Date Published: February 3, 2019
Author(s): Vernon Bond, Karissa Becknel, Krishna Kumar, James Dorsey, Vasavi R. Gorantla, Yulia A. Volkova, Richard M. Millis.
Obese African-American (AA) women are at high risk of hypertension (HT) and cardiovascular disease (CVD). Flow-mediated dilation (FMD) and arterial augmentation index (AI) are measures of endothelial function and arterial stiffness. Whether endothelial function and arterial stiffness predict risk of HT or CVD in obese African-American women with, versus without, parental histories of HT and whether aerobic exercise is an effective countermeasure remain unclear. The capacity for FMD is partly heritable. Therefore, we tested the hypotheses that less FMD and greater AI may be found in normotensive-obese, young-adult (18-26 year-old) AA women with hypertensive parents (n=10) than in a matched control group with normotensive parents (n=10) and that a single bout of aerobic exercise improves both endothelial function and arterial stiffness, with less improvement in the women with hypertensive parents. We studied each subject while at rest, 20 min before and 20 min after, 30 min of aerobic exercise. The exercise-induced changes and parental hypertension-related differences in AI were not significant. The exercise increased FMD in both of the groups with no significant difference in magnitude between the women with hypertensive and normotensive parents. FMD was significantly less in the women with hypertensive parents than in the women with normotensive parents after, but not before, the exercise (mean ±95% confidence interval of 11.3 ± 4.9% vs. 15.6 ± 4.9%, P=0.05). These findings suggest that a 30-min bout of aerobic exercise may improve FMD and unmask endothelial dysfunction in normotensive-obese, young-adult AA women with parental histories of HT. Future studies should determine whether regular aerobic exercise protects obese AA women from the endothelial dysfunction associated with diabetes and prevents CVD in this high-risk population.
Arterial pulse pressure, augmentation index (AI), and flow-mediated dilation (FMD) are well-established indicators of arterial stiffness and endothelial dysfunction . These measures of vascular structure and function are also purported to be useful markers for and early predictors of hypertension, atherosclerosis, and cardiovascular disease (CVD) [2, 3]. Vascular health is affected by many factors such as obesity, parental hypertension, ethnicity, and physical activity. Prior studies examining the relationship between ethnicity and vascular function have demonstrated that Americans of African descent have impaired endothelium-dependent and -independent vasodilatation compared to Americans of European descent (Caucasians) [4, 5]. In that regard, young African-American (AA) subjects free from prevalent CVD appear to exhibit a higher prevalence of abnormal blood pressure wave reflections, arterial wall thickness, and arterial stiffness than Caucasians .
This study tests the hypothesis that normotensive-obese young-adult AA women with hypertensive parents exhibit greater arterial stiffness and less endothelium-dependent vasodilation than a matched group with normotensive parents and that a single bout of aerobic exercise improves both endothelial function and arterial stiffness.
All participants entered the laboratory with prior instructions limiting food intake and exercise for 4 h. Initially, the participant was positioned supine and body composition was analyzed by the DEXA scan. The participant was instrumented with the SunTech 4240 automated blood pressure device (SunTech 4240, SunTech Medical, Morrisville, NC) and metabolic cart, and then performed the progressive exercise test determining VO2peak. Heart rate, blood pressure, and VO2 were measured continuously during the progressive exercise test. Approximately 1-3 weeks after determining VO2peak, participants entered the laboratory under conditions similar to that of the progressive exercise test of VO2peak. Measures of AI and FMD were determined before and after steady-state submaximal exercise. Subjects were placed in a supine position for 10 min before the Al measurement. Brachial systolic pressure and diastolic pressure were measured using the SunTech automated device. At least four brachial blood pressure measurements were taken within a 5-min interval until the differences between systolic pressures were <10 mmHg; the average of the last two blood pressure readings was used to determine the blood pressure parameters for the pulse wave analysis. The subjects performed the exercise protocol consisting of cycling for 30 min on the cycle ergometer at 60% of their predetermined VO2peak. Al and FMD were measured 20 min after the 30 min period of aerobic exercise. All variables were tested for a normal distribution of the data. Normally distributed data were expressed as means ± 95% confidence intervals. Differences for between and within groups were evaluated using ANOVA with post-hoc t-testing. Equality of variances was verified using the F-test for equal variances and the computed F-statistics were found to be less than the critical values of F. Correlations were found using Pearson's product-moment coefficient. Pre-postexercise percent changes were used to determine whether exercise improved FMD more in the comparison group with family histories of hypertension than in the control group without family histories of hypertension (one-tailed t-test for means with equal variances). P ≤ 0.05 was considered statistically significant. GraphPad Instat software (GraphPad Software, La Jolla, CA) was used for statistical analyses. This is the first study to compare arterial stiffness and endothelial function in normotensive-obese young-adult AA women, with and without family histories of hypertension. The main finding of the study is that less flow-mediated vasodilation associated with reactive hyperemia was found in the women with family histories of hypertension 20 min after a single bout of aerobic exercise. Although the exercise increased flow-mediated dilation (FMD) in both study groups, we found no evidence of that there was less exercise-induced improvement in FMD in the group of women with hypertensive parents than in the control group of women with normotensive parents. A group of normotensive-obese young-adult African-American women with hypertensive parents seem to exhibit less capacity for ischemia-induced flow-mediated vasodilation after aerobic exercise than a matched control group with normotensive parents. These findings suggest that endothelial function in normotensive-obese, African-American women with hypertensive parents is more likely to be impaired only after a bout of aerobic exercise. We found no evidence that the endothelial function of the women with hypertensive parents is more resistant to improvement by aerobic exercise. Aerobic exercise and physical activity, in general, play a large role as a preventive strategy and therapeutic treatment for hypertension and cardiovascular disease [51, 52]. Longitudinal studies on similar cohorts should help determine whether endothelial function in normotensive-obese AA women predicts their development of hypertension and whether it can be improved enough by aerobic exercise to prevent their development of hypertension and cardiovascular disease. Source: http://doi.org/10.1155/2019/5854219