Pancreatic β cell dedifferentiation in diabetes and redifferentiation following insulin therapy

Partial remission of type 1 diabetes: Do immunometabolic events define the honeymoon period?

Partial clinical remission in Type 1 diabetes (T1D) refers to a transient phase of improved glucose control following diagnosis. During this period, endogenous islet β-cells continue to produce and secrete insulin, resulting in lower exogenous insulin requirements and improved glycaemic status. Partial remission is often described colloquially as the 'honeymoon phase', a period lasting from months to years which is heterogeneous across patient groups. In this review, we discuss the immunometabolic events that may control the duration of the partial remission period by highlighting how glucose metabolism supports immune cell-driven inflammatory and autoimmune events. We thus propose that precise control of blood glucose within a healthy range delays the deleterious consequences that arise from autoimmune mechanisms within pancreatic islets, ultimately leading to the extension of the honeymoon phase. We further discuss data supporting the notion that managing blood glucose effectively also improves islet β-cell mass, function and maturity markers. Collectively, these paradigms help explain the success of recent clinical trial outcomes and offer novel opportunities to intervene in future study designs.

Integrating Spatial and Single-Nucleus Transcriptomic Data to Assess the Effects of Intrauterine Hyperglycemia on Fetal Pancreatic Development

Maternal pregestational diabetes mellitus (PGDM) can lead to adverse fetal outcomes, including lasting impacts on pancreatic development. However, the specific impacts of maternal PGDM on cellular functions and intercellular communication within the fetal pancreas remain poorly understood. Here, single-nucleus RNA sequencing and spatial transcriptomics (ST) are employed to investigate cellular responses and spatial changes in the fetal pancreas (E16.5 and E18.5) under maternal PGDM conditions. The findings reveal significant cellular heterogeneity among acinar and beta cells, along with pronounced metabolic stress responses. More importantly, decreased insulin secretion is observed and accompanied by the compensatory increase of Pdx1, Nkx6.2, and Mafa, and substantial alterations in cell-cell communication across multiple cell types. ST analysis further highlights enhanced spatial enrichment in cellular niches exposed to maternal PGDM. These findings provide valuable insights into the molecular mechanisms underlying fetal pancreatic response to maternal PGDM and offer a detailed spatiotemporal perspective on these processes.

Endoplasmic reticulum stress and forkhead box protein O1 inhibition mediate palmitic acid and high glucose-induced β-cell dedifferentiation

BACKGROUND

Type 2 diabetes mellitus is characterized by pancreatic β-cell dysfunction and insulin resistance. Studies have suggested that β-cell dedifferentiation is one of the pathogeneses of β-cell dysfunction, but the detailed mechanism is still unclear. Most studies of β-cell dedifferentiation rely on rodent models and human pathological specimens. The development of in vitro systems can facilitate the exploration of β-cell dedifferentiation.

AIM

To investigate the molecular mechanism of β-cell dedifferentiation. Hence, an in vitro model of β-cell dedifferentiation induced by palmitic acid and high glucose was established using the INS-1 832/13 cell line.

METHODS

The study was further analyzed using RNA-sequencing, transmission electron microscopy, quantitative real-time polymerase chain reaction and Western blot.

RESULTS

Results showed that the treatment of palmitic acid and high glucose significantly up-regulated β-cell forbidden genes and endocrine precursor cell marker genes, and down-regulated the expression of β-cell specific markers. Data showed that dedifferentiated INS-1 cells up-regulated the expression of endoplasmic reticulum (ER) stress-related genes. Moreover, the results also showed that forkhead box O1 (Foxo1) inhibition potentiated genetic changes in β-cell dedifferentiation induced by palmitic acid and high glucose.

CONCLUSION

ER stress is sufficient to trigger β-cell dedifferentiation and is necessary for palmitic acid and high glucose-induced β-cell dedifferentiation. Foxo1 inhibition can further enhance these phenomena.

Jiedu Tongluo Tiaogan Formula Modulates Glycolipid Metabolism in Type 2 Diabetes via Pyroptosis: Network Pharmacology and In Vivo Analysis

Type 2 diabetes mellitus (T2DM) is characterized by pancreatic β-cell dysfunction and insulin resistance, with pyroptosis emerging as a key contributor to β-cell loss. Jiedu Tongluo Tiaogan Formula (JTTF), a traditional Chinese medicine (TCM), has shown clinical efficacy in T2DM management, but its mechanism linking pyroptosis remains unexplored. This study integrates UPLC-MS/MS, network pharmacology, and in vivo experiments to elucidate JTTF's anti-diabetic mechanisms. UPLC-MS/MS identified 441 compounds in JTTF, predominantly alkaloids, flavonoids, phenols, and terpenoids. Network pharmacology revealed JTTF's multi-target effects on T2DM-associated pyroptosis, particularly via the NLRP3/Caspase-1/GSDMD pathway. In diabetic mice, JTTF dose-dependently reduced fasting blood glucose, insulin resistance, and dyslipidemia, while restoring pancreatic β-cell morphology. Mechanistically, JTTF suppressed NLRP3 inflammasome activation, downregulated Caspase-1 and GSDMD expression, and attenuated IL-1β/IL-18 release. Notably, this study provides the first evidence of JTTF's anti-pyroptotic effects in T2DM, highlighting its unique ability to modulate glycolipid metabolism and inflammatory cell death concurrently. These findings underscore JTTF's translational promise for preserving β-cell function and suggest future exploration of non-classical pyroptosis pathways. Our work bridges traditional medicine and molecular pharmacology, paving the way for clinical trials and integrative T2DM therapies.

β-Cell Dedifferentiation in HOMA-βlow and HOMA-βhigh Subjects

CONTEXT

β-Cell dedifferentiation ratio is increased in type 2 diabetes; but its direct link to in vivo β-cell function in human remains unclear.

OBJECTIVE

The present study was designed to investigate whether β-cell dedifferentiation in situ was closely associated with β-cell function in vivo and to identify targets crucial for β-cell dedifferentiation/function in human.

METHODS

We acquired homeostasis model assessment of β-cell function (HOMA-β) values, calculated the number of hormone-negative endocrine cells, and evaluated important markers and novel candidates for β-cell dedifferentiation/function on paraneoplastic pancreatic tissues from 13 patients with benign pancreatic cystic neoplasm or intrapancreatic accessory spleen.

RESULTS

Both the β-cell dedifferentiation ratio and the dedifferentiation marker (Aldh1a3) were inversely related to in vivo β-cell function (HOMA-β) and in situ β-cell functional markers Glut2 and Ucn3 in humans. Moreover, the islets from HOMA-βlow subjects were manifested as (1) increased β-cell dedifferentiation ratio, (2) enriched dedifferentiation maker Aldh1a3, and (3) lower expression of Glut2 and Ucn3 compared with those from HOMA-βhigh subjects. We found that basic leucine zipper transcription factor 2 (Bach2) expression was significantly induced in islets from HOMA-βlow patients and was positively correlated with the ratio of β-cell dedifferentiation in humans.

CONCLUSION

Our findings emphasize the contribution of β-cell dedifferentiation to β-cell dysfunction in humans. Bach2 induction in β-cells with higher frequency of dedifferentiation observed in HOMA-βlow subjects reinforces its distinctive role as a pharmaceutical target of β-cell dedifferentiation for the treatment of people with diabetes.

Retrograde mitochondrial signaling governs the identity and maturity of metabolic tissues

Mitochondrial damage is a hallmark of metabolic diseases, including diabetes, yet the consequences of compromised mitochondria in metabolic tissues are often unclear. In this work, we report that dysfunctional mitochondrial quality control engages a retrograde (mitonuclear) signaling program that impairs cellular identity and maturity in β cells, hepatocytes, and brown adipocytes. Targeted deficiency throughout the mitochondrial quality control pathway, including genome integrity, dynamics, or turnover, impaired the oxidative phosphorylation machinery, activating the mitochondrial integrated stress response, eliciting chromatin remodeling, and promoting cellular immaturity rather than apoptosis to yield metabolic dysfunction. Pharmacologic blockade of the integrated stress response in vivo restored β cell identity after the loss of mitochondrial quality control. Targeting mitochondrial retrograde signaling may therefore be promising in the treatment or prevention of metabolic disorders.

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.

In humans increase in intrapancreatic adipose tissue predicts beta-cell dedifferentiation score before diabetes onset: A pilot study

BACKGROUND

The role of intrapancreatic fat (WAT) in the development of T2D remains debated. In T2D, β-cell dedifferentiation is one of the mechanisms responsible for β-cell failure but its role in prediabetes is unknown. We aimed to investigate the relation between WAT and β-cell dedifferentiation prior to diabetes onset.

METHODS

We evaluated pancreatic samples from patients without history of diabetes, who had previously undergone an oral glucose tolerance test and hyperglycemic clamp. Subjects were divided into 3 glucose tolerance groups: normal (NGT), altered (IGT) or newly diagnosed diabetes (nDM). Dedifferentiation and WAT% were morphologically assessed.

RESULTS

WAT was higher in nDM patients compared to NGT and IGT (WAT nDM 43.79 ± 20.83 %, IGT 10.67 ± 8.5 %, NGT 4.43 ± 4.37 %). We observed a progressive increase in dedifferentiation score, in parallel with worsening glucose tolerance (from NGT to IGT to nDM; 4.8 ± 3.8; 32.37 ± 7.4; 40.38 ± 19 respectively). A strong linear regression established that WAT could statistically significantly predict dedifferentiated β-cells (R = 0.86, p = 0.005), and that the predicted increase in dedifferentiated β-cells was 1.25 points for every extra one-point change in WAT. Interestingly, the WAT and dedifferentiation score variable pair were significantly related to 1-hour post-load glycemia.

CONCLUSIONS

The accumulation of WAT might be responsible for dedifferentiation, making it a potential new target to curb diabetes onset.

The role of glucose-6-phosphatase activity in glucose homeostasis and its potential for diabetes therapy

Glucose-6-phosphatase catalytic subunit (G6PC)1 and G6PC2 are crucial for glucose metabolism, regulating processes like glycolysis, gluconeogenesis, and glycogenolysis. Despite their structural and functional similarities, G6PC1 and G6PC2 exhibit distinct tissue-specific expression patterns, G6P hydrolysis kinetics, and physiological functions. This review provides a comprehensive overview of their enzymology and distinct roles in glucose homeostasis. We examine how inactivating mutations in G6PC1 lead to glycogen storage disease, and how elevated G6PC1 and G6PC2 expression can affect the incidence of diabetic complications, risk for type 2 diabetes mellitus (T2DM) and various cancers. We also discuss the potential of inhibiting G6PC1 and G6PC2 to protect against complications from elevated blood glucose levels, and highlight drug development efforts targeting G6PC1 and G6PC2, and the therapeutic potential of inhibitors for disease prevention.

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.

Lineage tracing of pancreatic cells for mechanistic and therapeutic insights

Recent advances in lineage-tracing technologies have significantly improved our understanding of pancreatic cell biology, particularly in elucidating the ontogeny and regenerative capacity of pancreatic cells. A deeper appreciation of the mechanisms underlying pancreatic cell identity and plasticity holds the potential to inform the development of new therapeutic modalities for conditions such as diabetes and pancreatitis. With this goal in mind, here we summarize advances, challenges, and future directions in tracing pancreatic cell origins and fates using lineage-tracing technologies. Given their essential role for blood glucose regulation, we pay particular attention on the insights gained from endocrine cells, especially β-cells.

Beta cells are essential drivers of pancreatic ductal adenocarcinoma development

Pancreatic endocrine-exocrine crosstalk plays a key role in normal physiology and disease. For instance, endocrine islet beta (β) cell secretion of insulin or cholecystokinin (CCK) promotes progression of pancreatic adenocarcinoma (PDAC), an exocrine cell-derived tumor. However, the cellular and molecular mechanisms that govern endocrine-exocrine signaling in tumorigenesis remain incompletely understood. We find that β cell ablation impedes PDAC development in mice, arguing that the endocrine pancreas is critical for exocrine tumorigenesis. Conversely, obesity induces β cell hormone dysregulation, alters CCK-dependent peri-islet exocrine cell transcriptional states, and enhances islet proximal tumor formation. Single-cell RNA-sequencing, in silico latent-space archetypal and trajectory analysis, and genetic lineage tracing in vivo reveal that obesity stimulates postnatal immature β cell expansion and adaptation towards a pro-tumorigenic CCK+ state via JNK/cJun stress-responsive signaling. These results define endocrine-exocrine signaling as a driver of PDAC development and uncover new avenues to target the endocrine pancreas to subvert exocrine tumorigenesis.

Recent Glycemia Is a Major Determinant of β-Cell Function in Type 2 Diabetes Mellitus

BACKGRUOUND

Progressive deterioration of β-cell function is a characteristic of type 2 diabetes mellitus (T2DM). We aimed to investigate the relative contributions of clinical factors to β-cell function in T2DM.

METHODS

In a T2DM cohort of 470 adults (disease duration 0 to 41 years), β-cell function was estimated using insulinogenic index (IGI), disposition index (DI), oral disposition index (DIO), and homeostasis model assessment of β-cell function (HOMA-B) derived from a 75 g oral glucose tolerance test (OGTT). The relative contributions of age, sex, disease duration, body mass index, glycosylated hemoglobin (HbA1c) levels (at the time of the OGTT), area under the curve of HbA1c over time (HbA1c AUC), coefficient of variation in HbA1c (HbA1c CV), and antidiabetic agents use were compared by standardized regression coefficients. Longitudinal analyses of these indices were also performed.

RESULTS

IGI, DI, DIO, and HOMA-B declined over time (P<0.001 for all). Notably, HbA1c was the most significant factor affecting IGI, DI, DIO, and HOMA-B in the multivariable regression analysis. Compared with HbA1c ≥9%, DI was 1.9-, 2.5-, 3.7-, and 5.5-fold higher in HbA1c of 8%-<9%, 7%-<8%, 6%-<7%, and <6%, respectively, after adjusting for confounding factors (P<0.001). Conversely, β-cell function was not affected by the type or duration of antidiabetic agents, HbA1c AUC, or HbA1c CV. The trajectories of the IGI, DI, DIO, and HOMA-B mirrored those of HbA1c.

CONCLUSION

β-Cell function declines over time; however, it is flexible, being largely affected by recent glycemia in T2DM.

Harnessing beta cell regeneration biology for diabetes therapy

The pandemic scale of diabetes mellitus is alarming, its complications remain devastating, and current treatments still pose a major burden on those affected and on the healthcare system as a whole. As the disease emanates from the destruction or dysfunction of insulin-producing pancreatic β-cells, a real cure requires their restoration and protection. An attractive strategy is to regenerate β-cells directly within the pancreas; however, while several approaches for β-cell regeneration have been proposed in the past, clinical translation has proven challenging. This review scrutinizes recent findings in β-cell regeneration and discusses their potential clinical implementation. Hereby, we aim to delineate a path for innovative, targeted therapies to help shift from 'caring for' to 'curing' diabetes.

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

ETHNOPHARMACOLOGICAL RELEVANCE

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

AIM OF THE STUDY

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

MATERIALS AND METHODS

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

RESULT

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

CONCLUSIONS

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

A cellular identity crisis? Plasticity changes during aging and rejuvenation

Cellular plasticity in adult multicellular organisms is a protective mechanism that allows certain tissues to regenerate in response to injury. Considering that aging involves exposure to repeated injuries over a lifetime, it is conceivable that cell identity itself is more malleable-and potentially erroneous-with age. In this review, we summarize and critically discuss the available evidence that cells undergo age-related shifts in identity, with an emphasis on those that contribute to age-associated pathologies, including neurodegeneration and cancer. Specifically, we focus on reported instances of programs associated with dedifferentiation, biased differentiation, acquisition of features from alternative lineages, and entry into a preneoplastic state. As some of the most promising approaches to rejuvenate cells reportedly also elicit transient changes to cell identity, we further discuss whether cell state change and rejuvenation can be uncoupled to yield more tractable therapeutic strategies.

Intense simplified strategy for newly diagnosed type 2 diabetes in patients with severe hyperglycaemia: multicentre, open label, randomised trial

OBJECTIVE

To evaluate whether the intense simplified strategy, which comprises short term intensive insulin therapy (SIIT) followed by subsequent oral antihyperglycaemic regimens, could improve long term glycaemic outcomes in patients with newly diagnosed type 2 diabetes mellitus and severe hyperglycaemia.

DESIGN

Multicentre, open label, randomised trial.

SETTING

15 hospitals in China between December 2017 and December 2020.

PARTICIPANTS

412 patients with newly diagnosed type 2 diabetes and significant hyperglycaemia (HbA1c ≥8.5%).

INTERVENTIONS

All randomised participants initially received SIIT for 2-3 weeks, followed by linagliptin 5 mg/day, metformin 1000 mg/day, combination linagliptin plus metformin, or lifestyle modification alone (control) for 48 weeks.

MAIN OUTCOME MEASURES

The primary outcome was the percentage of participants achieving HbA1c <7.0% at week 48 after SIIT. Secondary outcomes included glycaemic control, β cell function, and variations in insulin sensitivity.

RESULTS

412 participants were randomised. At baseline, the mean age was 46.8 (standard deviation 11.2) years, mean body mass index was 25.8 (2.9), and mean HbA1c was 11.0% (1.9%). At week 48, 80% (78/97), 72% (63/88), and 73% (69/95) of patients in the linagliptin plus metformin, linagliptin, and metformin groups, respectively, achieved HbA1c <7.0%, compared with 60% (56/93) in the control group (P=0.02 overall; P=0.003 for linagliptin plus metformin versus control; P=0.12 for linagliptin versus control; P=0.09 for metformin versus control). Additionally, 70% (68/97), 68% (60/88), and 68% (65/95) of patients in the linagliptin plus metformin, linagliptin, and metformin group, respectively, achieved HbA1c <6.5% compared with 48% (45/93) in the control group (P=0.005 overall; P=0.005 for linagliptin plus metformin versus control; P=0.01 for linagliptin versus control; P=0.008 for metformin versus control; all were significant after adjustment for multiple comparisons). Thus, compared with the control group, participants in the linagliptin plus metformin group were more likely to achieve HbA1c <7.0% at week 48 (odds ratio 2.78, 95% confidence interval 1.37 to 5.65; P=0.005). Moreover, the linagliptin plus metformin group showed the most significant improvement in fasting plasma glucose and β cell function indices. All treatments were well tolerated.

CONCLUSIONS

The intense simplified strategy using subsequent oral therapies post-SIIT, especially the linagliptin plus metformin combination, sustainably improved glycaemic control and β cell function in patients with newly diagnosed type 2 diabetes mellitus and severe hyperglycaemia. This approach offers a promising direction for decision making in the clinical management of type 2 diabetes mellitus.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03194945.

Metabolic Stress Levels Influence the Ability of Myelin Transcription Factors to Regulate β-Cell Identity and Survival

A hallmark of type 2 diabetes (T2D) is endocrine islet β-cell failure, which can occur via cell dysfunction, loss of identity, and/or death. How each is induced remains largely unknown. We used mouse β-cells deficient for myelin transcription factors (Myt TFs; including Myt1, -2, and -3) to address this question. We previously reported that inactivating all three Myt genes in pancreatic progenitor cells (MytPancΔ) caused β-cell failure and late-onset diabetes in mice. Their lower expression in human β-cells is correlated with β-cell dysfunction, and single nucleotide polymorphisms in MYT2 and MYT3 are associated with a higher risk of T2D. We now show that these Myt TF-deficient postnatal β-cells also dedifferentiate by reactivating several progenitor markers. Intriguingly, mosaic Myt TF inactivation in only a portion of islet β-cells did not result in overt diabetes, but this created a condition where Myt TF-deficient β-cells remained alive while activating several markers of Ppy-expressing islet cells. By transplanting MytPancΔ islets into the anterior eye chambers of immune-compromised mice, we directly show that glycemic and obesity-related conditions influence cell fate, with euglycemia inducing several Ppy+ cell markers and hyperglycemia and insulin resistance inducing additional cell death. These findings suggest that the observed β-cell defects in T2D depend not only on their inherent genetic/epigenetic defects but also on the metabolic load.

ARTICLE HIGHLIGHTS

Dopamine-mediated autocrine inhibition of insulin secretion

The aim of the present research was to explore the mechanisms underlying the role of dopamine in the regulation of insulin secretion in beta cells. The effect of dopamine on insulin secretion was investigated on INS 832/13 cell line upon glucose and other secretagogues stimulation. Results show that dopamine significantly inhibits insulin secretion stimulated by both glucose and other secretagogues, while it has no effect on the basal secretion. This effect requires the presence of dopamine during incubation with the various secretagogues. Both electron microscopy and immunohistochemistry indicate that in beta cells the D2 dopamine receptor is localized within the insulin granules. Blocking dopamine entry into the insulin granules by inhibiting the VMAT2 transporter with tetrabenazine causes a significant increase in ROS production. Our results confirm that dopamine plays an important role in the regulation of insulin secretion by pancreatic beta cells through a regulated and precise compartmentalization mechanisms.

Implications of endoplasmic reticulum stress and beta-cell loss in immunodeficient diabetic NRG-Akita mice for understanding monogenic diabetes

BACKGROUND

Immunodeficient mice models have become increasingly important as in vivo models engrafted with human cells or tissues for research. The NOD-Rag1 null Ins2 Akita Il2r null (NRG-Akita) mice is a model combined with immunodeficient NRG and monogenic diabetes Akita mice that develop spontaneous hyperglycemia with progressive loss of pancreatic insulin-producing beta-cells with age. This model is one of the monogenic diabetic models, which has been providing a powerful platform for transplantation experiments of stem cells-generated human β-cells. This research aimed to provide insights into the mechanisms underlying this monogenic diabetes, which remains incompletely understood.

METHODS

Histological and immunofluorescence analyses were conducted on endocrine pancreatic islets to compare NRG wild-type (Wt) controls with NRG-Akita mice. Our investigation focused on assessing the expression of endocrine hormones, transcription factors, proliferation, ER stress, and apoptosis.

RESULTS

Histological analyses on NRG-Akita mice revealed smaller islets at 6-weeks-old, due to fewer β-cells in the islets, compared to NRG-Wt controls, which further progressed with age. The proliferation rate decreased, and apoptosis was abundant in β-cells in NRG-Akita mice. Interestingly, our mechanistic analyses revealed that β-cells in NRG-Akita mice progressively accumulated the endoplasmic reticulum (ER) stresses, leading to a decreased expression of pivotal β-cell transcriptional factor PDX1.

CONCLUSIONS

Altogether, our mechanistic insight into β-cell loss in this model could shed light on essential links between ER stress, proliferation, and cell identity, which might open the door to new therapeutic strategies for various diseases since ER stress is one of the most common features not only in diabetes but also in other degenerative diseases.

Preserving insulin function in diabetes: a case report

BACKGROUND

This case report explores the long-term dynamics of insulin secretion and glycemic control in two patients with diabetes mellitus type 2 over 20 years. The observations underscore the impact of lifestyle interventions, including weight loss and calorie restriction, on insulin secretion patterns and glucose levels during 75 g oral glucose tolerance tests. Additionally, the role of hemoglobin A1c fluctuations, influenced by various factors such as body weight, exercise, and pharmacological interventions, is investigated.

CASE PRESENTATION

Case 1 involves a Japanese woman now in her late 70s who successfully maintained her hemoglobin A1c below 7% for over two decades through sustained weight loss and lifestyle changes. Despite a gradual decline in the homeostasis model assessment of β cell function, the patient exhibited remarkable preservation of insulin secretion patterns over the 20-year follow-up. In case 2, a Japanese woman, now in her early 70s, experienced an improvement in hemoglobin A1c to 6.3% after a period of calorie limitation due to a wrist fracture in 2018. This incident seemed to trigger a temporary rescue of pancreatic β cell function, emphasizing the dynamic nature of insulin secretion. Both cases highlight the potential for pancreatic β cell rescue and underscore the persistence of insulin secretion over the 20-year follow-up. Additionally, we have briefly discussed three additional cases with follow-ups ranging from 10 to 17 years, demonstrating similar trends in glucose and insulin ratios.

CONCLUSIONS

Long-term lifestyle interventions, such as weight loss and calorie restriction, can preserve pancreatic β cell function and maintain glycemic control in type 2 diabetes patients over 20 years. Two patients showed stable or improved insulin secretion and favorable hemoglobin A1c levels, challenging the traditional view of irreversible β cell decline. The findings highlight the importance of personalized, nonpharmacological approaches, suggesting that sustained lifestyle changes can significantly impact diabetes management and potentially rescue β cell function.

β-cell neogenesis: A rising star to rescue diabetes mellitus

BACKGROUND

Diabetes Mellitus (DM), a chronic metabolic disease characterized by elevated blood glucose, is caused by various degrees of insulin resistance and dysfunctional insulin secretion, resulting in hyperglycemia. The loss and failure of functional β-cells are key mechanisms resulting in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).

AIM OF REVIEW

Elucidating the underlying mechanisms of β-cell failure, and exploring approaches for β-cell neogenesis to reverse β-cell dysfunction may provide novel strategies for DM therapy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Emerging studies reveal that genetic susceptibility, endoplasmic reticulum (ER) stress, oxidative stress, islet inflammation, and protein modification linked to multiple signaling pathways contribute to DM pathogenesis. Over the past few years, replenishing functional β-cell by β-cell neogenesis to restore the number and function of pancreatic β-cells has remarkably exhibited a promising therapeutic approach for DM therapy. In this review, we provide a comprehensive overview of the underlying mechanisms of β-cell failure in DM, highlight the effective approaches for β-cell neogenesis, as well as discuss the current clinical and preclinical agents research advances of β-cell neogenesis. Insights into the challenges of translating β-cell neogenesis into clinical application for DM treatment are also offered.

Atypical KCNQ1/Kv7 channel function in a neonatal diabetes patient: Hypersecretion preceded the failure of pancreatic β-cells

KCNQ1/Kv7, a low-voltage-gated K+ channel, regulates cardiac rhythm and glucose homeostasis. While KCNQ1 mutations are associated with long-QT syndrome and type2 diabetes, its function in human pancreatic cells remains controversial. We identified a homozygous KCNQ1 mutation (R397W) in an individual with permanent neonatal diabetes melitus (PNDM) without cardiovascular symptoms. To decipher the potential mechanism(s), we introduced the mutation into human embryonic stem cells and generated islet-like organoids (SC-islets) using CRISPR-mediated homology-repair. The mutation did not affect pancreatic differentiation, but affected channel function by increasing spike frequency and Ca2+ flux, leading to insulin hypersecretion. With prolonged culturing, the mutant islets decreased their secretion and gradually deteriorated, modeling a diabetic state, which accelerated by high glucose levels. The molecular basis was the downregulated expression of voltage-activated Ca2+ channels and oxidative phosphorylation. Our study provides a better understanding of the role of KCNQ1 in regulating insulin secretion and β-cell survival in hereditary diabetes pathology.

Biochemical and metabolic characterization of a G6PC2 inhibitor

Three glucose-6-phosphatase catalytic subunits, that hydrolyze glucose-6-phosphate (G6P) to glucose and inorganic phosphate, have been identified, designated G6PC1-3, but only G6PC1 and G6PC2 have been implicated in the regulation of fasting blood glucose (FBG). Elevated FBG has been associated with multiple adverse clinical outcomes, including increased risk for type 2 diabetes and various cancers. Therefore, G6PC1 and G6PC2 inhibitors that lower FBG may be of prophylactic value for the prevention of multiple conditions. The studies described here characterize a G6PC2 inhibitor, designated VU0945627, previously identified as Compound 3. We show that VU0945627 preferentially inhibits human G6PC2 versus human G6PC1 but activates human G6PC3. VU0945627 is a mixed G6PC2 inhibitor, increasing the Km but reducing the Vmax for G6P hydrolysis. PyRx virtual docking to an AlphaFold2-derived G6PC2 structural model suggests VU0945627 binds two sites in human G6PC2. Mutation of residues in these sites reduces the inhibitory effect of VU0945627. VU0945627 does not inhibit mouse G6PC2 despite its 84% sequence identity with human G6PC2. Mutagenesis studies suggest this lack of inhibition of mouse G6PC2 is due, in part, to a change in residue 318 from histidine in human G6PC2 to proline in mouse G6PC2. Surprisingly, VU0945627 still inhibited glucose cycling in the mouse islet-derived βTC-3 cell line. Studies using intact mouse liver microsomes and PyRx docking suggest that this observation can be explained by an ability of VU0945627 to also inhibit the G6P transporter SLC37A4. These data will inform future computational modeling studies designed to identify G6PC isoform-specific inhibitors.

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.

Gluco-regulation & type 2 diabetes: entrenched misconceptions updated to new governing principles for gold standard management

Our understanding of type 2 diabetes (T2D) has evolved dramatically. Advances have upended entrenched dogmas pertaining to the onset and progression of T2D, beliefs that have prevailed from the early era of diabetes research-and continue to populate our medical textbooks and continuing medical education materials. This review article highlights key insights that lend new governing principles for gold standard management of T2D. From the historical context upon which old beliefs arose to new findings, this article outlines evidence and perspectives on beta cell function, the underlying defects in glucoregulation, the remediable nature of T2D, and, the rationale supporting the shift to complication-centric prescribing. Practical approaches translate this rectified understanding of T2D into strategies that fill gaps in current management practices of prediabetes through late type 2 diabetes.

Loss of β-cell identity and dedifferentiation, not an irreversible process?

Type 2 diabetes (T2D) is a polygenic metabolic disorder characterized by insulin resistance in peripheral tissues and impaired insulin secretion by the pancreas. While the decline in insulin production and secretion was previously attributed to apoptosis of insulin-producing β-cells, recent studies indicate that β-cell apoptosis rates are relatively low in diabetes. Instead, β-cells primarily undergo dedifferentiation, a process where they lose their specialized identity and transition into non-functional endocrine progenitor-like cells, ultimately leading to β-cell failure. The underlying mechanisms driving β-cell dedifferentiation remain elusive due to the intricate interplay of genetic factors and cellular stress. Understanding these mechanisms holds the potential to inform innovative therapeutic approaches aimed at reversing β-cell dedifferentiation in T2D. This review explores the proposed drivers of β-cell dedifferentiation leading to β-cell failure, and discusses current interventions capable of reversing this process, thus restoring β-cell identity and function.

Real-world effectiveness of early insulin therapy on the incidence of cardiovascular events in newly diagnosed type 2 diabetes

Early insulin therapy is capable to achieve glycemic control and restore β-cell function in newly diagnosed type 2 diabetes (T2D), but its effect on cardiovascular outcomes in these patients remains unclear. In this nationwide real-world study, we analyzed electronic health record data from 19 medical centers across China between 1 January 2000, and 26 May 2022. We included 5424 eligible patients (mean age 56 years, 2176 women/3248 men) who were diagnosed T2D within six months and did not have prior cardiovascular disease. Multivariable Cox regression models were used to estimate the associations of early insulin therapy (defined as the first-line therapy for at least two weeks in newly diagnosed T2D patients) with the incidence of major cardiovascular events including coronary heart disease (CHD), stroke, and hospitalization for heart failure (HF). During 17,158 persons years of observation, we documented 834 incident CHD cases, 719 stroke cases, and 230 hospitalized cases for HF. Newly diagnosed T2D patients who received early insulin therapy, compared with those who did not receive such treatment, had 31% lower risk of incident stroke, and 28% lower risk of hospitalization for HF. No significant difference in the risk of CHD was observed. We found similar results when repeating the aforesaid analysis in a propensity-score matched population of 4578 patients and with inverse probability of treatment weighting models. These findings suggest that early insulin therapy in newly diagnosed T2D may have cardiovascular benefits by reducing the risk of incident stroke and hospitalization for HF.

A mathematical model for ketosis-prone diabetes suggests the existence of multiple pancreatic β-cell inactivation mechanisms

Ketosis-prone diabetes mellitus (KPD) is a subtype of type 2 diabetes, which presents much like type 1 diabetes, with dramatic hyperglycemia and ketoacidosis. Although KPD patients are initially insulin-dependent, after a few months of insulin treatment, ~ 70% undergo near-normoglycemia remission and can maintain blood glucose without insulin, as in early type 2 diabetes or prediabetes. Here, we propose that these phenomena can be explained by the existence of a fast, reversible glucotoxicity process, which may exist in all people but be more pronounced in those susceptible to KPD. We develop a simple mathematical model of the pathogenesis of KPD, which incorporates this assumption, and show that it reproduces the phenomenology of KPD, including variations in the ability for patients to achieve and sustain remission. These results suggest that a variation of our model may be able to quantitatively describe variations in the course of remission among individuals with KPD.

Endoplasmic reticulum stress in pancreatic β-cell dysfunction: The potential therapeutic role of dietary flavonoids

Diabetes mellitus (DM) is a global health burden that is characterized by the loss or dysfunction of pancreatic β-cells. In pancreatic β-cells, endoplasmic reticulum (ER) stress is a fact of life that contributes to β-cell loss or dysfunction. Despite recent advances in research, the existing treatment approaches such as lifestyle modification and use of conventional therapeutics could not prevent the loss or dysfunction of pancreatic β-cells to abrogate the disease progression. Therefore, targeting ER stress and the consequent unfolded protein response (UPR) in pancreatic β-cells may be a potential therapeutic strategy for diabetes treatment. Dietary phytochemicals have therapeutic applications in human health owing to their broad spectrum of biochemical and pharmacological activities. Flavonoids, which are commonly obtained from fruits and vegetables worldwide, have shown promising prospects in alleviating ER stress. Dietary flavonoids including quercetin, kaempferol, myricetin, isorhamnetin, fisetin, icariin, apigenin, apigetrin, vitexin, baicalein, baicalin, nobiletin hesperidin, naringenin, epigallocatechin 3-O-gallate hesperidin (EGCG), tectorigenin, liquiritigenin, and acacetin have shown inhibitory effects on ER stress in pancreatic β-cells. Dietary flavonoids modulate ER stress signaling components, chaperone proteins, transcription factors, oxidative stress, autophagy, apoptosis, and inflammatory responses to exert their pharmacological effects on pancreatic β-cells ER stress. This review focuses on the role of dietary flavonoids as potential therapeutic adjuvants in preserving pancreatic β-cells from ER stress. Highlights of the underlying mechanisms of action are also presented as well as possible strategies for clinical translation in the management of DM.

PAX4 gene delivery improves β-cell function in human islets of Type II diabetes

Aim: Type II diabetes (T2D) stems from insulin resistance, with β-cell dysfunction as a hallmark in its progression. Studies reveal that β cells undergo apoptosis or dedifferentiation during T2D development. The transcription factor PAX4 is vital for β differentiation and survival, thus may be a potential enhancer of β-cell function in T2D islets. Materials & methods: Human PAX4 cDNA was delivered into T2D human islets with an adenoviral vector, and its effects on β cells were examined. Results: PAX4 gene delivery significantly improved β-cell survival, and increased β-cell composition in the T2D human islets. Basal insulin and glucose-stimulated insulin secretion in PAX4-expressing islets were substantially higher than untreated or control-treated T2D human islets. Conclusion: Introduced PAX4 expression in T2D human islets improves β-cell function, thus could provide therapeutic benefits for T2D treatment.

Pancreatic β-Cell Identity Change through the Lens of Single-Cell Omics Research

The main hallmark in the development of both type 1 and type 2 diabetes is a decline in functional β-cell mass. This decline is predominantly attributed to β-cell death, although recent findings suggest that the loss of β-cell identity may also contribute to β-cell dysfunction. This phenomenon is characterized by a reduced expression of key markers associated with β-cell identity. This review delves into the insights gained from single-cell omics research specifically focused on β-cell identity. It highlights how single-cell omics based studies have uncovered an unexpected level of heterogeneity among β-cells and have facilitated the identification of distinct β-cell subpopulations through the discovery of cell surface markers, transcriptional regulators, the upregulation of stress-related genes, and alterations in chromatin activity. Furthermore, specific subsets of β-cells have been identified in diabetes, such as displaying an immature, dedifferentiated gene signature, expressing significantly lower insulin mRNA levels, and expressing increased β-cell precursor markers. Additionally, single-cell omics has increased insight into the detrimental effects of diabetes-associated conditions, including endoplasmic reticulum stress, oxidative stress, and inflammation, on β-cell identity. Lastly, this review outlines the factors that may influence the identification of β-cell subpopulations when designing and performing a single-cell omics experiment.

Single-cell sequencing: A promising approach for uncovering the characteristic of pancreatic islet cells in type 2 diabetes

Single-cell sequencing is a novel and rapidly advancing high-throughput technique that can be used to investigating genomics, transcriptomics, and epigenetics at a single-cell level. Currently, single-cell sequencing can not only be used to draw the pancreatic islet cells map and uncover the characteristics of cellular heterogeneity in type 2 diabetes, but can also be used to label and purify functional beta cells in pancreatic stem cells, improving stem cells and islet organoids therapies. In addition, this technology helps to analyze islet cell dedifferentiation and can be applied to the treatment of type 2 diabetes. In this review, we summarize the development and process of single-cell sequencing, describe the potential applications of single-cell sequencing in the field of type 2 diabetes, and discuss the prospects and limitations of single-cell sequencing to provide a new direction for exploring the pathogenesis of type 2 diabetes and finding therapeutic targets.

Remission of type 2 diabetes: always more questions, but enough answers for action

The concept of type 2 diabetes remission is evolving rapidly, and gaining wide public and professional interest, following demonstration that with substantial intentional weight loss almost nine in ten people with type 2 diabetes can reduce their HbA1c level below the diagnostic criterion (48 mmol/mol [6.5%]) without glucose-lowering medications, and improve all features of the metabolic syndrome. Pursuing nomoglycaemia with older drugs was dangerous because of the risk of side effects and hypoglycaemia, so the conventional treatment target was an HbA1c concentration of 53 mmol/mol (7%), meaning that diabetes was still present and allowing disease progression. Newer agents may achieve a normal HbA1c safely and, by analogy with treatments that send cancers or inflammatory diseases into remission, this might also be considered remission. However, although modern glucagon-like peptide-1 receptor agonists and related medications are highly effective for weight loss and glycaemic improvement, and generally safe, many people do not want to take drugs indefinitely, and their cost means that they are not available across much of the world. Therefore, there are strong reasons to explore and research dietary approaches for the treatment of type 2 diabetes. All interventions that achieve sustained weight loss of >10-15 kg improve HbA1c, potentially resulting in remission if sufficient beta cell capacity can be preserved or restored, which occurs with loss of the ectopic fat in liver and pancreas that is found with type 2 diabetes. Remission is most likely with type 2 diabetes of short duration, lower HbA1c and a low requirement for glucose-lowering medications. Relapse is likely with weight regain and among those with a poor beta cell reserve. On current evidence, effective weight management should be provided to all people with type 2 diabetes as soon as possible after diagnosis (or even earlier, at the stage of prediabetes, defined in Europe, Australasia, Canada [and most of the world] as ≥42 and <48 mmol/mol [≥6.0 and <6.5%], and in the USA as HbA1c ≥39 and <48 mmol/mol [≥5.7 and <6.5%]). Raising awareness among people with type 2 diabetes and their healthcare providers that remission is possible will enable earlier intervention. Weight loss of >10 kg and remission lasting 1-2 years may also delay vascular complications, although more evidence is needed. The greatest challenge for research is to improve long-term weight loss maintenance, defining cost-effective approaches tailored to the preferences and needs of people living with type 2 diabetes.

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.

Calorie Restriction Using High-Fat/Low-Carbohydrate Diet Suppresses Liver Fat Accumulation and Pancreatic Beta-Cell Dedifferentiation in Obese Diabetic Mice

In diabetes, pancreatic β-cells gradually lose their ability to secrete insulin with disease progression. β-cell dysfunction is a contributing factor to diabetes severity. Recently, islet cell heterogeneity, exemplified by β-cell dedifferentiation and identified in diabetic animals, has attracted attention as an underlying molecular mechanism of β-cell dysfunction. Previously, we reported β-cell dedifferentiation suppression by calorie restriction, not by reducing hyperglycemia using hypoglycemic agents (including sodium-glucose cotransporter inhibitors), in an obese diabetic mice model (db/db). Here, to explore further mechanisms of the effects of food intake on β-cell function, db/db mice were fed either a high-carbohydrate/low-fat diet (db-HC) or a low-carbohydrate/high-fat diet (db-HF) using similar calorie restriction regimens. After one month of intervention, body weight reduced, and glucose intolerance improved to a similar extent in the db-HC and db-HF groups. However, β-cell dedifferentiation did not improve in the db-HC group, and β-cell mass compensatory increase occurred in this group. More prominent fat accumulation occurred in the db-HC group livers. The expression levels of genes related to lipid metabolism, mainly regulated by peroxisome proliferator-activated receptor α and γ, differed significantly between groups. In conclusion, the fat/carbohydrate ratio in food during calorie restriction in obese mice affected both liver lipid metabolism and β-cell dedifferentiation.

Elucidation of the anti-β-cell dedifferentiation mechanism of a modified Da Chaihu Decoction by an integrative approach of network pharmacology and experimental verification

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Da Chaihu decoction (MDCH) is a traditional Chinese herbal prescription that has been used in the clinic to treat type 2 diabetes (T2D). Previous studies have confirmed that MDCH improves glycemic and lipid metabolism, enhances pancreatic function, and alleviates insulin resistance in patients with T2D and diabetic rats. Evidence has demonstrated that MDCH protects pancreatic β cells via regulating the gene expression of sirtuin 1 (SIRT1) and forkhead box protein O1 (FOXO1). However, the detailed mechanism remains unclear.

AIM OF THE STUDY

Dedifferentiation of pancreatic β cells mediated by FOXO1 has been recognized as the main pathogenesis of T2D. This study aims to investigate the therapeutic effects of MDCH on T2D in vitro and in vivo to elucidate the potential molecular mechanisms.

MATERIALS AND METHODS

To predict the key targets of MDCH in treating T2D, network pharmacology methods were used. A T2D model was induced in diet-induced obese (DIO) C57BL/6 mice with a single intraperitoneal injection of streptozotocin. Glucose metabolism indicators (oral glucose tolerance test, insulin tolerance test), lipid metabolism indicators (total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol), inflammatory factors (C-reactive protein, interleukin 6, tumor necrosis factor alpha), oxidative stress indicators (total antioxidant capacity, superoxide dismutase, malondialdehyde), and hematoxylin and eosin staining were analyzed to evaluate the therapeutic effect of MDCH on T2D. Immunofluorescence staining and quantification of FOXO1, pancreatic and duodenal homeobox 1 (PDX1), NK6 homeobox 1 (NKX6.1), octamer-binding protein 4 (OCT4), neurogenin 3 (Ngn3), insulin, and SIRT1, and Western blot analysis of insulin, SIRT1, and FOXO1 were performed to investigate the mechanism by which MDCH inhibited pancreatic β-cell dedifferentiation.

RESULTS

The chemical ingredients identified in MDCH were predicted to be important for signaling pathways related to lipid metabolism and insulin resistance, including lipids in atherosclerosis, the advanced glycation end product receptor of the advanced glycation end product signaling pathway, and the FOXO signaling pathway. Experimental studies showed that MDCH improved glucose and lipid metabolism in T2D mice, alleviated inflammation and oxidative stress damage, and reduced pancreatic pathological damage. Furthermore, MDCH upregulated the expression levels of SIRT1, FOXO1, PDX1, and NKX6.1, while downregulating the expression levels of OCT4 and Ngn3, which indicated that MDCH inhibited pancreatic dedifferentiation of β cells.

CONCLUSIONS

MDCH has therapeutic effects on T2D, through regulating the SIRT1/FOXO1 signaling pathway to inhibit pancreatic β-cell dedifferentiation, which has not been reported previously.

Pancreatic beta cell regenerative potential of Zanthoxylum chalybeum Engl. Aqueous stem bark extract

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum chalybeum Engl. is endemic to Africa and has been used traditionally to treat diabetes mellitus. Moreover, its pharmacological efficacy has been confirmed experimentally using in vitro and in vivo models of diabetes. However, the effects of Z. chalybeum extracts and its major constituent compounds on beta cell and islet regeneration are not clear. Further, the mechanisms associated with observed antidiabetic effects at the beta cell level are not fully elucidated.

AIM OF THE STUDY

We determined the beta cell regenerative efficacy of Z. chalybeum aqueous stem bark extract, identified the chemical compounds in Z. chalybeum aqueous stem bark extracts and explored their putative mechanisms of action.

MATERIALS AND METHODS

Phytochemical profiling of the Z. chalybeum extract was achieved using ultra high-performance liquid chromatography hyphenated to high-resolution mass spectrometry. Thereafter, molecular interactions of the compounds with beta cell regeneration targets were evaluated via molecular docking. In vitro, effects of the extract on cell viability, proliferation, apoptosis and oxidative stress were investigated in RIN-5F beta cells exposed to palmitate or streptozotocin. In vivo, pancreas tissue sections from streptozotocin-induced diabetic male Wistar rats treated with Z. chalybeum extract were stained for insulin, glucagon, pancreatic duodenal homeobox protein 1 (Pdx-1) and Ki-67.

RESULTS

Based on ligand target and molecular docking interactions diosmin was identified as a dual specificity tyrosine-phosphorylation-regulated kinase 1A (Dyrk1A) inhibitor. In vitro, Z. chalybeum augmented cell viability and cell proliferation while in palmitate-pre-treated cells, the extract significantly increased cell activity after 72 h. In vivo, although morphometric analysis showed decreased islet and beta cell size and density, observation of increased Pdx-1 and Ki-67 immunoreactivity in extract-treated islets suggests that Z. chalybeum extract has mild beta cell regenerative potential mediated by increased cell proliferation.

CONCLUSIONS

Overall, the mitogenic effects observed in vitro, were not robust enough to elicit sufficient recovery of functional beta cell mass in our in vivo model, in the context of a sustained diabetic milieu. However, the identification of diosmin as a potential Dyrk1A inhibitor merits further inquiry into the attendant molecular interactions.

Cyb5r3 activation rescues secondary failure to sulfonylurea but not β-cell dedifferentiation

Diabetes mellitus is characterized by insulin resistance and β-cell failure. The latter involves impaired insulin secretion and β-cell dedifferentiation. Sulfonylurea (SU) is used to improve insulin secretion in diabetes, but it suffers from secondary failure. The relationship between SU secondary failure and β-cell dedifferentiation has not been examined. Using a model of SU secondary failure, we have previously shown that functional loss of oxidoreductase Cyb5r3 mediates effects of SU failure through interactions with glucokinase. Here we demonstrate that SU failure is associated with partial β-cell dedifferentiation. Cyb5r3 knockout mice show more pronounced β-cell dedifferentiation and glucose intolerance after chronic SU administration, high-fat diet feeding, and during aging. A Cyb5r3 activator improves impaired insulin secretion caused by chronic SU treatment, but not β-cell dedifferentiation. We conclude that chronic SU administration affects progression of β-cell dedifferentiation and that Cyb5r3 activation reverses secondary failure to SU without restoring β-cell dedifferentiation.

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.

Sox9 regulates alternative splicing and pancreatic beta cell function

Despite significant research, mechanisms underlying the failure of islet beta cells that result in type 2 diabetes (T2D) are still under investigation. Here, we report that Sox9, a transcriptional regulator of pancreas development, also functions in mature beta cells. Our results show that Sox9-depleted rodent beta cells have defective insulin secretion, and aging animals develop glucose intolerance, mimicking the progressive degeneration observed in T2D. Using genome editing in human stem cells, we show that beta cells lacking SOX9 have stunted first-phase insulin secretion. In human and rodent cells, loss of Sox9 disrupts alternative splicing and triggers accumulation of non-functional isoforms of genes with key roles in beta cell function. Sox9 depletion reduces expression of protein-coding splice variants of the serine-rich splicing factor arginine SRSF5, a major splicing enhancer that regulates alternative splicing. Our data highlight the role of SOX9 as a regulator of alternative splicing in mature beta cell function.

Adjudin improves beta cell maturation, hepatic glucose uptake and glucose homeostasis

AIMS/HYPOTHESIS

Recovering functional beta cell mass is a promising approach for future diabetes therapies. The aim of the present study is to investigate the effects of adjudin, a small molecule identified in a beta cell screen using zebrafish, on pancreatic beta cells and diabetes conditions in mice and human spheroids.

METHODS

In zebrafish, insulin expression was examined by bioluminescence and quantitative real-time PCR (qPCR), glucose levels were examined by direct measurements and distribution using a fluorescent glucose analogue, and calcium activity in beta cells was analysed by in vivo live imaging. Pancreatic islets of wild-type postnatal day 0 (P0) and 3-month-old (adult) mice, as well as adult db/db mice (i.e. BKS(D)-Leprdb/JOrlRj), were cultured in vitro and analysed by qPCR, glucose stimulated insulin secretion and whole mount staining. RNA-seq was performed for islets of P0 and db/db mice. For in vivo assessment, db/db mice were treated with adjudin and subjected to analysis of metabolic variables and islet cells. Glucose consumption was examined in primary human hepatocyte spheroids.

RESULTS

Adjudin treatment increased insulin expression and calcium response to glucose in beta cells and decreased glucose levels after beta cell ablation in zebrafish. Adjudin led to improved beta cell function, decreased beta cell proliferation and glucose responsive insulin secretion by decreasing basal insulin secretion in in vitro cultured newborn mouse islets. RNA-seq of P0 islets indicated that adjudin treatment resulted in increased glucose metabolism and mitochondrial function, as well as downstream signalling pathways involved in insulin secretion. In islets from db/db mice cultured in vitro, adjudin treatment strengthened beta cell identity and insulin secretion. RNA-seq of db/db islets indicated adjudin-upregulated genes associated with insulin secretion, membrane ion channel activity and exocytosis. Moreover, adjudin promoted glucose uptake in the liver of zebrafish in an insulin-independent manner, and similarly promoted glucose consumption in primary human hepatocyte spheroids with insulin resistance. In vivo studies using db/db mice revealed reduced nonfasting blood glucose, improved glucose tolerance and strengthened beta cell identity after adjudin treatment.

CONCLUSIONS/INTERPRETATION

Adjudin promoted functional maturation of immature islets, improved function of dysfunctional islets, stimulated glucose uptake in liver and improved glucose homeostasis in db/db mice. Thus, the multifunctional drug adjudin, previously studied in various contexts and conditions, also shows promise in the management of diabetic states.

DATA AVAILABILITY

Raw and processed RNA-seq data for this study have been deposited in the Gene Expression Omnibus under accession number GSE235398 ( https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE235398 ).

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.

The Role of Diffusion-Weighted Imaging in the Evaluation of Treatment of Newly Diagnosed Type 2 Diabetic Patients

INTRODUCTION

To compare the pre and post-treatment pancreatic apparent diffusion coefficient (ADC) values of type II diabetes patients with control subjects, and also to evaluate its effectiveness in evaluating the response to treatment.

METHODS

The study included 35 newly diagnosed type 2 diabetic patients and 35 non-diabetic participants, matched for sex and age. Insulin and metformin treatment was given to the patients. Abdominal diffusion-weighted MR imaging was performed before and after the treatment. ADCs of the control group and patients pre and post-treatment were compared. In addition, the clinical parameters of the patients related to diabetes were recorded.

RESULTS

There was a significant difference between the median pancreatic ADC values of the patients pre and post-treatment. While there was a significant difference between the median pancreatic ADC values of the patient and the control groups before the treatment, no significant difference after the treatment was observed. There was a positive correlation between mean pancreatic ADC values and age, as well as a negative correlation with Hb1Ac level and eGFR.

CONCLUSION

Pancreatic ADC values of newly diagnosed type II diabetes patients can be used as a marker of pancreatic function in the evaluation of response to treatment and clinical decisions.

Talin-1 inhibits Smurf1-mediated Stat3 degradation to modulate β-cell proliferation and mass in mice

Insufficient pancreatic β-cell mass and reduced insulin expression are key events in the pathogenesis of diabetes mellitus (DM). Here we demonstrate the high expression of Talin-1 in β-cells and that deficiency of Talin-1 reduces β-cell proliferation, which leads to reduced β-cell mass and insulin expression, thus causing glucose intolerance without affecting peripheral insulin sensitivity in mice. High-fat diet fed exerbates these phenotypes. Mechanistically, Talin-1 interacts with the E3 ligase smad ubiquitination regulatory factor 1 (Smurf1), which prohibits ubiquitination of the signal transducer and activator of transcription 3 (Stat3) mediated by Smurf1, and ablation of Talin-1 enhances Smurf1-mediated ubiquitination of Stat3, leading to decreased β-cell proliferation and mass. Furthermore, haploinsufficiency of Talin-1 and Stat3 genes, but not that of either gene, in β-cell in mice significantly impairs glucose tolerance and insulin expression, indicating that both factors indeed function in the same genetic pathway. Finally, inducible deletion Talin-1 in β-cell causes glucose intolerance in adult mice. Collectively, our findings reveal that Talin-1 functions as a crucial regulator of β-cell mass, and highlight its potential as a therapeutic target for DM patients.

Global proteomics reveals insulin abundance as a marker of human islet homeostasis alterations

AIM

The variation in quality between the human islet samples represents a major problem for research, especially when used as control material. The assays assessing the quality of human islets used in research are non-standardized and limited, with many important parameters not being consistently assessed. High-throughput studies aimed at characterizing the diversity and segregation markers among apparently functionally healthy islet preps are thus a requirement. Here, we designed a pilot study to comprehensively identify the diversity of global proteome signatures and the deviation from normal homeostasis in randomly selected human-isolated islet samples.

METHODS

By using Tandem Mass Tag 16-plex proteomics, we focused on the recurrently observed disparity in the detected insulin abundance between the samples, used it as a segregating parameter, and analyzed the correlated changes in the proteome signature and homeostasis by pathway analysis.

RESULTS

In this pilot study, we showed that insulin protein abundance is a predictor of human islet homeostasis and quality. This parameter is independent of other quality predictors within their acceptable range, thus being able to further stratify islets samples of apparent good quality. Human islets with low amounts of insulin displayed changes in their metabolic and signaling profile, especially in regard to energy homeostasis and cell identity maintenance. We further showed that xenotransplantation into diabetic hosts is not expected to improve the pre-transplantation signature, as it has a negative effect on energy balance, antioxidant activity, and islet cell identity.

CONCLUSIONS

Insulin protein abundance predicts significant changes in human islet homeostasis among random samples of apparently good quality.

PAX4 loss of function increases diabetes risk by altering human pancreatic endocrine cell development

The coding variant (p.Arg192His) in the transcription factor PAX4 is associated with an altered risk for type 2 diabetes (T2D) in East Asian populations. In mice, Pax4 is essential for beta cell formation but its role on human beta cell development and/or function is unknown. Participants carrying the PAX4 p.His192 allele exhibited decreased pancreatic beta cell function compared to homozygotes for the p.192Arg allele in a cross-sectional study in which we carried out an intravenous glucose tolerance test and an oral glucose tolerance test. In a pedigree of a patient with young onset diabetes, several members carry a newly identified p.Tyr186X allele. In the human beta cell model, EndoC-βH1, PAX4 knockdown led to impaired insulin secretion, reduced total insulin content, and altered hormone gene expression. Deletion of PAX4 in human induced pluripotent stem cell (hiPSC)-derived islet-like cells resulted in derepression of alpha cell gene expression. In vitro differentiation of hiPSCs carrying PAX4 p.His192 and p.X186 risk alleles exhibited increased polyhormonal endocrine cell formation and reduced insulin content that can be reversed with gene correction. Together, we demonstrate the role of PAX4 in human endocrine cell development, beta cell function, and its contribution to T2D-risk.

NEUROD1 reinforces endocrine cell fate acquisition in pancreatic development

NEUROD1 is a transcription factor that helps maintain a mature phenotype of pancreatic β cells. Disruption of Neurod1 during pancreatic development causes severe neonatal diabetes; however, the exact role of NEUROD1 in the differentiation programs of endocrine cells is unknown. Here, we report a crucial role of the NEUROD1 regulatory network in endocrine lineage commitment and differentiation. Mechanistically, transcriptome and chromatin landscape analyses demonstrate that Neurod1 inactivation triggers a downregulation of endocrine differentiation transcription factors and upregulation of non-endocrine genes within the Neurod1-deficient endocrine cell population, disturbing endocrine identity acquisition. Neurod1 deficiency altered the H3K27me3 histone modification pattern in promoter regions of differentially expressed genes, which resulted in gene regulatory network changes in the differentiation pathway of endocrine cells, compromising endocrine cell potential, differentiation, and functional properties.

LncRNA LINC01018 Screens Type 2 Diabetes Mellitus and Regulates β Cell Function Through Modulating miR-499a-5p

Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia, which seriously endangers human health. The dysregulation of lncRNA LINC01018 in T2DM has been noticed in previous studies, but whether it served as a biomarker lacks validation. This study aimed to confirm the abnormal expression of LINC01018 in T2DM and reveals its specific function in regulating pancreatic β cell function. This study enrolled 77 T2DM patients and 41 healthy individuals and compared the plasma LINC01018 levels between two groups using PCR. The pancreatic β cell was induced with 25 mM glucose to mimic cell injury during T2DM. The effects of LINC01018 on β cell proliferation, dedifferentiation, and insulin production were evaluated by CCK8, western blotting, and ELISA. Moreover, the involvement of miR-499a-5p was also evaluated with luciferase reporter assay. Increased plasma LINC01018 was observed in T2DM patients compared with healthy individuals, which discriminates patients with high sensitivity and specificity. Upregulated LINC01018 was associated with patients' fasting blood glucose and weight loss. High glucose induced the increasing LINC01018 in pancreatic islet β cells and suppressed cell proliferation, insulin secretion, and promoted cell dedifferentiation. Silencing LINC01018 could alleviate the impaired function of β cells by high glucose, which was reversed by the knockdown by miR-499a-5p. Upregulated LINC01018 served as a potential diagnostic biomarker for T2DM and alleviated high glucose-induced β cell dysfunction via negatively modulating miR-499a-5p.