Abstract
This study tested the ISL against renal damage induced by a high-fat diet (HFD) and explored its underlying mechanisms. Adult male rats were assigned to four groups: (1) control on a standard diet (STD), (2) ISL on STD (30 mg/kg), (3) HFD, and (4) HFD + ISL (30 mg/kg). After 12 weeks of dietary intervention, ISL treatment led to significant reductions in body weight gain, visceral fat, and glucose and insulin levels in HFD-fed rats. Notably, ISL decreased serum urea and creatinine, increased serum albumin, and improved urinary profiles by lowering the urinary albumin and the albumin/creatinine ratio. Histological analyses revealed that ISL enhanced the glomerular structure and mitigated tubular damage, as evidenced by reduced urinary excretion of the kidney injury markers NGAL and KIM-1. Additionally, ISL significantly lowered cholesterol, triglycerides, and free fatty acids in both the control and HFD groups while also decreasing oxidized low-density lipoproteins (ox-LDLs) and malondialdehyde (MDA). Importantly, ISL enhanced renal antioxidant levels, increasing glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT). Moreover, ISL downregulated mRNA levels of MD-2, Toll-like receptor-4 (TLR-4), and NF-κB, leading to reduced NF-κB p65 levels in renal tissues. In conclusion, ISL offers substantial protection against HFD-induced renal toxicity through mechanisms that attenuate metabolic stress, enhance antioxidant defenses, and inhibit the MD-2/TLR4/NF-κB inflammatory pathway.