Abstract
ABSTRACTLeptin 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 the leptin system plays a role 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 the fasting stage, showing that seahorse might initiate the leptin system to regulate its energy metabolism while starving. Moreover, the expression of leptin-a in the brood pouch of pregnant seahorse was significantly upregulated compared with non-pregnant seahorse, whereas the expression of lepr was downregulated, suggesting that the leptin system might be involved in the male pregnancy. In conclusion, the leptin system plays a role in the energy metabolism and food intake, and might provide new insights into molecular regulation of male pregnancy in seahorse.
Highlights
Seahorses, which belong to the family Syngnathidae, are ovoviviparous fish whose embryos can obtain paternal nutrients during pregnancy through the male’s brood pouch and maternal nutrients from yolk (Foster and Vincent, 2004; Wilson et al, 2001)
The present study aimed to identify and characterize the leptin system in lined seahorse, and analyze the expression profiles of leptin system during nutrient transition and pregnant stages to detect the physiological roles of leptin system in male pregnancy species
Characterization of leptin-a and lepr genes Full-length cDNA sequences of leptin-a and lepr genes in adult seahorse were obtained through rapid amplification of cDNA ends (RACE)-PCR
Summary
Seahorses, which belong to the family Syngnathidae, are ovoviviparous fish whose embryos can obtain paternal nutrients during pregnancy through the male’s brood pouch and maternal nutrients from yolk (Foster and Vincent, 2004; Wilson et al, 2001). The molecular mechanism of energy regulation during seahorse starvation stage is still unknown. In teleosts and mammals, feeding is generally regulated by a number of peptides produced in brain and peripheral tissues, such as leptin (Schwartz et al, 2000). Leptin is an important hormone synthesized by the adipocytes which signal the peripheral energy reserves to the brain and regulate development, growth, energy metabolism and reproduction in mammals (Anubhuti and Arora, 2008). As the protein product of the obese (ob) gene, leptin is a kind of type-I cytokine hormone secreted by the adipocytes that acts upon the central nervous system to regulate food intake and energy metabolism in mammals (Morton et al, 2006). The leptin of ectotherm vertebrates, including fish, is rarely expressed in adipose tissue and is instead mainly expressed in the liver, brain and gonads in fish (Copeland et al, 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
