Association of vitamin D receptor genetic variants with susceptibility to asthma and atopy

Confirmation of an association between single nucleotide polymorphisms in the VDR gene with respiratory syncytial virus related disease in South African children

Respiratory syncytial virus is a leading cause of lower respiratory tract infection in infants. Disease severity has been linked to host immune responses and polymorphisms in genes associated with innate immunity. A large-scale genetics study of single nucleotide polymorphisms (SNPs) in children in the Netherlands identified SNPs in the vitamin D receptor (VDR) and JUN genes which have a strong association with an increased risk of developing bronchiolitis following the first respiratory syncytial virus (RSV) infection. The Toll-like receptor 4 (TLR4) gene has two SNPs which have been associated previously with RSV disease severity in various populations. The aim of this study was to determine if these SNPs may be associated with RSV disease in African children in South Africa. RSV patient (n = 296) and control (n = 113) groups were established (median ages: 3 and 3.5 months) and DNA extracted from the collected specimens. Real-time polymerase chain reaction using hydrolysis probes was used to screen for SNPs in the VDR (Thr1Meth; rs10735810), TLR4 (Asp299Gly; rs4986790 and Thr399Ile; rs4986791) and JUN (c.750G/A; rs11688) genes. Carriers of the VDR (Thr1Meth) SNP minor T allele were more prone to RSV disease than individuals in the control group. The TLR4 (Asp299Gly), TLR4 (Thr399Ile), and JUN (c.750G/A) SNPs showed no significant association with RSV disease. It is concluded that children carrying the minor T allele of the VDR (Thr1Meth) SNP may be predisposed to RSV disease, as this SNP was identified as a risk factor for severe RSV disease in South African children, confirming the findings in the Netherlands.

Fat-soluble vitamins and atopic disease: what is the evidence?

The prevalence of asthma and other atopic disorders continues to increase worldwide. Examination of the epidemiologic patterns has revealed that this rise has occurred primarily in western, industrialised countries and countries transitioning to this lifestyle. While many changes have occurred in human populations over the years, it has been hypothesised that some of the relevant changes that have led to the rise in asthma and atopic disorders have been the changes from a traditional diet to a more western diet consisting of decreased intake of fruits and vegetables (sources of antioxidant vitamins and carotenoids) leading to decreased intakes of vitamins E and A, and a decrease in sun exposure (e.g. greater time spent indoors and heavy use of sunscreen) leading to decreased circulating levels of vitamin D. This review will examine the evidence for an effect of fat-soluble vitamins (vitamins A, D and K) on the development and severity of asthma and allergies. While observational studies suggest that these vitamins may play a salutary role in asthma and allergies, large, well-designed clinical trials are lacking. Of the fat-soluble vitamins, vitamin D holds great promise as an agent for primary and secondary prevention of disease. Ongoing clinical trials will help determine whether results of observational studies can be applied to the clinical setting.

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.

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 and asthma

Vitamin D deficiency and asthma are common conditions that share risk factors such as African American ethnicity, inner-city residence, and obesity. This review provides a critical examination of current experimental and epidemiologic evidence of a causal association between vitamin D status and asthma or asthma morbidity, including potential protective mechanisms such as antiviral effects and enhanced steroid responsiveness. Because most published epidemiologic studies of vitamin D and asthma or asthma morbidity are observational, a recommendation for or against vitamin D supplementation as preventive or secondary treatment for asthma is not advisable and must await results of ongoing clinical trials. Should these trials confirm a beneficial effect of vitamin D, others will be needed to assess the role of vitamin D supplementation to prevent or treat asthma in different groups such as infants, children of school age, and ethnic minorities.

Vitamin D receptor gene polymorphism in children with urinary tract infection

It is known that small alterations leading to different vitamin D receptor (VDR) alleles affect resistance or susceptibility to infections. In this study, we examined VDR gene polymorphisms in urinary tract infections (UTI), which are common and an important cause of morbidity in children and subsequently of renal scar formation. We evaluated 92 patients diagnosed with UTI and 105 children without prior history of UTI as a control group. The VDR gene polymorphisms BsmI, FokI, ApaI, and TaqI were evaluated in patients and controls. BsmI polymorphism genotype distribution was similar between groups. There was a significant difference between groups for FokI (p =0 < 001); for the ff genotype, the risk of UTI was significantly increased (p < 0.01) ,at 3.94 times higher (odds ratio = 3.94; 95% confidence interval 1.71-9.09). ApaI polymorphism was significantly increased in the control group (p < 0.01) and evaluated as a protective factor. Comparing the TaqI genotype between groups, there was no statistically significant difference, but in both Tt and tt genotypes, there was minimal increased risk of UTI. The results of this study suggest that VDR gene polymorphisms can be important for susceptibility to UTI and renal scar formation. Association between VDR polymorphisms and UTI is in accordance with the understanding of how vitamin D modulates the immune response against infections.

Evidence for a causal relationship between respiratory syncytial virus infection and asthma

Respiratory syncytial virus (RSV) infects all children early in life, is the most common cause of infant lower respiratory tract infections, and causes disease exacerbations in children with asthma. Episodes of lower respiratory tract infection in early life are associated with asthma development. Whether RSV infection early in life directly causes asthma or simply identifies infants who are genetically predisposed to develop subsequent wheezing is debatable. Recent studies suggest that these two explanations are not mutually exclusive, and are likely both important in asthma development. An open-label study of RSV immunoprophylaxis administered to preterm infants reduced recurrent wheezing by 50%. Clinical trials of infant RSV prevention, delay or severity reduction on the outcome of childhood asthma would confirm the causal relationship between RSV infection and asthma, and offer a primary prevention strategy.

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.

Vitamin D in autoimmune, infectious and allergic diseases: a vital player?

Vitamin D is a steroid hormone that is acquired via diet or synthesized in the skin upon UV exposure and needs subsequent hydroxylation steps to become activated as 1,25-dihydroxyvitamin D. While widely known for its role in maintaining bone health, vitamin D receptors have also been identified in different immune cell types. Many immune cells can also convert vitamin D into its bioactive form, thus enhancing the locally available concentrations to those required for the immunomodulatory effects of vitamin D. In this review, we summarize the genetic and epidemiologic data potentially linking vitamin D to autoimmune, infectious and allergic diseases. We also discuss how vitamin D influences the immune responses in each of those conditions based on the data generated using patient samples or preclinical models of each of these diseases.

The relationship between serum 25 hydroxy vitamin d levels and asthma in children

Purpose

Asthma and other allergic disorders have increased over the past decades in nearly all nations. Many studies have suggested the role of vitamin D deficiency in both T-helper1 and T-helper2 diseases; however, the association between vitamin D, allergy, and asthma remains uncertain. In this study, the associations of 25-hydroxy vitamin D3 levels with asthma and with the severity of asthma were evaluated.

Methods

This cross-sectional study was conducted on 50 asthmatic children and 50 healthy controls aged 6-18 years. Serum 25-hydroxy vitamin D3 levels were determined and compared between the two groups. The relationship between serum vitamin D levels and pulmonary function test outcomes and eosinophil counts were examined in asthmatic patients.

Results

Univariate analysis of the relationship between asthma and vitamin D showed that decreased vitamin D levels were associated with significantly increased odds of asthmatic state (P=0.002). In a multivariate analysis after adjustment for age, body mass index, and sex, the relationship between vitamin D and asthma increased. In asthmatic patients, 25-hydroxy vitamin D levels had direct and significant correlations with both predicted FEV1 (R²=0.318; P=0.024) and FEV1/FVC (R²=0.315; P=0.026). There were no associations between vitamin D level and eosinophil counts, duration of disease, and the number of hospitalization or unscheduled visits in the previous year (P>0.05).

Conclusions

These results showed that serum 25-hydroxy vitamin D levels were inversely associated with asthma, and there was a direct and significant relationship between vitamin D levels and pulmonary function test outcomes in asthmatic children. An interventional study in asthmatic patients with low serum vitamin D concentration may establish a causal relationship between asthma and vitamin D.

The role of latitude, ultraviolet radiation exposure and vitamin D in childhood asthma and hayfever: an Australian multicenter study

Observations of increasing allergy prevalence with decreasing distance from the Equator and positive associations with ambient ultraviolet radiation have contributed to a growing interest in the possible role of vitamin D in the etiology of allergy. The aims of this study were to describe any latitudinal variation in the prevalence of childhood allergy in Australia and to evaluate, in parallel, the individual associations between ultraviolet radiation (UVR)- and vitamin D-related measures and hayfever asthma and both conditions. Participants were population-based controls who took part in a multicenter case-control study, aged 18-61 yr and resident in one of four study regions ranging in latitude from 27°S to 43°S. Data were derived from a self-administered questionnaire, interview and examination by a research officer and biologic sampling. Latitude and longitude coordinates were geocoded from participants' residential locations and climatic data were linked to postcodes of current residence. Stored serum was analyzed for 25-hydroxyvitamin D concentrations and silicone rubber casts of the skin were used as an objective measure of cumulative actinic damage. There was an inverse latitude gradient for asthma (a 9% decrease per increasing degree of latitude); however, this pattern did not persist after adjusting for average daily temperature. There was no association between any of the UVR- or vitamin D-related measures and childhood asthma, but greater time in the sun in winter between the ages 6-15 yr was associated with an increase in the odds of having hayfever [adjusted odds ratios (OR) 1.29; 95% CI 1.01-1.63]. Oral supplementation with cod liver oil in childhood increased the odds of a history of having both asthma and hayfever (2.87; 1.00-8.32). Further investigation of the possible role of early vitamin D supplementation in the development of allergy is warranted. Our results also suggest that solar exposure during childhood may be important in allergic sensitization. Plausible explanations, including biologic mechanisms, exist for both observations.

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.

The role of vitamin D in pulmonary disease: COPD, asthma, infection, and cancer

The role of vitamin D (VitD) in calcium and bone homeostasis is well described. In the last years, it has been recognized that in addition to this classical function, VitD modulates a variety of processes and regulatory systems including host defense, inflammation, immunity, and repair. VitD deficiency appears to be frequent in industrialized countries. Especially patients with lung diseases have often low VitD serum levels. Epidemiological data indicate that low levels of serum VitD is associated with impaired pulmonary function, increased incidence of inflammatory, infectious or neoplastic diseases. Several lung diseases, all inflammatory in nature, may be related to activities of VitD including asthma, COPD and cancer. The exact mechanisms underlying these data are unknown, however, VitD appears to impact on the function of inflammatory and structural cells, including dendritic cells, lymphocytes, monocytes, and epithelial cells. This review summarizes the knowledge on the classical and newly discovered functions of VitD, the molecular and cellular mechanism of action and the available data on the relationship between lung disease and VitD status.

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.

Genomic and genealogical investigation of the French Canadian founder population structure

Characterizing the genetic structure of worldwide populations is important for understanding human history and is essential to the design and analysis of genetic epidemiological studies. In this study, we examined genetic structure and distant relatedness and their effect on the extent of linkage disequilibrium (LD) and homozygosity in the founder population of Quebec (Canada). In the French Canadian founder population, such analysis can be performed using both genomic and genealogical data. We investigated genetic differences, extent of LD, and homozygosity in 140 individuals from seven sub-populations of Quebec characterized by different demographic histories reflecting complex founder events. Genetic findings from genome-wide single nucleotide polymorphism data were correlated with genealogical information on each of these sub-populations. Our genomic data showed significant population structure and relatedness present in the contemporary Quebec population, also reflected in LD and homozygosity levels. Our extended genealogical data corroborated these findings and indicated that this structure is consistent with the settlement patterns involving several founder events. This provides an independent and complementary validation of genomic-based studies of population structure. Combined genomic and genealogical data in the Quebec founder population provide insights into the effects of the interplay of two important sources of bias in genetic epidemiological studies, unrecognized genetic structure and cryptic relatedness.

Seasonal and regional variations of asthma and association with osteoporosis: possible role of vitamin D in asthma

BACKGROUND

Based on the evidence that vitamin D is involved in the development of immune system and vitamin D receptor gene is associated with asthma, we supposed that vitamin D is related to the development of asthma.

METHODS

Asthma patients were identified from the Swedish Hospital Discharge Register and the hospitalization rate was examined by different seasons and regions. Standardized incidence ratios (SIRs) for asthma were examined among patients hospitalized for osteoporosis compared with the general population.

RESULTS

A total of 172,384 patients were hospitalized for asthma in Sweden during 1965-2007. More patients were hospitalized in winter and North Sweden than in summer and South Sweden. The risk of asthma after osteoporosis was significantly increased, giving an overall SIR of 2.93. The risk was higher in male patients when compared with female subjects. Patients hospitalized for osteoporosis at age younger than 55 showed a high risk. Reversing the analyses and examining the risk of osteoporosis after hospitalization of asthma, SIR was significantly increased (3.54).

CONCLUSION

Our study suggests that vitamin D, as indicated by the high risk of asthma after osteoporosis and the seasonal and regional variations of hospitalization, could play an important role for the development of asthma.

Unifying candidate gene and GWAS Approaches in Asthma

The first genome wide association study (GWAS) for childhood asthma identified a novel major susceptibility locus on chromosome 17q21 harboring the ORMDL3 gene, but the role of previous asthma candidate genes was not specifically analyzed in this GWAS. We systematically identified 89 SNPs in 14 candidate genes previously associated with asthma in >3 independent study populations. We re-genotyped 39 SNPs in these genes not covered by GWAS performed in 703 asthmatics and 658 reference children. Genotyping data were compared to imputation data derived from Illumina HumanHap300 chip genotyping. Results were combined to analyze 566 SNPs covering all 14 candidate gene loci. Genotyped polymorphisms in ADAM33, GSTP1 and VDR showed effects with p-values <0.0035 (corrected for multiple testing). Combining genotyping and imputation, polymorphisms in DPP10, EDN1, IL12B, IL13, IL4, IL4R and TNF showed associations at a significance level between p = 0.05 and p = 0.0035. These data indicate that (a) GWAS coverage is insufficient for many asthma candidate genes, (b) imputation based on these data is reliable but incomplete, and (c) SNPs in three previously identified asthma candidate genes replicate in our GWAS population with significance after correction for multiple testing in 14 genes.

Vitamin D deficiency and chronic lung disease

Vitamin D deficiency is increasingly being recognized as a prevalent problem in the general population. Patients with chronic lung diseases such as asthma, cystic fibrosis, chronic obstructive lung disease and interstitial pneumonia appear to be at increased risk for vitamin D deficiency for reasons that are not clear. Several studies indicate that vitamin D possesses a range of anti-inflammatory properties and may be involved in processes other than the previously believed functions of calcium and phosphate homeostasis. Various cytokines, cellular elements, oxidative stress and protease/antiprotease levels appear to affect lung fibroproliferation, remodelling and function, which may be influenced by vitamin D levels. Chronic lung diseases such as asthma and chronic obstructive lung disease have also been linked to vitamin D on a genetic basis. This immune and genetic influence of vitamin D may influence the pathogenesis of chronic lung diseases. A recent observational study notes a significant association between vitamin D deficiency and decreased pulmonary function tests in a large ambulatory population. The present review will examine the current literature regarding vitamin D deficiency, its prevalence in patients with chronic lung disease, vitamin D anti-inflammatory properties and the role of vitamin D in pulmonary function.

Role of infection in the development and exacerbation of asthma

Respiratory infections are associated with wheezing illnesses in all ages and may also impact the development and severity of asthma. Respiratory tract infections caused by viruses, Chlamydophila or Mycoplasma have been hypothesized to have significant roles in the pathogenesis of asthma. Progress is being made toward establishing the mechanisms by which these agents can cause acute wheezing and impact the pathophysiology of asthma. Host factors probably contribute to the risk of asthma inception and exacerbation, and these contributions may also vary with respect to early- versus adult-onset disease. This review discusses these various associations as they pertain to the development and exacerbation of asthma.

Regulatory T cells, inflammation and the allergic response-The role of glucocorticoids and Vitamin D

Regulatory T cells (TRegs) play a central role in the maintenance of peripheral tolerance. They prevent inappropriate immune responses to ubiquitous allergens in healthy individuals, and contribute to the maintenance of immune homeostasis in the airways. Both Foxp3+ and IL-10+ TReg have been implicated in these functions. Glucocorticoids represent the mainstay of treatment for asthma and other allergic conditions, and evidence that steroids influence TReg function will be reviewed. Growing bodies of epidemiological and immunological data suggest a role for endogenous Vitamin D in immune regulation. This review will discuss the role of glucocorticoids and Vitamin D, and their potential interactions in promoting tolerance in the context of allergic disease and asthma.

Season of birth and food allergy in children

BACKGROUND

The prevalence of food allergy is rising, and etiologic factors remain uncertain. Evidence implicates a role for vitamin D in the development of atopic diseases. Based on seasonal patterns of UV-B exposure (and consequent vitamin D status), we hypothesized that patients with food allergy are more often born in fall or winter.

OBJECTIVE

To investigate whether season of birth is associated with food allergy.

METHODS

We performed a multicenter medical record review of all patients presenting to 3 Boston emergency departments (EDs) for food-related acute allergic reactions between January 1, 2001, and December 31, 2006. Months of birth in patients with food allergy were compared with that of patients visiting the ED for reasons other than food allergy.

RESULTS

We studied 1002 patients with food allergy. Of younger children with food allergy (age < 5 years), but not older children or adults, 41% were born in spring or summer compared with 59% in fall or winter (P = .002). This approximately 40:60 ratio differed from birth season in children treated in the ED for non-food allergy reasons (P = .002). Children younger than 5 years born in fall or winter had a 53% higher odds of food allergy compared with controls. This finding was independent of the suspected triggering food and allergic comorbidities.

CONCLUSIONS

Food allergy is more common in Boston children born in the fall and winter seasons. We propose that these findings are mediated by seasonal differences in UV-B exposure. These results add support to the hypothesis that seasonal fluctuations in sunlight and perhaps vitamin D may be involved in the pathogenesis of food allergy.

Implications of vitamin D deficiency in pregnancy and lactation

Vitamin D is an essential fat soluble vitamin and a key modulator of calcium metabolism in children and adults. Because calcium demands increase in the third trimester of pregnancy, vitamin D status becomes crucial for maternal health, fetal skeletal growth, and optimal maternal and fetal outcomes. Vitamin D deficiency is common in pregnant women (5-50%) and in breastfed infants (10-56%), despite the widespread use of prenatal vitamins, because these are inadequate to maintain normal vitamin D levels (>or=32 ng/mL). Adverse health outcomes such as preeclampsia, low birthweight, neonatal hypocalcemia, poor postnatal growth, bone fragility, and increased incidence of autoimmune diseases have been linked to low vitamin D levels during pregnancy and infancy. Studies are underway to establish the recommended daily doses of vitamin D in pregnant women. This review discusses vitamin D metabolism and the implications of vitamin D deficiency in pregnancy and lactation.

Role of nutrients in the development of neonatal immune response

Nutrients exert unique regulatory effects in the perinatal period that mold the developing immune system. The interactions of micronutrients and microbial and environmental antigens condition the post-birth maturation of the immune system, influencing reactions to allergens, fostering tolerance towards the emerging gastrointestinal flora and ingested antigens, and defining patterns of host defense against potential pathogens. The shared molecular structures that are present on microbes or certain plants, but not expressed by human cells, are recognized by neonatal innate immune receptors. Exposure to these activators in the environment through dietary intake in early life can modify the immune response to allergens and prime the adaptive immune response towards pathogens that express the corresponding molecular structures.

The role of vitamin D in asthma

OBJECTIVE

To review the current literature on vitamin D and asthma, discussing the possible roles of vitamin D on asthma pathogenesis and the potential consequences of vitamin D deficiency.

DATA SOURCES

PubMed database was searched from 1950 to 2009. Keywords used included asthma, vitamin D, inflammation, airway smooth muscle and cytokines.

STUDY SELECTION

Articles were selected based on relevance to the subject.

RESULTS

Vitamin D deficiency has been associated with epidemiologic patterns observed in the asthma epidemic. Vitamin D deficiency is more common with obesity, African American ethnicity, and westernization of countries with higher-risk populations for asthma. Evidence suggests that vitamin D deficiency is associated with increased airway hyperresponsiveness, lower pulmonary functions, worse asthma control, and possibly steroid resistance. Lung epithelial cells express high baseline levels of 1alpha-hydroxylase. This allows the conversion of inactive calcidiol to active calcitriol locally within the lung. Calcitriol has been shown to inhibit the synthesis and release of certain cytokines, such as RANTES, platelet-derived growth factor, and matrix metalloproteinases, from bronchial smooth muscle cells, thereby leading to decreased lung inflammation and smooth muscle cell proliferation. Vitamin D also increases synthesis of interleukin 10 by CD4+CD25+Foxp3+ T-regulatory cells and dendritic cells, while concurrently inhibiting dendritic cell activation by downregulating expression of costimulatory molecules CD40 and CD80/86. Vitamin D is also capable of inducing the expression of several anti-infective molecules, such as cathelicidin. Thus, vitamin D has a number of biologic effects that are likely important in regulating key mechanisms in asthma.

CONCLUSIONS

We hypothesize that vitamin D supplementation may lead to improved asthma control by inhibiting the influx of inflammatory cytokines in the lung and increasing the secretion of interleukin 10 by T-regulatory cells and dendritic cells.

Asthma and genes encoding components of the vitamin D pathway

BACKGROUND

Genetic variants at the vitamin D receptor (VDR) locus are associated with asthma and atopy. We hypothesized that polymorphisms in other genes of the vitamin D pathway are associated with asthma or atopy.

METHODS

Eleven candidate genes were chosen for this study, five of which code for proteins in the vitamin D metabolism pathway (CYP27A1, CYP27B1, CYP2R1, CYP24A1, GC) and six that are known to be transcriptionally regulated by vitamin D (IL10, IL1RL1, CD28, CD86, IL8, SKIIP). For each gene, we selected a maximally informative set of common SNPs (tagSNPs) using the European-derived (CEU) HapMap dataset. A total of 87 SNPs were genotyped in a French-Canadian family sample ascertained through asthmatic probands (388 nuclear families, 1064 individuals) and evaluated using the Family Based Association Test (FBAT) program. We then sought to replicate the positive findings in four independent samples: two from Western Canada, one from Australia and one from the USA (CAMP).

RESULTS

A number of SNPs in the IL10, CYP24A1, CYP2R1, IL1RL1 and CD86 genes were modestly associated with asthma and atopy (p < 0.05). Two-gene models testing for both main effects and the interaction were then performed using conditional logistic regression. Two-gene models implicating functional variants in the IL10 and VDR genes as well as in the IL10 and IL1RL1 genes were associated with asthma (p < 0.0002). In the replicate samples, SNPs in the IL10 and CYP24A1 genes were again modestly associated with asthma and atopy (p < 0.05). However, the SNPs or the orientation of the risk alleles were different between populations. A two-gene model involving IL10 and VDR was replicated in CAMP, but not in the other populations.

CONCLUSION

A number of genes involved in the vitamin D pathway demonstrate modest levels of association with asthma and atopy. Multilocus models testing genes in the same pathway are potentially more effective to evaluate the risk of asthma, but the effects are not uniform across populations.

Putting the puzzle together: epidemiological and clinical clues in the etiology of eosinophilic esophagitis

The cause of eosinophilic esophagitis remains unknown, but its epidemiology and clinical features provide pieces to the puzzle. Eosinophilic esophagitis probably emerged in the 1950s or early 1960s, has an increasing incidence, occurs in most developed countries, is related to food allergies, affects adults and children, has a strong male predominance, clusters in families, and is commonly associated with other allergic and atopic disorders. Several theories have been proposed to explain its evolution, but none has been convincingly demonstrated.

Vitamin D, respiratory infections, and asthma

Over the past decade, interest has grown in the role of vitamin D in many nonskeletal medical conditions, including respiratory infection. Emerging evidence indicates that vitamin D-mediated innate immunity, particularly through enhanced expression of the human cathelicidin antimicrobial peptide (hCAP-18), is important in host defenses against respiratory tract pathogens. Observational studies suggest that vitamin D deficiency increases risk of respiratory infections. This increased risk may contribute to incident wheezing illness in children and adults and cause asthma exacerbations. Although unproven, the increased risk of specific respiratory infections in susceptible hosts may contribute to some cases of incident asthma. Vitamin D also modulates regulatory T-cell function and interleukin-10 production, which may increase the therapeutic response to glucocorticoids in steroid-resistant asthma. Future laboratory, epidemiologic, and randomized interventional studies are needed to better understand vitamin D's effects on respiratory infection and asthma.

Childhood asthma may be a consequence of vitamin D deficiency

PURPOSE OF REVIEW

Vitamin D deficiency has been rediscovered as a public-health problem worldwide. It has been postulated that vitamin D deficiency may explain a portion of the asthma epidemic. The purpose of this review is to present the evidence for a role of vitamin D in asthma.

RECENT FINDINGS

Both animal models and studies in human fetal tissues show that vitamin D plays a role in fetal lung growth and maturation. Epidemiologic studies have also suggested that higher prenatal vitamin D intakes have a protective role against wheezing illnesses in young children. Vitamin D may protect against wheezing illnesses through its role in upregulating antimicrobial proteins or through its multiple immune effects. In addition, vitamin D may play a therapeutic role in steroid resistant asthmatics, and lower vitamin D levels have recently been associated with higher risks for asthma exacerbations.

SUMMARY

Improving vitamin D status holds promise in primary prevention of asthma, in decreasing exacerbations of disease, and in treating steroid resistance. However, the appropriate level of circulating vitamin D for optimal immune functioning remains unclear. Because vitamin D deficiency is prevalent even in sun-replete areas, clinical trials are needed to definitively answer questions about the role of vitamin D in asthma.

Association study between vitamin D receptor gene polymorphisms and asthma in the Chinese Han population: a case-control study

BACKGROUND

Modulation of the immune system is one of the principal roles of Vitamin D, for which the effects are exerted via the vitamin D receptor (VDR). Importantly, variants in the VDR gene have been susceptible in the past to raise the risk of asthma in several populations. These effects of VDR allelic markers remain speculative in the Chinese Han population.

RESULTS

A case-control study of 1090 individuals including 567 asthmatic patients was realized on five SNPs within the VDR gene. Only rs7975232 (ApaI) marker showed a significant association with asthma (P = 0.009). Haplotype analysis of the five VDR polymorphisms showed a significant association with asthma (global-p value = 0.012).

CONCLUSION

Although the susceptibility of VDR gene variants with asthma could not be confirmed for all SNPs tested in this study, the significant association obtained for rs7975232 provides evidence for a previously unknown report about the Chinese Han population and may raise the susceptibility of VDR to be a candidate gene for asthma.

A thymic stromal lymphopoietin gene variant is associated with asthma and airway hyperresponsiveness

BACKGROUND

The epithelial cell-derived protein thymic stromal lymphopoietin stimulates dendritic and mast cells to promote proallergic T(H)2 responses. Studies of transgenic expression of thymic stromal lymphopoietin and its receptor knockout mice have emphasized its critical role in the development of allergic inflammation. Association of genetic variation in thymic stromal lymphopoietin with IgE levels has been reported for human subjects.

OBJECTIVE

The aim of this study was to evaluate the relationship between variants of thymic stromal lymphopoietin and asthma and related phenotypes.

METHODS

We selected 6 single nucleotide polymorphisms in thymic stromal lymphopoietin and genotyped 5565 individuals from 4 independent asthma studies and tested for association with asthma, atopy, atopic asthma, and airway hyperresponsiveness by using a general allelic likelihood ratio test. P values were corrected for the effective number of independent single nucleotide polymorphisms and phenotypes.

RESULTS

The A allele of rs1837253, which is 5.7 kb upstream of the transcription start site of the gene, was associated with protection from asthma, atopic asthma, and airway hyperresponsiveness, with the odds ratios and corrected P values for each being 0.79 and 0.0058; 0.75 and 0.0074; and 0.76 and 0.0094, respectively. Associations between thymic stromal lymphopoietin and asthma-related phenotypes were the most statistically significant observations in our study, which has to date examined 98 candidate genes. Full results are available online at http://genapha.icapture.ubc.ca/.

CONCLUSIONS

A genetic variant in the region of the thymic stromal lymphopoietin gene is associated with the phenotypes of asthma and airway hyperresponsiveness.

Serum 25-hydroxyvitamin D and IgE - a significant but nonlinear relationship

BACKGROUND

Hormonal vitamin D system affects the determination of T-cell responses. It is unknown if there is an association between vitamin D status and allergic conditions. Our aim was to investigate differences in serum IgE concentrations by vitamin D status [measured by 25(OH)D] and by a genetic variation in a key vitamin D activation enzyme (CYP27B1) previously shown to be associated with type 1 diabetes.

METHODS

9377 participants in the 1958 British birth cohort completed a biomedical assessment at 45 years of age ; 7288 eligible participants had data on 25(OH)D and IgE, with 6429 having further information on CYP27B1 genotype ()1260C>A).

RESULTS

There was a nonlinear association between 25(OH)D and IgE (P-value for curvature = 0.0001). Compared with the reference group with the lowest IgE concentrations [25(OH)D 100-125 nmol/l], IgE concentrations were 29% higher (95% CI 9-48%) for participants with the 25(OH)D <25 nmol/l, and 56% higher (95% CI 17-95%) for participants with 25(OH)D >135 nmol/l (adjusted for sex, month, smoking, alcohol consumption, time spent outside, geographical location, social class, PC/TV time, physical activity, body mass index and waist circumference). CYP27B1 genotype was associated with both 25(OH)D (difference for A vs. C allele: 1.88%, 95% CI 0.37-3.4%, P = 0.01) and IgE concentrations ()6.59%, )11.6% to )1.42%, P = 0.01).

CONCLUSIONS

These data suggest that there may be a threshold effect with both low and high 25(OH)D levels associated with elevated IgE concentrations. The same CYP27B1 allele that is protective of diabetes was associated with increased IgE concentrations.

Analyses of associations with asthma in four asthma population samples from Canada and Australia

Asthma, atopy, and related phenotypes are heterogeneous complex traits, with both genetic and environmental risk factors. Extensive research has been conducted and over hundred genes have been associated with asthma and atopy phenotypes, but many of these findings have failed to replicate in subsequent studies. To separate true associations from false positives, candidate genes need to be examined in large well-characterized samples, using standardized designs (genotyping, phenotyping and analysis). In an attempt to replicate previous associations we amalgamated the power and resources of four studies and genotyped 5,565 individuals to conduct a genetic association study of 93 previously associated candidate genes for asthma and related phenotypes using the same set of 861 single-nucleotide polymorphisms (SNPs), a common genotyping platform, and relatively harmonized phenotypes. We tested for association between SNPs and the dichotomous outcomes of asthma, atopy, atopic asthma, and airway hyperresponsiveness using a general allelic likelihood ratio test. No SNP in any gene reached significance levels that survived correction for all tested SNPs, phenotypes, and genes. Even after relaxing the usual stringent multiple testing corrections by performing a gene-based analysis (one gene at a time as if no other genes were typed) and by stratifying SNPs based on their prior evidence of association, no genes gave strong evidence of replication. There was weak evidence to implicate the following: IL13, IFNGR2, EDN1, and VDR in asthma; IL18, TBXA2R, IFNGR2, and VDR in atopy; TLR9, TBXA2R, VDR, NOD2, and STAT6 in airway hyperresponsiveness; TLR10, IFNGR2, STAT6, VDR, and NPSR1 in atopic asthma. Additionally we found an excess of SNPs with small effect sizes (OR < 1.4). The low rate of replication may be due to small effect size, differences in phenotypic definition, differential environmental effects, and/or genetic heterogeneity. To aid in future replication studies of asthma genes a comprehensive database was compiled and is available to the scientific community at http://genapha.icapture.ubc.ca/.

Genome-wide identification of allelic expression in hypertensive rats

BACKGROUND

Identification of genes involved in complex cardiovascular disease traits has proven challenging. Inbred animal models can facilitate genetic studies of disease traits. The spontaneously hypertensive rat (SHR) is an inbred model of hypertension that exists in several closely related but genetically distinct lines.

METHODS AND RESULTS

We used renal gene-expression profiling across 3 distinct SHR lines to identify genes that show different expression in SHR than in the genetically related normotensive control strain, Wistar-Kyoto. To ensure robust discovery of genes showing SHR-specific expression differences, we considered only those genes in which differential expression is replicated in multiple animals of each of multiple hypertensive rat lines at multiple time points during the ontogeny of hypertension. Mutation analysis was performed on the identified genes to uncover allelic variation. We identified those genes in which all SHR lines share a single allele of the gene when normotensive controls (Wistar-Kyoto) have fixed the alternative allele. We then identified which of the differentially expressed genes show expression that is controlled by the alleleic variation present in and around the gene. Allelic expression was demonstrated by observing the effect on gene expression of alleles inherited in the freely segregating F(2) progeny of a cross between SHR and Wistar-Kyoto animals.

CONCLUSIONS

The result of these studies is the identification of several genes (Ptprj, Ela1, Dapk-2, and Gstt2) in which each of 4 SHR lines examined have fixed the same allele and in which each of 2 Wistar-Kyoto lines have a contrasting allele for which the inherited allele influences the level of gene expression. We further show that alleles of these genes lie in extensive haplotype blocks that have been inherited identical by descent in the hypertensive lines.

Serum vitamin D levels and markers of severity of childhood asthma in Costa Rica

RATIONALE

Maternal vitamin D intake during pregnancy has been inversely associated with asthma symptoms in early childhood. However, no study has examined the relationship between measured vitamin D levels and markers of asthma severity in childhood.

OBJECTIVES

To determine the relationship between measured vitamin D levels and both markers of asthma severity and allergy in childhood.

METHODS

We examined the relation between 25-hydroxyvitamin D levels (the major circulating form of vitamin D) and markers of allergy and asthma severity in a cross-sectional study of 616 Costa Rican children between the ages of 6 and 14 years. Linear, logistic, and negative binomial regressions were used for the univariate and multivariate analyses.

MEASUREMENTS AND MAIN RESULTS

Of the 616 children with asthma, 175 (28%) had insufficient levels of vitamin D (<30 ng/ml). In multivariate linear regression models, vitamin D levels were significantly and inversely associated with total IgE and eosinophil count. In multivariate logistic regression models, a log(10) unit increase in vitamin D levels was associated with reduced odds of any hospitalization in the previous year (odds ratio [OR], 0.05; 95% confidence interval [CI], 0.004-0.71; P = 0.03), any use of antiinflammatory medications in the previous year (OR, 0.18; 95% CI, 0.05-0.67; P = 0.01), and increased airway responsiveness (a < or =8.58-mumol provocative dose of methacholine producing a 20% fall in baseline FEV(1) [OR, 0.15; 95% CI, 0.024-0.97; P = 0.05]).

CONCLUSIONS

Our results suggest that vitamin D insufficiency is relatively frequent in an equatorial population of children with asthma. In these children, lower vitamin D levels are associated with increased markers of allergy and asthma severity.

Analysis of association of clinical aspects and vitamin D receptor gene polymorphism with dental implant loss

Osseointegration failure is a complex, multifactorial trait shown to concentrate in some treated populations. There has been shown evidence for genetic contribution to dental implant loss. Genetic polymorphisms have been classically considered as genetic risk factors for several diseases and, more recently, for dental implant loss.

OBJECTIVES

The purpose of this study was to access clinical factors related to failure process, and to investigate the relationship between a vitamin D receptor (VDR) polymorphism (rs731236, TaqI) and dental implant loss.

MATERIAL AND METHODS

Two hundred and seventeen unrelated patients, mean age 51.7+/-11.3 years, were divided into two groups: (i) control group (C), 137 individuals presenting at least one osseointegrated implant in function for 6 months or more and without any implant loss, and (ii) study group (S), 80 individuals presenting at least one implant loss. After DNA collection and purification, VDR TaqI polymorphism analysis was performed by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP). Differences between C and S, and between healthy (H; n=1232) and lost (L; n=135) implants were accessed.

RESULTS

Positive evidence of association has been detected between implant loss and the following variables: edentulism, implant position, primary stability, and implant length. Cox's regression model showed that primary stability, surgical technique and bone quantity were related to implant survival over time. No association between genotypes or alleles of VDR TaqI polymorphism and implant loss was found between the groups.

CONCLUSION

It was observed that clinical variables, but not the study polymorphism, were associated with dental implant loss.

Serum ferritin and transferrin levels as serologic markers of methylene diphenyl diisocyanate-induced occupational asthma

BACKGROUND

Although methylene diphenyl diisocyanate (MDI) may induce occupational asthma in the workplace, the pathogenic mechanisms are unclear.

OBJECTIVES

By using bronchoalveolar lavage fluid, we sought to identify proteins that were differentially expressed between subjects with MDI-induced occupational asthma (MDI-OA) and asymptomatic exposed controls (AECs).

METHODS

To find proteins that were differentially expressed between the MDI-OA and AEC groups, 2-dimensional electrophoresis was performed by using bronchoalveolar lavage fluid obtained from subjects after MDI-specific inhalation challenge. The selected protein spots were then identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The clinical relevance of the differentially expressed spots was compared by ELISA using sera from the MDI-OA/eosinophilic bronchitis, AEC, and unexposed healthy control groups. Receiver operating characteristic curves were then plotted, and the sensitivity and specificity were determined.

RESULTS

Twenty-three protein spots were identified that distinguished the subjects with MDI-OA from those in the AEC group. Among them, ferritin expression was downregulated whereas transferrin expression was upregulated in subjects with MDI-OA compared with AEC; these results were validated by ELISA using sera from the MDI-OA/EB and AEC groups. To identify subjects with MDI-OA, the optimal serum cutoff levels were 69.84 ng/mL for ferritin and 2.48 microg/mL for transferrin. When these 2 parameters were combined, the sensitivity was 71.43% and the specificity was 85.71%.

CONCLUSION

Serum ferritin and transferrin levels are associated with the phenotype of MDI-OA.

Maternal transmission of asthma risk

Maternal asthma significantly increases the risk of asthma in offspring, but the mechanisms remain poorly defined. We review animal models used to study the maternal effect, focusing on a murine model developed in our laboratory. Mother mice rendered allergic to ovalbumin produce offspring that are more susceptible to allergic sensitization, seen as airway hyperresponsiveness and allergic airway inflammation after a sensitization protocol, which has minimal effects on newborns from normal mothers. Mechanistic analyses identify a role for interleukin-4 (based on pre-mating injection of neutralizing antibodies), dendritic cells and allergen-specific T cells (based on adoptive transfer experiments). Other maternal exposures (e.g. pollutant exposure and non-pulmonary allergy) can increase asthma susceptibility in offspring. This observation implies that the maternal transmission of asthma represents a final common pathway to various types of inflammatory stimuli. Identification of the shared molecular mechanisms in these models may allow better prevention and therapy. Current knowledge, gaps in knowledge and future directions are discussed.

Genes to diseases (G2D) computational method to identify asthma candidate genes

Asthma is a complex trait for which different strategies have been used to identify its environmental and genetic predisposing factors. Here, we describe a novel methodological approach to select candidate genes for asthma genetic association studies. In this regard, the Genes to Diseases (G2D) computational tool has been used in combination with a genome-wide scan performed in a sub-sample of the Saguenay−Lac-St-Jean (SLSJ) asthmatic familial collection (n = 609) to identify candidate genes located in two suggestive loci shown to be linked with asthma (6q26) and atopy (10q26.3), and presenting differential parent-of-origin effects. This approach combined gene selection based on the G2D data mining analysis of the bibliographic and protein public databases, or according to the genes already known to be associated with the same or a similar phenotype. Ten genes (LPA, NOX3, SNX9, VIL2, VIP, ADAM8, DOCK1, FANK1, GPR123 and PTPRE) were selected for a subsequent association study performed in a large SLSJ sample (n = 1167) of individuals tested for asthma and atopy related phenotypes. Single nucleotide polymorphisms (n = 91) within the candidate genes were genotyped and analysed using a family-based association test. The results suggest a protective association to allergic asthma for PTPRE rs7081735 in the SLSJ sample (p = 0.000463; corrected p = 0.0478). This association has not been replicated in the Childhood Asthma Management Program (CAMP) cohort. Sequencing of the regions around rs7081735 revealed additional polymorphisms, but additional genotyping did not yield new associations. These results demonstrate that the G2D tool can be useful in the selection of candidate genes located in chromosomal regions linked to a complex trait.

Vitamin D and glucocorticoids differentially modulate chemokine expression in human airway smooth muscle cells

BACKGROUND AND PURPOSE

Chemokines play a critical role in the pathogenesis of asthma and facilitate the recruitment of inflammatory cells in the airways. Evidence now suggests that airway smooth muscle (ASM) may serve as a source of chemokines in inflamed airways. Although vitamin D has potent anti-inflammatory properties in vitro in some cell types, its effects on ASM cells remain unclear. Here, we investigated whether 1alpha, 25-dihydroxy vitamin D3 (calcitriol) modulated chemokine production in ASM.

EXPERIMENTAL APPROACH

Human ASM cell cultures were derived from tracheal samples taken during surgery. ASM cells were treated with tumour necrosis factor alpha (TNFalpha) and/or interferon gamma (IFNgamma) for 24 h in the presence of calcitriol and/or the glucocorticoid fluticasone added 2 h before. RANTES (regulated upon activation, normal T-cell expressed and secreted), interferon-inducible protein 10 (IP-10) and fractalkine (FKN) levels in cell supernatants were measured by ELISA.

KEY RESULTS

In TNFalpha-treated cells, calcitriol inhibited RANTES and IP-10 secretion in a concentration-dependent manner. FKN levels were negligible. In TNFalpha/IFNgamma-treated cells, whereas fluticasone or calcitriol alone partially inhibited RANTES secretion (by 38 and 20%, respectively), the combination of both drugs additively inhibited RANTES secretion (by 60%). No effect was observed on IP-10 secretion. Whereas fluticasone enhanced FKN secretion (by 50%), calcitriol significantly decreased FKN levels (by 50%). Interestingly, calcitriol blocked the stimulatory effect of fluticasone on FKN secretion, which was inhibited by 60% with the combination of calcitriol and fluticasone.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that vitamin D uniquely modulates human ASM expression of chemokines and may exert some beneficial effects in the treatment of steroid-resistant patients with asthma.

Asthma genetics: from linear to multifactorial approaches

Asthma risk has a clear hereditary component but, unexpectedly, the majority of reported associations between genetic variants and asthma have not been consistently replicated across studies. Methodological flaws have been indicated as a possible explanation for these inconsistencies. However, an alternative explanation is that the effects of genetic variants depend on other factors whose frequency and distribution vary, both across individuals and across populations. Within this framework, we review recent advances in asthma genetics and conclude that a paradigm shift is needed, because a static model in which the DNA sequence is associated with disease risk in a linear fashion fails to consider the interdependence of the diverse components of asthma risk. We propose an integrated approach, linking sequence variation to specific phenotypic manifestations of the disease by taking into account concurrent influences from biological systems and environmental factors that interact within specific developmental windows of opportunity.

Asthma and obesity: common early-life influences in the inception of disease

The respective prevalences of both asthma and obesity have seen a significant rise in the past few decades. Although the association between these 2 conditions has been found in many studies from different areas around the world, the exact mechanisms for how this association arises remains unresolved. Because both asthma and obesity appear to have their beginnings in early childhood, common exposures that predispose individuals to both these conditions may explain how they are associated. These exposures include common genetic predictors, prenatal exposure to specific nutrients and overall maternal nutrition, patterns of colonization of the neonatal and infant gut, birth weight and infant weight gain, sedentary behaviors, and levels of adipokines in early life.

Association of vitamin D receptor gene 3'-variants with Hashimoto's thyroiditis in the Croatian population

Hashimoto's thyroiditis (HT) is the most frequent autoimmune thyroid disease with strong genetic background. Vitamin D receptor (VDR) endocrine system affects immunosuppressive, regulatory and tolerogenic decisions required for induction and maintenance of peripheral immune tolerance. With respect to the biological function of the VDR and functionally plausible gene-expression data, we sought to test whether particular 3'-restriction fragment length polymorphisms (RFLP) and haplotypes previously directly or indirectly associated with VDR mRNA 3'-allelic imbalance phenotype and differences in total VDR mRNA expression are implicated in HT susceptibility. Thus, 145 Croatian HT patients and 145 age-, sex- and ethnically matched euthyroid controls were genotyped for VDR rs1544410 (BsmI), rs7975232 (ApaI) and rs731236 (TaqI) polymorphisms by polymerase chain reaction-RFLP method. Covariate-adjusted single-locus and haplotype-phenotype regression analyses were performed. Permutation corrections (P(c)) and Akaike Information Criteria were used for model comparisons. The best-fit [global P(c) = 7.2 x 10(-4)]BsmI-TaqI BT haplotype was found significantly more often in subjects without HT [12.2% vs. 3.7%; odds ratio (OR, 95% confidence intervals) = 0.28 (0.14-0.56), P(c) = 8 x 10(-4)], whereas the bT haplotype was significantly more frequent in individuals with HT [45.7% vs. 61.8%; OR = 1.91 (1.37-2.65), P(c) = 4 x 10(-4)]. Two extended BsmI-ApaI-TaqI RFLP haplotypes, the common baT [35.7 vs. 47.3%, OR = 1.63 (1.17-2.27), P(c) = 0.012] and rare BaT variants [6.5 vs. 1.2%, OR = 0.17 (0.06-0.55), P(c) = 1.2 x 10(-3)] were associated with HT, representing predisposing and protective haplotypes, respectively. In single-RFLP association analyses, only rs1544410 polymorphism was associated with HT phenotype (allelic P(c) = 0.0078) and appeared to function under the recessive model, with decreased risk of HT among the BB homozygotes [OR = 0.39 (0.21-0.7), P(c) = 0.0052] when compared to the reference b(+)-genotypes. These data suggest that common haplotypic variants within the VDR gene 3'-region previously linked to VDR mRNA expression and allelic imbalance could be associated with HT in the general population, and thus, may be involved in the pathogenesis of HT.

Developmental mismatch: consequences for later cardiorespiratory health

Clinical and epidemiological studies have established that people who were small at birth and had poor infant growth have an increased risk of adult cardiovascular and respiratory disease, particularly if their restricted early growth is followed by accelerated childhood weight gain. This relationship extends across the normal range of infant size in a graded manner. The 'mismatch hypothesis' proposes that ill health in later life originates through developmental plastic responses made by the fetus and infant; these responses increase the risk of adult disease if the environment in childhood and adult life differs from that predicted during early development.