Protocol Number: 05-AT-0047

Title:

Effects of Cocoa Consumption on Insulin Sensitivity and Capillary Recruitment in Subjects with Essential Hypertension

Number:

05-AT-0047

Summary:

This study will examine whether dark chocolate affects the way patients with hypertension (high blood pressure) respond to insulin, a hormone secreted by the pancreas that regulates blood glucose (sugar) levels. In many people with hypertension, insulin is not as effective in helping the body use glucose. This is called insulin resistance. Insulin also increases blood flow into muscle by opening inactive blood vessels. Laboratory studies suggest that eating dark chocolate may improve blood pressure. This study will determine whether dark chocolate improves insulin resistance or changes how blood vessels react to insulin in hypertensive people.

People between 21 and 65 years of age who have high blood pressure and are not pregnant may be eligible for this study. Candidates are screened with a medical history, physical examination, and blood and urine tests.

Participants refrain from eating foods containing chocolate or cocoa for 1 week and then come to the clinic on three separate occasions 3 weeks apart for a glucose clamp test and contrast ultrasound, described below. At the first glucose clamp test, subjects are randomly assigned to drink either a cocoa drink with high anti-oxidant content or one with a very low content of anti-oxidant. Each drink will be taken twice a day for 2 weeks. At the end of the 2 weeks, they return for a second glucose clamp test. At the second test, they stop taking the cocoa drink for 1 week and then start again for another 2 weeks. For this 2-week period, those who were given the high anti-oxidant content cocoa drink the first 2 weeks will take the placebo, very low anti-oxidant drink this time, and those who took the placebo will now have the high anti-oxidant cocoa drink. After this 2 weeks of taking the cocoa drink or placebo, they then take the third and last glucose clamp test.

Glucose clamp test: This test measures how the body responds to insulin. Subjects fast the night before each test and do not eat until the test is over, usually in the early afternoon. For the test, the subject lies in a bed or reclines in a chair. A needle is placed in a vein in each arm - one for collecting blood samples and the other for infusing glucose, insulin, and a potassium solution. Blood glucose and insulin levels are measured frequently during the test and the rate of the glucose infusion is adjusted to keep blood glucose at the baseline (fasting) level. Blood samples are tested for blood count, electrolytes, liver function, insulin, lipids, and other substances, in addition to glucose levels. The test takes about 4 hours. After the test, blood glucose levels are monitored for another 2 hours, and during this time, subjects eat a meal.

Contrast ultrasound: This test uses a contrast agent to measure blood flow in the brachial artery of the arm to assess how many capillaries (very small blood vessels) are being used to supply nutrients and oxygen to the muscle. One of the catheters placed in the arm for the glucose clamp test is used to infuse a microbubble contrast agent (gas-filled bubbles the size of red blood cells). The bubbles stay in the blood vessel and create a signal in response to ultrasound that helps give information about the distribution of capillaries in the forearm. The bubbles are infused once at the beginning of the glucose clamp test and again 2 hours later.

In addition to the above procedures, patients will be asked to stay off of their blood pressure medicine during the 6-week period of the study and to come to the clinic every Monday, Wednesday, and Friday during this period to have their blood pressure measured.

Sponsoring Institute:

National Center for Complementary and Alternative Medicine (NCCAM)

Recruitment Detail

Type: Completed Study; data analyses ongoing

Gender: Male & Female

Referral Letter Required: No

Population Exclusion(s): Children

Eligibility Criteria: This study is not currently recruiting new subjects. If you have questions about participating in a study, please contact the Patient Recruitment and Public Liaison Office, CC.

Special Instructions:

Currently Not Provided

Keyword(s):

Epicatechin

Polyphenols

Chocolate

Insulin Resistance

Endothelial Dysfunction

Recruitment Keyword(s):

Hypertension

Condition(s):

Hypertension

Investigational Drug(s):

None

Investigational Device(s):

None

Interventions:

Behavioral: Effects of dark chocolate

Supporting Site:

Naitonal Center for Complementary and Alternative Medicine, Office of Dietary Supplements

Contact(s):

This study is not currently recruiting new subjects. If you have questions about participating in a study, please contact the Patient Recruitment and Public Liaison Office, CC.

Citation(s):

Ferrannini E, Buzzigoli G, Bonadonna R, Giorico MA, Oleggini M, Graziadei L, Pedrinelli R, Brandi L, Bevilacqua S. Insulin resistance in essential hypertension. N Engl J Med. 1987 Aug 6;317(6):350-7.

Modan M, Halkin H, Almog S, Lusky A, Eshkol A, Shefi M, Shitrit A, Fuchs Z. Hyperinsulinemia. A link between hypertension obesity and glucose intolerance. J Clin Invest. 1985 Mar;75(3):809-17.

Zavaroni I, Mazza S, Dall'Aglio E, Gasparini P, Passeri M, Reaven GM. Prevalence of hyperinsulinaemia in patients with high blood pressure. J Intern Med. 1992 Mar;231(3):235-40.

• Questions about participating in a study, please contact the Patient Recruitment and Public Liaison Office, CC.
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