Leptin is an essential hormone for the regulation of energy metabolism and food intake in vertebrate animals. To better understand the physiological roles of leptin in nutrient regulation in paternal ovoviviparous fish (family Syngnathidae), the present study cloned the full-length of leptin-a and leptin receptor (lepr) genes in lined seahorse Hippocampus erectus. Results showed that there was a 576-bp intron between two exons in leptin-a gene but no leptin-b gene in seahorse. Although the primary amino acid sequence conservation of seahorse leptin-a was very low, the 3-D structure modeling of seahorse leptin-a revealed strong conservation of tertiary structure with other vertebrates. Seahorse leptin-a mRNA was highly expressed in brain, whereas lepr mRNA was mainly expressed in ovary and gill. Interestingly, both leptin-a and lepr mRNA were expressed in the brood pouch of male seahorse, suggesting leptin system plays roles during the male-pregnancy. Physiological experiments showed that the expression of hepatic leptin-a and lepr mRNA in unfed seahorses was significantly higher than that in those fed 100% as well as 60% of their food during fasting stage, showing that seahorse might initiate the leptin system regulate its energy metabolism while starving. Moreover, the expression of leptin-a in brood pouch of pregnant seahorse was significantly upregulated compared with non-pregnant seahorse, whereas the expression of lepr was downregulated, suggesting that leptin system might be involved in the male-pregnancy. In conclusion, the leptin system plays roles in the energy metabolism and food intake and might provide new insights into molecular regulation of male-pregnancy in seahorse.
- Received July 14, 2016.
- Accepted September 5, 2016.
- © 2016. Published by The Company of Biologists Ltd
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