Targeted disruption of the adipocyte lipid-binding protein (aP2 protein) gene impairs fat cell lipolysis and increases cellular fatty acid levels

• Published in: Journal of lipid research Vol. 40; no. 5; pp. 967 - 972
• Main Authors: Coe, N R, Simpson, M A, Bernlohr, D A
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01-05-1999
• Subjects: adipocyte; Adipocytes - metabolism; Animals; Carrier Proteins - genetics; Carrier Proteins - metabolism; fatty acid; Fatty Acid-Binding Protein 7; Fatty Acid-Binding Proteins; Fatty Acids - metabolism; Fatty Acids, Nonesterified - metabolism; Keratinocytes - metabolism; lipid binding proteins; lipolysis; Lipolysis - genetics; Lipolysis - physiology; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Myelin P2 Protein - genetics; Myelin P2 Protein - metabolism; Neoplasm Proteins; Nerve Tissue Proteins; RNA, Messenger - genetics; RNA, Messenger - metabolism
• ISSN: 0022-2275
• DOI: 10.1016/s0022-2275(20)32133-7

The availability of mice containing an adipocyte lipid-binding protein (ALBP/aP2) gene disruption allowed for a direct examination of the presumed role of lipid-binding proteins in the mobilization and trafficking of intracellular fatty acids. Total body and epididymal fat pad weights, as well as adipose cell morphology, were unaltered in male ALBP/aP2 disrupted mice when compared to their wild-type littermates. Analysis of adipocytes isolated from wild-type and ALBP/aP2 null mice revealed that a selective 40- and 13-fold increase in the level of the keratinocyte lipid-binding protein (KLBP) mRNA and protein, respectively, accompanied the ALBP/aP2 gene disruption. Although KLBP protein was significantly up-regulated, the total lipid-binding protein level decreased 8 -fold as a consequence of the disruption. There was no appreciable difference in the rate of fatty acid influx or esterification in adipocytes of wild-type and ALBP/aP2 null animals. To the contrary, basal lipolysis decreased approximately 40% in ALBP/aP2 nulls as compared to wild-type littermates. The glycerol release from isproterenol-stimulated ALBP/aP2 null fat cells was similarly reduced by approximately 35%. Consistent with a decrease in basal efflux, the non-esterified fatty acid (NEFA) level was nearly 3-fold greater in adipocytes from ALBP/aP2 nulls as compared to wild-type animals. The significant decrease in both basal and isoproterenol-stimulated lipolysis in adipose tissue of ALBP/aP2 null mice supports the model whereby intracellular lipid-binding proteins function as lipid chaperones, facilitating the movement of fatty acids out of the fat cell.