No funding

It has been shown that asymptomatic obese adolescents can demonstrate abnormal regional myocardial contraction, with preserved global cardiac function. Metformin has been shown to decrease cardiovascular mortality in patients with type 2 diabetes and insulin resistance, but the mechanism of cardiovascular protection is unknown.

The purpose of this study is to evaluate the reversibility of subclinical cardiovascular abnormalities in obese adolescents with insulin resistance after a six-month course of Metformin. The investigators hypothesized that the beneficial effects of Metformin will be progressive and sustained after six months of therapy.

Inclusion Criteria:

• Adolescents 12 to 17 years old under clinical care at the UCSF WATCH clinic
• Body mass index> 95th percentile for age and gender according to the Centers for Disease Control and Prevention 2000 growth charts for the United States
• Insulin resistant after 6 months of healthy diet and exercise
• Able to understand the assent form

Exclusion Criteria:

• Patients with known cardiac disease

• Patients with contraindications to metformin as listed below:

  • Renal disease or renal (serum creatinine levels ≥1.5 mg/dL for males, and ≥1.4 mg/dL for females;
  • Known hypersensitivity to Metformin;
  • Acute or chronic metabolic acidosis;

• Patients with contraindications to MRI including:

  • Cardiac pacemaker;
  • Claustrophobia;
  • Metallic foreign body in the eye,
  • Aneurysm clip in the brain

• Pregnancy;

• Patients who could not stay still for 30 minutes within the MRI scanner due to other reasons besides claustrophobia