Spatholobus suberectus Ameliorates Diabetes-Induced Renal Damage by Suppressing Advanced Glycation End Products in db/db Mice

Spatholobus suberectus (SS) is a medicinal herb commonly used in Asia to treat anemia, menoxenia and rheumatism. However, its effect of diabetes-induced renal damage and mechanisms of action against advanced glycation end-products (AGEs) are unclear. In this study, we evaluated the effects of SS on diabetes-induced renal damage and explored the possible underlying mechanisms using db/db type 2 diabetes mice. db/db mice were administered SS extract (50 mg/kg) orally for 6 weeks. SS-treated group did not change body weight, blood glucose and glycated hemoglobin (HbA1c) levels. However, SS treatment reversed diabetes-induced dyslipidemia and urinary albumin/creatinine ratio in db/db mice. Moreover, SS administration showed significantly increased protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2), which is a transcription factor for antioxidant enzyme. SS significantly upregulated glyoxalase 1 (Glo1) and NADPH quinine oxidoreductase 1 (NQO1) expression but reduced CML accumulation and downregulated receptor for AGEs (RAGE). Furthermore, SS showed significant decrease of periodic acid-Schiff (PAS)-positive staining and AGEs accumulation in histological and immunohistochemical analyses of kidney tissues. Taken together, we concluded that SS ameliorated the renal damage by inhibiting diabetes-induced glucotoxicity, dyslipidemia and oxidative stress, through the Nrf2/antioxidant responsive element (ARE) stress-response system.