The role of vitamin D in asthma

Vitamin D receptor (VDR) gene polymorphism and risk of rheumatoid arthritis (RA): systematic review and meta-analysis

Vitamin D is involved in immune system modulation as well as in calcium and bone homeostasis, hence plays a role in rheumatoid arthritis (RA) etiopathogenesis. A bulk of studies in different populations have assessed the association between the vitamin D receptor (VDR) gene polymorphisms and the risk of RA, reporting conflicting results. Therefore, we designed a meta-analysis to comprehensively evaluate the association of VDR gene polymorphisms and RA risk. All potential studies reporting the association between VDR gene polymorphisms and susceptibility to RA published till February 2020 were retrieved through systematic search of database, including Scopus and MEDLINE. Strength of pooled association was determined through calculating the pooled odds ratios (ORs) and 95% confidence intervals (CIs). Subgroup analysis was performed by stratifying the studies by population type. This meta-analysis included 23 eligible studies (21 articles) overall. We noticed that FokI SNP had a significant protective association with susceptibility to RA in the overall analysis as well as in Europeans and Asians. TaqI SNP decreased the RA risk in Africans and Arabs, but not in the overall analysis. Likewise, BsmI SNP and RA risk in the overall population analysis was not significant. Interestingly, BsmI polymorphism increased RA risk in Africans. This meta-analysis offers a significant association between VDR gene polymorphism and susceptibility to RA in both overall and ethnic-specific analysis. However, different polymorphisms acted inversely in increasing or decreasing RA risk in different populations.

Vitamin D Supplementation for Childhood Asthma: A Systematic Review and Meta-Analysis

Importance

There is growing evidence that vitamin D plays a role in the pathogenesis of asthma but it is unclear whether supplementation during childhood may improve asthma outcomes.

Objectives

The objective of this systematic review and meta-analysis was to evaluate the efficacy and safety of vitamin D supplementation as a treatment or adjunct treatment for asthma.

Data Sources

We searched MEDLINE, Embase, CENTRAL, and CINAHL through July 2014.

Study Selection

We included RCTs that evaluated vitamin D supplementation in children versus active control or placebo for asthma.

Data Extraction and Synthesis

One reviewer extracted data and one reviewer verified data accuracy. We qualitatively summarized the main results of efficacy and safety and meta-analyzed data on comparable outcomes across studies. We used GRADE for strength of evidence.

Main Outcome Measures

Main planned outcomes measures were ED visits and hospitalizations. As secondary outcomes, we examined measures of asthma control, including frequency of asthma exacerbations, asthma symptom scores, measures of lung function, β₂-agonist use and daily steroid use, adverse events and 25-hydroxyvitamin D levels.

Results

Eight RCTs (one parallel, one crossover design) comprising 573 children aged 3 to 18 years were included. One study (moderate-quality, n = 100) reported significantly less ED visits for children treated with vitamin D. No other studies examined the primary outcome (ED visits and hospitalizations). There was a reduced risk of asthma exacerbations in children receiving vitamin D (low-quality; RR 0.41, 95% CI 0.27 to 0.63, 3 studies, n = 378). There was no significant effect for asthma symptom scores and lung function. The serum 25(OH)D level was higher in the vitamin D group at the end of the intervention (low-quality; MD 19.66 nmol/L, 95% CI 5.96 nmol/L to 33.37 nmol/L, 5 studies, n = 167).

Limitations

We identified a high degree of clinical diversity (interventions and outcomes) and methodological heterogeneity (sample size and risk of bias) in included trials.

Conclusions and Relevance

Randomized controlled trials provide some low-quality evidence to support vitamin D supplementation for the reduction of asthma exacerbations. Evidence on the benefits of vitamin D supplementation for other asthma-related outcomes in children is either limited or inconclusive. We recommend that future trials focus on patient-relevant outcomes that are comparable across studies, including standardized definitions of asthma exacerbations.

Maternal vitamin D levels are inversely related to allergic sensitization and atopic diseases in early childhood

BACKGROUND

There are few studies addressing the impact of maternal vitamin D status on the vitamin D levels in offspring, their sensitization to common allergens and atopic disease development.

METHODS

Children aged 0 through 4 yr from a birth cohort in the Prediction of Allergies in Taiwanese Children (PATCH) study were enrolled. Time series of serum 25-hydroxyvitamin D (25(OH)D) levels were measured in maternal blood before delivery, cord blood, and at age 1.5, 3, and 4 using an electrochemiluminescence-based assay. Specific IgE antibodies against food and inhalant allergens were measured at 6 months, and 1, 1.5, 2, 3, and 4 yr of age.

RESULTS

A total of 164 mother-child pairs from a birth cohort were recruited in this study. The mean levels of maternal 25(OH)D were 23.2 ± 7.7 ng/ml with a high (up to 80%) prevalence of insufficient vitamin D status (< 30 ng/ml). A significant correlation was seen between maternal and cord blood 25(OH)D levels (p < 0.001), and a persistent lower 25(OH)D level was found in children born to mothers with deficient 25(OH)D levels. Deficient maternal 25(OH)D levels (<20 ng/ml) appeared to be associated with a higher prevalence of allergen sensitization before age 2. Higher maternal 25(OH)D levels were significantly associated with lower risk of eczema (OR 0.12; 95% CI 0.02-0.63; p = 0.012) and asthma (OR 0.22; 95% CI 0.06-0.92; p = 0.038) at age 4.

CONCLUSIONS

Low maternal 25(OH)D levels appear not only to be associated with an increase in the prevalence of allergic sensitization but also the risk of eczema and asthma in early childhood.

Association between vitamin D receptor polymorphisms and multiple sclerosis: systematic review and meta-analysis of case-control studies

Vitamin D receptor (VDR) polymorphisms have been studied as potential contributors to multiple sclerosis (MS). However, published studies differ with respect to study design and the significance of the effects detected. The aim of this study was to quantify the magnitude of the risk associated with the TaqI, BsmI, ApaI and FokI VDR polymorphisms in MS using a meta-analysis approach. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we conducted a systematic search and meta-analysis of the literature. Subgroup analyses were performed to detect potential sources of heterogeneity from the selected study characteristics. The stability of the summary risk was evaluated using sensitivity analyses. The meta-analysis included a total of 3300 cases and 3194 controls from 13 case-control studies. There were no significant associations found between TaqI and BsmI polymorphisms and MS risk. The association between the ApaI polymorphism and MS risk was significant in the homozygous and codominant models (P=0.013 and P=0.031, respectively), suggesting that the AA ApaI genotype might be a significant MS risk factor. Publication year and age significantly affected the association between TaqI polymorphisms and MS (P=0.014 and P=0.010, respectively), which indicates a protective effect of the major T allele. The AA ApaI and FF FokI genotypes are significant risk factors for MS. The association between the TaqI polymorphism and MS risk is significantly affected by study characteristics.

Effect of vitamin D3 on mild to moderate persistent asthmatic patients: A randomized controlled pilot study

Background:

Asthma is a common chronic inflammatory disease of the bronchial airways. Well defined treatment options for asthma are very few. The role of vitamin D₃ on asthma is still baffling. Aim: We have examined the effect of vitamin D₃ supplementation in mild to moderate persistent asthma patients.

Materials and Methods:

We conducted an open labeled, randomized comparative trial in 48 asthma patients. The study duration was about 90 days. The study had a run-in-period of 2 weeks. At the end of run-in-period, patients were divided into two groups: Usual care group (n = 31) patients received budesonide and formoterol and intervention care group (n = 32) patients received vitamin D₃ supplementation along with their regular medicine.

Results:

The primary outcome of the study was to measure the improvement in forced expiratory volume in 1 second (FEV₁). Patients in both groups had a significant improvement in FEV₁ at the end of the study. The mean difference in percentage predicted FEV₁ in usual care and intervention care group was 4.95 and 7.07 respectively.

Conclusion:

The study concluded that adjunctive therapy of vitamin D₃ is effective in asthma patients. The present study will be an evidence based report; however, future studies are warranted in longer duration of time to substantiate the present findings.

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.

Contribution of VDR polymorphisms to type 1 diabetes susceptibility: Systematic review of case-control studies and meta-analysis

Vitamin D receptor (VDR) polymorphisms have been inconsistently investigated in type 1 diabetes (T1D). However, the results are inconsistent and inconclusive. The current study aimed to investigate the role of TaqI, BsmI, ApaI and FokI VDR polymorphisms in T1D disease. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, a systematic search and meta-analysis of the literature, since 1998 until december 2013, was conducted. Subgroup analyses were performed to detect potential sources of heterogeneity from selected study characteristics. Meta-analyses yielded a non-significant association of TaqI polymorphism with T1D [OR=1.014 (0.783-1.312); P=0.918] in the recessive model. The BsmI polymorphism was not associated with T1D [OR=1.44 (0.944-1.386); P=0.171] in the dominant model. Also, ApaI polymorphism was not associated with T1D risk [OR=0.996 (0.859-1.155); P=0.960] in the homozygous model. The FokI polymorphism was not associated with T1D risk [OR=0.968 (0.743-1.263); P=0.813] in dominant model. Stratification according to study characteristics showed that publication year, age, gender, estimated vitamin D levels and latitude moderated significantly association between VDR polymorphisms and T1D disease. Meta-analysis on haplotypes revealed that BAT might be a significant risk factor for T1D [OR=1.331 (0.957-1.850; P=0.089]. However, the bAT was found to be a significant protective factor [OR=0.639 (0.460-0.887); P=0.007]. As conclusion, individual VDR polymorphisms seemed not to be associated with T1D risk. However, haplotypes contributed significantly to disease susceptibility. Study characteristics moderated the association between VDR polymorphisms and T1D. These results suggested that, in T1D pathogenesis, VDR polymorphisms interact with each other and with environmental factors.

Vitamin D deficiency in pregnancy after bariatric surgery

The objective of this study was to describe the main factors related to the installation and/or aggravation of vitamin D deficiency (VDD) and its clinical consequences in pregnant women after bariatric surgery. An electronic search on VDD in pregnancy and after bariatric surgery was conducted in publications from 1998 until 2012 that presented studies performed in humans. We provided an overview of VDD after bariatric surgery, in pregnancy, and in pregnancy in women who underwent bariatric surgery. In view of the high percentage of VDD postoperatively and the role of this vitamin in pregnancy, we recommend the investigation of vitamin D nutritional status in prenatal care.

Should vitamin D supplementation be a regular part of asthma care?

Vitamin D (vitD3) deficiency occurs frequently and has profound effects on health, especially asthma. This article examines how current knowledge of vitD3 actions and the worldwide distribution of vitD3 deficiency influences everyday clinical allergy practice. Within the limits of current knowledge, the article concisely explains the molecular nature of vitD3 actions, reviews key vitD3 research as it applies to clinical care, answers questions about the potential clinical impact of low vitD3 levels, and discusses use and safety of vitD3 supplements.

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.

Obesity and asthma: a coincidence or a causal relationship? A systematic review

BACKGROUND AND AIM

Epidemiological data has established increasing adiposity as a risk factor for incident asthma. However, the mechanisms underlying the association between obesity and asthma are incompletely understood. In the present paper, we review current knowledge of possible mechanisms mediating the observed association between obesity and asthma.

METHODS

Systematic literature review.

RESULTS

Obesity and asthma share some etiological factors, such as a common genetic predisposition and effects of in utero conditions, and may also have common predisposing factors such as physical activity and diet. Obesity results in important changes in the mechanical properties of the respiratory system which could explain the occurrence of asthma. However, there are also plausible biological mechanisms whereby obesity could be expected to either cause or worsen asthma. These include co-morbidities such as gastro-oesophageal reflux, complications from sleep-disordered breathing, breathing at low lung volumes, chronic systemic inflammation, and endocrine factors, including adipokines and reproductive hormones. Obesity related asthma is in general not associated with eosinophilic airway inflammation, and adipokines are likely to play important roles in the inflammatory pathogenesis of asthma in obese individuals.

CONCLUSION

The association between obesity and asthma is not straightforward, and further knowledge is clearly needed, as understanding the underlying mechanisms may lead to new therapeutic options for this high-risk part of the asthma population.

Widespread vitamin D deficiency among Indian health care professionals

Information on vitamin D status of Indian health care professionals is limited. Among 2,119 subjects studied, just 6 % were found to be sufficient in vitamin D status. There is urgent need of an integrated approach to detect and treat vitamin D deficiency among health care professionals to improve on-the-job productivity.

INTRODUCTION

Vitamin D deficiency is prevalent worldwide. India has been reported to be one of the worst affected countries. Several single-center studies from India have shown high prevalence of vitamin D deficiency. Little is known regarding the vitamin D status of Indian health care professionals.

AIM

This study aimed to determine prevalence of vitamin D deficiency among health care professionals in different regions of India.

METHOD

In this cross-sectional, multicenter study, we enrolled 2,119 medical and paramedical personnel from 18 Indian cities. Blood samples were collected from December 2010 to March 2011 and analyzed in a central laboratory by radioimmunoassay. Vitamin D deficiency was defined as 25-hydroxyvitamin D [25(OH)D] <20 ng/mL or <50 nmol/L, insufficiency as 25(OH)D = 20-30 ng/mL or 50-75 nmol/L, and sufficiency as 25(OH)D >30 ng/mL or >75 nmol/L.

RESULTS

Mean (±SD) age of subjects was 42.71 ± 6.8 years. Mean (±SD) 25(OH)D level was 14.35 ± 10.62 ng/mL (median 11.93 ng/mL). Seventy-nine percent of subjects were deficient, 15 % were insufficient, and just 6 % were sufficient in vitamin D status. No significant difference was found between vitamin D status in southern (25(OH)D = 13.3 ± 6.4 ng/mL) and northern (25(OH)D = 14.4 ± 8.5 ng/mL) parts of India.

CONCLUSION

Our study confirms the high prevalence of vitamin D deficiency all across India in apparently healthy, middle-aged health care professionals.