Insulinotropic actions of Moringa oleifera involves the induction of membrane depolarization and enhancement of intracellular calcium concentration

Abstract

Objective: Moringa oleifera extracts have been widely reported for insulinotropic and other antidiabetic effects. However, mechanisms behind these actions of M.oleifera extracts are not well understood. This study investigated a possible mechanism underlying the insulinotropic actions of acetone extract of M. oleifera Methods: Phytochemical composition of M.oleifera extract was determined using standard procedures. Total flavonoid and total phenolic compounds in the extract were also quantified. Effects of the extracts on glucose stimulated insulin secretion, membrane depolarization and intracellular calcium concentration were investigated using BRIN-BD11 clonal pancreatic beta cells. Results: Results obtained showed the preponderance of alkaloids, flavonoids, glycosides, phenols, saponins and tannins in the extract. The glucose dependent insulinotropic effects of the extract were significantly inhibited in the presence of diazoxide (48%) or verapamil (35%) and in the absence of extracellular calcium (47%). Co-incubation of cells with the extract and IBMX (3-isobutyl-1-methylxanthine) or tolbutamide increased insulin secretion by 2-fold while a 1.2-fold increase was observed in cells depolarized with 30 mM KCl in the presence of the plant extract. The extract significantly induced membrane depolarization (7.1-fold) and enhanced intracellular calcium concentration (2.6-fold) in BRIN-BD11 cells. Conclusion: These observations suggest that the insulinotropic actions of acetone extract of M.oleifera may be mediated via the KATP-dependent pathway of insulin release.