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首页> 外文期刊>Nutrition Metabolism >Validation of a single biopsy approach and bolus protein feeding to determine myofibrillar protein synthesis in stable isotope tracer studies in humans
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Validation of a single biopsy approach and bolus protein feeding to determine myofibrillar protein synthesis in stable isotope tracer studies in humans

机译：在稳定的同位素示踪剂研究中，对单个活检方法和推注蛋白质进料以确定肌原纤维蛋白合成的验证

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Background Minimizing the number of muscle biopsies has important methodological implications and minimizes subject discomfort during a stable isotope amino acid infusion. We aimed to determine the reliability of obtaining a single muscle biopsy for the calculation of muscle protein fractional synthetic rate (FSR) as well as the amount of incorporation time necessary to obtain that biopsy after initiating a stable isotope infusion (Study 1). The calculation of muscle protein FSR requires tracer steady-state during the stable isotope infusion. Therefore, a second aim was to examine if steady-state conditions are compromised in the precursor pools (plasma free or muscle intracellular [IC]) after ingestion of a tracer enriched protein drink and after resistance exercise (Study 2). Methods Sixteen men (23 ± 3 years; BMI = 23.8 ± 2.2 kg/m2, means ± SD) were randomized to perform Study 1 or Study 2 (n = 8, per study). Subjects received a primed, constant infusion of L-[ring-13C6]phenylalanine coupled with muscle biopsies of the vastus lateralis to measure rates of myofibrillar protein synthesis (MPS). Subjects in Study 2 were fed 25 g of whey protein immediately after an acute bout of unilateral resistance exercise. Results There was no difference (P = 0.3) in rates of MPS determined using the steady-state precursor-product equation and determination of tracer incorporation between sequential biopsies 150 min apart or using plasma protein as the baseline enrichment, provided the infusion length was sufficient (230 ± 0.3 min). We also found that adding a modest amount of tracer (4% enriched), calculated based on the measured phenylalanine content of the protein (3.5%) in the drink, did not compromise steady-state conditions (slope of the enrichment curve not different from zero) in the plasma free or, more importantly, the IC pool (both P > 0.05). Conclusions These data demonstrate that the single biopsy approach yields comparable rates of muscle protein synthesis, provided a longer incorporation time is utilized, to that seen with a traditional two biopsy approach. In addition, we demonstrate that enriching protein-containing drinks with tracer does not disturb isotopic steady-state and thus both are reliable techniques to determine rates of MPS in humans.
机译：背景技术最小化肌肉活检的数量具有重要的方法学意义，并且可以在稳定同位素氨基酸输注过程中最大程度地减少受试者的不适感。我们旨在确定获得单次肌肉活检以计算肌肉蛋白质分数合成速率（FSR）的可靠性，以及确定在开始稳定同位素输注后获得该活检所需的合并时间（研究1）。肌肉蛋白FSR的计算需要在稳定同位素注入过程中保持示踪剂稳态。因此，第二个目的是检查摄入富含示踪剂的蛋白质饮料后以及进行抵抗运动后，前体库（游离血浆或肌内细胞[IC]）的稳态条件是否受到损害（研究2）。方法将16名男性（23±3岁; BMI = 23.8±2.2 kg / m2，均值±SD）随机分为研究1或研究2（每研究n = 8）。受试者接受了L- [ring-13C6]苯丙氨酸的初次，恒定输注，以及外侧股肌的肌肉活检，以测量肌原纤维蛋白合成（MPS）的速率。急性单方面抵抗运动后，立即向研究2中的受试者喂食25 g乳清蛋白。结果间隔时间为150分钟的连续活检或血浆蛋白为基线富集时，使用稳态前体-产物方程式确定的MPS速率和使用示踪剂确定的MPS率没有差异（P = 0.3），前提是输注长度足够（230±0.3分钟）。我们还发现，根据饮料中蛋白质的测得的苯丙氨酸含量（3.5％）计算，添加适量的示踪剂（4％富集）不会损害稳态条件（富集曲线的斜率与零），或者更重要的是，没有IC池（均为P> 0.05）。结论这些数据表明，与传统的两次活检方法相比，如果采用更长的合并时间，则单次活检方法可产生相当的肌肉蛋白质合成速率。此外，我们证明了用示踪剂富集含蛋白质的饮料不会干扰同位素稳态，因此这两种都是确定人体内MPS率的可靠技术。

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