Role of Autophagy in the Pathogenesis of Diabetes and Therapeutic Potential of Autophagy Modulators in the Treatment of Diabetes and Metabolic Syndrome

Spatially resolved distribution of pancreatic hormones proteoforms by MALDI-imaging mass spectrometry

Zinc plays a crucial role both in the immune system and endocrine processes. Zinc restriction in the diet has been shown to lead to degeneration of the endocrine pancreas, resulting in hormonal imbalance within the β-cells. Proteostasismay vary depending on the stage of a pathophysiological process, which underscores the need for tools aimed at directly analyzing biological status. Among proteomics methods, MALDI-ToF-MS can serve as a rapid peptidomics tool for analyzing extracts or by histological imaging. Here we report the optimization of MALDI imaging mass spectrometry analysis of histological thin sections from mouse pancreas. This optimization enables the identification of the major islet peptide hormones as well as the major accumulated precursors and/or proteolytic products of peptide hormones. Cross-validation of the identified peptide hormones was performed by LC-ESI-MS from pancreatic islet extracts. Mice subjected to a zinc-restricted diet exhibited a relatively lower amount of peptide intermediates compared to the control group. These findings provide evidence for a complex modulation of proteostasis by micronutrients imbalance, a phenomenon directly accessed by MALDI-MSI.

New insights into the interplay between autophagy, gut microbiota and insulin resistance in metabolic syndrome

Metabolic syndrome (MetS) is a widespread and multifactorial disorder, and the study of its pathogenesis and treatment remains challenging. Autophagy, an intracellular degradation system that maintains cellular renewal and homeostasis, is essential for maintaining antimicrobial defense, preserving epithelial barrier integrity, promoting mucosal immune response, maintaining intestinal homeostasis, and regulating gut microbiota and microbial metabolites. Dysfunctional autophagy is implicated in the pathological mechanisms of MetS, involving insulin resistance (IR), chronic inflammation, oxidative stress, and endoplasmic reticulum (ER) stress, with IR being a predominant feature. The study of autophagy represents a valuable field of research with significant clinical implications for identifying autophagy-related signals, pathways, mechanisms, and treatment options for MetS. Given the multifactorial etiology and various potential risk factors, it is imperative to explore the interplay between autophagy and gut microbiota in MetS more thoroughly. This will facilitate the elucidation of new mechanisms underlying the crosstalk among autophagy, gut microbiota, and MetS, thereby providing new insights into the diagnosis and treatment of MetS.

USP24-i-101 targeting of USP24 activates autophagy to inhibit drug resistance acquired during cancer therapy

Drug resistance in cancer therapy is the major reason for poor prognosis. Addressing this clinically unmet issue is important and urgent. In this study, we found that targeting USP24 by the specific USP24 inhibitors, USP24-i and its analogues, dramatically activated autophagy in the interphase and mitotic periods of lung cancer cells by inhibiting E2F4 and TRAF6, respectively. USP24 functional knockout, USP24C1695A, or targeting USP24 by USP24-i-101 inhibited drug resistance and activated autophagy in gefitinib-induced drug-resistant mice with doxycycline-induced EGFRL858R lung cancer, but this effect was abolished after inhibition of autophagy, indicating that targeting USP24-mediated induction of autophagy is required for inhibition of drug resistance. Genomic instability and PD-L1 levels were increased in drug resistant lung cancer cells and were inhibited by USP24-i-101 treatment or knockdown of USP24. In addition, inhibition of autophagy by bafilomycin-A1 significantly abolished the effect of USP24-i-101 on maintaining genomic integrity, decreasing PD-L1 and inhibiting drug resistance acquired in chemotherapy or targeted therapy. In summary, an increase in the expression of USP24 in cancer cells is beneficial for the induction of drug resistance and targeting USP24 by USP24-i-101 optimized from USP24-i inhibits drug resistance acquired during cancer therapy by increasing PD-L1 protein degradation and genomic stability in an autophagy induction-dependent manner.

Knockdown of TXNIP alleviates gestational diabetes mellitus by activating autophagy to regulate cell proliferation and apoptosis in high glucose-treated trophoblasts

Dysregulated thioredoxin-interacting protein (TXNIP) has been observed in women with gestational diabetes mellitus (GDM), but the specific role of TXNIP in GDM and the underlying mechanism remain unclear. HTR-8/SVneo cells were treated with high glucose to mimic the injured trophoblasts of GDM. In vitro, TXNIP knockdown was performed by siRNA. RTqPCR was performed to determine the expression of the corresponding genes. Cell proliferation and apoptosis were measured using CCK-8, EdU and Annexin V/PI assays. The autophagosome number was assessed using transmission electron microscopy. The expression of the autophagy substrate sequestosome 1 (P62) was evaluated by immunofluorescence. Autophagy-related proteins, including P62, light chain 3 (LC3)-I, and LC3-II, were analysed by Western blotting. HTR-8/Svneo cells treated with high glucose demonstrated reduced proliferation, increased apoptosis, decreased autophagosome formation and overall decreased autophagy. However, knockdown of TXNIP reversed the effects of HG on HTR-8/Svneo cells. However, the effect of TXNIP knockdown on HG-treated HTR-8/Svneo cells was inhibited by 3-methyladenine (3-MA) (widely used as an inhibitor of autophagy). We concluded that knockdown of TXNIP has the potential to enhance the activity of high glucose-treated human trophoblasts through autophagic activation, thereby improving pregnancy outcomes in patients with GDM.

Sestrin2 in diabetes and diabetic complications

Diabetes is a global health problem which is accompanied with multi-systemic complications. It is of great significance to elucidate the pathogenesis and to identify novel therapies of diabetes and diabetic complications. Sestrin2, a stress-inducible protein, is primarily involved in cellular responses to various stresses. It plays critical roles in regulating a series of cellular events, such as oxidative stress, mitochondrial function and endoplasmic reticulum stress. Researches investigating the correlations between Sestrin2, diabetes and diabetic complications are increasing in recent years. This review incorporates recent findings, demonstrates the diverse functions and regulating mechanisms of Sestrin2, and discusses the potential roles of Sestrin2 in the pathogenesis of diabetes and diabetic complications, hoping to highlight a promising therapeutic direction.

Ginsenoside Rg1 Ameliorates Pancreatic Injuries via the AMPK/mTOR Pathway in vivo and in vitro

BACKGROUND

The main propanaxatriol-type saponin found in ginseng (Panax ginseng C. A. Mey), ginsenoside Rg1 (G-Rg1), has bioactivities that include anti-inflammatory, antioxidant, and anti-diabetic properties. This study aimed to investigate the effects of G-Rg1 on streptozotocin (STZ)-induced Type 1 Diabetes mellitus (T1DM) mice and the insulin-secreting cell line in RIN-m5F cells with high-glucose (HG) treatment.

METHODS

The STZ-induced DM mice model was treated with G-Rg1 alone or combined with 3-Methyladenine (3-MA, an autophagy inhibitor)/rapamycin (RAPA, an autophagy activator) for 8 weeks, and levels of glucose and lipid metabolism, histopathological changes, as well as autophagy and apoptosis of relevant markers were estimated. In vitro, the HG-induced RIN-m5F cells were treated with G-Rg1, 3-MA, and Compound C (CC), an AMPK inhibitor, or their combinations to estimate the influences on cell apoptosis, autophagy, and AMPK/mTOR pathway-associated target gene levels.

RESULTS

G-Rg1 treatment attenuated glucose and lipid metabolism disorder and pancreatic fibrosis in diabetic mice. In addition, subdued autophagy and p-AMPK protein expression, and enhanced p-mTOR protein expression and apoptosis levels in TIDM mice and HG-induced RIN-m5F cells were ameliorated by G-Rg1 treatment. Furthermore, these anti-apoptosis effects of G-Rg1 were partially abolished by 3-MA and CC.

CONCLUSION

Our findings revealed that G-Rg1 exhibits strong anti-apoptosis ability in pancreatic tissues of type 1 diabetic mice and HG-induced RIN-m5F cells, and the mechanisms involved in activating AMPK and inhibiting mTOR-mediated autophagy, indicating that G-Rg1 may have the therapeutic and preventive potential for treating pancreatic injury in diabetic patients.