Facilitative glucose transporters (GLUT) are transmembrane transporters involved in glucose transport across the plasma membrane. In this study, blunt snout bream GLUT2 gene was cloned, and its expression in various tissues and in liver in response to diets with different carbohydrate levels (17.1; 21.8; 26.4; 32.0; 36.3; and 41.9% of dry matter). Blunt snout bream GLUT2 was also characterized. A full-length cDNA fragment of 2577 bp was cloned, which contains a 5'-untranslated region (UTR) of 73 bp, a 3'-UTR of 992 bp, and an open reading frame of 1512 bp that encodes a polypeptide of 503 amino acids with predicted molecular mass of 55.046 kDa and theoretical isoelectric point was 7.52. The predicted GLUT2 protein has 12 transmembrane domains between amino acid residues at 7-29; 71-93; 106-123; 133-155; 168-190; 195-217; 282-301; 316-338; 345-367; 377-399; 412-434; and 438-460. Besides, the conservative structure domains located at 12-477 amino acids belong to the sugar porter family which is the major facilitator superfamily (MFS) of transporters. Blunt snout bream GLUT2 had the high degree of sequence identity to four GLUT2s from zebrafish, chicken, human, and mouse, with 91, 63, 57, and 54% identity, respectively. Quantitative real-time (qRT) PCR assays revealed that GLUT2 expression was high in the liver, intestine, and kidney; highest in the liver and was regulated by carbohydrate intake. Compared with the control group (17.1%), fed by 3 h with higher starch levels (32.0; 36.3; and 41.9%), increased plasma glucose levels and glycemic level went back to basal by 24 h after treatment. Furthermore, higher dietary starch levels significantly increase GLUT2, glucokinase (GK), and pyruvate kinase (PK) expression and concurrently decrease phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6P) mRNA levels (P < 0.05), and these changes were also back to basal levels after 24 h of any dietary treatment. These results indicate that the blunt snout bream is able to regulate their ability to metabolize glucose by improving GLUT2, GK, and PK expression levels and decreasing PEPCK and G6P expression levels.

Abstract:Facilitative glucose transporters (GLUT) are transmembrane transporter of proteins involved in glucose transport across the plasma membrane. To date, there is no information about glucose transporter 2 (GLUT2) in blunt snout bream (Megalobram aamblycephala). In this study, GLUT2 were cloned and characterized from blunt snout bream, and its-expression in response to diets with different carbohydrate levels (17.1%; 21.8%; 26.4%; 32.0%; 36.3% and 41.9% of dry matter). In this study, the full-length cDNA of GLUT2 was 2577 bp, including a 5'-untranslated region (UTR) of 73 bp, a 3'-UTR of 992 bp, and an open reading frame of 1512 bp, encoding a polypeptide of 503 amino acids with predicted molecular weight of 55.046 kDa and theoretical isoelectric point of 7.52. GLUT2 has twelve across the membrane area locating at 7-29; 71-93; 106-123; 133-155; 168-190; 195-217; 282-301; 316-338; 345-367; 377-399; 412-434; 438-460 aimo acids respectively.Conservative structure domains located at 12-477 aimo acids belonging to sugar porter family major facilitator superfamily (MFS) transporter. The blunt snout bream GLUT2 showed high identity to their orthologs in other fish species and mammals. Quantitative real-time (qRT)-PCR assays revealed that GLUT2 expression was high in the liver, intestine and kidney; highest in the liver. Compared with the control group (17.1%), high dietary carbohydrate levels (32.0%; 36.3% and 41.9%) resulted in high plasma glucose at 3h after Preprints (www.preprints.org) | NOT PEER-REVIEWED |