The gyk-foxq1 regulatory axis serves as a novel target and provides a breeding indicator for glucose homeostasis regulation in Micropterus salmoides

Improving farmed fish carbohydrate utilization reduces the feed fish meal level and lessens water pollution. Herein, the effects of glycerol kinase (gyk) and forkhead box (fox)-q1 on Micropterus salmoides glucose homeostasis were investigated, and a growth-linked marker in gyk on a carbohydrate-rich diet was developed. The data showed that gyk and foxq1 expression is negatively correlated with plasma glucose level. Although gyk and foxq1 showed no effect on plasma triglyceride, Cholesterol, low-density lipoprotein Cholesterol, high-density lipoprotein Cholesterol, hepatic triglyceride, and muscular triglyceride content, positive regulation of Insulin secretion, hepatic glycogen, and muscular glycogen level was observed. Overexpression and shRNA-mediated knockdown assays indicated that gyk and foxq1 positively regulate hepatic and muscular gene expression involved in triglyceride synthesis (fatty acid synthetase, Acetyl-CoA Carboxylase), glycolysis (phosphofructokinase, Glucokinase), glycogen synthesis (glycogen synthase), and pentose phosphate pathway (glucose-6-phosphate dehydrogenase), but negatively regulate gluconeogenesis gene (phosphoenolpyruvate carboxykinase, glucose-6-phosphatase). In vitro, - 1652 ~ - 2056 bp was determined to be the core promoter sequence of gyk using progressive deletion. Luciferase activity showed that gyk promoter activity decreased following foxq1 binding site mutation in this sequence, and it was enhanced by foxq1 overexpression. Moreover, foxq1 inhibition attenuated hypoglycemia induced by gyk overexpression, and its suppression relieved the increase in gyk-mediated plasma glucose. Besides, an insertion-deletion marker located at rs16857996 in gyk was developed. Individuals without deletion (aaaac) of this site had higher body weight, full length, and body length. This regulatory axis provides a theoretical target and breeding indicator for increasing carbohydrate utilization and reducing the dietary fish meal in M. salmoides.

Micropterus salmoides; Foxq1; Glucose homeostasis; Gyk; Indel marker.