Open AccessIncreased α‐tocopherol metabolism in horses with equine neuroaxonal dystrophy
Author(s) -
Hales Erin N.,
Habib Hadi,
Favro Gianna,
Katzman Scott,
Sakai R. Russell,
Marquardt Sabin,
Bordbari Matthew H.,
MingWhitfield Brittni,
Peterson Janel,
Dahlgren Anna R.,
Rivas Victor,
Ramirez Carolina Alanis,
Peng Sichong,
Donnelly Callum G.,
Dizmang BobbiSue,
Kallenberg Angelica,
Grahn Robert,
Miller Andrew D.,
Woolard Kevin,
Moeller Benjamin,
Puschner Birgit,
Finno Carrie J.
Publication year - 2021
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/jvim.16233
Subject(s) - tocopherol , vitamin e , medicine , horse , alpha tocopherol , endocrinology , physiology , biology , biochemistry , antioxidant , paleontology
Background Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is an inherited neurodegenerative disorder associated with a vitamin E deficiency within the first year of life. Vitamin E consists of 8 isoforms metabolized by the CYP4F2 enzyme. No antemortem diagnostic test currently exists for eNAD/EDM. Hypothesis/Objectives Based on the association of α‐tocopherol deficiency with the development of eNAD/EDM, we hypothesized that the rate of α‐tocopherol, but not γ‐tocopherol or tocotrienol metabolism, would be increased in eNAD/EDM‐affected horses. Animals Vitamin E metabolism: Proof of concept (POC) study; eNAD/EDM‐affected (n = 5) and control (n = 6) horses. Validation study: eNAD/EDM‐affected Quarter Horses (QHs; n = 6), cervical vertebral compressive myelopathy affected (n = 6) horses and control (n = 29) horses. CYP4F2 expression and copy number: eNAD/EDM‐affected (n = 12) and age‐ and sex‐matched control (n = 11‐12) horses. Methods The rates of α‐tocopherol/tocotrienol and γ‐tocopherol/tocotrienol metabolism were assessed in equine serum (POC and validation) and urine (POC only) using liquid chromatography tandem mass spectrometry (LC‐MS/MS). Quantitative reverse‐transcriptase PCR (qRT‐PCR) and droplet digital (dd)‐PCR were used to assay expression and genomic copy number of a CYP4F2 equine ortholog. Results Metabolic rate of α‐tocopherol was increased in eNAD/EDM horses (POC, P < .0001; validation, P = .03), with no difference in the metabolic rate of γ‐tocopherol. Horses with eNAD/EDM had increased expression of the CYP4F2 equine orthologue ( P = .02) but no differences in copy number. Conclusions and Clinical Importance Increased α‐tocopherol metabolism in eNAD/EDM‐affected QHs provides novel insight into alterations in vitamin E processing in eNAD/EDM and highlights the need for high‐dose supplementation to prevent the clinical phenotype in genetically susceptible horses.