Humbert Bernard, Nguyen Patrick, Dumon Henri, Deschamps Jack-Yves, Darmaun Dominique
INSERM U.539, Centre de Recherche en Nutrition Humaine, Hôtel-Dieu, 3ème Etage Aile Nord, 44093 Nantes Cedex 1, France.
Metabolism. 2002 May;51(5):628-35. doi: 10.1053/meta.2002.32018.
To determine whether enteral glutamine alters whole-body leucine metabolism in a state of hypercatabolism, 6 dogs adapted to a normocaloric, low-protein diet received intramuscular dexamethasone (0.44 mg. kg(-1). d(-1)) for 1 week, during 2 separate study periods. On the last day of each period, intravenous infusions of L-[1-(13)C]leucine and L-[2-(15)N]glutamine were performed to assess whole-body leucine and glutamine metabolism, and duodenal biopsies were obtained to determine gut protein fractional synthesis rate (FSR), while dogs were receiving enteral nutrition. The nutrient mixture supplied 6.2 kcal. h(-1) nonprotein energy per kg(0.75) of body weight (84% glucose, 16% fat) and 0.2 g amino acid per kg(-0.75). h(-1); the nutrient mixture was glutamine-free on the "control day," and supplemented with 1,150 micromol. kg(-1). h(-1) natural L-glutamine on the "glutamine day." Glutamine supplementation induced an approximately 56% rise in plasma glutamine appearance rate (P <.05), and was associated with an approximately 26% reduction in leucine oxidation (P <.05) with no change in leucine release from protein breakdown or nonoxidative leucine disposal, an index of whole-body protein synthesis. Glutamine supplementation improved net leucine balance (protein synthesis-protein breakdown) (-26 +/- 4 v -48 +/- 11 micromol. kg(-1). h(-1); P <.05). In addition, glutamine enhanced intestinal protein FSR by approximately 22% in the 4 dogs where it was assessed. We conclude that, in hypercatabolic adult dogs in the fed state, enteral glutamine supplementation acutely decreases leucine oxidation and improves net leucine balance, and may thus preserve body protein.
为了确定肠内谷氨酰胺是否会改变高分解代谢状态下的全身亮氨酸代谢，6只适应了正常热量、低蛋白饮食的犬在两个独立的研究阶段中接受了为期1周的肌肉注射地塞米松（0.44毫克·千克⁻¹·天⁻¹）。在每个阶段的最后一天，静脉输注L-[1-(¹³)C]亮氨酸和L-[2-(¹⁵)N]谷氨酰胺以评估全身亮氨酸和谷氨酰胺代谢，并在犬接受肠内营养时获取十二指肠活检样本以测定肠道蛋白质分数合成率（FSR）。营养混合物每千克⁰·⁷⁵体重提供6.2千卡·小时⁻¹的非蛋白能量（84%葡萄糖，16%脂肪）以及每千克⁻⁰·⁷⁵·小时⁻¹ 0.2克氨基酸；在“对照日”，营养混合物不含谷氨酰胺，而在“谷氨酰胺日”补充1150微摩尔·千克⁻¹·小时⁻¹的天然L-谷氨酰胺。补充谷氨酰胺使血浆谷氨酰胺出现率升高约56%（P < 0.05），并且与亮氨酸氧化减少约26%相关（P < 0.05），而蛋白质分解产生的亮氨酸释放或全身蛋白质合成指标非氧化亮氨酸处置没有变化。补充谷氨酰胺改善了亮氨酸净平衡（蛋白质合成 - 蛋白质分解）（-26 ± 4对 -48 ± 11微摩尔·千克⁻¹·小时⁻¹；P < 0.05）。此外，在4只接受评估的犬中，谷氨酰胺使肠道蛋白质FSR提高了约22%。我们得出结论，在进食状态下的高分解代谢成年犬中，肠内补充谷氨酰胺可急性降低亮氨酸氧化并改善亮氨酸净平衡，因此可能有助于维持机体蛋白质。
