title: Activation of the unfolded protein response in vascular endothelial cells of nondiabetic obese adults.
abstract: BACKGROUND
  Activation of the unfolded protein response (UPR) is emerging as an important molecular signature of cardiometabolic diseases associated with obesity. However, despite the well-established role of the vascular endothelium in obesity-related cardiometabolic dysfunction, it is unclear whether the UPR is activated in endothelial cells of obese adults.
  
  
  OBJECTIVE
  The objective of the study was to determine whether markers of UPR activation are increased in endothelial cells (ECs) of nondiabetic obese adults with impaired endothelial function.
  
  
  METHODS
  Endothelial cells were obtained from antecubital veins of the nondiabetic obese adults [body mass index (BMI) ≥ 30 kg/m(2), n = 12] with impaired endothelial function and from their nonobese peers (BMI < 30 kg/m(2), n = 14).
  
  
  METHODS
  UPR activation via expression (quantitative immunofluorescence) of the proximal UPR sensors, inositol-requiring endoplasmic reticulum (ER)-to-nucleus signaling protein 1 (IRE1), RNA-dependent protein kinase-like ER eukaryotic initiation factor-2α kinase (PERK), and activating transcription factor 6 (ATF6), were the main outcome variables.
  
  
  RESULTS
  IRE1 expression was greater in obese vs nonobese individuals (0.84 ± 0.09 vs 0.47 ± 0.02 IRE1 intensity/human umbilical vein EC (HUVEC) intensity (n = 10/8, P < .01). Obese individuals also had greater EC activation of UPR stress sensors PERK and ATF6, indicated by increased expression of phosphorylated PERK [p-PERK; 0.49 ± 0.05 vs 0.36 ± 0.03, p-PERK (threonine 981) intensity/HUVEC intensity, n = 10 men, 13 women, P < .05] and nuclear localization of ATF6 (0.38 ± 0.05 vs 0.23 ± 0.02, nuclear ATF6 intensity/HUVEC intensity, n = 5 men, 9 women, P < .01), respectively. Stepwise linear regression analysis revealed that indices of body fat (BMI and waist circumference) were the strongest independent predictors of all 3 UPR mediators, explaining between 18% and 59% of the variance in endothelial cell expression of IRE1, p-PERK, and nuclear ATF6 localization.
  
  
  CONCLUSIONS
  These results provide novel evidence for UPR activation in the endothelial cells of nondiabetic obese adults with vascular endothelial dysfunction.
authors.affiliation: Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Rachelle E
authors.initials: RE
authors.lastname: Kaplon
authors.forename: Eric
authors.initials: E
authors.lastname: Chung
authors.forename: Lauren
authors.initials: L
authors.lastname: Reese
authors.forename: Kimberly
authors.initials: K
authors.lastname: Cox-York
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Seals
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Gentile
mesh_terms: D051702:Activating Transcription Factor 6 / Q000378:metabolism; D000328:Adult; D000368:Aged; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004722:Endoribonucleases / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction; D056811:Unfolded Protein Response / Q000502:physiology*; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D008565:Membrane Proteins; C403982:ERN2 protein, human; C460640:EIF2AK3 protein, human; D017346:Protein Serine-Threonine Kinases; D019892:eIF-2 Kinase; D004722:Endoribonucleases
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