Metabolic Gene Expression in Blubber of Fasting Elephant Seals

Marine mammals such as elephant seals (Mirounga angustirostris) routinely fast from food for months while undergoing energetically demanding processes such as molting and reproduction on land. To gain insights into energy homeostasis during fasting, we used quantitative PCR to examine target gene expression in energy­rich blubber tissue collected from elephant seals at the beginning and end of their fasting periods. DNA sequences of transcription factors that regulate lipid metabolism and adipogenesis (FOXO1, DDIT4, PPARG, CEBPD, PGC1, SREBP1), metabolic enzymes (LPL), fatty acid transporters (FABP4), adipokines (LEP, ADIPOQ, RBP4, ANGPTL4), and hormone receptors (ADIPOR1, ADIPOR2, GHR) were identified in a previous elephant seal blubber transcriptome and used to design primers for targeted qPCR assays, with YHWAZ as the reference gene. We found that expression of enzymes such as lipoprotein lipase (LPL) increased, while expression of catabolic regulators such as forkead box protein O1 (FOXO1) decreased during fasting (p \u3c 0.05), suggesting that elephant seals tightly regulate lipid stores and their metabolism in blubber tissue during prolonged fasts