Relationship between serum Vitamin D and insulin resistance in pre-diabetic and diabetic states- A comparative study

Introduction: Pre-diabetes is an important risk factor for the development of overt diabetes as well as cardiovascular disease. Pre-diabetes is frequently associated with obesity which in turn is commonly associated with hypovitaminosis-D. Low Vitamin D levels impair synthesis & secretion of insulin and through many other mechanisms is attributed in the pathogenesis of diabetes. Pre-diabetes is a stage where prevention efforts have been shown to be effective in delaying or preventing the onset of diabetes. However, there are not many studies that have examined the association between low serum 25(OH) Vit D levels and prediabetes. The aim of this study was to compare Vit D levels between the normals, pre-diabetics & diabetics and study the relationship between insulin resistance and vitamin-D status among individuals with pre-diabetes and diabetes. Materials and Methods: 50 non diabetic, 50 pre-diabetic and 50 type 2 diabetics were included in the study. Waist hip ratio and Body mass index calculated. Fasting blood sugar, insulin, lipid profile, calcium, alkaline phosphatase and serum 25 hydroxy vitamin D were estimated. Insulin resistance (HOMA2-IR) and beta cell function (HOMA2-β) was calculated using HOMA 2 calculator. Result: Vitamin-D deficiency (<20 ng/ml) was seen in 20% normals, 36% of prediabetics and 48% of diabetics. BMI, WHR, Total cholesterol, triglycerides, LDL & VLDL were significantly increased & HDL decreased in prediabetic and diabetic groups when compared to normals (p<0.001).25 OH Vit D levels were significantly decreased (p<0.0001) in diabetics as compared to normals and pre diabetics (p<0.0001). There was a strong negative correlation between Vit D and HOMA 2-IR in diabetics (r= - 0.63) and prediabetic (r= - 0.77). Conclusion: Vit D deficiency is common in prediabetic state and subjects having severe vitamin D deficiency (<10 ng/ml), had the worst insulin resistance. Our study results help in proposing vitamin D levels as an early marker for diabetes and help in recommending vitamin D to be prescribed in the pre diabetic stage itself.