Copper's dual role: unravelling the link between copper homeostasis, cuproptosis, and cardiovascular diseases.

This graphic depicts the interplay between copper homeostasis and cuproptosis and their role in cardiovascular diseases. Copper is vital for cardiac mitochondrial function, while its dysregulation induces cuproptosis via Ferredoxin1 (FDX1) and lipoic acid synthase (LIAS). Cuproptosis is linked to myocardial ischemia/reperfusion injury, heart failure, atherosclerosis, and arrhythmias. Copper deficiency impacts atherosclerosis markers. Therapeutic interventions include copper chelators (e.g., ammonium tetrathiomolybdate), and oxidative phosphorylation inhibitors like elesclomol and copper ionophores (CuII(atsm), CuII(gtsm), and disulfiram). These interventions modulate intracellular copper, elevate NO, and reduce inflammatory cytokines, contributing to decreased cardiovascular diseases.

Trace element magnesium: a key player in hypertension management.

Magnesium deficit decreases nitric oxide production and oxidative stress, but calcium efflux in VSMC enhances proliferation, migration, and remodelling. These pathways contribute to cardiovascular disorders, hypertension, insulin resistance, sodium retention, fluid retention, and blood volume. Magnesium supplements could be beneficial.

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.

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.

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 TGFß/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-ß (TGF-ß) regulates immune function, proliferation, epithelial-mesenchymal transition, fibrosis, cancer, and vascular dysfunction. This study examined whether G6PD deficiencies can alter TGF-ß-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-ß components, NOX and its activity, and reactive oxygen species (ROS) were significantly upregulated in HAEC. The expression levels of TGF-ß 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-ß 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-ß 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-ß/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.

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.

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.

Novel Invasive and Noninvasive Cardiac-Specific Biomarkers in Obesity and Cardiovascular Diseases.

Cardiovascular disease (CVD) is the leading cause of fatality and disability worldwide regardless of gender. Obesity has reached epidemic proportions in population across different regions. According to epidemiological studies, CVD risk markers in childhood obesity are one of the significant risk factors for adulthood CVD, but have received disproportionally little attention. This review has examined the evidence for the presence of traditional cardiac biomarkers (nonspecific; lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatine kinase, myoglobulin, glycogen phosphorylase isoenzyme BB, myosin light chains, ST2, and ischemia-modified albumin) and novel emerging cardiac-specific biomarkers (cardiac troponins, natriuretic peptides, heart-type fatty acid-binding protein, and miRNAs). Besides, noninvasive anatomical and electrophysiological markers (carotid intima-media thickness, coronary artery calcification, and heart rate variability) in CVDs and obesity are also discussed. Modifiable and nonmodifiable risk factors associated with metabolic syndrome in the progression of CVD, such as obesity, diabetes, hypertension, dyslipidemia, oxidative stress, inflammation, and adipocytokines are also outlined. These underlying prognostic risk factors predict the onset of future microvascular and macrovascular complications. The understanding of invasive and noninvasive cardiac-specific biomarkers and the risk factors may yield valuable insights into the pathophysiology and prevention of CVD in a high-risk obese population at an early stage.

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.

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.

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

Chronic kidney disease (CKD) is a worldwide public health problem with an estimated prevalence of 8.2%. This study reports glutathione deficiency, excess oxidative stress, and altered vitamin D metabolism in the kidney of mice fed a high-fat diet (HFD). The levels of GCLC and GCLM gene expression were significantly downregulated and the protein carbonylation level, a hallmark of oxidative damage, was significantly increased in the kidney of HFD-fed mice. While the levels of VD-regulatory genes 1-alpha-hydroxylase (CYP27B1), VDR, and RXRα were significantly downregulated in the kidney of mice fed a HFD, those of 24-hydroxylase (CYP24A1) were significantly elevated. In vitro, GSH deficiency per se causes excess oxidative damage (protein carbonylation), and significantly decreases the levels of VD-regulatory genes (CYP27B1, VDR, and RXRα), but increases levels of CYP24A1 in human renal proximal tubule epithelial cells (RPTEC), similar to findings in the kidney of HFD-fed diabetic mice. L-cysteine supplementation restores GSH and prevents oxidative damage in RPTEC. These studies suggest a potential role of GSH precursor in reducing excess oxidative stress and renal injury that commonly accompanies obesity/diabetes.

Glucose-6-phosphate dehydrogenase deficiency increases cell adhesion molecules and activates human monocyte-endothelial cell adhesion: Protective role of l-cysteine.

Glucose-6-phosphate dehydrogenase is a major enzyme that supplies the reducing agent nicotinamide adenine dinucleotide phosphate hydrogen (NADPH), which is required to recycle oxidized/glutathione disulfide (GSSH) to reduced glutathione (GSH). G6PD-deficient cells are susceptible to oxidative stress and a deficiency of GSH. Endothelial dysfunction is characterized by the loss of nitric oxide (NO) bioavailability, which regulates leukocyte adhesion to endothelium. G6PD-deficient endothelial cells (EC) demonstrate reduced expression of endothelial nitric oxide synthase (eNOS) and NO levels along with reduced GSH. Whether G6PD deficiency plays any role in EC dysfunction is unknown. The chronic inflammation commonly seen in those with metabolic syndrome, characterized by elevated levels of tumor necrosis factor (TNF) and monocyte chemoattractant protein 1 (MCP-1), provided an incentive for investigation of these cytokines as well. A GSH/G6PD-deficient model was created using human umbilical vein endothelial cells (HUVEC) treated with either buthionine sulfoximine (BSO), a pharmacological inhibitor of the rate-limiting enzyme of GSH biosynthesis (γ-glutamylcysteine synthetase), or with 6-aminonicotinamide (6-AN), an inhibitor of G6PD or G6PD siRNA. Normal and G6PD-deficient cells were also treated with pro-atherosclerotic stimuli such as high glucose, TNF, and MCP-1. After inhibiting or knocking down G6PD/GSH, the capacity of endothelial cells for monocyte recruitment was assessed by determining the expression of the adhesion molecules intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), which was upregulated by G6PD deficiency and accompanied by the presence of the oxidative stress markers NADPH oxidase 4 (NOX4), inducible nitric oxide synthase (iNOS), and reactive oxygen species (ROS). Treatment with the inhibitors BSO and 6-AN caused increased levels of adhesion molecule mRNA and monocyte-EC adhesion. Following treatment with high glucose, G6PD-deficient cells showed an increase in levels of ICAM-1 and VCAM-1 mRNA, as well as monocyte-EC adherence, compared with results seen in control cells. Treatment with l-cysteine (a precursor of GSH) protected endothelial cells by increasing GSH and attenuating ROS, ICAM-1, VCAM-1, and monocyte-EC adhesion. These results suggest that G6PD/GSH deficiency plays a role in endothelial dysfunction and that supplementation with l-cysteine can restore GSH levels and reduce the EC activation markers in G6PD-deficient conditions.

Postnatal exposure to di-(2-ethylhexyl)phthalate alters cardiac insulin signaling molecules and GLUT4Ser488 phosphorylation in male rat offspring.

Di-(2-ethylhexyl)phthalate (DEHP), a distinctive endocrine-disrupting chemical, is widely used as a plasticizer in a variety of consumer products. It can easily cross the placenta and enter breast milk and then it is rapidly absorbed by offspring. Since it is generally accepted that individuals are more sensitive to chemical exposure during vital developmental periods, we investigated whether DEHP exposure during lactation affects cardiac insulin signaling and glucose homeostasis in the F1 male rat offspring at postnatal day 22 (PND22). Lactating Wistar rats were administered with DEHP (1, 10, and 100 mg/kg/d) or olive oil from lactation day 1 to 21 by oral gavage. All the male pups were perfused and killed on PND22. On the day before the killing, they were kept for fasting overnight and blood was collected. The cardiac muscle was dissected out, washed in ice-cold physiological saline repeatedly and used for the assay of various parameters. DEHP-exposed offspring had significantly lower body weight than the control. DEHP-exposed offspring showed elevated blood glucose, decreased 14 C-2-deoxyglucose uptake and 14 C-glucose oxidation in cardiac muscle at PND22. The concentration of upstream insulin signaling molecules such as insulin receptor subunit ß (InsRß) and insulin receptor substrate 1 (IRS1) were downregulated in DEHP-exposed offspring. However, no significant alterations were observed in protein kinase B (Akt) and Akt substrate of 160 kDa (AS160). Surprisingly, phosphorylation of IRS1 Tyr632 and Akt Ser473 were diminished. Low levels of glucose transporter type 4 (GLUT4) protein and increased GLUT4 Ser488 phosphorylation which decreases its intrinsic activity and translocation towards plasma membrane were also recorded. Lactational DEHP exposure predisposes F 1 male offspring to cardiac glucometabolic disorders at PND22, which may impair cardiac function.

Glutathione Stimulates Vitamin D Regulatory and Glucose-Metabolism Genes, Lowers Oxidative Stress and Inflammation, and Increases 25-Hydroxy-Vitamin D Levels in Blood: A Novel Approach to Treat 25-Hydroxyvitamin D Deficiency.

AIMS: 25-Hydroxyvitamin D [25(OH)VD] deficiency/inadequacy is a major public health issue affecting more than 1 billion people worldwide. A convincing association exists between low levels of circulating 25(OH)VD and the poor health outcomes associated with chronic diseases. However, high supraphysiological doses of VD are needed to achieve the required 25(OH)VD levels in the blood, because many subjects respond poorly to supplementation. RESULTS: This study reports a link between 25(OH)VD deficiency and a reduction in glutathione (GSH) in obese adolescents. The improvement in GSH status that results from cosupplementation with VD and l-cysteine (LC; a GSH precursor) significantly reduced oxidative stress in a mouse model of 25(OH)VD deficiency. It also positively upregulated VD regulatory genes (VDBP/VD-25-hydroxylase/VDR) in the liver and glucose metabolism genes (PGC-1α/VDR/GLUT-4) in muscle, boosted 25(OH)VD, and reduced inflammation and insulin resistance (IR) levels in the blood compared with supplementation with VD alone. In vitro GSH deficiency caused increased oxidative stress and downregulation of VDBP/VD-25-hydroxylase/VDR and upregulation of CYP24a1 in hepatocytes and downregulation of PGC-1α/VDR/GLUT-4 in myotubes. This study demonstrates that improvement in the GSH status exerts beneficial effects on the blood levels of 25(OH)VD, as well as on the inflammation and IR in a VD-deficient mouse model. Thus, the VD supplements widely consumed by the public are unlikely to be successful unless the GSH status is also corrected. INNOVATION: These studies demonstrate a previously undiscovered mechanism by which GSH status positively upregulates the bioavailability of 25(OH)VD. CONCLUSION: Supplementation with a combination of VD and LC or GSH precursor, rather than supplementation with VD alone, is beneficial and helps achieve more successful VD supplementation. Antioxid. Redox Signal. 00, 000-000.

L-Cysteine in vitro can restore cellular glutathione and inhibits the expression of cell adhesion molecules in G6PD-deficient monocytes.

L-Cysteine is a precursor of glutathione (GSH), a potent physiological antioxidant. Excess glucose-6-phosphate dehydrogenase (G6PD) deficiency in African Americans and low levels of L-cysteine diet in Hispanics can contributes to GSH deficiency and oxidative stress. Oxidative stress and monocyte adhesion was considered to be an initial event in the progression of vascular dysfunction and atherosclerosis. However, no previous study has investigated the contribution of GSH/G6PD deficiency to the expression of monocyte adhesion molecules. Using human U937 monocytes, this study examined the effect of GSH/G6PD deficiency and L-cysteine supplementation on monocyte adhesion molecules. G6PD/GSH deficiency induced by either siRNA or inhibitors (6AN/BSO, respectively) significantly (p < 0.005) increased the levels of cell adhesion molecules (ICAM-1, VCAM-1, SELL, ITGB1 and 2); NADPH oxidase (NOX), reactive oxygen species (ROS) and MCP-1 were upregulated, and decreases in levels of GSH, and nitric oxide were observed. The expression of ICAM-1 and VCAM-1 mRNA levels increased in high glucose, MCP-1 or TNF-α-treated G6PD-deficient compared to G6PD-normal cells. L-Cysteine treatment significantly (p < 0.005) increased G6PD activity and levels of GSH, and decreased NOX, ROS, and adhesion molecules. Thus, GSH/G6PD deficiency increases susceptibility to monocyte adhesion processes, whereas L-cysteine supplementation can restore cellular GSH/G6PD and attenuates NOX activity and expression of cell adhesion molecules.

Hydrogen sulfide increases glutathione biosynthesis, and glucose uptake and utilisation in C2C12 mouse myotubes.

Diabetic patients have lower blood concentrations of hydrogen sulfide (H2S), L-cysteine (LC), and glutathione (GSH). Using C2C12 mouse myotubes as a model, this study investigates the hypothesis that the beneficial effects of LC supplementation are mediated by upregulation of the H2S status under diabetic conditions. Results show that exogenous administration of sodium hydrosulfide (NaHS, 10 or 20 µM; 6 hours), a H2S donor, significantly (p < .05) upregulates the gene expression of cystathionine-γ-lyase (CSE), LC transporter (Slc7a11/xCT), and the genes involved in GSH biosynthesis. Additionally, it reduces homocysteine (HCys), reactive oxygen species (ROS) production, and enhances cellular LC, H2S, and glucose uptake and utilisation in myoblasts. The use of CSE siRNA to induce deficient endogenous H2S production causes an increase in H2O2, ROS, HCys levels, and downregulation of GSH biosynthesis pathway enzymes. In additional, CSE knockdown downregulates glucose transporter type 4 (GLUT4) and gene expression of its key transcription factors, and reduces glucose uptake in C2C12 myotubes. CSE knockdown cells showed specific increases in the protein S-glutathionylation of LC transporter and GLUT4 along with increased total protein S-glutathionylation. Taken together, evidence from this study provides molecular insights into the importance of the CSE/H2S system in maintaining the cellular glutathione and glucose homeostasis in C2C12 myotubes.