Vitamin D levels and microvascular complications in type 2 diabetes

BACKGROUND: Vitamin D has important actions on glucose metabolism. These include improved insulin exocytosis, direct stimulation of insulin receptor, improved uptake of glucose by peripheral tissues, improving insulin resistance. It has got various pleiotropic effects like suppression of cell mediated immunity, regulation of cell proliferation, stimulation of neurotropic factors such as nerve growth factor, Glial cell line-derived neurotrophic factor, neurotropin, suppression of RAAS, reduction of albuminuria, immunomodulatory effects, and anti-inflammatory effects. Thus, vitamin D is implicated in many ways in the pathogenesis of retinopathy, neuropathy and nephropathy. OBJECTIVES: To study the correlation of vitamin D levels with microvascular complications in type 2 diabetes. MATERIALS AND METHODS: Cross-sectional case-control study of 18 patients (18-70 years), who met the American Diabetes Association 2011 criteria for type 2 diabetes, was conducted. Age and sex matched healthy controls were taken. Subjects were evaluated for the presence of microvascular complications by clinical evaluation, urine examination, fundus examination, nerve conduction studies, and various biochemical tests. 25-OH cholecalciferol levels were done for each. Cut off level for vitamin D deficiency was 20 ng/ml. RESULTS: Mean vitamin D was lower in type 2 diabetics than healthy subjects (19.046 vs. 27.186 ng/ml). Prevalence of vitamin D deficiency and insufficiency was found to significantly higher in diabetics when compared to healthy subjects (P = 0.0001). Vitamin D deficiency was found to be significantly associated with neuropathy (χ(2) = 5.39, df = 1, P = 0.020), retinopathy, (χ(2) = 6.6, df = 1, P = 0.010) and nephropathy (χ(2) = 10. 52, df = 1, P = 0.001). Lower levels of vitamin D were found to be associated with increasing prevalence of combinations of microvascular complications namely neuropathy with retinopathy (P = 0.036), neuropathy with nephropathy (P = 0.029), retinopathy with nephropathy (P = 0.022) and neuropathy with retinopathy with nephropathy (P = 0.0001).