Measurement of 8‐hydroxy‐2′‐deoxyguanosine in serum and cerebrospinal fluid of horses with neuroaxonal degeneration and other causes of proprioceptive ataxia

Abstract Background Eight‐hydroxy‐2′‐deoxyguanosine (8‐OHdG), a biomarker of oxidative damage evaluated in human neurodegenerative disease, has potential to correlate with postmortem diagnosis of neuroaxonal dystrophy/degenerative myeloencephalopathy (NAD/DM) in horses. Hypothesis We hypothesized that 8‐OHdG will be higher in CSF and serum from NAD/DM horses compared with horses with other neurologic diseases (CVSM, EPM) and a control group of neurologically normal horses. We also hypothesized that 8‐OHdG will be higher in CSF compared with serum from NAD/DM horses. Animals Fifty client‐owned horses with postmortem diagnoses: 20 NAD/DM, 10 CVSM, 10 EPM, and 10 control horses. Serum and CSF samples were obtained between November 2010 and March 2022. Methods Case‐control study using biobanked samples was performed and commercial competitive ELISA kit (Highly Sensitive 8‐OHdG Check ELISA) utilized. Concentration of 8‐OHdG was quantitated in both CSF and serum and compared between groups. Results No correlation was established between the measures of 8‐OHdG in serum and CSF and group. CSF median [8‐OHdG] for NAD/DM was 169.9 pg/mL (IQR25‐75: 67.18‐210.6), CVSM 157.1 pg/mL (IQR25‐75: 132.1‐229.1), EPM 131.4 pg/mL (IQR25‐75: 102.1‐193.2), and control 149.8 pg/mL (IQR25‐75: 113.3‐196.4). Serum median [8‐OHdG] for NAD/DM was 130 pg/mL (IQR25‐75: 51.73‐157.2), CVSM 125.8 pg/mL (IQR25‐75: 62.8‐170.8), EPM 120.6 pg/mL (IQR25‐75: 87.23‐229.7), and control 157.6 pg/mL (IQR25‐75: 97.15‐245.6). Poisson regression analysis showed no difference established once confounding variables were considered. Conclusions Eight‐OHdG did not aid in antemortem diagnosis of NAD/DM in this cohort of horses. At the time of diagnosis horses with NAD/DM do not have ongoing oxidative stress.