Divisions of Endocrinology and Metabolism, Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas 77555, USA.
Am J Physiol Regul Integr Comp Physiol. 2011 Nov;301(5):R1408-17. doi: 10.1152/ajpregu.00211.2011. Epub 2011 Aug 31.
The combination of increasing blood flow and amino acid (AA) availability provides an anabolic stimulus to the skeletal muscle of healthy young adults by optimizing both AA delivery and utilization. However, aging is associated with a blunted response to anabolic stimuli and may involve impairments in endothelial function. We investigated whether age-related differences exist in the muscle protein anabolic response to AAs between younger (30 ± 2 yr) and older (67 ± 2 yr) adults when macrovascular and microvascular leg blood flow were similarly increased with the nitric oxide (NO) donor, sodium nitroprusside (SNP). Regardless of age, SNP+AA induced similar increases above baseline (P ≤ 0.05) in macrovascular flow (4.3 vs. 4.4 ml·min(-1)·100 ml leg(-1) measured using indocyanine green dye dilution), microvascular flow (1.4 vs. 0.8 video intensity/s measured using contrast-enhanced ultrasound), phenylalanine net balance (59 vs. 68 nmol·min(-1)·100 ml·leg(-1)), fractional synthetic rate (0.02 vs. 0.02%/h), and model-derived muscle protein synthesis (62 vs. 49 nmol·min(-1)·100 ml·leg(-1)) in both younger vs. older individuals, respectively. Provision of AAs during NO-induced local skeletal muscle hyperemia stimulates skeletal muscle protein metabolism in older adults to a similar extent as in younger adults. Our results suggest that the aging vasculature is responsive to exogenous NO and that there is no age-related difference per se in AA-induced anabolism under such hyperemic conditions.
增加血流和氨基酸 (AA) 的供应相结合，通过优化 AA 的输送和利用，为健康的年轻成年人的骨骼肌提供合成代谢刺激。然而，衰老与对合成代谢刺激的反应迟钝有关，并且可能涉及内皮功能障碍。我们研究了当大血管和微血管腿部血流量通过一氧化氮 (NO) 供体硝普钠 (SNP) 相似增加时，年龄相关的 AA 对肌肉蛋白合成代谢的反应在年轻（30 ± 2 岁）和老年（67 ± 2 岁）成年人之间是否存在差异。无论年龄大小，SNP+AA 都会引起类似的基线以上增加（P ≤ 0.05），大血管流量（用吲哚菁绿染料稀释法测量为 4.3 vs. 4.4 ml·min(-1)·100 ml 腿(-1)），微血管流量（用对比增强超声测量为 1.4 vs. 0.8 视频强度/s），苯丙氨酸净平衡（59 vs. 68 nmol·min(-1)·100 ml·leg(-1)），合成率（0.02 vs. 0.02%/h）和模型衍生的肌肉蛋白合成（62 vs. 49 nmol·min(-1)·100 ml·leg(-1)），分别在年轻个体与老年个体之间。在 NO 诱导的局部骨骼肌充血期间提供 AA 会以与年轻成年人相似的程度刺激老年成年人的骨骼肌蛋白代谢。我们的结果表明，衰老的脉管系统对外源性 NO 有反应，并且在这种充血条件下，AA 诱导的合成代谢本身没有年龄相关的差异。
