Meeting Abstract
Anthropogenic disturbance in marine ecosystems can impact the health and survival of marine mammals. Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, resulting in increased circulating glucocorticoids, which alter expression of target genes such as metabolic enzymes. Prolonged or repeated stress may increase catabolism of nutrient stores and suppress immune and reproductive functions, impacting fitness. Our objective was to develop a biomarker panel of stress that can discriminate between acute and chronic stress states in marine mammals. We previously characterized endocrine and metabolic profiles and identified genes differentially expressed in blubber in response to repeated adrenocorticotropic hormone (ACTH) administration in juvenile northern elephant seals. Upregulated genes included those encoding lipid particle proteins, adipokines, and antioxidant and lipid metabolism enzymes, while downregulated genes included inhibitors of adipogenesis, gluconeogenesis and inflammation. To validate our biomarker panel, we collected blood and blubber samples from elephant seals of varying body condition and baseline stress states. We measured endocrine (cortisol, aldosterone, total T3, reverse T3) and metabolic (triglyceride) markers in blood using immunoassays and colorimetric assays and candidate gene expression in blubber using RT-qPCR. Gene expression levels were significantly correlated with elevated stress hormones, decreased triglycerides and lower body condition index. These markers provide insights into molecular mediators of the stress response and comprise a potential diagnostic panel for differentiating stress states in marine mammals.
