Leptin Stimulates Prolactin mRNA Expression in the Goldfish Pituitary through a Combination of the PI3K/Akt/mTOR, MKK/pMAPK and MEK/ERK Signalling Pathways.
Journal:
International journal of molecular sciences
PMID:
29261147
Abstract
Leptin actions at the pituitary level have been extensively investigated in mammalian species, but remain insufficiently characterized in lower vertebrates, especially in teleost fish. Prolactin (PRL) is a pituitary hormone of central importance to osmoregulation in fish. Using goldfish as a model, we examined the global and brain-pituitary distribution of a leptin receptor (lepR) and examined the relationship between expression of and major pituitary hormones in different pituitary regions. The effects of recombinant goldfish leptin-AI and leptin-AII on mRNA expression in the pituitary were further analysed, and the mechanisms underlying signal transduction for leptin-induced expression were determined by pharmacological approaches. Our results showed that goldfish is abundantly expressed in the brain-pituitary regions, with highly overlapping transcripts within the pituitary. Recombinant goldfish leptin-AI and leptin-AII proteins could stimulate mRNA expression in dose- and time-dependent manners in the goldfish pituitary, by both intraperitoneal injection and primary cell incubation approaches. Moreover, the PI3K/Akt/mTOR, MKK/pMAPK, and MEK/ERK-but not JAK2/STAT 1, 3 and 5 cascades-were involved in leptin-induced mRNA expression in the goldfish pituitary.