Changes in the activities of the enzymes of hepatic fatty acid oxidation during development of the rat

Abstract

1. Changes in the activities of several enzymes involved in mitochondrial fatty acid oxidation were measured in the livers of developing rats between late foetal life and maturity. The enzymes studied are medium-and long-chain ATP-dependent acyl-CoA synthetases of the outer mitochondrial membrane and matrix, GTP-dependent acyl-CoA synthetase, camitine acyltransferase, enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, general 3-oxoacyl-CoA thiolase and acetoacetyl-CoA thiolase. Developmental changes in the activity of cytoplasmic acetoacetyl-CoA thiolase were also investigated. 2. The activities of all the mitochondrial enzymes studied increase markedly at birth and, except for enoyl-CoA hydratase, decrease at weaning. However, all the developmental patterns other than those of enoyl-CoA hydratase and acetoacetyl-CoA thiolase exhibit a fall followed by a rise in enzyme activity during the mid-suckling period. 3. The cytoplasmic acetoacetyl-CoA thiolase activity is low throughout suckling, but high before birth and after weaning. 4. The results are discussed in relation to changes in fatty acid supply to the liver and hormonal changes occurring during development.

Gene expression of mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase in a poorly ketogenic mammal: effect of starvation during the neonatal period of the piglet

“…Ketogenesis is also associated with increased substrate availability and changes in the activities of enzymes central to β-oxidation. Perinatal and dietary responses of rat hepatic mitochondrial HMG-CoA synthase coincide with changes in the expression and activity of liver carnitine palmitoyl transferase I (CPT-I) [6,[12][13][14][15], which suggests common regulatory mechanisms for these genes.…”

The development of ketogenesis at birth in the rat

“…After birth, apart from an increased delivery of non-esterified fatty acids to. the liver, there is an increase in the activity of the enzymes concerned with fl-oxidation in the liver, and particularly in the activity of the carnitine acyltransferase system (Augenfeld & Fritz, 1970;Foster & Bailey, 1976b). Carnitine also increases in concentration in liver after birth and it has been suggested that this is an important factor in the regulation of fatty acid oxidation and ketogenesis at this time (Robles-Valdes et al, 1976).…”

Changes in energy metabolism during the suckling and weaning period in the newborn

“…Ketone bodies are then released into the blood and carried to the extrahepatic tissues where they are utilized (Robinson and Williamson, 1980 ;Williamson, 19821. In the fetal rat liver, NEFA oxidative capacity is low ; it increases during the first 12 hrs after birth, remains high during the suckling period to decrease at weaning (Sly and Walker, 1978 ; Benito, Whitelaw and Williamson, 1979 ;Ferré et al, 1983 ;Decaux et al, 1985). Changes in the liver capacity to oxidize NEFA are paralleled by changes in the activity of the mitochondrial enzymes of Boxidation and ketone body synthesis (Foster and Bailey, 1976b ;ling, together with the high availability of NEFA in the plasma lead to high ketonebody blood concentrations which decrease after weaning (Lockwood and Bailey, 1971 ;Foster and Bailey, 1976a (Bougneres et al, 1986). Moreover, for a similar blood concentration, ketone-body utilization is 2-fold higher than in the adult.…”