289-OR: Aerobic Exercise Counteracts Mitochondrial Dysfunction in the Insulin Resistant Brain

Insulin resistance increases the risk for Alzheimer’s disease and other dementias; however, the underpinning mechanisms for this increased risk remain to be fully defined. Insulin resistance impairs mitochondrial oxidative metabolism and increases reactive oxygen species (ROS) in skeletal muscle, both of which are counteracted by aerobic exercise (AE). Therefore, we considered whether similar events occur in the brain, specifically in regions such as cerebrum and hippocampus which are rich in insulin receptors and mitochondria. We determined whether AE would counteract mitochondrial deficits in hippocampal and cerebral mitochondrial function in high fat diet (HFD) induced insulin resistance. Four weeks of HFD in mice induced hippocampal insulin resistance which was corrected by AE. HFD decreased ATP production and increased ROS emission in isolated cerebral mitochondria, which were rescued with AE. Impairments in mitochondrial function with HFD were paralleled by reductions in mtDNA copy number, mRNA expression of mitochondrial genes, and oxidative enzyme activities (e.g., citrate synthase, COX) in the hippocampus, which were corrected by AE. We also observed excessive mitochondrial fission in the hippocampus following HFD, which was prevented by AE. Proteomic analysis of the hippocampus showed that HFD led to oxidative post-translational modifications (PTMs) of mitochondrial proteins; however, this increase in oxidative PTMs to mitochondrial proteins with HFD was almost completely reversed by AE. Further, intranasal administration of the insulin receptor antagonist S961 prevented AE-induced improvements in ATP production and ROS emission in isolated cerebral mitochondrial during HFD, demonstrating that AE enhances cerebral mitochondrial function during HFD by resensitizing brain insulin signaling.