Effect of serum 25‐hydroxyvitamin D(3) on insulin resistance and β‐cell function in newly diagnosed type 2 diabetes patients

AIMS/INTRODUCTION: To evaluate serum 25‐hydroxyvitamin D(3) (25(OH)D(3)) in newly diagnosed type 2 diabetes patients and to explore the associations of 25(OH)D(3) with insulin resistance and β‐cell function. MATERIALS AND METHODS: A total of 97 newly diagnosed type 2 diabetes patients and 69 healthy controls were recruited. Serum 25(OH)D(3) was determined using high‐pressure liquid chromatography. Insulin resistance was measured using a homeostasis model assessment of insulin resistance (HOMA‐IR). β‐Cell function was determined using the HOMA β‐cell function index (HOMA‐β), early‐phase insulin secretion index (ΔI30/ΔG30) and area under the insulin curve (AUCins). Correlation analysis was carried out using Pearson's correlation and multiple stepwise regression analysis. RESULTS: Serum 25(OH)D(3) was much lower in patients with newly diagnosed type 2 diabetes (t = −13.00, P < 0.01), and the prevalence of hypovitaminosis 25(OH)D(3) was 62.9% (61/97) in diabetic patients. Among the diabetic patients, patients with hypovitaminosis 25(OH)D(3) showed higher glycosylated hemoglobin and AUCglu (P < 0.01) as well as lower HOMA‐β, ΔI30/ΔG30 and AUCins. Serum 25(OH)D(3) was independently positively correlated with ΔI30/ΔG30 and AUCins (P < 0.05), but was not significantly correlated with either HOMA‐IR or HOMA‐β. Only triglycerides, glycosylated hemoglobin and ΔI30/ΔG30 emerged as independent factors associated with serum 25(OH)D(3) in both diabetes patients and the health control group. CONCLUSIONS: The present results further showed a low serum 25(OH)D(3) concentration in patients with newly diagnosed type 2 diabetes. 25(OH)D(3) deficiency is associated with disturbances in glucose metabolism and lipid metabolism. Serum 25(OH)D(3) is not correlated with basal insulin resistance or β‐cell function, but is significantly positively correlated with glucose‐stimulated insulin secretion and β‐cell function.