title: Effect of vitamin D replacement on insulin sensitivity in subjects with vitamin D deficiency.
abstract: OBJECTIVE
  Low vitamin D levels correlate with measures of insulin resistance and prevalence of diabetes mellitus, but there are limited and conflicting data on changes in insulin resistance after vitamin D replacement. The objective of the current study was to examine whether vitamin D replacement improves insulin sensitivity.
  
  
  METHODS
  In this randomized double-blind placebo-controlled study, 12 healthy subjects with plasma 25-hydroxy vitamin D (25[OH]D) levels of less than 20 ng/mL were treated with ergocalciferol, 50,000 units, orally once a week for 8 weeks or matching placebo. The main outcome measure was insulin-stimulated glucose infusion rate during the last 20 minutes of a hyperinsulinemic-euglycemic glucose clamp study.
  
  
  RESULTS
  At baseline, plasma 25(OH)D levels were similar between the ergocalciferol and placebo groups (13.3 ± 3.8 and 15.7 ± 2.4 ng/mL, respectively; P = 0.3) but were higher in the ergocalciferol group at 8 weeks (18.8 ± 5 vs 12.5 ± 2.2 ng/mL; P = 0.02). Glucose infusion rate was similar between the 2 groups both at baseline and after 8 weeks of treatment. Changes in plasma 25(OH)D levels did not correlate with change in glucose infusion rate.
  
  
  CONCLUSIONS
  Administration of ergocalciferol, 50,000 units, weekly for 8 weeks in subjects with low vitamin D levels improves 25(OH)D levels but does not improve insulin sensitivity.
authors.affiliation: Department of Internal Medicine, Texas Tech University Health Sciences Center at Permian Basin, Odessa, TX, USA. simha.aj@mayo.edu
authors.forename: Vinaya
authors.initials: V
authors.lastname: Simha
authors.forename: Muhammad
authors.initials: M
authors.lastname: Mahmood
authors.forename: Mohammmed
authors.initials: M
authors.lastname: Ansari
authors.forename: Craig W
authors.initials: CW
authors.lastname: Spellman
authors.forename: Pankaj
authors.initials: P
authors.lastname: Shah
mesh_terms: D000328:Adult; D004311:Double-Blind Method; D004872:Ergocalciferols / Q000008:administration & dosage / Q000097:blood; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D016896:Treatment Outcome; D014807:Vitamin D / Q000008:administration & dosage* / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000188:drug therapy*
chemical_list: D004872:Ergocalciferols; D014807:Vitamin D