Gryllus bimaculatus-containing diets protect against dexamethasone-induced muscle atrophy, but not high-fat diet-induced obesity.

ABSTRACT

Sarcopenia and obesity are emerging as major social problems. In this study, we examined whether Gryllus bimaculatus (GB), an edible insect, prevents dexamethasone-induced muscle atrophy (sarcopenia) or high-fat diet (HFD)-induced obesity in mice. We generated a standard chow diet (SCD) + GB (85% SCD and 15% GB powder) and HFD + GB (85% HFD and 15% GB powder). SCD + GB feeding increased gains in body weight and white adipose tissue (WAT). Despite no difference in weight change between HFD + GB- and HFD-fed mice, HFD + GB feeding aggravated insulin resistance compared with HFD feeding. SCD + GB or HFD + GB feeding did not change most gene expressions in the liver and WAT but did increase MyHC1 expression in the muscle, meaning that GB increased muscle generation. Therefore, we fed SCD + GB with dexamethasone, which induces muscle degeneration. As a result, muscle fiber size increased, as did grip strength compared with dexamethasone-injected mice. In addition, SCD + GB reduced the expression of muscle degradation factors, such as atrogin1 and muscle RING-finger protein 1 (MuRF1). Furthermore, SCD + GB feeding increased Akt, mTOR, and p70S6K phosphorylation and MyHC1 expression, meaning that it may have increased protein synthesis. In conclusion, GB has great potential for inhibiting dexamethasone-induced muscle mass loss by increasing muscle protein synthesis and inhibiting muscle protein degradation.