Background

Limited data exist regarding the use of a genetic risk score for predicting risk of incident cardiovascular disease (CVD) in US based samples.

Methods and Results

Using findings from recent GWAS, we constructed genetic risk scores (GRS) comprised of 13 genetic variants associated with myocardial infarction (MI) or other manifestations of CHD and 102 genetic variants associated with CHD or its major risk factors. We also updated the 13 SNP GRS with 16 SNPs recently discovered by GWAS. We estimated the association, discrimination and risk reclassification of each GRS for incident cardiovascular events and for prevalent coronary artery calcium (CAC).

In analyses adjusted for age, sex, CVD risk factors and parental history of CVD, the 13 SNP GRS was significantly associated with incident hard CHD (HR 1.07, 95% CI 1.00-1.15, p=0.04), CVD (hazard ratio [HR] per-allele 1.05, 95% confidence interval [CI] 1.01-1.09; p=0.03), and high CAC (defined as >75th age and sex-specific percentile; odds ratio [OR] per-allele 1.18, 95% CI 1.11-1.26, p=3.4 × 10-7). The GRS did not improve discrimination for incident CHD or CVD but led to modest improvements in risk reclassification. However, significant improvements in discrimination and risk reclassification were observed for the prediction of high CAC. The addition of 16 newly discovered SNPs to the 13 SNP GRS did not significantly modify these results.

Conclusions

A GRS comprised of 13 SNPs associated with coronary disease is an independent predictor of cardiovascular events and of high CAC, modestly improves risk reclassification for incident CHD and significant improves discrimination for high CAC. The addition of recently discovered SNPs did not significantly improve the performance of this GRS.

Background

Recent genome-wide association studies have identified multiple genetic loci that increase the risk of chronic kidney disease (CKD) in the general population. We hypothesized that knowledge of these loci might permit improved CKD risk prediction beyond that provided by traditional phenotypic risk factors.

Study design

Observational cohort study

Setting and participants

Participants who attended the 15th (1977–1979) and 24th (1995–1998) examination cycles of the Original cohort or the 6th (1995–1998) and 8th cycles (2005–2008) of the Offspring cohort of the Framingham Heart Study (n=2,489).

Predictors

Single-nucleotide polymorphisms (SNPs) at 16 stage 3 CKD loci were genotyped and used to construct a genetic risk score. Standard clinical predictors of incident stage 3 CKD were also used.

Outcomes and Measurements

Incident stage 3 CKD was defined as eGFR <60 mL/min/1.73m2 at follow-up. Participants with baseline stage 3 CKD were excluded. Logistic regression was used to generate C statistics, which measured the power of the genetic risk score to discriminate risk of incident CKD stage 3 with and without traditional risk factors.

Results

There were 270 new stage 3 CKD cases during an average of 10.8 years follow-up. The mean (±SD) genetic risk score was 17.5±2.8 among those who developed stage 3 CKD and 17.3±2.6 among those who did not (P-value for genotype score difference=0.2). The odds ratio for stage 3 CKD was 1.06 (95% CI, 1.01–1.11; p=0.03) per additional risk allele, adjusting for age and sex. In the age and sex-adjusted model, the C statistic was 0.748 without the genotype score and 0.751 with the score (P-value for difference=0.3). The risk score was not statistically significant in a multivariable model adjusted for standard stage 3 CKD risk factors (p=0.07).

Limitations

Participants all of European ancestry; genotype score may not be valid in different ancestral groups.

Conclusions

A genetic score generated from 16 known CKD risk alleles did not predict new cases of stage 3 CKD in the community beyond knowledge of common, clinical risk factors alone.

Background

Coronary artery calcification (CAC) detected by computed tomography is a non-invasive measure of coronary atherosclerosis, that underlies most cases of myocardial infarction (MI). We aimed to identify common genetic variants associated with CAC and further investigate their associations with MI.

Methods and Results

Computed tomography was used to assess quantity of CAC. A meta-analysis of genome-wide association studies for CAC was carried out in 9,961 men and women from five independent community-based cohorts, with replication in three additional independent cohorts (n=6,032). We examined the top single nucleotide polymorphisms (SNPs) associated with CAC quantity for association with MI in multiple large genome-wide association studies of MI. Genome-wide significant associations with CAC for SNPs on chromosome 9p21 near CDKN2A and CDKN2B (top SNP: rs1333049, P=7.58×10−19) and 6p24 (top SNP: rs9349379, within the PHACTR1 gene, P=2.65×10−11) replicated for CAC and for MI. Additionally, there is evidence for concordance of SNP associations with both CAC and with MI at a number of other loci, including 3q22 (MRAS gene), 13q34 (COL4A1/COL4A2 genes), and 1p13 (SORT1 gene).

Conclusions

SNPs in the 9p21 and PHACTR1 gene loci were strongly associated with CAC and MI, and there are suggestive associations with both CAC and MI of SNPs in additional loci. Multiple genetic loci are associated with development of both underlying coronary atherosclerosis and clinical events.

Ectopic fat depots may mediate local and systemic disease. Animal models of diet-induced obesity demonstrate increased fat accumulation in the renal sinus. The association of renal sinus fat with hypertension, chronic kidney disease (CKD), and other metabolic disorders has not been studied in a large, community-based sample. Participants from the Framingham Heart Study (n=2923, mean age 54 years, 51% women) underwent quantification of renal sinus fat area using computed tomography. High renal sinus fat (“fatty kidney”) was defined using sex-specific 90th percentiles in a healthy referent sub-sample. Multivariable linear and logistic regression was used to model metabolic risk factors as a function of fatty kidney and log-transformed renal sinus fat. Multivariable models were adjusted for age, sex, outcome-specific covariates, and then additionally adjusted for body mass index (BMI) or abdominal visceral adipose tissue (VAT). The prevalence of fatty kidney was 30.1% (n=879). Individuals with fatty kidney had a higher odds ratio (OR) of hypertension (OR 2.12, p<0.0001), which persisted after adjustment for BMI (OR 1.49, p<0.0001) and VAT (OR 1.24, p=0.049). Fatty kidney was also associated with an increased odds ratio for CKD (OR 2.30, p=0.005), even after additionally adjusting for BMI (OR 1.86, p=0.04) or VAT (OR 1.86, p=0.05). We observed no association between fatty kidney and diabetes after adjusting for VAT. In conclusion, fatty kidney is a common condition that is associated with an increased risk of hypertension and chronic kidney disease. Renal sinus fat may play a role in blood pressure regulation and CKD.

Serum urate concentrations are highly heritable and elevated serum urate is a key risk factor for gout. Genome-wide association studies (GWAS) of serum urate in African American (AA) populations are lacking. We conducted a meta-analysis of GWAS of serum urate levels and gout among 5820 AA and a large candidate gene study among 6890 AA and 21 708 participants of European ancestry (EA) within the Candidate Gene Association Resource Consortium. Findings were tested for replication among 1996 independent AA individuals, and evaluated for their association among 28 283 EA participants of the CHARGE Consortium. Functional studies were conducted using 14C-urate transport assays in mammalian Chinese hamster ovary cells. In the discovery GWAS of serum urate, three loci achieved genome-wide significance (P< 5.0 × 10−8): a novel locus near SGK1/SLC2A12 on chromosome 6 (rs9321453, P= 1.0 × 10−9), and two loci previously identified in EA participants, SLC2A9 (P= 3.8 × 10−32) and SLC22A12 (P= 2.1 × 10−10). A novel rare non-synonymous variant of large effect size in SLC22A12, rs12800450 (minor allele frequency 0.01, G65W), was identified and replicated (beta −1.19 mg/dl, P= 2.7 × 10−16). 14C-urate transport assays showed reduced urate transport for the G65W URAT1 mutant. Finally, in analyses of 11 loci previously associated with serum urate in EA individuals, 10 of 11 lead single-nucleotide polymorphisms showed direction-consistent association with urate among AA. In summary, we identified and replicated one novel locus in association with serum urate levels and experimentally characterize the novel G65W variant in URAT1 as a functional allele. Our data support the importance of multi-ethnic GWAS in the identification of novel risk loci as well as functional variants.

Background

Early detection of individuals at high risk for chronic kidney disease (CKD) may aid prevention. Urinary levels of trefoil factor 3 (TFF3) are associated with acute kidney injury in animal models, but the association of TFF3 levels with incident CKD in humans is unknown.

Methods

We conducted a case-control study nested within the Atherosclerosis Risk in Communities (ARIC) Study and the ARIC Carotid MRI Study to determine whether urinary TFF3 levels predict incident CKD over 8.6 years of follow-up. A total of 143 participants with incident CKD (eGFR decreasing by ≥25% to <60 ml/min/1.73 m2) were matched on age, sex and race to 143 non-cases.

Results

Higher TFF3 levels at baseline were strongly associated with Black race, diabetes (both p = 0.002), and antihypertensive medication use (p = 0.02). Compared to participants with TFF3 levels in the lowest quartile, the odds ratio (OR) of incident CKD was 1.84 (95% confidence interval (CI): 0.80, 4.22) for individuals with TFF3 levels in the second quartile, 2.43 (95% CI: 1.06, 5.53) for the third quartile, and 2.77 (95% CI: 1.22, 6.28) for the fourth quartile (p trend = 0.02). Adjustment for covariates, including urinary albumin: creatinine ratio, did not markedly change the associations. Twofold higher TFF3 levels were strongly associated with incident CKD after adjustment for CKD risk factors (adjusted OR = 1.35; 95% CI: 1.11, 1.64).

Conclusions

Higher urinary TFF3 levels may indicate ongoing repair of damage in the kidney. Additional studies are needed to confirm whether TFF3 can be useful as a marker of increased risk for CKD.

Leukocyte telomere length (LTL) is associated with a number of common age-related diseases and is a heritable trait. Previous genome-wide association studies (GWASs) identified two loci on chromosomes 3q26.2 (TERC) and 10q24.33 (OBFC1) that are associated with the inter-individual LTL variation. We performed a meta-analysis of 9190 individuals from six independent GWAS and validated our findings in 2226 individuals from four additional studies. We confirmed previously reported associations with OBFC1 (rs9419958 P = 9.1 × 10−11) and with the telomerase RNA component TERC (rs1317082, P = 1.1 × 10−8). We also identified two novel genomic regions associated with LTL variation that map near a conserved telomere maintenance complex component 1 (CTC1; rs3027234, P = 3.6 × 10−8) on chromosome17p13.1 and zinc finger protein 676 (ZNF676; rs412658, P = 3.3 × 10−8) on 19p12. The minor allele of rs3027234 was associated with both shorter LTL and lower expression of CTC1. Our findings are consistent with the recent observations that point mutations in CTC1 cause short telomeres in both Arabidopsis and humans affected by a rare Mendelian syndrome. Overall, our results provide novel insights into the genetic architecture of inter-individual LTL variation in the general population.

Background. Elevations in serum phosphorus are associated with renal decline in animal models and progression of established chronic kidney disease (CKD) in human observational studies. We examined whether serum phosphorus levels increase the risk of incident CKD or end-stage renal disease (ESRD) in two population-based prospective cohort studies.

Methods. Overall, 2269 participants free of CKD [estimated glomerular filtration rate (eGFR) <60 mL/min/1.732] from the Framingham Heart Study (FHS; mean age 42 years; 53% women) and 13 372 participants from the Third National Health and Nutrition Examination Survey (NHANES III; mean age 44.3 years, 52% women) contributed to the present study. In the FHS, we evaluated the relationship between baseline phosphorus category (<2.5 mg/dL, 2.5–3.49 mg/dL, 3.5–3.99 mg/dL and ≥4 mg/dL) and incident CKD (n = 267). In NHANES, we examined the relationship between phosphorus below and above 4 mg/dL in relation to incident ESRD (n = 65).

Results. FHS participants in the highest phosphorus category had an increased risk of CKD [odds ratio 2.14; 95% confidence interval (CI), 1.07–4.28; P = 0.03] in multivariable-adjusted models when compared to the referent group (2.5–3.49 mg/dL). Similarly, NHANES III participants with phosphorus levels ≥4 mg/dL demonstrated an increased risk of incident ESRD compared to those <4 mg/dL (relative risk 1.90; 95% CI 1.03–3.53; P = 0.04).

Conclusions. In prospective studies of the general population, serum phosphorus levels in the upper-normal range were associated with a doubling in the risk of developing incident CKD and ESRD.

Polymorphisms in the MYH9 and adjacent APOL1 gene region demonstrate a strong association with non-diabetic kidney disease in African-Americans. However, it is not known to what extent these polymorphisms are present in other ethnic groups. To examine the association of genetic polymorphisms in this region with chronic kidney disease (CKD; estimated glomerular filtration rate <60 ml/min/1.73 m2) in individuals of European ancestry, we examined rs4821480, an MYH9 single-nucleotide polymorphism (SNP) recently identified as associated with kidney disease in African-Americans, in 13 133 participants from the Framingham Heart Study (FHS) and Atherosclerosis Risk in Communities (ARIC) Study. In addition, we further interrogated the MYH9/APOL1 gene region using 282 SNPs for association with CKD using age-, sex- and center-adjusted models and performed a meta-analysis of the results from both studies. Because of prior data linking rs4821480 and kidney disease, we used a P-value of <0.05 to test the association with CKD. In the meta-analysis, rs4821480 (minor allele frequency 4.45 and 3.96% in FHS and ARIC, respectively) was associated with higher CKD prevalence in participants free of diabetes (odds ratio 1.44; 95% confidence interval 1.15–1.80; P = 0.001). No other SNPs achieved significance after adjusting for multiple testing. Results utilizing directly genotyped data confirmed the results of the primary analysis. Recently identified APOL1 risk variants were also directly genotyped, but did not account for the observed MYH9 signal. These data suggest that the MYH9 polymorphism rs4821480 is associated with an increased risk of non-diabetic CKD in individuals of European ancestry.

Background

Connective tissue growth factor (CTGF) is involved in the development and progression of kidney diseases including diabetic nephropathy and kidney fibrosis, but may also play a role in mesangial repair following injury. It is unknown whether, in the general population, urinary CTGF levels are associated with reduction of estimated glomerular filtration rate (eGFR) to less than 60 ml/min/1.73m2 (ie, development of chronic kidney disease [CKD] stage 3).

Study Design

Nested case-control.

Setting & Participants

100 cases of incident CKD stage 3 and 100 age-and sex-matched controls in the Framingham Heart Study (FHS); 141 cases and 135 age-, sexand race-matched controls in the Atherosclerosis Risk in Communities (ARIC) Study. Controls had eGFR ≥60 ml/min/1.73m2 at follow-up in both studies.

Predictors

Urinary CTGF concentrations.

Outcomes

Incident CKD stage 3, defined as eGFR <60 ml/min/1.73m2.

Measurements

Stored urine samples from Framingham Heart Study and ARIC were measured for CTGF. Covariates were obtained from Framingham Heart Study and ARIC participant examinations.

Results

In Framingham Heart Study, the median baseline urinary CTGF concentration was lower among cases (1.35 ng/mL) than controls (2.35 ng/mL; paired t-test P<0.0001). The multivariable-adjusted OR for incident CKD stage 3 was 0.33 (95% confidence interval [CI] 0.17–0.64; P<0.001) per 1-standard deviation increase in log urinary CTGF after adjustment for CKD risk factors, baseline eGFR and baseline log urinary albumin-creatinine ratio, with similar results among participants without diabetes (n=184). Results were not materially different when urinary CTGF was indexed to urinary creatinine (multivariable-adjusted OR, 0.34; 95% CI, 0.21–0.56; P<0.001). A similar, but non-significant, trend of risk of incident CKD stage 3 with lower baseline urinary CTGF concentration was observed in an independent case-control study conducted in the ARIC Study, with the strongest results observed among participants free of diabetes. This inverse relationship was robust in meta-analysis of both the overall and diabetes-free groups.

Limitations

Observational study; causality cannot be inferred.

Conclusions

Lower urinary CTGF concentrations precede the onset of CKD stage 3 in the general population. Further work is required to fully characterize how CTGF influences risk of CKD.

Background

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.

Methods

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.

Results

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.

Conclusions

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.

Introduction

A younger age at menarche and an older age at menopause are well established risk factors for breast cancer. Recent genome-wide association studies have identified several novel genetic loci associated with these two traits. However, the association between these loci and breast cancer risk is unknown.

Methods

In this study, we investigated 19 and 17 newly identified single nucleotide polymorphisms (SNPs) from the ReproGen Consortium that have been associated with age at menarche and age at natural menopause, respectively, and assessed their associations with breast cancer risk in 6 population-based studies among up to 3,683 breast cancer cases and 34,174 controls in white women of European ancestry. In addition, we used these SNPs to calculate genetic risk scores (GRSs) based on their associations with each trait.

Results

After adjusting for age and potential population stratification, two age at menarche associated SNPs (rs1079866 and rs7821178) and one age at natural menopause associated SNP (rs2517388) were associated with breast cancer risk (p values, 0.003, 0.009 and 0.023, respectively). The odds ratios for breast cancer corresponding to per-risk-allele were 1.14 (95% CI, 1.05 to 1.24), 1.08 (95% CI, 1.02 to 1.15) and 1.10 (95% CI, 1.01 to 1.20), respectively, and were in the direction predicted by their associations with age at menarche or age at natural menopause. These associations did not appear to be attenuated by further controlling for self-reported age at menarche, age at natural menopause, or known breast cancer susceptibility loci. Although we did not observe a statistically significant association between any GRS for reproductive aging and breast cancer risk, the 4th and 5th highest quintiles of the younger age at menarche GRS had odds ratios of 1.14 (95% CI, 1.01 to 1.28) and 1.13 (95% CI, 1.00 to 1.27), respectively, compared to the lowest quintile.

Conclusions

Our study suggests that three genetic variants, independent of their associations with age at menarche or age at natural menopause, were associated with breast cancer risk and may contribute modestly to breast cancer risk prediction; however, the combination of the 19 age at menarche or the 17 age at natural menopause associated SNPs did not appear to be useful for identifying a high risk subgroup for breast cancer.

Objectives

To describe the clinical correlates and heritability of the early repolarization pattern (ERP) in two large population-based cohorts.

Background

There is growing recognition that ERP is associated with adverse outcomes.

Methods

Participants of the Framingham Heart Study (FHS, n = 3,995) and the Health 2000 Survey (H2K, n = 5,489) were included. ERP was defined as J-point elevation ≥0.1 mV in ≥2 leads in either the inferior (II, III, aVF) or lateral (I, aVL, V4–6) territory or both. We tested the association between clinical characteristics and ERP and estimated sibling recurrence risk.

Results

ERP was present in 243/3,955 (6.1%) of FHS and 180/5,489 (3.3%) of H2K subjects. Male sex, younger age, lower systolic blood pressure, higher Sokolow-Lyon index, and lower Cornell voltage were independently associated with the presence of ERP. In the FHS sample, siblings of individuals with ERP had an ERP prevalence of 11.6% (recurrence risk ratio of 1.89). Siblings of individuals with ERP had an increased unadjusted odds of ERP (OR 2.22, 95% CI 1.01–4.85, p = 0.047).

Conclusion

ERP shows strong association with clinical factors and has evidence for a heritable basis in general population. Further assessment of the genetic determinants of ERP is warranted.

Serum calcium levels are tightly regulated. We performed genome-wide association studies (GWAS) in population-based studies participating in the CHARGE Consortium to uncover common genetic variations associated with total serum calcium levels. GWAS of serum calcium concentrations was performed in 20 611 individuals of European ancestry for ∼2.5 million genotyped and imputed single-nucleotide polymorphisms (SNPs). The SNP with the lowest P-value was rs17251221 (P = 2.4 * 10−22, minor allele frequency 14%) in the calcium-sensing receptor gene (CASR). This lead SNP was associated with higher serum calcium levels [0.06 mg/dl (0.015 mmol/l) per copy of the minor G allele] and accounted for 0.54% of the variance in serum calcium concentrations. The identification of variation in CASR that influences serum calcium concentration confirms the results of earlier candidate gene studies. The G allele of rs17251221 was also associated with higher serum magnesium levels (P = 1.2 * 10−3), lower serum phosphate levels (P = 2.8 * 10−7) and lower bone mineral density at the lumbar spine (P = 0.038), but not the femoral neck. No additional genomic loci contained SNPs associated at genome-wide significance (P < 5 * 10−8). These associations resemble clinical characteristics of patients with familial hypocalciuric hypercalcemia, an autosomal-dominant disease arising from rare inactivating mutations in the CASR gene. We conclude that common genetic variation in the CASR gene is associated with similar but milder features in the general population.

Background

Predictors for incident albuminuria are not well-known in population based cohorts. The purpose of this study was to identify predictors of incident albuminuria in an unselected, middle-aged population.

Study Design

Observational cohort study

Setting and participants

Framingham Offspring Study participants who attended both the sixth (baseline; 1995–1998) and eighth (2005–2008) examination cycles.

Predictors

Standard clinical predictors were used. Predictors of incident albuminuria were identified by stepwise logistic regression analysis with age and sex forced into the model.

Outcomes and Measurements

Albuminuria was defined as urine albumin-creatinine ratio (UACR) ≥17 mg/g (men) or ≥ 25 mg/g (women). Individuals with albuminuria at baseline were excluded.

Results

1916 participants were available for analysis (mean age 56 years, 54% women). Albuminuria developed in 10.0% of participants (n=192) over 9.5 years. Age (odds ratio [OR], 2.09; p-value<0.001), baseline diabetes (OR, 1.93; p-value= 0.01), smoking (OR, 2.09; p-value <0.001) and baseline log UACR (OR per standard deviation increase in log UACR, 1.56; p-value <0.001) were associated with incident albuminuria in a stepwise model. An inverse relationship with female sex (OR, 0.53; p <0.001) and HDL cholesterol (OR, 0.80; p-value=0.007) was also observed. Results were similar when participants with baseline chronic kidney disease (n=102), defined as eGFR < 60 mL/min/1.73 m2, were excluded from the model. Age, male sex, low HDL-cholesterol, smoking and log UACR continued to be associated with incident albuminuria when baseline diabetes (n= 107) was excluded. Age, male sex and log UACR correlated with incident albuminuria after participants with baseline hypertension were excluded (n= 651).

Limitations

Causality may not be inferred due to the observational nature of the study. One-third of participants did not return for follow-up, potentially attenuating the observed risks for albuminuria.

Conclusions

The known cardiovascular risk factors of increasing age, male sex, diabetes, smoking, low HDL cholesterol, and albuminuria within the “normal range” are correlates of incident albuminuria in the general population.

Background

Ectopic fat accumulation in the renal sinus is associated with chronic kidney disease and hypertension. The genetic contributions to renal sinus fat accumulation in humans have not been well characterized.

Methods

The present analysis consists of participants from the Framingham Offspring and Third Generation who underwent computed tomography; renal sinus fat and visceral adipose tissue (VAT) were quantified. Renal sinus fat was natural log transformed and sex- and cohort-specific residuals were created, adjusted for (1) age, (2) age and body mass index (BMI), and (3) age and VAT. Residuals were pooled and used to calculate heritability using variance-components analysis in SOLAR. A genome-wide association study (GWAS) for renal sinus fat was performed using an additive model with approximately 2.5 million imputed single nucleotide polymorphisms (SNPs). Finally, we identified the associations of renal sinus fat in our GWAS results with validated SNPs for renal function (n = 16), BMI (n = 32), and waist-to-hip ratio (WHR, n = 14), and applied a multi-SNP genetic risk score method to determine if the SNPs for each renal and obesity trait were in aggregate associated with renal sinus fat.

Results

The heritability of renal sinus fat was 39% (p < 0.0001); results were not materially different after adjustment for BMI (39%) or VAT (40%). No SNPs reached genome-wide significance in our GWAS. In our candidate gene analysis, we observed nominal, direction consistent associations with renal sinus fat for one SNP associated with renal function (p = 0.01), two associated with BMI (p < 0.03), and two associated with WHR (p < 0.03); however, none remained significant after accounting for multiple testing. Finally, we observed that in aggregate, the 32 SNPs associated with BMI were nominally associated with renal sinus fat (multi-SNP genetic risk score p = 0.03).

Conclusions

Renal sinus fat is a heritable trait, even after accounting for generalized and abdominal adiposity. This provides support for further research into the genetic determinants of renal sinus fat. While our study was underpowered to detect genome-wide significant loci, our candidate gene BMI risk score results suggest that variability in renal sinus fat may be associated with SNPs previously known to be associated with generalized adiposity.

Background

Renal sinus fat may mediate obesity-related vascular disease, although this fat depot has not been assessed in a community-based sample. We sought to develop a protocol to quantify renal sinus fat accumulation using multi-detector computed tomography (MDCT).

Methods

Protocol development was performed in participants in the Framingham Offspring cohort who underwent MDCT. Volumetric renal sinus fat was measured separately within the right and left kidneys, and renal sinus fat area within a single MDCT scan slice was measured in the right kidney. Due to the high correlation of volumetric and single-slice renal sinus fat in the right kidney (Pearson correlation [r] = 0.85, p < 0.0001), we optimized a single-slice protocol to capture renal sinus fat in the right kidney alone. Pearson correlation coefficients were used to compare to assess the correlation of volumetric and single-slice renal sinus fat in the right kidney with other measures of adiposity. Inter- and intra-reader reproducibility was assessed using intra-class correlation coefficients.

Results

Single-slice measurements were obtained in 92 participants (mean age 60 years, 49% women, median renal sinus fat 0.43 cm2). Intra- and inter-reader intra-class correlation coefficients were 0.93 and 0.86, respectively. Single-slice renal sinus fat was correlated with body mass index (r = 0.35, p = 0.0006), waist circumference (r = 0.31, p = 0.003), and abdominal visceral fat (r = 0.48, p < 0.0001). Similar correlations were observed for volumetric renal sinus fat in the right kidney.

Conclusions

Measuring renal sinus fat is feasible and reproducible using MDCT scans in a community-based sample.

Background

Certain bone marrow-derived cell populations, termed endothelial progenitor cells (EPCs), have been reported to possess angiogenic activity. Experimental data suggest that depletion of these angiogenic cell populations may promote atherogenesis, but limited data are available regarding their relation to subclinical atherosclerotic cardiovascular disease in humans.

Methods and Results

We studied 889 participants of the Framingham Heart Study who were free of clinically apparent cardiovascular disease (mean age, 65 years; 55% women). Participants underwent EPC phenotyping using an early outgrowth colony forming unit (CFU) assay and cell surface markers. Participants also underwent non-contrast multidetector computed tomography to assess the presence of subclinical atherosclerosis, as reflected by burden of coronary artery calcification (CAC) and abdominal aortic calcification (AAC). In this study sample, we examined the association of EPC-related phenotypes with both CAC and AAC. Across decreasing tertiles of CFU, there was a progressive increase in median CAC and AAC scores. In multivariable analyses adjusting for traditional cardiovascular risk factors, each standard deviation increase in CFU was associated with an approximately 16% decrease in CAC (P=0.02) and 17% decrease in AAC (P=0.03). In contrast, neither CD34+/KDR+ nor CD34+ variation were associated with significant differences in coronary or aortic calcification.

Conclusion

In this large, community-based sample of men and women, lower CFU number was associated with a higher burden of subclinical atherosclerosis in the coronary arteries and aorta. Decreased angiogenic potential could contribute to the development of atherosclerosis in humans.

Background

Compared to those with health insurance, the uninsured receive less care for chronic conditions such as hypertension and diabetes and they experience higher mortality.

Methods

We investigated the relations of health insurance status to prevalence, treatment, and control of major cardiovascular disease risk factors, hypertension and elevated low-density lipoprotein (LDL) cholesterol, among Framingham Heart Study (FHS) participants in sex-specific age-adjusted analyses. Participants who attended either the seventh Offspring cohort examination cycle (1998–2001) or the first Third Generation cohort examination cycle (2002–2005) were studied.

Results

Among 6098 participants, 3.8% were uninsured at the time of the FHS clinic examination and participants’ ages ranged from 19 to 64 years. The prevalence of hypertension and elevated LDL cholesterol was similar for the insured and uninsured, however the proportion of those who obtained treatment and achieved control of these risk factors was lower among the uninsured. Uninsured men and women were less likely to be treated for hypertension with odds ratios for treatment of 0.19 (95% CI 0.07–0.56) for men and 0.31 (95% CI 0.12–0.79) for women. Among men, the uninsured were less likely to receive treatment or achieve control of elevated LDL cholesterol than the insured, with odds ratios of 0.12 (95% CI 0.04–0.38) for treatment and 0.17 (95% CI 0.05–0.56) for control.

Conclusions

The treatment and control of hypertension and hypercholesterolemia are lower among uninsured adults. Increasing the proportion of insured individuals may be a means to improve the treatment and control of cardiovascular disease risk factors and reduce health disparities.

Coronary artery calcium (CAC) predicts risk for coronary heart disease (CHD) events and it is possible that CAC testing may further stratify risk in individuals at intermediate CHD risk. We sought to determine the percentage of individuals at intermediate CHD risk who could potentially be reclassified as high CHD risk based on the presence of a high CAC score as well as the prevalence, treatment, and control of CHD risk factors in this group. Framingham Heart Study Offspring and Third Generation cohort participants underwent multidetector CT (n=3,529; mean age=51 years; 48% women). High CAC was defined as either ≥90th age- and sex-specific percentiles based on a healthy reference group or by an absolute modified Agatston score of 100 Hounsfield units (HU). The prevalence of CHD risk factors (hypertension, hypercholesterolemia, high low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol, smoking, and obesity), and their treatment, and control was compared between non-diabetic subjects with and without high CAC. Of the 595 participants at intermediate CHD risk, 22% had CAC ≥90th percentile and 39% had CAC ≥100 and could be eligible for reclassification as high CHD risk based on the presence of a high CAC score. There were no statistically significant differences in prevalence, treatment, and control of risk factors between those with and without high CAC. In conclusion, the prevalence of CHD risk factors did not differ between intermediate risk individuals with and without high CAC. Approximately 25% of intermediate risk persons have high CAC scores and may be eligible for reclassification into a higher risk category.

Chronic kidney disease (CKD) has a heritable component and is an important global public health problem because of its high prevalence and morbidity.1 We conducted genome-wide association studies (GWAS) to identify susceptibility loci for glomerular filtration rate estimated by serum creatinine (eGFRcrea), cystatin C (eGFRcys), and CKD (eGFRcrea<60 ml/min/1.73m2) in European-ancestry participants of four populations-based cohorts (ARIC, CHS, FHS, RS; n=19,877, 2,388 CKD cases), and tested for external replication in 21,466 participants (1,932 CKD cases). Significant associations (p<5*10−8) were identified for SNPs with [1] CKD at the UMOD locus; [2] eGFRcrea at the UMOD, SHROOM3, and GATM/SPATA5L1 loci; [3] eGFRcys at the CST and STC1 loci. UMOD encodes the most common protein in human urine, Tamm-Horsfall protein,2 and rare mutations in UMOD cause Mendelian forms of kidney disease.3 Our findings provide new insights into CKD pathogenesis and underscore the importance of common genetic variants influencing renal function and disease.

Background

Various measures of arterial stiffness and wave reflection have been proposed as cardiovascular risk markers. Prior studies have not assessed relations of a comprehensive panel of stiffness measures to prognosis in the community.

Methods and Results

We used proportional hazards models to analyze first-onset major cardiovascular disease (CVD) events (myocardial infarction, unstable angina, heart failure or stroke) in relation to arterial stiffness (pulse wave velocity, PWV), wave reflection (augmentation index, carotid-brachial pressure amplification) and central pulse pressure in 2232 participants (mean age 63 years, 58% women) in the Framingham Heart Study. During median follow-up of 7.8 (range 0.2 to 8.9) years, 151 of 2232 participants (6.8%) had an event. In multivariable models adjusting for age, sex, systolic blood pressure, use of antihypertensive therapy, total and HDL cholesterol concentrations, smoking and presence of diabetes, higher aortic PWV was associated with a 48% increase in CVD risk (95% CI, 1.16 to 1.91 per SD, P=0.002). After adding PWV to a standard risk factor model, integrated discrimination improvement was 0.7% (95% CI, 0.05 to 1.3%, P<0.05). In contrast, augmentation index, central pulse pressure and pulse pressure amplification were not related to CVD outcomes in multivariable models.

Conclusions

Higher aortic stiffness assessed by PWV is associated with increased risk for a first cardiovascular event. Aortic PWV improves risk prediction when added to standard risk factors and may represent a valuable biomarker of CVD risk in the community.

Body fat distribution may be differentially associated with subclinical cardiovascular disease. We sought to examine whether body mass index (BMI), waist circumference (WC), subcutaneous (SAT) and visceral (VAT) adipose tissue are associated with either prevalence of coronary (CAC) or abdominal aortic calcium (AAC) in the Framingham Heart Study. Participants (n=3130, mean age 52 years, 49% women) free of clinical cardiovascular disease from the Framingham Heart Study underwent multidetector computed tomography assessment for quantification of subcutaneous and visceral fat volume and coronary and abdominal aortic calcification. Coronary artery calcification (CAC) and abdominal aortic calcification (AAC) were examined in relation to BMI, WC, SAT, and VAT in age- sex- and multivariable-adjusted models. All measures of adiposity were associated with CAC in age-sex adjusted models (all p-values<0.008). All relations were attenuated in multivariable models (all p-value>0.14). BMI, WC, and VAT (but not SAT) were associated with abdominal aortic calcification in age- sex-adjusted models (all p-values<0.012). However, all relations were attenuated in multivariable models (all p-values>0.23). Similar findings were observed in quartile-based analyses. In conclusion, general measures of obesity and measures of central abdominal fat are related to CAC and AAC. However, these cross-sectional associations are attenuated by cardiovascular disease risk factors, possibly because they may mediate the association between adiposity measures and subclinical cardiovascular disease.

Magnesium, potassium, and sodium, cations commonly measured in serum, are involved in many physiological processes including energy metabolism, nerve and muscle function, signal transduction, and fluid and blood pressure regulation. To evaluate the contribution of common genetic variation to normal physiologic variation in serum concentrations of these cations, we conducted genome-wide association studies of serum magnesium, potassium, and sodium concentrations using ∼2.5 million genotyped and imputed common single nucleotide polymorphisms (SNPs) in 15,366 participants of European descent from the international CHARGE Consortium. Study-specific results were combined using fixed-effects inverse-variance weighted meta-analysis. SNPs demonstrating genome-wide significant (p<5×10−8) or suggestive associations (p<4×10−7) were evaluated for replication in an additional 8,463 subjects of European descent. The association of common variants at six genomic regions (in or near MUC1, ATP2B1, DCDC5, TRPM6, SHROOM3, and MDS1) with serum magnesium levels was genome-wide significant when meta-analyzed with the replication dataset. All initially significant SNPs from the CHARGE Consortium showed nominal association with clinically defined hypomagnesemia, two showed association with kidney function, two with bone mineral density, and one of these also associated with fasting glucose levels. Common variants in CNNM2, a magnesium transporter studied only in model systems to date, as well as in CNNM3 and CNNM4, were also associated with magnesium concentrations in this study. We observed no associations with serum sodium or potassium levels exceeding p<4×10−7. Follow-up studies of newly implicated genomic loci may provide additional insights into the regulation and homeostasis of human serum magnesium levels.

Author Summary

Magnesium, potassium, and sodium are involved in important physiological processes. To better understand how common genetic variation may contribute to inter-individual differences in serum concentrations of these electrolytes, we evaluated single nucleotide polymorphisms (SNPs) across the genome in association with serum magnesium, potassium, and sodium levels in 15,366 participants of European descent from the CHARGE Consortium. We then verified the associations in an additional 8,463 study participants. Six different genomic regions contain variants that are reproducibly associated with serum magnesium levels, and only one of the regions had been previously known to influence serum magnesium concentrations in humans. The identified SNPs also show association with clinically defined hypomagnesemia, and some of them with traits that have been linked to serum magnesium levels, including kidney function, fasting glucose, and bone mineral density. We further provide evidence for a physiological role of magnesium transporters in humans which have previously only been studied in model systems. None of the SNPs evaluated in our study are significantly associated with serum levels of sodium or potassium. Additional studies are needed to investigate the underlying molecular mechanisms in order to help us understand the contribution of these newly identified regions to magnesium homeostasis.