Objective: Epidemiological studies have identified hyperhomocyst(e)inemia as an independent risk factor for atherosclerosis. The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, might play a role in the development of coronary heart disease (CHD). In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and CHD in Chinese type 2 diabetic patients.
Methods: Two hundred and twenty-eight unrelated patients with type 2 diabetes mellitus (126 with coronary heart disease) and 114 healthy control subjects were recruited. The MTHFR genotype was analyzed by PCR followed by HinfI digestion. Plasma total homocysteine levels were measured using high-performance liquid chromatography (HPLC) with fluorescence detection.
Results: In 114 healthy control subjects, the frequency of the mutant T allele was 38.0%, comparable to that of a Hong Kong (Chinese) population. The genotype distribution did not differ between control subjects and type 2 diabetic patients (chi(2) = 3.67, P > 0.05). Genotypic analysis revealed that type 2 diabetic patients with CHD displayed a greater prevalence of T allele (45.2%) than type 2 diabetic patients without CHD (30.4%) (chi(2) = 8.72, P < 0.005). The odds ratio for CHD in type 2 diabetic patients in presence of T allele was 1.89 (CI 95%, 1.24-2.88). The MTHFR genotype were different between diabetic patients with and without CHD (chi(2) = 11.98, P < 0.005). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype or CC plus CT genotype.
Conclusions: The C677T mutation of MTHFR gene is common in the Chinese population. MTHFR C677T gene polymorphism associated with a predisposition to increased plasma homocysteine levels could constitute a useful predictive marker for CHD in Chinese type 2 diabetic patients.