Defining the ferroptotic phenotype of beta cells in type 1 diabetes and its inhibition as a potential antidiabetic strategy

Targeting ferroptosis: opportunities and challenges of mesenchymal stem cell therapy for type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is characterized by progressive β-cell death, leading to β-cell loss and insufficient insulin secretion. Mesenchymal stem cells (MSCs) transplantation is currently one of the most promising methods for β-cell replacement therapy. However, recent studies have shown that ferroptosis is not only one of the key mechanisms of β-cell death, but also one of the reasons for extensive cell death within a short period of time after MSCs transplantation. Ferroptosis is a new type of regulated cell death (RCD) characterized by iron-dependent accumulation of lipid peroxides. Due to the weak antioxidant capacity of β-cells, they are susceptible to cytotoxic stimuli such as oxidative stress (OS), and are therefore susceptible to ferroptosis. Transplanted MSCs are also extremely susceptible to perturbations in their microenvironment, especially OS, which can weaken their antioxidant capacity and induce MSCs death through ferroptosis. In the pathophysiological process of T1DM, a large amount of reactive oxygen species (ROS) are produced, causing OS. Therefore, targeting ferroptosis may be a key way to protect β-cells and improve the therapeutic effect of MSCs transplantation. This review reviews the research related to ferroptosis of β-cells and MSCs, and summarizes the currently developed strategies that help inhibit cell ferroptosis. This study aims to help understand the ferroptosis mechanism of β-cell death and MSCs death after transplantation, emphasize the importance of targeting ferroptosis for protecting β-cells and improving the survival and function of transplanted MSCs, and provide a new research direction for stem cells transplantation therapy of T1DM in the future.

Ferroptosis-associated alterations in diabetes following ischemic stroke: Insights from RNA sequencing

OBJECTIVE

Ferroptosis is an iron-dependent form of programmed cell death associated with lipid peroxidation. Though diabetes worsens cerebral injury and clinical outcomes in stroke, it is poorly understood whether ferroptosis contributes to diabetes-exacerbated stroke. This study aimed to identify ferroptosis-associated differentially expressed genes in ischemic stroke under diabetic condition and then explore their roles using comprehensive bioinformatics analyses.

METHODS

Type 1 diabetes (T1D) model was established in male mice at 8-10 weeks of age by one intraperitoneal injection of streptozotocin (110 mg/kg). Ischemic stroke was induced by a transient 45-minute middle cerebral artery occlusion and evaluated three days thereafter. Ischemic brain cortex was dissected 24 h after the reperfusion and subjected to bulk tissue RNA sequencing followed by bioinformatics analysis and verification of key findings via quantitative real-time PCR.

RESULTS

Enlarged infarct size was seen in diabetic, as compared with non-diabetic mice, in conjunction with worsened neurological behaviors. Both body and spleen weights were reduced in diabetic as compared with non-diabetic mice. There was a trend for reduced survival rate in diabetic mice following the stroke. In RNA sequencing analysis, we identified 1299 differentially expressed genes in ischemic brain between diabetic and non-diabetic mice, with upregulation and downregulation for 732 and 567 genes, respectively. Among these genes, 27 genes were associated with ferroptosis. Further analysis reveals that solute carrier family 25 member 28(SLC25A28) and sterol carrier protein 2(SCP2) were the top genes associated with ferroptosis in diabetic mice following ischemic stroke. In several bioinformatics analyses, we found SLC25A28, one of the top ferroptosis-related genes, is involved in several metabolic and regulatory pathways as well as the regulatory complexity of microRNAs and circular RNAs, which demonstrates the potential role of SLC25A28 in diabetes-exacerbated stroke. Drug network analysis suggests SLC25A28 as a potential therapeutic target for ameliorating ischemic injury in diabetes.

CONCLUSIONS

Our bulk RNA sequencing and bioinformatics analyses show that altered ferroptosis signaling pathway was associated with the exacerbation of experimental stroke injury under diabetic condition. Especially, additional investigation into the mechanisms of SLC25A28 and SCP2 in diabetes-exacerbated stroke will be explored in the future study.

PEGylated β-Cell-Targeting Exosomes from Mesenchymal Stem Cells Improve β Cell Function and Quantity by Suppressing NRF2-Mediated Ferroptosis

Background

The depletion of β cell mass is widely recognized as a significant contributor to the progression of type 2 diabetes mellitus (T2DM). Exosomes derived from mesenchymal stem cells (MSC-EXOs) hold promise as cell-free therapies for treating T2DM. However, the precise effects and mechanisms through which MSC-EXO affects β cell function remain incompletely understood, and the limited ability of MSC-EXO to target β cells and the short blood circulation time hampers its therapeutic effectiveness.

Methods

The effects of MSC-EXO were investigated in T2DM mice induced by a high-fat diet combined with STZ. Additionally, the high glucose-stimulated INS-1 cell line was used to investigate the potential mechanism of MSC-EXO. Michael addition reaction-mediated chemical coupling was used to modify the surface of the exosome membrane with a β-cell-targeting aptamer and polyethylene glycol (PEG). The β-cell targeting and blood circulation time were evaluated, and whether this modification enhanced the islet-protective effect of MSC-EXO was further analyzed.

Results

We observed that the therapeutic effects of MSC-EXO on T2DM manifested through the reduction of random blood glucose levels, enhancement of glucose and insulin tolerance, and increased insulin secretion. These effects were achieved by augmenting β cell mass via inhibiting nuclear factor erythroid 2-related factor 2 (NRF2)-mediated ferroptosis. Mechanistically, MSC-EXOs play a role in the NRF2-mediated anti-ferroptosis mechanism by transporting active proteins that are abundant in the AKT and ERK pathways. Moreover, compared to MSC-EXOs, aptamer- and PEG-modified exosomes (Apt-EXOs) were more effective in islet protection through PEG-mediated cycle prolongation and aptamer-mediated β-cell targeting.

Conclusion

MSC-EXO suppresses NRF2-mediated ferroptosis by delivering bioactive proteins to regulate the AKT/ERK signaling pathway, thereby improving the function and quantity of β cells. Additionally, Apt-EXO may serve as a novel drug carrier for islet-targeted therapy.

The significance of glutaredoxins for diabetes mellitus and its complications

Diabetes mellitus is a non-communicable metabolic disease hallmarked by chronic hyperglycemia caused by beta-cell failure. Diabetic complications affect the vasculature and result in macro- and microangiopathies, which account for a significantly increased morbidity and mortality. The rising incidence and prevalence of diabetes is a major global health burden. There are no feasible strategies for beta-cell preservation available in daily clinical practice. Therefore, patients rely on antidiabetic drugs or the application of exogenous insulin. Glutaredoxins (Grxs) are ubiquitously expressed and highly conserved members of the thioredoxin family of proteins. They have specific functions in redox-mediated signal transduction, iron homeostasis and biosynthesis of iron-sulfur (FeS) proteins, and the regulation of cell proliferation, survival, and function. The involvement of Grxs in chronic diseases has been a topic of research for several decades, suggesting them as therapeutic targets. Little is known about their role in diabetes and its complications. Therefore, this review summarizes the available literature on the significance of Grxs in diabetes and its complications. In conclusion, Grxs are differentially expressed in the endocrine pancreas and in tissues affected by diabetic complications, such as the heart, the kidneys, the eye, and the vasculature. They are involved in several pathways essential for insulin signaling, metabolic inflammation, glucose and fatty acid uptake and processing, cell survival, and iron and mitochondrial metabolism. Most studies describe significant changes in glutaredoxin expression and/or activity in response to the diabetic metabolism. In general, mitigated levels of Grxs are associated with oxidative distress, cell damage, and even cell death. The induced overexpression is considered a potential part of the cellular stress-response, counteracting oxidative distress and exerting beneficial impact on cell function such as insulin secretion, cytokine expression, and enzyme activity.