title: Insulin and adiponectin inhibit the TNFalpha-induced ADMA accumulation in human endothelial cells: the role of DDAH.
abstract: OBJECTIVE
  Insulin and adiponectin exert important effects on the vasculature. We wanted to explore whether the eNOS inhibitor asymmetric dimethylarginine (ADMA) contribute to their effects.
  
  
  METHODS
  Human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAECs) were incubated with growth medium in the presence or absence of tumor necrosis factor-alpha (TNFalpha), D-glucose, insulin or adiponectin. Further, cells exposed to TNFalpha for 24h were co-stimulated with insulin or adiponectin for additional 24h. Concentrations of ADMA in conditioned media and activity of dimethylarginine dimethylaminohydrolase (DDAH) in cell lysates were determined.
  
  
  RESULTS
  The dose-dependent TNFalpha-induced ADMA accumulation was significantly inhibited when co-stimulated with insulin or adiponectin in both cell lines (p<0.01 for all), accompanied by significant increases in DDAH activity in all conditions. Insulin alone resulted in a significant, but inversely dose-dependent accumulation of ADMA as compared to control cells in both cell lines, accompanied by increased DDAH activity. Adiponectin alone tended, dose-dependently to decrease ADMA, but without an increase of DDAH activity.
  
  
  CONCLUSIONS
  The results indicate that ADMA accumulation in human cultured endothelial cells is influenced by both insulin and adiponectin, and both mediators counteract the TNFalpha-induced accumulation of ADMA through the DDAH pathway.
authors.affiliation: Center for Clinical Research, Ullevaal University Hospital, Oslo, Norway. h.m.eid@medisin.uio.no
authors.forename: Hilde Marie Angell
authors.initials: HM
authors.lastname: Eid
authors.forename: Torstein
authors.initials: T
authors.lastname: Lyberg
authors.forename: Harald
authors.initials: H
authors.lastname: Arnesen
authors.forename: Ingebjørg
authors.initials: I
authors.lastname: Seljeflot
mesh_terms: D052242:Adiponectin / Q000502:physiology*; D000581:Amidohydrolases / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D052242:Adiponectin; D007328:Insulin; D014409:Tumor Necrosis Factor-alpha; C018524:N,N-dimethylarginine; D001120:Arginine; D000581:Amidohydrolases; C059999:dimethylargininase