Endocrine Abstracts

¹=School of Sciences, Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, UK ²= Department of Biochemistry, Obafemi Awolowo University, Ile-Ife, Nigeria³= IRiD Biosciences, Wilding Road, Ball Green, Stoke-on-Trent, ST6 8BQ

Aim: Vernonia amygdalina extract is used traditionally for type 2 diabetes treatment in developing countries. Studies have reported antidiabetic properties of aqueous and methanolic extracts of V. amygdalina but mechanisms underlying these actions are poorly understood. This study investigates effects of V. amygdalina extracts on insulin secretion, cytotoxicity, cells viability, mechanism of action and intracellular calcium.

Methods: Insulin-releasing effect of V. amygdalina extract (0 –1000µ g/ml) were investigated using BRIN-BD11 cells. Effects of the extract (100µ g/ml) on insulin secretion at various glucose concentration, presence of established modulators of insulin secretion and in the absence of extracellular calcium were also investigated. Insulin concentrations were measured by ELISA. Effect of the plant extract on cytotoxicity and intracellular calcium concentration were also assessed. Acute in vivo effects of the extract were investigated using mice with diet-induced obesity-diabetes.

Results: The extract had total flavonoid and total phenolic contents of **** QE/g and **** GE/g respectively. V. amygdalina extract stimulated insulin secretion at concentration ≥0.1ug/ml in a dose-dependent manner (1.4 to 2.5-fold, P<0.001). The insulinotropic effects of the plant extract was not associated with cytotoxicity or impaired cell viability. Insulin-release increase with increasing glucose concentration (1.1mM to 5.6mM, 10%, P<0.05, and 5.6mM to 16.7mM, 13%, P<0.05). Actions of the extract was reduced in the presence of diazoxide (300µ M, 46%, P<0.01), verapamil (50nM, 34%, P<0.01) and in the absence of extracellular calcium (20%, P<0.05). Enhanced insulin secretion was observed in incubations containing KCl (30mM, 3.0-fold, P<0.001) and IBMX (200μ M, 1.9-fold, P<0.01). V. amygdalina extracts enhanced intracellular calcium concentration by 24% (P<0.01). Glucose tolerance and insulin secretion also improved by 23% (P<0.01) and 34% (P<0.01) respectively in diet-induced mice treated with the extract.

Conclusion: These results suggest that the anti-diabetic properties of V. amygdalina extract may involve the activation of the ATP-dependent pathway of insulin secretion. These results encourage further investigations of the anti-diabetic actions of V. amygdalina extracts.