Effect of the aqueous extract of Gymnema sylvestre on some metabolic disturbances in a model of insulin resistant induced by dexamethasone and high sucrose diet on rat

Abstract

• The results of this study indicate that the aqueous extract of Gymnema sylvestre (AEGS) exhibited hypoglycemic activity in dexamethasone and high sucrose diet-induced insulin resistance rats. • AEGS has antioxidant activity by reducing tissue malondialdehyde levels (liver and kidney) and maintaining high levels of reduced glutathione, catalase, and tissue proteins in dexamethasone and high sucrose diet-induced insulin resistance rats. • AEGS reduces hepatic and renal transaminase levels in dexamethasone and high sucrose diet-induced insulin resistance rats. • AEGS regulates serum lipid profile parameters by lowering triglyceride and LDL cholesterol levels and increasing HDL cholesterol levels in dexamethasone and high sucrose diet-induced insulin resistance rats. • The results of this study also indicate that AEGS showed a correction of several histopathological alterations changes in the high sucrose diet-induced insulin resistance rats in the liver (leukocyte infiltrations) and kidney (Hypertrophied tubular cells). Insulin resistance (IR) is when cells don’t respond well to insulin and can’t easily take up glucose from the blood. Such situation may lead to chronic hyperglycemia and even diabetes. Gymnema sylvestre aqueous extract is known in traditional Chinese medicine for its hypoglycemic activity. Some studies suggest that gymnemic acids, triterpene glucosides, and saponins may be responsible for this plant's impact on blood glucose regulation. This study aimed to evaluate the effects of Gymnema sylvestre aqueous extract (AEGS) on rat model of IR. IR was induced in male Wistar rats aged between 5 and 6 weeks by a high sucrose diet during 20 weeks then an intraperitoneal injection of dexamethasone (4mg/kg) once daily during 7 consecutive days. IR rats were divided into 5 groups of 5 animals each and received orally the different treatments as follows: a negative IR control group (NC-IR) received distilled water (10mL/kg), a positive IR control group (PC-IR) received metformin (200mg/kg), three experimental groups received AEGS (50, 100 and 200 mg/kg respectively). The different treatments were administered for 14 days. At the end of treatment, animals were sacrificed after urine collection; serum and homogenates from liver kidney and pancreas were prepared for biochemical analysis and histology. Compared to NC-IR, AEGS at all doses tested significantly reduced IR. It is the same for glucose, creatinine, direct bilirubin, serum transaminase total proteins and uric acid. The histopathological study revealed that AEGS restored tissues injuries induced by dexamethasone combined with high-sucrose diet, thus justifying its empirical use. The results obtained in this study suggest that AEGS have hypoglycemic, hepatoprotective and nephroprotective properties.