title: Glargine and regular human insulin similarly acutely enhance endothelium-dependent vasodilatation in normal subjects.
abstract: OBJECTIVE
  Human insulin enhances the vasodilatory effect of acetylcholine (ACh), an endothelium-dependent vasodilator, in normal subjects. Structural changes in a long-acting insulin analog, insulin glargine, may change its binding properties to insulin receptor and structurally homologous receptors, such as the insulin-like growth factor-1 receptor, and thereby alter its vascular effects. In the present study, we compared effects of glargine and regular human insulin on blood flow responses to endothelium-dependent and endothelium-independent vasoactive agents in vivo in normal subjects.
  
  
  RESULTS
  Ten healthy men (age: 33+/-9 years [mean+/-SD]; BMI: 23+/-2 kg/m2) were studied on two separate occasions in a double-blind, randomized, crossover fashion. In each study, blood flow responses to intrabrachial artery infusions of ACh and SNP were determined during infusion of saline and intravenously maintained normoglycemic hyperinsulinemia. Hyperinsulinemia (120 minutes; infusion rate: 1 mU/kg per minute) was created by infusing either insulin glargine or human regular insulin. Glargine and human regular insulin similarly stimulated whole-body glucose metabolism and suppressed serum free-fatty acid (FFA) concentrations. Endothelium-independent blood flow responses to low (3 microg/min) and high (10 microg/min) doses of SNP were unaffected by insulin glargine (12.2+/-2.6 versus 13.4+/-4.6 and 19.1+/-4.2 versus 19.6+/-5.1 mL/dL per minute, saline versus insulin, low- and high-dose) and regular human insulin (11.2+/-3.4 versus 12.0+/-5.2 and 16.8+/-5.7 versus 18.4+/-7.7 mL/dL per minute, respectively). In contrast, endothelium-dependent blood flow responses to low (7.5 microg/min) and high (15 microg/min) doses of ACh increased significantly and similarly by insulin glargine, 13.9+/-4.8 versus 19.3+/-6.5 mL/dL per minute (saline versus insulin, +39%, P<0.01) for low-dose ACh and 17.3+/-6.3 versus 23.2+/-9.2 mL/dL per minute (+34%; P<0.02) for high-dose ACh, and regular human insulin, 11.5+/-6.0 versus 15.8+/-8.0 mL/dL per minute (+38%; P<0.05) and 14.0+/-7.5 versus 21.1+/-10.4 mL/dL per minute (+51%; P<0.01).
  
  
  CONCLUSIONS
  Insulin glargine and regular human insulin have similar acute stimulatory effects on endothelium-dependent vasodilation in humans.
authors.affiliation: Department of Medicine, Division of Diabetes, University of Helsinki, P.O. Box 340, FIN-00029 HUCH, Helsinki, Finland. jukka.westerbacka@helsinki.fi
authors.forename: Jukka
authors.initials: J
authors.lastname: Westerbacka
authors.forename: Robert
authors.initials: R
authors.lastname: Bergholm
authors.forename: Mirja
authors.initials: M
authors.lastname: Tiikkainen
authors.forename: Hannele
authors.initials: H
authors.lastname: Yki-Järvinen
mesh_terms: D000109:Acetylcholine / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D000328:Adult; D001775:Blood Circulation / Q000187:drug effects / Q000502:physiology; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology*; D004824:Epidural Space / Q000098:blood supply / Q000378:metabolism; D005215:Fasting / Q000097:blood / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007261:Infusions, Intra-Arterial / Q000379:methods; D007328:Insulin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000069036:Insulin Glargine; D049528:Insulin, Long-Acting; D008297:Male; D009599:Nitroprusside / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D007328:Insulin; D049528:Insulin, Long-Acting; D009599:Nitroprusside; D000069036:Insulin Glargine; D000109:Acetylcholine