title: Altered contractile response due to increased beta3-adrenoceptor stimulation in diabetic cardiomyopathy: the role of nitric oxide synthase 1-derived nitric oxide.
abstract: BACKGROUND
  In the diabetic heart, the positive inotropic response to beta-adrenoceptor stimulation is altered and beta1 and beta2 adrenoceptors are down-regulated, whereas beta3 adrenoceptor is up-regulated. In heart failure, beta3-adrenoceptor stimulation induces a negative inotropic effect that results from endothelial nitric oxide synthase (NOS3)-derived nitric oxide production. The objective of our study was to investigate the role of beta3-adrenoceptor in diabetic cardiomyopathy.
  
  
  METHODS
  beta-Adrenergic responses were investigated in vivo (dobutamine echocardiography) and in vitro (left ventricular papillary muscle) in healthy and streptozotocin-induced diabetic rats. The effect of beta3-adrenoceptor inhibition on the inotropic response was studied in vitro. Immunoblots and NOS activities were performed in heart homogenates (electron paramagnetic resonance) and isolated cardiomyocytes. Data are mean percentage of baseline +/- SD.
  
  
  RESULTS
  The impaired positive inotropic effect was confirmed in diabetes both in vivo (121 +/- 15% vs. 160 +/- 16%; P < 0.05) and in vitro (112 +/- 5% vs. 179 +/- 15%; P < 0.05). In healthy rat, the positive inotropic effect was not significantly modified in presence of beta3-adrenoceptor antagonist (174 +/- 20%), nonselective NOS inhibitor (N -nitro-l-arginine methylester [l-NAME]; 183 +/- 19%), or selective NOS1 inhibitor (vinyl-l-N-5-(1-imino-3-butenyl)-l-ornithine [l-VNIO]; 172 +/- 13%). In diabetes, in parallel with the increase in beta3-adrenoceptor protein expression, the positive inotropic effect was partially restored by beta3-adrenoceptor antagonist (137 +/- 8%; P < 0.05), l-NAME (133 +/- 11%; P < 0.05), or l-VNIO (130 +/- 13%; P < 0.05). Nitric oxide was exclusively produced by NOS1 within diabetic cardiomyocytes. NOS2 and NOS3 proteins were undetectable.
  
  
  CONCLUSIONS
  beta3-Adrenoceptor is involved in altered positive inotropic response to beta-adrenoceptor stimulation in diabetic cardiomyopathy. This effect is mediated by NOS1-derived nitric oxide in diabetic cardiomyocyte.
authors.affiliation: Department of Anesthesiology and Critical Care, Centre Hospitalier Universitaire Pitié-Salpêtrière, Paris, France. julien.amour@psl.aphp.fr
authors.forename: Julien
authors.initials: J
authors.lastname: Amour
authors.forename: Xavier
authors.initials: X
authors.lastname: Loyer
authors.forename: Morgan
authors.initials: M
authors.lastname: Le Guen
authors.forename: Nejma
authors.initials: N
authors.lastname: Mabrouk
authors.forename: Jean-Stéphane
authors.initials: JS
authors.lastname: David
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Camors
authors.forename: Nunzia
authors.initials: N
authors.lastname: Carusio
authors.forename: Benoît
authors.initials: B
authors.lastname: Vivien
authors.forename: Ramaroson
authors.initials: R
authors.lastname: Andriantsitohaina
authors.forename: Christophe
authors.initials: C
authors.lastname: Heymes
authors.forename: Bruno
authors.initials: B
authors.lastname: Riou
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D009202:Cardiomyopathies / Q000378:metabolism / Q000503:physiopathology*; D048909:Diabetes Complications / Q000378:metabolism* / Q000503:physiopathology; D004195:Disease Models, Animal; D004452:Echocardiography / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology; D032383:Myocytes, Cardiac / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
chemical_list: D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase