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Effect of fasting on hepatic lipase activity in the liver of developing rats
J Peinado-Onsurbe1, J Julve, X Galan
1Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, España. jpeinado@porthos.bio.ub.es
Insights
Fasting significantly reduces hepatic lipase in neonatal and adult rats by affecting enzyme distribution and secretion. This suggests similar post-translational processing mechanisms in both age groups.
Area of Science:
- Biochemistry
- Developmental Biology
- Metabolism
Background:
- Hepatic lipase is crucial for lipid metabolism.
- Its regulation during postnatal development is not fully understood.
- Fasting is known to influence enzyme activity.
Purpose of the Study:
- To investigate the effect of fasting on hepatic lipase during rat postnatal development.
- To examine how fasting alters hepatic lipase distribution and secretion.
- To determine if fasting impacts hepatic lipase mRNA levels.
Main Methods:
- Studied fasting effects on hepatic lipase in neonatal and adult rats.
- Analyzed enzyme distribution in perfused livers (heparin-releasable and residual).
- Assessed hepatic lipase secretion by isolated hepatocytes and measured mRNA abundance.
Main Results:
- Fasting decreased hepatic lipase activity in neonatal and adult rats.
- Fasting reduced both extracellular and intracellular hepatic lipase in perfused livers.
- Fasting lowered hepatic lipase secretion rate in isolated hepatocytes.
- No significant changes in hepatic lipase mRNA were observed.
Conclusions:
- Fasting impacts hepatic lipase activity, distribution, and secretion similarly in neonatal and adult rats.
- The underlying mechanisms likely involve post-translational modifications of the enzyme.
- This suggests conserved regulatory pathways for hepatic lipase during development.
Abstract:
The effect of fasting on hepatic lipase was studied during postnatal development in the rat. It was found that fasting produced a significant decrease in hepatic lipase only in neonatal (1-day-old) and adult (60-day-old) rats. We studied the effect of fasting on the distribution of hepatic lipase between extracellular (heparin-releasable) and intracellular (liver-retained or residual) compartments in perfused livers, and on the secretion of hepatic lipase by isolated hepatocytes. Fasting had similar effects in neonates and adults: it decreased both the heparin-releasing and the residual activities in perfused livers, and also decreased the rate of hepatic lipase secretion by isolated hepatocytes. Finally, the effect of fasting on hepatic lipase mRNA relative abundance in developing rat livers was determined. No difference was observed among the groups studied. It is concluded that the mechanisms involved in the effect of fasting on hepatic lipase appear to be similar in neonates and adult animals and may involve the post-translational processing of the enzyme.