Mitochondrial localization of vitamin D receptor in human platelets and differentiated megakaryocytes

1,25-Dihydroxyvitamin D3 attenuates platelet aggregation potentiated by SARS-CoV-2 spike protein via inhibiting integrin αIIbβ3 outside-in signaling

Platelet hyperreactivity contributes to the pathogenesis of COVID-19, which is associated with a hypercoagulability state and thrombosis disorder. It has been demonstrated that Vitamin D deficiency is associated with the severity of COVID-19 infection. Vitamin D supplement is widely used as a dietary supplement due to its safety and health benefits. In this study, we investigated the direct effects and underlying mechanisms of 1,25(OH)2D3 on platelet hyperreactivity induced by SRAS-CoV-2 spike protein via Western blot and platelet functional studies in vitro. Firstly, we found that 1,25(OH)2D3 attenuated platelet aggregation and Src-mediated signaling. We further observed that 1,25(OH)2D3 attenuated spike protein-potentiated platelet aggregation in vitro. Mechanistically, 1,25(OH)2D3 attenuated spike protein upregulated-integrin αIIbβ3 outside-in signaling such as platelet spreading and the phosphorylation of β3, c-Src and Syk. Moreover, using PP2, the Src family kinase inhibitor to abolish spike protein-stimulated platelet aggregation and integrin αIIbβ3 outside-in signaling, the combination of PP2 and 1,25(OH)2D3 did not show additive inhibitory effects on spike protein-potentiated platelet aggregation and the phosphorylation of β3, c-Src and Syk. Thus, our data suggest that 1,25(OH)2D3 attenuates platelet aggregation potentiated by spike protein via downregulating integrin αIIbβ3 outside-in signaling.

Vitamin D deficiency and VDR gene polymorphism FokI (rs2228570) are associated with diabetes mellitus in adults: COVID-inconfidentes study

BACKGROUND

Diabetes mellitus is a chronic and multifactorial condition, including environmental risk factors such as lifestyle habits and genetic conditions.

OBJECTIVE

We aimed to evaluate the association of VDR gene polymorphism (rs2228570) FokI and vitamin D levels with diabetes in adults.

METHODS

Cross-sectional population-based study in adults, conducted from October to December 2020 in two Brazilian cities. The outcome variable was diabetes, defined as glycated hemoglobin ≥ 6.5% or self-report medical diagnosis or use of oral hypoglycemic drugs. Vitamin D (25-hydroxyvitamin D) was measured by indirect electrochemiluminescence, and classified as deficiency when 25(OH)D < 20 ng/mL. All participants were genotyped for VDR FokI polymorphism by qPCR and classified as homozygous mutant (ff or GG), heterozygous (Ff or AG), or homozygous wild (FF or AA). A combined analysis between the FokI polymorphism and vitamin D levels with diabetes was also examined. A directed acyclic graph (DAG) was used to select minimal and sufficient adjustment for confounding variables by the backdoor criterion.

RESULTS

The prevalence of DM was 9.4% and vitamin D deficiency (VDD) was 19.9%. The genotype distribution of FokI polymorphism was 9.9% FF, 44.8% Ff, and 45.3% ff. It was possible to verify a positive association between vitamin D deficiency and DM (OR = 2.19; 95% CI: 1.06-4.50). Individuals with the altered allele (ff) had a 1.78 higher prevalence of DM (OR: 1.78; 95% CI; 1.10-2.87). Combined analyses, individuals with vitamin D deficiency and one or two copies of the altered FokI allele had a higher prevalence of DM (Ff + ff: OR: 1.67; 95% CI; 1.07-2.61; ff: OR: 3.60; 95% CI; 1.40-9.25).

CONCLUSION

Our data suggest that vitamin D deficiency and FokI polymorphism are associated with DM.

The immune cell transcriptome is modulated by vitamin D3 supplementation in people with a first demyelinating event participating in a randomized placebo-controlled trial

Vitamin D deficiency is a risk factor for developing multiple sclerosis. The PrevANZ trial was conducted to determine if vitamin D3 supplementation can prevent recurrent disease activity in people with a first demyelinating event. As a sub-study of this trial, we investigated the effect of supplementation on peripheral immune cell gene expression. Participants were randomized to 1000, 5000 or 10,000 international units daily of vitamin D3 or placebo. Peripheral blood was collected at baseline and 12 weeks and sent for ribonucleic acid sequencing. Datasets from 55 participants were included. Gene expression was modulated by high dose supplementation. Antigen presentation and viral response pathways were upregulated. Oxidative phosphorylation and immune signaling pathways, including tumor necrosis factor-alpha and interleukin-17 signaling, were downregulated. Overall, vitamin D3 supplementation for 12 weeks modulated the peripheral immune cell transcriptome with induction of anti-inflammatory gene expression profiles. Our results support a dose-dependent effect of vitamin D3 supplementation on immune gene expression.

VDR regulates mitochondrial function as a protective mechanism against renal tubular cell injury in diabetic rats

PURPOSE

To investigate the regulatory effect and mechanism of Vitamin D receptor (VDR) on mitochondrial function in renal tubular epithelial cell under diabetic status.

METHODS

The diabetic rats induced by streptozotocin (STZ) and HK-2 cells under high glocose(HG)/transforming growth factor beta (TGF-β) stimulation were used in this study. Calcitriol was administered for 24 weeks. Renal tubulointerstitial injury and some parameters of mitochondrial function including mitophagy, mitochondrial fission, mitochondrial ROS, mitochondrial membrane potential (MMP), mitochondrial ATP, Complex V activity and mitochondria-associated ER membranes (MAMs) integrity were examined. Additionally, paricalcitol, 3-MA (an autophagy inhibitor), VDR over-expression plasmid, VDR siRNA and Mfn2 siRNA were applied in vitro.

RESULTS

The expression of VDR, Pink1, Parkin, Fundc1, LC3II, Atg5, Mfn2, Mfn1 in renal tubular cell of diabetic rats were decreased significantly. Calcitriol treatment reduced the levels of urinary albumin, serum creatinine and attenuated renal tubulointerstitial fibrosis in STZ induced diabetic rats. In addition, VDR agonist relieved mitophagy dysfunction, MAMs integrity, and inhibited mitochondrial fission, mitochondrial ROS. Co-immunoprecipitation analysis demonstrated that VDR interacted directly with Mfn2. Mitochondrial function including mitophagy, mitochondrial membrane potential (MMP), mitochondrial Ca2+, mitochondrial ATP and Complex V activity were decreased dramatically in HK-2 cells under HG/TGF-β ambience. In vitro pretreatment of HK-2 cells with autophagy inhibitor 3-MA, VDR siRNA or Mfn2 siRNA negated the activating effects of paricalcitol on mitochondrial function. Pricalcitol and VDR over-expression plasmid activated Mfn2 and then partially restored the MAMs integrity. Additionally, VDR restored mitophagy was partially associated with MAMs integrity through Fundc1.

CONCLUSION

Activated VDR could contribute to restore mitophagy through Mfn2-MAMs-Fundc1 pathway in renal tubular cell. VDR could recover mitochondrial ATP, complex V activity and MAMs integrity, inhibit mitochondrial fission and mitochondrial ROS. It indicating that VDR agonists ameliorate renal tubulointerstitial fibrosis in diabetic rats partially via regulation of mitochondrial function.

Vitamin D and Cardiovascular Diseases: From Physiology to Pathophysiology and Outcomes

Vitamin D is rightly recognized as an essential key factor in the regulation of calcium and phosphate homeostasis, affecting primary adequate bone mineralization. In the last decades, a more complex and wider role of vitamin D has been postulated and demonstrated. Cardiovascular diseases have been found to be strongly related to vitamin D levels, especially to its deficiency. Pre-clinical studies have suggested a direct role of vitamin D in the regulation of several pathophysiological pathways, such as endothelial dysfunction and platelet aggregation; moreover, observational data have confirmed the relationship with different conditions, including coronary artery disease, heart failure, and hypertension. Despite the significant evidence available so far, most clinical trials have failed to prove any positive impact of vitamin D supplements on cardiovascular outcomes. This discrepancy indicates the need for further information and knowledge about vitamin D metabolism and its effect on the cardiovascular system, in order to identify those patients who would benefit from vitamin D supplementation.

The effect of vitamin D deficiency on platelet parameters in patients with COVID-19

Introduction

Since there is very little information about the relationship between platelet parameters and vitamin D concentration in patients with COVID-19, the aim of this study is to investigate the relationship between serum vitamin D level and platelet parameters in patients with COVID-19 and to compare these parameters in patients with COVID-19 without vitamin D deficiency and, subsequently, the prognostic value of these parameters in cases of vitamin D deficiency.

Methods

Seven hundred and forty-three patients diagnosed with COVID-19 were enrolled in this study. Patients were divided into two groups: those with and without vitamin D deficiency. The associations between platelet indices and vitamin D levels were analyzed by Pearson's correlation analysis and a one-way ANOVA test.

Results

Platelet count and mean platelet volume (MPV) were significantly higher in the patients with vitamin D deficiency than in the patients without vitamin D deficiency. There was a significant negative correlation between platelet count and MPV with vitamin D levels in patients with vitamin D deficiency (r = -0.835, P = 0.001 & r = -0.324, P = 0.042, respectively). Vitamin D levels in COVID-19 patients can determine the platelet count and MPV of the patients.

Discussion

The aforementioned results imply that maintaining an elevated concentration of vitamin D in COVID-19 patients is important because it is associated with a decrease in MPV, which in turn reduces susceptibility to diseases such as coronary artery disease.

Serum vitamin D3 (25-OH vit D3) concentrations and hemogram changes in calves with enzootic pneumonia

BACKGROUND

Enzootic pneumonia is an important disease complex associated with insufficient colostrum intake after birth, adverse environmental conditions, and stress. Vitamin D deficiency may be an important predisposing factor for this disease.

OBJECTIVE

This study aimed to investigate in calves with enzootic pneumonia.

METHODS

A total of 30 calves, aged 3-5 months, under the same care and feeding conditions were used. Groups were formed according to Clinical Respiratory Scoring as the group with mild/moderate enzootic pneumonia (n = 10), the group with severe enzootic pneumonia (n = 10), and the healthy control group (n = 10) without any disease. Blood samples were collected from the jugular vein of animals in all groups on Day 0; a complete blood count was performed, and serum vitamin D levels were measured using the Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method.

RESULTS

Although no statistical differences were observed in total leukocyte, lymphocyte, eosinophil, basophil, hemoglobin, and hematocrit levels between groups, statistically significant differences in blood neutrophil, monocyte, and erythrocyte counts were found between the groups. Monocyte counts were statistically decreased in the mild/moderate group compared with the control group. Neutrophil counts were significantly higher in the mild/moderate and severe groups than in the control group. Erythrocyte counts were increased in the mild/moderate and severe groups compared with the control group. Vitamin D concentrations were statistically lower in the mild/moderate and severe groups than in the control group. However, no statistical differences in Vitamin D concentrations were observed between the mild/moderate and severe groups. There was a negative and significant correlation between erythrocyte counts and vitamin D concentrations (r = -0.64, P < .0001). While erythrocyte counts increased in the severe group compared with the mild/moderate group, vitamin D concentrations decreased. Also, a negative and significant correlation was observed between platelet counts and vitamin D concentrations (r = -0.74, P < .0001).

CONCLUSIONS

The results of this study determined that serum vitamin D concentrations in calves with pneumonia were lower than those in healthy calves. Detailed studies on the etiologic and prognostic importance of low vitamin D levels in calves with enzootic pneumonia may provide valuable data for prevention and treatment.

The relationship between the level of vitamin D and ruptured intracranial aneurysms among patients with high sun exposure

Non-traumatic subarachnoid hemorrhage (SAH) accounts for 3-5% of acute strokes. Intracranial aneurysm is the most common cause of non-traumatic SAH. Vitamin D influences the cardiovascular system, including the formation and rupture of cerebral aneurysms. To evaluate the serum vitamin D level in patients living in the tropical zone who suffered aneurysmal subarachnoid hemorrhage and its correlation with demographic and neurological characteristics. This is an analytical cross-sectional study to assess the serum level of vitamin D in a study population of 99 patients treated and diagnosed with aSAH in a public hospital in Recife-PE over a period of 12 months. In the study sample, composed of individuals with high sun exposure due to the lifestyle they lead in a tropical region, we observed hypovitaminosis D (85.9%), with a median of 19.9 ng/ml, although the majority of individuals are skin with high concentration of melanin (Fitzpatrick skin type IV and V). In addition, rates of sun exposure are high to all patients (Solar Index 9.03 P50). Most individuals were female (79.8%); there was no statistical difference in solar exposure/solar index between genders. As for the neurological repercussions, there was no statistical relevance in the clinical prognostic scales evaluated. As the sample was composed mainly of individuals whose economic activity is agriculture, the values of solar index found are vastly higher than those of other studies conducted in high latitude regions. In line with the literature review, some aspects were raised with the objective of justifying such findings that go from the base of the poor diet of these individuals, the increase of melanin in the skin and genetic alterations that directs us to possible mechanisms of natural photoprotection to high sun exposure. Thus, we had a vast majority (85%) of hypovitaminosis D, which in fact makes us wonder if there is any influence of calcitriol on vitamin D receptors in vascular walls and in the cardiovascular system as a whole, which influence bleeding events of this nature. As for the neurological repercussions, measured using assessment scales (Glasgow coma scale, WFNS scale, Hunt-Hess and Fisher's tomographic scale) there was no significant difference in the results. As it is only a descriptive study, the causal relationship of the facts cannot be established. However, in a population exposed to high sun exposure and affected by aneurysmal SAH, there is a significant rate of hypovitaminosis D, which supports the hypothesis that vitamin D plays a role in vascular pathologies, such as cerebral aneurysms and SAH.

The Relationship between VDR Gene Polymorphisms Bsm1 and Apa1 with Breast Cancer Risk

Background  In addition to its multifaceted physiological functions, vitamin D is recognized for its protective role against cancer. To manifest its effects, vitamin D engages with the vitamin D receptor ( VDR ) gene responsible for its encoding. Investigations have unveiled that polymorphisms within the VDR gene exert influence over the expression and/or functionality of the VDR protein. Notably, certain VDR gene polymorphisms have emerged as particularly pertinent in the context of tumorigenesis, including Fok1 (rs2228570), Bsm1 (rs1544410), Taq1 (rs771236), and Apa1 (rs7975232). This study aims to scrutinize the correlation between the Bsm1 and Apa1 polymorphisms and the susceptibility to breast cancer development. Materials and Methods  In this study, 50 patients suffering from breast cancer with less than 6 months breast cancer diagnosis and 50 healthy control individuals have been chosen. Restriction fragment length polymorphism polymerase chain reaction was used to determine the genotype of polymorphisms. Results  The results of the statistical analysis showed that among the studied polymorphisms, there was no correlation with the development of breast cancer. Conclusion  Studies on various cancers have produced inconsistent results regarding vitamin D's role in the development and progression of cancer. Therefore, further research is necessary to determine vitamin D's role in cancer development and progression.

Metabolic and Genetic Association of Vitamin D with Calcium Signaling and Insulin Resistance

Various evidences have unveiled the significance of Vitamin D in diverse processes which include its action in prevention of immune dysfunction, cancer and cardiometabolic disorders. Studies have confirmed the function of VD in controlling the expression of approximately nine hundred genes including gene expression of insulin. VD insufficiency may be linked with the pathogenesis of diseases that are associated with insulin resistance (IR) including diabetes as well as obesity. Thus, VD lowers IR-related disorders such as inflammation and oxidative stress. This review provides an insight regarding the molecular mechanism manifesting, how insufficiency of VD may be connected with the IR and diabetes. It also discusses the effect of VD in maintaining the Ca2+ levels in beta cells of the pancreas and in the tissues that are responsive to insulin.

Platelets and the Atherosclerotic Process: An Overview of New Markers of Platelet Activation and Reactivity, and Their Implications in Primary and Secondary Prevention

The key role played by platelets in the atherosclerosis physiopathology, especially in the acute setting, is ascertained: they are the main actors during thrombus formation and, thus, one of the major investigated elements related to atherothrombotic process involving coronary arteries. Platelets have been studied from different points of view, according with the technology advances and the improvement in the hemostasis knowledge achieved in the last years. Morphology and reactivity constitute the first aspects investigated related to platelets with a significant body of evidence published linking a number of their values and markers to coronary artery disease and cardiovascular events. Recently, the impact of genetics on platelet activation has been explored with promising findings as additional instrument for patient risk stratification; however, this deserves further confirmations. Moreover, the interplay between immune system and platelets has been partially elucidated in the last years, providing intriguing elements that will be basic components for future research to better understand platelet regulation and improve cardiovascular outcome of patients.

Serum Vitamin D Level as a Risk Factor and Prognostic Marker for Acute Ischemic Stroke: A Case-Control Study at a Tertiary Care Centre in Northern India

Introduction Stroke is a predominant cause of death worldwide. Major risk factors for stroke in any age group are diabetes, hypertension, heart disease, smoking, and long-term alcohol abuse. It is of utmost importance to identify the risk factors for stroke to prevent recurrence. Vitamin D deficiency is identified as a risk factor for stroke. Therefore, we attempted to look for a correlation between vitamin D levels and acute ischemic stroke. Methods This observational case-control study was conducted with 150 patients (75 cases and 75 controls). On the day of admission, the National Institutes of Health Stroke Scale (NIHSS) score was calculated, and vitamin D levels were measured for each patient. The functional outcome was determined by the modified Rankin scale (mRS). Results The most common risk factors identified in this study were hypertension (61.3%), diabetes mellitus (41.3%), and smoking (37.3%). Out of 75 patients enrolled in the study, 49.4% had significant vitamin D deficiency, and 30.6% had insufficient vitamin D levels. Our study showed a significant correlation between vitamin D sufficiency in the body and the incidence of stroke (x2=3.888 and p=0.048). A significant correlation (p=0.03) was found between the NIHSS score and vitamin D levels in patients with acute ischemic stroke. Conclusion In this observational case-control study, we concluded that the increasing severity of vitamin D deficiency was associated with more deaths and poor outcomes.

Mechanisms Suggesting a Relationship between Vitamin D and Erectile Dysfunction: An Overview

Vitamin D deficiency (VDD) and erectile dysfunction (ED) heavily burden the male population. The higher prevalence of both conditions in the elderly suggests a possible relationship between the two conditions. In addition, in vitro, animal, and human studies have revealed several mechanisms that may relate VDD to ED. The main mechanism by which vitamin D might exert its action on sexual function appears to be through the regulation of endothelial function. Indeed, VDD correlates with several markers of endothelial function. The action of vitamin D on the endothelium would be exercised both indirectly through its intervention in inflammatory processes and through the production of oxygen free radicals, and directly through the regulation of vascular stiffness, the production of nitric oxide, and the regulation of vessel permeability. Furthermore, the ubiquitous distribution of the vitamin D receptor in the human body means that this hormone can also exert a beneficial effect on erectile function by interfering with those comorbidities significantly associated with ED, such as hypertension, diabetes mellitus, hypercholesterolemia, chronic kidney disease, and hypogonadism. In this review, we thoroughly and carefully presented the evidence and mechanisms that would appear to relate vitamin D levels to erectile function. Furthermore, we have summarized the meta-analytic evidence for and against this association to provide a true representation of this topic. Data published to date suggest that low levels of vitamin D could contribute to worsening erectile function through several mechanisms. Therefore, vitamin D levels should be measured in patients with ED and maintained at adequate levels by specific supplementation in case of deficiency. However, the low quality and heterogeneity of clinical trials evaluating the effects of vitamin D administration on erectile function and ED-associated comorbidities do not allow for a univocal conclusion, and indicate the need for further studies to analyze these aspects.

Vitamin D receptor regulates transcription of mitochondrial DNA and directly interacts with mitochondrial DNA and TFAM

Vitamin D receptor (VDR) is an essential transcription factor (TF) synthesized in different cell types. We hypothesized that VDR might also act as a mitochondrial TF. We conducted the experiments in primary cortical neurons, PC12, HEK293T, SH-SY5Y cell lines, human peripheral blood mononuclear cells (PBMC) and human brain. We showed that vitamin D/VDR affects the expression of mitochondrial DNA (mtDNA) encoded oxidative phosphorylation (OXPHOS) subunits. We observed the co-localization of VDR with mitochondria and the mtDNA with confocal microscopy. mtDNA-chromatin-immunoprecipitation and electrophoretic mobility shift assays indicated that VDR was able to bind to the mtDNA D-loop site in several locations, with a consensus sequence 'MMHKCA'. We also reported the possible interaction between VDR and mitochondrial transcription factor A (TFAM) and their binding sites located in close proximity in mtDNA. Consequently, our results showed for the first time that VDR was able to bind and regulate mtDNA transcription and interact with TFAM even in the human brain. These results not only revealed a novel function of VDR, but also showed that VDR is indispensable for energy demanded cells.

The Role of Maternal Vitamin D Deficiency in Offspring Obesity: A Narrative Review

Currently, vitamin D (VD) deficiency during pregnancy is widespread globally, causing unfavorable pregnancy outcomes for both mothers and infants for a longer time than expected, based on the Developmental Origins of Health and Disease (DOHaD) theory. As VD plays a key role in maintaining normal glucose and lipid metabolism, maternal VD deficiency may lead to obesity and other obesity-related diseases among offspring later in life. This review mainly focuses on the effect of maternal VD deficiency on offspring lipid metabolism, reviewing previous clinical and animal studies to determine the effects of maternal VD deficit on offspring obesity and potential mechanisms involved in the progression of offspring obesity. Emerging clinical evidence shows that a low VD level may lead to abnormal growth (either growth restriction or largeness for gestational age) and lipid and glucose metabolism disorders in offspring. Here, we also outline the link between maternal VD deficiency and life-long offspring effects, including the disorder of adipogenesis, the secretion of adipocytokines (including leptin, resistin, and adiponectin), activated systemic inflammation, increased oxidative reactions in adipose tissue, insulin resistance, and abnormal intestinal gut microbiota. Thus, there is an urgent need to take active steps to address maternal VD deficiency to relieve the global burden of obesity.

Role of Vitamin D Deficiency in the Pathogenesis of Cardiovascular and Cerebrovascular Diseases

Deficiency in vitamin D (VitD), a lipid-soluble vitamin and steroid hormone, affects approximately 24% to 40% of the population of the Western world. In addition to its well-documented effects on the musculoskeletal system, VitD also contributes importantly to the promotion and preservation of cardiovascular health via modulating the immune and inflammatory functions and regulating cell proliferation and migration, endothelial function, renin expression, and extracellular matrix homeostasis. This brief overview focuses on the cardiovascular and cerebrovascular effects of VitD and the cellular, molecular, and functional changes that occur in the circulatory system in VitD deficiency (VDD). It explores the links among VDD and adverse vascular remodeling, endothelial dysfunction, vascular inflammation, and increased risk for cardiovascular and cerebrovascular diseases. Improved understanding of the complex role of VDD in the pathogenesis of atherosclerotic cardiovascular diseases, stroke, and vascular cognitive impairment is crucial for all cardiologists, dietitians, and geriatricians, as VDD presents an easy target for intervention.

Vitamin D, a Secosteroid Hormone and Its Multifunctional Receptor, Vitamin D Receptor, in Alzheimer's Type Neurodegeneration

Vitamin D is a secosteroid hormone exerting neurosteroid-like properties. Its well-known nuclear hormone receptor, and recently proposed as a mitochondrial transcription factor, vitamin D receptor, acts for its primary functions. The second receptor is an endoplasmic reticulum protein, protein disulfide isomerase A3 (PDIA3), suggested to act as a rapid response. Vitamin D has effects on various systems, particularly through calcium metabolism. Among them, the nervous system has an important place in the context of our subject. Recent studies have shown that vitamin D and its receptors have numerous effects on the nervous system. Neurodegeneration is a long-term process. Throughout a human life span, so is vitamin D deficiency. Our previous studies and others have suggested that the out-come of long-term vitamin D deficiency (hypovitaminosis D or inefficient utilization of vitamin D), may lead neurons to be vulnerable to aging and neurodegeneration. We suggest that keeping vitamin D levels at adequate levels at all stages of life, considering new approaches such as agonists that can activate vitamin D receptors, and utilizing other derivatives produced in the synthesis process with UVB are crucial when considering vitamin D-based intervention studies. Given most aspects of vitamin D, this review outlines how vitamin D and its receptors work and are involved in neurodegeneration, emphasizing Alzheimer's disease.

Nongenomic Activities of Vitamin D

Vitamin D shows a variety of pleiotropic activities which cannot be fully explained by the stimulation of classic pathway- and vitamin D receptor (VDR)-dependent transcriptional modulation. Thus, existence of rapid and nongenomic responses to vitamin D was suggested. An active form of vitamin D (calcitriol, 1,25(OH)₂D₃) is an essential regulator of calcium-phosphate homeostasis, and this process is tightly regulated by VDR genomic activity. However, it seems that early in evolution, the production of secosteroids (vitamin-D-like steroids) and their subsequent photodegradation served as a protective mechanism against ultraviolet radiation and oxidative stress. Consequently, direct cell-protective activities of vitamin D were proven. Furthermore, calcitriol triggers rapid calcium influx through epithelia and its uptake by a variety of cells. Subsequently, protein disulfide-isomerase A3 (PDIA3) was described as a membrane vitamin D receptor responsible for rapid nongenomic responses. Vitamin D was also found to stimulate a release of secondary massagers and modulate several intracellular processes-including cell cycle, proliferation, or immune responses-through wingless (WNT), sonic hedgehog (SSH), STAT1-3, or NF-kappaB pathways. Megalin and its coreceptor, cubilin, facilitate the import of vitamin D complex with vitamin-D-binding protein (DBP), and its involvement in rapid membrane responses was suggested. Vitamin D also directly and indirectly influences mitochondrial function, including fusion-fission, energy production, mitochondrial membrane potential, activity of ion channels, and apoptosis. Although mechanisms of the nongenomic responses to vitamin D are still not fully understood, in this review, their impact on physiology, pathology, and potential clinical applications will be discussed.

Linoleic acid-derived oxylipins and isoprostanes plasma levels are influenced by 1,25-Dihydroxyvitamin D levels in middle-aged sedentary adults: The FIT-AGEING study

INTRODUCTION

Vitamin D - concretely its active form 1,25-dihydroxyvitamin D (1,25(OH)₂D) - maintains several physiological processes. Oxylipins are oxidized lipids derived from ω-6 and ω-3 polyunsaturated fatty acids involved in inflammation. Little is known about the association of 1,25(OH)₂D with inflammatory parameters in middle-aged populations - who could be at risk of vitamin D deficiency -. The aim of this study was to investigate the relationship between 1,25(OH)₂D plasma levels with circulating white blood cells, platelets counts and oxylipins levels.

MATERIALS AND METHODS

A total of 74 (53 % women) middle-aged (40-65 years old) adults were recruited for this cross-sectional study. 1,25(OH)₂D plasma levels were measured using an immunochemiluminometric assay. White blood cells and platelets were analyzed by hemocytometry. ω-6 and ω-3 oxylipins plasma levels were measured using liquid chromatography - tandem mass spectrometry. Simple and multiple linear regression models, and Pearson correlation analyses, were performed to study the association of 1,25(OH)₂D levels with WBC and platelets counts, and oxylipins, respectively.

RESULTS

1,25(OH)₂D plasma levels were positively related with linoleic acid-derived oxylipins and isoprostanes plasma levels, whereas an inverse relationship with dihomo-γ-linolenic acid/linoleic acid and arachidonic acid/linoleic acid ratios was unveiled. No significant associations were observed for circulating ω-3 oxylipins, white blood cells levels or platelets count.

CONCLUSIONS

Linoleic acid-derived oxylipins and isoprostanes plasma levels may be influenced by 1,25(OH)₂D plasma levels. Further investigations are needed to elucidate the impact of other vitamin D forms upon circulating oxylipins levels.

HEMATOLOGICAL INDICES RELATED TO VITAMIN D DEFICIENCY IN OBESE CHILDREN

Introduction

Vitamin D is involved in differentiation and induction of erythropoiesis in bone marrow cells.

Aim

We compared the serum 25(OH) vitamin D level in obese children versus control and found correlations between vitamin D level and hematological indices in obese children.

Materials and methods

25 overweight and obese patients and 15 normal weight children were enrolled in an observational study .

Results

In obese children, the serum level of 25(OH) vitamin D was significantly (p<0.04) lower (20.60 ng/mL) compared with the value from normal weight ones (25.63 ng/mL) and the body fat percentage BFP was higher. We found a positive correlation (r=0.44, p<0.05) between serum vitamin D and hemoglobin level and a negative one between serum vitamin D and the number of platelets (r= -0.43, p<0.05). Also, the serum iron was at the lower normal limit in the obese children and negatively correlated with the percent of the body fat (r= -0,62, p<0.05).

Conclusion

Obese children have vitamin D deficiency. The hemoglobin level and the number of platelets are correlated with the serum level of 25(OH) vitamin D. Supplements with vitamin D may have pleiotropic effects, including those on bone marrow activity.

Effects of Dietary Vitamin D Deficiency on Markers of Skeletal Muscle Mitochondrial Biogenesis and Dynamics

We examined the effects of dietary vitamin D deficiency on markers of mitochondrial biogenesis and dynamics in rat soleus muscle. Male Wistar rats were fed a chow with no vitamin D (No-D; 0 IU/kg) or a moderate dose (Mod-D; 2,000 IU/kg) of vitamin D chow for 8 wk. Compared to the Mod-D group, at 8 wk the No-D group showed significantly lower serum 25(OH)D levels. Although vitamin D deficiency had no effect on body composition, the No-D rats showed significantly decreased levels of PGC-1α, a marker of skeletal muscle mitochondrial biogenesis, and DRP1, a marker of skeletal muscle mitochondrial fission. The change in the PGC-1α protein expression and the serum 25(OH)D concentrations were significantly correlated. The change in DRP1 protein expression and the serum 25(OH)D concentrations tended to be correlated. There was no significant between-group difference in markers of mitochondrial fusion (MFN2 and OPA1) and mitophagy (PARKIN) in soleus muscle, and no relationship with serum 25(OH)D concentrations. Collectively our findings suggest that dietary vitamin D deficiency decreased PGC-1α and DRP1 protein expression in rat soleus muscle.

Hypocholesterolemia and Inflammatory Biomarkers Act as Predictors of Severe Vitamin D Deficiency in Patients With Crohn’s Disease: A Clinical Analysis of 862 Patients in China

Background

In this study, we enrolled 862 patients with Crohn’s disease (CD) in China to investigate the correlation between serum vitamin D (SVD) and serum lipids, inflammatory biomarkers, and important clinical parameters.

Materials and Methods

25(OH)D was measured by LS/MS/MS. Correlation analysis, chi-square tests, and logistic regression analysis were performed to determine the correlations between vitamin D and potential risk factors when vitamin D levels were lower than 10 ng/mL or 20 ng/mL.

Results

The incidence of severe vitamin D deficiency (SVD < 10 ng/mL) in patients with CD was significantly higher than that in healthy controls (28.9 vs. 9.5%). Multinomial logistic regression analysis showed that penetrating disease [odds ratio (OR) = 2.18], low levels of high-density lipoprotein cholesterol (HDL) (OR = 1.91), high erythrocyte sedimentation rate (OR = 1.73), and platelet count (PLT) (OR = 2.71) were regarded as predictors of severe vitamin D deficiency, while only PLT (OR = 1.90) and HDL (OR = 1.76) were considered as predictors of mild vitamin D deficiency (SVD 10–20 ng/mL).

Conclusion

Our results confirm a higher incidence of severe vitamin D deficiency in patients with CD in China and show that vitamin D deficiency could result from the combined effects of penetrating disease, inflammation, and low levels of HDL.

The Role of Vitamin D in Supporting Health in the COVID-19 Era

The genomic activity of vitamin D is associated with metabolic effects, and the hormone has a strong impact on several physiological functions and, therefore, on health. Among its renowned functions, vitamin D is an immunomodulator and a molecule with an anti-inflammatory effect, and, recently, it has been much studied in relation to its response against viral infections, especially against COVID-19. This review aims to take stock of the correlation studies between vitamin D deficiency and increased risks of severe COVID-19 disease and, similarly, between vitamin D deficiency and acute respiratory distress syndrome. Based on this evidence, supplementation with vitamin D has been tested in clinical trials, and the results are discussed. Finally, this study includes a biochemical analysis on the effects of vitamin D in the body's defense mechanisms against viral infection. In particular, the antioxidant and anti-inflammatory functions are considered in relation to energy metabolism, and the potential, beneficial effect of vitamin D in COVID-19 is described, with discussion of its influence on different biochemical pathways. The proposed, broader view of vitamin D activity could support a better-integrated approach in supplementation strategies against severe COVID-19, which could be valuable in a near future of living with an infection becoming endemic.

Old and Novel Therapeutic Approaches in the Management of Hyperglycemia, an Important Risk Factor for Atherosclerosis

Hyperglycemia is considered one of the main risk factors for atherosclerosis, since high glucose levels trigger multiple pathological processes, such as oxidative stress and hyperproduction of pro-inflammatory mediators, leading to endothelial dysfunction. In this context, recently approved drugs, such as glucagon-like-peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2i), could be considered a powerful tool for to reduce glucose concentration and cardiovascular risk. Interestingly, many patients with type 2 diabetes mellitus (T2DM) and insulin resistance have been found to be deficient in vitamin D. Recent studies pointed out the unfavorable prognostic values of T2DM and vitamin D deficiency in patients with cardiac dysfunction, either when considered individually or together, which shed light on the role of vitamin D in general health status. New evidence suggests that SGLT2i could adversely affect the production of vitamin D, thereby increasing the risk of fractures, which are common in patients with T2DM. Therefore, given the biological effects of vitamin D as an anti-inflammatory mediator and a regulator of endothelial function and calcium equilibrium, these new findings should be taken into consideration as well. The aim of this review is to gather the latest advancements regarding the use of antidiabetic and antiplatelet drugs coupled with vitamin D supplementation to control glucose levels, therefore reducing the risk of coronary artery disease (CAD).

Relationship Between Vitamin D Level and Platelet Parameters in Children With Viral Respiratory Infections

Apart from their classical roles, both platelets and vitamin D play important roles in inflammation and infectious diseases. This study evaluated the platelet response to viral respiratory tract infection in children aged 4-16 years, 32 with influenza, 27 with non-influenza viral infection tested by nasopharyngeal swab and 21 healthy children of the same age. Blood count, including platelet count (PLT), mean platelet volume (MPV) and other platelet indices, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and vitamin D (vit D) levels were compared. The influenza group showed lower PLT and platelet mass (PLT^*MPV), and the non-influenza group showed significantly lower MPV, which was correlated with the vit D levels, but not CRP or ESR, and the value vit D^*MPV was significantly lower in this group. These results revealed that platelet activation in viral respiratory tract infections in children, as measured by MPV, is related to the vit D level, with differences between influenza and non-influenza infection.

CONCLUSIONS

Viral respiratory tract infection in children can diminish the platelet size most likely by suppressing the platelet activation. This response is associated with low levels of vit D. Whether the vit D status is associated with the virus-platelet immune/inflammatory process needs further investigation.

Vitamin D status is favorably associated with the cardiovascular risk factors in adults with obesity

BACKGROUND & AIMS

Previous investigations have been indicated that vitamin D deficiency is an amendable risk for cardiovascular disease (CVD) in the general populations. Limited data is available concerning the relationship of vitamin D status and risk factors of CVD in the individuals with obesity and the existing data are highly controversial. We investigated whether serum vitamin D situation is related to multiple traditional CVD risk factors in Iranian obese subjects.

METHODS

A cross-sectional study was done among 214 Iranian adults with obesity (94 males and 120 females) aged 20-60 years, who attended the specialized outpatient clinics in Zabol city. Participants were categorized as vitamin D sufficient, insufficient, and deficient according to their serum 25(OH)D concentrations. Afterward, the presence of hypercholesterolemia, hypertriglyceridemia, low high-density lipoprotein cholesterol (HDL-C), high low-density lipoprotein cholesterol (LDL-C) as well as diabetes, hypertension, and high serum concentrations of high-sensitivity C-reactive protein (hs-CRP) as CVD risk factors were evaluated in the participants.

RESULTS

There was a noticeable regular trend regarding hypercholesterolemia (p = 0.008), high LDL-C (p = 0.024), hypertension (p = 0.021), and high hs-CRP (p < 0.0001) across various categories of vitamin D status. In adjusted model, vitamin D-deficient subjects were at higher risk for having hypercholesterolemia (OR: 3.22, p = 0.031), high LDL-C (OR: 2.37, p = 0.047), hypertension (OR: 2.32, p = 0.042), and high hs-CRP (OR: 5.49, p = 0.001) than ones with sufficient vitamin D status.

CONCLUSIONS

Vitamin D deficiency in obese subjects was found to be strongly related to higher risk of unfavorable lipid profile, hypertension, and high hs-CRP.

Narrative review of recent studies on the role of vitamin D in the prevention of cardiac and renal risk and additional considerations for COVID-19 vulnerability

The role of vitamin D in maintaining a healthy cardiovascular (CV) and the renal system has received increasing attention. Low vitamin D levels are associated with the incidence of hypertension, cardiac remodeling, and chronic congestive heart failure. Low vitamin D levels also influence renal disease progression and albuminuria deterioration. Moreover, recent research indicates that vitamin D deficiency can be a potential risk factor for coronavirus disease-19 (COVID-19) infection and poorer outcomes. Data are inconclusive as to whether supplementation with vitamin D agents reduces CV disease risk or COVID-19 severity. Conversely, in patients with kidney disease, vitamin D supplementation is associated with improved kidney function and albuminuria. This narrative review considers recent data on the effects of vitamin D on the CV and renal system, as well as its possible role regarding COVID-19 complications.

Vitamin D and Cardiovascular Disease: Current Evidence and Future Perspectives

Vitamin D deficiency is a prevalent condition, occurring in about 30–50% of the population, observed across all ethnicities and among all age groups. Besides the established role of vitamin D in calcium homeostasis, its deficiency is emerging as a new risk factor for cardiovascular disease (CVD). In particular, several epidemiological and clinical studies have reported a close association between low vitamin D levels and major CVDs, such as coronary artery disease, heart failure, and atrial fibrillation. Moreover, in all these clinical settings, vitamin deficiency seems to predispose to increased morbidity, mortality, and recurrent cardiovascular events. Despite this growing evidence, interventional trials with supplementation of vitamin D in patients at risk of or with established CVD are still controversial. In this review, we aimed to summarize the currently available evidence supporting the link between vitamin D deficiency and major CVDs in terms of its prevalence, clinical relevance, prognostic impact, and potential therapeutic implications.

Vitamin D Receptor Gene Polymorphism and Vitamin D Status in Population of Patients with Cardiovascular Disease-A Preliminary Study

The association between vitamin D receptor (VDR) polymorphism and the risk of cardiovascular diseases (CVD) remains unclear. This study aimed to assess a relationship between the VDR genotypes, plasma concentrations of vitamin D metabolites, and the occurrence of cardiovascular and metabolic disorders. Fifty-eight patients treated for various cardiological afflictions were included. Identification of VDR polymorphisms: ApaI, TaqI, BsmI, and FokI were carried out using the PCR-RFLP method. Plasma concentrations of 25-hydroxyvitamin-D2, 25-hydroxyvitamin-D3, and 3-epi-25-hydroxyvitamin D3 were assessed by the UPLC-MS/MS method. Lower incidence of BsmI AA genotype in the studied patients was observed compared with healthy controls, but the difference was insignificant. Among patients with the TT genotype, frequency of hypertension was higher than among carriers of other ApaI genotypes (p < 0.01). In addition, carriers of the TT ApaI, TC TaqI, and GA BsmI genotypes had an increased risk of obesity, while the presence of the FokI TT genotype was associated with a higher incidence of heart failure and hypertension. In conclusion, the BsmI AA genotype can be protective against CVD, but this observation needs study on a larger group of patients. Particular VDR genotypes were associated with 25-hydroxyvitamin-D levels, and the mechanism of this association should be further investigated.

Blood factors as biomarkers in osteoporosis: points from the COVID-19 era

The restrictions adopted during the coronavirus disease 2019 (COVID-19) pandemic limiting direct medical consultations and access to healthcare centers reduced the participation of patients with chronic diseases, such as osteoporosis (OP), in screening and monitoring programs. This highlighted the need for new screening diagnostic tools that are clinically effective, but require minimal technical and time commitments, to stratify populations and identify who is more at risk for OP and related complications. This paper provides an overview of the potential use of blood-related factors, such as platelet (PLT)- and monocyte-related factors, as biomarkers able to quickly screen, detect, and monitor OP in both sexes. Such biomarkers might be of key importance not only during the COVID-19 pandemic but also, even more importantly, during periods of better global health stability.

Expression of renal vitamin D receptors and metabolizing enzymes in IgA nephropathy

AIM

One of the main causes of end-stage renal disease (ESRD) in the world is IgA nephropathy (IgAN). Since kidney is a key player in vitamin D metabolism, we investigated the expression of renal vitamin D receptors (VDR) and metabolizing enzymes in IgA nephropathy patients (IgAN-P).

METHODS

The sample included twelve IgAN-P who underwent ultrasound-guided renal biopsies and five controls who underwent nephrectomy due to clear renal carcinoma. Immunofluorescent staining was used to determine the expression of VDR, 25-hydroxyvitamin D3 -alpha-hydroxylase (1alpha-OHase) and vitamin D3 24-hydroxylase (CYP24A1).

RESULTS

Significant increase in expression of VDR, which was prominent in distal tubular cells (DTCs) in tissues from IgAN-P, was found in comparison to the controls (p = 0.0368). The expression of 1alpha-OHase, calcitriol synthesizing enzyme, was significantly lower in IgAN-P, in comparison with controls (p < 0.0001). The opposite, expression of CYP24A1 (vitamin D degrading enzyme), was significantly higher in IgAN-P in comparison with controls (p = 0.0003). Additionally, we found significant negative correlation between percentage of CYP24A1 immunoreactive nuclei in proximal tubular cells (PTCs) and estimated glomerular filtration rate (eGFR) in IgAN-P (r = -0.6139; p = 0.0337).

CONCLUSIONS

Our research indicates substantially decreased renal calcitriol production and increased vitamin D degradation in kidneys of IgAN-P, but larger studies are needed to confirm our results.

Calcitriol attenuates the cytotoxicity induced by aluminium phosphide via inhibiting mitochondrial dysfunction and oxidative stress in rat isolated cardiomyocytes

These days, poisoning with aluminium phosphide (AlP), is one of the main health threats in human societies. Previous studies have been reported that cardiotoxicity induced by AlP, via mitochondrial dysfunction and oxidative stress is the main cause of death in victims. On the other, collectively, multiple lines of evidence strongly suggest that calcitriol has mitochondrial protective and antioxidant effects. Therefore, we assumed that calcitriol could presumably ameliorate AlP-induced oxidative stress and mitochondrial dysfunction in cardiomyocytes. Mitochondria and cardiomyocytes were isolated by differential centrifugation and collagenase perfusion respectively from rat heart. The isolated cardiomyocytes and mitochondria were cotreated with different concentrations of calcitriol (0.2, 0.4 and 1 μg/ml) and AlP (20 μg/ml) for 3 h. The parameters of cellular toxicity including; cytotoxicity, reactive oxygen species (ROS) formation, malondialdehyde (MDA) level, mitochondria membrane potential (ΔΨm) collapse, lysosomal membrane integrity, the level of oxidized and reduced glutathione (GSH and GSSG), and mitochondrial toxicity parameters including; succinate dehydrogenase (SDH) activity and mitochondrial swelling were analyzed using biochemical and flow cytometric evaluations. Administration of AlP significantly increased cytotoxicity, GSH depletion, cellular ROS formation, MDA level, mitochondrial and lysosomal dysfunction in isolated cardiomyocytes. In isolated mitochondria, AlP decreased SDH activity and mitochondrial swelling. The cotreatment of isolated cardiomyocytes and mitochondria with calcitriol (0.4 and 1 μg/ml) and AlP (20 μg/ml) showed the ability to reduce the toxic effects of AlP. These findings suggest a potential therapeutic role of calcitriol in protecting cardiomyocytes and cardiac mitochondria from oxidative damage induced by AlP. According to the results, calcitriol exerted ameliorative effects against AlP-induced cytotoxicity and mitochondrial toxicity, and the effect was attributed to the antioxidant properties.

Is Vitamin D Deficiency Related to Increased Cancer Risk in Patients with Type 2 Diabetes Mellitus?

There is mounting evidence that type 2 diabetes mellitus (T2DM) is related with increased risk for the development of cancer. Apart from shared common risk factors typical for both diseases, diabetes driven factors including hyperinsulinemia, insulin resistance, hyperglycemia and low grade chronic inflammation are of great importance. Recently, vitamin D deficiency was reported to be associated with the pathogenesis of numerous diseases, including T2DM and cancer. However, little is known whether vitamin D deficiency may be responsible for elevated cancer risk development in T2DM patients. Therefore, the aim of the current review is to identify the molecular mechanisms by which vitamin D deficiency may contribute to cancer development in T2DM patients. Vitamin D via alleviation of insulin resistance, hyperglycemia, oxidative stress and inflammation reduces diabetes driven cancer risk factors. Moreover, vitamin D strengthens the DNA repair process, and regulates apoptosis and autophagy of cancer cells as well as signaling pathways involved in tumorigenesis i.e., tumor growth factor β (TGFβ), insulin-like growth factor (IGF) and Wnt-β-Cathenin. It should also be underlined that many types of cancer cells present alterations in vitamin D metabolism and action as a result of Vitamin D Receptor (VDR) and CYP27B1 expression dysregulation. Although, numerous studies revealed that adequate vitamin D concentration prevents or delays T2DM and cancer development, little is known how the vitamin affects cancer risk among T2DM patients. There is a pressing need for randomized clinical trials to clarify whether vitamin D deficiency may be a factor responsible for increased risk of cancer in T2DM patients, and whether the use of the vitamin by patients with diabetes and cancer may improve cancer prognosis and metabolic control of diabetes.

TGF Beta Induces Vitamin D Receptor and Modulates Mitochondrial Activity of Human Pancreatic Cancer Cells

The inflammatory cytokine TGFβ is both a tumor suppressor during cancer initiation and a promoter of metastasis along cancer progression. Inflammation and cancer are strictly linked, and cancer onset often correlates with the insufficiency of vitamin D, known for its anti-inflammatory properties. In this study, we investigated the interplay between TGFβ and vitamin D in two models of human pancreatic cancer, and we analyzed the metabolic effects of a prolonged TGFβ treatment mimicking the inflammatory environment of pancreatic cancer in vivo. We confirmed the induction of the vitamin D receptor previously described in epithelial cells, but the inhibitory effects of vitamin D on epithelial-mesenchymal transition (EMT) were lost when the hormone was given after a long treatment with TGFβ. Moreover, we detected an ROS-mediated toxicity of the acute treatment with TGFβ, whereas a chronic exposure to low doses had a protumorigenic effect. In fact, it boosted the mitochondrial respiration and cancer cell migration without ROS production and cytotoxicity. Our observations shed some light on the multifaceted role of TGFβ in tumor progression, revealing that a sustained exposure to TGFβ at low doses results in an irreversibly increased EMT associated with a metabolic modulation which favors the formation of metastasis.

Vitamin D regulation of energy metabolism in cancer

Vitamin D exerts anti-cancer effects in recent clinical trials and preclinical models. The actions of vitamin D are primarily mediated through its hormonal form, 1,25-dihydroxyvitamin D (1,25(OH)₂ D). Previous literature describing in vitro studies has predominantly focused on the anti-tumourigenic effects of the hormone, such as proliferation and apoptosis. However, recent evidence has identified 1,25(OH)₂ D as a regulator of energy metabolism in cancer cells, where requirements for specific energy sources at different stages of progression are dramatically altered. The literature suggests that 1,25(OH)₂ D regulates energy metabolism, including glucose, glutamine and lipid metabolism during cancer progression, as well as oxidative stress protection, as it is closely associated with energy metabolism. Mechanisms involved in energy metabolism regulation are an emerging area in which vitamin D may inhibit multiple stages of cancer progression.

Tryptophan Metabolites and Aryl Hydrocarbon Receptor in Severe Acute Respiratory Syndrome, Coronavirus-2 (SARS-CoV-2) Pathophysiology

The metabolism of tryptophan is intimately associated with the differential regulation of diverse physiological processes, including in the regulation of responses to severe acute respiratory syndrome, coronavirus-2 (SARS-CoV-2) infection that underpins the COVID-19 pandemic. Two important products of tryptophan metabolism, viz kynurenine and interleukin (IL)4-inducible1 (IL41)-driven indole 3 pyruvate (I3P), activate the aryl hydrocarbon receptor (AhR), thereby altering the nature of immune responses to SARS-CoV-2 infection. AhR activation dysregulates the initial pro-inflammatory cytokines production driven by neutrophils, macrophages, and mast cells, whilst AhR activation suppresses the endogenous antiviral responses of natural killer cells and CD8+ T cells. Such immune responses become further dysregulated by the increased and prolonged pro-inflammatory cytokine suppression of pineal melatonin production coupled to increased gut dysbiosis and gut permeability. The suppression of pineal melatonin and gut microbiome-derived butyrate, coupled to an increase in circulating lipopolysaccharide (LPS) further dysregulates the immune response. The AhR mediates its effects via alterations in the regulation of mitochondrial function in immune cells. The increased risk of severe/fatal SARS-CoV-2 infection by high risk conditions, such as elderly age, obesity, and diabetes are mediated by these conditions having expression levels of melatonin, AhR, butyrate, and LPS that are closer to those driven by SARS-CoV-2 infection. This has a number of future research and treatment implications, including the utilization of melatonin and nutraceuticals that inhibit the AhR, including the polyphenols, epigallocatechin gallate (EGCG), and resveratrol.

Antagonistic effect of VDR/CREB1 pathway on cadmium-induced apoptosis in porcine spleen

Cadmium (Cd) is a toxic trace element that can enter the environment with industrial waste and accumulate in the body but the health effects of Cd on ternary pigs are still lacking in research. In order to explore the effect of Cd on the apoptosis of pig spleen and its mechanism, this study chose ternary pig as the research object to detect relevant indicators in pig spleen under Cd exposure. The results of this study showed that Cd exposure can induce apoptosis by promoting the absorption of various toxic trace elements in the spleen and inducing oxidative stress. We also found that the mechanism of Cd-induced apoptosis is closely related to the VDR/CREB1 pathway. On the one hand, Cd exposure can activate VDR, and indirectly regulate the CYP family, affecting the normal function of the spleen. On the other hand, VDR and its downstream genes antagonize the toxicity of Cd by maintaining the stability of the mitochondrial-related endoplasmic reticulum membrane structure. Our research will help researchers to further understand the physiological toxicity of Cd.

The mechanisms of skeletal muscle atrophy in response to transient knockdown of the vitamin D receptor in vivo

KEY POINTS

Reduced vitamin D receptor (VDR) expression prompts skeletal muscle atrophy. Atrophy occurs through catabolic processes, namely the induction of autophagy, while anabolism remains unchanged. In response to VDR-knockdown mitochondrial function and related gene-set expression is impaired. In vitro VDR knockdown induces myogenic dysregulation occurring through impaired differentiation. These results highlight the autonomous role the VDR has within skeletal muscle mass regulation.

ABSTRACT

Vitamin D deficiency is estimated to affect ∼40% of the world's population and has been associated with impaired muscle maintenance. Vitamin D exerts its actions through the vitamin D receptor (VDR), the expression of which was recently confirmed in skeletal muscle, and its down-regulation is linked to reduced muscle mass and functional decline. To identify potential mechanisms underlying muscle atrophy, we studied the impact of VDR knockdown (KD) on mature skeletal muscle in vivo, and myogenic regulation in vitro in C2C12 cells. Male Wistar rats underwent in vivo electrotransfer (IVE) to knock down the VDR in hind-limb tibialis anterior (TA) muscle for 10 days. Comprehensive metabolic and physiological analysis was undertaken to define the influence loss of the VDR on muscle fibre composition, protein synthesis, anabolic and catabolic signalling, mitochondrial phenotype and gene expression. Finally, in vitro lentiviral transfection was used to induce sustained VDR-KD in C2C12 cells to analyse myogenic regulation. Muscle VDR-KD elicited atrophy through a reduction in total protein content, resulting in lower myofibre area. Activation of autophagic processes was observed, with no effect upon muscle protein synthesis or anabolic signalling. Furthermore, RNA-sequencing analysis identified systematic down-regulation of multiple mitochondrial respiration-related protein and genesets. Finally, in vitro VDR-knockdown impaired myogenesis (cell cycling, differentiation and myotube formation). Together, these data indicate a fundamental regulatory role of the VDR in the regulation of myogenesis and muscle mass, whereby it acts to maintain muscle mitochondrial function and limit autophagy.

Relationship between vitamin D deficiency and psychophysiological variables: a systematic review of the literature

Vitamin D is a fat-soluble vitamin that plays a role not only in calcium homeostasis, but also in several other functions, including cell growth and immune functions, and is considered a neurosteroid. Vitamin D deficiency is highly prevalent worldwide and has been suggested to be associated with an increased risk of emotional disorders. Therefore, the association between vitamin D levels and psychophysiological disorders, such as depression, anxiety, and mood, has been investigated. To list these variables, a bibliographical literature research was conducted in the MEDLINE/PubMed, Web of Science, Scopus, Science Direct and PsycINFO databases, between November and December 2020, with no year limits of publication. The studies involved humans aged between 18 and 59 years without associated diseases. This review presents evidence of the main variables involved in this association, main tools used to verify these variables, and methods used to verify circulating vitamin D levels in populations. Most studies have indicated that the main psychophysiological variables involved with vitamin D levels are depression and anxiety followed by mood, and an association has been observed between increased serum vitamin D levels and reduction in symptoms of depression, anxiety, and mood, and there is a heterogeneity of methods for assessing vitamin D. More studies are clearly needed to improve our understanding of their role in modulating the psychophysiological aspects of vitamin D levels.

Prognostic impact of Vitamin D deficiency in patients with coronary artery disease undergoing percutaneous coronary intervention

BACKGROUND

Whether Vitamin D deficiency represents an independent predictor of mortality and major cardiovascular events or rather the mirror of a more advanced clinical condition with increased comorbidities is still debated. We aimed at assessing the impact of vitamin D levels on the long-term outcomes among patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention.

METHODS

Consecutive patients from a single centre were included. Vitamin D levels were measured at admission by chemiluminescence immunoassay kit LIAISON® Vitamin D assay (Diasorin Inc). Severe deficiency was defined for 25(OH)D < 10 ng/ml. The primary study endpoint was overall mortality. Secondary endpoints were cardiovascular mortality, recurrent acute coronary syndrome or major cardiovascular events (a composite of death, recurrent MI and target vessel revascularization) at the longest available follow-up.

RESULTS

We included a total of 705 patients, that were divided according to vitamin D tertiles (<12.7; 12.7-21.59; ≥21.6 ng/ml). Lower levels of Vitamin D were associated with renal failure (p=0.03), more severe coronary disease (p=0.001), diabetes mellitus and previous CABG (p<0.001), lower ejection fraction (p=0.02), acute presentation (p=0.04), use of statins (p=0.02), diuretics, nitrates and clopidogrel (p<0.001) and RASI (p=0.008). An inverse association was documented with BMI, glycemia, total cholesterol (p<0.001), creatinine and WBC (p=0.001). At a median follow-up of 996.5 [377-1552] days, 3.8% of the patients died. Vitamin D deficiency was significantly associated with overall mortality (7.6% vs 2.9% vs 0.4%, adjusted HR[95%CI]=3.6[1.43-8.9], p=0.006), MACE (adjusted HR[95%CI]=1.32[1.07-1.63], p=0.01) and the composite of death and MI (adjusted HR[95%CI]=1.3[1.03-1.65], p=0.03). A similarly increased risk was confirmed for all major higher-risk subsets of patients, with no significant interaction according to age, gender, diabetes mellitus or chronic kidney disease.

CONCLUSION

Among patients undergoing percutaneous coronary interventions, lower levels of vitamin D are associated with an over 3-fold increased risk of mortality and major cardiovascular events. Future larger studies are certainly warranted in order to define the prognostic implications of cholecalciferol supplementation among high-risk patients with established coronary artery disease.

Vitamin D high doses supplementation could represent a promising alternative to prevent or treat COVID-19 infection

Although we lack enough evidence to justify supplementing with vitamin D in the prevention and treatment of COVID-19 infection, it is increasingly feasible that this hypothesis is valid. Two general underlying mechanisms should be considered. One would be the anti-infectious and immunomodulatory action that it exerts by improving intercellular barriers by stimulating innate immunity, as well as by modulating adaptive immunity. Also, vitamin D reduces the production of inflammatory cytokines, such as IL-2 and interferon-gamma (INFγ). More recently, multiple pleiotropic effects have been demonstrated on the actions of vitamin D at the anti-inflammatory and immunomodulatory level with positive results in studies with influenza, coronavirus, and other respiratory infections. An inverse relationship between serum vitamin D levels and the prevalence of the respiratory infectious disease has been described. Of interest, another mechanistic approach responds to considering the inhibition of the renin-angiotensin-aldosterone system (RAAS), which is exacerbated in COVID-19 infection because the virus binds to the enzyme ACE2, making more angiotensin II available to cause damage. Vitamin D inhibits mediators of RAAS – present in all cells of the body – and by inhibiting ACE activity and increasing ACE2, it lowers angiotensin II levels. We present studies with proposals for recommended doses of vitamin D, and although a single guideline is not specified, the possible benefits are promising. Finally, the purpose of this review is to share this idea with health professionals to ignite the debate and call for critical reflection, so that it can contribute to the undertaking of more and better clinical designs to validate the benefits of using high doses of vitamin D for the benefit of public health and especially in times of crisis for COVID-19.

Vitamin D high doses supplementation could represent a promising alternative to prevent or treat COVID-19 infection

Although we lack enough evidence to justify supplementing with vitaminD in the prevention and treatment of COVID-19 infection, it is increasingly feasible that this hypothesis is valid. Two general underlying mechanisms should be considered. One would be the anti-infectious and immunomodulatory action that it exerts by improving intercellular barriers by stimulating innate immunity, as well as by modulating adaptive immunity. Also, vitaminD reduces the production of inflammatory cytokines, such as IL-2 and interferon-gamma (INF-γ). More recently, multiple pleiotropic effects have been demonstrated on the actions of vitaminD at the anti-inflammatory and immunomodulatory level with positive results in studies with influenza, coronavirus, and other respiratory infections. An inverse relationship between serum vitaminD levels and the prevalence of the respiratory infectious disease has been described. Of interest, another mechanistic approach responds to considering the inhibition of the renin-angiotensin-aldosterone system (RAAS), which is exacerbated in COVID-19 infection because the virus binds to the enzyme ACE2, making more angiotensinII available to cause damage. VitaminD inhibits mediators of RAAS - present in all cells of the body - and by inhibiting ACE activity and increasing ACE2, it lowers angiotensinII levels. We present studies with proposals for recommended doses of vitaminD, and although a single guideline is not specified, the possible benefits are promising. Finally, the purpose of this review is to share this idea with health professionals to ignite the debate and call for critical reflection, so that it can contribute to the undertaking of more and better clinical designs to validate the benefits of using high doses of vitaminD for the benefit of public health and especially in times of crisis for COVID-19.

Vitamin D supplementation as a rational pharmacological approach in the COVID-19 pandemic

The COVID-19 pandemic has reached most of the countries worldwide causing death, which often results from an inflammatory storm associated with severe acute respiratory syndrome (SARS). This has prompted researchers to seek specific novel and definitive treatments urgently. In this context, it is interesting to evaluate the preventive and therapeutic effects of existing pharmacological agents that could be useful. In this regard, vitamin D supplementation, particularly in individuals likely to be deficient, may be a promising option. Vitamin D is a hormone that modulates many of the same inflammatory and oxidative signaling pathways triggered during COVID-19. For example, vitamin D suppresses the actions of the renin-angiotensin system, which has a determining role in the pathophysiology of the inflammatory response related to COVID-19. This paper analyzes the evidence that vitamin D supplementation might be a valuable preventive/therapeutic measure in groups at risk for or infected with COVID-19. It also discusses how clinical studies could be best designed to evaluate the possible advantages of vitamin D supplementation for the benefit of public health during the pandemic.

Implications of Oxidative Stress and Potential Role of Mitochondrial Dysfunction in COVID-19: Therapeutic Effects of Vitamin D

Due to its high degree of contagiousness and like almost no other virus, SARS-CoV-2 has put the health of the world population on alert. COVID-19 can provoke an acute inflammatory process and uncontrolled oxidative stress, which predisposes one to respiratory syndrome, and in the worst case, death. Recent evidence suggests the mechanistic role of mitochondria and vitamin D in the development of COVID-19. Indeed, mitochondrial dynamics contribute to the maintenance of cellular homeostasis, and its uncoupling involves pathological situations. SARS-CoV-2 infection is associated with altered mitochondrial dynamics with consequent oxidative stress, pro-inflammatory state, cytokine production, and cell death. Furthermore, vitamin D deficiency seems to be associated with increased COVID-19 risk. In contrast, vitamin D can normalize mitochondrial dynamics, which would improve oxidative stress, pro-inflammatory state, and cytokine production. Furthermore, vitamin D reduces renin–angiotensin–aldosterone system activation and, consequently, decreases ROS generation and improves the prognosis of SARS-CoV-2 infection. Thus, the purpose of this review is to deepen the knowledge about the role of mitochondria and vitamin D directly involved in the regulation of oxidative stress and the inflammatory state in SARS-CoV-2 infection. As future prospects, evidence suggests enhancing the vitamin D levels of the world population, especially of those individuals with additional risk factors that predispose to the lethal consequences of SARS-CoV-2 infection.

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

Numerous studies have shown that vitamin D deficiency is very common in modern societies and is perceived as an important risk factor in the development of insulin resistance and related diseases such as obesity and type 2 diabetes (T2DM). While it is generally accepted that vitamin D is a regulator of bone homeostasis, its ability to counteract insulin resistance is subject to debate. The goal of this communication is to review the molecular mechanism by which vitamin D reduces insulin resistance and related complications. The university library, PUBMED, and Google Scholar were searched to find relevant studies to be summarized in this review article. Insulin resistance is accompanied by chronic hyperglycaemia and inflammation. Recent studies have shown that vitamin D exhibits indirect antioxidative properties and participates in the maintenance of normal resting ROS level. Appealingly, vitamin D reduces inflammation and regulates Ca²⁺ level in many cell types. Therefore, the beneficial actions of vitamin D include diminished insulin resistance which is observed as an improvement of glucose and lipid metabolism in insulin-sensitive tissues.

Vitamin D receptor(s): In the nucleus but also at membranes?

The genomic actions of the vitamin D are mediated via its biologically most potent metabolite 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂ D₃ ) and the transcription factor vitamin D receptor (VDR). Activation of VDR by 1,25(OH)₂ D₃ leads to change in the expression of more 1000 genes in various human tissues. Based on (epi)genome, transcriptome and crystal structure data the molecular details of this nuclear vitamin D signalling pathway are well understood. Vitamin D is known for its role on calcium homeostasis and bone formation, but it also modulates energy metabolism, innate and adaptive immunity as well as cellular growth, differentiation and apoptosis. The observation of rapid, non-genomic effects of 1,25(OH)₂ D₃ at cellular membranes and in the cytosol initiated the question, whether there are alternative vitamin D-binding proteins in these cellular compartments. So far, the best candidate is the enzyme PDIA3 (protein disulphide isomerase family A member 3), which is found at various subcellular locations. Furthermore, also VDR seems to play a role in membrane-based responses to vitamin D. In this viewpoint, we will dispute whether these rapid, non-genomic pathways are a meaningful addition to the genome-wide effects of vitamin D.

Vitamin D-mitochondria cross-talk could modulate the signaling pathway involved in hypertension development: a translational integrative overview

Vitamin D deficiency is a worldwide pandemic and results in osteoporosis, hypertension, and other cardiovascular diseases. At the cellular level, it produces significant oxidative stress, inflammatory markers, and mitochondrial damage. There is increasing evidence about the role of vitamin D in the regulation of the renin-angiotensin-aldosterone system (RAAS). Moreover, there is evidence of involvement in cardiovascular complications, as well as in the immune system disorders. Vitamin D values below 25ng/mL are related to an increase in vascular tone mediated by smooth muscle contraction. Furthermore, it can produce direct effects on vascular smooth muscle cells, RAAS over-regulation, modulation of calcium metabolism, and secondary hyperparathyroidism. All this predisposes patients to develop hypertrophy of the left ventricle and vascular wall, causing hypertension. In this work, a review is presented of the main mechanisms involved in the development of hypertension due to vitamin D deficiency. Among them are the link established between the levels of extra-mitochondrial inorganic phosphate, its main regulatory hormones -such as vitamin D-, the cardiovascular system, reactive oxygen species, and mitochondrial metabolism. The role of the mitochondrial vitamin D receptor and the regulation of the respiratory chain could influence arterial remodelling since its activation would reduce oxidative damage and preserve cell life. However, there are aspects not yet understood about the intricate signalling network that appeared simple in experimental trials, but complex in clinical studies. In this way, the completion of new studies as VITAL, could clarify, and thus support or refute the possible benefits of vitamin D in hypertensive cardiovascular disease.