Enhancing Acsl4 in absence of mTORC2/Rictor drove β-cell dedifferentiation via inhibiting FoxO1 and promoting ROS production

Downregulation of Sirt3 contributes to β-cell dedifferentiation via FoxO1 in type 2 diabetic mellitus

AIMS

FoxO1 is an important factor in the β-cell differentiation in type 2 diabetes mellitus (T2DM). Sirt3 is found to be involved in FoxO1 function. This study investigated the role of Sirt3 in the β-cell dedifferentiation and its mechanism.

METHODS

Twelve-week-old db/db mice and INS1 cells transfected with Sirt3-specific short hairpin RNA (shSirt3) were used to evaluate the dedifferentiation of β-cell. Insulin levels were measured by enzyme linked immunosorbent assay. The proteins of Sirt3, T-FoxO1, Ac-FoxO1 and differentiation indexes such as NGN3, OCT4, MAFA were determined by western blot or immunofluorescence staining. The combination of Sirt3 and FoxO1 was determined by the co-immunoprecipitation assay. The transcriptional activity of FoxO1 was detected by dual luciferase reporter assay.

RESULTS

Both the in vivo and in vitro results showed that Sirt3 was decreased along with β-cell dedifferentiation and decreased function of insulin secretion under high glucose conditions. When Sirt3 was knocked down in INS1 cells, increased β-cell dedifferentiation and lowered insulin secretion were observed. This effect was closely related to the amount loss and the decreased deacetylation of FoxO1, which resulted in a reduction in transcriptional activity.

CONCLUSION

Downregulation of Sirt3 contributes to β-cell dedifferentiation in high glucose via FoxO1. Intervention of Sirt3 may be an effective approach to prevent β-cell failure in T2DM.

Modulation of AKT Pathway-Targeting miRNAs for Cancer Cell Treatment with Natural Products

Many miRNAs are known to target the AKT serine-threonine kinase (AKT) pathway, which is critical for the regulation of several cell functions in cancer cell development. Many natural products exhibiting anticancer effects have been reported, but their connections to the AKT pathway (AKT and its effectors) and miRNAs have rarely been investigated. This review aimed to demarcate the relationship between miRNAs and the AKT pathway during the regulation of cancer cell functions by natural products. Identifying the connections between miRNAs and the AKT pathway and between miRNAs and natural products made it possible to establish an miRNA/AKT/natural product axis to facilitate a better understanding of their anticancer mechanisms. Moreover, the miRNA database (miRDB) was used to retrieve more AKT pathway-related target candidates for miRNAs. By evaluating the reported facts, the cell functions of these database-generated candidates were connected to natural products. Therefore, this review provides a comprehensive overview of the natural product/miRNA/AKT pathway in the modulation of cancer cell development.

mTORC1 is required for epigenetic silencing during β-cell functional maturation

Objective

The mechanistic target of rapamycin complex 1 (mTORC1) is a key molecule that links nutrients, hormones, and growth factors to cell growth/function. Our previous studies have shown that mTORC1 is required for β-cell functional maturation and identity maintenance; however, the underlying mechanism is not fully understood. This work aimed to understand the underlying epigenetic mechanisms of mTORC1 in regulating β-cell functional maturation.

Methods

We performed Microarray, MeDIP-seq and ATAC-seq analysis to explore the abnormal epigenetic regulation in 8-week-old immature βRapKO islets. Moreover, DNMT3A was overexpressed in βRapKO islets by lentivirus, and the transcriptome changes and GSIS function were analyzed.

Results

We identified two major epigenetic silencing mechanisms, DNMT3A-dependent DNA methylation and PRC2-dependent H3K27me3 modification, which are responsible for functional immaturity of Raptor-deficient β-cell. Overexpression of DNMT3A partially reversed the immature transcriptome pattern and restored the impaired GSIS in Raptor-deficient β-cells. Moreover, we found that Raptor directly regulated PRC2/EED and H3K27me3 expression levels, as well as a group of immature genes marked with H3K27me3. Combined with ATAC-seq, MeDIP-seq and ChIP-seq, we identified β-cell immature genes with either DNA methylation and/or H3K27me3 modification.

Conclusion

The present study advances our understanding of the nutrient sensor mTORC1, by integrating environmental nutrient supply and epigenetic modification, i.e., DNMT3A-mediated DNA methylation and PRC2-mediated histone methylation in regulating β-cell identity and functional maturation, and therefore may impact the disease risk of type 2 diabetes.

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Rescued DNMT3A expression in Raptor-deficient islets partially reversed the abnormal induction of immature genes.

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EED/H3K27me3 were impaired in Raptor-ablated β-cell.

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DNA methylation and H3K27me3 are required for mTORC1-dependent epigenetic silencing of immature genes in β-cell.

Ferroptosis is involved in PGPS-induced otitis media in C57BL/6 mice

Otitis media (OM) is a common disease that can cause hearing loss in children. Currently, the main clinical treatment for OM is antibiotics, but the overuse of antibiotics might lead to bacterial resistance, which is a worldwide public health challenge. Studying the pathogenesis of OM will help us develop new effective treatments. Ferroptosis is one type of programmed cell death characterized by the occurrence of lipid peroxidation driven by iron ions. Many studies have shown that ferroptosis is associated with infectious diseases. It is presently unclear whether ferroptosis is involved in the pathogenesis of OM. In this study, we explored the relationship between ferroptosis and OM by PGPS-induced OM in C57BL/6 mice and treating the induced OM with ferroptosis inhibitors deferoxamine (DFO), Ferrostatin-1 (Fer-1), and Liperoxstatin-1 (Lip-1). We examined the expression of ferroptosis-related proteins acyl-CoA synthetase long chain family member 4 (ACSL4) and prostaglandin-endoperoxide synthase 2 (Cox2), glutathione peroxidase 4 (GPX4) protein as well as lipid peroxidation markers 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA). The results showed that in PGPS-induced OM model mice, several ferroptosis-related proteins including ACSL4 and Cox2 were up-regulated compared to mice treated with saline. Meanwhile, a ferroptosis-related protein GPX4 was down-regulated upon PGPS treatment. The DFO treatment in PGPS-inoculated mice effectively inhibited the development of OM. The inhibitors treatment caused a significant decrease in the expression of ACSL4, Cox2, 4 HNE, MDA, reduction in free iron. Meanwhile, the ferroptosis inhibitors treatment caused increase in the expression of inflammation-related factors tumor necrosis factor-α (TNF-α) and antioxidant protein GPX4. Our results suggest that there is a crosstalk between ferroptosis signaling pathway and the pathogenesis of OM. Ferroptosis inhibition can alleviate PGPS-induced OM.