|VAN DER SCHOOR, S|
|VAN GOUDOEVER, J|
|Burrin, Douglas - Doug|
Submitted to: Gastroenterology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2001
Publication Date: 11/1/2001
Citation: Van Der Schoor,S.R., Van Goudoever,J.B., Henry,J.F., Rosenberger,J.R., Burrin,D.G., Reeds,P.J. 2001. The pattern of intestinal substrate oxidation is altered by protein restriction in pigs. Gastroenterology. 121(5):1167-1175.
Interpretive Summary: Amino acids and glucose are major nutrients used by the intestine for its energy needs. However, young infants are often malnourished and don't receive enough dietary protein. We wanted to see whether the intestine would use more glucose for growth when the dietary protein intake is significantly decreased. We fed young pigs either a normal or low protein diet for one week and then measured the amount of nutrients used by the intestine for energy. To do this, we surgically implanted the piglets with small tubes and electronic devices to allow us to collect samples and measure the flow of blood draining the intestine in conscious animals. We found that when the dietary protein intake is reduced, the intestine switches over to use more glucose for energy than amino acids. In general, the overall energy needs of the intestine were the same in pigs fed the normal and low protein diet, but the use of amino acids for energy was significantly reduced in the low protein group. However, the increased use of glucose did not entirely compensate for the reduced amino acid use, suggesting that the intestine increases its use of other nutrients, such as fat, for energy during low protein feeding.
Technical Abstract: Previous studies indicate that amino acids and glucose are the major oxidative substrates for intestinal energy generation. We hypothesized that low protein feeding would lower the contribution of amino acids to energy metabolism, thereby increasing the contribution of glucose. Piglets, implanted with portal, arterial, and duodenal catheters and a portal flow probe, were fed isocaloric diets of either a high protein (0.9 g/[kg/h] protein, 1.8 g/[kg/h] carbohydrate, and 0.4 g/[kg/h] lipid) or a low protein (0.4 g/[kg/h] protein, 2.2 g/[kg/h] carbohydrate, and 0.5 g/[kg/h] lipid) content. They received enteral or intravenous infusions of [1-13C]leucine (n = 17), [U-13C]glucose (n = 15), or enteral [U-13C]glutamate (n = 8). CO2 production by the splanchnic bed was not affected by the diet. The oxidation of leucine, glutamate, and glucose accounted for 82% of the total CO2 production in high protein-fed pigs. Visceral amino acid oxidation was substantially suppressed during a low protein intake. Although glucose oxidation increased to 50% of the total visceral CO2 production during a low protein diet, this increase did not compensate entirely for the fall in amino acid oxidation.Although low protein feeding increases the contribution of enteral glucose oxidation to total CO2 production, this adaptation is insufficient. To compensate for the fall in amino acid oxidation, other substrates become increasingly important to intestinal energy generation.