l-Cysteine Stimulates the Effect of Vitamin D on Inhibition of Oxidative Stress, IL-8, and MCP-1 Secretion in High Glucose Treated Monocytes

L-Cysteine Upregulates Testosterone Biosynthesis and Blood-Testis Barrier Genes in Cultured Human Leydig Cells and THP-1 Monocytes and Increases Testosterone Secretion in Human Leydig Cells

Leydig cells are the primary source of testosterone or androgen production in male mammals. The blood-testis barrier (BTB) maintains structural integrity and safeguards germ cells from harmful substances by blocking their entry into the seminiferous tubules. L-cysteine is essential to the production of glutathione, a powerful antioxidant crucial to protecting against oxidative stress-induced damage. Animal studies have demonstrated the protective effect of L-cysteine in preventing testicular damage caused by chemicals or radiation. This study examines whether L-cysteine enhances the expression of testosterone biosynthesis and the BTB genes in human Leydig cells and THP-1 monocytes. The Leydig cells and THP-1 monocytes were treated with L-cysteine for 24 h. RNA was extracted following treatment, and the gene expression was analyzed using quantitative RT-PCR. Testosterone levels in the cell supernatant were measured using an ELISA kit. L-cysteine treatment in Leydig cells significantly upregulated the expression of CYP11A1 (p = 0.03) and the BTB genes CLDN1 (p = 0.03), CLDN11 (p = 0.02), and TJP1 (p = 0.02). Similarly, L-cysteine significantly upregulated the expression of CYP11A1 (p = 0.03) and CYP19A1 (p < 0.01), and the BTB genes CLDN1 (p = 0.04), CLDN2 (p < 0.01), CLDN4 (p < 0.01), CLDN11 (p < 0.01), and TJP1 (p = 0.03) in THP-1 monocytes. Further, L-cysteine supplementation increased the testosterone secretion levels in human Leydig cells. The findings suggest that L-cysteine supplementation could be used as an adjuvant therapy to promote the integrity of the BTB genes, testosterone biosynthesis and secretion, and the maintenance of testicular functions, which in turn mitigates the risk of male infertility.

A, Lally MM, Vanchiere JA, Mhanna MJ, Shi R, Levine SN. Effects of vitamin D and L-cysteine cosupplementation on circulating bioavailable and total 25-hydroxy-vitamin D, the free/total testosterone ratio and inflammatory biomarkers in healthy vitamin D-deficient African Americans: a placebo-controlled double-blind clinical trial

Background

Subjects with metabolic syndrome and obesity have higher levels of inflammation with depression of the vitamin D (VD) hydroxylase/metabolising genes (CYP2R1/CYP27A1/CYP27B1/VDR) required to convert VD consumed in the diet into 25(OH)VD. Compared with total 25(OH)VD levels, measurement of bioavailable 25(OH)VD is a better method to determine the beneficial effect of VD.

Objective

This study investigates whether cosupplementation with VD and L-cysteine (LC), which downregulates inflammation and upregulates VD-regulating genes, provides a better therapeutic benefit than supplementation with VD-alone in African Americans (AA).

Methods

AA participants (men/women, aged 18-65 years; n=165) were block randomised into one of four groups and received daily, oral supplementation for 6 months with placebo, LC (1000 mg/day), VD (2000 IU/day) or VD+LC. Fasting blood collected at the baseline and final visits was analysed for total, free and bioavailable 25(OH)VD along with insulin, VD-binding protein (VDBP), sex hormone-binding globulin (SHBG), free and total testosterone, and inflammatory marker levels. Studies were carried out in THP-1 monocytes to elucidate the direct effect of LC and testosterone on VD-regulating genes.

Results

Baseline data showed no differences in age, body mass index, calcium, liver or kidney function among the groups. Compared with levels in the group that received VD-alone supplementation, levels of neutrophil-to-lymphocyte ratio, C reactive protein, HOMA-IR, VDBP and HbA1c were significantly lower in the VD+LC group while the VD+LC group showed a significant increase in bioavailable 25(OH)VD in both sexes, total 25(OH)VD levels were significantly elevated in men but not in women treated with VD+LC. Blood levels of SHBG and free/total testosterone were elevated in the VD+LC group but not in the VD-alone group. LC and testosterone treatment significantly upregulated VD-metabolising genes (CYP2R1/CYP27A1/CYP27B1/VDR) and SHBG in THP-1 monocytes.

Conclusions

VD cosupplemented with LC upregulates circulating bioavailable 25(OH)VD and reduces inflammation. Total 25(OH)VD levels were higher in men but not in women in the VD+LC group. This pilot study suggests that compared with supplementation with VD-alone, VD+LC cosupplementation could be a better approach to raising the total 25(OH)VD in men and the bioavailable 25(OH)VD in both sexes and lowering the inflammatory risk in the AA population.

Trial registration number

NCT04939792.

The Impact of Vitamin D and L-Cysteine Co-Supplementation on Upregulating Glutathione and Vitamin D-Metabolizing Genes and in the Treatment of Circulating 25-Hydroxy Vitamin D Deficiency

Vitamin D receptors are expressed in many organs and tissues, which suggests that vitamin D (VD) affects physiological functions beyond its role in maintaining bone health. Deficiency or inadequacy of 25(OH)VD is widespread globally. Population studies demonstrate that a positive association exists between a high incidence of VD deficiency and a high incidence of chronic diseases, including dementia, diabetes, and heart disease. However, many subjects have difficulty achieving the required circulating levels of 25(OH)VD even after high-dose VD supplementation, and randomized controlled clinical trials have reported limited therapeutic success post-VD supplementation. Thus, there is a discordance between the benefits of VD supplementation and the prevention of chronic diseases in those with VD deficiency. Why this dissociation exists is currently under debate and is of significant public interest. This review discusses the downregulation of VD-metabolizing genes needed to convert consumed VD into 25(OH)VD to enable its metabolic action exhibited by subjects with metabolic syndrome, obesity, and other chronic diseases. Research findings indicate a positive correlation between the levels of 25(OH)VD and glutathione (GSH) in both healthy and diabetic individuals. Cell culture and animal experiments reveal a novel mechanism through which the status of GSH can positively impact the expression of VD metabolism genes. This review highlights that for better success, VD deficiency needs to be corrected at multiple levels: (i) VD supplements and/or VD-rich foods need to be consumed to provide adequate VD, and (ii) the body needs to be able to upregulate VD-metabolizing genes to convert VD into 25(OH)VD and then to 1,25(OH)2VD to enhance its metabolic action. This review outlines the association between 25(OH)VD deficiency/inadequacy and decreased GSH levels, highlighting the positive impact of combined VD+LC supplementation on upregulating GSH, VD-metabolizing genes, and VDR. These effects have the potential to enhance 25(OH)VD levels and its therapeutic efficacy.

Alzheimer's Disease: A Review of Pathology, Current Treatments, and the Potential Therapeutic Effect of Decreasing Oxidative Stress by Combined Vitamin D and l-Cysteine Supplementation

Significance: Excess oxidative stress and neuroinflammation are risk factors in the onset and progression of Alzheimer's disease (AD) and its association with amyloid-β plaque accumulation. Oxidative stress impairs acetylcholine (ACH) and N-methyl-d-aspartate receptor signaling in brain areas that function in memory and learning. Glutathione (GSH) antioxidant depletion positively correlates with the cognitive decline in AD subjects. Treatments that upregulate GSH and ACH levels, which simultaneously decrease oxidative stress and inflammation, may be beneficial for AD. Recent Advances: Some clinical trials have shown a benefit of monotherapy with vitamin D (VD), whose deficiency is linked to AD or with l-cysteine (LC), a precursor of GSH biosynthesis, in reducing mild cognitive impairment. Animal studies have shown a simultaneous decrease in ACH esterase (AChE) and increase in GSH; combined supplementation with VD and LC results in a greater decrease in oxidative stress and inflammation, and increase in GSH levels compared with monotherapy with VD or LC. Therefore, cosupplementation with VD and LC has the potential of increasing GSH, downregulation of oxidative stress, and decreased inflammation and AChE levels. Future Directions: Clinical trials are needed to determine whether safe low-cost dietary supplements, using combined VD+LC, have the potential to alleviate elevated AChE, oxidative stress, and inflammation levels, thereby halting the onset of AD. Goal of Review: The goal of this review is to highlight the pathological hallmarks and current Food and Drug Administration-approved treatments for AD, and discuss the potential therapeutic effect that cosupplementation with VD+LC could manifest by increasing GSH levels in patients. Antioxid. Redox Signal. 40, 663-678.

Research Progress on the Weak Immune Response to the COVID-19 Vaccine in Patients with Type 2 Diabetes

Coronavirus Disease 2019 (COVID-19) is generally susceptible to the population, highly infectious, rapidly transmitted, and highly fatal. There is a lack of specific drugs against the virus at present and vaccination is the most effective strategy to prevent infection. However, studies have found that some groups, particularly patients with diabetes, show varying degrees of weak immune reactivity to various COVID-19 vaccines, resulting in poor preventive efficacy against the novel coronavirus in patients with diabetes. Therefore, in this study, patients with type 2 diabetes mellitus (T2DM) who had weak immune response to the COVID-19 vaccine in recent years were analyzed. This article reviews the phenomenon, preliminary mechanism, and related factors affecting weak vaccine response in patients with T2DM, which is expected to help in the development of new vaccines for high-risk groups for COVID-19.

Identification of sulfur metabolism-related gene signature in osteoarthritis and TM9SF2's sustenance effect on M2 macrophages' phagocytic activity

BACKGROUND

Osteoarthritis (OA) is a chronic and low-grade inflammatory disease associated with metabolism disorder and multiple cell death types in the synovial tissues. Sulfur metabolism has not been studied in OA.

METHODS

First, we calculated the single sample gene set enrichment analysis score of sulfur metabolism-associated annotations (i.e., cysteine metabolism process, regulation of sulfur metabolism process, and disulfidptosis) between healthy and synovial samples from patients with OA. Sulfur metabolism-related differentially expressed genes (DEGs) were analyzed in OA. Least absolute shrinkage and selection operator COX regression were used to identify the sulfur metabolism-associated gene signature for diagnosing OA. Correlation and immune cell deconvolution analyses were used to explore the correlated functions and cell specificity of the signature gene, TM9SF2. TM9SF2's effect on the phagocytosis of macrophages M2 was analyzed by coculturing macrophages with IgG-coated beads or apoptotic Jurkat cells.

RESULTS

A diagnostic six gene signature (i.e., MTHFD1, PDK4, TM9SF2, POU4F1, HOXA2, NCKAP1) was identified based on the ten DEGs, validated using GSE12021 and GSE1919 datasets. TM9SF2 was upregulated in the synovial tissues of OA at both mRNA and protein levels. The relationship between TM9SF2 and several functional annotations, such as antigen processing and presentation, lysosome, phagosome, Fcγ-mediated phagocytosis, and tyrosine metabolism, was identified. TM9SF2 and macrophages M2 were significantly correlated. After silencing TM9SF2 in THP-1-derived macrophages M2, a significantly reduced phagocytosis and attenuated activation of PLC-γ1 were observed.

CONCLUSION

A sulfur metabolism-associated six-gene signature for OA diagnosis was constructed and upregulation of the phagocytosis-associated gene, TM9SF2, was identified. The findings are expected to deepen our understanding of the molecular mechanism underlying OA development and be used as potential therapeutic targets.

A Review of Antibiotic Efficacy in COVID-19 Control

Severe acute respiratory disease is associated with chronic secondary infections that exacerbate symptoms and mortality. So far, many drugs have been introduced to treat this disease, none of which effectively control the coronavirus. Numerous studies have shown that mitochondria, as the center of cell biogenesis, are vulnerable to drugs, especially antibiotics. Antibiotics were widely prescribed during the early phase of the pandemic. We performed a literature review to assess the reasons, evidence, and practices on the use of antibiotics in coronavirus disease 2019 (COVID-19) in- and outpatients. The current research found widespread usage of antibiotics, mostly in an empirical context, among COVID-19 hospitalized patients. The effectiveness of this approach has not been established. Given the high death rate linked with secondary infections in COVID-19 patients and the developing antimicrobial resistance, further study is urgently needed to identify the most appropriate rationale for antibiotic therapy in these patients.

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-1β. 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.

Insight into SARS-CoV-2 Omicron variant immune escape possibility and variant independent potential therapeutic opportunities

The Omicron, the latest variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first detected in November 2021 in Botswana, South Africa. Compared to other variants of SARS-CoV-2, the Omicron is the most highly mutated, with 50 mutations throughout the genome, most of which are in the spike (S) protein. These mutations may help the Omicron to evade host immunity against the vaccine. Epidemiological studies suggest that Omicron is highly infectious and spreads rapidly, but causes significantly less severe disease than the wild-type strain and the other variants of SARS-CoV-2. With the increased transmissibility and a higher rate of re-infection, Omicron has now become a dominant variant worldwide and is predicted to be able to evade vaccine-induced immunity. Several clinical studies using plasma samples from individuals receiving two doses of US Food and Drugs Administration (FDA)-approved COVID-19 vaccines have shown reduced humoral immune response against Omicron infection, but T cell-mediated immunity was well preserved. In fact, T cell-mediated immunity protects against severe disease, and thus the disease caused by Omicron remains mild. In this review, I surveyed the current status of Omicron variant mutations and mechanisms of immune response in the context of immune escape from COVID-19 vaccines. I also discuss the potential implications of therapeutic opportunities that are independent of SARS-CoV-2 variants, including Omicron. A better understanding of vaccine-induced immune responses and variant-independent therapeutic interventions that include potent antiviral, antioxidant, and anti-cytokine activities may pave the way to reducing Omicron-related COVID-19 complications, severity, and mortality. Collectively, these insights point to potential research gaps and will aid in the development of new-generation COVID-19 vaccines and antiviral drugs to combat Omicron, its sublineages, or upcoming new variants of SARS-CoV-2.

Vitamin D role in hepatitis B: focus on immune system and genetics mechanism

According to the World Health Organization (WHO) report, viral hepatitis has been a problem in human society. Vitamins play a significant role in preventing the hepatocarcinoma and liver cirrhosis. In this report, we will first focus on the vitamin D function in the immune system reactions, and then investigate its role in the viral infections and the signaling pathway of hepatitis B virus. The existence of the cytochrome P450 (CYP) 27B1 enzyme, which is involved in vitamin D synthesis in immune system cells, has drawn researchers ' attention to the field of immune system. Toll like receptor (TLR) play a significant role in the immune system, and are one of the primary receptors of the innate immune system. In addition, the synthesis of inflammatory cytokines, such as Interferon γ (IFNγ) and Interleukin-2 (IL-2) is one of the key roles of T helper type 1 (Th1) cells; these cells can suppress two cited cytokines via vitamin D. In the chronic phase of hepatitis B, Cytotoxic T lymphocytes (CTLs) cells have weaker performance than the acute phase of the disease. The association between vitamin D physiologies with viral infections is also confirmed by genetic studies, carried out on genetic variations of vitamin D receptor (VDR) R-encoding disease susceptibility gene. Vitamin D affects different phases of the disease. Therefore, further experiments in this area are proposed.

Endothelial Dysfunction in COVID-19: A Unifying Mechanism and a Potential Therapeutic Target

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) generated a worldwide emergency, until the declaration of the pandemic in March 2020. SARS-CoV-2 could be responsible for coronavirus disease 2019 (COVID-19), which goes from a flu-like illness to a potentially fatal condition that needs intensive care. Furthermore, the persistence of functional disability and long-term cardiovascular sequelae in COVID-19 survivors suggests that convalescent patients may suffer from post-acute COVID-19 syndrome, requiring long-term care and personalized rehabilitation. However, the pathophysiology of acute and post-acute manifestations of COVID-19 is still under study, as a better comprehension of these mechanisms would ensure more effective personalized therapies. To date, mounting evidence suggests a crucial endothelial contribution to the clinical manifestations of COVID-19, as endothelial cells appear to be a direct or indirect preferential target of the virus. Thus, the dysregulation of many of the homeostatic pathways of the endothelium has emerged as a hallmark of severity in COVID-19. The aim of this review is to summarize the pathophysiology of endothelial dysfunction in COVID-19, with a focus on personalized pharmacological and rehabilitation strategies targeting endothelial dysfunction as an attractive therapeutic option in this clinical setting.

SARS-CoV-2 infection and oxidative stress: Pathophysiological insight into thrombosis and therapeutic opportunities

The current coronavirus disease 2019 (COVID-19) pandemic has presented unprecedented challenges to global health. Although the majority of COVID-19 patients exhibit mild-to-no symptoms, many patients develop severe disease and need immediate hospitalization, with most severe infections associated with a dysregulated immune response attributed to a cytokine storm. Epidemiological studies suggest that overall COVID-19 severity and morbidity correlate with underlying comorbidities, including diabetes, obesity, cardiovascular diseases, and immunosuppressive conditions. Patients with such comorbidities exhibit elevated levels of reactive oxygen species (ROS) and oxidative stress caused by an increased accumulation of angiotensin II and by activation of the NADPH oxidase pathway. Moreover, accumulating evidence suggests that oxidative stress coupled with the cytokine storm contribute to COVID-19 pathogenesis and immunopathogenesis by causing endotheliitis and endothelial cell dysfunction and by activating the blood clotting cascade that results in blood coagulation and microvascular thrombosis. In this review, we survey the mechanisms of how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces oxidative stress and the consequences of this stress on patient health. We further shed light on aspects of the host immunity that are crucial to prevent the disease during the early phase of infection. A better understanding of the disease pathophysiology as well as preventive measures aimed at lowering ROS levels may pave the way to mitigate SARS-CoV-2-induced complications and decrease mortality.

Vitamin D deficiency attenuates endothelial function by reducing antioxidant activity and vascular eNOS expression in the rat microcirculation

This study examined the effects of vitamin D deficiency on vascular function and tissue oxidative status in the microcirculation; and whether or not these effects can be ameliorated with calcitriol, the active vitamin D metabolite. Three groups (n = 10 each) of male Sprague Dawley rats were fed for 10 weeks with control diet (CR), vitamin D-deficient diet without (DR), or with oral calcitriol supplementation (0.15 μg/kg) for the last four weeks (DSR). After 10 weeks, rats were sacrificed; mesenteric arterial rings were studied using wire myograph. Oxidative stress biomarkers malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were measured in the mesenteric arterial tissue. Vascular protein expression of endothelial nitric oxide synthase (eNOS) was determined by Western blotting. Acetylcholine-induced endothelium-dependent relaxation of DR was lower than CR. eNOS expression and SOD activity were lower in mesenteric arterial tissue of DR compared to CR. Calcitriol supplementation to DSR did not ameliorate the above parameters; in fact, augmented endothelium-dependent contraction was observed. Serum calcium was higher in DSR compared to CR and DR. In conclusion, vitamin D deficiency impaired microvascular vasodilation, associated with eNOS downregulation and reduced antioxidant activity. Calcitriol supplementation to vitamin D-deficient rats at the dosage used augmented endothelium-dependent contraction, possibly due to hypercalcaemia.

Review on oxidative stress relation on COVID-19: Biomolecular and bioanalytical approach

COVID-19 disease has put life of people in stress worldwide from many aspects. Since the virus has mutated in absolutely short period of time the challenge to find a suitable vaccine has become harder. Infection to COVID-19, especially at severe life threatening states is highly dependent on the strength of the host immune system. This system is partially dependent on the balance between oxidative stress and antioxidant. Besides, this virus still has unknown mechanism of action companied by a probable commune period. From another hand, some reactive oxygen species (ROS) levels can be helpful on the state determination of the disease. Thus it could be possible to use modern bioanalytical techniques for their detection and determination, which could indicate the disease state at the golden time window since they have the potential to show whether specific DNA, RNA, enzymes and proteins are affected. This also could be used as a preclude study or a reliable pathway to define the best optimized time of cure beside effective medical actions. Herein, some ROS and their relation with SARS-CoV-2 virus have been considered. In addition, modern bioelectroanalytical techniques on this approach from quantitative and qualitative points of view have been reviewed.

Mechanisms Involved in the Relationship between Vitamin D and Insulin Resistance: Impact on Clinical Practice

Recent evidence has revealed anti-inflammatory properties of vitamin D as well as extra-skeletal activity. In this context, vitamin D seems to be involved in infections, autoimmune diseases, cardiometabolic diseases, and cancer development. In recent years, the relationship between vitamin D and insulin resistance has been a topic of growing interest. Low 25-hydroxyvitamin D (25(OH)D) levels appear to be associated with most of the insulin resistance disorders described to date. In fact, vitamin D deficiency may be one of the factors accelerating the development of insulin resistance. Vitamin D deficiency is a common problem in the population and may be associated with the pathogenesis of diseases related to insulin resistance, such as obesity, diabetes, metabolic syndrome (MS) and polycystic ovary syndrome (PCOS). An important question is the identification of 25(OH)D levels capable of generating an effect on insulin resistance, glucose metabolism and to decrease the risk of developing insulin resistance related disorders. The benefits of 25(OH)D supplementation/repletion on bone health are well known, and although there is a biological plausibility linking the status of vitamin D and insulin resistance supported by basic and clinical research findings, well-designed randomized clinical trials as well as basic research are necessary to know the molecular pathways involved in this association.

Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve?

Nutrition is an important tool that can be used to modulate the immune response during infectious diseases. In addition, through diet, important substrates are acquired for the biosynthesis of regulatory molecules in the immune response, influencing the progression and treatment of chronic lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). In this way, nutrition can promote lung health status. A range of nutrients, such as vitamins (A, C, D, and E), minerals (zinc, selenium, iron, and magnesium), flavonoids and fatty acids, play important roles in reducing the risk of pulmonary chronic diseases and viral infections. Through their antioxidant and anti-inflammatory effects, nutrients are associated with better lung function and a lower risk of complications since they can decrease the harmful effects from the immune system during the inflammatory response. In addition, bioactive compounds can even contribute to epigenetic changes, including histone deacetylase (HDAC) modifications that inhibit the transcription of proinflammatory cytokines, which can contribute to the maintenance of homeostasis in the context of infections and chronic inflammatory diseases. These nutrients also play an important role in activating immune responses against pathogens, which can help the immune system during infections. Here, we provide an updated overview of the roles played by dietary factors and how they can affect respiratory health. Therefore, we will show the anti-inflammatory role of flavonoids, fatty acids, vitamins and microbiota, important for the control of chronic inflammatory diseases and allergies, in addition to the antiviral role of vitamins, flavonoids, and minerals during pulmonary viral infections, addressing the mechanisms involved in each function. These mechanisms are interesting in the discussion of perspectives associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its pulmonary complications since patients with severe disease have vitamins deficiency, especially vitamin D. In addition, researches with the use of flavonoids have been shown to decrease viral replication in vitro. This way, a full understanding of dietary influences can improve the lung health of patients.

Relevance of vitamin D3 in COVID-19 infection

SARS-CoV-2 virus, the main culprit for COVID-19 disaster, has triggered a gust of curiosity both in the mechanism of action of this infection as well as potential risk factors for disease generation and regimentation. The prime focus of the present review, which is basically a narrative one, is in utilizing the current concepts of vitamin D3 as an agent with myriad functions, one of them being immunocompetence and a promising weapon for both innate and adaptive immunity against COVID-19 infection. Some of the manifestations of SARS-CoV-2 virus such as Acute Respiratory Distress Syndrome (ARDS) overlap with the pathophysiological effects that are overcome due to already established role of vitamin D3 e.g., amelioration of cytokine outburst. Additionally, the cardiovascular complications due to COVID-19 infection may also be connected to vitamin D3 levels and the activity of its active forms. Eventually, we summarise the clinical, observational and epidemiological data of the respiratory diseases including COVID-19 disease and try to bring its association with the potential role of vitamin D3, in particular, the activity of its active forms, circulating levels and its supplementation, against dissemination of this disease.

The possible benefits of vitamin D in COVID-19

Molecular studies have demonstrated the importance of the exacerbated immune response to SARS-CoV-2 infection, called the cytokine storm, in more severe COVID-19. The pathophysiology is complex and involves several homeostatic factors; among them, a deficit of vitamin D draws attention because of its high frequency in the population. Some evidence suggests that people with low serum vitamin D levels have worse outcomes, often requiring intensive care. This review analyzed the studies available in the global literature addressing the benefits of vitamin D in COVID-19, relating serum levels to the severity of the disease, and indicating vitamin D as a possible prophylactic and therapy in infection.