초록/요약

Given the increased concerns about the degenerative decline in the physical performance of the elderly, there is a need for developing effective strategies to suppress the age-related loss of skeletal muscle mass and functional capacity through a lifestyle intervention. This randomized controlled trial examined whether a combination of Korean mistletoe extract (KME) supplement and exercise affected muscle mass, muscle function, and targeted molecular expressions. Sixty-seven subjects aged 55–75 years were assigned to placebo, low-dose (1 g/d), or high-dose (2 g/d) of KME for 12 weeks. The body composition was significantly changed in the high-dose group during the intervention period as determined by skeletal muscle mass (P = 0.040), fat free mass (P = 0.042), soft lean mass (P = 0.023), skeletal muscle index (P = 0.041), fat-free mass index (P = 0.030), percent body fat (P = 0.044), and fat mass to lean mass ratio (P = 0.030). Knee strength was measured by Cybex, demonstrating a significant effect in the KME groups compared to the placebo group (P = 0.026 for peak torque and P = 0.057 for set total work), which was more pronounced after adjusting for age, gender, protein, and energy intake (P = 0.009 for peak torque and P = 0.033 for set total work). The dynamic balance ability was remarkably improved in the high-dose group over a 12-week period as determined by Timed “Up and Go” (P = 0.005 for fast walk test and P = 0.024 for ordinary walk test). Consistent with these results, RT-PCR, multiplex analyses, and immunocytofluorescence staining revealed that a high-dose KME supplementation was effective for suppressing intracellular pathways related to muscle protein degradation, but stimulating those related to myogenesis. In particular, significant differences were found in atrogin-1 mRNA (P = 0.002 at a single administration and P = 0.001 at a 12-week administration), myogenin mRNA (P < 0.0001 at a single administration and P = 0.040 at a 12-week administration), and insulin growth factor 1 receptor phosphorylation (P = 0.002 at a 12-week administration). These results suggest that KME supplementation together with resistance exercise may be useful in suppressing the age-related loss of muscle mass and strength in the elderly. © 2016 Elsevier Inc.