Association Of Methylenetetrahydrofolate Reductase C677T Polymorphism And Serum Lipid Levels In The Guangxi Bai Ku Yao And Han Populations

Objective Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme of folic acid and homocysteine metabolism. It plays an important role in folic acid metabolism, DNA methylation and DNA synthesis. The C677T polymorphism in the MTHFR gene, which encodes an enzyme involved in remethylation of homocysteine to methionine, leads to increased thermolability and impaired enzymatic activity. The association of MTHFR gene polymorphism and serum lipid profiles is still controversial in diverse ethnics. Bai Ku Yao (White-trouser Yao), an isolated subgroup of the Yao minority, is named so because all the men wear white knee-length knickerbockers. The population size is about 30000. Because of isolation from the other ethnic groups, the special customs and cultures including their clothing, intra-ethnic marriages, dietary habits, and corn wine and rum intakes are still completely preserved to the present day. This ethnic difference in serum lipid profiles is still not well known. Therefore, the aim of the present study was to detect the association of MTHFR C677T polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations. Methods A total of 780 subjects of Bai Ku Yao and 686 participants of Han Chinese were randomly selected from our previous stratified randomized cluster samples. Epidemiological data included demographics, socioeconomic status, smoking and alcohol information. Blood pressure, height, weight, serum lipid and apolipoprotein (Apo) levels were measured, and body mass index (BMI) was calculated as weight (kg) divided by height (m) squared. Genotyping of the MTHFR C677T was performed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis, and then confirmed by direct sequencing.Results (1) The levels of serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), ApoA1 and ApoB were lower in Bai Ku Yao than in Han (P < 0.05-0.001). There was no significant difference in the levels of serum triglyceride (TG) and the ratio of ApoA1 to ApoB (2) The frequency of C and T alleles was 77.4% and 22.6% in Bai Ku Yao, and 60.9% and 39.1% in Han (P < 0.001); respectively. The frequency of CC, CT and TT genotypes was 58.7%, 37.3% and 4.0% in Bai Ku Yao, and 32.6%, 56.4% and 11.0% in Han (P < 0.001); respectively. (3) The levels of TC and LDL-C in both ethnic groups were significant differences among the three genotypes (P < 0.05-0.01). The T allele carriers had higher serum TC and LDL-C levels than the T allele noncarriers. The levels of ApoB in Han were significant differences among the three genotypes (P < 0.05). The T allele carriers had higher serum ApoB levels as compared with the T allele noncarriers. (4) The levels of TC, TG and LDL-C in Bai Ku Yao were correlated with genotypes (P < 0.05-0.001), whereas the levels of LDL-C in Han were associated with genotypes (P < 0.001). Serum lipid parameters were also correlated with sex, age, body mass index, alcohol consumption, cigarette smoking, and blood pressure in the both ethnic groups.Conclusions The differences in serum TC, TG, LDL-C and ApoB levels between the two ethnic groups might partly result from different genotypic and allelic frequencies of the MTHFR C677T or different MTHFR gene-enviromental interactions.