Abstract To explore molecular targets for regulating glucose metabolism in carnivorous fish, the glucose tolerance test (GTT) was carried out on the Paralichthys olivaceus. The concentration of glucose and insulin in serum were measured at 0, 1, 3, 5, 7, 9, 12, 24, and 48h after intraperitoneal (IP) injecting. The concentration of insulin was the lowest after 3h of glucose injection, and that of glucose reached the highest after 5h. Therefore, 0h (IP0) was chosen as control group, 3h (IP3) and 5h (IP5) were selected as experimental groups, which the liver samples in three time points were used to high-throughput sequencing. Although, there were no significant KEGG and GO functional enrichment, the differential genes including MAPK binding protein 1 ( MAPKBP1 ), glycosyltransferase ( FNG ), suppressor of cytokine signaling 3 ( SOCS3 ), CCAAT/enhancer-binding protein alpha ( CEBP-α ) were closely related to glucose metabolism, among which SOCS3 was worthy of further explore. The full-length cDNA sequence of SOCS3 gene was cloned and the open reading frame (ORF) of SOCS3 encoded 225 amino acids including conserved domains SH2 and SOCS3-box. The results of tissue differential expression showed that SOCS3 was highly expressed in liver and intestine. The SOCS3 was knocked down by specific siRNA in the primary hepatocyte of P. olivaceus . Results showed that the gene expression of insulin receptor substrate 1 ( IRS1 ), protease B1 ( AKT1 ), glucose transporter 2 ( GLUT2 ), pyruvate kinase ( PK ) and glucokinase ( GK ) increased significantly after knocking down SOCS3 . Meanwhile, the phosphatidylinositol-3-hydroxykinase ( PI3K ) and glucose-6-phosphatase ( G6Pase) decreased significantly. The results of this study indicated that siSOSC3 enhanced the sensitivity of the insulin signaling pathway to promote glucose transport, thereby affecting gluconeogenesis and glycolysis to maintain glucose homeostasis.
Qin et al. (Fri,) studied this question.