Anti-diabetic activity and potential mechanism of total flavonoids of Selaginella tamariscina (Beauv.) Spring in rats induced by high fat diet and low dose STZ

Abstract Aim of the study To evaluate the anti-diabetic effects of the total flavonoids of Selaginella tamariscina (Beauv.) Spring (TFST), and to explore the pertinent mechanism. Materials and methods High fat diet and STZ (35 mg/kg) induced diabetic rats were administered with TFST at graded oral doses (100, 200 and 400 mg/kg/day, ig.) for 8 weeks. A range of parameters, including blood glucose and lipid, serum insulin and glucagon, glucose tolerance, were tested to evaluate its anti-diabetic effects. The determination of protein expression of peroxisome proliferator activated receptor γ (PPAR-γ) in adipose tissue and insulin receptor substrate 1 (IRS-1) in hepatic and skeletal muscle tissues was used to study the mechanism of TFST. Moreover, the preliminary study of TFST on the antioxidant activity was performed. Results The TFST possessed anti-diabetic activities as shown by the decreased serum levels of fast blood glucose (FBG), glycosylated hemoglobulin A1C (HbA1c), triglyceride (TG), total cholesterol (TC), free fatty acid (FFA), low density lipoprotein-cholesterol (LDL-C) and glucagon, as well as increased serum levels of high density lipoprotein-cholesterol (HDL-C), insulin and C-peptide. TFST also improved the oral glucose tolerance test (OGTT) to a certain degree. Furthermore, TFST increased the protein expression of PPAR-γ in adipose tissue, and increased the protein expressions of IRS-1 in hepatic and skeletal muscle tissues. These benefits were associated with increased superoxide dismutase (SOD) and decreased malondialdehyde (MDA) in serum. Conclusions TFST exert beneficial effects on hyperglycosemia and hyperlipoidemia in diabetic rats possibly through regulating the levers of PPAR-γ in adipose tissue and IRS-1 in hepatic and skeletal muscle tissues.