Diet during Pregnancy and Infancy and the Infant Intestinal Microbiome.

OBJECTIVES: To determine the association between diet during pregnancy and infancy, including breastfeeding vs formula feeding, solid food introduction, and the infant intestinal microbiome. STUDY DESIGN: Infants participating in the Vitamin D Antenatal Asthma Reduction Trial were included in this study (n = 323). Maternal and infant diets were assessed by questionnaire. Infant stool samples were collected at age 3-6 months. Stool sequencing was performed using the Roche 454 platform. Analyses were stratified by race/ethnicity. RESULTS: Breastfeeding, compared with formula feeding, was independently associated with infant intestinal microbial diversity. Breastfeeding also had the most consistent associations with individual taxa that have been previously linked to early-life diet and health outcomes (eg, Bifidobacterium). Maternal diet during pregnancy and solid food introduction were less associated with the infant gut microbiome than breastfeeding status. We found evidence of a possible interaction between breastfeeding and child race/ethnicity on microbial composition. CONCLUSIONS: Breastfeeding vs formula feeding is the dietary factor that is most consistently independently associated with the infant intestinal microbiome. The relationship between breastfeeding status and intestinal microbiome composition varies by child race/ethnicity. Future studies will need to investigate factors, including genomic factors, which may influence the response of the microbiome to diet. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00920621.

Factors influencing the infant gut microbiome at age 3-6 months: Findings from the ethnically diverse Vitamin D Antenatal Asthma Reduction Trial (VDAART).

BACKGROUND: The gut microbiome in infancy influences immune system maturation, and may have an important impact on allergic disease risk. OBJECTIVE: We sought to determine how prenatal and early life factors impact the gut microbiome in a relatively large, ethnically diverse study population of infants at age 3 to 6 months, who were enrolled in Vitamin D Antenatal Asthma Reduction Trial, a clinical trial of vitamin D supplementation in pregnancy to prevent asthma and allergies in offspring. METHODS: We performed 16S rRNA gene sequencing on 333 infants' stool samples. Microbial diversity was computed using the Shannon index. Factor analysis applied to the top 25 most abundant taxa revealed 4 underlying bacterial coabundance groups; the first dominated by Firmicutes (Lachnospiraceae/Clostridiales), the second by Proteobacteria (Klebsiella/Enterobacter), the third by Bacteriodetes, and the fourth by Veillonella. Scores for coabundance groups were used as outcomes in regression models, with prenatal/birth and demographic characteristics as independent predictors. Multivariate analysis, using all microbial community members, was also conducted. RESULTS: White race/ethnicity was associated with lower diversity but higher Bacteroidetes coabundance scores. C-section birth was associated with higher diversity, but decreased Bacteroidetes coabundance scores. Firmicutes scores were higher for infants born by C-section. Breast-fed infants had lower proportions of Clostridiales. Cord blood vitamin D was linked to increased Lachnobacterium, but decreased Lactococcus. CONCLUSIONS: The findings presented here suggest that race, mode of delivery, breast-feeding, and cord blood vitamin D levels are associated with infant gut microbiome composition, with possible long-term implications for immune system modulation and asthma/allergic disease incidence.

Allergen sensitization is associated with increased DNA methylation in older men.

BACKGROUND: Variation in epigenetic modifications, arising from either environmental exposures or internal physiological changes, can influence gene expression and may ultimately contribute to complex diseases such as asthma and allergies. We examined the association of asthma and allergic phenotypes with DNA methylation levels of retrotransposon-derived elements. METHODS: We used data from 704 men (mean age 73 years) in the longitudinal Normative Aging Study to assess the relationship between asthma, allergic phenotypes and DNA methylation levels of the retrotransposon-derived elements Alu and long interspersed nuclear element (LINE)-1. Retrotransposons represent a large fraction of the genome (>30%) and are heavily methylated to prevent expression. Percent methylation of Alu and LINE-1 elements in peripheral white blood cells was quantified using PCR pyrosequencing. Data on sensitization to common allergens from skin prick testing, asthma and methacholine responsiveness were gathered approximately 8 years prior to DNA methylation analysis. RESULTS: Prior allergen sensitization was associated with increased methylation of Alu (ß = 0.32 for sensitized vs. nonsensitized patients; p = 0.003) in models adjusted for pack-years of smoking, body mass index, current smoking, air pollutants, percentage of eosinophils, white blood cell count and age. Of the men interviewed, 5% of subjects reported a diagnosis of asthma. Neither Alu nor LINE-1 methylation was associated with asthma. CONCLUSIONS: These data suggest that increased DNA methylation of repetitive elements may be associated with allergen sensitization but does not appear to be associated with asthma. Future work is needed to identify potential underlying mechanisms for these relationships.

Vitamin D deficiency, smoking, and lung function in the Normative Aging Study.

RATIONALE: Vitamin D has immunomodulatory and antiinflammatory effects that may be modified by cigarette smoke and may affect lung function. OBJECTIVES: To examine the effect of vitamin D deficiency and smoking on lung function and lung function decline. METHODS: A total of 626 men from the Normative Aging Study had 25-hydroxyvitamin D levels measured at three different times between 1984 and 2003 with concurrent spirometry. Vitamin D deficiency was defined as serum level ≤ 20 ng/ml. Statistical analysis was performed using multivariable linear regression and mixed effects models. MEASUREMENTS AND MAIN RESULTS: In the overall cohort, there was no significant effect of vitamin D deficiency on lung function or on lung function decline. In both cross-sectional and longitudinal multivariable models, there was effect modification by vitamin D status on the association between smoking and lung function. Cross-sectional analysis revealed lower lung function in current smokers with vitamin D deficiency (FEV(1), FVC, and FEV(1)/FVC; P ≤ 0.0002), and longitudinal analysis showed more rapid rates of decline in FEV(1) (P = 0.023) per pack-year of smoking in subjects with vitamin D deficiency as compared with subjects who were vitamin D sufficient. CONCLUSIONS: Vitamin D deficiency was associated with lower lung function and more rapid lung function decline in smokers over 20 years in this longitudinal cohort of elderly men. This suggests that vitamin D sufficiency may have a protective effect against the damaging effects of smoking on lung function. Future studies should seek to confirm this finding in the context of smoking and other exposures that affect lung function.

Genome-wide association analysis of circulating vitamin D levels in children with asthma.

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.

Parental psychosocial stress and asthma morbidity in Puerto Rican twins.

BACKGROUND: Little is known about paternal psychosocial factors and childhood asthma. OBJECTIVE: We sought to examine the link between maternal and paternal psychosocial stress and asthma outcomes in young children. METHODS: Parents of 339 pairs of Puerto Rican twins were interviewed individually about their own psychosocial stress and about asthma in their children at age 1 year and again about their child's asthma at age 3 years. Fathers were asked about symptoms of posttraumatic stress disorder (PTSD), depression, and antisocial behavior. Mothers were asked about depressive symptoms. Outcomes assessed in children included recent asthma symptoms, oral steroid use and hospitalizations for asthma in the prior year, and asthma diagnosis. Generalized estimated equation models were used for the multivariate analysis of parental psychosocial stress and asthma morbidity in childhood. RESULTS: After multivariable adjustment, paternal PTSD symptoms, depression, and antisocial behavior were each associated with increased asthma symptoms at age 1 year (eg, odds ratio, 1.08 for each 1-point increase in PTSD score; 95% CI, 1.03-1.14). Maternal depressive symptoms were associated with an increased risk of asthma hospitalizations at age 1 year. At age 3 years, maternal depressive symptoms were associated with asthma diagnosis and hospitalizations for asthma (odds ratio for each 1-point increase in symptoms, 1.16; 95% CI, 1.00-1.36). In an analysis combining 1- and 3-year outcomes, paternal depression was associated with oral steroid use, maternal depressive symptoms were associated with asthma hospitalizations and asthma diagnosis, and parental depression was associated with hospitalizations for asthma. CONCLUSIONS: Both paternal and maternal psychosocial factors can influence asthma morbidity in young Puerto Rican children.

Comprehensive genetic assessment of a functional TLR9 promoter polymorphism: no replicable association with asthma or asthma-related phenotypes.

BACKGROUND: Prior studies suggest a role for a variant (rs5743836) in the promoter of toll-like receptor 9 (TLR9) in asthma and other inflammatory diseases. We performed detailed genetic association studies of the functional variant rs5743836 with asthma susceptibility and asthma-related phenotypes in three independent cohorts. METHODS: rs5743836 was genotyped in two family-based cohorts of children with asthma and a case-control study of adult asthmatics. Association analyses were performed using chi square, family-based and population-based testing. A luciferase assay was performed to investigate whether rs5743836 genotype influences TLR9 promoter activity. RESULTS: Contrary to prior reports, rs5743836 was not associated with asthma in any of the three cohorts. Marginally significant associations were found with FEV1 and FVC (p = 0.003 and p = 0.008, respectively) in one of the family-based cohorts, but these associations were not significant after correcting for multiple comparisons. Higher promoter activity of the CC genotype was demonstrated by luciferase assay, confirming the functional importance of this variant. CONCLUSION: Although rs5743836 confers regulatory effects on TLR9 transcription, this variant does not appear to be an important asthma-susceptibility locus.

Maternal dietary pattern during pregnancy is not associated with recurrent wheeze in children.

BACKGROUND: The rise in asthma prevalence over the last few decades may be a result of changes in prenatal or early-life environment, including maternal diet during pregnancy. Previous studies have found associations between individual foods or nutrients consumed during pregnancy and asthma or wheeze in children, but these may be confounded by overall dietary pattern. OBJECTIVE: To determine whether overall maternal dietary pattern during pregnancy is associated with recurrent wheeze in children. METHODS: A total of 1376 mother-infant pairs from Project Viva, a longitudinal prebirth cohort, who had responses for food frequency questionnaires in the first and second trimester and outcome data at 3 years of age were included. Multivariable logistic regression was used to look at associations between dietary pattern and the primary outcome of recurrent wheeze at 3 years. Overall dietary pattern was examined by using Mediterranean diet score, Alternate Healthy Eating Index modified for pregnancy (AHEI-P), and principal components analysis to look at Western and Prudent diets. RESULTS: None of these dietary patterns was associated with the primary outcome of recurrent wheeze in children in either the crude or the multivariable model (multivariable model, odds ratio per 1-point increase in Mediterranean diet, 0.98 [95% CI, 0.89-1.08]; AHEI-P, 1.07 [0.87-1.30]; Prudent, 1.02 [0.83-1.26]; Western, 0.98 [0.81-1.19]). CONCLUSION: Overall dietary pattern during pregnancy is not associated with recurrent wheeze in this cohort. Maternal intake of individual nutrients may be more important determinants of offspring wheeze-associated illness than is dietary pattern.

The Vitamin D Antenatal Asthma Reduction Trial (VDAART): rationale, design, and methods of a randomized, controlled trial of vitamin D supplementation in pregnancy for the primary prevention of asthma and allergies in children.

There is intense interest in the role of vitamin D in the development of asthma and allergies. However, studies differ on whether a higher vitamin D intake or status in pregnancy or at birth is protective against asthma and allergies. To address this uncertainty, the Vitamin D Antenatal Asthma Reduction Trial (VDAART) was developed. VDAART is a randomized, double-blind, placebo-controlled trial of vitamin D supplementation in pregnant women to determine whether prenatal supplementation can prevent the development of asthma and allergies in women's offspring. A secondary aim is to determine whether vitamin D supplementation can prevent the development of pregnancy complications, such as preeclampsia, preterm birth, and gestational diabetes. Women were randomized to the treatment arm of 4000IU/day of vitamin D3 plus a daily multivitamin that contained 400IU of vitamin D3 or the placebo arm of placebo plus a multivitamin that contained 400IU daily of vitamin D3. Women who were between the gestational ages of 10 and 18 weeks were randomized from three clinical centers across the United States - Boston Medical Center, Washington University in St. Louis, and Kaiser Permanente Southern California Region (San Diego, CA). Supplementation took place throughout pregnancy. Monthly monitoring of urinary calcium to creatinine ratio was performed in addition to medical record review for adverse events. Offspring are being evaluated quarterly through questionnaires and yearly during in-person visits until the 3rd birthday of the child. Ancillary studies will investigate neonatal T-regulatory cell function, maternal vaginal flora, and maternal and child intestinal flora.

Pre-hospital vitamin D concentration, mortality, and bloodstream infection in a hospitalized patient population.

OBJECTIVE: The study objective was to examine the association between pre-hospital serum vitamin D concentration and mortality after hospitalization. METHODS: We performed a retrospective cohort study in 2 tertiary hospitals in Boston, Mass, on 23,603 patients aged ≥18 years in whom 25(OH)D was measured before hospitalization between 1993 and 2010. The main outcome measures were all-cause mortality by day 30 post-hospital admission, in-hospital mortality, and community-acquired bloodstream infection. RESULTS: Compared with patients with pre-hospital 25(OH)D ≥30 ng/mL, patients with pre-hospital 25(OH)D ≤15 ng/mL or 15 to 30 ng/mL have higher odds of mortality 30 days after hospital admission. After adjustment for age, gender, race, Deyo-Charlson index, season, type (surgical vs medical), creatinine, blood urea nitrogen, hematocrit, and time between 25(OH)D draw and hospital admission, the adjusted odds ratio (OR) of 30-day mortality in patients with 25(OH)D ≤15 ng/mL is 1.45 (95% confidence interval [CI], 1.21-1.74; P<.0001) and the adjusted OR of 30-day mortality in patients with 25(OH)D 15 to 30 ng/mL is 1.30 (95% CI, 1.10-1.54; P = .003) both compared with patients with pre-hospital 25(OH)D ≥30 ng/mL. In a subgroup analysis of patients who had blood cultures drawn (n = 5628), pre-hospital serum 25(OH)D ≤15 ng/mL was associated with increased odds of community-acquired bloodstream infection (adjusted OR, 1.29; 95% CI, 1.06-1.57; P = .01) relative to patients with 25(OH)D ≥30 ng/mL. CONCLUSIONS: Analysis of 23,603 hospitalized patients identified both 25(OH)D ≤15 ng/mL and 25(OH)D 15 to 30 ng/mL before hospital admission as associated with the odds of all-cause patient mortality at 30 days after hospitalization. In addition, pre-hospital serum 25(OH)D ≤15 ng/mL is significantly associated with the odds of community-acquired bloodstream infection.

A twin study of early-childhood asthma in Puerto Ricans.

BACKGROUND: The relative contributions of genetics and environment to asthma in Hispanics or to asthma in children younger than 3 years are not well understood. OBJECTIVE: To examine the relative contributions of genetics and environment to early-childhood asthma by performing a longitudinal twin study of asthma in Puerto Rican children ≤ 3 years old. METHODS: 678 twin infants from the Puerto Rico Neo-Natal Twin Registry were assessed for asthma at age 1 year, with follow-up data obtained for 624 twins at age 3 years. Zygosity was determined by DNA microsatellite profiling. Structural equation modeling was performed for three phenotypes at ages 1 and 3 years: physician-diagnosed asthma, asthma medication use in the past year, and ≥ 1 hospitalization for asthma in the past year. Models were additionally adjusted for early-life environmental tobacco smoke exposure, sex, and age. RESULTS: The prevalences of physician-diagnosed asthma, asthma medication use, and hospitalization for asthma were 11.6%, 10.8%, 4.9% at age 1 year, and 34.1%, 40.1%, and 8.5% at 3 years, respectively. Shared environmental effects contributed to the majority of variance in susceptibility to physician-diagnosed asthma and asthma medication use in the first year of life (84%-86%), while genetic effects drove variance in all phenotypes (45%-65%) at age 3 years. Early-life environmental tobacco smoke, sex, and age contributed to variance in susceptibility. CONCLUSION: Our longitudinal study in Puerto Rican twins demonstrates a changing contribution of shared environmental effects to liability for physician-diagnosed asthma and asthma medication use between ages 1 and 3 years. Early-life environmental tobacco smoke reduction could markedly reduce asthma morbidity in young Puerto Rican children.

Psychosocial stress and asthma morbidity.

PURPOSE OF REVIEW: The objective of this review is to provide an overview and discussion of recent epidemiologic and mechanistic studies of stress in relation to asthma incidence and morbidity. RECENT FINDINGS: Recent findings suggest that stress, whether at the individual (i.e. epigenetics, perceived stress), family (i.e. prenatal maternal stress, early-life exposure, or intimate partner violence) or community (i.e. neighborhood violence; neighborhood disadvantage) level, influences asthma and asthma morbidity. Key recent findings regarding how psychosocial stress may influence asthma through Posttraumatic Stress Disorder, prenatal and postnatal maternal/caregiver stress, and community violence and deprivation are highlighted. SUMMARY: New research illustrates the need to further examine, characterize, and address the influence of social and environmental factors (i.e. psychological stress) on asthma. Further, research and innovative methodologies are needed to characterize the relationship and pathways associated with stress at multiple levels to more fully understand and address asthma morbidity, and to design potential interventions, especially to address persistent disparities in asthma in ethnic minorities and economically disadvantaged communities.

Alu and LINE-1 methylation and lung function in the normative ageing study.

OBJECTIVES: To investigate the association between methylation of transposable elements Alu and long-interspersed nuclear elements (LINE-1) and lung function. DESIGN: Cohort study. SETTING: Outpatient Veterans Administration facilities in greater Boston, Massachusetts, USA. PARTICIPANTS: Individuals from the Veterans Administration Normative Aging Study, a longitudinal study of aging in men, evaluated between 1999 and 2007. The majority (97%) were white. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary predictor was methylation, assessed using PCR-pyrosequencing after bisulphite treatment. Primary outcome was lung function as assessed by spirometry, performed according to American Thoracic Society/European Respiratory Society guidelines at the same visit as the blood draws. RESULTS: In multivariable models adjusted for age, height, body mass index (BMI), pack-years of smoking, current smoking and race, Alu hypomethylation was associated with lower forced expiratory volume in 1 s (FEV(1)) (ß=28 ml per 1% change in Alu methylation, p=0.017) and showed a trend towards association with a lower forced vital capacity (FVC) (ß=27 ml, p=0.06) and lower FEV(1)/FVC (ß=0.3%, p=0.058). In multivariable models adjusted for age, height, BMI, pack-years of smoking, current smoking, per cent lymphocytes, race and baseline lung function, LINE-1 hypomethylation was associated with more rapid decline of FEV(1) (ß=6.9 ml/year per 1% change in LINE-1 methylation, p=0.005) and of FVC (ß=9.6 ml/year, p=0.002). CONCLUSIONS: In multiple regression analysis, Alu hypomethylation was associated with lower lung function, and LINE-1 hypomethylation was associated with more rapid lung function decline in a cohort of older and primarily white men from North America. Future studies should aim to replicate these findings and determine if Alu or LINE-1 hypomethylation may be due to specific and modifiable environmental exposures.

Spirometry: don't blow it!

Spirometry is a useful test of pulmonary function and can be safely performed in a variety of clinical situations. Although the technique for performing the maneuver is straightforward, there are many sources of variability in results. Specific criteria must be met in order for the test to be considered valid. For the best results, proper instruction and coaching is essential, and patient understanding and effort must be maximized. Appropriate interpretation of spirometry requires several steps, including recognition and reporting of technically sound maneuvers, comparison to an appropriate reference population, and finally application of a well-developed interpretation scheme utilized in the context of patient symptoms and findings. Failure at any point along this path from performance to interpretation can yield misleading results that may ultimately poorly impact patient care. A clear understanding by the provider of proper coding and billing for spirometry is necessary to receive appropriate reimbursement from payers.

Vitamin D, the immune system and asthma.

The effects of vitamin D on bone metabolism and calcium homeostasis have long been recognized. Emerging evidence has implicated vitamin D as a critical regulator of immunity, playing a role in both the innate and cell-mediated immune systems. Vitamin D deficiency has been found to be associated with several immune-mediated diseases, susceptibility to infection and cancer. Recently, there has been increasing interest in the possible link between vitamin D and asthma. Further elucidation of the role of vitamin D in lung development and immune system function may hold profound implications for the prevention and treatment of asthma.