Acute phytoecdysteroid treatment increases PI3k‐Akt signaling in aged mouse skeletal muscle

Abstract

Activation of the PI3k‐Akt pathway leading to protein synthesis is diminished in aged skeletal muscle. Phytoecdysteroids, in particular 20‐hydroxyecdysone (20E), from the plant Ajuga turkestanica increases protein synthesis in C2C12 muscle cells. We previously reported that 21 mo old mice fed phytoecdysteroids for 28 d display larger fiber cross‐sectional area in the triceps brachii and plantaris muscles. The objective of this study was to determine the extent to which an acute dose of phytoecdysteroids activates PI3k‐Akt signaling in skeletal muscle of aged mice. Aged male C57BL/6 mice (20 mo) received a single gavage dose (50 mg/kg bw) of A. turkestanica extract (ATE), 20E, or vehicle (CT) and skeletal muscles were harvested 90 min later. Western blotting performed on gastrocnemius muscles revealed a significant 52% increase in Akt phosphorylation in 20E‐treated skeletal muscle of aged mice, compared to CT (p=0.006). The phosphorylation of p70, 4EBP1, and S6 ribosomal protein (downstream targets in the PI3k‐Akt pathway) were unaltered at this time point. In conclusion, these data suggest that a single dose of 20E activates Akt, a central component of the PI3k‐Akt pathway, in sedentary aged skeletal muscle.Supported in part by a USDA Kannapolis Scholars Fellowship.