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Effect of Vitamin D Replacement on Insulin Sensitivity in Subjects With Vitamin D Deficiency
  1. Vinaya Simha, MD*†,
  2. Muhammad Mahmood, MD*,
  3. Mohammmed Ansari, MD*,
  4. Craig W. Spellman, DO, PhD*,
  5. Pankaj Shah, MD
  1. From the *Department of Internal Medicine, Texas Tech University Health Sciences Center at Permian Basin, Odessa, TX; and †Division of Endocrinology, Diabetes and Metabolism, Mayo Clinic, Rochester, MN.
  1. Received July 31, 2012, and in revised form August 31, 2012.
  2. Accepted for publication August 31, 2012.
  3. Reprints: Vinaya Simha, MD, Division of Endocrinology, Diabetes and Metabolism, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail: simha.aj{at}mayo.edu.
  4. Supported by a seed grant from the Texas Tech University Health Sciences Center and by resources provided by the Center for Diabetes and Metabolic Research, Odessa, TX.

Abstract

Background and 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.

Conclusion 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.

Key Words
  • vitamin D deficiency
  • insulin sensitivity
  • glucose clamp
  • Ergocalciferol

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