Metformin attenuates folic-acid induced renal fibrosis in mice

Progressive tubulointerstitial fibrosis has been recognized as a common pathological process that leads to the progression of all chronic kidney disease (CKD). Innovative strategies are needed to both prevent and treat CKD. Inflammatory and fibrotic signaling pathways play central roles in the progression of CKD regardless of aetiology. Hence, targeting inflammatory and fibrotic responses holds promise to limit renal fibrosis. Metformin has been the most prescribed glucose-lowering medicine worldwide, and its potential for many other therapeutic applications is also being explored intensively. Increasing evidence indicates metformin may limit renal fibrosis. However, the exact mechanisms whereby metformin limits renal injury are not fully understood. The anti-fibrotic effects of metformin, independent of improved glycaemic control was examined in a folic acid-induced mouse model of nephropathy for 14 days. Human proximal tubular cells (HK2 cells) exposed to TGF-1 were used in in vitro models to examine mechanistic pathways. Folic acid induced nephropathy was associated with the overexpression of inflammatory markers MCP-1, F4/80, type IV collagen, fibronectin and TGF-1 compared to control groups, which were partially attenuated by metformin treatment. In vitro studies confirmed that metformin inhibited TGF-1 induced inflammatory and fibrotic responses through Smad3, ERK1/2, and P38 pathways in human renal proximal tubular cells. These results suggest that metoformin attenuates folic acid-induced renal interstitial fibrogenesis through TGF-1 signaling pathways.