Effets hépato et néphroprotecteurs de l’extrait aqueux de la partie aérienne de gymnema sylvestre (apocynaceae) sur l’insulinorésistance induite par le sucrose et la dexaméthasone chez le rat

Abstract

Insulin resistance is the decreased sensitivity of insulin receptors. is responsible for a number of disorders, particularly of the liver and kidneys, and can lead to type 2 diabetes. Its management by conventional medicine is based on the use of oral antidiabetics such as metformin and Thiazolidinediones which, however, present undesirable effects such as lactic acidosis and cardiovascular problems. This raises the need to resort to the use of medicinal plants. Gymnema sylvestre is a plant traditionally used to treat many conditions including hepatitis and kidney damage. The present study was undertaken to evaluate the hepato and nephroprotective effects of the aqueous extract of Gymnema sylvestre bundles on a rat model of insulin resistance. To achieve this, after weaning, male rats aged between 5 and 6 weeks were subjected to a 20-week high sucrose diet and a 20% sucrose water drink. They then received a daily intraperitoneal injection of dexamethasone at 4 mg/kg for 7 days. After confirmation of insulin resistance the rats were divided into 6 batches (5 animals per batch) including normal (T NOR which was added) and negative (T NEG) control batches receiving distilled water at 10 mL/kg, the positive control batch receiving metformin (200 mg/kg) and 3 batches receiving Gymnema sylvestre aqueous extract (50, 100 and 200 mg/kg respectively) during 14 days; while maintaining this diet. Fasting blood glucose levels and weights were recorded during treatment. At the end of the treatment, when blood glucose and insulin resistance were assessed, urine was collected, rats were sacrificed, the blood and organs were collected for the determination of biochemical parameters and for histological sections. The insulin resistance caused in T NEG a significant increased serum creatinine (P ˂ 0.001), uric acid (54 %), direct bilirubin (88 %), ALT (P ˂ 0.05), AST (P ˂ 0.05), proteins (38 %), and cholesterol (35 %), and a significant decrease in urinary creatinine (P ˂ 0.001) and uric acid (79 %) compared to T NOR. It caused oxidative stress, hepatic leukocyte infiltration, tubular cells hypertrophy and hypotrophy of the islets of Langerhans in T NEG. Administration of the aqueous extract of Gymnema sylvestre bundles restored these parameters, thus justifying its empirical use, the 100 mg/kg dose appearing to be the most effective.