Association of free vitamin D3 concentrations and asthma treatment failures in the VIDA Trial

Therapeutic Potential of Vitamin D in Management of Asthma: A Literature Review

Asthma, a prevalent chronic respiratory illness, affects a substantial number of individuals worldwide, with an estimated occurrence of 358 million cases. Evidence for the benefits of vitamin D in treating asthma is ambiguous and contradictory. The goal of this review article is to emphasize the value of vitamin D supplementation for people with asthma. Medical subject headings (MeSH) terminology was used to search the PubMed Central, MEDLINE, and PubMed databases for articles on vitamin D supplementation in asthma patients. We selected a comprehensive range of academic writing examples published in English, encompassing various types of texts. The study included a total of 37 papers, of which 18 were randomized controlled trials (RCTs) and five were meta-analyses. The use of a corticosteroid, with or without the inclusion of an adrenergic receptor agonist, improves the disease's symptoms, but it is unable to halt the long-term decline in lung function. Over the past 20 years, vitamin D has developed into a potent immunomodulator, influencing both immunological and structural cells, most notably airway smooth muscle cells. Among adults with low 25-hydroxyvitamin D levels, the administration of vitamin D supplements was found to have positive effects in a reduction in the likelihood of asthma exacerbations requiring systemic corticosteroids. The provision of vitamin D supplements during pregnancy significantly reduces the risk of asthma in babies. Both children and adults with inadequate vitamin D levels who have been given vitamin D supplements have shown evident preventive effects against asthma. Therefore, we conclude there should be a lower threshold for prescribing vitamin D to patients with asthma who are vitamin D deficient.

Targeting Vitamin D Deficiency to Limit Exacerbations in Respiratory Diseases: Utopia or Strategy With Potential?

Patients with respiratory diseases such as cystic fibrosis, chronic obstructive pulmonary disease, or asthma often experience an acute worsening of respiratory symptoms, termed exacerbations. Although the course of exacerbations is disease specific, they are mostly triggered by a respiratory infection. Exacerbations often require hospitalization and are an important cause of mortality. Treatments of exacerbations aim to minimize the negative impact and to prevent subsequent events. Despite many existing therapy options, many patients do not benefit from therapy and suffer from recurrent events. Vitamin D deficiency is a worldwide problem and is extremely prevalent in these patients. Vitamin D, known for its calcemic effects, also has immunomodulatory and anti-infectious actions and can therefore be a possible agent to treat or prevent exacerbations. This review will focus on vitamin D as a potential candidate to treat or prevent exacerbations in CF, COPD, and asthma.

Vitamin D Binding Protein and the Biological Activity of Vitamin D

Vitamin D has a long-established role in bone health. In the last two decades, there has been a dramatic resurgence in research interest in vitamin D due to studies that have shown its possible benefits for non-skeletal health. Underpinning the renewed interest in vitamin D was the identification of the vital role of intracrine or localized, tissue-specific, conversion of inactive pro-hormone 25-hydroxyvitamin D [25(OH)D] to active 1,25-dihydroxyvitamin D [1,25(OH)₂D]. This intracrine mechanism is the likely driving force behind vitamin D action resulting in positive effects on human health. To fully capture the effect of this localized, tissue-specific conversion to 1,25(OH)₂D, adequate 25(OH)D would be required. As such, low serum concentrations of 25(OH)D would compromise intracrine generation of 1,25(OH)₂D within target tissues. Consistent with this is the observation that all adverse human health consequences of vitamin D deficiency are associated with a low serum 25(OH)D level and not with low 1,25(OH)₂D concentrations. Thus, clinical investigators have sought to define what concentration of serum 25(OH)D constitutes adequate vitamin D status. However, since 25(OH)D is transported in serum bound primarily to vitamin D binding protein (DBP) and secondarily to albumin, is the total 25(OH)D (bound plus free) or the unbound free 25(OH)D the crucial determinant of the non-classical actions of vitamin D? While DBP-bound-25(OH)D is important for renal handling of 25(OH)D and endocrine synthesis of 1,25(OH)₂D, how does DBP impact extra-renal synthesis of 1,25(OH)₂D and subsequent 1,25(OH)₂D actions? Are their pathophysiological contexts where total 25(OH)D and free 25(OH)D would diverge in value as a marker of vitamin D status? This review aims to introduce and discuss the concept of free 25(OH)D, the molecular biology and biochemistry of vitamin D and DBP that provides the context for free 25(OH)D, and surveys in vitro, animal, and human studies taking free 25(OH)D into consideration.

Vitamin D binding protein is not affected by high-dose vitamin D supplementation: a post hoc analysis of a randomised, placebo-controlled study

Objectives

Vitamin D binding protein (VDBP) is the main transporter of 25-hydroxyvitamin D₃ (25-OHD) in the circulation. The aim of this study was to investigate if VDBP is affected by high dose vitamin D supplementation and if VDBP-levels correlate with free 25-OHD. Correlation between free 25-OHD measured with ELISA and total 25-OHD in the circulation was also analysed. Plasma samples from a randomized, controlled trial in which persistent MRSA-carriers were randomized to treatment with vitamin D, 4000 IE/day, (n = 27) or placebo (n = 32) for 12 months were used. Plasma from baseline and after 6 months of treatment were analysed for VDBP, 25-OHD and free 25-OHD.

Results

VDBP levels were not affected by vitamin D treatment, although the 25-OHD levels increased significantly in the vitamin D treated subjects. There was a strong correlation between 25-OHD and free 25-OHD (r² = 0.68, p < 0.0001), while there was no correlation between VDBP and free 25-OHD. Thus, our data shows that VDBP are not affected by vitamin D supplementation and the levels of VDBP are not associated with the free fraction of 25-OHD. Since there was a strong correlation between free 25-OHD and total 25-OHD it appears to be sufficient to measure only total 25-OHD.

Trial registrationhttp://www.clinicaltrials.gov; NCT02178488. Date of registration: June 30, 2014; Date of enrolment of the first participant: Dec 1, 2014

Dietary and Plasma Polyunsaturated Fatty Acids Are Inversely Associated with Asthma and Atopy in Early Childhood

BACKGROUND

Polyunsaturated fatty acids (PUFAs) influence immune function and risk of allergic disease. Prior evidence of the effect of PUFA intake on childhood asthma and allergy is inconclusive.

OBJECTIVES

To investigate associations of PUFA plasma levels and dietary intake with asthma and allergy at age 3 years in this ancillary study of the Vitamin D Antenatal Asthma Reduction Trial.

METHODS

Plasma PUFA levels were reported as relative abundances from mass spectrometry profiling, and dietary PUFA intake was derived from food frequency questionnaire responses. Associations between PUFA and outcomes, including asthma and/or recurrent wheeze, allergic sensitization, and total IgE at age 3 years, were evaluated in adjusted regression models. Additional regression models analyzed the combined effects of antenatal vitamin D and early childhood PUFA on outcomes.

RESULTS

Total, omega-3, and omega-6 plasma PUFA relative abundances were significantly (P < .05) inversely associated with both asthma and/or recurrent wheeze and allergic sensitization. Likewise, dietary PUFA intake was inversely associated with asthma and/or recurrent wheeze (P < .05 for omega-6 PUFA only). For both dietary and plasma measures of total, omega-3, and omega-6 PUFAs, inverse associations with outcomes were strongest among subjects with both high umbilical cord blood 25-hydroxyvitamin D and high PUFA at age 3 years.

CONCLUSIONS

PUFA dietary intake and plasma levels are inversely associated with asthma and/or recurrent wheeze and atopy at age 3 years. Antenatal vitamin D could modulate the effect of early childhood PUFA on risk of asthma and allergy.