Pdx1 maintains β cell identity and function by repressing an α cell program

HDL-Cholesterol and Triglycerides Dynamics: Essential Players in Metabolic Syndrome

Metabolic syndrome (MetS) is a complex cluster of interrelated metabolic disorders that significantly elevate the risk of cardiovascular disease, making it a pressing public health concern worldwide. Among the key features of MetS, dyslipidemia-characterized by altered levels of high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG)-plays a crucial role in the disorder's progression. This review aims to elucidate the intricate interplay between HDL-C and TG within the context of lipid metabolism and cardiovascular health, while also addressing the detrimental impact of various cardiovascular risk factors and associated comorbidities. The dynamics of HDL-C and TG are explored, highlighting their reciprocal relationship and respective contributions to the pathophysiology of MetS. Elevated levels of TGs are consistently associated with reduced concentrations of HDL-C, resulting in a lipid profile that promotes the development of vascular disease. Specifically, as TG levels rise, the protective cardiovascular effects of HDL-C are diminished, leading to the increased accumulation of pro-atherogenic TG-rich lipoproteins and low-density lipoprotein particles within the vascular wall, contributing to the progression of atheromas, which can ultimately result in significant ischemic cardiovascular events. Ultimately, this paper underscores the significance of HDL and TG as essential targets for therapeutic intervention, emphasizing their potential in effectively managing MetS and reducing cardiovascular risk.

Post translational modification regulation of transcription factors governing pancreatic β-cell identity and functional mass

Dysfunction of the insulin-secreting β-cells is a key hallmark of Type 2 diabetes (T2D). In the natural history of the progression of T2D, factors such as genetics, early life exposures, lifestyle, and obesity dictate an individual's susceptibility risk to disease. Obesity is associated with insulin resistance and increased demand for insulin to maintain glucose homeostasis. Studies in both mouse and human islets have implicated the β-cell's ability to compensate through proliferation and survival (increasing functional β-cell mass) as a tipping point toward the development of disease. A growing body of evidence suggests the reduction of β-cell mass in T2D is driven majorly by loss of β-cell identity, rather than by apoptosis alone. The development and maintenance of pancreatic β-cell identity, function, and adaptation to stress is governed, in part, by the spatiotemporal expression of transcription factors (TFs), whose activity is regulated by signal-dependent post-translational modifications (PTM). In this review, we examine the role of these TFs in the developing pancreas and in the mature β-cell. We discuss functional implications of post-translational modifications on these transcription factors' activities and how an understanding of the pathways they regulate can inform therapies to promoteβ-cell regeneration, proliferation, and survival in diabetes.

VPS41 deletion triggers progressive loss of insulin stores and downregulation of β-cell identity

Vacuolar protein sorting-associated protein 41 (VPS41) has been established as a requirement for normal insulin secretory function in pancreatic β cells. Genetic deletion of VPS41 in mouse pancreatic β cells results in diabetes, although the mechanisms are not understood. Presently, we show that VPS41 deletion results in rapid mature insulin degradation and downregulation of β-cell identity. This phenotype is observed in vivo, with VPS41KO mice displaying progressive loss of insulin content and β-cell function with age. In acute VPS41 depletion in vitro, the loss of insulin is associated with increased degradative pathway activity, increased Adapter Protein 3 complex colocalization with lysosomes, increased nuclear localization of transcription factor E3, and downregulation of PDX1 and INS mRNA expression. Inhibition of lysosomal degradation rescues the rapidly depleted insulin content. These data evidence a VPS41-dependent mechanism for both insulin content degradation and loss of β-cell identity in β cells.NEW & NOTEWORTHY In this study, we show that acute VPS41 deletion results in rapid degradation of insulin, whereas chronic VPS41 deletion results in downregulation of β-cell identity. In acute VPS41 depletion in vitro, the loss of insulin is associated with increased degradative pathway activity, increased Adapter Protein 3 complex colocalization with lysosomes, increased nuclear localization of transcription factor E3, and downregulation of PDX1 and INS mRNA expression. Inhibition of lysosomal degradation rescues the rapidly depleted insulin content.

High-Density Lipoprotein in Patients with Diabetic Kidney Disease: Friend or Foe?

High-density lipoprotein (HDL) exhibits multiple metabolic protective functions, such as facilitating cellular cholesterol efflux, antioxidant, anti-inflammatory, anti-apoptotic and anti-thrombotic properties, showing antidiabetic and renoprotective potential. Diabetic kidney disease (DKD) is considered to be associated with high-density lipoprotein cholesterol (HDL-C). The hyperglycemic environment, non-enzymatic glycosylation, carbamylation, oxidative stress and systemic inflammation can cause changes in the quantity and quality of HDL, resulting in reduced HDL levels and abnormal function. Dysfunctional HDL can also have a negative impact on pancreatic β cells and kidney cells, leading to the progression of DKD. Based on these findings, new HDL-related DKD risk predictors have gradually been proposed. Interventions aiming to improve HDL levels and function, such as infusion of recombinant HDL (rHDL) or lipid-poor apolipoprotein A-I (apoA-I), can significantly improve glycemic control and also show renal protective effects. However, recent studies have revealed a U-shaped relationship between HDL-C levels and DKD, and the loss of protective properties of high levels of HDL may be related to changes in composition and the deposition of dysfunctional particles that exacerbate damage. Further research is needed to fully elucidate the complex role of HDL in DKD. Given the important role of HDL in metabolic health, developing HDL-based therapies that augment HDL function, rather than simply increasing its level, is a critical step in managing the development and progression of DKD.

Protein kinase CK2 contributes to glucose homeostasis

In the early days of CK2 research, it was already published that the affinity of CK2 for its substrate casein was affected by insulin. Subsequent to the discovery of inhibitors of CK2 kinase activity, it was shown that CK2 has an influence on hormones that regulate glucose homeostasis and on enzymes that influence glucose metabolism in pancreatic islet cells as well as in hormone-sensitive target cells. This regulation includes the influence on transcription factors and thereby, gene expression, as well as direct modulation of the catalytic activity. The used CK2 inhibitors, especially the older ones, show a broad range of specificity, selectivity and off-target effects. Recently applied methods to down-regulate the expression of individual CK2 subunits using siRNA or CRISPR/Cas9 technology have contributed to the improvement of specificity. It was shown that inhibition of CK2 kinase activity or knock-down or knock-out of CK2α leads to an elevated synthesis and secretion of insulin in pancreatic β-cells and a down-regulation of the synthesis and secretion of glucagon from pancreatic α-cells. In the present review CK2-dependent molecular mechanisms will be addressed which contribute to the maintenance of glucose homeostasis.

A mechanism-informed deep neural network enables prioritization of regulators that drive cell state transitions

Cells are regulated at multiple levels, from regulations of individual genes to interactions across multiple genes. Some recent neural network models can connect molecular changes to cellular phenotypes, but their design lacks modeling of regulatory mechanisms, limiting the decoding of regulations behind key cellular events, such as cell state transitions. Here, we present regX, a deep neural network incorporating both gene-level regulation and gene-gene interaction mechanisms, which enables prioritizing potential driver regulators of cell state transitions and providing mechanistic interpretations. Applied to single-cell multi-omics data on type 2 diabetes and hair follicle development, regX reliably prioritizes key transcription factors and candidate cis-regulatory elements that drive cell state transitions. Some regulators reveal potential new therapeutic targets, drug repurposing possibilities, and putative causal single nucleotide polymorphisms. This method to analyze single-cell multi-omics data demonstrates how the interpretable design of neural networks can better decode biological systems.

Mechanism and therapeutic potential of hippo signaling pathway in type 2 diabetes and its complications

Loss of pancreatic islet cell mass and function is one of the most important factors in the development of type 2 diabetes mellitus, and hyperglycemia-induced lesions in other organs are also associated with apoptosis or hyperproliferation of the corresponding tissue cells. The Hippo signaling pathway is a key signal in the regulation of cell growth, proliferation and apoptosis, which has been shown to play an important role in the regulation of diabetes mellitus and its complications. Excessive activation of the Hippo signaling pathway under high glucose conditions triggered apoptosis and decreased insulin secretion in pancreatic islet cells, while dysregulation of the Hippo signaling pathway in the cells of other organ tissues led to proliferation or apoptosis and promoted tissue fibrosis, which aggravated the progression of diabetes mellitus and its complications. This article reviews the mechanisms of Hippo signaling, its individual and reciprocal regulation in diabetic pancreatic pathology, and its emerging role in the pathophysiology of diabetic complications. Potential therapeutics for diabetes mellitus that have been shown to target the Hippo signaling pathway are also summarized to provide information for the clinical management of type 2 diabetes mellitus.

Revealing the biological features of the axolotl pancreas as a new research model

Introduction

The pancreas plays a crucial role in digestion and blood glucose regulation. Current animal models, primarily mice and zebrafish, have limited the exploration of pancreatic biology from an evolutionary-developmental perspective. Tetrapod vertebrate axolotl (Ambystoma mexicanum) serves as a valuable model in developmental, regenerative, and evolutionary biology. However, the fundamental biology of the axolotl pancreas remains underexplored. This study aims to characterize the unique developmental, functional, and evolutionary features of the axolotl pancreas to expand the understanding of pancreatic biology.

Methods

We conducted morphological, histological, and transcriptomic analyses to investigate the axolotl pancreas. Pancreatic development was observed using in situ hybridization and immunostaining for key pancreatic markers. RNA sequencing was performed to profile global gene expression during larva and adult stages. And differential gene expression analysis was used to characterize the conserved and unique gene patterns in the axolotl pancreas. Functional assays, including glucose tolerance tests and insulin tolerance tests, were optimized for individual axolotls. To assess pancreatic gene function, Pdx1 mutants were generated using CRISPR/Cas9-mediated gene editing, and their effects on pancreatic morphology, endocrine cell populations, and glucose homeostasis were analyzed.

Results

The axolotl pancreas contains all known pancreatic cell types and develops from dorsal and ventral buds. Both of buds contribute to exocrine and endocrine glands. The dorsal bud produces the major endocrine cell types, while the ventral bud generates α and δ cells, but not β cells. Differential gene expression analysis indicated a transition in global gene expression from pancreatic cell fate commitment and the cell cycle to glucose response, hormone synthesis, and secretion, following the development progression. Notably, the adult axolotl pancreas exhibits slower metabolic activity compared to mammals, as evidenced by the results of GTT and ITT. The mutation of Pdx1 resulted in hyperglycemia and a significant reduction in pancreatic cell mass, including a complete loss of endocrine cells, although it did not lead to a lethal phenotype.

Discussion

This study examines the axolotl pancreas, highlighting the conservation of pancreatic development. Our study highlights the unique features of the axolotl pancreas and broadens the scope of animal models available for pancreatic evolution and disease research.

Type 2 Diabetes Mellitus: New Pathogenetic Mechanisms, Treatment and the Most Important Complications

Type 2 diabetes mellitus (T2DM), a prevalent chronic disease affecting over 400 million people globally, is driven by genetic and environmental factors. The pathogenesis involves insulin resistance and β-cell dysfunction, mediated by mechanisms such as the dedifferentiation of β-cells, mitochondrial dysfunction, and oxidative stress. Treatment should be based on non-pharmacological therapy. Strategies such as increased physical activity, dietary modifications, cognitive-behavioral therapy are important in maintaining normal glycemia. Advanced therapies, including SGLT2 inhibitors and GLP-1 receptor agonists, complement these treatments and offer solid glycemic control, weight control, and reduced cardiovascular risk. Complications of T2DM, such as diabetic kidney disease, retinopathy, and neuropathy, underscore the need for early diagnosis and comprehensive management to improve patient outcomes and quality of life.

Detection of Insulin in Insulin-Deficient Islets of Patients with Type 1 Diabetes

Type 1 diabetes (T1D) is related to the autoimmune destruction of β-cells, leading to their almost complete absence in patients with longstanding T1D. However, endogenous insulin secretion persists in such patients as evidenced by the measurement of plasma C-peptide. Recently, a low level of insulin has been found in non-β islet cells of patients with longstanding T1D, indicating that other islet cell types may contribute to persistent insulin secretion. The present study aimed to test the ability of various antibodies to detect insulin in insulin-deficient islets of T1D patients. Pancreatic autopsies from two children with recent-onset T1D, two adults with longstanding T1D, and three control subjects were examined using double immunofluorescent labeling with antibodies to insulin, glucagon and somatostatin. Immunoreactivity to insulin in glucagon+ cells of insulin-deficient islets was revealed using polyclonal antibodies and monoclonal antibodies simultaneously recognizing insulin and proinsulin. Along with this, immunoreactivity to insulin was observed in the majority of glucagon+ cells of insulin-containing islets of control subjects and children with recent-onset T1D. These results suggest that islet α-cells may contain insulin and/or other insulin-like proteins (proinsulin, C-peptide). Future studies are needed to evaluate the role of α-cells in insulin secretion and diabetes pathogenesis.

Astaxanthin-S-Allyl Cysteine Ester Protects Pancreatic β-Cell From Glucolipotoxicity by Suppressing Oxidative Stress, Endoplasmic Reticulum Stress and mTOR Pathway Dysregulation

Glucolipotoxicity (GLT) has emerged as established mechanism in the progression of diabetes. Identifying compounds that mitigate GLT-induced deleterious effect on β-cells are considered important strategy to overcome diabetes. Hence, in the present study, astaxanthin-s-allyl cysteine (AST-SAC) diester was studied against GLT in β-cells. Mus musculus pancreatic β-cell line (βTC-tet) was treated with high glucose (25 mM; HG) and 95 μM palmitate (PA) for 24 h to induce GLT. AST-SAC at various concentrations (5, 10, and 15 μg/ml) were treated to understand the protective effect against HG + PA exposure in β-cells. Under HG + PA exposure conditions oxidative stress, deregulation of mTOR pathway and endoplasmic reticulum (ER) stress are witnessed. AST-SAC treatment eased oxidative stress, mitochondrial depolarization, DNA damage, calcium overload and accumulation of autophagosome against HG + PA exposure conditions thereby protected the cell viability of β-cells. AST-SAC maintained the level of proteins involved in mTOR pathway under HG + PA exposure conditions. Also, AST-SAC treatment has mitigated the increased expression of genes and proteins such as IRE1 and PERK involved in ER stress-mediated unfolded protein response (UPR) signaling pathways. In correspondence to it, the expression of genes involved in insulin secretion was preserved by AST-SAC. Due to these protective effects of AST-SAC the insulin secretion was well-maintained in β-cells under HG + PA exposure conditions. AST-SAC through normalizing antioxidant status and mTOR axis as well as preventing the harmful effect of ER-stress mediated UPR pathway has promoted the β-cell survival and insulin secretion against GLT. Simultaneously targeting oxidative stress/mTOR axis/ER stress is required to efficiently overcome GLT in β-cells.

Exploring the key role of DNA methylation as an epigenetic modulator in oxidative stress related islet cell injury in patients with type 2 diabetes mellitus: a review

Type 2 diabetes mellitus (T2DM) is a multifactorial metabolic disorder characterised by impaired insulin secretion and action, often exacerbated by oxidative stress. Recent research has highlighted the intricate involvement of epigenetic mechanisms, particularly DNA methylation, in the pathogenesis of T2DM. This review aims to elucidate the role of DNA methylation as an epigenetic modifier in oxidative stress-mediated beta cell dysfunction, a key component of T2DM pathophysiology. Oxidative stress, arising from an imbalance between reactive oxygen species (ROS) production and antioxidant defence mechanisms, is a hallmark feature of T2DM. Beta cells, responsible for insulin secretion, are particularly vulnerable to oxidative damage due to their low antioxidant capacity. Emerging evidence suggests that oxidative stress can induce aberrant DNA methylation patterns in beta cells, leading to altered gene expression profiles associated with insulin secretion and cell survival. Furthermore, studies have identified specific genes involved in beta cell function and survival that undergo DNA methylation changes in response to oxidative stress in T2DM. These epigenetic modifications can perpetuate beta cell dysfunction by dysregulating key pathways essential for insulin secretion, such as the insulin signalling cascade and mitochondrial function. Understanding the interplay between DNA methylation, oxidative stress, and beta cell dysfunction holds promise for developing novel therapeutic strategies for T2DM. Targeting aberrant DNA methylation patterns may offer new avenues for restoring beta cell function and improving glycemic control in patients with T2DM. However, further research is needed to elucidate the complex mechanisms underlying epigenetic regulation in T2DM and to translate these findings into clinical interventions.

SRSF2 is essential for maintaining pancreatic beta-cell identity and regulating glucose homeostasis in mice

Diabetes is characterized by decreased beta-cell mass and islet dysfunction. The splicing factor SRSF2 plays a crucial role in cell survival, yet its impact on pancreatic beta cell survival and glucose homeostasis remains unclear. We observed that the deletion of Srsf2 specifically in beta cells led to time-dependent deterioration in glucose tolerance, impaired insulin secretion, decreased islet mass, an increased number of alpha cells, and the onset of diabetes by the age of 10 months in mice. Single-cell RNA sequencing (scRNA-seq) analyses revealed that, despite an increase in populations of unfolded protein response (UPR)-activated and undifferentiated beta cells within the SRSF2_KO group, there was a notable decrease in the expression of UPR-related and endoplasmic reticulum (ER)-related genes, accompanied by a loss of beta-cell identity. This suggests that beta cells have transitioned from an adaptive phase to a maladaptive phase in islets of 10-month-old SRSF2_KO mice. Further results demonstrated that deletion of SRSF2 caused decreased proliferation in beta cells within 3-month-old islets and Min6 cells. These findings underscore the essential role of SRSF2 in controlling beta-cell proliferation and preserving beta-cell function in mice.

Characterization and functional evaluation of goat PDX1 regulatory modules through comparative analysis of conserved interspecies homologs

PDX1 is a crucial transcription factor in pancreas development and mature β-cell function. However, the regulation of PDX1 expression in larger animals mirroring human pancreas morphogenesis and endocrine maturation remains poorly understood. Therefore, we conducted a comparative analysis to characterize regulatory regions of goat PDX1 gene and assessed their transcriptional activity by transient transfection of several transgenic EGFP constructs in β- and non-β cell lines. We recognized several highly conserved regions encompassing the promoter and cis-regulatory elements (Area I-IV) at 5' flanking sequence of the genes. Within the promoter, we identified that a key E-box and nearby CAAT element synergistically drive transcription, constituting the basal promoter of goat PDX1 gene. Furthermore, each recognized regulatory area separately enhances this basal promoter activity in β-cells compared to non-β cells; however, cooperatively, they exhibit a bifunctional regulatory effect on transcription. Additionally, the intact ~ 3 kb upstream region (Area I-III) functions as the most efficient reporter transgene in vitro and shows islet-specific expression in native rat pancreas. Together, our findings suggest that the regulation of goat PDX1 gene is governed by conserved regions similar to other mammals, while both structurally and functionally, these regions exhibit a closer resemblance to those found in humans.

Cryopreservation of Stem Cell-Derived β-Like Cells Enriches for Insulin-Producing Cells With Improved Function

The generation of stem cell-derived β-like cells (sBCs) holds promise as not only an abundant insulin-producing cell source for replacement therapy of type 1 diabetes (T1D) but also as an invaluable model system for investigating human β-cell development, immunogenicity, and function. Several groups have developed methodology to direct differentiate human pluripotent stem cells into pancreatic cell populations that include glucose-responsive sBCs. Nevertheless, the process of generating sBCs poses substantial experimental challenges. It involves lengthy differentiation periods, there is substantial variability in efficiency, and there are inconsistencies in obtaining functional sBCs. Here, we describe a simple and effective cryopreservation approach for sBC cultures that yields homogeneous sBC clusters that are enriched for insulin-expressing cells while simultaneously depleting proliferative progenitors. Thawed sBCs have enhanced glucose-stimulated insulin release compared with controls in vitro and can effectively engraft and function in vivo. Collectively, this approach alleviates current challenges with inefficient and variable sBC generation while improving their functional state. We anticipate that these findings can inform ongoing clinical application of sBCs for the treatment of patients with T1D and serve as an important resource for the wider diabetes field that will allow for accelerated research discoveries.

ARTICLE HIGHLIGHTS

Multiple promoter and enhancer differences likely contribute to augmented G6PC2 expression in human versus mouse pancreatic islet alpha cells

G6PC2 encodes a glucose-6-phosphatase catalytic subunit that opposes the action of glucokinase in pancreatic islets, thereby modulating the sensitivity of insulin and glucagon secretion to glucose. In mice, G6pc2 is expressed at ~20-fold higher levels in β-cells than in α-cells, whereas in humans G6PC2 is expressed at only ~5-fold higher levels in β-cells. We therefore hypothesize that G6PC2 likely influences glucagon secretion to a greater degree in humans. With a view to generating a humanized mouse that recapitulates augmented G6PC2 expression levels in α-cells, we sought to identify the genomic regions that confer differential mouse G6pc2 expression in α-cells versus β-cells as well as the evolutionary changes that have altered this ratio in humans. Studies in islet-derived cell lines suggest that the elevated G6pc2 expression in mouse β-cells versus α-cells is mainly due to a difference in the relative activity of the proximal G6pc2 promoter in these cell types. Similarly, the smaller difference in G6PC2 expression between α-cells and β-cells in humans is potentially explained by a change in relative proximal G6PC2 promoter activity. However, we show that both glucocorticoid levels and multiple differences in the relative activity of eight transcriptional enhancers between mice and humans likely contribute to differential G6PC2 expression. Finally, we show that a mouse-specific non-coding RNA, Gm13613, whose expression is controlled by G6pc2 enhancer I, does not regulate G6pc2 expression, indicating that altered expression of Gm13613 in a humanized mouse that contains both the human promoter and enhancers should not affect G6PC2 function.

Missense mutation of ISL1 (E283D) is associated with the development of type 2 diabetes

AIMS/HYPOTHESIS

Mutations in Isl1, encoding the insulin enhancer-binding protein islet-1 (ISL1), may contribute to attenuated insulin secretion in type 2 diabetes mellitus. We made an Isl1E283D mouse model to investigate the disease-causing mechanism of diabetes mellitus.

METHODS

The ISL1E283D mutation (c. 849A>T) was identified by whole exome sequencing on an early-onset type 2 diabetes family and then the Isl1E283D knockin (KI) mouse model was created and an IPGTT and IPITT were conducted. Glucose-stimulated insulin secretion (GSIS), expression of Ins2 and other ISL1 target genes and interacting proteins were evaluated in isolated pancreas islets. Transcriptional activity of Isl1E283D was evaluated by cell-based luciferase reporter assay and electrophoretic mobility shift assay, and the expression levels of Ins2 driven by Isl1 wild-type (Isl1WT) and Isl1E283D mutation in rat INS-1 cells were determined by RT-PCR and western blotting.

RESULTS

Impaired GSIS and elevated glucose level were observed in Isl1E283D KI mice while expression of Ins2 and other ISL1 target genes Mafa, Pdx1, Slc2a2 and the interacting protein NeuroD1 were downregulated in isolated islets. Transcriptional activity of the Isl1E283D mutation for Ins2 was reduced by 59.3%, and resulted in a marked downregulation of Ins2 expression when it was overexpressed in INS-1 cells, while overexpression of Isl1WT led to an upregulation of Ins2 expression.

CONCLUSIONS/INTERPRETATION

Isl1E283D mutation reduces insulin expression and secretion by regulating insulin and other target genes, as well as its interacting proteins such as NeuroD1, leading to the development of glucose intolerance in the KI mice, which recapitulated the human diabetic phenotype. This study identified and highlighted the Isl1E283D mutation as a novel causative factor for type 2 diabetes, and suggested that targeting transcription factor ISL1 could offer an innovative avenue for the precise treatment of human type 2 diabetes.

Bariatric surgery induces pancreatic cell transdifferentiation as indicated by single-cell transcriptomics in Zucker diabetic rats

AIMS

Bariatric surgery results in rapid recovery of glucose control in subjects with type 2 diabetes mellitus. However, the underlying mechanisms are still largely unknown. The present study aims to clarify how bariatric surgery modifies pancreatic cell subgroup differentiation and transformation in the single-cell RNA level.

METHODS

Male, 8-week-old Zucker diabetic fatty (ZDF) rats with obesity and diabetes phenotypes were randomized into sleeve gastrectomy (Sleeve, n = 9), Roux-en-Y gastric bypass (RYGB, n = 9), and Sham (n = 7) groups. Two weeks after surgery, the pancreas specimen was further analyzed using single-cell RNA-sequencing technique.

RESULTS

Two weeks after surgery, compared to the Sham group, the metabolic parameters including fasting plasma glucose, plasma insulin, and oral glucose tolerance test values were dramatically improved after RYGB and Sleeve procedures (p < .05) as predicted. In addition, RYGB and Sleeve groups increased the proportion of pancreatic β cells and reduced the ratio of α cells. Two multiple hormone-expressing cells were identified, the Gcg+/Ppy + and Ins+/Gcg+/Ppy + cells. The pancreatic Ins+/Gcg+/Ppy + cells were defined for the first time, and further investigation indicates similarities with α and β cells, with unique gene expression patterns, which implies that pancreatic cell transdifferentiation occurs following bariatric surgery.

CONCLUSIONS

For the first time, using the single-cell transcriptome map of ZDF rats, we reported a comprehensive characterization of the heterogeneity and differentiation of pancreatic endocrinal cells after bariatric surgery, which may contribute to the underlying mechanisms. Further studies will be needed to elucidate these results.

Targeting β-Cell Plasticity: A Promising Approach for Diabetes Treatment

The β-cells within the pancreas play a pivotal role in insulin production and secretion, responding to fluctuations in blood glucose levels. However, factors like obesity, dietary habits, and prolonged insulin resistance can compromise β-cell function, contributing to the development of Type 2 Diabetes (T2D). A critical aspect of this dysfunction involves β-cell dedifferentiation and transdifferentiation, wherein these cells lose their specialized characteristics and adopt different identities, notably transitioning towards progenitor or other pancreatic cell types like α-cells. This process significantly contributes to β-cell malfunction and the progression of T2D, often surpassing the impact of outright β-cell loss. Alterations in the expressions of specific genes and transcription factors unique to β-cells, along with epigenetic modifications and environmental factors such as inflammation, oxidative stress, and mitochondrial dysfunction, underpin the occurrence of β-cell dedifferentiation and the onset of T2D. Recent research underscores the potential therapeutic value for targeting β-cell dedifferentiation to manage T2D effectively. In this review, we aim to dissect the intricate mechanisms governing β-cell dedifferentiation and explore the therapeutic avenues stemming from these insights.

High-density lipoprotein in diabetes: Structural and functional relevance

Low levels of high-density lipoprotein-cholesterol (HDL-C) is considered a major cardiovascular risk factor. However, recent studies have suggested a more U-shaped association between HDL-C and cardiovascular disease. It has been shown that the cardioprotective effect of HDL is related to the functions of HDL particles rather than their cholesterol content. HDL particles are highly heterogeneous and have multiple functions relevant to cardiometabolic conditions including cholesterol efflux capacity, anti-oxidative, anti-inflammatory, and vasoactive properties. There are quantitative and qualitative changes in HDL as well as functional abnormalities in both type 1 and type 2 diabetes. Non-enzymatic glycation, carbamylation, oxidative stress, and systemic inflammation can modify the HDL composition and therefore the functions, especially in situations of poor glycemic control. Studies of HDL proteomics and lipidomics have provided further insights into the structure-function relationship of HDL in diabetes. Interestingly, HDL also has a pleiotropic anti-diabetic effect, improving glycemic control through improvement in insulin sensitivity and β-cell function. Given the important role of HDL in cardiometabolic health, HDL-based therapeutics are being developed to enhance HDL functions rather than to increase HDL-C levels. Among these, recombinant HDL and small synthetic apolipoprotein A-I mimetic peptides may hold promise for preventing and treating diabetes and cardiovascular disease.

Regulation of endocrine cell alternative splicing revealed by single-cell RNA sequencing in type 2 diabetes pathogenesis

The prevalent RNA alternative splicing (AS) contributes to molecular diversity, which has been demonstrated in cellular function regulation and disease pathogenesis. However, the contribution of AS in pancreatic islets during diabetes progression remains unclear. Here, we reanalyze the full-length single-cell RNA sequencing data from the deposited database to investigate AS regulation across human pancreatic endocrine cell types in non-diabetic (ND) and type 2 diabetic (T2D) individuals. Our analysis demonstrates the significant association between transcriptomic AS profiles and cell-type-specificity, which could be applied to distinguish the clustering of major endocrine cell types. Moreover, AS profiles are enabled to clearly define the mature subset of β-cells in healthy controls, which is completely lost in T2D. Further analysis reveals that RNA-binding proteins (RBPs), heterogeneous nuclear ribonucleoproteins (hnRNPs) and FXR1 family proteins are predicted to induce the functional impairment of β-cells through regulating AS profiles. Finally, trajectory analysis of endocrine cells suggests the β-cell identity shift through dedifferentiation and transdifferentiation of β-cells during the progression of T2D. Together, our study provides a mechanism for regulating β-cell functions and suggests the significant contribution of AS program during diabetes pathogenesis.

Beta cell dedifferentiation in type 1 diabetes: sacrificing function for survival?

The pathogeneses of type 1 and type 2 diabetes involve the progressive loss of functional beta cell mass, primarily attributed to cellular demise and/or dedifferentiation. While the scientific community has devoted significant attention to unraveling beta cell dedifferentiation in type 2 diabetes, its significance in type 1 diabetes remains relatively unexplored. This perspective article critically analyzes the existing evidence for beta cell dedifferentiation in type 1 diabetes, emphasizing its potential to reduce beta cell autoimmunity. Drawing from recent advancements in both human studies and animal models, we present beta cell identity as a promising target for managing type 1 diabetes. We posit that a better understanding of the mechanisms of beta cell dedifferentiation in type 1 diabetes is key to pioneering interventions that balance beta cell function and immunogenicity.

Enhancing β-cell function and identity in type 2 diabetes: The protective role of Coptis deltoidea C. Y. Cheng et Hsiao via glucose metabolism modulation and AMPK signaling activation

BACKGROUND

Abnormalities in glucose metabolism may be the underlying cause of β-cell dysfunction and identity impairment resulting from high glucose exposure. In China, Coptis deltoidea C. Y. Cheng et Hsiao (YL) has demonstrated remarkable hypoglycemic effects.

HYPOTHESIS/PURPOSE

To investigate the hypoglycemic effect of YL and determine the mechanism of YL in treating diabetes.

METHODS

A type 2 diabetes mouse model was used to investigate the pharmacodynamics of YL. YL was administrated once daily for 8 weeks. The hypoglycemic effect of YL was assessed by fasting blood glucose, an oral glucose tolerance test, insulin levels, and other indexes. The underlying mechanism of YL was examined by targeting glucose metabolomics, western blotting, and qRT-PCR. Subsequently, the binding capacity between predicted AMP-activated protein kinase (AMPK) and important components of YL (Cop, Ber, and Epi) were validated by molecular docking and surface plasmon resonance. Then, in AMPK knockdown MIN6 cells, the mechanisms of Cop, Ber, and Epi were inversely confirmed through evaluations encompassing glucose-stimulated insulin secretion, markers indicative of β-cell identity, and the examination of glycolytic genes and products.

RESULTS

YL (0.9 g/kg) treatment exerted notable hypoglycemic effects and protected the structural integrity and identity of pancreatic β-cells. Metabolomic analysis revealed that YL inhibited the hyperactivated glycolysis pathway in diabetic mice, thereby regulating the products of the tricarboxylic acid cycle. KEGG enrichment revealed the intimate relationship of this process with the AMPK signaling pathway. Cop, Ber, and Epi in YL displayed high binding affinities for AMPK protein. These compounds played a pivotal role in preserving the identity of pancreatic β-cells and amplifying insulin secretion. The mechanism underlying this process involved inhibition of glucose uptake, lowering intracellular lactate levels, and elevating acetyl coenzyme A and ATP levels through AMPK signaling. The use of a glycolytic inhibitor corroborated that attenuation of glycolysis restored β-cell identity and function.

CONCLUSION

YL demonstrates significant hypoglycemic efficacy. We elucidated the potential mechanisms underlying the protective effects of YL and its active constituents on β-cell function and identity by observing glucose metabolism processes in pancreatic tissue and cells. In this intricate process, AMPK plays a pivotal regulatory role.

The neutrophil-to-apolipoprotein A1 ratio is associated with adverse outcomes in patients with acute decompensated heart failure at different glucose metabolic states: a retrospective cohort study

BACKGROUND

The present study was performed to assess the association between the neutrophil-to-apolipoprotein A1 ratio (NAR) and outcomes in patients with acute decompensated heart failure (ADHF) at different glucose metabolism states.

METHODS

We recruited 1233 patients with ADHF who were admitted to Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University from December 2014 to October 2019. The endpoints were defined as composites of cardiovascular death, nonfatal myocardial infarction, nonfatal ischemic stroke and exacerbation of chronic heart failure. The restricted cubic spline was used to determine the best cutoff of NAR, and patients were divided into low and high NAR groups. Kaplan-Meier plots and multivariable Cox proportional hazard models were used to investigate the association between NAR and the risk of adverse outcomes.

RESULTS

During the five-year follow-up period, the composite outcome occurred in 692 participants (56.1%). After adjusting for potential confounding factors, a higher NAR was associated with a higher incidence of composite outcomes in the total cohort (Model 1: HR = 1.42, 95% CI = 1.22-1.65, P<0.001; Model 2: HR = 1.29, 95% CI = 1.10-1.51, P = 0.002; Model 3: HR = 1.20, 95% CI = 1.01-1.42, P = 0.036). At different glucose metabolic states, a high NAR was associated with a high risk of composite outcomes in patients with diabetes mellitus (DM) (Model 1: HR = 1.54, 95% CI = 1.25-1.90, P<0.001; Model 2: HR = 1.40, 95% CI = 1.13-1.74, P = 0.002; Model 3: HR = 1.31, 95% CI = 1.04-1.66, P = 0.022), and the above association was not found in patients with prediabetes mellitus (Pre-DM) or normal glucose regulation (NGR) (both P>0.05).

CONCLUSIONS

The NAR has predictive value for adverse outcomes of ADHF with DM, which implies that the NAR could be a potential indicator for the management of ADHF.

1-L Transcription of SARS-CoV-2 Spike Protein S1 Subunit

The COVID-19 pandemic prompted rapid research on SARS-CoV-2 pathogenicity. Consequently, new data can be used to advance the molecular understanding of SARS-CoV-2 infection. The present bioinformatics study discusses the "spikeopathy" at the molecular level and focuses on the possible post-transcriptional regulation of the SARS-CoV-2 spike protein S1 subunit in the host cell/tissue. A theoretical protein-RNA recognition code was used to check the compatibility of the SARS-CoV-2 spike protein S1 subunit with mRNAs in the human transcriptome (1-L transcription). The principle for this method is elucidated on the defined RNA binding protein GEMIN5 (gem nuclear organelle-associated protein 5) and RNU2-1 (U2 spliceosomal RNA). Using the method described here, it was shown that 45% of the genes/proteins identified by 1-L transcription of the SARS-CoV-2 spike protein S1 subunit are directly linked to COVID-19, 39% are indirectly linked to COVID-19, and 16% cannot currently be associated with COVID-19. The identified genes/proteins are associated with stroke, diabetes, and cardiac injury.

Intermittent fasting protects β-cell identity and function in a type-2 diabetes model

Type 2 diabetes (T2DM) is caused by the interaction of multiple genes and environmental factors. T2DM is characterized by hyperglycemia, insulin secretion deficiency and insulin resistance. Chronic hyperglycemia induces β-cell dysfunction, loss of β-cell mass/identity and β-cell dedifferentiation. Intermittent fasting (IF) a commonly used dietary regimen for weight-loss, also induces metabolic benefits including reduced blood glucose, improved insulin sensitivity, reduced adiposity, inflammation, oxidative-stress and increased fatty-acid oxidation; however, the mechanisms underlying these effects in pancreatic β-cells remain elusive. KK and KKAy, mouse models of polygenic T2DM spontaneously develop hyperglycemia, glucose intolerance, glucosuria, impaired insulin secretion and insulin resistance. To determine the long-term effects of IF on T2DM, 6-weeks old KK and KKAy mice were subjected to IF for 16 weeks. While KKAy mice fed ad-libitum demonstrated severe hyperglycemia (460 mg/dL) at 6 weeks of age, KK mice showed blood glucose levels of 230 mg/dL, but progressively became severely diabetic by 22-weeks. Strikingly, both KK and KKAy mice subjected to IF showed reduced blood glucose and plasma insulin levels, decreased body weight gain, reduced plasma triglycerides and cholesterol, and improved insulin sensitivity. They also demonstrated enhanced expression of the β-cell transcription factors NKX6.1, MAFA and PDX1, and decreased expression of ALDH1a3 suggesting protection from loss of β-cell identity by IF. IF normalized glucose stimulated insulin secretion in islets from KK and KKAy mice, demonstrating improved β-cell function. In addition, hepatic steatosis, gluconeogenesis and inflammation was decreased particularly in KKAy-IF mice, indicating peripheral benefits of IF. These results have important implications as an optional intervention for preservation of β-cell identity and function in T2DM.

Glucagon-producing α-cell transcriptional identity and reprogramming towards insulin production

β-Cell replacement by in situ reprogramming of non-β-cells is a promising diabetes therapy. Following the observation that near-total β-cell ablation in adult mice triggers the reprogramming of pancreatic α-, δ-, and γ-cells into insulin (INS)-producing cells, recent studies are delving deep into the mechanisms controlling adult α-cell identity. Systematic analyses of the α-cell transcriptome and epigenome have started to pinpoint features that could be crucial for maintaining α-cell identity. Using different transgenic and chemical approaches, significant advances have been made in reprogramming α-cells in vivo into INS-secreting cells in mice. The recent reprogramming of human α-cells in vitro is an important step forward that must now be complemented with a comprehensive molecular dissection of the mechanisms controlling α-cell identity.

Canalizing cell fate by transcriptional repression

Precision in the establishment and maintenance of cellular identities is crucial for the development of multicellular organisms and requires tight regulation of gene expression. While extensive research has focused on understanding cell type-specific gene activation, the complex mechanisms underlying the transcriptional repression of alternative fates are not fully understood. Here, we provide an overview of the repressive mechanisms involved in cell fate regulation. We discuss the molecular machinery responsible for suppressing alternative fates and highlight the crucial role of sequence-specific transcription factors (TFs) in this process. Depletion of these TFs can result in unwanted gene expression and increased cellular plasticity. We suggest that these TFs recruit cell type-specific repressive complexes to their cis-regulatory elements, enabling them to modulate chromatin accessibility in a context-dependent manner. This modulation effectively suppresses master regulators of alternative fate programs and their downstream targets. The modularity and dynamic behavior of these repressive complexes enables a limited number of repressors to canalize and maintain major and minor cell fate decisions at different stages of development.

Genetic lineage tracing identifies adaptive mechanisms of pancreatic islet β cells in various mouse models of diabetes with distinct age of initiation

During the pathogenesis of type 1 diabetes (T1D) and type 2 diabetes (T2D), pancreatic islets, especially the β cells, face significant challenges. These insulin-producing cells adopt a regeneration strategy to compensate for the shortage of insulin, but the exact mechanism needs to be defined. High-fat diet (HFD) and streptozotocin (STZ) treatment are well-established models to study islet damage in T2D and T1D respectively. Therefore, we applied these two diabetic mouse models, triggered at different ages, to pursue the cell fate transition of islet β cells. Cre-LoxP systems were used to generate islet cell type-specific (α, β, or δ) green fluorescent protein (GFP)-labeled mice for genetic lineage tracing, thereinto β-cell GFP-labeled mice were tamoxifen induced. Single-cell RNA sequencing (scRNA-seq) was used to investigate the evolutionary trajectories and molecular mechanisms of the GFP-labeled β cells in STZ-treated mice. STZ-induced diabetes caused extensive dedifferentiation of β cells and some of which transdifferentiated into a or δ cells in both youth- and adulthood-initiated mice while this phenomenon was barely observed in HFD models. β cells in HFD mice were expanded via self-replication rather than via transdifferentiation from α or δ cells, in contrast, α or δ cells were induced to transdifferentiate into β cells in STZ-treated mice (both youth- and adulthood-initiated). In addition to the re-dedifferentiation of β cells, it is also highly likely that these "α or δ" cells transdifferentiated from pre-existing β cells could also re-trans-differentiate into insulin-producing β cells and be beneficial to islet recovery. The analysis of ScRNA-seq revealed that several pathways including mitochondrial function, chromatin modification, and remodeling are crucial in the dynamic transition of β cells. Our findings shed light on how islet β cells overcome the deficit of insulin and the molecular mechanism of islet recovery in T1D and T2D pathogenesis.

Environmental factor reversibly determines cellular identity through opposing Integrators that unify epigenetic and transcriptional pathways

Organisms must adapt to environmental stresses to ensure their survival and prosperity. Different types of stresses, including thermal, mechanical, and hypoxic stresses, can alter the cellular state that accompanies changes in gene expression but not the cellular identity determined by a chromatin state that remains stable throughout life. Some tissues, such as adipose tissue, demonstrate remarkable plasticity and adaptability in response to environmental cues, enabling reversible cellular identity changes; however, the mechanisms underlying these changes are not well understood. We hypothesized that positive and/or negative "Integrators" sense environmental cues and coordinate the epigenetic and transcriptional pathways required for changes in cellular identity. Adverse environmental factors such as pollution disrupt the coordinated control contributing to disease development. Further research based on this hypothesis will reveal how organisms adapt to fluctuating environmental conditions, such as temperature, extracellular matrix stiffness, oxygen, cytokines, and hormonal cues by changing their cellular identities.

Repression of latent NF-κB enhancers by PDX1 regulates β cell functional heterogeneity

Interactions between lineage-determining and activity-dependent transcription factors determine single-cell identity and function within multicellular tissues through incompletely known mechanisms. By assembling a single-cell atlas of chromatin state within human islets, we identified β cell subtypes governed by either high or low activity of the lineage-determining factor pancreatic duodenal homeobox-1 (PDX1). β cells with reduced PDX1 activity displayed increased chromatin accessibility at latent nuclear factor κB (NF-κB) enhancers. Pdx1 hypomorphic mice exhibited de-repression of NF-κB and impaired glucose tolerance at night. Three-dimensional analyses in tandem with chromatin immunoprecipitation (ChIP) sequencing revealed that PDX1 silences NF-κB at circadian and inflammatory enhancers through long-range chromatin contacts involving SIN3A. Conversely, Bmal1 ablation in β cells disrupted genome-wide PDX1 and NF-κB DNA binding. Finally, antagonizing the interleukin (IL)-1β receptor, an NF-κB target, improved insulin secretion in Pdx1 hypomorphic islets. Our studies reveal functional subtypes of single β cells defined by a gradient in PDX1 activity and identify NF-κB as a target for insulinotropic therapy.

Pancreatic islet cell plasticity: Pathogenic or therapeutically exploitable?

The development of pancreatic islet endocrine cells is a tightly regulated process leading to the generation of distinct cell types harbouring different hormones in response to small changes in environmental stimuli. Cell differentiation is driven by transcription factors that are also critical for the maintenance of the mature islet cell phenotype. Alteration of the insulin-secreting β-cell transcription factor set by prolonged metabolic stress, associated with the pathogenesis of diabetes, obesity or pregnancy, results in the loss of β-cell identity through de- or transdifferentiation. Importantly, the glucose-lowering effects of approved and experimental antidiabetic agents, including glucagon-like peptide-1 mimetics, novel peptides and small molecules, have been associated with preventing or reversing β-cell dedifferentiation or promoting the transdifferentiation of non-β-cells towards an insulin-positive β-cell-like phenotype. Therefore, we review the manifestations of islet cell plasticity in various experimental settings and discuss the physiological and therapeutic sides of this phenomenon, focusing on strategies for preventing β-cell loss or generating new β-cells in diabetes. A better understanding of the molecular mechanisms underpinning islet cell plasticity is a prerequisite for more targeted therapies to help prevent β-cell decline in diabetes.

Dynamic regulation of pancreatic β cell function and gene expression by the SND1 coregulator in vitro

The pancreatic β cell synthesizes, packages, and secretes insulin in response to glucose-stimulation to maintain blood glucose homeostasis. Under diabetic conditions, a subset of β cells fail and lose expression of key transcription factors (TFs) required for insulin secretion. Among these TFs is Pancreatic and duodenal homeobox 1 (PDX1), which recruits a unique subset of transcriptional coregulators to modulate its activity. Here we describe a novel interacting partner of PDX1, the Staphylococcal Nuclease and Tudor domain-containing protein (SND1), which has been shown to facilitate protein-protein interactions and transcriptional control through diverse mechanisms in a variety of tissues. PDX1:SND1 interactions were confirmed in rodent β cell lines, mouse islets, and human islets. Utilizing CRISPR-Cas9 gene editing technology, we deleted Snd1 from the mouse β cell lines, which revealed numerous differentially expressed genes linked to insulin secretion and cell proliferation, including limited expression of Glp1r. We observed Snd1 deficient β cell lines had reduced cell expansion rates, GLP1R protein levels, and limited cAMP accumulation under stimulatory conditions, and further show that acute ablation of Snd1 impaired insulin secretion in rodent and human β cell lines. Lastly, we discovered that PDX1:SND1 interactions were profoundly reduced in human β cells from donors with type 2 diabetes (T2D). These observations suggest the PDX1:SND1 complex formation is critical for controlling a subset of genes important for β cell function and is targeted in diabetes pathogenesis.

Paired box 6 gene delivery preserves beta cells and improves islet transplantation efficacy

Loss of pancreatic beta cells is the central feature of all forms of diabetes. Current therapies fail to halt the declined beta cell mass. Thus, strategies to preserve beta cells are imperatively needed. In this study, we identified paired box 6 (PAX6) as a critical regulator of beta cell survival. Under diabetic conditions, the human beta cell line EndoC-βH1, db/db mouse and human islets displayed dampened insulin and incretin signalings and reduced beta cell survival, which were alleviated by PAX6 overexpression. Adeno-associated virus (AAV)-mediated PAX6 overexpression in beta cells of streptozotocin-induced diabetic mice and db/db mice led to a sustained maintenance of glucose homeostasis. AAV-PAX6 transduction in human islets reduced islet graft loss and improved glycemic control after transplantation into immunodeficient diabetic mice. Our study highlights a previously unappreciated role for PAX6 in beta cell survival and raises the possibility that ex vivo PAX6 gene transfer into islets prior to transplantation might enhance islet graft function and transplantation outcome.

Biological activity of recombinant human PDX1 protein produced from Escherichia coli

Pancreatic and duodenum homeobox 1 (PDX1) is considered as a pivotal transcription factor that acts as a "master regulator" in pancreatogenesis and maintenance of β-cells. Earlier study has reported that PDX1 also functions as a tumor suppressor in human gastric cancer cells by inhibiting cell growth. Here, we report the bioactivity of the purified human PDX1 fusion protein using various assays like cell migration, proliferation, cell cycle analysis, and gene expression. In cancer cells, recombinant PDX1 protein reduced cell migration and proliferation, and arrested cell growth by inducing apoptosis in gastric cancer cells. In pancreatic ductal cancer cells, the application of the PDX1 protein resulted in the induction of insulin gene expression. The results of these experiments demonstrate the biological activity imparted by recombinant human PDX1 fusion protein on gastric and pancreatic cancer cells and its usefulness as a biological tool to elucidate its function in various cellular processes.

m6 A mRNA methylation: Biological features, mechanisms, and therapeutic potentials in type 2 diabetes mellitus

As the most common internal post-transcriptional RNA modification in eukaryotic cells, N6-methyladenosine (m6 A) performs a dynamic and reversible role in a variety of biological processes mediated by methyltransferases (writers), demethylases (erasers), and m6 A binding proteins (readers). M6 A methylation enables transcriptome conversion in different signals that regulate various physiological activities and organ development. Over the past few years, emerging studies have identified that mRNA m6 A regulators defect in β-cell leads to abnormal regulation of the target mRNAs, thereby resulting in β-cell dysfunction and loss of β-cell identity and mass, which are strongly associated with type 2 diabetes mellitus (T2DM) pathogenesis. Also, mRNA m6 A modification has been implicated with insulin resistance in muscles, fat, and liver cells/tissues. In this review, we elaborate on the biological features of m6 A methylation; provide a comprehensive overview of the underlying mechanisms that how it controls β-cell function, identity, and mass as well as insulin resistance; highlight its connections to glucose metabolism and lipid metabolism linking to T2DM; and further discuss its role in diabetes complications and its therapeutic potentials for T2DM diagnosis and treatment.

Developmental dynamics of the single nucleus regulatory landscape of pig hippocampus

The hippocampus is a brain region associated with memory, learning and spatial navigation, its aging-related dysfunction is a common sign of Alzheimer's disease. Pig is a good model for human neurodegenerative disease, but our understanding of the regulatory program of the pig hippocampus and its cross-species conservation in humans remains limited. Here, we profiled chromatin accessibility in 33,409 high-quality nuclei and gene expression in 8,122 high-quality nuclei of the pig hippocampus at four postnatal stages. We identified 510,908 accessible chromatin regions (ACRs) in 12 major cell types, among which progenitor cells such as neuroblasts and oligodendrocyte progenitor cells showed a dynamic decrease from early to later developmental stages. We revealed significant enrichment of transposable elements in cell type-specific ACRs, particularly in neuroblasts. We identified oligodendrocytes as the most prominent cell type with the greatest number of genes that showed significant changes during the development. We identified ACRs and key transcription factors underlying the trajectory of neurogenesis (such as POU3F3 and EGR1) and oligodendrocyte differentiation (RXRA and FOXO6). We examined 27 Alzheimer's disease-related genes in our data and found that 15 showed cell type-specific activity (TREM2, RIN3 and CLU), and 15 genes displayed age-associated dynamic activity (BIN1, RABEP1 and APOE). We intersected our data with human genome-wide association study results to detect neurological disease-associated cell types. The present study provides a single nucleus-accessible chromatin landscape of the pig hippocampus at different developmental stages and is helpful for the exploration of pigs as a biomedical model in human neurodegenerative diseases.

Establishment of Pancreatic β-Cell-Specific Gene Knockout System Based on CRISPR-Cas9 Technology With AAV8-Mediated gRNA Delivery

The Cre-loxP system provides valuable resources to analyze the importance of tissue-specific gene knockout (KO), including pancreatic β-cells associated with the pathogenesis of diabetes. However, it is expensive and time consuming to generate transgenic mice harboring floxed genes of interest and cross them with cell-specific Cre expression mice. We establish a βCas9 system with mice expressing Cas9 in pancreatic β-cells and adeno-associated virus 8 (AAV8)-mediated guide RNA (gRNA) delivery based on CRISPR-Cas9 technology to overcome those shortcomings. Interbreeding CAG-loxP-STOP-loxP (LSL)-Cas9 with Ins1-Cre mice generates normal glucose-tolerant βCas9 mice expressing Cas9 with fluorescent reporter EGFP specifically in β-cells. We also show significant β-cell-specific gene KO efficiency with AAV8-mediated delivery of gRNA for EGFP reporter by intraperitoneal injection in the mice. As a proof of concept, we administered AAV8 to βCas9 mice for expressing gRNA for Pdx1, a culprit gene of maturity-onset diabetes of the young 4. As reported previously, we demonstrate that those mice show glucose intolerance with transdifferentiation of Pdx1 KO β-cells into glucagon-expressing cells. We successfully generated a convenient β-cell-specific gene KO system with βCas9 mice and AAV8-mediated gRNA delivery.

ARTICLE HIGHLIGHTS

MafB regulates NLRP3 inflammasome activation by sustaining p62 expression in macrophages

Activation of the NLRP3 inflammasome is a two-step process: the priming and the activating. The priming step involves the induction of NLRP3 and pro-IL-1β, while the activating step leads to the full inflammasome activation triggered by a NLRP3 activator. Although mechanisms underlying the NLRP3 inflammasome activation have been increasingly clear, the regulation of this process remains incompletely understood. In this study, we find that LPS and Pseudomonas aeruginosa cause a rapid downregulation in MafB transcription in macrophages, which leads to a quick decline in the level of MafB protein because MafB is short-lived and constantly degraded by the ubiquitin/proteasome system. We find that MafB knockdown or knockout markedly enhances the NLRP3, but not the NLRP1, NLRC4, or AIM2, inflammasome activation in macrophages. Conversely, pharmacological induction of MafB diminishes the NLRP3 inflammasome activation. Mechanistically, we find that MafB sustains the expression of p62, a key mediator of autophagy/mitophagy. We find that MafB inhibits mitochondrial damage, and mitochondrial ROS production and DNA cytoplasmic release. Furthermore, we find that myeloid MafB deficient mice demonstrate increased systemic and lung IL-1β production in response to LPS treatment and P. aeruginosa infection and deficient lung P. aeruginosa clearance in vivo. In conclusion, our study demonstrates that MafB is an important negative regulator of the NLRP3 inflammasome. Our findings suggest that strategies elevating MafB may be effective to treat immune disorders due to excessive activation of the NLRP3 inflammasome.

Oxidative Stress Biomarkers in Cystic Fibrosis and Cystic Fibrosis-Related Diabetes in Children: A Literature Review

The most common inherited condition that results in death, particularly in those of Caucasian heritage, is cystic fibrosis (CF). Of all the young adults diagnosed with cystic fibrosis, 20% will develop hyperglycemia as a complication, later classified as a disease associated with cystic fibrosis. Impaired insulin secretion and glucose intolerance represent the primary mechanisms associated with diabetes (type 1 or type 2) and cystic fibrosis. Oxidative stress represents the imbalance between oxygen-reactive species and antioxidant defense mechanisms. This pathogenic mechanism is vital in triggering other chronic diseases, including cystic fibrosis-related diabetes. It is essential to understand oxidative stress and the significant impact it has on CFRD. This way, therapies can be individually adjusted and tailored to each patient's needs. This review aims to understand the connection between CFRD and oxidative stress. As a subsidiary element, we analyzed the effects of glycemic balance on complications and their evolution over time, providing insights into their potential benefits in mitigating oxidative stress-associated complications.

Raptor levels are critical for β-cell adaptation to a high-fat diet in male mice

OBJECTIVE

The essential role of raptor/mTORC1 signaling in β-cell survival and insulin processing has been recently demonstrated using raptor knock-out models. Our aim was to evaluate the role of mTORC1 function in adaptation of β-cells to insulin resistant state.

METHOD

Here, we use mice with heterozygous deletion of raptor in β-cells (βraHet) to assess whether reduced mTORC1 function is critical for β-cell function in normal conditions or during β-cell adaptation to high-fat diet (HFD).

RESULTS

Deletion of a raptor allele in β-cells showed no differences at the metabolic level, islets morphology, or β-cell function in mice fed regular chow. Surprisingly, deletion of only one allele of raptor increases apoptosis without altering proliferation rate and is sufficient to impair insulin secretion when fed a HFD. This is accompanied by reduced levels of critical β-cell genes like Ins1, MafA, Ucn3, Glut2, Glp1r, and specially PDX1 suggesting an improper β-cell adaptation to HFD.

CONCLUSION

This study identifies that raptor levels play a key role in maintaining PDX1 levels and β-cell function during the adaptation of β-cell to HFD. Finally, we identified that Raptor levels regulate PDX1 levels and β-cell function during β-cell adaptation to HFD by reduction of the mTORC1-mediated negative feedback and activation of the AKT/FOXA2/PDX1 axis. We suggest that Raptor levels are critical to maintaining PDX1 levels and β-cell function in conditions of insulin resistance in male mice.

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.

Species-specific roles for the MAFA and MAFB transcription factors in regulating islet β cell identity

Type 2 diabetes (T2D) is associated with compromised identity of insulin-producing pancreatic islet β cells, characterized by inappropriate production of other islet cell-enriched hormones. Here, we examined how hormone misexpression was influenced by the MAFA and MAFB transcription factors, closely related proteins that maintain islet cell function. Mice specifically lacking MafA in β cells demonstrated broad, population-wide changes in hormone gene expression with an overall gene signature closely resembling islet gastrin+ (Gast+) cells generated under conditions of chronic hyperglycemia and obesity. A human β cell line deficient in MAFB, but not one lacking MAFA, also produced a GAST+ gene expression pattern. In addition, GAST was detected in human T2D β cells with low levels of MAFB. Moreover, evidence is provided that human MAFB can directly repress GAST gene transcription. These results support a potentially novel, species-specific role for MafA and MAFB in maintaining adult mouse and human β cell identity, respectively. Here, we discuss the possibility that induction of Gast/GAST and other non-β cell hormones, by reduction in the levels of these transcription factors, represents a dysfunctional β cell signature.

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

Introduction

Recently, the involvement of ferroptotic cell death in the reduction of β-cell mass in diabetes has been demonstrated. To elucidate the mechanisms of β-cell ferroptosis and potential antidiabetic effects of the ferroptosis inhibitor ferrostatin-1 (Fer-1) in vivo, a mouse model of type 1 diabetes (T1D) was used.

Methods

Animals were divided into three groups: control (vehicle-treated), diabetic (streptozotocin-treated, 40 mg/kg, from days 1-5), and diabetic treated with Fer-1 (1 mg/kg, from days 1-21). On day 22, glycemia and insulinemia were measured and pancreases were isolated for microscopic analyses.

Results

Diabetes disturbed general parameters of β-cell mass (islet size, β-cell abundance and distribution) and health (insulin and PDX-1 expression), increased lipid peroxidation in islet cells, and phagocytic removal of iron-containing material. It also downregulated the main players of the antiferroptotic pathway - Nrf2, GPX4, and xCT. In contrast, Fer-1 ameliorated the signs of deterioration of β-cell/islets, decreased lipid peroxidation, and reduced phagocytic activity, while upregulated expression of Nrf2 (and its nuclear translocation), GPX4, and xCT in β-cell/islets.

Discussion

Overall, our study confirms ferroptosis as an important mode of β-cell death in T1D and suggests antiferroptotic agents as a promising strategy for the prevention and treatment of diabetes.

IMT504 protects beta cells against apoptosis and maintains beta cell identity, without modifying proliferation

We have demonstrated that oligodeoxynucleotide IMT504 promotes significant improvement in the diabetic condition in diverse animal models. Based on these results, here we evaluated whether these effects observed in vivo could be due to direct effects on β-cells. We demonstrate by immunofluorescence that IMT504 enters the cell and locates in cytoplasm where it induces GSK-3β phosphorylation that inactivates this kinase. As GSK-3β tags Pdx1 for proteasomal degradation, by inactivating GSK-3β, IMT504 induces an increase in Pdx1 protein levels, demonstrated by Western blotting. Concomitantly, an increase in Ins2 and Pdx1 gene transcription was observed, with no significant increase in insulin content or secretion. Enhanced Pdx1 is promising since it is a key transcription factor for insulin synthesis and is also described as an essential factor for the maintenance β-cell phenotype and function. Dose-dependent inhibition of H2 O2 -induced apoptosis determined by ELISA as well as decreased expression of Bax was also observed. These results were confirmed in another β-cell line, beta-TC-6 cells, in which a cytokine mix induced apoptosis that was reversed by IMT504. In addition, an inhibitor of IMT504 entrance into cells abrogated the effect IMT504. Based on these results we conclude that the β-cell recovery observed in vivo may include direct effects of IMT504 on β-cells, by maintaining their identity/phenotype and protecting them from oxidative stress and cytokine-induced apoptosis. Thus, this work positions IMT504 as a promising option in the framework of the search of new therapies for type I diabetes treatment.

β-Cell-Specific E2f1 Deficiency Impairs Glucose Homeostasis, β-Cell Identity, and Insulin Secretion

The loss of pancreatic β-cell identity has emerged as an important feature of type 2 diabetes development, but the molecular mechanisms are still elusive. Here, we explore the cell-autonomous role of the cell-cycle regulator and transcription factor E2F1 in the maintenance of β-cell identity, insulin secretion, and glucose homeostasis. We show that the β-cell-specific loss of E2f1 function in mice triggers glucose intolerance associated with defective insulin secretion, altered endocrine cell mass, downregulation of many β-cell genes, and concomitant increase of non-β-cell markers. Mechanistically, epigenomic profiling of the promoters of these non-β-cell upregulated genes identified an enrichment of bivalent H3K4me3/H3K27me3 or H3K27me3 marks. Conversely, promoters of downregulated genes were enriched in active chromatin H3K4me3 and H3K27ac histone marks. We find that specific E2f1 transcriptional, cistromic, and epigenomic signatures are associated with these β-cell dysfunctions, with E2F1 directly regulating several β-cell genes at the chromatin level. Finally, the pharmacological inhibition of E2F transcriptional activity in human islets also impairs insulin secretion and the expression of β-cell identity genes. Our data suggest that E2F1 is critical for maintaining β-cell identity and function through sustained control of β-cell and non-β-cell transcriptional programs.

ARTICLE HIGHLIGHTS

β-Cell-specific E2f1 deficiency in mice impairs glucose tolerance. Loss of E2f1 function alters the ratio of α- to β-cells but does not trigger β-cell conversion into α-cells. Pharmacological inhibition of E2F activity inhibits glucose-stimulated insulin secretion and alters β- and α-cell gene expression in human islets. E2F1 maintains β-cell function and identity through control of transcriptomic and epigenetic programs.

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.

Characterization of cell-fate decision landscapes by estimating transcription factor dynamics

Time-specific modulation of gene expression during differentiation by transcription factors promotes cell diversity. However, estimating their dynamic regulatory activity at the single-cell level and in a high-throughput manner remains challenging. We present FateCompass, an integrative approach that utilizes single-cell transcriptomics data to identify lineage-specific transcription factors throughout differentiation. By combining a probabilistic framework with RNA velocities or differentiation potential, we estimate transition probabilities, while a linear model of gene regulation is employed to compute transcription factor activities. Considering dynamic changes and correlations of expression and activities, FateCompass identifies lineage-specific regulators. Our validation using in silico data and application to pancreatic endocrine cell differentiation datasets highlight both known and potentially novel lineage-specific regulators. Notably, we uncovered undescribed transcription factors of an enterochromaffin-like population during in vitro differentiation toward ß-like cells. FateCompass provides a valuable framework for hypothesis generation, advancing our understanding of the gene regulatory networks driving cell-fate decisions.

Pharmacological inhibition of human EZH2 can influence a regenerative β-like cell capacity with in vitro insulin release in pancreatic ductal cells

BACKGROUND

Therapeutic replacement of pancreatic endocrine β-cells is key to improving hyperglycaemia caused by insulin-dependent diabetes . Whilst the pool of ductal progenitors, which give rise to the endocrine cells, are active during development, neogenesis of islets is repressed in the human adult. Recent human donor studies have demonstrated the role of EZH2 inhibition in surgically isolated exocrine cells showing reactivation of insulin expression and the influence on the H3K27me3 barrier to β-cell regeneration. However, those studies fall short on defining the cell type active in transcriptional reactivation events. This study examines the role of the regenerative capacity of human pancreatic ductal cells when stimulated with pharmacological inhibitors of the EZH2 methyltransferase.

RESULTS

Human pancreatic ductal epithelial cells were stimulated with the EZH2 inhibitors GSK-126, EPZ6438, and triptolide using a 2- and 7-day protocol to determine their influence on the expression of core endocrine development marker NGN3, as well as β-cell markers insulin, MAFA, and PDX1. Chromatin immunoprecipitation studies show a close correspondence of pharmacological EZH2 inhibition with reduced H3K27me3 content of the core genes, NGN3, MAFA and PDX1. Consistent with the reduction of H3K27me3 by pharmacological inhibition of EZH2, we observe measurable immunofluorescence staining of insulin protein and glucose-sensitive insulin response.

CONCLUSION

The results of this study serve as a proof of concept for a probable source of β-cell induction from pancreatic ductal cells that are capable of influencing insulin expression. Whilst pharmacological inhibition of EZH2 can stimulate secretion of detectable insulin from ductal progenitor cells, further studies are required to address mechanism and the identity of ductal progenitor cell targets to improve likely methods designed to reduce the burden of insulin-dependent diabetes.