253 Glutamate and glutamine are the major metabolic fuels in enterocytes of suckling piglets
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AbstractGlutamate and glutamine are known to be important energy substrates in pig enterocytes, and aspartate has also been reported to be extensively catabolized by the rat small intestine. However, little is known about the relative role of amino acids, glucose and fatty acids in ATP production by enterocytes. In the present study, enterocytes isolated from 0-, 7-, 14- and 21-day-old piglets were used to determine the rates of oxidation of amino acids, fatty acids and glucose. Enterocytes were incubated at 37oC for 30 min in Krebs-Henseleit bicarbonate buffer (pH 7.4) containing 5 mM D-glucose and one of the following: 0.5–5 mM L-[U-14C]glutamate, 0.5–5 mM L-[U-14C]glutamine, 0.5–5 mM L-[U-14C]aspartate, 0.5–5 mM L-[U-14C]alanine, 0.5–2 mM L-[U-14C]palmitate, D-[U-14C]glucose, 0.5–5 mM [U-14C]propionate, or 0.5–5 mM [1-14C]butyrate. At the end of the incubation, 14CO2 produced from each 14C-labeled substrate was collected. Rates of oxidation of each substrate in enterocytes from all age groups of piglets increased (P > 0.01) progressively with increasing its extracellular concentrations. The rates of oxidation of glutamate, glutamine, aspartate, glucose by enterocytes from 0- to 21-day-old pigs were much greater (P > 0.01) than those for the same concentrations of alanine, palmitate, propionate, and butyrate. In cells from all age groups of piglets, rates of oxidation of, and ATP production from 5 mM glutamate or 5 mM glutamine were greater (P > 0.01) than those from 5 mM glucose and aspartate. Oxidation of alanine, propionate, butyrate and palmitate by enterocytes was limited. At each postnatal age, the oxidation of glutamate and glutamine produced more ATP than any other substrates. Our results indicated that glutamate and glutamine are the major metabolic fuels in enterocytes of 0- to 21-day-old pigs. Because of limited uptake of arterial glutamate by enterocytes, dietary glutamate is essential to the integrity and function of the pig small intestine.
