Abstract
Sarcopenia is an age-related skeletal muscle atrophy. Exercise is effective in improving sarcopenia via two mechanisms: activation of skeletal muscle satellite cells (SCs) and stimulation of muscle protein synthesis. In contrast, most nutritional approaches for improving sarcopenia focus mainly on muscle protein synthesis, and little is known about SC activation. Here, we investigated the effect of lemon myrtle extract (LM) on SC activation both in vitro and in vivo. Primary SCs or myoblast cell lines were treated with LM or its derived compounds, and incorporation of 5-bromo-2′-deoxyuridine, an indicator of cell cycle progression, was detected by immunocytochemistry. We found that LM significantly activated SCs (p < 0.05), but not myoblasts. We also identified casuarinin, an ellagitannin, as the active compound in LM involved in SC activation. The structure–activity relationship analysis showed that rather than the structure of each functional group of casuarinin, its overall structure is crucial for SC activation. Furthermore, SC activation by LM and casuarinin was associated with upregulation of interleukin-6 mRNA expression, which is essential for SC activation and proliferation. Finally, oral administration of LM or casuarinin to rats showed significant activation of SCs in skeletal muscle (p < 0.05), suggesting that LM and casuarinin may serve as novel nutritional interventions for improving sarcopenia through activating SCs.
Highlights
200 plant extracts andthe phytochemicals investigate whether activates satellite cells (SCs), we evaluated effects of lemon myrtle extract (LM) treat on SC activation in vitro and found that LM activated SCs in vitro
To ment on the activation of primary SCs and myoblast cell lines (L6 and C2C12) using in investigate whether LM activates SCs, we evaluated the effects of LM treatvitro bromo20 -deoxyuridine (BrdU)-incorporation assays
We found that casuarinin significantly promoted BrdU
Summary
Progression of sarcopenia is associated with many health risks, such as an increase in falls and fractures, loss of activities of daily living, and poor quality of life [2]. Sarcopenia was estimated to affect approximately 50 million people in 2010 and this number is expected to increase as the number of older adults increases [3]. The primary intervention for improving sarcopenia is exercise, which has been shown to benefit older adults with sarcopenia [1]. Resistance exercise is recommended for improving sarcopenia, but it should be performed considering the risks of a temporary increase in blood pressure [4] and injury [5]. Nutritional interventions are simple and safe approaches. Several nutritional approaches for sarcopenia have been reported, including adequate intake of protein [6], vitamin D [7], omega-3 polyunsaturated fatty acids [8], and leucine [9]. Effective nutritional interventions for sarcopenia have not yet been established [1], partly because the differences in skeletal muscle hypertrophy mechanisms between exercise and nutritional interventions are not fully understood
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