1. Academic Validation
  2. Ether lipid transfer across the blood-brain and placental barriers does not improve by inactivation of the most abundant ABC transporters

Ether lipid transfer across the blood-brain and placental barriers does not improve by inactivation of the most abundant ABC transporters

  • Brain Res Bull. 2022 Oct 15;189:69-79. doi: 10.1016/j.brainresbull.2022.08.006.
Fabian Dorninger 1 Frédéric M Vaz 2 Hans R Waterham 3 Jan B van Klinken 4 Gerhard Zeitler 1 Sonja Forss-Petter 1 Johannes Berger 5 Christoph Wiesinger 1
Affiliations

Affiliations

  • 1 Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria.
  • 2 Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases, Emma Children's Hospital, Meibergdreef 9, Amsterdam, the Netherlands; Amsterdam Gastroenterology Endocrinology Metabolism, Inborn errors of metabolism, Amsterdam, the Netherlands; Core Facility Metabolomics, Amsterdam UMC location University of Amsterdam, Amsterdam, the Netherlands.
  • 3 Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases, Emma Children's Hospital, Meibergdreef 9, Amsterdam, the Netherlands; Amsterdam Gastroenterology Endocrinology Metabolism, Inborn errors of metabolism, Amsterdam, the Netherlands; United for Metabolic Diseases, the Netherlands; Amsterdam Reproduction & Development, Amsterdam, the Netherlands.
  • 4 Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases, Emma Children's Hospital, Meibergdreef 9, Amsterdam, the Netherlands; Core Facility Metabolomics, Amsterdam UMC location University of Amsterdam, Amsterdam, the Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
  • 5 Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria. Electronic address: johannes.berger@meduniwien.ac.at.
Abstract

Phospholipid transport from the periphery to the brain is an understudied topic. When certain lipid species are deficient due to impaired synthesis, though, transfer across the blood-brain barrier is essential for replenishing lipids in the brain. For example, the deficiency in plasmalogens, the most abundant ether lipids in mammals, has detrimental effects on the brain, which is a major issue in inherited peroxisomal disorders but also contributes to more common disorders like Alzheimer's disease. Oral administration of alkylglycerols like batyl alcohol, which carry a pre-formed ether bond, enables replenishment of ether lipids in various peripheral tissues. However, plasmalogen deficiency in the brain cannot be overcome by this approach. Here, we tried to increase cerebral plasmalogen uptake by modulating the efflux transport across the blood-brain barrier. We hypothesized, based on previous literature, that at least some ether lipid species readily enter endothelial cells of the barrier through the transporter MFSD2A but are re-exported by ATP-binding cassette (ABC) transporters. By crossbreeding Mdr1a-/-/Mdr1b-/-/BCRP-/- and ether lipid-deficient Gnpat-/- mice as well as pharmacological inhibition with MK-571 to inactivate the major ABC transporters at the blood-brain barrier, we evaluated the potential of combined ABC transporter inhibition and oral batyl alcohol administration for the treatment of plasmalogen deficiency. We found that even in the absence of the most abundant ABC transporters, batyl alcohol supplementation did not restore plasmalogen levels in the brain, despite the presence of a wide spectrum of ether lipid subspecies in the plasma as demonstrated by lipidomic analysis. Surprisingly, batyl alcohol treatment of pregnant Gnpat+/- dams had beneficial effects on the plasmalogen levels of Gnpat-/- offspring with defective ether lipid biosynthesis, independently of ABC transporter status at the placental barrier. Our results underline the autonomy of brain lipid homeostasis and indicate that peripheral supplementation of ether lipids is not sufficient to supply the brain with larger amounts of plasmalogens. Yet, the findings suggest that alkylglycerol treatment during pregnancy may pose a viable option to ameliorate some of the severe developmental defects of inborn ether lipid deficiency.

Keywords

ATP-binding cassette transporter; Alzheimer’s disease; Blood-brain barrier; Peroxisome; Plasmalogen; Precursor supplementation.

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