Identification of transcriptional targets during pancreatic growth after partial pancreatectomy and exendin-4 treatment

Interdependencies of Gene Expression and Function between Two Redox Enzymes and REG Family Proteins in Murine Pancreatic Islets and Human Pancreatic Cells

Our laboratory previously revealed that regenerating islets-derived protein 2 (REG2) was diminished in pancreatic islets of glutathione peroxidase-1-overexpressing mice (Gpx1-OE). It remained unknown if there is an inverse relationship between the expression and function of all Reg family genes and antioxidant enzymes in the pancreatic islets or human pancreatic cells. This research was to determine how altering the Gpx1 and superoxide dismutase-1 (Sod1) genes alone or together (dKO) affected the expression of all seven murine Reg genes in murine pancreatic islets. In Experiment 1, Gpx1-/-, Gpx1-OE, their wild-type (WT), Sod1-/-, dKO, and their WT (male, 8-wk old, n = 4–6) were fed a Se-adequate diet and their islets were collected to assay the mRNA levels of Reg family genes. In Experiment 2, islets from the six groups of mice were treated with phosphate-buffered saline (PBS), REG2, or REG2 mutant protein (1 µg/mL), and/or GPX mimic (ebselen, 50 µM) and SOD mimic (copper [II] diisopropyl salicylate, CuDIPS, 10 µM) for 48 h before the proliferation assay using bromodeoxyuridine (BrdU). In Experiment 3, human pancreatic cells (PANC1) were treated with REG2 (1 µg/mL) and assayed for REG gene expression, GPX1 and SOD1 activities, viability, and responses to Ca2+. Compared with the WT, knockouts of Gpx1 and/or Sod1 up-regulated (p < 0.05) the mRNA levels of most of the murine Reg genes in islets whereas the Gpx1 overexpression down-regulated (p < 0.05) Reg mRNA levels. REG2, but not the REG2 mutant, inhibited islet proliferation in Gpx1 or Sod1-altered mice. Such inhibition was abolished by co-incubation the Gpx1-/- islets with ebselen and the Sod1-/- islets with CuDIPS. Treating PANC1 cells with murine REG2 protein induced expression of its human orthologue REG1B and three other REG genes, but decreased SOD1 and GPX1 activities and cell viability. In conclusion, our results revealed an interdependence of REG family gene expression and/or function on intracellular GPX1 and SOD1 activities in murine islets and human pancreatic cells.

Role and mechanism of REG2 depletion in insulin secretion augmented by glutathione peroxidase-1 overproduction

We previously reported a depletion of murine regenerating islet-derived protein 2 (REG2) in pancreatic islets of glutathione peroxidase-1 (Gpx1) overexpressing (OE) mice. The present study was to explore if and how the REG2 depletion contributed to an augmented glucose stimulated insulin secretion (GSIS) in OE islets. After we verified a consistent depletion (90%, p < 0.05) of REG2 mRNA, transcript, and protein in OE islets compared with wild-type (WT) controls, we treated cultured and perifused OE islets (70 islets/sample) with REG2 (1 μg/ml or ml · min) and observed 30-40% (p < 0.05) inhibitions of GSIS by REG2. Subsequently, we obtained evidences of co-immunoprecipitation, cell surface ligand binding, and co-immunofluorescence for a ligand-receptor binding between REG2 and transmembrane, L-type voltage-dependent Ca2+ channel (CaV1.2) in beta TC3 cells. Mutating the C-type lectin binding domain of REG2 or deglycosylating CaV1.2 removed the inhibition of REG2 on GSIS and(or) the putative binding between the two proteins. Treating cultured OE and perifused WT islets with REG2 (1 μg/ml or ml · min) decreased (p < 0.05) Ca2+ influx triggered by glucose or KCl. An intraperitoneal (ip) injection of REG2 (2 μg/g) to OE mice (6-month old, n = 10) decreased their plasma insulin concentration (46%, p < 0.05) and elevated their plasma glucose concentration (25%, p < 0.05) over a 60 min period after glucose challenge (ip, 1 g/kg). In conclusion, our study identifies REG2 as a novel regulator of Ca2+ influx and insulin secretion, and reveals a new cascade of GPX1/REG2/CaV1.2 to explain how REG2 depletion in OE islets could decrease its binding to CaV1.2, resulting in uninhibited Ca2+ influx and augmented GSIS. These findings create new links to bridge redox biology, tissue regeneration, and insulin secretion.

Glutathione peroxidase-1 inhibits transcription of regenerating islet-derived protein-2 in pancreatic islets

Our group previously demonstrated that overexpression of selenium-dependent glutathione peroxidase-1 (GPX1) in mice (OE) led to escalated glucose-stimulated insulin secretion and hyperinsulinemia. Because we found a strong correlation of this phenotype with a diminished expression of regenerating islet-derived protein 2 (REG2) in the OE pancreatic islets, the present study was to reveal underlying mechanisms for that down-regulation of REG2 by GPX1 as a major scavenger of reactive oxygen species. We first treated the OE and wild-type (WT) mice and their islets with ROS-generating diquat, streptozotocin, and H₂O₂ and ROS-scavenging ebselen and N-acetylcysteine (NAC). Their effects on pancreatic and islet REG2 protein and(or) secretion were opposite (P < 0.05). Thereafter, we identified 13 transcriptional factors with putative binding sites in the Reg2 proximate promoter, and found that only activator protein-1 (AP-1) and albumin D box-binding protein (DBP) mRNA and protein levels were affected (elevated) (P < 0.05) by the GPX1 overproduction in the OE pancreatic islets compared with the WT islets. Contrary to that of Reg2 expression, their mRNA abundances in the cultured islets were elevated (P < 0.05) by ebselen and NAC, but decreased (P < 0.05) by H₂O_2. Both AP-1 and DBP could bind to the Reg2 promoter at the location of -168 to 0 base pair (bp) in the OE islets. Deleting the AP-1 (-143/-137 and -60/-57 bp) and(or) DBP (-35/-29 bp) binding domains in the Reg2 promoter attenuated and(or) abolished the inhibition of Reg2 promoter activation by ebselen as the GPX1 mimic in βTC-3 cells. In conclusion, the down-regulation of Reg2 expression in the GPX1-overproducing pancreatic islets was mediated by a transcriptional inhibition of the gene through two ROS responsive transcription factors AP-1 and DBP. Our findings reveal GPX1 as a novel regulator of Reg2 expression, and linking these two previously-unrelated proteins will have broad biomedical implications.

GLP-1 signaling suppresses menin's transcriptional block by phosphorylation in β cells

Both menin and glucagon-like peptide 1 (GLP-1) pathways play central yet opposing role in regulating β cell function, with menin suppressing, and GLP-1 promoting, β cell function. However, little is known as to whether or how GLP-1 pathway represses menin function. Here, we show that GLP-1 signaling-activated protein kinase A (PKA) directly phosphorylates menin at the serine 487 residue, relieving menin-mediated suppression of insulin expression and cell proliferation. Mechanistically, Ser487-phosphorylated menin gains increased binding affinity to nuclear actin/myosin IIa proteins and gets sequestrated from the Ins1 promoter. This event leads to reduced binding of repressive epigenetic histone modifiers suppressor variegation 3-9 homologue protein 1 (SUV39H1) and histone deacetylases 1 (HDAC1) at the locus and subsequently increased Ins1 gene transcription. Ser487 phosphorylation of menin also increases expression of proproliferative cyclin D2 and β cell proliferation. Our results have uncovered a previously unappreciated physiological link in which GLP-1 signaling suppresses menin function through phosphorylation-triggered and actin/myosin cytoskeletal protein-mediated derepression of gene transcription.

Phosphorylation of carboxypeptidase B1 protein regulates β-cell proliferation

A reduction in pancreatic islet β-cells leads to the onset of diabetes. Hence, the identification of the mechanisms inducing β-cell proliferation is important for developing a treatment course against the disease. It has been well established that post-translational modifications (PTMs) of proteins affect their functionality. In addition, PTMs have been suggested to play important roles in organ regeneration. Therefore, in this study, we investigated PTMs associated with pancreatic regeneration using two-dimensional electrophoresis. Four carboxypeptidase B1 (CPB1) proteins were identified at different isoelectric points, with the same molecular weight. The motif of CPB1 PTMs was identified by mass spectrophotometry, and the downregulation of CPB1 phosphorylation in pancreatectomy was confirmed. The dephosphorylation of CPB1 induced β-cell proliferation. We thus surmise that the altered PTM of CPB1 is associated with pancreatic regeneration.

Maximizing endogenous β-cell regeneration

PURPOSE OF REVIEW

Inadequate insulin-producing pancreatic β-cell mass is a key feature of both type 1 and type 2 diabetes. Efforts to regenerate β-cell mass from pancreatic precursors may thus ameliorate absolute or relative insulin deficiency, thereby improving glucose homeostasis. A clear understanding of the processes that govern the generation of new β-cells in the mature pancreas will be fundamental to success in this effort. This review discusses the current state of knowledge regarding β-cell regeneration and emphasizes recent studies of significance.

RECENT FINDINGS

Recent reports demonstrate regenerative potential in the adult human pancreas. Further, they build on the strong existing evidence that proliferation of preexisting β-cells is the predominant source of new β-cells in adulthood by dissecting the cell cycle machinery components and critical signaling pathways required for β-cell proliferation. Finally, β-cell trophic peptides have demonstrated preclinical potential as pharmacologic regenerative agents and may form the basis for clinical interventions in the future.

SUMMARY

Efforts to augment β-cell regeneration by enhancing β-cell viability and proliferation may lead to novel therapeutic approaches for type 1 and type 2 diabetes. An intimate understanding of the molecular mechanisms underlying the regulation of β-cell proliferation and survival will be fundamental to the optimization of endogenous β-cell regeneration.

Reg2 Expression Is Required for Pancreatic Islet Compensation in Response to Aging and High-Fat Diet-Induced Obesity

Maintaining pancreatic β-cell mass and function is essential for normal insulin production and glucose homeostasis. Regenerating islet-derived 2 (Reg2, Reg II, human ortholog Reg1B) gene is normally expressed in pancreatic acinar cells and is significantly induced in response to diabetes, pancreatitis, and high-fat diet (HFD) and during pancreatic regeneration. To evaluate the role of endogenous Reg2 production in normal β-cell function, we characterized Reg2 gene-deficient (Reg2-/-) mice under normal conditions and when subjected to several pathological challenges. At a young age, Reg2 gene deficiency caused no obvious change in normal islet morphology or glucose tolerance. There was no change in the severity of streptozotocin-induced diabetes or caerulein-induced acute pancreatitis in the Reg2-/- mice, indicating that the increased Reg2 expression under those conditions was not essential to protect the islet or acinar cells. However, 13- to 14-month-old Reg2-/- mice developed glucose intolerance associated with significantly decreased islet β-cell ratio and serum insulin level. Similarly, after young mice were fed an HFD for 19 weeks, diminished islet mass expansion and serum insulin level were observed in Reg2-/- vs wild-type mice. This was associated with a decline in the rate of individual β-cell proliferation measured by Ki67 labeling. In both conditions, the β-cells were smaller in gene-deficient vs wild-type mice. Our results indicate that normal expression of Reg2 gene is required for appropriate compensations in pancreatic islet proliferation and expansion in response to obesity and aging.

Suppression of islet homeostasis protein thwarts diabetes mellitus progression

During progression to type 1 diabetes, insulin-producing β-cells are lost through an autoimmune attack resulting in unrestrained glucagon expression and secretion, activation of glycogenolysis, and escalating hyperglycemia. We recently identified a protein, designated islet homeostasis protein (IHoP), which specifically co-localizes within glucagon-positive α-cells and is overexpressed in the islets of both post-onset non-obese diabetic (NOD) mice and type 1 diabetes patients. Here we report that in the αTC1.9 mouse α-cell line, IHoP was released in response to high-glucose challenge and was found to regulate secretion of glucagon. We also show that in NOD mice with diabetes, major histocompatibility complex class II was upregulated in islets. In addition hyperglycemia was modulated in NOD mice via suppression of IHoP utilizing small interfering RNA (IHoP-siRNA) constructs/approaches. Suppression of IHoP in the pre-diabetes setting maintained normoglycemia, glyconeolysis, and fostered β-cell restoration in NOD mice 35 weeks post treatment. Furthermore, we performed adoptive transfer experiments using splenocytes from IHoP-siRNA-treated NOD/ShiLtJ mice, which thwarted the development of hyperglycemia and the extent of insulitis seen in recipient mice. Last, IHoP can be detected in the serum of human type 1 diabetes patients and could potentially serve as an early novel biomarker for type 1 diabetes in patients.

GLP-1 mimetic drugs and the risk of exocrine pancreatic disease: Cell and animal studies

BACKGROUND

Glucagon Like Peptide 1 (GLP-1) mimetic drugs or degradation inhibitors mimic the action of native GLP-1 as a incretin hormone and have become a common second line of therapy for Type 2 diabetes. However, an important clinical issue is whether these drugs increase the incidence of pancreatitis and pancreatic cancer.

OBJECTIVE

This paper reviews the physiology of GLP-1 including its synthesis, secretion and action of the peptide. Reported effects of the mimetic drugs on the exocrine pancreas in animal studies are also reviewed.

RESULTS

GLP-1 is synthesized in a specific class of enteroendocrine cell, the L-cell, by post-translational processing of proglucagon. It is released in response to the presence of nutrients in the small intestine and stimulates vagal afferent nerve endings as well as entering the blood where it is rapidly degraded by dipeptidyl peptidase IV. Its actions are mediated by specific G-protein coupled receptors. The major target tissues are the pancreatic islet beta cells, the brain and the heart but GLP-1 also affects gastrointestinal motility and secretion including the exocrine pancreas where its major systemic action is to inhibit secretion. In some animal, as well as human studies, the GLP-1 mimetic drugs are associated with pancreatitis or precursor lessions to pancreatic cancer but a mechanism is not clear. The most common occurrence of pathology in rodents is when the drugs are combined with a high fat diet.

CONCLUSIONS

There is nothing in the physiology of GLP-1 or animal toxicology studies to support a mechanism of action or a major concern about the action of GLP-1 mimetic drugs on the exocrine pancreas. Further studies are warranted using animal models of disease and high fat diets.

Diabetes Susceptibility Genes Pdx1 and Clec16a Function in a Pathway Regulating Mitophagy in β-Cells

Mitophagy is a critical regulator of mitochondrial quality control and is necessary for elimination of dysfunctional mitochondria to maintain cellular respiration. Here, we report that the homeodomain transcription factor Pdx1, a gene associated with both type 2 diabetes and monogenic diabetes of the young, regulates mitophagy in pancreatic β-cells. Loss of Pdx1 leads to abnormal mitochondrial morphology and function as well as impaired mitochondrial turnover. High-throughput expression microarray and chromatin occupancy analyses reveal that Pdx1 regulates the expression of Clec16a, a type 1 diabetes gene and itself a key mediator of mitophagy through regulation of the E3 ubiquitin ligase Nrdp1. Indeed, expression of Clec16a and Nrdp1 are both reduced in Pdx1 haploinsufficient islets, and reduction of Pdx1 impairs fusion of autophagosomes containing mitochondria to lysosomes during mitophagy. Importantly, restoration of Clec16a expression after Pdx1 loss of function restores mitochondrial trafficking during mitophagy and improves mitochondrial respiration and glucose-stimulated insulin release. Thus, Pdx1 orchestrates nuclear control of mitochondrial function in part by controlling mitophagy through Clec16a. The novel Pdx1-Clec16a-Nrdp1 pathway we describe provides a genetic basis for the pathogenesis of mitochondrial dysfunction in multiple forms of diabetes that could be targeted for future therapies to improve β-cell function.

Analysis of variants and mutations in the human winged helix FOXA3 gene and associations with metabolic traits

BACKGROUND/OBJECTIVES

The forkhead factor Foxa3 is involved in the early transcriptional events controlling adipocyte differentiation and plays a critical function in fat depot expansion in response to high-fat diet regimens and during aging in mice. No studies to date have assessed the potential associations of genetic variants in FOXA3 with human metabolic outcomes.

SUBJECTS/METHODS

In this study, we sequenced FOXA3 in 392 children, adolescents and young adults selected from several cohorts of subjects recruited at the National Institute of Child Health and Human Development of the National Institutes of Health based on the availability of dual-energy X-ray absorptiometry data, magnetic resonance imaging scans and DNA samples. We assessed the association between variants present in these subjects and metabolic traits and performed in vitro functional analysis of two novel FOXA3 missense mutations identified.

RESULTS

Our analysis identified 14 novel variants and showed that the common single-nucleotide polymorphism (SNP) rs28666870 is significantly associated with greater body mass index, lean body mass and appendicular lean mass (P values 0.009, 0.010 and 0.013 respectively). In vitro functional studies showed increased adipogenic function for the FOXA3 missense mutations c.185C>T (p.Ser62Leu) and c.731C>T (p.Ala244Val) compared with FOXA3-WT.

CONCLUSIONS

Our study identified novel FOXA3 variants and mutations, assessed the adipogenic capacity of two novel missense alterations in vitro and demonstrated for the first time the associations between FOXA3 SNP rs28666870 with metabolic phenotypes in humans.

Patent Highlights

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Extended exenatide administration enhances lipid metabolism and exacerbates pancreatic injury in mice on a high fat, high carbohydrate diet

This study expanded upon a previous study in mice reporting a link between exenatide treatment and exocrine pancreatic injury by demonstrating temporal and dose responses and providing an initial mechanistic hypothesis. The design of the present study included varying lengths of exenatide exposure (3, 6 weeks to 12 weeks) at multiple concentrations (3, 10, or 30 µg/kg) with multiple endpoints (histopathology evaluations, immunoassay for cytokines, immunostaining of the pancreas, serum chemistries and measurement of trypsin, amylase, and, lipase, and gene expression profiles). Time- and dose-dependent exocrine pancreatic injury was observed in mice on a high fat diet treated with exenatide. The morphological changes identified in the pancreas involved acinar cell injury and death (autophagy, apoptosis, necrosis, and atrophy), cell adaptations (hypertrophy and hyperplasia), and cell survival (proliferation/regeneration) accompanied by varying degrees of inflammatory response leading to secondary injury in pancreatic blood vessels, ducts, and adipose tissues. Gene expression profiles indicated increased signaling for cell survival and altered lipid metabolism in exenatide treated mice. Immunohistochemistry supported gene expression findings that exenatide caused and/or exacerbated pancreatic injury in a high fat diet environment potentially by further increasing high fat diet exacerbated lipid metabolism and resulting oxidative stress. Further investigation is required to confirm these findings and determine their relevance to human disease.

The diabetes susceptibility gene Clec16a regulates mitophagy

Clec16a has been identified as a disease susceptibility gene for type 1 diabetes, multiple sclerosis, and adrenal dysfunction, but its function is unknown. Here we report that Clec16a is a membrane-associated endosomal protein that interacts with E3 ubiquitin ligase Nrdp1. Loss of Clec16a leads to an increase in the Nrdp1 target Parkin, a master regulator of mitophagy. Islets from mice with pancreas-specific deletion of Clec16a have abnormal mitochondria with reduced oxygen consumption and ATP concentration, both of which are required for normal β cell function. Indeed, pancreatic Clec16a is required for normal glucose-stimulated insulin release. Moreover, patients harboring a diabetogenic SNP in the Clec16a gene have reduced islet Clec16a expression and reduced insulin secretion. Thus, Clec16a controls β cell function and prevents diabetes by controlling mitophagy. This pathway could be targeted for prevention and control of diabetes and may extend to the pathogenesis of other Clec16a- and Parkin-associated diseases.

β-Cell proliferation after a partial pancreatectomy is independent of IRS-2 in mice

The glucokinase-induced up-regulation of insulin receptor substrate 2 (IRS-2) plays an important role in β-cell adaptive proliferation in response to high-fat diet-induced insulin resistance. This study aimed to investigate the role of IRS-2 in the proliferation of β-cells after a 60% partial pancreatectomy. IRS-2-deficient (IRS-2(-/-)) mice or wild-type mice were subjected to a pancreatectomy (60% partial pancreatectomy) or a sham operation (Sham). The β-cell proliferation and gene expression profiles of the islets were then assessed. Gene expression in islets from pancreatectomized and Sham C57BL/6J male mice was analyzed using a cDNA microarray analysis. To compare with β-cell proliferation induced by a high-fat diet, Gck(+/-) mice subjected to a pancreatectomy were also analyzed. The IRS-2(-/-) mice exhibited β-cell expansion and a significant increase in β-cell proliferation after the pancreatectomy, compared with the Sham group. Although glucose-stimulated insulin secretion from islets was not impaired, IRS-2(-/-) mice manifested severe hyperglycemia after the pancreatectomy. The expression levels of Aurora kinase B, Cyclin A, and Cyclin B1 in the pancreatectomized islets were also enhanced in the IRS-2(-/-) mice. A gene set enrichment analysis suggested an association between the genes that were up-regulated in the pancreatectomized islets and those involved in M phase progression in the cell cycle. β-Cell proliferation after a pancreatectomy was observed even in the Gck(+/-) mice. In conclusion, IRS-2 was not required for β-cell proliferation but might be needed for functional β-cell mass, after a pancreatectomy. A partial pancreatectomy in mice may be an attractive model for the development of new strategy for exploring the unique nature of β-cell proliferation.

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Low birth weight and poor foetal growth following low protein (LP) exposure are associated with altered islet development and glucose intolerance in adulthood. Additionally, LP-fed offspring fail to regenerate their β-cells following depletion with streptozotocin (STZ) in contrast to control-fed offspring that restore β-cell mass. Our objective was to identify signalling pathways and cellular functions that may be critically altered in LP offspring rendering them susceptible to developing long-term glucose intolerance and decreased β-cell plasticity. Pregnant Balb/c mice were fed a control (C; 20% protein) or an isocaloric LP (8% protein) diet throughout gestation and C diet thereafter. Female offspring were injected intraperitoneally with 35 mg/kg STZ or vehicle on days 1 to 5 for each dietary treatment. At 30 days of age, total RNA was extracted from pancreatic tissue for microarray analysis using the Affymetrix GeneChip Mouse Genome 430 2.0. Gene and protein expression were quantified from isolated islets. Finally, β-cell proliferation was determined in vitro following REG1α treatment. The microarray data and GO enrichment analysis indicated that foetal protein restriction alters the early expression of genes necessary for many cell functions, such as oxidative phosphorylation and free radical scavenging. Expression of Reg1 was upregulated following STZ, whereas protein content was decreased in LP + STZ islets. Furthermore, REG1α failed to stimulate β-cell proliferation in vitro in LP + STZ islets. Therefore, early nutritional insults may programme the Reg1 pathway resulting in a limited ability to increase β-cell mass during metabolic stress. In conclusion, this study implicates the Reg1 pathway in β-cell regeneration and describes altered programming of gene expression in LP offspring, which underlies later development of cell dysfunction and glucose intolerance in adulthood.

Glucagon-like peptide-1 protects human islets against cytokine-mediated β-cell dysfunction and death: a proteomic study of the pathways involved

Glucagon-like peptide-1 (GLP-1) has been shown to protect pancreatic β-cells against cytokine-induced dysfunction and destruction. The mechanisms through which GLP-1 exerts its effects are complex and still poorly understood. The aim of this study was to analyze the protein expression profiles of human islets of Langerhans treated with cytokines (IL-1β and IFN-γ) in the presence or absence of GLP-1 by 2D difference gel electrophoresis and subsequent protein interaction network analysis to understand the molecular pathways involved in GLP-1-mediated β-cell protection. Co-incubation of cytokine-treated human islets with GLP-1 resulted in a marked protection of β-cells against cytokine-induced apoptosis and significantly attenuated cytokine-mediated inhibition of glucose-stimulated insulin secretion. The cytoprotective effects of GLP-1 coincided with substantial alterations in the protein expression profile of cytokine-treated human islets, illustrating a counteracting effect on proteins from different functional classes such as actin cytoskeleton, chaperones, metabolic proteins, and islet regenerating proteins. In summary, GLP-1 alters in an integrated manner protein networks in cytokine-exposed human islets while protecting them against cytokine-mediated cell death and dysfunction. These data illustrate the beneficial effects of GLP-1 on human islets under immune attack, leading to a better understanding of the underlying mechanisms involved, a prerequisite for improving therapies for diabetic patients.

Autophagy in pancreatic acinar cells in caerulein-treated mice: immunolocalization of related proteins and their potential as markers of pancreatitis

Drug-induced pancreatitis (DIP) is an underdiagnosed condition that lacks sensitive and specific biomarkers. To better understand the mechanisms of DIP and to identify potential tissue biomarkers, we studied experimental pancreatitis induced in male C57BL/6 mice by intraperitoneal injection of caerulein (10 or 50 μg/kg) at 1-hr intervals for a total of 7 injections. Pancreata from caerulein-treated mice exhibited consistent acinar cell autophagy and apoptosis with infrequent necrosis. Kinetic assays for serum amylase and lipase also showed a dose-dependent increase. Terminal deoxynucleotidyl transferase-mediated biotin-dNTP nick labeling (TUNEL) detected dose-dependent acinar cell apoptosis. By light microscopy, autophagy was characterized by the formation of autophagosomes and autolysosomes (ALs) within the cytoplasm of acinar cells. Immunohistochemical studies with specific antibodies for proteins related to autophagy and pancreatic stress were conducted to evaluate these proteins as potential biomarkers of pancreatitis. Western blots were used to confirm immunohistochemical results using pancreatic lysates from control and treated animals. Autophagy was identified as a contributing process in caerulein-induced pancreatitis and proteins previously associated with autophagy were upregulated following caerulein treatment. Autophagosomes and ALs were found to be a common pathway, in which cathepsins, lysosome-associated membrane protein 2, vacuole membrane protein 1, microtubule-associated protein 1 light chain 3 (LC3), autophagy-related protein 9, Beclin1, and pancreatitis-associated proteins were simultaneously involved in response to caerulein stimulus. Regenerating islet-derived 3 gamma (Reg3γ), a pancreatic acute response protein, was dose-dependently induced in caerulein-treated mice and colocalized with the autophagosomal marker, LC3. This finding supports Reg3γ as a candidate biomarker for pancreatic injury.

Profiling CCK-mediated pancreatic growth: the dynamic genetic program and the role of STATs as potential regulators

Feeding mice with protease inhibitor (PI) leads to increased endogenous cholecystokinin (CCK) release and results in pancreatic growth. This adaptive response requires calcineurin (CN)-NFAT and AKT-mTOR pathways, but the genes involved, the dynamics of their expression, and other regulatory pathways remain unknown. Here, we examined the early (1-8 h) transcriptional program that underlies pancreatic growth. We found 314 upregulated and 219 downregulated genes with diverse temporal and functional profiles. Several new identifications include the following: stress response genes Gdf15 and Txnip, metabolic mediators Pitpnc1 and Hmges2, as well as components of growth factor response Fgf21, Atf3, and Egr1. The genes fell into seven self-organizing clusters, each with a distinct pattern of expression; a representative gene within each of the upregulated clusters (Egr1, Gadd45b, Rgs2, and Serpinb1a) was validated by qRT-PCR. Genes up at any point throughout the time course and CN-dependent genes were subjected to further bioinformatics-based networking and promoter analysis, yielding STATs as potential transcriptional regulators. As shown by PCR, qPCR, and Western blots, the active phospho-form of STAT3 and the Jak-STAT feedback inhibitor Socs2 were both increased throughout early pancreatic growth. Moreover, immunohistochemistry showed a CCK-dependent and acinar cell-specific increase in nuclear localization of p-STAT3, with >75% nuclear occupancy in PI-fed mice vs. <0.1% in controls. Thus, the study identified novel genes likely to be important for CCK-driven pancreatic growth, characterized and biologically validated the dynamic pattern of their expression and investigated STAT-Socs signaling as a new player in this trophic response.

Body mass index and outcomes from pancreatic resection: a review and meta-analysis

INTRODUCTION

There are 1.6 billion adults worldwide who are overweight, with body mass indices (BMI) between 25 and 30, while more than 400 million are obese (BMI >30). Obesity predicts the incidence of and poor outcomes from pancreatic cancer. Obesity has also been linked to surgical complications in pancreatectomy, including increased length of hospital stay, surgical infections, blood loss, and decreased survival. However, BMI's impact on many complications following pancreatectomy remains controversial.

METHODS

We performed a MEDLINE search of all combinations of "BMI" with "pancreatectomy," "pancreatoduodenectomy," or "pancreaticoduodenectomy." From included studies, we created pooled and weighted estimates for quantitative and qualitative outcomes. We used the PRISMA criteria to ensure this project's validity.

RESULTS

Our primary cohort included 2,736 patients with BMI <30, 1,682 with BMI >25, and 546 with BMI between 25 and 30. Most outcomes showed no definitive differences across BMIs. Pancreatic fistula (PF) rates ranged from 4.7% to 31.0%, and four studies found multivariate association between BMI and PF (range odds ratio 1.6-4.2). Pooled analyses of PF by BMI showed significant association (p < 0.05).

CONCLUSION

BMI increases the operative complexity of pancreatectomy. However, with aggressive peri- and post-operative care, increases in BMI-associated morbidity and mortality may be mitigated.

Isolation of genes involved in pancreas regeneration by subtractive hybridization

The deterioration of β cells in the pancreas is a crucial factor in the progression of diabetes mellitus; therefore, the recovery of β cells is of vital importance for effective diabetic therapeutic strategies. Partially pancreatectomized rats have been used for the investigation of pancreatic regeneration. Because it was determined that tissue extract from the partially-dissected pancreas induces pancreatic differentiation in embryonic stem cells, paracrine factors were thought to be involved in the regeneration. In this study, we screened for genes that had higher mRNA levels 2 days after 60%-pancreatectomy. The genes were isolated using subtractive hybridization and DNA sequencing. Twelve genes (adipsin, Aplp2, Clu, Col1a2, Glul, Krt8, Lgmn, LOC299907, LOC502894, Pla2g1b, Reg3α and Xbp1) were identified, and RT-PCR and real-time PCR analyses were performed to validate their expression levels. Among the genes identified, three genes (Glul, Lgmn and Reg3a) were selected for further analyses. Assays revealed that Glul and Reg3α enhance cell growth. Glul, Lgmn and Reg3α change the expression level of islet marker genes, where NEUROD, NKX2.2, PAX4 and PAX6 are up-regulated and somatostatin is down-regulated. Thus, we believe that Glul, Lgmn and Reg3a can serve as novel targets in diabetes mellitus genetic therapy.

Coordinated age-dependent and pancreatic-specific expression of mouse Reg2Reg3α, and Reg3β genes

Reg family proteins such as Reg1 and islet neogenesis-associated protein (INGAP) have long been implicated in the growth and/or neogenesis of pancreatic islet cells. Recent reports further suggest similar roles to be played by new members such as Reg2, Reg3α, and Reg3β. We have studied their age-, isoform-, and tissue-specific expressions. RNA and protein were isolated from C57BL/6 mice aged 7, 30, and 90 days. Using real-time polymerase chain reaction, the levels of Reg gene expression in the pancreas were 20-600-fold higher than that in other tissues (≫duodenum>stomach>liver); gene expression of Reg2, Reg3α, and Reg3β was age dependent as it was hardly detectable at day 7, increased drastically at day 30, and significantly decreased at day 90; the levels of pancreatic proteins displayed similar age-dependent variations. Using dual-labeled immunofluorescence, Reg2, Reg3α, and Reg3β were abundantly expressed in most acinar cells of the pancreas, in contrast to INGAP which exhibited stepwise increases from day 7 to day 90 and colocalized with the α-cells. These new Reg genes were mainly expressed in the pancreas, with clear age-dependent and isoform-specific patterns.

Pancreatic islet-specific overexpression of Reg3β protein induced the expression of pro-islet genes and protected the mice against streptozotocin-induced diabetes mellitus

Reg family proteins have been implicated in islet β-cell proliferation, survival, and regeneration. The expression of Reg3β (pancreatitis-associated protein) is highly induced in experimental diabetes and acute pancreatitis, but its precise role has not been established. Through knockout studies, this protein was shown to be mitogenic, antiapoptotic, and anti-inflammatory in the liver and pancreatic acinars. To test whether it can promote islet cell growth or survival against experimental damage, we developed β-cell-specific overexpression using rat insulin I promoter, evaluated the changes in normal islet function, gene expression profile, and the response to streptozotocin-induced diabetes. Significant and specific overexpression of Reg3β was achieved in the pancreatic islets of RIP-I/Reg3β mice, which exhibited normal islet histology, β-cell mass, and in vivo and in vitro insulin secretion in response to high glucose yet were slightly hyperglycemic and low in islet GLUT2 level. Upon streptozotocin treatment, in contrast to wild-type littermates that became hyperglycemic in 3 days and lost 15% of their weight, RIP-I/Reg3β mice were significantly protected from hyperglycemia and weight loss. To identify specific targets affected by Reg3β overexpression, a whole genome DNA microarray on islet RNA isolated from the transgenic mice revealed more than 45 genes significantly either up- or downregulated. Among them, islet-protective osteopontin/SPP1 and acute responsive nuclear protein p8/NUPR1 were significantly induced, a result further confirmed by real-time PCR, Western blots, and immunohistochemistry. Our results suggest that Reg3β is unlikely an islet growth factor but a putative protector that prevents streptozotocin-induced damage by inducing the expression of specific genes.

Exenatide does not evoke pancreatitis and attenuates chemically induced pancreatitis in normal and diabetic rodents

The risk of developing pancreatitis is elevated in type 2 diabetes and obesity. Cases of pancreatitis have been reported in type 2 diabetes patients treated with GLP-1 (GLP-1R) receptor agonists. To examine whether the GLP-1R agonist exenatide potentially induces or modulates pancreatitis, the effect of exenatide was evaluated in normal or diabetic rodents. Normal and diabetic rats received a single exenatide dose (0.072, 0.24, and 0.72 nmol/kg) or vehicle. Diabetic ob/ob or HF-STZ mice were infused with exenatide (1.2 and 7.2 nmol·kg(-1)·day(-1)) or vehicle for 4 wk. Post-exenatide treatment, pancreatitis was induced with caerulein (CRN) or sodium taurocholate (ST), and changes in plasma amylase and lipase were measured. In ob/ob mice, plasma cytokines (IL-1β, IL-2, IL-6, MCP-1, IFNγ, and TNFα) and pancreatitis-associated genes were assessed. Pancreata were weighed and examined histologically. Exenatide treatment alone did not modify plasma amylase or lipase in any models tested. Exenatide attenuated CRN-induced release of amylase and lipase in normal rats and ob/ob mice but did not modify the response to ST infusion. Plasma cytokines and pancreatic weight were unaffected by exenatide. Exenatide upregulated Reg3b but not Il6, Ccl2, Nfkb1, or Vamp8 expression. Histological analysis revealed that the highest doses of exenatide decreased CRN- or ST-induced acute inflammation, vacuolation, and acinar single cell necrosis in mice and rats, respectively. Ductal cell proliferation rates were low and similar across all groups of ob/ob mice. In conclusion, exenatide did not modify plasma amylase and lipase concentrations in rodents without pancreatitis and improved chemically induced pancreatitis in normal and diabetic rodents.

Calcineurin signaling regulates human islet {beta}-cell survival

The calcium-regulated phosphatase calcineurin intersects with both calcium and cAMP-mediated signaling pathways in the pancreatic β-cell. Pharmacologic calcineurin inhibition, necessary to prevent rejection in the setting of organ transplantation, is associated with post-transplant β-cell failure. We sought to determine the effect of calcineurin inhibition on β-cell replication and survival in rodents and in isolated human islets. Further, we assessed whether the GLP-1 receptor agonist and cAMP stimulus, exendin-4 (Ex-4), could rescue β-cell replication and survival following calcineurin inhibition. Following treatment with the calcineurin inhibitor tacrolimus, human β-cell apoptosis was significantly increased. Although we detected no human β-cell replication, tacrolimus significantly decreased rodent β-cell replication. Ex-4 nearly normalized both human β-cell survival and rodent β-cell replication when co-administered with tacrolimus. We found that tacrolimus decreased Akt phosphorylation, suggesting that calcineurin could regulate replication and survival via the PI3K/Akt pathway. We identify insulin receptor substrate-2 (Irs2), a known cAMP-responsive element-binding protein target and upstream regulator of the PI3K/Akt pathway, as a novel calcineurin target in β-cells. Irs2 mRNA and protein are decreased by calcineurin inhibition in both rodent and human islets. The effect of calcineurin on Irs2 expression is mediated at least in part through the nuclear factor of activated T-cells (NFAT), as NFAT occupied the Irs2 promoter in a calcineurin-sensitive manner. Ex-4 restored Irs2 expression in tacrolimus-treated rodent and human islets nearly to baseline. These findings reveal calcineurin as a regulator of human β-cell survival in part through regulation of Irs2, with implications for the pathogenesis and treatment of diabetes following organ transplantation.

Reg2 protects mouse insulinoma cells from streptozotocin-induced mitochondrial disruption and apoptosis

We reported previously that pancreas-specific ablation of IGF-I in mice induced an increased expression of regenerating family proteins Reg2 and Reg3&#x03B2; in the pancreas and protected them from streptozotocin (Stz)-induced &#x03B2;-cell damage. We, therefore, assessed the effect of ectopically introduced Reg2 on Stz-induced apoptosis in MIN6 mouse insulinoma cells and report here that Reg2 protects MIN6 cells from Stz-induced apoptosis by attenuating its ability to disrupt mitochondrial membrane integrity, activate caspase-3 and promote poly-ADP ribose polymerase cleavage, and induce apoptosis. These changes correlated with suppression of c-jun N-terminal kinase (JNK) phosphorylation by Stz. Reg2 inhibited Stz-induced proapoptotic events as well as the inactivation of JNK. Inclusion of chemical inhibitor of JNK to Reg2 expressing cells rendered them sensitive to Stz. These data demonstrate that Reg2 protects insulin-producing cells against Stz-induced apoptosis by interfering with its cytotoxic signaling upstream of the intrinsic proapoptotic events by preventing its ability to inactivate JNK.

Adjuvant immunotherapy increases beta cell regenerative factor Reg2 in the pancreas of diabetic mice

Insulin-producing β cells can partially regenerate in adult pancreatic tissues, both in human and animal models of type 1 diabetes (T1D). Previous studies have shown that treatment with mycobacterial adjuvants such as CFA and bacillus Calmette-Guérin prevents induction and recurrence of T1D in NOD mice with partial recovery of β cell mass. In this study, we investigated factors involved in the regeneration of β cells in the pancreas of NOD mice during diabetes development and after treatment with adjuvants. The Regeneration (Reg) gene family is known to be involved in regeneration of various tissues including β cells. Reg2 expression was found to be upregulated in pancreatic islets both during diabetes development and as a result of adjuvant treatment in diabetic NOD mice and in C57BL/6 mice made diabetic by streptozotocin treatment. The upregulation of Reg2 by adjuvant treatment was independent of signaling through MyD88 and IL-6 because it was not altered in MyD88 or IL-6 knockout mice. We also observed upregulation of Reg2 in the pancreas of diabetic mice undergoing β cell regenerative therapy with exendin-4 or with islet neogenesis-associated protein. Reg2 expression following adjuvant treatment correlated with a reduction in insulitis, an increase in insulin secretion, and an increase in the number of small islets in the pancreas of diabetic NOD mice and with improved glucose tolerance tests in streptozotocin-treated diabetic C57BL/6 mice. In conclusion, adjuvant immunotherapy regulates T1D in diabetic mice and induces Reg2-mediated regeneration of β cells.

Glucagon-like peptide-1 receptor activation modulates pancreatitis-associated gene expression but does not modify the susceptibility to experimental pancreatitis in mice

OBJECTIVE

Clinical reports link use of the glucagon-like peptide-1 receptor (GLP-1R) agonists exenatide and liraglutide to pancreatitis. However, whether these agents act on the exocrine pancreas is poorly understood.

RESEARCH DESIGN AND METHODS

We assessed whether the antidiabetic agents exendin (Ex)-4, liraglutide, the dipeptidyl peptidase-4 inhibitor sitagliptin, or the biguanide metformin were associated with changes in expression of genes associated with the development of experimental pancreatitis. The effects of Ex-4 when administered before or after the initiation of caerulein-induced experimental pancreatitis were determined. The importance of endogenous GLP-1R signaling for gene expression in the exocrine pancreas and the severity of pancreatitis was assessed in Glp1r(-/-) mice.

RESULTS

Acute administration of Ex-4 increased expression of egr-1 and c-fos in the exocrine pancreas. Administration of Ex-4 or liraglutide for 1 week increased pancreas weight and induced expression of mRNA transcripts encoding the anti-inflammatory proteins pancreatitis-associated protein (PAP) (RegIIIbeta) and RegIIIalpha. Chronic Ex-4 treatment of high-fat-fed mice increased expression of PAP and reduced pancreatic expression of mRNA transcripts encoding for the proinflammatory monocyte chemotactic protein-1, tumor necrosis factor-alpha, and signal transducer and activator of transcription-3. Sitagliptin and metformin did not significantly change pancreatic gene expression profiles. Ex-4 administered before or after caerulein did not modify the severity of experimental pancreatitis, and levels of pancreatic edema and serum amylase were comparable in caerulein-treated Glp1r(-/-) versus Glp1r(+/+) mice.

CONCLUSIONS

These findings demonstrate that GLP-1 receptor activation increases pancreatic mass and selectively modulates the expression of genes associated with pancreatitis. However, activation or genetic elimination of GLP-1R signaling does not modify the severity of experimental pancreatitis in mice.

Exendin-4 normalizes islet vascularity in intrauterine growth restricted rats: potential role of VEGF

Intrauterine growth restriction (IUGR) induced by uterine artery ligation in pregnant rats leads to low birth weight and early insulin secretory defects followed by the development of insulin resistance, decline in beta-cell mass, and diabetes in adulthood. Neonatal administration of Exendin-4 (Ex-4) prevents the deterioration of beta-cell mass and the onset of adult-onset diabetes. Our aim was to determine whether this effect occurs through preservation of islet vascularization. In 2 wk-old IUGR rats, endothelial-specific lectin staining revealed a 40% reduction in islet vascular density (p = 0.027), which was normalized by neonatal Ex-4. VEGF-A protein expression was reduced in IUGR islets compared with controls at postnatal d 1 (P). Neonatal Ex-4 normalized islet VEGF protein expression at P7. Neither IUGR nor Ex-4 administration to IUGR rats affected relative VEGF splice isoform RNA levels. Together, the reduced vascularity in IUGR islets before the deterioration of beta-cell mass, and the enhancement of VEGF expression and normalization of islet vascularity by neonatal Ex-4, suggest islet vascularity as an early determinant of beta-cell mass and as a potential therapeutic target for diabetes prevention.

Overexpression of Reg3alpha increases cell growth and the levels of cyclin D1 and CDK4 in insulinoma cells

Regenerating gene (Reg) family protein Reg3alpha is normally expressed in pancreatic acinar and endocrine cells. In order to explore its effect on islet beta-cell replication, insulinoma MIN6 cells were stably transfected with murine Reg3alpha cDNA. Determined using real-time PCR and Western blots, the levels of Reg3alpha mRNA and protein in Reg3alpha-transfected clones were increased 10- and 6-fold, respectively. Western blots also revealed that the protein was released into the culture medium, consistent with an endocrine effect. In MTT cell proliferation assay, Reg3alpha-overexpressing cells exhibited a 2-fold increase in the rate of cell growth. In order to investigate the intracellular mechanism, we studied cell cycle regulatory proteins. In Reg3alpha-expressing cells, we detected 2.2- and 2.5-fold increased levels of cyclin D1 and CDK4, respectively, which paralleled a 1.8-fold increase in the rate of Akt phosphorylation. It is established that beta-cell replication is associated with increased cyclin D1 and CDK4 levels; deficiency in CDK4 or cyclin D2 results in reduced beta-cell mass and diabetes. Our results suggest that Reg3alpha stimulates beta-cell replication, by activating Akt kinase and increasing the levels of cyclin D1/CDK4.

Gene expression profiling of a mouse model of pancreatic islet dysmorphogenesis

Background

In the past decade, several transcription factors critical for pancreas organogenesis have been identified. Despite this success, many of the factors necessary for proper islet morphogenesis and function remain uncharacterized. Previous studies have shown that transgenic over-expression of the transcription factor Hnf6 specifically in the pancreatic endocrine cell lineage resulted in disruptions in islet morphogenesis, including dysfunctional endocrine cell sorting, increased individual islet size, increased number of peripheral endocrine cell types, and failure of islets to migrate away from the ductal epithelium. The mechanisms whereby maintained Hnf6 causes defects in islet morphogenesis have yet to be elucidated.

Methodology/Principal Findings

We exploited the dysmorphic islets in Hnf6 transgenic animals as a tool to identify factors important for islet morphogenesis. Genome-wide microarray analysis was used to identify differences in the gene expression profiles of late gestation and early postnatal total pancreas tissue from wild type and Hnf6 transgenic animals. Here we report the identification of genes with an altered expression in Hnf6 transgenic animals and highlight factors with potential importance in islet morphogenesis. Importantly, gene products involved in cell adhesion, cell migration, ECM remodeling and proliferation were found to be altered in Hnf6 transgenic pancreata, revealing specific candidates that can now be analyzed directly for their role in these processes during islet development.

Conclusions/Significance

This study provides a unique dataset that can act as a starting point for other investigators to explore the role of the identified genes in pancreatogenesis, islet morphogenesis and mature β cell function.

Reg genes are CCK2 receptor targets in ElasCCK2 mice pancreas

We previously demonstrated that expression of the gastrin receptor, CCK2R, in pancreatic acini of transgenic ElasCCK2 mice induced alteration of acinar morphology and differentiation, increased sensitivity to a carcinogen and development of preneoplastic lesions and tumours. Reg proteins are suggested to be involved in pancreatic cancer and in regeneration of endocrine pancreas. Reg I gene is a known target of gastrin. We examined whether an expression of CCK2R in the pancreatic acini of ElasCCK2 mice is linked to induction of Reg proteins expression. We analyzed Reg expression by Western-blot and immunohistochemistry in pancreas from ElasCCK2 and control mice. Islet neogenesis, glucose homeostasis, insulin secretion and content were also evaluated. Reg I is exclusively produced in acini in ElasCCK2 and control mice. In tumoral pancreas, Reg I and Reg III proteins are expressed in duct-like cells in preneoplastic lesions or in the periphery of tumours and in adjacent acini. The expression of Reg III proteins is increased in ElasCCK2 pancreas before the development of preneoplastic lesions in a subpopulation of islet cells and in small islet-like cell clusters dispersed within the acinar tissue. Several criteria of an enhanced neogenesis are fulfilled in ElasCCK2 pancreas. Moreover, ElasCCK2 mice have an improved response to glucose load, an increased insulin secretion and a doubling of insulin content compared to control mice. We show that Reg proteins are targets of CCK2R activation and are induced during early steps of carcinogenesis in ElasCCK2 mice pancreas. Alterations of exocrine tissue homeostasis in ElasCCK2 pancreas concomitantly activate regenerative responses of the endocrine pancreas possibly linked to paracrine actions of Reg III proteins.

Regenerative biology: a historical perspective and modern applications

Chronic diseases are both common and deadly. Due to the limitations of conventional therapies for chronic diseases such as advanced heart failure and diabetes mellitus, recent interest has been directed towards regenerative medicine. In this review, we examine the history of regenerative biology and emphasize the dynamic and multidisciplinary growth of this field. We highlight the spectrum of adult tissues that have a remarkable regenerative capacity (i.e., skeletal muscle) versus those that have a more limited regenerative capacity (i.e., heart). We further emphasize the use of relevant contemporary models for the study of regenerative biology (i.e., pancreatic regeneration), which highlight both the challenges for this field of study and the potential for regenerative medicine, including the use of cell-based strategies, to revolutionize medical therapies for chronic diseases.

The role of Islet Neogenesis-Associated Protein (INGAP) in islet neogenesis

Islet Neogenesis-Associated Protein (INGAP) is a member of the Reg family of proteins implicated in various settings of endogenous pancreatic regeneration. The expression of INGAP and other RegIII proteins has also been linked temporally and spatially with the induction of islet neogenesis in animal models of disease and regeneration. Furthermore, administration of a peptide fragment of INGAP (INGAP peptide) has been demonstrated to reverse chemically induced diabetes as well as improve glycemic control and survival in an animal model of type 1 diabetes. Cultured human pancreatic tissue has also been shown to be responsive to INGAP peptide, producing islet-like structures with function, architecture and gene expression matching that of freshly isolated islets. Likewise, studies in normoglycemic animals show evidence of islet neogenesis. Finally, recent clinical studies suggest an effect of INGAP peptide to improve insulin production in type 1 diabetes and glycemic control in type 2 diabetes.

Prospects and challenges for islet regeneration as a treatment for diabetes: a review of islet neogenesis associated protein

Diabetes mellitus results from inadequate insulin action, which can be viewed as a consequence of the limited ability to restore beta cells after they are lost as the result of metabolic exhaustion, autoimmune destruction, or surgical insult. Arguably, a uniformly effective therapeutic pathway to address all forms of diabetes would be to reverse the restrictions on beta-cell and islet regeneration. The development from progenitor cells of islets with normal endocrine function does occur in adult humans; it is referred to as islet neogenesis. The induction of islet neogenesis is an important, if not essential, therapeutic approach for curing type 1 diabetes mellitus (T1DM) and could be valuable in the treatment of type 2 diabetes mellitus (T2DM) as well. Islet neogenesis associated protein (INGAP) is the first therapeutic candidate to be identified as the result of a purposeful search for an endogenous molecule with islet neogenic activity. It was found that partial obstruction of the pancreatic duct in hamsters induced islet neogenesis; under this condition, a neogenesis-promoting activity was identified and partially purified from a soluble tissue fraction. A 168-kDa protein product of the cloned gene was found to be responsible for the neogenesis activity. This molecule named INGAP contains an active core sequence of amino acids called INGAP peptide. Results from in vitro, animal, and human studies suggest that INGAP and INGAP peptide are neogenic in at least several vertebrate species, including humans. INGAP has since been found to be a member of the family of Reg proteins, which are found across and in multiple versions within species and are closely associated with embryonic and regenerative processes. Clinical results suggest that INGAP peptide can be a suitable neogenesis therapy, but optimization of the therapy and more data are required to fully access this potential. Understanding of the signaling pathways of INGAP and other related Reg proteins is a promising means of advancing therapeutic development for people with T1DM and T2DM. The quest for the fundamental restorative approach to lost insulin secretion is an enticing target for drug development.