Effect of Vitamin D Repletion on Insulin Resistance and Systemic Inflammation

Study Overview
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Brief Summary
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The purpose of this research is to study the effects of Vitamin D supplementation on the body's response to insulin (a hormone that controls blood sugar), on inflammation, and on specific cells and processes in fat tissue.

Detailed Description
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Over the last several years, studies have shown that low vitamin D levels may increase risk of developing Type 2 Diabetes. The investigators will administer vitamin D3 (cholecalciferol) to non-diabetic, insulin resistant subjects with vitamin D deficiency (total vitamin D levels <20 ng/ml) to increase the level of vitamin D3. The investigators will study the effects of increased Vitamin D on insulin action, adipose tissue inflammation, and on certain cells and processes in fat tissue. Investigators will study participants with a procedure called a pancreatic clamp study. During the clamp procedure, glucose (a sugar) and insulin (a hormone produced in the pancreas that regulates the amount of glucose in the blood) are infused with an intravenous catheter, and blood samples are collected periodically throughout the procedure to measure blood sugar levels and the levels of several hormones that are found in the body and are related to glucose metabolism. Adipose tissue inflammation will be measured using the following inflammatory markers: IL-6, PAI-1, TNF-alpha, and iNOS.

Official Title
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Effect of Vitamin D Repletion on Insulin Resistance and Systemic Inflammation

Conditions
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Insulin Resistance

Intervention / Treatment
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* Drug: Vitamin D
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Serum 25(OH)D<20ng/ml Insulin Resistant based on HOMA-IR score of >3 Able and willing to provide informed consent BMI 20-35 Exclusion Criteria: HIV/AIDS History of any cancer Sarcoidosis Alcohol or substance abuse Cushing's syndrome Primary hyperparathyroidism Nephrolithiasis Pregnancy or breastfeeding Regular visits to a tanning salon Hypercalcemia or hypocalcemia Untreated or uncontrolled hypertension Any chronic illness requiring medication, other than arthritis, hypertension and hyperlipidemia

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Vitamin D<br>Participants received weekly oral vitamin D drops using a weight-based calculated dosage for up to six months. | Drug: Vitamin D<br> <br> * Other names: Vitamin D3 (cholecalciferol);|
| Placebo Comparator: Placebo<br>Participants received weekly oral placebo drops (similar in taste and appearance to vitamin D) for up to six months. | Drug: Placebo<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent Change in Hepatic Insulin Sensitivity | Endogenous glucose production (EGP) was assessed at each study visit to evaluate hepatic insulin sensitivity. Percent change between the EGP at baseline and second visit (after treatment for up to 3 months with Vitamin D to reach a target level of ≥30 ng/ml), and baseline and third visits (after treatment for up to 6 months with Vitamin D in order to reach a target level of ≥50 ng/ml) will be calculated. | 2nd clamp visit (after up to 3 months) and 3rd clamp visit (after up to 6 months) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent Change in Peripheral Glucose Uptake | The rate of glucose uptake to determine peripheral insulin sensitivity was measured using the rate of disappearance (Rd) of glucose at each study visit. Percent change between the Rd at baseline and second visit (after treatment with Vitamin D for up to 3 months to target level of ≥30 ng/ml), and baseline and third visits (after treatment with Vitamin D for up to 6 months to target level of ≥50 ng/ml) will be calculated. | 2nd clamp visit (up to 3 months) and 3rd clamp visit (up to 6 months) | 
| Evaluated Expression of Pro-inflammatory Gene TNF-α | Adipose tissue macrophages will be isolated from subcutaneous abdominal adipose tissue, and will be quantified by fluorescence activated cell sorting (FACS) analysis. TNF-α gene expression will be examined by real-time (rt-PCR) and will provide a measure of macrophage activation at baseline, at 2nd study visit (after treatment with Vitamin D to a goal level of ≥30 ng/ml), and at 3rd study visit (goal Vitamin D level of ≥50 ng/ml). The mRNA copy number is then compared with a reference gene copy number (5 commonly used house keeping genes [HKGs]) as a ratio, which is a measure of relative gene expression. | 2nd clamp visit (up to 3 months) and 3rd clamp visit (up to 6 months) | 
| Evaluated Expression of Pro-inflammatory Gene IL-6 | Adipose tissue macrophages will be isolated from subcutaneous abdominal adipose tissue, and will be quantified by fluorescence activated cell sorting (FACS) analysis. IL-6 gene expression will be examined by real-time (rt-PCR) and will provide a measure of macrophage activation at baseline, at 2nd study visit (after treatment with Vitamin D to a goal level of ≥30 ng/ml), and at 3rd study visit (goal Vitamin D level of ≥50 ng/ml). The mRNA copy number is then compared with a reference gene copy number (5 commonly used house keeping genes [HKGs]) as a ratio, which is a measure of relative gene expression. | 2nd clamp visit (up to 3 months) and 3rd clamp visit (up to 6 months) | 
| Evaluated Expression of Pro-inflammatory Gene iNOS | Adipose tissue macrophages will be isolated from subcutaneous abdominal adipose tissue, and will be quantified by fluorescence activated cell sorting (FACS) analysis. iNOS gene expression will be examined by real-time (rt-PCR) and will provide a measure of macrophage activation at baseline, at 2nd study visit (after treatment with Vitamin D to a goal level of ≥30 ng/ml), and at 3rd study visit (goal Vitamin D level of ≥50 ng/ml). The mRNA copy number is then compared with a reference gene copy number (5 commonly used house keeping genes [HKGs]) as a ratio, which is a measure of relative gene expression. | 2nd clamp visit (up to 3 months) and 3rd clamp visit (up to 6 months) | 
| Evaluated Expression of Pro-inflammatory Gene PAI-1 | Adipose tissue macrophages will be isolated from subcutaneous abdominal adipose tissue, and will be quantified by fluorescence activated cell sorting (FACS) analysis. PAI-1 gene expression will be examined by real-time (rt-PCR) and will provide a measure of macrophage activation at baseline, at 2nd study visit (after treatment with Vitamin D to a goal level of ≥30 ng/ml), and at 3rd study visit (goal Vitamin D level of ≥50 ng/ml). The mRNA copy number is then compared with a reference gene copy number (5 commonly used house keeping genes [HKGs]) as a ratio, which is a measure of relative gene expression. | 2nd clamp visit (up to 3 months) and 3rd clamp visit (up to 6 months) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Glucose Metabolism Disorders, Insulin Resistance, Endocrine System, Vitamin D