The insulin gene as an energy homeostasis biomarker in Yangtze sturgeon (Acipenser dabryanus)

Insulin plays an important role in maintaining energy homeostasis and has the potential to be an indicator of energy homeostasis in the Yangtze sturgeon, Acipenser dabryanus. In this study, the Yangtze sturgeon insulin (Adinsulin) was cloned and characterized. To evaluate the possibility of insulin as an energy state assessment indicator, quantification real-time PCR (qRT-PCR) was used to evaluate expression changes in different tissues (the whole brain, esophagus, cardiac stomach, pyloric stomach, pyloric caeca, duodenum, valvula intestine, rectum, liver, pancreas, spleen, kidney, heart, muscle, gill and eye) from 6 fish (average weight 325.7 ± 22.3 g) and in three experiments including postprandial, fasting and re-feeding, and glucose tolerance treatment in which fish were divided into two groups including a group that administered a glucose solution (1 ul/g body weight) and another group that administered sterile water as control. In these three experiments, 6 fish were sampled, respectively, then been used to evaluate expression changes of insulin. All fish in feeding groups were fed in tanks (60.0 cm × 50.0 cm × 40.0 cm) with a commercial diet (crude protein ≥ 40%, crude fat ≥ 12%, coarse fiber ≤ 6%, crude ash ≤ 18%; TONGWEI CO., LTD, China) once a day at 16:00. The result showed that Adinsulin was highly expressed in the pancreas, which was the basis for the next experiment to use the pancreas as the test target. Adinsulin expression significantly increased 1 h after feeding and decreased rapidly after 3 h of feeding, but it was still significantly higher than that of the group without feeding (P < 0.01). Compared to the feeding group, the expression of Adinsulin was significantly reduced in the fasting group of 3 days (P < 0.01), 6 days (P < 0.01), 10 days (P < 0.05), 11 days (P < 0.05) and 13 days (P < 0.01) and was no significant difference in re-feeding for 1st day, 2nd day and 4th day, but there was difference between re-feeding group and fasting group. After glucose tolerance treatment, serum glucose levels increased significantly (P < 0.05), accompanied by a significant increase (P < 0.001) in insulin expression. This study result shows that insulin has the capacity to measure the energy homeostasis of Yangtze sturgeon. Further development of detection methods for sturgeon plasma or serum insulin will avoid slaughtering animals and is more practical in energy homeostasis assessment.