Postprandial body protein synthesis and amino acid catabolism measured with leucine and phenylalanine-tyrosine tracers
Postprandial body protein synthesis and amino acid catabolism measured with leucine and phenylalanine-tyrosine tracers
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DOI：
10.1152/ajpendo.00416.2002
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发表时间：
2003-05-01
影响因子：
5.1
通讯作者：
Barazzoni, R
中科院分区：
文献类型：
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作者：
Tessari, P;Kiwanuka, E;Barazzoni, R
苯丙氨酸-酪氨酸（Phe-Tyr）示踪剂是否产生与广泛使用的亮氨酸（Leu）示踪剂相当的餐后蛋白质合成估计值尚不清楚。我们测量了Leu氧化（Ox），Phe羟基化（Hy），以及它们在混合餐（62 kJ/kg体重，22%的能量作为蛋白质）给药前后4小时内在健康受试者中进入全身蛋白质合成的处置。使用血浆和细胞内前体池。通过假设蛋白质中Leu与Phe的固定比例，将氨基酸数据外推至身体蛋白。在吸收后状态下，Leu和Phe-Tyr示踪剂的全身蛋白质合成（表示为mg.kg（-1）.min（-1））相似，与使用的前体池无关。餐后，Leu Ox、Phe Hy和身体蛋白质合成增加（P小于或等于0.01 vs.基础）。在使用细胞内前体库的情况下，使用Phe-Tyr（+0.51 +/-0.21 mg.kg（-1）.min（-1））和Leu示踪剂（+0.57 +/-0.14）的蛋白质合成的增加是相似的（P =不显著）。相比之下，对于血浆池，使用Phe-Tyr（+1.17 +/- 0.19 mg.kg（-1）.min（-1））的蛋白质合成增加是使用Leu（0.50 +/- 0.13 mg.kg（-1）.min（-1），P < 0.01）的两倍多。Leu和Ox之间存在直接相关性[使用血浆和细胞内池（r ≤ 0.65，P ≤ 0.01）]，但Phe与血浆或细胞内Hy之间不存在直接相关性。总之，1）Phe-Tyr和Leu示踪剂产生了餐后身体蛋白质合成的可比估计，前提是使用细胞内前体库; 2）Leu Ox和Phe Hy两者都受到混合膳食的刺激; 3）Phe与Hy不相关，其可能与（未知的）门静脉Phe更好地相关。
Whether phenylalanine-tyrosine (Phe-Tyr) tracers yield estimates of postprandial protein synthesis comparable to those of the widely used leucine (Leu) tracer is unclear. We measured Leu oxidation (Ox), Phe hydroxylation (Hy), and their disposal into whole body protein synthesis before and after the administration of a mixed meal (62 kJ/kg body wt, 22% of energy as protein), over 4 h in healthy subjects. Both plasma and intracellular precursor pools were used. The amino acid data were extrapolated to body protein by assuming a fixed ratio of Leu to Phe in the proteins. In the postabsorptive state, whole body protein synthesis (expressed as mg.kg(-1).min(-1)) was similar between Leu and Phe-Tyr tracers irrespective of the precursor pool used. After the meal, Leu Ox, Phe Hy, and body protein synthesis increased (P less than or equal to 0.01 vs. basal). With the use of intracellular precursor pools, the increase of protein synthesis with Phe-Tyr (+0.51 +/- 0.21 mg.kg(-1).min(-1)) and Leu tracers (+0.57 +/- 0.14) were similar (P = not significant). In contrast, with plasma pools the increase of protein synthesis was more than twofold greater with Phe-Tyr (+1.17 +/- 0.19 mg.kg(-1).min(-1)) than that with Leu (0.50 +/- 0.13 mg.kg(-1).min(-1), P < 0.01). Direct correlations were found between Leu and Ox [using both plasma and intracellular pools (r ≤ 0.65, P ≤ 0.01)] but not between Phe and either plasma or intracellular Hy. In conclusion, 1) Phe-Tyr and Leu tracers yield comparable estimates of body protein synthesis postprandially, provided that intracellular precursor pools are used; 2) both Leu Ox and Phe Hy are stimulated by a mixed meal; 3) Phe does not correlate with Hy, which might be better related to the ( unknown) portal Phe.