Vitamin D & its analogues in type 2 diabetic nephropathy: a systematic review

Nephropathy is one of the major complications of diabetes often leading to chronic kidney disease (CKD). Inflammation and oxidative stress are associated with pathogenesis of diabetic nephropathy (DN) and found to be regulated by nuclear receptors such as vitamin D receptors (VDR). Vitamin D and its analogues have been effectively used in patients with CKD. The review attempts to summarize the available evidence on the role of vitamin D in DN. Electronic databases (MEDLINE, EMBASE, and Cochrane Library) were searched for studies assessing the role of vitamin D or its analogues on kidney function in type 2 diabetic patients. Studies evaluating kidney functions (urinary albumin/protein creatinine ratio, albuminuria and eGFR) were included and quality and risk of bias assessment performed. Additionally effect on 25 (OH) vitamin D, calcium and HbA1c were evaluated. The mean or its % change along with their standard deviation (SD) was used for reporting our results. RevMan (V5.2) was used for data analysis. Six studies included in this review evaluated the role of cholecalciferol, calcitriol and paricalcitol in patients with DN. Study designs differed (three randomized, one non-randomized and two uncontrolled trials) with varying degree of quality and risk of biases. Vitamin D analogues showed significant improvement in kidney function in two randomized studies. None of the studies reported significant incidences of hypercalcemia. Vitamin D analogues show significant improvement of kidney function in DN. Randomized controlled trials with longer duration, comparing the efficacy of vitamin D and its analogues are needed.