ABSTRACT
OBJECTIVE: Ketogenic diets (KD) have been shown to alleviate insulin resistance (IR) by exerting anti-lipogenic and insulin sensitizing effects in the liver through a variety of pathways. The present study sought to investigate whether a ketogenic diet also improves insulin sensitization in skeletal muscle cells through alleviating endoplasmic reticulum stress. METHODS: High-fat diet-induced IR mice were allowed to a 2-week ketogenic diet. Insulin resistance and glucose tolerance were evaluated through GTT, ITT, and HOMA-IR. The C2C12 myoblasts exposed to palmitic acid were used to evaluate the insulin sensitization effects of ß-hydroxybutyric acid (ß-OHB). Molecular mechanisms concerning ER stress signaling activation and glucose uptake were assessed. RESULTS: The AKT/GSK3ß pathway was inhibited, ER stress signaling associated with IRE1, PERK, and BIP was activated, and the number of Glut4 proteins translocated to membrane decreased in the muscle of HFD mice. However, all these changes were reversed after 2 weeks of feeding on a ketogenic diet. Consistently in C2C12 myoblasts, the AKT/GSK3ß pathway was inhibited by palmitic acid (PA) treatment. The endoplasmic reticulum stress-related proteins, IRE1, and BIP were increased, and the number of Glut4 proteins on the cell membrane decreased. However, ß-OHB treatment alleviated ER stress and improved the glucose uptake of C2C12 cells. CONCLUSION: Our data reveal that KD ameliorated HFD-induced insulin resistance in skeletal muscle, which was partially mediated by inhibiting endoplasmic reticulum stress. The insulin sensitization effect of ß-OHB is associated with up regulation of AKT/GSK3ß pathway and the increase in the number of Glut4 proteins on the cell membrane.
