EFFECTS OF TPN ON BRAIN, LIVER, AND FOOD-INTAKE IN RATS

Postulating that total parenteral nutrition (TPN) has a direct metabol ic effect in the brain which may be similar to that in the liver, we s tudied the effects of TPN on brain glycogen and triglyceride in rats, Control rats (n = 24) received normal saline viajugular catheter for 1 8 days; TPN rats (n = 24) had normal saline for 10 days and then TPN-1 00 for 4 days, followed by normal saline for 4 more days, TPN-100 (cal oric ratio glucose: fat:amino acid = 50:30:20) provided 100% of the ra t's daily caloric needs, Chow and water were available ad libitum duri ng the study, Eight rats from each group were sacrificed after 1 and 4 days of TPN-100, and 4 days after stopping TPN-100, Glycogen in brain and liver glycogen, triglyceride, and glycogen synthetase and phospho rylase were measured, as were plasma glucose and insulin. Data were ev aluated using Student's t test, With TPN, the following occurred: (a) an 85% decrease (P < 0.05) of spontaneous food intake; (b) an elevated plasma glucose; (c) a three- to fivefold increase (P < 0.01) in plasm a insulin; (d) a 23% increase (P < 0.05) in whole brain glycogen but a 22-33% decrease (P < 0.05) in liver glycogen; (e) liver glycogen synt hetase and phosphorylase activity were unchanged while whole brain gly cogen synthetase activity decreased by 27% (P < 0.05) and phosphorylas e activity increased by 10-16%; and (f) whole brain triglyceride conte nt did not change, although there was a 155-241% increase (P < 0.01) i n liver triglyceride, Stopping TPN in study rats led to an increase an d normalization of food intake and reversal of the biochemical changes which did not significantly differ when compared to control rats on D ay 18. (C) 1995 Academic Press, Inc.