Introduction Glutathione is a major endogenous antioxidant and its deficiency is implicated in the etiology and progression of a number of human diseases. Vitamin D is important for the prevention of osteoporosis, cardiovascular disease, diabetes, autoimmune diseases, and some cancers. Using a monocyte cell model, this study examined the hypothesis that vitamin D upregulate glutamate cysteine ligase (GCLC) and glutathione reductase (GR), which catalyzes GSH biosynthesis. Methods U937 monocytes were pretreated with and without 1,25 (OH) vitamin D (10-25 nM) for 24 hr and then exposed to control and high glucose (HG, 25 mM) for 4 hr. Levels of GSH determined using HPLC; GR activity by oxidation of NADPH; GCLC protein, MCP-1 and IL-8 using ELISA kits. Results 1,25(OH)2 vitamin D supplementation significantly upregulated expression of GCLC and GR, levels of GCLC protein and GR activity, and formation of GSH in control and HG-treated monocytes. 1,25(OH)2 vitamin D caused significantly (p<0.05) lower secretion of IL-8 and MCP-1, and lower ROS levels in monocytes exposed to control and HG-treated monocytes. Conclusions This study demonstrates a positive link between vitamin D and GSH levels, and that some beneficial effects of vitamin D supplementation may be mediated by an improvement in the cellular GSH levels and a decrease in ROS and pro-inflammatory cytokines.

Background/Objective Vitamin D, L-cysteine (LC), and GSH levels are lower in the blood of diabetic patients. This study examined the hypothesis that the levels of vitamin D and LC correlate with those of GSH in the blood of type 2 diabetic patients (T2D), and that vitamin D and LC upregulate glutamate-cysteine ligase (GCLC), which catalyzes GSH biosynthesis, in cultured monocytes. Subjects/Methods Fasting blood was obtained after written informed consent from T2D (n=79) and healthy controls (n=22). U937 monocytes were pretreated with 1, 25 (OH)2 vitamin D (0–25 nM) or LC (0–500 µM) for 24 h and then exposed to control or high glucose (25 mM) for 4 h. Results Plasma levels of vitamin D, L-cysteine, GSH, and GCLC protein were significantly lower in T2D versus those in age-matched healthy controls. Multiple linear regression analyses and adjustment for body weight showed a significant positive correlation between plasma levels of vitamin D (r=0.26, p=0.05) and LC (r=0.81, p=0.001) and that of GSH, and between LC and vitamin D (r=0.27, p=0.045) levels. Plasma levels of GSH (r=−0.34, p=0.01) and LC (r=−0.33, r=0.01) showed a negative correlation with triglyceride levels. Vitamin D correlated inversely with HbA1C (−0.30, p=0.01) and HOMA IR (r=−0.31, p=0.03), which showed a significant positive correlation with triglycerides (r=0.44, p=0.001) in T2D. Cell culture studies demonstrate that supplementation with vitamin D and LC significantly increased GCLC expression and GSH formation in control and high glucose treated monocytes. Conclusions This study suggest a positive relationship between the concentrations of the micronutrients vitamin D and LC and that of GSH. Some of the beneficial effects of vitamin D and LC supplementation may be mediated by an increase in the levels of GSH and a decrease in triglyceride levels in type 2 diabetic patients.

ScopeVitamin D binding protein (VDBP) status has an effect on and can potentially improve the status of 25(OH) vitamin D and increase the metabolic actions of 25(OH) vitamin D under physiological and pathological conditions. Diabetes is associated with lower levels of glutathione (GSH) and 25(OH) vitamin D. This study examined the hypothesis that upregulation of GSH will also upregulate blood levels of VDBP and 25(OH) vitamin D in type 2 diabetic rats.Methods and resultsL‐cysteine (LC) supplementation was used to upregulate GSH status in a FL83B hepatocyte cell culture model and in vivo using Zucker diabetic fatty (ZDF) rats. Results show that LC supplementation upregulates both protein and mRNA expression of VDBP and vitamin D receptor (VDR) and GSH status in hepatocytes exposed to high glucose, and that GSH deficiency, induced by glutamate cysteine ligase knockdown, resulted in the downregulation of GSH, VDBP, and VDR and an increase in oxidative stress levels in hepatocytes. In vivo, LC supplementation increased GSH and protein and mRNA expression of VDBP and vitamin D 25‐hydroxylase (CYP2R1) in the liver, and simultaneously resulted in elevated blood levels of LC and GSH, as well as increases in VDBP and 25(OH) vitamin D levels, and decreased inflammatory biomarkers in ZDF rats compared with those in placebo‐supplemented ZDF rats consuming a similar diet.ConclusionLC supplementation may provide a novel approach by which to raise blood levels of VDBP and 25(OH) vitamin D in type 2 diabetes.

The axon initial segment (AIS) is the site of action potential initiation and serves as a cargo transport filter and diffusion barrier that helps maintain neuronal polarity. The AIS actin cytoskeleton comprises actin patches and periodic sub-membranous actin rings. We demonstrate that tropomyosin isoform Tpm3.1 co-localizes with actin patches and that the inhibition of Tpm3.1 led to a reduction in the density of actin patches. Furthermore, Tpm3.1 showed a periodic distribution similar to sub-membranous actin rings but Tpm3.1 was only partially congruent with submembranous actin rings. Nevertheless, the inhibition of Tpm3.1 affected the uniformity of the periodicity of actin rings. Furthermore, Tpm3.1 inhibition led to reduced accumulation of AIS structural and functional proteins, disruption in sorting somatodendritic and axonal proteins, and a reduction in firing frequency. These results show that Tpm3.1 is necessary for the structural and functional maintenance of the AIS.

African Americans (AA) have a higher incidence of cardiovascular disease and vitamin D (VD) deficiency compared with Caucasians. Hydrogen sulfide (H(2)S) is an important signaling molecule. This study examined the hypothesis that blood levels of H(2)S are lower in AA type 2 diabetic patients (T2D). Fasting blood was obtained from T2D and healthy controls. Results showed a significant decrease in plasma levels of cyclic adenosine monophosphate (cAMP) and H(2)S in AA T2D but not in Caucasian T2D when compared with those of respective age- and race-matched healthy controls. Plasma VD levels were significantly lower in AA T2D compared with Caucasian T2D. Cell culture studies demonstrate that 1,25(OH)(2)-VD supplementation significantly increased expression of cystathionine-γ-lyase (CSE), H(2)S formation, and cAMP secretion, but decreased reactive oxygen species in high glucose-treated U937 monocytes. This suggests that VD supplementation upregulates CSE and H(2)S formation and decreases oxidative stress, and that VD deficiency may contribute to the malfunctioning of H(2)S signaling and thus a higher incidence of vascular inflammation in AA. These results lead to the hypothesis that VD supplementation can replenish blood concentrations of H(2)S and cAMP and lower oxidative stress and cardiovascular disease in AA T2D.