Seebacher F, Tallis J, McShea K, James R S
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
Centre for Applied Biological and Exercise Sciences, Coventry University, Coventry, UK.
Int J Obes (Lond). 2017 Aug;41(8):1271-1278. doi: 10.1038/ijo.2017.81. Epub 2017 Mar 24.
BACKGROUND/OBJECTIVES: Obesity can affect muscle phenotypes, and may thereby constrain movement and energy expenditure. Weight loss is a common and intuitive intervention for obesity, but it is not known whether the effects of obesity on muscle function are reversible by weight loss. Here we tested whether obesity-induced changes in muscle metabolic and contractile phenotypes are reversible by weight loss.
SUBJECTS/METHODS: We used zebrafish (Danio rerio) in a factorial design to compare energy metabolism, locomotor capacity, muscle isometric force and work-loop power output, and myosin heavy chain (MHC) composition between lean fish, diet-induced obese fish, and fish that were obese and then returned to lean body mass following diet restriction.
Obesity increased resting metabolic rates (P<0.001) and decreased maximal metabolic rates (P=0.030), but these changes were reversible by weight loss, and were not associated with changes in muscle citrate synthase activity. In contrast, obesity-induced decreases in locomotor performance (P=0.0034), and isolated muscle isometric stress (P=0.01), work-loop power output (P<0.001) and relaxation rates (P=0.012) were not reversed by weight loss. Similarly, obesity-induced decreases in concentrations of fast and slow MHCs, and a shift toward fast MHCs were not reversed by weight loss.
Obesity-induced changes in locomotor performance and muscle contractile function were not reversible by weight loss. These results show that weight loss alone may not be a sufficient intervention.
背景/目的：肥胖会影响肌肉表型，进而可能限制运动和能量消耗。减肥是治疗肥胖常见且直观的干预措施，但肥胖对肌肉功能的影响是否能通过减肥逆转尚不清楚。在此，我们测试了减肥是否能逆转肥胖引起的肌肉代谢和收缩表型变化。
受试者/方法：我们采用斑马鱼（Danio rerio）进行析因设计，比较瘦鱼、饮食诱导肥胖的鱼以及肥胖后经饮食限制恢复到瘦体重的鱼之间的能量代谢、运动能力、肌肉等长力和功环功率输出，以及肌球蛋白重链（MHC）组成。
肥胖增加了静息代谢率（P<0.001）并降低了最大代谢率（P=0.030），但这些变化可通过减肥逆转，且与肌肉柠檬酸合酶活性变化无关。相比之下，肥胖导致的运动能力下降（P=0.0034）、离体肌肉等长张力（P=0.01）、功环功率输出（P<0.001）和舒张速率（P=0.012）并未因减肥而逆转。同样，肥胖导致的快、慢MHC浓度降低以及向快MHC的转变也未因减肥而逆转。
减肥不能逆转肥胖引起的运动能力和肌肉收缩功能变化。这些结果表明，单纯减肥可能不是一种充分的干预措施。
