The effects of vitamin D supplementation on adiponectin level and insulin resistance in first-degree relatives of subjects with type 2 diabetes: a randomized double-blinded controlled trial

BACKGROUND: Despite the certain role of both vitamin D and adiponectin in the regulation of insulin sensitivity, the interaction between these two agents has remained uncertain. OBJECTIVE: The present study aimed to determine whether vitamin D is able to change plasma adiponectin and affect glucose homeostasis and insulin sensitivity in first-degree relatives of subjects with type 2 diabetes. METHODS: This randomized clinical trial was conducted at Clinic of Shahid Sadoughi Hospital in Yazd, Iran, from January 25, 2012 to December 25, 2014. In this randomized, double-blinded controlled trial, 64 first-degree relatives of type 2 diabetic patients were assigned randomly to receive either vitamin D supplement (50000 IU vitamin D tablet weekly) plus lifestyle change as the intervention group (n = 32) or placebo plus lifestyle change as the control group (n = 32) for twelve weeks (three months). RESULTS: Fifty-three patients (28 in the intervention group and 25 in the control group) completed the study. Serum levels of vitamin D increased while insulin level and consequently insulin resistance (calculated by HOMA formula) significantly decreased in the case group (p-value <0.001 for all variables). Although the values of these three biomarkers showed a slight increase in control group, the changes were not statistically significant. The levels of the changes in other markers including adiponectin, Fasting Blood Sugar (FBS), triglyceride, and total cholesterol remained insignificant in both study groups after completing interventions compared with before interventions. CONCLUSION: This study showed that decreased insulin resistance is expected by administrating vitamin D supplement in first-degree relatives of the patients with diabetes mellitus. TRIAL REGISTRATION: The trial was registered at the Iranian Registry of Clinical Trials (http://www.irct.ir) with the IRCT ID: 201105176430N1. FUNDING: The authors received no financial support for the research or publication of this article.