Metformin Prevents Renal Stone Formation through an Antioxidant Mechanism In Vitro and In Vivo

Oxidative stress is a causal factor and key promoter of urolithiasis associated with renal tubular epithelium cell injury. The present study was designed to investigate the preventive effects of metformin on renal tubular cell injury induced by oxalate and stone formation in a hyperoxaluric rat model. MTT assays were carried out to determine the protection of metformin from oxalate-induced cytotoxicity. The intracellular superoxide dismutase (SOD) activities and malondialdehyde (MDA) levels were measured in vitro. Male Sprague-Dawley rats were divided into control group, ethylene glycol (EG) treated group, and EG + metformin treated group. Oxidative stress and crystal formations were evaluated in renal tissues after 8-week treatment. Metformin significantly inhibited the decrease of the viability in MDCK cells and HK-2 cells induced by oxalate. Besides, metformin markedly prevented the increased concentration of MDA and the decreased tendency of SOD in oxalate-induced MDCK cells and HK-2 cells. In vivo, the increased MDA levels and the reduction of SOD activity were detected in the EG treated group compared with controls, while these parameters reversed in the EG + metformin treated group. Kidney crystal formation in the EG + metformin treated group was decreased significantly compared with the EG treated group. Metformin suppressed urinary crystal deposit formation through renal tubular cell protection and antioxidative effects.