Meeting Abstract
2.7 Jan. 4 Leptin enhances growth and development under disease exposure in Xenopus laevis tadpoles HICKS-COURANT, Miranda L.*; CRESPI, Erica J.; Vassar College mihickscourant@vassar.edu
Leptin is a cytokine hormone that is best known for regulating food intake, energy expenditure, and reproduction, but recent studies have shown that it also affects immune response in mammals. While leptin has evolutionarily conserved energy balance functions in amphibians, it is unknown if leptin also plays a role in immune function, or when its role in immune function develops. We tested the hypothesis that leptin facilitates immune responses in amphibians and that this function develops during larval stages. First, we used RT-PCR to show that the leptin receptor is expressed in the spleen of Xenopus laevis tadpoles and juveniles. Because the spleen is the main site of lymphocyte production, this result supports a potential role of leptin signaling in immune function in amphibians. We then conducted two experiments in which tadpoles were exposed to a gram-negative bacterial pathogen to determine if intra-peritoneum injections of recombinant Xenopus leptin into X. laevis tadpoles would enhance survivorship, growth, and development. We found that leptin injections significantly increased survival in tadpoles exposed to high concentrations of bacteria in aquarium water relative to the saline-injected tadpoles (ANOVA p = 0.001). In a subsequent experiment in which tadpoles were exposed to a weaker bacterial dose, leptin injections facilitated growth and development while saline-injected tadpoles significantly lost weight and slowed development relative to non-injected tadpoles. These data show that elevated leptin levels enhance growth, development, and survival during an infection, although we cannot determine the specific mechanism of leptin action at this time. Furthermore, our results support a novel role of leptin as a growth factor during early development that may also be important in humans and other mammals.
