Department of Surgery, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Department of Pharmacy, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
JPEN J Parenter Enteral Nutr. 2018 Feb;42(2):361-370. doi: 10.1177/0148607116678831. Epub 2017 Dec 19.
We used the N glycine urinary end-product enrichment technique to quantify whole body protein turnover following thoracic surgery.
A single dose of N glycine (2 mg/kg) was administered orally on postoperative day 1 to children (1-18 years) following thoracic surgery. N enrichment of ammonia and urea was measured in mixed urine after 12 and 24 hours, respectively, and protein synthesis, breakdown, and net balance determined. Nitrogen balance (dietary intake minus urinary excretion) was calculated. Urinary 3-methylhistidine:creatinine ratio was measured as a marker of skeletal muscle protein breakdown.
We enrolled 19 subjects-median (interquartile range): age, 13.8 years (12.2-15.1); weight, 49.2 kg (38.4-60.8)-who underwent thoracotomy (n = 12) or thoracoscopic (n = 7) surgery. Protein synthesis and breakdown by N enrichment were 7.1 (5.5-9) and 7.1 (5.6-9) g·kg ·d with ammonia (12 hours) as the end product, and 5.8 (3.8-6.7) and 6.7 (4.5-7.6) with urea (24 hours), respectively. Net protein balance by the N glycine and urinary urea nitrogen methods were -0.34 (-0.47, -0.3) and -0.48 (-0.65, -0.28) g·kg ·d , respectively (r = 0.828, P < .001). Postoperative change in 3-methylhistidine:creatinine ratio did not correlate significantly with protein breakdown or balance.
The single-dose oral administration of N glycine stable isotope with measurement of urinary end-product enrichment is a feasible and noninvasive method to investigate whole body protein turnover in children. After major surgery, children manifest increased protein turnover and net negative balance due to increased protein breakdown.
我们使用 N-甘氨酸尿终产物富集技术来量化胸外科手术后的全身蛋白质周转率。
胸外科手术后第 1 天，儿童（1-18 岁）口服单剂量 2mg/kg 的 N-甘氨酸。分别在 12 小时和 24 小时后测量混合尿中的 N 富集氨和尿素，并确定蛋白质合成、分解和净平衡。计算氮平衡（饮食摄入减去尿排泄）。尿 3-甲基组氨酸：肌酐比值作为骨骼肌蛋白质分解的标志物进行测量。
我们纳入了 19 名受试者-中位数（四分位间距）：年龄，13.8 岁（12.2-15.1）；体重，49.2kg（38.4-60.8）-行开胸手术（n=12）或胸腔镜手术（n=7）。通过 N 富集的蛋白质合成和分解分别为 7.1（5.5-9）和 7.1（5.6-9）g·kg·d，以氨（12 小时）作为终产物，分别为 5.8（3.8-6.7）和 6.7（4.5-7.6）g·kg·d，以尿素（24 小时）作为终产物。通过 N-甘氨酸和尿尿素氮方法的净蛋白质平衡分别为-0.34（-0.47，-0.3）和-0.48（-0.65，-0.28）g·kg·d，分别（r=0.828，P<.001）。术后 3-甲基组氨酸：肌酐比值的变化与蛋白质分解或平衡无显著相关性。
单次口服 N-甘氨酸稳定同位素并测量尿终产物富集是一种可行的非侵入性方法，可用于研究儿童的全身蛋白质周转率。在大手术后，儿童由于蛋白质分解增加而表现出蛋白质周转率增加和净负平衡。
