Effects of C-peptide on forearm blood flow and brachial artery dilatation in patients with type 1 diabetes mellitus

Recent studies suggest that C-peptide increases blood flow in both exercisi ng and resting forearm in patients with type 1 diabetes. Now we have studie d the effect of C-peptide administration on endothelial-mediated and non-en dothelial-mediated arterial responses as well as central haemodynamics in 1 0 patients with type 1 diabetes in a placebo-controlled double-blind study. Euglycaemia was maintained with an i.v. insulin infusion before and during the study. A high-resolution ultrasound technique and Doppler echocardiogr aphy were used to assess haemodynamic functions. Brachial artery blood flow and brachial artery diameter were measured in the basal state, 1 and 10 mi n after reactive hyperaemia and 4 min after sublingual glyceryl trinitrate administration (GTN; endothelial-independent vasodilatation), both before a nd after the end of 60-min C-peptide (6 pmol kg(-1) min(-1)) or saline infu sion periods. Echocardiographic measurements were also performed before and at the end of the infusion periods. Seven healthy age-matched males served as controls for vascular studies. The patients showed a blunted brachial d ilatation after reactive hyperaemia in comparison with the healthy controls (2.1 +/- 0.5% vs. 9.3 +/- 0.3%, P < 0.001), indicating a disturbed endothe lial function. C-peptide infusion compared with saline resulted in increase d basal blood flow (33 +/- 6%, P < 0.001) and brachial arterial dilatation (4 +/- 1%, P < 0.05). Left ventricular ejection fraction seemed to be impro ved (5 +/- 2%, P < 0.05) at the end of C-peptide infusion compared with pla cebo. The vascular response to reactive hyperaemia and GTN was not affected by C-peptide infusion. Our results demonstrate that physiological concentr ations of C-peptide increase resting forearm blood flow, brachial artery di ameter and left ventricular systolic function in patients with type 1 diabe tes.