A Clinical Service to Support the Return of Secondary Genomic Findings in Human Research.

Human genome and exome sequencing are powerful research tools that can generate secondary findings beyond the scope of the research. Most secondary genomic findings are of low importance, but some (for a current estimate of 1%-3% of individuals) confer high risk of a serious disease that could be mitigated by timely medical intervention. The impact and scope of secondary findings in genome and exome sequencing will only increase in the future. There is considerable agreement that high-impact findings should be returned to participants, but many researchers performing genomic research studies do not have the background, skills, or resources to identify, verify, interpret, and return such variants. Here, we introduce a proposal for the formation of a secondary-genomic-findings service (SGFS) that would support researchers by enabling the return of clinically actionable sequencing results to research participants in a standardized manner. We describe a proposed structure for such a centralized service and evaluate the advantages and challenges of the approach. We suggest that such a service would be of greater benefit to all parties involved than present practice, which is highly variable. We encourage research centers to consider the adoption of a centralized SGFS.

Weight Loss Programs May Have Beneficial or Adverse Effects on Fat Mass and Insulin Sensitivity in Overweight and Obese Black Women.

OBJECTIVE: Weight loss interventions have produced little change in insulin sensitivity in black women, but mean data may obscure metabolic benefit to some and adverse effects for others. Accordingly, we analyzed insulin sensitivity relative to fat mass change following a weight loss program. DESIGN AND METHODS: Fifty-four black women (BMI range 25.9 to 54.7 kg/m2) completed the 6-month program that included nutrition information and worksite exercise facilities. Fat mass was measured by dual-energy X-ray absorptiometry, and insulin sensitivity index (SI) was calculated from an insulin-modified intravenous glucose tolerance test using the minimal model. RESULTS: Baseline SI (range 0.74 to 7.58 l/mU-1•min-1) was inversely associated with fat mass (r = -0.516, p < 0.001), independent of age. On average, subjects lost fat mass (baseline 40.8 ± 12.4 to 39.4 ± 12.6 kg [mean ± SD], P < 0.01), but 17 women (32 %) actually gained fat mass. SI for the group was unchanged (baseline 3.3 ± 1.7 to 3.2 ± 1.6, P = 0.67). However, the tertile with greatest fat mass loss (-3.6 kg, range -10.7 to -1.7 kg) improved insulin sensitivity (SI +0.3 ± 1.2), whereas the tertile with net fat mass gain (+0.9 kg, range -0.1 to +3.8 kg) had reduced insulin sensitivity (SI -0.7 ± 1.3) from baseline values (P < 0.05 by ANOVA). CONCLUSIONS: Black women in a weight loss program who lose fat mass may have improved insulin sensitivity, but fat mass gain with diminished sensitivity is common. Additional support for participants who fail to achieve fat mass loss early in an intervention may be required for success.

Shear stress-induced mechanotransduction protein deregulation and vasculopathy in a mouse model of progeria.

INTRODUCTION: A mouse model of progeria derived by insertion of the human mutant LMNA gene (mLMNA), producing mutant lamin A, shows loss of smooth muscle cells in the media of the ascending aorta. We hypothesized that high shear stress, in the presence of mutant lamin A, induces this vasculopathy and tried to define the molecular and cellular basis for aortic vasculopathy. METHODS: Ascending and descending aortas from wild type (WT) and mLMNA+ mice were compared using proteomics, Western blots, PCR and immunostaining. To determine whether high fluidic shear stress, known to occur in the ascending aorta, contributed to the vasculopathy, we exposed descending aortas of mLMNA+ mice, with no apparent vasculopathy, to 75 dynes/cm2 shear stress for 30 minutes using a microfluidic system. RESULTS: When the mice were one year of age, expression of several mechanotransduction proteins in the ascending aorta, including vimentin, decreased in mLMNA+ mice but no decrease occurred in the descending aorta. High fluidic shear stress produced a significant reduction in vimentin of mLMNA+ mice but not in similarly treated WT mice. CONCLUSIONS: The occurrence of mutant lamin A and high shear stress correlate with a reduction in the level of mechanotransduction proteins in smooth muscle cells of the media. Reduction of these proteins may contribute over time to development of vasculopathy in the ascending aorta in progeria syndrome.

Effect of extended-release niacin on serum lipids and on endothelial function in adults with sickle cell anemia and low high-density lipoprotein cholesterol levels.

Through bound apolipoprotein A-I (apoA-I), high-density lipoprotein cholesterol (HDL-C) activates endothelial nitric oxide synthase, inducing vasodilation. Because patients with sickle cell disease (SCD) have low apoA-I and endothelial dysfunction, we conducted a randomized, double-blinded, placebo-controlled trial to test whether extended-release niacin (niacin-ER) increases apoA-I-containing HDL-C and improves vascular function in SCD. Twenty-seven patients with SCD with levels of HDL-C <39 mg/dl or apoA-I <99 mg/dl were randomized to 12 weeks of niacin-ER, increased in 500-mg increments to a maximum of 1,500 mg/day, or placebo. The primary outcome was the absolute change in HDL-C level after 12 weeks, with endothelial function assessed before and at the end of treatment. Niacin-ER-treated patients trended to greater increase in HDL-C level compared with placebo treatment at 12 weeks (5.1 ± 7.7 vs 0.9 ± 3.8 mg/dl, 1-tailed p = 0.07), associated with significantly greater improvements in the ratios of low-density lipoprotein to HDL-C levels (1.24 vs 1.95, p = 0.003) and apolipoprotein B to apoA-I levels (0.46 vs 0.58, p = 0.03) compared with placebo-treated patients. No improvements were detected in 3 independent vascular physiology assays of endothelial function. Thus, the relatively small changes in HDL-C levels achieved by the dose of niacin-ER used in our study are not associated with improved vascular function in patients with SCD with initially low levels of apoA-I or HDL-C.

Infrared imaging of nitric oxide-mediated blood flow in human sickle cell disease.

Vascular dysfunction is an important pathophysiologic manifestation of sickle cell disease (SCD), a condition that increases risk of pulmonary hypertension and stroke. We hypothesized that infrared (IR) imaging would detect changes in cutaneous bloodflow reflective of vascular function. We performed IR imaging and conventional strain gauge plethysmography in twenty-five adults with SCD at baseline and during intra-arterial infusions of an endothelium-dependent vasodilator acetylcholine (ACh), an endothelium-independent vasodilator sodium nitroprusside (SNP), and a NOS inhibitor L-NMMA. Skin temperature measured by IR imaging increased in a dose-dependent manner to graded infusions of ACh (+1.1°C, p<0.0001) and SNP (+0.9°C, p<0.0001), and correlated with dose-dependent increases in forearm blood flow (ACh: +19.9 mL/min/100 mL, p<0.0001; r(s)=0.57, p=0.003; SNP: +8.6 mL/min/100 mL, p<0.0001; r=0.70, p=0.0002). Although IR measurement of skin temperature accurately reflected agonist-induced increases in blood flow, it was less sensitive to decreases in blood flow caused by NOS inhibition. Baseline forearm skin temperature measured by IR imaging correlated significantly with baseline forearm blood flow (31.8±0.2°C, 6.0±0.4 mL/min/100 mL; r=0.58, p=0.003), and appeared to represent a novel biomarker of vascular function. It predicted a blunted blood flow response to SNP (r=-0.61, p=0.002), and was independently associated with a marker of pulmonary artery pressure, as well as hemoglobin level, diastolic blood pressure, homocysteine, and cholesterol (R(2)=0.84, p<0.0001 for the model). IR imaging of agonist-stimulated cutaneous blood flow represents a less cumbersome alternative to plethysmography methodology. Measurement of baseline skin temperature by IR imaging may be a useful new marker of vascular risk in adults with SCD.

Diet-induced weight loss in overweight or obese women and changes in high-density lipoprotein levels and function.

Diet-induced weight loss in women may be associated with decreases not only in plasma levels of low-density lipoprotein cholesterol (LDL-C), but also in high-density lipoprotein cholesterol (HDL-C). Whether a decrease in HDL-C is associated with altered HDL function is unknown. One hundred overweight or obese women (age 46 ± 11 years, 60 black; 12 diabetic) were enrolled in the 6-month program of reduced fat and total energy diet and low-intensity exercise. Serum cholesterol efflux capacity was measured in (3)H-cholesterol-labeled BHK cells expressing ABCA1, ABCG1, or SR-B1 transporters and incubated with 1% apolipoprotein B (apoB)-depleted serum. Antioxidant properties of HDL were estimated by paraoxonase-1 (PON1) activity and oxygen radical absorbance capacity (ORAC). Endothelial nitric oxide synthase (eNOS) activation was measured by conversion of L-arginine to L-citrulline in endothelial cells incubated with HDL from 49 subjects. Participants achieved an average weight loss of 2.2 ± 3.9 kg (P < 0.001), associated with reductions in both LDL-C (-6 ± 21 mg/dl, P = 0.004) and HDL-C (-3 ± 9 mg/dl, P = 0.016). Cholesterol efflux capacity by the ABCA1 transporter decreased by 10% (P = 0.006); efflux capacities by the ABCG1 and SR-B1 transporters were not significantly altered. ORAC decreased by 15% (P = 0.018); neither PON1 activity nor eNOS activation was significantly altered by reduction in HDL-C. Findings were similar for diabetic and nondiabetic subjects. Diet-induced weight loss in overweight or obese women is associated with a decrease in HDL-C levels, but overall HDL function is relatively spared, suggesting that decrease in HDL-C in this setting is not deleterious to cardiovascular risk.

High-density lipoprotein cholesterol efflux, nitration of apolipoprotein A-I, and endothelial function in obese women.

Subjects at risk of atherosclerosis might have dysfunctional high-density lipoprotein (HDL) despite normal cholesterol content in the plasma. We considered whether the efflux of excess cellular cholesterol to HDL from obese subjects is associated with impaired arterial endothelial function, a biomarker of cardiovascular risk. A total of 54 overweight (body mass index [BMI] 25 to 29.9 kg/m(2)) or obese (BMI ≥30 kg/m(2)) women, aged 46 ± 11 years, were enrolled in a worksite wellness program. The HDL cholesterol averaged 57 ± 17 mg/dl and was inversely associated with the BMI (r = -0.419, p = 0.002). Endothelial function was assessed using brachial artery flow-mediated dilation. Cholesterol efflux from (3)H-cholesterol-labeled baby hamster kidney cells transfected with the adenosine triphosphate-binding cassette transporter 1 showed 8.2% to 22.5% cholesterol efflux within 18 hours when incubated with 1% serum and was positively correlated with brachial artery flow-mediated dilation (p <0.05), especially in the 34 subjects with BMI ≥30 kg/m(2) (r = 0.482, p = 0.004). This relation was independent of age, HDL or low-density lipoprotein cholesterol concentrations in plasma, blood pressure, or insulin resistance on stepwise multiple regression analysis (ß = 0.31, R(2) = 0.21, p = 0.007). Nitration of apolipoprotein A-I tyrosine residues (using sandwich enzyme-linked immunosorbent assay) was significantly greater in women with a BMI ≥30 kg/m(2) and the lowest cholesterol efflux than in women with a BMI of 25 to 29.9 kg/m(2) and the greatest cholesterol efflux (p = 0.01). In conclusion, we have shown that decreased cholesterol efflux by way of the adenosine triphosphate-binding cassette transporter 1 is associated with increased nitration of apolipoprotein A-I in HDL and is an independent predictor of impaired endothelial function in women with a BMI of ≥30 kg/m(2). This finding suggests that the functional measures of HDL might be better markers for cardiovascular risk than the HDL cholesterol levels in this population.

Transcriptional profiling of CD133(+) cells in coronary artery disease and effects of exercise on gene expression.

BACKGROUND AIMS: Bone marrow (BM)-derived progenitor cells are under investigation for cardiovascular repair but may be altered by disease. Our aim was to identify differences in gene expression in CD133(+) cells of patients with coronary artery disease (CAD) and healthy controls, and determine whether exercise modifies gene expression. METHODS: CD133(+) cells were flow-sorted from 10 CAD patients and four controls, and total RNA was isolated for microarray-based gene expression profiling. Genes that were found to be differentially regulated in patients were analyzed further to investigate whether exercise had any normalizing effect on CD133(+) cells in CAD patients following 3 months of an exercise program. RESULTS: Improvement in effort tolerance and increases in the number of CD133(+) cells were observed in CAD patients after 3 months of exercise. Gene expression analysis of the CD133(+) cells identified 82 differentially expressed genes (2-fold cut-off, 25% false-discovery rate and % present calls) in patients compared with controls, of which 59 were found to be up-regulated and 23 down-regulated. These genes were found to be involved in carbohydrate metabolism, cell cycle, cellular development and signaling, and molecular transport. Following completion of the exercise program, gene expression patterns resembled those of controls in seven of 10 patients. CONCLUSIONS: Alterations in gene expression of BM-derived CD133(+) progenitor cells were found in CAD patients, which in part may be normalized by exercise.

Targeted antagonism of CXCR4 mobilizes progenitor cells under investigation for cardiovascular disease.

BACKGROUND AIMS: Bone marrow (BM)-derived cells may repair cardiovascular injury but populations of interest circulate in small numbers. Cytokines such as granulocyte-colony-stimulating factor mobilize cells under investigation for this purpose, including CD133+ but require injections over multiple days and may promote inflammation. The purpose of this study was to evaluate the effects of a novel CXCR4 inhibitor (plerixafor), previously shown to mobilize CD34+ stem cells, on CD133+ mobilization and markers of inflammation. METHODS: Healthy subjects received a single subcutaneous injection of plerixafor in escalating doses: 240 mcg/kg (n = 3), 320 mcg/kg (n = 5) and 400 mcg/kg (n = 7). CD133+ and CD133+/VEGFR-2+ cells were measured by flow cytometry at baseline, then 4-6 h following plerixafor injection. Markers of inflammation in serum were measured at baseline, then again 10 h following injection of the 400 mcg/kg dose. RESULTS: Across all doses, white blood cells increased on average three-fold from baseline values. CD133+ cells increased on average 24-fold (from 616 +/- 141 cells/mL to 14 713 +/- 4423 cells/mL, P = 0.0064) without clear evidence of a dose effect. CD133+/VEGFR-2+ cells ranged from 0 to 20 cells/mL at baseline and from 0 to 124 cells/mL following plerixafor administration, although the rarity of these cells precluded a statistical analysis of this population. C-reactive protein and serum amyloid type A were not increased after the 400 mcg/kg dose. Pro-inflammatory cytokine levels were undetectable before and after plerixafor, except for macrophage inflammatory protein-1 beta, which increased slightly but significantly after the 400 mcg/kg dose of plerixafor (P = 0.0156). CONCLUSIONS: CD133+ cells are mobilized into the circulation following a single injection of the CXCR4 antagonist plerixafor, without clear evidence for systemic activation of inflammation. This effect may be of importance in cell-based approaches for treating cardiovascular diseases.

Microvascular angina and the continuing dilemma of chest pain with normal coronary angiograms.

Since initial reports over 4 decades ago, cases of patients with angina-like chest pain whose coronary angiograms show no evidence of obstructive coronary artery disease and who have no structural heart disease continue to be a common occurrence for cardiologists. Many features of this patient population have remained constant with successive reports over time: a female predominance, onset of symptoms commonly between 40 and 50 years of age, pain that is severe and disabling, and inconsistent responses to conventional anti-ischemic therapy. Because patients may have had abnormal noninvasive testing that led to performance of coronary angiography, investigators have sought to show an association of this syndrome with myocardial ischemia. Abnormalities in coronary flow and metabolic responses to stress have been reported by several groups, findings consistent with a microvascular etiology for ischemia and symptoms, but others have questioned the presence of ischemia, even in patients selected for abnormal noninvasive testing. Despite considerable efforts by many groups over 4 decades, the syndrome remains controversial with regard to pathophysiology, diagnosis, and management.

The ClinSeq Project: piloting large-scale genome sequencing for research in genomic medicine.

ClinSeq is a pilot project to investigate the use of whole-genome sequencing as a tool for clinical research. By piloting the acquisition of large amounts of DNA sequence data from individual human subjects, we are fostering the development of hypothesis-generating approaches for performing research in genomic medicine, including the exploration of issues related to the genetic architecture of disease, implementation of genomic technology, informed consent, disclosure of genetic information, and archiving, analyzing, and displaying sequence data. In the initial phase of ClinSeq, we are enrolling roughly 1000 participants; the evaluation of each includes obtaining a detailed family and medical history, as well as a clinical evaluation. The participants are being consented broadly for research on many traits and for whole-genome sequencing. Initially, Sanger-based sequencing of 300-400 genes thought to be relevant to atherosclerosis is being performed, with the resulting data analyzed for rare, high-penetrance variants associated with specific clinical traits. The participants are also being consented to allow the contact of family members for additional studies of sequence variants to explore their potential association with specific phenotypes. Here, we present the general considerations in designing ClinSeq, preliminary results based on the generation of an initial 826 Mb of sequence data, the findings for several genes that serve as positive controls for the project, and our views about the potential implications of ClinSeq. The early experiences with ClinSeq illustrate how large-scale medical sequencing can be a practical, productive, and critical component of research in genomic medicine.

Bone marrow-derived cells do not repair endothelium in a mouse model of chronic endothelial cell dysfunction.

AIMS: Bone marrow (BM)-derived endothelial progenitor cells (EPCs) in the circulation replace damaged vascular endothelium. We assessed the hypothesis that a BM transplant from healthy animals would restore normal arterial endothelium and prevent hypertension in young endothelial nitric oxide synthase-deficient (eNOS(-/-)) mice. METHODS AND RESULTS: Radiation or busulfan-induced BM ablation in eNOS(-/-) mice on day 6, day 14, or day 28 was followed by a BM transplant consisting of enhanced green fluorescent protein positive (EGFP(+)) cells from C57BL/6J mice. Peripheral blood cell chimerism was always greater than 85% at 4 months after BM transplant. Molecular assays of heart, kidney, and liver revealed low-level chimerism in all treatment groups, consistent with residual circulating EGFP(+) blood cells. When aorta, coronary, renal, hepatic, and splenic arteries in BM-transplanted eNOS(-/-) mice were examined by confocal microscopy, there were no EGFP- or eNOS-positive endothelial cells detected in these vessels in any of the treatment groups. Likewise, telemetry did not detect any reduction in blood pressure. Thus, no differences were observed in our measurements using several different treatment protocols. CONCLUSION: We found no evidence for BM-derived EPC renewal of endothelium in this eNOS-deficient mouse model of a chronic vascular disease or in wild-type mice during postnatal growth. Hence, renewal of chronic dysfunctional endothelium and endothelial homeostasis may be dependent on resident vascular progenitor cells.

Variability of C-reactive protein levels among patients with stable coronary artery disease and on statin therapy.

BACKGROUND: High sensitivity C-reactive protein, a marker of inflammation, has been proposed to stratify coronary artery disease risk and is lowered by HMG-CoA reductase (statin) therapy. However, the reproducibility of persistently elevated hs-CRP levels and association with other markers of inflammation in patients with stable CAD on aggressive statin therapy is unknown. OBJECTIVES: To determine the reproducibility of hs-CRP levels measured within 2 weeks in patients with documented CAD with stable symptoms and to identify associations with other markers of inflammation. METHODS: Levels of hs-CRP were measured twice within 14 days (7 +/- 4) in 23 patients (22 males and 1 female, average age 66 +/- 10 years) with stable CAD and hs-CRP > or = 2.0 mg/L but < or = 10 mg/L at visit 1. All patients had received statins for cholesterol management (low density lipoprotein-cholesterol 84 +/- 25 mg/dl) with no dose change for > 3 months. None had a history or evidence of malignancy, chronic infection or inflammation, or recent trauma. There was no change in medications between visits 1 and 2, and no patient reported a change in symptoms or general health during this interval. White blood cell count and pro- and anti-inflammatory cytokines were measured at both visits. RESULTS: hs-CRP levels tended to be lower at visit 2 (median 2.4 mg/L, range 0.8-11 mg/L) than at visit 1 (median 3.3 mg/L, range 2.0-9.7; P = 0.1793). However, between the two visits hs-CRP levels decreased by more than 1.0 mg/L in 10 patients and increased by more than 1.0 mg/L in 4 patients. Changes in hs-CRP levels were unrelated to changes in levels of white blood cells (P = 0.4353). Of the cytokines tested, only the antiinflammatory cytokine interleukin-1 receptor antagonist and the pro-inflammatory cytokine interleukin-8 were above lower limits of detection, but there were no correlations between changes in these values and changes in hs-CRP (both P > 0.5). CONCLUSIONS: In stable CAD patients on aggressive statin therapy, hs-CRP levels may fluctuate over brief periods in the absence of changes in health, cardiac symptom status and medications, and without corroboration with other measures of inflammation. Accordingly, elevated hs-CRP levels should be interpreted with caution in this setting.

Microarray-based characterization of a colony assay used to investigate endothelial progenitor cells and relevance to endothelial function in humans.

OBJECTIVE: An assay proposed to quantify endothelial progenitor cell (EPC) colonies in humans was investigated to determine the phenotype of recovered cells and their relevance to in vivo endothelial function. METHODS AND RESULTS: Twelve sedentary subjects participating in a worksite wellness program underwent endothelial flow-mediated dilation (FMD) testing of the brachial artery and blood sampling for EPC colony assay. Microarray-based genotypic characterization of colonies showed surface markers consistent with T lymphocyte phenotype, but not with an EPC (CD34, CD133, VEGFR-2) or endothelial (CD146) phenotype. Gene expression patterns more closely matched T lymphocytes (r=0.87) than endothelial cells (r=0.66) in our microarray database. Flow cytometry of colonies confirmed large populations of CD3+CD45+ T cells (>75%) and few CD146+CD45- endothelial cells (<1%). Further, there was no correlation between colony number and the magnitude of FMD (r=-0.1512, P=0.6389). After exercise training, subjects improved FMD, from 6.7+/-2.0 to 8.7+/-1.9% (P=0.0043). Colonies also increased (P=0.0210), but without relation to FMD (r=0.1074, P=0.7396). T lymphocyte phenotype persisted after exercise (r=0.87). CONCLUSIONS: Cells in a commonly used EPC colony assay have a gene expression and cell surface marker profile consistent with a predominance of T lymphocytes and have an unclear relevance to endothelial function, either before or after exercise training.

Predictors of endothelial function in employees with sedentary occupations in a worksite exercise program.

A sedentary workforce may be at increased risk for future cardiovascular disease. Exercise at the work site has been advocated, but effects on endothelium as a biomarker of risk and relation to weight loss, lipid changes, or circulating endothelial progenitor cells (EPCs) have not been reported. Seventy-two office and laboratory employees (58 women; average age 45 years, range 22 to 62; 26 with body mass index values >30 kg/m(2)) completed 3 months of participation in the National Heart, Lung, and Blood Institute's Keep the Beat program, with the determination of vital signs, laboratory data, and peak oxygen consumption (VO(2)) during treadmill exercise. Brachial artery endothelium was tested by flow-mediated dilation (FMD), which at baseline was inversely associated with Framingham risk score (r = -0.3689, p <0.0001). EPCs were quantified by colony assay. With exercise averaging 98 +/- 47 minutes each workweek, there was improvement in FMD (from 7.8 +/- 3.4% to 8.5 +/- 3.0%, p = 0.0096) and peak VO(2) (+1.2 +/- 3.1 ml O(2)/kg/min, p = 0.0028), with reductions in diastolic blood pressure (-2 +/- 8 mm Hg, p = 0.0478), total cholesterol (-8 +/- 25 mg/dl, p = 0.0131), and low-density lipoprotein cholesterol (-7 +/- 19 mg/dl, p = 0.0044) but with a marginal reduction in weight (-0.5 +/- 2.1 kg, p = 0.0565). By multiple regression modeling, lower baseline FMD, greater age, reductions in total and low-density lipoprotein cholesterol and diastolic blood pressure, and increases in EPC colonies and peak VO(2) were jointly statistically significant predictors of change in FMD and accounted for 47% of the variability in FMD improvement with program participation. Results were similar when modeling was performed for women only. In contrast, neither adiposity at baseline nor change in weight was a predictor of improved endothelial function. In conclusion, daily exercise achievable at their work sites by employees with sedentary occupations improves endothelial function, even with the absence of weight loss, which may decrease cardiovascular risk, if sustained.

Relation of endothelial function to cardiovascular risk in women with sedentary occupations and without known cardiovascular disease.

Our purpose was to determine predictors of endothelial function and potential association with cardiovascular risk in women with sedentary occupations, in whom obesity-associated risk factors may contribute to excess morbidity and mortality. Ninety consecutive women (age range 22 to 63 years, 22 overweight (body mass index [BMI] > or =25 to 29.9 kg/m(2)) and 42 obese (BMI > or = 30 kg/m(2)), had vital signs, lipids, insulin, glucose, high-sensitivity C-reactive protein, and sex hormones measured. Endothelial function was determined using brachial artery flow-mediated dilation after 5 minutes of forearm ischemia. Treadmill stress testing was performed with gas exchange analysis at peak exercise (peak oxygen consumption [Vo(2)]) to assess cardiorespiratory fitness. Brachial artery reactivity was negatively associated with Framingham risk score (r = -0.3542, p = 0.0007). Univariate predictors of endothelial function included peak Vo(2) (r = 0.4483, p <0.0001), age (r = -0.3420, p = 0.0010), BMI (r = -0.3065, p = 0.0035), and high-sensitivity C-reactive protein (r = -0.2220, p = 0.0400). Using multiple linear regression analysis with stepwise modeling, peak Vo(2) (p = 0.0003) was the best independent predictor of brachial artery reactivity, with age as the only other variable reaching statistical significance (p = 0.0436) in this model. In conclusion, endothelial function was significantly associated with cardiovascular risk in women with sedentary occupations, who were commonly overweight or obese. Even in the absence of routine exercise, cardiorespiratory fitness, rather than conventional risk factors or body mass, is the dominant predictor of endothelial function and suggests a modifiable approach to risk.