4-BROMOCROTONIC ACID ENHANCES BASAL BUT INHIBITS INSULIN-STIMULATED GLUCOSE-TRANSPORT IN 3T3-L1 ADIPOCYTES

Inhibitors of fatty acid oxidation, 2-bromopalmitic acid (Br-C16) and 4-bromocrotonic acid (Br-C4) were examined for their effect on glucose transport in 3T3-L1 adipocytes. Whereas Br-C16 was without effect, Br -C4 augmented basal but inhibited insulin-stimulated a-deoxyglucose up take in a dose-and time-dependent manner. Immunoblot analysis indicate d that following Br-C4 pretreatment, the content of GLUT1 in plasma me mbranes was increased whereas insulin-induced translocation of GLUT4 w as greatly eliminated. The total cellular amount of GLUT1 or GLUT4, on the other hand, was not altered. Thus these results seem to suggest t hat Br-C4 has opposite effect on basal and insulin-stimulated glucose transport by a mechanism other than its inhibition of fatty acid oxida tion. The translocation processes for both GLUT1 and GLUT4 transporter s appears to be altered. (C) 1998 Academic Press.