Hypovitaminosis D Associations with Adverse Metabolic Parameters Are Accentuated in Patients with Diabetes Mellitus Type 2 : a BMI-Independent Role of Adiponectin?

Background: Hypovitaminosis D has been associated with an increased prevalence of diabetes mellitus type 2 (DMT2) and metabolic syndrome manifestations. The purpose of this study was to examine the association between 25-hydroxy-vitamin D (25-OHD) levels and indices of insulin resistance, including adipocytokines, in a Saudi population with or without DMT2. Subjects and Methods: A total of 266 subjects (153 DMT2 and 113 healthy controls) aged 26-80 years old were randomly selected from the existing Biomarkers Screening in Riyadh Program (RIYADH Cohort). Subjects were assessed clinically, anthropometry was performed, morning blood chemistries, including fasting glucose, triglycerides, total cholesterol, LDL-C, and HDL-C were obtained. HOMA-IR was calculated, and serum 25- OHD, leptin, adiponectin, resistin, insulin, hsCRP, and TNF-α concentrations were measured using specific assays. Results: In DMT2 subjects, negative correlations between 25-OHD and BMI, fasting glucose, insulin, HOMA-IR, cholesterol, LDL-C and hsCRP were observed, while a positive correlation between 25-OHD and adiponectin was detected. The later remained significant after controlling for BMI. Interestingly, only weak and non significant associations between 25-OH-VitD and metabolic parameters were observed in the control group, whereas, when the entire population was examined, negative correlations were evident primarily between 25-OH-VitD and fasting glucose, HOMA-IR, total cholesterol, LDL-C. These associations remained significant after controlling for BMI. Conclusion: These results suggest that hypovitaminosis D associations with metabolic disturbances are accentuated in DMT2. The BMI-independent positive correlation between 25-OH-VitD and adiponectin suggests a potential role for this adipocytokine as a link between 25-OH-D and insulin resistance in patients with DMT2