Silymarin attenuates diabetic nephropathy in rats via modulation of the miRNA-223/NLRP3/caspase-1/GSDMD axis and inflammasome-related pyroptotic signaling.

Abstract

Diabetic nephropathy (DN) is a progressive microvascular complication of diabetes and a leading cause of end-stage renal disease, with limited disease-modifying therapeutic options. DN is characterized by progressive renal dysfunction, oxidative stress, inflammation, fibrosis, and activation of inflammasome-related pathways. Silymarin, a natural compound with antioxidant and anti-inflammatory properties, has demonstrated renoprotective potential; however, its association with miRNA-223/NLRP3/caspase-1/GSDMD signaling in DN remains incompletely defined. Therefore, the present study investigated the potential renoprotective effects of silymarin in a high-fat diet/streptozotocin (HFD/STZ)-induced rat model of DN, with particular focus on miRNA-223 expression and inflammasome-associated pyroptotic signaling. Diabetic rats received oral silymarin (100 mg/kg/day) either for 12 weeks as an early intervention or 4 weeks as a delayed treatment. Renal function indices, blood glucose, HbA1c, serum insulin, HOMA-IR, LDH, lipid profile, body weight, kidney weight/body weight index, oxidative stress markers, and histopathological changes were evaluated. Renal expression of miRNA-223, NOD-like receptor family pyrin domain-containing 3 (NLRP3), caspase-1, gasdermin D (GSDMD), nuclear factor-kappa B (NF-κB) (p65), hypoxia-inducible factor-1 alpha (HIF-1α), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and fibronectin was assessed using RT-qPCR, ELISA, and immunohistochemistry. Silymarin significantly improved renal function, glycemic control, insulin resistance, lipid profile, oxidative stress, inflammatory mediators, HIF-1α expression, LDH activity, histopathological injury, and fibrosis relative to untreated DN rats. Moreover, silymarin was associated with increased renal miRNA-223 expression and reduced expression of NLRP3, caspase-1, and GSDMD. These effects were more pronounced in the early intervention group compared with delayed treatment. In conclusion, silymarin attenuated experimental DN via modulation of the miRNA-223/NLRP3/caspase-1/GSDMD axis and suppression of pyroptosis-associated signaling, alongside improvement of oxidative stress, inflammation, hypoxia, fibrosis, and metabolic disturbances. Further mechanistic studies are warranted to clarify the causal relationship between miRNA-223 modulation and the observed renoprotective effects of silymarin.