Branched-chain amino acid (BCAA) concentrations are elevated in response to overnutrition, and can affect both insulin sensitivity and secretion. Alterations in their metabolism may therefore play a role in the early pathogenesis of type 2 diabetes in overweight children.
To determine whether pediatric obesity is associated with elevations in fasting circulating concentrations of branched-chain amino acids (isoleucine, leucine, and valine), and whether these elevations predict future insulin resistance.
Research Design and Methods
Sixty-nine healthy subjects, ages 8 to18 years, were enrolled as a cross-sectional cohort. A subset who were pre- or early-pubertal, ages 8 to 13 years, were enrolled in a prospective longitudinal cohort for 18 months (n=17 with complete data).
Elevations in the concentrations of BCAA’s were significantly associated with BMI Z-score (Spearman’s Rho 0.27, p=0.03) in the cross-sectional cohort. In the subset of subjects followed longitudinally, baseline BCAA concentrations were positively associated with HOMA-IR measured 18 months later after controlling for baseline clinical factors including BMI Z-score, sex, and pubertal stage (p=0.046).
Elevations in the concentrations of circulating branched-chain amino acids are significantly associated with obesity in children and adolescents, and may independently predict future insulin resistance.
branched-chain amino acids; insulin resistance; pediatric obesity; metabolomics; type 2 diabetes
Water and sodium retention precedes the development of high blood pressure (BP) and explains a compensatory rise in B-type natriuretic peptide (BNP) concentrations. It is unclear if BNP concentrations antedate the BP progression. We hypothesized higher BNP concentrations in our African American cohort will be associated with longitudinal increases in BP, progression of BP stage and incident hypertension.
Our study sample consisted of 888 normotensive [based on BP at Examination 1(2000-04)] participants of the Jackson Heart Study (mean age 47±12 years, 61% women). We examined the relation of BNP concentrations at the baseline examination to change in systolic and diastolic BP, BP progression (an increase by one BP stage as defined by JNC VI) and incident hypertension by Examination 2 (2005-08) adjusting for baseline BP stages, systolic and diastolic BP, traditional risk factors and echocardiographic LV mass.
Over a median follow-up period of 5.0± 0.8 years, 36.9% progressed to a higher BP stage and 19.3% developed hypertension. In multivariable regression models, higher log-BNP concentrations at Examination 1 were significantly and positively associated with changes in systolic and diastolic BP (p <0.05 for both). Baseline log-BNP was significantly associated with BP progression (p = 0.046). Every SD increase in baseline log BNP was associated with a 12% increased risk of BP progression. Log-BNP was not significantly associated with incident hypertension (p=0.12).
In our community-based sample of African Americans, higher BNP concentrations predict longitudinal increase in systolic and diastolic BP and progression of BP stage.
Blood Pressure; B-type Natriuretic Peptide; African Americans
Low serum magnesium has been linked to increased risk of atrial fibrillation (AF) following cardiac surgery. It is unknown whether hypomagnesemia predisposes to AF in the community.
Methods and Results
We studied 3,530 participants (mean age, 44 years; 52% women) from the Framingham Offspring Study who attended a routine examination, and were free of AF and cardiovascular disease. We used Cox proportional hazard regression analysis to examine the association between serum magnesium at baseline and risk of incident AF. Analyses were adjusted for conventional AF risk factors, use of antihypertensive medications, and serum potassium. During up to 20 years of follow-up, 228 participants developed AF. Mean serum magnesium was 1.88 mg/dl. The age- and sex-adjusted incidence rate of AF was 9.4 per 1,000 person-years (95% confidence interval, 6.7 to 11.9) in the lowest quartile of serum magnesium (≤1.77 mg/dl), compared with 6.3 per 1,000 person-years (95% confidence interval, 4.1 to 8.4) in the highest quartile (≥1.99 mg/dl). In multivariable-adjusted models, individuals in the lowest quartile of serum magnesium were approximately 50% more likely to develop AF (adjusted hazard ratio, 1.52, 1.00 to 2.31; P=0.05), compared with those in the upper quartiles. Results were similar after excluding individuals on diuretics.
Low serum magnesium is moderately associated with the development of AF in individuals without cardiovascular disease. Because hypomagnesemia is common in the general population, a link with AF may have potential clinical implications. Further studies are warranted to confirm our findings and elucidate the underlying mechanisms.
arrhythmia; epidemiology; atrial fibrillation; magnesium
Biomarkers for predicting cardiovascular events in community-based populations have not consistently added information to standard risk factors. A limitation of many previously studied biomarkers is their lack of cardiovascular specificity.
Methods and Results
To determine the prognostic value of 3 novel biomarkers induced by cardiovascular stress, we measured soluble ST2, growth differentiation factor-15, and high-sensitivity troponin I in 3,428 participants (mean age 59, 53% women) in the Framingham Heart Study. We performed multivariable-adjusted proportional hazards models to assess the individual and combined ability of the biomarkers to predict adverse outcomes. We also constructed a “multimarker” score composed of the 3 biomarkers, in addition to B-type natriuretic peptide and high-sensitivity C-reactive protein. During a mean follow-up of 11.3 years, there were 488 deaths, 336 major cardiovascular events, 162 heart failure events, and 142 coronary events. In multivariable-adjusted models, the 3 new biomarkers were associated with each endpoint (p<0.001) except for coronary events. Individuals with multimarker scores in the highest quartile had a 3-fold risk of death (adjusted hazard ratio, 3.2, 95% CI, 2.2–4.7; p<0.001), 6-fold risk of heart failure (6.2, 95% CI, 2.6–14.8; p<0.001), and 2-fold risk of cardiovascular events (1.9, 95% CI, 1.3–2.7; p=0.001). Addition of the multimarker score to clinical variables led to significant increases in the c-statistic (p=0.007 or lower) and net reclassification improvement (p=0.001 or lower).
Multiple biomarkers of cardiovascular stress are detectable in ambulatory individuals, and add prognostic value to standard risk factors for predicting death, overall cardiovascular events, and heart failure.
biomarkers; risk assessment; risk prediction
Improvements in metabolite-profiling techniques are providing increased breadth of coverage of the human metabolome and may highlight biomarkers and pathways in common diseases such as diabetes. Using a metabolomics platform that analyzes intermediary organic acids, purines, pyrimidines, and other compounds, we performed a nested case-control study of 188 individuals who developed diabetes and 188 propensity-matched controls from 2,422 normoglycemic participants followed for 12 years in the Framingham Heart Study. The metabolite 2-aminoadipic acid (2-AAA) was most strongly associated with the risk of developing diabetes. Individuals with 2-AAA concentrations in the top quartile had greater than a 4-fold risk of developing diabetes. Levels of 2-AAA were not well correlated with other metabolite biomarkers of diabetes, such as branched chain amino acids and aromatic amino acids, suggesting they report on a distinct pathophysiological pathway. In experimental studies, administration of 2-AAA lowered fasting plasma glucose levels in mice fed both standard chow and high-fat diets. Further, 2-AAA treatment enhanced insulin secretion from a pancreatic β cell line as well as murine and human islets. These data highlight a metabolite not previously associated with diabetes risk that is increased up to 12 years before the onset of overt disease. Our findings suggest that 2-AAA is a marker of diabetes risk and a potential modulator of glucose homeostasis in humans.
Animal studies suggest that the arginine vasopressin (AVP) system may play a role in glucose metabolism, but data from humans are limited.
Methods and Results
We analysed plasma copeptin (copeptin), a stable C-terminal fragment of the AVP pro-hormone. Using baseline and longitudinal data from a Swedish population-based sample (n=4742, mean age 58 years, 60% women), we examined the association of increasing quartiles of copeptin (lowest quartile as reference) with prevalent diabetes at baseline, insulin resistance (top quartile of fasting plasma insulin among non-diabetic subjects), and incident diabetes on long-term follow up using multivariable logistic regression. New-onset diabetes was ascertained through 3 national and regional registers. All models were adjusted for clinical and anthropometric risk factors, cystatin C, and C-reactive protein. In cross-sectional analyses, increasing copeptin was associated with prevalent diabetes (P=0.04) and insulin resistance (P<0.001). During 12.6 years of follow up 174 subjects (4%) developed new-onset diabetes. The odds of developing diabetes increased across increasing quartiles of copeptin, even after additional adjustment for baseline fasting glucose and insulin (adjusted odds ratios 1.0, 1.37, 1.79, and 2.09; P for trend =0.004). The association with incident diabetes remained significant in analyses restricted to subjects with fasting whole blood glucose <5.4 mmol/L at baseline (adjusted odds ratios 1.0, 1.80, 1.92, and 3.48; P=0.001).
Elevated copeptin predicts increased risk for diabetes, independent of established clinical risk factors, including fasting glucose and insulin. These findings could have implications for risk assessment, novel anti-diabetic treatments, and metabolic side effects from AVP system modulation.
arginine vasopressin; copeptin; diabetes mellitus; risk factors; epidemiology
Inferior lead early repolarization pattern (ERP) has recently been associated with sudden cardiac death. Although ERP is common among athletes, prevalence, ECG lead distribution, clinical characteristics, and effects of physical training remain uncertain. We sought to examine the non-anterior early repolarization pattern (ERP) in competitive athletes.
Methods and Results
ERP was assessed in a cross-sectional cohort of collegiate athletes (n=879). The relationship between ERP and cardiac structure were then examined in a longitudinal subgroup (n=146) before and after a 90-day period of exercise training. ERP was defined as J-point elevation ≥ 0.1 mV in at least two leads within a non-anterior territory (inferior [II, III, aVF] or lateral [I, aVL, V4-V6]). Non-anterior ERP was present in 25.1% (221/879) of athletes including the inferior subtype in 3.8% (33/879). Exercise training led to significant increases in the prevalence of ERP and the inferior subtype but there were no associations between ERP and echocardiographic measures of left ventricular remodeling. In a multivariable model, ERP was associated with black race (OR 5.84, CI 3.54-9.61, p<0.001), increased QRS voltage (OR 2.08, CI 1.71-2.52, p<0.001), and slower HR (OR 1.54, CI 1.26-1.87, p<0.001).
Non-anterior ERP including the inferior subtype are common and have strong clinical associations among competitive athletes. The finding of increased ERP prevalence following intense physical training establishes a strong association between exercise and the ERP.
exercise; electrocardiography; electrophysiology athlete’s heart; early repolarization
Current data suggest that increases in hemoglobin may decrease nitric oxide and adversely affect vascular function. In the preclinical setting, these changes could precipitate the development of heart failure (HF). We hypothesized that higher hematocrit (HCT) would be associated with an increased incidence of new-onset HF in the community. We evaluated 3,523 participants (59% women) from the Framingham Heart Study who were 50 to 65 years old and free of HF. Participants were followed prospectively until an HF event, death, or the end of 20 years of follow up. HCT was subdivided into 4 gender-specific categories (women: HCT 36.0 to 40.0, 40.1 to 42.0, 42.1 to 45.0, >45.0; men: 39.0 to 44.0, 44.1 to 45.0, 45.1 to 49.0, >49.0). Gender-pooled multivariable Cox proportional hazards models were used to estimate the association of HCT with incident HF, adjusting for clinical risk factors. During the follow-up period (61,417 person-years), 217 participants developed HF (100 events in women). There was a linear increase in risk of HF across the 4 HCT categories (p for trend = 0.002). Hazards ratios for HF in the low–normal, normal, and high HCT categories were 1.27 (95% confidence interval 0.82 to 1.97), 1.47 (1.01 to 2.15), and 1.78 (1.15 to 2.75), respectively, compared to the lowest HCT category (p for trend <0.0001). Adjustment for interim development of other cardiovascular diseases and restriction of the sample to nonsmokers did not alter the results. In conclusion, higher levels of HCT, even within the normal range, were associated with an increased risk of developing HF in this long-term follow-up study.
Several biomarkers have been individually associated with vascular brain injury but no prior study has explored the simultaneous association of a biologically plausible panel of biomarkers with the incidence of stroke/TIA, and the prevalence of subclinical brain injury.
Methods and Results
In 3127 stroke-free Framingham Offspring (59±10 yrs, 54%F), we related a panel of 8 biomarkers assessing inflammation(C-reactive protein[CRP]), hemostasis(D-dimer and plasminogen activator inhibitor-1), neurohormonal activity(aldosterone-to renin ratio, B-type natriuretic peptide[BNP] and N-terminal pro-atrial natriuretic peptides) and endothelial function (homocysteine and urinary albumin/creatinine ratio[UACR]) measured at the 6th examination(1995–98) to risk of incident stroke/TIA. In a subset of 1901 participants with available brain MRI (1999–2005), we further related these biomarkers to total cerebral brain volume (TCBV), covert brain infarcts (CBI), and large white matter hyperintensity volume(LWMHV).
During a median follow-up of 9.2 years, 130 participants experienced incident stroke/TIA. In multivariable analyses adjusted for stroke risk factors, the biomarker panel was associated with incident stroke/TIA and with TCBV (p<0.05 for both), but not with CBI or LWMHV (p >0.05). In backwards elimination analyses higher log-BNP (hazards ratio [HR] 1.39/SD, p=0.002) and log-UACR (HR1.31/SD, p=0.004) were associated with increased risk of stroke/TIA and improved risk prediction over using the Framingham stroke risk profile alone; using <5%, 5–15% or >15% 10-year risk categories the net reclassification index was 0.109;p=0.037). Higher CRP (β=−0.21/SD,p=0.008), D-dimer(β==−0.18/SD,p=0.041), tHcy(β=−0.21/SD,p=0.005), and UACR(β=−0.15/SD,p=0.042) were associated with lower TCBV.
In a middle-aged community sample, we identified multiple biomarkers that were associated with clinical and subclinical vascular brain injury and could improve risk stratification.
biomarkers; epidemiology; magnetic resonance imaging; risk stratification; stroke prevention
In the primary prevention of cardiovascular disease, the study of biomarkers to identify at-risk individuals is an expanding field. Several developments have fueled this trend, including improved understanding of the pathophysiological processes underlying atherosclerosis, advances in imaging technology to enable the quantification of subclinical disease burden, and the identification of new genetic susceptibility variants for cardiovascular disease. Furthermore, the advent of high-throughput platforms for molecular profiling has increased the pace of biomarker discovery. The rising interest in biomarkers has been balanced by the recognition that standardized and rigorous statistical approaches are needed to evaluate the clinical utility of candidate risk markers. This article reviews the issues surrounding the evaluation of biomarkers, evidence from studies of existing biomarkers, and recent applications of biomarker discovery platforms.
Soluble ST2 (sST2) is a cardiac biomarker whose concentration rises in response to myocardial strain. Increased sST2 concentrations may predict adverse outcomes in patients with heart failure and myocardial infarction. Because sST2 was largely undetectable with first-generation assays in ambulatory individuals, there are few data regarding its distribution and correlates in community-based populations.
We measured sST2 using a highly sensitive ELISA in 3450 Framingham Heart Study participants who attended a routine examination. We used multivariable linear regression models to identify covariates associated with sST2 in the general sample. We obtained a reference sample (n = 1136) by excluding individuals with prevalent coronary disease, heart failure, atrial fibrillation, diabetes, hypertension, obesity, valvular disease, left ventricular systolic dysfunction, and pulmonary and renal dysfunction. We used empiric and quantile regression techniques to estimate the 2.5th, 50th, 97.5th, and 99th quantiles.
In the general sample (mean age 59 years, 55% women), systolic blood pressure (P = 0.006), antihypertensive medication use (P = 0.03), and diabetes (P < 0.001) were associated with sST2 concentrations. In the reference sample (mean age 55, 59% women), male sex (P < 0.0001) and older age (P = 0.004) were predictive of higher sST2 concentrations. Quantile and empirical methods were used to define the reference intervals. Using the empirical approach, upper 99% percentile values in different age groups ranged from 46.6 to 64.4 μg/L in men and 36.7 to 53.0 μg/L in women.
In a well-characterized, community-based cohort, values for sST2 differ between men and women, increase with age, and are associated with diabetes and hypertension.
Diabetes mellitus and obesity are increasing in prevalence and are associated with an elevated risk of atrial fibrillation (AF). Given the aging of the US population, AF is projected to concomitantly increase in prevalence in the upcoming decades. Both diabetes and obesity are associated with insulin resistance. Whether insulin resistance is an intermediate step for the development of AF is uncertain. We hypothesized that insulin resistance is associated with an increased risk of incident AF. We examined the association of insulin resistance with incident AF using multivariable Cox proportional hazards regression adjusting for established AF risk factors (age, sex, systolic blood pressure, hypertension treatment, PR interval, significant heart murmur, heart failure and body mass index). Of the 3,023 eligible participants (55% women; mean age 59 years) representing 4,583 persons-examinations (Framingham Offspring 5th and 7th examination cycles), 279 individuals developed AF (9.3%) up to 10 years of follow-up. With multivariable modeling, insulin resistance was not significantly associated with incident AF (hazard ratio comparing the top with the other three quartiles of homeostatic model assessment index (HOMA) 1.18, 95% confidence interval 0.84 to 1.65, p = 0.34). In a community-based cohort with up to 10 years follow-up, no significant association was observed between insulin resistance and incident AF.
Insulin resistance; atrial fibrillation; risk factors; epidemiology
Several bone marrow-derived cell populations have been identified that may possess angiogenic activity and contribute to vascular homeostasis in experimental studies. We examined the extent to which lower quantities of these circulating angiogenic cell phenotypes may be related to impaired vascular function and greater arterial stiffness.
We studied 1,948 Framingham Heart Study participants (mean age, 66±9 years; 54% women) who were phenotyped for circulating angiogenic cells: CD34+, CD34+/KDR+, and early outgrowth colony forming units (CFU). Participants underwent non-invasive assessments of vascular function including peripheral arterial tone (PAT), arterial tonometry, and brachial reactivity testing.
In unadjusted analyses, higher CD34+ and CD34+/KDR+ concentrations were modestly associated with lower PAT ratio (β=−0.052±0.011, P<0.001 and β=−0.030±0.011, P=0.008, respectively) and with higher carotid-brachial pulse wave velocity (β=0.144±0.043, P=0.001 and β=0.112±0.043, P=0.009), but not with flow-mediated dilation; higher CD34+ was also associated with lower carotid-femoral pulse wave velocity (β=−0.229±0.094, P=0.015) However, only the association of lower CD34+ concentration with higher PAT ratio persisted in multivariable analyses that adjusted for standard cardiovascular risk factors. In all analyses, CFU was not associated with measures of vascular function or arterial stiffness.
In our large, community-based sample of men and women, circulating angiogenic cell phenotypes largely were not associated with measures of vascular function or arterial stiffness in analyses adjusting for traditional risk factors.
angiogenesis; vascular function; risk factors; endothelium; epidemiology
N-terminal-pro-B-type natriuretic peptide (NT-proBNP) is a commonly measured cardiovascular biomarker in both ambulatory and hospital settings. Nonetheless, there are limited data regarding “normal” ranges for NT-proBNP in healthy individuals, despite the importance of such information for interpreting natriuretic peptide measurements. We examined a healthy reference sample free of cardiovascular disease from the Framingham Heart Study Generation 3 cohort; there were 2,285 subjects (mean age 38 years, 56% women). Plasma NT-proBNP levels were measured using the Roche Diagnostics Elecsys 2010 assay, and reference values (2.5, 50, 97.5 quantiles) were determined using empiric and quantile regression methods. Gender, age, and body mass index accounted for approximately 33% of the inter-individual variability in NT-proBNP in the reference sample. NT-proBNP values were substantially higher in women compared with men at every age, and levels increased with increasing age for both sexes. Using quantile regression, the upper reference values (97.5 quantile) for NT-proBNP were 42.5 pg/ml to 106.4 pg/ml in men (depending on age), and 111.0 pg/ml to 215.9 pg/ml in women. Intra-individual variability was assessed in an additional 12 healthy individuals, who had serial NT-proBNP measurements over a month. Intra-class correlation was 0.85, indicating that most of the variability in NT-proBNP concentrations was among-persons rather than within-persons. However, the reference change value was 100%, suggesting that small proportional differences in NT-proBNP could be attributable to analytic variability. In conclusion, the reference limits obtained from this large, healthy community-based sample may aid in the evaluation of NT-proBNP concentrations measured for both clinical and research purposes.
Natriuretic peptides; Cardiac Biomarkers; Heart Failure
Currently available screening tools for left ventricular (LV) hypertrophy (LVH) and systolic dysfunction (LVSD) are either expensive (echocardiography) or perform suboptimally (B‐type natriuretic peptide [BNP]). It is unknown whether newer biomarkers are associated with LVH and LVSD and can serve as screening tools.
Methods and Results
We studied 2460 Framingham Study participants (mean age 58 years, 57% women) with measurements of biomarkers mirroring cardiac biomechanical stress (soluble ST‐2 [ST2], growth differentiation factor‐15 [GDF‐15] and high‐sensitivity troponin I [hsTnI]) and BNP. We defined LVH as LV mass/height2 ≥the sex‐specific 80th percentile and LVSD as mild/greater impairment of LV ejection fraction (LVEF) or a fractional shortening <0.29. Adjusting for standard risk factors in logistic models, BNP, GDF‐15, and hsTnI were associated with the composite echocardiographic outcome (LVH or LVSD), odds ratios (OR) per SD increment in log‐biomarker 1.29, 1.14, and 1.18 (95% CI: 1.15 to 1.44, 1.004 to 1.28, and 1.06 to 1.31), respectively. The C‐statistic for the composite outcome increased from 0.765 with risk factors to 0.770 adding BNP, to 0.774 adding novel biomarkers. The continuous Net Reclassification Improvement was 0.212 (95% CI: 0.119 to 0.305, P<0.0001) after adding the novel biomarkers to risk factors plus BNP. BNP was associated with LVH and LVSD in multivariable models, whereas GDF‐15 was associated with LVSD (OR 1.41, 95% CI: 1.16 to 1.70), and hsTnI with LVH (OR 1.22, 95% CI: 1.09 to 1.36). ST2 was not significantly associated with any outcome.
Our community‐based investigation suggests that cardiac stress biomarkers are associated with LVH and LVSD but may have limited clinical utility as screening tools.
biomarkers; echocardiography; heart failure; hypertrophy; screening
Lower plasma B-type natriuretic peptide (BNP) concentrations in obese individuals (‘natriuretic handicap’) may play a role in the pathogenesis of obesity-related hypertension. Whether this phenomenon may contribute to hypertension in African Americans is unknown. We tested the hypothesis that body mass index (BMI) is inversely related to BNP concentrations in African Americans.
Methods and Results
We examined the relation of plasma BNP to BMI in 3,742 Jackson Heart Study participants (mean age: 55±13, 62% women) without heart failure using multivariable linear and logistic regression, adjusting for clinical and echocardiographic covariates. The multivariable adjusted mean BNP was higher for lean participants compared to obese participants in both normotensive (p<0.0001) and hypertensive (p<0.0012) groups. In sex-specific analyses, the adjusted mean BNP was higher in lean-hypertensive individuals compared to obese-hypertensive individuals for both men (20.5 pg/mL vs. 10.9 pg/mL; p=0.0009) and women (20.0 pg/mL vs. 13.8 pg/mL; p=0.011) respectively. The differences between lean and obese participants were more pronounced in normotensive participants (men, 9.0 pg/mL vs. 4.4 pg/mL; p<0.0001 and women, 12.8 pg/mL vs. 8.4 pg/mL; p=0.0005). For both hypertensive and normotensive individuals in the pooled sample, multivariable adjusted BNP was significantly related to both continuous BMI (p<0.05 and p<0.0001 respectively) and categorical BMI (p for trend <0.006 and <0.0001 respectively).
Our cross-sectional study of a large community-based sample of African-Americans demonstrates that higher BMI is associated with lower circulating BNP concentrations, thereby extending the concept of a ‘natriuretic handicap’ in obese individuals observed in non-Hispanic whites to this high-risk population.
Natriuretic peptide; obesity; hypertension
To assess the relationship between sex hormones and natriuretic peptide levels in community-based adults
Women have higher circulating natriuretic peptide concentrations than men, but the mechanisms for these sex-related differences and the impact of hormone therapy are unclear. Experimental studies suggest that androgens may suppress natriuretic peptide secretion.
We measured plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP), total testosterone, and sex hormone binding globulin (SHBG) in 4,056 men and women (mean age 40±9 years) from the Framingham Heart Study Third Generation cohort. Sex/hormone status was grouped as: 1) men, 2) postmenopausal women not receiving hormone replacement therapy, 3) premenopausal women not receiving hormonal contraceptives, 4) postmenopausal women receiving hormone replacement therapy and 5) premenopausal women receiving hormonal contraceptives.
Circulating NT-proBNP was associated with sex/hormone status (overall P<0.0001). Men had lower NT-proBNP than women of all menopause or hormone groups, and women receiving hormonal contraceptives had higher NT-proBNP than women who were not receiving hormone therapy (all P<0.0001). These relationships remained significant after adjusting for age, body mass index, and cardiovascular risk factors. Across sex/hormone status groups, FT decreased and SHBG increased in tandem with increasing NT-proBNP. In sex-specific analyses, NT-proBNP decreased across increasing quartiles of free testosterone in men (P for trend<0.01) and in women (P for trend<0.0001). Adjustment for FT markedly attenuated the association between sex/hormone status and NT-proBNP concentrations.
These findings suggest that lower circulating androgens and the potentiating effect of exogenous female hormone therapy contribute to the higher circulating NT-proBNP concentrations in women.
natriuretic peptides; sex; hormones
Salt sensitivity, a trait characterized by a pressor blood pressure (BP) response to increased dietary salt intake, has been associated with higher rates of cardiovascular target organ damage and cardiovascular disease events. Recent experimental studies have highlighted the potential role of the natriuretic peptides and aldosterone in mediating salt sensitivity.
Methods and Results:
We evaluated 1575 non-hypertensive Framingham Offspring cohort participants (mean age 55±9 years, 58% women) who underwent routine measurements of circulating aldosterone and N-terminal proatrial natriuretic peptide (NT-ANP) and assessment of dietary sodium intake. Participants were categorized as potentially ‘salt-sensitive’ if their serum aldosterone was >sex-specific median but plasma NT-ANP was ≤sex-specific median value. Dietary sodium intake was categorized as lower versus higher (dichotomized at the sex-specific median). We used multivariable linear regression to relate presence of salt sensitivity (as defined above) to longitudinal changes (Δ) in systolic and diastolic BP on follow-up (median 4 years). Participants who were ‘salt-sensitive’ (N=437) experienced significantly greater increases in BP (Δ systolic, +4.4 and +2.3 mmHg; Δ diastolic, +1.9 and −0.3 mmHg; on a higher versus lower sodium diet, respectively) as compared to the other participants (Δ systolic, +2.8 and +1.0 mmHg; Δ diastolic, +0.5 and −0.2 mmHg; on higher versus lower sodium diet, respectively; p=0.033 and p=0.0127 for differences between groups in Δ systolic and Δ diastolic BP, respectively).
Our observational data suggest that higher circulating aldosterone and lower NT-ANP concentrations may be markers of salt sensitivity in the community. Additional studies are warranted to confirm these observations.
salt sensitivity; aldosterone; N-terminal proatrial natriuretic peptide; ANP
This study was carried out to investigate the prognostic utility of biomarkers in advanced stage heart failure (HF) patients requiring ICU admission for pulmonary artery catheter (PAC) guided therapy.
Thirty patients admitted to an ICU for PAC guided HF therapy were enrolled; concentrations of soluble ST2 (sST2), highly sensitive troponin I, an experimental ultrasensitive troponin I, amino-terminal pro-B type natriuretic peptide, cystatin C, and myeloperoxidase were measured over the first 48 hours. Outcomes included response of filling pressures and hemodynamics to tailored therapy and 90-day event-free survival (death, left ventricular assist device implantation, transplant).
Of the biomarkers evaluated, only sST2 concentrations were higher in those who failed to achieve goals for central venous pressure ((CVP), 225.3 versus 104.6 ng/mL; P = 0.003) and pulmonary capillary wedge pressure ((PCWP), 181.7 versus 88.2 ng/mL; P = 0.05). Only sST2 concentrations were associated with adverse events (186.7 versus 92.2 ng/mL; P = 0.01). In age-adjusted Cox proportional hazards analysis, an elevated sST2 during the first 48 hours following ICU admission independently predicted 90-day outcomes (Hazard Ratio = 5.53; P = 0.03) superior to the Simplified Acute Physiology Score for this application; in Kaplan-Meier analysis the risk associated with elevated sST2 concentrations was present early and sustained through the duration of follow-up (log rank P = 0.01).
In patients undergoing HF therapy guided by invasive monitoring, sST2 concentrations were associated with impending failure to reduce filling pressures and predicted impending events. Elevated sST2 values early in the ICU course theoretically could assist therapeutic decision-making in advanced stage HF patients.
ClinicalTrials.gov Identifier: NCT00595738
Vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] <50 nmol/L) is commonly reported in both children and adults worldwide, and growing evidence indicates that vitamin D deficiency is associated with many extraskeletal chronic disorders, including the autoimmune diseases type 1 diabetes and multiple sclerosis.
RESEARCH DESIGN AND METHODS
We measured 25(OH)D concentrations in 720 case and 2,610 control plasma samples and genotyped single nucleotide polymorphisms from seven vitamin D metabolism genes in 8,517 case, 10,438 control, and 1,933 family samples. We tested genetic variants influencing 25(OH)D metabolism for an association with both circulating 25(OH)D concentrations and disease status.
Type 1 diabetic patients have lower circulating levels of 25(OH)D than similarly aged subjects from the British population. Only 4.3 and 18.6% of type 1 diabetic patients reached optimal levels (≥75 nmol/L) of 25(OH)D for bone health in the winter and summer, respectively. We replicated the associations of four vitamin D metabolism genes (GC, DHCR7, CYP2R1, and CYP24A1) with 25(OH)D in control subjects. In addition to the previously reported association between type 1 diabetes and CYP27B1 (P = 1.4 × 10−4), we obtained consistent evidence of type 1 diabetes being associated with DHCR7 (P = 1.2 × 10−3) and CYP2R1 (P = 3.0 × 10−3).
Circulating levels of 25(OH)D in children and adolescents with type 1 diabetes vary seasonally and are under the same genetic control as in the general population but are much lower. Three key 25(OH)D metabolism genes show consistent evidence of association with type 1 diabetes risk, indicating a genetic etiological role for vitamin D deficiency in type 1 diabetes.
Animal studies suggest that local adipocyte-mediated activity of the renin-angiotensin-aldosterone system (RAAS) contributes to circulating levels, and may promote the development of obesity-related hypertension in rodents.
We examined relations of systemic RAAS activity, as assessed by circulating plasma renin activity (PRA), serum aldosterone level, and aldosterone:renin ratio (ARR), with specific regional adiposity measures in a large, community-based sample. Third Generation Framingham Heart Study participants underwent multidetector computed tomography assessment of SAT and VAT volumes during Exam 1 (2002 and 2005). PRA and serum aldosterone were measured after approximately 10 minutes of supine rest; results were log-transformed for analysis. Correlation coefficients between log-transformed RAAS measures and adiposity measurements were calculated, adjusted for age and sex. Partial correlations between log-transformed RAAS measures and adiposity measurements were also calculated, adjusted for standard CVD risk factors.
Overall, 992 women and 897 men were analyzed (mean age 40 years; 7% hypertension; 3% diabetes). No associations were observed with SAT (renin r = 0.04, p = 0.1; aldosterone r = -0.01, p = 0.6) or VAT (renin r = 0.03, p = 0.2; aldosterone r = -0.03, p = 0.2). Similar results were observed for ARR, in sex-stratified analyses, and for BMI and waist circumference. Non-significant partial correlations were also observed in models adjusted for standard cardiovascular risk factors.
Regional adiposity measures were not associated with circulating measures of RAAS activity in this large population-based study. Further studies are required to determine whether adipocyte-derived RAAS components contribute to systemic RAAS activity in humans.
Biomarkers of multiple pathophysiological pathways have been related to incident atrial fibrillation (AF), but their predictive ability remains controversial.
Methods and Results
In 3120 Framingham cohort participants (mean age 58.4±9.7, 54% women), we related 10 biomarkers representing inflammation (C-reactive protein [CRP], fibrinogen), neurohormonal activation (B-type natriuretic peptide [BNP], N-terminal pro-atrial natriuretic peptide), oxidative stress (homocysteine), renin-angiotensin-aldosterone system (renin, aldosterone), thrombosis and endothelial function (D-dimer, plasminogen-activator inhibitor 1 [PAI-1]), and microvascular damage (urine albumin excretion, n=2673) with incident AF (n=209, 40% women) over a median follow-up of 9.7 years (range 0.05–12.8 years).
In multivariable-adjusted analyses, the biomarker panel was associated with incident AF (P<0.0001). In stepwise selection models (P<0.01 for entry and retention), log-transformed BNP, hazard ratio [HR] per standard deviation 1.62 (95% confidence interval [CI] 1.41–1.85, P<0.0001), and CRP, HR 1.25 (95% CI 1.07–1.45, P=0.004), were chosen.
The addition of BNP to variables recently combined in a risk score for AF increased the C-statistic from 0.78 (95%CI 0.75–0.81 to 0.80 (95% CI 0.78–0.83), and showed an integrated discrimination improvement of 0.03 (95% CI 0.02–0.04, P<0.0001) with 34.9% relative improvement in reclassification analysis. The combined analysis of BNP and CRP did not appreciably improve risk prediction over the model incorporating BNP in addition to the risk factors.
BNP is a predictor of incident AF and improves risk stratification based on well-established clinical risk factors. Whether knowledge of BNP concentrations may be used to target individuals at risk of AF for more intensive monitoring or primary prevention needs further investigation.
atrial fibrillation; biomarkers; epidemiology; cohort; risk assessment
We sought to validate a recently published risk algorithm for incident atrial fibrillation (AF) in independent cohorts and other race/ethnic groups.
We evaluated the performance of a Framingham Heart Study (FHS)-derived risk algorithm modified for 5-year incidence of AF in the FHS (n=4764 participants) and two geographically and ethnically diverse cohorts: AGES (Age, Gene/Environment Susceptibility-Reykjavik Study, n=4238), and CHS (Cardiovascular Health Study, n=5410 of whom 874 (16.2%) were African Americans (AA)); aged 45–95 years. The risk algorithm included age, sex, body mass index, systolic blood pressure, electrocardiographic PR-interval, hypertension treatment, and heart failure.
We observed 1359 incident AF events in 100,074 person-years of follow-up. Unadjusted five-year event-rates differed by cohort (AGES 12.8 cases/1000 person-years; CHS whites 22.7 cases/1000 person-years; FHS 4.5 cases/1000 person-years) and race/ethnicity (CHS AA 18.4 cases/1000 person-years).
The strongest risk factors in all samples were age and heart failure. The relative risks for incident AF associated with risk factors were comparable across cohorts and race groups. After recalibration for baseline incidence and risk factor distribution, the Framingham algorithm performed reasonably well in all samples (AGES C-statistic 0.67, 95% confidence interval 0.64–0.71; CHS whites, 0.68, 0.66–0.70; CHS AA 0.66, 0.61–0.71). Risk factors combined in the algorithm explained between 47.0% (AGES) and 63.6% (FHS) of the population attributable risk.
Risk of incident AF in community-dwelling whites and AA can be assessed reliably by routinely available and potentially modifiable clinical variables. Seven risk factors accounted for up to 64% percent of risk.
atrial fibrillation; risk score; epidemiology; cohort study; race/ethnicity
To assess the predictive accuracy of conventional cardiovascular risk factors for incident heart failure(HF) and atrial fibrillation(AF) and the added benefit of multiple biomarkers reflecting diverse pathophysiological pathways.
HF and AF are interrelated cardiac diseases associated with substantial morbidity and mortality and increasing incidence. Data on prediction and prevention of these diseases in healthy individuals is limited.
In 5,187 individuals from the community-based Malmö Diet and Cancer study, we studied the performance of conventional risk factors and six biomarkers including midregional pro-atrial natriuretic peptide(MR-proANP), N-terminal pro-B-type natriuretic peptide(Nt-proBNP), midregional pro-adrenomedullin, cystatin C, C-reactive protein(CRP) and copeptin.
During a mean follow-up of 14 years,112 individuals were diagnosed with HF and 284 individuals with AF. Nt-proBNP(HR=1.63 per SD,95%CI=1.29–2.06,p<0.001), CRP(HR=1.57 per SD,95%CI=1.28–1.94,p<0.001) and MR-proANP(HR=1.26 per SD,95%CI=1.02-1-56,p=0.03) predicted incident HF independently of conventional risk factors and other biomarkers. MR-proANP(HR=1.62,95%CI=1.42-1.84,p<0.001) and CRP(HR=1.18,95%CI=1.03–1.34,p=0.01) independently predicted AF. Addition of biomarkers to conventional risk factors improved C-statistics from 0.815 to 0.842 for HF and from 0.732 to 0.753 for AF and the Integrated discriminatory index for both diseases(p<0.001). Net reclassification improvement with biomarkers was observed in 22% of individuals for HF(NRI,p<0.001) and in 7% for AF(NRI,p=0.06), mainly due to up-classification of individuals who developed disease(HF:29%,AF:19%). Addition of CRP to natriuretic peptides did not improve discrimination or reclassification.
Conventional cardiovascular risk factors predict incident HF and AF with reasonable accuracy in middle-aged individuals free from disease. Natriuretic peptides, but not other biomarkers, improve discrimination modestly for both diseases above and beyond conventional risk factors and substantially improve classification for HF.
Atrial Fibrillation; Heart failure; Prediction; Natriuretic peptides; Risk factors; Epidemiology