Tuvdendorj Demidmaa, Chinkes David L, Bahadorani John, Zhang Xiao-jun, Sheffield-Moore Melinda, Killewich Lois A, Wolfe Robert R
Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX; Shriners Hospitals for Children, Galveston, TX.
Department of Surgery, University of Texas Medical Branch, Galveston, TX; Shriners Hospitals for Children, Galveston, TX.
Metabolism. 2014 Dec;63(12):1562-7. doi: 10.1016/j.metabol.2014.09.009. Epub 2014 Sep 28.
The use of stable isotope tracer techniques to measure muscle protein fractional synthesis rate (FSR) has been well established and widely used. The most common method that has been utilized so far is a primed constant infusion (CI) method, which requires 3-4 h of tracer infusion. However, recently our group has developed a bolus injection (BI) method, which requires an injection of bolus of tracer and can be completed within 1 h. In this study, we compared calf (gastrocnemius) muscle protein FSR measured using these two different methods--CI and BI.
FSRs were measured in eight people (5 men and 3 women; age: 62.3±6.9 years (mean±SD); body weight: 75.4±21.5 kg) at basal, postabsorptive state using L-[ring-2H5]-phenylalanine. In the CI protocol, a primed continuous infusion was given for 4 h, and muscle biopsies were taken at 120 and 240 min; in the BI, a bolus injection of the tracer was given at 0 min and biopsies were taken at 5 and 60 min. Tracer enrichments in blood and muscle tissue were determined by gas chromatography-mass spectrometry. Data are expressed as mean±SE; t-test, linear regression and Levene Median equal variance test analyses were performed.
CI FSR was 0.066±0.006%/h, whereas BI FSR was 0.058±0.008%/h, p=NS. The linear regression analysis showed a significant relationship between BI and CI, p=0.038. The intra-class correlation coefficient was 0.83. The standard deviation of the differences in the measurements was 0.015%/h. The Levene Median equal variance test demonstrated no difference in variance between the CI and BI measurements (p=0.722).
No difference could be detected in calf muscle protein FSR measured by CI and BI methods; the BI method can be used for the measurement of muscle protein FSR in humans.
使用稳定同位素示踪技术测量肌肉蛋白质分数合成率（FSR）已得到充分确立并被广泛应用。迄今为止最常用的方法是单次快速静脉注射并持续输注（CI）法，该方法需要3 - 4小时的示踪剂输注。然而，最近我们团队开发了一种单次快速静脉注射（BI）法，该方法只需注射一次示踪剂推注，且可在1小时内完成。在本研究中，我们比较了使用这两种不同方法——CI法和BI法测量的小腿（腓肠肌）肌肉蛋白质FSR。
使用L - [环 - 2H5] - 苯丙氨酸在8名受试者（5名男性和3名女性；年龄：62.3±6.9岁（均值±标准差）；体重：75.4±21.5千克）的基础、吸收后状态下测量FSR。在CI方案中，进行4小时的单次快速静脉注射并持续输注，在120分钟和240分钟时采集肌肉活检样本；在BI方案中，在0分钟时给予一次示踪剂推注，并在5分钟和60分钟时采集活检样本。通过气相色谱 - 质谱法测定血液和肌肉组织中的示踪剂富集情况。数据以均值±标准误表示；进行了t检验、线性回归和Levene中位数等方差检验分析。
CI法测量的FSR为0.066±0.006%/小时，而BI法测量的FSR为0.058±0.008%/小时，p = 无显著性差异。线性回归分析显示BI法和CI法之间存在显著相关性，p = 0.038。组内相关系数为0.83。测量差异的标准差为0.015%/小时。Levene中位数等方差检验表明CI法和BI法测量的方差无差异（p = 0.722）。
CI法和BI法测量的小腿肌肉蛋白质FSR未检测到差异；BI法可用于测量人体肌肉蛋白质FSR。
