Enhanced protective effect of whey protein fermented with Lacticaseibacillus rhamnosus IM36 on dexamethasone-induced myotube atrophy

This study investigated the preventive potential of whey protein fermented with Lacticaseibacillus rhamnosus IM36 (FWP) against muscle atrophy induced by dexamethasone (DEX). FWP exhibited enhanced antioxidant activities compared with those of unfermented whey protein, effectively suppressing DEX-induced reactive oxygen species production. FWP was treated before the administration of 100 μM DEX on C2C12 myotubes and compared to unfermented whey (WP). DEX significantly inhibited myotube viability and muscle protein synthesis and enhanced degradation. FWP exhibited a dose-dependent attenuation of cell viability loss compared with that of WP. Additionally, FWP stimulated the formation of myotubes and muscle protein synthesis by upregulating myogenesis and insulin-like growth factor-1 expression. Furthermore, FWP significantly attenuated forkhead box protein O3a-mediated ubiquitin ligases and autophagy of lysosomes activated by DEX, inhibiting pathways that lead to muscle protein breakdown. These findings suggest that FWP enhances antioxidant activity and prevented DEX-induced muscle atrophy by regulating muscle protein homeostasis.