在患有 COPD 的老年受试者中，牛奶蛋白小口喂养可增强合成代谢反应，与多种氨基酸的内脏摄取减少有关。
Enhanced anabolic response to milk protein sip feeding in elderly subjects with COPD is associated with a reduced splanchnic extraction of multiple amino acids.
机构信息
Center for Translational Research in Aging & Longevity, Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
出版信息
Clin Nutr. 2012 Oct;31(5):616-24. doi: 10.1016/j.clnu.2012.04.006. Epub 2012 Jun 6.
BACKGROUND & AIMS: We previously observed in elderly subjects with Chronic Obstructive Pulmonary Disease (COPD) an enhanced anabolic response to milk protein sip feeding, associated with reduced splanchnic extraction (SPE) of phenylalanine. Milk proteins are known for their high Branched-chain Amino Acids (BCAA) content, but no information is present about splanchnic extraction and metabolism of the individual BCAA in COPD.
OBJECTIVE
To investigate whether BCAA metabolism and SPE of the individual BCAA are altered in COPD during milk protein sip feeding.
DESIGN
In elderly subjects with COPD and in healthy age-matched elderly SPE, endogenous rate of appearance (Raendo) of the leucine (LEU), isoleucine (ILE) and valine (VAL) were measured before and during sip feeding of a Whey protein meal. To study the effect of aging, the healthy elderly were compared to a group of healthy young subjects. Stable isotopes of l-[(2)H(3)]-LEU, l-[1-(13)C]-ILE and l-[1-(13)C]-VAL were given on two separate test days orally or intravenously. Simultaneously, l-[ring-(2)H(5)]-phenylalanine (PHE) and l-[ring-(2)H(2)]-tyrosine (TYR) were given to determine the whole body protein breakdown (WbPB), synthesis (WbPS) and NetPS.
RESULTS
SPE of all BCAA, TYR, and PHE (p < 0.01) were lower in the COPD group, and the increase in netPS during feeding was higher in the COPD group (P < 0.01) due to higher values for PS (P < 0.001). Raendo of all BCAA, PHE and TYR were higher in the COPD than the healthy elderly group (P < 0.05) before and during feeding (P < 0.001). Sip feeding resulted in a reduction of Raendo of PHE, ILE and VAL (P < 0.05). Postabsorptive Raendo was not different for any of the measured amino acids between the healthy elderly and young group, while sip feeding resulted in a reduction of Raendo of PHE. Only SPE of TYR was higher in the elderly (P < 0.05) and the increase in netPS during sip feeding was independent of aging.
CONCLUSION
The enhanced anabolic response to milk protein sip feeding in normal-weight COPD patients is associated with a reduced splanchnic extraction of multiple amino acids including all branched-chain amino acids. Registration ClinicalTrials.gov = NCT01418469.
背景与目的
我们之前在患有慢性阻塞性肺疾病（COPD）的老年患者中观察到，牛奶蛋白小口喂养会增强合成代谢反应，同时减少苯丙氨酸的内脏提取（SPE）。牛奶蛋白以其高支链氨基酸（BCAA）含量而闻名，但目前尚不清楚 COPD 患者中单个 BCAA 的内脏提取和代谢情况。
目的
研究 COPD 患者在牛奶蛋白小口喂养期间，BCAA 代谢和单个 BCAA 的 SPE 是否发生改变。
设计
在 COPD 老年患者和健康年龄匹配的老年 SPE 中，在口服乳清蛋白餐前后，测量亮氨酸（LEU）、异亮氨酸（ILE）和缬氨酸（VAL）的内源性出现率（Raendo）。为了研究衰老的影响，将健康老年人与一组健康的年轻受试者进行了比较。在两天的不同测试中，通过口服或静脉内给予 l-[(2)H(3)]-LEU、l-[1-(13)C]-ILE 和 l-[1-(13)C]-VAL 的稳定同位素。同时，给予 l-[ring-(2)H(5)]-苯丙氨酸（PHE）和 l-[ring-(2)H(2)]-酪氨酸（TYR），以确定全身蛋白质分解（WbPB）、合成（WbPS）和净 PS。
结果
COPD 组所有 BCAA、TYR 和 PHE 的 SPE（p < 0.01）均较低，由于 PS 较高（p < 0.001），喂养期间的净 PS 增加也较高（p < 0.01）。与喂养前和喂养期间的健康老年人组相比，COPD 组的所有 BCAA、PHE 和 TYR 的 Raendo 均较高（p < 0.05）（p < 0.001）。小口喂养导致 PHE、ILE 和 VAL 的 Raendo 降低（p < 0.05）。在健康老年人和年轻组之间，任何测量的氨基酸的餐后 Raendo 均无差异，而小口喂养会导致 PHE 的 Raendo 降低。只有 TYR 的 SPE 较高（p < 0.05），而小口喂养期间的净 PS 增加与衰老无关。
结论
在体重正常的 COPD 患者中，对牛奶蛋白小口喂养的合成代谢反应增强与多种氨基酸（包括所有支链氨基酸）的内脏提取减少有关。临床试验注册ClinicalTrials.gov = NCT01418469。
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