Vitamin D deficiency is associated with COVID-19 positivity and severity of the disease

Vitamin D: A key player in COVID-19 immunity and lessons from the pandemic to combat immune-evasive variants

As of the 7th of July 2024, 775,754,322 confirmed cases of COVID-19, including 7,053,902 deaths worldwide, had been reported to the WHO (World Health Organization). Nevertheless, untill the 15th of July 2024, a total of 13,578,710,228 vaccine doses had been administered, with almost no country spared from COVID-19 attacks. The pathophysiology of this virus is complicated, and several symptoms require a deep understanding of the actual mechanisms. It is unclear why some patients develop severe symptoms while others do not, although literature suggests a role for vitamin D. Vitamin D plays a crucial role in the infection or in ameliorating the severity of symptoms. The mechanism of action of vitamin D and vitamin D deficiency (VDD) is well understood. VDD is associated with increased hospitalization of severely ill patients and increased levels of COVID-19-caused mortality. Recent studies suggest that vitamin D levels and genetic variations in the vitamin D receptor (VDR) gene significantly impact the severity and outcomes of COVID-19, especially in the infections caused by Delta and Omicron variants. Furthermore, VDD causes immune system dysregulation upon infection with SARS-CoV-2, indicating that vitamin D sufficiency is crucial in fighting against COVID-19 infection. The therapeutic effect of vitamin D raises interest in its potential role as a prophylactic and treatment adjunct. We evaluate the immunomodulatory effects of vitamin D and its ability to enhance the efficacy of new antiviral drugs like molnupiravir and paxlovid against SARS-CoV-2. This review discusses the role of vitamin D sufficiency and VDD in COVID-19 initiation and progression, emphasizing the molecular mechanisms by which vitamin D exerts its actions as a proactive step for the next pandemic. However, there is still no clear evidence of vitamin D's impact on prevention and treatment, leading to contradictory findings. Therefore, large-scale randomized trials are required to reach a definitive conclusion. A bibliometric analysis of publications related to vitamin D, immunity, and COVID-19 revealed a significant increase in research activity in this area, particularly in 2020-2024, underscoring the growing recognition of vitamin D's potential role in the context of the pandemic.

Development and validation of a semi-quantitative food frequency questionnaire as a tool for assessing dietary vitamin D intake among Korean women

BACKGROUND/OBJECTIVES

Appropriate vitamin D status improves bone health and chronic diseases; it has shown benefits during the coronavirus disease 2019 pandemic. Therefore, assessing vitamin D status is crucial. However, limited research on vitamin D intake among Koreans complicates understanding of its consumption. This study aimed to develop and validate a semi-quantitative food frequency questionnaire (FFQ) to assess vitamin D intake among Koreans.

SUBJECTS/METHODS

A vitamin D FFQ was developed to include 31 vitamin D source foods from 8 food groups frequently consumed by Korean adults. The study included 152 women residing in a major city in South Korea. From September 2020 to August 2022, intake was surveyed using a 12-day dietary record (12-day DR) across 4 seasons, and 2 vitamin D FFQs were conducted approximately 9-11 months apart (FFQ1 and FFQ2). Reproducibility (FFQ1 vs. FFQ2) and validity (FFQ2 vs. 12-day DR) were verified using Spearman's rank correlation, weighted kappa coefficient, intraclass correlation, and Bland-Altman plots.

RESULTS

The vitamin D intake of Korean women using the newly developed vitamin D FFQ was higher at FFQ1 (4.90 µg/day) and FFQ2 (4.58 µg/day) compared with the 12-day DR (4.07 µg/day). Additionally, the results for reproducibility and validity were demonstrated through the Spearman's rank correlation coefficient (reproducibility, 0.592; validity, 0.460), weighted kappa coefficient (reproducibility, 0.379; validity, 0.284), intraclass correlation coefficient (reproducibility, 0.599; validity, 0.543), and Bland-Altman plots (reproducibility index, 3.95%; validity index, 3.95%).

CONCLUSION

This study confirmed the newly developed vitamin D FFQ is reliable and valid for assessing vitamin D intake among Korean women. These results suggest the FFQ is an effective tool for dietary assessment, particularly in large-scale studies where year-round monitoring may not be feasible. Further validation in Korean men is crucial to enhance its applicability, enabling significant contributions to assessing vitamin D intake among Korean adults.

Clinical and Epidemiological Features of Pediatric COVID-19: A Retrospective Study

Background and Aims

There is a demand for additional data regarding the impact of coronavirus disease 2019 (COVID-19) on the pediatric population. This study sought to determine the clinical and epidemiological features of pediatric COVID-19 in Iran.

Methods

A retrospective study was performed to assess medical records of children with COVID-19 admitted to Abuzar Hospital in Ahvaz (Iran). Their clinical and demographic data were recorded.

Results

In this study, 600 medical records of pediatric COVID-19 patients were evaluated. Over 50% of them were boys. Mild, moderate, and severe manifestations of COVID-19 were identified in 250, 200, and 150 children, respectively. Patients with severe or moderate COVID-19 had substantially higher levels of various inflammatory markers (C-reactive protein (CRP), fibrinogen, and d-dimer), alanine transaminase (ALT), creatine kinase (CPK), blood urea nitrogen (BUN), neutrophils, lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatinine (Cr), bilirubin, and gamma-glutamyl transferase (GGT) compared to children with mild COVID-19 (p < 0.001); they also had lower levels of lymphocytes, hemoglobin (Hb), and vitamin D than patients with mild COVID-19 (p < 0.001). In addition, children with severe or moderate COVID-19 had a notably higher incidence of fever or dry cough and longer hospital stays than those with mild COVID-19 (p < 0.001). The prevalence of malnutrition and anemia in patients was 50.6% and 31.5%, respectively. A significant proportion of children who were underweight and stunted experienced moderate to severe COVID-19. Furthermore, there was a considerably higher prevalence of malnutrition, anemia, and vitamin D insufficiency, or deficiency in children with moderate-to-severe COVID-19 compared to patients with mild COVID-19 (p < 0.001).

Conclusion

The outcomes of this study revealed a significantly higher prevalence of malnutrition, anemia, vitamin D insufficiency or deficiency, elevated liver and kidney function test results, and increased inflammatory markers in children with moderate to severe COVID-19 compared to those with mild COVID-19.

Serum vitamin D levels and the severity and clinical course of COVID-19

Low vitamin D levels are associated with different pulmonary diseases, such as chronic obstructive pulmonary disease, bronchial asthma, and obstructive sleep apnea. In this study, we aimed to assess the relation between vitamin D levels and COVID-19 severity. Positive COVID-19 patients were subjected to clinical examination, computed tomography of the chest, and laboratory investigations. Serum vitamin D level was measured and correlated with the severity and the clinical course of the disease. The study included 72 patients, classified into four groups according to the severity of the disease. There was a statistically significant difference between the four groups regarding age, lymphocyte count, serum vitamin D, C-reactive protein, and lactate dehydrogenase levels. Serum vitamin D levels can be correlated with COVID-19 severity and clinical course.

Role of Calcitriol and Vitamin D Receptor (VDR) Gene Polymorphisms in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) buildup and neuronal degeneration. An association between low serum vitamin D levels and an increased risk of AD has been reported in several epidemiological studies. Calcitriol (1,25-dihydroxycholecalciferol) is the active form of vitamin D, and is generated in the kidney and many other tissues/organs, including the brain. It is a steroid hormone that regulates important functions like calcium/phosphorous levels, bone mineralization, and immunomodulation, indicating its broader systemic significance. In addition, calcitriol confers neuroprotection by mitigating oxidative stress and neuroinflammation, promoting the clearance of Aβ, myelin formation, neurogenesis, neurotransmission, and autophagy. The receptors to which calcitriol binds (vitamin D receptors; VDRs) to exert its effects are distributed over many organs and tissues, representing other significant roles of calcitriol beyond sustaining bone health. The biological effects of calcitriol are manifested through genomic (classical) and non-genomic actions through different pathways. The first is a slow genomic effect involving nuclear VDR directly affecting gene transcription. The association of AD with VDR gene polymorphisms relies on the changes in vitamin D consumption, which lowers VDR expression, protein stability, and binding affinity. It leads to the altered expression of genes involved in the neuroprotective effects of calcitriol. This review summarizes the neuroprotective mechanism of calcitriol and the role of VDR polymorphisms in AD, and might help develop potential therapeutic strategies and markers for AD in the future.

Association between Average Vitamin D Levels and COVID-19 Mortality in 19 European Countries-A Population-Based Study

Early epidemic reports have linked low average 25(OH) vitamin D levels with increased COVID-19 mortality. However, there has been limited updated research on 25(OH) vitamin D and its impact on COVID-19 mortality. This study aimed to update the initial report studying the link between vitamin D deficiency and COVID-19 mortality by using multi-country data in 19 European countries up to the middle of June 2023. COVID-19 data for 19 European countries included in this study were downloaded from Our World in Data from 1 March 2020, to 14 June 2023, and were included in the statistical analysis. The 25(OH) vitamin D average data were collected by conducting a literature review. A generalized estimation equation model was used to model the data. Compared to European countries with 25(OH) vitamin D levels of ≤50 nmol/L, European countries with 25(OH) vitamin D average levels greater than 50 nmol/L had lower COVID-19 mortality rates (RR = 0.794, 95% CI: 0.662-0.953). A statistically significant negative Spearman rank correlation was observed between 25(OH) vitamin D average levels and COVID-19 mortality. We also found significantly lower COVID-19 mortality rates in countries with high average 25(OH) vitamin D levels. Randomized trials on vitamin D supplementation are needed. In the meantime, the issue of vitamin D use should be debated in relation to the ongoing discussions of national post-COVID-19 resilience against future pandemics.

Vitamin D as a predictor of negative outcomes in hospitalized COVID-19 patients: An observational study

Introduction

Serum vitamin D deficiency is thought to be associated with worse clinical outcomes in COVID-19 patients.

Methods

This single-centre observational study evaluated the association between serum vitamin D levels and negative outcomes in hospitalized COVID-19 patients in Ukraine. We included hospitalized patients with COVID-19 confirmed by PCR and serum vitamin D measurement on admission. Patients were divided into two groups based on their serum vitamin D level: with adequate vitamin D (≥ 30 ng/ml) and with low vitamin D (<30 ng/ml). Outcomes such as death and the need for respiratory support were recorded.

Results

A total of 70 patients were included. The gender; severity of COVID-19; comorbidities such as hypertension, diabetes mellitus type 2, obesity; type of respiratory support, and the length of hospital stay did not differ in both groups. Patients with low serum vitamin D levels have higher C-reactive protein levels 26.14 mg/L [Q1, Q3: 16.61, 57.79] compared to another group 13.43 mg/L [Q1, Q3: 8.84, 27.58]. Low vitamin D level was associated with an increased risk of respiratory support need OR [Odds ratio] 2.925 [95% CI, 1.0839 to 7.8931]. However, after adjustment for age, gender, and common comorbidities, it did not remain significant. Vitamin D serum levels did not significantly differ in patients who died during hospitalization compared to those who survived.

Conclusion

The role of vitamin D as a sole predictor of mortality and respiratory support appears to be overestimated. Low vitamin D levels may have a greater impact on COVID-19 outcomes in hospitalized elderly patients with comorbidities.

Impact of Vitamin D Therapy on C-Reactive Protein, Ferritin, and IL-6 Levels in Hospitalised Covid-19 Patients

Vitamin D insufficiency is associated with poor prognosis in COVID-19 patients. Vitamin D supplementation is related to improved clinical outcomes in terms of intensive care unit admission and death, particularly in individuals with moderate-to-severe forms of COVID-19. The placebo-controlled five-day study was performed on 99 hospitalised COVID-19 patients with vitamin D insufficiency randomised into two groups. Vitamin D in the form of a sublingual sprayable microemulsion was given three times daily (daily dose 12,000 IU) to 51 patients with blood 25(OH)D levels below 30 ng/ml. Forty-eight patients in the control group received a placebo spray in the same daily regimen. Intention-to-treat (ITT) analysis and pre-protocol analysis were used to verify the impact of 25(OH)D level elevation on inflammatory markers. There was a statistically significant increase by 8.7 ± 7.6 ng/ml in 25(OH)D level from the baseline level of 15.6 ± 6.5 ng/ml in the case group. Individuals with moderately severe disease showed negative correlation between changes in 25(OH)D and C-reactive protein (CRP) levels in both ITT and pre-protocol analysis (p < 0.05). Mild and severe cases showed no statistical significance in CRP levels. There were no statistically significant changes in ferritin and IL-6 levels in ITT and pre-protocol analysis. In conclusion, high-dose vitamin D therapy was accompanied by significant decrease in CRP levels in COVID-19 patients with a moderate to severe illness.

Vitamin D Deficiency in COVID-19 Patients and Role of Calcifediol Supplementation

Hypovitaminosis D has been associated with worse outcome in respiratory tract infections, with conflicting opinions regarding its role in Coronavirus-19 disease (COVID-19). Our study aimed to evaluate the possible relationship between 25-OH vitamin D (25OHD) values and the following conditions in patients hospitalized for COVID-19: prognosis, mortality, invasive (IV) and non-invasive (NIV) mechanical ventilation, and orotracheal intubation (OTI). A further objective was the analysis of a possible positive effect of supplementation with calcifediol on COVID-19 severity and prognosis. We analyzed 288 patients hospitalized at the San Giovanni di Dio Hospital in Florence and the Santa Maria alle Scotte Hospital in Siena, from November 2020 to February 2021. The 25OHD levels correlated positively with the partial pressure of oxygen and FiO2 (PaO2/FiO2) ratio (r = 0.17; p < 0.05). Furthermore, when we analyzed the patients according to the type of respiratory support, we found that 25OHD levels were markedly reduced in patients who underwent non-invasive ventilation and orotracheal intubation (OTI). The evaluation of the length of hospitalization in our population evidenced a longer duration of hospitalization in patients with severe 25OHD deficiency (<10 ng/mL). Moreover, we found a statistically significant difference in the mortality rate between patients who had 25OHD levels below 10 ng/mL and those with levels above this threshold in the total population (50.8% vs. 25.5%, p = 0.005), as well as between patients with 25OHD levels below 20 ng/mL and those with levels above that threshold (38.4% vs. 24.6%, p = 0.04). Moreover, COVID-19 patients supplemented with calcifediol presented a significantly reduced length of hospitalization (p < 0.05). Interestingly, when we analyzed the possible effects of calcifediol on mortality rate in patients with COVID-19, we found that the percentage of deaths was significantly higher in patients who did not receive any supplementation than in those who were treated with calcifediol (p < 0.05) In conclusion, we have demonstrated with our study the best prognosis of COVID-19 patients with adequate vitamin D levels and patients treated with calcifediol supplementation.

High-dose vitamin D supplementation is related to an improvement in serum alkaline phosphatase in COVID-19 patients; a randomized double-blinded clinical trial

BACKGROUND

The benefits and harms of vitamin D supplementation in the treatment of COVID-19 have not yet been fully documented. In this study, we aimed to evaluate the effects of high-dose vitamin D supplementation on liver function tests in COVID-19.

METHOD

This double-blinded randomized clinical trial was conducted on 140 hospitalized patients aged > 30 years. Patients were randomly allocated to receive either intervention group (n = 70 receiving 50,000 IU of vitamin D capsules orally as a single dose and then 10,000 IU syrup daily from the second day of admission for 30 days) and the control group (n = 70 receiving 1000 IU vitamin D syrup orally per day). Liver function tests (LFT), including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), and Lactate Dehydrogenase (LDH) were evaluated at baseline and at the end of the intervention. Decision tree analysis was performed to identify the predictors for change in liver enzymes.

RESULTS

Among COVID-19 patients, a significant decrease was observed in serum level of ALP between intervention and placebo groups (p = 0.04). In addition, decision tree analysis revealed that GGT, temperature, serum magnesium level at baseline and gender were the most important predictors of ALT changes in COVID-19 patients.

CONCLUSION

High-dose vitamin D supplementation improved ALP markers among COVID-19 patients. More randomized controlled trials with longer follow-up times will be required.

Long-term in vivo vitamin D3 supplementation modulates bovine IL-1 and chemokine responses

Vitamin D deficiency at birth, followed by prolonged insufficiency in early life may predispose bovine calves to infection and disease. However, the effects of vitamin D levels on innate immunity are unclear due to the lack of long-term supplementation trials in vivo and reliable approaches for reproducibly assessing immune function. Here, a standardized whole blood immunophenotyping assay was used to compare innate immune responses to infection relevant ligands (LPS, Pam3CSK4 and R848) between Holstein-Friesian calves supplemented with vitamin D (n = 12) from birth until 7 months of age and control calves (n = 10) raised on an industry standard diet. Transcriptomic analysis in unstimulated whole blood cells revealed increased expression of type I interferons and chemokines in vitamin D supplemented calves, while IL-1 and inflammasome gene expression was decreased. In response to stimulation with the bacterial ligand LPS, supplemented calves had significantly increased expression of CASP1, CX3CR1, CAT, whereas STAT1 was decreased. Stimulation with the bacterial ligand Pam3CSK4 revealed increased expression of IL1A, IL1B and CAT genes; and decreased C5AR1 expression. In response to the viral ligand R848, STAT1 and S100A8 expression was significantly decreased. An increased IL-1 and inflammasome gene expression signature in vitamin D supplemented calves in response to LPS and Pam3CSK4 was also found, with ELISA confirming increased IL-1β protein production. In contrast, a decreased chemokine gene expression signature was found in response to R848 in supplemented animals, with decreased IL-8 protein expression exhibited in response to all PAMPs also found. These results demonstrated expression of several cytokine, chemokine and inflammasome genes were impacted by vitamin D supplementation in the first 7 months of life, with IL-8 expression particularly responsive to vitamin D. Overall, vitamin D supplementation induced differential innate immune responses of blood immune cells that could have important implications for disease susceptibility in cattle.

SARS-COV-2 infection and Parkinson's disease: Possible links and perspectives

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra. The hallmarks are the presence of Lewy bodies composed mainly of aggregated α-synuclein and immune activation and inflammation in the brain. The neurotropism of SARS-CoV-2 with induction of cytokine storm and neuroinflammation can contribute to the development of PD. Interestingly, overexpression of α-synuclein in PD patients may limit SARS-CoV-2 neuroinvasion and degeneration of dopaminergic neurons; however, on the other hand, this virus can speed up the α-synuclein aggregation. The review aims to discuss the potential link between COVID-19 and the risk of PD, highlighting the need for further studies to authenticate the potential association. We have also overviewed the influence of SARS-CoV-2 infection on the PD course and management. In this context, we presented the prospects for controlling the COVID-19 pandemic and related PD cases that, beyond global vaccination and novel anti-SARS-CoV-2 agents, may include the development of graphene-based nanoscale platforms offering antiviral and anti-amyloid strategies against PD.

Vitamin D as a prognostic biomarker in COVID-19: single-center study and meta-analyses

Vitamin D was investigated as a prognostic biomarker in COVID-19, in relation to both disease susceptibility and outcomes in infected individuals. Patients admitted to the hospital with a confirmed COVID-19 diagnosis were included if they had a vitamin D measurement prior to hospitalization. Using age- and sex-matched controls, vitamin D levels were investigated for an association with COVID-19 related hospitalizations. Further, vitamin D levels were investigated for an association with 30-day mortality in hospitalized COVID-19 patients. Additionally, three meta-analyses were conducted, investigating the association of vitamin D with the following outcomes: Having a positive SARS-CoV-2 test, hospitalization with COVID-19, and mortality in COVID-19 patients. A total of 685 hospitalized COVID-19 patients were included in the single-center study. Compared to controls, they had higher vitamin D levels. Unadjusted analysis of these 685 cases found higher vitamin D levels associated with increased 30-day mortality. This association disappeared after adjusting for age. In the fully adjusted model, no association between vitamin D and 30-day mortality was found. The meta-analyses found significant associations between lower vitamin D and having a positive SARS-CoV-2 test, and mortality among hospital-admitted COVID-19 patients. The relationship between lower vitamin D and COVID-19 related hospital admissions trended towards being positive but was not statistically significant. Many factors seem to influence the associations between vitamin D and COVID-19 related outcomes. Consequently, we do not believe that vitamin D in and of itself is likely to be a clinically useful and widely applicable predictor for the susceptibility and severity of COVID-19 infections.

Potential treatments of COVID-19: Drug repurposing and therapeutic interventions

The coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The infection is caused when Spike-protein (S-protein) present on the surface of SARS-CoV-2 interacts with human cell surface receptor, Angiotensin-converting enzyme 2 (ACE2). This binding facilitates SARS-CoV-2 genome entry into the human cells, which in turn causes infection. Since the beginning of the pandemic, many different therapies have been developed to combat COVID-19, including treatment and prevention. This review is focused on the currently adapted and certain other potential therapies for COVID-19 treatment, which include drug repurposing, vaccines and drug-free therapies. The efficacy of various treatment options is constantly being tested through clinical trials and in vivo studies before they are made medically available to the public.

Vitamin D on COVID-19 Patients During the Pandemic, 2022. A Systematic Review and Meta-Analysis

Numerous connections between the level of vitamin D (Vit-D) and the novel coronavirus disease -19 (COVID-19) have surfaced during the pandemic. So, we conducted this systematic review and meta-analysis to explore the effect of Vit-D deficiency and its supplementation on the clinical outcomes of COVID-19 patients. We looked for relevant articles in Cochrane Library, Scopus, Web Science, PubMed, and EBSCO up until the end of 2022. The Open Meta Analyst software was used to analyze the extracted data. We classified them into two main categories based on their objectives. First, the studies that evaluated the effects of Vit-D deficiency in patients, and lastly, the studies that evaluated Vit-D as a supplement, both on mortality rate, hospitalization duration, ICU admission rate, and mechanical ventilation rate. A total of 8001 COVID-19 patients from 42 studies were included. A high serum Vit-D concentration compared to those with lower levels was associated with a significantly lower mortality rate (RR = 1.5, 95% CI = 1.11: 2.02, p = 0.01). According to the estimated effect of 18 studies, those who took Vit-D supplements had a significantly lower mortality rate, hospitalization duration, ICU admission rate, and mechanical ventilation rate than those who did not. The group receiving Vit-D doses between 50 000 to 100 000 IU had a significantly better clinical outcome compared to lower and higher doses. COVID-19 patients with normal Vit-D levels had significantly lower death rates than those with hypovitaminosis. Vit-D supplements in COVID-19 significantly improved clinical outcomes. Vit-D supplementation between 50 000 to 100 000 IU, in patients with COVID-19 significantly outperformed other doses in terms of mortality.

Association of Vitamin D levels on the Clinical Outcomes of Patients Hospitalized for COVID-19 in a Tertiary Hospital

OBJECTIVES

This study aimed to compare the severity of COVID-19, inflammatory parameters and clinical outcomes among patients with normal and subnormal levels of Vitamin D.

METHODOLOGY

This is a retrospective cohort study of 135 patients admitted in a tertiary hospital for COVID-19. Patients were grouped according to their Vitamin D level. Primary outcome measure was the composite of all-cause mortality and morbidity. Other outcome measures determined were the comparison among the groups on the severity of COVID-19 infection, changes in inflammatory parameters, length of hospital stay and duration of respiratory support.

RESULTS

There was a significant trend of higher ICU admission (p=0.024), mortality (p=0.006) and poor clinical outcome (p=0.009) among the Vitamin D deficient group. No significant difference was found for most of the inflammatory parameters, duration of hospital stay and respiratory support. Overall, patients with deficient, but not insufficient Vitamin D level had 6 times higher odds of composite poor outcome than those with normal Vitamin D (crude OR=5.18, p=0.003; adjusted OR=6.3, p=0.043).

CONCLUSION

The inverse relationship between Vitamin D level and poor composite outcome observed in our study suggests that low Vitamin D may be a risk factor for poor prognosis among patients admitted for COVID-19.

COVID-19 and Multiple Sclerosis: A Complex Relationship Possibly Aggravated by Low Vitamin D Levels

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an exceptionally transmissible and pathogenic coronavirus that appeared at the end of 2019 and triggered a pandemic of acute respiratory disease, known as coronavirus disease 2019 (COVID-19). COVID-19 can evolve into a severe disease associated with immediate and delayed sequelae in different organs, including the central nervous system (CNS). A topic that deserves attention in this context is the complex relationship between SARS-CoV-2 infection and multiple sclerosis (MS). Here, we initially described the clinical and immunopathogenic characteristics of these two illnesses, accentuating the fact that COVID-19 can, in defined patients, reach the CNS, the target tissue of the MS autoimmune process. The well-known contribution of viral agents such as the Epstein-Barr virus and the postulated participation of SARS-CoV-2 as a risk factor for the triggering or worsening of MS are then described. We emphasize the contribution of vitamin D in this scenario, considering its relevance in the susceptibility, severity and control of both pathologies. Finally, we discuss the experimental animal models that could be explored to better understand the complex interplay of these two diseases, including the possible use of vitamin D as an adjunct immunomodulator to treat them.

The Pandemic and Your Skin—Direct and Indirect Impact of COVID-19

Apart from well-known respiratory symptoms, less frequent symptoms also appear as a direct result of COVID-19 infection, or as indirect effects of the recommended quarantine and related lifestyle changes. The impact of the COVID-19 pandemic on human skin is predominantly focused on in this article. Cutaneous manifestations, including redness, chilblain-like symptoms (COVID toes), hives or urticaria rash, water blisters, and fishing net-like red-blue patterns on the skin, may appear as accompanying or as systemic COVID-19 symptoms with potential lesions at different skin sites. These symptoms were related to skin phototypes and vitamin D deficiency. Moreover, Black, Asian, and minority ethnic origin patients are found to be more sensitive to COVID-19 infection than Caucasians because of vitamin D deficiency. The region of population with lighter skin phototypes have a significantly higher chance to develop cutaneous manifestations than population with dark skin. In addition, adverse effects, such as skin barrier damage and irritation, may also occur due to extensive personal protective equipment usage (e.g., masks, protective suits, and a few others) and predominately alcohol-based sanitizers. This manuscript covers various aspects of COVID-19 and its clinical skin manifestations.

Effect of Vitamin D3 Supplementation vs. Dietary-Hygienic Measures on SARS-CoV-2 Infection Rates in Hospital Workers with 25-Hydroxyvitamin D3 [25(OH)D3] Levels ≥20 ng/mL

Background: There is scant information on the effect of supplementation with vitamin D3 in SARS-CoV-2 infection cases when patient 25-hydroxyvitamin D3 [25(OH)D3] levels are between 20-100 ng/mL. We aimed to evaluate the effect of supplementation with vitamin D3 vs. dietary-hygienic measures on the SARS-CoV-2 infection rate in participants with serum 25(OH)D3 levels ≥20 ng/mL. Methods: This study was quasi-experimental. We invited hospital workers with 25(OH)D3 levels between 20-100 ng/mL and no previous SARS-CoV-2 infection. They were randomized as follows: treatment options were a) vitamin D3 supplementation (52,000 IU monthly, G1) or b) dietary-hygienic measures (G2). We conducted a 3- to 6-month follow-up of SARS-CoV-2 infections. Participants with 25(OH)D3 levels <20 ng/mL were also analyzed. We divided these latter participants depending on whether they were supplemented (G3) or not (G4). Results: We analyzed 198 participants, with an average age of 44.4 (SD 9) years, and 130 (65.7%) were women. G1 had fewer cases of SARS-CoV-2 infection than G2 after a follow-up of 3- to 6-months (p < 0.05). There were no differences between G3 and G4 at the 3- and 6-month follow-up cutoff points (p > 0.05). Using a mixed effect Cox regression analysis in the 164 participants that completed six months of follow-up, vitamin D3 supplementation appeared to act as a protective factor against SARS-CoV-2 infection (HR 0.21, p = 0.008) in G1 and G2. None of the participants treated with the supplementation doses had serum 25(OH)D3 levels >100 ng/mL. Conclusions: Vitamin D3 supplementation in participants with 25(OH)D3 levels between 20-100 ng/mL have a lower rate of SARS-CoV-2 infection compared with the use of dietary-hygienic measures at six months follow-up.

Neutrophilia and its correlation with increased inflammatory response in COVID-19 in diabetic and pre-diabetic patients

Background: Hyperglycemic patients are at a high risk of COVID-19 severity. Neutrophils have been considered critical effector cells in COVID-19 development. Vitamin D deficiency is prevalent in hyperglycemic patients and was found to adversely associate with the neutrophil count.

Aim: The goal of this work was to evaluate the characteristics of diabetic and pre-diabetic COVID-19 patients and discovered changes in neutrophils and their correlation, if any, with disease clinical presentation.

Patients and Methods: The study included total of (514) Covid-19 positive patients confirmed by PCR and recruited from the Prince Mohammad Bin Abdulaziz Hospital in Riyadh, Saudi Arabia. Patient’s clinical characteristics were collected for all patients. Laboratory tests include HbA1c, neutrophil count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), ferritin, D- dimer, 25 hydroxy vitamin D (25(OH)D), and folate.

Results: The results found that 286 patients (55.6%) were diabetic, 77 patients (15%) were pre-diabetic and 151 (29.4%) were normoglycaemic. A significant difference was exhibited regarding the neutrophil count and inflammatory factors of COVID-19 severity. Furthermore, the neutrophil count was found to be directly correlated with the severity monitoring biochemical markers for Covid-19: CRP, ESR, ferritin, and D-dimer and inversely associated with vitamin D levels in diabetic and pre-diabetic patients.

Conclusion: Our findings highlight the change of neutrophils in COVID-19 diabetic and pre-diabetic patients that was found to correlate positively with CRP, ESR, ferritin, and D-dimer, and negatively with 25(OH)D, but their correlation with the clinical presentation of the disease need further large investigations.

The association between serum 25-hydroxyvitamin D and the prevalence of herpes simplex virus

Previous studies have reported a potential anti-infection effect for vitamin D. However, the relationship between vitamin D status and herpes simplex virus (HSV) infection has not yet been evaluated. Therefore, this study aimed to determine the association between serum 25-hydroxyvitamin D [25(OH)D] and infection with HSV types 1 and 2 (HSV-1 and HSV-2). Data were collected from the National Health and Nutrition Examination Survey from 2007 to 2016. The association between 25(OH)D and HSV prevalence was evaluated using propensity score matching (PSM) and univariate and multivariate logistic regression analyses. Overall, 14 174 participants were included in the final analysis. Before PSM, 8639 (60.9%) had positive HSV-1 and 2636 (18.6%) had HSV-2. The HSV-1 and HSV-2 positive groups had more females and older individuals (p < 0.05). The HSV-2 patients had lower 25(OH)D levels than those with HSV-1. Age and gender did not differ in the groups after PSM (p > 0.05). The 25(OH)D level was significantly lower in the HSV-1 and HSV-2 groups than in the non-HSV infection groups. Multivariate logistic regression showed that serum 25(OH)D level was negatively associated with HSV-1 and HSV-2 infection (odds ratio [OR] = 0.730 and 0.691, p < 0.001, respectively). Vitamin D deficiency was an independent risk factor for both HSV-1 and HSV-2 (adjusted OR = 2.205 and 2.704, p < 0.001, respectively). Lower serum 25(OH)D levels correlated significantly with increased HSV-1 and HSV-2 infection risk.

Immunomodulatory and therapeutic implications of vitamin D in the management of COVID-19

COVID-19 has caused severe financial, clinical, and sociological consequences besides posing a burden on healthcare. Many nutritional approaches have been employed to manage the deleterious consequences of COVID-19. Among the several micronutrients, vitamin D deprivation has been linked to an increased likelihood of hospitalization of COVID-19 patients. Vitamin D has been reported to be a critical regulator of the renin-angiotensin system, which is used by the SARS-CoV-2 to access the host cell. Vitamin D also modulates the multiple immune system mechanisms to contain the virus, including the curtailment of the viral entry into the host cell. The adequate levels of vitamin D in the host have been associated with the reduced release of proinflammatory cytokines, thus lowering the risk of a cytokine storm; increased levels of anti-inflammatory cytokines and enhanced secretion of natural antimicrobial peptides. It may also be involved in the enhancement of the Th2 immune response and activation of defensive cells such as macrophages. Contrary to these findings, several studies have concluded that there is no direct association between vitamin D concentrations and poor prognosis of the disease. Hence, this paper aims to decipher the immunoregulatory properties of vitamin D and its possible involvement in management of COVID-19.

Examining the role of micronutrients on improving long COVID sleep-related symptoms

AIMS AND OBJECTIVES

Long COVID is defined as the continuation of symptoms for four or more weeks after initial contraction of the virus. This review article examines the role of four select micronutrients (zinc, vitamins C, D and polyphenols) for their anti-inflammatory and therapeutic potential to improve sleep-related symptoms in persons with long COVID.

BACKGROUND

Evidence suggests a link between long COVID and increased inflammation. There are currently no therapeutic interventions for common sleep-related symptoms associated with long COVID. Micronutrients, due to their antioxidant and anti-inflammatory properties, may have a role in the treatment of sleep-related symptoms in the context of long COVID.

DESIGN

A narrative literature review was conducted and guided by the PRISMA checklist.

METHODS

All articles were screened from PubMed, ScienceDirect, NCBI or Google Scholar and were limited to human studies. The following keywords were used: 'COVID-19', 'sleep symptoms', 'zinc', 'vitamin C', 'vitamin D', 'polyphenols' and 'micronutrients'.

RESULTS

There are currently no studies that examine the usage of micronutrients and its impacts on long-term, sleep-related symptoms post-COVID-19 infection. We focussed our review on prior studies that examined micronutrients in the context of sleep symptoms and inflammation, while exploring the potential for micronutrients to help improve sleep-related symptoms associated with long COVID.

CONCLUSIONS

There is evidence to suggest that sleep-related symptoms associated with long COVID, such as fatigue and poor sleep quality, are associated with inflammation. Zinc, vitamins C, D and polyphenols all have the potential to improve both inflammation and sleep quality to alleviate symptoms. Future research should further examine these micronutrients in the context of long COVID to improve sleep and quality of life.

RELEVANCE TO CLINICAL PRACTICE

This article provides implications for clinicians to be at the forefront of research on the usage of micronutrients to improve sleep-related symptoms in persons with long COVID.

Can vitamin D status influence seroconversion to SARS-COV2 vaccines?

Existing data indicate an association between vitamin D deficiency and increased severity of respiratory distress due to COVID-19 infection, especially in high-risk populations. To date, the effect of vitamin D on immunogenicity to SARS-CoV-2 vaccines has been investigated solely in young healthcare workers in a few studies, yielding conflicting findings, yet highlighting that the response to immunization is inversely related to age. Vitamin D status can potentially influence the antibody titers in people with a previous (or naïve) SARS-CoV-2 infection and vaccination, given its role in immune regulatory functions. From this standpoint, vitamin D supplementation can help reduce the risk of SARS-CoV-2 infection, COVID-19 severity/mortality and rebalance immunological function, particularly in subjects with vigorous T lymphocyte responses to COVID-19. However, more research is needed to establish a correlation between vitamin D status and the generation of protective serological responses to SARS-CoV-2 vaccination.

Vitamin D Deficiency Association with Comorbid Diseases in Palestine: "A Cross-Sectional Observation Study"

BACKGROUND

Vitamin D deficiency (VDD) is a global health concern. This study aimed to determine the prevalence of vitamin D deficiency and its associated comorbidities in Palestine, such as diabetes mellitus, hypertension, hyperlipidemia, and cardiovascular and autoimmune diseases.

METHODS

A retrospective, descriptive study retrieved medical data from the Nat Health insurance processor database from 2014 to 2020. Patient information included age, sex, vitamin D laboratory order, symptoms, and comorbidities. This study included patients prescribed vitamin D at a dose of 50000IU for vitamin D deficiency confirmed by a serum vitamin D laboratory test. The collected data were analyzed using IBM SPSS. In addition, a chi-square test was conducted to assess the association between vitamin D deficiency, symptoms, and comorbidities.

RESULTS

Data of 3011 patients were collected; 639 patients were diagnosed with osteoporosis, and 39 patients prescribed vitamin D without a laboratory test were excluded. Approximately, 1837 (78%) participants had vitamin D deficiency. A total of 1330 women (81.3%) were significantly more likely to have vitamin D deficiency than males, 507 (72.7%; P < 0.001). Joint pain, back pain, and cervicalgia were significantly associated with vitamin D deficiency (P < 0.001). Asymptomatic participants (2.1%) were significantly less likely to have vitamin D deficiency than symptomatic participants (9.5%, p < 0.001). Hypothyroidism is significantly associated with vitamin D deficiency (p = 0.048).

CONCLUSION

In this retrospective study, the prevalence of vitamin D was high and alarming. There was a significant association between VDD, patients who presented with back pain, arthritis, and cervicalgia symptoms, and patients diagnosed with hypothyroidism. Therefore, health initiative programs are warranted to increase awareness regarding screening, prevention, and treatment. Further studies are needed to confirm the relationship between vitamin D supplementation and the reduced risk of comorbid diseases.

SARS-CoV-2 infection and diabetes: Pathophysiological mechanism of multi-system organ failure

Since the discovery of the coronavirus disease 2019 outbreak, a vast majority of studies have been carried out that confirmed the worst outcome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in people with preexisting health conditions, including diabetes, obesity, hypertension, cancer, and cardiovascular diseases. Likewise, diabetes itself is one of the leading causes of global public health concerns that impose a heavy global burden on public health as well as socio-economic development. Both diabetes and SARS-CoV-2 infection have their independent ability to induce the pathogenesis and severity of multi-system organ failure, while the co-existence of these two culprits can accelerate the rate of disease progression and magnify the severity of the disease. However, the exact pathophysiology of multi-system organ failure in diabetic patients after SARS-CoV-2 infection is still obscure. This review summarized the organ-specific possible molecular mechanisms of SARS-CoV-2 and diabetes-induced pathophysiology of several diseases of multiple organs, including the lungs, heart, kidneys, brain, eyes, gastrointestinal system, and bones, and sub-sequent manifestation of multi-system organ failure.

The impact of vitamin and mineral supplements usage prior to COVID-19 infection on disease severity and hospitalization

The COVID-19 pandemic has caused a global public health emergency. Nutritional status is suggested to be related to the severity of COVID-19 infection. Herein, we aimed to explore the impact of using vitamin and mineral supplements prior to COVID-19 infection on disease severity and hospitalization. In addition, the prior use of aspirin as an anticoagulant on the disease severity was investigated. A cross-sectional, self-administered survey was conducted between March and July 2021. Recovered COVID-19 individuals (age ≥ 18 years, n = 2148) were recruited in the study. A multivariate logistic regression was used to evaluate the associations of supplements and aspirin use with COVID-19 disease severity and hospitalization status. Among the participants, 12.1% reported symptoms consistent with severe COVID-19, and 10.2% were hospitalized due to COVID-19. After adjustment for confounding variables (age, gender, BMI, cigarette smoking status, and the number of comorbidities), the multivariate logistic regression model showed that the consumption of vitamin D supplements prior to COVID-19 infection was associated with a significant decrease in disease severity (OR = 0.68, 95% CI 0.50 - 0.92; P = 0.01), and a lower risk of hospitalization (OR = 0.64, 95% CI 0.45 - 0.89; P = 0.01). On the other hand, there were no significant differences in the frequencies of severe illness and hospitalizations with the consumption of vitamin A, folic acid, vitamin B12, vitamin B complex, vitamin C, zinc, iron, selenium, calcium, magnesium, omega 3, and aspirin before COVID-19 infection. Among the investigated nutrients, the use of vitamin D prior to COVID-19 infection was associated with reduced disease severity and hospitalization. However, more studies are required to confirm this finding.

Long-term implications of COVID-19 on bone health: pathophysiology and therapeutics

BACKGROUND

SARS-CoV-2 is a highly infectious respiratory virus associated with coronavirus disease (COVID-19). Discoveries in the field revealed that inflammatory conditions exert a negative impact on bone metabolism; however, only limited studies reported the consequences of SARS-CoV-2 infection on skeletal homeostasis. Inflammatory immune cells (T helper-Th17 cells and macrophages) and their signature cytokines such as interleukin (IL)-6, IL-17, and tumor necrosis factor-alpha (TNF-α) are the major contributors to the cytokine storm observed in COVID-19 disease. Our group along with others has proven that an enhanced population of both inflammatory innate (Dendritic cells-DCs, macrophages, etc.) and adaptive (Th1, Th17, etc.) immune cells, along with their signature cytokines (IL-17, TNF-α, IFN-γ, IL-6, etc.), are associated with various inflammatory bone loss conditions. Moreover, several pieces of evidence suggest that SARS-CoV-2 infects various organs of the body via angiotensin-converting enzyme 2 (ACE2) receptors including bone cells (osteoblasts-OBs and osteoclasts-OCs). This evidence thus clearly highlights both the direct and indirect impact of SARS-CoV-2 on the physiological bone remodeling process. Moreover, data from the previous SARS-CoV outbreak in 2002-2004 revealed the long-term negative impact (decreased bone mineral density-BMDs) of these infections on bone health.

METHODOLOGY

We used the keywords "immunopathogenesis of SARS-CoV-2," "SARS-CoV-2 and bone cells," "factors influencing bone health and COVID-19," "GUT microbiota," and "COVID-19 and Bone health" to integrate the topics for making this review article by searching the following electronic databases: PubMed, Google Scholar, and Scopus.

CONCLUSION

Current evidence and reports indicate the direct relation between SARS-CoV-2 infection and bone health and thus warrant future research in this field. It would be imperative to assess the post-COVID-19 fracture risk of SARS-CoV-2-infected individuals by simultaneously monitoring them for bone metabolism/biochemical markers. Importantly, several emerging research suggest that dysbiosis of the gut microbiota-GM (established role in inflammatory bone loss conditions) is further involved in the severity of COVID-19 disease. In the present review, we thus also highlight the importance of dietary interventions including probiotics (modulating dysbiotic GM) as an adjunct therapeutic alternative in the treatment and management of long-term consequences of COVID-19 on bone health.

Influence of vitamin D levels on outcomes and nosocomial COVID-19 infection in patients undergoing total knee arthroplasty- a cohort study

Purpose

This study aimed to audit the effects of vitamin D3 on the early functional outcomes, the incidence of nosocomial COVID-19 infection and complications in patients undergoing elective Total Knee Arthroplasty (TKA).

Methods

This was a retrospective study involving patients undergoing primary unilateral TKA between January 2020 to May 2021 operated by a single surgeon using a single implant. Participants were divided into two cohorts, Deficient-vitamin D3 level <20 ng/ml and Sufficient-vitamin D3 level ≥20 ng/ml. Assessment for Knee Society Score and Oxford Knee Score (OKS) was done preoperatively and one year after TKA. Nosocomial COVID-19 infection rate, 30-day re-admissions and complications were noted during the study.

Results

235 patients were divided into 2 cohorts matched by age, gender and ASA grades. 74 patients belonged to the deficient group and 161 belonged to the sufficient group. The mean preoperative scores in the sufficient group were higher than the deficient group (OKS = 15.74 vs 12.95; KSS = 88.91vs 85.62). Similarly, the one-year postoperative scores in the sufficient group were significantly higher (OKS = 36.54 vs 35.16; KSS = 164.01 vs 161.22). A linear correlation was present between preoperative score (r = 0.273) & post-operative scores (r = 0.141) with serum vitamin D3 levels. Vitamin D3 deficient individuals had higher nosocomial COVID-19 infection rate (10.81% vs 4.96%,p = 0.16). The incidence of complications like DVT, embolism, stroke, infection and fracture were not statistically different in the two groups.

Conclusion

Vitamin D positively influences the outcomes of TKA and protects against nosocomial COVID-19 infection in patients undergoing elective TKA.

VDR gene polymorphisms are associated with the increased susceptibility to COVID-19 among iranian population: A case-control study

Coronavirus disease 2019 (COVID‐19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), but the pathogenesis is unclear. Host genetic background is one of the main factors influencing the patients' susceptibility to several viral infectious diseases. This study aimed to investigate the association between host genetic polymorphisms of two genes, including vitamin D receptor (VDR) and vitamin D binding protein (DBP), and susceptibility to COVID‐19 in a sample of the Iranian population. This case‐control study enrolled 188 hospitalized COVID‐19 patients as the case group and 218 suspected COVID‐19 patients with mild signs as the control group. The VDR (rs7975232, rs731236 and rs2228570) and DBP (rs7041) gene single nucleotide polymorphisms (SNPs) were genotyped by Polymerase Chain Reaction Restriction – Fragment Length Polymorphism (PCR‐RFLP) method. A significant association between rs2228570 SNP in the VDR gene and the susceptibility of COVID‐19 was found between case and control groups. The CT genotype (Heterozygous) of rs2228570 C > T polymorphism showed significant association with a 3.088 fold increased odds of COVID‐19 (p < .0001; adjusted OR: 3.088; 95% CI: 1.902–5.012). In addition, a significant association between CC genotype of rs2228570 CT polymorphism and increased odds of COVID‐19 in male and female groups (p = .001; adjusted OR: 3.125; 95% CI: 1.630–5.991 and p = .002; adjusted OR: 3.071; 95% CI: 1.485–6.354 respectively) were determined. Our results revealed no significant differences in the frequency of genotype and allele of VDR (rs7975232 and rs731236) and DBP (rs7041) between SARS‐CoV‐2‐infected patients and controls (p > .05). Our results showed that polymorphism of VDR (rs2228570) probably could influence individual susceptibility to COVID‐19. The polymorphisms of VDR (rs7975232 and rs731236) and DBP (rs7041) were not associated with SARS‐CoV‐2 infection susceptibility.

Prognostic and Therapeutic Role of Vitamin D in COVID-19: Systematic Review and Meta-analysis

PURPOSE

Vitamin D deficiency/insufficiency may increase the susceptibility to coronavirus disease 2019 (COVID-19). We aimed to determine the association between vitamin D deficiency/insufficiency and susceptibility to COVID-19, its severity, mortality, and role of vitamin D in its treatment.

METHODS

We searched CINAHL, Cochrane library, EMBASE, PubMED, Scopus, and Web of Science up to May 30, 2021, for observational studies on association between vitamin D deficiency/insufficiency and susceptibility to COVID-19, severe disease, and death among adults, and, randomized controlled trials (RCTs) comparing vitamin D treatment against standard care or placebo, in improving severity or mortality among adults with COVID-19. Risk of bias was assessed using Newcastle-Ottawa scale for observational studies and AUB-KQ1 Cochrane tool for RCTs. Study-level data were analyzed using RevMan 5.3 and R (v4.1.0). Heterogeneity was determined by I2 and sources were explored through prespecified sensitivity analyses, subgroup analyses, and meta-regressions.

RESULTS

Of 1877 search results, 76 studies satisfying eligibility criteria were included. Seventy-two observational studies were included in the meta-analysis (n = 1 976 099). Vitamin D deficiency/insufficiency increased the odds of developing COVID-19 (odds ratio [OR] 1.46; 95% CI, 1.28-1.65; P < 0.0001; I2 = 92%), severe disease (OR 1.90; 95% CI, 1.52-2.38; P < 0.0001; I2 = 81%), and death (OR 2.07; 95% CI, 1.28-3.35; P = 0.003; I2 = 73%). The 25-hydroxy vitamin D concentrations were lower in individuals with COVID-19 compared with controls (mean difference [MD] -3.85 ng/mL; 95% CI, -5.44 to -2.26; P ≤ 0.0001), in patients with severe COVID-19 compared with controls with nonsevere COVID-19 (MD -4.84 ng/mL; 95% CI, -7.32 to -2.35; P = 0.0001) and in nonsurvivors compared with survivors (MD -4.80 ng/mL; 95% CI, -7.89 to -1.71; P = 0.002). The association between vitamin D deficiency/insufficiency and death was insignificant when studies with high risk of bias or studies reporting unadjusted effect estimates were excluded. Risk of bias and heterogeneity were high across all analyses. Discrepancies in timing of vitamin D testing, definitions of severe COVID-19, and vitamin D deficiency/insufficiency partly explained the heterogeneity. Four RCTs were widely heterogeneous precluding meta-analysis.

CONCLUSION

Multiple observational studies involving nearly 2 million adults suggest vitamin D deficiency/insufficiency increases susceptibility to COVID-19 and severe COVID-19, although with a high risk of bias and heterogeneity. Association with mortality was less robust. Heterogeneity in RCTs precluded their meta-analysis.

Vitamin D: The Missing Nutrient Behind the Two Deadly Pandemics, COVID-19 and Cardiovascular Diseases

The coronavirus (COVID-19) pandemic is claiming millions of lives and creating an additional burden on health care, which is already affected by the rise of non-communicable diseases (NCDs). The scientific community, on the other side, is enormously engaged with studies to best identify the characteristics of the virus and minimize its effect while supporting the fight to contain NCDs, mainly cardiovascular diseases (CVDs), which are contributing hugely to the global death toll. Hence, the roles of vitamin D in COVID-19 immunity and cardiovascular health are gaining traction recently. 

This literature review will mainly focus on summarizing pertinent studies and scientific publications which highlight the association of vitamin D levels with the various outcomes of COVID-19 and CVDs. It will also address how low vitamin D correlates with the epidemiology of CVDs and the inflammatory mechanisms attributed to COVID-19 severity. We believe that our review may open up hindsight perspectives and further discussions among the physicians in tapping the potential of vitamin D supplementation to tackle the morbidity, mortality, and health care cost of the two deadly diseases, COVID-19 and CVDs. 

Relationship of anti-SARS-CoV-2 IgG antibodies with Vitamin D and inflammatory markers in COVID-19 patients

Several studies have found an association of COVID-19 disease severity with Vitamin D deficiency and higher levels of anti-SARS-CoV-2 IgGs. The aim of this study was to determine whether levels of Vitamin D and "inflammatory state" influence the magnitude of anti-SARS-CoV-2 IgGs levels in COVID-19 patients. For this purpose, in 67 patients levels of anti-SARS-CoV-2 IgG were measured in week 4 whereas in 52 patients levels of Vitamin D were measured in week 1 after symptom onset. We found that low Vitamin D levels were significantly associated with age and disease severity whereas there was a trend without significance, towards negative correlation of Vitamin D with anti-SARS-CoV-2 IgG. Anti-SARS-CoV-2 IgG were significantly higher in older ages, patients with severe disease, diabetes and those who received corticosteroid and antibiotic therapy. There was a positive correlation of anti-SARS-CoV-2 IgG with IL-6, CRP, LDH, ESR and with percentages of granulocytes. In conclusion, Vitamin D and anti-SARS-CoV-2 IgG share common parameters associated with inflammatory state. However, even though Vitamin D protects against severe forms of COVID-19 it could not directly affect anti-SARS-CoV-2 IgG production.

Association of vitamin D status with COVID-19 disease severity in pediatric patients: A retrospective observational study

Background and Aims

Vitamin D deficiency is associated with increased vulnerability to respiratory infections. This study aimed to determine the potential relationships between coronavirus disease 2019 (COVID-19) severity, serum vitamin D concentrations, and some inflammatory markers among pediatric COVID-19 patients in Iran.

Methods

A retrospective study was conducted among hospitalized pediatric COVID-19 cases in Abuzar Hospital (Ahvaz, Iran) for 6 months. The COVID-19 diagnosis was based on the real-time reverse transcription-polymerase chain reaction technique. Demographic and clinical data of patients were recorded. Patients with serum vitamin D levels lower than 20 ng/ml were assigned as Group 1 and those with serum vitamin D concentrations equal to or more than 20 ng/ml were considered as Group 2.

Results

A total of 144 patients were enrolled. Their mean age was 80  ±  49 months (range: 1-16 years). Patients in Group 1 had significantly lower levels of serum vitamin D, calcium, and lymphocytes, as well as higher fibrinogen, d-dimer, and C-reactive protein (CRP) levels compared with those in Group 2 (p < 0.001). In addition, they had a significantly higher dry cough, fever, chest radiographic findings, respiratory rate, and longer hospital length of stay than patients in Group 2. Serum concentrations of vitamin D were positively correlated with levels of serum calcium, lymphocytes, and neutrophils but negatively correlated with CRP, fibrinogen, and d-dimer values. Furthermore, patients with moderate or severe courses of COVID-19 had significantly higher inflammatory markers (CRP, d-dimer, and fibrinogen), as well as lower levels of serum calcium, vitamin D, lymphocytes, and neutrophils than those with mild COVID-19 (p < 0.001). In the multivariate analysis, fibrinogen level on admission was detected as the independent predictor of severe COVD-19 (odds ratio = 1.06, 95% confidence interval: 1.03-1.09; p < 0.001).

Conclusion

This study indicated associations between the severity of COVID-19, serum vitamin D concentrations, and some inflammatory markers in pediatric COVID-19 patients.

Vitamin D can reduce severity in COVID-19 through regulation of PD-L1

COVID-19 is a highly contagious viral infection that has killed millions of people around the world. The most important diagnostic feature of COVID-19 is lymphocyte depletion, particularly the depletion of T cells. In COVID-19 infections, there is a link between destruction of T cells and increased expression of inhibitory immune checkpoint molecules (PD-1/PD-L1) on T cell surfaces. It was shown that PD-1/PD-L1 levels increase in severely COVID-19 infected individuals. Higher proinflammatory cytokine levels cause increased PD-1/PD-L1 expression. In severe COVID-19, higher proinflammatory cytokine levels may increase PD-1/PD-L1. Vitamin-D is an important immune regulator. It is known that the numbers of CD4⁺ and CD8⁺ T lymphocytes decrease in vitamin D deficiency while vitamin D supplementation increases CD + 4 lymphocytes. Vitamin D can increase regulatory T cell (Treg) activity. Vitamin D also has a diminishing effect on proinflammatory cytokines. In severe COVID-19 cases, vitamin D supplementation may inhibit the increase of PD-L1 expression through reducing proinflammatory cytokine levels. Thus, vitamin D supplementation could eliminate the suppressive effect of PD-L1 on CD4⁺ and CD8⁺ T cells, preventing lymphopenia and reducing disease severity and mortality in patients infected with COVID-19. Besides, vitamin D supplementation can reduce inflammation by increasing Treg activity. The aim of this letter is to discuss the functions of inhibitory immune checkpoint molecules and their effects on dysfunction and depletion of T-cells as well as to explain the possible modulatory effect of vitamin D on these checkpoints and T cells.

Type 2 Diabetes Contributes to Altered Adaptive Immune Responses and Vascular Inflammation in Patients With SARS-CoV-2 Infection

SARS-CoV-2, which initially emerged in November of 2019, wreaked havoc across the globe by leading to clinical acute respiratory distress syndrome and continues to evade current therapies today due to mutating strains. Diabetes mellitus is considered an important risk factor for progression to severe COVID disease and death, therefore additional research is warranted in this group. Individuals with diabetes at baseline have an underlying inflammatory state with elevated levels of pro-inflammatory cytokines and lower levels of anti-inflammatory cytokines, both of which cause these individuals to have higher susceptibility to SARS- CoV2 infection. The detrimental effects of SARS-CoV-2 has been attributed to its ability to induce a vast cell mediated immune response leading to a surge in the levels of pro-inflammatory cytokines. This paper will be exploring the underlying mechanisms and pathophysiology in individuals with diabetes and insulin resistance making them more prone to have worse outcomes after SARS- CoV2 infection, and to propose an adjunctive therapy to help combat the cytokine surge seen in COVID-19. It will also look at the immunomodulatory effects of glutathione, an antioxidant shown to reduce immune dysregulation in other diseases; Vitamin D, which has been shown to prevent COVID-19 patients from requiring more intensive care time possibly due to its ability to decrease the expression of certain pro-inflammatory cytokines; and steroids, which have been used as immune modulators despite their ability to exacerbate hyperglycemia.

Cholecalciferol level and its impact on COVID-19 patients

BACKGROUND

Cholecalciferol is an important nutrient and essential to build body, maintain strong bones, and improves immunity.The main source for vitamin D is the body's skin which absorbs the sun's ultraviolet rays and convert them into vitamin D; at the same time, deficiency can occur or people may not get enough supplementation; this occurs mainly in old age, not taking healthy food, or have darker skin, and this deficient cases can raise the risk of severe COVID-19 if infected.Vitamin D boosts immunity and decreases inflammation. Poorer outcome of corona virus-disease (COVID-19) has been suggested to be due to vitamin D deficiency.We suggested to find the effect of cholecalciferol levels 25-hydroxy vitamin D (25 OHD) on the severity and mortality in patients suffering from COVID-19.

METHODS

Our study is a prospective following of 414 patients admitted in Helwan University Hospitals in the period of June 2020 till October 2021 for severely symptomatic. COVID-19 patients with median of age 54.55 ± 14.27, with a definite range of APACHE II score ranging from 15 to 19 where we measured vitamin D3 level (cholecalciferol level), correlating the assay level to the inflammatory cytokine storm markers on admission, on the fifth day and after 10 days also the level of vitamin D3 was correlated to the length of stay mechanical ventilation days and mortality.

RESULTS

Lower level of vitamin D3 on admission was strongly evident in patients with severely symptomatic and in mortality of COVID-19 patients 58.25 ± 24.59 nmol/L when compared with patients who survived 103.97 ± 36.14 nmol/L with P value < 0.001.Also, when correlating the initial level of vitamin D3 on admission with the level of the inflammatory cytokine storm markers on admission, on fifth day from admission and on the tenth day, it shows a strong inverse correlation between vitamin D3 level on admission and ferritin level on fifth day ρ-0.739 p value < 0.001 also on the tenth day ρ-0.885, P value < 0.001, in comparing also with D-dimer on fifth day ρ-0.858, p value < 0.001 also showing a strong inverse correlation with a highly significant p value this also evident on the D-dimer level on the tenth day ρ-0.889 with p value < 0.001, CRP at fifth and tenth day ρ-0.868, P value < 0.001, ρ-0.891, P value < 0.001 respectively also in correlating the LDH level on the fifth and tenth day with the initial level of vitamin D3 it shows a strong inverse correlation with a highly significant p value. ρ-0.887, P value < 0.001, ρ-0.878, p value < 0.001 respectively, in the fifth and tenth day. Neutrophil to lymphocyte ratio was strongly, inversely correlated to the vitamin D3 level (cholecalciferol) on admission with ρ-0.753, p < 0.001, ρ-0.882, P < 0.001 respectively. Also, chest computed tomography in the fifth and tenth day of admission showed a very strong inverse correlation with vitamin D level and a highly significant statistical difference ρ-0.655, p value < 0.001 respectively.Length of stay and mechanical ventilation days were also strongly inversely correlated to the cholecalciferol level ρ-0.795, p < 0.001, ρ- 0.879, P < 0.001 ROC curve of vitamin D3 to predict mortality (RR 0.865, 95% CI 0.828-0.896, P < 0.001, with cut off-value for vit. D3 < 60 nmol/L, regardless of other factors like age, gender, and presence of other co-morbidities.

CONCLUSION

Low level of cholecalciferol was strongly inversely correlated with cytokine storm markers and independent predictor of severity and mortality in COVID-19 patients.

The Impact of Vitamin D Status on COVID-19 Severity among Hospitalized Patients in the Western Region of Saudi Arabia: A Retrospective Cross-Sectional Study

The coronaviruses disease 2019 (COVID-19) spreads continuously worldwide. The new vaccines and drugs have been approved. The prevention of disease is crucial, and some studies reveal the promising effect of alternative therapies such as vitamin D supplementations on COVID-19 prevention, but they still require sufficient evidence. Therefore, the current retrospective multicenter cross-sectional study aims to determine the primary association between the vitamin D status of hospitalized COVID-19 and its severity as well as mortality. A total of 197 COVID-19 were admitted at King Faisal Hospital, Al Noor Specialist Hospital in Makkah, and at Complex King Faisal Hospital in Taif in the Westering region of Saudi Arabia (SA) between June and August 2020. The demographic and clinical characteristics, laboratory tests included serum 25(OH)D and admission for intensive care unit (ICU), length of stay in the hospital, mechanical ventilation (MV) support, and mortality were recorded and analyzed. Vitamin D deficiency (25(OH)D < 20 ng/mL) was found in 73.10% of all study population. Multiple logistic regression was used after adjusted covariances such as age, gender, diabetes, hypertension, and chronic kidney disease (CKD). No statistically significant was shown for ICU admission [Odd Ratio, OR 1.25 (95% confidence interval, CI 0.41-3.88) p = 0.70], MV support [Odd Ratio, OR 3.12 (95% confidence interval, CI 0.74-13.21) p = 0.12] and mortality [Odd Ratio, OR 2.39 (95% confidence interval, CI 0.31-18.11), p = 0.40]. These data didn't support the association between serum 25(OH)D and the severity of the disease among hospitalized COVID-19 patients.

Nutritional risk of vitamin D, vitamin C, zinc, and selenium deficiency on risk and clinical outcomes of COVID-19: A narrative review

The pathogenicity of the current coronavirus disease (COVID-19) shows postulates that optimal status of essential nutrients is crucial in supporting both the early viraemic and later hyperinflammatory phases of COVID-19. Micronutrients such as vitamin C, D, zinc, and selenium play roles in antioxidant, anti-inflammatory, antithrombotic, antiviral, and immuno-modulatory functions and are useful in both innate and adaptive immunity. The purpose of this review is to provide a high-level summary of evidence on clinical outcomes associated with nutritional risk of these micronutrients observed in patients with COVID-19. A literature search was performed on PubMed and Google Scholar to obtain findings of cross-sectional and experimental studies in humans. The search resulted in a total of 1212 reports including all nutrients, but only 85 were included according to the eligibility criteria. Despite the diversity of studies and the lack of randomized clinical trials and prospective cohorts, there is evidence of the potential protective and therapeutic roles of vitamin C, D, zinc, and selenium in COVID-19. The findings summarized in this review will contribute to guide interventions in clinical practice or in future clinical studies.

Is There a Crucial Link Between Vitamin D Status and Inflammatory Response in Patients With COVID-19?

Background

Hypovitaminosis D has been suggested to play a possible role in coronavirus disease 2019 (COVID-19) infection.

Methods

The aim of this study is to analyze the relationship between vitamin D status and a biochemical panel of inflammatory markers in a cohort of patients with COVID-19. A secondary endpoint was to evaluate the correlation between 25OHD levels and the severity of the disease. Ninety-three consecutive patients with COVID-19-related pneumonia were evaluated from March to May 2020 in two hospital units in Pisa, in whom biochemical inflammatory markers, 25OHD levels, P/F ratio at nadir during hospitalization, and complete clinical data were available.

Results

Sixty-five percent of patients presented hypovitaminosis D (25OHD ≤ 20 ng/ml) and showed significantly higher IL-6 [20.8 (10.9-45.6) vs. 12.9 (8.7-21.1) pg/ml, p = 0.02], CRP [10.7 (4.2-19.2) vs. 5.9 (1.6-8.1) mg/dl, p = 0.003], TNF-α [8.9 (6.0-14.8) vs. 4.4 (1.5-10.6) pg/ml, p = 0.01], D-dimer [0.53 (0.25-0.72) vs. 0.22 (0.17-0.35) mg/l, p = 0.002], and IL-10 [3.7 (1.8-6.9) vs. 2.3 (0.5-5.8) pg/ml, p = 0.03]. A significant inverse correlation was found between 25OHD and all these markers, even adjusted for age and sex. Hypovitaminosis D was prevalent in patients with severe ARDS, compared with the other groups (75% vs. 68% vs. 55%, p < 0.001), and 25OHD levels were lower in non-survivor patients.

Conclusions

The relationship between 25OHD levels and inflammatory markers suggests that vitamin D status needs to be taken into account in the management of these patients. If vitamin D is a marker of poor prognosis or a possible risk factor with beneficial effects from supplementation, this still needs to be elucidated.

Oxidative stress status and vitamin D levels of asymptomatic to mild symptomatic COVID‐19 infections during the third trimester of pregnancy: A retrospective study in Metz, France

It is believed that the subtle equilibrium between tolerance and immunity during the unique biological state of pregnancy, which is characterized by further physiological and hormonal changes, rends pregnant women more vulnerable to coronavirus disease 2019 (COVID-19). In this retrospective study, confirmed COVID-19-positive pregnant women (n = 15) during their third trimester, comprising asymptomatic (n = 7) and mild symptomatic (n = 8), and healthy pregnant controls (n = 20), were enrolled between June 1, 2020 and  June 1, 2021 from the Hospital CHR Metz-Thionville in Metz, France. Vitamin D concentrations, C-reactive protein (CRP), and oxidative stress markers including superoxide dismutase (SOD), catalase (CAT), reduced (GSH) and oxidized (GSSG) glutathione levels, hydrogen peroxide (H₂ O₂ ), and the total antioxidant capacity, measured the ferric reducing ability of plasma (FRAP), were evaluated in the serum of patients and controls. Results showed that all pregnant women (patients and controls) enrolled in this study were vitamin D deficient (<20 ng/ml). However, mild COVID-19 pregnant women were severely vitamin D deficient (<12 ng/ml), which may suggest a link between vitamin D deficiency and the symptomatology of COVID-19 illness in singleton pregnancy. No differences between the levels of CRP and the majority of the studied oxidative stress markers in COVID-19-positive pregnant women (asymptomatic and/or mildly symptomatic patients) versus COVID-19-negative pregnant women were found, suggesting the absence or a low magnitude of oxidative stress in pregnant women with COVID-19. This may also explain the absence of severe courses of COVID-19 infection. More studies are warranted to investigate the role of vitamin D supplementation and antioxidant-rich diets in the prevention against severe forms of COVID-19 in pregnant women.

Hospital length of stay for COVID-19 patients: a systematic review and meta-analysis

The length of stay in the hospital for COVID-19 can aid in understanding the disease's prognosis. Thus, the goal of this study was to collectively estimate the hospital length of stay (LoS) in COVID-19 hospitalized individuals. To locate related studies, international databases (including Google Scholar, Science Direct, PubMed, and Scopus) were searched. The I2 index, the Cochran Q test, and T2 were used to analyze study heterogeneity. The mean LoS in COVID- 19 hospitalized patients was estimated using a random-effects model. COVID-19's total pooled estimated hospital LoS was 15.35, 95%CI:13.47-17.23; p<0.001, I2 = 80.0). South America had the highest pooled estimated hospital LoS of COVID-19 among the continents, at 20.85 (95%CI: 14.80-26.91; p<0.001, I2 = 0.01), whereas Africa had the lowest at 8.56 8 (95%CI: 1.00-22.76). The >60 age group had the highest pooled estimated COVID-19 hospital LoS of 16.60 (95%CI: 12.94-20.25; p<0.001, I2 = 82.6), while the 40 age group had the lowest hospital LoS of 10.15 (95% CI: 4.90-15.39, p<0.001, I2 = 22.1). The metanalysis revealed that COVID-19's hospital LoS was more than 10 days. However, it appears that this duration varies depending on a number of factors, including the patient's age and the availability of resources.

Serum vitamin D level in COVID-19 patients and its correlation with disease severity

Background

Severe coronavirus disease 2019 (COVID-19) infections are associated with increased levels of C-reactive protein (CRP) and several pro-inflammatory cytokines leading to cytokine storm. Vitamin D has been proved to be associated with biological activities of the innate and adaptive immune systems. There is a growing number of data showing an association between serum vitamin D level and the different clinical outcomes of COVID-19 infection. Our aim is to evaluate the relation between serum vitamin D levels and the severity and mortality of COVID-19 infection in an Egyptian cohort.

Results

The study included 80 COVID-19 patients, 38 males (47.5%) and 42 females (52.5%), with a mean age of 52 ± 11.4 years (18–80 years). The serum vitamin D levels ranged between 2 and 30 ng/mL with a mean of 12.05 ± 9.04. Patients who were intubated had the lowest levels of serum vitamin D (7.26 ng/ml ± 5.21), while patients who had no need for oxygen supply had the highest levels (20.00 ng/ml ± 9.23) (P = 0.025). A highly significant negative correlation was found between serum vitamin D level and each of CRP and serum ferritin (r = − 0.346 and − 0.313) (P = 0.002 and 0.005). Of the enrolled 80 patients, 63 (79%) recovered (group 1) and 17 (21%) died (group 2). Group 2 had significantly lower vitamin D levels (6.17 ng/mL ± 3.22) and hemoglobin (10.75 ± 1.74) than group 1 patients (13.63ng/mL ± 9.46) (12.10 ± 1.85) (P = 0.002 and 0.009 respectively).

Conclusion

Serum vitamin D levels are significantly lower in patients needing mechanical ventilation, and in deceased patients, and are inversely related to the inflammatory markers CRP and serum ferritin, suggesting a relation between vitamin D insufficiency and poor COVID-19 outcome.

Seasonal UV exposure and vitamin D: association with the dynamics of COVID-19 transmission in Europe

Several recent studies have demonstrated that low plasma 25(OH) vitamin D levels are associated with the risk of COVID-19 infection. The primary source of vitamin D production in humans is environmental UV radiation. In many viral respiratory diseases, peak infection rates are observed during winter due to reduced UV exposure and low temperatures. In Europe, the second wave of COVID-19 began early in the winter of 2020. Investigating the impact of seasonal temperature and UV exposure on COVID-19 transmission could thus aid in prevention and intervention. As such, we first performed a comprehensive meta-analysis of all related published literature based on the association between vitamin D and COVID-19, which supported the hypothesis that the low vitamin D level is a critical risk factor for COVID-19 infection. Next, to understand the potential impact of seasonal UV and temperature levels on COVID-19 cases, we analyzed meteorological data and daily COVID-19 cases per million in the populations of 26 European countries. We observed that low temperature, UV index, and cloud-free vitamin D UV dose (UVDVF) levels are negatively correlated with COVID-19 prevalence in Europe. Furthermore, a distributed lag nonlinear model was used to assess the nonlinear delayed effects of individual seasonal factors on COVID-19 cases. Such analysis highlighted the significantly delayed impact of UVDVF on the cumulative relative risk of COVID-19 infection. The findings of this study suggest that low UV exposure can affect the required production of vitamin D in the body, which substantially influences the dynamics of COVID-19 transmission and severity.

Vitamin D Status and SARS-CoV-2 Infection and COVID-19 Clinical Outcomes

Background: Several studies suggest an association between serum 25-hydroxyvitamin D (25OHD) and the outcomes of Severe Acute Respiratory Syndrome Corona-Virus-2 (SARS-CoV-2) infection, in particular Coronavirus Disease-2019 (COVID-19) related severity and mortality. The aim of the present meta-analysis was to investigate whether vitamin D status is associated with the COVID-19 severity, defined as ARDS requiring admission to intensive care unit (ICU) or mortality (primary endpoints) and with the susceptibility to SARS-CoV-2 and COVID-19-related hospitalization (secondary endpoints). Methods: A search in PubMed, ScienceDirect, Web of Science, Google Scholar, Scopus, and preprints repositories was performed until March 31th 2021 to identify all original observational studies reporting association measures, or enough data to calculate them, between Vitamin D status (insufficiency <75, deficiency <50, or severe deficiency <25 nmol/L) and risk of SARS-CoV-2 infection, COVID-19 hospitalization, ICU admission, or death during COVID-19 hospitalization. Findings: Fifty-four studies (49 as fully-printed and 5 as pre-print publications) were included for a total of 1,403,715 individuals. The association between vitamin D status and SARS-CoV2 infection, COVID-19 related hospitalization, COVID-19 related ICU admission, and COVID-19 related mortality was reported in 17, 9, 27, and 35 studies, respectively. Severe deficiency, deficiency and insufficiency of vitamin D were all associated with ICU admission (odds ratio [OR], 95% confidence intervals [95%CIs]: 2.63, 1.45-4.77; 2.16, 1.43-3.26; 2.83, 1.74-4.61, respectively), mortality (OR, 95%CIs: 2.60, 1.93-3.49; 1.84, 1.26-2.69; 4.15, 1.76-9.77, respectively), SARS-CoV-2 infection (OR, 95%CIs: 1.68, 1.32-2.13; 1.83, 1.43-2.33; 1.49, 1.16-1.91, respectively) and COVID-19 hospitalization (OR, 95%CIs 2.51, 1.63-3.85; 2.38, 1.56-3.63; 1.82, 1.43-2.33). Considering specific subgroups (i.e., Caucasian patients, high quality studies, and studies reporting adjusted association estimates) the results of primary endpoints did not change. Interpretations: Patients with low vitamin D levels present an increased risk of ARDS requiring admission to intensive care unit (ICU) or mortality due to SARS-CoV-2 infection and a higher susceptibility to SARS-CoV-2 infection and related hospitalization.

Pathogenesis of COVID-19 described through the lens of an undersulfated and degraded epithelial and endothelial glycocalyx

The glycocalyx surrounds every eukaryotic cell and is a complex mesh of proteins and carbohydrates. It consists of proteoglycans with glycosaminoglycan side chains, which are highly sulfated under normal physiological conditions. The degree of sulfation and the position of the sulfate groups mainly determine biological function. The intact highly sulfated glycocalyx of the epithelium may repel severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) through electrostatic forces. However, if the glycocalyx is undersulfated and 3-O-sulfotransferase 3B (3OST-3B) is overexpressed, as is the case during chronic inflammatory conditions, SARS-CoV-2 entry may be facilitated by the glycocalyx. The degree of sulfation and position of the sulfate groups will also affect functions such as immune modulation, the inflammatory response, vascular permeability and tone, coagulation, mediation of sheer stress, and protection against oxidative stress. The rate-limiting factor to sulfation is the availability of inorganic sulfate. Various genetic and epigenetic factors will affect sulfur metabolism and inorganic sulfate availability, such as various dietary factors, and exposure to drugs, environmental toxins, and biotoxins, which will deplete inorganic sulfate. The role that undersulfation plays in the various comorbid conditions that predispose to coronavirus disease 2019 (COVID-19), is also considered. The undersulfated glycocalyx may not only increase susceptibility to SARS-CoV-2 infection, but would also result in a hyperinflammatory response, vascular permeability, and shedding of the glycocalyx components, giving rise to a procoagulant and antifibrinolytic state and eventual multiple organ failure. These symptoms relate to a diagnosis of systemic septic shock seen in almost all COVID-19 deaths. The focus of prevention and treatment protocols proposed is the preservation of epithelial and endothelial glycocalyx integrity.

The Renin-Angiotensin System: A Key Role in SARS-CoV-2-Induced COVID-19

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), was first identified in Eastern Asia (Wuhan, China) in December 2019. The virus then spread to Europe and across all continents where it has led to higher mortality and morbidity, and was declared as a pandemic by the World Health Organization (WHO) in March 2020. Recently, different vaccines have been produced and seem to be more or less effective in protecting from COVID-19. The renin-angiotensin system (RAS), an essential enzymatic cascade involved in maintaining blood pressure and electrolyte balance, is involved in the pathogenicity of COVID-19, since the angiotensin-converting enzyme II (ACE2) acts as the cellular receptor for SARS-CoV-2 in many human tissues and organs. In fact, the viral entrance promotes a downregulation of ACE2 followed by RAS balance dysregulation and an overactivation of the angiotensin II (Ang II)-angiotensin II type I receptor (AT1R) axis, which is characterized by a strong vasoconstriction and the induction of the profibrotic, proapoptotic and proinflammatory signalizations in the lungs and other organs. This mechanism features a massive cytokine storm, hypercoagulation, an acute respiratory distress syndrome (ARDS) and subsequent multiple organ damage. While all individuals are vulnerable to SARS-CoV-2, the disease outcome and severity differ among people and countries and depend on a dual interaction between the virus and the affected host. Many studies have already pointed out the importance of host genetic polymorphisms (especially in the RAS) as well as other related factors such age, gender, lifestyle and habits and underlying pathologies or comorbidities (diabetes and cardiovascular diseases) that could render individuals at higher risk of infection and pathogenicity. In this review, we explore the correlation between all these risk factors as well as how and why they could account for severe post-COVID-19 complications.