Decreased glucose transporter (GLUT 4) content in insulin-sensitive tissues of obese aurothioglucose- and monosodium glutamate-treated mice.
We assessed the content of two isoforms of glucose transporter (GLUT 1 and GLUT 4) in insulin-sensitive tissues of hypothalamic obese mice treated with either aurothioglucose (AuTG) or monosodium glutamate (MSG). The animals were studied when obesity had reached a plateau, and they were clearly insulin resistant. We studied different membrane fractions from white adipose tissue (WAT), such as fat-free extract (FFE), plasma membrane (PM) and microsomal (M) fractions. GLUT 4 expressed per protein content displayed a decrease of 50% (p < 0.001) in all membrane fractions of AuTG- and MSG-treated mice. The PM GLUT 4 content, expressed per cell surface area, was reduced by 70% (p < 0.001) in obese mice, and the total FFE GLUT 4, expressed per total fat mass, was 5 times reduced in obese mice. Compared to control mice, obese mice showed a reduction (p < 0.01) of the GLUT 4 amount by 30% (AuTG) and by 40% (MSG) in total membrane fraction (TM) of skeletal and cardiac muscles. Similarly, a reduction of the GLUT 4 amount by 40% (AuTG) and by 45% (MSG) in FFE of brown adipose tissue was observed. The GLUT 1 content in FFE of WAT and TM of skeletal muscle showed no significant difference among the different animal groups. These results confirm a decreased expression of GLUT 4, but not of GLUT 1, in insulin-sensitive tissues, which may contribute to the impaired glucose utilization in these obese animals.
Machado
U F
UF
Department of Biochemistry, Faculty of Veterinary Medicine, Hokkaido University, Japan.
Shimizu
Y
Y
Saito
M
M
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D006051:Aurothioglucose / Q000494:pharmacology*; D015153:Blotting, Western; D005260:Female; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009765:Obesity / Q000378:metabolism*; D011247:Pregnancy; D012970:Sodium Glutamate / Q000494:pharmacology*
D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; D006051:Aurothioglucose; D012970:Sodium Glutamate