title: Uncoupling protein-2 mediates the protective action of berberine against oxidative stress in rat insulinoma INS-1E cells and in diabetic mouse islets.
abstract: OBJECTIVE
  Uncoupling protein-2 (UCP2) may regulate glucose-stimulated insulin secretion. The current study investigated the effects of berberine, an alkaloid found in many medicinal plants, on oxidative stress and insulin secretion through restoration of UCP2 expression in high glucose (HG)-treated INS-1E cells and rat islets or in db/db mouse islets.
  
  
  METHODS
  Mouse and rat pancreatic islets were isolated. Nitrotyrosine, superoxide dismutase (SOD)-1 and UCP2 expression and AMPK phosphorylation were examined by Western blotting. Insulin secretion was measured by ELISA. Mitochondrial reactive oxygen species (ROS) production was detected by confocal microscopy.
  
  
  RESULTS
  Incubation of INS-1E cells and rat islets with HG (30 mmol·L(-1); 8 h) elevated nitrotyrosine level, reduced SOD-1 and UCP2 expression and AMPK phosphorylation, and inhibited glucose-stimulated insulin secretion. HG also increased mitochondrial ROS in INS-1E cells. Co-treatment with berberine inhibited such effects. The AMPK inhibitor compound C, the UCP2 inhibitor genipin and adenovirus ucp2 shRNA inhibited these protective effects of berberine. Furthermore, compound C normalized berberine-stimulated UCP2 expression but genipin did not affect AMPK phosphorylation. Islets from db/db mice exhibited elevated nitrotyrosine levels, reduced expression of SOD-1 and UCP2 and AMPK phosphorylation, and decreased insulin secretion compared with those from db/m(+) mice. Berberine also improved these defects in diabetic islets and genipin blocked the effects of berberine.
  
  
  CONCLUSIONS
  Berberine inhibited oxidative stress and restored insulin secretion in HG-treated INS-IE cells and diabetic mouse islets by activating AMPK and UCP2. UCP2 is an important signalling molecule in mediating anti-diabetic effects of berberine.
authors.affiliation: Department of Physiology and Pathophysiology, Peking University Health Science Center, Peking, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Liu
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Gao
authors.forename: Xiaoxing
authors.initials: X
authors.lastname: Yu
authors.forename: Gang
authors.initials: G
authors.lastname: Xu
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D001599:Berberine / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007340:Insulinoma / Q000473:pathology*; D007473:Ion Channels / Q000378:metabolism*; D039823:Iridoids / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000473:pathology; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D010190:Pancreatic Neoplasms / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071246:Uncoupling Protein 2
chemical_list: D007328:Insulin; D007473:Ion Channels; D039823:Iridoids; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; C000604390:Ucp2 protein, mouse; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2; D001599:Berberine; C007834:genipin; D055372:AMP-Activated Protein Kinases; D005947:Glucose
keywords: INS-1E cells; berberine; insulin secretion; islets; oxidative stress; uncoupling protein-2