Kaczmarczyk S J, Andrikopoulos S, Favaloro J, Domenighetti A A, Dunn A, Ernst M, Grail D, Fodero-Tavoletti M, Huggins C E, Delbridge L M, Zajac J D, Proietto J
University of Melbourne, Department of Medicine, The Royal Melbourne Hospital, Parkville, VIC 3050, Australia.
J Mol Endocrinol. 2003 Dec;31(3):449-59. doi: 10.1677/jme.0.0310449.
The aim of this study was to investigate the metabolic and structural consequences of a decrease in glucose transporter-4 (GLUT4) levels on the heart. The CreLoxP system was utilised to delete GLUT4 in muscle tIssue including heart. The presence of the PGK-neoR cassette in the GLUT4-Lox mice resulted in reduced expression in all tIssues to levels 15-30% of wild-type control mice. In mice expressing Cre recombinase, there was a further reduction of GLUT4 in cardiac tIssue to almost undetectable levels. Cardiac glucose uptake was measured basally and during a euglycaemic/hyperinsulinaemic clamp using 2-deoxy-[1-(14)C]glucose. Insulin-stimulated glucose uptake was normal in hearts expressing 15% of normal GLUT4 levels but markedly reduced in mice with more profound reduction in GLUT4. Cardiac enlargement occurred only when GLUT4 levels were less than 5% of normal values. In heart there is a threshold level of GLUT4 above which insulin-stimulated glucose uptake is maintained. As little as 5% of normal GLUT4 levels expressed in heart is sufficient to prevent the development of cardiac hypertrophy.
