THE ROLE OF FATTY ACID COMPOSITION IN RACIAL AND ETHNIC DIFFERENCES IN DM2

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This study proposes to explore the hypothesis that the increased risk for diabetes mellitus 2 (DM2) in African Americans is related in part to differences in the metabolic response to dietary carbohydrate, resulting in increased saturated fatty acid (SFA) production in susceptible individuals. The following hypothesis links obesity and insulin resistance: poorly oxidized SFA accumulate within insulin sensitive tissues and impair insulin action. The SFA may be derived from either endogenous synthesis or diet. Links between dietary fat and impaired glucose tolerance have been known for many years and evidence supporting the long-held contention that fatty acid composition plays an important role in glucose tolerance is now accumulating. Epidemiologic studies in man have established the association between a diet high in fat and glucose intolerance and DM2, with saturated fatty acids most closely linked. Dietary fat does not appear to explain the greater risk for diabetes in African American (AA) individuals. In most studies, habitual consumption of dietary fat is either the same or decreased in AA compared to Caucasian (C) individuals. The role of carbohydrate intake in diabetes risk is controversial. Differences in dietary fiber and glycemic load have been observed which predict risk for DM2. However, most but not all studies which have examined the relationship between carbohydrate intake and risk for diabetes conclude that increased carbohydrate (and decreased fat) intake is associated with greater insulin sensitivity. The inclusion of high risk AA individuals in the proposed study will enhance our ability to detect ethnic differences which may explain their increased risk for diabetes mellitus. Obese African American and Caucasian women between the ages of 18 and 55 will be recruited for the proposed studies in equal numbers. Racial and ethnic classification will be defined by self-report. Subjects will undergo the following: a glucose tolerance test, body composition measurements, a needle biopsy of subcutaneous adipose tissue, and a dietary assessment. Metabolic studies will then be performed.