Extract of Alnus japonica prevents dexamethasone-induced muscle atrophy in mice

As part of our effort to search for food ingredients with ability to inhibit muscle wasting, we found that extract of Alnus japonica (AJE) and its main constituent, oregonin, could prevent muscle atrophy from in vitro and in vivo studies. Oregonin rich extract of AJ improved muscle strengths of dexamethasone-induced atrophied mice as evidenced by decreased expression of muscle protein-degradative factors and increased muscle mass. In C2C12 myoblasts, oregonin stimulated myogenesis, showing increased expression of MHC and myogenin via p38 mitogen-activated protein kinase (MAPK) activation. In differentiated myotubes, AJE and oregonin protected against dexamethasone-induced loss of myotubes by suppressing expressions of MAFbx and MuRF1, while increasing MHC expression and mTOR phosphorylation. These dual effects of oregonin might have contributed to its ability to protect against loss of myotubes. Taken together, our results suggest that AJE has a favorable alleviating effect on sarcopenia via regulation of muscle protein synthesis and degradation.