Serum vitamin D level is associated with smell dysfunction independently of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis in children

Vitamin D levels and olfactory dysfunction in multiple sclerosis patients

OBJECTIVE

The objective was to explore the possible relationship between the serum vitamin D level and olfactory impairment in a population of multiple sclerosis (MS) patients in Guizhou, China.

METHODS

We included 25 patients with MS and 18 healthy controls (HCs) who were recruited from the Affiliated Hospital of Guizhou Medical University from February 2021 to September 2021. The University of Pennsylvania Smell Identification Test (UPSIT) was used to test the patients' sense of smell, and the level of serum 25-hydroxyethylene polyprotein D was measured.

RESULTS

Serum vitamin D levels and UPSIT scores were significantly different between the MS group and the control group (both p < 0.001). Moreover, a significant positive correlation emerged between vitamin D levels and UPSIT scores in MS patients (r = 0.537, p = 0.021).

CONCLUSIONS

The serum vitamin D level may be involved in the regulation of olfactory dysfunction in MS patients in Guizhou, China.

Intranasal Calcitriol Accelerates Improvement of Sinonasal Inflammation and Olfactory Impairment in Mice After Cessation of Chronic Cigarette-Smoke Exposure

RATIONALE

Smoking has been shown to be associated with circulating deficiencies in 25(OH)D3 and reduced sinonasal tissue levels of the active form of vitamin D, 1,25(OH)2D3. Given vitamin D's ability to reduce inflammation, we sought to examine if intranasal (IN) delivery of calcitriol [clinical analog of 1,25(OH)2D3] could reduce inflammation and improve disease severity in a murine model of chronic cigarette smoke-induced sinonasal inflammation (CS-SI).

METHODS

Mice were exposed to CS 5 h/day, 5 days/week for 9 months, and then began IN calcitriol three times per week for 4 weeks. Micro-CT was used to assess disease severity. Sinonasal tissues were collected for RNA-seq analysis. Olfactory function was assessed using a T-maze odorant avoidance sniff behavior test. Nasal lavage fluid (NALF) was used for cytology and cytokines analysis.

RESULTS

Quantification of disease severity by micro-CT showed IN calcitriol reduced opacification by 18%, as compared to smoke cessation alone, in which only a 5% reduction was noted. H&E analysis of NAFL demonstrated heightened neutrophil infiltration and neutrophil-associated chemokines in CS-SI mice, which was reduced with IN calcitriol treatment. RNA-seq pathway analysis demonstrated that smoking was associated with odorant binding changes and that calcitriol treatment reduced neutrophil migration and inflammation. Lastly, IN calcitriol reversed olfactory loss caused in CS-SI.

CONCLUSIONS

IN delivery of calcitriol accelerates inflammatory resolution in the nose and olfactory mucosa after prolonged CS exposure. Furthermore, treatment was associated with improved olfactory function in mice CS-SI, as such local delivery of calcitriol may serve as a novel treatment for modulating sinonasal inflammation.

Vitamin D and smell impairment: a systematic literature review

OBJECTIVE

Smell impairment affects 60-80 per cent of individuals aged over 80 years. This review aimed to identify any association between vitamin D deficiency and smell impairment, and determine the efficacy of vitamin D to treat smell impairment.

METHODS

A literature search was conducted across four databases between the years 2000 and 2022. The literature screen was performed by two independent reviewers.

RESULTS

Seven articles were included in this review. Four studies examined the association between vitamin D deficiency and smell impairment, with three studies identifying a significant relationship. Three studies investigated the use of vitamin D as treatment for smell impairment, which found complete resolution or significant symptom improvement after vitamin D deficiency was treated.

CONCLUSION

This review identified limited studies on this topic. As vitamin D supplementation is relatively cost-efficient, further large-scale studies should be carried out to investigate the efficacy of vitamin D for treating anosmia.

Breastfeeding and vitamin D

The recent re-emergence of vitamin D deficiency (VDD) and rickets among breastfed infants without adequate sunlight exposure and vitamin D supplementation has been reported worldwide. Breastfed infants are particularly vulnerable to VDD because of the low vitamin D content of breast milk, restricted sunlight exposure, increased pollution, and limited natural dietary sources of vitamin D. The prevalence of VDD in breastfed infants differs vastly between studies and nations at 0.6%-91.1%. The recommended intake of vitamin D for lactating mothers to optimize their overall vitamin D status and, consequently, of their breast milk is 200-2,000 IU/day, indicating a lack of consensus. Some studies have suggested that maternal high-dose vitamin D supplementation (up to 6,400 IU/day) can be used as an alternate strategy to direct infant supplementation. However, concern persists about the safety of maternal high-dose vitamin D supplementation. Direct infant supplementation is the currently available option to support vitamin D status in breastfed infants. The recommended dose for vitamin D supplementation in breastfed infants according to various societies and organizations worldwide is 200-1,200 IU/day. Most international guidelines recommend that exclusively or partially breastfed infants be supplemented with 400 IU/day of vitamin D during their first year of life. However, domestic studies on the status and guidelines for vitamin D in breastfed infants are insufficient. This review summarizes the prevalence of VDD in breastfed infants, vitamin D content of breast milk, and current guidelines for vitamin D supplementation of lactating mothers and infants to prevent VDD in breastfed infants.

A Novel Strategy for the Treatment of Allergic Rhinitis: Regulating Treg/Th17 and Th1/Th2 Balance In Vivo by Vitamin D

Objective

This prospective study is aimed at observing the number of nasal itching and sneezing in rats from the macroscopic level and examine the pathological changes of nasal mucosa, Th1 and Th2-related cytokines, and Treg/Th17 by vitamin D3 administration from the microscopic level, in order to explore the role of vitamin D in allergic rhinitis and to provide theoretical guidance for prevention and treatment.

Results

There were significant differences in nasal itching and sneezing between the administration groups and the positive groups. Meanwhile, the level of Th1 and Treg in the administration groups increased, while the level of Th2 and Th17 decreased, indicating that the balance of Th1/Th2 was corrected. Our study revealed that vitamin D3 has preventive and therapeutic effects on allergic rhinitis, which provides theoretical guidance for practical application.

Association of 25-hydroxyvitamin D status with brain volume changes

Vitamin D is critical to brain function and its deficiency accelerates cognitive impairment. There is limited understanding of the brain-specific areas that undergo volume change in relation to blood vitamin D levels. The objective of this study was to evaluate the association between blood 25-hydroxyvitamin D (25(OH)D) concentration and structural changes in the brain. We analyzed structural three-dimensional T1 MRI images of 201 elderly individuals (mean age = 74.91 ± 9.21 years; 68.1% female; mean 25(OH)D = 18.05 nmol/L), with 10 community-based normal healthy subjects, 33 with subjective cognitive decline, 97 with mild cognitive impairment, and 61 with Alzheimer's disease (AD). To analyze the structural changes in the brain respective to blood 25(OH)D, multiple regression analyses were performed using voxel-based morphometry with age and total intracranial volume as covariates. Lower 25(OH)D level were associated with reduced brain volume in right olfactory, rectus GM regions (FWE-corr, p < .05) for entire subjects. For AD subjects, left parahippocampal, fusiform, and hippocampal areas were positively associated with 25(OH)D (FWE-corr, p < .05). Low blood 25(OH)D was associated with reduced volumes in olfactory and hippocampal regions in elderly patients with cognitive decline. Our results may provide insight into the neurological pathophysiology of vitamin D.