|Burrin, Douglas - Doug|
Submitted to: The American Journal of Clinical Nutrition
Publication Type: Review Article
Publication Acceptance Date: 9/1/2008
Publication Date: 8/1/2009
Citation: Burrin, D.G., Stoll, B. 2009. Metabolic fate and function of dietary glutamate in the gut. American Journal of Clinical Nutrition. 90(suppl):1S-7S.
Technical Abstract: Glutamate is a major 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, the majority of glutamate molecule is either oxidized as energy or metabolized by the mucosa into other nonessential amino acids. Glutamate is not considered 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 intestine epithelial cells. Our studies also suggest that at high dietary intakes, free glutamate may be absorbed via the stomach as well as the small intestine, implicating the gastric mucosa in the metabolism of dietary glutamate. As a key excitatory amino acid, metabolism and neural sensing of dietary glutamate in the developing gastric mucosa may play a functional role in gastric emptying, which is poorly developed in premature infants. These and other recent reports raise the question as to the metabolic role of glutamate in gastric function. The physiologically significance of glutamate as an oxidative fuel and its potential role in gastric function during infancy will be discussed.