Abstract
BackgroundSkeletal muscle atrophy is caused by a variety of diseases and conditions. In particular, skeletal muscle atrophy in the elderly contributes to a loss of independence with advanced age and increases the risk of falling. However, the effect of food consumed on a daily basis on skeletal muscle atrophy has been the focus of little research. In this study, the effects of dietary supplementation with shiikuwasha extract or grape extract on dexamethasone-induced skeletal muscle atrophy were evaluated in aged rats.MethodsAged male rats (15-month-old) were fed a diet supplemented with either 1 % shiikuwasha extract or 1 % grape extract for 19 days. During the last 5 days of the feeding period, rats were injected with dexamethasone to induce muscle atrophy.ResultsBody weight and hind-limb muscle weight were significantly decreased by dexamethasone treatment. The supplementation of shiikuwasha extract showed no effect on body weight loss, but markedly attenuated tibialis anterior muscle weight loss induced by dexamethasone. On the other hand, grape extract did not affect muscle weight loss. Furthermore, shiikuwasha extract significantly reduced dexamethasone-induced expression of atrogin-1 and MuRF1 mRNA, but did not reduce LC3B-II protein levels.ConclusionThese results suggest that shiikuwasha extract may partially inhibit the activation of the ubiquitin–proteasome system and may consequently attenuate skeletal muscle atrophy induced by dexamethasone in aged rats.
Highlights
Skeletal muscle atrophy is caused by a variety of diseases and conditions including malnutrition, disuse, sepsis, cachexia, and glucocorticoid excess
It has been reported that both pathways are activated during skeletal muscle atrophy induced by glucocorticoids, showing increased mRNA expression of muscle-specific ubiquitin E3 ligases, atrogin-1 and MuRF1 (Auclair et al 1997), and the lipidated form of LC3 (LC3-II) protein, which is known as marker of autophagy (Penna et al 2013)
We found that shiikuwasha extract attenuated dexamethasone-induced skeletal muscle atrophy in aged rats
Summary
Skeletal muscle atrophy in the elderly contributes to a loss of independence with advanced age and increases the risk of falling. Glucocorticoids such as dexamethasone induce body weight loss, skeletal muscle atrophy, and acute insulin resistance (Pagano et al 1983; Ruzzin et al 2005). Glucocorticoid excess was observed to induce a prolonged leucine resistance in muscle protein synthesis in aged rats (Rieu et al 2004). These results indicate that aging increases the sensitivity to glucocorticoid-induced muscle atrophy
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