Infection impairs insulin-dependent hepatic glucose uptake during total parenteral nutrition

Abstract

Total parenteral nutrition (TPN) markedly augments net hepatic glucose uptake (NHGU) and hepatic glycolysis in the presence of mild hyperglycemia and hyperinsulinemia. This increase is impaired by an infection. We determined whether the adaptation to TPN alters the responsiveness of the liver to insulin and whether infection impairs that response. Chronically catheterized dogs received TPN for 5 days. On day 3 of TPN, either a nonlethal hypermetabolic infection was induced (INF, n = 5) or a sham surgery was performed (SHAM, n = 5). Forty-two hours after clot implantation, somatostatin and glucagon (34 ± 3 vs. 84 ± 11 pg/ml in artery, SHAM vs. INF) were infused, and a three-step (120 min each) isoglycemic (∼120 mg/dl) hyperinsulinemic (∼12, 25, and 50 μU/ml) clamp was performed to simulate levels seen in normal, infected, and exogenous insulin treatment states. In SHAM, NHGU (3.5 ± 0.2 to 4.2 ± 0.4 to 4.6 ± 0.5 mg · kg−1· min−1) modestly increased. In INF, NHGU was consistently lower at each insulin step (1.1 ± 0.5 to 2.6 ± 0.5 to 2.8 ± 0.7 mg · kg−1· min−1). Although NHGU increased from the first to the second step in INF, it did not increase further with the highest dose of insulin. Despite increases in NHGU, net hepatic lactate release did not increase in SHAM and fell in INF. In summary, in the TPN-adapted state, liver glucose uptake is unresponsive to increases in insulin above the basal level. Although the infection-induced increase in insulin sustains NHGU, further increments in insulin enhance neither NHGU nor glycolysis.