Glucose-responsive Insulin Secretion Research Articles

8433 Elucidation of the Molecular Basis of Human and Mouse Pancreatic β-Cell Senescence Induced by Hyperglycemia

Abstract Disclosure: K. Iwasaki: None. P. Carapeto: None. C. Aguayo-Mazzucato: None. Background and AIM: Senescent cells accumulate with age and contribute to the development of chronic diseases, including Type 2 Diabetes (T2D). Whereas senescence is an important pathogenic mechanism in diabetes, the role of hyperglycemia as a metabolic driver of pancreatic β-cells has not been clarified. The aim of this study is to elucidate the molecular basis of hyperglycemia-induced pancreatic β-cell senescence using human and rodent islets. Methods: 1) Human islets were cultured for 2 weeks in 20.2 mM high (HG) or 2.8mM low glucose (LG), and analyzed by qPCR and glucose-responsive insulin secretion (GSIS) to explore the molecular basis of senescence in ex vivo. To test the effects of senescent cell removal, senolytics Dasatinib (1μM) and Quercetin (20μM) (DQ) were used. 2) To evaluate the effects of hyperglycemia in vivo, we transplanted mouse and human islets under the kidney capsule of normoglycemic (NG) or streptozocin-induced hyperglycemic (Stz-Db) immunodeficient mice for two weeks. Graft function was evaluated by intraperitoneal glucose tolerance test and cellular identity using qPCR or immunohistochemistry. DQ (5mg/kg/day + 50mg/kg/day) was used to evaluate the effects of removing senescent cells in transplantation (Tx). To investigate the effect of specific removal of p16-positive senescent β-cells in transplanted islets, INK-ATTAC mice islets (p16Ink4a-mediated apoptosis by targeted activation of caspases) were transplanted into Stz-Db and treated with BB homodimer (BB) to remove p16+ cells or vehicle. Results: (1) Human islets from 5 healthy donors cultured in HG had an increased senescence index (mean of senescence markers p16, p21 and HMGB1 mRNA) when compared to LG islets (p<0.05) and lost glucose responsiveness as evaluated by ex vivo GSIS compared to LG (p<0.05). 2) Human islets (1000IEQ) were transplanted to Stz-Db or NG mice. In Stz-Db graft, P21 mRNA significantly increased with decreased expression of β-cell genes when compared to NG. Stz-Db mice treated with DQ (Db-DQ) for 5 days after Tx, significantly decreased expression of senescence index (p<0.05) and increased in β-cell index (mean of β-cell hallmark genes) (p<0.05) at mRNA levels. Stz-Db mice transplanted with INK-ATTAC mice islets had lower fed glucose levels, decreased p16 mRNA, increased expression β-cell hallmark genes and improved insulin secretion ex vivo after removal of p16+ cells. Conclusion: Sustained exposure of human islets to hyperglycemia induced cellular senescence, leading to pancreatic β-cell dysfunction and loss of cellular identity. Furthermore, elimination of senescent cells may protect pancreatic β-cells from hyperglycemia-induced functional decline, which may have potential clinical application in both Type 1 Diabetes and T2D. Presentation: 6/2/2024

Scalable Generation of 3D Pancreatic Islet Organoids from Human Pluripotent Stem Cells in Suspension Bioreactors.

We describe a scalable method for the robust generation of 3D pancreatic islet-like organoids from human pluripotent stem cells using suspension bioreactors. Our protocol involves a 6-stage, 20-day directed differentiation process, resulting in the production of 104-105 organoids. These organoids comprise α- and β-like cells that exhibit glucose-responsive insulin and glucagon secretion. We detail methods for culturing, passaging, and cryopreserving stem cells as suspended clusters and for differentiating them through specific growth media and exogenous factors added in a stepwise manner. Additionally, we address quality control measures, troubleshooting strategies, and functional assays for research applications.

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

Aims/hypothesisRecovering 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.MethodsIn 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.ResultsAdjudin 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/interpretationAdjudin 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 availabilityRaw 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).Graphical

Glucose-stimulated insulin secretion depends on FFA1 and Gq in neonatal mouse islets

Aims/hypothesisAfter birth, the neonatal islets gradually acquire glucose-responsive insulin secretion, a process that is subjected to maternal imprinting. Although NEFA are major components of breastmilk and insulin secretagogues, their role for functional maturation of neonatal beta cells is still unclear. NEFA are the endogenous ligands of fatty acid receptor 1 (FFA1, encoded by Ffar1 in mice), a Gq-coupled receptor with stimulatory effect on insulin secretion. This study investigates the role of FFA1 in neonatal beta cell function and in the adaptation of offspring beta cells to parental high-fat feeding.MethodsWild-type (WT) and Ffar1−/− mice were fed high-fat (HFD) or chow diet (CD) for 8 weeks before mating, and during gestation and lactation. Blood variables, pancreas weight and insulin content were assessed in 1-, 6-, 11- and 26-day old (P1–P26) offspring. Beta cell mass and proliferation were determined in P1–P26 pancreatic tissue sections. FFA1/Gq dependence of insulin secretion was evaluated in isolated islets and INS-1E cells using pharmacological inhibitors and siRNA strategy. Transcriptome analysis was conducted in isolated islets.ResultsBlood glucose levels were higher in CD-fed Ffar1−/− P6-offspring compared with CD-fed WT P6-offspring. Accordingly, glucose-stimulated insulin secretion (GSIS) and its potentiation by palmitate were impaired in CD Ffar1−/− P6-islets. In CD WT P6-islets, insulin secretion was stimulated four- to fivefold by glucose and five- and sixfold over GSIS by palmitate and exendin-4, respectively. Although parental HFD increased blood glucose in WT P6-offspring, it did not change insulin secretion from WT P6-islets. In contrast, parental HFD abolished glucose responsiveness (i.e. GSIS) in Ffar1−/− P6-islets. Inhibition of Gq by FR900359 or YM-254890 in WT P6-islets mimicked the effect of Ffar1 deletion, i.e. suppression of GSIS and of palmitate-augmented GSIS. The blockage of Gi/o by pertussis toxin (PTX) enhanced (100-fold) GSIS in WT P6-islets and rendered Ffar1−/− P6-islets glucose responsive, suggesting constitutive activation of Gi/o. In WT P6-islets, FR900359 cancelled 90% of PTX-mediated stimulation, while in Ffar1−/− P6-islets it completely abolished PTX-elevated GSIS. The secretory defect of Ffar1−/− P6-islets did not originate from insufficient beta cells, since beta cell mass increased with the offspring’s age irrespective of genotype and diet. In spite of that, in the breastfed offspring (i.e. P1–P11) beta cell proliferation and pancreatic insulin content had a genotype- and diet-driven dynamic. Under CD, the highest proliferation rate was reached by the Ffar1−/− P6 offspring (3.95% vs 1.88% in WT P6), whose islets also showed increased mRNA levels of genes (e.g. Fos, Egr1, Jun) typically high in immature beta cells. Although parental HFD increased beta cell proliferation in both WT (4.48%) and Ffar1−/− (5.19%) P11 offspring, only the WT offspring significantly increased their pancreatic insulin content upon parental HFD (5.18 µg under CD to 16.93 µg under HFD).Conclusions/interpretationFFA1 promotes glucose-responsive insulin secretion and functional maturation of newborn islets and is required for adaptive offspring insulin secretion in the face of metabolic challenge, such as parental HFD.Graphical

Aberrant Expression of Rest4 Gene in Low-Functioning Pancreatic Beta Cell Line.

Repressor element-1 silencing transcription factor (Rest) is not expressed in pancreatic beta cells and neuronal cells. However, Rest4, a truncated form of Rest, is expressed in high passaged MIN6 (HP-MIN6) cells, a pancreatic beta cell line that lost glucose-responsive insulin secretion. Rest4 is also expressed in injured MIN6 cells and isolated islets. Herein, the forced expression of dominant negative form of Rest in HP-MIN6 cells was subjected to microarray analysis of gene expression to investigate the role of Rest4 gene in MIN6 cells. Furthermore, the forced expression of Rest4 gene in MIN6 cells was subjected to microarray analysis of gene expression to investigate the function of Rest4 in normal insulin-producing cells. The results showed that Rest4 inhibits cell proliferation and DNA and RNA metabolism and stimulates secretory mechanisms and nervous system gene expression. These findings suggest that Rest4 may act defensively against cellular injury in pancreatic beta cells.

A FFAR1 full agonist restores islet function in models of impaired glucose-stimulated insulin secretion and diabetic non-human primates.

The free fatty acid receptor 1 (FFAR1/GPR40) mediates fatty acid-induced insulin secretion from pancreatic β-cells. At least 3 distinct binding sites exist on the FFAR1 receptor and numerous synthetic ligands have been investigated for their anti-diabetic actions. Fasiglifam, binds to site-1 and stimulates intra-cellular calcium release and improves glycemic control in diabetic patients. Recently, small molecule FFAR1 agonists were discovered which bind to site-3, stimulating both intra-cellular calcium and cAMP, resulting in insulin and glucagon-like peptide-1 (GLP-1) secretion. The ability of our site-3 FFAR1 agonist (compound A) to control blood glucose was evaluated in spontaneously diabetic cynomolgus monkeys during an oral glucose tolerance test. In type-2 diabetic (T2D) animals, significant reductions in blood glucose and insulin were noted. To better understand the mechanism of these in vivo findings, we evaluated the effect of compound A in islets under several conditions of dysfunction. First, healthy human and non-human primate islets were treated with compound A and showed potentiation of insulin and glucagon secretion from both species. Next, we determined glucose-responsive insulin secretion under gluco-lipotoxic conditions and from islets isolated from type-2 diabetic humans. Despite a dysfunctional phenotype that failed to secrete insulin in response to glucose, site-3 FFAR1 agonism not only enhanced insulin secretion, but restored glucose responsiveness across a range of glucose concentrations. Lastly, we treated ex vivo human islets chronically with a sulfonylurea to induce secondary beta-cell failure. Again, this model showed reduced glucose-responsive insulin secretion that was restored and potentiated by site-3 FFAR1 agonism. Together these data suggest a mechanism for FFAR1 where agonists have direct effects on islet hormone secretion that can overcome a dysfunctional T2D phenotype. These unique characteristics of FFAR1 site-3 agonists make them an appealing potential therapy to treat type-2 diabetes.

Islet allografts expressing a PD-L1 and IDO fusion protein evade immune rejection and reverse preexisting diabetes in immunocompetent mice without systemic immunosuppression

Allogeneic islet transplantation is a promising experimental therapy for poorly controlled diabetes. Despite pharmacological immunosuppression, long-term islet engraftment remains elusive. Here, we designed a synthetic fusion transgene coupling PD-L1 and indoleamine dioxygenase [hereafter PIDO] whose constitutive expression prevents immune destruction of genetically engineered islet allograft transplanted in immunocompetent mice. PIDO expressing murine islets maintain robust dynamic insulin secretion in vitro and when transplanted in allogeneic hyperglycemic murine recipients reverse pre-existing streptozotocin-induced and autoimmune diabetes in the absence of pharmacological immunosuppression for more than 50 and 8 weeks, respectively, and is dependent on host CD4 competence. Additionally, PIDO expression in allografts preserves endocrine functional viability of islets and promotes a localized tolerogenic milieu characterized by the suppression of host CD8 T cell and phagocyte recruitment and accumulation of FOXP3+ Tregs. Furthermore, in the canine model of xenogeneic islet transplantation, muscle implanted PIDO-expressing porcine islets displayed physiological glucose-responsive insulin secretion competency in euglycemic recipient for up to 20 weeks. In conclusion, the PIDO transgenic technology enables host CD4+ T cell-modulated immune evasiveness and long-term functional viability of islet allo- and xenografts in immune-competent recipients without the need for pharmacological immune suppression and would allow for improved outcomes for tissue transplantation.

Controlled Release of Insulin Based on Temperature and Glucose Dual Responsive Biomicrocapsules.

The treatment of diabetes lies in developing novel functional carriers, which are expected to have the unique capability of monitoring blood glucose levels continuously and dispensing insulin correctly and timely. Hence, this study is proposing to create a smart self-regulated insulin delivery system according to changes in glucose concentration. Temperature and glucose dual responsive copolymer microcapsules bearing N-isopropylacrylamide and 3-acrylamidophenylboronic acid as main components were developed by bottom-spray coating technology and template method. The insulinoma β-TC6 cells were trapped in the copolymer microcapsules by use of temperature sensitivity, and then growth, proliferation, and glucose-responsive insulin secretion of microencapsulated cells were successively monitored. The copolymer microcapsules showed favorable structural stability and good biocompatibility against β-TC6 cells. Compared with free cells, the biomicrocapsules presented a more effective and safer glucose-dependent insulin release behavior. The bioactivity of secreted and released insulin did not differ between free and encapsulated β-TC6 cells. The results demonstrated that the copolymer microcapsules had a positive effect on real-time sensing of glucose and precise controlled release of insulin. The intelligent drug delivery system is supposed to mimic insulin secretion in a physiological manner, and further provide new perspectives and technical support for the development of artificial pancreas.

Functional, metabolic and transcriptional maturation of human pancreatic islets derived from stem cells

Transplantation of pancreatic islet cells derived from human pluripotent stem cells is a promising treatment for diabetes. Despite progress in the generation of stem-cell-derived islets (SC-islets), no detailed characterization of their functional properties has been conducted. Here, we generated functionally mature SC-islets using an optimized protocol and benchmarked them comprehensively against primary adult islets. Biphasic glucose-stimulated insulin secretion developed during in vitro maturation, associated with cytoarchitectural reorganization and the increasing presence of alpha cells. Electrophysiology, signaling and exocytosis of SC-islets were similar to those of adult islets. Glucose-responsive insulin secretion was achieved despite differences in glycolytic and mitochondrial glucose metabolism. Single-cell transcriptomics of SC-islets in vitro and throughout 6 months of engraftment in mice revealed a continuous maturation trajectory culminating in a transcriptional landscape closely resembling that of primary islets. Our thorough evaluation of SC-islet maturation highlights their advanced degree of functionality and supports their use in further efforts to understand and combat diabetes.

RECENT APPROACHES IN GLUCOSE RESPONSIVE INSULIN DELIVERY SYSTEM

Diabetes mellitus is a chronic medical condition currently affecting 382 million people across the globe, caused due to increased blood glucose levels due to less insulin production or insulin resistance. Subcutaneous insulin administration for diabetes is the only most accepted therapy for maintaining blood glucose levels in diabetic patients. Many patients with advanced type II diabetes mellitus need to regularly monitor their blood glucose level to keep their blood glucose level in the target range. However long-term insulin therapy through an invasive route of administration causes problems with patient compliance and a sudden decrease in blood glucose levels. An artificial closed-loop insulin release system that mimics the glucose-responsive insulin secretion by β-cells of pancreas is one of the ways to overcome the problem faced with the conventional method of insulin administration. Many polymeric formulations showed an improved glucose-responsive release of insulin when incorporated with glucose-responsive catalysts such as glucose oxidase, phenylboronic acid, and glucose binding proteins, the release rate can be controlled by optimizing the concentration of glucose-responsive catalysts. This article is been focused on different mechanisms of glucose-responsive release by incorporation with glucose-responsive catalysts.

STEM CELL therapy and Diabetes

Diabetes is the most prevailing disease with progressive incidence worldwide. To the moment, there is no permanent treatment available for diabetes. Hopefully, stem cell-derived islets may likely be the future therapy. However, the field has limited capability to generate beta-like cells with both phenotypic maturation and functional glucose stimulated insulin secretion that is like primary human islets. Several promising approaches to cure diabetes are to use Mesenchymal stem cells (MSCs) from perinatal tissues or human pluripotent stem cells (hPSCs), including embryonic stem cells (hESCs) and human induced PCSs (hiPSCs). It is also crucial to establish a reliable method of delivering the cells to patients ensuring rapid in-vivo engraftment and function. Overcoming these barriers to beta cell differentiation and transplantation will be key to bring this dream to the clinic. Much research reported the generation of stem cell-derived beta-like cells expressing key maturation genes and capable of dynamic glucose-responsive insulin secretion. Other have investigated the potential of vascularized transplant scaffolds, as well as gas chamber to support beta cell survival and function following transplantation. Here, we summarize recent advances in the differentiation of MSCs and hPSCs into pancreatic beta cells. The generation of stem cell-derived islets with functional glucose stimulated insulin secretion has brought the field closer to clinical translation, but still the challenges for the need of improving their insulin content and secretory capacity.

Inceptor intercepts insulin signaling in pancreatic β-cells.

Insulin resistance and pancreatic beta-cell failure are two major pathological mechanisms in type 2 diabetes mellitus. It is known that at the very least, beta-cell failure involves a decrease in glucose-responsive insulin secretion and a decrease in cell volume.

Erythrocyte-Membrane-Enveloped Biomineralized Metal–Organic Framework Nanoparticles Enable Intravenous Glucose-Responsive Insulin Delivery

A "closed-loop" insulin delivery system that can mimic the dynamic and glucose-responsive insulin secretion as islet β-cells is desirable for the therapy of type 1 and advanced type 2 diabetes mellitus (T1DM and T2DM). Herein, we introduced a kind of "core-shell"-structured glucose-responsive nanoplatform to achieve intravenous "smart" insulin delivery. A finely controlled one-pot biomimetic mineralization method was utilized to coencapsulate insulin, glucose oxidase (GOx), and catalase (CAT) into the ZIF-8 nanoparticles (NPs) to construct the "inner core", where an efficient enzyme cascade system (GOx/CAT group) served as an optimized glucose-responsive module that could rapidly catalyze glucose to yield gluconic acid to lower the local pH and effectively consume the harmful byproduct hydrogen peroxide (H2O2), inducing the collapse of pH-sensitive ZIF-8 NPs to release insulin. The erythrocyte membrane, a sort of natural biological derived lipid bilayer membrane which has intrinsic biocompatibility, was enveloped onto the surface of the "inner core" as the "outer shell" to protect them from elimination by the immune system, thus making the NPs intravenously injectable and could stably maintain a long-term existence in blood circulation. The in vitro and in vivo results indicate that our well-designed nanoplatform possesses an excellent glucose-responsive property and can maintain the blood glucose levels of the streptozocin (STZ)-induced type 1 diabetic mice at the normoglycemic state for up to 24 h after being intravenously administrated, confirming an intravenous insulin delivery strategy to overcome the deficits of conventional daily multiple subcutaneous insulin administration and offering a potential candidate for long-term T1DM treatment.

ILDR2 stabilization is regulated by its interaction with GRP78

Ildr2 was initially identified as a genetic modifier of diabetes susceptibility in B6.DBA Lepob congenic mice, and was associated with decreased β-cell replication rates, reduced β-cell mass, and persistent mild hypoinsulinemic hyperglycemia. However, the molecular mechanisms of how the ILDR2 protein is involved in these effects are largely unknown. We sought to identify ILDR2-interacting proteins to further elucidate the molecular mechanisms underpinning ILDR2 function in pancreatic β-cells. Using TAP tag technology, we purified proteins interacting with ILDR2 in the pancreatic β-cell line MIN6, and identified the endoplasmic reticulum resident chaperones, GRP78 and PDIA1, as novel proteins interacting with ILDR2. We demonstrated that GRP78 interacted with ILDR2 and was possibly involved in ILDR2 stabilization by inhibiting ubiquitin–proteasome degradation. Additionally, adenoviral ILDR2 knockdown led to reduced glucose-responsive insulin secretion in MIN6 β-cells, suggesting ILDR2 may be implicated in a new pathway in hypoinsulinemic hyperglycemia. These data provide evidence for a novel association between GRP78 and ILDR2, and suggest GPR78-ILDR2 may a novel target for diabetic therapeutic modulation in decreased insulin secretion.

The hepatokine fetuin-A disrupts functional maturation of pancreatic beta cells

Aims/hypothesisNeonatal beta cells carry out a programme of postnatal functional maturation to achieve full glucose responsiveness. A partial loss of the mature phenotype of adult beta cells may contribute to a reduction of functional beta cell mass and accelerate the onset of type 2 diabetes. We previously found that fetuin-A, a hepatokine increasingly secreted by the fatty liver and a determinant of type 2 diabetes, inhibits glucose-stimulated insulin secretion (GSIS) of human islets. Since fetuin-A is a ubiquitous fetal glycoprotein that declines peripartum, we examined here whether fetuin-A interferes with the functional maturity of beta cells.MethodsThe effects of fetuin-A were assessed during in vitro maturation of porcine neonatal islet cell clusters (NICCs) and in adult human islets. Expression alterations were examined via microarray, RNA sequencing and reverse transcription quantitative real-time PCR (qRT-PCR), proteins were analysed by western blotting and immunostaining, and insulin secretion was quantified in static incubations.ResultsNICC maturation was accompanied by the gain of glucose-responsive insulin secretion (twofold stimulation), backed up by mRNA upregulation of genes governing beta cell identity and function, such as NEUROD1, UCN3, ABCC8 and CASR (Log2 fold change [Log2FC] > 1.6). An active TGFβ receptor (TGFBR)–SMAD2/3 pathway facilitates NICC maturation, since the TGFBR inhibitor SB431542 counteracted the upregulation of aforementioned genes and de-repressed ALDOB, a gene disallowed in mature beta cells. In fetuin-A-treated NICCs, upregulation of beta cell markers and the onset of glucose responsiveness were suppressed. Concomitantly, SMAD2/3 phosphorylation was inhibited. Transcriptome analysis confirmed inhibitory effects of fetuin-A and SB431542 on TGFβ-1- and SMAD2/3-regulated transcription. However, contrary to SB431542 and regardless of cMYC upregulation, fetuin-A inhibited beta cell proliferation (0.27 ± 0.08% vs 1.0 ± 0.1% Ki67-positive cells in control NICCs). This effect was sustained by reduced expression (Log2FC ≤ −2.4) of FOXM1, CENPA, CDK1 or TOP2A. In agreement, the number of insulin-positive cells was lower in fetuin-A-treated NICCs than in control NICCs (14.4 ± 1.2% and 22.3 ± 1.1%, respectively). In adult human islets fetuin-A abolished glucose responsiveness, i.e. 1.7- and 1.1-fold change over 2.8 mmol/l glucose in control- and fetuin-A-cultured islets, respectively. In addition, fetuin-A reduced SMAD2/3 phosphorylation and suppressed expression of proliferative genes. Of note, in non-diabetic humans, plasma fetuin-A was negatively correlated (p = 0.013) with islet beta cell area.Conclusions/interpretationOur results suggest that the perinatal decline of fetuin-A relieves TGFBR signalling in islets, a process that facilitates functional maturation of neonatal beta cells. Functional maturity remains revocable in later life, and the occurrence of a metabolically unhealthy milieu, such as liver steatosis and elevated plasma fetuin-A, can impair both function and adaptive proliferation of beta cells.Data availabilityThe RNAseq datasets and computer code produced in this study are available in the Gene Expression Omnibus (GEO): GSE144950; https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE144950Graphical abstract

FSTL3-Neutralizing Antibodies Enhance Glucose-Responsive Insulin Secretion in Dysfunctional Male Mouse and Human Islets.

Diabetes is caused by insufficient insulin production from pancreatic beta cells or insufficient insulin action, leading to an inability to control blood glucose. While a wide range of treatments exist to alleviate the symptoms of diabetes, therapies addressing the root cause of diabetes through replacing lost beta cells with functional cells remain an object of active pursuit. We previously demonstrated that genetic deletion of Fstl3, a critical regulator of activin activity, enhanced beta cell number and glucose-responsive insulin production. These observations suggested the hypothesis that FSTL3 neutralization could be used to therapeutically enhance beta cell number and function in humans. To pursue this possibility, we developed an FSTL3-neutralizing antibody, FP-101, and characterized its ability to prevent or disrupt FSTL3 from complexing with activin or related ligands. This antibody was selective for FSTL3 relative to the closely related follistatin, thereby reducing the chance for off-target effects. In vitro assays with FP-101 and activin revealed that FP-101-mediated neutralization of FSTL3 can enhance both insulin secretion and glucose responsiveness to nonfunctional mouse and human islets under conditions that model diabetes. Thus, FSTL3 neutralization may provide a novel therapeutic strategy for treating diabetes through repairing dysfunctional beta cells.

Advances Toward Engineering Functionally Mature Human Pluripotent Stem Cell-Derived β Cells.

Human stem cell-derived β (SC-β) cells have the potential to revolutionize diabetes treatment through disease modeling, drug screening, and cellular therapy. SC-β cells are likely to represent an early clinical translation of differentiated human pluripotent stem cells (hPSC). In 2014, two groups generated the first in vitro-differentiated glucose-responsive SC-β cells, but their functional maturation at the time was low. This review will discuss recent advances in the engineering of SC-β cells to understand and improve SC-β cell differentiation and functional maturation, particularly new differentiation strategies achieving dynamic glucose-responsive insulin secretion with rapid correction to normoglycemia when transplanted into diabetic mice.

A Nutrient-Sensing Transition at Birth Triggers Glucose-Responsive Insulin Secretion

A drastic transition at birth, from constant maternal nutrient supply in utero to intermittent postnatal feeding, requires changes in the metabolic system of the neonate. Despite their central role in metabolic homeostasis, little is known about how pancreatic β cells adjust to the new nutritional challenge. Here, we find that after birth β cell function shifts from amino acid- to glucose-stimulated insulin secretion in correlation with the change in the nutritional environment. This adaptation is mediated by a transition in nutrient sensitivity of the mTORC1 pathway, which leads to intermittent mTORC1 activity. Disrupting nutrient sensitivity of mTORC1 in mature β cells reverts insulin secretion to a functionally immature state. Finally, manipulating nutrient sensitivity of mTORC1 in stem cell-derived β cells invitro strongly enhances their glucose-responsive insulin secretion. These results reveal a mechanism by which nutrients regulate β cell function, thereby enabling a metabolic adaptation for the newborn.

A CRISPR/Cas9 genome editing pipeline in the EndoC-βH1 cell line to study genes implicated in beta cell function.

Type 2 diabetes (T2D) is a global pandemic with a strong genetic component, but most causal genes influencing the disease risk remain unknown. It is clear, however, that the pancreatic beta cell is central to T2D pathogenesis. In vitro gene-knockout (KO) models to study T2D risk genes have so far focused on rodent beta cells. However, there are important structural and functional differences between rodent and human beta cell lines. With that in mind, we have developed a robust pipeline to create a stable CRISPR/Cas9 KO in an authentic human beta cell line (EndoC-βH1). The KO pipeline consists of a dual lentiviral sgRNA strategy and we targeted three genes ( INS, IDE, PAM) as a proof of concept. We achieved a significant reduction in mRNA levels and complete protein depletion of all target genes. Using this dual sgRNA strategy, up to 94kb DNA were cut out of the target genes and the editing efficiency of each sgRNA exceeded >87.5%. Sequencing of off-targets showed no unspecific editing. Most importantly, the pipeline did not affect the glucose-responsive insulin secretion of the cells. Interestingly, comparison of KO cell lines for NEUROD1 and SLC30A8 with siRNA-mediated knockdown (KD) approaches demonstrate phenotypic differences. NEUROD1-KO cells were not viable and displayed elevated markers for ER stress and apoptosis. NEUROD1-KD, however, only had a modest elevation, by 34%, in the pro-apoptotic transcription factor CHOP and a gene expression profile indicative of chronic ER stress without evidence of elevated cell death. On the other hand, SLC30A8-KO cells demonstrated no reduction in K ATP channel gene expression in contrast to siRNA silencing. Overall, this strategy to efficiently create stable KO in the human beta cell line EndoC-βH1 will allow for a better understanding of genes involved in beta cell dysfunction, their underlying functional mechanisms and T2D pathogenesis.

Distinct alterations of gut morphology and microbiota characterize accelerated diabetes onset in nonobese diabetic mice

Distinct alterations of gut morphology and microbiota characterize accelerated diabetes onset in nonobese diabetic mice