The effect of adipose cell size on the measurement of GLUT 4 in white adipose tissue of obese mice

RESUMO

Glucose transporter (GLUT 4) was assessed in subcellular membrane fractions of white adipose tissue (WAT) from obese insulin-resistant aurothioglucose (AuTG)- or monosodium glutamate (MSG)-treated mice. Obesitywas demonstrable by increased body weight and/ or Lee index, as well as by the heavier WAT and brown adipose tissue in relation to similar weights of gastrocnemius and heart. In vivo insulin-resistance in obese animals was suggested by moderate hyperglycemia and severe hyperinsulinemia. Morphological analyses of adipose cells showed a > 10-fold increase in cell volume of obese mice. Subcellular fractionation indicated a reduced (P<0.01) protein membrane content in the fat-free extract (FFE) from obese mice. However, the specific activity of 5'nucleotidase, a plasma membrane (PM) marker, in EFE and PM did not differ among groups. In addition, the total PM enzyme activity per unit of cell surface area was also unchanged. The GLUT 4 content, assessed by Western blotting and expressed per µg membrane protein, was reduced by ~50 percent (P<0.01) in all membrane fractions from obese animals. However, the total FFE GLUT 4 content per cell was increased...