Murnin M, Kumar A, Li G D, Brown M, Sumpio B E, Basson M D
Department of Surgery, Yale University, New Haven, CT 06520, USA.
J Gastrointest Surg. 2000 Jul-Aug;4(4):435-42. doi: 10.1016/s1091-255x(00)80025-6.
Enteral feeding with small amounts to stimulate bowel motility, and glutamine supplementation, which provides nutrients selectively used by intestinal epithelial cells, might preserve the gut mucosa during fasting. We evaluated the effects of the interaction between mechanical strain and glutamine supplementation in human Caco-2 intestinal epithelial cells, and pursued the finding of equivalent effects of L- and D-glutamine in Caco-2, HT-29, and primary malignant human colonocytes. Caco-2 cells were subjected to repetitive strain in media containing 2 mmol/L of L-glutamine and media supplemented with L- or D-glutamine. Proliferation was determined by automated cell counting. Differentiation and cellular production of L-glutamine were determined spectroscopically. Rhythmic deformation stimulated Caco-2 proliferation in a frequency-dependent manner. Maximal stimulation occurred at 10 cpm, consistent with in vivo frequencies of peristalsis and villous motility. Deformation at 10 cpm and L-glutamine supplementation from 2 to 5 mmol/L concentrations independently stimulated Caco-2 proliferation; the combination further increased proliferation. D-Glutamine supplementation yielded similar results, although with lesser potency. Furthermore, both L- and D-glutamine equivalently reduced Caco-2 dipeptidyl dipeptidase activity. The effects of each isoform were blocked by 1 to 3 mmol/L acivicin, a selective antagonist of glutamine metabolism. Indeed Caco-2 and HT-29 cells and primary malignant colonocytes each metabolized D-glutamine to L-glutamine. Glutamine supplementation in fasting patients might prove synergistic with stimulation of bowel motility by non-nutritive feeding, whereas tissue-specific variations in D-glutamine metabolism might facilitate selective nutripharmaceutical targeting of the gut mucosa.
给予少量肠内营养以刺激肠道蠕动，以及补充谷氨酰胺（它能提供被肠道上皮细胞选择性利用的营养物质），可能在禁食期间保护肠道黏膜。我们评估了机械应变与补充谷氨酰胺在人Caco-2肠上皮细胞中的相互作用效果，并探究了L-谷氨酰胺和D-谷氨酰胺在Caco-2、HT-29及原发性人恶性结肠细胞中的等效作用。将Caco-2细胞置于含有2 mmol/L L-谷氨酰胺的培养基以及补充了L-或D-谷氨酰胺的培养基中，使其受到重复性应变。通过自动细胞计数来测定细胞增殖。用光谱法测定L-谷氨酰胺的分化和细胞生成。节律性变形以频率依赖的方式刺激Caco-2细胞增殖。最大刺激发生在10次/分钟，这与体内蠕动和绒毛运动的频率一致。10次/分钟的变形以及将L-谷氨酰胺浓度从2 mmol/L补充至5 mmol/L可独立刺激Caco-2细胞增殖；二者联合使用可进一步增加增殖。补充D-谷氨酰胺也产生了类似结果，尽管效力较低。此外，L-谷氨酰胺和D-谷氨酰胺均可同等程度地降低Caco-2二肽基肽酶活性。每种异构体的作用均被1至3 mmol/L的阿西维辛（一种谷氨酰胺代谢的选择性拮抗剂）阻断。事实上，Caco-2细胞、HT-29细胞及原发性恶性结肠细胞均将D-谷氨酰胺代谢为L-谷氨酰胺。对于禁食患者，补充谷氨酰胺可能与通过非营养性喂养刺激肠道蠕动具有协同作用，而D-谷氨酰胺代谢的组织特异性差异可能有助于对肠道黏膜进行选择性营养药物靶向治疗。
