Highlights Vitamin D deficiency increases the severity of the ARDS in COVID-19 infection. Vitamin D receptors are expressed in the macrophages and other immune cells. Vitamin D supplementation may influence macrophage inflammatory response, subdue the cytokine storm and lessen the ARDS in COVID-19 patients.
Background: The main source of vitamin D is skin synthesis, which depends on sunlight exposure. During the pandemic, COVID-19 children were obliged to home confinement, which potentially limiting sunlight exposure. The aim of this study was to evaluate whether home confinement led to decreased vitamin D serum levels in children in Warsaw, Poland. Methods: The study included 1472 children who were divided into two groups, based on the date of 25(OH)D level blood sampling: before and during the pandemic. Children under 1 year of age (infants) were analysed separately. Results: A statistically significant decrease in the average level of vitamin D was observed between groups of children over 1 year of age (35 ng/mL ± 18 vs. 31 ng/mL ± 14). In infants from both groups, the mean vitamin D levels were within the normal range (Group 1 inf 54 ng/mL ± 21 vs. Group 2 inf 47 ng/mL ± 15). The characteristic seasonal variability was observed before the pandemic, with maximal vitamin D levels in summer (40 ng/mL ± 17) and minimal levels in winter (30 ng/mL ± 14). During the pandemic, no seasonal variability was observed (summer 30 ng/mL ± 11 vs. winter 30 ng/mL ± 19). Conclusions: The COVID-19 pandemic restrictions led to a significant decrease in vitamin D serum levels in children.
Vitamin D is a hormone regulating the immune system and playing a pivotal role in responses to microbial infections. It regulates inflammatory processes by influencing the transcription of immune-response genes in macrophages, T cells, and dendritic cells. The proven role of vitamin D in many infectious diseases of the respiratory tract indicated that vitamin D should also play a role in SARS-CoV-2 infection. Vitamin D inhibits cytokine storm by switching the pro-inflammatory Th1 and Th17 to the anti-inflammatory Th2 and Treg response. Vitamin D is therefore expected to play a role in preventing, relieving symptoms, or treating SARS-CoV-2 infection symptoms, including severe pneumonia. There are several possible mechanisms by which vitamin D may reduce the risk of COVID-19 infection, such as induction of the transcription of cathelicidin and defensin. Also a nongenomic antiviral action of vitamin D and lumisterol, the molecule closely related to vitamin D, was reported. Despite this enormous progress, currently, there is still insufficient scientific evidence to support the claim that vitamin D supplementation may help treat COVID-19 infection. The pandemic restrictions were also shown to impact vitamin D uptake by limiting exposure to sunlight.
Due to the increased incidence of allergic diseases and emerging effects of unsatisfactory control of asthma, new mechanisms for supervising the immune system should be searched. The aim of the study was to analyze the percentage of CD3, CD4, CD8, CD19, CD16/56, NKT, CD3 anti-HLADR3 and Foxp3 regulatory lymphocytes in patients with asthma. Additionally the correlation between immune parameters, severity of asthma and serum concentration of vitamin D was performed. 25 children diagnosed with asthma were enrolled. Disease severity was assessed with the Asthma Control Test (ACT) and spirometry. The control group consisted of 15 healthy children. Venous blood from each patient was collected on EDTA or on “clott”. Phenotypes of lymphocytes were evaluated by flow cytometry. Vitamin D concentration was assessed by chemiluminescent immunoassay (CLIA) technology. There was a significant decrease in the percentage of T regulatory cells (p < 0.006) in children with asthma compared to the control group. There were no significant differences in the other investigated immunological parameters. In addition, in asthma group statistically significant decreased of vitamin D concentration (p < 0.04) was observed. There were also no significant correlations between vitamin D3 concentration and the course of asthma or percentage of regulatory cells. The results confirmed the role of regulatory T cells in the pathogenesis of asthma. Effects of vitamin D on the severity of the disease has not been proven.
Vitamin D, in addition to its superior role as a factor regulating calcium-phosphate metabolism, shows wide effects in other processes in the human body, including key functions of the immune system. This is due to the presence of vitamin D receptors in most cells of the human body. In our study, we aimed to assess whether there is a correlation between vitamin D content and the clinical course of allergic diseases as well as establish their immunological parameters in children. We found that vitamin D deficiency was significantly more frequent in the group of children with an allergic disease than in the control group (p = 0.007). Statistically significant higher vitamin D concentrations in blood were observed in the group of children with a mild course of the disease compared to children with a severe clinical course (p = 0.03). In the group of children with vitamin D deficiency, statistically significant lower percentages of NKT lymphocytes and T-regulatory lymphocytes were detected compared to the group of children without deficiency (respectively, p = 0.02 and p = 0.05), which highlights a potential weakness of the immune system in these patients. Furthermore, statistically higher levels of interleukin-22 were observed in the group of children with vitamin D deficiency (p = 0.01), suggesting a proinflammatory alert state. In conclusion, these results confirm the positive relationship between the optimal content of vitamin D and the lesser severity of allergic diseases in children, establishing weak points in the immune system caused by vitamin D deficiency in children.
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