Exploratory Analysis of Epilepsy Biomarkers Using Untargeted Metabolomics Across Multiple Cohorts

Kaisa Teele Oja^1,2*Mihkel Ilisson²Karit Reinson^1,2Kai Muru^1,2Tiia Reimand^1,2Hedi Peterson³Dmytro Fishman^3,4Toomas Haller⁵Jaanika Kronberg⁵Estonian Biobank Research Team⁵Monica H Wojcik^6,7,8Adam Kennedy⁹Laura Sommerville⁹Gregory Michelotti⁹Anne O'Donnell-Luria^10,6Eve Õiglane-Šlik^11,12Sander Pajusalu^13,14Katrin Õunap^13,14

• ¹Department of Genetics and Personalized Medicine, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia
• ²Genetics and Personalized Medicine Clinic, Tartu University Hospital, Tartu, Estonia
• ³Tartu Ulikooli Arvutiteaduse instituut, Tartu, Estonia
• ⁴STACC OÜ, Tartu, Estonia
• ⁵Tartu Ulikool Eesti Geenivaramu, Tartu, Estonia
• ⁶Center for Mendelian Genomics, Broad Institute of MIT and Harvard, Cambridge, MA, United States
• ⁷Division of Genetics and Genomics, Department of Pediatrics, Boston Children's Hospital, Boston, United States
• ⁸Division of Newborn Medicine, Department of Pediatrics, Boston Children’s Hospital, Boston, MA, United States
• ⁹Metabolon Inc, Research Triangle Park, United States
• ¹⁰Division of Genetics and Genomics, Department of Pediatrics, Boston Children's Research, Boston, United States
• ¹¹Department of Pediatrics, Tartu Ulikool Kliinilise meditsiini instituut, Tartu, Estonia
• ¹²Tartu Ulikooli Kliinikum Lastekliinik, Tartu, Estonia
• ¹³Department of Genetics and Personalized Medicine, Tartu Ulikool Kliinilise meditsiini instituut, Tartu, Estonia
• ¹⁴Genetics and Personalized Medicine Clinic, Tartu Ulikooli Kliinikum, Tartu, Estonia

This is a provisional file, not the final typeset article Epilepsy is a common central nervous system disorder characterized by abnormal brain electrical activity. Diagnosing epilepsy can be challenging, as it has various causes and different clinical manifestations. We aimed to analyze whether there are similarities in the metabolic profiles of patients with epilepsy despite different etiology, seizure frequency, seizure type, and patient age. Untargeted metabolomics analysis results were analyzed in three cohorts. The pediatric cohort (PED-C) consisted of 110 pediatric individuals with suspicion of a genetic disorder with unclear etiology; the adult cohort (AD-C) of 250 adults from the Estonian Biobank (EstBB), and the elderly cohort (ELD-C) of 583 adults ≥ 69 years from the EstBB. Epilepsy was diagnosed in 35, 11 and 26 cases, respectively. Significant differences (FDR corrected p-value <0.05) were detected in the PED-C in eight metabolites, mainly for lipids. Restricting the analysis to individuals with epilepsy and without any changes in brain magnetic resonance imaging increased the number of significant metabolites to 16. Nine significantly altered lipids were found in the AD-C, mainly triacylglycerides (TAGs). In the ELD-C, significant changes in twenty metabolites, including multiple TAGs, were observed in the metabolic profile of participants with previously diagnosed epilepsy. Several components of cell membranes were among the altered metabolites, indicating that cell membrane fluidity may have a significant role in the mechanism of epilepsy, and changes in lipid balance may indicate epilepsy. However, further studies are needed to evaluate whether untargeted metabolomics analysis could prove helpful in diagnosing epilepsy earlier.