Stimulation of endothelial nitric oxide synthase by proinsulin C-peptide

Thomas Wallerath, Thomas Kunt, Thomas Forst, Ellen I. Closs, Ralf Lehmann, Thomas Flohr, Matthias Gabriel, Dirk Schäfer, Andrea Göpfert, Andreas Pfützner, Jürgen Beyer, Ulrich Förstermann

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Abstract

There is increasing evidence for biological functions of human C-peptide. Recently, we have described that proinsulin C-peptide increases nutritive capillary blood flow and restores erythrocyte deformability in type 1 diabetic patients, whereas it has no such effect in non-diabetic subjects. The aim of the current study was to elucidate cellular mechanisms of this vasodilator effect in vitro by measuring the nitric oxide (NO)-mediated increase of cGMP production in a RFL-6 reporter cell assay and by demonstrating endothelial calcium influx with the Fluo-3 technique. C-peptide increased the release of NO from endothelial NO synthase (eNOS) in bovine aortic endothelial cells in a concentration- and time-dependent manner. At physiological concentrations of C-peptide, endothelial NO production was more than doubled (208±12% vs control; p<0.001). The NO release was abolished by the inhibitor of NO synthase NG-nitro-L-arginine or when Ca2+ was removed from the medium superfusing the endothelial cells. C-peptide stimulated the influx of Ca2+ into endothelial cells. No change in Ser-1179 phosphorylation of eNOS was detected after 6.6nM C-peptide. C-peptide did not change eNOS mRNA levels after 1, 6 or 24h. These data indicate that C-peptide is likely to stimulate the activity of the Ca2+-sensitive eNOS by increasing the influx of Ca2+ into endothelial cells. We suggest that this effect may contribute to the increase in skin and muscle blood flow previously demonstrated in human in vivo.

Original languageEnglish
Pages (from-to)95-102
Number of pages8
JournalNitric Oxide - Biology and Chemistry
Volume9
Issue number2
DOIs
Publication statusPublished - Sep 2003
Externally publishedYes

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Keywords

  • C-peptide
  • Ca influx
  • Endothelial nitric oxide synthase

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

Cite this

Wallerath, T., Kunt, T., Forst, T., Closs, E. I., Lehmann, R., Flohr, T., Gabriel, M., Schäfer, D., Göpfert, A., Pfützner, A., Beyer, J., & Förstermann, U. (2003). Stimulation of endothelial nitric oxide synthase by proinsulin C-peptide. Nitric Oxide - Biology and Chemistry, 9(2), 95-102. https://doi.org/10.1016/j.niox.2003.08.004