Oleic Acid Activates Mitochondrial Energy Metabolism and Reduces Oxidative Stress Resistance in the Pancreatic β-Cell Line INS-1.

Elevated concentration of saturated fatty acids in plasma adversely affects pancreatic β-cells, but the effects of unsaturated fatty acids are controversial. In this study, we examined the effects of oleic acid (OA), a monounsaturated fatty acid, on mitochondrial function, which is important for insulin secretion, using INS-1 cells, a pancreatic β-cell line derived from rats. Observations of mitochondrial membrane potential and intracellular ATP concentration showed that the electron transport chain was enhanced and ATP production increased in cells treated with OA, indicating that the response that occurs from sensing an increase in glucose concentration to the production of ATP was accelerated. Measurements of intracellular reactive oxygen species (ROS) indicated that the rate of increase in ROS after glucose stimulation was significantly higher in OA-treated cells. The mRNA expression levels of superoxide dismutase 1 and 2, which are responsive to ROS and other substances, were significantly increased in OA 1-d treated cells, but decreased in OA 7-d treated cells. It can be inferred that continued exposure to high concentrations of OA reduced ROS processing capacity and increased intracellular ROS levels. The mRNA expression of apoptosis-inducing enzyme Caspase-3 was significantly increased in OA-treated cells, although its activity was not high. However, the apoptosis induction rate after H₂O₂ stimulation was significantly higher in OA-treated cells. The high OA environment was shown to promote mitochondrial energy metabolism, leading to an increase in glucose sensitivity and a decrease in oxidative stress resistance.