Omega-3 Fatty Acids Control Productions of Superoxide and Nitrogen Oxide and Insulin Content in INS-1E Cells

Omega-3 fatty acids have multiple effects in peripheral tissues and pancreatic beta cell function. Dietary depletion of omega-3 fatty acids is associated with pancreatic islet dysfunction and insulin resistance in rats. Herein, the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on pancreatic beta cell redox state and function were investigated. INS-1E insulin-secreting cells were incubated with EPA and DHA in combination with palmitic acid, and productions of reactive oxygen species (ROS), nitric oxide (NO) and insulin were measured. The involvement of the NADPH oxidase complex in ROS production and expression of the antioxidant enzymes was also investigated. After incubation for 1 or 48 h, productions of superoxide (by hydroethidine method), nitric oxide (by 4,5-diaminofluorescein diacetate-DAF-2DA assay), insulin (by radioimmunoassay), and expressions (by western blot analysis) of glutathione peroxidase (GPx-1) and gp91 were measured. EPA and DHA reduced superoxide production after 1-h incubation. After 48 h, palmitic acid reduced superoxide production that was normalized by EPA treatment. Palmitic acid increased NO production that was reverted by EPA and DHA. Palmitic acid increased insulin secretion after 48 h, whereas both omega-3 fatty acids increased intracellular insulin content. EPA and DHA enhanced GPx-1 expression as well as gp91 glycosylated form. In conclusion, EPA and DHA increased intracellular insulin content and antioxidant enzymatic defense capacity and decreased pro-oxidant generating activities that are associated with maintenance of pancreatic beta cell redox state in response to palmitic acid.