title: Direct effects of rapid-acting insulin analogues on insulin signaling in human pancreatic islets in vitro.
abstract: OBJECTIVE
  Studies suggest that insulin-signaling molecules are present in the pancreatic islets. For this reason, the effects of insulin glulisine, insulin aspart and regular human insulin (RHI) on the function and molecular features of isolated human pancreatic islets were investigated.
  
  
  METHODS
  Human pancreatic islets were prepared by collagenase digestion and density-gradient purification of pancreata from multiple organ donors. Islets were then cultured for 48 h in the presence of 5.5 (normal) or 22.2 (high) mmol/L of glucose with and without glulisine, aspart and RHI (10 or 100 nmol/L). Functional (glucose-stimulated insulin secretion) and molecular (quantitative RT-PCR and immunoblot) studies were performed at the end of the different incubation conditions.
  
  
  RESULTS
  Glucose-stimulated insulin secretion was blunted in islets cultured in 22.2 mmol/L of glucose, with no significant effects from the exogenous added insulins. In islets maintained at 5.5 mmol/L of glucose, insulin receptor (IR) expression was reduced by low RHI, while phosphatidylinositol-3 kinase p110-alpha (PI3K) was enhanced by both concentrations of glulisine and aspart, and by high RHI. In islets preexposed to high glucose, IR expression was increased by both concentrations of aspart and RHI, but not by glulisine. Glulisine at high concentration significantly (P<0.05) increased PI3K expression. Glulisine and RHI significantly increased IRS-2 phosphorylation compared with control and aspart (P<0.05).
  
  
  CONCLUSIONS
  Insulin analogues have differential effects on the expression of insulin-signaling molecules in human pancreatic islets that are also dependent on the degree of glucose exposure.
authors.affiliation: Department of Endocrinology and Metabolism, Ospedale Cisanello, via Paradisa 2, University of Pisa, 56121 Pisa, Italy.
authors.forename: V
authors.initials: V
authors.lastname: D'Aleo
authors.forename: R
authors.initials: R
authors.lastname: Mancarella
authors.forename: S
authors.initials: S
authors.lastname: Del Guerra
authors.forename: U
authors.initials: U
authors.lastname: Boggi
authors.forename: F
authors.initials: F
authors.lastname: Filipponi
authors.forename: P
authors.initials: P
authors.lastname: Marchetti
authors.forename: R
authors.initials: R
authors.lastname: Lupi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D002478:Cells, Cultured; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D061267:Insulin Aspart / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011972:Receptor, Insulin / Q000378:metabolism*
chemical_list: D007328:Insulin; C479079:insulin glulisine; D061267:Insulin Aspart; D058543:Class Ia Phosphatidylinositol 3-Kinase; D011972:Receptor, Insulin; D005947:Glucose