 mg) for 3 months. Each active treatment arm also received 500 microg vitamin B12 and 12.5 mg vitamin B6. Total plasma homocysteine levels were measured after 30 and 90 days. Folic acid 400 microg reduced homocysteine levels from 13.8 +/- 8.8 to 9.6 +/- 2.0 micromol/L at 90 days (p = 0.001). On 1- and 5-mg folic acid, levels decreased from 13.0 +/- 6.4 to 9.8 +/- 4.0 micromol/L (p = 0.001) and from 14.8 +/- 6.9 to 9.7 +/- 3.3 micromol/L (p < 0.001), respectively. The decrease was similar in all treatment groups. There was no significant change with placebo. Although the sample size is small, these findings suggest that daily administration of 400 microg/day folic acid combined with vitamin B12 and vitamin B6 may be equivalent to higher doses in reducing homocysteine levels in patients with CAD.     

Renal insufficiency, vitamin B(12) status, and population attributable risk for mild hyperhomocysteinemia among coronary artery disease patients in the era of folic acid-fortified cereal grain flour

Fortification of enriched cereal grain flour products with folic acid has drastically reduced the prevalence of deficient plasma folate status, a major determinant of plasma total homocysteine (tHcy) levels. We hypothesized that even more liberally defined "suboptimal" plasma folate status might no longer contribute importantly to the population attributable risk (PAR) for mild hyperhomocysteinemia, a putative atherothrombotic risk factor. We determined fasting plasma tHcy, folate, vitamin B(12), and pyridoxal 5'-phosphate levels, along with serum creatinine and albumin levels, in 267 consecutive patients (aged 61+/-9 [mean+/-SD] years, 76.4% men and 26.6% women) with stable coronary artery disease (CAD) who were nonusers of vitamin supplements or had abstained from supplement use for at least 6 weeks before examination. Subjects were evaluated a minimum of 3 months after the implementation of flour fortification was largely completed. Relative risk estimates for the calculation of PAR were derived from a multivariable-adjusted logistic regression model with >/=12 micromol/L tHcy as the dependent variable and with age, sex, pyridoxal 5'-phosphate (continuous), albumin (continuous), <5 ng/mL folate, <250 pg/mL vitamin B(12), and >/=1.3 mg/dL creatinine as the independent variables. The prevalence of >/=12 micromol/L plasma tHcy was 11.2% (30 of 267 patients). PAR estimates (percentage) for >/=12 micromol/L tHcy were as follows: <5 ng/mL folate (<1%), <250 pg/mL vitamin B(12) (24.5%), and >/=1.3 mg/dL creatinine (37.5%). In the era of folic acid-fortified cereal grain flour, renal insufficiency and suboptimal vitamin B(12) status (but not folate status) contribute importantly to the PAR for mild hyperhomocysteinemia among patients with stable CAD.     

Mild hyperhomocysteinemia and the common C677T polymorphism of methylene tetrahydrofolate reductase gene are not associated with the metabolic syndrome in Type 2 diabetes

A moderate increase of total homocysteine (tHcy) plasma levels seems to increase cardiovascular disease (CVD) risk in Type 2 diabetic subjects, but its relationship with diabetes and insulin-resistance is still controversial. We examined whether mild hyperhomocysteinemia and its major genetic determinant would cluster with the metabolic syndrome (MS) in Type 2 diabetes. One hundred Type 2 diabetic subjects with and without MS were enrolled in the study. Fasting tHcy, vitamin B12, and folate plasma levels, insulin-resistance [assessed by homeostasis model assessment, (HOMAIR)] and the methylene tetrahydrofolate reductase (MTHFR) C677T genotype were assessed in all the participants. Geometric mean tHcy concentration and the prevalence of mild hyperhomocysteinemia, as commonly defined by tHcy >/=15 micromol/l, were comparable in diabetic subjects with and without MS, even after adjustment for age, sex, vitamin B12, folate and creatinine levels. In both groups, the MTHFR C677T genotype distribution was not significantly different from the Hardy-Weinberg equilibrium, with a TT homozygous frequency of 21% in subjects with and 18% in those without the syndrome (p=ns). tHcy plasma levels and the degree of insulin-resistance did not differ across MTHFR genotypes in both groups, even after multivariable adjustment. Overall, tHcy significantly correlated with creatinine (r=0.25; p=0.009) and trygliceride concentrations (r=0.24; p=0.02), but not with HOMAIR. At multivariate analysis, only creatinine was significantly correlated with tHcy levels (beta=0.42; p=0.001). In conclusion, hyperhomocysteinemia and the common C677T variant of MTHFR gene are not associated with MS in Type 2 diabetic subjects.