Carnitine palmitoyltransferase I control of acetogenesis, the major pathway of fatty acid {beta}-oxidation in liver of neonatal swine.
To examine the regulation of hepatic acetogenesis in neonatal swine, carnitine palmitoyltransferase I (CPT I) activity was measured in the presence of varying palmitoyl-CoA (substrate) and malonyl-CoA (inhibitor) concentrations, and [1-(14)C]-palmitate oxidation was simultaneously measured. Accumulation rates of (14)C-labeled acetate, ketone bodies, and citric acid cycle intermediates within the acid-soluble products were determined using radio-HPLC. Measurements were conducted in mitochondria isolated from newborn, 24-h (fed or fasted), and 5-mo-old pigs. Acetate rather than ketone bodies was the predominant radiolabeled product, and its production increased twofold with increasing fatty acid oxidation during the first 24-h suckling period. The rate of acetogenesis was directly proportional to CPT I activity. The high activity of CPT I in 24-h-suckling piglets was not attributable to an increase in CPT I gene expression, but rather to a large decrease in the sensitivity of CPT I to malonyl-CoA inhibition, which offset a developmental decrease in affinity of CPT I for palmitoyl-CoA. Specifically, the IC(50) for malonyl-CoA inhibition and K(m) value for palmitoyl-CoA measured in 24-h-suckling pigs were 1.8- and 2.7-fold higher than measured in newborn pigs. The addition of anaplerotic carbon from malate (10 mM) significantly reduced (14)C accumulation in acetate (P < 0.003); moreover, the reduction was much greater in newborn (80%) than in 24-h-fed (72%) and 5-mo-old pigs (55%). The results demonstrate that acetate is the primary product of hepatic mitochondrial beta-oxidation in Sus scrofa and that regulation during early development is mediated primarily via kinetic modulation of CPT I.
Laboratory of Developmental Nutrition, Department of Animal Science, North Carolina State University, Raleigh, NC 27695, USA.
Xi
X
Lin
Kwanseob
K
Shim
Jack
J
Odle
D000085:Acetates / Q000378:metabolism*; D000104:Acetyl-CoA Hydrolase / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D000833:Animals, Suckling; D002250:Carbon Radioisotopes; D002334:Carnitine O-Palmitoyltransferase / Q000235:genetics / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism; D002952:Citric Acid Cycle / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D005227:Fatty Acids / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D007657:Ketone Bodies / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008316:Malonyl Coenzyme A / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology; D010084:Oxidation-Reduction; D010168:Palmitates / Q000493:pharmacokinetics; D010171:Palmitoyl Coenzyme A / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034421:Sus scrofa / Q000378:metabolism*
D000085:Acetates; D002250:Carbon Radioisotopes; D005227:Fatty Acids; D007657:Ketone Bodies; D010168:Palmitates; D012333:RNA, Messenger; D010171:Palmitoyl Coenzyme A; D019343:Citric Acid; D008316:Malonyl Coenzyme A; D002334:Carnitine O-Palmitoyltransferase; D000104:Acetyl-CoA Hydrolase