University of California, San Francisco, CA, USA.
Am J Clin Nutr. 2013 Mar;97(3):497-504. doi: 10.3945/ajcn.112.048074. Epub 2013 Jan 30.
Muscle wasting is a consequence of many primary conditions including sarcopenia, cachexia, osteoporosis, HIV/AIDS, and chronic kidney disease. Unfortunately, there is not a clinically accessible method to measure total body protein, which is the functional mass of muscle.
We sought to derive a simple method to measure total body protein by using dual-energy X-ray absorptiometry (DXA) and bioimpedance analysis (BIA).
We retrospectively analyzed a clinical convenience sample of individuals with numerous metabolic conditions from the Monash Medical Centre, Melbourne, Australia, who had a concurrent protein measure by using neutron activation analysis-derived protein (NAA-TBPro), water measure by using BIA, and whole-body DXA scan. The study was split into calibration and validation data sets by using simple random sampling stratified by sex, BMI category, and age decade. We generated a protein estimate direct-calibration protein (DC-TBPro) derived from BIA water, bone mass, and body volume. We compared NAA-TBPro with DC-TBPro and 2 protein estimates from the literature, one that used the DC-TBPro equation with fixed coefficients [4-compartment Lohman method for analysis of total body protein (4CL-TBPro)] and another that used fat-free mass, age, and sex [Wang equation-derived protein (W-TBPro)].
A total of 187 participants [119 women; mean (±SD) age: 37.0 ± 15.4 y; mean (±SD) BMI (in kg/m(2)) 24.5 ± 7.7] were included. When plotted against NAA-TBPro, DC-TBPro had the highest correlation [coefficient of determination (R(2)) = 0.87], lowest root mean squared error (RMSE; 0.87 kg), and fewest outliers compared with 4CL-TBPro (R(2) = 0.75; RMSE = 1.22 kg) and W-TBPro (R(2) = 0.80; RMSE = 1.10 kg).
A simple method to measure total body protein by using a DXA system and BIA unit was developed and compared with NAA as proof of principle. With additional validation, this method could provide a clinically useful way to monitor muscle-wasting conditions.
肌肉减少症是多种原发性疾病的后果，包括肌少症、恶病质、骨质疏松症、HIV/AIDS 和慢性肾脏病。遗憾的是，目前还没有一种临床可接受的方法来测量全身蛋白质，而全身蛋白质是肌肉的功能质量。
我们试图通过使用双能 X 射线吸收法（DXA）和生物电阻抗分析法（BIA）来建立一种测量全身蛋白质的简单方法。
我们回顾性地分析了来自澳大利亚墨尔本莫纳什医疗中心的具有多种代谢疾病的临床便利样本个体的资料，这些个体同时进行了中子激活分析衍生蛋白（NAA-TBPro）的蛋白测量、生物电阻抗分析衍生蛋白（BIA-TBPro）的水测量以及全身 DXA 扫描。该研究通过简单随机抽样，按性别、BMI 类别和年龄十年进行了校准和验证数据集的划分。我们从 BIA 水、骨量和体容积中生成了一种直接校准蛋白（DC-TBPro）的蛋白估算值。我们将 NAA-TBPro 与 DC-TBPro 以及文献中的两种蛋白估算值进行了比较，一种使用了固定系数的四腔室洛曼法分析全身蛋白（4CL-TBPro），另一种使用了去脂体重、年龄和性别[Wang 方程衍生蛋白（W-TBPro）]。
共纳入 187 名参与者[119 名女性；平均（±SD）年龄：37.0 ± 15.4 岁；平均（±SD）BMI（kg/m²）：24.5 ± 7.7]。与 NAA-TBPro 相比，DC-TBPro 的相关性最高[决定系数（R²）=0.87]，均方根误差（RMSE；0.87kg）最低，异常值最少，而与 4CL-TBPro（R²=0.75；RMSE=1.22kg）和 W-TBPro（R²=0.80；RMSE=1.10kg）相比。
我们建立了一种使用 DXA 系统和 BIA 单元测量全身蛋白质的简单方法，并通过 NAA 作为原理证明进行了比较。通过进一步验证，这种方法可以为监测肌肉减少症等疾病提供一种临床有用的方法。
