Prospective Association of 25-Hydroxyvitamin D3 and D2 with Childhood Lung Function, Asthma, Wheezing, and Flexural Dermatitis

Analysis of 25-hydroxy cholecalciferol, immunoglobulin E, and vitamin D receptor single nucleotide polymorphisms (Apa1, Taq1, and Bsm1), among sample of Egyptian children with bronchial asthma: A case-control study

PURPOSE

The current study aimed to assess the serum levels of vitamin D and immunoglobulin E (IgE) among asthmatic Egyptian children and to find out the possible associations of vitamin D receptor (VDR) polymorphisms with bronchial asthma development.

METHODS

The study included 100 Egyptian children, 50 asthmatic children who were comparable with 50 age, sex, and body mass index-matched, unrelated healthy controls (HCs) clinical assessments of asthmatic children were done using global initiative of asthma. Pulmonary function tests (forced expiratory volume in 1 second [FEV1], forced vital capacity [FVC], FEV1/FVC ratio) were performed. Enzyme-linked immunosorbent assays of serum vitamin D3 and total IgE were done. VDR-single nucleotide polymorphisms (SNPs) (ApaI, TaqI, and BsmI) detection has performed using polymerase chain reaction through restriction fragment length polymorphism technique. Data analysis was performed using SPSS version 20.0. The studied SNPs were followed the Hardy Weinberg equation.

RESULTS

The mean serum level of 25(OH) D3 was significantly lower among asthmatic children (13.46 ng/mL ± 10.50 SD) in comparison to HCs (37.53 ng/mL ± 13. 0.40 SD), P < .05. Vitamin D deficiency was detected in 72% of cases with no significant difference in its level regarding asthma control. There was significantly higher IgE level among asthmatic children (99.83 ku/L ± 233.81 SD) versus HCs (7.52 ku/L ± 3.32 SD), P < .05. Asthmatic children were presented more commonly with TaqI t allele (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.28-3.96; P < .05) and BsmI b allele (OR, 1.83; 95% CI, 1.05-3.21; P < .05). ApaI a allele was not significantly different among patients versus controls (P > .05). TT + Tt and Bb + bb genotypes were significantly higher among cases versus the controls, P < .05 for all.

CONCLUSIONS

TaqI and BsmI were associated with risk of bronchial asthma development among Egyptian children. High IgE and Low vitamin D status were frequently occurring among asthmatic children.

Effect of Prenatal versus Postnatal Vitamin D Deficiency on Pulmonary Structure and Function in Mice

Epidemiologic studies have linked gestational vitamin D deficiency to respiratory diseases, although mechanisms have not been defined. We hypothesized that antenatal vitamin D deficiency would impair airway development and alveolarization in a mouse model. We studied the effect of antenatal vitamin D deficiency by inducing it in pregnant mice and then compared lung development and function in their offspring to littermate controls. Postnatal vitamin D deficiency and sufficiency models from each group were also studied. We developed a novel tracheal ultrasound imaging technique to measure tracheal diameter in vivo. Histological analysis estimated tracheal cartilage total area and thickness. We found that vitamin D-deficient pups had reduced tracheal diameter with decreased tracheal cartilage minimal width. Vitamin D deficiency increased airway resistance and reduced lung compliance, and led to alveolar simplification. Postnatal vitamin D supplementation improved lung function and radial alveolar count, a parameter of alveolar development, but did not correct tracheal narrowing. We conclude that antenatal vitamin D deficiency impairs airway and alveolar development and limits lung function. Reduced tracheal diameter, cartilage irregularity, and alveolar simplification in vitamin D-deficient mice may contribute to increased airways resistance and diminished lung compliance. Vitamin D supplementation after birth improved lung function and, potentially, alveolar simplification, but did not improve defective tracheal structure. This mouse model offers insight into the mechanisms of vitamin D deficiency-associated lung disease and provides an in vivo model for investigating preclinical preventive and therapeutic strategies.

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.

Vitamin D as an adjunctive therapy in asthma. Part 2: A review of human studies

Vitamin D deficiency (VDD) is highly prevalent worldwide, with adverse effects on bone health but also potentially other unfavorable consequences. VDD and asthma-incidence/severity share many common risk factors, including winter season, industrialization, poor diet, obesity, dark skin pigmentation, and high latitude. Multiple anatomical areas relevant to asthma contain both the enzyme responsible for producing activated vitamin D and the vitamin D receptor suggesting that activated vitamin D (1,25-dihydroxyvitamin D) may have important local effects at these sites. Emerging evidence suggests that VDD is associated with increased airway hyperresponsiveness, decreased pulmonary function, worse asthma control, and possibly decreased response to standard anti-asthma therapy. However the effect is inconsistent with preliminary evidence from different studies suggesting vitamin D is both beneficial and detrimental to asthma genesis and severity. Current evidence suggests that supplementation with moderate doses of vitamin D may be appropriate for maintenance of bone health in asthmatics, particularly steroid users. However emerging data from an increasing number of randomized, controlled, intervention studies of vitamin D supplementation in pediatric and adult asthma are becoming available and should help determine the importance, if any of vitamin D for asthma pathogenesis. The purpose of this second of a two-part review is to review the current human literature on vitamin D and asthma, discussing the possible consequences of VDD for asthma and the potential for vitamin D repletion as adjunct therapy.

Vitamin D levels and status amongst asthmatic and non-asthmatic adolescents in Cyprus: a comparative cross-sectional study

BACKGROUND

Emerging evidence suggests that vitamin D might be implicated in asthma pathophysiology. This study aims to compare Vitamin D mean serum levels and status between asthmatic and non-asthmatic adolescents and investigate the association of vitamin D with asthma severity.

METHODS

In a cohort of adolescents aged 16-17 years, those reporting wheezing in the past 12 months and Ever asthma on the ISAAC questionnaire were invited to participate and formed the Active Asthmatics group. Controls were selected amongst Never Wheezers/Never Asthmatics (NWNA). Differences in mean 25(OH)D serum levels and vitamin D status between AA and NWNA were examined in multivariate linear and logistic regression models respectively, adjusting for potential confounders. Within AA, differences in vitamin D levels were assessed across asthma severity indicators.

RESULTS

A total of 69 AA and 671 NWNA participated in the study. Unadjusted mean 25(OH)D serum levels were 22.90 (SD 6.41), and 21.15 (SD 5.59) ng/mL in NWNA and AA respectively (p = 0.03). In adjusted models, mean 25(OH)D levels remained significantly lower amongst AA compared to NWNA (adjusted beta coefficient -1.68, 95% CI -3.24, -0.13). Severe (<12 ng/mL), moderate (<25 ng/mL) or insufficient (<30 ng/mL) vitamin D status was more prevalent among AA who were 1.6 times (95% CI 1.01, 2.53) more likely to belong to a lower vitamin D category compared to NWNA. Within AA, there was a negative trend between vitamin D levels and the number of reported asthma severity indicators.

CONCLUSIONS

Levels of vitamin D tend to be lower among asthmatic compared to non-asthmatic children and in those with severe asthma independent of important confounders.

Vitamin D deficiency induces Th2 skewing and eosinophilia in neonatal allergic airways disease

BACKGROUND

Associations between vitamin D status and childhood asthma are increasingly reported, but direct causation and mechanisms underlying an effect remain unknown. We investigated the effect of early-life vitamin D deficiency on the development of murine neonatal allergic airways disease (AAD).

METHODS

In utero and early-life vitamin D deficiency was achieved using a vitamin D-deficient diet for female mice during the third trimester of pregnancy and lactation. Offspring were weaned onto a vitamin D-deficient or vitamin D-replete diet, and exposure to intranasal house dust mite (HDM) or saline was commenced from day 3 of life for up to 6 weeks, when airway hyper-responsiveness (AHR), airway inflammation and remodelling were assessed.

RESULTS

Neonatal mice that had in utero and early-life vitamin D deficiency had significantly increased pulmonary CD3(+) CD4(+) T1ST2(+) cells and reduced CD4(+) IL-10(+) cells. This effect was enhanced following HDM exposure. AHR in HDM-exposed mice was unaffected by vitamin D status. Introduction of vitamin D into the diet at weaning resulted in a significant reduction in serum IgE levels, reduced pulmonary eosinophilia and peri-bronchiolar collagen deposition.

CONCLUSION

Peri-natal vitamin D deficiency alone has immunomodulatory effects including Th2 skewing and reduced IL-10-secreting T regulatory cells, exaggerated with additional allergen exposure. Vitamin D deficiency in early life does not affect AHR, but contributes to disease severity with worse eosinophilic inflammation and airway remodelling. Importantly, supplementation with vitamin D improves both of these pathological abnormalities.