Asthma and genes encoding components of the vitamin D pathway

Gene susceptibility in Iranian asthmatic patients: a narrative review

As environmental factors are important in the development of asthma, genetic factors could have a critical role in the expression of the disease. Hence, we carried out a systematic review to assess the susceptible genes for asthma in Iranian population. We conducted a literature search by using the electronic database PubMed, Biological Abstracts Web of Science, Current Contents Connect, Cinahl, ScienceDirect, Scopus, IranMedex, and Scientific Information Database to identify articles that evaluated the association between genetic variants and the risk of asthma in Iranian population (until April 30, 2012). The search terms were used include: Asthma and gene in combination with Iran for international database. The following criteria were used for selecting literatures in this review: The study should evaluate the association between gene polymorphism and risk of asthma in Iranian population, and the study should be a case-control design with normal subject as ac control group that published in a journal. Finally, 14 case-control studies were extracted from local and international database. In this study, we reviewed 38 polymorphisms in 19 genes. Polymorphism in interleukin-13 (IL-13), IL-10, IL-1, IL-2, IL-12, E-Selectin, S128R and Exon 9 Vitamin D Receptor were susceptible for asthma and polymorphism in chemokine receptor 5, transforming growth factor-a (TGF-a), Intron 8 of the Vitamin D Receptor, angiotensin-converting enzyme gene, IL-6 and interferon-c were not susceptible for asthma in Iranian population. Polymorphism in IL-4, tumor necrosis factor-α and TGF-b had inconsistent findings. This systematic review indicated that three polymorphisms (IL-13, IL-10, and IL-1) are associated with risk of asthma in Iranian population.

Vitamin D insufficiency in Arabs and South Asians positively associates with polymorphisms in GC and CYP2R1 genes

Background

A number of genetic studies have reported an association between vitamin D related genes such as group-specific component gene (GC), Cytochrome P450, family 2, subfamily R, polypeptide 1 (CYP2R1) and 7-dehydrocholesterol reductase/nicotinamide-adenine dinucleotide synthetase 1 (DHCR7/NADSYN1) and serum levels of the active form of Vitamin D, 25 (OH) D among African Americans, Caucasians, and Chinese. Little is known about how genetic variations associate with, or contribute to, 25(OH)D levels in Arabs populations.

Methods

Allele frequencies of 18 SNPs derived from CYP2R1, GC, and DHCR7/NADSYN1 genes in 1549 individuals (Arabs, South Asians, and Southeast Asians living in Kuwait) were determined using real time genotyping assays. Serum levels of 25(OH)D were measured using chemiluminescence immunoassay.

Results

GC gene polymorphisms (rs17467825, rs3755967, rs2282679, rs7041 and rs2298850) were found to be associated with 25(OH)D serum levels in Arabs and South Asians. Two of the CYP2R1 SNPs (rs10500804 and rs12794714) and one of GC SNPs (rs1155563) were found to be significantly associated with 25(OH)D serum levels only in people of Arab origin. Across all three ethnicities none of the SNPs of DHCR7/NADSYN1 were associated with serum 25(OH)D levels and none of the 18 SNPs were significantly associated with serum 25(OH)D levels in people from South East Asia.

Conclusion

Our data show for the first time significant association between the GC (rs2282679 and rs7041), CYP2R1 (rs10741657) SNPs and 25(OH)D levels. This supports their roles in vitamin D Insufficiency in Arab and South Asian populations respectively. Interestingly, two of the CYP2R1 SNPs (rs10500804 and rs12794714) and one GC SNP (rs1155563) were found to correlate with vitamin D in Arab population exclusively signifying their importance in this population.

Common genetic variations in the vitamin D pathway in relation to blood pressure

BACKGROUND

Vitamin D is involved in blood pressure (BP) regulation. Genetic variations may influence the effect of vitamin D on BP, but data from epidemiologic studies remain inconsistent.

METHODS

We conducted a comprehensive genetic association study in the Women's Genome Health Study (WGHS) with genome-wide genotype data among 23,294 women of European ancestry and in the International Consortium of Blood Pressure (ICBP) with genome-wide meta-analysis results from 69,395 men and women of European ancestry.

RESULTS

First, we found none of 5 selected vitamin D-related candidate single nucleotide polymorphisms (SNPs) was associated with systolic BP (SBP) or diastolic BP (DBP). Second, in 61 candidate SNPs involved in vitamin D metabolism and signaling, rs1507023 (in RBFOX1) and rs2296241 (in CYP24A1) showed significant associations with SBP, DBP, mean arterial pressure, or pulse pressure in the WGHS before, but not after, multiple testing corrections. Nominally significant associations in the ICBP were also not significant after corrections. Third, among 24 candidate genes across vitamin D pathway, associations with BP traits that meet gene-wide significance level were found for NCOA3 (rs2235734), RXRA (rs875444), DHCR7 (rs1790370), VDR (rs2544037), and NCOR2 (rs1243733, rs1147289) in the WGHS and NCOR1, TP53BP1, and TYRP1 in the ICBP. However, none of these associations reached significance threshold in both studies.

CONCLUSIONS

Our study did not replicate previously observed associations of vitamin D-related SNPs with BP. There was suggestive evidence for associations in other vitamin D pathway genes; however, these associations either did not reach the significance threshold or were not replicated.

Vitamin D receptor ApaI a allele is associated with better childhood asthma control and improvement in ability for daily activities

Vitamin D levels have been suggested as a marker of disease severity in asthmatic children. Our aim was to investigate possible associations between the vitamin D receptor (VDR) FokI, BsmI, ApaI, and TaqI polymorphisms and asthma susceptibility and control in children. 127 Greek children with asthma and 91 healthy controls were genotyped for VDR FokI, BsmI ApaI, and TaqI polymorphisms using Sequenom MassARRAY iPLEX platform. Asthma control was assessed according to the Global Initiative for Asthma guidelines (GINA) and Childhood Asthma Control Test (C-ACT) and, for the first time, tested for its possible association with VDR SNPs. Asthmatic children were grouped as "controlled (n=49)", "partially controlled (n=38)," and "uncontrolled (n=40)," according to GINA classification. No association was found between VDR polymorphisms and asthma prevalence. Asthmatic children with the VDR ApaI aa genotype had significantly higher C-ACT score compared with asthmatic children carrying the AA/AC VDR ApaI genotypes (p=0.011). The frequency of VDR ApaI aa genotype was significantly higher in controlled asthma group (n=92) than uncontrolled asthma group (n=35), according to C-ACT (24.5% vs 0.0%, p<0.001) and GINA (32.7% vs 7.5%, p=0.001). Also, VDR ApaI aa genotype was negatively associated with limitation in daily activities because of asthma (p=0.004). VDR ApaI aa genotype was positively associated with well-controlled asthma according to GINA and C-ACT questionnaire and negatively associated with decreased limitation in daily activities in asthmatic children, further supporting the importance of Vitamin D pathway in asthma.

Vitamin D supplementation blocks pulmonary structural and functional changes in a rat model of perinatal vitamin D deficiency

Whereas epidemiological data strongly link vitamin D (VD) deficiency to childhood asthma, the underlying molecular mechanisms remain unknown. Although VD is known to stimulate alveolar epithelial-mesenchymal interactions, promoting perinatal lung maturation, whether VD supplementation during this period protects against childhood asthma has not been demonstrated experimentally. Using an in vivo rat model, we determined the effects of perinatal VD deficiency on overall pulmonary function and the tracheal contraction as a functional marker of airway contractility. One month before pregnancy, rat dams were put on either a no cholecalciferol-added or a 250, 500, or 1,000 IU/kg cholecalciferol-added diet, which was continued throughout pregnancy and lactation. At postnatal day 21, offspring plasma 25(OH)D levels and pulmonary function (whole body plethysmography and tracheal contraction response to acetylcholine) were determined. 25(OH)D levels were lowest in the no cholecalciferol-supplemented group, increasing incrementally in response to cholecalciferol supplementation. Compared with the 250 and 500 IU/kg VD-supplemented groups, the no cholecalciferol-supplemented group demonstrated a significant increase in airway resistance following methacholine challenge. However, the cholecalciferol deficiency-mediated increase in tracheal contractility in the cholecalciferol-depleted group was only blocked by supplementation with 500 IU/kg cholecalciferol. Therefore, in addition to altering alveolar epithelial-mesenchymal signaling, perinatal VD deficiency also alters airway contractility, providing novel insights to asthma pathogenesis in perinatally VD-deficient offspring. Perinatal VD supplementation at 500 IU/kg appears to effectively block these effects of perinatal VD deficiency in the rat model used, providing a strong clinical rationale for effective perinatal VD supplementation for preventing childhood asthma.

Environmental and genetic determinants of vitamin D insufficiency in 12-month-old infants

We aimed to investigate the relationship between genetic and environmental exposure and vitamin D status at age one, stratified by ethnicity. This study included 563 12-month-old infants in the HealthNuts population-based study. DNA from participants' blood samples was genotyped using Sequenom MassARRAY MALDI-TOF system on 28 single nucleotide polymorphisms (SNPs) in six genes. Using logistic regression, we examined associations between environmental exposure and SNPs in vitamin D pathway and filaggrin genes and vitamin D insufficiency (VDI). VDI, defined as serum 25-hydroxyvitamin D3(25(OH)D3) level ≤50nmol/L, was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Infants were stratified by ethnicity determined by parent's country of birth. Infants formula fed at 12 months were associated with reduced odds of VDI compared to infants with no current formula use at 12 months. This association differed by ethnicity (Pinteraction=0.01). The odds ratio (OR) of VDI was 0.29 for Caucasian infants (95% CI, 0.18-0.47) and 0.04 for Asian infants (95% CI, 0.006-0.23). Maternal vitamin D supplementation during pregnancy and/or breastfeeding were associated with increased odds of infants being VDI (OR, 2.39; 95% CI, 1.11-5.18 and OR, 2.5; 95% CI, 1.20-5.24 respectively). Presence of a minor allele for any GC SNP (rs17467825, rs1155563, rs2282679, rs3755967, rs4588, rs7041) was associated with increased odds of VDI. Caucasian infants homozygous (AA) for rs4588 had an OR of 2.49 of being associated with VDI (95% CI, 1.19-5.18). In a country without routine infant vitamin D supplementation or food chain fortification, formula use is strongly associated with a reduced risk of VDI regardless of ethnicity. There was borderline significance for an association between filaggrin mutations and VDI. However, polymorphisms in vitamin D pathway related genes were associated with increased likelihood of being VDI in infancy.

Association of vitamin D receptor gene polymorphisms with asthma risk: systematic review and updated meta-analysis of case-control studies

BACKGROUND

The association between vitamin D receptor (VDR) polymorphisms and asthma risk has been inconsistently investigated, but published studies demonstrated conflicting results. The aim of the current study was to investigate the impact of TaqI, BsmI, ApaI, and FokI VDR polymorphisms on asthma disease by using a meta-analysis approach.

METHODS

Following the preferred reporting items for systematic reviews and meta-analyses guidelines, a systematic search and meta-analysis of the literature were conducted. Subgroup analyses were performed to detect potential sources of heterogeneity from selected study characteristics.

RESULTS

A total of 2,097 cases and 1,968 controls in eight case-control studies were included in meta-analyses. A significant association was found between TaqI polymorphisms and asthma risk [OR 1.488 (95 % CI 1.019-2.174); P = 0.040] in a codominant model. In the same way, BsmI was significantly associated with asthma risk [OR 2.017 (95 % CI 1.236-3.851); P = 0.017] in the codominant model. The homozygote BB BsmI genotype was found to confer significant asthma risk. FokI polymorphism was marginally associated with asthma risk [OR 1.187 (95 % CI 0.975-1.446); P = 0.088] in the codominant model. In contrast, no significant association was found between ApaI polymorphism and asthma risk. Subgroup analyses revealed that gender and age modified significantly the association between FokI polymorphisms and asthma risk (P = 0.035 and 0.013, respectively). Publication year and serum 25(OH) D level tended, marginally, to moderate the association between FokI polymorphism and asthma risk.

CONCLUSION

TaqI, BsmI, and FokI VDR polymorphisms contribute to asthma susceptibility. The association between FokI polymorphism and asthma risk is influenced by study characteristics.

Vitamin D in ankylosing spondylitis: review and meta-analysis

BACKGROUND

The role of vitamin D in ankylosing spondylitis (AS) is largely unknown. This paper aims to examine the association between serum vitamin D levels and susceptibility and disease activity of AS.

METHODS

We searched the relevant literatures in PubMed, Elsevier Science Direct, Chinese Biomedical Database (CBM), Chinese National Knowledge Infrastructure (CNKI) and Wanfang (Chinese) Database published before June 2014. Eight independent case-control studies with a total of 533 AS patients and 478 matching controls were selected into this meta-analysis. Standard mean differences (SMDs) with 95% confidence intervals (CIs) were used to assess the levels of serum vitamin D, parathyroid hormone (PTH), serum calcium and alkaline phosphatase (ALP) in cases and controls, respectively. Correlation coefficients (CORs) have been performed to value the correlationship between vitamin D and disease activity (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)) of AS patients.

RESULTS

Meta-analysis results suggested that vitamin D may play a protective role in AS (for total vitamin D: SMD=-0.71, P<0.001; for 25OHD: SMD=-0.66, P=0.002; for 1,25OHD: SMD=-0.72, P=0.19). Differences in PTH and serum calcium levels were not significant in AS (SMD=-0.10, P=0.67; SMD=0.12, P=0.17 respectively), while ALP was associated with AS susceptibility (SMD=0.20, P=0.04). The relationship between serum vitamin D levels and disease activity was statistically significant except for 25OHD versus (vs.) CRP or BASDAI (for CRP vs. 25OHD: COR=-0.22, P=0.08; for BASDAI vs. 25OHD: COR=-0.20, P=0.06, respectively).

CONCLUSION

The higher levels of serum vitamin D were associated with a decreased risk of AS, and showed an inverse relationship with AS activity.

Vitamin D and Its Role as a Protective Factor in Allergy

The relationship between vitamin D status and asthma has been subject to several studies in the last decade. Epidemiological data suggest that incidence of asthma and atopic diseases increased significantly in most Westernized countries. The significant variation between countries suggests that besides genetic factors, environmental aspects play a role in the pathogenesis of atopy. The prevalence of hypovitaminosis D is high in many industrialized countries. In addition to its relationship with bone metabolism, vitamin D is recognized as an immunomodulator, with important effects on both adaptive and innate immunity. Correlations between vitamin D status and asthma have been formulated, with a considerable interest in assessing whether this vitamin protects against or reduces asthma morbidity. In this review, we discuss recent findings regarding vitamin D status throughout Europe and its influence over asthma and allergic rhinitis prevalence. Geographical latitude and dietary habits may explain the lower prevalence of allergic disease in Albania. We also consider the effects of vitamin D supplementation in allergic disease. Several clinical trials are under way and their results are needed in order to make definitive recommendations about the optimal dose of vitamin D for prevention and treatment of asthma and allergic disease.

Effect of vitamin D-binding protein genotype on the development of asthma in children

BACKGROUND

Potential vitamin D-related influences on inflammatory diseases such as asthma are controversial, including the suggestion that vitamin D insufficiency is associated with increased asthma morbidity. Vitamin D-binding protein transports vitamin D metabolites in the circulation. Single nucleotide polymorphisms in the GC gene encoding vitamin D-binding protein are associated with circulating vitamin D metabolite levels in healthy infants and toddlers.

OBJECTIVE

To test the hypothesis that GC single nucleotide polymorphisms encoding the D432E and T436K variants predict subsequent development of asthma in healthy children.

METHODS

A retrospective medical record review was performed to determine the development of asthma in 776 children in whom GC genotype, vitamin D-binding protein concentration, and circulating 25-hydroxyvitamin D had been determined at 6 to 36 months of age. Demographic and detailed current clinical data were collected and criteria for asthma were recorded.

RESULTS

GC genotype was available for 463 subjects. After an initial analysis of all subject data, the analysis was limited to the predominant Hispanic population (72.1%) to minimize potential confounding effects of ethnicity. Asthma was diagnosed in 87 children (26%). Subjects with the GC genotype encoding the ET/ET (Gc1s/Gc1s) variant had lower odds of developing asthma, representing a protective effect compared with subjects with the DT/DT (Gc1f/Gc1f) variant.

CONCLUSION

In the Hispanic population of inner-city New Haven, Connecticut, the ET/ET (Gc1s/Gc1s) genotype of vitamin D-binding protein might confer protection against the development of asthma compared with the wild-type genotype DT/DT (Gc1f/Gc1f).

Immunoregulatory mechanisms of vitamin D relevant to respiratory health and asthma

Vitamin D deficiency is prevalent among people with various immune-mediated conditions, including autoimmune diseases and asthma. Serum 25(OH)D levels inversely correlate with asthma severity, glucocorticoid responsiveness/dosage, and markers of pathogenesis, such as airway remodeling, IgE, and eosinophilia. Trials involving supplementation with active vitamin D or a precursor are beginning to emerge with variable results that, in part, reflect differences in study design. This review looks at the mechanisms by which vitamin D may protect against asthma, including increasing glucocorticoid responsiveness, skewing immune cells towards a regulatory phenotype, reducing the incidence of infections, airway remodeling, eosinophilia, and lowering the levels of IgE. Also discussed is the therapeutic potential for vitamin D, which is likely to be applicable to immune-mediated conditions beyond simply asthma.

The Interaction Between Allelic Variants of CD86 and CD40LG: A Common Risk Factor of Allergic Asthma and Rheumatoid Arthritis

PURPOSE

Allergic asthma (AA) and rheumatoid arthritis (RA) are immune tolerance-related diseases, and immune tolerance is known to be influenced by costimulatory molecules. In this study, we sought to identify common genetic susceptibility in AA and RA.

METHODS

Two hundred cases of AA, 184 cases of RA, and 182 healthy controls were recruited at the Seoul National University Hospital, Seoul, Korea. Eight single nucleotide polymorphisms (SNPs) in five genes coding costimulatory molecules, namely, -318C>T, +49A>G, and 6230G>A in CTLA4, IVS3+17T>C in CD28, -3479T>G and I179V in CD86, -1C>T in CD40, and -3458A>G in CD40LG were scored, and genetic interactions were evaluated by multifactor dimensionality reduction (MDR) analysis.

RESULTS

MDR analysis revealed a significant gene-gene interaction between -3479T>G CD86 and -3458A>G CD40LG for AA. Subjects with the T/T genotype of -3479T>G CD86 and the A/A genotype of -3458A>G CD40LG were found to be significantly more likely to develop AA than those with the T/T genotype of -3479T>G CD86 and A/- genotype of -3458A>G CD40LG (adjusted OR, 6.09; 95% CI, 2.89-12.98; logistic regression analysis controlled by age). Similarly those subjects showed a significant risk of developing RA (adjusted OR, 39.35; 95% CI, 15.01-107.00, logistic regression analysis controlled by age).

CONCLUSIONS

Our findings suggest that a genetic interaction between CD86 and CD40LG favors the development of both AA and RA.

The nuclear factor I/A (NFIA) gene is associated with the asthma plus rhinitis phenotype

BACKGROUND

A previous genome-wide linkage scan in 295 families of the French Epidemiological Study on the Genetics and Environment of Asthma (EGEA) showed strong evidence of linkage of the 1p31 region to the combined asthma plus allergic rhinitis (AR) phenotype.

OBJECTIVE

Our purpose was to conduct fine-scale mapping of the 1p31 linkage region to identify the genetic variants associated with asthma plus AR.

METHODS

Association analyses with the asthma plus rhinitis phenotype were first conducted in the EGEA family sample using the family-based association method (FBAT) and logistic regression. The test of homogeneity of association between asthma plus AR versus asthma alone or AR alone was also applied. Replication of EGEA findings was sought in French-Canadian and United Kingdom family samples.

RESULTS

We found a significant association between asthma plus rhinitis and a 1p31 genetic variant (P = 2 × 10(-5) for rs12122228, which reached the multiple testing-corrected threshold) in EGEA using FBAT. There was evidence of heterogeneity of association between asthma plus AR versus asthma alone or AR alone (P = .03). A Meta-analysis of FBAT results from EGEA and French-Canadian families improved evidence for both association and heterogeneity (P = 5 × 10(-6) and P = .008, respectively), whereas a meta-analysis of EGEA, French-Canadian, and United Kingdom samples based on logistic regression slightly increased the evidence for heterogeneity.

CONCLUSION

The single nucleotide polymorphism specifically associated to asthma plus rhinitis is located in the flanking 5' untranslated region of the nuclear factor I/A (NFIA) gene, a strong candidate gene for asthma and AR.

DO IT Trial: vitamin D Outcomes and Interventions in Toddlers - a TARGet Kids! randomized controlled trial

BACKGROUND

Vitamin D levels are alarmingly low (<75 nmol/L) in 65-70% of North American children older than 1 year. An increased risk of viral upper respiratory tract infections (URTI), asthma-related hospitalizations and use of anti-inflammatory medication have all been linked with low vitamin D. No study has determined whether wintertime vitamin D supplementation can reduce the risk of URTI and asthma exacerbations, two of the most common and costly illnesses of early childhood. The objectives of this study are: 1) to compare the effect of 'high dose' (2000 IU/day) vs. 'standard dose' (400 IU/day) vitamin D supplementation in achieving reductions in laboratory confirmed URTI and asthma exacerbations during the winter in preschool-aged Canadian children; and 2) to assess the effect of 'high dose' vitamin D supplementation on vitamin D serum levels and specific viruses that cause URTI.

METHODS/DESIGN

This study is a pragmatic randomized controlled trial. Over 4 successive winters we will recruit 750 healthy children 1-5 years of age. Participating physicians are part of a primary healthcare research network called TARGet Kids!. Children will be randomized to the 'standard dose' or 'high dose' oral supplemental vitamin D for a minimum of 4 months (200 children per group). Parents will obtain a nasal swab from their child with each URTI, report the number of asthma exacerbations and complete symptom checklists. Unscheduled physician visits for URTIs and asthma exacerbations will be recorded. By May, a blood sample will be drawn to determine vitamin D serum levels. The primary analysis will be a comparison of URTI rate between study groups using a Poisson regression model. Secondary analyses will compare vitamin D serum levels, asthma exacerbations and the frequency of specific viral agents between groups.

DISCUSSION

Identifying whether vitamin D supplementation of preschoolers can reduce wintertime viral URTIs and asthma exacerbations and what dose is optimal may reduce population wide morbidity and associated health care and societal costs. This information will assist in determining practice and health policy recommendations related to vitamin D supplementation in healthy Canadian preschoolers.

Vitamin D supplementation reduces airway hyperresponsiveness and allergic airway inflammation in a murine model

BACKGROUND

Asthma is a chronic disease associated with airway hyperresponsiveness (AHR), airway obstruction and airway remodelling. NF-κB is a transcriptional factor that regulates and co-ordinates the expression of various inflammatory genes. The NF-κB subunits, p50 and Rel-A, are translocated to the nucleus by importin α3 and importin α4. There is growing evidence that vitamin D is a potent immunomodulator. However, the evidence for beneficial or adverse effects of vitamin D in asthma is still unclear.

OBJECTIVE

In this study, we examined the effect of vitamin D status on AHR, airway inflammation and cytokines in the bronchoalveolar lavage fluid (BALF) in a murine model of allergic asthma.

METHODS

Female BALB/c mice were fed with special vitamin D-deficient or vitamin D-sufficient (2000 IU/kg) or vitamin D-supplemented (10,000 IU/kg) diet for 13 weeks. Mice were sensitized and challenged with ovalbumin (OVA). The effect of vitamin D on lung histology, AHR, T regulatory cells (Tregs) and BALF cytokines was examined. The expression of importin-α3 and Rel-A in the lung of OVA-sensitized mice was analysed using immunofluorescence.

RESULTS

Vitamin D deficiency was associated with higher AHR in OVA-sensitized and challenged mice than those in vitamin D-sufficient mice. This was accompanied with marked signs of airway remodelling, high BALF eosinophilia, increased BALF pro-inflammatory cytokines, reduced BALF IL-10 levels, reduced blood Tregs, increased expression of importin-α3 and Rel-A in the lung tissue. Vitamin D supplementation attenuated the pro-inflammatory effects, but did not completely reverse the features of allergic airway inflammation.

CONCLUSION AND CLINICAL RELEVANCE

Vitamin D could be beneficial as an adjunct therapy in the treatment of allergic asthma.

Eczema phenotypes are associated with multiple vitamin D pathway genes in Chinese children

BACKGROUND

Vitamin D is increasingly recognized to play crucial roles in cutaneous immunity, and vitamin D treatment improved eczema control in small clinical trials. Several vitamin D-related genes were associated with asthma, but there are no data for eczema.

METHODS

Twenty-three single-nucleotide polymorphisms (SNPs) of five vitamin D-related genes (CYP27A1, CYP2R1, CYP27B1, GC and VDR) were genotyped in 1442 Chinese children with eczema and 1231 non-allergic controls. SNPs that followed Hardy-Weinberg equilibrium and yielded ≥ 95% genotyping call-rate were included. Haplotypic associations and SNP-SNP interactions for eczema diagnosis and subphenotypes were analysed.

RESULTS

Atopic eczema was associated with rs4674343 of CYP27A1 (odds ratio 0.66, 95% confidence interval 0.53-0.83, P = 0.0004). Increased eosinophil percentage was associated with CYP2R1 rs2060793A (P = 0.001) and rs1933064A (P = 0.001). Two CYP2R1 haplotypes increased eczema risk whereas one VDR haplotype lowered eczema risk. GC rs7041 and CYP2R1 rs7935792 interacted to modulate total IgE (cross-validation consistency 10/10, P = 0.047). Specifically, high-risk eczema patients had higher log-transformed total IgE than low-risk patients (2.76 ± 0.76 vs 2.60 ± 0.80, P = 0.002).

CONCLUSION

A vitamin D-related SNP rs4674343 on CYP27A1 was found to be protective against atopic eczema. CYP2R1 and VDR haplotypes altered eczema susceptibility and eosinophil percentage, and GC and CYP2R1 interacted to determine total IgE among eczema patients.

Vitamin D in asthma and future perspectives

Humans have the ability to synthesize vitamin D during the action of ultraviolet (UV) radiation upon the skin. Apart from the regulation of calcium and phosphate metabolism, another critical role for vitamin D in immunity and respiratory health has been revealed, since vitamin D receptors have also been found in other body cells. The term "vitamin D insufficiency" has been used to describe low levels of serum 25-hydroxyvitamin D that may be associated with a wide range of pulmonary diseases, including viral and bacterial respiratory infection, asthma, chronic obstructive pulmonary disease, and cancer. This review focuses on the controversial relationship between vitamin D and asthma. Also, it has been found that different gene polymorphisms of the vitamin D receptor have variable associations with asthma. Other studies investigated the vitamin D receptor signaling pathway in vitro or in experimental animal models and showed either a beneficial or a negative effect of vitamin D in asthma. Furthermore, a range of epidemiological studies has also suggested that vitamin D insufficiency is associated with low lung function. In the future, clinical trials in different asthmatic groups, such as infants, children of school age, and ethnic minorities are needed to establish the role of vitamin D supplementation to prevent and/or treat asthma.

Beneficial role of vitamin D3 in the prevention of certain respiratory diseases

There is evidence of aberrations in the vitamin D-endocrine system in subjects with respiratory diseases. Vitamin D deficiency is highly prevalent in patients with respiratory diseases, and patients who receive vitamin D have significantly larger improvements in inspiratory muscle strength and maximal oxygen uptake. Studies have provided an opportunity to determine which proteins link vitamin D to respiratory pathology, including the major histocompatibility complex class II molecules, vitamin D receptor, vitamin D-binding protein, chromosome P450, Toll-like receptors, poly(ADP-ribose) polymerase-1, and the reduced form of nicotinamide adenine dinucleotide phosphate. Vitamin D also exerts its effect on respiratory diseases through cell signaling mechanisms, including matrix metalloproteinases, mitogen-activated protein kinase pathways, the Wnt/β-catenin signaling pathway, prostaglandins, reactive oxygen species, and nitric oxide synthase. In conclusion, vitamin D plays a significant role in respiratory diseases. The best form of vitamin D for use in the treatment of respiratory diseases is calcitriol because it is the active metabolite of vitamin D3 and modulates inflammatory cytokine expression. Further investigation of calcitriol in respiratory diseases is needed.

Allergic rhinitis and serum 25-hydroxyvitamin D level in Korean adults

BACKGROUND

Recently, it has been suggested that airway hyper-responsiveness, asthma, and atopic dermatitis are associated with a low vitamin D level.

OBJECTIVE

To evaluate whether the occurrence of allergic rhinitis (AR) is related to serum vitamin D levels in the general Korean adult population.

METHODS

Data obtained as part of the fourth annual Korean National Health and Nutrition Examination Survey (2009) of 8,012 adults older than 18 years were analyzed. The correlation between serum 25-hydroxyvitamin D (25[OH]D) level and presence of AR using questionnaires on symptoms, history of diagnosis of AR, and rhinoscopic findings were analyzed. All estimates were calculated based on sampling weight.

RESULTS

Mean age was 44.41 years and men constituted 49.8% of the sample. Participants with diagnosed AR constituted 11.1%. The mean 25(OH)D level of the AR group was lower than that of the non-AR group (16.71 ± 0.30 vs 17.75 ± 0.25 ng/mL, P < .001). A comparison of the prevalence of AR in the 3 groups showed that AR steadily decreased in the higher 25(OH)D groups (13.0% in group I [<15 ng/mL], 11.5% in group II [≥15-<25 ng/mL], and 7.2% in group III [≥25 ng/mL], P < .001). After adjusting for body mass index, smoking status, age, sex, sun exposure, income quartile, exercise, and body fat percentage, lower serum 25(OH)D levels remained significantly associated with the presence of AR compared with group III (hazard ratio 1.559 in group I and 1.430 in group II).

CONCLUSION

This study suggested a potential association between low vitamin D levels and AR prevalence in Korean adults.

Associations between genetic polymorphisms in IL-33, IL1R1 and risk for inflammatory bowel disease

BACKGROUND

Recent evidence suggests that the IL-33/IL1RL1 axis plays a critical role in several autoimmune and inflammatory disorders; however, its mechanistic role in inflammatory bowel disease (IBD) has not been clearly defined. We investigated the contribution of IL-33 and IL1RL1 polymorphisms to IBD risk, and possible correlations with phenotype in an Italian cohort of adult and pediatric patients.

METHODS

We evaluated the association of six SNPs in IL-33 and IL1RL1 genes, in 805 Crohn's disease (CD), 816 ulcerative colitis (UC), and 752 controls, using Taqman. IL-33 and IL1RL1 mRNA expression was also analyzed.

RESULTS

Significant allele and genotype associations with IL-33 rs3939286 were found in CD (P = 0.004; P = 0.035) and UC patients (P = 0.002; P = 0.038). After stratifying the cohort for age at diagnosis, the differences remained significant only in the IBD adult-onset. Significant associations were also obtained in CD patients with two IL1RL1 polymorphisms (rs13015714 and rs2058660, P<0.015). By combining homo- and heterozygous carriers of the rs13015714 risk allele, differences were still significant for both CD adult- and pediatric-onset. Upon genotype-phenotype evaluation, an increased frequency of extensive colitis in adult UC (P = 0.019) and in steroid-responsive pediatric patients (P = 0.024) carrying the IL-33 rs3939286 risk genotype, was observed. mRNA expression of IL-33 and IL1RL1 in inflamed IBD biopsy samples was significantly increased.

CONCLUSIONS

Common IL-33 and IL1RL1 polymorphisms contribute to the risk of IBD in an Italian cohort of adult and pediatric patients, with some influence on sub-phenotypes.

Genetic association analysis of vitamin D pathway with obesity traits

Objective

Observational studies have examined the link between vitamin D deficiency and obesity traits. Some studies have reported associations between vitamin D pathway genes such as VDR, GC and CYP27B1 with body mass index (BMI) and waist circumference (WC); however, the findings have been inconsistent. Hence, we investigated the involvement of vitamin D metabolic pathway genes in obesity-related traits in a large population-based study.

Methods

We undertook a comprehensive analysis between 100 tagging polymorphisms (tagSNPs) in genes encoding for DHCR7, CYP2R1, VDBP, CYP27B1, CYP27A1, CYP24A1, VDR and RXRG and obesity traits in 5,224 participants (aged 45 years) in the 1958 British birth cohort (1958BC). We further extended our analyses to investigate the associations between SNPs and obesity traits using the summary statistics from the GIANT (Genetic Investigation of Anthropometric Traits) consortium (n=123,865).

Results

In the 1958BC (n=5,224), after Bonferroni correction, none of the tagSNPs were associated with obesity traits except for one tagSNP from CYP24A1 that was associated with waist-hip ratio (WHR) (rs2296239, P=0.001). However, the CYP24A1 SNP was not associated with BMI-adjusted WHR (WHRadj) in the 1958BC (rs2296239, P=1.00) and GIANT results (n=123,865, P=0.18). There was also no evidence for an interaction between the tagSNPs and obesity on BMI, WC, WHR and WHRadj in the 1958BC. In the GIANT consortium, none of the tagSNPs were associated with obesity traits.

Conclusions

Despite a very large study, our findings suggest that the vitamin D pathway genes are unlikely to have a major role in obesity-related traits in the general population.

Decoding asthma: translating genetic variation in IL33 and IL1RL1 into disease pathophysiology

Asthma is a complex disease that results from the interaction between genetic predisposition and environmental factors. Recently, genome-wide association studies have identified a number of genes that significantly contribute to asthma. Two of these genes, IL33 and IL-1 receptor-like 1 (IL1RL1), act in one signal transduction pathway. IL33 encodes a cytokine released on damage of cells, whereas IL1RL1 encodes part of the IL-33 receptor complex. Recent progress made in functional studies in human subjects and mouse models of allergic airway disease indicate a central role of IL-33 signaling in driving TH2 inflammation, which is central to eosinophilic allergic asthma. Here, IL-33 acts on cells of both the adaptive and innate immune systems. Very recently, a novel population of IL-33-responsive innate immune cells, the type 2 innate lymphoid cells, was found to produce hallmark TH2 cytokines, such as IL-5 and IL-13. The relevance of these cells for asthma is underscored by the identification of retinoic acid-related orphan receptor α(RORA), the gene encoding the transcription factor critical for their differentiation, as another asthma gene in genome-wide association studies. This review describes the mechanisms through which genetic variation at the IL33 and IL1RL1 loci translates into increased susceptibility for asthma. We propose that genetic variation associated with asthma at the IL33 and IL1RL1 loci can be dissected into independent signals with distinct functional consequences for this pathway that is central to asthma pathogenesis.

The ANO3/MUC15 locus is associated with eczema in families ascertained through asthma

BACKGROUND

A previous genome-wide linkage scan in 295 families of the French Epidemiological Study on the Genetics and Environment of Asthma (EGEA) reported strong evidence of linkage of 11p14 to eczema.

OBJECTIVE

Our purpose was to conduct fine-scale mapping of the 11p14 region to identify the genetic variants associated with eczema.

METHODS

Association analyses were first conducted in the family sample from the French EGEA by using 2 methods: the family-based association method and logistic regression. Replication of the EGEA findings was sought in French Canadian and United Kingdom family samples, which, similarly to EGEA samples, were ascertained through asthma. We also tested for association in 2 German samples ascertained through eczema.

RESULTS

We found significant association of eczema with 11p14 genetic variants in the vicinity of the linkage peak in EGEA (P = 10(-4) for rs1050153 by using the family-based association method, which reached the multiple testing-corrected threshold of 10(-4); P = .003 with logistic regression). Pooled analysis of the 3 asthma-ascertained samples showed strong improvement in the evidence for association (P = 6 × 10(-6) for rs293974, P = 3 × 10(-5) for rs1050153, and P = 8 × 10(-5) for rs15783). No association was observed in the eczema-ascertained samples.

CONCLUSION

The significant single nucleotide polymorphisms are located within the overlapping anoctamin 3 (ANO3) and mucin 15 (MUC15) genes. Several lines of evidence suggest that MUC15 is a strong candidate for eczema. Further investigation is needed to confirm our findings and to better understand the role of the ANO3/MUC15 locus in eczema and its relationship with respect to asthma.

Common variants of the vitamin D binding protein gene and adverse health outcomes

The vitamin D binding protein (DBP) is the major plasma carrier for vitamin D and its metabolites, but it is also an actin scavenger, and is the precursor to the immunomodulatory protein, Gc-MAF. Two missense variants of the DBP gene - rs7041 encoding Asp432Glu and rs4588 encoding Thr436Lys - change the amino acid sequence and alter the protein function. They are common enough to generate population-wide constitutive differences in vitamin D status, based on assay of the serum metabolite, 25-hydroxyvitamin D (25OHD). Whether these variants also influence the role of vitamin D in an immunologic milieu is not known. However, the issue is relevant, given the immunomodulatory effects of DBP and the role of protracted innate immune-related inflammation in response to tissue injury or repeated infection. Indeed, DBP and vitamin D may jointly or independently contribute to a variety of adverse health outcomes unrelated to classical notions of their function in bone and mineral metabolism. This review summarizes the reports to date of associations between DBP variants, and various chronic and infectious diseases. The available information leads us to conclude that DBP variants are a significant and common genetic factor in some common disorders, and therefore, are worthy of closer attention. In view of the heightened interest in vitamin D as a public health target, well-designed studies that look simultaneously at vitamin D and its carrier in relation to genotypes and adverse health outcome should be encouraged.

Association of vitamin D receptor gene polymorphisms with susceptibility to asthma in Tunisian children: A case control study

BACKGROUND

Vitamin D and its nuclear receptor (VDR) are linked to asthma in a genetic and immunologic basis. Polymorphisms in the VDR gene may alter the actions of vitamin D and then influence the development and the severity of asthma.

AIMS

We aimed at elucidating the genetic association of VDR gene polymorphisms with susceptibility to asthma in Tunisian children and with serum vitamin D levels.

METHODS

The study included 155 patients recruited from Abderrahmen MAMI hospital in Tunisia and two hundred twenty five healthy individuals matched with patients in age and sex for comparison. VDR genotypes were determined by PCR-RFLP method using endonuclease FokI, BsmI, TaqI and ApaI and vitamin D was assessed with a radioimmunoassay kit.

RESULTS

The distribution of genotype frequencies differed significantly between asthmatics and controls (FokI: P=0.04; BsmI: P=0.006; TaqI: P=0.006). Haplotype analyses revealed a significant association between bAt and bat haplotypes and asthma (P=0.00076, P=0.016). When patients were stratified according to atopic status and stage of severity, no significant association was detected with VDR variants. No association was found between VDR SNPs and serum 25-hydroxyvitamin D levels.

CONCLUSION

Our study shows a relation between VDR gene polymorphisms and susceptibility to asthma in children.

Vitamin D and asthma

Asthma, one of the most prevalent diseases affecting people worldwide, is a chronic respiratory disease characterized by heightened airway inflammation, airway hyperresponsiveness and airflow obstruction in response to specific triggers. While the specific mechanisms responsible for asthma are not well understood, changing environmental factors associated with urban lifestyles may underlie the increased prevalence of the disorder. Vitamin D is of particular interest in asthma since vitamin D concentrations decrease with increased time spent indoors, decreased exposure to sunlight, less exercise, obesity, and inadequate calcium intake. Additionally, a growing body of literature suggests that there is a relationship between vitamin D status and respiratory symptoms, presumably through immunomodulatory effects of vitamin D. This review discusses vitamin D as it relates to asthma across the age spectrum, with a focus on human studies.

Vitamin D and atopy and asthma phenotypes in children

PURPOSE OF REVIEW

To give an overview of the recent research into whether a lack of vitamin D contributes to the development of atopy and asthma in childhood.

RECENT FINDINGS

I describe here the recent epidemiological studies relating vitamin D status to atopy and asthma in children, focusing on determinants of major asthma phenotypes in childhood. Recent findings include the observations that vitamin D levels are inversely associated with degree of corticosteroid use, worsening airflow limitation and increased exacerbations among asthmatics. Low vitamin D has been associated with atopy and asthma in children and adolescents in a community cohort, predominantly in boys, with vitamin D at age 6 predicting these outcomes at 14. I also detail the mechanistic studies examining relevant vitamin D-regulated processes; recent findings include the demonstration that offspring of mice with vitamin D deficiency in pregnancy show reduced lung volume and function.

SUMMARY

The current literature suggests that intervention to ensure adequate vitamin D levels during both pregnancy and childhood may reduce the development of atopy and asthma in children. However, important questions need to be answered regarding the levels of vitamin D required, which may vary between the sexes and between individuals, and the optimal timing and duration of such intervention.

Evidence for a genetic interaction in allergy-related responsiveness to vitamin D deficiency

BACKGROUND

The hormonal form of vitamin D affects both adaptive and innate immune functions involved in the development of allergies. Certain genotypes have been seen to alter the association between vitamin D deficiency (VDD) and the risk of food sensitization in children.

METHODS

We examined 27 functional single nucleotide polymorphisms (SNPs) in/near selected candidate genes for association with total immunoglobulin E (IgE) and effect modification by 25-hydroxyvitamin D in the 1958 British birth cohort (aged 45 years, n = 4921). A cut-off value of 50 nmol/L was used to define VDD.

RESULTS

Four SNPs (in FCER1A, IL13, and CYP24A1) and three SNPs (in IL4 and CYP24A1) were associated with total IgE and specific IgE, respectively, after correction for multiple testing. As in a previous study, MS4A2 (rs512555, P(interaction) = 0.04) and IL4 (rs2243250, P(interaction) = 0.02), and their composite score (P(interaction) = 0.009) modified the association between VDD and allergy-related outcome. Vitamin D deficiency was associated with higher total IgE only in the carriers of the 'C' allele (IL4), which is present in 86% of white Europeans, while only 26% of Chinese and <20% of some African populations are carriers.

CONCLUSIONS

Our study on white European adults was consistent with a previous study on children from largely non-white ethnic groups, suggesting that IL4 and MS4A2 genotypes modify the association between VDD and allergy risk. The risk allele in IL4 is present in nearly 90% of white Europeans, while less than a quarter are carriers in some other populations, highlighting the need to consider possible ethnic differences in allergy-related responsiveness to VDD.

The role of vitamin D in asthma

Vitamin D metabolites are important immune-modulatory hormones and are able to suppress Th2-mediated allergic airway disease. Some genetic factors that may contribute to asthma are regulated by vitamin D, such as vitamin D receptor (VDR), human leukocyte antigen genes (HLA), human Toll-like receptors (TLR), matrix metalloproteinases (MMPs), a disintegrin and metalloprotein-33 (ADAM-33), and poly(ADP-ribosyl) polymerase- 1 (PARP-1). Vitamin D has also been implicated in asthma through its effects on the obesity, bacillus Calmettee Guérin (BCG) vaccination and high vitamin D level, vitamin D supplement, checkpoint protein kinase 1 (Chk1), plasminogen activator inhibitor-1 (PAI-1) and gamma delta T cells (gdT). Vitamin D plays a role in asthma and exerts its action through either genomic and/or non-genomic ways.

Calcitriol decreases expression of importin α3 and attenuates RelA translocation in human bronchial smooth muscle cells

PURPOSE

A potent immunomodulatory role of Vitamin D in both innate and adaptive immunity has recently been appreciated. In allergic asthma, activation of NF-кB induces transcription of various cytokines and chemokines involved in allergic airway inflammation. The nuclear import of activated NF-кB p50/RelA subunit is dependent on importin α3 (KPNA4) and importin α4 (KPNA3). In this study, we examined the role of importin α3 in immunomodulatory effect of calcitriol in human bronchial smooth muscle cells (HBSMCs).

METHODS

Cultured HBSMCs were stimulated with calcitriol in the presence and absence of cytokines, TNF-α, IL-1β, and IL-10. The mRNA transcripts of importin α3 and α4 were analyzed using qPCR while protein expression of importin α3, α4 and nuclear RelA was analyzed by immunoblotting.

RESULTS

Calcitriol significantly decreased mRNA and protein expression of importin α3 as well as nuclear protein expression of NF-кB p65 (RelA). The decreased activation of RelA by calcitriol was confirmed by decreased release of RelA-inducible molecules, including IL-5, IL-6 and IL-8, by HBSMCs upon calcitriol treatment. Calcitriol attenuated the effect of TNF-α and IL-1β to upregulate mRNA and protein expression of importin α3. IL-10 significantly decreased the TNF-α induced expression of importin α3 and this effect was further potentiated by calcitriol.

CONCLUSIONS

These data suggest that under inflammatory conditions, calcitriol decreases the expression of importin α3 resulting in decreased nuclear import of activated RelA. This could be a novel mechanism by which calcitriol could exert its immunomodulatory effects to reduce allergic airway inflammation and thus may alleviate the symptoms in allergic asthma.

Vitamin D deficiency decreases the expression of VDR and prohibitin in the lungs of mice with allergic airway inflammation

AIMS

Asthma is one of the most common chronic inflammatory diseases of the airways. Calcitriol exerts its action through Vitamin D receptor (VDR), which is a high affinity nuclear receptor. VDR is a transcription factor that alters the transcription of target genes which are involved in a wide spectrum of biological responses. Lower serum vitamin D levels are associated with airway hyperresponsiveness and increased asthma severity. Prohibitin is a ubiquitously expressed protein localized to the cell and mitochondrial membranes and the nucleus.

METHODS AND RESULTS

HBSMCs were cultured and treated with calcitriol and/or TNF-α. The mRNA and protein expression of prohibitin and VDR were analyzed using qPCR and immunoblotting, respectively. In the in vivo studies, female BALB/c mice were fed with special vitamin D-deficient or 2000IU/kg of vitamin D-supplemented diet for 13weeks. Mouse model of allergic airway inflammation was developed by OVA-sensitization and challenge. The expression pattern of TNF-α, prohibitin and VDR in the lung of OVA-sensitized mice was analyzed using immunofluorescence. Calcitriol significantly increased and TNF-α decreased the protein and mRNA expression of prohibitin and VDR in HBSMCs. There was significantly increased expression of TNF-α and decreased expression of VDR and prohibitin in the lung of vitamin D-deficient mouse model of allergic airway inflammation.

CONCLUSION

These results suggest that under inflammatory conditions there is decreased expression of VDR resulting in decreased expression of prohibitin, which is a vitamin D target gene. Vitamin D deficiency causes increase in the expression of TNF-α, thereby increasing inflammation and decreases the expression of VDR and prohibitin. Supplementation with vitamin D might reduce the levels of TNF-α, thereby increasing the expression of VDR and prohibitin that could be responsible for reducing allergic airway inflammation.

Relevance and implication of genetic determinants to asthma pathophysiology

PURPOSE OF REVIEW

The number of single nucleotide polymorphisms (SNPs) found to be associated with asthma and related phenotypes outnumbers those with functional impacts. In this review we briefly described some of the approaches used to investigate functionality of SNPs, and summarized recent findings related to the characterization of functional SNPs in asthma.

RECENT FINDINGS

For disease-associated SNPs residing in the promoter or 3' untranslated regions, differential protein binding affinity between the major and minor alleles is often the first logical area of investigation. In this review, we described SNPs associated with asthma or related phenotypes in five genes which in the past 12 months have new data implicating potential mechanisms in asthma development.

SUMMARY

Variability in treatment responses poses a great challenge in asthma management. It is established that the genetic makeup of individuals plays a role in asthma development, yet the mechanisms remain unclear. Investigations on the functional impacts of disease-associated SNPs will help us gain insights into potential disease mechanisms, and ultimately lead to effective therapies for those who suffer from asthma.

Asthma, allergy and respiratory infections: the vitamin D hypothesis

The recent discovery that every tissue in the human body has vitamin D receptors and that vitamin D has pleiotropic effects has prompted an increased interest in this hormone. Vitamin D deficiency is widespread and on the increase. There is no consensus on the serum vitamin D levels to consider appropriate for global health, the cutoffs for its deficiency, or the doses to use for its supplementation. Vitamin D seems to correlate closely with host reactions against various respiratory infections. Epidemiological studies have shown that low serum 25-hydroxyvitamin D levels are associated with a higher risk of upper and lower respiratory infections in children and a shortage of vitamin D may contribute to asthmatic patients' symptoms and morbidity rates. There are studies highlighting associations between childhood asthma, fetal lung and/or immune development, and maternal vitamin D intake. An insufficiency of this vitamin also seems to be implicated in the onset of childhood atopy and food allergies. The hypothesis is that vitamin D could have a central role in these pathological situations and that it may represent a novel preventive and/or therapeutic strategy. This article reviews and discusses published data on the relationship between vitamin D and asthma and allergy, emphasizing the need for controlled, prospective studies on vitamin D supplementation to clarify whether it has a role in the prevention of and treatment for asthma and allergic conditions.

Vitamin D and allergic disease: sunlight at the end of the tunnel?

A role for vitamin D in the regulation of immune function was first proposed after the identification of Vitamin D receptors in lymphocytes. It has since been recognized that the active form of vitamin D, 1α,25(OH)₂D₃, has direct affects on naïve and activated helper T cells, regulatory T cells, activated B cells and dendritic cells. There is a growing body of literature linking vitamin D (serum 25(OH)D, oral intake and surrogate indicators such as latitude) to various immune-related conditions, including allergy, although the nature of this relationship is still unclear. This review explores the findings of epidemiological, clinical and laboratory research, and the potential role of vitamin D in promoting the inappropriate immune responses which underpin the rise in a broad range of immune diseases.

Gene-vitamin D interactions on food sensitization: a prospective birth cohort study

BACKGROUND

It has been hypothesized that vitamin D deficiency (VDD) contributes to the development of food sensitization (FS) and then food allergy. However, the epidemiological evidence is conflicting. We aim to examine whether cord blood VDD is associated with FS and whether such association can be modified by genetic variants in a prospective birth cohort.

METHODS

This study included 649 children who were enrolled at birth and followed from birth onward at the Boston Medical Center. We defined VDD as cord blood 25(OH)D < 11 ng/ml, and FS as specific IgE ≥ 0.35 kUA/l to any of eight common food allergens in early childhood. We genotyped potentially functional single-nucleotide polymorphisms (SNPs) in 11 genes known to be involved in regulating IgE and 25(OH)D concentrations. Logistic regressions were used to test the effects of VDD on FS individually and jointly with SNPs.

RESULTS

Among the 649 children, 44% had VDD and 37% had FS. When examined alone, VDD was not associated with FS. When examined jointly with SNPs, a significant interaction between IL4 gene polymorphism (rs2243250) and VDD (p(interaction) = 0.003, p(FDR) = 0.10) was found: VDD increased the risk of FS among children carrying CC/CT genotypes (OR = 1.79, 95%CI: 1.15-2.77). Similar but weaker interactions were observed for SNPs in MS4A2 (rs512555), FCER1G (rs2070901), and CYP24A1 (rs2762934). When all four SNPs were simultaneously considered, a strong gene-VDD interaction was evident (p(interaction) = 9 × 10(-6) ).

CONCLUSIONS

Our data demonstrate that VDD may increase the risk of FS among individuals with certain genotypes, providing evidence of gene-vitamin D interaction on FS.

Genome-wide association study reveals class I MHC-restricted T cell-associated molecule gene (CRTAM) variants interact with vitamin D levels to affect asthma exacerbations

BACKGROUND

It has recently been shown that vitamin D deficiency can increase asthma development and severity and that variations in vitamin D receptor genes are associated with asthma susceptibility.

OBJECTIVE

We sought to find genetic factors that might interact with vitamin D levels to affect the risk of asthma exacerbation.

METHODS

We conducted a genome-wide study of gene-vitamin D interaction on asthma exacerbations using population-based and family-based approaches on 403 subjects and trios from the Childhood Asthma Management Program. Twenty-three polymorphisms with significant interactions were studied in a replication analysis in 584 children from a Costa Rican cohort.

RESULTS

We identified 3 common variants in the class I MHC-restricted T cell-associated molecule gene (CRTAM) that were associated with an increased rate of asthma exacerbations based on the presence of a low circulating vitamin D level. These results were replicated in a second independent population (unadjusted combined interaction, P = .00028-.00097; combined odds ratio, 3.28-5.38). One variant, rs2272094, is a nonsynonymous coding polymorphism of CRTAM. Functional studies on cell lines confirmed the interaction of vitamin D and rs2272094 on CRTAM expression. CRTAM is highly expressed in activated human CD8(+) and natural killer T cells, both of which have been implicated in asthmatic patients.

CONCLUSION

The findings highlight an important gene-environment interaction that elucidates the role of vitamin D and CD8(+) and natural killer T cells in asthma exacerbation in a genome-wide gene-environment interaction study that has been replicated in an independent population. The results suggest the potential importance of maintaining adequate vitamin D levels in subsets of high-risk asthmatic patients.

Vitamin D binding protein variants associate with asthma susceptibility in the Chinese Han population

Background

Asthma is a genetically heterogeneous disease. Polymorphisms of genes encoding components of the vitamin D pathway have been reported to associate with the risk of asthma. We have previously demonstrated that vitamin D status was associated with lung function in Chinese asthma patients. In this study, we tested whether polymorphisms of genes encoding for vitamin D receptor (VDR), vitamin D 25-hydroxylase (CYP2R1) and vitamin D binding protein (GC) were associated with asthma in the Chinese Han population.

Methods

We sequenced all 8 exons of VDR and all 5 exons of CYP2R1 in a Chinese case-control cohort of asthma consisting of 467 cases and 288 unrelated healthy controls. Two mutations were identified in these regions. These variants were specified as rs2228570 in exon 2 of VDR and rs12794714 in exon 1 of CYP2R1. We also genotyped two common polymorphisms in GC gene (rs4588 and rs7041) by a PCR-restriction fragment length polymorphism (RFLP) method. We analyzed the association between these 4 polymorphisms and asthma susceptibility and asthma-related traits.

Results

Polymorphic markers in VDR and CYP2R1 were not associated with asthma in the Chinese Han cohort. Importantly, variants in GC gene, which give rise to the two most common electrophoretic isoforms of the vitamin D binding protein, were associated with asthma susceptibility. Compared with isoform Gc1, Gc2 was significantly associated with the risk of asthma (OR = 1.35, 95% CI = 1.01-1.78 p = 0.006).

Conclusions

The results provide supporting evidence for association between GC variants and asthma susceptibility in the Chinese Han population.

Involvement of IL-10 gene promoter polymorphisms in the susceptibility for childhood asthma

Asthma and atopy have a complex background that may result from the interaction of genes and the environment. Interleukin (IL)-10 is known to play various roles in immune-regulating and anti-inflammatory responses. The aim of this study was to evaluate the possible effect of the IL-10 promoter polymorphisms on susceptibility to childhood asthma. We recruited 333 patients with atopic asthma, 55 with nonatopic asthma, and 248 normal controls. We performed a genetic association study of three genetic polymorphisms (IL-10 -1082A>G, IL-10 -819T>C, and IL-10 -592A>C) of the IL-10 promoter. There was no difference between atopic asthma, nonatopic asthma, and normal controls with respect to allele, genotype, or haplotype frequencies of these IL-10 polymorphisms. However, the -1082A>G polymorphism and ATA haplotype in the IL-10 promoter gene were associated with airway hyper responsiveness (AHR) and the -819T>C, -592A>C, and ATA and ACC haplotypes were also shown to be related to serum eosinophil cationic protein (ECP). Our results suggest that the polymorphisms within the IL-10 promoter may have a disease-modifying effect in the asthmatic airway.

Genetics of interleukin 1 receptor-like 1 in immune and inflammatory diseases

Interleukin 1 receptor-like 1 (IL1RL1) is gaining in recognition due to its involvement in immune/inflammatory disorders. Well-designed animal studies have shown its critical role in experimental allergic inflammation and human in vitro studies have consistently demonstrated its up-regulation in several conditions such as asthma and rheumatoid arthritis. The ligand for IL1RL1 is IL33 which emerged as playing an important role in initiating eosinophilic inflammation and activating other immune cells resulting in an allergic phenotype.An IL1RL1 single nucleotide polymorphism (SNP) was among the most significant results of a genome-wide scan investigating eosinophil counts; in the same study, this SNP associated with asthma in 10 populations.The IL1RL1 gene resides in a region of high linkage disequilibrium containing interleukin 1 receptor genes as well as interleukin 18 receptor and accessory genes. This poses a challenge to researchers interested in deciphering genetic association signals in the region as all of the genes represent interesting candidates for asthma and allergic disease.The IL1RL1 gene and its resulting soluble and receptor proteins have emerged as key regulators of the inflammatory process implicated in a large variety of human pathologies We review the function and expression of the IL1RL1 gene. We also describe the role of IL1RL1 in asthma, allergy, cardiovascular disease, infections, liver disease and kidney disease.

Expression analysis of asthma candidate genes during human and murine lung development

BACKGROUND

Little is known about the role of most asthma susceptibility genes during human lung development. Genetic determinants for normal lung development are not only important early in life, but also for later lung function.

OBJECTIVE

To investigate the role of expression patterns of well-defined asthma susceptibility genes during human and murine lung development. We hypothesized that genes influencing normal airways development would be over-represented by genes associated with asthma.

METHODS

Asthma genes were first identified via comprehensive search of the current literature. Next, we analyzed their expression patterns in the developing human lung during the pseudoglandular (gestational age, 7-16 weeks) and canalicular (17-26 weeks) stages of development, and in the complete developing lung time series of 3 mouse strains: A/J, SW, C57BL6.

RESULTS

In total, 96 genes with association to asthma in at least two human populations were identified in the literature. Overall, there was no significant over-representation of the asthma genes among genes differentially expressed during lung development, although trends were seen in the human (Odds ratio, OR 1.22, confidence interval, CI 0.90-1.62) and C57BL6 mouse (OR 1.41, CI 0.92-2.11) data. However, differential expression of some asthma genes was consistent in both developing human and murine lung, e.g. NOD1, EDN1, CCL5, RORA and HLA-G. Among the asthma genes identified in genome wide association studies, ROBO1, RORA, HLA-DQB1, IL2RB and PDE10A were differentially expressed during human lung development.

CONCLUSIONS

Our data provide insight about the role of asthma susceptibility genes during lung development and suggest common mechanisms underlying lung morphogenesis and pathogenesis of respiratory diseases.

Vitamin D and asthma

PURPOSE OF REVIEW

asthma is a disease that continues to carry a significant health burden on humanity. Vitamin D is thought to play a role in many chronic diseases as it may possess immunomodulatory properties. This article will review the role of vitamin D regulation on the immune system and its potential implication in the pathophysiology of asthma.

RECENT FINDINGS

vitamin D receptors are present on many cells in the body, specifically peripheral blood mononuclear cells. Vitamin D has been shown to regulate the balance of several pro-inflammatory and anti-inflammatory responses in the immune system. Studies have suggested that prenatal vitamin D intake has an effect on childhood wheezing and asthma. Additionally, vitamin D may play a role in asthma exacerbations, and recent evidence also suggests its importance in steroid resistant asthma.

SUMMARY

vitamin D has a complex role on the immune system and its regulation of various aspects of immunity has allowed speculation on its potential role in asthma. However, the net effect of vitamin D on the immune system and its role in asthma still remains unanswered. More research needs to address the diagnostic and therapeutic implications vitamin D may have in the future of asthma management.

Differential serum cytokine levels are associated with cytokine gene polymorphisms in north Indians with active pulmonary tuberculosis

Globally only 5-10% of people encountering Mycobacterium tuberculosis have a lifetime risk of active disease indicating a strong host genetic bias towards development of tuberculosis. In the current study we investigated genotype variants pertaining to five cytokine genes namely IFNG, TNFA, IL4, IL10 and IL12 in the north Indian population with active pulmonary tuberculosis (APTB) and correlated the serum cytokine levels with the corresponding genotypes. Twenty five single nucleotide polymorphisms (SNPs) including six loci examined for the first time in tuberculosis were selected for genotyping in 108 patients with APTB from north India and 48 healthy regional controls (HC). Applying exclusion criteria 12 SNPs passed all the filters and were analysed further. The serum cytokine concentrations were measured by ELISA. Compared to HC mean serum IFN-γ, IL-12, IL-4, and IL-10 levels were higher in APTB (p = 0.3661, p = 0.0186, p = 0.003, p = 0.7, respectively). In contrast the mean serum TNF-α level was higher in HC (p = 0.007). Comparison of genotypes and serum levels of the corresponding cytokine genes reveal that though IFN-γ and IL-4 levels were higher in APTB the genotype variants showed no difference between HC and APTB. In contrast the genotypes of the selected rsIDs in the TNFA, IL12 and IL10 genes showed significant association with the varying serum levels of corresponding cytokines. The variant of the TNFA gene at rs3093662, the IL12 gene at rs3213094 and rs3212220 and the IL10 gene at rs3024498 did show a strong indication to be of relevance to the immunity to tuberculosis. To our knowledge this is the first report from this region relating genotypes and serum cytokine levels in north Indian population.

Asthma and endocrine disorders: shared mechanisms and genetic pleiotropy

Asthma is a common inflammatory disease for which the cause is not yet known. Studies of the epidemiology and natural history of childhood asthma into adulthood demonstrate a change in gender prevalence with age. Hormones and inflammation may interact in asthma pathogenesis and determine its course. The same may be true for some endocrine disorders, including diabetes and obesity. Obesity plays a major role in the development of the metabolic syndrome and has been identified as an important risk factor for chronic diseases such as type 2 diabetes mellitus. The prevalence of asthma has paralleled the rise in obesity, suggesting that shared environmental factors could affect both conditions. In addition, endocrine diseases and asthma may share common genetic determinants. In the first part of this review we assess endocrine influences on asthma and overlaps between endocrine disorders and asthma while in the second part we explore the potential benefit of comparative genetic analyses between asthma and endocrine diseases.

Total serum IgE levels in systemic lupus erythematosus and associations with childhood onset allergies

Elevated serum IgE has been described in systemic lupus erythematosus (SLE), but associations with disease risk and characteristics remain unresolved. We assessed total serum IgE levels and atopy (IgE > 100 IU/ml) in recently diagnosed SLE patients (n = 228) compared with population controls (n = 293) and in relation to disease activity, autoantibodies, clinical features, total immunoglobulins, C-reactive protein, and allergy history. Multivariate models estimated determinants of IgE and atopy in patients and controls, and associations of SLE with allergy and atopy. Total IgE levels were higher in patients than controls (median = 42 vs. 29 IU/ml); 32% of patients and 25% of controls were atopic (p = 0.06). IgE levels were significantly higher in non-Whites and patients reporting childhood onset (<18 years) asthma and hives, and in controls reporting childhood asthma, hay fever, eczema, and adult onset hives. After accounting for racial differences, atopy was not associated with SLE, nephritis, or other clinical and laboratory parameters. In sum, our findings provide limited evidence of a direct association between total serum IgE and SLE overall or with other disease characteristics after adjusting for demographic characteristics and allergy history. Future studies may want to explore potentially shared risk factors for development of allergy, atopy, and SLE.