Proteomic and Lipidomic Plasma Evaluations Reveal Biomarkers for Domoic Acid Toxicosis in California Sea Lions.

Domoic acid is a neurotoxin secreted by the marine diatom genus Pseudo-nitzschia during toxic algal bloom events. California sea lions (Zalophus californianus) are exposed to domoic acid through the ingestion of fish that feed on toxic diatoms, resulting in domoic acid toxicosis (DAT), which can vary from mild to fatal. Sea lions with mild disease can be treated if toxicosis is detected early after exposure. Therefore, rapid diagnosis of DAT is essential but also challenging. In this work, we performed multiomics analyses, specifically proteomic and lipidomic, on blood samples from 31 California sea lions. Fourteen sea lions were diagnosed with DAT based on clinical signs and post-mortem histological examination of brain tissue, and 17 had no evidence of DAT. Proteomic analyses revealed 31 statistically significant proteins in the DAT individuals compared to the non-DAT individuals (adjusted p < 0.05). Of these proteins, 19 were decreased in the DAT group of which three were apolipoproteins that are known to transport lipids in the blood, prompting lipidomic analyses. In the lipidomic analyses, 331 lipid species were detected with high confidence and multidimensional separations, and 29 were found to be statistically significant (adjusted p < 0.05 and log2(FC) < -1 or >1) in the DAT versus non-DAT comparison. Of these, 28 were lower in the DAT individuals, while only 1 was higher. Furthermore, 15 of the 28 lower concentration lipids were triglycerides, illustrating their putative connection with the perturbed apolipoproteins and potential use in rapid DAT diagnoses.