The Relationship between Renal Injury and Change in Vitamin D Metabolism in Aged Rats with Insulin Resistance or Type 2 Diabetes Mellitus

Abstract

Insulin resistance (IR), IR treated with vitamin D, IR treated with 1alpha-hydroxyvitamin D (1alpha-(OH)D), type 2 diabetes mellitus (T2DM), T2DM treated with vitamin D and T2DM treated with 1alpha-(OH)D were studied in animal models using aged Wistar rats. Glucose infusion rates and levels of urinary albumin (UA), serum 25-hydroxyvitamin D (25-(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured. T2DM rats had higher UA than IR or normal rats, and levels of 25-(OH)D in all models weresimilar. IR rats had higher 1,25-(OH)2D levels than T2DM rats, and had lower 1,25-(OH)2D levels than normal rats. Treating IR or T2DM rats with vitamin D had no effect on 25-(OH)D or 1,25-(OH)2D. Administration of 1alpha-(OH)D significantly increased 1,25-(OH)2D in IR rats to above-normal levels, and significantly increased 1,25-(OH)2D in T2DM rats to normal levels. In IR or T2DM, abnormal vitamin D metabolism is characterized by 1,25-(OH)2D deficiency and is related to renal injury.