Route-dependent effect of nutritional support on liver glucose uptake

The liver is a major site of glucose disposal during chronic (5 day) total parenteral (TPN) and enteral (TEN) nutrition. Net hepatic glucose uptake (NHGU) is dependent on the route of delivery when only glucose is delivered acutely; however, the hepatic response to chronic TPN and TEN is very similar. We aimed to determine whether the route of nutrient delivery altered the acute (first 8 h) response of the liver and whether chronic enteral delivery of glucose alone could augment the adaptive response to TPN. Chronically catheterized conscious dogs received either TPN or TEN containing glucose, Intralipid, and Travasol for either 8 h or 5 days. Another group received TPN for 5 days, but similar to 50% of the glucose in the nutrition was given via the enteral route ( TPN + EG). Hepatic metabolism was assessed with tracer and arteriovenous difference techniques. In the presence of similar arterial plasma glucose levels (similar to 6 mM), NHGU and net hepatic lactate release increased approximately twofold between 8 h and 5 days in TPN and TEN. NHGU (26 +/- 1 vs. 23 +/- 3 mu mol-kg(-1)-min(-1)) and net hepatic lactate release (44 +/- 1 vs. 34 +/- 6 mu mol-kg(-1)-min(-1)) in TPN + EG were similar to results for TPN, despite lower insulin levels (96 +/- 6 vs. 58 +/- 16 pM, TPN vs. TPN + EG). TEN does not acutely enhance NHGU or disposition above that seen with TPN. However, partial delivery of enteral glucose is effective in decreasing the insulin requirement during chronic TPN.