Short-chain Fatty Acids Inhibit NLRP3 Inflammasome to Alleviate Inflammation and Epithelial-mesenchymal Transition in Diabetic Nephropathy Rats via GPR41/43

Background: The role of Short-chain fatty acids (SCFAs) and their G-protein-coupled receptors (GPRs) in mitigating diabetic nephropathy (DN) has been recognized. This study aimed to investigate the impact of SCFAs on inflammation in DN via G-protein-coupled receptors 41 and 43 ( GPR41/43 ). Methods: Human kidney tubular HK-2 cells were transfected to silence GPR41/43 and treated with sodium acetate (Ac, 48 mmol/L)/sodium propionate (Pr, 24 mmol/L)/sodium butyrate (But, 8 mmol/L) under high glucose (HG, 30 mM) or normal glucose conditions. Rats were administered lentivirus solution to silence GPR41/43 and streptozotocin (STZ, 60 mg/kg) to induce DN, followed by treatment with But (100 mmol/L). Diabetic symptoms and renal function were evaluated, kidney weight/body weight (KW/BW) was calculated, and renal histopathology was examined using hematoxylin-eosin, periodic acid-Schiff, and Masson staining. Quantitative real-time polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay, and immunohistochemistry were employed to assess epithelial-mesenchymal transition (EMT)-related proteins, GPR41 , GPR43 , NLR family pyrin domain containing 3 (NLRP3), and inflammatory factor levels in HK-2 cells and kidney tissues. Results: Ac/Pr/But reversed HG-induced downregulation in GPR41 / GPR43 and upregulation of NLRP3 /tumor necrosis factor-α ( TNF-α )/interleukin-18 ( IL-18 )/ IL-6 / IL-1β in HK-2 cells ( p < 0.001). But attenuated HG-induced decrease in epithelial cadherin (E-cadherin) ( p < 0.001) and increase in alpha-smooth muscle actin (α-SMA) ( p < 0.05) in HK-2 cells. Silencing GPR41/43 reversed the effects of But ( p < 0.05). STZ induced diabetic symptoms, increased urine albumin level, serum creatinine/ blood urea nitrogen (BUN) level, KW/BW, α-SMA, NLRP3, and inflammatory factor levels in kidney tissues, exacerbated kidney morphology, and downregulated E-cadherin and GPR41 / GPR43 in kidney tissues in rats ( p < 0.001). But attenuated these effects of STZ, which were reversed by silencing GPR41/43 ( p < 0.05). Conclusions: SCFAs inhibit NLRP3 inflammasome activation, thus alleviating inflammation and EMT in DN by upregulating GPR41/43 .