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The relationship between fat synthesis and oxidation in the liver after re-feeding and its regulation by thyroid
M J Holness1, T J French, P S Schofield
1Department of Chemical Pathology, London Hospital Medical College, U.K.
Abstract:
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.