Effects of vitamin D combined with pioglitazone hydrochloride on bone mineral density and bone metabolism in Type 2 diabetic nephropathy

The study aims to investigate the effect of vitamin D (VD) combined with pioglitazone hydrochloride (PIO) on bone mineral density (BMD) and bone metabolism in patients with Type 2 diabetic nephropathy (T2DN). T2DN patients were selected and assigned into mild, moderate, and severe groups. In each group, three therapy regimens (VD, PIO, and VD plus PIO) were administered. X-ray absorptiometry was used to measure BMD. Intact parathyroid hormone (iPTH) and 25-hydroxyvitamin D3 (25-OH-VD3) were measured by chemiluminescence meter. ELISA was applied to detect levels of osteoprotegerin (OPG), bone gla protein (BGP), C-terminal telopeptides of type I collagen (β-CTX), procollagen type I N-propeptide (PINP), pyridinoline (Pyr), and deoxypyridinoline (D-Pyr). Compared with the mild group, T2DN patients in the moderate and severe groups had longer course of disease and higher levels of total cholesterol (TC), triglyceride (TG), serum phosphorus, fasting plasma glucose (FPG), glycosylated hemoglobin (HbAlc) and creatine (Cr), and lower blood calcium. The BMD in different parts increased among the mild, moderate, and severe groups, and the highest BMD was found after VD plus PIO treatment. OPG, iPTH, BGP, β-CTX, Pyr/Cr, and D-Pyr/Cr levels were reduced, while 25-OH-VD3 and PINP levels were elevated among three groups after different treatments, and the most obvious change was observed after VD plus PIO treatment. Our findings indicate that VD combined with PIO may be more effective in improving BMD and bone metabolism than VD or PIO alone in the treatment of T2DN patients, especially for T2DN patients with mild disease.