Endoplasmic reticulum stress and eIF2α phosphorylation: The Achilles heel of pancreatic β cells

The role of taurine through endoplasmic reticulum in physiology and pathology

Taurine is a sulfur-containing amino acid found in many cell organelles that plays a wide range of biological roles, including bile salt production, osmoregulation, oxidative stress reduction, and neuromodulation. Taurine treatments have also been shown to ameliorate the onset and development of many diseases, including hypertension, fatty liver, neurodegenerative diseases and ischemia-reperfusion injury, by exerting antioxidant, anti-inflammatory, and antiapoptotic effects. The endoplasmic reticulum (ER) is a dynamic organelle involved in a wide range of cellular functions, including lipid metabolism, calcium storage and protein stabilization. Under stress, the disruption of the ER environment leads to the accumulation of misfolded proteins and a characteristic stress response called the unfolded protein response (UPR). The UPR protects cells from stress and helps to restore cellular homeostasis, but its activation promotes cell death under prolonged ER stress. Recent studies have shown that ER stress is closely related to the onset and development of many diseases. This article reviews the beneficial effects and related mechanisms of taurine by regulating the ER in different physiological and pathological states, with the aim of providing a reference for further research and clinical applications.

Endoplasmic reticulum stress in pancreatic β-cell dysfunctionality and diabetes mellitus: a promising target for generation of functional hPSC-derived β-cells in vitro

Diabetes mellitus (DM), is a chronic disorder characterized by impaired glucose homeostasis that results from the loss or dysfunction of pancreatic β-cells leading to type 1 diabetes (T1DM) and type 2 diabetes (T2DM), respectively. Pancreatic β-cells rely to a great degree on their endoplasmic reticulum (ER) to overcome the increased secretary need for insulin biosynthesis and secretion in response to nutrient demand to maintain glucose homeostasis in the body. As a result, β-cells are potentially under ER stress following nutrient levels rise in the circulation for a proper pro-insulin folding mediated by the unfolded protein response (UPR), underscoring the importance of this process to maintain ER homeostasis for normal β-cell function. However, excessive or prolonged increased influx of nascent proinsulin into the ER lumen can exceed the ER capacity leading to pancreatic β-cells ER stress and subsequently to β-cell dysfunction. In mammalian cells, such as β-cells, the ER stress response is primarily regulated by three canonical ER-resident transmembrane proteins: ATF6, IRE1, and PERK/PEK. Each of these proteins generates a transcription factor (ATF4, XBP1s, and ATF6, respectively), which in turn activates the transcription of ER stress-inducible genes. An increasing number of evidence suggests that unresolved or dysregulated ER stress signaling pathways play a pivotal role in β-cell failure leading to insulin secretion defect and diabetes. In this article we first highlight and summarize recent insights on the role of ER stress and its associated signaling mechanisms on β-cell function and diabetes and second how the ER stress pathways could be targeted in vitro during direct differentiation protocols for generation of hPSC-derived pancreatic β-cells to faithfully phenocopy all features of bona fide human β-cells for diabetes therapy or drug screening.

Beyond insulin: Unraveling the complex interplay of ER stress, oxidative damage, and CFTR modulation in CFRD

CF-related diabetes (CFRD) is a prevalent comorbidity in people with Cystic Fibrosis (CF), significantly impacting morbidity and mortality rates. This review article critically evaluates the current understanding of CFRD molecular mechanisms, including the role of CFTR protein, oxidative stress, unfolded protein response (UPR) and intracellular communication. CFRD manifests from a complex interplay between exocrine pancreatic damage and intrinsic endocrine dysfunction, further complicated by the deleterious effects of misfolded CFTR protein on insulin secretion and action. Studies indicate that ER stress and subsequent UPR activation play critical roles in both exocrine and endocrine pancreatic cell dysfunction, contributing to β-cell loss and insulin insufficiency. Additionally, oxidative stress and altered calcium flux, exacerbated by CFTR dysfunction, impair β-cell survival and function, highlighting the significance of antioxidant pathways in CFRD pathogenesis. Emerging evidence underscores the importance of exosomal microRNAs (miRNAs) in mediating inflammatory and stress responses, offering novel insights into CFRD's molecular landscape. Despite insulin therapy remaining the cornerstone of CFRD management, the variability in response to CFTR modulators underscores the need for personalized treatment approaches. The review advocates for further research into non-CFTR therapeutic targets, emphasizing the need to address the multifaceted pathophysiology of CFRD. Understanding the intricate mechanisms underlying CFRD will pave the way for innovative treatments, moving beyond insulin therapy to target the disease's root causes and improve the quality of life for individuals with CF.

Targeting Protein Kinases to Protect Beta-Cell Function and Survival in Diabetes

The prevalence of diabetes is increasing worldwide. Massive death of pancreatic beta-cells causes type 1 diabetes. Progressive loss of beta-cell function and mass characterizes type 2 diabetes. To date, none of the available antidiabetic drugs promotes the maintenance of a functional mass of endogenous beta-cells, revealing an unmet medical need. Dysfunction and apoptotic death of beta-cells occur, in particular, through the activation of intracellular protein kinases. In recent years, protein kinases have become highly studied targets of the pharmaceutical industry for drug development. A number of drugs that inhibit protein kinases have been approved for the treatment of cancers. The question of whether safe drugs that inhibit protein kinase activity can be developed and used to protect the function and survival of beta-cells in diabetes is still unresolved. This review presents arguments suggesting that several protein kinases in beta-cells may represent targets of interest for the development of drugs to treat diabetes.

UNVEILING THE PROTECTIVE MECHANISMS OF PUERARIN AGAINST ACUTE LUNG INJURY: A COMPREHENSIVE EXPLORATION OF THE ROLES AND MECHANISMS OF MST1/ERS SIGNALING

ABSTRACT

Objectives: Puerarin, the principal active constituent extracted from Pueraria, is believed to confer protection against sepsis-induced lung injury. The study aimed to elucidate the role and mechanism of Mst1/ERS in puerarin-mediated protection against acute lung injury (ALI). Methods: Monolayer vascular endothelial cell permeability was assessed by gauging the paracellular flow of FITC-dextran 40,000 (FD40). ELISA was employed for the quantification of inflammatory cytokines. Identification of target proteins was conducted through western blotting. Histological alterations and apoptosis were scrutinized using hematoxylin-eosin staining and TUNEL staining, respectively. The ultrastructure of the endoplasmic reticulum was observed via transmission electron microscopy. Results: Puerarin significantly protected mice from LPS-induced ALI, reducing lung interstitial width, neutrophil and lymphocyte infiltration, pulmonary interstitial and alveolar edema, and lung apoptosis. Puerarin treatment also markedly attenuated levels of TNF-α and IL-1β in both alveolar lavage fluid and serum. Furthermore, puerarin significantly attenuated LPS-induced increases in Mst1, GRP78, CHOP, and Caspase12 protein expression and blunted LPS-induced decrease in ZO-1 protein expression in lung tissues. Puerarin obviously reduced endoplasmic reticulum expansion and vesiculation. Similarly, puerarin significantly mitigated the LPS-induced reduction in HUVEC cell viability and ZO-1 expression. Puerarin also attenuated LPS-induced increase in apoptosis, TNF-α and IL-1β, FD40 flux, and Mst1, GRP78, CHOP, and Caspase12 expression in HUVEC cells. Nevertheless, the inhibitory impact of puerarin on vascular endothelial cell injury, lung injury, and endoplasmic reticulum stress (ERS) was diminished by Mst1 overexpression. Conclusion: These findings demonstrated that the Mst1/ERS signaling pathway played a pivotal role in the development of LPS-induced vascular endothelial cell dysfunction and ALI. Puerarin exhibited the ability to attenuate LPS-induced vascular endothelial cell dysfunction and ALI by inhibiting the Mst1/ERS signaling pathway.

Mammalian integrated stress responses in stressed organelles and their functions

The integrated stress response (ISR) triggered in response to various cellular stress enables mammalian cells to effectively cope with diverse stressful conditions while maintaining their normal functions. Four kinases (PERK, PKR, GCN2, and HRI) of ISR regulate ISR signaling and intracellular protein translation via mediating the phosphorylation of eukaryotic translation initiation factor 2 α (eIF2α) at Ser51. Early ISR creates an opportunity for cells to repair themselves and restore homeostasis. This effect, however, is reversed in the late stages of ISR. Currently, some studies have shown the non-negligible impact of ISR on diseases such as ischemic diseases, cognitive impairment, metabolic syndrome, cancer, vanishing white matter, etc. Hence, artificial regulation of ISR and its signaling with ISR modulators becomes a promising therapeutic strategy for relieving disease symptoms and improving clinical outcomes. Here, we provide an overview of the essential mechanisms of ISR and describe the ISR-related pathways in organelles including mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Meanwhile, the regulatory effects of ISR modulators and their potential application in various diseases are also enumerated.

Adipocyte-released adipomes in Chagas cardiomyopathy: Impact on cardiac metabolic and immune regulation

Chronic Trypanosoma cruzi infection leads to Chagas cardiomyopathy (CCM), with varying manifestations such as inflammatory hypertrophic cardiomyopathy, arrhythmias, and dilated cardiomyopathy. The factors responsible for the increasing risk of progression to CCM are not fully understood. Previous studies link adipocyte loss to CCM progression, but the mechanism triggering CCM pathogenesis remains unexplored. Our study uncovers that T. cruzi infection triggers adipocyte apoptosis, leading to the release of extracellular vesicles named "adipomes". We developed an innovative method to isolate intact adipomes from infected mice's adipose tissue and plasma, showing they carry unique lipid cargoes. Large and Small adipomes, particularly plasma-derived infection-associated L-adipomes (P-ILA), regulate immunometabolic signaling and induce cardiomyopathy. P-ILA treatment induces hypertrophic cardiomyopathy in wild-type mice and worsens cardiomyopathy severity in post-acute-infected mice by regulating adipogenic/lipogenic and mitochondrial functions. These findings highlight adipomes' pivotal role in promoting inflammation and impairing myocardial function during cardiac remodeling in CD.

Illness stress-induced transient hyperglycemia in a patient with a novel YIPF5 homozygous missense variant: expanding the phenotype

A recently described type of neonatal diabetes mellitus is caused by mutations in the YIPF5 gene and is combined with manifestations from the central nervous system, including developmental delay, epilepsy, and microcephaly. The molecular pathophysiology behind this phenotype involves the breakdown of the endoplasmic reticulum stress response due to the loss of protein folding capacity. This results in overt diabetes present from very early in life. Herein, we describe a patient with a newly reported variant in the YIPF5 gene, who presented with short events of severe hyperglycemia, induced by the stress of common illnesses, which completely resolved after recovery. We discuss the nature of transient hyperglycemia in the context of the YIPF5 gene variant and compare this phenotype with the previously described cases.

Identification of common genes and pathways between type 2 diabetes and COVID-19

Background

Numerous studies have reported a high incidence and risk of severe illness due to coronavirus disease 2019 (COVID-19) in patients with type 2 diabetes (T2DM). COVID-19 patients may experience elevated or decreased blood sugar levels and may even develop diabetes. However, the molecular mechanisms linking these two diseases remain unclear. This study aimed to identify the common genes and pathways between T2DM and COVID-19.

Methods

Two public datasets from the Gene Expression Omnibus (GEO) database (GSE95849 and GSE164805) were analyzed to identify differentially expressed genes (DEGs) in blood between people with and without T2DM and COVID-19. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed on the common DEGs. A protein-protein interaction (PPI) network was constructed to identify common genes, and their diagnostic performance was evaluated by receiver operating characteristic (ROC) curve analysis. Validation was performed on the GSE213313 and GSE15932 datasets. A gene co-expression network was constructed using the GeneMANIA database to explore interactions among core DEGs and their co-expressed genes. Finally, a microRNA (miRNA)-transcription factor (TF)-messenger RNA (mRNA) regulatory network was constructed based on the common feature genes.

Results

In the GSE95849 and GSE164805 datasets, 81 upregulated genes and 140 downregulated genes were identified. GO and KEGG enrichment analyses revealed that these DEGs were closely related to the negative regulation of phosphate metabolic processes, the positive regulation of mitotic nuclear division, T-cell co-stimulation, and lymphocyte co-stimulation. Four upregulated common genes (DHX15, USP14, COPS3, TYK2) and one downregulated common feature gene (RIOK2) were identified and showed good diagnostic accuracy for T2DM and COVID-19. The AUC values of DHX15, USP14, COPS3, TYK2, and RIOK2 in T2DM diagnosis were 0.931, 0.917, 0.986, 0.903, and 0.917, respectively. In COVID-19 diagnosis, the AUC values were 0.960, 0.860, 1.0, 0.9, and 0.90, respectively. Validation in the GSE213313 and GSE15932 datasets confirmed these results. The miRNA-TF-mRNA regulatory network showed that TYH2 was targeted by PITX1, PITX2, CRX, NFYA, SREBF1, RELB, NR1L2, and CEBP, whereas miR-124-3p regulates THK2, RIOK2, and USP14.

Conclusion

We identified five common feature genes (DHX15, USP14, COPS3, TYK2, and RIOK2) and their co-regulatory pathways between T2DM and COVID-19, which may provide new insights for further molecular mechanism studies.

Insights into the mechanism of transcription factors in Pb2+-induced apoptosis

The health risks associated with exposure to heavy metals, such as Pb2+, are increasingly concerning the public. Pb2+ can cause significant harm to the human body through oxidative stress, autophagy, inflammation, and DNA damage, disrupting cellular homeostasis and ultimately leading to cell death. Among these mechanisms, apoptosis is considered crucial. It has been confirmed that transcription factors play a central role as mediators during the apoptosis process. Interestingly, these transcription factors have different effects on apoptosis depending on the concentration and duration of Pb2+ exposure. In this article, we systematically summarize the significant roles of several transcription factors in Pb2+-induced apoptosis. This information provides insights into therapeutic strategies and prognostic biomarkers for diseases related to Pb2+ exposure.

Endoplasmic reticulum stress and its role in various neurodegenerative diseases

The Endoplasmic reticulum (ER), a critical cellular organelle, maintains cellular homeostasis by regulating calcium levels and orchestrating essential functions such as protein synthesis, folding, and lipid production. A pivotal aspect of ER function is its role in protein quality control. When misfolded proteins accumulate within the ER due to factors like protein folding chaperone dysfunction, toxicity, oxidative stress, or inflammation, it triggers the Unfolded protein response (UPR). The UPR involves the activation of chaperones like calnexin, calreticulin, glucose-regulating protein 78 (GRP78), and Glucose-regulating protein 94 (GRP94), along with oxidoreductases like protein disulphide isomerases (PDIs). Cells employ the Endoplasmic reticulum-associated degradation (ERAD) mechanism to counteract protein misfolding. ERAD disruption causes the detachment of GRP78 from transmembrane proteins, initiating a cascade involving Inositol-requiring kinase/endoribonuclease 1 (IRE1), Activating transcription factor 6 (ATF6), and Protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathways. The accumulation and deposition of misfolded proteins within the cell are hallmarks of numerous neurodegenerative diseases. These aberrant proteins disrupt normal neuronal signalling and contribute to impaired cellular homeostasis, including oxidative stress and compromised protein degradation pathways. In essence, ER stress is defined as the cellular response to the accumulation of misfolded proteins in the endoplasmic reticulum, encompassing a series of signalling pathways and molecular events that aim to restore cellular homeostasis. This comprehensive review explores ER stress and its profound implications for the pathogenesis and progression of neurodegenerative diseases.

The advancement of polysaccharides in disease modulation: Multifaceted regulation of programmed cell death

Programmed cell death (PCD), also known as regulatory cell death (RCD), is a process that occurs in all organisms and is closely linked to both normal physiological processes and disease states. Various signaling pathways, such as TP53, KRAS, NOTCH, hypoxia, and metabolic reprogramming, have been found to regulate RCD. Polysaccharides, which are essential natural products, have been the subject of extensive research in the fields of food, nutrition, and medicine due to their wide range of pharmacological effects. Studies have shown that polysaccharides have biological activities and the potential to target signal transduction pathways for the treatment of diseases. This paper provides a review of the mechanisms through which polysaccharides exert their therapeutic effects at different levels and explores the relationship between different types of RCD and human diseases. The aim of this review is to provide a theoretical basis for the further clinical use and application of polysaccharide bioactivities.

Effect of CB1 Receptor Deficiency on Mitochondrial Quality Control Pathways in Gastrocnemius Muscle

This study aims to explore the complex role of cannabinoid type 1 receptor (CB1) signaling in the gastrocnemius muscle, assessing physiological processes in both CB1+/+ and CB1-/- mice. The primary focus is to enhance our understanding of how CB1 contributes to mitochondrial homeostasis. At the tissue level, CB1-/- mice exhibit a substantial miRNA-related alteration in muscle fiber composition, characterized by an enrichment of oxidative fibers. CB1 absence induces a significant increase in the oxidative capacity of muscle, supported by elevated in-gel activity of Complex I and Complex IV of the mitochondrial respiratory chain. The increased oxidative capacity is associated with elevated oxidative stress and impaired antioxidant defense systems. Analysis of mitochondrial biogenesis markers indicates an enhanced capacity for new mitochondria production in CB1-/- mice, possibly adapting to altered muscle fiber composition. Changes in mitochondrial dynamics, mitophagy response, and unfolded protein response (UPR) pathways reveal a dynamic interplay in response to CB1 absence. The interconnected mitochondrial network, influenced by increased fusion and mitochondrial UPR components, underlines the dual role of CB1 in regulating both protein quality control and the generation of new mitochondria. These findings deepen our comprehension of the CB1 impact on muscle physiology, oxidative stress, and MQC processes, highlighting cellular adaptability to CB1-/-. This study paves the way for further exploration of intricate signaling cascades and cross-talk between cellular compartments in the context of CB1 and mitochondrial homeostasis.

Investigating the Role of 17-Beta Estradiol in the Regulation of the Unfolded Protein Response (UPR) in Pancreatic Beta Cells

Diabetes mellitus is clinically defined by chronic hyperglycemia. Sex differences in the presentation and outcome of diabetes exist with premenopausal women having a reduced risk of developing diabetes, relative to men, or women after menopause. Accumulating evidence shows a protective role of estrogens, specifically 17-beta estradiol, in the maintenance of pancreatic beta cell health; however, the mechanisms underlying this protection are still unknown. To elucidate these potential mechanisms, we used a pancreatic beta cell line (BTC6) and a mouse model of hyperglycemia-induced atherosclerosis, the ApoE-/-:Ins2+/Akita mouse, exhibiting sexual dimorphism in glucose regulation. In this study we hypothesize that 17-beta estradiol protects pancreatic beta cells by modulating the unfolded protein response (UPR) in response to endoplasmic reticulum (ER) stress. We observed that ovariectomized female and male ApoE-/-:Ins2+/Akita mice show significantly increased expression of apoptotic UPR markers. Sham operated female and ovariectomized female ApoE-/-:Ins2+/Akita mice supplemented with exogenous 17-beta estradiol increased the expression of adaptive UPR markers compared to non-supplemented ovariectomized female ApoE-/-:Ins2+/Akita mice. These findings were consistent to what was observed in cultured BTC6 cells, suggesting that 17-beta estradiol may protect pancreatic beta cells by repressing the apoptotic UPR and enhancing the adaptive UPR activation in response to pancreatic ER stress.

Role of cytosolic and endoplasmic reticulum Ca2+ in pancreatic beta-cells: pros and cons

Pancreatic beta cells utilize Ca2+ to secrete insulin in response to glucose. The glucose-dependent increase in cytosolic Ca2+ concentration ([Ca2+]C) activates a series of insulin secretory machinery in pancreatic beta cells. Therefore, the amount of insulin secreted in response to glucose is determined in a [Ca2+]C-dependent manner, at least within a moderate range. However, the demand for insulin secretion may surpass the capability of beta cells. Abnormal elevation of [Ca2+]C levels beyond the beta-cell endurance capacity can damage them by inducing endoplasmic reticulum (ER) stress and cell death programs such as apoptosis. Therefore, while Ca2+ is essential for the insulin secretory functions of beta cells, it could affect their survival at pathologically higher levels. Because an increase in beta-cell [Ca2+]C is inevitable under certain hazardous conditions, understanding the regulatory mechanism for [Ca2+]C is important. Therefore, this review discusses beta-cell function, survival, ER stress, and apoptosis associated with intracellular and ER Ca2+ homeostasis.

Independent activation of CREB3L2 by glucose fills a regulatory gap in mouse β-cells by co-ordinating insulin biosynthesis with secretory granule formation

OBJECTIVE

Although individual steps have been characterized, there is little understanding of the overall process whereby glucose co-ordinates the biosynthesis of insulin with its export out of the endoplasmic reticulum (ER) and incorporation into insulin secretory granules (ISGs). Here we investigate a role for the transcription factor CREB3L2 in this context.

METHODS

MIN6 cells and mouse islets were analysed by immunoblotting after treatment with glucose, fatty acids, thapsigargin and various inhibitors. Knockdown of CREB3L2 was achieved using si or sh constructs by transfection, or viral delivery. In vivo metabolic phenotyping was conducted after deletion of CREB3L2 in β-cells of adult mice using Ins1-CreER+. Islets were isolated for RNAseq and assays of glucose-stimulated insulin secretion (GSIS). Trafficking was monitored in islet monolayers using a GFP-tagged proinsulin construct that allows for synchronised release from the ER.

RESULTS

With a Km ≈3.5 mM, glucose rapidly (T1/2 0.9 h) increased full length (FL) CREB3L2 followed by a slower rise (T1/2 2.5 h) in its transcriptionally-active cleavage product, P60 CREB3L2. Glucose stimulation repressed the ER stress marker, CHOP, and this was partially reverted by knockdown of CREB3L2. Activation of CREB3L2 by glucose was not due to ER stress, however, but a combination of O-GlcNAcylation, which impaired proteasomal degradation of FL-CREB3L2, and mTORC1 stimulation, which enhanced its conversion to P60. cAMP generation also activated CREB3L2, but independently of glucose. Deletion of CREB3L2 inhibited GSIS ex vivo and, following a high-fat diet (HFD), impaired glucose tolerance and insulin secretion in vivo. RNAseq revealed that CREB3L2 regulated genes controlling trafficking to-and-from the Golgi, as well as a broader cohort associated with β-cell compensation during a HFD. Although post-Golgi trafficking appeared intact, knockdown of CREB3L2 impaired the generation of both nascent ISGs and proinsulin condensates in the Golgi, implying a defect in ER export of proinsulin and/or its processing in the Golgi.

CONCLUSION

The stimulation of CREB3L2 by glucose defines a novel, rapid and direct mechanism for co-ordinating the synthesis, packaging and storage of insulin, thereby minimizing ER overload and optimizing β-cell function under conditions of high secretory demand. Upregulation of CREB3L2 also potentially contributes to the benefits of GLP1 agonism and might in itself constitute a novel means of treating β-cell failure.

The role of autophagy in insulin resistance and glucolipid metabolism and potential use of autophagy modulating natural products in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a severe, long-term condition characterised by disruptions in glucolipid and energy metabolism. Autophagy, a fundamental cellular process, serves as a guardian of cellular health by recycling and renewing cellular components. To gain a comprehensive understanding of the vital role that autophagy plays in T2DM, we conducted an extensive search for high-quality publications across databases such as Web of Science, PubMed, Google Scholar, and SciFinder and used keywords like 'autophagy', 'insulin resistance', and 'type 2 diabetes mellitus', both individually and in combinations. A large body of evidence underscores the significance of activating autophagy in alleviating T2DM symptoms. An enhanced autophagic activity, either by activating the adenosine monophosphate-activated protein kinase and sirtuin-1 signalling pathways or inhibiting the mechanistic target of rapamycin complex 1 signalling pathway, can effectively improve insulin resistance and balance glucolipid metabolism in key tissues like the hypothalamus, skeletal muscle, liver, and adipose tissue. Furthermore, autophagy can increase β-cell mass and functionality in the pancreas. This review provides a narrative summary of autophagy regulation with an emphasis on the intricate connection between autophagy and T2DM symptoms. It also discusses the therapeutic potentials of natural products with autophagy activation properties for the treatment of T2DM conditions. Our findings suggest that autophagy activation represents an innovative approach of treating T2DM.

Endoplasmic reticulum stress exacerbates microplastics-induced toxicity in animal cells

Human and animal exposure to microplastics (MPs) contained in food is inevitable because of their widespread existence in the environment. Nevertheless, MPs toxicity studies in ruminants often lack attention. Here, we assessed the cytotoxicity of polystyrene microplastics (PS MPs) on goat mammary epithelial cells (GMECs). Compared to controls, PS MPs treatment significantly reduced cell viability, altered cell morphology and disrupted organelle integrity. Detection of membrane potential and reactive oxygen species (ROS) suggested that PS MPs induced mitochondrial dysfunction and oxidative stress. Further transcriptome analysis also confirmed alterations in these pathways. In addition, several genes related to endoplasmic reticulum (ER) homeostasis were significantly regulated in the transcriptional profile. Subsequent experiments confirmed that PS MPs induce ER stress via the PERK/eIF2α/CHOP pathway, accompanied by intracellular Ca2+ overload. Meanwhile, downstream activation of the Bax/Bcl-2 pathway and caspase cascade released apoptotic signals, which led to apoptosis in GMECs. Interestingly, the addition of PERK inhibitor (ISRIB) attenuated PS MPs-induced ER stress and apoptosis, which suggests that ER stress may exacerbate PS MPs-induced cytotoxicity. This work reveals the impact of MPs on mammalian cytotoxicity, enriches the mechanisms for the toxicity of MPs, and provides insight for further assessment of the risk of MPs in food.

Endoplasmic Reticulum Stress and Its Impact on Adipogenesis: Molecular Mechanisms Implicated

Endoplasmic reticulum (ER) stress plays a pivotal role in adipogenesis, which encompasses the differentiation of adipocytes and lipid accumulation. Sustained ER stress has the potential to disrupt the signaling of the unfolded protein response (UPR), thereby influencing adipogenesis. This comprehensive review illuminates the molecular mechanisms that underpin the interplay between ER stress and adipogenesis. We delve into the dysregulation of UPR pathways, namely, IRE1-XBP1, PERK and ATF6 in relation to adipocyte differentiation, lipid metabolism, and tissue inflammation. Moreover, we scrutinize how ER stress impacts key adipogenic transcription factors such as proliferator-activated receptor γ (PPARγ) and CCAAT-enhancer-binding proteins (C/EBPs) along with their interaction with other signaling pathways. The cellular ramifications include alterations in lipid metabolism, dysregulation of adipokines, and aged adipose tissue inflammation. We also discuss the potential roles the molecular chaperones cyclophilin A and cyclophilin B play in adipogenesis. By shedding light on the intricate relationship between ER stress and adipogenesis, this review paves the way for devising innovative therapeutic interventions.

Neuroinflammation-Modulating Agent SB1617 Enhances LC3-Associated Phagocytosis to Mitigate Tau Pathology

Tau protein aggregation and propagation in neurons and surrounding microglia are well-known risk factors for neurodegenerative diseases. Therefore, emerging therapeutic strategies that target neuroinflammatory activity in microglia have the potential to prevent tauopathy. Here, we explored the microglia-mediated neuroprotective function of SB1617 against tau aggregation. Our study revealed that SB1617-inactivated pathogenic M1-like microglia, reduced the secretion of pro-inflammatory cytokines via translational regulation, and induced microglial polarization toward the M2 phenotype and phagocytic function. Furthermore, we observed that extracellular pathogenic tau aggregates were eliminated via LC3-associated phagocytosis. The in vivo efficacy of SB1617 was confirmed in mice with traumatic brain injury in which SB1617 exerted neuroprotective effects by reducing pathogenic tau levels through microglia-mediated anti-inflammatory activity. Our results indicated that SB1617-mediated microglial surveillance with LC3-associated phagocytosis is a critical molecular mechanism in the regulation of tau proteostasis. This study provides new insights into tauopathies and directions for developing novel therapies for neurodegenerative diseases.

Sustained hyperglycemia specifically targets translation of mRNAs for insulin secretion

Pancreatic β cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair β cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion is similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on β cell mRNA translation. Before induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our study uncovered a translational regulatory circuit during β cell glucose toxicity that impairs expression of proteins with critical roles in β cell function.

Characterizing the extracellular vesicle proteomic landscape of the human airway using in vitro organotypic multi-cellular models

Extracellular vesicle (EV)-mediated intercellular communication significantly influences pulmonary cell health and disease, yet in vitro methods to investigate these mechanisms are limited. We hypothesize that organotypic models of the airway can be leveraged to investigate EV-mediated intercellular signaling, focusing on EV proteomic content as a case study. Two in vitro airway culture models were evaluated by mass spectrometry-based proteomics analysis: a tri-culture model consisting of alveolar epithelial, fibroblast, and lung microvascular endothelial cells and a co-culture model of alveolar epithelial and fibroblasts. EVs isolated from the tri-culture model were enriched with EV proteins regulating RNA-to-protein translation. EVs isolated from the co-culture model were enriched with EV biogenesis and extracellular matrix signaling proteins. These model-specific differences suggest that different pulmonary cell types uniquely affect EV composition and the biological pathways influenced by the EV proteome in recipient cells. These findings can inform future studies surrounding EV-related pulmonary disease pathogenesis and therapeutics.

Nrf2: Therapeutic target of islet function protection in diabetes and islet transplantation

Nuclear factor-erythroid 2-related factor 2 (Nrf2) has been reported as a major intracellular regulator of antioxidant stress, notably in islet β cells with low antioxidant enzyme content. Nrf2 is capable of regulating antioxidant function, while it can also regulate insulin secretion, proliferation, and differentiation of β cells, ER stress, as well as mitochondrial function. Thus, Nrf2 pharmacological activators have been employed in the laboratory for the treatment of diabetic mice. Islet cells are exposed to oxidative environment when islet is being transplanted. Accordingly, less than 50% of islet cells are well transplanted, and their normal function is maintained. The pharmacological activation of Nrf2 has been confirmed to protect islet cells at different stages of transplantation stages during experiments for islet transplantation.

Sustained hyperglycemia specifically targets translation of mRNAs for insulin secretion

Pancreatic β-cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair β-cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion are similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on β-cell mRNA translation. Prior to induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also of mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex-vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our findings uncover a translational regulatory circuit during β-cell glucose toxicity that impairs expression of proteins with critical roles in β-cell function.

DSCC1 interacts with HSP90AB1 and promotes the progression of lung adenocarcinoma via regulating ER stress

Lung cancer is a leading cause of cancer-related deaths, and the most common type is lung adenocarcinoma (LUAD). LUAD is frequently diagnosed in people who never smoked, patients are always diagnosed at advanced inoperable stages, and the prognosis is ultimately poor. Thus, there is an urgent need for the development of novel targeted therapeutics to suppress LUAD progression. In this study, we demonstrated that the expression of DNA replication and sister chromatid cohesion 1 (DSCC1) was higher in LUAD samples than normal tissues, and the overexpression of DSCC1 or its coexpressed genes were highly correlated with poor outcomes of LUAD patients, highlighting DSCC1 might be involved in LUAD progression. Furthermore, the expression of DSCC1 was positively correlated with multiple genetic mutations which drive cancer development, including TP53, TTN, CSMD, and etc. More importantly, DSCC1 could promote the cell proliferation, stemness, EMT, and metastatic potential of LUAD cells. In addition, DSCC1 interacted with HSP90AB1 and promoted the progression of LUAD via regulating ER stress. Meanwhile, DSCC1 expression negatively correlated with immune cell infiltration in lung cancer, and DSCC1 positively regulated the expression of PD-L1 in LUAD cells. Collectively, this study revealed that DSCC1 is a novel therapeutic target to treat LUAD and a biomarker for predicting the efficiency of PD-1/PD-L1 blockade treatment.

Inferring regulators of cell identity in the human adult pancreas

Cellular identity during development is under the control of transcription factors that form gene regulatory networks. However, the transcription factors and gene regulatory networks underlying cellular identity in the human adult pancreas remain largely unexplored. Here, we integrate multiple single-cell RNA-sequencing datasets of the human adult pancreas, totaling 7393 cells, and comprehensively reconstruct gene regulatory networks. We show that a network of 142 transcription factors forms distinct regulatory modules that characterize pancreatic cell types. We present evidence that our approach identifies regulators of cell identity and cell states in the human adult pancreas. We predict that HEYL, BHLHE41 and JUND are active in acinar, beta and alpha cells, respectively, and show that these proteins are present in the human adult pancreas as well as in human induced pluripotent stem cell (hiPSC)-derived islet cells. Using single-cell transcriptomics, we found that JUND represses beta cell genes in hiPSC-alpha cells. BHLHE41 depletion induced apoptosis in primary pancreatic islets. The comprehensive gene regulatory network atlas can be explored interactively online. We anticipate our analysis to be the starting point for a more sophisticated dissection of how transcription factors regulate cell identity and cell states in the human adult pancreas.

FoxM1 coordinates cell division, protein synthesis, and mitochondrial activity in a subset of β cells during acute metabolic stress

Pancreatic β cells display functional and transcriptional heterogeneity in health and disease. The sequence of events leading to β cell heterogeneity during metabolic stress is poorly understood. Here, we characterize β cell responses to early metabolic stress in vivo by employing RNA sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), single-cell RNA-seq (scRNA-seq), chromatin immunoprecipitation sequencing (ChIP-seq), and real-time imaging to decipher temporal events of chromatin remodeling and gene expression regulating the unfolded protein response (UPR), protein synthesis, mitochondrial function, and cell-cycle progression. We demonstrate that a subpopulation of β cells with active UPR, decreased protein synthesis, and insulin secretary capacities is more susceptible to proliferation after insulin depletion. Alleviation of endoplasmic reticulum (ER) stress precedes the progression of the cell cycle and mitosis and ensures appropriate insulin synthesis. Furthermore, metabolic stress rapidly activates key transcription factors including FoxM1, which impacts on proliferative and quiescent β cells by regulating protein synthesis, ER stress, and mitochondrial activity via direct repression of mitochondrial-encoded genes.

Reversing pancreatic β-cell dedifferentiation in the treatment of type 2 diabetes

The maintenance of glucose homeostasis is fundamental for survival and health. Diabetes develops when glucose homeostasis fails. Type 2 diabetes (T2D) is characterized by insulin resistance and pancreatic β-cell failure. The failure of β-cells to compensate for insulin resistance results in hyperglycemia, which in turn drives altered lipid metabolism and β-cell failure. Thus, insulin secretion by pancreatic β-cells is a primary component of glucose homeostasis. Impaired β-cell function and reduced β-cell mass are found in diabetes. Both features stem from a failure to maintain β-cell identity, which causes β-cells to dedifferentiate into nonfunctional endocrine progenitor-like cells or to trans-differentiate into other endocrine cell types. In this regard, one of the key issues in achieving disease modification is how to reestablish β-cell identity. In this review, we focus on the causes and implications of β-cell failure, as well as its potential reversibility as a T2D treatment.

Endoplasmic reticulum stress: a novel targeted approach to repair bone defects by regulating osteogenesis and angiogenesis

Bone regeneration therapy is clinically important, and targeted regulation of endoplasmic reticulum (ER) stress is important in regenerative medicine. The processing of proteins in the ER controls cell fate. The accumulation of misfolded and unfolded proteins occurs in pathological states, triggering ER stress. ER stress restores homeostasis through three main mechanisms, including protein kinase-R-like ER kinase (PERK), inositol-requiring enzyme 1ɑ (IRE1ɑ) and activating transcription factor 6 (ATF6), collectively known as the unfolded protein response (UPR). However, the UPR has both adaptive and apoptotic effects. Modulation of ER stress has therapeutic potential for numerous diseases. Repair of bone defects involves both angiogenesis and bone regeneration. Here, we review the effects of ER stress on osteogenesis and angiogenesis, with emphasis on ER stress under high glucose (HG) and inflammatory conditions, and the use of ER stress inducers or inhibitors to regulate osteogenesis and angiogenesis. In addition, we highlight the ability for exosomes to regulate ER stress. Recent advances in the regulation of ER stress mediated osteogenesis and angiogenesis suggest novel therapeutic options for bone defects.

Heterophyllin B ameliorates gastric cancer tumor growth through activating ER stress

BACKGROUND

Gastric cancer (GC) is the third leading cause of cancer-related death worldwide. Heterophyllin B (HB) has been proved to be a potential drug in cancer treatment.

METHODS

In the current study, GC cells were treated with 0, 10, 25, or 50 μM of HB. Cell viability was determined by utilizing MTT assay. Flow cytometry was carried out for cell apoptosis and cell cycle analysis. The expression levels of IRE1, CHOP, GRP78 and Bcl-2 in cells and tumors were measured by Western blot and immunohistochemistry, respectively.

RESULTS

Our data uncovered that HB administration significantly suppressed GC cell viability, but facilitated GC cell apoptosis and cell cycle arrest at G0/G1 phase. The effects of HB on GC cell proliferation, apoptosis and cell cycle showed dosage-dependent manner. Furthermore, expression of ER stress-associated proteins like IRE1, CHOP and GRP78 was markedly upregulated, while anti-apoptosis protein Bcl2 expression was inhibited by HB treatment in a dosage-dependent manner. Our data indicated that HB treatment facilitated caspase-3 expression in a dose-dependent manner, but had no effect on caspase-8 expression. Importantly, the inhibition of HB to GC cell apoptosis and cell cycle process and the promotion of HB to GC cell proliferation were partly rescued by inhibition of ER stress utilizing 4-PBA. In animal experiments, HB administration suppressed GC tumor growth, boosted IRE1, CHOP and GRP78 expression and inhibited Bcl-2 expression.

CONCLUSION

All in all, HB treatment could effectively suppress GC cells proliferation and tumors growth and facilitate GC cells apoptosis and cell cycle arrest through activating ER stress. Our data indicated that HB may be a potential drug for GC treatment.

Signaling pathways and intervention for therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents one of the fastest growing epidemic metabolic disorders worldwide and is a strong contributor for a broad range of comorbidities, including vascular, visual, neurological, kidney, and liver diseases. Moreover, recent data suggest a mutual interplay between T2DM and Corona Virus Disease 2019 (COVID-19). T2DM is characterized by insulin resistance (IR) and pancreatic β cell dysfunction. Pioneering discoveries throughout the past few decades have established notable links between signaling pathways and T2DM pathogenesis and therapy. Importantly, a number of signaling pathways substantially control the advancement of core pathological changes in T2DM, including IR and β cell dysfunction, as well as additional pathogenic disturbances. Accordingly, an improved understanding of these signaling pathways sheds light on tractable targets and strategies for developing and repurposing critical therapies to treat T2DM and its complications. In this review, we provide a brief overview of the history of T2DM and signaling pathways, and offer a systematic update on the role and mechanism of key signaling pathways underlying the onset, development, and progression of T2DM. In this content, we also summarize current therapeutic drugs/agents associated with signaling pathways for the treatment of T2DM and its complications, and discuss some implications and directions to the future of this field.

BACE cleavage of APP does not drive the diabetic phenotype of PLB4 mice

BACKGROUND

Alzheimer's Disease (AD) and Type 2 Diabetes Mellitus (T2DM), two prevalent diseases related to ageing, often share common pathologies including increased inflammation, endoplasmic reticulum (ER) stress, and impaired metabolic homeostasis predominantly affecting different organs. Therefore, it was unexpected to find in a previous study that neuronal hBACE1 knock-in (PLB4 mouse) leads to both an AD- and T2DM- like phenotype. The complexity of this co-morbidity phenotype required a deeper systems approach to explore the age-related changes in AD and T2DM-like pathologies of the PLB4 mouse. Therefore, we here analysed key neuronal and metabolic tissues comparing associated pathologies to those of normal ageing.

METHODS

Glucose tolerance, insulin sensitivity and protein turnover were assessed in 5-h fasted 3- and 8-month-old male PLB4 and wild-type mice. Western Blot and quantitative PCR were performed to determine regulation of homeostatic and metabolic pathways in insulin-stimulated brain, liver and muscle tissue.

RESULTS

Neuronal hBACE1 expression caused early pathological cleavage of APP (increased monomeric Aβ (mAβ) levels at 3-months), in parallel with brain ER stress (increased phosphorylation of the translation regulation factor (p-eIF2α) and the chaperone binding immunoglobulin protein (BIP)). However, APP processing shifted over time (higher full-length APP and sAPPβ levels, alongside lower mAβ and secreted APPα at 8 months), along with increased ER stress (phosphorylated/total inositol-requiring enzyme 1α (IRE1α)) in brain and liver. Metabolically, systemic glucose intolerance was evident from 3 months, yet metabolic signalling varied greatly between tissues and ages, and was confined to the periphery (muscle insulin receptors (IR), dipeptidyl-peptidase-4 (DPP4) levels, and decreased phosphorylated protein Kinase B (p-Akt), alongside increased liver DPP4 and fibroblast growth factor 21 (FGF21)), all of which normalised to wild-type levels at 8 months.

CONCLUSION

Our data suggest that the murine nervous system is affected early by APP misprocessing as a result of hBACE1 introduction, which coincided with ER stress, but not IR changes, and was alleviated with age. Peripheral metabolic alterations occurred early and revealed tissue-specific (liver vs. muscle) adaptations in metabolic markers but did not correlate with neuronal APP processing. Compensatory vs. contributory neuronal mechanisms associated with hBACE1 expression at different ages may explain why mice intrinsically do not develop AD pathologies and may offer new insights for future interventions.

Pharmacological inhibitors of β-cell dysfunction and death as therapeutics for diabetes

More than 500 million adults suffer from diabetes worldwide, and this number is constantly increasing. Diabetes causes 5 million deaths per year and huge healthcare costs per year. β-cell death is the major cause of type 1 diabetes. β-cell secretory dysfunction plays a key role in the development of type 2 diabetes. A loss of β-cell mass due to apoptotic death has also been proposed as critical for the pathogenesis of type 2 diabetes. Death of β-cells is caused by multiple factors including pro-inflammatory cytokines, chronic hyperglycemia (glucotoxicity), certain fatty acids at high concentrations (lipotoxicity), reactive oxygen species, endoplasmic reticulum stress, and islet amyloid deposits. Unfortunately, none of the currently available antidiabetic drugs favor the maintenance of endogenous β-cell functional mass, indicating an unmet medical need. Here, we comprehensively review over the last ten years the investigation and identification of molecules of pharmacological interest for protecting β-cells against dysfunction and apoptotic death which could pave the way for the development of innovative therapies for diabetes.

Exercise as a non-pharmacological intervention to protect pancreatic beta cells in individuals with type 1 and type 2 diabetes

AIMS/HYPOTHESIS

Diabetes is characterised by progressive loss of functional pancreatic beta cells. None of the therapeutic agents used to treat diabetes arrest this process; preventing beta cell loss remains a major unmet need. We have previously shown that serum from eight young healthy male participants who exercised for 8 weeks protected human islets and insulin-producing EndoC-βH1 cells from apoptosis induced by proinflammatory cytokines or the endoplasmic reticulum (ER) stressor thapsigargin. Whether this protective effect is influenced by sex, age, training modality, ancestry or diabetes is unknown.

METHODS

We enrolled 82 individuals, male or female, non-diabetic or diabetic, from different origins, in different supervised training protocols for 8-12 weeks (including training at home during the COVID-19 pandemic). EndoC-βH1 cells were treated with 'exercised' serum or with the exerkine clusterin to ascertain cytoprotection from ER stress.

RESULTS

The exercise interventions were effective and improved [Formula: see text] values in both younger and older, non-obese and obese, non-diabetic and diabetic participants. Serum obtained after training conferred significant beta cell protection (28% to 35% protection after 4 and 8 weeks of training, respectively) from severe ER stress-induced apoptosis. Cytoprotection was not affected by the type of exercise training or participant age, sex, BMI or ancestry, and persisted for up to 2 months after the end of the training programme. Serum from exercised participants with type 1 or type 2 diabetes was similarly protective. Clusterin reproduced the beneficial effects of exercised sera.

CONCLUSIONS/INTERPRETATION

These data uncover the unexpected potential to preserve beta cell health by exercise training, opening a new avenue to prevent or slow diabetes progression through humoral muscle-beta cell crosstalk.

The mechanism of programmed death and endoplasmic reticulum stress in pulmonary hypertension

Pulmonary hypertension (PH) was a cardiovascular disease with high morbidity and mortality. PH was a chronic disease with complicated pathogenesis and uncontrollable factors. PH was divided into five groups according to its pathogenesis and clinical manifestations. Although the treatment and diagnosis of PH has made great progress in the past ten years. However, the diagnosis and prognosis of the PAH had a great contrast, which was not conducive to the diagnosis and treatment of PH. If not treated properly, it will lead to right ventricular failure or even death. Therefore, it was necessary to explore the pathogenesis of PH. The problem we urgently need to solve was to find and develop drugs for the treatment of PH. We reviewed the PH articles in the past 10 years or so as well as systematically summarized the recent advance. We summarized the latest research on the key regulatory factors (pyroptosis, apoptosis, necroptosis, ferroptosis, and endoplasmic reticulum stress) involved in PH. To provide theoretical basis and basis for finding new therapeutic targets and research directions of PH.

Sex differences in islet stress responses support female β cell resilience

OBJECTIVE

Pancreatic β cells play a key role in maintaining glucose homeostasis; dysfunction of this critical cell type causes type 2 diabetes (T2D). Emerging evidence points to sex differences in β cells, but few studies have examined male-female differences in β cell stress responses and resilience across multiple contexts, including diabetes. Here, we address the need for high-quality information on sex differences in β cell and islet gene expression and function using both human and rodent samples.

METHODS

In humans, we compared β cell gene expression and insulin secretion in donors with T2D to non-diabetic donors in both males and females. In mice, we generated a well-powered islet RNAseq dataset from 20-week-old male and female siblings with similar insulin sensitivity. Our unbiased gene expression analysis pointed to a sex difference in the endoplasmic reticulum (ER) stress response. Based on this analysis, we hypothesized female islets would be more resilient to ER stress than male islets. To test this, we subjected islets isolated from age-matched male and female mice to thapsigargin treatment and monitored protein synthesis, cell death, and β cell insulin production and secretion. Transcriptomic and proteomic analyses were used to characterize sex differences in islet responses to ER stress.

RESULTS

Our single-cell analysis of human β cells revealed sex-specific changes to gene expression and function in T2D, correlating with more robust insulin secretion in human islets isolated from female donors with T2D compared to male donors with T2D. In mice, RNA sequencing revealed differential enrichment of unfolded protein response pathway-associated genes, where female islets showed higher expression of genes linked with protein synthesis, folding, and processing. This differential expression was physiologically significant, as islets isolated from female mice were more resilient to ER stress induction with thapsigargin. Specifically, female islets showed a greater ability to maintain glucose-stimulated insulin production and secretion during ER stress compared with males.

CONCLUSIONS

Our data demonstrate sex differences in β cell gene expression in both humans and mice, and that female β cells show a greater ability to maintain glucose-stimulated insulin secretion across multiple physiological and pathological contexts.

Obesity and type 2 diabetes mellitus: connections in epidemiology, pathogenesis, and treatments

The prevalence of obesity and diabetes mellitus (DM) has been consistently increasing worldwide. Sharing powerful genetic and environmental features in their pathogenesis, obesity amplifies the impact of genetic susceptibility and environmental factors on DM. The ectopic expansion of adipose tissue and excessive accumulation of certain nutrients and metabolites sabotage the metabolic balance via insulin resistance, dysfunctional autophagy, and microbiome-gut-brain axis, further exacerbating the dysregulation of immunometabolism through low-grade systemic inflammation, leading to an accelerated loss of functional β-cells and gradual elevation of blood glucose. Given these intricate connections, most available treatments of obesity and type 2 DM (T2DM) have a mutual effect on each other. For example, anti-obesity drugs can be anti-diabetic to some extent, and some anti-diabetic medicines, in contrast, have been shown to increase body weight, such as insulin. Meanwhile, surgical procedures, especially bariatric surgery, are more effective for both obesity and T2DM. Besides guaranteeing the availability and accessibility of all the available diagnostic and therapeutic tools, more clinical and experimental investigations on the pathogenesis of these two diseases are warranted to improve the efficacy and safety of the available and newly developed treatments.

Jiedutongluotiaogan formula restores pancreatic function by suppressing excessive autophagy and endoplasmic reticulum stress

CONTEXT

Jiedutongluotiaogan formula (JTTF), a traditional Chinese medicine (TCM), could promote islet function. However, the potential effect of JTTF on endoplasmic reticulum stress (ERS) and autophagy have not been reported.

OBJECTIVE

This study explores the potential effect of JTTF on ERS and autophagy in the pancreas.

MATERIALS AND METHODS

The Zucker diabetic fatty (ZDF) rats were randomised into five groups, control, model, JTTF (1, 3, 5 g/kg/day for 12 weeks). LPS induced pancreatic β-cells were treated with JTTF (50, 100, 200 μg/mL). LPS was used to induce pancreatic β-cell injury, with cell viability and insulin secretion evaluated using MTT, glucose-stimulated insulin secretion (GSIS) assays, and PCR. Intracellular Ca²⁺ concentration was measured using flow cytometry, while ERS and autophagy levels were monitored via Western blotting and/or immunostaining.

RESULTS

Compared with the model group, body weight, FGB, HbA1c, IPGTT, FINs, and HOMA-IR in JTTF treatment groups were significantly reduced. In islets cells treated with JTTF, the pancreatic islet cells in the JTTF group were increased, lipid droplets were reduced, and there was a decrease in Ca²⁺ (16.67%). After JTTF intervention, PERK, p-PERK, IRE1α, p- IRE1α, ATF6, eIF2α, GRP78, p-ULK1, LC3 and p62 expression decreased, whereas Beclin1and p-mTOR expression increased. In addition, the expression of proteins related to apoptosis in the JTTF groups were lower than those in the control group.

DISCUSSION AND CONCLUSIONS

JTTF may alleviate pancreatic β-cell injury by inhibiting ER stress and excessive autophagy in diabetic rats. This provides a new direction for treating diabetes and restoring pancreatic dysfunction by TCM.

PAHSAs reduce cellular senescence and protect pancreatic beta cells from metabolic stress through regulation of Mdm2/p53

Senescence in pancreatic beta cells plays a major role in beta cell dysfunction, which leads to impaired glucose homeostasis and diabetes. Therefore, prevention of beta cell senescence could reduce the risk of diabetes. Treatment of nonobese diabetic (NOD) mice, a model of type 1 autoimmune diabetes (T1D), with palmitic acid hydroxy stearic acids (PAHSAs), a novel class of endogenous lipids with antidiabetic and antiinflammatory effects, delays the onset and reduces the incidence of T1D from 82% with vehicle treatment to 35% with PAHSAs. Here, we show that a major mechanism by which PAHSAs protect islets of the NOD mice is by directly preventing and reversing the initial steps of metabolic stress-induced senescence. In vitro PAHSAs increased Mdm2 expression, which decreases the stability of p53, a key inducer of senescence-related genes. In addition, PAHSAs enhanced expression of protective genes, such as those regulating DNA repair and glutathione metabolism and promoting autophagy. We demonstrate the translational relevance by showing that PAHSAs prevent and reverse early stages of senescence in metabolically stressed human islets by the same Mdm2 mechanism. Thus, a major mechanism for the dramatic effect of PAHSAs in reducing the incidence of type 1 diabetes in NOD mice is decreasing cellular senescence; PAHSAs may have a similar benefit in humans.

Inside the β Cell: Molecular Stress Response Pathways in Diabetes Pathogenesis

The pathogeneses of the 2 major forms of diabetes, type 1 and type 2, differ with respect to their major molecular insults (loss of immune tolerance and onset of tissue insulin resistance, respectively). However, evidence suggests that dysfunction and/or death of insulin-producing β-cells is common to virtually all forms of diabetes. Although the mechanisms underlying β-cell dysfunction remain incompletely characterized, recent years have witnessed major advances in our understanding of the molecular pathways that contribute to the demise of the β-cell. Cellular and environmental factors contribute to β-cell dysfunction/loss through the activation of molecular pathways that exacerbate endoplasmic reticulum stress, the integrated stress response, oxidative stress, and impaired autophagy. Whereas many of these stress responsive pathways are interconnected, their individual contributions to glucose homeostasis and β-cell health have been elucidated through the development and interrogation of animal models. In these studies, genetic models and pharmacological compounds have enabled the identification of genes and proteins specifically involved in β-cell dysfunction during diabetes pathogenesis. Here, we review the critical stress response pathways that are activated in β cells in the context of the animal models.

Sex Differences in the Molecular Programs of Pancreatic Cells Contribute to the Differential Risks of Type 2 Diabetes

Epidemiology studies demonstrate that women are at a significantly lower risk of developing type 2 diabetes (T2D) compared to men. However, the molecular basis of this risk difference is not well understood. In this study, we examined the sex differences in the genetic programs of pancreatic endocrine cells. We combined pancreas perifusion data and single-cell genomic data from our laboratory and from publicly available data sets to investigate multiple axes of the sex differences in the human pancreas at the single-cell type and single-cell level. We systematically compared female and male islet secretion function, gene expression program, and regulatory principles of pancreatic endocrine cells. The perifusion data indicate that female endocrine cells have a higher secretion capacity than male endocrine cells. Single-cell RNA-sequencing analysis suggests that endocrine cells in male controls have molecular signatures that resemble T2D. In addition, we identified genomic elements associated with genome-wide association study T2D loci to have differential accessibility between female and male delta cells. These genomic elements may play a sex-specific causal role in the pathogenesis of T2D. We provide molecular mechanisms that explain the differential risk of T2D between women and men. Knowledge gained from our study will accelerate the development of diagnostics and therapeutics in sex-aware precision medicine for diabetes.

An expansion of phenotype: novel homozygous variant in the MED17 identified in patients with progressive microcephaly and global developmental delay

Global developmental delay (GDD) is a lifelong disability that affects 1-3% of the population around the globe. It is phenotypically variable and highly heterogeneous in terms of the underlying genetics. Patients with GDD are intellectually disabled (ID) manifesting cognitive impairment and deficient adaptive behavior. Here, we investigated a two-looped consanguineous family segregating severe ID, seizure, and progressive microcephaly. Magnetic resonance imaging (MRI) of the brain showed mild brain atrophy and myelination defect. Whole exome sequencing (WES) was performed on the DNA samples of two patients and a novel homozygous missense variant (Chr11:g0.93528085; NM_004268.5_c.871T > C; p. Trp291Gly) was identified in the MED17 gene. Sanger sequencing revealed that the identified variant is heterozygous in both parents and healthy siblings. This variant is conserved among different species, causes a non-conserved amino acid change, and is predicted deleterious by various in silico tools. The variant is not reported in population variant databases. MED17 (OMIM: 613668) encodes for the mediator of RNA polymerase II transcription complex subunit 17. Structure modeling of MED17 protein revealed that Trp291 is involved in different inter-helical interactions, providing structural stability. Replacement of Trp291Gly, a less hydrophobic amino acid loses the inter-helical interaction leading to a perturb variant of MED17 protein.

Novel AR/AR-V7 and Mnk1/2 Degrader, VNPP433-3β: Molecular Mechanisms of Action and Efficacy in AR-Overexpressing Castration Resistant Prostate Cancer In Vitro and In Vivo Models

Prostate cancer (PCa) relies in part on AR-signaling for disease development and progression. Earlier, we developed drug candidate galeterone, which advanced through phase 2-clinical trials in treating castration-resistant PCa (CRPC). Subsequently, we designed, synthesized, and evaluated next-generation galeterone-analogs including VNPP433-3β which is potently efficacious against pre-clinical models of PCa. This study describes the mechanism of action of VNPP433-3β that promotes degradation of full-length AR (fAR) and its splice variant AR-V7 besides depleting MNK1/2 in in vitro and in vivo CRPC models that stably overexpresses fAR. VNPP433-3β directly engages AR within the cell and promotes proteasomal degradation of fAR and its splice variant AR-V7 by enhancing the interaction of AR with E3 ligases MDM2/CHIP but disrupting AR-HSP90 binding. Next, VNPP433-3β decreases phosphorylation of 4EBP1 and abates binding of eIF4E and eIF4G to 5' cap of mRNA by depleting MNK1/2 with consequent depletion of phosphorylated eIF4E. Finally, RNA-seq demonstrates modulation of multiple pathways that synergistically contribute to PCa inhibition. Therefore, VNPP433-3β exerts its antitumor effect by imposing 1) transcriptional regulation of AR and AR-responsive oncogenes 2) translational regulation by disrupting mRNA-5'cap-dependent translation initiation, 3) reducing AR half-life through enhanced proteasomal degradation in vitro and AR-overexpressing tumor xenografts in vivo.

In depth functional characterization of human induced pluripotent stem cell-derived beta cells in vitro and in vivo

In vitro differentiation of human induced pluripotent stem cells (iPSCs) into beta cells represents an important cell source for diabetes research. Here, we fully characterized iPSC-derived beta cell function in vitro and in vivo in humanized mice. Using a 7-stage protocol, human iPSCs were differentiated into islet-like aggregates with a yield of insulin-positive beta cells comparable to that of human islets. The last three stages of differentiation were conducted with two different 3D culture systems, rotating suspension or static microwells. In the latter, homogeneously small-sized islet-like aggregates were obtained, while in rotating suspension size was heterogeneous and aggregates often clumped. In vitro function was assessed by glucose-stimulated insulin secretion, NAD(P)H and calcium fluctuations. Stage 7 aggregates slightly increased insulin release in response to glucose in vitro. Aggregates were transplanted under the kidney capsule of NOD-SCID mice to allow for further in vivo beta cell maturation. In transplanted mice, grafts showed glucose-responsiveness and maintained normoglycemia after streptozotocin injection. In situ kidney perfusion assays showed modulation of human insulin secretion in response to different secretagogues. In conclusion, iPSCs differentiated with equal efficiency into beta cells in microwells compared to rotating suspension, but the former had a higher experimental success rate. In vitro differentiation generated aggregates lacking fully mature beta cell function. In vivo, beta cells acquired the functional characteristics typical of human islets. With this technology an unlimited supply of islet-like organoids can be generated from human iPSCs that will be instrumental to study beta cell biology and dysfunction in diabetes.

Progress in Research on the Alleviation of Glucose Metabolism Disorders in Type 2 Diabetes Using Cyclocarya paliurus

Globally, the incidence of diabetes is increasing annually, and China has the largest number of patients with diabetes. Patients with type 2 diabetes need lifelong medication, with severe cases requiring surgery. Diabetes treatment may cause complications, side-effects, and postoperative sequelae that could lead to adverse health problems and significant social and economic burdens; thus, more efficient hypoglycemic drugs have become a research hotspot. Glucose metabolism disorders can promote diabetes, a systemic metabolic disease that impairs the function of other organs, including the heart, liver, and kidneys. Cyclocarya paliurus leaves have gathered increasing interest among researchers because of their effectiveness in ameliorating glucose metabolism disorders. At present, various compounds have been isolated from C. paliurus, and the main active components include polysaccharides, triterpenes, flavonoids, and phenolic acids. C. paliurus mainly ameliorates glucose metabolism disorders by reducing glucose uptake, regulating blood lipid levels, regulating the insulin signaling pathway, reducing β-cell apoptosis, increasing insulin synthesis and secretion, regulating abundances of intestinal microorganisms, and exhibiting α-glucosidase inhibitor activity. In this paper, the mechanism of glucose metabolism regulation by C. paliurus was reviewed to provide a reference to prevent and treat diabetes, hyperlipidaemia, obesity, and other metabolic diseases.

Congenital beta cell defects are not associated with markers of islet autoimmunity, even in the context of high genetic risk for type 1 diabetes

AIMS/HYPOTHESIS

A key unanswered question in type 1 diabetes is whether beta cells initiate their own destruction or are victims of an aberrant immune response (beta cell suicide or homicide?). To investigate this, we assessed islet autoantibodies in individuals with congenital beta cell defects causing neonatal diabetes mellitus (NDM).

METHODS

We measured autoantibodies to GAD (GADA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A) in 242 individuals with NDM (median age diagnosed 1.8 months [IQR 0.39-2.9 months]; median age collected 4.6 months [IQR 1.8-27.6 months]; median diabetes duration 2 months [IQR 0.6-23 months]), including 75 whose NDM resulted from severe beta cell endoplasmic reticulum (ER) stress. As a control cohort we also tested samples from 69 diabetes-free individuals (median age collected 9.9 months [IQR 9.0-48.6 months]) for autoantibodies.

RESULTS

We found low prevalence of islet autoantibodies in individuals with monogenic NDM; 13/242 (5.4% [95% CI 2.9, 9.0%]) had detectable GADA, IA-2A and/or ZnT8A. This was similar to the proportion in the control participants who did not have diabetes (1/69 positive [1.4%, 95% CI 0.03, 7.8%], p=0.3). Importantly, monogenic individuals with beta cell ER stress had a similar rate of GADA/IA-2A/ZnT8A positivity to non-ER stress aetiologies (2.7% [95% CI 0.3, 9.3%] vs 6.6% [95% CI 3.3, 11.5%] p=0.4). We observed no association between islet autoimmunity and genetic risk, age at testing (including 30 individuals >10 years at testing) or diabetes duration (p>0.4 for all).

CONCLUSIONS/INTERPRETATION

Our data support the hypothesis that beta cell stress/dysfunction alone does not lead to the production of islet autoantibodies, even in the context of high-risk HLA types. This suggests that additional factors are required to trigger an autoimmune response towards beta cells.

miR-25 and miR-92b regulate insulin biosynthesis and pancreatic β-cell apoptosis

PURPOSE

Pancreatic β-cell failure is a central hallmark of the pathogenesis of diabetes mellitus; however, the molecular basis underlying chronic inflammation-caused β-cell failure remains unclear. This study reported here specifically assessed the association between miR-25/miR-92b family and β-cell failure in diabetes.

METHODS

IL-1β and two additional ER stress activators, palmitate and tunicamycin were applied to evaluate the expression level miR-25 by Taqman^® RT-PCR. Glucose- and potassium-stimulated insulin secretion assays were performed to assess β-cell function. Dual-luciferase activity, and western blotting assays were utilized for miR-25 target gene verification. CCK-8 and TUNEL staining were used to evaluate β-cell viability and apoptosis.

RESULTS

miRNA ChIP identified the increased level of miR-25 in INS-1 cells by IL-1β treatment. Expression levels of miR-25 were significantly upregulated with the treatment of IL-1β, palmitate or tunicamycin in both INS-1 cells and human islets. Ectopic elevation of miR-25 recapitulated most featured β-cell defects caused by IL-1β, including inhibition of insulin biosynthesis and increased β-cell apoptosis. These detrimental effects of miR-25 relied on its seed sequence recognition and repressed expression of its target genes Neurod1 and Mcl1. The miR-25/NEUROD1 axis reduced insulin biosynthesis via transcriptional regulation of β-cell specific genes. The miR-25/MCL1 axis caused β-cell apoptosis in a CASPASE-3/PARP1-dependent manner. Comparable impairments were generated by miR-92b and miR-25, emphasizing the redundant biological roles of miRNA family members with the same seed sequence.

CONCLUSION

MiR-25/miR-92b family plays a major role in β-cell failure occurring under inflammation and diabetes states.

Metabolites of Gut Microbiota and Possible Implication in Development of Diabetes Mellitus

Diabetes mellitus is characterized by having a disorder of glucose metabolism. The types of diabetes mellitus include type 1 diabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus, and other specific types of diabetes mellitus. Many risk factors contribute to diabetes mellitus mainly including genetics, environment, obesity, and diet. In the recent years, gut microbiota has been shown to be linked to the development of diabetes. It has been reported that the gut microbiota composition of diabetic patients is different from that of healthy people. Although the mechanism behind the abnormality remains to be explored, most hypotheses focus on the inflammation response and leaky gut in relation to the changes in production of endotoxins and metabolites derived from the intestinal flora. Consequently, the above-mentioned abnormalities trigger a series of metabolic changes, gradually leading to development of hyperglycemia, insulin resistance, and diabetes. This review is (i) to summarize the differences in gut microbiota between diabetic patients and healthy people, (ii) to discuss the underlying mechanism(s) by which how lipopolysaccharide, diet, and metabolites of the gut microbiota affect diabetes, and (iii) to provide a new insight in the prevention and treatment of diabetes.