Finerenone Improves Albuminuria via MR-TRPC Signaling in Diabetic Kidney Disease

BACKGROUND: Recent studies have confirmed the protective effects of nonsteroidal MR (mineralocorticoid receptor) antagonists in diabetic kidney disease. However, the physiological mechanisms underlying their albuminuria-reducing effects remain incompletely defined. We hypothesized that inhibition of the MR could protect podocytes by limiting excessive calcium influx via TRPC (transient receptor potential canonical) 5, thereby reducing albuminuria. METHODS: We evaluated the effects of the nonsteroidal MR antagonist finerenone on albuminuria, podocyte morphology, and glomerular function in diabetic mice. Reactive oxygen species generation and single-nephron glomerular filtration rate were analyzed using in vivo imaging. Cultured podocytes were used to assess MR-TRPC5 signaling through measurements of Sgk1 (serum- and glucocorticoid-regulated kinase 1) and TRPC5 expression, intracellular calcium, and actin cytoskeletal organization. RESULTS: Finerenone significantly reduced albuminuria, ameliorated podocyte morphological abnormalities, and decreased glomerular reactive oxygen species production in diabetic mice. In cultured podocytes, aldosterone increased Sgk1 and TRPC5 expression, elevated intracellular calcium, and induced actin reorganization; these changes were attenuated by finerenone and by the AC1903 (TRPC5 inhibitor). Activation of MR-TRPC signaling was associated with increased calcium influx and features of podocyte injury. In vivo imaging further indicated that finerenone was associated with lower single-nephron glomerular filtration rate, consistent with an attenuation of glomerular hyperfiltration. CONCLUSIONS: Finerenone is associated with reductions in albuminuria in diabetic kidney disease, together with improvements in podocyte injury indices and glomerular hemodynamics. These benefits may be mediated in part through MR-TRPC5 signaling although additional pathways are likely to contribute.