Effects of Oral Glucosamine on Insulin and Blood Vessel Activity in Normal and Obese People
Status:
Completed
Trial end date:
2006-06-01
Target enrollment:
Participant gender:
Summary
This study will examine whether glucosamine affects the way the body responds to insulin.
Insulin is a hormone that causes the body to use glucose (sugar). Insulin does not work as
well in overweight people, causing a condition called insulin resistance. Insulin also
increases the flow of blood into muscle by opening inactive blood vessels. This study will
test whether glucosamine, a nutritional supplement that many people take to treat arthritis,
can cause or worsen insulin resistance or change how blood vessels react to insulin in normal
weight and overweight people.
Healthy normal weight and overweight volunteers between 21 and 65 years of age may be
eligible for this study. Candidates will be screened with a brief physical examination,
medical history, and blood and urine tests. After screening, participants will have three
additional outpatient clinic visits for the following procedures:
Visit 1
- Glucose clamp test to measure the body's response to insulin: For this procedure, a
needle is placed in a vein of each arm, one for drawing blood samples, and one for
infusing glucose and a potassium solution. The glucose is infused continuously during
this 4-hour test and blood is drawn frequently to monitor glucose and insulin levels.
After the test, blood glucose levels are monitored for another 2 hours to make sure they
remain at an adequate level to prevent hypoglycemia (low blood sugar).
- Blood flow measurement: Blood flow in the brachial artery of the arm is measured to
assess how many capillaries (very small blood vessels) are being used to supply
nutrients and oxygen to the muscle in the forearm. This test is done at the same time as
the glucose clamp test. Blood flow is measured using a technique called contrast
ultrasound. A small amount of contrast agent consisting of gas-filled bubbles the size
of red blood cells is infused over 10 minutes through one of the catheters placed in the
vein for the glucose clamp test. The contrast agent is infused twice, once at the
beginning of the glucose clamp test and once at the end of the test. The contrast
material creates a signal in response to ultrasound that provides information about the
distribution of capillaries in the forearm.
- Assignment to medication group: Participants are randomly assigned to take either
glucosamine or placebo three times a day by mouth for 6 weeks. At the end of the 6
weeks, no study drug is taken for 1 week, and then participants "cross-over"
medications, those who took glucosamine for the first 6 weeks take placebo for the next
6 weeks and vice versa.
Visits 2 and 3
For these visits, the glucose clamp test and blood flow measurements are repeated. Visit 2 is
scheduled at the end of the first 6-week treatment period, and Visit 3 is scheduled at the
end of the second 6-week treatment period.
Phase:
Phase 1
Details
Lead Sponsor:
National Center for Complementary and Integrative Health (NCCIH)