Exercise beneficially reshapes fasted rat skeletal muscle involving the combined action of beta-hydroxybutyrate and palmitoleic acid

ABSTRACT: We previously observed that mild exercise causes structural and functional modifications in fasted skeletal muscle, both in rodents and humans. Wistar rats, housed at thermoneutrality, were submitted to mild exercise during a 66h-period of fasting by five 30-min-treadmill runs at 15 m/min without inclination. We showed that exercise induced an increase in AMPK and Akt phosphorylation during fasting in gastrocnemius muscle, as well as normalization of mTOR signaling. To gain deeper insight in the underlying mechanisms/factors this project aimed to study alterations in the proteome, lipidome, and cellular signaling/metabolic pathways comparing the combined intervention to each separate intervention. We performed untargeted proteome analysis and targeted lipidomic analysis in gastrocnemius muscle, to study how exercise during fasting influences structural/functional changes as well as the lipid profile within the muscle. We previously observed that muscle beta-hydroxybutyrate (BHB) increased in this condition. To our knowledge, no studies exist that focus on how altered levels of BHB and fatty acids within the muscle underly metabolic and structural changes during these physiological challenges, and how these factors mediate AMPK, Akt and mTOR signaling. Using our rat model, we applied untargeted proteome analysis to verify if the gastrocnemius muscle proteome profile in response to the combined intervention was indicative of restored muscle mass and quality. Applying a previously set up quantitative approach of tissue lipid measurement, we verified whether this intervention leads to changes in the gastrocnemius muscle FA profile and whether these changes, combined with the previously measured changes in muscle BHB levels, may contribute to the signaling responses we observed previously. Untargeted proteome analysis of gastrocnemius muscle revealed that exercise with fasting inversely modulated proteome networks involved in the proteasome, cellular respiration and muscle development with respect to fasting alone. Targeted lipidomic analysis revealed palmitoleic acid (P) to be increased by exercise in fasted muscle, an observation that adds to the previously observed increase in muscle beta-hydroxybutyrate (BHB). In muscle L6 myoblasts, cultured under conditions that mimicked fasting, we studied P vs BHB-induced alterations in Akt, AMPK, and mTOR signaling, crucial for glucose metabolism and myogenesis. We observed that P counteracted the repressing effect of BHB in L6 muscle cells on Akt Ser 473 phosphorylation and did not induce AMPK Thr172 phosphorylation, as opposed to BHB. These observations reflect the response to exercise we previously observed in fasting muscle. Both compounds increased sarcolemmal GLUT4 levels. BHB normalized P-induced inhibition of mTOR signaling. Finally, the myogenic factors Myogenin and MyoD expression were inversely regulated by BHB and P. In conclusion, this project aided to identify P and BHB as important players in the response to exercise during fasting regarding glucose sensitivity and muscle maintenance.

INSTRUMENT(S):

ORGANISM(S): Rattus Norvegicus (rat) Mus Musculus (mouse)

TISSUE(S): Gastrocnemius

SUBMITTER: Gabriella Pinto  

LAB HEAD: Prof. Angela Amoresano

PROVIDER: PXD074027 | Pride | 2026-02-18

REPOSITORIES: Pride