title: Stimulation of β-adrenergic receptors plays a protective role via increased expression of RAF-1 and PDX-1 in hyperglycemic rat pancreatic islet (RIN-m5F) cells.
abstract: BACKGROUND
  It is a widely held view that a progressive reduction of beta-cell mass occurs in the progression of diabetes. RAF-1 kinase and pancreas duodenal homeobox 1 (PDX-1) are major factors that promote survival of cells and maintain normal insulin functions. In this study we investigated the effect of a β-adrenergic receptor agonist and antagonist on RAF-1 and PDX-1, and their respective effects on apoptosis and insulin release in RIN-m5F cells.
  
  
  METHODS
  RIN-m5F cells were cultured in normal (5 mM) and high (25 mM) glucose to mimic diabetic conditions, followed by treatment with 5 µM, 10 µM and 20 µM of isoproterenol and isoproterenol + propranolol for 6, 12 and 24 h. Western blotting and reverse transcription analysis were performed to examine the expression of RAF-1 and PDX-1. Annexin-V-FITC and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays were used to investigate apoptosis. ELISA was used to measure insulin levels. Reverse transcription polymerase chain reaction was conducted to investigate the expression of genes.
  
  
  RESULTS
  Stimulation of β-adrenergic receptors with isoproterenol significantly induced RAF-1 and PDX-1 genes in a concentration-dependent and time-independent manner. Changes were significant both at protein and mRNA levels. Up-regulation of RAF-1 and PDX-1 was accompanied by improved insulin levels and reduced apoptosis. Concentrations of 10 µM and 20 µM for 12 and 24 h were more effective in achieving significant differences in the experimental and control groups. Propranolol reversed the effect of isoproterenol mostly at maximum concentrations and time periods.
  
  
  CONCLUSIONS
  A positive effect of a β-adrenergic agonist on RAF-1 and PDX-1, reduction in β-cell apoptosis and improved insulin contents can help to understand the pathogenesis of diabetes and to develop novel approaches for the β-cell dysfunction in diabetes.
authors.affiliation: Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Interdisciplinary Research Center in Biomedical Materials (IRCBM), COMSATS Institute of Information Technology, Lahore, Pakistan.
authors.forename: Sher Zaman
authors.initials: SZ
authors.lastname: Safi
authors.affiliation: Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Rajes
authors.initials: R
authors.lastname: Qvist
authors.affiliation: Department of Anesthesiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Gracie
authors.initials: G
authors.lastname: Ong
authors.affiliation: Department of Pharmacy, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Hamed
authors.initials: H
authors.lastname: Karimian
authors.affiliation: Biochemistry Section, Institute of Chemical Sciences, University of Peshawar, Peshawar, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Imran
authors.affiliation: Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Ikram
authors.initials: I
authors.lastname: Shah
keywords: apoptosis; hyperglycemia; insulin; pancreas duodenal homeobox 1; v-raf-leukemia viral oncogene 1; β-adrenergic receptors