Meeting Abstract
P3.42 Monday, Jan. 6 15:30 Seasonality of metabolic hormones in a seasonal carnivore, the Steller sea lion Eumetopias jubatus AMATULI, KC*; ROSEN, DAS; RICHMOND, JP; University of North Florida, Jacksonville; University of British Columbia, Canada; University of North Florida, Jacksonville kris.amatuli@unf.edu
Seasonal changes in body mass, nutrient partitioning, and food intake are strongly influenced by metabolic hormones. As a part of normal life history patterns, Steller sea lions (SSL) exhibit dynamic seasonal changes in intake during the summer breeding season. Previous research found seasonality of metabolic hormones in males but not female SSL likely due to the artificially consistent feeding regime during the study. The current study investigates seasonal patterns of growth hormone (GH), insulin-like growth factor (IGF)-I, and ghrelin in adult female SSL, fed a diet reflective of normal life history patterns. Specifically, SSL were fed ad libitum during most of the year, but intake was reduced in early summer. Following increased intake in fall and winter (74575±2101kJ; p<0.01), mass was greatest in winter and spring (159.5±1.9kg; p<0.01). Known to stimulate GH release, ghrelin was positively correlated to GH (p<0.01) in the spring; however, exhibited a negative correlation in winter and fall. Ghrelin stimulates appetite, especially during periods of fasting. SSL ghrelin was negatively correlated with intake (p<0.01) in winter and spring, but positively correlated in summer and fall. IGF-I concentrations were positively correlated (p<0.01) with intake independent of season. The inverse relationship between GH and ghrelin during the breeding season likely suppresses the urge to feed (reduced ghrelin) during these extended periods of restricted intake and facilitates use of adipose for energy (increased GH). Increased ghrelin with reduced GH in the winter is likely a mechanism to facilitate winter fattening. Dynamic seasonality in metabolic hormones was observed in female SSL suggesting seasonal change in nutrient partitioning priorities.
