Cloning of grass carp (Ctenopharyngodon idella) SGLT1/2 genes and effect of glucose on its mRNA expression

As the co-transporters, SGLTs (Sodium-glucose co-transporters) play a pivotal role in the absorption of the substances. As the important member of SGLTs, SGLT1 and SGLT2 are involved in keeping blood glucose homeostasis by regulation of glucose uptake. To investigate the role of SGLT1 and SGLT2 in the glucose uptake of grass carp (Ctenopharyngodon idella), a series of experiments were performed. In this study, the C. idella sglt1 and sglt2 were cloned in foregut and kidney by RT-PCR, and the sequences were analyzed by bioinformatics and the mRNA expressions were detected by real-time PCR. The results showed that the ORF of C. idella sglt1 and sglt2 were 1 977 and 1 989 bp, which encode 658 and 662 amino acids. Based on amino acids sequence, the structure of SGLT1 and SGLT2 protein were 14 transmembrane, and the results of sequence alignment and phylogenetic tree showed that the C. idella SGLT1 and SGLT2 proteins were closest to those of Carassius auratus and Sinocyclocheilus grahami. The real-time PCR results indicated that the higher expression of sglt1 was in the intestine and kidney, and the low expression of sglt1 was in other tissues of C. idella. The higher expression of sglt2 was in the kidney, and the low expression of sglt2 was in other tissues of C. idella. In OGTT experiment, the sglt1 mRNA expression was significantly increased in C. idella foregut, and the sglt2 mRNA expression was markedly increased in C. idella kidney by glucose treatment for 1 h. In in vitro experiment, the sglt1 and sglt2 mRNA expressions were markedly increased in the CIK cells by glucose treatment. In conclusion, the C. idella sglt1/2 were cloned and played a role in glucose uptake. The results will provide the data basis for consummating SGLTs functions and theoretical foundation for investigating the regulation of glucose homeostasis in fish.