Meeting Abstract

P2.152  Tuesday, Jan. 5  Adiposity, development and lactation impact responses to glucagon in northern elephant seals FOWLER, Melinda, A.*; CHAMPAGNE, Cory, D.; HOUSER, Dorian, S.; CROCKER, Daniel, E.; University of California, Santa Cruz; University of California, Santa Cruz; Sonoma State University; Sonoma State University mfowler@biology.ucsc.edu

Northern elephant seals, Mirounga angustirostris, fast while lactating, creating a metabolic conflict between the energy demands of lactogenesis and the energy-conserving physiological mechanisms associated with fasting. One important constraint on the ability to fast while lactating is the need to provide carbohydrate for glucose-dependent tissues while sparing lean body tissues, yet our previous investigations revealed high rates of glucose production throughout lactation. Subsequent studies revealed that the insulin response to a glucose challenge declined with adipose tissue reserves across lactation suggesting progressive insulin insensitivity. We challenged lactating and molting females with pharmacological doses of glucagon, a gluconeogenic hormone, to better understand hormonal regulation of glucose production. This study revealed a moderate, delayed, monophasic increase in plasma glucose levels, the magnitude of which declined with adipose tissue reserves and became negligible late in lactation. Plasma glucose directly varied with elevations in plasma urea nitrogen, suggesting that glucagon enhanced gluconeogenesis from amino acids. Glucagon stimulated ketogenesis, independent of adiposity or lactation status. When we repeated this study in fasting weaned pups, we found no gluconeogenic or ketogenic responses. Together these studies suggest that high rates of gluconeogenesis in fasting elephant seals involve significant glucose cycling and that hormonal regulation of glucose production during fasting varies significantly with development, adiposity and lactation status.