P-0555-Association of reduced serum vitamin D levels with insulin resistance in Bangladeshi impaired glucose tolerance subjects
Author block: Afroz MS1, Hossain IA2, Azam MZ1, Khan MH1, Ali L2 
 1Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh; 2Department of Biochemistry and Cell Biology, Bangladesh University of Health Sciences (BUHS), Dhaka, Bangladesh.
Background: Impaired glucose tolerant (IGT) subjects, the subgroup of prediabetes in Bangladeshi population have previously been shown to have insulin resistance; however, the underlying mechanism(s) of this defect is still unclear. Circulating vitamin D is known to play a role in insulin sensitivity by expressing the vitamin D binding protein in pancreatic cell. A number of studies have been conducted between the relationships of serum vitamin D levels with insulinemic indices in type 2 diabetic subjects but in IGT state, there is paucity of data regarding this association.
 Objective: The present study has been explored to evaluate the levels of reduced vitamin D levels and its association with insulin resistance in IGT subjects. 
Methods: Under a case-control design a total of 20 IGT subjects (M/F, 9/11; age in years, 46±9; BMI in kg/m2, 25±3; M±SD) and 27 age, sex and BMI- matched Healthy Controls (M/F, 14/13; age in years, 45±12; BMI in kg/m2, 26.84±4.34) were investigated. IGT was diagnosed as per WHO Study Group criteria following a 2- sample OGTT. Serum insulin and vitamin D were measured by ELISA techniques. Insulin resistance (HOMA-IR) was calculated by homeostasis model assessment (HOMA). 
Results: Compared to the Control, the IGT subjects had significantly higher levels of HOMA-IR (1.760.4 vs 2.541.2, M±SD, p=0.011). On Pearson’s correlation analysis, vitamin D showed significant positive correlation with fasting serum insulin (r=0.435, p=0.004) and HOMA-IR (r=0.396, p=0.007) in IGT subjects. On multiple linear regression analysis, HOMA-IR showed significant positive association with vitamin D (β=0.625, p=0.019) after adjusting the effects of major confounding variables of body mass index (BMI), triglyceride (TG) and HbA1c. 
Conclusions: From the above study results, it may conclude that circulating vitamin D levels is reduced in IGT subjects and this reduction is seemed to be mediated by insulin resistance among these subjects.