Therapeutic opportunities for pancreatic β-cell ER stress in diabetes mellitus

Pharmacological landscape of endoplasmic reticulum stress: Uncovering therapeutic avenues for metabolic diseases

The endoplasmic reticulum (ER) plays a fundamental role in maintaining cellular homeostasis by ensuring proper protein folding, lipid metabolism, and calcium regulation. However, disruptions to ER function, known as ER stress, activate the unfolded protein response (UPR) to restore balance. Chronic or unresolved ER stress contributes to metabolic dysfunctions, including insulin resistance, non-alcoholic fatty liver disease (NAFLD), and neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Recent studies have also highlighted the importance of mitochondria-ER contact sites (MERCs) and ER-associated inflammation in disease progression. This review explores the current pharmacological landscape targeting ER stress, focusing on therapeutic strategies for rare metabolic and neurodegenerative diseases. It examines small molecules such as tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA), repurposed drugs like 17-AAG (17-N-allylamino-17demethoxygeldanamycin (tanespimycin)) and berberine, and phytochemicals such as resveratrol and hesperidin. Additionally, it discusses emerging therapeutic areas, including soluble epoxide hydrolase (sEH) inhibitors for metabolic disorders and MERCs modulation for neurological diseases. The review emphasizes challenges in translating these therapies to clinical applications, such as toxicity, off-target effects, limited bioavailability, and the lack of large-scale randomized controlled trials (RCTs). It also highlights the potential of personalized medicine approaches and pharmacogenomics in optimizing ER stress-targeting therapies.

ACSS2 mediates an epigenetic pathway to regulate β-cell adaptation during gestation in mice

Maternal pancreatic β-cells undergo adaptive changes to meet the metabolic demands of pregnancy, and disruptions in this adaptation can lead to gestational diabetes mellitus. However, the mechanisms governing this adaptation remain largely unexplored. Using single-cell transcriptome combined with genetic analyses, we identified a precise process of β-cell adaptation in mice, characterized by progressive metabolic stress-related β-cell dysfunction, increased acetyl-CoA biosynthesis, and gene element-specific histone acetylation. STAT3 recruits p300 to promote histone acetylation of pregnancy-associated genes, a process enhanced by Acetyl-CoA Synthetase 2 (ACSS2). High-fat feeding induces hyperacetylation of chromatin regions specifically opened during pregnancy, leading to the overexpression of genes that impair β-cell function. However, these impairments can be rescued by β-cell-specific deletion of Acss2. Notably, ACSS2 is functionally implicated in the early establishment of β-cell adaptation in HFD-fed mice but does not appear to play a role in standard diet-fed mice until after the initiation of adaptation. Our study uncovers a finely regulated β-cell adaptation process at the single-cell level during pregnancy and identifies a specific epigenetic pathway that governs this process. These findings provide insights into β-cell plasticity and potential therapeutic strategies for gestational diabetes mellitus.

ER stress disrupts insulin release in murine models of type 2 diabetes by impairing retromer action and constitutive secretion

Using in vitro models of lipotoxicity and islets from the db/db mouse model of type 2 diabetes (T2D), we show that endoplasmic reticulum (ER) stress impairs β cell function. This is unrelated to apoptosis or alterations in insulin content or proinsulin processing, despite expansion of the Golgi compartment. Instead, the constitutive secretory pathway and endocytic recycling are disrupted, as revealed by depletion of glycosylated proteins and syntaxins from the plasma membrane (PM) and accumulation of E-cadherin in the retromer. This involves the PERK arm of the unfolded protein response. Proteomics identified multiple PM proteins mislocalized by ER stress, notably axon-guidance and cell-adhesion proteins, and many with glycosylphosphatidylinositol linkages. A retromer chaperone attenuated defective insulin secretion from islets of both db/db and high-fat-fed mice. By identifying different endpoints and mechanisms, our results redefine the relevance of ER stress to β cell failure. They also implicate retromer chaperones as potential T2D therapeutics.

METTL3 promotes human amniotic epithelial stem cells differentiation into insulin-producing cells by regulation of MaFA expression

OBJECTIVE

Generating mature β-cells from stem cells remains a significant challenge in diabetes cell therapy. Human amniotic epithelial stem cells (hAESCs) have made their mark in regenerative medicine, and provide several advantages compared to other stem cells. Methyltransferase-like 3 (METTL3), an essential RNA methyltransferase participating in N6-methyladenosine (m6A) mRNA methylation, plays a critical role in the normal development of β-cells, yet its deletion in β-cells leads to β-cell dysfunction and hyperglycemia.

METHODS

In this study, we isolated and characterized hAESCs from human amniotic membranes, differentiated these hAESCs into insulin-producing cells (IPCs), and explored the role of METTL3 in such differentiation. We examined the expression of METTL3 and insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2, a decodes m6A methylation "reader") in the generated IPCs. Subsequently, we suppressed METTL3 using an inhibitor (STM2457) and overexpressed METTL3 via plasmid transfection (METTL3-OE). The differentiated STM2457 and METTL3-OE IPCs were compared to normal induction (WT) IPCs regarding the expression of β-cell markers by RT-qPCR and western blotting, immunofluorescence, C-peptide release, and glucose-stimulated insulin secretion (GSIS). Methylated RNA immunoprecipitation (MeRIP)-qPCR was used to examine the molecular mechanism underlying METTL3/m6A signaling axis in MaFA (endocrine pancreatic β-cells marker) expression. We examined the potential therapeutic uses and efficacy of IPCs through streptozotocin (STZ)-induced C57BL/6 DM.

RESULTS

Isolated hAESCs displayed all characteristics of ESCs and could generate IPCs. METTL3 and IGF2BP2 were elevated during differentiation. Overexpressing METTL3 improved the expression of β-cell markers in the final differentiated IPCs, improved C-peptide release, and demonstrated increased insulin secretion upon challenging with high glucose conditions, whereas inhibiting METTL3 attenuated these effects. Moreover, METTL3 modulated the MaFA expression in an m6A-dependent manner.

CONCLUSIONS

These findings suggest METTL3 as a promoting factor of IPCs generation, with its up-regulation potentially generating more mature IPCs for hAESCs therapy of diabetes mellitus.

Ryanodine Receptors in Islet Cell Function: Calcium Signaling, Hormone Secretion, and Diabetes

Ryanodine receptors (RyRs) are large intracellular Ca2+ release channels primarily found in muscle and nerve cells and also present at low levels in pancreatic islet endocrine cells. This review examines the role of RyRs in islet cell function, focusing on calcium signaling and hormone secretion, while addressing the ongoing debate regarding their significance due to their limited expression. We explore conflicting experimental results and their potential causes, synthesizing current knowledge on RyR isoforms in islet cells, particularly in beta and delta cells. The review discusses how RyR-mediated calcium-induced calcium release enhances, rather than drives, glucose-stimulated insulin secretion. We examine the phosphorylation-dependent regulation of beta-cell RyRs, the concept of "leaky ryanodine receptors", and the roles of RyRs in endoplasmic reticulum stress, apoptosis, store-operated calcium entry, and beta-cell electrical activity. The relationship between RyR dysfunction and the development of impaired insulin secretion in diabetes is assessed, noting their limited role in human diabetes pathogenesis given the disease's polygenic nature. We highlight the established role of RyR-mediated CICR in the mechanism of action of common type 2 diabetes treatments, such as glucagon-like peptide-1, which enhances insulin secretion. By integrating findings from electrophysiological, molecular, and clinical studies, this review provides a balanced perspective on RyRs in islet cell physiology and pathology, emphasizing their significance in both normal insulin secretion and current diabetes therapies.

Excess Fructose Intake Activates Hyperinsulinemia and Mitogenic MAPK Pathways in Association With Cellular Stress, Inflammation, and Apoptosis in the Pancreas of Rats

The increase in sugar consumption has been associated with current metabolic disease epidemics. This study aimed to investigate the pancreatic molecular mechanisms involved in cellular stress, inflammation, mitogenesis, and apoptosis in metabolic disease induced by high-fructose diet. Here, we used biochemical, histopathological, Western blot, and immunohistochemistry methods to determine the metabolic and pancreatic alterations in male Wistar rats fed 20% fructose in drinking water for 15 weeks. High-fructose consumption in rats increased the immunopositivity and protein expression of glucose transporter 2 (GLUT2) and insulin in the pancreatic tissue, in association with abdominal adiposity, hyperglycemia, and hypertriglyceridemia. The expressions of cellular stress markers, glucose-regulated protein-78 (GRP78) and PTEN-induced putative kinase 1 (PINK1), were increased in the pancreas. The levels of interleukin (IL)-6, nuclear factor kappa B (NFκB), tumor necrosis factor α (TNFα), and IL-1β and components of the Nod-like receptor protein 3 (NLRP3) inflammasome were elevated. Excess fructose intake stimulated the activation of mitogenic extracellular signal-regulated kinases 1/2 (ERK1/2), p38, and c-Jun N-terminal kinase (JNK)1 as well as the apoptotic p53 and Fas pathways in the pancreas of rats. There was also an increase in caspase-8 and caspase-3 cleavage. Our findings revealed that dietary high-fructose in the pancreas causes hyperinsulinemia due to the upregulation of GLUT2 together with cellular stress and inflammatory markers, thereby stimulates mitogenic mitogen-activated protein kinase (MAPK) and apoptosis pathways, resulting in a complex pathological situation.

TRAF3IP3 Induces ER Stress-Mediated Apoptosis with Protective Autophagy to Inhibit Lung Adenocarcinoma Proliferation

TNF receptor-associated factor 3 interacting protein 3 (TRAF3IP3/T3JAM) exhibits dual roles in cancer progression. While upregulated in most malignancies and critical for immune regulation. However, the specific effects and molecular mechanisms of TRAF3IP3 on the progression of lung adenocarcinoma (LUAD) remains poorly understood. This study reveals TRAF3IP3 is upregulated in several tumor tissues but exclusively decreased in LUAD and Lung squamous cell carcinoma (LUSC) tissues, consequential in a favorable overall survival (OS) in LUAD rather than LUSC. Herein, it is reported that TRAF3IP3 can suppress cell proliferation and promote the apoptosis rate of LUAD cells by inducing excessive ER stress-related apoptosis. Importantly, TRAF3IP3 triggers ER stress via the PERK/ATF4/CHOP pathway, accompanied by stimulated ER stress-induced cytoprotective autophagy in LUAD cells. Through IP-MS analysis, STRN3 is identified as a direct downstream interactor with TRAF3IP3 and corroborated to regulate ER stress positively. Mechanistically, TRAF3IP3 facilitates the recruitment of STRN3 to the ER lumen through its transmembrane domain and fulfills its functional role in ER stress in an STRN3-dependent manner in LUAD cells. Given its dual role in orchestrating ER stress-associated apoptosis and autophagy in LUAD cell fate determination, the importance of TRAF3IP3 is highlighted as novel therapeutic target for LUAD treatment.

A Compound Screen Based on Isogenic hESC-Derived β Cell Reveals an Inhibitor Targeting ZnT8-Mediated Zinc Transportation to Protect Pancreatic β Cell from Stress-Induced Cell Death

Pancreatic β cell loss by cellular stress contributes to diabetes pathogenesis. Nevertheless, the fundamental mechanism of cellular stress regulation remains elusive. Here, it is found that elevated zinc transportation causes excessive cellular stress in pancreatic β cells in diabetes. With gene-edited human embryonic stem cell-derived β cells (SC-β cells) and human primary islets, the results reveal that elevated zinc transportation initiates the integrated stress response (ISR), and ultimately leads to β cell death. By contrary, genetic abolishment of zinc transportation shields β cells from exacerbated endoplasmic reticulum stress (ER stress) and concurrent ISR. To target excessive zinc transportation with a chemical inhibitor, an isogenic SC-β cells based drug-screening platform is established. Surprisingly, independent of its traditional role as protein synthesis inhibitor at a high-dose (10 µm), low-dose (25 nm) anisomycin significantly inhibits zinc transportation and effectively prevents β cell loss. Remarkably, in vivo administration of anisomycin in mice demonstrates protective effects on β cells and prevents type 2 diabetes induced by high-fat diet. Overall, elevated zinc transportation is identified as a crucial driver of β cell loss and low-dose anisomycin as a potential therapeutic molecule for diabetes.

Low-intensity Pulsed Ultrasound Stimulation of the Intestine Improves Insulin Resistance in Type 2 Diabetes

OBJECTIVE

Ultrasound stimulation of internal organs and peripheral nerves has demonstrated promising potential in regulating blood glucose metabolism. This study aims to assess the effectiveness of low-intensity pulsed ultrasound stimulation (LIPUS) on intestine in improving insulin resistance with type 2 diabetes mellitus (T2DM).

METHODS

C57BL/6J mice, both normal and T2DM, were randomly divided into three groups: Control, T2D-sham, and T2D-LIPUS. The T2D-LIPUS group received LIPUS stimulation in the intestine. The parameters were as follows: 1 MHz frequency, 1.0 kHz pulse repetition frequency (PRF), 20% duty cycle, 100 mW/cm² intensity spatial average temporal average (ISATA), for 20 minutes per session, five days per week, over four weeks.

RESULTS

Blood glucose analysis indicated that mice in the T2D-LIPUS group displayed significantly lower area under the curve (AUC) of glucose tolerance tests (GTT) and insulin tolerance tests (ITT) (p < 0.001), HOMA-IR (p < 0.001), and fasting serum insulin levels (p < 0.01) compared to the T2D-sham group. LIPUS treatment effectively lowered serum levels of IL-1β (p < 0.001) and TNF-α (p < 0.01) along with mRNA expression levels of IL-1β (p < 0.01) and IL-18 (p < 0.001) in the intestines of T2DM mice. Additionally, Western blot analysis revealed a reduction in the protein levels of NLRP3, caspase-1, and GSDMD-N in the intestinal tissues of mice treated with LIPUS.

CONCLUSION

These findings suggest that LIPUS can reduce inflammation and cellular apoptosis, while improving insulin resistance by inhibiting the NLRP3/Caspase-1/GSDMD signaling pathway. This research introduces a novel, non-pharmacological approach for managing T2DM.

Atf4 Protects Islet β-Cell Identity and Function Under Acute Glucose-Induced Stress but Promotes β-Cell Failure in the Presence of Free Fatty Acid

Glucolipotoxicity, caused by combined hyperglycemia and hyperlipidemia, results in β-cell failure and type 2 diabetes via cellular stress-related mechanisms. Activating transcription factor 4 (Atf4) is an essential effector of stress response. We show here that Atf4 expression in β-cells is minimally required for glucose homeostasis in juvenile and adolescent mice but it is needed for β-cell function during aging and under obesity-related metabolic stress. Henceforth, Atf4-deficient β-cells older than 2 months after birth display compromised secretory function under acute hyperglycemia. In contrast, they are resistant to acute free fatty acid-induced dysfunction and reduced production of several factors essential for β-cell identity. Atf4-deficient β-cells downregulate genes involved in protein translation. They also upregulate several lipid metabolism or signaling genes, likely contributing to their resistance to free fatty acid-induced dysfunction. These results suggest that Atf4 activation is required for β-cell identity and function under high glucose. But Atf4 activation paradoxically induces β-cell failure in high levels of free fatty acids. Different transcriptional targets of Atf4 could be manipulated to protect β-cells from metabolic stress-induced failure.

ARTICLE HIGHLIGHTS

The Impact of Major and Minor Phytocannabinoids on the Maintenance and Function of INS-1 β-Cells Under High-Glucose and High-Lipid Conditions

Type 2 diabetes mellites (T2DM) is the most common form of diabetes and affects a significant portion of the population. Obesity-related increases in free fatty acids and glucose in the diet contribute to β-cell dysfunction and loss, ultimately leading to the onset of T2DM. The endocannabinoid system, which is present throughout the body, plays a vital role in regulating various physiological processes, including those in the pancreas. This system has been implicated in metabolic disorders like obesity and diabetes, as it helps to regulate appetite, food intake, and fat production. Phytocannabinoids from Cannabis sativa have the potential to influence the endocannabinoid system, offering a promising therapeutic approach for diabetes and its complications. Using high-glucose-high-lipid (HGHL)-induced INS-1 β-cells, we investigated the protective effects of two major (THC and CBD) and three minor (THCV, CBC, and CBG) phytocannabinoids on high glucose-high lipid (HGHL)-induced apoptosis, cell cycle disruption, and impaired function of beta-cells. Our results showed that all five phytocannabinoids reduced HGHL-induced apoptosis, likely by decreasing TXNIP protein levels. Additionally, THC and all three minor phytocannabinoids provided protective effects against functional impairments caused by HGHL exposure.

Ophiopogonin D improves pancreatic islet cell dedifferentiation to treat diabetes by regulating the GRP78/ROS/PDX1 signaling pathway

Introduction

The incidence of diabetes is rising annually, significantly impacting public health and imposing a substantial economic burden on society. Ophiopogonin D (Op D) exhibits certain hypoglycemic effects; however, its mechanisms remain unclear.

Methods

β-cell dedifferentiation, distinct from β-cell apoptosis, is a pathogenic mechanism we aim to explore regarding Op D's regulatory effects. We established an animal model of β-cell dedifferentiation to assess Op D's impact on glucose tolerance, blood glucose levels, and insulin secretion. We employed immunohistochemistry and immunofluorescence to analyze the expression levels of dedifferentiation-related proteins. Additionally, we created an in vitro β-cell dedifferentiation model using INS-1 cells to evaluate Op D's influence on insulin secretion and dedifferentiation. Transcriptomic analysis was conducted to explore potential mechanisms by which Op D ameliorates dedifferentiation, with further validation via Western blotting and immunofluorescence. Flow cytometry, fluorescence microscopy, and related assays were used to assess Op D's effects on oxidative stress. Endoplasmic reticulum (ER) tracing agents marked the ER, and laser confocal microscopy examined ER morphology, with ER stress inducers and inhibitors employed to clarify Op D's mechanisms.

Results

Results indicated that Op D reduced blood glucose levels, improved glucose tolerance, enhanced insulin secretion, mitigated pancreatic atrophy, and increased PDX1 and FOXO1 expression levels. Furthermore, Op D inhibited ER stress, decreased GRP78 expression, reduced NGN3 levels, elevated PDX1, NKX6.1, and MAFA expression, and decreased oxidative stress-related products (ROS, MDA) while increasing SOD and GSH levels.

Discussion

These findings demonstrate that Op D can improve β-cell dedifferentiation by modulating the GRP78/ROS/PDX1 pathway to inhibit ER stress.

Diabetes-associated MYT1 and MYT3 regulate human β-cell insulin secretion and survival via other diabetes-risk genes

Genetic and environmental factors together cause islet β-cell failure, leading to Type 2 diabetes (T2D). Yet how they integrate to regulate β-cells remains largely unclear. Here, we examined how two members of the Myelin transcription factor family (MYT1, 2, and 3) prevent human β-cell failure under obesity-related stress. We have reported that obesity-related nutrient levels induce these factors. They prevent β-cell failure in mouse islets and human β-cell lines. Their variants are all associated with human T2D, and their downregulation accompanies β-cell dysfunction. By knocking down MYT1 or MYT3 separately in primary human donor islets, we show here that they have overlapping but distinct functions. Under normal culture conditions, MYT1 - knockdown (KD) causes β-cell death, while MYT3 - KD compromises glucose-stimulated insulin secretion. Under obesity-induced metabolic stress in vivo , MYT3 - KD also causes β-cell death. Accordingly, these TFs regulate common and unique genes, with MYT1 - KD de-regulating several genes in cell death and Ca 2+ binding, while MYT3-KD de-regulating genes involved in mitochondria, ER, etc. Intriguingly, the MYT1 and MYT3-regulated genes are enriched for T2D-associated genes. These findings suggest that the MYT TFs complement each other to serve as a node that integrates genetic and environmental factors to prevent β-cell failure and T2D.

Research in Context

It is now known that: All MYT TFs (including MYT1, 2, 3) are associated with the risk of T2D, and their downregulation accompanies β-cell failure during human T2D development.besity-related high glucose/free fatty acids regulate the levels and/or nuclear localization of MYT1 and MYT3 in primary human β-cells, implying them as integrators of genetic and nutrition factors to determine the risk of β-cell failure and T2D.Myt TFs, via coregulators including Sin3, work together to prevent postnatal β-cell failure in mice and the death of a human β-cell line, suggesting they are essential switches for β-cell protection.The key remaining question is: How do these TFs regulate primary human β-cell failure in response to different nutritional signals?Our new findings are: Reduced MYT1 or MYT3 expression levels in primary human islets via knockdown compromised β-cell survival or secretion, respectively, under normal physiology.MYT3-knockdown compromises human β-cell survival in obesity.MYT1/MYT3-regulated genes are enriched for those associated with T2D risk.Impact: Manipulating MYT TF activities, via modulating their associations with coregulators, could be explored to attenuate β-cell failure and risk of T2D.

Causal association between endocrine diseases and lymphoid malignancies explored through two-sample Mendelian randomization analysis

Endocrine diseases are suspected contributors to lymphoid malignancies, but their precise association is unclear. This study aimed to investigate the causal relationship between various endocrine diseases-specifically type 2 diabetes, obesity, diabetic hypoglycemia, hyperlipidemia, and hyperthyroidism-and lymphoid malignancies, including lymphocytic leukemia and non-Hodgkin's lymphoma with subtypes like diffuse large B-cell lymphoma and follicular lymphoma. Utilizing data from genome-wide association studies, a two-sample Mendelian randomization analysis was performed. The primary approach involved the inverse-variance weighted method, supplemented by other robust techniques such as the weighted median and MR-Egger regression to ensure reliability. The analysis indicated a significant causal connection between genetically predicted diabetic hypoglycemia and lymphocytic leukemia (Odds ratio = 1.0004, 95% Confidence interval = 1-1.0007, P = 0.03). Conversely, no associations were found for the other endocrine diseases with lymphoid malignancies (P > 0.05 for all). The findings suggest that while diabetic hypoglycemia may influence lymphocytic leukemia risk, further research is necessary to clarify the roles of other endocrine diseases in lymphoid malignancies, including cross-population validations and biological investigations.

Insulin resistance in type 2 diabetes mellitus

Insulin resistance is an integral pathophysiological feature of type 2 diabetes mellitus. Here, we review established and emerging cellular mechanisms of insulin resistance, their complex integrative features and their relevance to disease progression. While recognizing the heterogeneity of the elusive fundamental disruptions that cause insulin resistance, we endorse the view that effector mechanisms impinge on insulin receptor signalling and its relationship with plasma levels of insulin. We focus on hyperinsulinaemia and its consequences: acutely impaired but persistent insulin action, with reduced ability to lower glucose levels but preserved lipid synthesis and lipoprotein secretion. We emphasize the role of insulin sensitization as a therapeutic goal in type 2 diabetes mellitus.

Orally Administered ZnxCeyO2/Se Hydrogel with Effective Antioxidant Activity for Treating Inflammatory Bowel Disease by Inhibiting Ferroptosis

Oxidative stress leads to intestinal barrier damage, which induces immune responses to occur and further promotes oxidative stress exacerbating inflammatory bowel disease (IBD). In this work, the multifunctional ZnxCeyO2/Se (ZCSO) nanozyme wrapped with acid-resistant calcium alginate hydrogel designed for oral administration is prepared. The ZCSO nanozyme can promote the activation of the Nrf2 oxidative stress pathway, then significantly improve the efficiency of scavenging reactive oxygen species (ROS) and up-regulate the protein expression of glutathione peroxidase 4 (GPx4), which is closely related to the inhibition of ferroptosis. In addition, the ZCSO nanozyme inhibiting the growth of some pathogenic bacteria proliferating due to oxidative stress shows a positive regulation of the intestinal flora and reduces the secretion of pro-inflammatory factors and the levels of inflammatory macrophages, achieving the significant preventive and delayed therapeutic effect of colitis mice. Consequently, the distinctive properties of ZCSO nanozyme render it a promising candidate for the treatment of IBD by effectively scavenging ROS, thereby interrupting the detrimental cycle between oxidative stress and immune response, ultimately promoting the proliferation of epithelial cells to reestablish the integrity of the intestinal mucosal barrier.

Optimized Effects of Fisetin and Hydroxychloroquine on ER Stress and Autophagy in Nonalcoholic Fatty Pancreas Disease in Mice

Background: Fat accumulation in the pancreas, known as nonalcoholic fatty pancreatic disease (NAFPD), is associated with obesity and may lead to prediabetes and Type 2 diabetes. Reducing endoplasmic reticulum stress and enhancing autophagy could offer therapeutic benefits. This study examines the effects of fisetin (FSN) and hydroxychloroquine (HCQ) on NAFPD. Method: Forty-eight Male C57BL/6 J mice were assigned to a standard chow diet (SCD) or a high-fat diet (HFD) for 16 weeks. The HFD group was divided into five subgroups; each group contains eight mice: HFD, HFD + V (vehicle), HFD + FSN, HFD + HCQ, and HFD + FSN + HCQ. FSN was given daily at 80 mg/kg, and HCQ was injected IP at 50 mg/kg twice weekly for more 8 weeks. Insulin resistance was assessed through OGTT and HOMA-IR. Histological analysis of pancreatic tissue was conducted, and the protein and mRNA levels of molecules associated with ER stress and autophagy were assessed using PCR and immunoblotting techniques. Result: FSN and HCQ significantly reduced weight gain, pancreatic adipocyte accumulation, and insulin resistance caused by HFD in obese mice, with the combination of the two compounds producing even more pronounced effects. Additionally, the HFD increased the expression of UPR markers ATF4 and CHOP, a response that was further intensified by HCQ. In contrast, FSN attenuated the UPR by regulating GRP78 levels. Furthermore, the HFD resulted in a significant decrease in the LC3II/LC3I ratio and an accumulation of p62 protein due to reduced p-AMPK levels. Following treatment with FSN, these alterations were reversed, leading to decreased mTOR expression and increased levels of autophagy markers such as ATG5 and Beclin1. Conclusion: Our study reveals that FSN and HCQ effectively combat HFD-induced NAFPD, improving insulin sensitivity and addressing pancreatic fat deposition linked to metabolic syndrome. While HCQ may cause endoplasmic reticulum stress, FSN offers protective effects, supporting their combined use for better treatment outcomes.

The role of endoplasmic reticulum stress in type 2 diabetes mellitus mechanisms and impact on islet function

Type 2 diabetes mellitus (T2DM) is a globally prevalent metabolic disorder characterized by insulin resistance and dysfunction of islet cells. Endoplasmic reticulum (ER) stress plays a crucial role in the pathogenesis and progression of T2DM, especially in the function and survival of β-cells. β-cells are particularly sensitive to ER stress because they require substantial insulin synthesis and secretion energy. In the early stages of T2DM, the increased demand for insulin exacerbates β-cell ER stress. Although the unfolded protein response (UPR) can temporarily alleviate this stress, prolonged or excessive stress leads to pancreatic cell dysfunction and apoptosis, resulting in insufficient insulin secretion. This review explores the mechanisms of ER stress in T2DM, particularly its impact on islet cells. We discuss how ER stress activates UPR signaling pathways to regulate protein folding and degradation, but when stress becomes excessive, these pathways may contribute to β-cell death. A deeper understanding of how ER stress impacts islet cells could lead to the development of novel T2DM treatment strategies aimed at improving islet function and slowing disease progression.

Crosstalk Between Phase-Separated Membraneless Condensates and Membrane-Bound Organelles in Cellular Function and Disease

Compartmentalization in eukaryotic cells allows the spatiotemporal regulation of biochemical processes, in addition to allowing specific sets of proteins to interact in a regulated as well as stochastic manner. Although membrane-bound organelles are thought to be the key players of cellular compartmentalization, membraneless biomolecular condensates such as stress granules, P bodies, and many others have recently emerged as key players that are also thought to bring order to a highly chaotic environment. Here, we have evaluated the latest studies on biomolecular condensates, specifically focusing on how they interact with membrane-bound organelles and modulate each other's functions. We also highlight the importance of this interaction in neurodegenerative and cardiovascular diseases as well as in cancer.

Impact of DPP-4 Inhibitors on Interleukin Levels in Type 2 Diabetes Mellitus

BACKGROUND AND OBJECTIVE

Accumulating evidence had implicated pathological involvement of interleukins (ILs) in progression and complications in patients with type 2 diabetes mellitus (T2DM). Dipeptidyl peptidase-4 inhibitors (DPP-4i) produced favorable effects on glucose homeostasis in T2DM. This study aimed to evaluate the impact of DPP-4i on IL concentrations in T2DM.

DATA SOURCES

PubMed, Embase, and the Cochrane library were systematically searched for relevant articles from inception to May 31, 2024. The search included DPP-4i, T2DM, and randomized controlled trials (RCTs) and related terms.

STUDY SELECTION AND DATA EXTRACTION

Placebo- or active agents-controlled human studies were screened. All the RCTs were identified if they provided detailed information on changes of ILs during DPP-4i treatment.

DATA SYNTHESIS

A total of 14 RCTs involving 850 participants were identified. Pooled estimates revealed that DPP-4i significantly lowered IL-6 concentrations (-0.54 pg/mL; 95% CI, -0.82 to -0.25; I2 = 10%, P = .0003) compared to placebo. Similar effects were demonstrated for IL-1β (-16.33 pg/mL; 95% CI, -19.56 to -13.11; I2 = 0%, P < .00001), whereas the effect on IL-18 was not statistically significant (-13.55 pg/mL; 95% CI, -76.95 to 49.85; I2 = 0%, P = .68). Subgroup analysis on IL-6 demonstrated that marked effects were found in groups of basal IL-6 concentrations (< 5 pg/mL), body mass index (≥ 28 kg/m2) and type of DPP-4i (linagliptin).

CONCLUSION

DPP-4i favorably decreased IL-6 levels in patients with T2DM. The impact of DPP-4i on IL-1β and IL-18 needed to be explored with more studies. Further trials should be performed to elucidate this anti-inflammatory effect of DPP-4i during treatment of T2DM.

LEF1 influences diabetic retinopathy and retinal pigment epithelial cell ferroptosis via the miR-495-3p/GRP78 axis through lnc-MGC

BACKGROUND

Diabetic retinopathy (DR) is one of the major eye diseases contributing to blindness worldwide. Endoplasmic reticulum (ER) stress in retinal cells is a key factor leading to retinal inflammation and vascular leakage in DR, but its mechanism is still unclear.

AIM

To investigate the potential mechanism of LEF1 and related RNAs in DR.

METHODS

ARPE-19 cells were exposed to high levels of glucose for 24 hours to simulate a diabetic environment. Intraperitoneally injected streptozotocin was used to induce the rat model of DR. The expression levels of genes and related proteins were measured by RT-qPCR and Western blotting; lnc-MGC and miR-495-3p were detected by fluorescent in situ hybridization; CCK-8 and TUNEL assays were used to detect cell viability and apoptosis; enzyme-linked immunosorbent assay was used to detect inflammatory factors; dual-luciferase gene assays were used to verify the targeting relationship; and the retina was observed by HE staining.

RESULTS

LEF1 and lnc-MGC have binding sites, and lnc-MGC can regulate the miR-495-3p/GRP78 molecular axis. In high glucose-treated cells, inflammation was aggravated, the intracellular reactive oxygen species concentration was increased, cell viability was reduced, apoptosis was increased, the ER response was intensified, and ferroptosis was increased. As an ER molecular chaperone, GRP78 regulates the ER and ferroptosis under the targeting of miR-495-3p, whereas inhibiting LEF1 can further downregulate the expression of lnc-MGC, increase the level of miR-495-3p, and sequentially regulate the level of GRP78 to alleviate the occurrence and development of DR. Animal experiments indicated that the knockdown of LEF1 can affect the lnc-MGC/miR-495-3p/GRP78 signaling axis to restrain the progression of DR.

CONCLUSION

LEF1 knockdown can regulate the miR-495-3p/GRP78 molecular axis through lnc-MGC, which affects ER stress and restrains the progression of DR and ferroptosis in retinal pigment epithelial cells.

The PERK-eIF2α-ATF4 Axis Is Involved in Mediating ER-Stress-Induced Ferroptosis via DDIT4-mTORC1 Inhibition and Acetaminophen-Induced Hepatotoxicity

Ferroptosis, a regulated form of cell death characterized by lipid peroxidation and iron accumulation, is increasingly recognized for its role in disease pathogenesis. The unfolded protein response (UPR) has been implicated in both endoplasmic reticulum (ER) stress and ferroptosis-mediated cell fate decisions; yet, the specific mechanism remains poorly understood. In this study, we demonstrated that ER stress induced by tunicamycin and ferroptosis triggered by erastin both activate the UPR, leading to the induction of ferroptotic cell death. This cell death was mitigated by the application of chemical chaperones and a ferroptosis inhibitor. Among the three arms of the UPR, the PERK-eIF2α-ATF4 signaling axis was identified as a crucial mediator in this process. Mechanistically, the ATF4-driven induction of DDIT4 plays a pivotal role, facilitating ferroptosis via the inhibition of the mTORC1 pathway. Furthermore, acetaminophen (APAP)-induced hepatotoxicity was investigated as a model of eIF2α-ATF4-mediated ferroptosis. Our findings reveal that the inhibition of eIF2α-ATF4 or ferroptosis protects against APAP-induced liver damage, underscoring the therapeutic potential of targeting these pathways. Overall, this study not only clarifies the intricate role of the PERK-eIF2α-ATF4 axis in ER-stress-and erastin-induced ferroptosis but also extends these findings to a clinically relevant model, providing a foundation for potential therapeutic interventions in conditions characterized by dysregulated ferroptosis and ER stress.

Customizable gene sensing and response without altering endogenous coding sequences

Synthetic biology aims to modify cellular behaviors by implementing genetic circuits that respond to changes in cell state. Integrating genetic biosensors into endogenous gene coding sequences using clustered regularly interspaced short palindromic repeats and Cas9 enables interrogation of gene expression dynamics in the appropriate chromosomal context. However, embedding a biosensor into a gene coding sequence may unpredictably alter endogenous gene regulation. To address this challenge, we developed an approach to integrate genetic biosensors into endogenous genes without modifying their coding sequence by inserting into their terminator region single-guide RNAs that activate downstream circuits. Sensor dosage responses can be fine-tuned and predicted through a mathematical model. We engineered a cell stress sensor and actuator in CHO-K1 cells that conditionally activates antiapoptotic protein BCL-2 through a downstream circuit, thereby increasing cell survival under stress conditions. Our gene sensor and actuator platform has potential use for a wide range of applications that include biomanufacturing, cell fate control and cell-based therapeutics.

Homeostasis control in health and disease by the unfolded protein response

Cells rely on the endoplasmic reticulum (ER) to fold and assemble newly synthesized transmembrane and secretory proteins - essential for cellular structure-function and for both intracellular and intercellular communication. To ensure the operative fidelity of the ER, eukaryotic cells leverage the unfolded protein response (UPR) - a stress-sensing and signalling network that maintains homeostasis by rebalancing the biosynthetic capacity of the ER according to need. The metazoan UPR can also redirect signalling from cytoprotective adaptation to programmed cell death if homeostasis restoration fails. As such, the UPR benefits multicellular organisms by preserving optimally functioning cells while removing damaged ones. Nevertheless, dysregulation of the UPR can be harmful. In this Review, we discuss the UPR and its regulatory processes as a paradigm in health and disease. We highlight important recent advances in molecular and mechanistic understanding of the UPR that enable greater precision in designing and developing innovative strategies to harness its potential for therapeutic gain. We underscore the rheostatic character of the UPR, its contextual nature and critical open questions for its further elucidation.

Molecular puzzle of insulin: structural assembly pathways and their role in diabetes

Properly folded proteins are essential for virtually all cellular processes including enzyme catalysis, signal transduction, and structural support. The cells have evolved intricate mechanisms of control, such as the assistance of chaperones and proteostasis networks, to ensure that proteins mature and fold correctly and maintain their functional conformations. Here, we review the mechanisms governing the folding of key hormonal regulators or glucose homeostasis. The insulin synthesis in pancreatic β-cells begins with preproinsulin production. During translation, the insulin precursor involves components of the endoplasmic reticulum (ER) translocation machinery, which are essential for proper orientation, translocation, and cleavage of the signal peptide of preproinsulin. These steps are critical to initiate the correct folding of proinsulin. Proinsulin foldability is optimized in the ER, an environment evolved to support the folding process and the formation of disulfide bonds while minimizing misfolding. This environment is intricately linked to ER stress response pathways, which have both beneficial and potentially harmful effects on pancreatic β-cells. Proinsulin misfolding can result from excessive biosynthetic ER load, proinsulin gene mutations, or genetic predispositions affecting the ER folding environment. Misfolded proinsulin leads to deficient insulin production and contributes to diabetes pathogenesis. Understanding the mechanisms of protein folding is critical for addressing diabetes and other protein misfolding-related diseases.

Sirtuin1 Deficiency Could Exacerbate Melanocyte Apoptosis Under Endoplasmic Reticulum Stress

Vitiligo is a depigmentation disease caused by the targeted destruction of melanocytes, resulting in skin and hair depigmentation and significant psychological stress. However, the mechanisms underlying its onset and progression remain unclear. Endoplasmic reticulum (ER) stress, which is linked with oxidative stress and autoimmunity, is involved in the development of vitiligo, and prolonged ER stress induces apoptosis. Sirtuin 1 (Sirt1) might be a key regulator of ER stress. Thus, we explored how Sirt1 modulates ER stress-induced melanocyte apoptosis in vitro and in vivo. Our results showed that Sirt1 affected ER stress-induced apoptosis of melanocyte apoptosis when upon to ER stress in vitro. Sirt1 inhibition aggravated the vitiligo phenotype in mice; thereby protecting against the stress response, and abating the unfolded protein response. These results suggest that Sirt1 impairment could accelerate melanocyte apoptosis in vitiligo.

Pancreatic β-Cells, Diabetes and Autophagy

PURPOSE

Pancreatic β-cells play a critical role in regulating plasma insulin levels and glucose metabolism balance, with their dysfunction being a key factor in the progression of diabetes. This review aims to explore the role of autophagy, a vital cellular self-maintenance process, in preserving pancreatic β-cell functionality and its implications in diabetes pathogenesis.

METHODS

We examine the current literature on the role of autophagy in β-cells, highlighting its function in maintaining cell structure, quantity, and function. The review also discusses the effects of both excessive and insufficient autophagy on β-cell dysfunction and glucose metabolism imbalance. Furthermore, we discuss potential therapeutic agents that modulate the autophagy pathway to influence β-cell function, providing insights into therapeutic strategies for diabetes management.

RESULTS

Autophagy acts as a self-protective mechanism within pancreatic β-cells, clearing damaged organelles and proteins to maintain cellular stability. Abnormal autophagy activity, either overactive or deficient, can disrupt β-cell function and glucose regulation, contributing to diabetes progression.

CONCLUSION

Autophagy plays a pivotal role in maintaining pancreatic β-cell function, and its dysregulation is implicated in the development of diabetes. Targeting the autophagy pathway offers potential therapeutic strategies for diabetes management, with agents that modulate autophagy showing promise in preserving β-cell function.

γ-Glutamylcysteine restores glucolipotoxicity-induced islet β-cell apoptosis and dysfunction via inhibiting endoplasmic reticulum stress

PURPOSE

The impaired function of islet β-cell is associated with the pathogenesis of type 2 diabetes mellitus (T2DM). γ-glutamylcysteine (γ-GC), an immediate precursor of glutathione (GSH), has antioxidant and neuroprotective functions. Its level has been reported to be down-regulated in hyperglycemia. However, whether γ-GC has a protective effect on islet β-cell dysfunction remains elusive. Recently, we explore the molecular mechanism by which γ-GC protects islet β-cell from glucolipotoxicity-induced dysfunction.

METHODS

In vivo mice models and in vitro cell models were established to examine the therapeutic effects and molecular mechanisms of γ-GC.

RESULTS

db mice develop impaired glucose-stimulated insulin secretion (GSIS) due to reduced islet number and damaged islet microstructure. Serious oxidative damage, apoptosis and lipid accumulation are also observed in β-cell stimulated by glucolipotoxicity. Mechanistic studies suggest that glucolipotoxicity inhibits PDX-1 nuclear translocation by inducing endoplasmic reticulum (ER) stress, which leads to impaired insulin (INS) secretion in β-cell. Nevertheless, γ-GC as an inhibitor of ER stress can alleviate the damage of islet microstructure in db mice. Importantly, γ-GC promotes INS gene expression and GSIS through driving nuclear translocation of PDX-1, thereby enhancing intracellular INS content. Moreover, treatment with γ-GC can also mitigate oxidative damage, apoptosis and lipid accumulation of β-cell, resulting in ameliorating islet β-cell dysfunction induced by glucolipotoxicity.

CONCLUSION

Our results support the use of γ-GC as an inhibitor of ER stress for prevention and treatment of T2DM in the future.

Genetic underpinnnings of type 2 diabetes

Genetics is a significant risk factor for developing type 2 diabetes, with a family history conferring a 1.5-3-fold increased risk. Intriguingly, this heritable risk is higher when the affected parent is the mother, suggesting a potential role of mitochondrial genetics -maternally inherited DNA - in diabetes pathogenesis, a hypothesis this chapter will explore. While obesity mediates some of the genetic risk of type 2 diabetes, the chapter and will focus on genetic influences on diabetes independent of obesity. Mechanistically, genetic variants directly or indirectly contribute to insulin resistance across key tissues, including liver, muscle and adipose tissue. This insulin resistance prevents the liver from efficiently suppressing glucose production in response to insulin and impairs glucose uptake in muscle during postprandial states. Insulin resistance is driven by complex interactions between the genome and environmental, which can, in turn, influence gene expression and contribute to worsening of metabolic dysfunction. This chapter examines how tissue-specific genetic changes drive insulin resistance in individual organs and how these localized dysfunctions contribute to the broader, multi-organ metabolic dysfunction that characterize type 2 diabetes.

Pentraxin 3 deficiency ameliorates streptozotocin-induced pancreatic toxicity via regulating ER stress and β-cell apoptosis

The long pentraxin 3 (PTX3), a marker of inflammation, has been associated with cardiovascular disease, obesity, and metabolic syndrome. Recently, elevated serum PTX3 levels have been linked to type 2 diabetes in obese patients with nonalcoholic fatty liver disease. Diabetes mellitus is a metabolic syndrome characterized by hyperglycemia resulting from insufficient insulin secretion or action. However, the precise role of PTX3 in hyperglycemia remains unclear. This study aimed to investigate the physiological roles of PTX3 in vivo. The deformation of pancreatic islets was mitigated in PTX3-deficient mice treated with streptozotocin (STZ) compared to control C57BL/6J mice. In addition, PTX3 deficiency prevented STZ-induced unfolded protein responses and pancreatic β-cell death. Immunoblotting data revealed significant inhibition of inositol-requiring protein1α and C/EBP homologous protein (CHOP) protein expression in PTX3 KO mice administered tunicamycin which is a chemical endoplasmic reticulum stress inducer. Similarly, tunicamycin-induced Grp78, Grp94, ATF6, and CHOP mRNA levels were reduced in PTX3 KO mice. Moreover, recombinant PTX3-induced CHOP expression and β-cell apoptosis in primary mouse islets. These findings suggest that PTX3 plays a critical role in STZ-induced deformation of pancreatic islets via regulating endoplasmic reticulum stress and β-cell apoptosis.

Targeting programmed cell death in diabetic kidney disease: from molecular mechanisms to pharmacotherapy

Diabetic kidney disease (DKD), one of the most prevalent microvascular complications of diabetes, arises from dysregulated glucose and lipid metabolism induced by hyperglycemia, resulting in the deterioration of renal cells such as podocytes and tubular epithelial cells. Programmed cell death (PCD), comprising apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis, represents a spectrum of cell demise processes intricately governed by genetic mechanisms in vivo. Under physiological conditions, PCD facilitates the turnover of cellular populations and serves as a protective mechanism to eliminate impaired podocytes or tubular epithelial cells, thereby preserving renal tissue homeostasis amidst hyperglycemic stress. However, existing research predominantly elucidates individual modes of cell death, neglecting the intricate interplay and mutual modulation observed among various forms of PCD. In this comprehensive review, we delineate the diverse regulatory mechanisms governing PCD and elucidate the intricate crosstalk dynamics among distinct PCD pathways. Furthermore, we review recent advancements in understanding the pathogenesis of PCD and explore their implications in DKD. Additionally, we explore the potential of natural products derived primarily from botanical sources as therapeutic agents, highlighting their multifaceted effects on modulating PCD crosstalk, thereby proposing novel strategies for DKD treatment.

Relevant Serum Endoplasmic Reticulum Stress Biomarkers in Type 2 Diabetes and Its Complications: A Systematic Review and Meta-Analysis

Endoplasmic reticulum stress (ERS) is activated in all cells by stressors such as hyperglycemia. However, it remains unclear which specific serum biomarkers of ERS are consistently altered in type 2 diabetes (T2D). We aimed to identify serum ERS biomarkers that are consistently altered in T2D and its complications, and their correlation with metabolic and anthropometric variables. We performed a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-Analyses and Systematic Reviews of Observational Studies (MOOSE). The risk of bias was assessed using the Newcastle-Ottawa scale. Random-effects models weighted by the inverse variance were employed to estimate the standardized mean difference and correlations as effect size measures. Indicators of heterogeneity and meta-regressions were evaluated. Of the 1206 identified studies, 22 were finally included, representing 11,953 subjects (2224 with T2D and 9992 non-diabetic controls). Most studies were of high quality. Compared with controls, subjects with T2D had higher circulating levels of heat shock protein 70 (HSP70; SMD: 2.30, 95% CI 1.13-3.46; p < 0.001) and secretagogin (SMD: 0.60, 95%CI 0.19-1.01; p < 0.001). They also had higher serum levels of peroxiredoxin-1, -2, -4, and -6. Secretagogin inversely correlated with HOMA-IR, yet positively correlated with HOMA-B, HbA1c, and FPG. PRX4 negatively correlated with HbA1c and FPG, while HSP70 positively correlated with HbA1c. In conclusion, six ERS biomarkers are consistently elevated in human T2D and correlate with glycemic control, insulin resistance, and β-cell function. Emerging evidence links serum ERS biomarkers to diabetes complications, but further research should evaluate their prognostic implications.

Role of Sec61α2 Translocon in Insulin Biosynthesis

Translocational regulation of proinsulin biosynthesis in pancreatic β-cells is unknown, although several studies have reported an important accessory role for the Translocon-Associated Protein complex to assist preproinsulin delivery into the endoplasmic reticulum via the heterotrimeric Sec61 translocon (comprising α, β, and γ subunits). The actual protein-conducting channel is the α-subunit encoded either by Sec61A1 or its paralog Sec61A2. Although the underlying channel selectivity for preproinsulin translocation is unknown, almost all studies of Sec61α to date have focused on Sec61α1. There is currently no evidence to suggest that this gene product plays a major role in proinsulin production, whereas genome-wide association studies indicate linkage of Sec61A2 with diabetes. Here, we report that evolutionary differences in mouse preproinsulin signal peptides affect proinsulin biosynthesis. Moreover, we find that, although some preproinsulin translocation can proceed through Sec61α1, Sec61α2 has a greater impact on proinsulin biosynthesis in pancreatic β-cells. Remarkably, Sec61α2 translocon deficiency exerts a significant inhibitory effect on the biosynthesis of preproinsulin itself, including a disproportionate increase of full-length nascent chain unreleased from ribosomes. This study not only reveals novel translocational regulation of proinsulin biosynthesis but also provides a rationale for genetic evidence suggesting an important role of Sec61α2 in maintaining blood glucose homeostasis.

ARTICLE HIGHLIGHTS

Zebrafish as a model to study PERK function in developmental diseases: implications for Wolcott-Rallison syndrome

Developmental diseases are challenging to investigate due to their clinical heterogeneity and relatively low prevalence. The Wolcott-Rallison Syndrome (WRS) is a rare developmental disease characterized by skeletal dysplasia and permanent neonatal diabetes due to loss-of-function mutations in the endoplasmic reticulum stress kinase PERK (EIF2AK3). The lack of efficient and less invasive therapies for WRS highlights the need for new animal models that replicate the complex pathological phenotypes, while preserving scalability for drug screening. Zebrafish exhibits high fecundity and rapid development that facilitate efficient and scalable in vivo drug testing. Here, we aimed to assess the potential of zebrafish to study PERK function and its pharmacological modulation, and as model organism of developmental diseases such as the WRS. Using bioinformatic analyses, we showed high similarity between human and zebrafish PERK. We used the pharmacological PERK inhibitor GSK2606414, which was bioactive in zebrafish, to modulate PERK function. Using transgenic zebrafish expressing fluorescent pancreatic markers and a fluorescent glucose probe, we observed that PERK inhibition decreased β cell mass and disrupted glucose homeostasis. By combining behavioural and functional assays, we show that PERK-inhibited zebrafish present marked skeletal defects and defective growth, as well as neuromuscular and cardiac deficiencies, which are clinically relevant in WRS patients, while sparing parameters like otolith area and eye/body ratio which are not associated with WRS. These results show that zebrafish holds potential to study PERK function and its pharmacological modulation in developmental disorders like WRS, assisting research on their pathophysiology and experimental treatments.

Multi-omic human pancreatic islet endoplasmic reticulum and cytokine stress response mapping provides type 2 diabetes genetic insights

Endoplasmic reticulum (ER) and inflammatory stress responses contribute to islet dysfunction in type 2 diabetes (T2D). Comprehensive genomic understanding of these human islet stress responses and whether T2D-associated genetic variants modulate them is lacking. Here, comparative transcriptome and epigenome analyses of human islets exposed ex vivo to these stressors revealed 30% of expressed genes and 14% of islet cis-regulatory elements (CREs) as stress responsive, modulated largely in an ER- or cytokine-specific fashion. T2D variants overlapped 86 stress-responsive CREs, including 21 induced by ER stress. We linked the rs6917676-T T2D risk allele to increased islet ER-stress-responsive CRE accessibility and allele-specific β cell nuclear factor binding. MAP3K5, the ER-stress-responsive putative rs6917676 T2D effector gene, promoted stress-induced β cell apoptosis. Supporting its pro-diabetogenic role, MAP3K5 expression correlated inversely with human islet β cell abundance and was elevated in T2D β cells. This study provides genome-wide insights into human islet stress responses and context-specific T2D variant effects.

Dysregulation of pancreatic β-cell autophagy and the risk of type 2 diabetes

Macroautophagy/autophagy is an essential degradation process that removes abnormal cellular components, maintains homeostasis within cells, and provides nutrition during starvation. Activated autophagy enhances cell survival during stressful conditions, although overactivation of autophagy triggers induction of autophagic cell death. Therefore, early-onset autophagy promotes cell survival whereas late-onset autophagy provokes programmed cell death, which can prevent disease progression. Moreover, autophagy regulates pancreatic β-cell functions by different mechanisms, although the precise role of autophagy in type 2 diabetes (T2D) is not completely understood. Consequently, this mini-review discusses the protective and harmful roles of autophagy in the pancreatic β cell and in the pathophysiology of T2D.

The rs2341471-G/G genotype of activating transcription factor 6 (ATF6) is the risk factor of type 2 diabetes in subjects with obesity or overweight

BACKGROUND

Numerous studies have demonstrated that the onset of type 2 diabetes (T2D) is linked to the reduction in ß-cell mass caused by apoptosis, a process initiated by endoplasmic reticulum (ER) stress. The aim of this study was to investigate the associations between single nucleotide polymorphisms (SNPs) in the ATF6 gene (activating transcription factor 6), a key sensor of ER stress, and T2D susceptibility.

METHODS

The study involved 3229 unrelated individuals, including 1569 patients with T2D and 1660 healthy controls from Central Russia. Four functionally significant intronic SNPs, namely rs931778, rs90559, rs2341471, and rs7517862, were genotyped using the MassARRAY-4 system.

RESULTS

The rs2341471-G/G genotype of ATF6 was found to be associated with an increased risk of T2D (OR = 1.61, 95% CI 1.37-1.90, PFDR < 0.0001). However, a BMI-stratified analysis showed that this genotype and haplotypes CGGA and TAGA are associated with T2D risk exclusively in subjects with obesity or overweight (PFDR < 0.05). Despite these patients being found to have higher consumption of high-carbohydrate and high-calorie diets compared to normal-weight individuals (P < 0.0001), the influence of the rs7517862 polymorphism on T2D risk was observed independently of these dietary habits. Functional SNP annotation revealed the following: (1) the rs2341471-G allele is associated with increased ATF6 expression; (2) the SNP is located in a region exhibiting enhancer activity epigenetically regulated in pancreatic islets; (3) the rs2341471-G was predicted to create binding sites for 18 activating transcription factors that are part of gene-regulatory networks controlling glucose metabolism and maintaining proteostasis.

CONCLUSIONS

The present study revealed, for the first time, a strong association between the rs2341471-G/G ATF6 genotype and an increased risk of type 2 diabetes in people with obesity or overweight, regardless of known dietary risk factors. Further research is needed to support the potential of silencing the ATF6 gene as a means for the treatment and prevention of type 2 diabetes.

Bioinformatical analysis and experimental validation of endoplasmic reticulum stress-related biomarker genes in type 2 diabetes mellitus

Introduction

Endoplasmic reticulum stress (ERS) is a prominent etiological factor in the pathogenesis of diabetes. Nevertheless, the mechanisms through which ERS contributes to the development of diabetes remain elusive.

Methods

Transcriptional expression profiles from the Gene Expression Omnibus (GEO) datasets were analyzed and compared to obtain the differentially expressed genes (DEGs) in T2DM. Following the intersection with ERS associated genes, the ERS related T2DM DEGs were identified. Receiver operating characteristic (ROC) and Least Absolute Shrinkage and Selection Operator (LASSO) analysis were performed to screen out the ERS related biomarker genes and validate their diagnostic values. Gene expression level was detected by qPCR and Elisa assays in diabetic mice and patient serum samples.

Results

By analyzing the transcriptional expression profiles of the GEO datasets, 49 T2DM-related DEGs were screened out in diabetic islets. RTN1, CLGN, PCSK1, IAPP, ILF2, IMPA1, CCDC47, and PTGES3 were identified as ERS-related DEGs in T2DM, which were revealed to be involved in protein folding, membrane composition, and metabolism regulation. ROC and LASSO analysis further screened out CLGN, ILF2, and IMPA1 as biomarker genes with high value and reliability for diagnostic purposes. These three genes were then demonstrated to be targeted by the transcription factors and miRNAs, including CEBPA, CEBPB, miR-197-5p, miR-6133, and others. Among these miRNAs, the expression of miR-197-5p, miR-320c, miR-1296-3P and miR-6133 was down-regulated, while that of miR-4462, miR-4476-5P and miR-7851-3P was up-regulated in diabetic samples. Small molecular drugs, including D002994, D001564, and others, were predicted to target these genes potentially. qPCR and Elisa analysis both validated the same expression alteration trend of the ERS-related biomarker genes in diabetic mice and T2DM patients.

Discussion

These findings will offer innovative perspectives for clinical diagnosis and treatment strategies for T2DM.

Combination therapy enhances efficacy and overcomes toxicity of metal-based anti-diabetic agent

BACKGROUND AND PURPOSE

Metal-based therapeutic agents are limited by the required concentration of metal-based agents. Hereby, we determined if combination with 17β-oestradiol (E2) could reduce such levels and the therapy still be effective in type 2 diabetes mellitus (T2DM).

EXPERIMENTAL APPROACH

The metal-based agent (vanadyl acetylacetonate [VAC])- 17β-oestradiol (E2) combination is administered using the membrane-permeable graphene quantum dots (GQD), the vehicle, to form the active GQD-E2-VAC complexes, which was characterized by fluorescence spectra, infrared spectra and X-ray photoelectron spectroscopy. In db/db type 2 diabetic mice, the anti-diabetic effects of GQD-E2-VAC complexes were evaluated using blood glucose levels, oral glucose tolerance test (OGTT), serum insulin levels, homeostasis model assessment (homeostasis model assessment of insulin resistance [HOMA-IR] and homeostasis model assessment of β-cell function [HOMA-β]), histochemical assays and western blot.

KEY RESULTS

In diabetic mice, GQD-E2-VAC complex had comprehensive anti-diabetic effects, including control of hyperglycaemia, improved insulin sensitivity, correction of hyperinsulinaemia and prevention of β-cell loss. Co-regulation of thioredoxin interacting protein (TXNIP) activation by the combination of metal complex and 17β-oestradiol contributed to the enhanced anti-diabetic effects. Furthermore, a potent mitochondrial protective antioxidant, coniferaldehyde, significantly potentiates the protective effects of GQD-E2-VAC complexes.

CONCLUSION AND IMPLICATIONS

A metal complex-E2 combinatorial approach achieved simultaneously the protection of β cells and insulin enhancement at an unprecedented low dose, similar to the daily intake of dietary metals in vitamin supplements. This study demonstrates the positive effects of combination and multi-modal therapies towards type 2 diabetes treatment.

Islet Transplantation: Current Limitations and Challenges for Successful Outcomes

Islet transplantation is a promising approach for treating patients with unstable T1DM. However, it is confronted with numerous obstacles throughout the various stages of the transplantation procedure. Significant progress has been made over the last 25 years in understanding the mechanisms behind the loss of functional islet mass and in developing protective strategies. Nevertheless, at present, two to three pancreases are still needed to treat a single patient, which limits the maximal number of patients who can benefit from islet transplantation. Thus, this publication provides an overview of recent scientific findings on the various issues affecting islet transplantation. Specifically, we will focus on the understanding of the mechanisms involved and the strategies developed to alleviate these problems from the isolation stage to the post-transplantation phase. Finally, we hope that this review will highlight new avenues of action, enabling us to propose pancreatic islet transplantation to a maximum number of patients with T1DM.

Inhibition of endoplasmic reticulum stress and excessive autophagy by Jiedu Tongluo Tiaogan Formula via a CaMKKβ/AMPK pathway contributes to protect pancreatic β-cells

ETHNOPHARMACOLOGICAL RELEVANCE

Jiedu Tongluo Tiaogan Formula (JTTF), a traditional Chinese herbal decoction, exhibits the potential to treat type 2 diabetes mellitus (T2DM) by inhibiting endoplasmic reticulum stress (ERS) and excessive autophagy, which are the risk factors for the abnormal development and progression of β cells.

AIM OF THE STUDY

We aimed to assess the effect of JTTF on pancreatic glucotoxicity by inhibiting ERS and excessive autophagy, for which db/db mice and INS-1 insulinoma cells were used.

MATERIALS AND METHODS

The chemical composition of the JTTF was analyzed by UPLC-Q/TOF-MS. Diabetic (db/db) mice were treated with distilled water or JTTF (2.4 and 7.2 g/kg/day) for 8 weeks. Furthermore, INS-1 cells induced by high glucose (HG) levels were treated with or without JTTF (50, 100, and 200 μg/mL) for 48 h to elucidate the protective mechanism of JTTF on glucose toxicity. The experimental methods included an oral glucose tolerance test, hematoxylin-eosin staining, immunohistochemistry, western blotting, RT-qPCR, and acridine orange staining.

RESULT

28 chemical components of JTTF were identified. Additionally, treatment with JTTF significantly decreased the severity of glycemic symptoms in the db/db mice. Moreover, the treatment partially restored glucose homeostasis in the db/db mice and protected the pancreatic β-cell function. JTTF protected INS-1 cells from HG injury by upregulating GSIS and PDX1, MafA mRNA expression. Further, treatment with JTTF downregulated GRP78 and ATF6 expression, whereas it inhibited Beclin-1 and LC3 activation. The treatment protected the cells from HG-induced ERS and excessive autophagy by downregulating the CaMKKβ/AMPK pathway.

CONCLUSIONS

The present study findings show that JTTF may protects β-cells by inhibiting the CaMKKβ/AMPK pathway, which deepens our understanding of the effectiveness of JTTF as a treatment strategy against T2DM.

Visualization of Diabetes Progression by an Activatable NIR-IIb Luminescent Probe

Developing NIR-IIb luminescence probes with rapid visualization and a high penetration depth is essential for diabetes research. Combining a sensitizing switch with lanthanide-doped nanoparticles (LnNPs) has been employed to fabricate the NIR-IIb probes. However, these probes mainly adopt heptamethine cyanine dye as the antenna, and the NIR-IIb signal is activated by inhibiting the photoinduced electron transfer (PET) of the dye. Due to limited recognition units, this strategy makes many biomolecules undetectable, such as cysteine (Cys), which is closely related to diabetes. Herein, in this article, hemicyanine dye, NFL-OH, was verified as a new antenna to sensitize NIR-IIb emission from LnNPs. Unlike traditional cyanine dyes, hemicyanine's fluorescence intensity can also be modulated by intramolecular charge transfer (ICT), thereby expanding the range of detectable targets for NIR-IIb probes based on sensitization mechanism. Through switching the hemicyanine-sensitized NIR-IIb emission, we successfully fabricated an NFL-Cys-LnNPs' nanoprobe, which can effectively monitor Cys concentration in the liver of diabetic mice during diabetes progression and evaluate the efficacy of diabetic drugs. Our work not only presents an excellent tool for Cys imaging but also introduces new concepts for designing NIR-IIb probes.

UTRs and Ago-2/miR-335 Complex Restricts Amylin Translation in Insulinoma and Human Pancreatic β-Cells

Amylin promoter and transcriptional factors are well-established, inducible factors in the production of the main amyloidogenic pancreatic hormone, human islet amyloid peptide (hIAPP) or amylin. However, posttranscriptional mechanisms driving hIAPP expression in pancreas remain enigmatic, and hence were explored here. The translational assay revealed that both 5' and 3' untranslated regions (UTRs) of hIAPP restricted expression of the luciferase constructs only in constructs driven by the hIAPP promoter. Bioinformatics analysis revealed several putative seed sequences for a dozen micro RNAs (miRNAs) in hIAPP's 3' UTR. miR-182, miR-335, and miR-495 were the most downregulated miRNAs in stressed human islets exposed to endoplasmic reticulum (ER) or metabolic stressors, thapsigargin (TG) or high glucose (HG). Correspondingly, miR-335 mimics alone or in combination with miR-495 and miR-182 mimics significantly and potently (>3-fold) reduced hIAPP protein expression in HG-treated cultured human islets. siRNA-mediated silencing of Ago2 but not Ago1 significantly stimulated hIAPP expression and secretion from transfected, HG-treated human islets. Conversely, ectopic expression of Ago2 in hIAPP-expressing RIN-m5F cell line driven by CMV promoter reduced hIAPP intracellular protein levels. Collectively, the results point to a novel and synergistic role for hIAPP promoter, 5/3' UTRs and Ago-2/miR-335 complex in post-transcriptional regulation of hIAPP gene expression in normal and metabolically active β-cells.

The emerging roles of UFMylation in the modulation of immune responses

Post-translational modification is a rite of passage for cellular functional proteins and ultimately regulate almost all aspects of life. Ubiquitin-fold modifier 1 (UFM1) system represents a newly identified ubiquitin-like modification system with indispensable biological functions, and the underlying biological mechanisms remain largely undiscovered. The field has recently experienced a rapid growth of research revealing that UFMylation directly or indirectly regulates multiple immune processes. Here, we summarised important advances that how UFMylation system responds to intrinsic and extrinsic stresses under certain physiological or pathological conditions and safeguards immune homeostasis, providing novel perspectives into the regulatory framework and functions of UFMylation system, and its therapeutic applications in human diseases.

Endoplasmic Reticulum Membrane Homeostasis and the Unfolded Protein Response

The endoplasmic reticulum (ER) is the key organelle for membrane biogenesis. Most lipids are synthesized in the ER, and most membrane proteins are first inserted into the ER membrane before they are transported to their target organelle. The composition and properties of the ER membrane must be carefully controlled to provide a suitable environment for the insertion and folding of membrane proteins. The unfolded protein response (UPR) is a powerful signaling pathway that balances protein and lipid production in the ER. Here, we summarize our current knowledge of how aberrant compositions of the ER membrane, referred to as lipid bilayer stress, trigger the UPR.

Identification of unique cell type responses in pancreatic islets to stress

Diabetes involves the death or dysfunction of pancreatic β-cells. Analysis of bulk sequencing from human samples and studies using in vitro and in vivo models suggest that endoplasmic reticulum and inflammatory signaling play an important role in diabetes progression. To better characterize cell type-specific stress response, we perform multiplexed single-cell RNA sequencing to define the transcriptional signature of primary human islet cells exposed to endoplasmic reticulum and inflammatory stress. Through comprehensive pair-wise analysis of stress responses across pancreatic endocrine and exocrine cell types, we define changes in gene expression for each cell type under different diabetes-associated stressors. We find that β-, α-, and ductal cells have the greatest transcriptional response. We utilize stem cell-derived islets to study islet health through the candidate gene CIB1, which was upregulated under stress in primary human islets. Our findings provide insights into cell type-specific responses to diabetes-associated stress and establish a resource to identify targets for diabetes therapeutics.

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.

The Impact of Weight Cycling on Health and Obesity

Obesity is a systemic and chronic inflammation, which seriously endangers people's health. People tend to diet to control weight, and the short-term effect of dieting in losing weight is significant, but the prognosis is limited. With weight loss and recovery occurring frequently, people focus on weight cycling. The effect of weight cycling on a certain tissue of the body also has different conclusions. Therefore, this article systematically reviews the effects of body weight cycling on the body and finds that multiple weight cycling (1) increased fat deposition in central areas, lean mass decreased in weight loss period, and fat mass increased in weight recovery period, which harms body composition and skeletal muscle mass; (2) enhanced the inflammatory response of adipose tissue, macrophages infiltrated into adipose tissue, and increased the production of pro-inflammatory mediators in adipocytes; (3) blood glucose concentration mutation and hyperinsulinemia caused the increase or decrease in pancreatic β-cell population, which makes β-cell fatigue and leads to β-cell failure; (4) resulted in additional burden on the cardiovascular system because of cardiovascular rick escalation. Physical activity combined with calorie restriction can effectively reduce metabolic disease and chronic inflammation, alleviating the adverse effects of weight cycling on the body.

LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes

Proteotoxicity is a contributor to the development of type 2 diabetes (T2D), but it is unknown whether protein misfolding in T2D is generalized or has special features. Here, we report a robust accumulation of misfolded proteins within the mitochondria of human pancreatic islets in T2D and elucidate its impact on β cell viability. Surprisingly, quantitative proteomics studies of protein aggregates reveal that human islets from donors with T2D have a signature more closely resembling mitochondrial rather than ER protein misfolding. The matrix protease LonP1 and its chaperone partner mtHSP70 were among the proteins enriched in protein aggregates. Deletion of LONP1 in mice yields mitochondrial protein misfolding and reduced respiratory function, ultimately leading to β cell apoptosis and hyperglycemia. Intriguingly, LONP1 gain of function ameliorates mitochondrial protein misfolding and restores human β cell survival following glucolipotoxicity via a protease-independent effect requiring LONP1-mtHSP70 chaperone activity. Thus, LONP1 promotes β cell survival and prevents hyperglycemia by facilitating mitochondrial protein folding. These observations may open novel insights into the nature of impaired proteostasis on β cell loss in the pathogenesis of T2D that could be considered as future therapeutic targets.

Immunopeptidome mining reveals a novel ERS-induced target in T1D

Autoreactive CD8+ T cells play a key role in type 1 diabetes (T1D), but the antigen spectrum that activates autoreactive CD8+ T cells remains unclear. Endoplasmic reticulum stress (ERS) has been implicated in β-cell autoantigen generation. Here, we analyzed the major histocompatibility complex class I (MHC-I)-associated immunopeptidome (MIP) of islet β-cells under steady and ERS conditions and found that ERS reshaped the MIP of β-cells and promoted the MHC-I presentation of a panel of conventional self-peptides. Among them, OTUB258-66 showed immunodominance, and the corresponding autoreactive CD8+ T cells were diabetogenic in nonobese diabetic (NOD) mice. High glucose intake upregulated pancreatic OTUB2 expression and amplified the OTUB258-66-specific CD8+ T-cell response in NOD mice. Repeated OTUB258-66 administration significantly reduced the incidence of T1D in NOD mice. Interestingly, peripheral blood mononuclear cells (PBMCs) from patients with T1D, but not from healthy controls, showed a positive IFN-γ response to human OTUB2 peptides. This study provides not only a new explanation for the role of ERS in promoting β-cell-targeted autoimmunity but also a potential target for the prevention and treatment of T1D. The data are available via ProteomeXchange with the identifier PXD041227.