title: APPL1 counteracts obesity-induced vascular insulin resistance and endothelial dysfunction by modulating the endothelial production of nitric oxide and endothelin-1 in mice.
abstract: OBJECTIVE
  Insulin stimulates both nitric oxide (NO)-dependent vasodilation and endothelin-1 (ET-1)-dependent vasoconstriction. However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear. This study aimed to investigate the roles of the multidomain adaptor protein APPL1 in modulating vascular actions of insulin in mice and in endothelial cells.
  
  
  METHODS
  Both APPL1 knockout mice and APPL1 transgenic mice were generated to evaluate APPL1's physiological roles in regulating vascular reactivity and insulin signaling in endothelial cells.
  
  
  RESULTS
  Insulin potently induced NO-dependent relaxations in mesenteric arteries of 8-week-old mice, whereas this effect of insulin was progressively impaired with ageing or upon development of obesity induced by high-fat diet. Transgenic expression of APPL1 prevented age- and obesity-induced impairment in insulin-induced vasodilation and reversed obesity-induced augmentation in insulin-evoked ET-1-dependent vasoconstriction. By contrast, genetic disruption of APPL1 shifted the effects of insulin from vasodilation to vasoconstriction. At the molecular level, insulin-elicited activation of protein kinase B (Akt) and endothelial NO synthase and production of NO were enhanced in APPL1 transgenic mice but were abrogated in APPL1 knockout mice. Conversely, insulin-induced extracellular signal-related kinase (ERK)1/2 phosphorylation and ET-1 expression was augmented in APPL1 knockout mice but was diminished in APPL1 transgenic mice. In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.
  
  
  CONCLUSIONS
  APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.
authors.affiliation: Department of Medicine, Division of Endocrinology and Metabolism, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Kenneth K Y
authors.initials: KK
authors.lastname: Cheng
authors.forename: Karen S L
authors.initials: KS
authors.lastname: Lam
authors.forename: Donghai
authors.initials: D
authors.lastname: Wu
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.forename: Paul M
authors.initials: PM
authors.lastname: Vanhoutte
authors.forename: Gary
authors.initials: G
authors.lastname: Sweeney
authors.forename: Yiming
authors.initials: Y
authors.lastname: Li
authors.forename: Aimin
authors.initials: A
authors.lastname: Xu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology*; D005786:Gene Expression Regulation; D020868:Gene Silencing; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D008638:Mesenteric Arteries / Q000187:drug effects / Q000503:physiopathology; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009569:Nitric Oxide / Q000378:metabolism*; D009765:Obesity / Q000503:physiopathology*; D015398:Signal Transduction / Q000187:drug effects; D014652:Vascular Diseases / Q000209:etiology / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000378:metabolism / Q000494:pharmacology; D014665:Vasodilator Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: C464801:APPL1 protein, human; D048868:Adaptor Proteins, Signal Transducing; C510733:Appl1 protein, mouse; D019332:Endothelin-1; D007328:Insulin; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009569:Nitric Oxide