Dela F, Mikines K J, Larsen J J, Galbo H
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
J Gerontol A Biol Sci Med Sci. 1996 Jul;51(4):B247-52. doi: 10.1093/gerona/51a.4.b247.
Age-induced reduction of whole body insulin action has been attributed to decreased insulin action in skeletal muscle. Physical training improves insulin action, but the effect has never been investigated specifically in aged human skeletal muscle. Seven young men [age: 23 +/- 1 yr (mean +/- SE; range, 21-24 yr); weight: 70 +/- 1 kg; body fat: 8 +/- 1%] and eight aged men [59 +/- 1 yr (range, 58-64 yr); 83 +/- 2 kg; 20 +/- 2%] performed one-legged bicycle training on a modified ergometer cycle for 10 weeks, 6 days/week, at 70% of VO2 peak. Glucose clearance rates in whole body and leg were measured 16 hr after training by a hyperinsulinemic (28, 88, and 480 mU.min-1.min-2), isoglycemic clamp combined with leg balance technique. Peak oxygen uptake during the bicycle test was always lower (p < .05) in aged vs. young subjects. Furthermore, VO2 peak was higher after training in trained (T) vs. untrained (UT) (p < .05) legs. Whole body glucose clearance rate was lower in aged vs. young subjects (p < .05) when expressed per kg body weight, but similar when expressed relative to fat free mass. Leg blood flow was always lower in aged vs. young men (p < .05). At basal and during insulin infusion, leg blood flow in young men did not differ significantly in T vs. UT legs (maximum insulin: 81 +/- 7 vs. 71 +/- 5 ml.min-1.kg leg-1), while in aged subjects it increased (p < .05) with training (maximum insulin: 57 +/- 5 vs. 48 +/- 5 ml.min-1.kg leg-1). Leg glucose extraction was always higher in aged vs. young men during the two last clamp steps (p < .05). Furthermore, leg glucose extraction was increased by training in young (p < .05) but not significantly in aged subjects. Leg glucose clearance rates increased (p < .05) with training and was similar in aged men (T: 1 +/- 1, 8 +/- 1, 21 +/- 2, and 24 +/- 2; UT: 1 +/- 1, 6 +/- 1, 14 +/- 2, and 20 +/- 2 ml.min-1.kg leg-1) and young men (T: 1 +/- 1, 12 +/- 3, 23 +/- 3, and 26 +/- 3; UT: 1 +/- 1, 8 +/- 2, 17 +/- 2, and 21 +/- 2 ml.min-1.kg leg-1). Therefore, insulin action in muscle is not reduced by aging. At high insulin concentrations, the leg blood flow is lower, whereas glucose extraction is higher in aged compared with young men. Training increases overall insulin action on glucose clearance in skeletal muscle identically in aged and young subjects.
年龄导致的全身胰岛素作用降低被认为是由于骨骼肌中胰岛素作用减弱。体育锻炼可改善胰岛素作用，但这一效果从未在老年人体骨骼肌中进行过专门研究。七名年轻男性[年龄：23±1岁（平均值±标准误；范围，21 - 24岁）；体重：70±1千克；体脂：8±1%]和八名老年男性[59±1岁（范围，58 - 64岁）；83±2千克；20±2%]在改良的测力计自行车上进行单腿自行车训练，为期10周，每周6天，强度为最大摄氧量的70%。训练16小时后，通过高胰岛素（28、88和480 mU·min⁻¹·min⁻²）、等血糖钳夹结合腿部平衡技术测量全身和腿部的葡萄糖清除率。在自行车测试中，老年受试者的最大摄氧量始终低于年轻受试者（p < 0.05）。此外，训练后，训练（T）腿与未训练（UT）腿相比，最大摄氧量更高（p < 0.05）。按每千克体重计算，老年受试者的全身葡萄糖清除率低于年轻受试者（p < 0.05），但相对于去脂体重计算时则相似。老年男性的腿部血流量始终低于年轻男性（p < 0.05）。在基础状态和胰岛素输注期间，年轻男性T腿和UT腿的腿部血流量无显著差异（最大胰岛素剂量时：81±7 vs. 71±5 ml·min⁻¹·kg腿部⁻¹），而老年受试者训练后腿部血流量增加（p < 0.05）（最大胰岛素剂量时：57±5 vs. 48±5 ml·min⁻¹·kg腿部⁻¹）。在最后两个钳夹步骤中，老年男性的腿部葡萄糖摄取始终高于年轻男性（p < 0.05）。此外，训练使年轻受试者的腿部葡萄糖摄取增加（p < 0.05），但老年受试者无显著增加。腿部葡萄糖清除率随训练增加（p < 0.05），老年男性（T：1±1、8±1、21±2和24±2；UT：1±1、6±1、14±2和20±2 ml·min⁻¹·kg腿部⁻¹）和年轻男性（T：1±1、12±3、23±3和26±3；UT：1±1、8±2、17±2和21±2 ml·min⁻¹·kg腿部⁻¹）相似。因此，衰老不会降低肌肉中的胰岛素作用。在高胰岛素浓度下，老年男性的腿部血流量较低，而葡萄糖摄取较高。训练对老年和年轻受试者骨骼肌葡萄糖清除的总体胰岛素作用的增强效果相同。
