Parenteral nutrition results in impaired lactose digestion and hexose absorption when enteral feeding is initiated in infant pigs

Preterm infants often receive total parenteral nutrition (TPN) before enteral feeding. Although TPN has been linked to mucosal atrophy, its effects on intestinal digestion, absorption, and metabolism are unknown. Our aim was to determine the effects of TPN on rates of intestinal nutrient absorption and metabolism in infant pigs after initiation of enteral feeding. Piglets were surgically implanted with catheters in the carotid artery, jugular vein, portal vein, and duodenum; an ultrasonic blood flow probe was inserted in the portal vein. Piglets were given TPN (TPN group) or enterally fed formula (enteral group) for 6 d. On day 7, both groups were enterally fed a milk-based formula, and the net portal absorption and metabolism of enteral [(2)H]glucose and [(13)C]leucine were measured. After enteral feeding began, portal blood flow increased by 27% and 41% above the basal rate in the enteral and TPN groups, respectively; oxygen consumption remained lower in the TPN group. During enteral feeding, the net portal absorption of glucose was lower in the TPN group and that of galactose was not significantly different between the groups; lactate release was higher in the TPN group. Portal absorption accounted for only approximately 37% of galactose intake in both groups. The TPN group had lower net portal absorption of arginine, lysine, threonine, and glycine. The portal absorption of dietary leucine was not significantly different between the groups; the arterial utilization and oxidation of leucine were significantly lower in the TPN group. Short-term TPN results in decreased lactose digestion and hexose absorption and increased intestinal utilization of key essential amino acids when enteral feeding is initiated in piglets