Introduction and Objective: Type 2 diabetes (T2D) is closely linked to insulin resistance and loss of functional β-cell mass. However, not all insulin-resistant individuals develop T2D. We aimed to investigate the transcriptomic and m6A RNA methylation modifications in β-cells during their successful adaptation to insulin resistance (IR). Methods: We performed mRNA-seq on sorted β-cells from mouse models with graded compensation to IR: (a) a dietary model (HFD), (b) a genetic model (LIRKO, liver-specific insulin receptor KO on chow), and (c) a combined model (LIRKO on a HFD) (n=86 mice). We correlated transcriptomic data with β-cell compensation readouts, and integrated these findings with scRNA-seq datasets from human β-cells with/without T2D. Additionally, we conducted m6A-seq in these mouse islets (n=155 mice). Results: Our analyses identified the ubiquitin-ligase substrate adaptor KCTD17 as a key regulator of β-cell adaptation. Expression of KCTD17 positively correlated with increased β-cell function and mass in mouse models but was downregulated at both mRNA and protein levels in human T2D β-cells. KCTD17 KD in human β-cells increased apoptosis and impaired GSIS. Transcriptomic analysis of KCTD17 KD cells revealed dysregulated pathways linked to β-cell function and identity. Antibody-microarray analysis showed reductions in MAPK and insulin signaling. Co-immunoprecipitation experiments demonstrated that KCTD17 binds and regulates the degradation of clathrin, a key player in insulin receptor internalization. m6A-seq revealed differential methylation of chromatin-modifying enzymes during β-cell compensation. Supporting this, ATAC-seq data from human T2D islets showed decreased chromatin accessibility at the KCTD17 locus. Conclusion: These findings position KCTD17 as a novel regulator of β-cells, and demonstrate the importance of m6A methylation in chromatin remodeling and transcriptional regulation during β-cell adaptation to IR. D.F. De Jesus: None. N.K. Brown: None. Z. Zhang: None. G. Fogarty: None. J. Wei: None. J. Hu: None. S. Kahraman: Employee; Boehringer-Ingelheim. A. El Ouaamari: None. E. Dirice: None. C. He: None. R. Kulkarni: Advisory Panel; Novo Nordisk, Biomea Fusion, REDD Pharma, Inversago Pharma. Research Support; Inversago Pharma. Stock/Shareholder; Biomea Fusion. NIH (R01 DK067536, UC4 DK116278, RC2 DK139552, and K99 DK135927)

Type 1 diabetes (T1D) results from autoimmune-mediated destruction of insulin-producing β cells in the pancreatic islet. This process is modulated by pro-inflammatory cytokine signaling, which has been previously shown to alter protein expression in ex vivo islets. Herein, we applied top-down proteomics to globally evaluate proteoforms from human islets treated with proinflammatory cytokines (interferon-γ and interleukin-1β). We measured 1636 unique proteoforms across six donors and two time points (control and 24 h post-treatment) and observed consistent changes in abundance across the glicentin-related pancreatic polypeptide (GRPP) and major proglucagon fragment regions of glucagon, as well as the LF-19/catestatin and vasostatin-1/2 region of chromogranin-A. We also observe several proteoforms that increase after cytokine-treatment or are exclusively observed after cytokine-treatment, including forms of beta-2 microglobulin (B2M), high-mobility group N2 protein (HMGN2), and chemokine (C-X-C motif) ligands (CXCL). Together, our quantitative results provide a baseline proteoform profile for human islets and identify several proteoforms that may serve as interesting candidate markers for T1D progression or therapeutic intervention. SUMMARY: This work applies a top-down proteomics workflow for the characterization and label-free quantification of proteoforms from human islets in the context of inflammation. The workflow is optimized for challenges unique to the islet proteome including high disulfide-linkage content and frequent truncation events, resulting in many proteoforms < 5kDa. There are limited examples of top-down proteomics characterization of human islets, thus this study provides a baseline characterization of the proteoforms of major hormones including chromogranin-A (CHGA), chromogranin-B/ secretogranin-1 (CHGB/SCG1), chromogranin-C/ secretogranin-2 (CHGC/SCG2), islet amyloid polypeptide (amylin/IAPP), insulin (INS), glucagon (GCG), pancreatic polypeptide prohormone (PPY), somatostatin (SST), and neurosecretory protein VGF (VGF). The quantitative results of proteoform abundances before and after cytokine treatment, which mimics the proinflammatory environment during T1D progression, provides interesting insights on how prohormone processing is altered under a proinflammatory environment.

Maturity onset diabetes of the young type 8 (MODY8) is caused by genetic mutations in the CEL gene which is expressed primarily in pancreatic acinar cells. MODY8 patients develop pancreatic exocrine and endocrine dysfunction. How the enzymatic function of mutant (MUT) CEL contributes to the development of diabetes in MODY8 is unknown. Palmitic Acid Hydroxy Stearic Acids (PAHSAs) are signaling lipids that augment glucose-stimulated insulin secretion (GSIS). CEL is the major PAHSA hydrolytic enzyme in the pancreas. Aim: To determine whether CEL regulates insulin secretion and whether the increased PAHSA hydrolytic activity of MUT CEL contributes to MODY8 pathogenesis. Methods: We overexpressed wildtype (WT) or MUT CEL in acinar cells in vitro and in vivo. In vivo, we used 2 approaches both with AAV8 driven by an acinar cell specific promoter: intraductal AAV injections in wildtype mice and intraperitoneal AAV injections in CEL KO mice. CEL overexpression was detected exclusively in acinar cells. Results: 9-PAHSA augments GSIS in human pancreatic beta cells. Recombinant CEL inhibits the PAHSA effect. MUT CEL overexpression in acinar cells increases 9-PAHSA hydrolytic activity compared to WT CEL. In vivo, MUT CEL expression in acinar cells of wildtype mice markedly impairs glucose tolerance. In CEL KO mice, expression of MUT CEL in acinar cells impairs GSIS. Both WT and MUT CEL reduce total pancreatic PAHSA levels in CEL KO mice. However, 12/13-PAHSAs were reduced only with MUT CEL expression. Conclusions: 1) CEL in acinar cells alters PAHSA hydrolysis and modulates insulin secretion. 2) MUT CEL potentially contributes to the development of diabetes by increasing PAHSA hydrolysis and thereby limiting the normal PAHSA-induced augmentation of GSIS. 3) These data highlight the critical role of acinar-beta cell interactions and the physiologic role of PAHSAs in insulin secretion and provide opportunities for developing strategies to treat MODY8 and other forms of diabetes. Disclosure A. Santoro: None. S. Kahraman: Employee; Boehringer-Ingelheim. G. Basile: None. K. El Jellas: None. J. Hu: None. R. Tarpey: None. B.B. Johansson: None. E. Dirice: None. I. Syed: None. D. Siegel: None. A. Molven: None. B.B. Kahn: Advisory Panel; Janssen Pharmaceuticals, Inc. Consultant; Vida Ventures Advisors, Arrowhead Pharmaceuticals, Inc. R. Kulkarni: Advisory Panel; Novo Nordisk, Biomea Fusion, Inc. Consultant; Inversago Pharma. Advisory Panel; REDD Pharmaceutical. Funding K01 DK128075 (Anna Santoro), U01DK135095 (Rohit N. Kulkarni), R01DK067536 (Rohit N. Kulkarni), NIH R01 DK106210 (Barbara B. Kahn), JPB foundation (Barbara B. Kahn), and NIH P30 DK135043 (Barbara B. Kahn). Anna Santoro, Sevim Kahraman, Barbara B. Kahn and Rohit N. Kulkarni contributed equally.

Vascular function is dynamically regulated and dependent on a bevy of cell types and factors that work in concert across the vasculature. The vasoactive eicosanoid, 20-Hydroxyeicosatetraenoic acid (20-HETE) is a key player in this system influencing the sensitivity of the vasculature to constrictor stimuli, regulating endothelial function, and influencing the renin angiotensin system (RAS), as well as being a driver of vascular remodeling independent of blood pressure elevations. Several of these bioactions are accomplished through the ligand-receptor pairing between 20-HETE and its high-affinity receptor, GPR75. This 20-HETE axis is at the root of various vascular pathologies and processes including ischemia induced angiogenesis, arteriogenesis, septic shock, hypertension, atherosclerosis, myocardial infarction and cardiometabolic diseases including diabetes and insulin resistance. Pharmacologically, several preclinical tools have been developed to disrupt the 20-HETE axis including 20-HETE synthesis inhibitors (DDMS and HET0016), synthetic 20-HETE agonist analogues (20-5,14-HEDE and 20-5,14-HEDGE) and 20-HETE receptor blockers (AAA and 20-SOLA). Systemic or cell-specific therapeutic targeting of the 20-HETE-GPR75 axis continues to be an invaluable approach as studies examine the molecular underpinnings activated by 20-HETE under various physiological settings. In particular, the development and characterization of 20-HETE receptor blockers look to be a promising new class of compounds that can provide a considerable benefit to patients suffering from these cardiovascular pathologies.

Objective: G-protein coupled receptor 75 (GPR75) has been identified as the high-affinity receptor of 20-hydroxyeicosatetraenoic acid (20-HETE), a vasoactive and proinflammatory lipid, and mice overproducing 20-HETE have been shown to develop insulin resistance when fed a high-fat diet (HFD), which was prevented by a 20-HETE receptor blocker. Simultaneously, a large-scale exome sequencing of 640,000 subjects identified an association between loss-of-function GPR75 variants and protection against obesity.Methods: Wild-type (WT) and Gpr75-deficient mice were placed on HFD for 14 weeks, and their obesity phenotype was examined.Results: Male and female Gpr75 null (knockout [KO]) and heterozygous mice gained less weight than WT mice when placed on HFD. KO mice maintained the same level of energy expenditure during HFD feeding, whereas WT mice showed a significant reduction in energy expenditure. Diet-driven adiposity and adipocyte hypertrophy were greatly lessened in Gpr75-deficient mice. HFD-fed KO mice did not develop insulin resistance. Adipose tissue from Gpr75-deficient mice had increased expression of thermogenic genes and decreased levels of inflammatory markers. Moreover, insulin signaling, which was impaired in HFD-fed WT mice, was unchanged in KO mice.Conclusions: These findings suggest that GPR75 is an important player in the control of metabolism and glucose homeostasis and a likely novel therapeutic target to combat obesity-driven metabolic disorders.

Type 2 diabetes (T2D) is characterized by decreased functional β-cell mass and poor compensation to insulin resistance. Thus, understanding of the mechanism(s) responsible for the physiological adaptation of β-cells to states of high metabolic demand is desirable. We aimed to dissect the transcriptome and m6A mRNA methylation landscape in the β-cell adaptation to insulin resistance. To this end we conducted RNA-sequencing in sorted β-cells and m6A-sequencing in whole islets from three mouse models: a) a dietary model (60% high-fat diet: Control-HF), b) a genetic model (liver-specific insulin receptor KO mouse on chow: LIRKO-C), and c) a superimposed dietary and genetic model of insulin resistance (LIRKO on a high fat diet: LIRKO-HF). These data were compared to littermate controls fed a chow diet (Control-C). Control-HF, LIRKO-C and LIRKO-HF each presented an increase in insulin resistance compared to Control-C. However, LIRKO-C and LIRKO-HF presented a robust insulin secretion capacity and a graded increase in β-cell proliferation and mass compared to Control-C. First, we correlated the transcriptome with surrogates of β-cell adaptation such as insulin secretion, β-cell mass or proliferation. Next, we intersected the genes that positively correlated with β-cell compensation with single-cell RNA seq datasets performed in islets from humans with or without T2D. This bioinformatics analyses identified extracellular matrix (ECM) as the most enriched pathway in the β-cell adaptation to insulin resistance. On the other hand, m6A-sequencing of Control-C, LIRKO-C and LIRKO-HF islets and the intersection of this dataset with the differentially methylated genes in human T2D islets, revealed enrichment in pathways associated with chromatin modifications. Together, these results point to ECM pathways as being important in the transcriptomic remodeling and that m6A acts on chromatin-modifying enzymes in the β-cell compensation to mammalian insulin resistance. Disclosure D.F.De jesus: None. Z.Zhang: Research Support; SinoVac. J.Wei: None. N.K.Brown: None. J.Hu: None. S.Kahraman: Employee; Boehringer Ingelheim Pharmaceuticals Inc. E.Dirice: None. R.Kulkarni: Advisory Panel; Novo Nordisk, Inversago, Biomea Fusion, Inc., REDD Pharma, Research Support; Inversago. Funding American Diabetes Association (7-21-PDF-140 to D.F.DJ.); National Institutes of Health (R01067536)

Growing evidence indicates an important link between gut microbiota, obesity, and metabolic syndrome. Alterations in exocrine pancreatic function are also widely present in patients with diabetes and obesity. To examine this interaction, C57BL/6J mice were fed either a chow diet, high-fat diet (HFD) or HFD plus oral vancomycin or metronidazole to modify the gut microbiome. HFD alone leads to a 40% increase in pancreas weight, decreased glucagon-like peptide-1 and peptide YY levels, and increased glucose-dependent insulinotropic peptide in the plasma. Quantitative proteomics identified 138 host proteins in fecal samples of these mice, of which 32 were significantly changed by HFD. The most significant of these were the pancreatic enzymes. These changes in amylase and elastase were reversed by antibiotic treatment. These alterations could be reproduced by transferring gut microbiota from donor C57BL/6J mice to germ-free. By contrast, antibiotics had no effect on pancreatic size or exocrine function in C57BL/6J mice fed a chow diet. Further, one week vancomycin administration significantly increased amylase and elastase levels in obese prediabetic men. Thus, the alterations in gut microbiota in obesity can alter pancreatic growth, exocrine function and gut endocrine function, and may contribute to the alterations observed in patients with obesity and diabetes.

Obesity related conditions including atherosclerosis and type 2 diabetes mellitus (T2DM) have a profound effect on cardiovascular health and morbidity. Recent reports by Akbari et. al. indicate that truncated loss of function variants of the orphan G-protein coupled receptor, GPR75, are associated with 5.3 kg lower bodyweight and 54% lower odds of obesity in heterozygous individuals (Science, 2021) . Based on these findings, we hypothesized that whole body deletion of Gpr75 protects against diet-induced obesity (DIO) and the resulting insulin resistance. Wild-type and Gpr75 null mice were subjected to 14 weeks of regular chow or high-fat diet (HFD) feeding. Body weight, intraperitoneal glucose and insulin tolerance tests, and pro-inflammatory cytokine gene expressions were measured initially and at week 14. There were no significant differences in body weight, glucose homeostasis, and tumor necrosis factor alpha (TNF-α) expression between wild-type (WT) and Gpr75 -/- (KO) mice at baseline. However, WT mice obtained a diabetogenic phenotype after HFD-feeding while the KO counterparts were protected as indicated by reduced body weight, (45.32 ± 1.387 grams vs. 28.29 ± 1.47 grams) and increased sensitivity to insulin (blood glucose 30 min after insulin injection as percent change, -28.5 ± 4.41% vs. -50.68 ± 4.15%, p<0.0001) . This correlated with a 1.98-fold decrease in brown adipose tissue (BAT) and 2.31-fold decrease in subcutaneous adipose tissue (SAT) TNF-α mRNA expression in KO compared to WT mice. Furthermore, there was a 3.19-fold reduction in circulating chemokine ligand 5 (CCL5) in KO compared to WT mice. This data may provide a potential novel target for the control of obesity-driven disorders such as inflammation and insulin resistance. Disclosure S. Hossain: None. E. Dirice: None. Funding NIH123203

MODY8 (maturity-onset diabetes of the young, type 8) is a dominantly inherited monogenic form of diabetes associated with mutations in the carboxyl ester lipase ( CEL ) gene expressed by pancreatic acinar cells. MODY8 patients develop childhood-onset exocrine pancreas dysfunction followed by diabetes during adulthood. However, it is unclear how CEL mutations cause diabetes. In the present study, we report the transfer of CEL proteins from acinar cells to β-cells as a form of cross-talk between exocrine and endocrine cells. Human β-cells show a relatively higher propensity for internalizing the mutant versus the wild-type CEL protein. After internalization, the mutant protein forms stable intracellular aggregates leading to β-cell secretory dysfunction. Analysis of pancreas sections from a MODY8 patient reveals the presence of CEL protein in the few extant β-cells. The present study provides compelling evidence for the mechanism by which a mutant gene expressed specifically in acinar cells promotes dysfunction and loss of β-cells to cause diabetes.

The CDC estimates the prevalence of obesity in the United States to be over 42.5% in 2021. With obesity related conditions including hypertension, heart disease, and type 2 diabetes, therapeutic approaches to treat obesity are necessary to prevent premature death. Recent studies have identified the orphan G-protein coupled receptor, GPR75, as a possible target. For example, Akbari et. al., (Science, 2021) found that truncated loss of function variants of GPR75 were associated with 5.3 kg lower bodyweight and 54% lower odds of obesity in heterozygous individuals. Based on these findings, we hypothesized that global deletion of Gpr75 protects against diet-induced obesity (DIO) and insulin resistance. Wild-type and Gpr75null mice were subjected to 14 weeks of regular chow or high-fat diet (HFD) feeding. Body composition, intraperitoneal glucose and insulin tolerance tests, and oxygen consumption were measured initially and at week 14. There were no significant differences in body composition, glucose homeostasis, and oxygen consumption between wild-type (WT), Gpr75 (KO) and Gpr75 (HET) mice initially. However, WT mice obtained a diabetogenic phenotype after HFD-feeding while KO and HET counterparts were robustly protected as indicated by reduced body weight, (45.32 ± 1.387 grams, 28.29 ± 1.47 grams, and 36.60 ± 1.8 grams respectively) and increased sensitivity to insulin (blood glucose 30 min after insulin injection as percent change, -28.5 ± 4.41%, -50.68 ± 4.15% and -39.07 ± 1.79% respectively, p<0.0001). Weekly energy intake calculated from food consumption showed no significant differences between all three groups. However, oxygen consumption measured over 60 minutes indicated an increase in energy expenditure in KO compared to WT mice (73.76 ml/min/kg vs. 44.61 ml/min/kg respectively, p<0.0001). This correlated with a 2.63-fold increase in brown adipose tissue (BAT) UCP1 mRNA expression in KO compared to WT mice. While the abundance of BAT is low in humans compared to mice, our findings suggest that improved glucose homeostasis as a result of GPR75 deficiency is linked to increased BAT thermogenesis. This may provide a potential novel route for the control of metabolism to combat obesity-driven metabolic disorders.

Insulin insufficiency is a common problem for both type 1 and type 2 diabetes. While pancreas and islet transplantation emerged as a potential treatment in type 1 diabetes, insubstantial long-term outcomes and the limitations in donor tissue availability, quality, and distribution prompt scientists for alternative sources. Stem cell therapy is a promising alternative approach. Following the discovery of reprogramming of somatic cells into inducible human pluripotent stem cells, many studies focused on the differentiation protocols and quality control steps to generate differentiated end-stage cells that are safe, functional, and at a scale sufficient to replace damaged cells. This chapter focuses on the role of stem cells and their applications in diabetes.

Analogs of the incretin hormones Gip and Glp-1 are used to treat type 2 diabetes and obesity. Findings in experimental models suggest that manipulating several hormones simultaneously may be more effective. To identify small molecules that increase the number of incretin-expressing cells, we established a high-throughput in vivo chemical screen by using the gip promoter to drive the expression of luciferase in zebrafish. All hits increased the numbers of neurogenin 3-expressing enteroendocrine progenitors, Gip-expressing K-cells, and Glp-1-expressing L-cells. One of the hits, a dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) inhibitor, additionally decreased glucose levels in both larval and juvenile fish. Knock-down experiments indicated that nfatc4, a downstream mediator of DYRKs, regulates incretin+ cell number in zebrafish, and that Dyrk1b regulates Glp-1 expression in an enteroendocrine cell line. DYRK inhibition also increased the number of incretin-expressing cells in diabetic mice, suggesting a conserved reinforcement of the enteroendocrine system, with possible implications for diabetes.

Adaptation to increased insulin demand is mediated by β cell proliferation and neogenesis, among other mechanisms. Although it is known that pancreatic β cells can arise from ductal progenitors, these observations have been limited mostly to the neonatal period. We have recently reported that the duct is a source of insulin-secreting cells in adult insulin-resistant states. To further explore the signaling pathways underlying the dynamic β cell reserve during insulin resistance, we undertook human islet and duct transplantations under the kidney capsule of immunodeficient NOD/SCID-γ (NSG) mouse models that were pregnant, were insulin-resistant, or had insulin resistance superimposed upon pregnancy (insulin resistance + pregnancy), followed by single-nucleus RNA-Seq (snRNA-Seq) on snap-frozen graft samples. We observed an upregulation of proliferation markers (e.g., NEAT1) and expression of islet endocrine cell markers (e.g., GCG and PPY), as well as mature β cell markers (e.g., INS), in transplanted human duct grafts in response to high insulin demand. We also noted downregulation of ductal cell identity genes (e.g., KRT19 and ONECUT2) coupled with upregulation of β cell development and insulin signaling pathways. These results indicate that subsets of ductal cells are able to gain β cell identity and reflect a form of compensation during the adaptation to insulin resistance in both physiological and pathological states.

Large-scale human exome sequencing can identify rare protein-coding variants with a large impact on complex traits such as body adiposity. We sequenced the exomes of 645,626 individuals from the United Kingdom, the United States, and Mexico and estimated associations of rare coding variants with body mass index (BMI). We identified 16 genes with an exome-wide significant association with BMI, including those encoding five brain-expressed G protein-coupled receptors (CALCR, MC4R, GIPR, GPR151, and GPR75). Protein-truncating variants in GPR75 were observed in ~4/10,000 sequenced individuals and were associated with 1.8 kilograms per square meter lower BMI and 54% lower odds of obesity in the heterozygous state. Knock out of Gpr75 in mice resulted in resistance to weight gain and improved glycemic control in a high-fat diet model. Inhibition of GPR75 may provide a therapeutic strategy for obesity.

The regulation of glucose-stimulated insulin secretion and glucose excursion has a sensory component that operates in a sex-dependent manner. Objective: Here, we aim to dissect the basis of the sexually dimorphic interaction between sensory neurons and pancreatic β cells and its overall impact on insulin release and glucose homeostasis. Methods: We used viral retrograde tracing techniques, surgical and chemodenervation models, and primary cell-based co-culture systems to uncover the biology underlying sex differences in sensory modulation of pancreatic β-cell activity. Results: Retrograde transsynaptic labeling revealed a sex difference in the density of sensory innervation in the pancreas. The number of sensory neurons emanating from the dorsal root and nodose ganglia that project in the pancreas is higher in male than in female mice. Immunostaining and confocal laser scanning microscopy confirmed the higher abundance of peri-islet sensory axonal tracts in the male pancreas. Capsaicin-induced sensory chemodenervation concomitantly enhanced glucose-stimulated insulin secretion and glucose clearance in male mice. These metabolic benefits were blunted when mice were orchidectomized prior to the ablation of sensory nerves. Interestingly, orchidectomy also lowered the density of peri-islet sensory neurons. In female mice, capsaicin treatment did not affect glucose-induced insulin secretion nor glucose excursion and ovariectomy did not modify these outcomes. Interestingly, same- and opposite-sex sensory-islet co-culture paradigms unmasked the existence of potential gonadal hormone-independent mechanisms mediating the male-female difference in sensory modulation of islet β-cell activity. Conclusion: Taken together, these data suggest that the sex-biased nature of the sensory control of islet β-cell activity is a result of a combination of neurodevelopmental inputs, sex hormone-dependent mechanisms and the potential action of somatic molecules encoded by the sex chromosome complement.

Strategies to increase functional pancreatic beta cell mass is of great interest in diabetes-related research. TNF-related apoptosis-inducing ligand (TRAIL) is well-known to promote proliferation and survival in various cell types, including vascular smooth muscle and endothelial cells. Correlation between the protective nature of TRAIL on these cells and its proliferative effect is noteworthy. TRAIL’s seemingly protective/therapeutic effect in diabetes prompted us to question whether it may act as an inducer of proliferation in pancreatic beta cells. We used rat primary islet cells and MIN6 mouse beta cell line to investigate TRAIL-induced proliferation. Cell viability and/or death was analysed by MTT, WST-1, and annexin-V/PI assays, while proliferation rates and pathways were assessed via immunocytochemical and Western blot analyses. Receptor neutralization antibodies identified the mediator receptors. Recombinant soluble TRAIL (sTRAIL) treatment led to 1.6-fold increased proliferation in insulin-positive cells in dispersed rat islets compared to the untreated group, while adenovirus-mediated overexpression of TRAIL increased the number of proliferating beta cells up to more than 6-fold. sTRAIL or adenoviral vector-mediated TRAIL overexpression induced proliferation in MIN6 cells also. TRAIL’s proliferative effect was mediated via AKT activation, which was suppressed upon specific inhibition. Neutralization of each TRAIL receptor reversed the proliferative effect to some degree, with the highest level of inhibition in death receptor 5 (DR5) blockage in MIN6 cells, and in decoy receptor 1 (DcR1) blockage in primary rat beta cells. Thus, TRAIL induces proliferation in rodent pancreatic beta cells through activation of the AKT pathway.

The study uses a reaction probe to target insulin-expressing pancreatic β-cells and β-like cells derived from pluripotent stem cells by harnessing high intracellular Zn(II) concentration. Highly sensitive approaches to target insulin-expressing cells would allow more effective imaging, sorting, and analysis of pancreatic β-cells. Here, we introduce the use of a reaction-based probe, diacetylated Zinpyr1 (DA-ZP1), to image pancreatic β-cells and β-like cells derived from human pluripotent stem cells. We harness the high intracellular zinc concentration of β-cells to induce a fluorescence signal in cells after administration of DA-ZP1. Given its specificity and rapid uptake by cells, we used DA-ZP1 to purify live stem cell-derived β-like cells as confirmed by immunostaining analysis. We tested the ability of DA-ZP1 to image transplanted human islet grafts and endogenous mouse pancreatic islets in vivo after its systemic administration into mice. Thus, DA-ZP1 enables purification of insulin-secreting β-like cells for downstream applications, such as functional studies, gene-expression, and cell–cell interaction analyses and can be used to label engrafted human islets and endogenous mouse islets in vivo.