Park W, Paust H, Brösicke H, Knoblach G, Mesche M, Helge H
Infusionsther Klin Ernahr. 1987 Apr;14(2):66-70.
The branched-chain amino acid leucine plays an important role in the protein metabolism of human beings. It not only inhibits protein degradation but also stimulates protein synthesis. The oxidation rate of leucine and the influence which nutritional conditions have on this amino acid can be measured with the intravenous 13C-leucine breath test. In order the apply the breath test on newborn infants, the required dosage of L-(1-13C)-leucine and the reproducibility of the test had, firstly, to be determined. Following this, the extent to which the leucine oxidation rate was influenced by a simultaneous carbohydrate intake was investigated. An evident discrimination between the 13CO2-exhalation and the 13CO2-baseline exhalation is demonstrated after a bolus injection of 1 mg L-(1-13C)-leucine/kg B.W. We were able to measure reproducible values of the leucine oxidation rate in newborn infants with a tracer dosage of 4 mg L-(1-13C)-leucine/kg B.W. We found that a higher intake of carbohydrate given at the same time produced a lower rate of leucine oxidation, which indicates increased utilization of leucine for the benefit of protein synthesis.
支链氨基酸亮氨酸在人体蛋白质代谢中发挥着重要作用。它不仅抑制蛋白质降解，还能刺激蛋白质合成。亮氨酸的氧化率以及营养状况对这种氨基酸的影响可以通过静脉注射13C-亮氨酸呼气试验来测定。为了将该呼气试验应用于新生儿，首先需要确定L-(1-13C)-亮氨酸的所需剂量以及试验的可重复性。在此之后，研究了同时摄入碳水化合物对亮氨酸氧化率的影响程度。静脉注射1mg L-(1-13C)-亮氨酸/千克体重后，呼出的13CO2与基线呼出的13CO2之间呈现出明显的差异。我们能够用4mg L-(1-13C)-亮氨酸/千克体重的示踪剂量测量新生儿亮氨酸氧化率的可重复值。我们发现，同时摄入较高量的碳水化合物会使亮氨酸氧化率降低，这表明亮氨酸为了有利于蛋白质合成而增加了利用率。
