Diagnosis of atypical myopathy based on organic acid and acylcarnitine profiles and evolution of biomarkers in surviving horses

Abstract

Background Atypical myopathy (AM), an acquired multiple acyl-CoA dehydrogenase deficiency (MADD) in horses, induce changes in mitochondrial metabolism. Only few veterinary laboratories offer diagnostic testing for this disease. Inborn and acquired MADD exist in humans, therefore determination of organic acids (OA) in urine and acylcarnitines (AC) in blood by assays available in medical laboratories can serve as AM diagnostics. The evolution of OA and AC profiles in surviving horses is unreported. Methods AC profiles using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and OA in urine using gas chromatography mass spectrometry (GC–MS) were determined in dried blot spots (DBS, n = 7) and urine samples ( n = 5) of horses with AM ( n = 7) at disease presentation and in longitudinal samples from 3/4 survivors and compared to DBS ( n = 16) and urine samples (n = 7) from control horses using the Wilcoxon test. Results All short- (C2-C5) and medium-chain (C6-C12) AC in blood differed significantly ( p < 0.008) between horses with AM and controls, except for C5:1 ( p = 0.45) and C5OH + C4DC ( p = 0.06). In AM survivors the AC concentrations decreased over time but were still partially elevated after 7 days. 14/62 (23%) of OA differed significantly between horses with AM and control horses. Concentrations of ethylmalonic acid, 2-hydroxyglutaric acid and the acylglycines (butyryl-, valeryl-, and hexanoylglycine) were highly elevated in the urine of all horses with AM at the day of disease presentation. In AM survivors, concentrations of those metabolites were initially lower and decreased during remission to approach normalization after 7 days. Conclusion OA and AC profiling by specialized human medical laboratories was used to diagnose AM in horses. Elevation of specific metabolites were still evident several days after disease presentation, allowing diagnosis via analysis of samples from convalescent animals.

Dynamics of acylcarnitines, hypoglycin A, méthylènecyclopropylglycine and their metabolites in a Kladruber stallion with atypical myopathy

“…In the study of Votion et al ( 2014 ) mild increases of C4, C5, C6 and C8 above the reference range were present in the horse with the lowest MCPA-carnitine concentration. The occurrence of acylcarnitines in the time profile was recently described in the study of Mathis et al (Mathis et al 2021 ), who focused on the levels of these metabolites in two horses with AM. In one of them, an increased C8 was detected by the 4th day after diagnosis.…”

“…The profile of acylcarnitines ( Figure 2A and B ) was measured over 15 days after the first signs of HGA/MCPrG poisoning. In most studies describing hypoglycin A intoxication, an increase in short (C2–C5), medium (C6–C13) and long-chain (C14–C20) acylcarnitines was observed in affected horses (Westermann et al 2008; Valberg et al 2013 ; Votion et al 2014 ; Karlíková et al 2016 ; Sander et al 2016 , 2018 ; Mathis et al 2021 ). However, in 2013 Valberg et al observed elevated C5-C10 and a slight increase of C12 and C16 in one surviving AM patient (Valberg et al 2013 ).…”

“…Bochnia et al (Bochnia et al 2018 ) described changes in HGA and MCPA-carnitine in the peripheral blood of a horse suffering from AM for three days of the disease progression. A study examining changes in the acylcarnitines profile in two horses with AM on days 7 and 9 from the diagnosis was recently published by Mathis et al (Mathis et al 2021 ). Of note, some of these metabolites have been observed in one person after ingestion of canned ackee ( Blighia sapida ) (Sander et al 2020 ).…”

New Pathophysiological Insights from Serum Proteome Profiling in Equine Atypical Myopathy

“…To confirm the biological significance of the proteomics data set, we extensively examined if previously reported findings in blood analyses of diseased horses − were also present in the proteomic analysis. Starting with CK (muscle type), we found a 22-fold elevation in AM horses compared to cograzers.…”