Metabolic fate and function of dietary glutamate in the gut
Metabolic fate and function of dietary glutamate in the gut
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DOI：
10.3945/ajcn.2009.27462y
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发表时间：
2009-09-01
影响因子：
7.1
通讯作者：
Stoll, Barbara
中科院分区：
文献类型：
--
作者：
Burrin, Douglas G.;Stoll, Barbara
谷氨酸是膳食蛋白质的主要成分，也以谷氨酸钠的形式作为添加剂存在于许多预制食品中。来自人类和动物研究的证据表明，谷氨酸是肠道的主要氧化燃料，饮食中的谷氨酸在肠道的第一次代谢中被广泛代谢。谷氨酸也是包括谷胱甘肽在内的生物活性分子的重要前体，并作为关键的神经递质发挥作用。谷氨酸作为氧化燃料的主导作用可能具有改善婴儿肠道功能的治疗潜力，婴儿肠道表现出较高的上皮细胞更新率。我们最近对仔猪的研究表明，当谷氨酸饲喂量高于正常饲料量（4倍）时，大多数谷氨酸分子要么被氧化，要么被粘膜代谢成其他非必需氨基酸。谷氨酸不被认为是一种必需的饮食，但最近的研究表明，饮食中谷氨酸的水平可以影响一些必需氨基酸的氧化，即亮氨酸。鉴于亮氨酸在肠道中发生大量氧化，正在进行的研究正在调查饮食中的谷氨酸是否会影响肠上皮细胞中亮氨酸的氧化。我们的研究还表明，在高膳食摄入量下，游离谷氨酸可能被胃和小肠吸收，从而暗示胃粘膜参与了膳食谷氨酸的代谢。谷氨酸是一种重要的兴奋性氨基酸，在早产儿发育不良的胃黏膜中，膳食谷氨酸的代谢和神经感知可能在胃排空中发挥功能作用。这些和其他最近的报告提出了关于谷氨酸在胃功能中的代谢作用的问题。本文讨论了谷氨酸作为一种氧化燃料的生理意义及其在婴儿期胃功能中的潜在作用。m J . clinn [2009]；90(增刊):850 s-6s。
Glutamate is a main constituent of dietary protein and is also consumed in many prepared foods as an additive in the form of monosodium glutamate. Evidence from human and animal studies indicates that glutamate is a major oxidative fuel for the gut and that dietary glutamate is extensively metabolized in first pass by the intestine. Glutamate also is an important precursor for bioactive molecules, including glutathione, and functions as a key neurotransmitter. The dominant role of glutamate as an oxidative fuel may have therapeutic potential for improving function of the infant gut, which exhibits a high rate of epithelial cell turnover. Our recent studies in infant pigs show that when glutamate is fed at higher (4-fold) than normal dietary quantities, most glutamate molecules are either oxidized or metabolized by the mucosa into other nonessential amino acids. Glutamate is not considered to be a dietary essential, but recent studies suggest that the level of glutamate in the diet can affect the oxidation of some essential amino acids, namely leucine. Given that substantial oxidation of leucine occurs in the gut, ongoing studies are investigating whether dietary glutamate affects the oxidation of leucine in the intestinal epithelial cells. Our studies also suggest that at high dietary intakes, free glutamate maybe absorbed by the stomach as well as the small intestine, thus implicating the gastric mucosa in the metabolism of dietary glutamate. Glutamate is a key excitatory amino acid, and metabolism and neural sensing of dietary glutamate in the developing gastric mucosa, which is poorly developed in premature infants, may play a functional role in gastric emptying. These and other recent reports raise the question as to the metabolic role of glutamate in gastric function. The physiologic significance of glutamate as an oxidative fuel and its potential role in gastric function during infancy are discussed. Am J Clin Nutr 2009; 90(suppl): 850S-6S.