GLUT4 protein is differently modulated during development of obesity in monosodium glutamate-treated mice.
The aim of the present study was to investigate the GLUT4 protein expression during the development of obesity in monosodium glutamate- (MSG) treated mice. Control (C) and neonatally MSG-treated 2-month-old (2-mo), 4-month-old (4-mo) and 7-month-old (7-mo) mice were analyzed. Anthropometric data, basal glycemia and insulinemia were measured; and the GLUT4 protein was assessed by Western blotting in white adipose tissue (WAT), skeletal muscle gastrocnemius (SM) and heart (H). Compared to age-matched C mice, the 2-mo and 4-mo MSG mice were already obese, but metabolically they showed increased or preserved whole-body insulin sensitivity, respectively. At these ages they showed unchanged total GLUT4 content in SM and H. However, in plasma membrane fraction from WAT, the MSG showed increased GLUT4 content at both 2- (by 60%) and 4-month (by 45%) of age. When the GLUT4 protein was expressed by unit of adipocyte surface area the protein amount was increased by 36 and 220% in 2-mo and 4-mo MSG mice, respectively. At 7 months of age, obesity was fully established in MSG mice, showing a strongly insulin resistant condition. Additionally, in the 7-mo MSG-mice the GLUT4 protein was reduced in SM (by 40%), H (by 28%), PM and M fractions of WAT (by approximately 70%), and PM expressed by unit of adipocyte surface area (by 92%). The data demonstrate that early, during the accelerated development of obesity in MSG-treated mice, the GLUT4 content was increased in WAT, and that may play a key role in the development of obesity. Later on, when obesity is fully established, the GLUT4 protein was reduced in SM, heart and WAT, and that may be involved in the insulin resistance present in this condition.
de Carvalho Papa
Paula
P
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 1524, São Paulo (SP), 05508-900,, Brazil.
Vargas
Alessandra Martins
AM
da Silva
José Luciano Tavares
JL
Nunes
Maria Tereza
MT
Machado
Ubiratan F
UF
D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001835:Body Weight / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D006706:Homeostasis / Q000187:drug effects; D007333:Insulin Resistance; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009765:Obesity / Q000139:chemically induced* / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D012970:Sodium Glutamate; D013347:Subcellular Fractions / Q000378:metabolism
D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495693:Slc2a4 protein, mouse; D005947:Glucose; D012970:Sodium Glutamate