Isoliquiritigenin Protects Against Diabetic Nephropathy in db/db Mice by Inhibiting Advanced Glycation End Product–Receptor for Advanced Glycation End Product Axis

Diabetes nephropathy (DN) is a severe diabetic chronic microvascular complication and the major cause of end-stage renal disease (ESRD). Our study aimed to investigate the effects of isoliquiritigenin (ISL) a natural flavonoid compound on DN and to explore the underlying mechanisms. The db/db mice were received intragastric treatments of ISL (5, 10, or 20 mg/kg), vehicle or positive drug metformin (300 mg/kg) once a day for 12 weeks, and the db/m mice treated with vehicle were used as controls. ISL significantly ameliorated pathological changes and functional injury in the kidneys of db/db mice in a dose-dependent manner. The administration of 20 mg/kg ISL reduced the levels of serum creatinine (Scr; 49.0 ± 1.7 vs. 56.9 ± 2.9 μmol/L; p < 0.01), blood urine nitrogen (BUN; 9.6 ± 1.3 vs. 12.0 ± 1.1 mmol/L; p < 0.05), albumin to creatinine ratio (ACR; 1925.8 ± 798.1 vs. 4269.4 ± 925.6 μg/mg; p < 0.01) and urinary albumin (276.2 ± 39.9 vs. 576.9 ± 108.9 μg; p < 0.05). Further study identified advanced glycation end product (AGE)–receptor for AGE (RAGE) axis as a target of ISL. ISL (20 mg/kg) lowered renal AGE level (2.5 ± 0.5 vs. 3.8 ± 0.6 μg/mg; p < 0.01) and RAGE expression, leading to improvements in renal fibrosis, oxidative stress, and inflammation. To sum up, our study demonstrated that ISL displayed preventive effects on the experimental model of DN through suppressing AGE–RAGE pathway, and provided some insights into the application of ISL in DN treatment.