Differential effects of leucine supplementation in young and aged mice at the onset of skeletal muscle regeneration

Abstract

Aging decreases the ability of skeletal muscle to respond to injury. Leucine has been demonstrated to target protein synthetic pathways in skeletal muscle thereby enhancing this response. However, the effect of aging on leucine-induced alterations in protein synthesis at the onset of skeletal muscle regeneration has not been fully elucidated. The purpose of this study was to determine if aging alters skeletal muscle regeneration and leucine-induced alterations in markers of protein synthesis. The tibialis anterior of young (3 months) and aged (24 months) female C57BL/6J mice were injected with either bupivacaine or PBS, and the mice were given ad libitum access to leucine-supplemented or normal drinking water. Protein and gene expression of markers of protein synthesis and degradation, respectively, were analyzed at three days post-injection. Following injury in young mice, leucine supplementation was observed to elevate only p-p70S6K. In aged mice, leucine was shown to elicit higher p-mTOR content with and without injury, and p-4EBP-1 content post-injury. Additionally in aged mice, leucine was shown to elicit higher content of relative p70S6K post-injury. Our study shows that leucine supplementation affects markers of protein synthesis at the onset of skeletal muscle regeneration differentially in young and aged mice.

PGC‐1α4 gene expression is suppressed by the IL‐6—MEK—ERK 1/2 MAPK signalling axis and altered by resistance exercise, obesity and muscle injury

“…TA mass and body weights have been previously reported in ageing animals (Perry et al . ,b); in that report, raw TA mass was not different between young and aged animals. However, aged animals presented greater body weights and tibia lengths than did young, such that similar muscle masses were noted despite aged animals being larger.…”

“…, Perry et al . ,b). Therefore, to improve comparison across time we tested the control 18S gene across studies in the same real‐time RT‐PCR run and found no difference in 18S cycle threshold between studies.…”

“…, Perry et al . ,b). We observed a time‐dependent alteration in Pgc1α4 mRNA content post‐injury whereby Pgc1α4 and Il‐6 content was approx.…”

“…We have previously reported on these same animals (Perry et al . ,b). C57BL/6J mice were purchased from Jackson Laboratories.…”

Effect of 8-week leucine supplementation and resistance exercise training on muscle hypertrophy and satellite cell activation in rats

“…Perry et al. () reported that while leucine ingestion combined with exercise may promote protein synthesis, the effects of leucine on protein synthesis are minimal because the signaling pathways involved in hypertrophy are mainly affected by the upregulation of IGF‐1 proteins following exercise. Our results are consistent with this finding.…”