The metabolomics of asthma control: a promising link between genetics and disease

Short-acting β agonists (e.g., albuterol) are the most commonly used medications for asthma, a disease that affects over 300 million people in the world. Metabolomic profiling of asthmatics taking β agonists presents a new and promising resource for identifying the molecular determinants of asthma control. The objective is to identify novel genetic and biochemical predictors of asthma control using an integrative "omics" approach. We generated lipidomic data by liquid chromatography tandem mass spectrometry (LC-MS), - using plasma samples from 20 individuals with asthma. The outcome of interest was a binary indicator of asthma control defined by the use of albuterol inhalers in the preceding week. We integrated metabolomic data with genome-wide genotype, gene expression, and methylation data of this cohort to identify genomic and molecular indicators of asthma control. A Conditional Gaussian Bayesian Network (CGBN) was generated using the strongest predictors from each of these analyses. Integrative and metabolic pathway over-representation analyses (ORA) identified enrichment of known biological pathways within the strongest molecular determinants. Of the 64 metabolites measured, 32 had known identities. The CGBN model based on four SNPs (rs9522789, rs7147228, rs2701423, rs759582) and two metabolites-monoHETE_0863 and sphingosine-1-phosphate (S1P) could predict asthma control with an AUC of 95%. Integrative ORA identified 17 significantly enriched pathways related to cellular immune response, interferon signaling, and cytokine-related signaling, for which arachidonic acid, PGE2 and S1P, in addition to six genes (CHN1, PRKCE, GNA12, OASL, OAS1, and IFIT3) appeared to drive the pathway results. Of these predictors, S1P, GNA12, and PRKCE were enriched in the results from integrative and metabolic ORAs. Through an integrative analysis of metabolomic, genomic, and methylation data from a small cohort of asthmatics, we implicate altered metabolic pathways, related to sphingolipid metabolism, in asthma control. These results provide insight into the pathophysiology of asthma control.

Genome-wide site-specific differential methylation in the blood of individuals with Klinefelter syndrome

Klinefelter syndrome (KS) (47 XXY) is a common sex-chromosome aneuploidy with an estimated prevalence of one in every 660 male births. Investigations into the associations between DNA methylation and the highly variable clinical manifestations of KS have largely focused on the supernumerary X chromosome; systematic investigations of the epigenome have been limited. We obtained genome-wide DNA methylation data from peripheral blood using the Illumina HumanMethylation450K platform in 5 KS (47 XXY) versus 102 male (46 XY) and 113 female (46 XX) control subjects participating in the COPDGene Study. Empirical Bayes-mediated models were used to test for differential methylation by KS status. CpG sites with a false-discovery rate < 0.05 in the discovery cohort which were available on the first-generation HumanMethylation 27 K platform were further examined in an independent replication cohort of 2 KS subjects, 590 male, and 495 female controls drawn from the International COPD Genetics Network (ICGN). Differential methylation at sites throughout the genome were identified, including 86 CpG sites that were differentially methylated in KS subjects relative to both male and female controls. CpG sites annotated to the HEN1 methyltransferase homolog 1 (HENMT1), calcyclin-binding protein (CACYBP), and GTPase-activating protein (SH3 domain)-binding protein 1 (G3BP1) genes were among the "KS-specific" loci that were replicated in ICGN. We conclude that site-specific differential methylation exists throughout the genome in KS. The functional impact and clinical relevance of these differentially methylated loci should be explored in future studies.

Prediagnostic Body-mass Index, Smoking and Prostate Cancer Survival: A Cohort Consortium Study of Over 10,000 White Men with Prostate Cancer

Few prospective studies have investigated the relationship between pre-diagnostic obesity, smoking and prostate cancer (PCa) survival by timing of measurement, by age at diagnosis, and evaluated the interaction between obesity and smoking. METHODS: We conducted a multinational survival analysis among 10,106 PCa cases (1,007 PCa deaths and 2,893 total deaths) from eight cohorts with an average of 8.2 years of follow up. Hazard ratio (HR) of PCa death was estimated using Cox proportional hazard model, adjusting for age, alcohol intake, diabetes status, cohort and duration between baseline and diagnosis and subsequently adjusted for tumor stage and grade. RESULTS: Higher prediagnostic BMI was related to higher risk of PCa death. With each 5 kg/m2 increase in BMI, the multivariate HR for PCa death was 1.08 (95% CI, 1.02–1.14) among overall participants (p-trend = 0.01) and 1.33 (95% CI, 1.18–1.51) among never or former smokers (p-trend &lt; 0.001). This positive trend for PCa mortality was mainly observed among men with BMI measured more than 5 years before diagnosis, and among those age &gt;65 years old at diagnosis. Compared with never smokers, current smokers had significantly elevated risk of PCa death, with a HR of 1.92 (95% CI, 1.52–2.43) regardless of the time of measurement, age at diagnosis and BMI. After further adjusting for tumor stage and grade, the association between BMI, smoking and PCa death was attenuated but remained statistical significant. CONCLUSIONS: In this consortium study of eight large cohorts, smoking and overweight/obesity before diagnosis were significant predictors for subsequent PCa-specific mortality. Smoking significantly modifies the association of BMI and PCa-specific mortality.

Folic acid supplementation and dietary folate intake, and risk of preeclampsia

BACKGROUND/OBJECTIVES

Folic acid supplementation has been suggested to reduce the risk of preeclampsia. However, results from few epidemiologic studies have been inconclusive. We investigated the hypothesis that folic acid supplementation and dietary folate intake before conception and during pregnancy reduce the risk of preeclampsia.

SUBJECTS/METHODS

A birth cohort study was conducted in 2010-2012 at the Gansu Provincial Maternity & Child Care Hospital in Lanzhou, China. A total of 10,041 pregnant women without chronic hypertension or gestational hypertension were enrolled.

RESULTS

Compared with nonusers, folic acid supplement users had a reduced risk of preeclampsia (OR=0.61, 95% CI: 0.43-0.87). A significant dose-response of duration of use was observed among women who used folic acid supplemention during pregnancy only (P-trend=0.007). The reduced risk associated with folic acid supplement was similar for mild or severe preeclampsia and for early- or late-onset preeclampsia, although the statistical significant associations were only observed for mild (OR=0.50, 95% CI: 0.30-0.81) and late-onset (OR=0.60, 95% CI: 0.42-0.86) preeclampsia. The reduced risk associated with dietary folate intake during pregnancy was only seen for severe preeclampsia (OR=0.52, 95% CI: 0.31-0.87, for the highest quartile of dietary folate intake compared with the lowest).

CONCLUSIONS

Our study results suggest that folic acid supplementation and higher dietary folate intake during pregnancy reduce the risk of preeclampsia. Future studies are needed to confirm the associations.

Identifying a gene expression signature of frequent COPD exacerbations in peripheral blood using network methods

Background

Exacerbations of chronic obstructive pulmonary disease (COPD), characterized by acute deterioration in symptoms, may be due to bacterial or viral infections, environmental exposures, or unknown factors. Exacerbation frequency may be a stable trait in COPD patients, which could imply genetic susceptibility. Observing the genes, networks, and pathways that are up- and down-regulated in COPD patients with differing susceptibility to exacerbations will help to elucidate the molecular signature and pathogenesis of COPD exacerbations.

Methods

Gene expression array and plasma biomarker data were obtained using whole-blood samples from subjects enrolled in the Treatment of Emphysema With a Gamma-Selective Retinoid Agonist (TESRA) study. Linear regression, weighted gene co-expression network analysis (WGCNA), and pathway analysis were used to identify signatures and network sub-modules associated with the number of exacerbations within the previous year; other COPD-related phenotypes were also investigated.

Results

Individual genes were not found to be significantly associated with the number of exacerbations. However using network methods, a statistically significant gene module was identified, along with other modules showing moderate association. A diverse signature was observed across these modules using pathway analysis, marked by differences in B cell and NK cell activity, as well as cellular markers of viral infection. Within two modules, gene set enrichment analysis recapitulated the molecular signatures of two gene expression experiments; one involving sputum from asthma exacerbations and another involving viral lung infections. The plasma biomarker myeloperoxidase (MPO) was associated with the number of recent exacerbations.

Conclusion

A distinct signature of COPD exacerbations may be observed in peripheral blood months following the acute illness. While not predictive in this cross-sectional analysis, these results will be useful in uncovering the molecular pathogenesis of COPD exacerbations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-014-0072-y) contains supplementary material, which is available to authorized users.

A disease module in the interactome explains disease heterogeneity, drug response and captures novel pathways and genes in asthma

Recent advances in genetics have spurred rapid progress towards the systematic identification of genes involved in complex diseases. Still, the detailed understanding of the molecular and physiological mechanisms through which these genes affect disease phenotypes remains a major challenge. Here, we identify the asthma disease module, i.e. the local neighborhood of the interactome whose perturbation is associated with asthma, and validate it for functional and pathophysiological relevance, using both computational and experimental approaches. We find that the asthma disease module is enriched with modest GWAS P-values against the background of random variation, and with differentially expressed genes from normal and asthmatic fibroblast cells treated with an asthma-specific drug. The asthma module also contains immune response mechanisms that are shared with other immune-related disease modules. Further, using diverse omics (genomics, gene-expression, drug response) data, we identify the GAB1 signaling pathway as an important novel modulator in asthma. The wiring diagram of the uncovered asthma module suggests a relatively close link between GAB1 and glucocorticoids (GCs), which we experimentally validate, observing an increase in the level of GAB1 after GC treatment in BEAS-2B bronchial epithelial cells. The siRNA knockdown of GAB1 in the BEAS-2B cell line resulted in a decrease in the NFkB level, suggesting a novel regulatory path of the pro-inflammatory factor NFkB by GAB1 in asthma.

Characterization of the promoter of Grapevine vein clearing virus

Grapevine vein clearing virus (GVCV) is a recently discovered DNA virus in grapevine that is closely associated with the grapevine vein clearing syndrome observed in vineyards in Missouri and surrounding states. The genome sequence of GVCV indicates that it belongs to the genus Badnavirus in the family Caulimoviridae. To identify the GVCV promoter, we cloned portions of the GVCV large intergenic region in front of a GFP gene present in an Agrobacterium tumefaciens binary vector. GFP expression was assessed by ELISA 3 days after agroinfiltration of Nicotiana benthamiana leaves. We found that the GVCV DNA segment between nts 7332 and 7672 directed expression of GFP and this expression was stronger than expression using the Cauliflower mosaic virus 35S promoter. It was revealed by 5' and 3' RACE that transcription was initiated predominantly at nt 7571 and terminated at nt 7676.

Combinatorial effects of arginine and fluoride on oral bacteria

Dental caries is closely associated with the microbial disequilibrium between acidogenic/aciduric pathogens and alkali-generating commensal residents within the dental plaque. Fluoride is a widely used anticaries agent, which promotes tooth hard-tissue remineralization and suppresses bacterial activities. Recent clinical trials have shown that oral hygiene products containing both fluoride and arginine possess a greater anticaries effect compared with those containing fluoride alone, indicating synergy between fluoride and arginine in caries management. Here, we hypothesize that arginine may augment the ecological benefit of fluoride by enriching alkali-generating bacteria in the plaque biofilm and thus synergizes with fluoride in controlling dental caries. Specifically, we assessed the combinatory effects of NaF/arginine on planktonic and biofilm cultures of Streptococcus mutans, Streptococcus sanguinis, and Porphyromonas gingivalis with checkerboard microdilution assays. The optimal NaF/arginine combinations were selected, and their combinatory effects on microbial composition were further examined in single-, dual-, and 3-species biofilm using bacterial species-specific fluorescence in situ hybridization and quantitative polymerase chain reaction. We found that arginine synergized with fluoride in suppressing acidogenic S. mutans in both planktonic and biofilm cultures. In addition, the NaF/arginine combination synergistically reduced S. mutans but enriched S. sanguinis within the multispecies biofilms. More importantly, the optimal combination of NaF/arginine maintained a "streptococcal pressure" against the potential growth of oral anaerobe P. gingivalis within the alkalized biofilm. Taken together, we conclude that the combinatory application of fluoride and arginine has a potential synergistic effect in maintaining a healthy oral microbial equilibrium and thus represents a promising ecological approach to caries management.

Genetic control of gene expression at novel and established chronic obstructive pulmonary disease loci

Genetic risk loci have been identified for a wide range of diseases through genome-wide association studies (GWAS), but the relevant functional mechanisms have been identified for only a small proportion of these GWAS-identified loci. By integrating results from the largest current GWAS of chronic obstructive disease (COPD) with expression quantitative trait locus (eQTL) analysis in whole blood and sputum from 121 subjects with COPD from the ECLIPSE Study, this analysis identifies loci that are simultaneously associated with COPD and the expression of nearby genes (COPD eQTLs). After integrative analysis, 19 COPD eQTLs were identified, including all four previously identified genome-wide significant loci near HHIP, FAM13A, and the 15q25 and 19q13 loci. For each COPD eQTL, fine mapping and colocalization analysis to identify causal shared eQTL and GWAS variants identified a subset of sites with moderate-to-strong evidence of harboring at least one shared variant responsible for both the eQTL and GWAS signals. Transcription factor binding site (TFBS) analysis confirms that multiple COPD eQTL lead SNPs disrupt TFBS, and enhancer enrichment analysis for loci with the strongest colocalization signals showed enrichment for blood-related cell types (CD3 and CD4+ T cells, lymphoblastoid cell lines). In summary, integrative eQTL and GWAS analysis confirms that genetic control of gene expression plays a key role in the genetic architecture of COPD and identifies specific blood-related cell types as likely participants in the functional pathway from GWAS-associated variant to disease phenotype.

Genome-wide interaction studies reveal sex-specific asthma risk alleles

Asthma is a complex disease with sex-specific differences in prevalence. Candidate gene studies have suggested that genotype-by-sex interaction effects on asthma risk exist, but this has not yet been explored at a genome-wide level. We aimed to identify sex-specific asthma risk alleles by performing a genome-wide scan for genotype-by-sex interactions in the ethnically diverse participants in the EVE Asthma Genetics Consortium. We performed male- and female-specific genome-wide association studies in 2653 male asthma cases, 2566 female asthma cases and 3830 non-asthma controls from European American, African American, African Caribbean and Latino populations. Association tests were conducted in each study sample, and the results were combined in ancestry-specific and cross-ancestry meta-analyses. Six sex-specific asthma risk loci had P-values < 1 × 10(-6), of which two were male specific and four were female specific; all were ancestry specific. The most significant sex-specific association in European Americans was at the interferon regulatory factor 1 (IRF1) locus on 5q31.1. We also identify a Latino female-specific association in RAP1GAP2. Both of these loci included single-nucleotide polymorphisms that are known expression quantitative trait loci and have been associated with asthma in independent studies. The IRF1 locus is a strong candidate region for male-specific asthma susceptibility due to the association and validation we demonstrate here, the known role of IRF1 in asthma-relevant immune pathways and prior reports of sex-specific differences in interferon responses.

Integrated genome-wide association, coexpression network, and expression single nucleotide polymorphism analysis identifies novel pathway in allergic rhinitis

BACKGROUND

Allergic rhinitis is a common disease whose genetic basis is incompletely explained. We report an integrated genomic analysis of allergic rhinitis.

METHODS

We performed genome wide association studies (GWAS) of allergic rhinitis in 5633 ethnically diverse North American subjects. Next, we profiled gene expression in disease-relevant tissue (peripheral blood CD4+ lymphocytes) collected from subjects who had been genotyped. We then integrated the GWAS and gene expression data using expression single nucleotide (eSNP), coexpression network, and pathway approaches to identify the biologic relevance of our GWAS.

RESULTS

GWAS revealed ethnicity-specific findings, with 4 genome-wide significant loci among Latinos and 1 genome-wide significant locus in the GWAS meta-analysis across ethnic groups. To identify biologic context for these results, we constructed a coexpression network to define modules of genes with similar patterns of CD4+ gene expression (coexpression modules) that could serve as constructs of broader gene expression. 6 of the 22 GWAS loci with P-value ≤ 1x10-6 tagged one particular coexpression module (4.0-fold enrichment, P-value 0.0029), and this module also had the greatest enrichment (3.4-fold enrichment, P-value 2.6 × 10-24) for allergic rhinitis-associated eSNPs (genetic variants associated with both gene expression and allergic rhinitis). The integrated GWAS, coexpression network, and eSNP results therefore supported this coexpression module as an allergic rhinitis module. Pathway analysis revealed that the module was enriched for mitochondrial pathways (8.6-fold enrichment, P-value 4.5 × 10-72).

CONCLUSIONS

Our results highlight mitochondrial pathways as a target for further investigation of allergic rhinitis mechanism and treatment. Our integrated approach can be applied to provide biologic context for GWAS of other diseases.

Outcomes following primary percutaneous coronary intervention in the setting of cardiac arrest: a registry database study

BACKGROUND

The mortality rate among patients undergoing primary percutaneous coronary intervention (PPCI) in the setting of cardiac arrest (CA) and whether the location where the patient sustains CA influences the outcome is not known in the contemporary era.

METHODS

Prospectively collected data at a tertiary cardiac centre on all patients undergoing PPCI for ST elevation myocardial infarction (STEMI) in the setting of CA was analysed.

RESULTS

In total, 484/4118 (11.8%) patients sustained CA during the study period. Of these, 91/484 (18.8%) sustained CA prior to ambulance arrival, the remainder occurred either after ambulance arrival or in hospital. The overall in-hospital mortality was 20.5% in this cohort. Those sustaining CA before ambulance arrival experienced the highest unadjusted mortality compared to those that had CA after ambulance arrival, in hospital and in the catheterisation laboratory (29.7% versus 12.0%, 16.1% and 23.8% respectively, p=0.03). Multiple logistic regression analysis showed that the following parameters are independent predictors of in-hospital mortality: age (odds ratio (OR) for each year increment of age 1.05; 95% confidence interval (CI) 1.02-1.08, p=0.0009); female gender (OR 2.42; 95% CI 1.17-4.99, p=0.0173); previous PCI (OR 7.59; 95% CI 1.72-33.53, p=0.0075); asystole/ electromechanical dissociation (EMD) (OR 13.43; 95% CI 5.34-33.80, p<0.0001); and patient location at arrest (OR 5.77 for before ambulance arrival; 95% CI 2.55-13.07, p<0.0001).

CONCLUSIONS

In conclusion, in-hospital mortality remains high among patients undergoing PPCI in the context of CA, particularly among those that arrest prior to ambulance arrival.

Pharmacogenomics: novel loci identification via integrating gene differential analysis and eQTL analysis

Nearly one-half of asthmatic patients do not respond to the most commonly prescribed controller therapy, inhaled corticosteroids (ICS). We conducted an expression quantitative trait loci (eQTL) analysis using >300 expression microarrays (from 117 lymphoblastoid cell lines) in corticosteroid (dexamethasone) treated and untreated cells derived from asthmatic subjects in the Childhood Asthma Management Program (CAMP) clinical trial. We then tested the associations of eQTL with longitudinal change in airway responsiveness to methacholine (LnPC20) on ICS. We identified 2484 cis-eQTL affecting 767 genes following dexamethasone treatment. A significant over-representation of lnPC20-associated cis-eQTL [190 single-nucleotide polymorphisms (SNPs)] among differentially expressed genes (odds ratio = 1.76, 95% confidence interval: 1.35-2.29) was noted in CAMP Caucasians. Forty-six of these 190 clinical associations were replicated in CAMP African Americans, including seven SNPs near six genes meeting criteria for genome-wide significance (P < 2 × 10(-7)). Notably, the majority of genome-wide findings would not have been uncovered via analysis of untreated samples. These results indicate that identifying eQTL after relevant environmental perturbation enables identification of true pharmacogenetic variants.

Sublytic C5b-9 triggers glomerular mesangial cell apoptosis via XAF1 gene activation mediated by p300-dependent IRF-1 acetylation

The apoptosis of glomerular mesangial cells (GMCs) in rat Thy-1 nephritis (Thy-1N), a model of human mesangioproliferative glomerulonephritis (MsPGN), is accompanied by sublytic C5b-9 deposition. However, the mechanism by which sublytic C5b-9 induces GMC apoptosis is unclear. In the present studies, the effect of X-linked inhibitor of apoptosis-associated factor 1 (XAF1) expression on GMC apoptosis and the role of p300 and interferon regulatory factor-1 (IRF-1) in mediating XAF1 gene activation were determined, both in the GMCs induced by sublytic C5b-9 (in vitro) and in the renal tissues of rats with Thy-1N (in vivo). The in vitro studies demonstrated that IRF-1-enhanced XAF1 gene activation and its regulation by p300-mediated IRF-1 acetylation were involved in GMC apoptosis induced by sublytic C5b-9. The element of IRF-1 binding to XAF1 promoter and two acetylated sites of IRF-1 protein were also revealed. In vivo, silence of p300, IRF-1 or XAF1 genes in the renal tissues diminished GMC apoptosis and secondary GMC proliferation as well as urinary protein secretion in Thy-1N rats. Together, these data implicate that sublytic C5b-9 induces the expression of both p300 and IRF-1, as well as p300-dependent IRF-1 acetylation that may contribute to XAF1 gene activation and subsequent GMC apoptosis in Thy-1N rats.

Fundamental limits to extinction by metallic nanoparticles

We show that there are shape-independent upper bounds to the extinction cross section per unit volume of dilute, randomly arranged nanoparticles, given only material permittivity. Underlying the limits are restrictive sum rules that constrain the distribution of quasistatic eigenvalues. Surprisingly, optimally designed spheroids, with only a single quasistatic degree of freedom, reach the upper bounds for four permittivity values. Away from these permittivities, we demonstrate computationally optimized structures that surpass spheroids and approach the fundamental limits.

Increased soluble C5b-9 in CSF of neuromyelitis optica

Neuromyelitis optica (NMO) and multiple sclerosis (MS) are two of the autoimmune inflammatory demyelinating diseases in the central nervous system. Complement is thought to have an important role in pathogenesis of these diseases, especially in NMO. However, the change of terminal complement complex (TCC, C5b-9) in patients with NMO is still unclear. Cerebrospinal fluid (CSF) C3a, C5a, sC5b-9 were measured by enzyme-linked immunosorbent assay in patients with NMO (n = 26), MS (n = 25) and other neurological disease (OND, n = 19). CSF levels of C5a in patients with NMO were higher than patients with OND (P = 0.006). Increased CSF sC5b-9 were found in the patients with NMO compared with patients with MS (P = 0.029) and OND (P = 0.0001). CSF sC5b-9 in patients with MS were also higher than patients with OND (P = 0.030). Patients with NMO revealed a trend to an increased disease disability with increased CSF sC5b-9 during relapse but not in MS (NMO: P = 0.006, MS: P = 0.097). CSF levels of sC5b-9 are increased in patients with NMO and reflect the activation of complement in NMO.

Inhaled corticosteroid treatment modulates ZNF432 gene variant's effect on bronchodilator response in asthmatics

BACKGROUND

Single nucleotide polymorphisms (SNPs) influence a patient's response to inhaled corticosteroids and β2-agonists, and the effect of treatment with inhaled corticosteroids is synergistic with the effect of β2-agonists. We hypothesized that use of inhaled corticosteroids could influence the effect of SNPs associated with a bronchodilator response.

OBJECTIVE

To assess whether, among subjects with asthma, the association of SNPs with bronchodilator response is different between those treated with inhaled corticosteroids versus those on placebo.

METHODS

A genome-wide association analysis was conducted by using 581 white subjects from the Childhood Asthma Management Program. By using data for 449,540 SNPs, we conducted a gene by environment analysis in PLINK with inhaled corticosteroid treatment as the environmental exposure and bronchodilator response as the outcome measure. We attempted to replicate the top 12 SNPs in the Leukotriene Modifier or Corticosteroid or Corticosteroid-Salmeterol Trial.

RESULTS

The combined P value for the Childhood Asthma Management Program and Leukotriene Modifier or Corticosteroid or Corticosteroid-Salmeterol Trial populations was 4.8 × 10(-8) for rs3752120, which is located in the zinc finger protein gene ZNF432 and has an unknown function.

CONCLUSIONS

Inhaled corticosteroids appear to modulate the association of bronchodilator response with variant(s) in the ZNF432 gene among adults and children with asthma.

Vitamin D deficiency and coronary artery disease: a review of the evidence

Coronary artery disease remains the leading cause of death in developed countries despite significant progress in primary prevention and treatment strategies. Older patients are at particularly high risk of poor outcomes following acute coronary syndrome and impaired nutrition, including low vitamin D levels, may play a role. The extraskeletal effects of vitamin D, in particular, its role in maintaining a healthy cardiovascular system are receiving increased attention. Longitudinal studies have demonstrated increased cardiovascular mortality and morbidity associated with vitamin D deficiency. Low vitamin D levels have been linked to inflammation, higher coronary artery calcium scores, impaired endothelial function and increased vascular stiffness. However, so far, few randomized controlled trials have investigated the potential benefits of vitamin D supplementation in preventing cardiovascular events, and most available trials have tested low doses of supplementation in relatively low-risk populations. Whether vitamin D supplementation will be beneficial among patients with coronary artery disease, including high risk older patients presenting with acute coronary syndrome, is unknown and warrants further investigation.

A genome-wide association study of bronchodilator response in asthmatics

Reversibility of airway obstruction in response to β2-agonists is highly variable among asthmatics, which is partially attributed to genetic factors. In a genome-wide association study of acute bronchodilator response (BDR) to inhaled albuterol, 534 290 single-nucleotide polymorphisms (SNPs) were tested in 403 white trios from the Childhood Asthma Management Program using five statistical models to determine the most robust genetic associations. The primary replication phase included 1397 polymorphisms in three asthma trials (pooled n=764). The second replication phase tested 13 SNPs in three additional asthma populations (n=241, n=215 and n=592). An intergenic SNP on chromosome 10, rs11252394, proximal to several excellent biological candidates, significantly replicated (P=1.98 × 10(-7)) in the primary replication trials. An intronic SNP (rs6988229) in the collagen (COL22A1) locus also provided strong replication signals (P=8.51 × 10(-6)). This study applied a robust approach for testing the genetic basis of BDR and identified novel loci associated with this drug response in asthmatics.