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.

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.

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.