Engelen Mariëlle P K J, Rutten Erica P A, De Castro Carmen L N, Wouters Emiel F M, Schols Annemie M W J, Deutz Nicolaas E P
Department of Respiratory Medicine and Surgery, Maastricht University, Maastricht, Netherlands.
Am J Clin Nutr. 2005 Aug;82(2):366-72. doi: 10.1093/ajcn.82.2.366.
Previously, we reported increased values for whole-body protein turnover in patients with chronic obstructive pulmonary disease (COPD) in the postabsorptive state.
The objective was to investigate whether intake of a carbohydrate-protein meal influences whole-body protein turnover differently in COPD patients and control subjects.
Eight normal-weight patients with moderate COPD and 8 healthy control subjects were examined in the postabsorptive state and after 2 h of repeatedly ingesting a maltodextrin casein-based protein meal (0.02 g x kg body wt(-1) x 20 min(-1)). Combined simultaneous, continuous, intravenous infusion of L-[ring-2H5]-phenylalanine and L-[ring-2H2]-tyrosine tracer and oral repeated ingestion of 1-13C-phenylalanine were performed to measure whole-body protein synthesis (WbPS) and first-pass splanchnic extraction of phenylalanine. Endogenous rate of appearance of phenylalanine as the measure of whole-body protein breakdown (WbPB) and netWbPS was calculated as WbPS--WbPB. Arterialized venous blood was sampled for amino acid enrichment and concentration analyses.
Feeding induced an increase in WbPS and a reduction in WbPB. The reduction in WbPB was larger in the COPD group than in the control group (P < 0.05) and was related to the lower splanchnic extraction of phenylalanine in the patients. Consequently, netWbPS increased more after feeding in the COPD group than in the control group (P < 0.05).
Feeding induces more protein anabolism in normal-weight patients with moderate COPD than in healthy control subjects. This is probably because these COPD patients are characterized by an adaptive interorgan response to feeding to prevent or delay weight loss at this disease stage.
此前，我们报道过处于空腹状态的慢性阻塞性肺疾病（COPD）患者全身蛋白质周转率升高。
研究碳水化合物 - 蛋白质餐的摄入对COPD患者和对照受试者全身蛋白质周转率的影响是否不同。
对8名体重正常的中度COPD患者和8名健康对照受试者进行研究，分别在空腹状态以及反复摄入基于麦芽糊精 - 酪蛋白的蛋白质餐（0.02 g×kg体重⁻¹×20 min⁻¹）2小时后进行检查。同时进行L-[环 - 2H₅]-苯丙氨酸和L-[环 - 2H₂]-酪氨酸示踪剂的联合持续静脉输注以及1-¹³C-苯丙氨酸的口服反复摄入，以测量全身蛋白质合成（WbPS）和苯丙氨酸的首过内脏提取率。计算苯丙氨酸的内源性出现率作为全身蛋白质分解（WbPB）的指标，净WbPS计算为WbPS - WbPB。采集动脉化静脉血进行氨基酸富集和浓度分析。
进食导致WbPS增加和WbPB减少。COPD组WbPB的减少幅度大于对照组（P < 0.05），且与患者较低的苯丙氨酸内脏提取率有关。因此，COPD组进食后净WbPS的增加幅度大于对照组（P < 0.05）。
与健康对照受试者相比，进食对体重正常的中度COPD患者诱导的蛋白质合成代谢更多。这可能是因为这些COPD患者的特征是在疾病这个阶段对进食有适应性的器官间反应，以防止或延缓体重减轻。
