The Effect of Vitamin D Repletion on Insulin Resistance

Not Applicable

Completed

• Conditions: Obesity

• Registration Number: NCT00606957
• Lead Sponsor: Rockefeller University

Brief Summary

The reason for doing this study is to learn whether raising a person's vitamin D level from below normal to normal levels will improve his or her body's ability to use sugar. Vitamin D is well known to be an important vitamin for the development and maintenance of bones. Recently, scientists have learned that vitamin D may have a role in the prevention of cancer, diabetes, and autoimmune diseases. The investigators are specifically interested in studying this question in the overweight/obese population as they are at greater risk for both vitamin D deficiency and impaired ability to metabolize sugar (glucose intolerance).

Primary Hypotheses:

Vitamin D repletion (increasing the serum 25(OH)D level from ≤ 20 ng/ml to ≥ 30 ng/ml) will improve insulin sensitivity in individuals who are overweight/obese and insulin resistant.

Secondary Hypotheses:

1.Vitamin D repletion will improve biomarkers of cardiovascular risk and inflammation (directly altering macrophage cytokine production and/or indirectly as a result of improvement in insulin sensitivity.) 2.30,000 IU (0.25 mg) weekly of cholecalciferol (vitamin D3) will raise serum 25(OH)D levels from ≤ 20 ng/ml to ≥ 30 ng/ml overweight/obese population.

Detailed Description

Not available

Study Timeline

• Study Start: 2008-01
• Study First Submitted: 2008-01-22
• Study First Submitted QC: 2008-02-04
• Study First Posted: 2008-02-05
• Primary Completion: 2009-05
• Study Completion: 2009-05
• Status Verified: 2011-10
• Last Update Submitted: 2011-10-12
• Last Update Posted: 2011-10-13

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 10

Inclusion Criteria

• Nonsmoking men and women, ages 18-65
• Body mass index (BMI) ≥ 28 kg/m² and within 10% of maximum weight
• Serum 25(OH)D level ≤ 20 ng/ml
• Serum insulin level ≥ 7.2 mU/l
• Willingness to maintain current body weight for the duration of the study
• Willingness to maintain baseline lifestyle activities and routines for the duration of the study
• Willingness to avoid the use of non-steroidal anti-inflammatory drugs (NSAIDS), including low-dose daily aspirin, for at least ten days prior to each admission (due to the potential effects of these agents on inflammatory markers.)
• Willingness to avoid the use of all over-the-counter or prescription vitamins, dietary supplements, and herbal products during the study, with the exception of a basic multivitamin supplement.
• If of childbearing potential, willingness to use highly effective contraception for the duration of the study.

Exclusion Criteria

• Current tobacco smoking
• History of bleeding or coagulation disorders
• Gastrointestinal disease resulting in significant gastrointestinal dysfunction or malabsorption
• History of diabetes, or diagnosed during screening OGTT
• Current treatment with hypertensive medications
• History of cardiovascular disease
• Renal disease, as evidenced by a serum creatinine above the upper limit of normal on more than one screening visit
• History of kidney stones
• History of chronic hepatitis, or liver enzymes (AST or ALT) more than 2.5 times the upper limit of normal
• Primary hyperparathyroidism or baseline hypercalcemia from any cause
• Current treatment with over-the-counter or prescription weight loss medications, such as orlistat or sibutramine
• History of bariatric surgery
• Current treatment with any cholesterol-lowering medications, such as statins, niacin, fibrates, or ezetimibe
• Blood pressure ≥ 145/90 after ten minutes of rest on more than one screen visit
• Hyperthyroidism or untreated hypothyroidism. Subjects with chronic, treated, stable hypothyroidism may be included in the study at the discretion of the Principal Investigator.
• Pregnancy, desired pregnancy, or lactation within the study period.
• HIV, Hepatitis B and C
• Medical conditions requiring daily calcium supplementation or antacid use
• Use of medications known to interact with calcium or vitamin D metabolism (bisphosphonates, corticosteroids, thiazide diuretics, cholestyramine, colestipol, mineral oil, phenytoin, barbituates, dititalis glycosides, antacids)
• Subjects with known hypersensitivity to cholecalciferol
• Participation in an investigational drug study within one month of screening
• History, physical, or laboratory findings suggestive of any other medical or psychological condition that would, in the opinion of the principal investigator, make the candidate ineligible for the study

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Primary Outcome Measures

Name	Time	Method
The primary outcome is change in insulin sensitivity over time, as measured by the glucose clamp, HOMA and OGTT.	14 weeks

Trial Locations

Locations (1)

Rockefeller University; 🇺🇸 New York, New York, United States