IN-VIVO EFFECTS OF DEXAMETHASONE AND SUCROSE ON GLUCOSE-TRANSPORT (GLUT-4) PROTEIN TISSUE DISTRIBUTION

Tissue-specific changes in GLUT-4 were compared in the following three different rat models by inducing varying degrees of hyperinsulinemia with or without hyper glycemia and hypertriglyceridemia: 1) sucrose fe eding (Suc), 2) subcutaneous dexamethasone administration (Dex), and 3 ) a combination of both treatments (Dex/Suc). Suc raised circulatory i nsulin and triglyceride levels without affecting plasma glucose, where as both Lex and Dex/Suc induced significant hyperinsulinemia, hypergly cemia, and hypertriglyceridemia. In adipocytes and skeletal muscle, Su c feeding was not associated with any change in total cellular GLUT-4 levels. However, Suc induced a sevenfold increase in fat cell plasma m embrane GLUT-4 levels in the basal state and inhibited GLUT-4 transloc ation in response to insulin. Administration of Dex or Dex/Suc diminis hed GLUT-4 expression in fat cells, increased it in skeletal muscle, b ut did not induce any change in heart. Similar to Suc feeding, Dex and Dex/Suc also increased the amount of GLUT-4 detected at the plasma me mbrane of adipocytes in the basal state and inhibited GLUT-4 transloca tion in response to insulin. These results emphasize the specific regu lation of GLUT-4 in insulin-sensitive tissues.