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.
Lin
Xi
X
Laboratory of Developmental Nutrition, Department of Animal Science, North Carolina State University, Raleigh, NC 27695, USA.
Shim
Kwanseob
K
Odle
Jack
J
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