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Researchers Identify Biomarkers for Diagnosis and Treatment of Threatened Sea Lion

Researchers Identify Biomarkers for Diagnosis and Treatment of Threatened Sea Lion



 

 

Associate Professor Erin Baker is co-author of the study, which published in the Journal of Proteome Research.

January 18, 2025 I By Dave DeFusco

The California coastline is a tapestry of natural beauty and ecological complexity, home to diverse marine life. Among its most iconic residents are California sea lions (Zalophus californianus), playful and intelligent pinnipeds whose lives are intricately tied to the health of their marine ecosystem. However, these animals face a growing threat from domoic acid toxicosis (DAT), a condition caused by a neurotoxin secreted by harmful algal blooms.

A recent study, “Proteomic and Lipidomic Plasma Evaluations Reveal Biomarkers for Domoic Acid Toxicosis in California Sea Lions,” co-authored by Dr. Erin Baker, associate professor in the Department of Chemistry at UNC-Chapel Hill, and published in the Journal of Proteome Research, offers insights into the molecular underpinnings of DAT. Using proteomic and lipidomic analyses, the researchers identified biomarkers that could change the diagnosis and treatment of this devastating condition.

Domoic acid is produced by the marine diatom Pseudo-nitzschia, which proliferates during harmful algal blooms. Sea lions are exposed to the toxin through their diet, primarily by consuming anchovies and sardines that have accumulated domoic acid. Once ingested, the toxin binds to glutamate receptors in the brain, causing neurological dysfunction such as seizures, ataxia and even fatal heart complications.

“While severe cases of DAT are often evident through clinical signs, diagnosing mild or early-stage cases remains a challenge,” said Dr. Baker. “Domoic acid metabolizes rapidly, disappearing from the bloodstream within 24 hours, making traditional diagnostic methods like blood or urine tests unreliable.”

Dr. Baker and her colleagues sought to address this diagnostic gap using a multiomics approach, analyzing both proteins (proteomics) and lipids (lipidomics) in the blood plasma of 31 sea lions—14 diagnosed with DAT and 17 with no evidence of the condition. Their findings revealed molecular markers that could pave the way for rapid and accurate diagnosis.

The proteomic analysis identified 245 proteins, of which 31 showed statistically significant differences between DAT and non-DAT sea lions. Notably, 19 of these proteins were decreased in the DAT group, including three apolipoproteins (APOE, APOC3 and APOB). Apolipoproteins are critical for lipid transport in the blood, suggesting a link between protein dysregulation and lipid metabolism in DAT.

The lipidomic analysis detected 331 unique lipids, with 29 showing significant differences between the groups. Of these, 28 lipids, including 15 triglycerides, were found at lower levels in DAT-affected sea lions. The researchers observed trends in fatty acid composition, with many of the affected lipids containing long-chain fatty acids and double bonds, hinting at enzymatic activity changes associated with DAT.

“The study’s findings hold promise for transforming how veterinarians diagnose and treat DAT,” said Dr. Baker. “The identified biomarkers—particularly the apolipoproteins and triglycerides—could form the basis of a blood panel assay, enabling rapid, cost-effective testing. This approach would complement clinical observations, such as seizures, providing a more robust diagnostic framework.”

Such advancements are critical for facilities like The Marine Mammal Center in Sausalito, Calif., which has treated over 11,000 sea lions for DAT since 1998. Early and accurate diagnosis could allow for timely interventions, such as administering anti-seizure medications and supportive fluids, significantly improving survival rates.

“The rise in harmful algal blooms, driven by climate change and nutrient runoff, underscores the urgency of understanding and mitigating their impacts on marine ecosystems,” said Dr. Baker. “By shedding light on the molecular mechanisms of DAT, this study not only aids in the conservation of California sea lions but also contributes to broader efforts to protect marine biodiversity.”


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