Regulation of hepatic carnitine palmitoyltransferase activity during the foetal-neonatal transition

Area of Science:

• Biochemistry
• Mitochondrial Metabolism
• Neonatal Physiology

Background:

• Carnitine palmitoyl transferase (CPT1) is crucial for mitochondrial fatty acid oxidation.
• Understanding CPT1 regulation is key to neonatal metabolic adaptation.
• Foetal and neonatal liver mitochondrial enzyme activity differs significantly.

Purpose of the Study:

• To investigate changes in overt carnitine palmitoyl transferase (CPT1) activity in rat liver mitochondria during the transition from foetal to neonatal life.
• To assess the impact of birth on CPT1 sensitivity to malonyl CoA inhibition.
• To examine alterations in kinetic parameters (nH and S0.5 for palmitoyl CoA) of CPT1 post-birth.

Main Methods:

• Mitochondrial isolation from foetal (21 days gestation) and neonatal (1 day post-partum) rat livers.
• Assay of overt carnitine palmitoyl transferase (CPT1) activity.
• Determination of enzyme kinetics and sensitivity to malonyl CoA inhibition.

Main Results:

• A 6-fold increase in overt CPT1 activity was observed in neonatal rat liver mitochondria compared to foetal.
• CPT1 demonstrated a 14-fold decrease in sensitivity to malonyl CoA inhibition after birth.
• Kinetic parameters, including nH and S0.5 for palmitoyl CoA, were significantly altered in neonatal CPT1.

Conclusions:

• Birth triggers a substantial upregulation of hepatic CPT1 activity in rats.
• Neonatal CPT1 exhibits reduced sensitivity to malonyl CoA, facilitating increased fatty acid oxidation.
• These adaptations are vital for meeting the heightened energy demands of the neonate through enhanced fatty acid metabolism.