Leptin in fish - exploring the actions of a novel hormone and its role in control of appetite, growth and puberty in Atlantic salmon and cod

In mammals, leptin is a hormone produced by adipose tissue and has been established as a key signal for regulating adiposity. Until last month (May 2005), when our collaborators at National Research Institute of Aquaculture, Mie Japan published their disc overy of the leptin gene and its expression in fish (Kurokawa et al. 2005), all evidence concerning the existence of leptin in fish and other poikilothermic vertebrates has been circumstantial and inconclusive (Volkoff et al. 2005). Thus, the proposed pro ject will be the first, where the physiological role of leptin can be studied in fish using methodologies based on homologous fish gene/peptide sequences. The possible elucidation of an adiposity signal in fish would have huge ramifications for the under standing of several key physiological processes such as appetite, development, growth and puberty in these species, as energy balance and fat stores are believed to be of crucial importance. If leptin in fish turns out to have a different regulatory role than in mammals, such information would be fundamental to the understanding of endocrine evolution and the regulation of energy balance among vertebrates.