Lipogenic regulators are elevated with age and chronic overload in rat skeletal muscle

Aim:  Both muscle mass and strength decline with ageing, but the loss of strength far surpasses what is projected based on the decline in mass. Interestingly, the accumulation of fat mass has been shown to be a strong predictor of functional loss and disability. Furthermore, there is a known attenuated hypertrophic response to skeletal muscle overload with ageing. The purpose of this study was to determine the effect of 28 days of overload on the storage of intramuscular triglycerides {(IMTG)} and metabolic regulators of lipid synthesis in young and old skeletal muscle. Methods:  The phosphorylation and expression of essential lipogenic regulators were determined in the plantaris of young {(YNG;} 6-month-old) and aged {(OLD;} 30-month-old) rats subjected to bilateral synergist ablation {(SA)} of two-thirds of the gastrocnemius muscle or sham surgery. Results:  We demonstrate that age-induced increases in {IMTG} are associated with enhancements in the expression of lipogenic regulators in muscle. We also show that the phosphorylation and concentration of the {5'AMP-activated} protein kinase {(AMPK)} isoforms are altered in {OLD.} We observed increases in the expression of lipogenic regulators and {AMPK} signalling after {SA} in {YNG,} despite no increase in {IMTG.} Markers of oxidative capacity were increased in {YNG} after {SA.} These overload-induced effects were blunted in {OLD.} Conclusion:  These data suggest that lipid metabolism may be altered in ageing skeletal muscle and is unaffected by mechanical overload via {SA.} By determining the role of increased lipid storage on skeletal muscle mass during ageing, possible gene targets for the treatment of sarcopenia may be identified.