The relationship between fat synthesis and oxidation in the liver after re-feeding and its regulation by thyroid hormone.
The administration of glucose to 48 h-starved euthyroid or hyperthyroid rats led to decreased blood concentrations of fatty acids and ketone bodies in both groups, but fatty acid concentrations were higher and ketone-body concentrations lower in the latter group. Decreased ketonaemia was not due to increased ketone-body clearance. Flux through carnitine palmitoyltransferase 1 was increased, consistent with the effects of hyperthyroidism on enzyme activity demonstrated in vitro. Correlations between the concentrations of ketone bodies and long-chain acylcarnitine measured in freeze-clamped liver samples indicated that a lower proportion of the product of beta-oxidation was used for ketone-body synthesis. Citrate concentrations were unaffected by hyperthyroidism, but lipogenesis was increased. The results are discussed in relation to the factors controlling hepatic carbon flux and energy requirements after re-feeding.
Department of Chemical Pathology, London Hospital Medical College, U.K.
M J
MJ
Holness
T J
TJ
French
P S
PS
Schofield
M C
MC
Sugden
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives / Q000378:metabolism; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005260:Female; D005502:Food; D006980:Hyperthyroidism / Q000378:metabolism; D007657:Ketone Bodies / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000096:biosynthesis; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010848:Picolinic Acids / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*
D005230:Fatty Acids, Nonesterified; D007657:Ketone Bodies; D008055:Lipids; D010848:Picolinic Acids; D014284:Triiodothyronine; D000105:Acetyl Coenzyme A; C008363:3-mercaptopicolinic acid; D002334:Carnitine O-Palmitoyltransferase; D002331:Carnitine