Background and objectives:Excessive activation of certain lipid mediator (LM) pathways play a role in the complex pathogenesis of multiple sclerosis (MS). However, the relation between bioactive LMs and different aspects of CNS-related pathophysiological processes remains largely unknown. Therefore, we here assessed the association of bioactive LMs belonging to the ω-3 / ω-6 lipid classes with clinical, biochemical (serum neurofilament light (sNfL) and serum glial fibrillary acidic protein (sGFAP)) parameters and MRI-based brain volumes in patients with MS (PwMS) and healthy controls (HC).Methods:A targeted high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) approach was used on plasma samples of PwMS and HC of the Project Y cohort, a cross-sectional population based cohort that contains PwMS all born in 1966 in the Netherlands and age-matched HCs. LMs were compared between PwMS and HC and were correlated with levels of sNfL, sGFAP, disability (EDSS) and brain volumes. Finally, significant correlates were included in a backward multivariate regression model to identify which LMs best related to disability.Results:The study sample consisted of 170 patients with relapsing remitting MS (RRMS), 115 patients with progressive MS (PMS) and 125 HC. LM profiles of patients with PMS significantly differed from RRMS and HC, in particular, patients with PMS showed elevated levels of several arachidonic acid (AA) derivatives. In particular 15-HETE (r = 0.24,p< 0.001), positively correlated (average r = 0.2,p< 0.05) with clinical and biochemical parameters such as EDSS and sNfL. In addition, higher 15-HETE levels were related to lower total brain (r = -0.24,p= 0.04) and deep gray matter volumes (r = -0.27,p= 0.02) in patients with PMS and higher lesion volume (r = 0.15,p =0.03) in all PwMS.Discussion:In PwMS of the same birth year, we show that ω-3 and -6 LMs are associated with disability, biochemical (sNfL, GFAP) and MRI measures. Furthermore, our findings indicate that particularly in patients with PMS, elevated levels of specific products of the AA pathway, such as 15-HETE, associate with neurodegenerative processes. Our findings highlight the potential relevance of ω-6 LMs in the pathogenesis of MS.