title: Insulin attenuates apoptosis induced by high glucose via the PI3-kinase/Akt pathway in rat peritoneal mesothelial cells.
abstract: BACKGROUND
  Peritoneal mesothelial cells play an important role in peritoneal dialysis and are often exposed to dialysis fluid containing high glucose levels. Loss of peritoneal function is a major complication associated with long-term peritoneal dialysis. In this study, we hypothesized that high glucose levels induce apoptosis, and that insulin attenuates this apoptosis in peritoneal mesothelial cells. To clarify this hypothesis, we examined the effects of insulin on the phosphatidylinositol 3-kinase/Akt signaling pathway and apoptosis in rat peritoneal mesothelial cells.
  
  
  METHODS
  Phosphorylated insulin receptor and Akt were detected by western blot analysis. Apoptosis was evaluated by measuring caspase 3 activity and by TUNNEL staining.
  
  
  RESULTS
  Insulin (100 nmol/L) increased tyrosine phosphorylation of insulin receptor in peritoneal mesothelial cells. Furthermore, insulin (1-100 nmol/L) dose-dependently stimulated Akt phosphorylation. Treatment with the phosphatidylinositol 3-kinase inhibitors wortmannin (100 nmol/L) and LY294002 (10 micromol/L) attenuated insulin-induced Akt phosphorylation, indicating that insulin phosphorylates Akt via a phosphatidylinositol 3-kinase-dependent pathway. Insulin attenuated caspase 3 activity and decreased the number of TUNNEL-positive cells. The phosphatidylinositol 3-kinase inhibitors and overexpression of a dominant-negative mutant of Akt inhibited the effect of insulin on apoptosis.
  
  
  CONCLUSIONS
  The present data indicate that insulin attenuates high glucose-induced apoptosis via the phosphatidylinositol 3-kinase/Akt signaling pathway in peritoneal mesothelial cells. Therefore, the insulin signaling pathway may play a protective role in peritoneal function.
authors.affiliation: Department of Cardiorenal and Cerebrovasular Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Kaifu
authors.forename: Hideyasu
authors.initials: H
authors.lastname: Kiyomoto
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hitomi
authors.forename: Keisuke
authors.initials: K
authors.lastname: Matsubara
authors.forename: Taiga
authors.initials: T
authors.lastname: Hara
authors.forename: Kumiko
authors.initials: K
authors.lastname: Moriwaki
authors.forename: Genei
authors.initials: G
authors.lastname: Ihara
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Fujita
authors.forename: Noriko
authors.initials: N
authors.lastname: Sugasawa
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nagata
authors.forename: Akira
authors.initials: A
authors.lastname: Nishiyama
authors.forename: Masakazu
authors.initials: M
authors.lastname: Kohno
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D018929:Cell Culture Techniques; D002867:Chromones / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D005947:Glucose / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D010537:Peritoneum / Q000187:drug effects* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002867:Chromones; D005947:Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one