Carnitine palmitoyltransferase modulation of hepatic fatty acid metabolism and radio-HPLC evidence for low ketogenesis in neonatal pigs.

A neonatal piglet model was used to study hepatic fatty acid metabolism during the early postnatal period. Hepatocytes were isolated from pigs at birth or after 24 h, in fed or unfed states (n = 4 pigs/group). Cells were incubated with 1 mmol/L [1-(14)C]-octanoate (C8) or -palmitate (C16) in the presence or absence of 1 mmol/L L-carnitine, carnitine plus tetradecylglycidic acid (TDGA; 10 mumol/L) or carnitine plus glucagon (0.5 microgram/L). Accumulation of radiolabel [nmol/(h. 10(6) cells)] in CO2 and acid-soluble products (ASP) was higher (3.5- and 4.5-fold, respectively) from C8 than from C16 (P < 0.0001). Glucagon, carnitine and TDGA had no effect on the oxidation of C8 (P > 0.1). Carnitine addition tended to increase C16 flux to ASP [from 5.3 to 7.6 nmol/(h. 10(6) cells); P < 0.1], whereas carnitine plus TDGA decreased flux (from 7.6 to 2.1; P < 0.001). Esterified products accounted for 70% of metabolized label in control C16 incubations; this was reduced to 62% by carnitine (P < 0.05) and increased to 80% by the addition of carnitine plus TDGA (P < 0.0001). The 1-(14)C flux to CO2 in cells from 24-h-old unfed piglets was 47% lower than from fed pigs (P < 0.01) but 28% higher than in pigs at birth. Radiolabel contained in ASP and total metabolized label were 48% lower from unfed pigs compared with the piglets at birth and 24-h-old fed pigs (P < 0.01) and were paralleled by changes in oxygen consumption.(ABSTRACT TRUNCATED AT 250 WORDS)