VHL-mediated disruption of Sox9 activity compromises β-cell identity and results in diabetes mellitus

The MODY-associated KCNK16 L114P mutation increases islet glucagon secretion and limits insulin secretion resulting in transient neonatal diabetes and glucose dyshomeostasis in adults

The gain-of-function mutation in the TALK-1 K+ channel (p.L114P) is associated with maturity-onset diabetes of the young (MODY). TALK-1 is a key regulator of β-cell electrical activity and glucose-stimulated insulin secretion. The KCNK16 gene encoding TALK-1 is the most abundant and β-cell-restricted K+ channel transcript. To investigate the impact of KCNK16 L114P on glucose homeostasis and confirm its association with MODY, a mouse model containing the Kcnk16 L114P mutation was generated. Heterozygous and homozygous Kcnk16 L114P mice exhibit increased neonatal lethality in the C57BL/6J and the CD-1 (ICR) genetic background, respectively. Lethality is likely a result of severe hyperglycemia observed in the homozygous Kcnk16 L114P neonates due to lack of glucose-stimulated insulin secretion and can be reduced with insulin treatment. Kcnk16 L114P increased whole-cell β-cell K+ currents resulting in blunted glucose-stimulated Ca2+ entry and loss of glucose-induced Ca2+ oscillations. Thus, adult Kcnk16 L114P mice have reduced glucose-stimulated insulin secretion and plasma insulin levels, which significantly impairs glucose homeostasis. Taken together, this study shows that the MODY-associated Kcnk16 L114P mutation disrupts glucose homeostasis in adult mice resembling a MODY phenotype and causes neonatal lethality by inhibiting islet insulin secretion during development. These data suggest that TALK-1 is an islet-restricted target for the treatment for diabetes.

The MODY-associated KCNK16 L114P mutation increases islet glucagon secretion and limits insulin secretion resulting in transient neonatal diabetes and glucose dyshomeostasis in adults

The gain-of-function mutation in the TALK-1 K + channel (p.L114P) is associated with maturity-onset diabetes of the young (MODY). TALK-1 is a key regulator of β-cell electrical activity and glucose-stimulated insulin secretion (GSIS). The KCNK16 gene encoding TALK-1, is the most abundant and β-cell-restricted K + channel transcript. To investigate the impact of KCNK16 L114P on glucose homeostasis and confirm its association with MODY, a mouse model containing the Kcnk16 L114P mutation was generated. Heterozygous and homozygous Kcnk16 L114P mice exhibit increased neonatal lethality in the C57BL/6J and the mixed C57BL/6J:CD-1(ICR) genetic background, respectively. Lethality is likely a result of severe hyperglycemia observed in the homozygous Kcnk16 L114P neonates due to lack of glucose-stimulated insulin secretion and can be reduced with insulin treatment. Kcnk16 L114P increased whole-cell β-cell K + currents resulting in blunted glucose-stimulated Ca 2+ entry and loss of glucose-induced Ca 2+ oscillations. Thus, adult Kcnk16 L114P mice have reduced glucose-stimulated insulin secretion and plasma insulin levels, which significantly impaired glucose homeostasis. Taken together, this study shows that the MODY-associated Kcnk16 L114P mutation disrupts glucose homeostasis in adult mice resembling a MODY phenotype and causes neonatal lethality by inhibiting islet hormone secretion during development. These data strongly suggest that TALK-1 is an islet-restricted target for the treatment of diabetes.

Permanent neonatal diabetes-causing insulin mutations have dominant negative effects on beta cell identity

OBJECTIVE

Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM), requiring insulin therapy similar to T1D. While the negative effects on insulin processing and secretion are known, how dominant insulin mutations result in a continued decline of beta cell function after birth is not well understood.

METHODS

We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations using patient-derived iPSCs and mutated hESCs.

RESULTS

we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on beta-cell mass and function after transplantation into mice. In addition to anticipated ER stress, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon.

CONCLUSIONS

These results highlight a novel mechanism, the loss of beta cell identity, contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.

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.

Permanent Neonatal diabetes-causing Insulin mutations have dominant negative effects on beta cell identity

Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM) that results from beta cell failure. We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations. Using b and mutated hESCs, we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on the in vivo performance of patient-derived SC-beta cells after transplantation into NSG mice. These insulin mutations derange endoplasmic reticulum (ER) homeostasis, and result in the loss of beta-cell mass and function. In addition to anticipated apoptosis, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon. These results highlight both known and novel mechanisms contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.

Cross-regulation between SOX9 and the canonical Wnt signalling pathway in stem cells

SOX9, a member of the SRY-related HMG-box transcription factors, has been reported to critically regulate fetal development and stem cell homeostasis. Wnt signalling is a highly conserved signalling pathway that controls stem cell fate decision and stemness maintenance throughout embryonic development and adult life. Many studies have shown that the interactions between SOX9 and the canonical Wnt signalling pathway are involved in many of the physiological and pathological processes of stem cells, including organ development, the proliferation, differentiation and stemness maintenance of stem cells, and tumorigenesis. In this review, we summarize the already-known molecular mechanism of cross-interactions between SOX9 and the canonical Wnt signalling pathway, outline its regulatory effects on the maintenance of homeostasis in different types of stem cells, and explore its potential in translational stem cell therapy.

Cell Replacement Therapy for Type 1 Diabetes Patients: Potential Mechanisms Leading to Stem-Cell-Derived Pancreatic β-Cell Loss upon Transplant

Cell replacement therapy using stem-cell-derived insulin-producing β-like cells (sBCs) has been proposed as a practical cure for patients with type one diabetes (T1D). sBCs can correct diabetes in preclinical animal models, demonstrating the promise of this stem cell-based approach. However, in vivo studies have demonstrated that most sBCs, similarly to cadaveric human islets, are lost upon transplantation due to ischemia and other unknown mechanisms. Hence, there is a critical knowledge gap in the current field concerning the fate of sBCs upon engraftment. Here we review, discuss effects, and propose additional potential mechanisms that could contribute toward β-cell loss in vivo. We summarize and highlight some of the literature on phenotypic loss in β-cells under both steady, stressed, and diseased diabetic conditions. Specifically, we focus on β-cell death, dedifferentiation into progenitors, trans-differentiation into other hormone-expressing cells, and/or interconversion into less functional β-cell subtypes as potential mechanisms. While current cell replacement therapy efforts employing sBCs carry great promise as an abundant cell source, addressing the somewhat neglected aspect of β-cell loss in vivo will further accelerate sBC transplantation as a promising therapeutic modality that could significantly enhance the life quality of T1D patients.

Aging Impairs Adaptive Unfolded Protein Response and Drives Beta Cell Dedifferentiation in Humans

CONTEXT

Diabetes is an age-related disease; however, the mechanism underlying senescent beta cell failure is still unknown.

OBJECTIVE

The present study was designed to investigate whether and how the differentiated state was altered in senescent human beta cells by excluding the effects of impaired glucose tolerance.

METHODS

We calculated the percentage of hormone-negative/chromogranin A-positive endocrine cells and evaluated the expressions of forkhead box O1 (FoxO1) and Urocortin 3 (UCN3) in islets from 31 nondiabetic individuals, divided into young (<40 years), middle-aged (40-60 years) and elderly (>60 years) groups. We also assessed adaptive unfolded protein response markers glucose-regulated protein 94 (GRP94), and spliced X-box binding protein 1 (XBP1s) in senescent beta cells and their possible contributions to maintaining beta cell identity and differentiation state.

RESULTS

We found an almost 2-fold increase in the proportion of dedifferentiated cells in elderly and middle-aged groups compared with the young group (3.1 ± 1.0% and 3.0 ± 0.9% vs 1.7 ± 0.5%, P < .001). This was accompanied by inactivation of FoxO1 and loss of UCN3 expression in senescent human beta cells. In addition, we demonstrated that the expression levels of adaptive unfolded protein response (UPR) components GRP94 and XBP1s declined with age. In vitro data showed knockdown GRP94 in Min6-triggered cells to dedifferentiate and acquire progenitor features, while restored GRP94 levels in H2O2-induced senescent Min6 cells rescued beta cell identity.

CONCLUSION

Our finding highlights that the failure to establish proper adaptive UPR in senescent human beta cells shifts their differentiated states, possibly representing a crucial step in the pathogenesis of age-related beta cell failure.

Retinal hemangioblastoma in a patient with Von Hippel-Lindau disease: A case report and literature review

BACKGROUND

Retinal hemangioblastoma (RH) is a rare benign tumor and a considerable number of which are caused by Von Hippel-Lindau disease (VHL). Herein, we described a case of VHL-associated RH with retinal detachment who underwent both laser photocoagulation and vitreoretinal surgery and received satisfactory visual recovery. In addition, we reviewed the current diagnosis, genotype-phenotype association, and treatment of VHL-associated RH.

CASE DESCRIPTION

A 34-year-old woman presented with vision loss in the right eye at our hospital. Fundus photography and angiography showed retinal detachment and multiple large hemangiomas in the right eye. The visual acuity improved significantly after laser photocoagulation and vitreoretinal surgery. Genetic analyses showed a p.Asn78Ser (c.233A>G) heterozygous missense mutation in the VHL gene.

CONCLUSION

We described a rare case of VHL-associated RH and may provide a new perspective towards diagnosis and treatment of this disease. RH is one of the most common manifestations of VHL and poses a serious threat to vision. Ophthalmic examination methods include fundus examination and fundus photography, etc. The management of the disease emphasizes timely follow-up, early detection of the lesion, and the decision of treatment options according to the size, location and complications of the lesion, including ablation therapy and vitreoretinal surgery. Clinicians should strengthen the understanding of this rare disease for early detection and treatment.

Transgenic overexpression of microRNA-30d in pancreatic beta-cells progressively regulates beta-cell function and identity

Abnormal microRNA functions are closely associated with pancreatic β-cell loss and dysfunction in type 2 diabetes. Dysregulation of miR-30d has been reported in the individuals with diabetes. To study how miR-30d affects pancreatic β-cell functions, we generated two transgenic mouse lines that specifically overexpressed miR-30d in β-cells at distinct low and high levels. Transgenic overexpressed miR-30d systemically affected β-cell function. Elevated miR-30d at low-level (TgL, 2-fold) had mild effects on signaling pathways and displayed no significant changes to metabolic homeostasis. In contrast, transgenic mice with high-level of miR-30d expression (TgH, 12-fold) exhibited significant diet-induced hyperglycemia and β-cell dysfunction. In addition, loss of β-cell identity was invariably accompanied with increased insulin/glucagon-double positive bihormonal cells and excess plasma glucagon levels. The transcriptomic analysis revealed that miR-30d overexpression inhibited β-cell-enriched gene expression and induced α-cell-enriched gene expression. These findings implicate that an appropriate miR-30d level is essential in maintaining normal β-cell identity and function.

XBP1 maintains beta cell identity, represses beta-to-alpha cell transdifferentiation and protects against diabetic beta cell failure during metabolic stress in mice

AIMS/HYPOTHESIS

Pancreatic beta cell dedifferentiation, transdifferentiation into other islet cells and apoptosis have been implicated in beta cell failure in type 2 diabetes, although the mechanisms are poorly defined. The endoplasmic reticulum stress response factor X-box binding protein 1 (XBP1) is a major regulator of the unfolded protein response. XBP1 expression is reduced in islets of people with type 2 diabetes, but its role in adult differentiated beta cells is unclear. Here, we assessed the effects of Xbp1 deletion in adult beta cells and tested whether XBP1-mediated unfolded protein response makes a necessary contribution to beta cell compensation in insulin resistance states.

METHODS

Mice with inducible beta cell-specific Xbp1 deletion were studied under normal (chow diet) or metabolic stress (high-fat diet or obesity) conditions. Glucose tolerance, insulin secretion, islet gene expression, alpha cell mass, beta cell mass and apoptosis were assessed. Lineage tracing was used to determine beta cell fate.

RESULTS

Deletion of Xbp1 in adult mouse beta cells led to beta cell dedifferentiation, beta-to-alpha cell transdifferentiation and increased alpha cell mass. Cell lineage-specific analyses revealed that Xbp1 deletion deactivated beta cell identity genes (insulin, Pdx1, Nkx6.1, Beta2, Foxo1) and derepressed beta cell dedifferentiation (Aldh1a3) and alpha cell (glucagon, Arx, Irx2) genes. Xbp1 deletion in beta cells of obese ob/ob or high-fat diet-fed mice triggered diabetes and worsened glucose intolerance by disrupting insulin secretory capacity. Furthermore, Xbp1 deletion increased beta cell apoptosis under metabolic stress conditions by attenuating the antioxidant response.

CONCLUSIONS/INTERPRETATION

These findings indicate that XBP1 maintains beta cell identity, represses beta-to-alpha cell transdifferentiation and is required for beta cell compensation and prevention of diabetes in insulin resistance states.

Pancreatic β-Cell Development and Regeneration

The pancreatic β-cells are essential for regulating glucose homeostasis through the coordinated release of the insulin hormone. Dysfunction of the highly specialized β-cells results in diabetes mellitus, a growing global health epidemic. In this review, we describe the development and function of β-cells the emerging concept of heterogeneity within insulin-producing cells, and the potential of other cell types to assume β-cell functionality via transdifferentiation. We also discuss emerging routes to design cells with minimal β-cell properties and human stem cell differentiation efforts that carry the promise to restore normoglycemia in patients suffering from diabetes.

Effects of water stably-enriched with oxygen as a novel method of tissue oxygenation on mitochondrial function, and as adjuvant therapy for type 2 diabetes in a randomized placebo-controlled trial

Background

Diabetes mellitus is associated with inadequate delivery of oxygen to tissues. Cellular hypoxia is associated with mitochondrial dysfunction which increases oxidative stress and hyperglycaemia. Hyperbaric oxygenation therapy, which was shown to improve insulin sensitivity, is impractical for regular use. We evaluated the effects of water which is stably-enriched with oxygen (ELO water) to increase arterial blood oxygen levels, on mitochondrial function in the presence of normal- or high-glucose environments, and as glucose-lowering therapy in humans.

Methods

We compared arterial blood oxygen levels in Sprague-Dawley rats after 7 days of ad libitum ELO or tap water consumption. Mitochondrial stress testing, and flow cytometry analysis of mitochondrial mass and membrane potential, were performed on human HepG2 cells cultured in four Dulbecco’s Modified Eagle Medium media, made with ELO water or regular (control) water, at normal (5.5 mM) or high (25 mM) glucose concentrations. We also randomized 150 adults with type 2 diabetes (mean age 53 years, glycated haemoglobin HbA1c 8.9% [74 mmol/mol], average duration of diabetes 12 years) to drink 1.5 litres daily of bottled ELO water or drinking water.

Results

ELO water raised arterial oxygen tension pO2 significantly (335 ± 26 vs. 188 ± 18 mmHg, p = 0.006) compared with tap water. In cells cultured in control water, mitochondrial mass and membrane potential were both significantly lower at 25 mM glucose compared with 5.5 mM glucose; in contrast, mitochondrial mass and membrane potential did not differ significantly at normal or high glucose concentrations in cells cultured in ELO water. The high-glucose environment induced a greater mitochondrial proton leak in cells cultured in ELO water compared to cells cultured in control medium at similar glucose concentration. In type 2 diabetic adults, HbA1c decreased significantly (p = 0.002) by 0.3 ± 0.7% (4 ± 8 mmol/mol), with ELO water after 12 weeks of treatment but was unchanged with placebo.

Conclusions

ELO water raises arterial blood oxygen levels, appears to have a protective effect on hyperglycaemia-induced reduction in mitochondrial mass and mitochondrial dysfunction, and may be effective adjuvant therapy for type 2 diabetes.

Dynamics of total volume of pancreatic α- and β -cells under the influence sulfonylureas and their combination with dipeptidyl peptidase-4 inhibitors

Objective

Sulfonylureas and dipeptidyl peptidase‐4 inhibitors have a multidirectional effect on pancreatic cells. We aimed to evaluate the effects of these drugs on β‐ and α‐cells in rats aged 12 months with type 2 diabetes mellitus when administered in combination with various sulfonylureas.

Methods

Streptozotocin‐nicotinamide induced type 2 diabetes mellitus was induced in rats aged 12 months. Animals received the sulfonylureas gliclazide or glibenclamide for 24 weeks alone or in combination with the dipeptidyl peptidase‐4 inhibitor vildagliptin or vildagliptin monotherapy. Blood glucose and animal weights were measured before and during the experiment. The oral glucose tolerance test was conducted before therapy initiation. Immunohistochemical analyses were conducted after the end of the experiment using glucagon and insulin antibodies. The total volumes of α and β cells were estimated in relation to the volume of the pancreatic islets.

Results

The total volumes of β‐cells did not differ between the sulfonylurea group and the untreated type 2 diabetes mellitus group. The addition of dipeptidyl peptidase‐4 inhibitors to sulfonylureas normalized the total volumes of β cells. The total volumes of α‐cells in the gliclazide group and combination of gliclazide with dipeptidyl peptidase‐4 inhibitor was comparable to that in the control group of intact animals, in contrast with the glibenclamide group.

Conclusion

The combination of vildagliptin to both sulfonylureas contributed to the normalisation of β‐cells number. Normalisation of the total volumes of α‐cells was observed with gliclazide therapy and combination of gliclazide with dipeptidyl peptidase‐4 inhibitor.

The crosstalk of hedgehog, PI3K and Wnt pathways in diabetes

Hyperglycaemia causes pancreatic β-cells to release insulin that then attaches to a specific expression of receptor isoform and reverses high glucose concentrations. It is well known that insulin is capable of initiating insulin-receptor substrate (IRS)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) signaling pathways in target cells; such as liver, adipose tissues, and muscles. However, recent discoveries indicate that many other pathways, such as the Hedgehog (Hh) and growth factor-stimulating Wingless-related integration (Wnt) signaling pathways; are activated in hyperglycaemia as well. Although these two pathways are traditionally thought to have a decisive role in cellular growth and differentiation only, recent reports show that they are involved in regulating cellular homeostasis and energy balance. While insulin-activated IRS/PI3K/PKB pathway cascades are primarily known to reduce glucose production, it was recently discovered to increase the Hh signaling pathway's stability, thereby activating the PI3K/PKB/mammalian target of rapamycin complex 2 (mTORC2) signaling pathway. The Hh signaling pathway not only plays a role in lipid metabolism, insulin sensitivity, inflammatory response, diabetes-related complications, but crosstalks with the Wnt signaling pathway resulting in improved insulin sensitivity and decrease inflammatory response in diabetes.

HIFα Regulates Developmental Myelination Independent of Autocrine Wnt Signaling

The developing CNS is exposed to physiological hypoxia, under which hypoxia-inducible factor α (HIFα) is stabilized and plays a crucial role in regulating neural development. The cellular and molecular mechanisms of HIFα in developmental myelination remain incompletely understood. A previous concept proposes that HIFα regulates CNS developmental myelination by activating the autocrine Wnt/β-catenin signaling in oligodendrocyte progenitor cells (OPCs). Here, by analyzing a battery of genetic mice of both sexes, we presented in vivo evidence supporting an alternative understanding of oligodendroglial HIFα-regulated developmental myelination. At the cellular level, we found that HIFα was required for developmental myelination by transiently controlling upstream OPC differentiation but not downstream oligodendrocyte maturation and that HIFα dysregulation in OPCs but not oligodendrocytes disturbed normal developmental myelination. We demonstrated that HIFα played a minor, if any, role in regulating canonical Wnt signaling in the oligodendroglial lineage or in the CNS. At the molecular level, blocking autocrine Wnt signaling did not affect HIFα-regulated OPC differentiation and myelination. We further identified HIFα-Sox9 regulatory axis as an underlying molecular mechanism in HIFα-regulated OPC differentiation. Our findings support a concept shift in our mechanistic understanding of HIFα-regulated CNS myelination from the previous Wnt-dependent view to a Wnt-independent one and unveil a previously unappreciated HIFα-Sox9 pathway in regulating OPC differentiation.SIGNIFICANCE STATEMENT Promoting disturbed developmental myelination is a promising option in treating diffuse white matter injury, previously called periventricular leukomalacia, a major form of brain injury affecting premature infants. In the developing CNS, hypoxia-inducible factor α (HIFα) is a key regulator that adapts neural cells to physiological and pathologic hypoxic cues. The role and mechanism of HIFα in oligodendroglial myelination, which is severely disturbed in preterm infants affected with diffuse white matter injury, is incompletely understood. Our findings presented here represent a concept shift in our mechanistic understanding of HIFα-regulated developmental myelination and suggest the potential of intervening with an oligodendroglial HIFα-mediated signaling pathway to mitigate disturbed myelination in premature white matter injury.

TBK1 regulates regeneration of pancreatic β-cells

Small-molecule inhibitors of non-canonical IκB kinases TANK-binding kinase 1 (TBK1) and IκB kinase ε (IKKε) have shown to stimulate β-cell regeneration in multiple species. Here we demonstrate that TBK1 is predominantly expressed in β-cells in mammalian islets. Proteomic and transcriptome analyses revealed that genetic silencing of TBK1 increased expression of proteins and genes essential for cell proliferation in INS-1 832/13 rat β-cells. Conversely, TBK1 overexpression decreased sensitivity of β-cells to the elevation of cyclic AMP (cAMP) levels and reduced proliferation of β-cells in a manner dependent on the activity of cAMP-hydrolyzing phosphodiesterase 3 (PDE3). While the mitogenic effect of (E)3-(3-phenylbenzo[c]isoxazol-5-yl)acrylic acid (PIAA) is derived from inhibition of TBK1, PIAA augmented glucose-stimulated insulin secretion (GSIS) and expression of β-cell differentiation and proliferation markers in human embryonic stem cell (hESC)-derived β-cells and human islets. TBK1 expression was increased in β-cells upon diabetogenic insults, including in human type 2 diabetic islets. PIAA enhanced expression of cell cycle control molecules and β-cell differentiation markers upon diabetogenic challenges, and accelerated restoration of functional β-cells in streptozotocin (STZ)-induced diabetic mice. Altogether, these data suggest the critical function of TBK1 as a β-cell autonomous replication barrier and present PIAA as a valid therapeutic strategy augmenting functional β-cells.

Patients with type 2 diabetes present with multiple anomalies of the pancreatic arterial tree on abdominal computed tomography: comparison between patients with type 2 diabetes and a matched control group

Background

Studies suggest that cardio-vascular risk factors could foster the development of type 2 diabetes (T2D). This could partly be mediated by pancreatic atherosclerosis resulting in pancreatic ischemia. We hypothesized that patients with T2D present with more severe atherosclerosis of pancreas-bound arteries than control patients without T2D.

Methods

We performed a retrospective study comparing the abdominal computed tomography of patients with T2D and of control subjects matched for gender and for age. We performed a multivariate logistic regression with adjustment for age, gender, BMI and the presence or absence of hypertension.

Results

Forty-eight patients with T2D and 48 control subjects were included. A calcification score of the splenic artery was defined (from 0: no calcification to 3: continuous linear calcifications). Seventeen percent of the patients with T2D presented with a high calcification score (i.e. 2 or 3), versus only 2% of the control subjects (p = 0.04). The mean number of pancreas-bound branches among the greater pancreatic artery, dorsal pancreatic artery and inferior pancreatic artery (from 0 to 3) was lower in patients with T2D than in control subjects (1.1 vs 1.7, p = 0.003). The mean number of visible intrapancreatic arterial subdivisions (from 0 to 2) was lower in patients with T2D than in control subjects (0.7 vs 1.3, p = 0.0017). All these differences hold true using multivariate logistic regression. None of these differences correlated with the duration of diabetes. The relationship between pancreas volume and BMI seen in control subjects was not confirmed in patients with T2D. Conversely, in patients with T2D but not in control subjects, the splenic artery diameter correlated with the pancreas volume.

Conclusions

Patients with T2D present with more calcifications of the splenic artery and with a less dense pancreatic arterial tree than control subjects.

Paraneoplastic β Cell Dedifferentiation in Nondiabetic Patients with Pancreatic Cancer

CONTEXT

Beta-cell dedifferentiation was recently proposed as a mechanism of β-cell dysfunction, but whether it can be a trigger of β-cell failure preceding hyperglycemia in humans is uncertain. Pancreatic cancer can cause new-onset diabetes, yet the underlying mechanism is unknown.

OBJECTIVE

To investigate whether β-cell dedifferentiation is present in nondiabetic pancreatic ductal adenocarcinoma (PDAC) patients, we examined pancreatic islets from 15 nondiabetic patients with benign tumors (control) and 15 nondiabetic PDAC patients.

DESIGN

We calculated the number of hormone-negative endocrine cells and evaluated important markers of β-cell dedifferentiation and function in the paraneoplastic islets. We assessed tumor-related inflammatory changes under the pancreatic cancer microenvironment and their influence on β-cell identity.

RESULTS

We found nearly 10% of nonhormone expressing endocrine cells in nondiabetic PDAC subjects. The PDAC islets were dysfunctional, evidenced by low expression of Glucose transporter 2 (GLUT2) and Urocortin3 (UCN3), and concomitant upregulation of Aldehyde Dehydrogenase 1 Family Member A3 (ALDH1A3) expression and proinsulin accumulation. Pancreatic cancer caused paraneoplastic inflammation with enhanced tissue fibrosis, monocytes/macrophages infiltration, and elevated inflammatory cytokines. Moreover, we detected β-cell dedifferentiation and defects in GSIS in islets exposed to PANC-1 (a cell line established from a pancreatic carcinoma of ductal origin from a 56-year-old Caucasian male)-conditioned medium. In a larger cohort, we showed high prevalence of new-onset diabetes in PDAC subjects, and fasting blood glucose (FBG) was found to be an additional useful parameter for early diagnosis of PDAC.

CONCLUSIONS

Our data provide a rationale for β-cell dedifferentiation in the pathogenesis of pancreatic cancer-associated diabetes. We propose that β-cell dedifferentiation can be a trigger for β-cell failure in humans, before hyperglycemia occurs.

Cyb5r3 links FoxO1-dependent mitochondrial dysfunction with β-cell failure

OBJECTIVE

Diabetes is characterized by pancreatic β-cell dedifferentiation. Dedifferentiating β cells inappropriately metabolize lipids over carbohydrates and exhibit impaired mitochondrial oxidative phosphorylation. However, the mechanism linking the β-cell's response to an adverse metabolic environment with impaired mitochondrial function remains unclear.

METHODS

Here we report that the oxidoreductase cytochrome b5 reductase 3 (Cyb5r3) links FoxO1 signaling to β-cell stimulus/secretion coupling by regulating mitochondrial function, reactive oxygen species generation, and nicotinamide actin dysfunction (NAD)/reduced nicotinamide actin dysfunction (NADH) ratios.

RESULTS

The expression of Cyb5r3 is decreased in FoxO1-deficient β cells. Mice with β-cell-specific deletion of Cyb5r3 have impaired insulin secretion, resulting in glucose intolerance and diet-induced hyperglycemia. Cyb5r3-deficient β cells have a blunted respiratory response to glucose and display extensive mitochondrial and secretory granule abnormalities, consistent with altered differentiation. Moreover, FoxO1 is unable to maintain expression of key differentiation markers in Cyb5r3-deficient β cells, suggesting that Cyb5r3 is required for FoxO1-dependent lineage stability.

CONCLUSIONS

The findings highlight a pathway linking FoxO1 to mitochondrial dysfunction that can mediate β-cell failure.

Stearoyl CoA desaturase is a gatekeeper that protects human beta cells against lipotoxicity and maintains their identity

AIMS/HYPOTHESIS

During the onset of type 2 diabetes, excessive dietary intake of saturated NEFA and fructose lead to impaired insulin production and secretion by insulin-producing pancreatic beta cells. The majority of data on the deleterious effects of lipids on functional beta cell mass were obtained either in vivo in rodent models or in vitro using rodent islets and beta cell lines. Translating data from rodent to human beta cells remains challenging. Here, we used the human beta cell line EndoC-βH1 and analysed its sensitivity to a lipotoxic and glucolipotoxic (high palmitate with or without high glucose) insult, as a way to model human beta cells in a type 2 diabetes environment.

METHODS

EndoC-βH1 cells were exposed to palmitate after knockdown of genes related to saturated NEFA metabolism. We analysed whether and how palmitate induces apoptosis, stress and inflammation and modulates beta cell identity.

RESULTS

EndoC-βH1 cells were insensitive to the deleterious effects of saturated NEFA (palmitate and stearate) unless stearoyl CoA desaturase (SCD) was silenced. SCD was abundantly expressed in EndoC-βH1 cells, as well as in human islets and human induced pluripotent stem cell-derived beta cells. SCD silencing induced markers of inflammation and endoplasmic reticulum stress and also IAPP mRNA. Treatment with the SCD products oleate or palmitoleate reversed inflammation and endoplasmic reticulum stress. Upon SCD knockdown, palmitate induced expression of dedifferentiation markers such as SOX9, MYC and HES1. Interestingly, SCD knockdown by itself disrupted beta cell identity with a decrease in mature beta cell markers INS, MAFA and SLC30A8 and decreased insulin content and glucose-stimulated insulin secretion.

CONCLUSIONS/INTERPRETATION

The present study delineates an important role for SCD in the protection against lipotoxicity and in the maintenance of human beta cell identity.

DATA AVAILABILITY

Microarray data and all experimental details that support the findings of this study have been deposited in in the GEO database with the GSE130208 accession code.

Hypoxia-inducible factor-1α mediates the expression of mature β cell-disallowed genes in hypoxia-induced β cell dedifferentiation

Hypoxia affects the function of pancreatic β cells, and the molecular mechanism underlying hypoxia-related β cell dysfunction in human type 2 diabetes mellitus (T2DM) remains to be elucidated. In this study, by comparing the gene expression profiles of islets from nondiabetic and T2D subjects using gene chip array, we aimed to elucidate that hypoxia signaling pathways are activated in human T2DM islets. CoCl₂ treatment, which was employed to mimic hypoxic stimulation in human islets, decreased insulin secretion, insulin content, and the functional gene expression of human islets. In parallel, the expression of mature β cell-disallowed genes was upregulated by CoCl₂, including progenitor cell marker NGN3, β cell differentiation marker ALDH1A3, and genes that are typically inhibited in mature β cells, namely, GLUT1 and LDHA, indicating that CoCl₂-mimicked hypoxia induced β cell dedifferentiation of human islets. This finding in human islets was confirmed in mouse β cell line NIT-1. By using Dimethyloxalylglycine (DMOG) to activate hypoxia-inducible factor-1α (HIF-1α) or siRNAs to knockdown HIF-1α, we found that HIF-1α was a key regulator of hypoxia-induced dedifferentiation of β cells by upregulating mature β cell-disallowed genes. Our findings suggested that HIF-1α activation might be an important contributor to β cell dedifferentiation in human T2DM islets, and HIF-1α-targeted therapies may have the potential to reverse β cell dedifferentiation of human T2DM islets.

Induction of α cell-restricted Gc in dedifferentiating β cells contributes to stress-induced β-cell dysfunction

Diabetic β cell failure is associated with β cell dedifferentiation. To identify effector genes of dedifferentiation, we integrated analyses of histone methylation as a surrogate of gene activation status and RNA expression in β cells sorted from mice with multiparity-induced diabetes. Interestingly, only a narrow subset of genes demonstrated concordant changes to histone methylation and RNA levels in dedifferentiating β cells. Notable among them was the α cell signature gene Gc, encoding a vitamin D-binding protein. While diabetes was associated with Gc induction, Gc-deficient islets did not induce β cell dedifferentiation markers and maintained normal ex vivo insulin secretion in the face of metabolic challenge. Moreover, Gc-deficient mice exhibited a more robust insulin secretory response than normal controls during hyperglycemic clamps. The data are consistent with a functional role of Gc activation in β cell dysfunction, and indicate that multiparity-induced diabetes is associated with altered β cell fate.

β-Cell Dedifferentiation in Patients With T2D With Adequate Glucose Control and Nondiabetic Chronic Pancreatitis

CONTEXT

Type 2 diabetes (T2D) and pancreatogenic diabetes are both associated with loss of functional β-cell mass. Previous studies have proposed β-cell dedifferentiation as a mechanism of islet β-cell failure, but its significance in humans is still controversial.

OBJECTIVE

To determine whether β-cell dedifferentiation occurs in human T2D with adequate glucose control and in nondiabetic chronic pancreatitis (NDCP), we examined pancreatic islets from nine nondiabetic controls, 10 patients with diabetes with well-controlled fasting glycemia, and four individuals with NDCP.

DESIGN

We calculated the percentage of hormone-negative endocrine cells and multihormone endocrine cells and scored the pathological characteristics; that is, inflammatory cell infiltration, fibrosis, atrophy, and steatosis, in each case.

RESULTS

We found a nearly threefold increase in dedifferentiated cells in T2D with adequate glucose control compared with nondiabetic controls (10.0% vs 3.6%, T2D vs nondiabetic controls, P < 0.0001). The dedifferentiation rate was positively correlated with the duration of diabetes. Moreover, we detected a considerable proportion of dedifferentiated cells in NDCP (10.4%), which correlated well with the grade of inflammatory cell infiltration, fibrosis, and atrophy.

CONCLUSIONS

The data support the view that pancreatic β-cells are dedifferentiated in patients with T2D with adequate glucose control. Furthermore, the existence of abundant dedifferentiated cells in NDCP suggests that inflammation-induced β-cell dedifferentiation can be a cause of pancreatogenic diabetes during disease progress.

Notch signaling dynamically regulates adult β cell proliferation and maturity

Notch signaling regulates differentiation of the pancreatic endocrine lineage during embryogenesis, but the role of Notch in mature β cells is unclear. We found that islets derived from lean mice show modest β cell Notch activity, which increases in obesity and in response to high glucose. This response appeared maladaptive, as mice with β cell-specific-deficient Notch transcriptional activity showed improved glucose tolerance when subjected to high-fat diet feeding. Conversely, mice with β cell-specific Notch gain of function (β-NICD) had a progressive loss of β cell maturity, due to proteasomal degradation of MafA, leading to impaired glucose-stimulated insulin secretion and glucose intolerance with aging or obesity. Surprisingly, Notch-active β cells had increased proliferative capacity, leading to increased but dysfunctional β cell mass. These studies demonstrate a dynamic role for Notch in developed β cells for simultaneously regulating β cell function and proliferation.

Stabilization of HIF-2α impacts pancreas growth

Hypoxia inducible factors (HIFs) are critical regulators of the response to oxygen deficiency by activating target genes involved in a variety of biological functions. HIFs have been implicated in the pathophysiology of numerous pathologies including cancer. Patients with mutations in the von Hippel-Lindau (VHL) gene, an essential regulator of HIF activity, develop tumors in several organs including the pancreas. Previous functional studies of HIF activation in the pancreas have used Vhlh (the murine homolog of VHL) deficient mice. However, the role of each specific HIF transcription factors in the pancreas has not been thoroughly examined. We derived mice that constitutively express a normoxia-stable form of HIF2α in the pancreas. Activation of HIF2α in the pancreas severely impairs postnatal exocrine pancreas. Mice with pancreas-specific activation of HIF2α develop histological features reminiscent of pancreatitis including loss of acinar cells, ductal dilation and fibrosis. Moreover, we provide evidence that signaling pathways important for acinar cell homeostasis are altered in HIF2α-overexpressing pancreata.

The Polycomb-Dependent Epigenome Controls β Cell Dysfunction, Dedifferentiation, and Diabetes

To date, it remains largely unclear to what extent chromatin machinery contributes to the susceptibility and progression of complex diseases. Here, we combine deep epigenome mapping with single-cell transcriptomics to mine for evidence of chromatin dysregulation in type 2 diabetes. We find two chromatin-state signatures that track β cell dysfunction in mice and humans: ectopic activation of bivalent Polycomb-silenced domains and loss of expression at an epigenomically unique class of lineage-defining genes. β cell-specific Polycomb (Eed/PRC2) loss of function in mice triggers diabetes-mimicking transcriptional signatures and highly penetrant, hyperglycemia-independent dedifferentiation, indicating that PRC2 dysregulation contributes to disease. The work provides novel resources for exploring β cell transcriptional regulation and identifies PRC2 as necessary for long-term maintenance of β cell identity. Importantly, the data suggest a two-hit (chromatin and hyperglycemia) model for loss of β cell identity in diabetes.

Modeling human pancreatic beta cell dedifferentiation

OBJECTIVE

Dedifferentiation could explain reduced functional pancreatic β-cell mass in type 2 diabetes (T2D).

METHODS

Here we model human β-cell dedifferentiation using growth factor stimulation in the human β-cell line, EndoC-βH1, and human pancreatic islets.

RESULTS

Fibroblast growth factor 2 (FGF2) treatment reduced expression of β-cell markers, (INS, MAFB, SLC2A2, SLC30A8, and GCK) and activated ectopic expression of MYC, HES1, SOX9, and NEUROG3. FGF2-induced dedifferentiation was time- and dose-dependent and reversible upon wash-out. Furthermore, FGF2 treatment induced expression of TNFRSF11B, a decoy receptor for RANKL and protected β-cells against RANKL signaling. Finally, analyses of transcriptomic data revealed increased FGF2 expression in ductal, endothelial, and stellate cells in pancreas from T2D patients, whereas FGFR1, SOX,9 and HES1 expression increased in islets from T2D patients.

CONCLUSIONS

We thus developed an FGF2-induced model of human β-cell dedifferentiation, identified new markers of dedifferentiation, and found evidence for increased pancreatic FGF2, FGFR1, and β-cell dedifferentiation in T2D.

Virus-like infection induces human β cell dedifferentiation

Type 1 diabetes (T1D) is a chronic disease characterized by an autoimmune-mediated destruction of insulin-producing pancreatic β cells. Environmental factors such as viruses play an important role in the onset of T1D and interact with predisposing genes. Recent data suggest that viral infection of human islets leads to a decrease in insulin production rather than β cell death, suggesting loss of β cell identity. We undertook this study to examine whether viral infection could induce human β cell dedifferentiation. Using the functional human β cell line EndoC-βH1, we demonstrate that polyinosinic-polycytidylic acid (PolyI:C), a synthetic double-stranded RNA that mimics a byproduct of viral replication, induces a decrease in β cell-specific gene expression. In parallel with this loss, the expression of progenitor-like genes such as SOX9 was activated following PolyI:C treatment or enteroviral infection. SOX9 was induced by the NF-κB pathway and also in a paracrine non-cell-autonomous fashion through the secretion of IFN-α. Lastly, we identified SOX9 targets in human β cells as potentially new markers of dedifferentiation in T1D. These findings reveal that inflammatory signaling has clear implications in human β cell dedifferentiation.

Replication confers β cell immaturity

Pancreatic β cells are highly specialized to regulate systemic glucose levels by secreting insulin. In adults, increase in β-cell mass is limited due to brakes on cell replication. In contrast, proliferation is robust in neonatal β cells that are functionally immature as defined by a lower set point for glucose-stimulated insulin secretion. Here we show that β-cell proliferation and immaturity are linked by tuning expression of physiologically relevant, non-oncogenic levels of c-Myc. Adult β cells induced to replicate adopt gene expression and metabolic profiles resembling those of immature neonatal β that proliferate readily. We directly demonstrate that priming insulin-producing cells to enter the cell cycle promotes a functionally immature phenotype. We suggest that there exists a balance between mature functionality and the ability to expand, as the phenotypic state of the β cell reverts to a less functional one in response to proliferative cues.

Adult beta cells, which are highly specialised insulin-secreting cells, rarely replicate. Puri et al. demonstrate that beta cell proliferative capacity is inversely correlated with their functionality and differentiation state, by inducing proliferation of adult cells with ectopic overexpression of the cell cycle regulator c-Myc.

Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions

Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.

Neuronal PAS Domain Protein 4 Suppression of Oxygen Sensing Optimizes Metabolism during Excitation of Neuroendocrine Cells

Depolarization of neuroendocrine cells results in calcium influx, which induces vesicle exocytosis and alters gene expression. These processes, along with the restoration of resting membrane potential, are energy intensive. We hypothesized that cellular mechanisms exist to maximize energy production during excitation. Here, we demonstrate that NPAS4, an immediate early basic helix-loop-helix (bHLH)-PAS transcription factor, acts to maximize energy production by suppressing hypoxia-inducible factor 1α (HIF1α). As such, knockout of Npas4 from insulin-producing β cells results in reduced OXPHOS, loss of insulin secretion, β cell dedifferentiation, and type 2 diabetes. NPAS4 plays a similar role in the nutrient-sensing cells of the hypothalamus. Its knockout here results in increased food intake, reduced locomotor activity, and elevated peripheral glucose production. In conclusion, NPAS4 is critical for the coordination of metabolism during the stimulation of electrically excitable cells; its loss leads to the defects in cellular metabolism that underlie the cellular dysfunction that occurs in metabolic disease.

Mitigating Ischemic Injury of Stem Cell-Derived Insulin-Producing Cells after Transplant

The advent of large-scale in vitro differentiation of human stem cell-derived insulin-producing cells (SCIPC) has brought us closer to treating diabetes using stem cell technology. However, decades of experiences from islet transplantation show that ischemia-induced islet cell death after transplant severely limits the efficacy of the therapy. It is unclear to what extent human SCIPC are susceptible to ischemia. In this study, we show that more than half of SCIPC die shortly after transplantation. Nutrient deprivation and hypoxia acted synergistically to kill SCIPC in vitro. Amino acid supplementation rescued SCIPC from nutrient deprivation, likely by providing cellular energy. Generating SCIPC under physiological oxygen tension of 5% conferred hypoxia resistance without affecting their differentiation or function. A two-pronged strategy of physiological oxygen acclimatization during differentiation and amino acid supplementation during transplantation significantly improved SCIPC survival after transplant.

•

Stem cell-derived insulin-producing cells (SCIPC) are susceptible to ischemic injury

•

Amino acid supplementation prevents nutrient-deprivation-induced SCIPC death

•

Generation of SCIPC at physiological oxygen levels protects them against hypoxia

•

Both strategies combined preserve SCIPC graft viability in vivo upon transplant

A2A adenosine receptors control pancreatic dysfunction in high-fat-diet-induced obesity

Adenosine, a key extracellular signaling mediator, regulates several aspects of metabolism by activating 4 G-protein-coupled receptors, the A₁, A_2A, A_2B, and A₃ adenosine receptors (ARs). The role of A_2AARs in regulating high-fat-diet (HFD)-induced metabolic derangements is unknown. To evaluate the role of A_2AARs in regulating glucose and insulin homeostasis in obesity, we fed A_2AAR-knockout (KO) and control mice an HFD for 16 wk to initiate HFD-induced metabolic disorder. We found that genetic deletion of A_2AARs caused impaired glucose tolerance in mice fed an HFD. This impaired glucose tolerance was caused by a decrease in insulin secretion but not in insulin sensitivity. Islet size and insulin content in pancreata of A_2AAR-deficient mice were decreased compared with control mice after consuming an HFD. A_2AAR-KO mice had decreased expression of the β-cell-specific markers pdx1, glut2, mafA, and nkx6.1 and increased expression of the dedifferentiation markers sox2 and hes1. Ex vivo islet experiments confirmed the role of A_2AARs in protecting against decreased insulin content and release caused by HFD. Other experiments with bone marrow chimeras revealed that inflammation was not the primary cause of decreased insulin secretion in A_2AAR-KO mice. Altogether, our data showed that A_2AARs control pancreatic dysfunction in HFD-induced obesity.-Csóka, B., Törő, G., Vindeirinho, J., Varga, Z. V., Koscsó, B., Németh, Z. H., Kókai, E., Antonioli, L., Suleiman, M., Marchetti, P., Cseri, K., Deák, Á., Virág, L., Pacher, P., Bai, P., Haskó, G. A_2A adenosine receptors control pancreatic dysfunction in high-fat-diet-induced obesity.

The molecular and morphogenetic basis of pancreas organogenesis

The pancreas is an essential endoderm-derived organ that ensures nutrient metabolism via its endocrine and exocrine functions. Here we review the essential processes governing the embryonic and early postnatal development of the pancreas discussing both the mechanisms and molecules controlling progenitor specification, expansion and differentiation. We elaborate on how these processes are orchestrated in space and coordinated with morphogenesis. We draw mainly from experiments conducted in the mouse model but also from investigations in other model organisms, complementing a recent comprehensive review of human pancreas development (Jennings et al., 2015) [1]. The understanding of pancreas development in model organisms provides a framework to interpret how human mutations lead to neonatal diabetes and may contribute to other forms of diabetes and to guide the production of desired pancreatic cell types from pluripotent stem cells for therapeutic purposes.

MiRNAs in β-Cell Development, Identity, and Disease

Pancreatic β-cells regulate glucose metabolism by secreting insulin, which in turn stimulates the utilization or storage of the sugar by peripheral tissues. Insulin insufficiency and a prolonged period of insulin resistance are usually the core components of type 2 diabetes (T2D). Although, decreased insulin levels in T2D have long been attributed to a decrease in β-cell function and/or mass, this model has recently been refined with the recognition that a loss of β-cell “identity” and dedifferentiation also contribute to the decline in insulin production. MicroRNAs (miRNAs) are key regulatory molecules that display tissue-specific expression patterns and maintain the differentiated state of somatic cells. During the past few years, great strides have been made in understanding how miRNA circuits impact β-cell identity. Here, we review current knowledge on the role of miRNAs in regulating the acquisition of the β-cell fate during development and in maintaining mature β-cell identity and function during stress situations such as obesity, pregnancy, aging, or diabetes. We also discuss how miRNA function could be harnessed to improve our ability to generate β-cells for replacement therapy for T2D.

When β-cells fail: lessons from dedifferentiation

Diabetes is caused by a combination of impaired responsiveness to insulin and reduced production of insulin by the pancreas. Until recently, the decline of insulin production had been ascribed to β-cell death. But recent research has shown that β-cells do not die in diabetes, but undergo a silencing process, termed "dedifferentiation." The main implication of this discovery is that β-cells can be revived by appropriate treatments. We have shown that mitochondrial abnormalities are a key step in the progression of β-cell dysfunction towards dedifferentiation. In normal β-cells, mitochondria generate energy required to sustain insulin production and its finely timed release in response to the body's nutritional status. A normal β-cell can adapt its mitochondrial fuel source based on substrate availability, a concept known as "metabolic flexibility." This capability is the first casualty in the progress of β-cell failure. β-Cells lose the ability to select the right fuel for mitochondrial energy production. Mitochondria become overloaded, and accumulate by-products derived from incomplete fuel utilization. Energy production stalls, and insulin production drops, setting the stage for dedifferentiation. The ultimate goal of these investigations is to explore novel treatment paradigms that will benefit people with diabetes.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Life and death of β cells in Type 1 diabetes: A comprehensive review

Type 1 diabetes (T1D) is an autoimmune disorder characterized by the destruction of insulin-producing pancreatic β cells. Immune modulators have achieved some success in modifying the course of disease progression in T1D. However, there are parallel declines in C-peptide levels in treated and control groups after initial responses. In this review, we discuss mechanisms of β cell death in T1D that involve necrosis and apoptosis. New technologies are being developed to enable visualization of insulitis and β cell mass involving positron emission transmission that identifies β cell ligands and magnetic resonance imaging that can identify vascular leakage. Molecular signatures that identify β cell derived insulin DNA that is released from dying cells have been described and applied to clinical settings. We also consider changes in β cells that occur during disease progression including the induction of DNA methyltransferases that may affect the function and differentiation of β cells. Our findings from newer data suggest that the model of chronic long standing β cell killing should be reconsidered. These studies indicate that the pathophysiology is accelerated in the peridiagnosis period and manifest by increased rates of β cell killing and insulin secretory impairments over a shorter period than previously thought. Finally, we consider cellular explanations to account for the ongoing loss of insulin production despite continued immune therapy that may identify potential targets for treatment. The progressive decline in β cell function raises the question as to whether β cell failure that is independent of immune attack may be involved.

Evidence of β-Cell Dedifferentiation in Human Type 2 Diabetes

CONTEXT

Diabetes is associated with a deficit of insulin-producing β-cells. Animal studies show that β-cells become dedifferentiated in diabetes, reverting to a progenitor-like stage, and partly converting to other endocrine cell types.

OBJECTIVE

To determine whether similar processes occur in human type 2 diabetes, we surveyed pancreatic islets from 15 diabetic and 15 nondiabetic organ donors.

DESIGN

We scored dedifferentiation using markers of endocrine lineage, β-cell-specific transcription factors, and a newly identified endocrine progenitor cell marker, aldehyde dehydrogenase 1A3.

RESULTS

By these criteria, dedifferentiated cells accounted for 31.9% of β-cells in type 2 diabetics vs 8.7% in controls, and for 16.8% vs 6.5% of all endocrine cells (P < .001). The number of aldehyde dehydrogenase 1A3-positive/hormone-negative cells was 3-fold higher in diabetics compared with controls. Moreover, β-cell-specific transcription factors were ectopically found in glucagon- and somatostatin-producing cells of diabetic subjects.

CONCLUSIONS

The data support the view that pancreatic β-cells become dedifferentiated and convert to α- and δ-"like" cells in human type 2 diabetes. The findings should prompt a reassessment of goals in the prevention and treatment of β-cell dysfunction.

Lack of Prox1 Downregulation Disrupts the Expansion and Maturation of Postnatal Murine β-Cells

Transcription factor expression fluctuates during β-cell ontogeny, and disruptions in this pattern can affect the development or function of those cells. Here we uncovered that murine endocrine pancreatic progenitors express high levels of the homeodomain transcription factor Prox1, whereas both immature and mature β-cells scarcely express this protein. We also investigated if sustained Prox1 expression is incompatible with β-cell development or maintenance using transgenic mouse approaches. We discovered that Prox1 upregulation in mature β-cells has no functional consequences; in contrast, Prox1 overexpression in immature β-cells promotes acute fasting hyperglycemia. Using a combination of immunostaining and quantitative and comparative gene expression analyses, we determined that Prox1 upregulation reduces proliferation, impairs maturation, and enables apoptosis in postnatal β-cells. Also, we uncovered substantial deficiency in β-cells that overexpress Prox1 of the key regulator of β-cell maturation MafA, several MafA downstream targets required for glucose-stimulated insulin secretion, and genes encoding important components of FGF signaling. Moreover, knocking down PROX1 in human EndoC-βH1 β-cells caused increased expression of many of these same gene products. These and other results in our study indicate that reducing the expression of Prox1 is beneficial for the expansion and maturation of postnatal β-cells.

The new biology of diabetes

Until recently, type 2 diabetes was seen as a disease caused by an impaired ability of insulin to promote the uptake and utilisation of glucose. Work on forkhead box protein O (FOXO) transcription factors revealed new aspects of insulin action that have led us to articulate a liver- and beta cell-centric narrative of diabetes pathophysiology and treatment. FOXO integrate a surprisingly diverse subset of biological functions to promote metabolic flexibility. In the liver, they controls the glucokinase/glucose-6-phosphatase switch and bile acid pool composition, directing carbons to glucose or lipid utilisation, thus providing a unifying mechanism for the two abnormalities of the diabetic liver: excessive glucose production and increased lipid synthesis and secretion. Moreover, FOXO are necessary to maintain beta cell differentiation, and diabetes development is associated with a gradual loss of FOXO function that brings about beta cell dedifferentiation. We proposed that dedifferentiation is the main cause of beta cell failure and conversion into non-beta endocrine cells, and that treatment should restore beta cell differentiation. Our studies investigating these proposals have revealed new dimensions to the pathophysiology of diabetes that can be leveraged to design new therapies.

Legacy Effect of Foxo1 in Pancreatic Endocrine Progenitors on Adult β-Cell Mass and Function

β-Cell dysfunction in diabetes results from abnormalities of insulin production, secretion, and cell number. These abnormalities may partly arise from altered developmental programming of β-cells. Foxo1 is important to maintain adult β-cells, but little is known about its role in pancreatic progenitor cells as determinants of future β-cell function. We addressed this question by generating an allelic series of somatic Foxo1 knockouts at different stages of pancreatic development in mice. Surprisingly, ablation of Foxo1 in pancreatic progenitors resulted in delayed appearance of Neurogenin3(+) progenitors and their persistence into adulthood as a self-replicating pool, causing a fourfold increase of β-cell mass. Similarly, Foxo1 ablation in endocrine progenitors increased their numbers, extended their survival, and expanded β-cell mass. In contrast, ablation of Foxo1 in terminally differentiated β-cells did not increase β-cell mass nor did it affect Neurogenin3 expression. Despite the increased β-cell mass, islets from mice lacking Foxo1 in pancreatic or endocrine progenitors responded poorly to glucose, resulting in glucose intolerance. We conclude that Foxo1 integrates cues that determine developmental timing, pool size, and functional features of endocrine progenitor cells, resulting in a legacy effect on adult β-cell mass and function. Our results illustrate how developmental programming predisposes to β-cell dysfunction in adults and raise questions on the desirability of increasing β-cell mass for therapeutic purposes in type 2 diabetes.

Insulin-like Growth Factor 2 Overexpression Induces β-Cell Dysfunction and Increases Beta-cell Susceptibility to Damage

The human insulin-like growth factor 2 (IGF2) and insulin genes are located within the same genomic region. Although human genomic studies have demonstrated associations between diabetes and the insulin/IGF2 locus or the IGF2 mRNA-binding protein 2 (IGF2BP2), the role of IGF2 in diabetes pathogenesis is not fully understood. We previously described that transgenic mice overexpressing IGF2 specifically in β-cells (Tg-IGF2) develop a pre-diabetic state. Here, we characterized the effects of IGF2 on β-cell functionality. Overexpression of IGF2 led to β-cell dedifferentiation and endoplasmic reticulum stress causing islet dysfunction in vivo. Both adenovirus-mediated overexpression of IGF2 and treatment of adult wild-type islets with recombinant IGF2 in vitro further confirmed the direct implication of IGF2 on β-cell dysfunction. Treatment of Tg-IGF2 mice with subdiabetogenic doses of streptozotocin or crossing these mice with a transgenic model of islet lymphocytic infiltration promoted the development of overt diabetes, suggesting that IGF2 makes islets more susceptible to β-cell damage and immune attack. These results indicate that increased local levels of IGF2 in pancreatic islets may predispose to the onset of diabetes. This study unravels an unprecedented role of IGF2 on β-cells function.

Epigenetic modifications and long noncoding RNAs influence pancreas development and function

Insulin-producing β cells within the pancreatic islet of Langerhans are responsible for maintaining glucose homeostasis; the loss or malfunction of β cells results in diabetes mellitus. Recent advances in cell purification strategies and sequencing technologies as well as novel molecular tools have revealed that epigenetic modifications and long noncoding RNAs (lncRNAs) represent an integral part of the transcriptional mechanisms regulating pancreas development and β cell function. Importantly, these findings have uncovered a new layer of gene regulation in the pancreas that can be exploited to enhance the restoration and/or repair of β cells to treat diabetes.

Functional and morphological changes in endocrine pancreas following cola drink consumption in rats

Aim

We report the effects of long-term cola beverage drinking on glucose homeostasis, endocrine pancreas function and morphology in rats.

Methods

Wistar rats drank: water (group W), regular cola beverage (group C, sucrose sweetened) or “light” cola beverage (group L, artificially sweetened). After 6 months, 50% of the animals in each group were euthanized and the remaining animals consumed water for the next 6 months when euthanasia was performed. Biochemical assays, insulinemia determination, estimation of insulin resistance (HOMA-IR), morphometry and immunohistochemistry evaluations were performed in pancreas.

Results

Hyperglycemia (16%, p<0.05), CoQ₁₀ (coenzyme-Q₁₀) decrease (−52%,p<0.01), strong hypertriglyceridemia (2.8-fold, p<0.01), hyperinsulinemia (2.4 fold, p<0.005) and HOMA-IR increase (2.7 fold, p<0.01) were observed in C. Group C showed a decrease in number of α cells (−42%, p<0.01) and β cells (−58%, p<0.001) and a moderate increase in α cells’ size after wash-out (+14%, p<0.001). Group L showed reduction in β cells’ size (−9%, p<0.001) and only after wash-out (L₁₂) a 19% increase in size (p<0.0001) with 35% decrease in number of α cells (p<0.01). Groups C and L showed increase in α/β-cell ratio which was irreversible only in C (α/β = +38% in C₆,+30% in C₁₂, p<0.001vs.W₆). Regular cola induced a striking increase in the cytoplasmic expression of Trx1 (Thioredoxin-1) (2.25-fold in C₆ vs. W₆; 2.7-fold in C₁₂ vs. W_12, p<0.0001) and Prx2 (Peroxiredoxin-2) (3-fold in C₆ vs. W₆; 2-fold in C₁₂ vs. W_12, p<0.0001). Light cola induced increase in Trx1 (3-fold) and Prx2 (2-fold) after wash-out (p<0.0001, L₁₂ vs. W₁₂).

Conclusion

Glucotoxicity may contribute to the loss of β cell function with depletion of insulin content. Oxidative stress, suggested by increased expression of thioredoxins and low circulating levels of CoQ₁₀, may follow sustained hyperglycemia. A likely similar panorama may result from the effects of artificially sweetened cola though via other downstream routes.

Glucose induces sensitivity to oxygen deprivation and modulates insulin/IGF-1 signaling and lipid biosynthesis in Caenorhabditis elegans

Diet is a central environmental factor that contributes to the phenotype and physiology of individuals. At the root of many human health issues is the excess of calorie intake relative to calorie expenditure. For example, the increasing amount of dietary sugars in the human diet is contributing to the rise of obesity and type 2 diabetes. Individuals with obesity and type 2 diabetes have compromised oxygen delivery, and thus it is of interest to investigate the impact a high-sugar diet has on oxygen deprivation responses. By utilizing the Caenorhabditis elegans genetic model system, which is anoxia tolerant, we determined that a glucose-supplemented diet negatively impacts responses to anoxia and that the insulin-like signaling pathway, through fatty acid and ceramide synthesis, modulates anoxia survival. Additionally, a glucose-supplemented diet alters lipid localization and initiates a positive chemotaxis response. Use of RNA-sequencing analysis to compare gene expression responses in animals fed either a standard or glucose-supplemented diet revealed that glucose impacts the expression of genes involved with multiple cellular processes including lipid and carbohydrate metabolism, stress responses, cell division, and extracellular functions. Several of the genes we identified show homology to human genes that are differentially regulated in response to obesity or type 2 diabetes, suggesting that there may be conserved gene expression responses between C. elegans fed a glucose-supplemented diet and a diabetic and/or obesity state observed in humans. These findings support the utility of the C. elegans model for understanding the molecular mechanisms regulating dietary-induced metabolic diseases.