title: Adipocyte exosomes induce transforming growth factor beta pathway dysregulation in hepatocytes: a novel paradigm for obesity-related liver disease.
abstract: BACKGROUND
  The pathogenesis of nonalcoholic fatty liver disease (NAFLD) has been attributed to increased systemic inflammation and insulin resistance mediated by visceral adipose tissue (VAT), although the exact mechanisms are undefined. Exosomes are membrane-derived vesicles containing messenger RNA, microRNA, and proteins, which have been implicated in cancer, neurodegenerative, and autoimmune diseases, which we postulated may be involved in obesity-related diseases. We isolated exosomes from VAT, characterized their content, and identified their potential targets. Targets included the transforming growth factor beta (TGF-β) pathway, which has been linked to NAFLD. We hypothesized that adipocyte exosomes would integrate into HepG2 and hepatic stellate cell lines and cause dysregulation of the TGF-β pathway.
  
  
  METHODS
  Exosomes from VAT from obese and lean patients were isolated and fluorescently labeled, then applied to cultured hepatic cell lines. After incubation, culture slides were imaged to detect exosome uptake. In separate experiments, exosomes were applied to cultured cells and incubated 48-h. Gene expression of TGF-β pathway mediators was analyzed by polymerase chain reaction, and compared with cells, which were not exposed to exosomes.
  
  
  RESULTS
  Fluorescent-labeled exosomes integrated into both cell types and deposited in a perinuclear distribution. Exosome exposure caused increased tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and integrin ανβ-5 expression and decreased matrix metalloproteinase-7 and plasminogen activator inhibitor-1 expression in to HepG2 cells and increased expression of TIMP-1, TIMP-4, Smad-3, integrins ανβ-5 and ανβ-8, and matrix metalloproteinase-9 in hepatic stellate cells.
  
  
  CONCLUSIONS
  Exosomes from VAT integrate into liver cells and induce dysregulation of TGF-β pathway members in vitro and offers an intriguing possibility for the pathogenesis of NAFLD.
authors.affiliation: Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Medical Center, Washington, DC.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Koeck
authors.affiliation: Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Medical Center, Washington, DC.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Iordanskaia
authors.affiliation: Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Medical Center, Washington, DC.
authors.forename: Samantha
authors.initials: S
authors.lastname: Sevilla
authors.affiliation: Department of Integrative Systems Biology, George Washington University School of Medicine and Health Sciences, Washington, DC; Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Ferrante
authors.affiliation: Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Medical Center, Washington, DC; Department of Integrative Systems Biology, George Washington University School of Medicine and Health Sciences, Washington, DC; Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC.
authors.forename: Monica J
authors.initials: MJ
authors.lastname: Hubal
authors.affiliation: Department of Integrative Systems Biology, George Washington University School of Medicine and Health Sciences, Washington, DC; Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC; Division of Emergency Medicine, Children's National Medical Center, Washington, DC.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Freishtat
authors.affiliation: Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Medical Center, Washington, DC; Department of Integrative Systems Biology, George Washington University School of Medicine and Health Sciences, Washington, DC. Electronic address: enadler@childrensnational.org.
authors.forename: Evan P
authors.initials: EP
authors.lastname: Nadler
mesh_terms: D017667:Adipocytes / Q000378:metabolism* / Q000473:pathology; D000293:Adolescent; D055354:Exosomes / Q000378:metabolism*; D005260:Female; D056945:Hep G2 Cells; D055166:Hepatic Stellate Cells / Q000378:metabolism / Q000473:pathology; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D016023:Integrins / Q000378:metabolism; D050152:Intra-Abdominal Fat / Q000378:metabolism / Q000473:pathology; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism; D065626:Non-alcoholic Fatty Liver Disease / Q000378:metabolism* / Q000473:pathology; D009765:Obesity / Q000378:metabolism* / Q000473:pathology; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D019030:Receptors, Vitronectin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051900:Smad3 Protein / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D000097792:Tissue Inhibitor of Metalloproteinase-4
chemical_list: D016023:Integrins; D020783:Matrix Metalloproteinase 7; D017395:Plasminogen Activator Inhibitor 1; D019030:Receptors, Vitronectin; D051900:Smad3 Protein; D019715:Tissue Inhibitor of Metalloproteinase-1; D019714:Tissue Inhibitor of Metalloproteinases; D053773:Transforming Growth Factor beta1; D000097792:Tissue Inhibitor of Metalloproteinase-4; C051321:SERPINE1 protein, human; C497790:SMAD3 protein, human; C560822:TIMP1 protein, human; C064660:integrin alphaVbeta5; C403414:integrin alphavbeta8; C060932:MMP7 protein, human
keywords: Exosomes; Factor beta; Nonalcoholic fatty liver disease; Obesity; Pediatric surgery; Transforming growth