Glutathione deficiency alters the vitamin D-metabolizing enzymes CYP27B1 and CYP24A1 in human renal proximal tubule epithelial cells and kidney of HFD-fed mice

Redox modulation via a synthetic thiol compound reshapes energy metabolism in endothelial cells and ameliorates angiogenic expression in a co-culture study with activated macrophages

The vascular endothelium is the first interface exposed to circulating compounds and oxidative as well as pro-inflammatory stimuli. Nowadays, cysteine pro-drugs are emerging as new and potential therapies in cardiovascular and inflammatory diseases due to their cytoprotective effects. In this study, the effects of redox modulation by a synthetic thiol compound, i.e., I-152, a precursor of N-acetylcysteine (NAC) and cysteamine (MEA), were evaluated after 6 h and 24 h treatment on human umbilical cord endothelial cell (HUVECs) energy metabolism. Following I-152 treatment, higher cysteine and glutathione (GSH) content were detected via HPLC, in concomitance with I-152 derivatives, i.e., NAC and MEA. Untargeted metabolomics confirmed GSH upregulation and NAC presence in addition to I-152 itself and other metabolites, such as dithiol compound (NACMEAA) and triacetylated I-152. Mass spectrometry revealed that I-152 boosted ATP production, specifically through the mitochondrial OXPHOS, as determined via Seahorse assay without inducing oxidative stress. Additionally, I-152 treatment of HUVECs before co-culture with LPS-stimulated macrophages provided GSH and cysteine sustainment and attenuated the transcription of adhesion molecules as well as iNOS expression. Identifying the impact of redox regulation in physiological conditions and the possible metabolic targets could aid the application of novel thiol-based therapeutics.

Vitamin D alleviates HFD-induced hepatic fibrosis by inhibiting DNMT1 to affect the TGFβ1/Smad3 pathway

Increasing evidence points toward vitamin D (VD) having lipometabolism and immune-related properties to protect against related metabolic diseases through influencing DNA methylation with inconsistent results. Simultaneously, its relatively precise molecular metabolism on the progression of metabolic-associated fatty liver disease (MAFLD) remains uncertain. Here, we report an unprecedented role and possible mechanism for VD supplementation on the alleviation of high-fat diet (HFD)-induced MAFLD. Over time, our results demonstrated that metabolic disorders in the HFD-induced MAFLD were aggravated with a certain time-response dependence and accompanied by reduced VD metabolites. All these could be alleviated under sufficient VD supplementation in vivo and vitro. It was partially by inhibiting the expressions of DNMT1 to reverse the epigenetic patterns on the VD metabolism genes and TGFβR1, which ultimately triggered the TGFβ1/Smad3 pathway to result in the development of MAFLD. Furthermore, the protective effects of VD were weakened by the treatment with gene silencing of DNMT1.

Ubiquinone (Coenzyme Q-10) Supplementation Influences Exercise-Induced Changes in Serum 25(OH)D3 and the Methyl-Arginine Metabolites: A Double-Blind Randomized Controlled Trial

Researchers have studied the effects of exercise on serum methyl-arginine and vitamin D metabolites; however, the effects of exercise combined with antioxidants are not well documented. Since oxidative stress affects the metabolism of vitamin D and methyl-arginine, we hypothesised that the antioxidant coenzyme Q10 (CoQ10) might modulate exercise-induced changes. A group of twenty-eight healthy men participated in this study and were divided into two groups: an experimental group and a control group. The exercise test was performed until exhaustion, with gradually increasing intensity, before and after the 21-day CoQ10 supplementation. Blood samples were collected before, immediately after, and 3 and 24 h after exercise. CoQ10, vitamin D metabolites, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine, methylarginine, dimethylamine, arginine, citrulline, and ornithine were analysed in serum samples. CoQ10 supplementation caused a 2.76-fold increase in the concentration of serum CoQ10. Conversely, the 25(OH)D3 concentration increased after exercise only in the placebo group. ADMA increased after exercise before supplementation, but a decrease was observed in the CoQ10 supplementation group 24 h after exercise. In conclusion, our data indicate that CoQ10 supplementation modifies the effects of exercise on vitamin D and methyl-arginine metabolism, suggesting its beneficial effects. These findings contribute to the understanding of how antioxidants like CoQ10 can modulate biochemical responses to exercise, potentially offering new insights for enhancing athletic performance and recovery.

Accumulated LPS induced by colitis altered the activities of vitamin D-metabolizing hydroxylases and decreased the generation of 25-hydroxyvitamin D

It is generally accepted that low vitamin D (VD) levels are associated with a high prevalence factor for Inflammatory bowel disease (IBD). IBD patients have observed higher levels of lipopolysaccharide (LPS), ALT, and AST than healthy people. Gut-derived LPS causes inflammatory injury in the liver and kidney. The VD-metabolizing mechanism is involved in the liver and kidney, which means IBD might impact VD metabolism. However, whether IBD affects VD metabolism has not been studied. In vitro LPS resulted in decreased CYP2R1 in liver cells as well as decreased CYP27B1 and increased CYP24A1 in kidney cells, revealing that LPS changed the activities of several hydroxylases. Mice with acute colitis had an increased LPS in serum and liver with mild hepatic injuries, while mice with chronic colitis had a significant elevation of LPS in serum, liver, and kidney with hepatorenal injuries. Thus, the liver hydroxylase for VD metabolism would be the first to be affected in IBD. Consequently, serum 25-hydroxyvitamin D declined dramatically with a significant elevation of 24,25-dihydroxyvitamin D and 1,24,25-trihydroxyvitamin D. Unchanged serum levels of 1,25-dihydroxyvitamin D might be the result of other factors in vivo. In acute colitis, a small dosage (4 IU/day) of cholecalciferol could protect the colon, decrease the serum level of LPS, and finally increase serum 25-hydroxyvitamin D. However, this improvement of cholecalciferol was fading in chronic colitis. These results suggested that VD supplementations for preventing and curing IBD in the clinic should consider hepatorenal hydroxylases and be employed as soon as possible for a better outcome.

Roles of Sirt1 and its modulators in diabetic microangiopathy: A review

Diabetic vascular complications include diabetic macroangiopathy and diabetic microangiopathy. Diabetic microangiopathy is characterised by impaired microvascular endothelial function, basement membrane thickening, and microthrombosis, which may promote renal, ocular, cardiac, and peripheral system damage in diabetic patients. Therefore, new preventive and therapeutic strategies are urgently required. Sirt1, a member of the nicotinamide adenine dinucleotide-dependent histone deacetylase class III family, regulates different organ growth and development, oxidative stress, mitochondrial function, metabolism, inflammation, and aging. Sirt1 is downregulated in vascular injury and microangiopathy. Moreover, its expression and distribution in different organs correlate with age and play critical regulatory roles in oxidative stress and inflammation. This review introduces the background of diabetic microangiopathy and the main functions of Sirt1. Then, the relationship between Sirt1 and different diabetic microangiopathies and the regulatory roles mediated by different cells are described. Finally, we summarize the modulators that target Sirt1 to ameliorate diabetic microangiopathy as an essential preventive and therapeutic measure for diabetic microangiopathy. In conclusion, targeting Sirt1 may be a new therapeutic strategy for diabetic microangiopathy.

Cynapanoside A exerts protective effects against obesity-induced diabetic nephropathy through ameliorating TRIM31-mediated inflammation, lipid synthesis and fibrosis

Obesity is a major predictive factor for the diabetic nephropathy (DN). However, the precise mechanism and therapeutic approach still require to be investigated. Cynapanosides A (CPS-A) is a glycoside derived from the Chinese drug Cynanchum paniculatum that has numerous pharmacological activities, but its regulatory function on obesity-induced kidney disease is still obscure. In the present study, we attempted to explore the renoprotective effects of CPS-A on the established DN in high fat diet (HFD)-fed mice, and the underlying mechanisms. We initially found that CPS-A significantly ameliorated the obesity and metabolic syndrome in mice with HFD feeding. Mice with HFD-induced DN exerted renal dysfunctions, indicated by the elevated functional parameters, including up-regulated blood urea nitrogen (BUN), urine albumin and creatinine, which were significantly attenuated by CPS-A in obese mice. Moreover, histological changes including glomerular enlargement, sclerosis index and collagen deposition in kidney of obese mice were detected, while being strongly ameliorated by CPS-A. Additionally, podocyte loss induced by HFD was also markedly mitigated in mice with CPS-A supplementation. HFD feeding also led to lipid deposition and inflammatory response in renal tissues of obese mice, whereas being considerably attenuated after CPS-A consumption. Intriguingly, we found that tripartite motif-containing protein 31 (TRIM31) signaling might be a crucial mechanism for CPS-A to perform its renoprotective functions in mice with DN. The anti-inflammatory, anti-fibrotic and anti-dyslipidemia capacities of CPS-A were confirmed in the mouse podocytes under varying metabolic stresses, which were however almost abolished upon TRIM31 ablation. These data elucidated that TRIM31 expression was largely required for CPS-A to perform its renoprotective effects. Collectively, our study is the first to reveal that CPS-A may be a promising therapeutic strategy for the treatment of obesity-induced DN or associated kidney disease.

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.

Hydrogen Sulfide Regulates Irisin and Glucose Metabolism in Myotubes and Muscle of HFD-Fed Diabetic Mice

Irisin, a novel myokine, is secreted by the muscle following proteolytic cleavage of fibronectin type III domain containing 5 (FNDC5) and is considered a novel regulator of glucose homeostasis. Cystathionine γ-lyase (CSE) produces hydrogen sulfide (H₂S) and is involved in glucose homeostasis. We examined the hypothesis that H₂S deficiency leads to decreased FNDC5 and irisin secretion, and thereby alters glucose metabolism. High-fat diet-fed mice exhibited elevated blood glucose and significantly reduced levels of CSE, H₂S, and PGC-1α, with decreased FNDC5/irisin levels and increased oxidative stress in the muscle compared with those of normal diet-fed mice (control). High glucose or palmitate decreases CSE/PGC-1α/FNDC5 levels and glucose uptake in myotubes. Inhibitors (propargylglycine and aminooxyacetate) of H₂S producing enzymes or CSE siRNA significantly decreased levels of H₂S and FNDC5 along with PGC-1α; similar H₂S-deficient conditions also resulted in decreased GLUT4 and glucose uptake. The levels of H₂S, PGC-1α, and FNDC5 and glucose uptake were significantly upregulated after treatment with l-cysteine or an H₂S donor. Myoblast differentiation showed upregulation of PGC-1α and FNDC5, which was consistent with the increased expression of CSE/H₂S. These findings suggest that the upregulation of H₂S levels can have beneficial effects on glucose homeostasis via activation of the PGC-1α/FNDC5/irisin signaling pathway.

Urinary Sulfate, Kidney Failure, and Death in CKD: The African American Study of Kidney Disease and Hypertension

Background

Sulfur is an important mineral element whose principal source is animal protein. Animal protein contributes to the daily acid load, which is associated with poor outcomes in individuals with chronic kidney disease (CKD). We hypothesized that higher urinary sulfate, as a reflection of the daily acid load, is associated with a greater risk of death and CKD progression.

Methods

Urinary sulfate was measured in 1057 African American Study of Kidney Disease and Hypertension (AASK) participants at baseline. Participants were categorized by tertiles of daily sulfate excretion. The longitudinal outcome of interest was the composite of death, dialysis, or 50% reduction in measured glomerular filtration rate (GFR). Multivariable adjusted Cox regression models were fit to relate the composite outcome to daily sulfate excretion using the lowest tertile as the reference.

Results

Participants in the highest urinary sulfate tertile were more likely to be men and have a higher body mass index, protein intake, measured GFR, and urinary ammonium and phosphate excretion, and lower urinary protein/creatinine. Compared with those in the lowest tertile of sulfate, those in the highest tertile had a 44% lower hazard (95% CI, 0.37 to 0.84), and those in the middle tertile had a 27% lower hazard (95% CI, 0.55 to 0.96) of death, dialysis, or 50% reduction in measured GFR during follow-up after adjusting for demographics, GFR, protein intake, and other potential confounders. Protein intake was not associated with risk of these events.

Conclusions

Higher urinary sulfate excretion is associated with more favorable outcomes in Blacks who have CKD attributed to hypertension.

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.

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.

PD-1 immunobiology in glomerulonephritis and renal cell carcinoma

BACKGROUND

Programmed cell death protein (PD)-1 receptors and ligands on immune cells and kidney parenchymal cells help maintain immunological homeostasis in the kidney. Dysregulated PD-1:PD-L1 binding interactions occur during the pathogenesis of glomerulopathies and renal cell carcinoma (RCC). The regulation of these molecules in the kidney is important to PD-1/PD-L1 immunotherapies that treat RCC and may induce glomerulopathies as an adverse event.

METHODS

The expression and function of PD-1 molecules on immune and kidney parenchymal cells were reviewed in the healthy kidney, PD-1 immunotherapy-induced nephrotoxicity, glomerulopathies and RCC.

RESULTS

PD-1 and/or its ligands are expressed on kidney macrophages, dendritic cells, lymphocytes, and renal proximal tubule epithelial cells. Vitamin D3, glutathione and AMP-activated protein kinase (AMPK) regulate hypoxic cell signals involved in the expression and function of PD-1 molecules. These pathways are altered in kidney disease and are linked to the production of vascular endothelial growth factor, erythropoietin, adiponectin, interleukin (IL)-18, IL-23, and chemokines that bind CXCR3, CXCR4, and/or CXCR7. These factors are differentially produced in glomerulonephritis and RCC and may be important biomarkers in patients that receive PD-1 therapies and/or develop glomerulonephritis as an adverse event CONCLUSION: By comparing the functions of the PD-1 axis in glomerulopathies and RCC, we identified similar chemokines involved in the recruitment of immune cells and distinct mediators in T cell differentiation. The expression and function of PD-1 and PD-1 ligands in diseased tissue and particularly on double-negative T cells and parenchymal kidney cells needs continued exploration. The possible regulation of the PD-1 axis by vitamin D3, glutathione and/or AMPK cell signals may be important to kidney disease and the PD-1 immunotherapeutic response.

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

Objective: Vitamin D deficiency is common in the general population and diabetic patients, and supplementation with vitamin D is widely used to help lower oxidative stress and inflammation. The cytokine storm in SARS-CoV2 infection has been linked with both diabetes and Vitamin D deficiency. This study examined the hypothesis that supplementation with vitamin D, in combination with l-cysteine (LC), is better at reducing oxidative stress and thereby, more effective, at inhibiting the secretion of the pro-inflammatory cytokines, Interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) in U937 monocytes exposed to high glucose concentrations. Methods: U937 monocytes were pretreated with 1,25 (OH)₂ vitamin D (VD, 10 nM) or LC (250 µM) or VD + LC for 24 h and then exposed to control or high glucose (HG, 25 mM) for another 24 h. Results: There were significantly greater reactive oxygen species (ROS) levels in monocytes treated with HG than those in controls. Combined supplementation with VD and LC showed a more significant reduction in ROS (46%) in comparison with treatment with LC (19%) or VD (26%) alone in monocytes exposed to HG. Similarly, VD supplementation, together with LC, caused a more significant inhibition in the secretion of IL-8 (36% versus 16%) and MCP-1 (46% versus 26%) in comparison with that of VD (10 nM) alone in high-glucose treated monocytes. Conclusions: These results suggest that combined supplementation with vitamin D and LC has the potential to be more effective than either VD or LC alone in lowering the risk of oxidative stress and inflammation associated with type 2 diabetes or COVID-19 infection. Further, this combined vitamin D with LC/N-acetylcysteine may be a potent alternative therapy for SARS-CoV2 infected subjects. This approach can prevent cellular damage due to cytokine storm in comorbid systemic inflammatory conditions, such as diabetes, obesity, and hypertension.

Vitamin D supplementation protects against reductions in plasma 25-hydroxyvitamin D induced by open-heart surgery: Assess-d trial

Low vitamin D (serum or plasma 25‐hydroxyvitamin D (25(OH)D)) is a global pandemic and associates with a greater prevalence in all‐cause and cardiovascular mortality and morbidity. Open‐heart surgery is a form of acute stress that decreases circulating 25(OH)D concentrations and exacerbates the preponderance of low vitamin D in a patient population already characterized by low levels. Although supplemental vitamin D increases 25(OH)D, it is unknown if supplemental vitamin D can overcome the decreases in circulating 25(OH)D induced by open‐heart surgery. We sought to identify if supplemental vitamin D protects against the acute decrease in plasma 25(OH)D propagated by open‐heart surgery during perioperative care. Participants undergoing open‐heart surgery were randomly assigned (double‐blind) to one of two groups: (a) vitamin D (n = 75; cholecalciferol, 50,000 IU/dose) or (b) placebo (n = 75). Participants received supplements on three separate occasions: orally the evening before surgery and either orally or per nasogastric tube on postoperative days 1 and 2. Plasma 25(OH)D concentrations were measured at baseline (the day before surgery and before the first supplement bolus), after surgery on postoperative days 1, 2, 3, and 4, at hospital discharge (5–8 days after surgery), and at an elective outpatient follow‐up visit at 6 months. Supplemental vitamin D abolished the acute decrease in 25(OH)D induced by open‐heart surgery during postoperative care. Moreover, plasma 25(OH)D gradually increased from baseline to day 3 and remained significantly increased thereafter but plateaued to discharge with supplemental vitamin D. We conclude that perioperative vitamin D supplementation protects against the immediate decrease in plasma 25(OH)D induced by open‐heart surgery.

ClinicalTrials.gov Identifier: NCT02460211.

The potential link between inherited G6PD deficiency, oxidative stress, and vitamin D deficiency and the racial inequities in mortality associated with COVID-19

There is a marked variation in mortality risk associated with COVID-19 infection in the general population. Low socioeconomic status and other social determinants have been discussed as possible causes for the higher burden in African American communities compared with white communities. Beyond the social determinants, the biochemical mechanism that predisposes individual subjects or communities to the development of excess and serious complications associated with COVID-19 infection is not clear. Virus infection triggers massive ROS production and oxidative damage. Glutathione (GSH) is essential and protects the body from the harmful effects of oxidative damage from excess reactive oxygen radicals. GSH is also required to maintain the VD-metabolism genes and circulating levels of 25-hydroxyvitamin D (25(OH)VD). Glucose-6-phosphate dehydrogenase (G6PD) is necessary to prevent the exhaustion and depletion of cellular GSH. X-linked genetic G6PD deficiency is common in the AA population and predominantly in males. Acquired deficiency of G6PD has been widely reported in subjects with conditions of obesity and diabetes. This suggests that individuals with G6PD deficiency are vulnerable to excess oxidative stress and at a higher risk for inadequacy or deficiency of 25(OH)VD, leaving the body unable to protect its 'oxidative immune-metabolic' physiological functions from the insults of COVID-19. An association between subclinical interstitial lung disease with 25(OH)VD deficiencies and GSH deficiencies has been previously reported. We hypothesize that the overproduction of ROS and excess oxidative damage is responsible for the impaired immunity, secretion of the cytokine storm, and onset of pulmonary dysfunction in response to the COVID-19 infection. The co-optimization of impaired glutathione redox status and excess 25(OH)VD deficiencies has the potential to reduce oxidative stress, boost immunity, and reduce the adverse clinical effects of COVID-19 infection in the AA population.

l-Cysteine and Vitamin D Co-Supplementation Alleviates Markers of Musculoskeletal Disorders in Vitamin D-Deficient High-Fat Diet-Fed Mice

Vitamin D (VD) deficiency is associated with musculoskeletal disorders. This study examines whether co-supplementation of l-cysteine (LC) and VD is better than monotherapy with LC or VD at alleviating musculoskeletal dyshomeostasis in the skeletal muscle of VD-deficient high-fat diet (HFD-VD-) fed mice. Mice were fed a healthy diet or an HFD; for VD-deficient animals, the mice were maintained on a HFD-VD-diet (16 weeks); after the first 8 weeks, the HFD-VD-diet-fed mice were supplemented for another 8 weeks with LC, VD-alone, or the same doses of LC + VD by oral gavage. Saline and olive oil served as controls. Myotubes were exposed with high-glucose, palmitate, Monocyte Chemoattractant Protein 1 (MCP-1), and Tumor Necrosis Factor (TNF), to mimic the in vivo microenvironment. In vitro deficiencies of glutathione and hydrogen sulfide were induced by knockdown of GCLC and CSE genes. Relative gene expression of biomarkers (myogenic: MyoD, Mef2c, Csrp3; muscle dystrophy: Atrogin1, Murf1, and Myostatin; bone modeling and remodeling: RANK, RANKL, OPG) were analyzed using qRT-PCR. Co-supplementatoin with LC + VD showed beneficial effects on gene expression of myogenic markers and OPG but reduced markers of dystrophy, RANK/RANKL in comparison to LC or VD alone-supplementation. In vitro myotubes treated with glutathione (GSH) precursors also showed a positive effect on OPG and the myogenesis genes, and inhibited RANK/RANKL and muscle-dystrophy markers. This study reveals that the co-supplementation of LC with VD significantly alleviates the markers of musculoskeletal disorders in the skeletal muscle better than monotherapy with LC or VD in HFD-VD-fed mice.

Glucose-6-Phosphate Dehydrogenase Deficiency Activates Endothelial Cell and Leukocyte Adhesion Mediated via the TGFβ/NADPH Oxidases/ROS Signaling Pathway

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common genetic inherited trait among humans, affects ~7% of the global population, and is associated with excess risk of cardiovascular disease (CVD). Transforming growth factor-β (TGF-β) regulates immune function, proliferation, epithelial-mesenchymal transition, fibrosis, cancer, and vascular dysfunction. This study examined whether G6PD deficiencies can alter TGF-β-mediated NADPH oxidases (NOX) and cell adhesion molecules (CAM) in human aortic endothelial cells (HAEC). Results show that treatment with high glucose and the saturated free fatty acid palmitate significantly downregulated G6PD; in contrast, mRNA levels of TGF-β components, NOX and its activity, and reactive oxygen species (ROS) were significantly upregulated in HAEC. The expression levels of TGF-β and its receptors, NOX and its activity, and ROS were significantly higher in HG-exposed G6PD-deficient cells (G6PD siRNA) compared to G6PD-normal cells. The protein levels of adhesion molecules (ICAM-1 and VCAM-1) and inflammatory cytokines (MCP-1 and TNF) were significantly increased in HG-exposed G6PD-deficient cells compared to G6PD-normal cells. The adherence of monocytes (SC cells) to HAEC was significantly elevated in HG-treated G6PD-deficient cells compared to control cells. Pharmacological inhibition of G6PD enhances ROS, NOX and its activity, and endothelial monocyte adhesion; these effects were impeded by NOX inhibitors. The inhibition of TGF-β prevents NOX2 and NOX4 mRNA expression and activity, ROS, and adhesion of monocytes to HAEC. L-Cysteine ethyl ester (cell-permeable) suppresses the mRNA levels of TGF-β and its receptors, along with NOX2 and NOX4, and decreases NOX activity, ROS, and adhesion of monocytes to HAEC. This suggests that G6PD deficiency promotes TGF-β/NADPH oxidases/ROS signaling, the expression of ICAM-1 and VCAM-1, and the adhesion of leukocytes to the endothelial monolayer, which can contribute to a higher risk for CVD.

Vitamin D in Prevention and Treatment of COVID-19: Current Perspective and Future Prospects

Vitamin D deficiency (VDD) partly explains geographical differences in COVID-19 susceptibility, severity, and mortality. VDD among African-Americans, diabetics, hypertensive, and aged populations possibly explain the higher death rate, aggravated by cocooning. Vitamin D is pleiotropic, mediating bone metabolism, calcium homeostasis, and immune functions, whereas VDD is associated with inflammatory reactions and immune dysfunction, predisposing individuals to severe infections. Vitamin D modulates innate and adaptive immunity via the expression of genes that code antimicrobial peptides (AMPs). And the expression of cluster of differentiation (CD)14, the co-receptor for epidermal toll-like receptor (TLR)4. AMPs stimulate TLR2 in macrophages, increasing the conversion of vitamin D into its active form by cytochrome P450 27B1. Antiviral properties of vitamin D-induced AMPs can shift the polarization of the adaptive immune response from helper T cells (Th)1 to the more regulatory Th2 responses that suppress immune over-reactivity by preventing cytokine storm, which is already demonstrated during the Spanish flu episode. Vitamin D induces antiviral effects by both direct and indirect mechanisms via AMPs, immunomodulation, the interplay between major cellular and viral elements, induction of autophagy and apoptosis, variation of genetic and epigenetic factors. The crosstalk between vitamin D and intracellular signaling pathways may operate as a primary regulatory action on viral gene transcription. VDD may increase the likelihood of infection with enveloped viruses, including retrovirus, hepatitis, and dengue. Global data correlates severe VDD with COVID-19 associated coagulopathy, disrupted immune response and mortality, reduced platelet count, and prolonged prothrombin time, suggesting benefits from supplementation.Key teaching pointsVitamin D induces antiviral effects by direct and indirect mechanisms via AMPs, immunomodulation, induction of autophagy, etc.Epidemiology of VDD partly explains geographical differences in COVID-19 susceptibility, severity, and mortality.Global data correlates severe VDD with COVID-19 associated coagulopathy, disrupted immune response and mortality, reduced platelet count, and prolonged prothrombin time, together suggesting benefits from supplementation.Many clinical trials are underway globally to delineate the role of vitamin D in both prevention and treatment of COVID-19.

Can Vitamin D and L-Cysteine Co-Supplementation Reduce 25(OH)-Vitamin D Deficiency and the Mortality Associated with COVID-19 in African Americans?

Early reports indicate an association between the severity of the COVID-19 infection and the widespread 25-hydroxy vitamin D deficiency known to exist in populations around the world. Vitamin D deficiency is extremely common among African American (AA) communities, where the COVID-19 infection rate is three-fold higher, and the mortality rate nearly six-fold higher, compared with rates in predominantly white communities. COVID-19 infection primarily affects the lungs and airways. Previous reports have linked 25-hydroxy vitamin D deficiency with subclinical interstitial lung disease. AA are at risk for lower cellular glutathione (GSH) levels, and GSH deficiency epigenetically impairs VD biosynthesis pathway genes. Compared with vitamin D alone, co-supplementation of vitamin D and L-cysteine (a GSH precursor) showed a better efficacy in improving levels of GSH and VD-regulatory genes at the cellular/tissue level, increasing 25(OH) vitamin D levels, and reducing inflammation biomarkers in the blood in mice studies. We propose that randomized clinical trials are needed to examine the potential of co-supplementation with anti-inflammatory antioxidants, vitamin D and L-cysteine in correcting the 25(OH)VD deficiency and preventing the 'cytokine storm,' one of the most severe consequences of infection with COVID-19, thereby preventing the adverse clinical effects of COVID-19 infection in the vulnerable AA population.

Vitamin D and N-Acetyl Cysteine Supplementation in Treatment-Resistant Depressive Disorder Patients: A General Review

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Major Depressive Disorder (MDD) is often a lifetime disabling mental illness as individuals with MDD might not benefit from standard-therapy, including both pharmacological and psychosocial interventions. Novel therapies are, therefore, required.

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It was shown by recent preclinical and clinical studies that the dysfunction of glutamatergic neurotransmission might be involved in the pathophysiology of MDD. Furthermore, neuroimmune alterations could have a significant role in the pathogenesis of MDD.

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Vitamin D is a neurosteroid hormone essential for several metabolic processes, immune responses, and for regulating neurotrophic-neuroprotective processes, neurotransmission and synaptic plasticity. Recent studies have also shown Vitamin D deficiency in patients with severe psychiatric disorders, including MDD.

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Lately, clinical studies have shown the neuroprotective action of N-acetyl cysteine (NAC) through the modulation of inflammatory pathways and via the modulation of synaptic release of glutamate in cortico-subcortical brain regions; the cysteine-glutamate antiporter.

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This paper reviews the therapeutic use of Vitamin D and NAC and among individuals with refractory MDD to the first- line pharmacological interventions, reviewing the clinical studies published in the last decade.

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A detailed summary of the current evidence in this area aims to better inform psychiatrists and general practitioners on the potential benefits of Vitamin D and NAC supplementation for this disorder.

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Nutraceutical supplementation with Vitamin D and NAC in treatment-resistant MDD patients may be important not only for improving depressive clinical manifestations but also for their safety and tolerability profile. This is of great interest, especially considering the need for treating special populations affected by MDD, such as youngsters and elders. Finally, the nutraceutical approach represents a good choice, considering its better compliance by the patients compared to traditional psychopharmacological treatment.

Alterations in glutathione, nitric oxide and 3-nitrotyrosine levels following exercise and/or hyperbaric oxygen treatment in mice with diet-induced diabetes

Oxidative stress is involved in the development of diabetes. Nitric oxide (NO) contributes to oxidative stress, affects the synthesis of glutathione (GSH) in tissues and also regulates important physiological processes. The levels of nitrosative stress, assessed by measuring the levels of 3-nitrotirosina (3NT) as well as the bioavailability of NO are modulated by exercise and hyperbaric oxygenation (HBO). The aim of the present study was to evaluate the effects of exercise and HBO on the levels of NO, 3NT and GSH in tissues of various organs obtained from diabetic mice. Female mice were fed a high-fat/high-fructose diet to induce diabetes. Mice with diabetes were subjected to exercise and/or HBO. Initial and final concentrations of NO, 3NT and GSH were assessed in the muscle, liver, kidney, heart, spleen, lung, brain, visceral adipose, thoracic aorta and small intestine. Diabetes did not affect initial values of NO, although it significantly increased the levels of 3NT. The basal level of GSH in the diabetic group was lower than or comparable to that of the control group in the majority of the organs assessed. A negative correlation was observed between 3NT and GSH levels in the initial values of all tissues of the control group only, whereas all pathological tissues showed a positive correlation between NO and GSH. There was an increase or a stabilization of GSH levels in the majority of the organs in all treated mice despite the increase in nitrosative stress.

1α,25-Dihydroxyvitamin D3 prevents renal oxidative damage via the PARP1/SIRT1/NOX4 pathway in Zucker diabetic fatty rats

Diabetic nephropathy (DN) is one of the most important renal complications associated with diabetes, and the mechanisms are yet to be fully understood. To date, few studies have shown the antioxidant effects of 1α,25-dihydroxyvitamin-D₃ [1,25(OH)₂D₃] on hyperglycemia-induced renal injury. The aim of the present study was to explore the potential mechanism by which 1,25(OH)₂D₃ reduced oxidative stress in diabetic rat kidneys. In this study, we established a vitamin D-deficient spontaneous diabetes model: 5-6 wk of age Zucker diabetic fatty (ZDF) rats were treated with or without 1,25(OH)₂D₃ for 7 wk, age-matched Zucker lean rats served as control. Results showed that ZDF rats treated with 1,25(OH)₂D₃ had decreased body mass, food intake, water intake, and urine volume. 1,25(OH)₂D₃ ameliorated urine glucose, blood glucose and abnormal glucose tolerance. Additionally, 1,25(OH)₂D₃ significantly lowered microalbuminuria, decreased the glomerular basement membrane thickness, and in some degree inhibited glomerular hypertrophy, mesangial expansion, and tubular dilatation. Furthermore, 1,25(OH)₂D₃ attenuated renal oxidative damage, as reflected by the levels of malondialdehyde, reduced glutathione, 4-hydroxynonenal, 8-hydroxy-2'-deoxyguanosine, and reactive oxygen species production, and notably inhibited poly(ADP-ribose) polymerase-1 (PARP1), activated sirtuin 1 (SIRT1), and decreased the expression of NADPH oxidase 4 (NOX4). Of interest, the abovementioned proteins could be involved in the antioxidant mechanism of 1,25(OH)₂D₃ in diabetic rat kidneys. Our study showed that oxidative stress might be a major contributor to DN pathogenesis and uncovered the antioxidant role of 1,25(OH)₂D₃ in diabetic nephropathy that was associated with the PARP1/SIRT1/ NOX4 pathway.

Type 2 Diabetes Mellitus and Altered Immune System Leading to Susceptibility to Pathogens, Especially Mycobacterium tuberculosis

There has been an alarming increase in the incidence of Type 2 Diabetes Mellitus (T2DM) worldwide. Uncontrolled T2DM can lead to alterations in the immune system, increasing the risk of susceptibility to infections such as Mycobacterium tuberculosis (M. tb). Altered immune responses could be attributed to factors such as the elevated glucose concentration, leading to the production of Advanced Glycation End products (AGE) and the constant inflammation, associated with T2DM. This production of AGE leads to the generation of reactive oxygen species (ROS), the use of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) via the Polyol pathway, and overall diminished levels of glutathione (GSH) and GSH-producing enzymes in T2DM patients, which alters the cytokine profile and changes the immune responses within these patients. Thus, an understanding of the intricate pathways responsible for the pathogenesis and complications in T2DM, and the development of strategies to enhance the immune system, are both urgently needed to prevent co-infections and co-morbidities in individuals with T2DM.

Glutathione deficiency induces epigenetic alterations of vitamin D metabolism genes in the livers of high-fat diet-fed obese mice

Obesity has been correlating with low levels of glutathione (GSH) and 25-hydroxyvitamin D3 (25(OH)VD3). The liver is the principal site for the 25(OH)VD3 biosynthesis. This study investigated whether GSH deficiency induces epigenetic alterations that impair Vitamin D (VD) metabolism genes in the livers of HFD-fed mice. The expression of the VD metabolism genes CYP2R1 and CYP27A1 (25-hydroxylase), CYP27B1 (1-α-hydroxylase), and vitamin D receptor (VDR) were downregulated in the livers of mice fed an HFD (GSH- deficient) compared with control diet-fed group. The expression of CYP24A1 (24-hydroxylase) was significantly increased, which catabolizes both 25(OH)VD3 and 1α,25-hydroxyvitaminD3. Gene-specific hypermethylation of 25-hydroxylase, 1-α-hydroxylase, and VDR, and hypomethylation of CYP24A1 was observed in HFD-fed mice. GSH deficiency induced in cultured hepatocytes caused an increase in oxidative stress and alterations in VD regulatory genes. Similarly, elevated global DNA methylation, Dnmt activity, and 5-methylcytosine but decreased Tet activity and 5-hydroxymethylcytosine were observed in the GSH-deficient hepatocytes and the liver of HFD-fed mice. Replenishment of GSH by its prodrugs treatment beneficially altered epigenetic enzymes, and VD-metabolism genes in hepatocytes. HFD-induces GSH deficiency and epigenetically alters VD-biosynthesis pathway genes. This provides a biochemical mechanism for the VD-deficiency and potential benefits of GSH treatment in reducing 25(OH)VD3-deficiency.

Vitamin D protects against oxidative stress, inflammation and hepatorenal damage induced by acute paracetamol toxicity in rat

Acute paracetamol (APAP) toxicity is a leading cause of liver, and less commonly renal, injuries through oxidative stress and inflammation. Albeit vitamin D (VD) is a well-known anti-oxidant and anti-inflammatory hormone, there is no report on its potential protective/therapeutic actions against APAP acute toxicity. This study, therefore, measured the interplay between APAP toxicity and the hepatorenal expressions of the VD-metabolising enzymes (Cyp2R1, Cyp27b1 & cyp24a1), receptor (VDR) and binding protein (VDBP) alongside the effects of VD treatment on APAP-induced hepatorenal injuries. Thirty-two male rats were distributed equally into negative (NC) and positive (PC) controls besides VD prophylactic (P-VD) and therapeutic (T-VD) groups. All groups, except the NC, received a single oral dose of APAP (1200 mg/kg). The P-VD also received by intraperitoneal injection two cycles of VD3 (1000 IU/Kg/day; 5 days/week) prior to, and a third round after, APAP administration. Similarly, the T-VD group received VD3 (3000 IU/Kg/day) for five successive days post-APAP intoxication. Euthanasia was on the sixth day post-APAP toxicity. The PC group had marked alterations in the hepatorenal biochemical parameters, upregulation in cellular cleaved caspase-3 as well as pronounced increase in the numbers of apoptotic/necrotic cells by TUNEL technique. The PC group plasma levels of 25-hydroxyvitamin D (25-OH VD) also declined markedly and coincided with significant inhibitions in the expression of Cyp2R1 and Cyp27b1 enzymes and VDR, whereas the VDBP and Cyp24a1 increased substantially, in the hepatorenal tissues at the gene and protein levels compared with the NC group. Coherently, the lipid peroxidation marker (MDA) and pro-inflammatory cytokines (IL1β, IL6, IL17A, IFN-γ & TNF-α) augmented significantly, while the anti-oxidative markers (GSH, GPx & CAT) and anti-inflammatory cytokines (IL10 & IL22) diminished substantially, in the PC hepatorenal tissues. Both VD regimens alleviated the APAP-induced hepatorenal damages and restored the 25-OH VD levels together with the hepatorenal expression of Cyp2R1, Cyp27b1, Cyp24a1, VDR and VDBP. Additionally, MDA and all the targeted pro-inflammatory cytokines declined, whereas all the anti-oxidative and anti-inflammatory markers increased, in both VD groups hepatorenal tissues and the results were significantly different than the PC group. Although the P-VD anti-inflammatory and anti-oxidative stress actions were more pronounced than the T-VD group, the results remained markedly abnormal than the NC group. In conclusion, this report is the first to reveal that the circulatory VD levels alongside the hepatorenal VD-metabolising enzymes and VDR are pathologically altered following acute APAP toxicity. Moreover, the prophylactic protocol showed better anti-oxidative and anti-inflammatory effects than the therapeutic regimen against APAP-induced hepatorenal injuries.

Hydrogen sulfide regulates circadian-clock genes in C2C12 myotubes and the muscle of high-fat-diet-fed mice

Hydrogen sulfide (H₂S) is an endogenous novel gasotransmitter which is implicated in the pathophysiology of the metabolic syndrome. Core clock genes (CCG) and its controlled genes disruption is implicated in the progression of metabolic syndrome. We examined whether H₂S has any effect on CCG in the skeletal muscle of mice fed a high-fat diet (HFD) and in myotubes. In the muscle of HFD-mice, the expression of H₂S biosynthesis enzyme genes (CSE, CBS, and 3-Mpst) along with antioxidant genes (GCLC, GCLM, GSS, and GSR) involved in GSH biosynthesis and recycling were reduced significantly, but the oxidative stress (OS) increased. Expression of the CCG (Bmal1, Clock, RORα, Cry2, Per2) and clock-controlled genes (PPARγ, PGC-1α, RXRα) was downregulated, whereas the levels of PPARα mRNA were upregulated. Similar to that in the muscle of HFD-mice, in vitro myotubes exposed to high glucose or palmitate to mimic metabolic syndrome, showed an increased OS and decreased in CSE mRNA, H₂S production and CCG mRNA levels were also downregulated. TNF and MCP-1 treatment on the myotubes was similar to that observed in HFD-muscle, with that the Rev-erbα mRNA was upregulated. Inhibition (siRNA/pharmacological inhibitors) of both CSE and GCLC (the rate-limiting enzyme in GSH biosynthesis) decreased H₂S, and increased OS; Bmal1 and Clock mRNA levels were downregulated, while Rev-erbα increased significantly in these conditions. CSE KD myotubes were post-treated with an H₂S donor partially restored the mRNA levels of core clock genes. These findings report that the deficiencies of H₂S/GSH impair expression of CCG and treatment with H₂S donor or GSH precursor exert a positive effect over CCG. Thus, suggest that H₂S as a new endogenous factor for regulating circadian clock, and its donors could provide a novel chrono-pharmacological therapy to manage metabolic disorders.