Postprandial endothelial function does not differ in women by race: an insulin resistance paradox?

摘要

Insulin resistance is associated with endothelial dysfunction, because African-American women are more insulin-resistant than white women, it is assumed that African-American women have impaired endothelial function. However, racial differences in postprandial endothelial function have not been examined. In this study, we test the hypothesis that African-American women have impaired postprandial endothelial function compared with white women. Postprandial endothelial function following a breakfast (20% protein, 40% fat, and 40% carbohydrate) was evaluated in 36 (18 African-American women, 18 white women) age- and body mass index (BMI)-matched (age: 37 +- 11 yr; BMI: 30 +- 6 kg/m~2) women. Endothelial function, defined by percent change in brachial artery flow-mediated dilation (FMD), was measured at 0, 2, 4, and 6 h following a meal. There were no significant differences between the groups in baseline FMD, total body fat, abdominal visceral fat, and fasting levels of glucose, insulin, total cholesterol, low-density lipoprotein cholesterol, or serum estradiol. Although African-American women were less insulin-sensitive [insulin sensitivity index (mean +- SD): 3.6 +- 1.5 vs. 5.2 +- 2.6, P = 0.02], both fasting triglyceride (TG: 56 +- 37 vs. 97 +- 49 mg/dl, P = 0.007) and incremental TG area under the curve (AUC_(0-6hr): 279 +-190 vs. 492 +- 255 mg centre dot dl~(-1) centre dot min~(-1) centre dot 10~(-2), P = 0.008) were lower in African-American than white women. Breakfast was associated with a significant increase in FMD in whites and African-Americans, and there was no significant difference in postprandial FMD between the groups (P > 0.1 for group X time interactions). Despite being insulin-resistant, postprandial endothelial function in African-American women was comparable to white women. These results imply that insulin sensitivity may not be an important determinant of racial differences in endothelial function.