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1.  A Meta-analysis of Genome-wide Association Studies for Serum Total IgE in Diverse Study Populations 
Immunoglobulin E (IgE) is both a marker and mediator of allergic inflammation. Despite reported differences in serum total IgE levels by race-ethnicity, African American and Latino individuals have not been well represented in genetic studies of total IgE.
To identify the genetic predictors of serum total IgE levels.
We used genome wide association (GWA) data from 4,292 individuals (2,469 African Americans, 1,564 European Americans, and 259 Latinos) in the EVE Asthma Genetics Consortium. Tests for association were performed within each cohort by race-ethnic group (i.e., African American, Latino, and European American) and asthma status. The resulting p-values were meta-analyzed accounting for sample size and direction of effect. Top single nucleotide polymorphism (SNP) associations from the meta-analysis were reassessed in six additional cohorts comprising 5,767 individuals.
We identified 10 unique regions where the combined association statistic was associated with total serum IgE levels (P-value <5.0×10−6) and the minor allele frequency was ≥5% in two or more population groups. Variant rs9469220, corresponding to HLA-DQB1, was the most significantly associated SNP with serum total IgE levels when assessed in both the replication cohorts and the discovery and replication sets combined (P-value = 0.007 and 2.45×10−7, respectively). In addition, findings from earlier GWA studies were also validated in the current meta-analysis.
This meta-analysis independently identified a variant near HLA-DQB1 as a predictor of total serum IgE in multiple race-ethnic groups. This study also extends and confirms the findings of earlier GWA analyses in African American and Latino individuals.
PMCID: PMC3596497  PMID: 23146381
meta-analysis; genome wide association study; total immunoglobulin E; race-ethnicity; continental population groups
2.  Further Replication Studies of the EVE Consortium Meta-Analysis Identifies Two Asthma Risk Loci in European Americans 
Genome-wide association studies of asthma have implicated many genetic risk factors, with well-replicated associations at approximately 10 loci that account for only a small proportion of the genetic risk.
We aimed to identify additional asthma risk loci by performing an extensive replication study of the results from the EVE Consortium meta-analysis.
We selected 3186 SNPs for replication based on the p-values from the EVE Consortium meta-analysis. These SNPs were genotyped in ethnically diverse replication samples from nine different studies, totaling to 7202 cases, 6426 controls, and 507 case-parent trios. Association analyses were conducted within each participating study and the resulting test statistics were combined in a meta-analysis.
Two novel associations were replicated in European Americans: rs1061477 in the KLK3 gene on chromosome 19 (combined OR = 1.18; 95% CI 1.10 – 1.25) and rs9570077 (combined OR =1.20 95% CI 1.12–1.29) on chromosome 13q21. We could not replicate any additional associations in the African American or Latino individuals.
This extended replication study identified two additional asthma risk loci in populations of European descent. The absence of additional loci for African Americans and Latino individuals highlights the difficulty in replicating associations in admixed populations.
PMCID: PMC3666859  PMID: 23040885
Asthma; genetic risk factors; meta-analysis; KLK3
3.  Very important pharmacogene summary for VDR 
Pharmacogenetics and genomics  2012;22(10):758-763.
PMCID: PMC3678550  PMID: 22588316
drug response; genetic variants; pharmacogenomics; vitamin D receptor
5.  Delivery by caesarean section and risk of obesity in preschool age children: a prospective cohort study 
Archives of disease in childhood  2012;97(7):610-616.
To examine whether delivery by caesarean section is a risk factor for childhood obesity.
Prospective pre-birth cohort study (Project Viva).
Eight outpatient multi-specialty practices based in the Boston, Massachusetts area.
We recruited women during early pregnancy between 1999 and 2002, and followed their children after birth. We included 1255 children with body composition measured at 3 years of age.
Main outcome measures
Body mass index (BMI) z-score, obesity (BMI for age and sex ≥ 95th percentile), and sum of triceps + subscapular skinfold thicknesses, at 3 years of age.
284 children (22.6 percent) were delivered by caesarean section. At age 3, 15.7% of children delivered by caesarean section were obese, compared with 7.5% of children born vaginally. In multivariable logistic and linear regression models adjusting for maternal pre-pregnancy BMI, birth weight, and other covariates, birth by caesarean section was associated with a higher odds of obesity at age 3 (OR 2.10, 95%CI 1.36 to 3.23), higher mean BMI z-score (0.20 units, 95% CI 0.07 to 0.33), and higher sum of triceps + subscapular skinfold thicknesses (0.94 mm, 95% CI 0.36 to 1.51).
Infants delivered by caesarean section may be at increased risk of childhood obesity. Further studies are needed to confirm our findings and to explore mechanisms underlying this association.
PMCID: PMC3784307  PMID: 22623615
6.  Effect of Vitamin D and Inhaled Corticosteroid Treatment on Lung Function in Children 
Rationale: Low vitamin D levels are associated with asthma and decreased airway responsiveness. Treatment with inhaled corticosteroids improves airway responsiveness and asthma control.
Objectives: To assess the effect of vitamin D levels on prebronchodilator FEV1, bronchodilator response, and responsiveness to methacholine (PC20, provocative concentration of methacholine producing a 20% decline in FEV1) in patients with asthma treated with inhaled corticosteroids.
Methods: We measured 25-hydroxyvitamin D levels in the serum of children with persistent asthma at the time of enrollment in the Childhood Asthma Management Program. We divided subjects into the vitamin D sufficiency (>30 ng/ml), insufficiency (20–30 ng/ml), and deficiency (<20 ng/ml) groups. Covariates included age, treatment, sex, body mass index, race, history of emergency department visits, hospitalizations, and season that vitamin D specimen was drawn. Our main outcome measures were change in prebronchodilator FEV1, bronchodilator response, and PC20 from enrollment to 8–12 months.
Measurements and Main Results: Of the 1,024 subjects, 663 (65%) were vitamin D sufficient, 260 (25%) were insufficient, and 101 (10%) were deficient. Vitamin D–deficient subjects were more likely to be older, African American, and have a higher body mass index compared with the vitamin D–sufficient and insufficient subjects. In the inhaled corticosteroid treatment group, prebronchodilator FEV1 increased from randomization to 12 months by 140 ml in the vitamin D–deficient group and prebronchodilator FEV1 increased by 330 ml in the vitamin D insufficiency group and by 290 ml in the vitamin D sufficiency group (P = 0.0072), in adjusted models.
Conclusions: In children with asthma treated with inhaled corticosteroids, vitamin D deficiency is associated with poorer lung function than in children with vitamin D insufficiency or sufficiency.
PMCID: PMC3480528  PMID: 22798322
asthma; vitamin D; lung function; forced expiratory volume; children
7.  Genome-wide association analysis of circulating vitamin D levels in children with asthma 
Human genetics  2012;131(9):1495-1505.
Vitamin D deficiency is becoming more apparent in many populations. Genetic factors may play a role in the maintenance of vitamin D levels. The objective of this study was to perform a genome-wide analysis (GWAS) of vitamin D levels, including replication of prior GWAS results. We measured 25-hydroxyvitamin D (25(OH)D) levels in serum collected at the time of enrollment and at year 4 in 572 Caucasian children with asthma, who were part of a multi-center clinical trial, the Childhood Asthma Management Program. Replication was performed in a second cohort of 592 asthmatics from Costa Rica and a third cohort of 516 Puerto Rican asthmatics. In addition, we attempted replication of three SNPs that were previously identified in a large GWAS of Caucasian individuals. The setting included data from a clinical trial of childhood asthmatics and two cohorts of asthmatics recruited for genetic studies of asthma. The main outcome measure was circulating 25(OH)D levels. The 25(OH)D levels at the two time-points were only modestly correlated with each other (intraclass correlation coefficient = 0.33) in the CAMP population. We identified SNPs that were nominally associated with 25(OH)D levels at two time-points in CAMP, and replicated four SNPs in the Costa Rican cohort: rs11002969, rs163221, rs1678849, and rs4864976. However, these SNPs were not significantly associated with 25(OH)D levels in a third population of Puerto Rican asthmatics. We were able to replicate the SNP with the strongest effect, previously reported in a large GWAS: rs2282679 (GC), and we were able to replicate another SNP, rs10741657 (CYP2R1), to a lesser degree. We were able to replicate two of three prior significant findings in a GWAS of 25(OH)D levels. Other SNPs may be additionally associated with 25(OH)D levels in certain populations.
PMCID: PMC3648789  PMID: 22673963
8.  Key findings and clinical implications from The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study 
Patients with severe or difficult-to-treat asthma are an understudied population but account for considerable asthma morbidity, mortality, and costs. The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study was a large, 3-year, multicenter, observational cohort study of 4756 patients (n = 3489 adults ≥18 years of age, n = 497 adolescents 13-17 years of age, and n = 770 children 6-12 years of age) with severe or difficult-to-treat asthma. TENOR's primary objective was to characterize the natural history of disease in this cohort. Data assessed semiannually and annually included demographics, medical history, comorbidities, asthma control, asthma-related health care use, medication use, lung function, IgE levels, self-reported asthma triggers, and asthma-related quality of life. We highlight the key findings and clinical implications from more than 25 peer-reviewed TENOR publications. Regardless of age, patients with severe or difficult-to-treat asthma demonstrated high rates of health care use and substantial asthma burden despite receiving multiple long-term controller medications. Recent exacerbation history was the strongest predictor of future asthma exacerbations. Uncontrolled asthma, as defined by the 2007 National Heart, Lung, and Blood Institute guidelines’ impairment domain, was highly prevalent and predictive of future asthma exacerbations; this assessment can be used to identify high-risk patients. IgE and allergen sensitization played a role in the majority of severe or difficult-to-treat asthmatic patients.
PMCID: PMC3622643  PMID: 22694932
TENOR; severe or difficult-to-treat asthma; asthma control; asthma exacerbations; burden; medication; quality of life; allergy; IgE
9.  Corticosteroid use and bone mineral accretion in children with asthma: effect modification by vitamin D 
The adverse effects of corticosteroids on bone mineral accretion (BMA) have been well documented. Vitamin D insufficiency, a prevalent condition in the pediatric population, has also been associated with decreased bone mineral density (BMD).
To determine whether children with asthma who have lower vitamin D levels are more susceptible to the negative effects of corticosteroids on BMD over time.
Children aged 5–12 years with mild-to-moderate asthma who participated in the Childhood Asthma Management Program were followed for a mean of 4.3 years. Total doses of inhaled and oral corticosteroids (OCS) were recorded, serum 25-hydroxyvitamin D3 levels were measured at the beginning of the trial and serial DEXA scans of the lumbar spine were performed. Annual BMA rates were defined as: [(BMD at 4 years follow-up − BMD at baseline)/4 years].
BMA was calculated for 780 subjects. In boys, baseline vitamin D levels significantly modified the relationship between OCS and BMA (vitamin D x OCS interaction, p=0.023). Stratification by vitamin D levels showed a decrease in BMA with increased use of OCS in vitamin D insufficient boys only (p<0.001). Compared to vitamin D sufficient boys, vitamin D insufficient boys exposed to more than 2 courses of oral corticosteroids per year had twice the decrease in BMA rate (relative to boys who were OCS-unexposed).
Vitamin D levels significantly modified the effect of oral corticosteroids on bone mineral accretion in boys. Further research is needed to examine whether vitamin D supplementation in children with poorly controlled asthma may confer benefits to bone health.
PMCID: PMC3387323  PMID: 22608570
Asthma; vitamin D; bone mineral density; corticosteroids
10.  Genomewide association study of the age of onset of childhood asthma 
Childhood asthma is a complex disease with known heritability and phenotypic diversity. Although an earlier onset has been associated with more severe disease, there has been no genome-wide association study of the age of onset of asthma in children.
To identify genetic variants associated with earlier onset of childhood asthma.
We conducted the first genome-wide association study (GWAS) of the age of onset of childhood asthma among participants in the Childhood Asthma Management Program (CAMP), and used three independent cohorts from North America, Costa Rica, and Sweden for replication.
Two SNPs were associated with earlier onset of asthma in the combined analysis of CAMP and the replication cohorts: : rs9815663 (Fisher’s P value=2.31 × 10−8) and rs7927044 (P=6.54 × 10−9). Of these two SNPs, rs9815663 was also significantly associated with earlier asthma onset in an analysis including only the replication cohorts. Ten SNPs in linkage disequilibrium with rs9815663 were also associated with earlier asthma onset (2.24 × 10−7 < P < 8.22 ×10−6). Having ≥1 risk allele of the two SNPs of interest (rs9815663 and rs7927044) was associated with lower lung function and higher asthma medication use during 4 years of follow-up in CAMP.
We have identified two SNPs associated with earlier onset of childhood asthma in four independent cohorts.
PMCID: PMC3387331  PMID: 22560479
Asthma; pediatrics; age of onset; asthma genetics; C1orf100; genome-wide association study; pediatric asthma
11.  Evaluation of Asymmetric Dimethylarginine, Arginine, and Carnitine Metabolism in Pediatric Sepsis 
Pediatric Critical Care Medicine  2012;13(4):e210-e218.
Increased plasma concentrations of the endogenous nitric oxide (NO) synthase inhibitor, asymmetric dimethylarginine (ADMA), decreased arginine bioavailability, and mitochondrial dysfunction have been reported in adult sepsis. We studied whether ADMA, arginine, and carnitine metabolism (a measure of mitochondrial dysfunction) are altered in pediatric sepsis and whether these are clinically useful biomarkers.
Prospective, observational study
Pediatric intensive care unit at an academic medical center
Ninety patients ≤ 18 years-old—30 with severe sepsis or septic shock compared with thirty age-matched febrile and thirty age-matched healthy controls.
Measurements and Main Results
Plasma ADMA and whole blood arginine, citrulline, ornithine, and acylcarnitine:free carnitine (AC:FC) ratio were measured daily for septic patients and once for controls using tandem mass spectrometry. Plasma ADMA concentration (median, IQR µmol/L) on day 1 was lower in severe sepsis and septic shock (0.38, 0.30–0.56) compared with febrile (0.45, 0.40–0.59) and healthy (0.60, 0.54–0.67) controls (p<0.001), though decreased ADMA was predominantly found in neutropenic patients. Day 1 arginine was lower in septic (10, IQR 7–20 µmol/L) compared with healthy patients (32, IQR 23–40; p<0.001), and the arginine:ornithine ratio was decreased in sepsis, indicating increased arginase activity (an alternative pathway for arginine metabolism). The arginine:ADMA and AC:FC ratios did not differ between septic and control patients. ADMA was inversely correlated with organ dysfunction by PELOD score (r=−0.50, p=0.009), interleukin-6 (r=−0.55, p=0.01), and interleukin-8 (r=−0.52, p=0.03) on admission. Arginine, arginine:ADMA, and AC:FC were not associated with organ dysfunction or outcomes.
ADMA was decreased in pediatric sepsis and was inversely associated with inflammation and organ dysfunction. This suggests that inhibition of NO synthase by ADMA accumulation is unlikely to impact sepsis pathophysiology in septic children despite decreased arginine bioavailability. We did not find an association of ADMA with altered carnitine metabolism, nor were ADMA, arginine, and AC:FC useful as clinical biomarkers.
PMCID: PMC3392424  PMID: 22460770
Nitric oxide; nitric oxide synthase; arginine; carnitine; sepsis; intensive care units, pediatric
12.  Genome-wide Association Identifies the T Gene as a Novel Asthma Pharmacogenetic Locus 
Rationale: To date, most studies aimed at discovering genetic factors influencing treatment response in asthma have focused on biologic candidate genes. Genome-wide association studies (GWAS) can rapidly identify novel pharmacogenetic loci.
Objectives: To investigate if GWAS can identify novel pharmacogenetic loci in asthma.
Methods: Using phenotypic and GWAS genotype data available through the NHLBI-funded Single-nucleotide polymorphism Health association-Asthma Resource Project, we analyzed differences in FEV1 in response to inhaled corticosteroids in 418 white subjects with asthma. Of the 444,088 single nucleotide polymorphisms (SNPs) analyzed, the lowest 50 SNPs by P value were genotyped in an independent clinical trial population of 407 subjects with asthma.
Measurements and Main Results: The lowest P value for the GWAS analysis was 2.09 × 10−6. Of the 47 SNPs successfully genotyped in the replication population, three were associated under the same genetic model in the same direction, including two of the top four SNPs ranked by P value. Combined P values for these SNPs were 1.06 × 10−5 for rs3127412 and 6.13 × 10−6 for rs6456042. Although these two were not located within a gene, they were tightly correlated with three variants mapping to potentially functional regions within the T gene. After genotyping, each T gene variant was also associated with lung function response to inhaled corticosteroids in each of the trials associated with rs3127412 and rs6456042 in the initial GWAS analysis. On average, there was a twofold to threefold difference in FEV1 response for those subjects homozygous for the wild-type versus mutant alleles for each T gene SNP.
Conclusions: Genome-wide association has identified the T gene as a novel pharmacogenetic locus for inhaled corticosteroid response in asthma.
PMCID: PMC3381232  PMID: 22538805
polymorphism; genome; pharmacogenomics; glucocorticoid
13.  Maternal intestinal flora and wheeze in early childhood 
Increasing evidence links altered intestinal flora in infancy to eczema and asthma. No studies have investigated the influence of maternal intestinal flora on wheezing and eczema in early childhood.
To investigate the link between maternal intestinal flora during pregnancy and development of wheeze and eczema in infancy.
Sixty pregnant women from the Boston area gave stool samples during the third trimester of their pregnancy and answered questions during pregnancy about their own health, and about their children’s health when the child was 2 and 6 months of age. Quantitative culture was performed on stool samples and measured in log10colony-forming units(CFU)/gram stool. Primary outcomes included infant wheeze and eczema in the first 6 months of life. Atopic wheeze, defined as wheeze and eczema, was analyzed as a secondary outcome.
In multivariate models adjusted for breastfeeding, daycare attendance and maternal atopy, higher counts of maternal total aerobes (TA) and enterococci (E) were associated with increased risk of infant wheeze (TA: OR 2.32 for 1 log increase in CFU/g stool [95% CI 1.22, 4.42]; E: OR 1.57 [95% CI 1.06, 2.31]). No organisms were associated with either eczema or atopic wheeze.
Conclusions & Clinical Relevance
In our cohort, higher maternal total aerobes and enterococci were related to increased risk of infant wheeze. Maternal intestinal flora may be an important environmental exposure in early immune system development.
PMCID: PMC3428746  PMID: 22909161
infant wheeze; eczema; asthma; microbiota; intestinal flora; maternal flora
14.  Gene-by-environment effect of house dust mite on purinergic receptor P2Y12 (P2RY12) and lung function in children with asthma 
Clinical and Experimental Allergy  2012;42(2):229-237.
Distinct receptors likely exist for leukotriene(LT)E4, a potent mediator of airway inflammation. Purinergic receptor P2Y12 is needed for LTE4-induced airways inflammation, and P2Y12 antagonism attenuates house dust mite-induced pulmonary eosinophilia in mice. Although experimental data support a role for P2Y12 in airway inflammation, its role in human asthma has never been studied.
To test for association between variants in the P2Y12 gene (P2RY12) and lung function in human subjects with asthma, and to examine for gene-by-environment interaction with house dust mite exposure.
19 single nucleotide polymorphisms (SNPs) in P2RY12 were genotyped in 422 children with asthma and their parents (n=1266). Using family-based methods, we tested for associations between these SNPs and five lung function measures. We performed haplotype association analyses and tested for gene-by-environment interactions using house dust mite exposure. We used the false discovery rate to account for multiple comparisons.
Five SNPs in P2RY12 were associated with multiple lung function measures (P values 0.006–0.025). Haplotypes in P2RY12 were also associated with lung function (P values 0.0055–0.046). House dust mite exposure modulated associations between P2RY12 and lung function, with minor allele homozygotes exposed to house dust mite demonstrating worse lung function than those unexposed (significant interaction P values 0.0028–0.040).
Conclusions and clinical relevance
P2RY12 variants were associated with lung function in a large family-based asthma cohort. House dust mite exposure caused significant gene-by-environment effects. Our findings add the first human evidence to experimental data supporting a role for P2Y12 in lung function. P2Y12 could represent a novel target for asthma treatment.
PMCID: PMC3353543  PMID: 22010907
Purinergic receptor; leukotriene; asthma; house dust mite; lung function
15.  Assessment of asthma control and asthma exacerbations in the epidemiology and natural history of asthma: outcomes and treatment regimens (TENOR) observational cohort 
Current Respiratory Care Reports  2012;1(4):259-269.
Patients with severe or difficult-to-treat asthma account for substantial asthma morbidity, mortality, and healthcare burden despite comprising only a small proportion of the total asthma population. TENOR, a multicenter, observational, prospective cohort study was initiated in 2001. It enrolled 4,756 adults, adolescents and children with severe or difficult-to-treat asthma who were followed semi-annually and annually for three years, enabling insight to be gained into this understudied population. A broad range of demographic, clinical, and patient self-reported assessments were completed during the follow-up period. Here, we present key findings from the TENOR registry in relation to asthma control and exacerbations, including the identification of specific subgroups found to be at particularly high-risk. Identification of the factors and subgroups associated with poor asthma control and increased risk of exacerbations can help physicians design individual asthma management, and improve asthma-related health outcomes for these patients.
PMCID: PMC3485530  PMID: 23136642
Severe asthma; Difficult-to-treat asthma; Asthma control; Exacerbation
16.  Genome-Wide Association Analysis in Asthma Subjects Identifies SPATS2L as a Novel Bronchodilator Response Gene 
PLoS Genetics  2012;8(7):e1002824.
Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function (i.e. FEV1) before and after the administration of a short-acting β2-agonist, the most common rescue medications used for the treatment of asthma. BDR also serves as a test of β2-agonist efficacy. BDR is a complex trait that is partly under genetic control. A genome-wide association study (GWAS) of BDR, quantified as percent change in baseline FEV1 after administration of a β2-agonist, was performed with 1,644 non-Hispanic white asthmatic subjects from six drug clinical trials: CAMP, LOCCS, LODO, a medication trial conducted by Sepracor, CARE, and ACRN. Data for 469,884 single-nucleotide polymorphisms (SNPs) were used to measure the association of SNPs with BDR using a linear regression model, while adjusting for age, sex, and height. Replication of primary P-values was attempted in 501 white subjects from SARP and 550 white subjects from DAG. Experimental evidence supporting the top gene was obtained via siRNA knockdown and Western blotting analyses. The lowest overall combined P-value was 9.7E-07 for SNP rs295137, near the SPATS2L gene. Among subjects in the primary analysis, those with rs295137 TT genotype had a median BDR of 16.0 (IQR = [6.2, 32.4]), while those with CC or TC genotypes had a median BDR of 10.9 (IQR = [5.0, 22.2]). SPATS2L mRNA knockdown resulted in increased β2-adrenergic receptor levels. Our results suggest that SPATS2L may be an important regulator of β2-adrenergic receptor down-regulation and that there is promise in gaining a better understanding of the biological mechanisms of differential response to β2-agonists through GWAS.
Author Summary
Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function before and after the administration of short-acting β2-agonists, common medications used for asthma treatment. We performed a genome-wide association study of BDR with 1,644 white asthmatic subjects from six drug clinical trials and attempted to replicate these findings in 1,051 white subjects from two independent cohorts. The most significant associated variant was near the SPATS2L gene. We knocked down SPATS2L mRNA in human airway smooth muscle cells and found that β2-adrenergic receptor levels increased, suggesting that SPATS2L may be a regulator of BDR. Our results highlight the promise of pursuing GWAS results that do not necessarily reach genome-wide significance and are an example of how results from pharmacogenetic GWAS can be studied functionally.
PMCID: PMC3390407  PMID: 22792082
17.  Pilot Study of the Association of the DDAH2 −449G Polymorphism with Asymmetric Dimethylarginine and Hemodynamic Shock in Pediatric Sepsis 
PLoS ONE  2012;7(3):e33355.
Genetic variability in the regulation of the nitric oxide (NO) pathway may influence hemodynamic changes in pediatric sepsis. We sought to determine whether functional polymorphisms in DDAH2, which metabolizes the NO synthase inhibitor asymmetric dimethylarginine (ADMA), are associated with susceptibility to sepsis, plasma ADMA, distinct hemodynamic states, and vasopressor requirements in pediatric septic shock.
Methodology/Principal Findings
In a prospective study, blood and buccal swabs were obtained from 82 patients ≤18 years (29 with severe sepsis/septic shock plus 27 febrile and 26 healthy controls). Plasma ADMA was measured using tandem mass spectrometry. DDAH2 gene was partially sequenced to determine the −871 6g/7g insertion/deletion and −449G/C single nucleotide polymorphisms. Shock type (“warm” versus “cold”) was characterized by clinical assessment. The −871 7g allele was more common in septic (17%) then febrile (4%) and healthy (8%) patients, though this was not significant after controlling for sex and race (p = 0.96). ADMA did not differ between −871 6g/7g genotypes. While genotype frequencies also did not vary between groups for the −449G/C SNP (p = 0.75), septic patients with at least one −449G allele had lower ADMA (median, IQR 0.36, 0.30–0.41 µmol/L) than patients with the −449CC genotype (0.55, 0.49–0.64 µmol/L, p = 0.008) and exhibited a higher incidence of “cold” shock (45% versus 0%, p = 0.01). However, after controlling for race, the association with shock type became non-significant (p = 0.32). Neither polymorphism was associated with inotrope score or vasoactive infusion duration.
The −449G polymorphism in the DDAH2 gene was associated with both low plasma ADMA and an increased likelihood of presenting with “cold” shock in pediatric sepsis, but not with vasopressor requirement. Race, however, was an important confounder. These results support and justify the need for larger studies in racially homogenous populations to further examine whether genotypic differences in NO metabolism contribute to phenotypic variability in sepsis pathophysiology.
PMCID: PMC3299781  PMID: 22428028

Results 1-17 (17)