This study will examine whether epigallocatechin gallate (EGCG), a major component of green
tea, affects how the body responds to insulin in healthy and obese people. Insulin is not as
effective in people who are overweight, have high blood pressure or diabetes. This condition
is known as insulin resistance. Laboratory studies suggest that green tea or EGCG treatment
lowers blood pressure, lowers blood sugar and increases blood flow. This study will see if
EGCG improves insulin resistance or insulin's effects on blood flow in people with insulin
resistance.
Healthy normal weight or overweight people between 21 and 65 years of age may be eligible for
this study. Participants are randomly assigned to take EGCG or a placebo ( inactive dummy
pill ) in two 4-week treatment phases with a 2-week period of no study medication before each
treatment phase. After the first 4-week treatment, patients on placebo are switched to EGCG
and those on EGCG are switched to placebo. In addition to treatment, participants undergo the
following procedures during the study period:
- Screening, including medical history, physical examination and blood and urine tests,
and finger-stick blood sugar measurement for patients with diabetes
- Complete a dietary and physical activity questionnaire and consult with a dietitian
- Blood and urine tests
- At-home and clinic blood pressure monitoring
- Glucose clamp test to measure how the body responds to insulin. This test is done three
times during the study. A needle is placed in a vein in each of the subject's arms, one
for sampling blood and the other for infusing insulin, glucose and potassium. Glucose
and insulin levels, electrolytes, lipids, fatty acids, cytokines and epicatechin are
measured.
- Forearm blood flow measurement with microbubbles and ultrasound. Before beginning the
glucose clamp test, a test of how well the blood vessels relax is done. A device that
measures the size of the artery in the upper arm is placed above the elbow. Blood flow
in the muscle of the forearm is measured by ultrasound using a small infusion through a
vein of microbubble contrast agent consisting of gas-filled bubbles the size of red
blood cells. The contrast agent is infused over a 7- to 9-minute period at the beginning
of the glucose clamp test and again 2 hours after the beginning of the test.
Phase:
Phase 2
Details
Lead Sponsor:
University of Maryland University of Maryland, Baltimore