Effects of Moringa oleifera extract on reactive oxygen species-induced beta-cell death

Abstract

Introduction: Oxidative stress plays a major role in the pathogenesis of both type 1 and type 2 diabetes mellitus as a result of increased formation of reactive oxygen species (ROS), which overwhelm endogenous beta-cell antioxidant capacity, contributing to cellular dysfunction and death. Several studies point to an important role of dietary antioxidants as potential therapeutics in the alleviation of oxidative damage. Moringa oleifera is a plant widely used in Indian, Arabic and African traditional medicine. Objectives: To determine the potential antioxidant and cytoprotective activity of Moringa oleifera extract against hydrogen peroxide-induced cell death in the rat pancreatic beta cell line, BRIN-BD11. Materials and methods: Antioxidant activity of Moringa extract was determined using a NADH/phenazine methosulphate/nitroblue tetrazolium (NBT) superoxide-generating assay, using epigallocatechin gallate (EGCG) as a positive control. The extract was also tested against hydrogen peroxide-induced loss of cell viability in BRIN-BD11 pancreatic beta cells using the MTTreduction assay. Results: Initial results showed that Moringa oleifera extract at 20μg/ml displayed superoxide scavenging activity with 30% inhibition of NBT reduction. Preliminary cytotoxicity studies showed that Moringa concentrations below 20μg/ml were non-toxic to BRIN-BD11 cells and that 75μM hydrogen peroxide decreased viability to 60% of control over 24hours. At these concentrations, Moringa extract showed no protective activity against loss of viability induced by hydrogen peroxide over 24-hour incubation. To further investigate any potential activity, cells were treated for 24hours with Moringa extract (10– 100μg/ml) prior to 1 hour’ s treatment with 75μM hydrogen peroxide. Pretreatment with all tested concentrations of Moringa for 24hours significantly increased viability following 1-hour exposure to 75μM hydrogen peroxide. Conclusions: Pretreatment with Moringa extract for 24hours significantly increased viability, and that indicates a possible effect of the extract on gene expression of endogenous antioxidant enzymes of beta cells rather than it just working as a scavenger. Acknowledgements: Dr David Watson and Dr Waleed Alshaqha for supervising this project.