Vitamin D and diabetes in chronic kidney disease

Abstract

The relation between the kidney and vitamin D is well known. Vitamin D has also been recognized to regulate endocrine pancreatic function; it stimulates pancreatic beta cells proliferation and insulin secretion. And several studies suggest that vitamin D status may have a significant role in glucose homeostasis in general, and on the pathophysiology and progression of metabolic syndrome and type-2 diabetes in particular. The deficiency in vitamin D is associated with a reduced insulin secretion, which might be an important factor for the susceptibility of developing diabetes. Vitamin D has been proposed also as a possible therapeutic agent in the prevention and treatment of type-1 and type-2 diabetes. In diabetic patients at various CKD stages, circulating 25(OH)D levels are negatively correlated with glycosylated hemoglobin (HbA1c) values, which suggests that increasing circulating vitamin levels may have a beneficial effect of the glycemic control. Likewise, the activation of the vitamin D receptor (VDR) can reduce proteinuria and contribute to the nephroprotection. Low circulating 25(OH)D levels in CKD patients have been associated with a higher risk of all-cause mortality and faster progression of kidney disease. Unfortunately, the level of evidence to support 25(OH)D therapy for CKD or diabetes mellitus is low. Several studies of nutritional vitamin D supplementation in patients with CKD and type-2 diabetes are actually ongoing, although their results are not yet available.