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: 0
• Participant gender: All

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
• Accepts Healthy Volunteers?: Accepts Healthy Volunteers

Details

• Lead Sponsor: National Center for Complementary and Integrative Health (NCCIH)
• Treatments: Insulin

Criteria

• INCLUSION CRITERIA:

HEALTHY VOLUNTEERS:

Males or females in good general health with no significant underlying illnesses, on no medication, between the ages of 21-65 years of age with HbA1C less than 6.5, fasting blood glucose less than 100 mg/dl, blood pressure less than 130/85, and BMI between 20-26 kg/m(2). Subjects should have never smoked tobacco or not smoked within the previous 2 years.

OBESE SUBJECTS:

Males or females in good general health with no significant underlying illnesses, on no medication, between the ages of 21-65 years of age with HbA1C less than 6.5, fasting blood glucose less than 110 mg/dl, blood pressure less than 130/85, and BMI between 30-40 kg/m(2).

EXCLUSION CRITERIA:

Subjects will be excluded if they have diabetes, hypertension, pregnancy, liver disease, pulmonary disease, renal insufficiency, coronary heart disease, heart failure, peripheral vascular disease, coagulopathy, actively smoking within last two years, in treatment for any form of cancer, positive tests for HIV, hepatitis B or C, or take systemic corticosteroids.

Subjects will also be excluded if they have an allergy to shellfish since glucosamine is derived from shellfish. Subjects will be excluded if they have taken glucosamine within the last three months. Subjects with allergies to blood products or eggs or known hypersensitivity to albumin will also be excluded from participating because of potential adverse effects from microbubble contrast agent. Subjects will be excluded from this study because children do not typically take glucosamine or have osteoarthritis.