Smeuninx Benoit, Mckendry James, Wilson Daisy, Martin Una, Breen Leigh
School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
J Clin Endocrinol Metab. 2017 Sep 1;102(9):3535-3545. doi: 10.1210/jc.2017-00869.
A diminished muscle anabolic response to protein nutrition may underpin age-associated muscle loss.
To determine how chronological and biological aging influence myofibrillar protein synthesis (MyoPS).
Cross-sectional comparison.
Clinical research facility.
Ten older lean [OL: 71.7 ± 6 years; body mass index (BMI) ≤25 kg ⋅ m-2], 7 older obese (OO: 69.1 ± 2 years; BMI ≥30 kg ⋅ m-2), and 18 young lean (YL) individuals (25.5 ± 4 years; BMI ≤25 kg ⋅ m-2).
Skeletal muscle biopsies obtained during a primed-continuous infusion of l-[ring-13C6]-phenylalanine.
Anthropometrics, insulin resistance, inflammatory markers, habitual diet, physical activity, MyoPS rates, and fiber-type characteristics.
Fat mass, insulin resistance, inflammation, and type II fiber intramyocellular lipid were greater, and daily step count lower, in OO compared with YL and OL. Postprandial MyoPS rates rose above postabsorptive values by ∼81% in YL (P < 0.001), ∼38% in OL (P = 0.002, not different from YL), and ∼9% in OO (P = 0.11). Delta change in postprandial MyoPS from postabsorptive values was greater in YL compared with OL (P = 0.032) and OO (P < 0.001). Absolute postprandial MyoPS rates and delta postprandial MyoPS change were associated with step count (r2 = 0.33; P = 0.015) and leg fat mass (r2 = 0.4; P = 0.006), respectively, in older individuals. Paradoxically, lean mass was similar between groups, and muscle fiber area was greater in OO vs OL (P = 0.002).
Age-related muscle anabolic resistance is exacerbated in obese inactive individuals, with no apparent detriment to muscle mass.
对蛋白质营养的肌肉合成代谢反应减弱可能是与年龄相关的肌肉流失的基础。
确定日历年龄和生物学年龄如何影响肌原纤维蛋白合成（MyoPS）。
横断面比较。
临床研究机构。
10名老年瘦者[OL：71.7±6岁；体重指数（BMI）≤25 kg·m-2]，7名老年肥胖者（OO：69.1±2岁；BMI≥30 kg·m-2），以及18名年轻瘦者（YL）（25.5±4岁；BMI≤25 kg·m-2）。
在持续输注l-[环-13C6]-苯丙氨酸期间获取骨骼肌活检样本。
人体测量学指标、胰岛素抵抗、炎症标志物、习惯饮食、身体活动、MyoPS速率和纤维类型特征。
与YL和OL相比，OO的脂肪量、胰岛素抵抗、炎症和II型纤维肌内脂质更高，每日步数更低。餐后MyoPS速率在YL中比吸收后值升高约81%（P<0.001），在OL中升高约38%（P=0.002，与YL无差异），在OO中升高约9%（P=0.11）。与OL（P=0.032）和OO（P<0.001）相比，YL餐后MyoPS相对于吸收后值的变化更大。在老年人中，餐后绝对MyoPS速率和餐后MyoPS变化分别与步数（r2=0.33；P=0.015）和腿部脂肪量（r2=0.4；P=0.006）相关。矛盾的是，各组之间的瘦体重相似，且OO的肌纤维面积大于OL（P=0.002）。
在肥胖且不活动的个体中，与年龄相关的肌肉合成代谢抵抗加剧，但对肌肉量无明显损害。
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