RESUMEN
Here we investigated the biological functions of adiponectin/ACRP30, a fat-derived hormone, by disrupting the gene that encodes it in mice. Adiponectin/ACRP30-knockout (KO) mice showed delayed clearance of free fatty acid in plasma, low levels of fatty-acid transport protein 1 (FATP-1) mRNA in muscle, high levels of tumor necrosis factor-alpha (TNF-alpha) mRNA in adipose tissue and high plasma TNF-alpha concentrations. The KO mice exhibited severe diet-induced insulin resistance with reduced insulin-receptor substrate 1 (IRS-1)-associated phosphatidylinositol 3 kinase (PI3-kinase) activity in muscle. Viral mediated adiponectin/ACRP30 expression in KO mice reversed the reduction of FATP-1 mRNA, the increase of adipose TNF-alpha mRNA and the diet-induced insulin resistance. In cultured myocytes, TNF-alpha decreased FATP-1 mRNA, IRS-1-associated PI3-kinase activity and glucose uptake, whereas adiponectin increased these parameters. Our results indicate that adiponectin/ACRP30 deficiency and high TNF-alpha levels in KO mice reduced muscle FATP-1 mRNA and IRS-1-mediated insulin signaling, resulting in severe diet-induced insulin resistance.
Asunto(s)
Dieta , Ácidos Grasos no Esterificados/sangre , Proteínas de Peces , Resistencia a la Insulina/fisiología , Péptidos y Proteínas de Señalización Intercelular , Metabolismo de los Lípidos , Proteínas/fisiología , Factor de Necrosis Tumoral alfa/genética , Adiponectina , Tejido Adiposo/metabolismo , Animales , Proteínas Portadoras/metabolismo , Células Cultivadas , Proteínas de Unión a Ácidos Grasos , Proteínas Sustrato del Receptor de Insulina , Ratones , Ratones Noqueados , Miocardio/citología , Miocardio/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Fosfoproteínas/metabolismo , Proteínas/genética , ARN Mensajero/genética , Transcripción GenéticaRESUMEN
Human GD3 synthase gene consisted of five exons and span about 135 kilobases. The 5'-flanking region lacked canonical TATA and CAAT boxes, but contained SP1 binding site(s) as in rat and mouse. The promoter activity in the 5'-flanking region (-2262 approximately +1) became definite when SV40 enhancer was added to the reporter plasmid. Luciferase assay with deletion mutants suggested the existence of a silencer region between -2262 and -978 nt similarly with those in mouse and rat. They also commonly contained a GT/CG repeat sequence at upstream of -1200 approximately -1300 nt, suggesting that they form Z-type DNA, and are involved in the gene regulation.