title: Effects of high doses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract.
abstract: OBJECTIVE
  Vitamin D is well known for its effects on bone mineralisation but has also been attributed immunomodulatory properties. It positively influences human health, but in vivo data describing vitamin D effects on the human gut microbiome are missing. We aimed to investigate the effects of oral vitamin D3 supplementation on the human mucosa-associated and stool microbiome as well as CD8(+) T cells in healthy volunteers.
  
  
  METHODS
  This was an interventional, open-label, pilot study. Sixteen healthy volunteers (7 females, 9 males) were endoscopically examined to access a total of 7 sites. We sampled stomach, small bowel, colon, and stools before and after 8 weeks of vitamin D3 supplementation. Bacterial composition was assessed by pyrosequencing the 16S rRNA gene (V1-2), and CD8(+) T cell counts were determined by flow cytometry.
  
  
  RESULTS
  Vitamin D3 supplementation changed the gut microbiome in the upper GI tract (gastric corpus, antrum, and duodenum). We found a decreased relative abundance of Gammaproteobacteria including Pseudomonas spp. and Escherichia/Shigella spp. and increased bacterial richness. No major changes occurred in the terminal ileum, appendiceal orifice, ascending colon, and sigmoid colon or in stools, but the CD8(+) T cell fraction was significantly increased in the terminal ileum.
  
  
  CONCLUSIONS
  Vitamin D3 modulates the gut microbiome of the upper GI tract which might explain its positive influence on gastrointestinal diseases, such as inflammatory bowel disease or bacterial infections. The local effects of vitamin D demonstrate pronounced regional differences in the response of the GI microbiome to external factors, which should be considered in future studies investigating the human microbiome.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria.
authors.forename: Mina
authors.initials: M
authors.lastname: Bashir
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Prietl
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Tauschmann
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria.
authors.forename: Selma I
authors.initials: SI
authors.lastname: Mautner
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Patrizia K
authors.initials: PK
authors.lastname: Kump
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria.
authors.forename: Gerlies
authors.initials: G
authors.lastname: Treiber
authors.affiliation: Institute of Pathology, Medical University of Graz, Graz, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Wurm
authors.affiliation: Institute of Pathology, Medical University of Graz, Graz, Austria.
authors.forename: Gregor
authors.initials: G
authors.lastname: Gorkiewicz
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Graz, Austria. christoph.hoegenauer@medunigraz.at.
authors.forename: Christoph
authors.initials: C
authors.lastname: Högenauer
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria. endo@medunigraz.at.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Pieber
mesh_terms: D000293:Adolescent; D000328:Adult; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology; D002762:Cholecalciferol / Q000494:pharmacology*; D005243:Feces / Q000382:microbiology; D005260:Female; D020563:Gammaproteobacteria / Q000187:drug effects / Q000302:isolation & purification; D000069196:Gastrointestinal Microbiome / Q000187:drug effects*; D041981:Gastrointestinal Tract / Q000382:microbiology*; D016480:Helicobacter pylori / Q000187:drug effects; D006801:Humans; D008297:Male; D009092:Mucous Membrane / Q000382:microbiology*; D010865:Pilot Projects; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D055815:Young Adult
chemical_list: D012336:RNA, Ribosomal, 16S; D002762:Cholecalciferol
keywords: Gammaproteobacteria; Human gut microbiome; IBD; Inflammation; Vitamin D