Seashore J H, Huszar G B, Davis E M
J Pediatr Surg. 1980 Aug;15(4):400-4.
Conventional methods of assessing adequate nutrition in children may be inaccurate or change too slowly to be helpful during acute illness. Techniques to measure protein synthesis or breakdown provide more accurate information. Three-methylhistidine (3MH), an unusual amino acid found in actin and myosin, is not further metabolized and is quantitatively excreted following muscle degradation. Urinary excretion of 3MH has, therefore, been proposed as a marker of protein catabolism. The ratio of 3MH to creatinine in 24-hr urine collectons was studied in 14 healthy or stressed premature infants, and compared to nitrogen balance (N bal), caloric intake and clinical course. There is a significant inverse correlation between 3MH/Cr ratio and N Bal (R = -.507). The mean 3MH/Cr ratio was 0.140 +/- 0.037 mu mole/mg (n = 37) in healthy growing premature infants and 0.296 +/- 0.160 (n = 26) in infants who were stressed and/or had inadequate nutrient intake. Healthy growing infants almost invariably had a ratio below 0.200. Serial determinations in three infants consistently showed a rise in the ratio to above 0.200 during periods of stress or decreased intake. The 3MH/Cr ratio may be a more sensitive indicator of metabolic status and may be useful clinically, especially in infants receiving total parenteral nutrition.
评估儿童营养是否充足的传统方法可能不准确，或者变化过于缓慢，在急性疾病期间无法提供帮助。测量蛋白质合成或分解的技术能提供更准确的信息。三甲基组氨酸（3MH）是一种存在于肌动蛋白和肌球蛋白中的特殊氨基酸，不会进一步代谢，在肌肉降解后会定量排出。因此，尿中3MH的排泄量被提议作为蛋白质分解代谢的标志物。对14名健康或处于应激状态的早产儿进行了研究，测定了他们24小时尿液收集样本中3MH与肌酐的比值，并与氮平衡（N bal）、热量摄入和临床病程进行了比较。3MH/Cr比值与N Bal之间存在显著的负相关（R = -0.507）。健康成长的早产儿平均3MH/Cr比值为0.140±0.037微摩尔/毫克（n = 37），而处于应激状态和/或营养摄入不足的婴儿该比值为0.296±0.160（n = 26）。健康成长的婴儿该比值几乎总是低于0.200。对三名婴儿进行的连续测定一致显示，在应激或摄入量减少期间，该比值会升至0.200以上。3MH/Cr比值可能是代谢状态更敏感的指标，在临床上可能有用，尤其是对于接受全胃肠外营养的婴儿。
