Association between vitamin D receptor polymorphism and type 2 diabetes or metabolic syndrome in community-dwelling older adults: The Rancho Bernardo Study

Vitamin D receptor (VDR) polymorphism influences susceptibility to type 1 diabetes, but the association with type 2 diabetes is not clear. We investigated the association between VDR polymorphism and type 2 diabetes and metabolic syndrome in a community-based study of unrelated older adults without known diabetes. Oral glucose tolerance test (75 g), plasma glucose and insulin measurement, homeostasis model assessment (HOMA), and VDR genotyping were performed. The distributions of genotype frequencies of ApaI, BsmI, and TaqI polymorphism did not differ between persons with and without diabetes, but the frequency of aa genotype of ApaI polymorphism was marginally higher in persons with type 2 diabetes (P = .058). Fasting plasma glucose (P < .05) and prevalence of glucose intolerance (P < .05) were significantly higher in nondiabetic persons with aa genotype compared with those with AA genotype. The bb genotype of BsmI polymorphism was associated with insulin resistance as assessed by HOMA after adjustment for age, sex, body mass index (BMI), and calcium and vitamin D use in persons without diabetes (P < .05). Our research suggests that ApaI polymorphism may be associated with glucose intolerance independent of defective insulin secretion and BsmI polymorphism with insulin resistance in a nondiabetic Caucasian population. Copyright (C) 2002 by W.B. Saunders Company.