Characterization, phylogeny, and responses of leptin to different nutritional states in critically endangered Yangtze sturgeon (Acipenser dabryanus)

Leptin is an important energy homeostasis hormone in mammals. However, the role of leptin in energy balance of fish remains controversial. In this study, we characterized Yangtze sturgeon (Acipenser dabryanus) leptin (Adleptin) with a full-length 507 bp coding sequence (CDS) encoding 168 amino acids (aa) and we used phylogenetic analysis to identify it as leptin A. The tissue expression profiles suggested that Adleptin is widely expressed in various types of tissues, mainly in the liver. Moreover, the Adleptin level was detected during several important nutritional states. The Adleptin mRNA levels significantly increased in the liver after feeding while the levels were dramatically decreased during 10 days of fasting and increased upon refeeding. In comparison to the Tubificidae group, the Adleptin level in the formulated feed group was significantly lower on the 2nd and 5th days; after 2nd day, the level began to increase until it was significantly increased on the 8th day. These results indicate that leptin is an endocrine indicator of nutritional state in Yangtze sturgeon. This indicator can be used to monitor whether artificial nutrient conditions meet the nutritional requirements of Yangtze sturgeon and aid in developing and optimizing protection strategies for this species.