MECHANISM OF ANTI-DIABETIC ACTIVITIES OF Musa sapientum LEAF EXTRACT IN RATS TREATED WITH ALLOXAN

Abstract

Diabetes mellitus results from necrosis of pancreatic β-cell and insulin resistance at the cellular level. Musa sapientum has been shown to possess anti-diabetic properties. However, the mechanism of its action is unknown. The anti-diabetic mechanism of defatted Methanol Extract of Musa sapientum Leaves (MEMSL) and two of its fractions were investigated. Fractions of MEMSL were obtained using column chromatography. Defatted MEMSL and its most active fractions were assessed for anti-diabetic properties. Diabetes was induced with a single dose of alloxan monohydrate (120 mg/kg) intraperitoncally after an overnight fast (12hrs). Male albino rats (180-200 g) were divided into 7 groups of 15 rats each: control (non-diabetic), Diabetic Untreated (DU), diabetic rats treated orally with MEMSL (250 and 500 mg/kg), active column fractions (100 pg/kg) and glibenclamide (5 mg/kg) (DG) p.o. On days 2, 7 and 14 post- treatments, blood glucose, electrolytes (sodium, potassium, phosphate, chloride, calcium, bicarbonate ion), lipid profile, lipid peroxidation, antioxidant status (superoxide dismutase, catalase and diphenylpicrylhydrazyl (DPPH) scavenging), α-amylase activity and liver glycogen were measured using spectrophotometric methods. Calcium ion transport in pancreatic β-ce11 was assessed using confocal microscopy. The expressions of mitochondrial proteins: NADH dehydrogenase, succinate dehydrogenase, cytochrome-c reductase, cytochrome-c oxidase and ATP synthase were determined by western blotting, Histology of the pancreas was done using Gomoris stain. Data were analysed using ANOVA and Duncan multiple range test at p= 0.05. Seven fractions (F1-F7) were obtained with Fractions 2 and 5 having the most potent anti-diabetic activity. Blood glucose levels in control and DU rats were 62.3±0.9, 61.9±1.5, 61.7±2.0 mg/dL and 398±30.7, 363±24.9, 292±11.2 mg/dL on days 2, 7 and 14 respectively. The MEMSL, F2 and F5 exhibited significant hypoglycaemic activities at day 14 of treatment (100.0±3.7mg/dL, 152.9±8.2 mg/dL, 93.9±3.5 mg/dL) compared with DU (292±11.2 mg/dL). Sodium, potassium, phosphate ions and high-density lipoprotein levels were significantly increased (21.1%, 292.3%, 127.8% and 117.7%) respectively in MEMSL treated diabetic rats compared with DU. Total cholesterol, triglycerides, and low-density lipoproteins were significantly reduced (69.4%, 85.5%, and 81.8%) respectively in MENSL treated diabetic rats compared with DU. The extract and its fractions showed significant increases in antioxidants and reductions in lipid peroxidation. The MEMSL, F2 and F5 exhibited DPPH scavenging activity and significant α-amylase inhibition (79.6%, 79.0% and 74.1%) in vitro comparable to acarbose (75.9%), a standard α-amylase inhibitor. In vitro, MEMSL caused an increase in Ca-influx in pancreatic β-cell and mitochondrial ATP synthase expression, indicating an increase in insulin secretion. Liver glycogen in diabetic animals treated with MEMSL, F2 and F5 were significantly increased (5.9.±0.7, 3.6±0.5, 8.0±0.4 mg/100gwt, liver) compared with DU (1.2±0.3 mg/100gwt. liver) suggesting an increase in glucose storage or reduction in glycogen breakdown. Pancreatic lesions were significantly reduced in treated rats compared with DU. The anti-diabetic effects of Musa sapientum may be mediated via inhibition of α-amylase, reduced free radical-induced oxidative damage, increased Ca2+ influx in the pancreatic β-cell and increased liver glycogen content. Musa sapientum leaves could be a potential drug candidate for diabetes.