[2006] [4136.6] Gut Glutamate Metabolism Is Extensive in Piglets Supplemented with Dietary Glutamate

Michael J. Janeczko, Barbara Stoll, Douglas G. Burrin. USDA-ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX.

BACKGROUND: Glutamate (GLU) is a key intestinal oxidative fuel and neurotransmitter. GLU may be a therapeutic nutrient in enhancing intestinal growth and function in premature neonates; however increased systemic GLU levels may be neurotoxic. We hypothesized that the rates of intestinal GLU absorption are relatively low in piglets even when fed diets supplemented with GLU in excess of the normal dietary intake.
OBJECTIVE: To quantify the net rates of intestinal metabolism, oxidation, and absorption of GLU in infant piglets given diets supplemented with GLU in excess of the normal dietary intake.
DESIGN/METHODS: Piglets (14d-old) were surgically implanted with catheters in the jugular vein, carotid artery, portal vein, and in the stomach. An ultrasonic flow probe was placed on the portal vein to measure blood flow. Piglets were fed two of three dietary glutamate intakes (650, 1300, 1950µmol/kg/hr, which is 100, 200, and 300% of normal intake, respectively) on two separate days in a randomized, cross-over design, such that 10 pigs were studied at each dietary intake. Dietary GLU was administered intragastrically along with 13C-GLU over a 6-hour period. Blood samples were collected prior to feeding, and during feeding for determination of plasma GLU concentrations, net GLU absorption and metabolism to 13CO2.
RESULTS: Fasted arterial GLU concentrations and postprandial portal blood flow were not affected by GLU intake level. The postprandial arterial GLU concentration was increased (P<0.01) compared to the fasted level at 300%, but not at the 100% or 200% intake. There was significant net GLU absorption in all treatment groups (108 vs. 253 vs. 562 µmol/kg/hr), but the only difference among treatment groups occurred between the 100% and 300% treatment groups (P<0.01). Expressed relative to dietary intake, the rates of GLU absorption (17%, 20%, 29%) increased (p=0.055) and gut metabolism (83%, 80%, 71%) decreased (P<0.01) in the 100%, 200% and 300% groups.
CONCLUSIONS: In infant piglets, a majority of the dietary GLU is metabolized by the gut even during dietary excess of 300%. However, the net GLU absorption rate and postprandial arterial concentration were significantly increased at the 300% intake.
First Author is a Fellow in Training



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