Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 1995
Publication Date: N/A
Interpretive Summary: Increased rates of growth and milk production in ruminants lead to increased yields of high quality human edible protein. Regulation of growth and milk production are partially a function of available nutrients. A principal nutrient required in both tissue growth and milk production is glucose. In ruminants, glucose is primarily produced by the liver and regulation of glucose release by the liver may regulate animal production. This study was done to determine if increasing glucose availability to the animal would decrease the ability of the liver to produce glucose, and thus, result in no net gain in glucose available to the animal. This study showed that glucose production by the liver was only depressed for a short time during glucose infusion, suggesting that a large fraction of the liver glucose production could be maintained. The study further showed that oxygen consumption by the liver was decreased, suggesting that energy expenditure by the animal may have decreased. This study would suggest that feeding strategies that increase glucose release, either dietary or through glucose production by the liver, will not be offset by inhibition of liver glucose production.
Technical Abstract: Multicatheterized ewes were used to determine the effect of exogenous glucose infusion on net glucose, insulin, lactate, and oxygen flux by the portal-drained viscera (PDV) and liver of conscious sheep. Glucose was infused into either the mesenteric vein or abdominal vena cava at the same rate as the net hepatic release of glucose for 240 min and net fluxes were determined every 30 min. Site of glucose infusion did not preferentially affect net PDV insulin or oxygen flux or the net liver glucose, insulin or oxygen flux (P>.05). Net PDV glucose release was lower (P=.03) during mesenteric infusion (-3.6 +\- 1.4 mmol/h) than during abdominal vena cava infusion (3.6 +\- 1.3 mmol/h). Net PDV insulin release (P=.03) increased with glucose infusion. Net PDV lactate release (P=.27) and oxygen consumption (P=.26) did not differ over the infusion period. Net hepatic glucose release (P=.03) and oxygen consumption (P=.04) decreased during the infusion period. Net hepatic lactate (P=.11) and insulin release (P=.47) did not differ over the infusion period. Exogenous glucose infusion decreases hepatic aerobic metabolism and the extent that net glucose and insulin fluxes is affected is dependent on length of infusion.