C-reactive protein, vitamin B12 and C677T polymorphism of N-5,10-methylenetetrahydrofolate reductase gene are related to insulin resistance and risk factors for metabolic syndrome in Chinese population

Purpose: Metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) are complex diseases affected by both dietary intake and genetic background. Whether N-5, 10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, high-sensitivity C-reactive protein (hs-CRP) and dietary components folate and vitamin B12 are associated with MS in Asian has not been determined. Methods: We hypothesized that MTHFR gene C677T, folate, vitamin B12 and hs-CRP are associated with MS and factors related to MS in northern Han Chinese. To test this hypothesis, MTHFR C677T gene polymorphism was determined by PCR-RFLP, serum insulin, folate and vitamin B12 levels by radioimmunoassay, and hs-CRP by immunoturbidimetry in newly diagnosed T2DM patients with MS (118) and without MS (40), and in 55 healthy subjects. Results: Results indicated that MS-associated T2DM accounts for 75% of newly diagnosed T2DM in Han Chinese. Serum hs-CRP was higher and serum vitamin B12 was lower in subjects with TT genotype in comparison with those with CC or CT genotypes. Total T frequency was significantly higher in MS-associated T2DM patients (45.3%) compared to 26.3% in non-MS-associated T2DM patients. MTHFR C677T gene polymorphism and vitamin B12 levels were associated with MS-associated T2DM. Conclusion: MTHFR C677T gene polymorphism may contribute to insulin resistance in Han Chinese with MS by increasing hs-CRP and decreasing vitamin B12, and consequently play an important role in development of MS-associated T2DM.