Clinical and genetic correlates of circulating angiopoietin-2 and soluble Tie-2 in the community

BACKGROUND

Experimental studies suggest that endothelial growth factors play an important role in angiogenesis and vascular remodeling. The clinical and genetic correlates of circulating angiopoietin-2 (Ang-2) and its soluble receptor/regulator Tie-2 (sTie-2) have not been determined in a community-based sample.

METHODS AND RESULTS

Serum Ang-2 and sTie-2 were assayed in 3778 third-generation cohort participants of the Framingham Heart Study (mean age, 40+/-9 years; 53% women). Clinical correlates and heritability of both biomarkers were assessed using generalized estimating equations and variance-component analyses. Ang-2 levels were higher and sTie-2 levels were lower in women than in men. Ang-2 was positively related to age, smoking, systolic blood pressure, hypertension treatment, and diabetes (P<0.05 for all) but was inversely associated with total cholesterol and diastolic blood pressure (P<0.0001 for both), and sTie-2 was positively associated with body mass index, diabetes, and triglycerides but was inversely related to age, alcohol consumption, and glomerular filtration rate (P<0.05 for all). Both Ang-2 and sTie-2 were higher in participants with metabolic syndrome (P<0.005), with stronger associations of Ang-2 with blood pressure traits and of sTie-2 with obesity-dyslipidemia components. Heritability estimates for Ang-2 and sTie-2 were 27% and 56%, respectively (P<0.0001). A region on chromosome 9 was significantly linked to circulating sTie-2 levels (logarithm of the odds score, 8.31).

CONCLUSION

Circulating levels of Ang-2 and sTie-2 are heritable traits associated with cardiovascular disease risk factors, including the metabolic syndrome. These observations are consistent with the notion that angiogenesis and vascular remodeling are determined in part by genetic influences and associated with metabolic risk factors.

Longitudinal tracking of left atrial diameter over the adult life course: Clinical correlates in the community

BACKGROUND

Increased left atrial diameter (LAD) is associated with elevated risk of atrial fibrillation (AF) and cardiovascular disease. Information is limited regarding the short- or long-term correlates of LAD.

METHODS AND RESULTS

We evaluated clinical correlates of LAD for a 16-year period in 4403 Framingham Study participants (mean age, 45 years; 52% women; median observations/participant=3) using multilevel modeling. We related age, sex, body mass index (BMI), systolic and diastolic blood pressure (BP), diabetes, and antihypertensive treatment to LAD. Sex-specific growth curves for LAD were estimated for individuals with low, intermediate, and high risk factor burden. We also related risk factors to changes in LAD during a 4-year period in 3365 participants. Age, male sex (3.83 mm compared to women), greater BMI, higher systolic BP (0.24 mm per 10 mm Hg increment), and antihypertensive treatment (0.54 mm) were associated positively with LAD (P<0.001). Men had a greater increase in LAD with BMI than women (2.02 versus 1.77 mm in women, per 5-unit increment), and individuals receiving antihypertensive treatment experienced a greater increase in LAD with age (0.95 versus 0.63 mm per 10-year age increment) when compared with those not receiving antihypertensive treatment. Overall, greater risk factor burden was positively associated with LAD. These risk factors were also associated positively with 4-year change in LAD (P<0.001).

CONCLUSIONS

Our longitudinal study of a large community-based sample identified higher BP and greater BMI as key modifiable correlates of LAD, suggesting that maintaining optimal levels of these risk factors through the life course may prevent atrial remodeling and AF.

Association of the endogenous nitric oxide synthase inhibitor ADMA with carotid artery intimal media thickness in the Framingham Heart Study offspring cohort

BACKGROUND AND PURPOSE

Higher plasma concentrations of the endogenous nitric oxides synthase inhibitor asymmetrical dimethylarginine (ADMA) are associated with increased risk of cardiovascular and cerebrovascular events and death, presumably by promoting endothelial dysfunction and subclinical atherosclerosis. We hypothesized that plasma ADMA concentrations are positively related to common carotid artery intimal-media thickness (CCA-IMT) and to internal carotid (ICA)/bulb IMT.

METHODS

We investigated the cross-sectional relations of plasma ADMA with CCA-IMT and ICA/bulb IMT in 2958 Framingham Heart Study participants (mean age, 58 years; 55% women).

RESULTS

In unadjusted analyses, ADMA was positively related to both CCA-IMT (beta per SD increment, 0.012; P<0.001) and ICA/bulb IMT (beta per SD increment, 0.059; P<0.001). In multivariable analyses (adjusting for age, sex, systolic blood pressure, antihypertensive treatment, smoking status, diabetes, BMI, total-to-HDL cholesterol ratio, log C-reactive protein, and serum creatinine), plasma ADMA was not associated with CCA-IMT (P=0.991), but remained significantly and positively related to ICA/bulb IMT (beta per SD increment, 0.0246; P=0.002).

CONCLUSIONS

In our large community-based sample, we observed that higher plasma ADMA concentrations were associated with greater ICA/bulb IMT, but not with CCA-IMT. These data are consistent with the notion that ADMA promotes subclinical atherosclerosis in a site-specific manner, with a greater proatherogenic influence at known vulnerable sites in the arterial tree.

Asymmetric dimethylarginine reference intervals determined with liquid chromatography-tandem mass spectrometry: results from the Framingham offspring cohort

BACKGROUND

Accumulating evidence links higher circulating asymmetric dimethylarginine (ADMA) to greater risk of cardiovascular disease (CVD). Relatively small differences in ADMA concentrations between healthy individuals and those with disease underscore the need to formulate reference intervals that may aid risk stratification of individuals.

METHODS

We formulated reference intervals for plasma ADMA concentrations using a community-based reference sample from the Framingham Offspring Study consisting of 1126 nonsmoking individuals [mean (SD) age 56 (9) years; 60% women] who were free of clinical CVD, hypertension, diabetes, and obesity and who attended a routine examination at which ADMA was assayed. ADMA concentrations were determined using a validated tandem mass spectrometry-liquid chromatography assay.

RESULTS

In the study sample, the mean ADMA concentration was 0.52 (0.11) micromol/L, and the reference limits were 0.311 and 0.732 (2.5th and 97.5th percentile). The sex-specific reference limits were 0.310 and 0.745 in men and 0.313 and 0.721 micromol/L in women. In multivariable regression analysis, ADMA plasma concentrations were positively correlated with age and total plasma homocysteine (both P < 0.001).

CONCLUSIONS

Reference limits calculated for circulating ADMA in our large community-based healthy reference sample confirm the previous observation of a relatively narrow distribution of concentrations. This suggests a tight physiological control of ADMA plasma concentrations, presumably by dimethylarginine dimethylaminohydrolase (DDAH) metabolism of ADMA.

Longitudinal tracking of left ventricular mass over the adult life course: clinical correlates of short- and long-term change in the framingham offspring study

BACKGROUND

Information is limited on the longitudinal tracking of left ventricular (LV) mass over the adult life course and the determinants of such change.

METHODS AND RESULTS

We used multilevel modeling to evaluate the correlates of LV mass prospectively over a 16-year period in 4217 Framingham study participants (mean age 45 years, 53% women) using up to 4 serial routine echocardiographic observations on each individual (11 762 observations). Age, sex, body mass index, systolic blood pressure, antihypertensive treatment, smoking, and diabetes mellitus were related to longitudinal measures of LV mass. Women and participants with diabetes mellitus experienced a steeper increase in LV mass with advancing age (compared with men and those without diabetes mellitus; P for interactions <0.0001 and 0.0003, respectively). Women also displayed greater increments in LV mass with increasing body mass index (compared with men, P=0.04 for interaction). Participants with optimal values of these risk factors experienced lesser increases in LV mass over time. Analyses evaluating short-term (4-year) changes in LV mass (2605 unique individuals providing 4494 observations) identified the same key determinants that influenced its long-term trajectory (ie, body mass index, sex, systolic blood pressure, antihypertensive treatment, and smoking).

CONCLUSIONS

Our longitudinal observations on a large community-based sample identified higher blood pressure, excess adiposity, smoking, and diabetes mellitus as fundamental determinants of LV mass tracking over the adult life course. These observations are consistent with the notion that maintenance of optimal levels of these risk factors in midlife will reduce the burden of LV hypertrophy, and possibly heart failure, in older age.

Plasma asymmetric dimethylarginine, L-arginine and left ventricular structure and function in a community-based sample

OBJECTIVE

Increasing evidence indicates that cardiac structure and function are modulated by the nitric oxide (NO) system. Elevated plasma concentrations of asymmetric dimethylarginine (ADMA; a competitive inhibitor of NO synthase) have been reported in patients with end-stage renal disease. It is unclear if circulating ADMA and L-arginine levels are related to cardiac structure and function in the general population.

METHODS

We related plasma ADMA and L-arginine (the amino acid precursor of NO) to echocardiographic left ventricular (LV) mass, left atrial (LA) size and fractional shortening (FS) using multivariable linear regression analyses in 1919 Framingham Offspring Study participants (mean age 57 years, 58% women).

RESULTS

Overall, neither ADMA or L-arginine, nor their ratio was associated with LV mass, LA size and FS in multivariable models (p>0.10 for all). However, we observed effect modification by obesity of the relations of ADMA and LA size (p for interaction p=0.04): ADMA was positively related to LA size in obese individuals (adjusted-p=0.0004 for trend across ADMA quartiles) but not in non-obese people.

CONCLUSION

In our large community-based sample, plasma ADMA and l-arginine concentrations were not related to cardiac structure or function. The observation of positive relations of LA size and ADMA in obese individuals warrants confirmation.

Plasma asymmetric dimethylarginine and incidence of cardiovascular disease and death in the community

BACKGROUND

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, induces endothelial dysfunction. Although elevated ADMA has been associated with an increased risk of cardiovascular disease events and death in referral samples, the prognostic significance of ADMA in the community has not been adequately evaluated.

METHODS AND RESULTS

We related plasma ADMA, l-arginine (Arg), and the ratio of Arg to ADMA to the incidence of cardiovascular disease (fatal or nonfatal myocardial infarction, coronary insufficiency, angina pectoris, stroke or transient ischemic attack, intermittent claudication, or heart failure) and death in 3320 Framingham Offspring Study participants (1769 women; mean age, 59 years). Over a follow-up period of 10.9 years, 281 individuals of 2956 free of cardiovascular disease at baseline developed incident cardiovascular disease, and 285 participants died. In multivariable models adjusting for established risk factors and other biomarkers (B-type natriuretic peptide, renin, homocysteine, urine albumin excretion, and C-reactive protein), ADMA and the ratio of Arg to ADMA were significantly associated with all-cause mortality (adjusted-hazard ratio [HR] per 1-SD increment, 1.21; 95% CI, 1.07 to 1.37; and HR per 1-SD increment, 0.80; 95% CI, 0.69 to 0.93, respectively), whereas Arg was not (HR per 1-SD increment, 0.89; 95% CI, 0.77 to 1.02). We noted effect modification by diabetes status; ADMA was associated with death in individuals without diabetes (adjusted HR per 1-SD increment, 1.30; 95% CI, 1.13 to 1.50) but not in individuals with diabetes (adjusted HR per 1-SD increment, 0.85; 95% CI, 0.62 to 1.16). ADMA, Arg, and the ratio of Arg to ADMA were not associated with cardiovascular disease incidence (P>0.10).

CONCLUSIONS

In our large community-based sample, ADMA was significantly associated with all-cause mortality, particularly in nondiabetic individuals.

Vascular endothelial growth factor, its soluble receptor, and hepatocyte growth factor: clinical and genetic correlates and association with vascular function

AIMS

Growth factors play an important role in regulating vascular function. Data are limited regarding clinical and genetic correlates of endothelial growth factors and their associations with vascular function.

METHODS AND RESULTS

We evaluated clinical and genetic correlates of circulating vascular endothelial growth factor A (VEGF), its soluble receptor sFlt-1, and hepatocyte growth factor (HGF) in 3754 Framingham Study participants. We also related the growth factors to measures of brachial artery function. Serum VEGF and HGF were higher and sFLt-1 was lower in women and smokers. VEGF and HGF were associated positively with body mass index; both displayed strong positive associations with the metabolic syndrome (P < 0.001) and its components. The heritabilities of VEGF, sFlt-1, and HGF were 78, 13, and 38%, respectively. VEGF and HGF were related positively to baseline brachial diameter (P < 0.01) and to baseline mean flow velocity (P < 0.001) in age- and sex-adjusted models, but the multivariable models failed to reach significance. None of the growth factors were related to flow-mediated dilation.

CONCLUSION

In our community-based sample, circulating VEGF and HGF demonstrated high heritabilities and a sexual dimorphism. Increased angiogenesis and greater endothelial cell turnover may underlie associations of these growth factors with risk factors including smoking.