Identifying Risk for Diabetes and Heart Disease in Women

African-American women experience disproportionately high rates of conditions related to insulin resistance, specifically type 2 diabetes (T2D) and cardiovascular disease (CVD). In Africa, T2D and CVD have also become leading causes of death for women. Early recognition of risk and the implementation of preventive measures could improve both quality of life and longevity as well as decrease health care expenditures. However, screening tests for the early detection of T2D and CVD were developed several decades ago in large studies with mostly white participants. Emerging evidence suggests that there are racial differences in the ability and importance of various risk factors to predict the development of diabetes and CVD. Consequently tests used to screen for T2D and CVD are often not effective in women of African descent. Thus, women of African descent lose the opportunity and benefit of early intervention.

Designing tests to determine risk for T2D and CVD in women of African descent requires an appreciation of why current tests do not work. Screening tests to detect risk for T2D and CVD usually rely on the observation that insulin resistance is associated with increased hepatic fat, high fasting glucose and high triglyceride (TG) levels. However, while insulin-resistant white women usually have high liver fat, high fasting glucose and high TG levels, insulin-resistant African-American women often have normal TG levels, normal fasting glucose and low hepatic fat. Therefore, these tests routinely fail to detect risk in African-American women.

The relationship between TG levels to insulin resistance, hepatic glucose production and liver fat has not been studied in African women. To improve diagnosis, we propose a study of race differences in TG levels, fasting glucose levels and hepatic fat comparing 3 groups of women who are federal employees or contractors: African-American African (born in subSaharan Africa and immigrated to the United States) and white. This design ensures all enrollees will have health insurance, a similar work environment and a comparable distribution of position (i.e. scientific, administrative, support). Analyses to detect differences in diet, physical activity and other psychosocial factors will be undertaken.

There will be 4 outpatient visits for 360 non-diabetic women (120 African-American, 120 African and 120 white, aged 25 to 65 years, BMI 20 to 45 kg/m2) enrolled. At Visit 1, a medical history, physical exam and screening labs will be done. Participants will record food intake and monitor physical activity wear an activity monirot (accelerometer) during a 7-day period between visits. At Visit 2 an oral glucose tolerance test will be performed. Studies to examine body fat content and distribution will also be done. At Visit 3, insulin resistance will be measured with an intravenous glucose tolerance test. At Visit 4, breakfast will be eaten with blood samples taken before and after the meal.

In addition to the 4 outpatient visits described, there will be an optional overnight stay the evening before visit 3 for 60 women (30 African descent and 30 white). The purpose of this smaller study is to determine if race differences in the production of glucose by the liver contribute to race differences in fasting glucose levels. Eligible women will be in good health, between 25 and 50 years of age and have a BMI 25-45kg/m2.

This study will be the first time (a) TG levels in African immigrants are compared to African-American and white women (b) hepatic glucose production is assessed by race, and (c) the relationship of TG to insulin resistance, liver fat, body fat distribution, diet, physical activity and psychosocial factors are examined in these 3 groups of women under similar metabolic and economic conditions. While failure of screening tests means a lost opportunity for early intervention, effective screening tests can change outcomes, improve lives and minimize health care expenditures. This protocol is building a foundation on which effective screening tests for diabetes and heart disease can be built.