The Influence of Age and APOE Genotype on the L-carnitine System in the Brain

Published on January 6, 2023

Imagine the L-carnitine system as a highway for lipid bioenergetics in the brain. In this study, scientists investigated how age and a specific gene variant called APOE E4 affect this highway and its associated metabolites. They used mice as a model and evaluated levels of L-carnitine and its metabolites at different ages. The results showed that as the mice aged, those with the APOE E4 variant had an increase in certain acylcarnitines, which are important components of the L-carnitine system. Additionally, when the mice were given L-carnitine orally, those with the APOE E4 variant had higher levels of certain metabolites in the brain and decreased ratios of acylcarnitines between the blood and brain compared to other genotypes. These findings suggest that the presence of the APOE E4 variant, combined with aging, may contribute to alterations in the L-carnitine bioenergetic system and potentially impact cerebrovascular function. Understanding these molecular changes could provide insights into how aging and genetics influence neurodegenerative diseases like Alzheimer’s. To dive deeper into this fascinating research, check out the full article!

With age the apolipoprotein E (APOE) E4 allele (involved in lipid homeostasis) is associated with perturbation of bioenergetics pathways in Alzheimer’s disease (AD). We therefore hypothesized that in aging mice APOE genotype would affect the L-carnitine system (central to lipid bioenergetics), in the brain and in the periphery. Using liquid chromatography-mass spectrometry, levels of L-carnitine and associated metabolites: γ-butyrobetaine (GBB), crotonobetaine, as well as acylcarnitines, were evaluated at 10-, 25-, and 50-weeks, in the brain and the periphery, in a targeted replacement mouse model of human APOE (APOE-TR). Aged APOE-TR mice were also orally administered 125 mg/kg of L-carnitine daily for 7 days followed by evaluation of brain, liver, and plasma L-carnitine system metabolites. Compared to E4-TR, an age-dependent increase among E2- and E3-TR mice was detected for medium- and long-chain acylcarnitines (MCA and LCA, respectively) within the cerebrovasculature and brain parenchyma. While following L-carnitine oral challenge, E4-TR mice had higher increases in the L-carnitine metabolites, GBB and crotonobetaine in the brain and a reduction of plasma to brain total acylcarnitine ratios compared to other genotypes. These studies suggest that with aging, the presence of the E4 allele may contribute to alterations in the L-carnitine bioenergetic system and to the generation of L-carnitine metabolites that could have detrimental effects on the vascular system. Collectively the E4 allele and aging may therefore contribute to AD pathogenesis through aging-related lipid bioenergetics as well as cerebrovascular dysfunctions.

Read Full Article (External Site)

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes:

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>