Serum 25-hydroxyvitamin D, genetic susceptibility, and the risk of incident type 2 diabetes: A prospective cohort in East China

Abstract. Background:. The serum vitamin D level varies widely by population, and studies have linked vitamin D levels with the risk of type 2 diabetes mellitus (T2DM). However, the relationship is inconsistent and the impact of vitamin D on T2DM among East Chinese adults is unclear. The study aimed to investigate the association between serum 25-hydroxyvitamin D (25[OH]D) levels and the risk of T2DM and evaluated whether the association is modified by genetic predisposition. Methods:. In the Survey on Prevalence in East China for Metabolic Diseases and Risk Factors (SPECT-China) cohort, 1862 participants free of T2DM at baseline were included. A weighted genetic risk score was calculated with 28 variants associated with T2DM. Hierarchical logistic models were used to examine the association of serum 25(OH)D and genetic risk with T2DM. Results:. After a 5-year follow-up, 132 cases of T2DM were documented. We observed no significant association between quartiles of serum 25(OH)D and T2DM risk after multivariable adjustment (χ2 = 0.571, Pfor trend = 0.426). Compared to those in the lowest quartile of 25(OH)D, the odds ratios (ORs) (95% confidence interval [CI]) for participants with increased quartiles were 1.29 (0.74–2.25), 1.35 (0.77–2.36), and 1.27 (0.72–2.24), respectively. We observed a positive association of glycated hemoglobin (HbA1c) with 25(OH)D at baseline (β = 1.752, P = 0.001) and after follow-up (β = 1.385, P = 0.003), and a negative association of ln conversion homeostasis model assessment (HOMA)-β with 25(OH)D at baseline (β = -0.982, P = 0.021). There was no significant interaction between 25(OH)D and diabetes genetic predisposition on the risk of T2DM (χ2 = 2.710, Pfor interaction = 0.100). The lowest OR (95% CI) of T2DM was among participants with low genetic risk and the highest quartile of 25(OH)D (0.17 [0.05–0.62]). Conclusion:. Serum 25(OH)D may be irrelevant to the risk of incident T2DM among East Chinese adults regardless of genetic predisposition.