title: C-peptide does not affect ocular blood flow in patients with type 1 diabetes.
abstract: OBJECTIVE
  The aim of the present study was to investigate the effect of intravenous C-peptide infusion on ocular blood flow in patients with type 1 diabetes under euglycemic conditions.
  
  
  METHODS
  The study was performed in a randomized, placebo-controlled, double-masked, two-way, crossover design in 10 type 1 diabetic patients. C-peptide was intravenously administered at two different dosages (dosage 1: 25 pmol . kg(-1) . min(-1) bolus followed by 5 pmol . kg(-1) . min(-1) continuous infusion; dosage 2: six times higher than dosage 1), each for 60 min. Physiologic saline solution was used as a control for C-peptide on a different study day. On both study days, euglycemic clamps were performed. To assess retinal blood flow, laser Doppler velocimetry (blood flow velocities) and retinal vessel analyzer (vessels diameters) measurements were performed. Laser interferometric measurements of fundus pulsation were used to assess pulsatile choroidal blood flow. Blood velocities in the ophthalmic artery were measured using color Doppler imaging.
  
  
  RESULTS
  Eight patients (two female and six male) completed the study according to the protocol and without adverse events. One patient developed an anaphylactic reaction to C-peptide, which resolved without sequelae. The following results originate from the remaining eight subjects. Systemic hemodynamic parameters remained stable during both study days. Infusion of C-peptide did not affect any ocular hemodynamic parameter.
  
  
  CONCLUSIONS
  The data of the present study indicate that exogenous C-peptide exerts no effect on ocular hemodynamic parameters in type 1 diabetic patients under euglycemic conditions. The maximum detectable change in these parameters was <25%.
authors.affiliation: Department of Clinical Pharmacology, Division of Opthalmo-Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. leopold.schmetterer@meduniwien.ac.at
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Polska
authors.forename: Julia
authors.initials: J
authors.lastname: Kolodjaschna
authors.forename: Fatmire
authors.initials: F
authors.lastname: Berisha
authors.forename: Maria M
authors.initials: MM
authors.lastname: Malec
authors.forename: Christian
authors.initials: C
authors.lastname: Simader
authors.forename: Michaela
authors.initials: M
authors.lastname: Bayerle-Eder
authors.forename: Michael
authors.initials: M
authors.lastname: Roden
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D002096:C-Peptide / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005123:Eye / Q000098:blood supply*; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D009880:Ophthalmic Artery / Q000187:drug effects / Q000503:physiopathology; D012171:Retinal Vessels / Q000187:drug effects / Q000503:physiopathology
chemical_list: D002096:C-Peptide