Effect of Vitamin D Supplementation on Oral Glucose Tolerance Among Obese Adolescents
Condition: Insulin Resistance
MeSH terms: Insulin Resistance
Study type: Interventional

Summary: 
      Childhood obesity is a rapidly growing epidemic in the US and the world. Current estimates
      suggest that 30% of our nation's children are either overweight ot obese. Obesity is a major
      risk factor towards the development of insulin resistance, which, in turn is a major risk
      factor for the development of type 2 diabetes. Prior research has suggested that vitamin D
      therapy may be a safe, inexpensive, and effective method of reducing insulin resistance and a
      person's risk of developing diabetes.

      The investigators' prior studies have shown that daily 4,000 IU vitamin D therapy is a safe
      and effective method of improving insulin resistance based on a calculation called the
      HOMA-IR.

      The next step in identifying whether vitamin D truly improves insulin resistance is to use
      oral glucose tolerance testing (OGTT), which is a better real-life measure of insulin
      resistance compared to the previously used HOMA-IR.
    

Detailed description: 
      The investigators intend to recruit 20 obese adolescent subjects from the PI's obesity clinic
      to participate in the study. Investigators expect 5 to drop out, therefore leaving 15
      subjects to complete the study. Eligible and assenting subjects (with consent from a parent)
      will be admitting to the Pediatric Procedure Suite and MU Women's and Children's Hospital.
      They will have an IV placed in the arm by a nurse experienced with working with children. The
      subjects will have blood drawn from the IV checking for vitamin D level, insulin, glucose,
      and c-peptide level (another marker for insulin status). The subject will then be asked to
      drink a 75 gram glucose solution. Additional blood will be drawn from the IV site to check
      for glucose, insulin, and c-peptide levels at 30 minutes, 60 minutes, 90 minutes, and 120
      minutes. A total of 30 mL (2 tablespoons) of blood will be drawn that day. The subject will
      have the IV removed and will be discharged to then take two 2,000 IU vitamin D3 pills (total
      4,000 IU) daily for six months.

      At a routine 3 months clinical visit, the subject will be tested for routine, standard of
      care, basic metabolic profile (BMP) with 4 ml of blood (less than 1 teaspoon) to assess for
      high calcium levels, a potential complication of vitamin D therapy. In the investigators'
      previous study of adolescents taking 4,000 IU vitamin D daily for six months, no subject
      developed a high calcium level.

      At six months, the subject will return to the Pediatric procedure suite to have another OGTT
      and labs via IV as described above.
    

Intervention name(s): 4,000 IU vitamin D3
Intervention type(s): Dietary Supplement
Intervention description(s): two 2,000 IU vitamin D3 pills (total 4,000 IU) daily for six months.
Intervention MeSH terms: Vitamin D; Cholecalciferol
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment