Lipid peroxidation biomarkers for evaluating oxidative stress in equine neuroaxonal dystrophy

BACKGROUND: Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is a neurodegenerative disorder affecting genetically predisposed foals maintained on an α‐tocopherol (α‐TOH) deficient diet. Currently no antemortem diagnostic test for eNAD/EDM is available. HYPOTHESIS: Because α‐TOH deficiency is associated with increased lipid peroxidation, it was hypothesized that F(2)‐isoprostanes (F(2)IsoP), F(4)‐neuroprostanes (F(4)NP) and oxysterols derived from free radical oxidation would be increased in the cerebrospinal fluid (CSF) and neural tissue of eNAD/EDM affected horses and could serve as potential biomarkers for disease. ANIMALS: Isoprostane Study A: 14 Quarter horse foals (10 healthy foals and 4 eNAD/EDM affected foals) at 1 and 6 months of age. Isoprostane Study B: 17 eNAD/EDM affected and 10 unaffected horses ≥ 1‐4 years of age. Oxysterol study: eNAD/EDM affected (n = 14, serum; n = 11, CSF; n = 10, spinal cord [SC]) and unaffected horses 1‐4 years of age (n = 12, serum; n = 10, CSF; n = 7, SC). PROCEDURES: Cerebrospinal fluid [F(2)IsoP] and [F(4)NP] were assessed using gas chromatography‐negative ion chemical ionization mass spectrometry. Serum, CSF, and cervical SC [oxysterols] were quantified using high performance liquid chromatography mass spectrometry. Results were compared with respective α‐TOH concentrations. RESULTS: Spinal cord [7‐ketocholesterol], [7‐hydroxycholesterol], and [7‐keto‐27‐hydrocholesterol] were higher in eNAD/EDM horses whereas [24‐ketocholesterol] was lower. No significant difference was found in CSF [F(2)IsoP] and [F(4)NP], serum [oxysterols] and CSF [oxysterols] between eNAD/EDM affected and unaffected horses. No correlation was found between [F(2)IsoP], [F(4)NP], or [oxysterols] and respective [α‐TOH]. CONCLUSIONS AND CLINICAL IMPORTANCE: In the SC, targeted markers of cholesterol oxidation were significantly increased in horses with eNAD/EDM.