Time‐Course Analysis of Flow Mediated Dilation for the Evaluation of Endothelial Function After a High‐Fat Meal in African Americans

Abstract

BackgroundFlow‐mediated dilation (FMD) is used to assess endothelial function through changes in vascular diameter after hyperemia. High‐fat meal (HFM) has been shown to induce endothelial dysfunction; recent studies, however, reported conflicting results in obese African American women (AAW). Differences in the method used to analyze FMD may explain these discrepancies.Methods and ResultsIn protocol 1, we assessed the time course of FMD and compared the repeatability of FMD using the individual maximum peak dilation (FMD peak) and the dilation at 60 seconds (FMD 60). Sixteen AAW (age, 42±10.4 years; body mass index [BMI], 39±5.8 kg/m2) were studied on 2 occasions, 4 weeks apart, under fasting conditions (study 1 and study 2). In protocol 2, we used the most repeatable measurement from protocol 1 to assess changes in endothelial function after an HFM in 17 AAW (agen 42±11.1 years; BMIn 38±5.6 kg/m2). We found that FMD peak was the most repeatable measurement (N=16; study 1, 5.31±3.12% and study 2, 5.80±2.91%; r=0.94). After an HFM, the baseline brachial artery diameter significantly increased at 2 hours (0.10 mm; 95% confidence interval [CI], 0.01–0.18; P=0.03) and at 4 hours (0.17 mm; 95% CI, 0.09–0.25; P<0.001). At 2 hours, the FMD peak decreased compared with pre‐HFM (−1.76; 95% CI, −3.55–0.02; P≤0.05).ConclusionsThe individual's maximum peak dilation after hyperemia is the most consistent measure to assess the effect of an HFM on endothelial function. Endothelial dysfunction occurred at 2 hours after an HFM in AAW.Clinical Trial Registration URL: https://clinicaltrials.gov/ Unique identifiers: NCT01334554 and NCT02126735.

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“…Measurements were performed early in the morning after a minimum 8 hours fast, in a quiet, temperature-controlled room (22-23°C). Subjects were kept in the supine position for 20 minutes before starting FMD measurements as previously described (27). Blood samples were obtained for fasting free FA, glucose, insulin and estradiol levels.…”

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“…The maximum diameter post-hyperemia was obtained using previously described custom design software which automatically calculates the time to peak and peak dilation. (22) This software implements the method validated by Green et al which uses a smoothing algorithm to correct for changes in the brachial artery diameter during the cardiac cycle. (23) The percent change in diameter, following reactive hyperemia and nitroglycerin, was then calculated as percent vasodilation=[(peak diameter-baseline diameter)/baseline diameter]*100.…”

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“…To our knowledge, there are few reports of FMD under fasting and non-fasting conditions. However, a time-course analysis of FMD in African American participants found that baseline brachial artery diameter significantly (p = 0.03) increased 2 h after a high-fat meal, indicating the importance of measurements under postprandial conditions [25].…”