To the Editor: Chronic hypertension is associated with arterial endothelial dysfunction, the precursor to atherosclerosis (1); however, less is known about the effects of brief episodes of hypertension on endothelial function. Lamping and Dole (2) demonstrated that Ͻ5 min of moderate elevations in perfusion pressure reduces conduit coronary arterial endothelial function for up to 2.5 h. This endothelial dysfunction also extends to the human microcirculation (3).Cardiovascular benefits of exercise extend to both aerobic and resistance exercise and include improved endothelial function (4). However, weight lifting elevates systolic blood pressure (SBP) up to 400 mm Hg (5), possibly impairing endothelial function. We examined whether brief elevations in arterial pressure during weight lifting impair brachial arterial endothelial function assessed by flow-mediated vasodilation (FMD).Nine men and 5 women, age 28 Ϯ 2 years (mean Ϯ SE), who engaged in regular weight training (1 h, 3 times per week) constituted the conditioned weight lifter (CWL) group. Eleven men and 5 women, age 33 Ϯ 2 years, who did not regularly engage in exercise constituted the non-weight lifter (NWL) group. Those with known risk factors for coronary endothelial dysfunction or with prior adverse reaction to nitroglycerin were excluded. The Institutional Review Board of the Medical College of Wisconsin and of the local General Clinical Research Center approved the protocol.Brachial artery FMD was assessed before and within 1 h after leg press exercise. Ultrasound imaging of brachial artery diameter and flow velocity was performed using standard methods (6) at baseline and after a 4.5-min suprasystolic blood pressure cuff inflation. This process was repeated after 30 min of resistance exercise, followed by assessment of endothelium-independent vasodilation using 0.4 mg sublingual nitroglycerin (NTG).Diastolic brachial artery diameters were digitally recorded from longitudinal images and analyzed using an automated edgedetection algorithm (Medical Imaging, Iowa City, Iowa). Percentage dilation was calculated from baseline to peak values obtained after cuff release (FMD) or NTG.Subjects performed 2 to 3 sets of 6 to 8 repetitions each to near maximal exertion, serving as their own controls. Brachial artery diameter, FMD before and after weight lifting, peak SBP during exercise versus baseline were each compared using a paired t test. Changes in FMD (%) between groups were compared using an unpaired t test. Correlations between FMD before and after exercise were made using Pearson correlates. Data are reported as mean Ϯ SE with p Ͻ 0.05 considered to be significant.The mean age of all subjects was 31 Ϯ 1 (range 21 to 40) years. There were no differences in arterial blood pressure, heart rate, or lipid profiles between CWL and NWL groups, and these values were within the normal range (data not shown). However, 1 CWL and 1 NWL subject had previously undetected hypercholesterolemia (LDL 181 and 170 mg/dl, respectively) but normal FMD and were included in a...

Abstract-Obesity is associated with impaired endothelial-dependent flow-mediated dilation, a precursor to hypertension and atherosclerosis. Although dieting generally improves cardiovascular risk factors, the direct effect of different dietary strategies on vascular endothelial function is not known. The purpose of this study was to test the hypothesis that a low-fat (LF) diet improves endothelial function compared with an isocaloric low-carbohydrate (LC) diet. Obese (nϭ20; body mass index: 29 to 39; mean systolic blood pressure: 107 to 125 mm Hg) and otherwise healthy volunteers were randomly assigned to either the American Heart Association modeled LF (30% fat calories) diet or an isocaloric LC Atkins' style diet (20 g of carbohydrates) for 6 weeks (4-week weight loss and 2-week maintenance phase). Brachial flow-mediated dilation and dilation to nitroglycerin were measured with ultrasound using automated edge detection technology (baseline, week 2, and week 6). Blood pressure, weight loss, and cholesterol profiles were measured throughout the study. Key Words: diet Ⅲ weight loss Ⅲ endothelium Ⅲ obesity Ⅲ blood pressure O besity is a risk factor for atherosclerosis, a major cause of morbidity and mortality throughout the world. In the United States, the incidence of obesity has risen dramatically in the past decade. Public awareness of the "obesity epidemic" has resulted in various dietary weight loss strategies, and it is estimated that 45% of American women and 30% of American men diet to lose weight. 1 However, the nutrientspecific effects of these diets on cardiovascular health are largely unknown.Mounting evidence suggests that the integrity of the vascular endothelium is critical in the prevention of atherosclerosis, likely through release of endothelial-derived factors such as NO, which confer antiproliferative, antiinflammatory, and antithrombotic properties, in addition to vasodilation. 2,3 Abnormal endothelial function marked by reduced dilation to an increase in flow (endotheliumdependent flow-mediated dilation [FMD]) is an early hallmark of cardiovascular disease and a strong prognostic factor for future cardiovascular events. 4 -9 Most risk factors for coronary artery disease are associated with reduced FMD. 10 Weight loss through conventional low-fat (LF) diets improve endothelial function 11,12 ; however, some currently popular diets emphasize low-carbohydrate (LC) intake supplemented by high dietary fat and protein. Initial reports show sustained weight loss while on LC diets without detrimental effects on serum lipid levels. 13,14 Further benefit may be derived from the reduction in arterial pressure from either LF or LC diets. However, it is unclear whether these cardiovascular benefits of weight loss on a LC diet are negated by the known detrimental effects on endothelial function of even a single high-fat meal. [15][16][17] Weight loss is similar on LC and LF diets, but effects on cardiovascular health, a major anticipated benefit of most weight-loss regimens, may diverge. Therefore, the pur...

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