β-cell dedifferentiation in type 2 diabetes: Interplay of metabolic stress, endoplasmic reticulum dysfunction, and forkhead box protein O1 inhibition

Abstract

In this editorial, we highlight the study by Wang et al published in a recent issue of the World Journal of Diabetes. Type 2 diabetes is increasingly recognized as a β-cell dysfunction disorder, with apoptosis and dedifferentiation being key factors in insulin secretion loss. β-cell dedifferentiation is a regression from a mature insulin-secretory phenotype to a progenitor-like state, characterized by the loss of key transcription factors such as pancreatic and duodenal homeobox 1 and MAF bZIP transcription factor A, and the ectopic expression of developmental markers such as neurogenin 3 and aldehyde dehydrogenase 1 family member A3. This editorial discusses the key role of metabolic stress-saturated fatty acids and high glucose-in triggering dedifferentiation through endoplasmic reticulum (ER) stress and repression of the forkhead box protein O1 (FoxO1) transcription factor. The study by Wang et al demonstrated how ER dysfunction and FoxO1 suppression collaborate to destabilize β-cell identity. Notably, evidence suggests that this process can be reversed under certain circumstances, with potential for therapies aiming to redifferentiate β-cells or prevent identity loss. We also outline the therapeutic potential of modulating ER stress pathways, controlling FoxO1 activity, and developing biomarkers to track β-cell plasticity in patients. Overall, β-cell dedifferentiation knowledge and manipulation offer new avenues for the treatment of diabetes by restoring functional β-cell mass.

Key Words: Diabetes; Pancreatic β-cells; Dedifferentiation; Endoplasmic reticulum stress; Forkhead box protein O1; Aldehyde dehydrogenase 1 family member A3

Core Tip: This editorial highlights the emerging role of β-cell dedifferentiation as a central mechanism of β-cell failure in type 2 diabetes, alongside apoptosis. We emphasize recent findings that chronic metabolic stressors, namely glucotoxicity and lipotoxicity, initiate ER stress and suppress forkhead box protein O1 activity, leading to the loss of β-cell identity and function. The reversibility of this process introduces new therapeutic possibilities aimed at preserving or restoring endogenous insulin production.

INTRODUCTION

Type 2 diabetes (T2D) is a growing global health crisis characterized by insulin resistance and involving pancreatic β-cell dysfunction. While β-cell apoptosis has long been considered the primary mechanism of β-cell failure in diabetes, recent research has revealed β-cell dedifferentiation to be an equally important pathologic process[1,2]. Dedifferentiation implicates the functional regression of mature insulin-producing cells into a progenitor-like phenotype, marked by the downregulation of key β-cell identity markers such as pancreatic and duodenal homeobox 1 (PDX1), MAF bZIP transcription factor A (MAFA), and insulin, with concomitant aberrant re-expression of progenitor cell markers such as neurogenin 3 (Ngn3) and POU class 5 homeobox 1/octamer-binding transcription factor 4[3]. The rediscovery of β-cell plasticity through dedifferentiation has transformed our understanding of diabetes pathophysiology, suggesting that functional β-cell mass is more dynamic than previously appreciated[4].

The recent work by Wang et al[5] has advanced this field by delineating the molecular mechanisms whereby endoplasmic reticulum (ER) stress and forkhead box protein O1 (FoxO1) inhibition drive β-cell dedifferentiation in the context of metabolic stress. Their findings provide valuable insights into how chronic nutrient excess, a hallmark of T2D, initiates cellular reprogramming mechanisms that compromise β-cell identity and function. This editorial synthesizes the current understanding of β-cell dedifferentiation, discussing its cellular characteristics, molecular inducers, and therapeutic promise as a target in the treatment of diabetes. We assess the multifaceted interplay among metabolic stress, ER dysfunction, and transcriptional regulation in driving β-cell identity loss, while evaluating new strategies to prevent or reverse the process for therapeutic benefit.

CHARACTERISTICS OF Β-CELL DEDIFFERENTIATION

β-cell dedifferentiation is a pathologic reversion of specialized endocrine cells towards a less differentiated state, effectively altering their transcriptional program and functional capacity[6]. The process is characterized by three signature molecular features that collectively result in loss of β-cell identity[3]. First, the significant downregulation of β-cell-enriched genes, including key transcription factors PDX1, MAFA, and Nkx6.1, which are crucial for maintaining the function of mature β-cells, and reduction in the expression of genes involved in glucose sensing and insulin biosynthesis. Second, dedifferentiated cells exhibit aberrant expression of “forbidden” genes that are normally suppressed in mature β-cells such as aldehyde dehydrogenase 1 family member A3 (Aldh1a3), a biomarker of the dedifferentiated state[2,7]. Third, there is reactivation of endocrine progenitor markers, such as Ngn3, hairy and enhancer of split family basic helix-loop-helix transcription factor 1, and POU class 5 homeobox 1/octamer-binding transcription factor 4, reflecting partial reversal to an earlier developmental state[8].

At the functional level, these molecular changes manifest as impaired glucose-stimulated insulin secretion and cellular metabolism abnormalities. Interestingly, dedifferentiation appears to be a graded process rather than an all-or-none phenomenon, and cells may exist in various intermediate developmental stages along the differentiation spectrum. This plasticity may underlie the observations of some studies reporting the existence of insulin-positive cells with progenitor marker expression in diabetic islets[2]. Notably, the reversibility of dedifferentiation, as shown by redifferentiation potential experiments under appropriate conditions, offers exciting therapeutic promise for diabetes treatment[9,10].

EVIDENCE FROM HUMAN STUDIES AND ANIMAL MODELS

The pathophysiological relevance of β-cell dedifferentiation has been firmly established by both human pathology research and experimental animal models. Post-mortem examination of pancreatic tissue from patients with T2D has shown the presence of β-cells co-expressing insulin with progenitor markers such as Ngn3 and Aldh1a3, with direct demonstration of dedifferentiation in human diabetes[2]. These data were complemented by observations from rodent models of diabetes. In db/db mice, a classic model of obesity-induced diabetes, progressive β-cell dysfunction is coupled with mounting expression of dedifferentiation markers and loss of mature β-cell identity[11,12]. Similarly, mice subjected to high-fat diets develop β-cell dedifferentiation phenotypes that resemble human T2D, including reduced PDX1 expression and elevated Aldh1a3[13]. Genetic models have further lent credence to the dedifferentiation concept as a pathophysiological mechanism; for instance, β-cell-specific FoxO1 knockout in mice leads to dedifferentiation upon exposure to metabolic stress conditions like aging or multiparity[1]. Importantly, the extent of dedifferentiation appears to correlate with disease severity in the different models, suggesting that it may be an adaptive response to chronic metabolic stress that later becomes maladaptive. Furthermore, the conserved dedifferentiation phenomena across different species strengthens its fundamental role in diabetes pathogenesis and argues for the translational relevance of mechanistic studies in model systems.

TRIGGERS OF Β-CELL DEDIFFERENTIATION

The initiation and progression of β-cell dedifferentiation are driven by several correlated factors, with metabolic stress emerging as a prominent trigger. Chronic hyperglycemia and elevated free fatty acids, in particular palmitic acid, create a toxic environment that hinders normal β-cell function and identity[5]. High glucose suppresses major β-cell transcription factors such as PDX1, MAFA, and paired box protein 6, while activating stress-response pathways that trigger phenotypic conversion[14]. Lipotoxicity, mediated through saturated fatty acids such as palmitate, exacerbates these effects through the induction of oxidative stress and ER dysfunction[15]. Synergy between glucotoxicity and lipotoxicity is particularly potent at inducing dedifferentiation, as demonstrated by Wang et al[5], who found synergistic effects when insulinoma (INS-1) β-cells were exposed to both high glucose and palmitic acid.

Other than metabolic effects, inflammatory cytokines associated with diabetes (e.g., interleukin-1 beta, tumor necrosis factor alpha) can also induce dedifferentiation, most likely through the activation of stress kinase pathways[16]. There is also a genetic predisposition, as illustrated by reports that mutations in β-cell transcription factors or ion channels can predispose to dedifferentiation in the absence of overt metabolic stress[17]. The coincidence of such diverse triggers on common downstream pathways, particularly those involving ER stress and transcriptional reprogramming, is consistent with the hypothesis that dedifferentiation represents a final common pathway for β-cell dysfunction in response to various insults. These triggers must be understood to establish a targeted therapy that prevents or reverses the process.

ROLE OF ER STRESS

ER stress is a central mediator of β-cell dedifferentiation under conditions of metabolic overload. The ER, which is responsible for protein folding and calcium homeostasis, becomes overwhelmed when β-cells are chronically exposed to high glucose and fatty acids, inducing activation of the unfolded protein response (UPR)[5]. Wang et al[5] provided direct ultrastructural evidence of ER stress in dedifferentiating β-cells, demonstrating the severe dilation of the ER lumen in palmitic acid-stressed and high glucose-stressed INS-1 cells. Molecular examination revealed concurrent upregulation of UPR markers such as phosphorylated eukaryotic translation initiation factor alpha and activating transcription factor 4. The causal contribution of ER stress has been further supported by experiments showing that chemical chaperones like 4-phenylbutyric acid can rescue dedifferentiation, while ER stressors like tunicamycin can replicate the phenotype[5]. These findings are in line with previous work showing that ER stress pathways are activated in the β-cells of T2D human and animal models[3]. Interestingly, the interaction between ER stress and dedifferentiation also appears to be bidirectional; while ER stress causes loss of β-cell identity, dedifferentiated cells can also become more susceptible to subsequent ER stress, creating a vicious cycle that exacerbates β-cell dysfunction. The inositol-requiring enzyme 1 alpha branch of the UPR also seems particularly important in this context, as its genetic deletion has been shown to induce dedifferentiation but also unexpectedly to protect against autoimmune destruction in non-obese diabetic mice[18]. Such complex interactions place ER stress as both a driver and a consequence of β-cell dedifferentiation and thus make it an attractive candidate for therapeutic intervention.

FOXO1 INHIBITION AND β-CELL IDENTITY

The forkhead box transcription factor FoxO1 plays a pivotal role in the preservation of β-cell identity under stress, and its failure contributes significantly to dedifferentiation processes. FoxO1 is generally a nutrient sensor and stability factor for mature β-cells, and it regulates the expression of important β-cell identity genes like PDX1 and MAFA[19]. Wang et al[5] demonstrated that metabolic stress conditions lead to the inhibition of FoxO1 through post-translational modifications and reduced nuclear localization, thus suppressing its transcriptional activity. Their use of the selective FoxO1 inhibitor AS1842856 has provided compelling evidence for the protective role of FoxO1 by showing that pharmacological inhibition exacerbates palmitate/glucose-induced dedifferentiation. These findings are consistent with genetic studies that have shown β-cell-specific FoxO1 knockout mice to develop diabetes with dramatic dedifferentiation characteristics under metabolic stress[1].

Mechanistically, FoxO1 appears to maintain β-cell identity via several mechanisms, namely promoting the expression of mature β-cell genes, suppressing progenitor markers, and controlling cellular metabolism toward glucose-stimulated insulin secretion[19]. Of particular interest is the crosstalk between FoxO1 and ER stress pathways. While FoxO1 activity can mitigate ER stress, chronic ER stress can conversely inhibit FoxO1, creating another vicious cycle in the development of diabetes[5]. Paradoxically, the role of FoxO1 in β-cells appears to be context-dependent, with both overactivation and inhibition being deleterious, suggesting that modulation, rather than outright inhibition or activation, may be required for therapeutic benefit. The convergence of metabolic stress, ER dysfunction, and FoxO1 inhibition on β-cell dedifferentiation highlights the complexity of diabetes pathophysiology while identifying enticing nodal points for intervention.

THERAPEUTIC IMPLICATIONS AND FUTURE DIRECTIONS

The recognition of β-cell dedifferentiation as a major contributor to diabetes pathogenesis opens new possibilities for the development of therapeutic strategies aimed at the maintenance or recovery of β-cell function. Several promising strategies have been proposed by recent research. First, targeting ER stress with chemical chaperones like 4-phenylbutyric acid or tauroursodeoxycholic acid could be a means to maintain β-cell identity by eliminating one of the main drivers of dedifferentiation[5]. Second, control of FoxO1 activity, directly through pharmacological means or indirectly through upstream regulators like sirtuin 1 activators, has the potential to stabilize the mature β-cell phenotype[19,20]. Third, promoting the redifferentiation of regressed β-cells using growth factors or extracellular matrix proteins has shown promise in model systems[10]. However, there are significant challenges in translating these approaches to the clinic.

From a diagnostic perspective, the development of robust biomarkers to monitor β-cell dedifferentiation state in patients would be a major advance, with the potential to facilitate earlier intervention[2]. Elevated levels of Aldh1a3 correlate with β-cell dysfunction in the early stages of T2D, offering a promising biomarker for presymptomatic diagnosis. In both human and murine studies[2,21], β-cells that acquire a progenitor-like state during dedifferentiation upregulate Aldh1a3; however, its detection in blood or islet-derived exosomes has yet to be determined. Nevertheless, specificity concerns remain because Aldh1a3 is also expressed in other tissues (e.g., liver, adipose), and its dynamic regulation during T2D progression has to be validated[22,23]. Combining Aldh1a3 with complementary biomarkers, such as β-cell identity transcripts (insulin, PDX1) in circulating free DNA or exosomal microRNAs (e.g., microRNA-375), can further enhance diagnostic precision. Moreover, circulating Aldh1a3 can complement imaging by providing molecular insights into identity loss. Non-invasive imaging targeting β-cells specific markers could revolutionize the monitoring of β-cell health by enabling real-time, longitudinal assessment of functional mass, identity, and stress states without invasive biopsies. The use of positron emission tomography and magnetic resonance imaging probes that bind to β-cell surface proteins or metabolic activity markers (e.g., vesicular monoamine transporter 2 or glucagon-like peptide-1 receptor) also offer non-invasive ways to visualize and assess the state of β-cells[24].

Additional studies are also needed to tackle the possibility of heterogeneity in dedifferentiation patterns in different patient groups and diabetes subtypes. The dedifferentiation of pancreatic β-cells in diabetes depends on diabetes duration, genetic susceptibility, and comorbidity. Prolonged diabetes impairs glucotoxicity/Lipotoxicity and reduces β-cell identity factors (e.g., PDX1, MAFA), which may lead to irreversible epigenetic changes[14,25]. Genetic risk alleles (transcription factor-7-like 2 protein, hepatocyte nuclear factor 1 alpha) impair stress tolerance, whereas protective variants (solute carrier family 30 member 8) may set back dedifferentiation[26-28]. Furthermore, β-cell dysfunction accelerates in comorbid conditions like obesity and hypertension, in synergy with oxidative stress or hyperglycemia via inflammatory factors (interleukin-6, tumor necrosis factor alpha)[29]. Heterogeneity has also been reported across diabetes subtypes. Type 1 diabetes has cytokine-mediated dedifferentiation pre-autoimmunity[30], while T2D is associated with severity of metabolic stress, and monogenic (e.g., hepatocyte nuclear factor 1 alpha-maturity-onset diabetes of the young) forms reflect mutation-specific transcriptional failure[31]. Epigenetic drivers, silencing INS/PDX1 via DNA methylation, loss of microRNA-375, and histone modifications-deliver reversible therapeutic targets (e.g., histone deacetylase inhibitors)[32,33].

Further work should also explore how epigenetic modifications function to initiate and maintain dedifferentiated states, since this could reveal new targets for therapy[34]. Any treatment targeting β-cell identity will also need to be carefully titrated for benefit vs risk, particularly with regard to the potential for off-target effects on other cell types. As mechanisms of β-cell dedifferentiation become better understood, the potential will increase to develop new, potentially disease-modifying treatments for diabetes that address the fundamental deficiency of functional β-cell mass.

Notably, ER stress inhibitors and FoxO1 activators are being investigated in clinical trials for diseases linked to cellular dysfunction. In patients with T2D with metabolic syndromes and their complications, ER stress inhibitors and FoxO1 activators have been tested[35]. FoxO1 activators, such as metformin, which indirectly enhance FoxO1 via AMP-activated protein kinase, and experimental compounds, like AS1842856, are under investigation for treatment of T2D and cardiovascular diseases, to boost oxidative stress resistance and glucose regulation[36-38]. Challenges include balancing FoxO1’s dual roles in cytoprotection and potential tumorigenesis.

STUDY LIMITATIONS

Although comprehensive, the study by Wang et al[5] had limitations. The INS-1 cell line, while valuable, lacks the vitality and complexity of human islets. Furthermore, rat and human β-cells differ in several key aspects, including islet composition and gene regulation[39]. The study would be strengthened by validation in human-derived β-like cells or cadaveric islets. The pharmacological inhibition of FoxO1 could potentially have off-target effects not elucidated in the study. Additional studies utilizing clustered regularly interspaced short palindromic repeats-mediated knockout or rescue experiments could delineate direct vs indirect effects. Furthermore, long-term studies to assess the stability and plasticity of dedifferentiated cells are recommended.

CONCLUSION

Wang et al[5] have reported a robust and multifaceted examination of β-cell dedifferentiation driven in response to metabolic stress. Their demonstration that ER stress is both an inducer and regulator of dedifferentiation, and that FoxO1 acts as a master molecular brake advances our understanding of β-cell plasticity in diabetes. As the field evolves toward regenerative therapy, the molecular landscape mapped here will undoubtedly be an important roadmap. However, translating these findings into clinical practice will require first addressing significant challenges. For instance, ER stress or FoxO1 targeting in humans will require balancing efficacy with safety, as systemic inhibition of these pathways carries the potential for off-target effects on other cell types or organ systems. Furthermore, heterogeneity of diabetes from autoimmune β-cell destruction in type 1 diabetes to metabolic derangement in T2D necessitates constituency-specific design to confirm intervention effects are context-specific. Combinatorial strategies, i.e. co-administering FoxO1 modulation with existing treatments such as glucagon-like peptide-1 agonists, to synergistically enhance β-cell regeneration might be explored in the future. Understanding temporal dynamics of dedifferentiation (e.g., determining whether early-stage interventions are more effective) and applying single-cell technologies to map patient-specific dedifferentiation trajectories might also further improve precision medicine paradigms. Finally, the development of in vitro human β-cell models or organoid systems that recapitulate diabetic microenvironments would secure the transition of mechanistic understanding to clinically relevant strategies. In an era of increasing diabetes prevalence and treatment complexity, understanding how β-cells lose, and perhaps regain, their identity is of the utmost importance. Studies like this form a foundation for precision in β-cell recovery and preservation, ultimately improving the quality of life for individuals with diabetes. To realize this potential, transdisciplinary collaboration among basic researchers, clinicians, and bioengineers will be necessary, as will longitudinal clinical trials to assess durability and safety of dedifferentiation-targeted therapy.