Elephant Seal Blubber Under Multiple Stressors: Persistent Organic Pollutants, Stress Hormones and Hydrostatic Pressure Alter Transcriptome, Lipolysis and Leptin Secretion.

Anthropogenic stressors represent major threats to marine mammals. Yet, their combined effects on health remain poorly understood. To address this, precision-cut adipose tissue slices (PCATS) from weaned northern elephant seal (NES - Mirounga angustirostris) blubber were exposed to three treatments: (i) epinephrine (acute stress), (ii) cortisol, persistent organic pollutants (Aroclor 1254, BDE-47, BDE-99 and 4,4'-DDE) and variations of hydrostatic pressure mimicking NES diving conditions (chronic stress), and (iii) a combination of acute and chronic stressors. Compared to controls, acute, chronic and combined stressors altered the expression of 4854, 1544, and 8930 genes, respectively. Acute stress upregulated the expression of genes associated with inflammation and hypoxia and downregulated genes involved in lipid and xenobiotic metabolism. Chronic stressors activated inflammation, hypoxia and xenobiotic metabolism genes in exposed PCATS. Combined stress exerted the greatest impact on PCATS transcriptome, uniquely altering 4870 genes and regulating genes involved in lipid metabolism, inflammation and hypoxia. Epinephrine also stimulated PCATS lipolysis, while reducing leptin secretion. This study highlights how multiple stressors disrupt blubber metabolic functions, which are crucial for maintaining homeostasis during energy-demanding periods in marine mammals.