Effect of Diet on Vascular Disease: Study of African American & Caucasian Women

本研究将入组96名女性（48名非裔美国人和48名白色女性）。我们正在招募18至64岁的女性。 该研究将涉及到NIH临床中心的几次门诊访视。第一次访视将是一次筛选，以确定合格性。在第二次访视时，将进行一项测试以测量胰岛素抵抗。这种测试被称为频繁采样静脉葡萄糖耐量试验。第三次访视将针对试验餐。 在餐前和餐后2、4和6小时，将抽取血液并测量血管功能。通过测量血压，然后用超声波测量手臂的血流量来确定血管功能。饮食的个体差异可能会影响试验餐当天的血管研究结果。因此，在试验餐前7天，NIH临床中心将以托盘或盒装餐的形式向每位受试者提供所有膳食。这些膳食将包括典型的美国饮食，33%的脂肪，15%的蛋白质和52%的碳水化合物。 在设计这些膳食时，营养师将考虑个人的食物偏好。46名女性（23名非洲裔美国人和23名白色人）现已完成研究。目前正在对已收集的数据进行登记和分析。 我们的早期发现是，非裔美国妇女比白色妇女更胰岛素抵抗和高胰岛素血症。此外，与白色女性相比，非裔美国女性在空腹和餐后均具有较低的TG和较低的apoCIII水平。 非裔美国妇女的高胰岛素血症是导致高游离脂肪酸清除率和低TG水平的主要因素。 此外，由于高胰岛素血症导致游离脂肪酸清除率更高，这可能是解释非裔美国女性外周脂肪程度高于白色女性和内脏肥胖程度较低的主要因素。先前未在非裔美国女性中进行餐后研究的ApoCIII在非裔美国女性中低于白色女性。ApoCIII抑制脂蛋白脂酶的活性，脂蛋白脂酶是从循环中清除TG的酶。因此，虽然高apoCIII是高TG水平的原因，而低apoCIII至少是解释非裔美国妇女低TG水平的一个因素。

For this study we will enroll 96 women (48 African American and 48 white women). We are enrolling women between the ages of 18 and 64 years. The study will involve several outpatient visits to the NIH Clinical Center. The first visit will be a screening to determine eligibility. At the second visit a test will be performed to measure insulin resistance. This test is called a frequently sampled intravenous glucose tolerance test. The third visit will be for the test meal. Before and at 2, 4 and 6 hours after the meal, blood will be drawn and vascular function measured. Vascular function is determined by taking blood pressure and then measuring blood flow in the arm with ultrasound. It is possible that individual differences in diet could affect the results of the vascular study on the day of the test meal. Therefore for 7 days prior to the test meal, the NIH Clinical Center will provide to each participant all their meals in the form of either trays or meals in a box. These meals will consist of the typical American diet and be 33% fat, 15% protein and 52% carbohydrate. In designing these meals, the dietician will take into account individual food preferences. Forty-six women (23 African American and 23 white) have now completed the study. Enrollment and analysis of data already collected is underway. Our early findings are that African American women are more insulin resistant and hyperinsulinemic than white women. In addition, African American women have lower TG and lower apoCIII levels both fasting and postprandially than white women. Hyperinsulinemia in African American women is a major factor accounting for high free fatty acid clearance and low TG levels. In addition, because hyperinsulinemia is responsible for greater clearance of free fatty acids, this may be a major factor explaining higher degree of peripheral fat and lower visceral adiposity in African American women than white women. ApoCIII which has not been previously studied postprandially in African-American women is lower in African American than white women. ApoCIII inhibits activity of lipoprotein lipase, the enzyme which clears TG from the circulation. Therefore while high apoCIII is responsible for high TG levels and low apoCIII is at least one factor explaining low TG levels in African American women.