In mammals, the hormone leptin – produced primarily by fat cells – regulates energy balance and maintains long-term fat stores. It also has roles in maintaining glucose balance and signaling reproductive competence.
Roger Cone, Ph.D., and postdoctoral fellow Max Michel, Ph.D., explored roles for leptin in zebrafish. They discovered that zebrafish without a functional leptin receptor do not exhibit the overeating or obesity characteristic of leptin deficiency in mammals. The leptin receptor-deficient fish also have normal fertility. Defective leptin signaling in zebrafish did impact glucose homeostasis: the leptin-mutant fish had increased numbers of pancreatic beta cells and increased levels of insulin messenger RNA.
The findings, reported in the Proceedings of the National Academy of Sciences, suggest that a role for leptin in regulating beta cell mass and glucose homeostasis is conserved across vertebrates. The hormone’s regulation of fat stores may have been acquired during the evolution of mammals, the authors propose.
This research was supported by grants from the National Institutes of Health (MH065215, DK059637, DK020593).
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