The functional consequences of trait associated SNPs are often investigated using expression quantitative trait locus (eQTL) mapping. While trait-associated variants may operate in a cell-type specific manner, eQTL datasets for such cell-types may not always be available. We performed a genome-environment interaction (GxE) meta-analysis on data from 5,683 samples to infer the cell type specificity of whole blood cis-eQTLs. We demonstrate that this method is able to predict neutrophil and lymphocyte specific cis-eQTLs and replicate these predictions in independent cell-type specific datasets. Finally, we show that SNPs associated with Crohn’s disease preferentially affect gene expression within neutrophils, including the archetypal NOD2 locus.
Many variants in the genome, including variants associated with disease, affect the expression of genes. These so-called expression quantitative trait loci (eQTL) can be used to gain insight in the downstream consequences of disease. While it has been shown that many disease-associated variants alter gene expression in a cell-type dependent manner, eQTL datasets for specific cell types may not always be available and their sample size is often limited. We present a method that is able to detect cell type specific effects within eQTL datasets that have been generated from whole tissues (which may be composed of many cell types), in our case whole blood. By combining numerous whole blood datasets through meta-analysis, we show that we are able to detect eQTL effects that are specific for neutrophils and lymphocytes (two blood cell types). Additionally, we show that the variants associated with some diseases may preferentially alter the gene expression in one of these cell types. We conclude that our method is an alternative method to detect cell type specific eQTL effects, that may complement generating cell type specific eQTL datasets and that may be applied on other cell types and tissues as well.
Genome-wide association studies (GWAS) have uncovered numerous genetic variants (SNPs) that are associated with blood pressure (BP). Genetic variants may lead to BP changes by acting on intermediate molecular phenotypes such as coded protein sequence or gene expression, which in turn affect BP variability. Therefore, characterizing genes whose expression is associated with BP may reveal cellular processes involved in BP regulation and uncover how transcripts mediate genetic and environmental effects on BP variability. A meta-analysis of results from six studies of global gene expression profiles of BP and hypertension in whole blood was performed in 7017 individuals who were not receiving antihypertensive drug treatment. We identified 34 genes that were differentially expressed in relation to BP (Bonferroni-corrected p<0.05). Among these genes, FOS and PTGS2 have been previously reported to be involved in BP-related processes; the others are novel. The top BP signature genes in aggregate explain 5%–9% of inter-individual variance in BP. Of note, rs3184504 in SH2B3, which was also reported in GWAS to be associated with BP, was found to be a trans regulator of the expression of 6 of the transcripts we found to be associated with BP (FOS, MYADM, PP1R15A, TAGAP, S100A10, and FGBP2). Gene set enrichment analysis suggested that the BP-related global gene expression changes include genes involved in inflammatory response and apoptosis pathways. Our study provides new insights into molecular mechanisms underlying BP regulation, and suggests novel transcriptomic markers for the treatment and prevention of hypertension.
The focus of blood pressure (BP) GWAS has been the identification of common DNA sequence variants associated with the phenotype; this approach provides only one dimension of molecular information about BP. While it is a critical dimension, analyzing DNA variation alone is not sufficient for achieving an understanding of the multidimensional complexity of BP physiology. The top loci identified by GWAS explain only about 1 percent of inter-individual BP variability. In this study, we performed a meta-analysis of gene expression profiles in relation to BP and hypertension in 7017 individuals from six studies. We identified 34 differentially expressed genes for BP, and discovered that the top BP signature genes explain 5%–9% of BP variability. We further linked BP gene expression signature genes with BP GWAS results by integrating expression associated SNPs (eSNPs) and discovered that one of the top BP loci from GWAS, rs3184504 in SH2B3, is a trans regulator of expression of 6 of the top 34 BP signature genes. Our study, in conjunction with prior GWAS, provides a deeper understanding of the molecular and genetic basis of BP regulation, and identifies several potential targets and pathways for the treatment and prevention of hypertension and its sequelae.
In mouse models, CCAAT enhancer-binding protein beta (CEBPB) is necessary for M2 macrophage-mediated regeneration after muscle injury. In humans, CEBPB expression in blood was strongly associated with muscle strength. In this study we aimed to test whether CEBPB expression in blood in people is increased 2 days after exercise designed to induce muscle damage and subsequent repair. Sixteen healthy male volunteers undertook elbow flexor exercises designed to induce acute muscle micro-damage. Peripheral blood samples were collected at baseline and days 1, 2, 4 and 7 following exercise. Expression of CEBPB and related genes were analysed by qRT-PCR. Extent of muscle damage was determined by decline in maximal voluntary isometric torque and by plasma creatine kinase activity. Nine subjects had peak (day 4) creatine kinase activity exceeding 10,000 U/l. In this subgroup, CEBPB expression was elevated from baseline to 2 days post exercise (paired-samples t(1,8) = 3.72, p = 0.006). Related expression and selected cytokine changes after exercise did not reach significance. Muscle-damaging exercise in humans can be followed by induction of CEBPB transcript expression in peripheral blood. Associations between CEBPB expression in blood and muscle strength may be consistent with the CEBPB-dependent muscle repair process.
Electronic supplementary material
The online version of this article (doi:10.1007/s12576-014-0350-7) contains supplementary material, which is available to authorized users.
Muscle strength; Inflammation; CEBPB; Macrophage; Muscle damage; Muscle repair
Initial results from sequencing studies suggest that there are relatively few low-frequency (<5%) variants associated with large effects on common phenotypes. We performed low-pass whole-genome sequencing in 680 individuals from the InCHIANTI study to test two primary hypotheses: (i) that sequencing would detect single low-frequency–large effect variants that explained similar amounts of phenotypic variance as single common variants, and (ii) that some common variant associations could be explained by low-frequency variants. We tested two sets of disease-related common phenotypes for which we had statistical power to detect large numbers of common variant–common phenotype associations—11 132 cis-gene expression traits in 450 individuals and 93 circulating biomarkers in all 680 individuals. From a total of 11 657 229 high-quality variants of which 6 129 221 and 5 528 008 were common and low frequency (<5%), respectively, low frequency–large effect associations comprised 7% of detectable cis-gene expression traits [89 of 1314 cis-eQTLs at P < 1 × 10−06 (false discovery rate ∼5%)] and one of eight biomarker associations at P < 8 × 10−10. Very few (30 of 1232; 2%) common variant associations were fully explained by low-frequency variants. Our data show that whole-genome sequencing can identify low-frequency variants undetected by genotyping based approaches when sample sizes are sufficiently large to detect substantial numbers of common variant associations, and that common variant associations are rarely explained by single low-frequency variants of large effect.
Children of centenarians have lower cardiovascular disease prevalence and live longer. We aimed to estimate associations between the full range of parental attained ages and health status in a middle-aged U.S. representative sample.
Using Health and Retirement Study data, models estimated disease incidence and mortality hazards for respondents aged 51–61 years at baseline, followed up for 18 years. Full adjustment included sex, race, smoking, wealth, education, body mass index, and childhood socioeconomic status. Mother’s and father’s attained age distributions were used to define short-, intermediate-, and long-lived groups, yielding a ranked parental longevity score (n = 6,055, excluding short–long discordance). Linear models (n = 8,340) tested mother’s or father’s attained ages, adjusted for each other.
With increasing mother’s or father’s survival (>65 years), all-cause mortality declined 19% (hazard ratio [HR] = 0.81, 95% CI: 0.76–0.86, p < .001) and 14% per decade (HR = 0.87, 95% CI: 0.81–0.92, p < .001). Estimates changed only modestly when fully adjusted. Parent-in-law survival was not associated with mortality (n = 1,809, HR = 1.00, 95% CI: 0.90–1.12, p = .98). Offspring with one or two long-lived parents had lower cancer incidence (938 cases, HR per parental longevity score = 0.76, 95% CI: 0.61–0.94, p = .01) versus two intermediate parents. Similar HRs for diabetes (HR = 0.89, 95% CI: 0.84–0.96, p = .001), heart disease (HR = 0.88, 95% CI: 0.82–0.93, p < .001), and stroke (HR = 0.86, 95% CI: 0.78–0.95, p = .002) were significant, but there was no trend for arthritis.
The results provide the first robust evidence that increasing parental attained age is associated with lower cancer incidence in offspring. Health advantages of having centenarian parents extend to a wider range of parental longevity and may provide a quantitative trait of slower aging.
Family history; Parental longevity; Cancer; Cardiovascular disease; Centenarian.
Background: the oldest old (85+) pose complex medical challenges. Both underdiagnosis and overdiagnosis are claimed in this group.
Objective: to estimate diagnosis, prescribing and hospital admission prevalence from 2003/4 to 2011/12, to monitor trends in medicalisation.
Design and setting: observational study of Clinical Practice Research Datalink (CPRD) electronic medical records from general practice populations (eligible; n = 27,109) with oversampling of the oldest old.
Methods: we identified 18 common diseases and five geriatric syndromes (dizziness, incontinence, skin ulcers, falls and fractures) from Read codes. We counted medications prescribed ≥1 time in all quarters of studied years.
Results: there were major increases in recorded prevalence of most conditions in the 85+ group, especially chronic kidney disease (stages 3–5: prevalence <1% rising to 36.4%). The proportions of the 85+ group with ≥3 conditions rose from 32.2 to 55.1% (27.1 to 35.1% in the 65–84 year group). Geriatric syndrome trends were less marked. In the 85+ age group the proportion receiving no chronically prescribed medications fell from 29.6 to 13.6%, while the proportion on ≥3 rose from 44.6 to 66.2%. The proportion of 85+ year olds with ≥1 hospital admissions per year rose from 27.6 to 35.4%.
Conclusions: there has been a dramatic increase in the medicalisation of the oldest old, evident in increased diagnosis (likely partly due to better record keeping) but also increased prescribing and hospitalisation. Diagnostic trends especially for chronic kidney disease may raise concerns about overdiagnosis. These findings provide new urgency to questions about the appropriateness of multiple diagnostic labelling.
oldest; prevalence; admission; prescribing; kidney; older people
Background: little is known about changes in the quality of medical care for older adults over time.
Objective: to assess changes in technical quality of care over 6 years, and associations with participants' characteristics.
Design: a national cohort survey covering RAND Corporation-derived quality indicators (QIs) in face-to-face structured interviews in participants' households.
Participants: a total of 5,114 people aged 50 or more in four waves of the English Longitudinal Study of Ageing.
Methods: the percentage achievement of 24 QIs in 10 general medical and geriatric clinical conditions was calculated for each time point, and associations with participants' characteristics were estimated using logistic regression.
Results: participants were eligible for 21,220 QIs. QI achievement for geriatric conditions (cataract, falls, osteoarthritis and osteoporosis) was 41% [95% confidence interval (CI): 38–44] in 2004–05 and 38% (36–39) in 2010–11. Achievement for general medical conditions (depression, diabetes mellitus, hypertension, ischaemic heart disease, pain and cerebrovascular disease) improved from 75% (73–77) in 2004–05 to 80% (79–82) in 2010–11. Achievement ranged from 89% for cerebrovascular disease to 34% for osteoarthritis. Overall achievement was lower for participants who were men, wealthier, infrequent alcohol drinkers, not obese and living alone.
Conclusion: substantial system-level shortfalls in quality of care for geriatric conditions persisted over 6 years, with relatively small and inconsistent variations in quality by participants' characteristics. The relative lack of variation by participants' characteristics suggests that quality improvement interventions may be more effective when directed at healthcare delivery systems rather than individuals.
quality of care; geriatrics; epidemiology; older people
To our knowledge, no prospective study has examined the association between vitamin D and cognitive decline or dementia.
We determined whether low levels of serum 25-hydroxyvitamin D (25[OH]D) were associated with an increased risk of substantial cognitive decline in the InCHIANTI population–based study conducted in Italy between 1998 and 2006 with follow-up assessments every 3 years. A total of 858 adults 65 years or older completed interviews, cognitive assessments, and medical examinations and provided blood samples. Cognitive decline was assessed using the Mini-Mental State Examination (MMSE), and substantial decline was defined as 3 or more points. The Trail-Making Tests A and B were also used, and substantial decline was defined as the worst 10% of the distribution of decline or as discontinued testing.
The multivariate adjusted relative risk (95% confidence interval [CI]) of substantial cognitive decline on the MMSE in participants who were severely serum 25 (OH)D deficient (levels <25 nmol/L) in comparison with those with sufficient levels of 25(OH)D (≥75 nmol/L) was 1.60 (95% CI, 1.19-2.00). Multivariate adjusted random-effects models demonstrated that the scores of participants who were severely 25(OH)D deficient declined by an additional 0.3 MMSE points per year more than those with sufficient levels of 25(OH)D. The relative risk for substantial decline on Trail-Making Test B was 1.31 (95% CI, 1.03-1.51) among those who were severely 25(OH)D deficient compared with those with sufficient levels of 25(OH)D. No significant association was observed for Trail-Making Test A.
Low levels of vitamin D were associated with substantial cognitive decline in the elderly population studied over a 6-year period, which raises important new possibilities for treatment and prevention.
Common variation at chromosome 9p21 (marked by rs10757278 or rs1333049) is associated with coronary artery disease (CAD) and peripheral vascular disease. A decreasing effect at older age was suggested, and effects on long-term mortality are unclear. We estimated 9p21 associations with CAD and all-cause mortality in a CAD diagnosis–free older population. We also estimated classification gains on adding the variant to the Framingham Risk Score (FRS) for CAD.
Methods and Results
DNA was from an Established Populations for Epidemiological Study of the Elderly–Iowa cohort from 1988 (participants >71 years), with death certificates obtained to 2008 for 92% of participants. Cox regression models were adjusted for confounders and CAD risk factors. Of 1095 CAD diagnosis–free participants, 52% were heterozygous (CG) and 22% were homozygous (CC) for the risk C allele rs1333049. Unadjusted CAD-attributed death rates in the CC group were 30 vs 22 per 1000 person-years for the GG group. The C allele was associated with all-cause (hazard ratio, 1.19; 95% CI, 1.08–1.30) and CAD (hazard ratio, 1.29; 95% CI, 1.08–1.56) mortality, independent of CAD risk factors. There was no association with stroke deaths. Variant associations with CAD mortality were attenuated after the age of 80 years (age-interaction term P=0.05). In age group 71 to 80 years, FRS classified as high risk 21% of respondents who died of CAD within 10 years; adding 9p21 identified 27% of respondents.
In 71- to 80-year-old subjects free of CAD diagnoses, 9p21 is associated with excess mortality, mainly attributed to CAD mortality. Adding 9p21 to the FRS may improve the targeting of CAD prevention in older people, but validation in independent samples is needed for confirmation.
coronary artery disease; genetic variation; myocardial infarction; survival; Framingham Risk Score
With white blood cell count emerging as an important risk factor for chronic inflammatory diseases, genetic associations of differential leukocyte types, specifically monocyte count, are providing novel candidate genes and pathways to further investigate. Circulating monocytes play a critical role in vascular diseases such as in the formation of atherosclerotic plaque. We performed a joint and ancestry-stratified genome-wide association analyses to identify variants specifically associated with monocyte count in 11 014 subjects in the electronic Medical Records and Genomics Network. In the joint and European ancestry samples, we identified novel associations in the chromosome 16 interferon regulatory factor 8 (IRF8) gene (P-value = 2.78×10(−16), β = −0.22). Other monocyte associations include novel missense variants in the chemokine-binding protein 2 (CCBP2) gene (P-value = 1.88×10(−7), β = 0.30) and a region of replication found in ribophorin I (RPN1) (P-value = 2.63×10(−16), β = −0.23) on chromosome 3. The CCBP2 and RPN1 region is located near GATA binding protein2 gene that has been previously shown to be associated with coronary heart disease. On chromosome 9, we found a novel association in the prostaglandin reductase 1 gene (P-value = 2.29×10(−7), β = 0.16), which is downstream from lysophosphatidic acid receptor 1. This region has previously been shown to be associated with monocyte count. We also replicated monocyte associations of genome-wide significance (P-value = 5.68×10(−17), β = −0.23) at the integrin, alpha 4 gene on chromosome 2. The novel IRF8 results and further replications provide supporting evidence of genetic regions associated with monocyte count.
Interventions which inhibit TOR activity (including rapamycin and caloric restriction) lead to downstream gene expression changes and increased lifespan in laboratory models. However, the role of mTOR signaling in human aging is unclear.
We tested the expression of mTOR-related transcripts in two independent study cohorts; the InCHIANTI population study of aging and the San Antonio Family Heart Study (SAFHS). Expression of 27/56 (InCHIANTI) and 19/44 (SAFHS) genes were associated with age after correction for multiple testing. 8 genes were robustly associated with age in both cohorts. Genes involved in insulin signaling (PTEN, PI3K, PDK1), ribosomal biogenesis (S6K), lipid metabolism (SREBF1), cellular apoptosis (SGK1), angiogenesis (VEGFB), insulin production and sensitivity (FOXO), cellular stress response (HIF1A) and cytoskeletal remodeling (PKC) were inversely correlated with age, whereas genes relating to inhibition of ribosomal components (4EBP1) and inflammatory mediators (STAT3) were positively associated with age in one or both datasets.
We conclude that the expression of mTOR-related transcripts is associated with advancing age in humans. Changes seen are broadly similar to mTOR inhibition interventions associated with increased lifespan in animals. Work is needed to establish whether these changes are predictive of human longevity and whether further mTOR inhibition would be beneficial in older people.
Aging; aging mechanisms; mTOR; human population
Identifying the downstream effects of disease-associated single nucleotide polymorphisms (SNPs) is challenging: the causal gene is often unknown or it is unclear how the SNP affects the causal gene, making it difficult to design experiments that reveal functional consequences. To help overcome this problem, we performed the largest expression quantitative trait locus (eQTL) meta-analysis so far reported in non-transformed peripheral blood samples of 5,311 individuals, with replication in 2,775 individuals. We identified and replicated trans-eQTLs for 233 SNPs (reflecting 103 independent loci) that were previously associated with complex traits at genome-wide significance. Although we did not study specific patient cohorts, we identified trait-associated SNPs that affect multiple trans-genes that are known to be markedly altered in patients: for example, systemic lupus erythematosus (SLE) SNP rs49170141 altered C1QB and five type 1 interferon response genes, both hallmarks of SLE2-4. Subsequent ChIP-seq data analysis on these trans-genes implicated transcription factor IKZF1 as the causal gene at this locus, with DeepSAGE RNA-sequencing revealing that rs4917014 strongly alters 3’ UTR levels of IKZF1. Variants associated with cholesterol metabolism and type 1 diabetes showed similar phenomena, indicating that large-scale eQTL mapping provides insight into the downstream effects of many trait-associated variants.
Depression is a heritable trait that exists on a continuum of varying severity and duration. Yet, the search for genetic variants associated with depression has had few successes. We exploit the entire continuum of depression to find common variants for depressive symptoms.
In this genome-wide association study, we combined the results of 17 population-based studies assessing depressive symptoms with the Center for Epidemiological Studies Depression Scale. Replication of the independent top hits (p < 1 × 10−5) was performed in five studies assessing depressive symptoms with other instruments. In addition, we performed a combined meta-analysis of all 22 discovery and replication studies.
The discovery sample comprised 34,549 individuals (mean age of 66.5) and no loci reached genome-wide significance (lowest p = 1.05 × 10−7). Seven independent single nucleotide polymorphisms were considered for replication. In the replication set (n = 16,709), we found suggestive association of one single nucleotide polymorphism with depressive symptoms (rs161645, 5q21, p = 9.19 × 10−3). This 5q21 region reached genome-wide significance (p = 4.78 × 10−8) in the overall meta-analysis combining discovery and replication studies (n = 51,258).
The results suggest that only a large sample comprising more than 50,000 subjects may be sufficiently powered to detect genes for depressive symptoms.
Center for Epidemiologic Studies Depression Scale; CHARGE consortium; depression; depressive symptoms; genetics; genome-wide association study; meta-analysis
In recent years there has been an exponential increase in tungsten demand, potentially increasing human exposure to the metal. Currently, the toxicology of tungsten is poorly understood, but mounting evidence suggests that both the elemental metal and its alloys have cytotoxic effects. Here, we investigate the association between tungsten and cardiovascular disease (CVD) or stroke using six waves of the National Health and Nutrition Examination Survey (NHANES).
We investigated associations using crude and adjusted logistic regression models in a cohort of 8614 adults (18–74 years) with 193 reported stroke diagnoses and 428 reported diagnoses of CVD. We also stratified our data to characterize associations in a subset of younger individuals (18–50 years).
Elevated tungsten concentrations were strongly associated with an increase in the prevalence of stroke, independent of typical risk factors (Odds Ratio (OR): 1.66, 95% Confidence Interval (95% CI): 1.17, 2.34). The association between tungsten and stroke in the young age category was still evident (OR: 2.17, 95% CI: 1.33, 3.53).
This study represents the most comprehensive analysis of the human health effects of tungsten to date. Individuals with higher urinary tungsten concentrations have double the odds of reported stroke. We hypothesize that the pathological pathway resulting from tungsten exposure may involve oxidative stress.
Circulating inflammatory markers may play an important role in cognitive impairment at older ages. Mice deficient for the chemokine (C-C motif) receptor 2 (CCR2) develop an accelerated Alzheimer-like pathology. CCR2 is also important in neurogenesis. To identify human gene transcripts most closely associated with Mini-Mental State Examination (MMSE) scores, we undertook a genome-wide and inflammation specific transcriptome screen in circulating leukocytes from a population-based sample.
We measured in vivo transcript levels by microarray analysis in 691 subjects (mean age 72.6 years) in the InCHIANTI study (Invecchiare in Chianti, aging in the Chianti area). We assessed expression associations with MMSE performance at RNA collection and prior 9-year change in MMSE score in linear regression models.
In genome-wide analysis, raised CCR2 expression was cross-sectionally the most strongly associated transcript with lower MMSE score (beta=−0.16, p=5.1×10−6, false discovery rate (FDR; q=0.077). Amongst inflammatory transcripts, only CCR2 expression was associated with both MMSE score and accelerated decline in score over the preceding 9 years (beta=−0.16, p=5.1×10−6, q=0.003; and beta=−0.13, p=5.5×10−5, q=0.03, respectively). CCR2 expression was also positively associated with apolipoprotein E (ApoE) e4 Alzheimer disease risk haplotype.
We show for the first time that CCR2 expression is associated with lower MMSE scores in an older human population. Laboratory models of Ccr2-mediated β-amyloid removal and regulation of neurogenesis affecting cognitive function may be applicable in humans. CCR2-mediated pathways may provide a possible focus for intervention to potentiate protective reactions to Alzheimer pathology in older people, including for people with an adverse ApoE haplotype.
Genome-wide association (GWA) studies have been limited by the reliance on common variants present on microarrays or imputable from the HapMap Project data. More recently, the completion of the 1000 Genomes Project has provided variant and haplotype information for several million variants derived from sequencing over 1,000 individuals. To help understand the extent to which more variants (including low frequency (1% ≤ MAF <5%) and rare variants (<1%)) can enhance previously identified associations and identify novel loci, we selected 93 quantitative circulating factors where data was available from the InCHIANTI population study. These phenotypes included cytokines, binding proteins, hormones, vitamins and ions. We selected these phenotypes because many have known strong genetic associations and are potentially important to help understand disease processes. We performed a genome-wide scan for these 93 phenotypes in InCHIANTI. We identified 21 signals and 33 signals that reached P<5×10−8 based on HapMap and 1000 Genomes imputation, respectively, and 9 and 11 that reached a stricter, likely conservative, threshold of P<5×10−11 respectively. Imputation of 1000 Genomes genotype data modestly improved the strength of known associations. Of 20 associations detected at P<5×10−8 in both analyses (17 of which represent well replicated signals in the NHGRI catalogue), six were captured by the same index SNP, five were nominally more strongly associated in 1000 Genomes imputed data and one was nominally more strongly associated in HapMap imputed data. We also detected an association between a low frequency variant and phenotype that was previously missed by HapMap based imputation approaches. An association between rs112635299 and alpha-1 globulin near the SERPINA gene represented the known association between rs28929474 (MAF = 0.007) and alpha1-antitrypsin that predisposes to emphysema (P = 2.5×10−12). Our data provide important proof of principle that 1000 Genomes imputation will detect novel, low frequency-large effect associations.
Genetic determinants of peripheral arterial disease (PAD) remain largely unknown. To identify genetic variants associated with the ankle-brachial index (ABI), a noninvasive measure of PAD, we conducted a meta-analysis of genome-wide association study data from 21 population-based cohorts.
Methods and Results
Continuous ABI and PAD (ABI≤0.9) phenotypes adjusted for age and sex were examined. Each study conducted genotyping and imputed data to the ~2.5 million SNPs in HapMap. Linear and logistic regression models were used to test each SNP for association with ABI and PAD using additive genetic models. Study-specific data were combined using fixed-effects inverse variance weighted meta-analyses. There were a total of 41,692 participants of European ancestry (~60% women, mean ABI 1.02 to 1.19), including 3,409 participants with PAD and with GWAS data available. In the discovery meta-analysis, rs10757269 on chromosome 9 near CDKN2B had the strongest association with ABI (β= −0.006, p=2.46x10−8). We sought replication of the 6 strongest SNP associations in 5 population-based studies and 3 clinical samples (n=16,717). The association for rs10757269 strengthened in the combined discovery and replication analysis (p=2.65x10−9). No other SNP associations for ABI or PAD achieved genome-wide significance. However, two previously reported candidate genes for PAD and one SNP associated with coronary artery disease (CAD) were associated with ABI : DAB21P (rs13290547, p=3.6x10−5); CYBA (rs3794624, p=6.3x10−5); and rs1122608 (LDLR, p=0.0026).
GWAS in more than 40,000 individuals identified one genome-wide significant association on chromosome 9p21 with ABI. Two candidate genes for PAD and 1 SNP for CAD are associated with ABI.
cohort study; genetic association; genome-wide association study; meta-analysis; peripheral vascular disease
Declining muscle strength is a core feature of aging. Several mechanisms have been postulated, including CCAAT/enhancer-binding protein-beta (C/EBP-β) triggered macrophage-mediated muscle fibre regeneration after micro-injury, evidenced in a mouse model. We aimed to identify in-vivo circulating leukocyte gene expression changes associated with muscle strength in the human adult population.
We undertook a genome wide expression microarray screen, using peripheral blood RNA samples from InCHIANTI study participants (ages 30–104 yrs). Logged expression intensities were regressed with muscle strength using models adjusted for multiple confounders. Key results were validated by real-time PCR. The Short Physical Performance Battery score (SPPB) tested walk speed, chair stand and balance.
CEBPB expression levels were associated with muscle strength (beta coefficient = 0.20560, p=1.03*10−6, false discovery rate q=0.014). The estimated handgrip strength in 70 year old men in the lowest CEBPB expression tertile was 35.2 kg compared to 41.2 kg in the top tertile. CEBPB expression was also associated with hip, knee, ankle and shoulder strength and the SPPB performance score (p=0.018). Near study-wide associations were also noted for TGFB3 (p=3.4*10−5, q=0.12) and CEBPD expression (p=9.67E−5, q=0.18) but not for CEBPA expression.
We report here a novel finding that raised CEBPB expression in circulating leukocyte derived RNA samples in-vivo is associated with greater muscle strength and better physical performance in humans. This association may be consistent with mouse model evidence of CEBPB triggered muscle repair: if this mechanism is confirmed it may provide a target for intervention to protect and enhance aging muscle.
macrophage; inflammation; transcription; regeneration; population; mechanism
Aging is a major risk factor for chronic disease in the human population, but there is little human data on gene expression alterations that accompany the process. We examined human peripheral blood leucocyte in-vivo RNA in a large-scale transcriptomic microarray study (subjects aged 30 to 104 years). We tested associations between probe expression intensity and advancing age (adjusting for confounding factors), initially in a discovery set (n = 458), following-up findings in a replication set (n=240). We confirmed expression of key results by real-time PCR. Of 16,571 expressed probes, only 295 (2%) were robustly associated with age. Just six probes were required for a highly efficient model for distinguishing between young and old (Area Under the Curve in replication set; 95%). The focussed nature of age-related gene expression may therefore provide potential biomarkers of aging. Similarly, only 7 of 1065 biological or metabolic pathways were age-associated, in Gene Set Enrichment Analysis (GSEA), notably including the processing of messenger RNAs (mRNAs); (p<0.002, FDR q<0.05). This is supported by our observation of age-associated disruption to the balance of alternatively-expressed isoforms for selected genes, suggesting that modification of mRNA processing may be a feature of human aging.
Aging; Gene expression; mRNA processing; Cell senescence; predictive model
To identify novel loci for age at natural menopause, we performed a meta-analysis of 22 genome-wide association studies in 38,968 women of European descent, with replication in up to 14,435 women. In addition to four known loci, we identified 13 new age at natural menopause loci (P < 5 × 10−8). The new loci included genes implicated in DNA repair (EXO1, HELQ, UIMC1, FAM175A, FANCI, TLK1, POLG, PRIM1) and immune function (IL11, NLRP11, BAT2). Gene-set enrichment pathway analyses using the full GWAS dataset identified exodeoxyribonuclease, NFκB signalling and mitochondrial dysfunction as biological processes related to timing of menopause.
Bisphenol A is widely used in food and drinks packaging. There is evidence of associations between raised urinary bisphenol A (uBPA) and increased incidence of reported cardiovascular diagnoses.
To estimate associations between BPA exposure and angiographically graded coronary atherosclerosis. 591 patients participating in The Metabonomics and Genomics in Coronary Artery Disease (MaGiCAD) study in Cambridgeshire UK, comparing urinary BPA (uBPA) with grades of severity of coronary artery disease (CAD) on angiography. Linear models were adjusted for BMI, occupational social class and diabetes status. Severe (one to three vessel) CAD was present in 385 patients, 86 had intermediate disease (n = 86) and 120 had normal coronary arteries. The (unadjusted) median uBPA concentration was 1.28 ng/mL with normal coronary arteries, and 1.53 ng/mL with severe CAD. Compared to those with normal coronary arteries, uBPA concentration was significantly higher in those with severe CAD (OR per uBPA SD = 5.96 ng/ml OR = 1.43, CI 1.03 to 1.98, p = 0.033), and near significant for intermediate disease (OR = 1.69, CI 0.98 to 2.94, p = 0.061). There was no significant uBPA difference between patients with severe CAD (needing surgery) and the remaining groups combined.
BPA exposure was higher in those with severe coronary artery stenoses compared to those with no vessel disease. Larger studies are needed to estimate true dose response relationships. The mechanisms underlying the association remain to be established.
Exposure to heavy metals can promote oxidative stress and damage to cellular components, and may accelerate age-related disease and disability.. Physical mobility is a validated biomarker of age-related disability and is predictive of hospitalization and mortality.
To examine associations between selected heavy metals and impaired lower limb mobility in a representative older human population.
Data for 1615 adults aged ≥60 years from the National Health and Nutrition Examination Survey (NHANES) 1999 to 2004 were used to identify associations between urinary concentrations of 10 metals with self-reported and measured walking impairments (at p<0.01). Models were adjusted for confounding factors, including smoking.
In models adjusted for age, sex and ethnicity, elevated levels of cadmium, cobalt and uranium were associated with impairment of the ability to walk a quarter mile. In fully adjusted models, cobalt was the only metal that remained associated: the odds ratio for reporting walking problems with a 1-unit increase in logged cobalt concentration (μg L-1) was 1.43 (95% CI 1.12 to 1.84). Cobalt was also the only metal associated with an increased measured time to walk a 20 foot course (p=0.008). In analyses of disease categories to explain the mobility finding, cobalt was associated with physician diagnosed arthritis (1-unit increase OR=1.22 (95% CI 1.00 to 1.49, p=0.045).
Low level cobalt exposure, assessed through urinary concentrations of this essential heavy metal may be a risk factor for age-related physical impairments. Independent replication is needed to confirm this association.
Cobalt; aging; NHANES; arthritis; gait speed
To identify predictors of extraordinary survival (ES).
Longitudinal study of a cohort of elderly people followed up until almost all have died
Two counties in Iowa, USA, a part of the Epidemiological Study of the Elderly.
2890 community-dwelling citizens, 65–85 years at baseline, surviving at least three years.
Data relating to age, sex, birth order, parental longevity, marital status, education, family income, social support, self-reported health, chronic diseases, blood pressure, body mass index, physical ability, exercises, life attitude and mental health were obtained. Extraordinary survivors were defined as those belonging to approximately top 10% longest survivors for their sex group.
253 ES were far more likely to have never smoked. In basic models (age/sex/smoking adjusted) for earlier-life factors, parent’s longevity, being earlier in the birth order (in women only) and BMI at age 50 were associated with ES.
In similar models for predictors at age 65–85 years (later-life or baseline), ES was associated with excellent self-reported health, fewest chronic diseases, better physical mobility, memory and positive attitude towards life, but not with depression, anxiety or sleep. In multi-variable models, attitude towards life was not an independent predictor. On a cumulative score of independent predictors, women in the top third of longevity attributes were 9.26 (CI 4.38–19.57, p<0.0001) times as likely to reach ES compared to bottom third.
Extraordinary survivors had fewer ‘classical’ risk factors and were in better health than their contemporaneous controls. Earlier-life, possibly genetic factors appear less predictive in men.
Extraordinary survivor; oldest old; predictors; heritable
Recent European studies suggest that vitamin D deficiency may be associated with increased odds of cognitive impairment in older persons, although findings from the United States are equivocal. Our objective was to investigate the association between vitamin D deficiency and cognitive impairment in the elderly U.S. population.
Three thousand and three hundred twenty-five adults aged 65 years or more completed cognitive assessments, medical examinations, and physical performance measures and provided blood samples in the Third National Health and Nutrition Examination Survey, a nationally representative cross-sectional study of the U.S. noninstitutionalized population. We determined whether low levels of serum 25-hydroxyvitamin D (25(OH)D) were associated with increased odds of cognitive impairment using logistic regression models. Cognitive impairment was assessed using measures of immediate and delayed verbal memory, orientation, and attention (impairment was defined as the worst 10% of the distribution of combined scores).
The multivariate adjusted odds ratios (95% confidence interval) of cognitive impairment in participants who were 25(OH)D insufficient (≥50 < 75 nmol/L), deficient (≥25 < 50 nmol/L), and severely deficient (<25 nmol/L) in comparison with those sufficient (≥75 nmol/L) were 0.9 (0.6–1.3), 1.4 (1.0–2.1), and 3.9 (1.5–10.4), respectively (p for linear trend = .02). Log-transformed levels of 25(OH)D were also significantly associated with the odds of cognitive impairment (p = .02).
These findings suggest that vitamin D deficiency is associated with increased odds of cognitive impairment in the elderly U.S. population. Further exploration of a possible causal relationship between vitamin D deficiency and cognitive impairment is warranted.
Cognitive impairment; Cognition; Dementia; Vitamin D; Serum 25-hydroxyvitamin D