The amount of GSSG was already very low and no further change could be detected after CML exposure. A decrease in GSH content has been associated with diabetes in previous studies, e.g. levels of GSH were lower in erythrocytes of type 2 diabetes patients [41].

This decrease was associated with a lower activity of the enzyme γ-GCS which is involved in the biosynthesis of GSH [41]. We did not find a change in gene expression of γ-GCS after exposing the cells to CML. Replenishment of the GSH pool by GR is dependent on the GSSG pool and the availability of NADPH. Since we do not see changes in the GSSG concentration, the amount of available NADPH limits the glutathione reductase activity after CML exposure. CML increased the expression of GST in both cell culture and animal models [42]. However, they also found increased GSH concentrations DAPT datasheet with a higher expression of GST. This seemed to be associated with activation of the transcription factor AP-1 by RAGE, which in turn might be involved in the induction of GST and γ-GCS [42]. We did find an increase in GSTP1 expression, however we did not find an increase in expression of RAGE and γ-GCS, which could explain

why we did not find an increase in GSH. It is known that expression of Grx is high in beta cells and that Grx might play a regulatory role in insulin exocytosis Selleckchem Torin 1 [43]. Glutaredoxin-1 expression has been linked to diabetic retinopathy, by inducing NF-κB translocation and expression of intercellular adhesion molecule-1 (ICAM-1) in rat retinal Müller cells [44]. A recent study in patients with abnormal glucose levels found a higher Grx activity in plasma and serum of these patients compared to healthy subjects [45]. We did not find any significant changes after 24 hour exposure MTMR9 to CML in activity levels of Grx or expression of glutaredoxin-2. In conclusion, we found that CML was able to induce cell death in human pancreatic beta cells, which was accompanied by

an increase in intracellular oxidative stress. We did not find changes in the expression of RAGE, but we found an increase in the level of a target cytokine of RAGE after CML exposure. Additionally we found that CML exposure lowered the levels of GSH. Also other components of the glutathione system were affected, we found a decrease in glutathione reductase activity and an increase in the expression of GSTP1 (Figure 5). These changes in GSH levels and activities of components of the glutathione system indicate that the cells are even more vulnerable for oxidative stress after exposure to CML. Since beta cells are low in antioxidant enzymes and repair for oxidized DNA, it might be that AGEs like CML can accelerate beta cell dysfunction and beta cell death during hyperglycemia. The authors declare that there is no conflict of interests regarding the publication of this article.