GLUT8 is a glucose transporter responsible for insulin-stimulated glucose uptake in the blastocyst

Mammalian preimplantation blastocysts exhibit insulin-stimulated glucose up take despite the absence of the only known insulin-regulated transporter, G LUT4, We describe a previously unidentified member of the mammalian facilit ative GLUT superfamily that exhibits approximate to 20-25% identity with ot her murine facilitative GLUTs. Insulin induces a change in the intracellula r localization of this protein, which translates into increased glucose upt ake into the blastocyst. a process that is inhibited by antisense oligoprob es. Presence of this transporter may be necessary for successful blastocyst development, fuel metabolism, and subsequent implantation. Moreover, the e xistence of an alternative transporter may explain examples in other tissue s of insulin-regulated glucose transport in the absence of GLUT4.