title: Insulin stimulates endothelin-1 secretion from human endothelial cells and modulates its circulating levels in vivo.
abstract: Endothelin-1 (ET-1) is a potent vasoactive and mitogenic peptide produced by the vascular endothelium. In this study, we evaluated whether insulin stimulates ET-1 secretion by human endothelial cells derived from umbilical cord veins and by human permanent endothelial hybrid cells Ea.hy 926. Moreover, to provide evidence that insulin may stimulate ET-1 secretion in vivo, plasma ET-1 levels were evaluated in 7 type II diabetic normotensive males (mean age, 54.3 +/- 4.0 yr) during 2-h hyperinsulinemic euglycemic clamps (287 pmol insulin/m2.min-1) as well as in 12 obese hypertensive males (mean age, 44.2 +/- 4.6 yr) before and after a 12-week period of caloric restriction. Our results showed that insulin stimulated ET-1 release from cultured endothelial cells in a dose-dependent fashion. ET-1 release persisted for 24 h and was also observed at physiological insulin concentrations (10(-9) mol/L). The insulin-induced ET-1 secretion was inhibited by genistein, a tyrosine kinase inhibitor, and by cycloheximide, a protein synthesis inhibitor, suggesting that it requires de novo protein synthesis rather than ET-1 release from intracellular stores. In the in vivo experiments, plasma ET-1 levels rapidly increased during euglycemic hyperinsulinemic clamps (from 0.76 +/- 0.18 pg/mL at time zero to 1.65 +/- 0.21 pg/mL at 60 min; P < 0.05) and persisted elevated until the end of insulin infusion (1.37 +/- 0.37 pg/mL at 120 min; P < 0.05 vs. time zero). In obese hypertensives, plasma ET-1 levels significantly decreased after 12 weeks of caloric restriction (from 0.85 +/- 0.51 to 0.48 +/- 0.28 pg/mL; P < 0.04). The decrease in body weight induced by caloric restriction was accompanied by a significant reduction in fasting insulin levels (from 167.2 +/- 94.0 to 98.9 +/- 44.9 pmol/L; P < 0.05) which correlated with the reduction in plasma ET-1 levels (r = 0.78; P < 0.003). In conclusion, our data show that insulin stimulates both in vitro and in vivo ET-1 secretion. Such interaction could play a significant role in the development of atherosclerotic lesions in hyperinsulinemic conditions.
authors.affiliation: University La Sapienza, Institute of I Clinica Medica, Andrea Cesalpino Foundation, Rome, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Ferri
authors.forename: V
authors.initials: V
authors.lastname: Pittoni
authors.forename: A
authors.initials: A
authors.lastname: Piccoli
authors.forename: O
authors.initials: O
authors.lastname: Laurenti
authors.forename: M R
authors.initials: MR
authors.lastname: Cassone
authors.forename: C
authors.initials: C
authors.lastname: Bellini
authors.forename: G
authors.initials: G
authors.lastname: Properzi
authors.forename: G
authors.initials: G
authors.lastname: Valesini
authors.forename: G
authors.initials: G
authors.lastname: De Mattia
authors.forename: A
authors.initials: A
authors.lastname: Santucci
mesh_terms: D000328:Adult; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000097:blood / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D016232:Endothelins; D007328:Insulin; D011994:Recombinant Proteins; D005947:Glucose