title: The effect of vitamin D supplementation on peripheral regulatory T cells and β cell function in healthy humans: a randomized controlled trial.
abstract: BACKGROUND
  Increasing evidence supports the role of vitamin D (vitD) in modifying the risk to develop type 1 diabetes (T1D) and other autoimmune diseases. VitD3 might stimulate regulatory T cells (Tregs), a central player in the maintenance of self-tolerance. In addition, direct effects of vitD on β-cell function are postulated. The aim of our study was to evaluate the effect of a high dose vitD supplementation on Tregs frequency (%Tregs) and β-cell function assessed by a mixed meal tolerance test (MMTT) in healthy humans.
  
  
  METHODS
  A double-blind, placebo controlled trial was performed in 59 healthy adult subjects (49% females). Subjects received oral vitD3 (140,000 IU monthly) or placebo for 3 months. %Tregs within 20,000 CD4+ T cells of peripheral blood was determined by multi-parametric FACS-analysis. A liquid MMTT was carried out before and after treatment.
  
  
  RESULTS
  %Tregs increased significantly in the vitD group, but remained unchanged in the placebo group. Fasting C-peptide concentrations did not change significantly in either group. Similarly, the mean AUC for C-peptide after 3 months and the change in mean values from baseline to the end of the treatment were comparable in both groups.
  
  
  CONCLUSIONS
  A short time high dose vitD3 supplementation significantly increased the frequency of Tregs, but did not further improve β-cell function in apparently healthy subjects. The immunomodulatory potential of vitD might be an important mechanistic link for the association of vitD and T1D.
authors: Department of Endocrinology and Metabolism, Medical University of Graz, Graz, Austria. gerlies.bock@medunigraz.at
authors: Gerlies
authors: G
authors: Bock
authors: Barbara
authors: B
authors: Prietl
authors: Julia K
authors: JK
authors: Mader
authors: Evelyne
authors: E
authors: Höller
authors: Michael
authors: M
authors: Wolf
authors: Stefan
authors: S
authors: Pilz
authors: Winfried B
authors: WB
authors: Graninger
authors: Barbara M
authors: BM
authors: Obermayer-Pietsch
authors: Thomas R
authors: TR
authors: Pieber
mesh_terms: D000328:Adult; D002096:C-Peptide / Q000097:blood; D002762:Cholecalciferol / Q000008:administration & dosage / Q000627:therapeutic use*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D056747:Immunomodulation / Q000187:drug effects / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000502:physiology*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects*
chemical_list: D002096:C-Peptide; D002762:Cholecalciferol