title: A novel role for vitamin D: modulation of expression and function of the local renin-angiotensin system in mouse pancreatic islets.
abstract: OBJECTIVE
  The aim of this study was to demonstrate that hormonal vitamin D (calcitriol) modulates the local pancreatic islet renin-angiotensin system (RAS) whilst improving islet beta cell secretory function.
  
  
  METHODS
  Isolated islets cultured ex vivo under high- or low-glucose conditions and treated with or without calcitriol were examined for changes in RAS component activity and glucose-stimulated insulin secretion (GSIS). Isolated islets from vitamin D receptor knockout (VDR-KO) mice were compared with islets from wild-type (WT) mice for major RAS component expression and RAS protein production.
  
  
  RESULTS
  Isolated islets incubated ex vivo under high-glucose conditions showed increased expression and production of major RAS components; this was prevented and reversed by calcitriol in parallel with increases in GSIS. VDR-KO mice displayed increased RAS component mRNA expression and protein production as compared with WT mice, despite comparable glucose homeostasis.
  
  
  CONCLUSIONS
  Young mice with vitamin D receptor ablation showed abnormal increases in islet RAS components at mRNA and protein levels, despite unaltered glucose homeostasis. Calcitriol prevents and can correct induction of RAS component production under high-glucose conditions in parallel with the well-known effect of calcitriol on increasing islet beta cell secretory responses to glucose.
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, People's Republic of China.
authors.forename: Q
authors.initials: Q
authors.lastname: Cheng
authors.forename: Y C
authors.initials: YC
authors.lastname: Li
authors.forename: B J
authors.initials: BJ
authors.lastname: Boucher
authors.forename: P S
authors.initials: PS
authors.lastname: Leung
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology; D005786:Gene Expression Regulation; D005947:Glucose / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000187:drug effects* / Q000502:physiology*; D014807:Vitamin D / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D018167:Receptors, Calcitriol; D014807:Vitamin D; D002117:Calcitriol; D005947:Glucose