Lower Vitamin D Levels, but Not VDR Polymorphisms, Influence Type 2 Diabetes Mellitus in Brazilian Population Independently of Obesity

Abstract

Background and Objectives: Vitamin D levels have been associated with a diversity of diseases, including obesity. Vitamin D presents a pleiotropic action, and can regulate insulin secretion and inflammatory responses. Vitamin D receptor (VDR) gene polymorphisms are involved in the gene expression regulation and have been associated with type 2 diabetes mellitus (T2DM). This study aimed to evaluate the association between the polymorphisms ApaI (rs7975232), BsmI (rs1544410), FokI (rs10735810), and TaqI (rs731236) in the VDR gene in people diagnosed with T2DM, and plasma 25-hydroxivitamin D levels [25(OH)D]. Materials and Methods: A total of 101 T2DM patients and 62 gender, age, and body mass index (BMI) matched non-diabetic controls were included in this study. Molecular analyzes were performed by polymerase chain reaction−restriction fragment length polymorphism (PCR-RFLP). The plasma 25(OH)D levels were measured by high performance liquid chromatography. Results: The plasma 25(OH)D levels were lower in T2DM patients (17.2 (16.6) ng/mL) when compared with the control subjects (30.8 (16.2) ng/mL, p < 0.0001), independently of obesity status. We found no difference between genotypic and allelic frequencies of the VDR polymorphisms when comparing the T2DM group and control group (p > 0.05 for all), and did not show any association with plasma 25(OH)D levels. Conclusions: These results suggest that T2DM is associated with lower plasma 25(OH)D levels, which are not related to BMI and VDR gene polymorphisms.

Keywords

• vitamin D
• obesity
• type 2 diabetes mellitus
• vitamin D receptor
• polymorphisms