The effect of adipose cell size on the measurement of GLUT 4 in white adipose tissue of obese mice.
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. Obesity was demonstrated 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 FFE 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 microgram membrane protein, was reduced by approximately 50% (P < 0.01) in all membrane fractions from obese animals. However, the total FFE GLUT 4 content per cell was increased (P < 0.01), from 23.5 +/- 1.8 in controls to 62.4 +/- 7.6 and 47.4 +/- 5.9 cpm cell-1 10(-3) in AuTG and MSG, respectively, but the total PM GLUT 4 content per unit of cell surface area was highly reduced (P < 0.01), from 165.1 +/- 16.7 in controls to 53.8 +/- 10.9 and 32.0 +/- 5.3 cpm microns-2 10(-9) in AuTG and MSG, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brasil.
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Fabres-Machado
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Saito
D000273:Adipose Tissue / Q000737:chemistry* / Q000473:pathology*; D000818:Animals; D001835:Body Weight; D005260:Female; D051275:Glucose Transporter Type 4; D051379:Mice; D008820:Mice, Obese; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D009124:Muscle Proteins; D009765:Obesity / Q000473:pathology*; D011247:Pregnancy
D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495693:Slc2a4 protein, mouse