title: Ethanol inhibits leptin-induced STAT3 activation in Huh7 cells.
abstract: Leptin, an adipocyte-derived hormone, regulates food intake and energy expenditure in the hypothalamus via its receptor, member of the class I cytokine receptor family. Leptin resistance has been observed in rodents and in humans. However, the mechanisms could not be explained in most cases of human obesity, except for rare cases with mutations in the leptin receptor. Recent reports demonstrated that ethanol inhibited the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway activated by some members of the class I cytokine receptor family. In this study, we examined the effects of ethanol on the leptin-induced JAK/STAT signaling pathway using human hepatoma cell lines transiently expressing long form of the leptin receptor. A 30 min pretreatment with ethanol dose-dependently inhibited the leptin-induced STAT3 phosphorylation. Furthermore, to determine the time course of ethanol inhibitory effects, the cells were incubated in 10 mM ethanol for various times. Partial inhibition of leptin-induced STAT3 activation was seen after 1 min of treatment with ethanol and completely inhibited after 30 min pretreatment. SB 202190, a p38 mitogen-activated protein kinase (MAPK) inhibitor, partly prevented this inhibition by ethanol of leptin-induced STAT3 activation. These findings suggest that ethanol time- and dose-dependently inhibits the leptin action, in part via p38 MAPK.
authors.affiliation: First Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, 852-8501, Nagasaki, Japan.
authors.forename: Mikako
authors.initials: M
authors.lastname: Degawa-Yamauchi
authors.forename: Shigeo
authors.initials: S
authors.lastname: Uotani
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Ryoko
authors.initials: R
authors.lastname: Takahashi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Abe
authors.forename: Hironaga
authors.initials: H
authors.lastname: Kuwahara
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamasaki
authors.forename: Katsumi
authors.initials: K
authors.lastname: Eguchi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D053614:Janus Kinase 2; D020738:Leptin / Q000494:pharmacology*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C515448:LEPR protein, human; D020738:Leptin; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; C515447:leptin receptor, mouse; D000431:Ethanol; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2