Protective effects of sarsasapogenin against early stage of diabetic nephropathy in rats.

Rhizome of Anemarrhena asphodeloides Bunge (AA, family Liliaceae) has been widely used in China for thousands of years to treat febrile diseases and diabetes. Steroidal saponins from AA show good antidiabetes effects and ameliorate diabetic complications. This study was designed to investigate the effects of sarsasapogenin (Sar), a major sapogenin from AA, on diabetic nephropathy (DN) in rats, and to explore the possible mechanisms. Diabetic rats were divided into 3 groups treated orally with Sar (0, 20, or 60 mg/kg) and carboxymethylcellulose sodium, whereas normal rats for Sar (0 or 60 mg/kg) and carboxymethylcellulose sodium. We found that chronic treatment with Sar for 9 weeks significantly ameliorated renal dysfunction of diabetic rats, as evidenced by decreases in albuminuria, kidney weight index, serum uric acid, and morphologic changes such as extracellular matrix expansion and accumulation (fibronectin and collagen IV levels, etc.). Meanwhile, Sar treatment resulted in decreases in interleukin-18, NLRP3, and activated caspase 1 levels as well as advanced glycation endproducts (AGEs) and their receptor (RAGE) levels in the renal cortex of diabetic rats. However, Sar has no effects on the above indices in the normal rats. Therefore, Sar can markedly ameliorate diabetic nephropathy in rats via inhibition of NLRP3 inflammasome activation and AGEs-RAGE interaction.

Sarsasapogenin suppresses Aß overproduction induced by high glucose in HT-22 cells.

The aim of this study is to investigate effects and potential mechanisms of sarsasapogenin (Sar), an active component purified from Rhizoma Anemarrhenae, on high glucose-induced amyloid-beta (Aß) peptide overproduction in HT-22 cells. HT-22 cells were divided into normal glucose; high glucose (HG); HG co-treated with low, middle, and high concentration of Sar (1, 5, 25 µmol/L); and peroxisome proliferator-activated receptor γ (PPARγ) agonist (10 µmol/L pioglitazone). After treatment for 24 h, protein expression of Aß and ß-site Aß precursor protein cleaving enzyme 1 (BACE1) and activated PPARγ level were determined by Western blot; Aß42 levels were also measured by using both immunofluorescence and ELISA methods. BACE1 activity and mRNA level were assessed by fluorospectrophotometry and quantitative PCR, respectively. Cell viability was assayed with a CCK-8 kit. Elevated Aß expression and Aß42 level were found in HG-treated HT-22 cells, accompanied by increased BACE1 protein and mRNA levels as well as enzymatic activity, which was markedly attenuated by three concentrations of Sar and pioglitazone. Moreover, HG reduced nuclear PPARγ levels, which was reversed by middle and high concentrations of Sar as well as pioglitazone. PPARγ antagonist GW9662 (20 µmol/L) pretreatment reversed the effect of Sar on BACE1 protein expression in HG-cultured HT-22 cells. Additionally, Sar suppressed HG-induced decreases in cell viability of HT-22 cells. High glucose can induce an increase in Aß levels and a decrease in cell viability in HT-22 cells, while co-treatment with Sar improves these results, which is mediated likely through activation of PPARγ and subsequent downregulation of BACE1.