Effect of Vitamin D3 on Vascular Function
Condition: Vitamin D Deficiency
MeSH terms: Vitamin D Deficiency
Study type: Interventional

Summary: 
      Vitamin D is a natural nutrient. A little comes from our normal daily diet. Most of it comes
      from our skin after we have been in sunlight. If we have darker skin, we make less vitamin D.
      Vitamin D balances the calcium in our body. If our vitamin D levels get too low, it can cause
      health problems. It may increase our chance of getting high blood pressure or diabetes.
      Another problem we may have if our vitamin D levels are low is that our blood vessels may not
      work normally. These are important health problems for anyone. Because African Americans have
      darker skin, they are more likely than most other racial/ethnic groups to have low vitamin D
      levels. This study will look at treating African Americans with low vitamin D levels.

      The goal of this study is to see how vitamin D helps blood vessels work. The investigators
      will do this study in African Americans who are overweight, have high blood pressure and have
      low vitamin D levels. The investigators will see if getting the vitamin D level to a normal
      value will improve how blood vessels work. The dose of vitamin D that will be given in this
      study is a high dose that is given to people with low vitamin D levels.
    

Detailed description: 
      Cardiovascular Disease (CVD) and related disorders remain the leading cause of death in the
      nation. Hypovitaminosis D has been linked not only to several cardiovascular (CV) risk
      factors including hypertension, diabetes, obesity but also to increased rates of CVD.
      Thus,hypovitaminosis D presents a common pathway for a select subgroup with a clustering of
      CV risk factors in a profile that is predominant among ethnic minorities. Indeed,
      hypovitaminosis D is highly prevalent with an estimated 55% of the US adult population having
      levels at or below 30 ng/ml, and over 80% of African Americans having suboptimal values.
      Thus, we propose a twelve week randomized double-blind, placebo controlled pilot trial to
      assess the effect on vascular function and CV risk factors of 100,000 IU Vitamin D3 given
      every 4 weeks to overweight, hypertensive African-Americans with hypovitaminosis D. To our
      knowledge, the proposed project is the first to assess the effect of 'high-dose' Vitamin D3
      administration on vascular function.We believe this study is also the first to examine the
      impact at a molecular level of Vitamin D3 repletion on the key mediators of cardio-metabolic
      pathways in humans. If our study results support our working hypothesis, we will be
      positioned to propose a larger scale study to detect a therapeutic effect on more definitive,
      clinical cardiovascular endpoints across a more diverse population.

      Objectives:

      1. Assess the role of Vitamin D3 treatment on vascular function in high risk subjects.

      Primary Outcome: The primary outcome variable is pulse wave velocity (PWV, unit - m/s) for
      vascular stiffness assessed by radial artery tonometry (via SphygmoCor). The hypothesis for
      the primary analysis is that a greater increase in the PWV will occur in the Vitamin D3
      treatment group than in the placebo group.

      Secondary Outcome: Vascular/endothelial function as determined by measuring non-invasive
      vascular finger plethysmography (via EndoPat). Additional surrogates to be assessed as
      secondary markers of vascular/endothelial function include sitting and 24 hour ambulatory
      blood pressure measurements and spot urine protein/creatinine ratio.
    

Intervention name(s): Vitamin D; Placebo
Intervention type(s): Drug; Drug
Intervention description(s): Two 50,000 IU tablets of oral Vitamin D3 will be given every 4 weeks.; Two tablets of oral placebo (microcrystalline cellulose),matching in appearance to the Vitamin D3, will be given every 4 weeks.
Intervention MeSH terms: Vitamin D
Allocation: Randomized
Intervention model: Single Group Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Prevention
Keywords: cardiovascular disease; vitamin D; african american; low vitamin D levels