Homocysteine: the new player in the field of coronary risk

The association of MTHFR C677T gene variants and lipid profiles or body mass index in patients with diabetic and nondiabetic coronary heart disease

BACKGROUND

The aim of this study is to investigate whether methylenetetrahydrofolate reductase (MTHFR) C677T mutation is associated with the development of hyperlipoproteinemia and obesity in coronary heart disease (CHD).

METHODS

This study was carried out in 82 diabetic and 112 nondiabetic patients with CHD and in 138 CHD-free healthy controls. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and agarose gel electrophoresis techniques were used to determine the MTHFR C677T.

RESULTS

Distributions of MTHFR genotypes (C677T dbSNP: rs1801133) were similar in our study groups (P > 0.05). There was no statistical association between biochemical parameters and genotype distribution in nondiabetic CHD patients, while diabetic CC genotype carriers have elevated levels of body mass index (BMI) independently from lipid profiles (P = 0.002). In diabetic CHD patients, while evaluating the clinical parameters according to gender, it was found that gender had an impact on BMI (P = 0.013). Due to this gender effect, a multivariate analysis was conducted on the diabetic CHD patient group. The multivariate logistic regression analysis confirmed that the MTHFR-CC genotype was associated with elevated BMI levels in diabetic CHD patients (odds ratio [OR] = 5.42, P = 0.003).

CONCLUSION

The results of the present study demonstrated that possessing T allele of MTHFR C677T mutation indicates a protective association on BMI independently from other risk factors.

The relationship between plasma homocysteine level and different treatment modalities in patients with ankylosing spondylitis

To determine plasma homocysteine levels in ankylosing spondylitis (AS) and their correlation with disease activity measurements. To examine the effects of different treatment modalities on homocysteine levels. One hundred eight patients diagnosed with AS according to New York criteria and 65 healthy individuals matched in terms of age and gender were enrolled in the study. Patients were given detailed physical examinations. The Bath AS Disease Activity Index (BASDAI) was used for disease activity, the Bath AS Metrology Index (BASMI) for spinal mobility, the Bath AS Functional Index (BASFI) to determine functional status and the Bath AS Radiological Index (BASRI) for radiological analysis. Sedimentation rate (ESR) and C reactive protein (CRP) levels, acute phase reactants, were measured. Plasma homocysteine levels, serum interleukin (IL) -6 and serum tumor necrosis factor- α (TNF- α) levels were investigated using the enzyme-linked immunosorbent assay (ELISA) method. Plasma homocysteine levels in AS patients were statistically significantly lower compared with those in the healthy control group (P = 0.0001). There was no significant difference among sub-groups established on the basis of medical treatments and disease activity (BASDAI ≤4 and >4). No statistically significant correlation was determined between homocysteine level and disease activity parameters, radiological score and functional indices. A significant negative correlation was, however, established between age and homocysteine level in the AS group (P < 0.05, r = -0.426). Plasma homocysteine was lower in AS patients compared with the control group. This is not correlated with disease activation and medical treatment employed.

Homocysteine levels in patients treated with lipid apheresis: effect of a vitamin therapy

BACKGROUND

Patients treated with lipid apheresis already suffer from familial hypercholesterolemia and severe coronary heart disease: any additional risk factor is dangerous for these patients. Hyperhomocysteinemia has been recognized as an independent risk factor for atherosclerotic disease. We checked the frequency of hyperhomocysteinemia in lipid apheresis patients and measured the effect of a vitamin therapy.

MATERIALS AND METHODS

Sixteen heterozygous patients (10 males, 6 females) were studied, who were being treated by three different apheresis procedures. Homocysteine was measured using an enzyme conversion immunoassay. Cystathionine and methylmalonic acid were assessed by gas chromatography/mass spectrometry. Serum levels of folic acid, vitamin B12, and vitamin B6 were also determined. The patients received a vitamin therapy (3 mg folate, 60 microg cyanocobalamine, 10 mg pyridoxine hydrochloride daily) for 12 weeks.

RESULTS

In 9 out of 16 patients, plasma homocysteine levels were found to be elevated (> 12 micromol L(-1)). Cystathionine concentrations were also increased, especially in those patients with elevated homocysteine. Methylmalonic acid levels were not elevated. Serum folic acid, vitamin B6, and vitamin B12 concentrations were initially in the normal range and not correlated to plasma homocysteine. The vitamin therapy reduced the plasma homocysteine concentrations in all patients significantly by 33%. Among those patients with elevated homocysteine levels, the optimal range < 12 micromol L(-1) for homocysteine was rarely reached.

CONCLUSIONS

In patients treated with lipid apheresis, a hyperhomocysteinemia can be frequently seen. The constellation of both elevated homocysteine and cystathionine levels points to the existence of tissue vitamin deficiencies, folate and vitamin B-6, which were improved by vitamin supplements. Because methylmalonic acid was mostly normal, a vitamin B-12 deficiency was not proven.

The importance of hyperhomocysteinemia as a risk factor for diseases: an overview

Hyperhomocysteinemia is the result of a disturbed methionine metabolism. It results from enzyme and/or vitamin deficiency. Epidemiological studies have proven, that hyperhomocysteinemia is a risk factor for atherosclerotic cardiovascular diseases, stroke, peripheral arterial occlusive disease and venous thrombosis. Conflicting results come from prospective studies. Trials which are now in progress may clarify the "causality" of high homocysteine concentrations and will assess the value of homocysteine-lowering therapy. The induction of the atherogenic process by hyperhomocysteinemia seems to be associated with an alteration of endothelial and smooth muscle cell function leading to an accelerated formation of reactive oxygen species. An increased endothelial expression of adhesion molecules will then lead to an enhanced deposition of oxidized LDL in the vessel wall with the formation of foam cells. Additionally, hyperhomocysteinemia interferes with the coagulation system and thus also has prothrombotic effects. There is a high prevalence of hyperhomocysteinemia as a sign of a vitamin deficiency in elderly subjects which strongly increases with age. Elderly people have a high frequency of vitamin B12 deficiency which can be diagnosed more reliably by the measurement of serum methylmalonic acid (MMA) level than by serum vitamin B12. Subjects following a strict vegetarian diet also have a high prevalence of hyperhomocysteinemia caused by functional vitamin B12 deficiency (increased MMA level). Last but not least, hyperhomocysteinemia is a factor in the pathogenesis of neural tube defects and pre-eclampsia. An early diagnosis of vitamin B12 deficiency is important for the prevention of neurological damages. Homocysteine should be measured in patients with a history of atherothrombotic vessel diseases, in patients with diabetes or hyperlipidemia, in renal patients, in obese subjects, in elderly people, in postmenopausal women, and in early pregnancy. A specific diagnosis of an underlying vitamin deficiency is important for adequate treatment. Individuals with homocysteine level >12 micromol/l should increase and/or supplement their dietary intake of vitamins.

Total Homocysteine, Vitamin B12, and Total Antioxidant Status in Vegetarians

Background: Decreasing or eliminating animal products from the diet decreases the intake of some essential nutrients, such as vitamin B12, which may lead to hyperhomocysteinemia. We investigated vitamin B12-dependent metabolism and oxidative stress in groups with various or no intake of meat or animal products.

Methods: We investigated 44 high meat eaters, 19 low meat eaters, 34 lacto-ovo/lacto vegetarians, and 7 vegan vegetarians. Homocysteine (HCY) was assayed by HPLC, methylmalonic acid (MMA) by capillary gas chromatography–mass spectrometry, serum folate and vitamin B12 with a chemiluminescence immunoassay, and total antioxidant status (TAS) by a Randox method.

Results: The mean serum HCY concentration of vegetarians was significantly increased, and in vegans the median concentration exceeded 15 μmol/L. Vegetarians had a higher serum concentration of MMA but a lower TAS. Vitamin B12 and folate did not differ significantly between vegetarian and omnivorous subjects. Overall, HCY and MMA were significantly correlated. Vitamin B12 correlated negatively with MMA, HCY, and folate, whereas the correlation with TAS was positive. Backward regression analysis revealed an independent influence of MMA on HCY, of HCY and vitamin B12 on MMA, and of vitamin B12 on TAS. The increased MMA concentration suggested a 25% frequency of functional vitamin B12 deficiency in all vegetarians. Serum vitamin B12 was below the lower reference limit in only five subjects.

Conclusions: Functional vitamin B12 deficiency in vegetarians may contribute to hyperhomocysteinemia and decreased TAS, which may partly counteract the beneficial lifestyle of vegetarians. However, increased serum HCY is most likely not responsible for the lower TAS values in vegetarians. We recommend assaying of MMA and HCY to investigate functional vitamin B12 status.

Methylene tetrahydrofolate reductase genotype and the risk and extent of coronary artery disease in a population with low plasma folate

OBJECTIVE

To determine the effects of the thermolabile methylene tetrahydrofolate reductase (MTHFR) mutation on the presence and extent of coronary atherosclerosis in a population with low plasma folate.

METHODS

242 consecutive patients undergoing coronary angiography were prospectively evaluated for conventional risk factors, plasma homocysteine, vitamin B-12, and folate, and MTHFR genotype. The severity of coronary atherosclerosis was determined by the Leaman score.

RESULTS

Mean (SD) plasma homocysteine was 15.6 (10) micromol/l in controls and 18.5 (11) micromol/l in patients with coronary artery disease (p > 0.05). Plasma homocysteine concentrations above 15 micromol/l were a risk factor for coronary artery disease (p = 0.03, risk ratio 2.1, 95% confidence interval (CI) 1.07 to 4.4). Homocysteine remained an independent risk factor on multivariate analysis when conventional risk factors were taken into account (p = 0.04). Homocysteine concentrations above 15 micromol/l were correlated with the extent of atherosclerosis (p = 0. 04, risk ratio 3.2, 95% CI 1.3 to 8.2). Homocysteine had no effect on other lipid variables (p > 0.05). Plasma folate was 15.8 (7.2) nmol/l in controls and 11.5 (2.9) nmol/l in patients with coronary artery disease. Plasma folate concentrations below 12.9 nmol/l (5.7 ng/ml) conferred a risk for coronary artery disease (p = 0.03, risk ratio 2.42, 95% CI 1.05 to 5.59). When the MTHFR genotype was determined, the TT genotype was present in 7.4% of patients and 5.2% of controls (p > 0.05). The prevalence of alleles was within the Hardy-Weinberg equilibrium (TT 7, CT 40, CC 53, chi2 = 2.3, p = 0.3). The highest homocysteine concentrations were found in patients with the TT genotype and folate below the median of the population (p = 0. 01). The extent of coronary atherosclerosis judged by the Leaman score was significantly higher in patients with the TT genotype (p = 0.03).

CONCLUSIONS

Plasma homocysteine over 15 micromol/l was a significant risk factor for the presence and extent of coronary artery disease. The mean plasma folate of the population was low and correlated negatively with homocysteine. Although TT genotype was not an independent predictor of coronary artery disease, it was an important predictor of the extent of coronary atherosclerosis and plasma homocysteine, especially in the presence of plasma folate values below the median of the population. These findings may have important implications for folate replacement in patients with the TT genotype.

[Laboratory diagnosis in preventive cardiology]

In recent years a large number of coronary artery disease risk factors were discovered. The knowledge of these factors improves the estimate of the coronary artery disease (CAD) risk--however it still remains to be only an "estimate". A perfect prediction of an upcoming CAD event is not possible, despite all high score laboratory technology. Therefore the use of specialized laboratory procedures should be applied carefully. Knowing the blood levels of cholesterol, triglycerides, HDL- and LDL-cholesterol and Lp(a) can be sufficient for many therapeutical decisions. Severe dyslipidemia, familial CAD and CAD without any obvious reasons demand a more specialized work-up, however, risk stratification factors such as family history, clinical history (CAD, hypertension, diabetes mellitus, smoker) and genetics are crucial, apart from the above mentioned laboratory values. Purely on the basis of the lipidologic baseline concentrations we can't give well based recommendations for the treatment of individual patients. Currently there are expert systems available which allow a risk estimate once important laboratory values (LDL cholesterol, HDL cholesterol, Triglycerides) as well as clinical data (blood pressure, family history, clinical history) are available. This system can be accessed by internet under "http:/(/)www.chd-taskforce.com".

Plasma homocysteine and the extent of atherosclerosis in patients with coronary artery disease

Homocysteine is a graded risk factor for the incidence of stroke and for the degree of carotid atherosclerosis. Homocysteine is also a graded risk factor for the incidence of myocardial infarction but we do not know its precise relations to the severity of atherosclerosis in coronary patients. Seventy five symptomatic coronary patients were recruited for the study. Fifty of these patients had coronary artery disease only and were compared in a case-control manner to 50 healthy controls matched for age and sex. The 25 other coronary patients had also symptoms in another atherosclerotic territory (cerebral, peripheral or both) and were also compared to 25 matched controls. Mean plasma homocysteine level was significantly higher in coronary patients than in controls (11.7 +/- 0.7 mumol l-1, n = 50 versus 9.9 +/- 0.5 mumol l-1, n = 50, p < 0.05). Homocysteine in patients with symptomatic atherosclerosis in two or three arterial sites was 15.7 +/- 1.5 mumol l-1 which differed significantly from matched controls and from patients with coronary artery disease only (p = 0.01). The extent of coronary atherosclerosis evaluated by an angiographic coronary score correlated weakly to plasma homocysteine levels (r = 0.25, p < 0.05). The patients with both hypertension and high levels of homocysteine (> 11.3 mumol l-1, median value) had more severe coronary atherosclerosis (coronary score of 16.3 +/- 2.3 versus 11.9 +/- 0.9, p < 0.05) and more diffuse atherosclerosis (number of atherosclerotic territories of 1.5 +/- 0.2 versus 1.2 +/- 0.7, p = 0.08) than the coronary patients without this association. There were no other high risk association when considering the other classical risk factors. Thus, the highest levels of homocysteine were present in patients with coronary disease and another symptomatic localisation of atherosclerosis. A small gradient in the extent of coronary atherosclerosis was found with increasing levels of homocysteine. The presence of both hypertension and hyperhomocysteinemia was associated with more severe coronary atherosclerosis.