Parimi Prabhu S, Devapatla Srisatish, Gruca Lourdes, O'Brien Alicia M, Hanson Richard W, Kalhan Satish C
Department of Pediatrics, Robert Schwartz M.D. Center for Metabolism and Nutrition, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44109-1998, USA.
Am J Physiol Endocrinol Metab. 2002 Mar;282(3):E618-25. doi: 10.1152/ajpendo.00403.2001.
Glutamine kinetics and its relation to transamination of leucine and urea synthesis were quantified in 16 appropriate-for-gestational-age infants, four small-for-gestational-age infants, and seven infants of diabetic mothers. Kinetics were measured between 4 and 5 h after the last feed (fasting) and in response to formula feeding using [5-(15)N]glutamine, [1-(13)C,(15)N]leucine, [(2)H(5)]phenylalanine, and [(15)N(2)]urea tracers. Leucine nitrogen and glutamine kinetics during fasting were significantly higher than those reported in adults. De novo synthesis accounted for approximately 85% of glutamine turnover. In response to formula feeding, a significant increase (P = 0.04) in leucine nitrogen turnover was observed, whereas a significant decrease (P = 0.002) in glutamine and urea rate of appearance was seen. The rate of appearance of leucine nitrogen was positively correlated (r(2) = 0.59, P = 0.001) with glutamine turnover. Glutamine flux was negatively correlated (r(2) = 0.39, P = 0.02) with the rate of urea synthesis. These data suggest that, in the human newborn, glutamine turnover is related to a high anaplerotic flux into the tricarboxylic acid cycle as a consequence of a high rate of protein turnover. The negative relationship between glutamine turnover and the irreversible oxidation of protein (urea synthesis) suggests an important role of glutamine as a nitrogen source for other synthetic processes and accretion of body proteins.
对16名适于胎龄儿、4名小于胎龄儿和7名糖尿病母亲的婴儿进行了谷氨酰胺动力学及其与亮氨酸转氨基作用和尿素合成关系的定量研究。在最后一次喂食（禁食）后4至5小时以及使用[5-(15)N]谷氨酰胺、[1-(13)C,(15)N]亮氨酸、[(2)H(5)]苯丙氨酸和[(15)N(2)]尿素示踪剂进行配方奶喂养时测量动力学。禁食期间亮氨酸氮和谷氨酰胺动力学显著高于成人报道的值。从头合成约占谷氨酰胺周转的85%。配方奶喂养后，亮氨酸氮周转显著增加（P = 0.04），而谷氨酰胺和尿素出现率显著降低（P = 0.002）。亮氨酸氮出现率与谷氨酰胺周转呈正相关（r(2) = 0.59，P = 0.001）。谷氨酰胺通量与尿素合成率呈负相关（r(2) = 0.39，P = 0.02）。这些数据表明，在人类新生儿中，由于蛋白质周转率高，谷氨酰胺周转与进入三羧酸循环的高回补通量有关。谷氨酰胺周转与蛋白质不可逆氧化（尿素合成）之间的负相关表明谷氨酰胺作为其他合成过程和身体蛋白质积累的氮源具有重要作用。
