The Effect of Vitamin D Repletion on Insulin Resistance

Rockefeller University

Status

Completed

Conditions

Obesity

Treatments

Dietary Supplement: Vitamin D3 (cholecalciferol)

Study type

Interventional

Funder types

Other

Identifiers

NCT00606957

RUH IRB# AGR-0623

Details and patient eligibility

About

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.

Enrollment

10 estimated patients

Sex

All

Ages

18 to 65 years old

Volunteers

Accepts Healthy Volunteers

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