Meeting Abstract
Adipose tissue is a complex energy storage and endocrine organ that regulates metabolic homeostasis via adipocyte-derived hormones (adipokines). Excess adiposity in humans is correlated with increased adipokine levels, insulin resistance, and inflammation, and is a major risk factor for metabolic pathologies. With some of the largest subcutaneous adipose stores in the animal kingdom, marine mammals may provide valuable insights into the role of adipose tissue in health and disease. Capital breeding marine mammals rely on lipid stores in blubber to sustain fasting periods associated with terrestrial breeding and migration. Northern elephant seals (Mirounga angustirostris) undergo two annual fasts during breeding and molting haul-outs, losing up to half of their fat mass over a period of 1-3 months while maintaining high circulating fatty acid and glucose levels and insulin resistance, similarly to obese humans. We examined changes in expression of genes associated with obesity in humans in blubber of fasting adult female elephant seals using quantitative PCR. Target genes included leptin, adiponectin, resistin, retinol-binding protein 4, and visfatin, among others. Normalized gene expression values were compared between early breeding, late breeding, early molting, and late molting groups using linear mixed models. Expression values were significantly different between groups and the majority of adipokine genes were upregulated in late fasting compared with early fasting seals, despite a concomitant decline in fat mass. This suggests a mechanism by which elephant seals maintain insulin resistance and lipid oxidation during fasting periods characterized by high energy expenditure, and provides insights into rapid weight gain and loss in mammals.
