Original ArticleVitamin D3 supplementation improves insulin sensitivity in subjects with impaired fasting glucose
Section snippets
Study participants
Study participants were recruited through primary care and endocrinology clinics affiliated with Hennepin County Medical Center and the University of Minnesota (Minneapolis, Minn). Participants included adults, ages 18 to 65, with fasting glucose levels ≥100 mg/dL but less than 126 mg/dL, and serum 25-OH vitamin D levels ≤30 ng/mL. We used this latter concentration as patients with values less than this are stated to be at increased risk for the development of type 2 diabetes.1 Exclusion
Methods
The consent form and process were approved by the Institutional Review Boards at the University of Minnesota and Hennepin County Medical Center. The research was carried out according to the principles of the Declaration of Helsinki. Qualified subjects presented to the GCRC after an overnight 12-h fast. Two intravenous catheters were established, 1 for blood samples and another for administration of insulin and glucose. Baseline laboratories (performed at the University of Minnesota Clinical
Results
Eleven subjects provided consent and completed preintervention and postintervention assessment with the mFSIGT. However, vitamin D measurements were reported only after completion of all testing. Consequently, 3 subjects were excluded from analysis as they were not VDD at baseline. Therefore, 8 eligible subjects (3 men and 5 women) who completed the study were used for the final analysis.
Table I gives the patient characteristics, pre- and post-25-hydroxyvitamin D levels, pre- and post-PTH
Discussion
The influence of vitamin D on beta cell function and insulin sensitivity has been demonstrated in animal and in vitro studies. In human studies, a strong correlation exists between VDD and reduced insulin sensitivity.14 However, the therapeutic usefulness of these findings has been difficult to demonstrate. Interventional trials using vitamin D supplementation in subjects with existing type 2 diabetes have shown no overall improvement in beta cell function or insulin resistance.6, 11, 12 These
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Supported by a grant-in-aid from the Minneapolis Research Foundation and by Grant T32 DK007203 from the National Institutes of Health.