Boosting the Immune System with Vitamin D: Special Focus on Prevention of COVID-19 and Complications

In addition to the classical functions of the musculoskeletal system and calcium homeostasis, the function of vitamin D as an immune modulator is well established. The vitamin D receptors and enzymes that metabolize vitamin D are ubiquitously expressed in most cells in the body, including T and B lymphocytes, antigen-presenting cells, monocytes, macrophages and natural killer cells that trigger immune and antimicrobial responses. Many in vitro and in vivo studies revealed that vitamin D promotes tolerogenic immunological action and immune modulation. Vitamin D adequacy positively influences the expression and release of antimicrobial peptides, such as cathelicidin, defensin, and anti-inflammatory cytokines, and reduces the expression of proinflammatory cytokines. Evidence suggestss that vitamin D's protective immunogenic actions reduce the risk, complications, and death from COVID-19. On the contrary, vitamin D deficiency worsened the clinical outcomes of viral respiratory diseases and the COVID-19-related cytokine storm, acute respiratory distress syndrome, and death. The study revealed the need for more preclinical studies and focused on well-designed clinical trials with adequate sizes to understand the role of vitamin D on the pathophysiology of immune disorders and mechanisms of subduing microbial infections, including COVID-19.Copyright © 2023 Bentham Science Publishers.

Highlights from the 24th workshop on vitamin D in Austin, September 2022.

The 24th Workshop on Vitamin D was held September 7-9, 2022 in Austin, Texas and covered a wide diversity of research in the vitamin D field from across the globe. Here, we summarize the meeting, individual sessions, awards and presentations given.

Vitamin D and SARS-CoV-2.

The single-stranded RNA virus, SARS-CoV-2, causing the COVID-19 pandemic, has severely impacted daily life globally. It has been suggested to supplement the general population with vitamin D to reduce the impact of COVID-19. Nevertheless, no clear consensus can be found as to whether vitamin D affects COVID-19 disease burden. Some studies found that vitamin D levels and/or vitamin D supplementation alleviated COVID-19 disease severity and mortality. Contrarily, other studies found no such effects of vitamin D. To understand this lack of consensus, it is relevant to investigate molecular studies of the vitamin D receptor (VDR), as such studies might explain apparent controversies. We have investigated recent studies of how transcriptional regulation by the VDR affects the immune response against SARS-CoV-2. One study found that cells from severe COVID-19 patients displayed a dysregulated vitamin D response. Contrarily, another study observed a normal immune response towards SARS-CoV-2 in a patient with a non-functional VDR. These observations indicate that hypovitaminosis D is not a prerequisite for an efficient immune response against SARS-CoV-2 and therefore not a driving factor for developing severe COVID-19. However, should a patient develop severe COVID-19, vitamin D seems to be beneficial potentially by dampening the cytokine storm.

Plasma 25-Hydroxyvitamin D Level and VDR Gene Single Nucleotide Polymorphism rs2228570 Influence on COVID-19 Susceptibility among the Kazakh Ethnic Group-A Pilot Study.

Low plasma levels of the vitamin D metabolite 25-hydroxyvitamin D [25(OH)D] and the vitamin D receptor (VDR) gene single nucleotide polymorphisms (SNPs) have been associated with the body's susceptibility to infectious diseases, including COVID-19. In this pilot retrospective study, representatives of the Kazakh population (central Kazakhstan) were divided into groups based on the test for IgM and IgG for coronavirus infection. We compared the 25(OH)D plasma levels and concluded that the COVID-19-positive group values (25.17 ng/mL ± 16.65) were statistically lower (p = 0.0114) compared to the COVID-19-negative ones (35.58 ng/mL ± 20.67). There was no association between age, gender and 25(OH)D concentration within the groups (p > 0.05). The genotyping of rs2228570 was performed using a TaqMan Real-Time PCR assay. Allele C predominated among the COVID-19-negative participants and significantly reduced the likelihood of coronavirus infection (p < 0.0001; OR = 0.0804; 95% CI 0.02357-0.2798). There were no statistically significant differences in the frequencies of the A, G and T alleles in the studied groups (p > 0.05). The GG genotype of rs2228570 was associated with a 4.131-fold increased likelihood of COVID-19 infection (p = 0.0288; χ2 = 5.364; OR = 4.131; 95% CI 1.223-13.71). Comprehensive studies are required to determine whether low 25(OH)D plasma concentrations and genetic background represent a risk factor for COVID-19 infection.

The role of vitamin D receptor and IL-6 in COVID-19.

BACKGROUND: Vitamin D (Vit.D) has an important role in protecting COVID-19 patients. This study investigated the changes in vitamin D receptor (VDR) expression and interleukin 6 levels in patients with COVID-19. MATERIALS AND METHODS: 120 hospitalized patients and 120 healthy people participated in this study, both group adjusted by sex and age. Vit.D was measured with HPLC, the expression of VDR gene was done with Real-time PCR, and IL-6 was measured with ELISA assay. RESULTS: Our findings showed no significant difference in the case of Vit.D (25-OH-D3) between the two studied groups, interestingly the expression of VDR was statistically lower in the patients with COVID-19, p-value = 0.003. VDR expression was lower in the patient with diabetes, hypertension and cardiovascular disease, significantly, p-value = 0.002. The level of IL-6 was statistically higher in the COVID-19 group, p-value = 0.003. CONCLUSION: Alongside the important role of 25-OH-D3 in COVID-19 patients, the quality and quantity of the VDR expression and its role in the level of IL-6 are the promising risk factors in the future. Further studies are needed to determine the factors increasing the expression level of VDR, especially in the patients with diabetes, hypertension and cardiovascular disease.

Vitamin D and COVID-19: where are we now?

The pandemic caused by the SARS-CoV-2 virus has triggered great interest in the search for the pathophysiological mechanisms of COVID-19 and its associated hyperinflammatory state. The presence of prognostic factors such as diabetes, cardiovascular disease, hypertension, obesity, and age influence the expression of the disease's clinical severity. Other elements, such as 25-hydroxyvitamin D (25(OH)D3) concentrations, are currently being studied. Various studies, mostly observational, have sought to demonstrate whether there is truly a relationship between 25(OH)D3 levels and the acquisition and/or severity of the disease. The objective of this study was to carry out a review of the current data that associate vitamin D status with the acquisition, evolution, and/or severity of infection by the SARS-CoV-2 virus and to assess whether prevention through vitamin D supplementation can prevent infection and/or improve the evolution once acquired. Vitamin D system has an immunomodulatory function and plays a significant role in various bacterial and viral infections. The immune function of vitamin D is explained in part by the presence of its receptor (VDR) and its activating enzyme 25-hydroxyvitamin D-1alpha-hydroxylase (CYP27B1) in immune cells. The vitamin D, VDR, and Retinoid X Receptor complex allows the transcription of genes with antimicrobial activities, such as cathelicidins and defensins. COVID-19 characteristically presents a marked hyperimmune state, with the release of proinflammatory cytokines such as IL-6, TNF-α, and IL-1ß. Thus, there are biological factors linking vitamin D to the cytokine storm, which can herald some of the most severe consequences of COVID-19, such as acute respiratory distress syndrome. Hypovitaminosis D is widespread worldwide, so the prevention of COVID-19 through vitamin D supplementation is being considered as a possible therapeutic strategy easy to implement. However, more-quality studies and well-designed randomized clinical trials are needed to address this relevant question.

Vitamin D: immune function, inflammation, infections and auto-immunity.

Vitamin D plays an active role beyond mineral metabolism and skeletal health, including regulation of the immune system. Vitamin D deficiency is widely prevalent, and observational studies link low vitamin D status to a risk of infections and auto-immune disorders. Reports indicate an inverse relationship between vitamin D status and such conditions. This review details vitamin D signalling interactions with the immune system and provides experimental and clinical evidence evaluating vitamin D status, vitamin D supplementation and host susceptibility to infections, inflammation and auto-immunity. The published literature including related reviews, systematic reviews, meta-analyses, randomised controlled trials (RCTs), observational studies and basic science reports have been synthesised. Meta-analyses of observational studies have demonstrated a link between low vitamin D status and risk of acute respiratory infections, COVID-19 disorders, multiple sclerosis, type 1 diabetes (T1DM), inflammatory bowel disease (IBD), systemic lupus erythematosus and other auto-immune disorders. Observational studies suggest that vitamin D supplementation may protect against several infectious and auto-immune conditions. Meta-analyses of RCTs had mixed results, demonstrating a small protective role for vitamin D supplementation against acute respiratory infections, especially in those with vitamin D deficiency and children, and providing modest benefits for the management of T1DM and IBD. Vitamin D status is inversely associated with the incidence of several infectious and auto-immune conditions. Supplementation is recommended for those with vitamin D deficiency or at high risk of deficiency, and it might provide additional benefit in acute respiratory infections and certain auto-immune conditions.

The One-Hundred-Year Anniversary of the Discovery of the Sunshine Vitamin D3: Historical, Personal Experience and Evidence-Based Perspectives.

The discovery of a fat-soluble nutrient that had antirachitic activity and no vitamin A activity by McCollum has had far reaching health benefits for children and adults. He named this nutrient vitamin D. The goal of this review and personal experiences is to give the reader a broad perspective almost from the beginning of time for how vitamin D evolved to became intimately involved in the evolution of land vertebrates. It was the deficiency of sunlight causing the devastating skeletal disease known as English disease and rickets that provided the first insight as to the relationship of sunlight and the cutaneous production of vitamin D3. The initial appreciation that vitamin D could be obtained from ultraviolet exposure of ergosterol in yeast to produce vitamin D2 resulted in the fortification of foods with vitamin D2 and the eradication of rickets. Vitamin D3 and vitamin D2 (represented as D) are equally effective in humans. They undergo sequential metabolism to produce the active form of vitamin D, 1,25-dihydroxyvitamin D. It is now also recognized that essentially every tissue and cell in the body not only has a vitamin D receptor but can produce 1,25-dihydroxyvitamin D. This could explain why vitamin D deficiency has now been related to many acute and chronic illnesses, including COVID-19.

Genetic Variations of the Vitamin D Metabolic Pathway and COVID-19 Susceptibility and Severity: Current Understanding and Existing Evidence.

The immunomodulatory and metabolic effects of vitamin D receptor (VDR) activation have been considered beneficial in mitigating the susceptibility and severity of COVID-19 infection. Furthermore, vitamin D-binding protein (DBP) has pleiotropic effects on the immune system that may influence inflammation associated with COVID-19. Multiple observational studies have demonstrated an association between low levels of serum 25-hydroxyvitamin D and risk and the severity of COVID-19 infection. However, the impact of vitamin D supplementation as an adjunctive treatment for COVID-19 based on evidence from randomized clinical trials is unclear. Equally important is that certain variations of the genes involved in the vitamin D metabolic pathway have been shown to affect immune function and linked with various clinical outcomes, including cardio-metabolic disorders, autoimmune diseases, infections, and cancers. This indicates inter-individual difference in body response to vitamin D. There is also emerging evidence that common polymorphisms of these genes may influence the susceptibility and severity of COVID-19, although the confidence of these findings is limited by a small number of studies and participants. Further studies are needed to address the potential role of VDR activation and DBP in the pathophysiology of COVID-19 which take into account the genetic variations of vitamin D metabolic pathway.

Relationship between vitamin D status, rs2228570 vitamin D receptor polymorphism genotypes, and cholecalciferol supplementation in school-age children with COVID-19

Purpose - to study the features of vitamin D status and the effect of vitamin D3 supplementation on 25(OH)D in the serum of school-age children with COVID-19, taking into account the genotype of the rs2228570 polymorphism of the vitamin D receptor (VDR) gene. Materials and methods. The pilot, prospective, open-lapel study included 36 schoolchildren aged 9-16 who experienced asymptomatic (12 children) and mild / moderate (24 children) COVID-19. In all children were studied the content of 25(OH)D in blood serum and its dynamics underthe influence of supplementation of 10001U per day for 12 weeks, taking into account the genotypes and frequency of distribution of alleles of the rs2228570 polymorphism of the VDR gene (26 children). Results. Children with asymptomatic COVID-19 were characterized by normal values of 25(OH)D (32.68+2.12 ng/ml). Children who underwent mild / moderate COVID-19 were probably more (41.7%) likely to have a state of hypovitaminosis vitamin D (27.36+2.12 ng/ml) and fewer children (58.3%) with an optimal level of 25(OH)D than children with asymptomatic disease. In 80.7% of the examined children, the genotype was determined by the rs2228570 polymorphism of the VDR gene, which includes the G allele with greater transcriptional activity of the VDR receptor. Supplementation of 1000 IU of cholecalciferol per day, regardless of 25(OH)D status and genotype for this polymorphism probably increased the supply of vitamin D in examined children with a tendency to increase 25(OH)D in children with genotype by polymorphism rs2228570 VDR gene, which includes allele G. Conclusions. Vitamin D deficiency can be considered as a risk factor for the symptomatic course of COVID-19 in children, which requires monitoring and correction of vitamin D status, the effectiveness of which can be determined bythe genotype of the rs2228570 polymorphism of the VDR gene. Further studies of the role of vitamin D/VDR complex in the development and severity of COVID-19 in children will significantly expand the understanding of the pathogenetic relationship, to suggest and predict the effectiveness of personalized vitamin D supplementation regimens. © 2022 by the Author(s).

Evaluating the Role of BglI rs739837 and TaqI rs731236 Polymorphisms in Vitamin D Receptor with SARS-CoV-2 Variants Mortality Rate.

A lack of vitamin D is a potential risk factor for coronavirus disease (COVID-19). Variants in the Vitamin D Receptor (VDR) gene, such as BglI rs739837 and TaqI rs731236, are associated with various viral infection progressions. This study aimed to evaluate the relationship between the BglI rs739837 and TaqI rs731236 polymorphisms and the mortality rate of COVID-19 based on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. The genotyping of BglI rs739837 and TaqI rs731236 genotypes was analyzed using the polymerase chain reaction-restriction fragment length polymorphism in 1734 improved and 1450 deceased patients positive for SARS-CoV-2. In this study, the rate of COVID-19 mortality was correlated with TaqI rs731236 TC and CC in the α variant and with TaqI rs731236 CC in the Delta variant, whereas no relationship was found in the Omicron BA.5 variant. In addition, the rate of COVID-19 mortality was associated with BglI rs739837 GT and TT in the Omicron BA.5 variant, while there was no association between BglI rs739837 and COVID-19 mortality in the α and Delta variants. The TG haplotype was more common in all SARS-CoV-2 variants, while the CT haplotype was associated with COVID-19 mortality in the Delta and Omicron BA.5 variants. In conclusion, this study indicated that the impacts of BglI rs739837 and TaqI rs731236 polymorphisms were related to SARS-CoV-2 variants. However, further research is still needed to approve our findings.

Vitamin D in defense against the terrorism of coronavirus disease 2019: A meta-analysis

Background: Coronavirus disease 2019 (COVID-19) pandemic was also spread during winter time in December from Wuhan the city of China to worldwide. Various studies conducted throughout the world have indicated the possible relationship between Vitamin D and COVID-19 infection. Aim: This narrative review is designed to support Vitamin D role and its efficacy in managing COVID-19 menace. Materials and Methods: Latest 50 articles for Vitamin D, and COVID-19 relationship and management were scrutinized to summarize this article from data bases of PubMed and Google scholar in English language. Diagrams were created by biorender.com to summarize pictorial relations. Conclusions: Higher mortality is associated with countries of high-level Vitamin D deficiencies. Many studies have found a significant relation between Vitamin D deficiency and COVID-19 complications and related comorbidities. It is highly supported by many literature to recommend daily dose of Vitamin D3 10,000 IU/day for a few weeks to rapidly increase 25-hydroxyvitamin D levels above 40–60 ng/mL, in population at higher risk.

Vitamin D supplementation and immune-related markers: an update from nutrigenetic and nutrigenomic studies

Vitamin D is both a nutrient and a neurologic hormone that plays a critical role in modulating immune responses. While low levels of vitamin D are associated with increased susceptibility to infections and immune-related disorders, vitamin D supplementation has demonstrated immunomodulatory effects that can be protective against various diseases and infections. Vitamin D receptor is expressed in immune cells that have the ability to synthesise the active vitamin D metabolite. Thus, vitamin D acts in an autocrine manner in a local immunologic milieu in fighting against infections. Nutrigenetics and nutrigenomics are the new disciplines of nutritional science that explore the interaction between nutrients and genes using distinct approaches to decipher the mechanisms by which nutrients can influence disease development. Though molecular and observational studies have proved the immunomodulatory effects of vitamin D, only very few studies have documented the molecular insights of vitamin D supplementation. Until recently, researchers have investigated only a few selected genes involved in the vitamin D metabolic pathway that may influence the response to vitamin D supplementation and possibly disease risk. This review summarises the impact of vitamin D supplementation on immune markers from nutrigenetics and nutrigenomics perspective based on evidence collected through a structured search using PubMed, EMBASE, Science Direct and Web of Science. The research gaps and shortcomings from the existing data and future research direction of vitamin D supplementation on various immune-related disorders are discussed.

Management of COVID-19-A Review

Coronavirus disease-2019 (COVID-19) has gained much popularity not only in the Wuhan city of China but internationally also;in January 2020, the corona rapidly spread to many countries like the USA, Italy, Russia, India, Singapore, Pakistan, Thailand, Canada, Australia, England, and so on through passengers traveling to other countries. Corona patients can be cured with synthetic drugs, traditional herbal medicines (THM), use of Vitamin D and the quarantine approach. Different allopathic medicines, herbal extracts, and vitamin D have been observed to be useful in the treatment of novel coronavirus, like Remdesivir, hydroxychloroquine, Teicoplanin, Lopinavir+ Ritonavir, Ribavirin + corticosteroids, Glycyrrhizin, Sanguisorbae radix, Acanthopanacis cortex, Sophorae radix, etc. Various antiviral drugs are used to treat COVID-19, alone or in combination with other medications like Interferon-α, Lopinavir + Ritonavir, Arbidol, corticosteroids, etc., and some herbal extracts;also quarantine approach and Vitamin D are used that not only cure the infection but also boost up our immunity. For this review article, different papers were searched on Google Scholar, Scopus, WHO’s website, PubMed, clinicaltrials.gov and other relevant scientific research websites. In this review article, we have discussed the current strategies that are being used to treat COVID-19. Along with allopathic drugs, some herbal extracts can also be used to treat this novel coronavirus, like Glycyrrhizin, Sanguisorbae radix, Acanthopanacis cortex, Sophorae radix, etc. and even vitamin D.

Vitamin d in transcriptional regulation of immune response and inflammation

The predominance of the expression of pro-inflammatory genes is a sign of the inflammation onset. Overwhelming evidence suggests a role for vitamin D3 sufficiency or supplementation in reducing the inflammatory response. In addition to mineral and bone homeostasis, vitamin D3 has important effects, which include modulating innate and adaptive immunity and maintaining a tight balance between pro- and anti-inflammatory responses. In recent years, genome-wide and transcriptome-wide studies have led to a deeper understanding of the signaling network, which is responsible for cell-specific and locus-dependent gene activation by ligandregulated transcription factors. Modulation of transcription factors such as NF-?B, STAT, NFAT, AP-1, HIF-1, SMAD, PPAR etc., as well as glucocorticoid receptor signaling, may play a crucial role in the immunomodulatory activity of the hormonally active form of vitamin D3 - 1a,25(OH)2D3. Acting through the vitamin D receptor (VDR), which is a member of the nuclear receptor family of ligandregulated transcription factors, 1a,25(OH)2D3 may ensure a reduction of the inflammatory response by direct and/or indirect mechanisms. Therefore, this chapter focuses on the cross-talk of the VDR with other transcription factors in the context of antiinflammatory defense. The mechanisms involved in this modulation are usually associated with competitive binding and interactions between signaling pathways at different levels, including the gene level. We have summarized recent discoveries regarding the immunomodulatory effects of vitamin D3 on human health, with an emphasis on the interplay of transcription factors. In light of the global spread of the novel COVID-19 disease, the newly discovered importance of proper vitamin D3 status for an adequate immune response to the SARS-CoV-2 coronavirus has also been elucidated. We reviewed the most recent recommendations based on new clinical evidence for vitamin D3 dosages for the prevention and treatment of COVID-19. © 2021 by Nova Science Publishers, Inc. All rights reserved.

Calcifediol for Use in Treatment of Respiratory Disease.

Calcifediol is the prohormone of the vitamin D endocrine system (VDES). It requires hydroxylation to move to 1,25(OH)2D3 or calcitriol, the active form that exerts its functions by activating the vitamin D receptor (VDR) that is expressed in many organs, including the lungs. Due to its rapid oral absorption and because it does not require first hepatic hydroxylation, it is a good option to replace the prevalent deficiency of vitamin D (25 hydroxyvitamin D; 25OHD), to which patients with respiratory pathologies are no strangers. Correcting 25OHD deficiency can decrease the risk of upper respiratory infections and thus improve asthma and COPD control. The same happens with other respiratory pathologies and, in particular, COVID-19. Calcifediol may be a good option for raising 25OHD serum levels quickly because the profile of inflammatory cytokines exhibited by patients with inflammatory respiratory diseases, such as asthma, COPD or COVID-19, can increase the degradation of the active metabolites of the VDES. The aim of this narrative revision is to report the current evidence on the role of calcifediol in main respiratory diseases. In conclusion, good 25OHD status may have beneficial effects on the clinical course of respiratory diseases, including COVID-19. This hypothesis should be confirmed in large, randomized trials. Otherwise, a rapid correction of 25(OH)D deficiency can be useful for patients with respiratory disease.

Immunohistochemical Expression of VDR in Myocardium: Postmortem Evaluation of COVID-19 Patients.

Morphological data on heart damage and its mechanisms due to extremely severe course of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection are limited, as well as data on the correlation of damage and expression of vitamin D receptors (VDRs). In this study, we analyzed a series of myocardial samples obtained during postmortem autopsy of 48 critically ill patients with COVID-19 who died with SARS-CoV-2-associated pneumonia. The purpose of the study was to evaluate immunohistochemical VDR expression in the myocardium. The results showed the only minimal or no immunohistochemical expression of VDR in the nuclei of cardiomyocytes in most cases, along with the persisted strong expression in lymphoid cells. To the best of our knowledge, it is the first study and data provided were regarding myocardial VDR expression in COVID-19 patients. The results are of interest in terms of further study of the effects of ligand-associated VDR activation on the cardiovascular system.

Effects of VDR polymorphisms on the COVID-19 Symptoms

Vitamin D [25 (OH)D] plays a role in many of biological processes, such as bone metabolism, immunomodulation, cell proliferation, differentiation, and regulation. Also, it has anti-inflammatory, antifibrotic, and antioxidant effects. Due to the immunomodulatory effects of 25 (OH)D, its deficiency is blamed for a higher risk for COVID-19 infection. Serum concentrations of 25 (OH)D were inversely associated with proinflammatory cytokines such as increased IL-6, CRP levels, and increased risk of pneumonia or ARDS. Lower 25 (OH)D concentrations are associated with a higher risk for infections, especially from the respiratory tract [1]. Chronic vitamin D deficiency can induce the renin-angiotensin system activation and leads to fibrotic changes that can cause lung injury by inducing proinflammatory cytokine production in human monocytes/macrophages (2). Increased frequency of COVID-19 infection at high latitudes and worse prognosis of these cases made clinicians to think that 25 (OH)D levels may affect the risk and prognosis of COVID-19 infection [3]. In previous reports, in the early pandemic, a higher prevalence of vitamin D deficiency has been reported to be related to high rates of COVID-19 infection, higher risk of invasive mechanical ventilation (IMV), and mortality [6]. Whilst, it is reported that 25 (OH)D may not protect against COVID-19 infection in recent studies. Moreover, it was not associated with disease severity or lethality [4-6]. The active form of vitamin D binds to its receptor (VDR) and modulates its responses. VDR is located on chromosome 12q13, consisting of 9 exons. Vitamin D-VDR signaling regulates the expression of a wide range of physiological functions. Herein, VDR polymorphisms cause a dysfunctional receptor that affects VDR activity. Both innate and adaptive immune responses can vary according to different polymorphisms of VDR. Also VDR polymorphisms have been previously found to be associated with bacterial infections such as tuberculosis [7] and severe Respiratory Syncytial Virus (RSV) bronchiolitis in respect to vitamin D deficiency [8]. Moreover, it was demonstrated that different VDR polymorphisms such as FokI, BsmI, ApaI, and TaqI could change the course of RSV infection in several studies, respectively [8-10]. This study aimed to evaluate if there is any association between the VDR gene polymorphism at FokI, TaqI, BsmI, and ApaI alleles and the prognosis of COVID-19 in respect to vitamin D deficiency. Two-hundred ninety-seven (n=297) patients with reverse-transcription polymerase chain reaction (RT-PCR)-confirmed COVID-19 who were admitted to Marmara University Education and Research Hospital between April and October 2020 were enrolled. The severity of COVID-19 patients was classified into 1-10 according to WHO criteria. The patients' requirement for noninvasive mechanical ventilation (NIMV) or reservoir mask, their requirement for admission to intensive care unit (ICU), mortality, and WHO clinical progression scales were reviewed. Four variant regions of vitamin D receptor (VDR);FokI, BsmI, ApaI, and TaqI were determined using the Restriction Fragment Length Polymorphism (RFLP) technique. To conclude;The effect of VDR polymorphisms on the receptor function causes intensive care unit treatment, disease severity and mortality differences among patients with covid-19 infection in the clinical set-up. VDR Ff genotype was related with disease severity, TT with disease severity and aa with mortality respectively. As a result we have detected that 25 (OH)D levels were not related to COVID-19 infection severity and mortality. Additionally, it indicated that VDR polymorphisms are independently associated with the severity of COVID-19 and the survival of patients. More extensive studies are needed to determine the impact of polymorphisms on COVID-19 and explain the underlying cause.

Association of Vitamin D receptor gene polymorphisms and clinical/severe outcomes of COVID-19 patients.

INTRODUCTION: Growing evidence documented the critical impacts of vitamin D (VD) in the prognosis of COVID-19 patients. The functions of VD are dependent on the vitamin D receptor (VDR) in the VD/VDR signaling pathway. Therefore, we aimed to assess the association of VDR gene polymorphisms with COVID-19 outcomes. METHODS: In the present study, eight VDR single nucleotide polymorphisms (SNPs) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 500 COVID-19 patients in Iran, including 160 asymptomatic, 250 mild/moderate, and 90 severe/critical cases. The association of these polymorphisms with severity, clinical outcomes, and comorbidities were evaluated through the calculation of the Odds ratio (OR). RESULTS: Interestingly, significant associations were disclosed for some of the SNP-related alleles and/or genotypes in one or more genetic models with different clinical data in COVID-19 patients. Significant association of VDR-SNPs with signs, symptoms, and comorbidities was as follows: ApaI with shortness of breath (P ˂ 0.001) and asthma (P = 0.034) in severe/critical patients (group III); BsmI with chronic renal disease (P = 0.010) in mild/moderate patients (group II); Tru9I with vomiting (P = 0.031), shortness of breath (P = 0.04), and hypertension (P = 0.030); FokI with fever and hypertension (P = 0.027) in severe/critical patients (group III); CDX2 with shortness of breath (P = 0.022), hypertension (P = 0.036), and diabetes (P = 0.042) in severe/critical patients (group III); EcoRV with diabetes (P ˂ 0.001 and P = 0.045 in mild/moderate patients (group II) and severe/critical patients (group III), respectively). However, the association of VDR TaqI and BglI polymorphisms with clinical symptoms and comorbidities in COVID-19 patients was not significant. CONCLUSION: VDR gene polymorphisms might play critical roles in the vulnerability to infection and severity of COVID-19, probably by altering the risk of comorbidities. However, these results require further validation in larger studies with different ethnicities and geographical regions.