title: No Effect of High-Dose Vitamin D Treatment on β-Cell Function, Insulin Sensitivity, or Glucose Homeostasis in Subjects With Abnormal Glucose Tolerance: A Randomized Clinical Trial.
abstract: OBJECTIVE
  There has been conflicting evidence regarding the potential role of vitamin D in glucose homeostasis. This study was designed to investigate the effect of high-dose vitamin D3 treatment on β-cell function, insulin sensitivity, and glucose tolerance in subjects with prediabetes or diet-treated type 2 diabetes.
  
  
  METHODS
  Subjects (n = 44) were randomized to 30,000 IU vitamin D3 once weekly or placebo for 8 weeks. Hyperglycemic clamp assessed first-phase (0-12 min) and second-phase (12-120 min) insulin response, insulin sensitivity, and disposition index (DI). An oral glucose tolerance test assessed glucose tolerance and glycosylated hemoglobin assessed glycemic control.
  
  
  RESULTS
  A total of 21 (vitamin D) and 22 (placebo) subjects completed the study, respectively. Season-adjusted 25-OH-vitamin D [25(OH)D] levels were doubled in the active treated group (43-82 nmol/L). No effect of vitamin D treatment, compared with placebo, was seen on first-phase or second-phase insulin secretion. There were no group differences in insulin sensitivity, DI, or any measures of glycemic control. No hypercalcemia or other adverse effects of vitamin D treatment were seen compared with placebo. Subgroup analyses of those with the lowest basal and greatest increase in 25(OH)D levels did not change these results.
  
  
  CONCLUSIONS
  This study gives no support for any substantial effect of high-dose vitamin D treatment for 8 weeks in prediabetes or diet-treated type 2 diabetes on β-cell function, insulin sensitivity, or glycemic control.
authors.affiliation: Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden henrik.wagner@sodersjukhuset.se.
authors.forename: Henrik
authors.initials: H
authors.lastname: Wagner
authors.affiliation: Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Alvarsson
authors.affiliation: Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Buster
authors.initials: B
authors.lastname: Mannheimer
authors.affiliation: Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Degerblad
authors.affiliation: Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Claes-Göran
authors.initials: CG
authors.lastname: Östenson
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000494:pharmacology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000178:diet therapy / Q000188:drug therapy*; D005260:Female; D018149:Glucose Intolerance / Q000188:drug therapy; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood / Q000188:drug therapy*; D014815:Vitamins / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D001786:Blood Glucose; D002762:Cholecalciferol; D006442:Glycated Hemoglobin; D014815:Vitamins