title: In vivo and ex vivo regulation of visfatin production by leptin in human and murine adipose tissue: role of mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways.
abstract: Visfatin is an adipogenic adipokine with increased levels in obesity, properties common to leptin. Thus, leptin may modulate visfatin production in adipose tissue (AT). Therefore, we investigated the effects of leptin on visfatin levels in 3T3-L1 adipocytes and human/murine AT, with or without a leptin antagonist. The potential signaling pathways and mechanisms regulating visfatin production in AT was also studied. Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of visfatin. ELISA was performed to measure visfatin levels in conditioned media of AT explants, and small interfering RNA technology was used to reduce leptin receptor expression. Leptin significantly (P < 0.01) increased visfatin levels in human and murine AT with a maximal response at leptin 10(-9) M, returning to baseline at leptin 10(-7) M. Importantly, ip leptin administration to C57BL/6 ob/ob mice further supported leptin-induced visfatin protein production in omental AT (P < 0.05). Additionally, soluble leptin receptor levels rose with concentration dependency to a maximal response at leptin 10(-7) M (P < 0.01). The use of a leptin antagonist negated the induction of visfatin and soluble leptin receptor by leptin. Furthermore, leptin-induced visfatin production was significantly decreased in the presence of MAPK and phosphatidylinositol 3-kinase inhibitors. Also, when the leptin receptor gene was knocked down using small interfering RNA, leptin-induced visfatin expression was significantly decreased. Thus, leptin increases visfatin production in AT in vivo and ex vivo via pathways involving MAPK and phosphatidylinositol 3-kinase signaling. The pleiotropic effects of leptin may be partially mediated by visfatin.
authors.affiliation: Endocrinology and Metabolism Group, Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom. b.k.tan.1@warwick.ac.uk
authors.forename: Bee K
authors.initials: BK
authors.lastname: Tan
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: James
authors.initials: J
authors.lastname: Brown
authors.forename: Raghu
authors.initials: R
authors.lastname: Adya
authors.forename: Manjunath
authors.initials: M
authors.lastname: Ramanjaneya
authors.forename: Vinod
authors.initials: V
authors.lastname: Menon
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Bailey
authors.forename: Hendrik
authors.initials: H
authors.lastname: Lehnert
authors.forename: Harpal S
authors.initials: HS
authors.lastname: Randeva
mesh_terms: D041721:3T3-L1 Cells; D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D066298:In Vitro Techniques; D020738:Leptin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009025:Morpholines / Q000494:pharmacology; D054409:Nicotinamide Phosphoribosyltransferase / Q000235:genetics / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; D054411:Receptors, Leptin / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D002070:Butadienes; D002867:Chromones; D017077:Culture Media, Conditioned; D020738:Leptin; D009025:Morpholines; D009570:Nitriles; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; D054411:Receptors, Leptin; C113580:U 0126; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D054409:Nicotinamide Phosphoribosyltransferase; D020928:Mitogen-Activated Protein Kinases