Impact of alpha-tocopherol deficiency and supplementation on sacrocaudalis and gluteal muscle fiber histopathology and morphology in horses.

BackgroundA subset of horses deficient in alpha-tocopherol (α-TP) develop muscle atrophy and vitamin E-responsive myopathy (VEM) characterized by mitochondrial alterations in the sacrocaudalis dorsalis medialis muscle (SC).ObjectivesTo quantify muscle histopathologic abnormalities in subclinical α-TP deficient horses before and after α-TP supplementation and compare with retrospective (r)VEM cases.AnimalsProspective study; 16 healthy α-TP-deficient Quarter Horses. Retrospective study; 10 retrospective vitamin E-responsive myopathy (rVEM) cases .MethodsBlood, SC, and gluteus medius (GM) biopsy specimens were obtained before (day 0) and 56 days after 5000 IU/450 kg horse/day PO water dispersible liquid α-TP (n = 8) or control (n = 8). Muscle fiber morphology and mitochondrial alterations were compared in samples from days 0 and 56 and in rVEM cases.ResultsMitochondrial alterations more common than our reference range (<2.5% affected fibers) were present in 3/8 control and 4/8 treatment horses on day 0 in SC but not in GM (mean, 2.2; range, 0%-10% of fibers). Supplementation with α-TP for 56 days did not change the percentage of fibers with mitochondrial alterations or anguloid atrophy, or fiber size in GM or SC. Clinical rVEM horses had significantly more mitochondrial alterations (rVEM SC, 13% ± 7%; GM, 3% ± 2%) and anguloid atrophy compared to subclinical day 0 horses.Conclusions and clinical importanceClinically normal α-TP-deficient horses can have mitochondrial alterations in the SC that are less severe than in atrophied VEM cases and do not resolve after 56 days of α-TP supplementation. Preventing α-TP deficiency may be of long-term importance for mitochondrial viability

An innate immune response and altered nuclear receptor activation defines the spinal cord transcriptome during alpha-tocopherol deficiency in Ttpa-null mice

Mice with deficiency in tocopherol (alpha) transfer protein gene develop peripheral tocopherol deficiency and sensory neurodegeneration. Ttpa-/- mice maintained on diets with deficient α-tocopherol (α-TOH) had proprioceptive deficits by six months of age, axonal degeneration and neuronal chromatolysis within the dorsal column of the spinal cord and its projections into the medulla. Transmission electron microscopy revealed degeneration of dorsal column axons. We addressed the potential pathomechanism of α-TOH deficient neurodegeneration by global transcriptome sequencing within the spinal cord and cerebellum. RNA-sequencing of the spinal cord in Ttpa-/- mice revealed upregulation of genes associated with the innate immune response, indicating a molecular signature of microglial activation as a result of tocopherol deficiency. For the first time, low level Ttpa expression was identified in the murine spinal cord. Further, the transcription factor liver X receptor (LXR) was strongly activated by α-TOH deficiency, triggering dysregulation of cholesterol biosynthesis. The aberrant activation of transcription factor LXR suppressed the normal induction of the transcription factor retinoic-related orphan receptor-α (RORA), which is required for neural homeostasis. Thus we find that α-TOH deficiency induces LXR, which may lead to a molecular signature of microglial activation and contribute to sensory neurodegeneration

Increased α-tocopherol metabolism in horses with equine neuroaxonal dystrophy.

BackgroundEquine 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/objectivesBased 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.AnimalsVitamin 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.MethodsThe 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.ResultsMetabolic 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 importanceIncreased 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