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Systematic Evaluation of Key L-Carnitine Homeostasis Mechanisms during Postnatal Development in Rat
Binbing Ling1, Caroline Aziz, Jane Alcorn
1College of Pharmacy and Nutrition, University of Saskatchewan, 110 Science Place, Saskatoon, SK, S7N 5C9, Canada. jane.alcorn@usask.ca.
Insights
This study tracked how L-carnitine (a vital nutrient) levels and its transport systems develop in young rats. Understanding these changes in L-carnitine homeostasis is key for neonatal development.
Area of Science:
- Nutritional Biochemistry
- Developmental Physiology
- Neonatal Metabolism
Background:
- L-carnitine is a conditionally essential nutrient crucial for neonatal growth and development.
- Its homeostasis mechanisms are complex and undergo significant changes during early life.
- Understanding these ontogenic changes is vital for addressing potential nutritional deficiencies in neonates.
Purpose of the Study:
- To systematically evaluate developmental changes in key L-carnitine homeostasis mechanisms in postnatal rats.
- To understand the interrelationship between these pathways and L-carnitine levels during development.
- To provide a foundation for future research on factors influencing neonatal L-carnitine metabolism.
Main Methods:
- Quantitative RT-PCR was used to measure mRNA expression of L-carnitine transporters (Octn1, Octn2), liver enzymes (Bbh, Tmlh), and heart enzymes (Cpt).
- L-Carnitine levels were quantified using HPLC-UV.
- Enzyme activities of Cpt and Bbh were assessed spectrophotometrically and by HPLC, respectively.
Main Results:
- Serum and heart L-carnitine levels increased with postnatal development in rats.
- Increased serum L-carnitine correlated with higher renal Octn2 and intestinal Octn1 expression, and hepatic γ-Bbh activity.
- Heart L-carnitine levels correlated with cardiac Octn2 expression, while Cpt1b and Cpt2 mRNA increased without a corresponding activity rise.
Conclusions:
- Multiple L-carnitine homeostasis pathways exhibit significant ontogenesis during rat postnatal development.
- This developmental data is crucial for future studies on L-carnitine metabolism in neonates.
- Understanding these mechanisms can inform interventions for growth and developmental issues related to L-carnitine.
Background:
The conditionally essential nutrient, L-carnitine, plays a critical role in a number of physiological processes vital to normal neonatal growth and development. We conducted a systematic evaluation of the developmental changes in key L-carnitine homeostasis mechanisms in the postnatal rat to better understand the interrelationship between these pathways and their correlation to ontogenic changes in L-carnitine levels during postnatal development.
Methods:
mRNA expression of heart, kidney and intestinal L-carnitine transporters, liver γ-butyrobetaine hydroxylase (Bbh) and trimethyllysine hydroxylase (Tmlh), and heart carnitine palmitoyltransferase (Cpt) were measured using quantitative RT-PCR. L-Carnitine levels were determined by HPLC-UV. Cpt and Bbh activity were measured by a spectrophotometric method and HPLC, respectively.
Results:
Serum and heart L-carnitine levels increased with postnatal development. Increases in serum L-carnitine correlated significantly with postnatal increases in renal organic cation/carnitine transporter 2 (Octn2) expression, and was further matched by postnatal increases in intestinal Octn1 expression and hepatic γ-Bbh activity. Postnatal increases in heart L-carnitine levels were significantly correlated to postnatal increases in heart Octn2 expression. Although cardiac high energy phosphate substrate levels remained constant through postnatal development, creatine showed developmental increases with advancing neonatal age. mRNA levels of Cpt1b and Cpt2 significantly increased at postnatal day 20, which was not accompanied by a similar increase in activity.
Conclusions:
Several L-carnitine homeostasis pathways underwent significant ontogenesis during postnatal development in the rat. This information will facilitate future studies on factors affecting the developmental maturation of L-carnitine homeostasis mechanisms and how such factors might affect growth and development.
