Abstract: Methods for treating diabetes by administering an inhibitor of GDF-8, or a related member of Transforming Growth Factor-beta (TGF-&bgr;) superfamily of structurally-related growth factors (e.g., GDF-11) are disclosed. Also disclosed are methods for upregulating expression of hexose transporters, such as GLUT4 and GLUT1, in a subject by administering an inhibitor of GDF-8. Also disclosed are methods for increasing glucose uptake by cells in a subject, by administering an inhibitor of GDF-8.