Increased lipolysis in transgenic animals overexpressing the epithelial fatty acid binding protein in adipose cells.
Fatty acid binding proteins (FABPs) are low-molecular-mass, soluble, intracellular lipid carriers. Previous studies on adipocytes from adipocyte fatty acid binding protein (A-FABP)-deficient mice have revealed that both basal and isoproterenol-stimulated lipolysis were markedly reduced (Coe et al. 1999. J. Lipid Res. 40: 967-972). Herein, we report the construction of transgenic mice overexpressing the FABP5 gene encoding the epithelial fatty acid binding protein (E-FABP) in adipocytes, thereby allowing evaluation of the effects on lipolysis of increased FABP levels and of type specificity. In adipocytes from FABP5 transgenic mice, the total FABP protein level in the adipocyte was increased to 150% as compared to the wild type due to a 10-fold increase in the level of E-FABP and an unanticipated 2-fold down-regulation of the A-FABP. There were no significant differences in body weight, serum FFA, or fat pad mass between wild-type and FABP5 transgenic mice. Importantly, both basal and hormone-stimulated lipolysis increased in adipocytes from the FABP5 transgenic animals. The molecular composition of the fatty acid pool from either the intracellular compartment or that effluxed from the adipocyte was unaltered. These results demonstrate that there is a positive relationship between lipolysis and the total level of FABP but not between lipolysis and a specific FABP type.
Hertzel
Ann Vogel
AV
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455, USA.
Bennaars-Eiden
Assumpta
A
Bernlohr
David A
DA
D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002849:Chromatography, Gas; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D007545:Isoproterenol / Q000378:metabolism; D050356:Lipid Metabolism; D008066:Lipolysis / Q000235:genetics* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011401:Promoter Regions, Genetic
D002352:Carrier Proteins; C082667:Fabp5 protein, mouse; C086936:Fabp7 protein, mouse; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D007545:Isoproterenol