Clinical Trial: Heart Disease Risk Factors in African Americans


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Sponsored by:	National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Information provided by:	Warren G Magnuson Clinical Center (CC)

Scientific studies have shown that obesity and increased levels of fat content in the blood are important risk factors for heart disease in Caucasian women. However, similar studies in African American women have failed to show the same correlation. In fact, it appears that African American women in all three body weight groupings, nonobese, overweight, and obese experience high death rates due to heart disease. In addition, prior research has shown that obese African American men tend to have elevated levels of fat in the blood while African American women have normal blood fat levels. Therefore, if high levels of triglycerides (fat found in the blood) are not seen in non-diabetic obese African American women, it cannot be considered a risk factor in this population. This suggests that studies conducted on Caucasian women may not provide insight into heart disease risk factors in African American women.

Condition
Coronary Disease Obesity

This study is designed to investigate in African Americans the relationship of obesity to coronary artery disease risk factors, specifically fasting plasma triglyceride concentration and the triglyceride related risk factors of small dense low density lipoprotein (LDL), high density lipoprotein (HDL) and visceral fat.

The Framingham Study has demonstrated that obesity and elevated triglyceride levels are important risk factors for coronary artery disease mortality in Caucasian women. However, studies that have had significant participation of African American women such as the Charleston Heart Study, have failed to show a relationship of obesity or central obesity to coronary artery disease mortality in African American women. In fact, it appears that African American women in all three body weight groupings, nonobese, overweight and obese experience high rates of mortality from coronary artery disease. Further our earlier research has demonstrated that obese African American men have elevated triglyceride levels but obese African American women have normal triglyceride levels. Consequently if elevated triglyceride levels do not occur in obese nondiabetic African American women, then elevated triglyceride levels can not represent a major cardiovascular risk for African American women. This suggests that studies of cardiovascular risk factors that have been carried out in predominantly Caucasian populations may not provide significant insight into cardiovascular risk for African Americans.

The study, Heart Disease Risk Factors in African Americans, examines if there are differences by sex and body size in cardiovascular risk factors in African American men and women. We believe that obesity will be associated with a greater number and severity of cardiovascular risk factors in African American men. In contrast for African American women, cardiovascular risk factors that are etiologically linked to elevated triglyceride levels will not be magnified by obesity. Diabetes increases the risk of heart disease. Therefore diabetics will not be included in the study. Including diabetics would obscure the association between obesity and heart disease.

This study will be a cross-sectional examination of 160 healthy, nondiabetic African American men and women (age range 18-50) grouped by sex (80 men and 80 women) and body mass index (3 subgroups: nonobese, overweight and obese). In a series of five outpatient visits to the NIH Clinical Center participants will have body fat analyses, resting energy expenditure measurements, an electrocardiogram, blood tests which include fasting lipid profiles, an oral glucose tolerance test, an intravenous glucose tolerance test, and postheparin lipoprotein lipase analysis.

This study has the potential to provide significant insight into the pathophysiology of obesity and cardiovascular risk in African Americans

INCLUSION CRITERIA:
This is a study only of African Americans.
Subjects will be allowed to participate if they self-identify as African Americans.
The age range of the participants will be between 18 and 50
years.
To participate in the study subjects should identify themselves as healthy.
People with established coronary artery as evidenced by history of myocardial infarction, coronary artery bypass surgery or PTCA will be allowed to participate if they are not currently having angina.
Women must give a history of regular monthly cycles (24-35 days) for at least one year.
EXCLUSION CRITERIA:
People that take medications that are known to alter the parameters which are under investigation in this study will be excluded.
Subjects takimg oral contraceptives will not be enrolled.
Subjects on thyroid hormone replacement will be included if their TSH is normal.
Subjects taking oral contraceptives will not be enrolled.
Subjects receiving antihypertensive medication will not be enrolled.
All people with diabetes even if the diabetes is controlled with diet alone will not be enrolled in the study.
Women must who are breastfeeding or have an infant that is less than four months of age will be excluded.
Women with a history of irregular menstrual cycles in the year prior to the study will be excluded.
Women in the following categories, regardless of age, will be excluded: history of hysterectomy, history of bilateral oophorectomy, use of Norplant or Depo-Provera for contraception.
History of bleeding diathesis.