Effect of β-sitosterol on insulin resistance & protein expression of insulin signalling molecules in quadriceps muscle of high fat diet-induced type-2 diabetic rats

Changes in life style, such as high-calorie diet intake and lack of exercise, have increased the global prevalence of obesity and diabetes. The major pathophysiological event contributing to the development of type 2 diabetes mellitus is the target tissues to insulin action. Currently available drugs are unsuccessful for the treatment of type 2 diabetes due to their unwanted side effects. Hence, search drugs, from plant sources. β-sitosterol is plant sterols with structurally almost like that of cholesterol. It is widely present in various medicinal plants. It has been reported to elicit multitude of bioactivities including anti-lipidemic and anti-hyperglycemic activity. However, specific effect of β-sitosterol on insulin signalling molecules of quadriceps muscle remains unclear. Hence, the study aimed to assess the beneficial role of β-sitosterol on the expression of insulin signalling molecules in quadriceps muscle of high fat diet and sucrose-induced type-2 diabetic rats. The oral effective dose of β-sitosterol (25 mg/kg body weight) was given once each day until the end of the study (30 days post‑induction of diabetes) to HFD- fed diabetic rats. At the end of the experimental period, fasting blood sugar (FBG), oral glucose (OGTT) and insulin tolerances (IT), Tissue glycogen, Serum insulin, Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) and Quantitative Insulin Sensitivity Check Index (QUICKI), as well as the levels of insulin signalling molecules like insulin receptor (IR), glucose transporter subtype 4 (GLUT4) proteins and glycogen concentration within the quadriceps muscle were assessed. A diabetic rat indicates impaired glucose and insulin tolerances and insulin signalling molecules (IR and GLUT4) proteins and glycogen concentration. Serum insulin, were found to be increased in diabetic rats. The treatment with β-sitosterol normalized the altered levels of blood glucose, serum insulin, and IR and GLUT4 protein levels. Thus, we concluded that β-sitosterol enhances glycemic control through activation of IR and GLUT4 in the quadriceps muscle of high fat diet and sucrose‑induced type2 diabetic rats.