Kumar Vinod, Selby Anna, Rankin Debbie, Patel Rekha, Atherton Philip, Hildebrandt Wulf, Williams John, Smith Kenneth, Seynnes Olivier, Hiscock Natalie, Rennie Michael J
University of Nottingham, School of Graduate Entry Medicine and Health, City Hospital, Uttoxeter Road, Derby, DE22 3DT, UK.
J Physiol. 2009 Jan 15;587(1):211-7. doi: 10.1113/jphysiol.2008.164483. Epub 2008 Nov 10.
We investigated how myofibrillar protein synthesis (MPS) and muscle anabolic signalling were affected by resistance exercise at 20-90% of 1 repetition maximum (1 RM) in two groups (25 each) of post-absorptive, healthy, young (24 +/- 6 years) and old (70 +/- 5 years) men with identical body mass indices (24 +/- 2 kg m(-2)). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-(13)C] leucine (gas chromatography-combustion-mass spectrometry using plasma [1,2-(13)C]alpha-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose-response relationship between MPS at 1-2 h post-exercise and exercise intensity, which was blunted (P < 0.05) in the older men. At all intensities, MPS fell in both groups to near-basal values by 2-4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60-90% 1 RM was blunted in older men. At 1 h post-exercise at 60-90% 1 RM, p70s6K phosphorylation predicted the rate of MPS at 1-2 h post-exercise in the young but not in the old. The results suggest that in the post-absorptive state: (i) MPS is dose dependant on intensity rising to a plateau at 60-90% 1 RM; (ii) older men show anabolic resistance of signalling and MPS to resistance exercise.
我们研究了两组（每组25人）处于空腹状态、健康的年轻（24±6岁）和老年（70±5岁）男性，在进行相当于1次重复最大值（1RM）的20%-90%的阻力训练时，肌原纤维蛋白合成（MPS）和肌肉合成代谢信号是如何受到影响的。这两组男性的体重指数相同（24±2kg/m²）。我们假设，运动后，合成代谢信号分子磷酸化和MPS会以剂量依赖的方式发生改变，但在老年男性中这种改变程度较小。在运动前、运动后即刻以及运动后1、2和4小时采集股外侧肌样本。通过掺入[1,2-(13)C]亮氨酸来测量MPS（使用血浆[1,2-(13)C]α-酮异己酸作为替代前体，采用气相色谱-燃烧-质谱法）；使用抗磷酸化抗体通过蛋白质免疫印迹法测量p70核糖体S6激酶（p70s6K）和真核起始因子4E结合蛋白1（4EBP1）的磷酸化。在每组中，运动后1-2小时的MPS与运动强度之间存在S形剂量反应关系，而在老年男性中这种关系减弱（P<0.05）。在所有强度下，两组的MPS在运动后2-4小时均降至接近基础值。在相当于1RM的60%-90%强度下，老年男性中p70s6K和4EBP1的磷酸化减弱。在相当于1RM的60%-90%强度下运动后1小时，p70s6K磷酸化可预测年轻男性运动后1-2小时的MPS速率，但在老年男性中则不然。结果表明，在空腹状态下：（i）MPS在强度上呈剂量依赖性，在相当于1RM的60%-90%时达到平台期；（ii）老年男性在信号传导和MPS方面对阻力训练表现出合成代谢抵抗。
