Background
Sarcopenia has been associated with a decreased regenerative capacity of skeletal muscle. This leads to reduced muscle strength, metabolic disturbances and a lower quality of life. Aging associated impairments in muscle regeneration can be caused by a decreased differentiation capacity of muscle satellite cells. Oxidative stress plays a major role in this process.  Development of nutritional strategies aiming to attenuate the aging induced decline in muscle regeneration is of great importance to address this health issue and increase quality of life. The aim of this study is to investigate if the orange- and pomegranate derived polyphenols hesperetin and ellagic acid prevent the oxidative stress-induced decline in C2C12 cell proliferation and differentiation. 

Methods
C2C12 cells were grown until 60-70% confluence and incubated in growth medium with or without oxidative stress inducing compound menadione (9µM), hesperetin (5, 20 or 50µM), ellagic acid (0.05 or 0.1 µM) or a combination of these (hesperetin 20µM, ellagic acid 0.05µM) for 2h. The amount of proliferating cells was assessed using fluorescent labeling of incorporated 5-ethynyl-2’-deoxyuridine (EdU). Cells were cultured until 95% confluence in growth medium, which was replaced by differentiation medium with or without menadione, hesperetin, ellagic acid or a combination. After 5 days of differentiation, cells were stained for myosin heavy chain 1 (MyHC1) and MyHC1 expression was assessed by fluorescence microscopy. 

Preliminary results
Hesperetin decreased the amount of proliferating cells, while menadione nor ellagic acid affected cell proliferation. Menadione treatment decreased MyHC1 expression compared to control (p=0.019), which was prevented by co-treatment with 20µM hesperetin and by a combination of 20µM hesperetin and 0.05µM ellagic acid. Treatment with polyphenols alone did not affect MyHC1 expression. 

Conclusion
Results suggest that hesperetin prevents the negative effects of oxidative stress on myoblast differentiation and may be used as nutritional strategy to maintain muscle health during aging.