Augusto A. Litonjua

Ambient Pollution and Heart Rate Variability

BACKGROUND We investigated associations between ambient pollution levels and cardiovascular function in a repeated measures study including 163 observations on twenty-one 53- to 87-year-old active Boston residents observed up to 12 times from June to September 1997. Particles with aerodynamic diameter </=2.5 microm (PM(2.5)) were measured continuously using a tapered element oscillating microbalance. METHODS AND RESULTS The protocol involved 25 minutes per week of continuous Holter ECG monitoring, including 5 minutes of rest, 5 minutes of standing, 5 minutes of exercise outdoors, 5 minutes of recovery, and 20 cycles of slow breathing. Heart rate variability (HRV) was assessed through time domain variables: the standard deviation of normal RR intervals (SDNN) and the square root of the mean of the squared differences between adjacent normal RR intervals (r-MSSD). Mean 4-hour PM(2.5) levels ranged from 3 to 49 microg/m(3); 1-hour ozone levels ranged from 1 to 77 ppb. In multivariate analyses, significantly less HRV (SDNN and r-MSSD) was associated with elevated PM(2.5). During slow breathing, a reduction in r-MSSD of 6.1 ms was associated with an interquartile (14.3 microg/m(3)) increase in PM(2.5) during the hour of and the 3 hours previous to the Holter session (P=0.006). During slow breathing, a multiple pollution model was associated with a reduction in r-MSSD of 5.4 ms (P=0.02) and 5.5 ms (P=0.03) for interquartile changes in PM(2.5) and ozone, respectively, resulting in a combined effect equivalent to a 33% reduction in the mean r-MSSD. CONCLUSIONS Particle and ozone exposure may decrease vagal tone, resulting in reduced HRV.

Rapid DNA methylation changes after exposure to traffic particles.

RATIONALE Exposure to particulate air pollution has been related to increased hospitalization and death, particularly from cardiovascular disease. Lower blood DNA methylation content is found in processes related to cardiovascular outcomes, such as oxidative stress, aging, and atherosclerosis. OBJECTIVES We evaluated whether particulate pollution modifies DNA methylation in heavily methylated sequences with high representation throughout the human genome. METHODS We measured DNA methylation of long interspersed nucleotide element (LINE)-1 and Alu repetitive elements by quantitative polymerase chain reaction-pyrosequencing of 1,097 blood samples from 718 elderly participants in the Boston area Normative Aging Study. We used covariate-adjusted mixed models to account for within-subject correlation in repeated measures. We estimated the effects on DNA methylation of ambient particulate pollutants (black carbon, particulate matter with aerodynamic diameter < or = 2.5 microm [PM2.5], or sulfate) in multiple time windows (4 h to 7 d) before the examination. We estimated standardized regression coefficients (beta) expressing the fraction of a standard deviation change in DNA methylation associated with a standard deviation increase in exposure. MEASUREMENTS AND MAIN RESULTS Repetitive element DNA methylation varied in association with time-related variables, such as day of the week and season. LINE-1 methylation decreased after recent exposure to higher black carbon (beta = -0.11; 95% confidence interval [CI], -0.18 to -0.04; P = 0.002) and PM2.5 (beta = -0.13; 95% CI, -0.19 to -0.06; P < 0.001 for the 7-d moving average). In two-pollutant models, only black carbon, a tracer of traffic particles, was significantly associated with LINE-1 methylation (beta = -0.09; 95% CI, -0.17 to -0.01; P = 0.03). No association was found with Alu methylation (P > 0.12). CONCLUSIONS We found decreased repeated-element methylation after exposure to traffic particles. Whether decreased methylation mediates exposure-related health effects remains to be determined.

Serum Vitamin D Levels and Markers of Severity of Childhood Asthma in Costa Rica

RATIONALE Maternal vitamin D intake during pregnancy has been inversely associated with asthma symptoms in early childhood. However, no study has examined the relationship between measured vitamin D levels and markers of asthma severity in childhood. OBJECTIVES To determine the relationship between measured vitamin D levels and both markers of asthma severity and allergy in childhood. METHODS We examined the relation between 25-hydroxyvitamin D levels (the major circulating form of vitamin D) and markers of allergy and asthma severity in a cross-sectional study of 616 Costa Rican children between the ages of 6 and 14 years. Linear, logistic, and negative binomial regressions were used for the univariate and multivariate analyses. MEASUREMENTS AND MAIN RESULTS Of the 616 children with asthma, 175 (28%) had insufficient levels of vitamin D (<30 ng/ml). In multivariate linear regression models, vitamin D levels were significantly and inversely associated with total IgE and eosinophil count. In multivariate logistic regression models, a log(10) unit increase in vitamin D levels was associated with reduced odds of any hospitalization in the previous year (odds ratio [OR], 0.05; 95% confidence interval [CI], 0.004-0.71; P = 0.03), any use of antiinflammatory medications in the previous year (OR, 0.18; 95% CI, 0.05-0.67; P = 0.01), and increased airway responsiveness (a < or =8.58-mumol provocative dose of methacholine producing a 20% fall in baseline FEV(1) [OR, 0.15; 95% CI, 0.024-0.97; P = 0.05]). CONCLUSIONS Our results suggest that vitamin D insufficiency is relatively frequent in an equatorial population of children with asthma. In these children, lower vitamin D levels are associated with increased markers of allergy and asthma severity.

Serum vitamin D levels and severe asthma exacerbations in the Childhood Asthma Management Program study

BACKGROUND Asthma exacerbations, most often caused by respiratory tract infections, are the leading causes of asthma morbidity and comprise a significant proportion of asthma-related costs. Vitamin D status might play a role in preventing asthma exacerbations. OBJECTIVES We sought to assess the relationship between serum vitamin D levels and subsequent severe asthma exacerbations. METHODS We measured 25-hydroxyvitamin D levels in sera collected from 1024 children with mild-to-moderate persistent asthma at the time of enrollment in a multicenter clinical trial of children randomized to receive budesonide, nedocromil, or placebo (as-needed beta-agonists): the Childhood Asthma Management Program. Using multivariable modeling, we examined the relationship between baseline vitamin D levels and the odds of any hospitalization or emergency department visit over the 4 years of the trial. RESULTS Thirty-five percent of all subjects were vitamin D insufficient, as defined by a level of 30 ng/mL or less 25-hydroxyvitamin D. Mean vitamin D levels were lowest in African American subjects and highest in white subjects. After adjusting for age, sex, body mass index, income, and treatment group, insufficient vitamin D status was associated with a higher odds of any hospitalization or emergency department visit (odds ratio, 1.5; 95% CI, 1.1-1.9; P = .01). CONCLUSION Vitamin D insufficiency is common in this population of North American children with mild-to-moderate persistent asthma and is associated with higher odds of severe exacerbation over a 4-year period.

MMP12, lung function, and COPD in high-risk populations.

BACKGROUND Genetic variants influencing lung function in children and adults may ultimately lead to the development of chronic obstructive pulmonary disease (COPD), particularly in high-risk groups. METHODS We tested for an association between single-nucleotide polymorphisms (SNPs) in the gene encoding matrix metalloproteinase 12 (MMP12) and a measure of lung function (prebronchodilator forced expiratory volume in 1 second [FEV(1)]) in more than 8300 subjects in seven cohorts that included children and adults. Within the Normative Aging Study (NAS), a cohort of initially healthy adult men, we tested for an association between SNPs that were associated with FEV(1) and the time to the onset of COPD. We then examined the relationship between MMP12 SNPs and COPD in two cohorts of adults with COPD or at risk for COPD. RESULTS The minor allele (G) of a functional variant in the promoter region of MMP12 (rs2276109 [-82A-->G]) was positively associated with FEV(1) in a combined analysis of children with asthma and adult former and current smokers in all cohorts (P=2x10(-6)). This allele was also associated with a reduced risk of the onset of COPD in the NAS cohort (hazard ratio, 0.65; 95% confidence interval [CI], 0.46 to 0.92; P=0.02) and with a reduced risk of COPD in a cohort of smokers (odds ratio, 0.63; 95% CI, 0.45 to 0.88; P=0.005) and among participants in a family-based study of early-onset COPD (P=0.006). CONCLUSIONS The minor allele of a SNP in MMP12 (rs2276109) is associated with a positive effect on lung function in children with asthma and in adults who smoke. This allele is also associated with a reduced risk of COPD in adult smokers.

Race, socioeconomic factors, and area of residence are associated with asthma prevalence

Asthma prevalence in the United States has been reported to be higher in minority groups such as Blacks and Hispanics. Because a disproportionate number of individuals from such minority groups are of low socioeconomic status (SES), it is unclear how much of the racial/ethnic differences in asthma prevalence is related to low SES. We investigated the effect of SES on the relationship between race/ethnicity and asthma prevalence in a cohort of families with a history of asthma or allergies from the Boston, Massachusetts area. From 499 families, a cohort of 998 parents and 307 children was identified. We used total yearly family income (<

Genomewide Association between GLCCI1 and Response to Glucocorticoid Therapy in Asthma

50,000 vs. ≥

Traffic related pollution and heart rate variability in a panel of elderly subjects

50,000), highest level of education (≤high school vs. ≥college), and residence in high‐poverty areas vs. low‐poverty areas as measures of SES.

Ischemic heart disease and stroke in relation to blood DNA methylation

BACKGROUND The response to treatment for asthma is characterized by wide interindividual variability, with a significant number of patients who have no response. We hypothesized that a genomewide association study would reveal novel pharmacogenetic determinants of the response to inhaled glucocorticoids. METHODS We analyzed a small number of statistically powerful variants selected on the basis of a family-based screening algorithm from among 534,290 single-nucleotide polymorphisms (SNPs) to determine changes in lung function in response to inhaled glucocorticoids. A significant, replicated association was found, and we characterized its functional effects. RESULTS We identified a significant pharmacogenetic association at SNP rs37972, replicated in four independent populations totaling 935 persons (P=0.0007), which maps to the glucocorticoid-induced transcript 1 gene (GLCCI1) and is in complete linkage disequilibrium (i.e., perfectly correlated) with rs37973. Both rs37972 and rs37973 are associated with decrements in GLCCI1 expression. In isolated cell systems, the rs37973 variant is associated with significantly decreased luciferase reporter activity. Pooled data from treatment trials indicate reduced lung function in response to inhaled glucocorticoids in subjects with the variant allele (P=0.0007 for pooled data). Overall, the mean (±SE) increase in forced expiratory volume in 1 second in the treated subjects who were homozygous for the mutant rs37973 allele was only about one third of that seen in similarly treated subjects who were homozygous for the wild-type allele (3.2±1.6% vs. 9.4±1.1%), and their risk of a poor response was significantly higher (odds ratio, 2.36; 95% confidence interval, 1.27 to 4.41), with genotype accounting for about 6.6% of overall inhaled glucocorticoid response variability. CONCLUSIONS A functional GLCCI1 variant is associated with substantial decrements in the response to inhaled glucocorticoids in patients with asthma.

Genome-wide association study identifies three new susceptibility loci for adult asthma in the Japanese population

Background: Particulate air pollution has been associated with increased cardiovascular deaths and hospital admissions. To help understand the mechanisms, the types of particles most involved, and the types of persons most susceptible, the association between exposure to summertime air pollution and heart rate variability (HRV) was examined in a panel study of 28 elderly subjects. Methods: Subjects were seen once a week for up to 12 weeks and HRV (SDNN, r-MSSD, PNN50, low frequency/high frequency ratio (LFHFR)) was measured for approximately 30 minutes at each session using a defined protocol. Temperature, day of the week, and hour of the day were controlled, and dummy variables for each subject were controlled for subject specific risk factors. Results: PM2.5 was associated with r-MSSD (−10.1% change for an interquartile range (IQR) increase in exposure (95% CI −2.8 to −16.9)) and PNN50, but stronger associations were seen with black carbon, an indicator of traffic particles, which was also associated with SDNN (−4.6% per IQR (95% CI −2.0 to −7.2)) and LFHFR. Secondary particles were more weakly associated with r-MSSD, as was ozone. No associations were seen with SO2 or NO2. CO had similar patterns of association to black carbon, which disappeared after controlling for black carbon. Black carbon had a substantially higher effect on SDNN in subjects who had had a previous myocardial infarction (−12.7%, 95% CI −5.7 to −19.25). Conclusions: Particles, especially from traffic, are associated with disturbances of autonomic control of the heart.