Meeting Abstract

140.2  Monday, Jan. 7  Impact of nutritional status on ghrelin and growth hormone in phocid seal pups DAILEY, R.E.*; RICHMOND, J.P.; University of North Florida, Jacksonville; University of North Florida, Jacksonville rachael.dailey@unf.edu

Marine mammals have unique metabolic demands related to adipose accretion, yet previous studies show metabolic hormones involved in nutrient partitioning follow similar patterns to terrestrial mammals. Growth hormone (GH) and other components of the somatotropic axis promote growth, regulate nutrient partitioning, and are responsive to nutrient intake. In terrestrial mammals, GH increases with undernutrition, decreases with refeeding, and inhibits adipose accretion. Ghrelin responds similarly to GH with changes in nutrient intake, but has the opposite effect on adipose. Given this promotion of adiposity and the importance of adipose to marine mammals, we hypothesized that ghrelin may have a differential response to increased nutrient intake in marine mammals. This longitudinal study quantified ghrelin and GH from a fasted state through refeeding in harbor seal (n=10) and northern elephant seal (n=9) pups bi-weekly for 8 weeks. Body condition increased during refeeding (p < 0.005), reflecting lean tissue growth and adipose accretion. Surprisingly, ghrelin concentrations increased upon refeeding in both species (p < 0.05). However, in northern elephant seals ghrelin increased at week 2 (p < 0.001) while in harbor seals ghrelin increased at week 4 (p < 0.05). As expected, GH concentrations decreased throughout refeeding for both species (p < 0.01). While reduced GH concentrations favor adipose accretion, the atypical response of ghrelin may be a mechanism for promoting rapid compensatory deposition of lipids after fasting. Because significant adipose accretion is vital for survival in pinnipeds, this response to refeeding could be an adaptation to preferentially allocate nutrients to adipose when faced with nutritional challenges.