Metformin has protective effects on diabetic nephropathy. However, the mechanism underlying the renoprotective action of metformin in spontaneously hypertensive rats (SHR) is not completely understood. We determined the role of metformin in proteinuria and investigated the mechanism. We measured the urinary protein concentration (mg/day) in 48-week-old SHR. Matched control animals were of the same genetic strain, Wistar-Kyoto (WKY). The rats received metformin (100 mg/kg/day) or vehicle for 10 months. Metformin improved renal function and reduced the proteinuria (urine protein: 48.4 ± 3.7 vs. 25.4 ± 1.8 mg, P < 0.01) induced by long-term high blood pressure. Metformin increased the production of vascular endothelial growth factor (VEGF)-A in rat kidneys and cultured rat podocytes. Metformin activated hypoxia-inducible factor-2α (Hif-2α) in response to VEGF but did not affect Hif-1α in rat kidneys and cultured rat podocytes. Metformin reduced the proteinuria induced by long-term high blood pressure in vivo and increased the VEGF-A production in rat kidneys and cultured rat podocytes, probably by activating the Hif-2α-VEGF signaling pathway. These findings provide a new mechanism for the renoprotective effects of metformin.
Keywords: HIF; Hypertension; Metformin; Proteinuria; VEGF.
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