Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil.
FASEB J. 2018 Jan;32(1):265-275. doi: 10.1096/fj.201700158RR. Epub 2017 Sep 12.
Preservation of lean body mass (LBM) may be important during dietary energy restriction (ER) and requires equal rates of muscle protein synthesis (MPS) and muscle protein breakdown (MPB). Currently, the relative contribution of MPS and MPB to the loss of LBM during ER in humans is unknown. We aimed to determine the impact of dietary protein intake and resistance exercise on MPS and MPB during a controlled short-term energy deficit. Adult men (body mass index, 28.6 ± 0.6 kg/m; age 22 ± 1 yr) underwent 10 d of 40%-reduced energy intake while performing unilateral resistance exercise and consuming lower protein (1.2 g/kg/d, = 12) or higher protein (2.4 g/kg/d, = 12). Pre- and postintervention testing included dual-energy X-ray absorptiometry, primed constant infusion of -[C]phenylalanine, and [N]phenylalanine to measure acute postabsorptive MPS and MPB; DO to measure integrated MPS; and gene and protein expression. There was a decrease in acute MPS after ER (higher protein, 0.059 ± 0.006 to 0.051 ± 0.009%/h; lower protein, 0.061 ± 0.005 to 0.045 ± 0.006%/h; < 0.05) that was attenuated with resistance exercise (higher protein, 0.067 ± 0.01%/h; lower protein, 0.061 ± 0.006%/h), and integrated MPS followed a similar pattern. There was no change in MPB (energy balance, 0.080 ± 0.01%/hr; ER rested legs, 0.078 ± 0.008%/hr; ER exercised legs, 0.079 ± 0.006%/hr). We conclude that a reduction in MPS is the main mechanism that underpins LBM loss early in ER in adult men.-Hector, A. J., McGlory, C., Damas, F., Mazara, N., Baker, S. K., Phillips, S. M. Pronounced energy restriction with elevated protein intake results in no change in proteolysis and reductions in skeletal muscle protein synthesis that are mitigated by resistance exercise.
在能量限制（ER）期间，保留瘦体重（LBM）可能很重要，这需要肌肉蛋白质合成（MPS）和肌肉蛋白质分解（MPB）的同等速率。目前，在人类 ER 期间，MPS 和 MPB 对 LBM 损失的相对贡献尚不清楚。我们旨在确定在受控短期能量不足期间，饮食蛋白质摄入量和阻力运动对 MPS 和 MPB 的影响。成年男性（体重指数 28.6 ± 0.6 kg/m；年龄 22 ± 1 岁）在进行单侧阻力运动的同时，进行了 10 天的 40%能量摄入减少，摄入的蛋白质分别为低蛋白（1.2 g/kg/d，n = 12）或高蛋白（2.4 g/kg/d，n = 12）。干预前后的测试包括双能 X 射线吸收法、-[C]苯丙氨酸的脉冲恒速输注以及[N]苯丙氨酸以测量急性餐后 MPS 和 MPB；DO 测量综合 MPS；以及基因和蛋白质表达。ER 后急性 MPS 下降（高蛋白，0.059 ± 0.006 至 0.051 ± 0.009%/h；低蛋白，0.061 ± 0.005 至 0.045 ± 0.006%/h； < 0.05），阻力运动可减弱这种下降（高蛋白，0.067 ± 0.01%/h；低蛋白，0.061 ± 0.006%/h），综合 MPS 也呈现类似模式。MPB 没有变化（能量平衡，0.080 ± 0.01%/hr；ER 静息腿，0.078 ± 0.008%/hr；ER 运动腿，0.079 ± 0.006%/hr）。我们得出的结论是，MPS 的减少是 ER 早期成人 LBM 损失的主要机制。-赫克托，A. J.，麦格劳，C.，达马斯，F.，马扎拉，N.，贝克，S. K.，菲利普斯，S. M. 高蛋白摄入的明显能量限制导致蛋白水解无变化，骨骼肌蛋白质合成减少，但阻力运动可减轻这种减少。
