Cocoa flavanols have been shown to improve muscle function and may offer a novel approach to protect against muscle atrophy. Hippuric acid (HA) is a colonic metabolite of (-)-epicatechin (EPI), the primary bioactive compound of cocoa, and may be responsible for the associations between cocoa supplementation and muscle metabolic alterations. Accordingly, we investigated the effects of EPI and HA upon skeletal muscle morphology and metabolism within an in vitro model of muscle atrophy. Under atrophy-like conditions (24h 100μM dexamethasone (DEX)), C2C12 myotube diameter was significantly greater following co-incubation with either 25μM HA (11.19±0.39μm) or 25μM EPI (11.01±0.21μm) compared to the vehicle control (VC; 7.61±0.16μm, both P < .001). In basal and leucine-stimulated states, there was a significant reduction in myotube protein synthesis (MPS) rates following DEX treatment in VC (P = .024). Interestingly, co-incubation with EPI or HA abrogated the DEX-induced reductions in MPS rates, whereas no significant differences versus control treated myotubes (CTL) were noted. Furthermore, co-incubation with EPI or HA partially attenuated the increase in proteolysis seen in DEX-treated cells, preserving LC3 α/β II:I and caspase-3 protein expression in atrophy-like conditions. The protein content of PGC1α, ACC, and TFAM (regulators of mitochondrial function) were significantly lower in DEX-treated versus. CTL cells (all P < .050). However, co-incubation with EPI or HA was unable to prevent these DEX-induced alterations. For the first time we demonstrate that EPI and HA exert anti-atrophic effects on C2C12 myotubes, providing novel insight into the association between flavanol supplementation and favourable effects on muscle health.

Muscle atrophy

dexamethasone

mitochondria

flavanols

epicatechin

hippuric acid

eukaryotic initiation factor 4E binding protein 1

acetyl-CoA carboxylase

5′ AMP-activated protein kinase

24h control (no atrophic stimulus)

24h 100μM dexamethasone treatment

HA

25μM hippuric acid supplementation

microtubule-associated proteins 1A/1B light chain 3B

90mins of 5mM leucine stimulation

muscle atrophy f-box

total mechanistic target of rapamycin

muscle ring finger protein 1

peroxisome proliferator-activated receptor gamma coactivator 1-alpha

ribosomal protein S6 kinase beta-1

mitochondrial transcription factor A

ethanol matched vehicle control

© 2022 The Author(s). Published by Elsevier Inc.