Plasma FGF21 Concentrations, Adipose Fibroblast Growth Factor Receptor-1 and β-Klotho Expression Decrease with Fasting in Northern Elephant Seals

• Published in: General and Comparative Endocrinology
• Main Authors: Suzuki, Miwa, Lee, Andrew, Vázquez-Medina, Jose Pablo, Viscarra, Jose A., Crocker, Daniel E., Ortiz, Rudy M.
• Format: Text
• Language: English
• Published: 2015
• Subjects: Article; Elephant Seal; Elephant Seals
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4457680/; http://www.ncbi.nlm.nih.gov/pubmed/25857751; https://doi.org/10.1016/j.ygcen.2015.03.009

Fibroblast growth factor (FGF)-21 is secreted from the liver, pancreas, and adipose in response to prolonged fasting/starvation to facilitate lipid and glucose metabolism. Northern elephant seals naturally fast for several months, maintaining a relatively elevated metabolic rate to satisfy their energetic requirements. Thus, to better understand the impact of prolonged food deprivation on FGF21-associated changes, we analyzed the expression of FGF21, FGF receptor-1 (FGFR1), β-klotho (KLB; a co-activator of FGFR) in adipose, and plasma FGF21, glucose and 3-hydroxybutyrate in fasted elephant seal pups. Expression of FGFR1 and KLB mRNA decreased 98% and 43%, respectively, with fasting duration. While the 80% decrease in mean adipose FGF21 mRNA expression with fasting did not reach statistical significance, it paralleled the 39% decrease in plasma FGF21 concentrations suggesting that FGF21 is suppressed with fasting in elephant seals. Data demonstrate an atypical response of FGF21 to prolonged fasting in a mammal suggesting that FGF21-mediated mechanisms have evolved differentially in elephant seals. Furthermore, the typical fasting-induced, FGF21-mediated actions such as the inhibition of lipolysis in adipose may not be required in elephant seals as part of a naturally adapted mechanism to support their unique metabolic demands during prolonged fasting.