title: A glucagon-like peptide-1 (GLP-1) analogue, liraglutide, upregulates nitric oxide production and exerts anti-inflammatory action in endothelial cells.
abstract: OBJECTIVE
  Glucagon-like peptide-1 (GLP-1), a member of the proglucagon-derived peptide family, was seen to exert favourable actions on cardiovascular function in preclinical and clinical studies. The mechanisms through which GLP-1 modulates cardiovascular function are complex and incompletely understood. We thus investigated whether the GLP-1 analogue, liraglutide, which is an acylated GLP-1, has protective effects on vascular endothelial cells.
  
  
  METHODS
  Nitrite and nitrate were measured in medium with an automated nitric oxide detector. Endothelial nitric oxide synthase (eNOS) activation was assessed by evaluating the phosphorylation status of the enzyme and evaluating eNOS activity by citrulline synthesis. Nuclear factor kappaB (NF-kappaB) activation was assessed by reporter gene assay.
  
  
  RESULTS
  Liraglutide dose-dependently increased nitric oxide production in HUVECs. It also caused eNOS phosphorylation, potentiated eNOS activity and restored the cytokine-induced downregulation of eNOS (also known as NOS3) mRNA levels, which is dependent on NF-kappaB activation. We therefore examined the effect of liraglutide on TNFalpha-induced NF-kappaB activation and NF-kappaB-dependent expression of proinflammatory genes. Liraglutide dose-dependently inhibited NF-kappaB activation and TNFalpha-induced IkappaB degradation. It also reduced TNFalpha-induced MCP-1 (also known as CCL2), VCAM1, ICAM1 and E-selectin mRNA expression. Liraglutide-induced enhancement of nitric oxide production and suppression of NF-kappaB activation were attenuated by the AMP-activated protein kinase (AMPK) inhibitor compound C or AMPK (also known as PRKAA1) small interfering RNA. Indeed, liraglutide induced phosphorylation of AMPK, which occurs through a signalling pathway independent of cyclic AMP.
  
  
  CONCLUSIONS
  Liraglutide exerts an anti-inflammatory effect on vascular endothelial cells by increasing nitric oxide production and suppressing NF-kappaB activation, partly at least through AMPK activation. These effects may explain some of the observed vasoprotective properties of liraglutide, as well as its beneficial effects on the cardiovascular system.
authors.affiliation: Department of Endocrinology and Metabolism, Dokkyo University School of Medicine, Mibu, Tochigi 321-0293, Japan. yhattori@dokkyomed.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Hattori
authors.forename: T
authors.initials: T
authors.lastname: Jojima
authors.forename: A
authors.initials: A
authors.lastname: Tomizawa
authors.forename: H
authors.initials: H
authors.lastname: Satoh
authors.forename: S
authors.initials: S
authors.lastname: Hattori
authors.forename: K
authors.initials: K
authors.lastname: Kasai
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1 / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D000069450:Liraglutide; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000235:genetics; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D016207:Cytokines; D052002:NF-kappa B p50 Subunit; C489548:NFKB1 protein, human; D009569:Nitric Oxide; D000069450:Liraglutide; D052216:Glucagon-Like Peptide 1; D052250:Nitric Oxide Synthase Type III