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The pancreas is a mixed exocrine and endocrine gland which plays an essential role in our body's digestive system and nutrient metabolism. The exocrine pancreas secretes digestive enzymes for the breakdown of carbohydrates, proteins and lipids. The roles of these enzymes as biomarkers for cellular damage in pancreatitis are further discussed in this article. The endocrine function is involved in the regulation of appetite, glucose homeostasis and gastrointestinal secretions. We will explore the highly coordinated feedback mechanisms of the secretion of these pancreatic hormones and their effects on effector organs such as muscles and adipose tissues. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) is widely considered to result from the autoimmune destruction of insulin-producing β cells. This concept has been a central tenet for decades of attempts seeking to decipher the disorder's pathogenesis and prevent/reverse the disease. Recently, this and many other disease-related notions have come under increasing question, particularly given knowledge gained from analyses of human T1D pancreas. Perhaps most crucial are findings suggesting that a collective of cellular constituents—immune, endocrine, and exocrine in origin—mechanistically coalesce to facilitate T1D. This review considers these emerging concepts, from basic science to clinical research, and identifies several key remaining knowledge voids. Atkinson and Mirmira consider recent knowledge gains from studies of human pancreas that suggest immune, endocrine, and exocrine cells mechanistically coalesce to facilitate type 1 diabetes pathogenesis, portraying a more complex orchestration of this disease than was previously appreciated. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) occurs because of islet infiltration by autoreactive immune cells leading to destruction of beta cells and it is becoming evident that beta cell dysfunction partakes in this process. We previously reported that genetic deletion and pharmacological antagonism of the cannabinoid 1 receptor (CB1) in mice improves insulin synthesis and secretion, upregulates glucose sensing machinery, favors beta cell survival by reducing apoptosis, and enhances beta cell proliferation. Moreover, beta cell specific deletion of CB1 protected mice fed a high fat high sugar diet against islet inflammation and beta cell dysfunction. Therefore, we hypothesized that it would mitigate the dysfunction of beta cells in the precipitating events leading to T1D. We genetically deleted CB1 specifically from beta cells in non-obese diabetic (NOD; NOD RIP Cre+ Cnr1 fl/fl) mice. We evaluated female NOD RIP Cre+ Cnr1 fl/fl mice and their NOD RIP Cre− Cnr1 fl/fl and NOD RIP Cre+ Cnr1 Wt/Wt littermates for onset of hyperglycemia over 26 weeks. We also examined islet morphology, islet infiltration by immune cells and beta cell function and proliferation. Beta cell specific deletion of CB1 in NOD mice significantly reduced the incidence of hyperglycemia by preserving beta cell function and mass. Deletion also prevented beta cell apoptosis and aggressive insulitis in NOD RIP Cre+ Cnr1 fl/fl mice compared to wild-type littermates. NOD RIP Cre+ Cnr1 fl/fl islets maintained normal morphology with no evidence of beta cell dedifferentiation or appearance of extra islet beta cells, indicating that protection from autoimmunity is inherent to genetic deletion of beta cell CB1. Pancreatic lymph node T reg cells were significantly higher in NOD RIP Cre+ Cnr1 fl/fl vs NOD RIP Cre− Cnr1 fl/fl. Collectively these data demonstrate how protection of beta cells from metabolic stress during the active phase of T1D can ameliorate destructive insulitis and provides evidence for CB1 as a potential pharmacologic target in T1D. • Beta cell specific CB1 deletion protects islets from the detrimental effects of prolonged nutrient overload and inflammation. • Beta cells in T1D are subjected to endoplasmic reticulum stress because of increasing demands to synthesize insulin. • Beta cell specific CB1 deletion in NOD mice prevents hyperglycemia and insulitis and preserves beta cell mass and function. • NOD beta cells lacking CB1 had reduced expression of the beta cell antigen presenting molecule MHC class I. • CB1 blockade should be considered a target for prevention of T1D as it protects beta cells and improves beta cell function. [ABSTRACT FROM AUTHOR]

The pathophysiology of diabetes is complex and recent research put focus on the pancreatic islets of Langerhans and the insulin-secreting beta cells as central in the development of the disease. MicroRNAs (miRNAs), the small non-coding RNAs regulating post-transcriptional gene expression, are significant regulators of beta cell function. One of the most abundant miRNAs in the islets is miR-375. This review focus on the role of miR-375 in beta cell function, including effects in development and differentiation, proliferation and regulation of insulin secretion. It also discusses the regulation of miR-375 expression, miR-375 as a potential circulating biomarker in type 1 and type 2 diabetes, and the need for the beta cell to keep expression of miR-375 within optimal levels. The summed picture of miR-375 is a miRNA with multiple functions with importance in the formation of beta cell identity, control of beta cell mass and regulation of insulin secretion. [ABSTRACT FROM AUTHOR]

Background Plasma insulin levels are predominantly the product of the morphological mass of insulin producing beta cells in the pancreatic islets of Langerhans and the functional status of each of these beta cells. Thus, deficiency in either beta cell mass or function, or both, can lead to insufficient levels of insulin, resulting in hyperglycemia and diabetes. Nonetheless, the precise contribution of beta cell mass and function to the pathogenesis of diabetes as well as the underlying mechanisms are still unclear. In the past, this was largely due to the restricted number of technologies suitable for studying the scarcely accessible human beta cells. However, in recent years, a number of new platforms have been established to expand the available techniques and to facilitate deeper insight into the role of human beta cell mass and function as cause for diabetes and as potential treatment targets. Scope of Review This review discusses the current knowledge about contribution of human beta cell mass and function to different stages of type 1 and type 2 diabetes pathogenesis. Furthermore, it highlights standard and newly developed technological platforms for the study of human beta cell biology, which can be used to increase our understanding of beta cell mass and function in human glucose homeostasis. Major Conclusions In contrast to early disease models, recent studies suggest that in type 1 and type 2 diabetes impairment of beta cell function is an early feature of disease pathogenesis while a substantial decrease in beta cell mass occurs more closely to clinical manifestation. This suggests that, in addition to beta cell mass replacement for late stage therapies, the development of novel strategies for protection and recovery of beta cell function could be most promising for successful diabetes treatment and prevention. The use of today's developing and wide range of technologies and platforms for the study of human beta cells will allow for a more detailed investigation of the underlying mechanisms and will facilitate development of treatment approaches to specifically target human beta cell mass and function. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are cellular, short, non-coding ribonucleotides acting as endogenous posttranscriptional repressors following incorporation in the RNA-induced silencing complex. Despite being chemically and mechanistically very similar, miRNAs exert a multitude of different cellular effects by acting on mRNA species, whose gene-products partake in a wide array of processes. Here, the aim was to review the knowledge of miRNA expression and action in the islet of Langerhans. We have focused on: 1) physiological consequences of islet or beta cell specific inhibition of miRNA processing, 2) mechanisms regulating processing of miRNAs in islet cells, 3) presence and function of miRNAs in alpha versus beta cells – the two main cell types of islets, and 4) miRNA mediators of beta cell decompensation. It is clear that miRNAs regulate pancreatic islet development, maturation, and function in vivo . Moreover, processing of miRNAs appears to be altered by obesity, diabetes, and aging. A number of miRNAs (such as miR-7, miR-21, miR-29, miR-34a, miR-212/miR-132, miR-184, miR-200 and miR-375) are involved in mediating beta cell dysfunction and/or compensation induced by hyperglycemia, oxidative stress, cytotoxic cytokines, and in rodent models of fetal metabolic programming prediabetes and overt diabetes. Studies of human type 2 diabetic islets underline that these miRNA families could have important roles also in human type 2 diabetes. Furthermore, there is a genuine gap of knowledge regarding miRNA expression and function in pancreatic alpha cells. Progress in this area would be enhanced by improved in vitro alpha cell models and better tools for islet cell sorting. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) is caused by autoimmune destruction of islet of Langerhans β-cells. P2X7 receptors (P2X7R) modulate proinflammatory immune responses by binding extracellular ATP, a classic ‘danger signal’. Here, we evaluated whether the P2X7R has a role in T1D development. P2X7 −/− mice are resistant to TD1 induction by streptozotocin (STZ) treatment, with no increase in blood glucose, decrease in insulin-positive cells, and pancreatic islet reduction, compared to WT (C57BL/6) mice. Also, the levels of proinflammatory mediators (IL-1β, IFN-γ and NO) did not increase after STZ treatment in P2X7 −/− animals, with reduced infiltration of CD4 + , CD8 + , B220 + , CD11b + and CD11c + cells in the pancreatic lymph nodes. Treatment with a P2X7 antagonist mimicked the effect of P2X7 knockout, preventing STZ-induced diabetes. Our results show that the absence of the P2X7R provides resistance in the induction of diabetes in this model, and suggest that therapy targeting the P2X7R may be useful against clinical T1D. [ABSTRACT FROM AUTHOR]

The development and plasticity of the endocrine pancreas responds to both the intrauterine and postnatal exposome in a constant attempt to predict and respond to alterations in nutritional availability and metabolic requirements. Both under- and over-nutrition in utero, or exposure to adverse environmental pollutants or maternal behaviors, can each lead to altered β-cell or function at birth, and a subsequent mismatch in pancreatic hormonal demands and secretory capacity postnatally. This can be further exacerbated by metabolic stress postnatally such as from obesity or pregnancy, resulting in an increased risk of gestational diabetes, type 2 diabetes, and even type 1 diabetes. This review will discuss evidence identifying the cellular pathways in early life whereby the plasticity of the endocrine pancreatic can become pathologically limited. By necessity, much of this evidence has been gained from animal models, although extrapolation to human fetal development is possible from the fetal growth trajectory and study of the newborn. Cellular limitations to plasticity include the balance between β-cell proliferation and apoptosis, the appearance of β-cell oxidative stress, impaired glucose-stimulated insulin secretion, and sensitivity to circulating cytokines and responsiveness to programmed death receptor-1. Evidence suggests that many of the cellular pathways responsible for limiting β-cell plasticity are related to paracrine interactions within the islets of Langerhans. [ABSTRACT FROM AUTHOR]

Coordinated pulses of electrical activity and insulin secretion are a hallmark of the islet of Langerhans. These coordinated behaviors are lost when β cells are dissociated, which also leads to increased insulin secretion at low glucose levels. Islets without gap junctions exhibit asynchronous electrical activity similar to dispersed cells, but their secretion at low glucose levels is still clamped off, putatively by a juxtacrine mechanism. Mice lacking β cell gap junctions have near-normal average insulin levels, but are glucose intolerant due to reduced first-phase and pulsatile insulin secretion, illustrating the importance of temporal dynamics. Here, we review the quantitative data on islet synchronization and the current mathematical models that have been developed to explain these behaviors and generate greater understanding of the underlying mechanisms. [ABSTRACT FROM AUTHOR]

Until recently, communication between neighboring cells in islets of Langerhans was overlooked by genomic technologies, which require rigorous tissue dissociation into single cells. We utilize sorting of physically interacting cells (PICs) with single-cell RNA-sequencing to systematically map cellular interactions in the endocrine pancreas after pancreatectomy. The pancreas cellular landscape features pancreatectomy associated heterogeneity of beta-cells, including an interaction-specific program between paired beta and delta-cells. Our analysis suggests that the particular cluster of beta-cells that pairs with delta-cells benefits from stress protection, implying that the interaction between beta- and delta-cells might safeguard against pancreatectomy associated challenges. The work encourages testing the potential relevance of physically-interacting beta-delta-cells also in diabetes mellitus. • Single-cell RNA-sequencing systematically maps physically interacting endocrine cells in the pancreas. • The landscape of pancreatectomy associated beta-cell heterogeneity is mapped in a single cell resolution. • Interaction-specific beta - delta cellular program safeguards beta cells against pancreatectomy-associated stress. • Physically interacting beta delta pairs were discovered in an injury model and may also be relevant in diabetes. [ABSTRACT FROM AUTHOR]

Abstract: The retinoic-acid-related receptor family of orphan receptors (RORs) act as transcriptional activators or repressors. One of their functions involves integrated actions within circadian oscillators, particularly of the periphery. The present paper describes differential expression of the orphan receptors RORα, RORβ and RORγ and of the nuclear retinoid receptor RXRα in the pancreas and islet of rats. Immunohistochemistry of rodent islets detected nuclear receptor expression. The RORα and RORβ signals were visualised in α-cells, whereas that of RORγ was largely confined to β-cells. RXRα was expressed throughout the islets. Quantitative RT-PCR revealed circadian expression in the rat pancreas for RORγ, RORα and RXRα, but not for RORβ. Circadian expression of RORγ mRNA was verified in mouse pancreas and in rat INS-1 β cells by serum shock experiments. The results point to differential and circadian expression and thus cell-type-specific functions of RORα and RORγ in islet cells secreting glucagon or insulin. [Copyright &y& Elsevier]

Abstract: An unresolved obstacle in transplantation of islets of Langerhans is the early graft loss caused by thrombotic reactions on the surface of islets after intraportal transplantation. We investigated a versatile method for modifying the surface of islets with liposomes carrying the anticoagulant argatroban using an amphiphilic poly(ethylene glycol)-phospholipid conjugate derivative (PEG-lipid) and DNA hybridization. Argatroban was gradually released from the liposomes on the islets, and antithrombic activity was detected in culture medium. Modified islets retained the ability to control insulin release in response to glucose concentration changes. Although we mainly examined surface modification of islets, this technique may be useful for immobilizing various types of small molecules on cells and tissues and thus may have many applications in cell therapy and regenerative medicine. [Copyright &y& Elsevier]

Abstract: ATP-sensitive potassium channels (KATP) regulate electrical activity and insulin secretion in pancreatic β-cells. When glucose concentration increases, the [ATP]/[ADP] ratio rises closing KATP channels, and the membrane potential depolarizes, triggering insulin secretion. This pivotal role of KATP channels is used not only by glucose but also by neurotransmitters, hormones and other physiological agents to modulate electrical and secretory β-cell response. In recent years, it has been demonstrated that estrogens and estrogen receptors are involved in glucose homeostasis, and that they can modulate the electrical activity and insulin secretion of pancreatic β-cells. The hormone 17β-estradiol (E2), at physiological levels, is implicated in maintaining normal insulin sensitivity for β-cell function. Long term exposure to E2 increases insulin content, insulin gene expression and insulin release via the estrogen receptor α (ERα), while rapid responses to E2 can regulate KATP channels increasing cGMP levels through the estrogen receptor β (ERβ) and type A guanylate cyclase receptor (GC-A). This review summarizes the main actions of 17β-estradiol on KATP channels and the subsequent insulin release in pancreatic β-cells. [Copyright &y& Elsevier]

Abstract: A capillary electrophoresis competitive immunoassay was developed for the simultaneous quantitation of insulin, glucagon, and islet amyloid polypeptide (IAPP) secretion from islets of Langerhans. Separation buffers and conditions were optimized for the resolution of fluorescein isothiocyanate (FITC)-labeled glucagon and IAPP immunoassay reagents, which were excited with the 488nm line of an Ar+ laser and detected at 520nm with a photomultiplier tube (PMT). Cy5-labeled insulin immunoassay reagents were excited by a 635nm laser diode module and detected at 700nm with a separate PMT. Optimum resolution was achieved with a 20mM carbonate separation buffer at pH 9.0 using a 20cm effective separation length with an electric field of 500V/cm. Limits of detection for insulin, glucagon, and IAPP were 2, 3, and 3nM, respectively. This method was used to monitor the simultaneous secretion of these peptides from as few as 14 islets after incubation in 4, 11, and 20mM glucose for 6h. For insulin and IAPP, a statistically significant increase in secretion levels was observed, while glucagon levels were significantly reduced in the 4 and 11mM glucose conditions. To further demonstrate the utility of the assay, the Ca2+-dependent secretion of these peptides was demonstrated which agreed with published reports. The ability to examine the secretion of multiple peptides may allow for the determination of regulation of secretory processes within islets of Langerhans. [Copyright &y& Elsevier]

Abstract: Transplantation of islets of Langerhans is a promising method for treating patients with insulin-dependent diabetes mellitus. The major obstacle in clinical settings is early graft loss due to inflammation triggered by blood coagulation and complement activation on the surface of the islets after intraportal transplantation. We propose a versatile method for modifying the surface of islets with the fibrinolytic enzyme urokinase and the soluble domain of the anticoagulant enzyme thrombomodulin. The surfaces of islets were modified with a poly(ethylene glycol)–phospholipid conjugate bearing a maleimide group (Mal–PEG–lipid; PEG MW=5000kDa). The Mal–PEG–lipid anchored to the cell membranes of islets, resulting in the presentation of functional maleimide groups on the islet surface. The surface was further treated with thiolated urokinase and thrombomodulin that conjugated by thiol/maleimide bonding. No practical islet volume increase was observed after surface modification, and the modifications did not impair insulin release in response to glucose stimulation. Furthermore, the activity of the immobilized urokinase and thrombomodulin was maintained. These modifications could help to improve graft survival by preventing thrombus formation on the surface of transplanted islets. [Copyright &y& Elsevier]

Abstract: Glucokinase activators increase insulin release from pancreatic β-cells and hepatic glucose utilization by modifying the activity of glucokinase, a key enzyme in glucose-sensing and glycemic regulation. Sulfonylureas are antihyperglycemic agents that stimulate insulin secretion via a glucose-independent mechanism that is vulnerable to secondary failure through β-cell desensitization. The present study determined whether glucokinase activator treatment retains its glucose-lowering efficacy in male, adult, non-diabetic Sprague–Dawley rats desensitized to sulfonylurea treatment and whether glucose-lowering during chronic glucokinase activator treatment is subject to secondary failure. Animals were given food containing either glimepiride (a sulfonylurea), Compound B (3-[(1S)-2-hydroxy-1-methylethoxy]-5-[4-(methylsulfonyl)phenoxy]-N-1,3-thiazol-2-ylbenzamide, an experimental glucokinase activator), or no drug for up to 5weeks. Food containing 0.04% of either drug produced acute (within 4–8h) and significant (P <0.05) reductions in blood glucose to approximately 50% of control levels. Chronic treatment with either 0.01% or 0.04% glimepiride resulted in complete failure of glucose-lowering efficacy within 3days whereas the efficacy of Compound B was sustained throughout the entire study. Glipizide, also a sulfonylurea, had no glucose-lowering effect when given by gavage (3mg/kg) to glimepiride-desensitized animals whereas Compound B retained full glucose-lowering efficacy in glimepiride-desensitized animals. Oral glucose tolerance was significantly impaired, compared with controls, in animals treated with glimepiride for two weeks but was enhanced to a small extent in animals treated with Compound B. Compound B also significantly increased pancreatic insulin content, compared with controls. These findings suggest that Compound B has sustained glucose-lowering effects in a rat model of sulfonylurea failure. [Copyright &y& Elsevier]

Abstract: The concept of glucolipotoxicity refers to the combined, deleterious effects of elevated glucose and fatty acid levels on pancreatic beta-cell function and survival. Significant progress has been made in recent years towards a better understanding of the cellular and molecular basis of glucolipotoxicity in the beta cell. The permissive effect of elevated glucose on the detrimental actions of fatty acids stems from the influence of glucose on intracellular fatty acid metabolism, promoting the synthesis of cellular lipids. The combination of excessive levels of fatty acids and glucose therefore leads to decreased insulin secretion, impaired insulin gene expression, and beta-cell death by apoptosis, all of which probably have distinct underlying mechanisms. Recent studies from our laboratory have identified several pathways implicated in fatty acid inhibition of insulin gene expression, including the extracellular-regulated kinase (ERK1/2) pathway, the metabolic sensor Per-Arnt-Sim kinase (PASK), and the ATF6 branch of the unfolded protein response. We have also confirmed in vivo in rats that the decrease in insulin gene expression is an early defect which precedes any detectable abnormality in insulin secretion. While the role of glucolipotoxicity in humans is still debated, the inhibitory effects of chronically elevated fatty acid levels has been clearly demonstrated in several studies, at least in individuals genetically predisposed to developing type 2 diabetes. It is therefore likely that glucolipotoxicity contributes to beta-cell failure in type 2 diabetes as well as to the decline in beta-cell function observed after the onset of the disease. [Copyright &y& Elsevier]

The endogenous cannabinoid system participates in the regulation of energy homeostasis, and this fact led to the identification of a new group of therapeutic agents for complicated obesity and diabetes. Cannabinoid receptor antagonists are now realities in clinical practice. The use of such antagonists for reducing body weight gain, lowering cholesterol and improving glucose homeostasis is based on the ability of the endocannabinoids to coordinately regulate energy homeostasis by interacting with central and peripheral targets, including adipose tissue, muscle, liver and endocrine pancreas. In this review we will analyse the presence of this system in the main cell types of the islets of Langerhans, as well as the physiological relevance of the endocannabinoids and parent acylethanolamides in hormone secretion and glucose homeostasis. We will also analyse the impact that these findings may have in clinical practice and the potential outcome of new therapeutic strategies for modulating glucose homeostasis and insulin/glucagon secretion. [Copyright &y& Elsevier]

Abstract: This study was performed on the basis of previously obtained investigative gene array data concerning the over-expression of CXCL12/SDF-1 in human insulinomas versus human pancreatic islet preparations. The presence of CXCL12/SDF-1 was studied by RT-qPCR in human insulinomas (n =8) versus pancreatic islets (n =3), and was found to be significantly up-regulated in the former (p <0.012). The mRNA data were confirmed by immunostaining and confocal microscopy of human normal pancreatic islets, which showed the absence of CXCL12 protein and high expression in insulinoma tissue. Individual human insulinoma cells at cytospins stained positive for CXCL12 in the paranuclear region. These morphological data were extended by consecutive immunoblotting for cell-compartment-specific marker proteins of fractions obtained by sucrose gradient fractionation using Rin-5F insulinoma cells. CXCL12-containing fractions were positive for the membrane marker NSF but negative for SNAP-25 and appeared at a lighter density in the gradient than heavy insulin granules, suggesting packaging in specific granules different from insulin. In order to determine the biological relevance of the protein in insulinomas, we investigated the colony-forming potential of human CXCL12 stable-transfected rat Rin-5F insulinoma cells. These clones secreted human CXCL12 and contained 50–1000-fold higher copy numbers compared to its endogenous rat homologue. In colony-forming assays, these transfectant clones developed greater colony numbers, which were larger than wild-type and sham transfectants. To elucidate the mechanism of action, we identified a CXCL12 transfectant-specific increase in the pro-survival factor Mn-SOD, which is considered important for the inactivation of reactive oxygen species, thereby prolonging cell survival. These data demonstrate the importance of CXCL12 in the tumor biology of insulinoma. [Copyright &y& Elsevier]

Abstract: Estrogens have been related to energy balance and glucose metabolism for a long time; however, the mechanisms involved in their actions are now being unveiled. The development of ERα and ERβ knockout mice has demonstrated the participation of these receptors in the regulation of many processes related to the control of energy homeostasis. These include food intake and energy expenditure, insulin sensitivity in the liver and muscle, adipocyte growth and its body distribution as well as the pancreatic β-cell function. In addition, other membrane receptors unrelated to ERα and ERβ function in key tissues involved in energy balance and glucose homeostasis, i.e. the islet of Langerhans and the hypothalamus. Along with naturally occurring estrogens, there are endocrine disrupters that act as environmental estrogens and can impair the physiological action of ERα, ERβ and other membrane ERs. New research is revealing a link between environmental estrogenic pollutants and the metabolic syndrome. [Copyright &y& Elsevier]

Abstract: Enterovirus infections of the pancreatic islets are believed to trigger or precipitate the near total destruction of β-cells that constitutes type 1 diabetes (T1D). This study investigated the ability of an anti-picornaviral compound, pleconaril, to block the replication of two β-cell tropic Coxsackie B4 virus (CBV-4) strains in isolated human islets. The two strains, VD2921 and V89 4557, with demonstrated abilities to cause non-lytic persistence or lytic infection, respectively, in islets, represented two different potential mechanisms behind virus-induced T1D. The virus replication in the islets was studied with and without addition of pleconaril. In addition, islet morphology was studied every day. To test the effects of pleconaril and/or DMSO on the β-cells’ insulin secretion, glucose perifusions were performed on treated and untreated islets. Virus titrations showed a clear reduction of the replication of both strains after pleconaril treatment. The VD2921 strain was inhibited to undetectable levels. The V89 4557 strain, however, showed an initial reduction of titers but virus titers then increased despite the addition of a second dose of pleconaril. This incomplete inhibition of viral replication suggested the existence of a resistant subtype within this strain. Pleconaril treatment reduced the β-cells’ insulin secretion in response to glucose stimulation in some experiments and induced slight morphological changes to the islets compared to untreated controls. In summary, pleconaril reduced the replication of the two β-cell tropic CBV-4 strains in human islets. However, genetic differences between these strains influenced the effectiveness of pleconaril treatment. This stresses the importance of using multiple viral strains in antiviral tests. [Copyright &y& Elsevier]

Abstract: Glucagon-like peptide 1 (GLP-1) is a hormone that is encoded in the proglucagon gene. It is mainly produced in enteroendocrine L cells of the gut and is secreted into the blood stream when food containing fat, protein hydrolysate, and/or glucose enters the duodenum. Its particular effects on insulin and glucagon secretion have generated a flurry of research activity over the past 20 years culminating in a naturally occurring GLP-1 receptor (GLP-1R) agonist, exendin 4 (Ex-4), now being used to treat type 2 diabetes mellitus (T2DM). GLP-1 engages a specific guanine nucleotide-binding protein (G-protein) coupled receptor (GPCR) that is present in tissues other than the pancreas (brain, kidney, lung, heart, and major blood vessels). The most widely studied cell activated by GLP-1 is the insulin-secreting β cell where its defining action is augmentation of glucose-induced insulin secretion. Upon GLP-1R activation, adenylyl cyclase (AC) is activated and cAMP is generated, leading, in turn, to cAMP-dependent activation of second messenger pathways, such as the protein kinase A (PKA) and Epac pathways. As well as short-term effects of enhancing glucose-induced insulin secretion, continuous GLP-1R activation also increases insulin synthesis, β cell proliferation, and neogenesis. Although these latter effects cannot be currently monitored in humans, there are substantial improvements in glucose tolerance and increases in both first phase and plateau phase insulin secretory responses in T2DM patients treated with Ex-4. This review will focus on the effects resulting from GLP-1R activation in the pancreas. [Copyright &y& Elsevier]

Abstract: Primary nonfunction (PNF) adversely impacts islet transplantation. In addition to determining whether sodium 4-phenylbutyrate (4-SPB), an anti-inflammatory agent, reduces PNF, this study investigates how 4-SPB affects PNF. Streptozotocin-induced diabetic C57BL/6 mice, that received 75 syngeneic islets underneath left subrenal space, were fed twice daily of either 4-SPB at 500 mg/kg body weight or isotonic saline (NaCl) from 2 days before through 7 days after transplantation. The graft was removed at days 3, 10 and 84 following transplantation. At 68 h following transplantation, serum levels of interleukin-1β (IL-1β) were 2.2±0.4 and 0.4±0.2 pmol/L (n =6, p <0.005) for NaCl and 4-SPB groups, respectively. Graft genetic expression of IL-1β was significantly suppressed in 4-SPB group (p <0.01). At day 10, the blood glucose levels were 22.7±1.0 and 17.1±1.7 mmol/L (n =12, p <0.05) and graft insulin contents (IC) were 35.0±8.3 and 107.6±29.7 pmol (n =12, p <0.05) for NaCl and 4-SPB groups, respectively. Moreover, the 4-SPB group had a shorter temporary hyperglycemia (15±2, n =21 vs. 25±2 days, n =19, p =0.001) and a higher cumulative cure rate of diabetes (p <0.001) than the NaCl group. In-vitro studies indicated that 4-SPB did not impact the islets function. These experimental results demonstrated that perioperative administration of 4-SPB decreased serum level and graft genetic expression of IL-1β and attenuated PNF, which enhanced islet engraftment in a syngeneic transplantation mouse model. [Copyright &y& Elsevier]

Summary: The cholecystokinin (CCK) family of peptides and receptors is present throughout the brain and gastrointestinal tract including pancreatic tissue. The expression of these molecules in the gut and pancreas is species-specifically regulated and the role of CCK in porcine pancreatic islet hormone secretion is still a matter of discussion. Therefore, in this study we have determined the cell-type specific localization of CCK and its high affinity CCKA-receptor in islet cells using immunohistochemical techniques. Serial sectioning followed by double-immunostaining of methanol/acetic acid-fixed, paraffin-embedded pancreatic tissues were performed with antibodies against CCK, CCKA-receptor, glucagon and somatostatin. To determine whether CCK specific mRNA is locally expressed, total RNA was isolated, transcribed to cDNA and analysed with specific primer for CCK gene expression. Our results clearly show that CCK and the CCKA-receptor coexist in glucagon – but not in somatostatin-producing cells. Moreover our RT-PCR experiments demonstrate that there is no local gene expression of CCK in the porcine pancreas. Our results provide evidence that, in the porcine species, blood-borne CCK binds specifically to the CCKA-receptor and may thereby modulate the glucose homeostasis via a direct action on A-cells. [Copyright &y& Elsevier]

Abstract: Aim of the study. – The allograft of pancreatic islets represents a potential alternative to insulin therapy in patients suffering from the most severe forms of Type 1 diabetes. Here we report our experience of pancreatic procurement for isolation and islet allograft. Materials and methods. – Pancreata were procured in brain-dead donors. The islets were isolated using techniques developed and validated in pigs and men. Injection of a given preparation was decided after quantitative and qualitative controls. Islets were transplanted in Type 1 diabetic patients already grafted with a kidney or suffering from severe and/or unstable diabetes, after percutaneous or surgical settlement of an intra-portal catheter. Patients received an “Edmonton-like” immunosuppressive protocol. Grafts were repeated once or twice until a total quantity of 10,000 transplanted islet-equivalents was obtained. Results. – Twenty-nine pancreata were procured and 14 preparations were grafted to 7 patients. Eleven graftings were done percutaneously and three were surgical. The initial function of the 14 transplants was confirmed by secretion of C-peptide and decrease of insulin doses. Insulin therapy was completely interrupted in the 5 patients having received at least two grafts. Conclusion. – These preliminary clinical results confirmed that the isolation technique of human islets and the technique of pancreas procurement are mastered by our team. If the results of this assay (assessment one year after graft) confirm our hopes, we will be able to offer islet allografts to an increasing number of patients with severe Type 1 diabetes. [Copyright &y& Elsevier]

Abstract: Diabetes is one of the most common chronic diseases in our society. While insulin treatment for diabetes type I could delay and reduce the incidence of diabetic complications, it is associated with an increased risk of severe hypoglycemia. To restore physiologic insulin metabolism, transplantation of insulin producing cells (Pancreatic Beta cells) represent the sole available therapy. It could be done either through pancreas or islet of Langerhans transplantation. In this paper, we review actual knowledge regarding these two types of transplantations. [Copyright &y& Elsevier]

The expression of K+–Cl− cotransporters (KCC) was examined in pancreatic islet cells. mRNA for KCC1, KCC3a, KCC3b and KCC4 were identified by RT-PCR in islets isolated from rat pancreas. In immunocytochemical studies, an antibody specific for KCC1 and KCC4 revealed the expression of KCC protein in α-cells, but not pancreatic β-cells nor δ-cells. A second antibody which does not discriminate among KCC isoforms identified KCC expression in both α-cell and β-cells. Exposure of isolated α-cells to hypotonic solutions caused cell swelling was followed by a regulatory volume decrease (RVD). The RVD was blocked by 10 μM [dihydroindenyl-oxy] alkanoic acid (DIOA; a KCC inhibitor). DIOA was without effect on the RVD in β-cells. NEM (0.2 mM), a KCC activator, caused a significant decrease of α-cell volume, which was completely inhibited by DIOA. By contrast, NEM had no effects on β-cell volume. In conclusion, KCCs are expressed in pancreatic α-cells and β-cells. However, they make a significant contribution to volume homeostasis only in α-cells. [Copyright &y& Elsevier]

A role for prolactin (PRL) in the regulation of adenylyl cyclase (AC), cyclic AMP (cAMP) formation and insulin secretion was studied in isolated rat pancreatic islets cultured for 4 days at 5.5 mM glucose in the absence (control) or presence of PRL (500 ng/ml). In PRL-treated islets, stimulation by glucose (8 mM), carbamylcholine chloride (CCh) and phorbol dibutyrate increased cAMP levels 40, 89, and 151%, respectively, above similarly stimulated control islets without PRL. Moreover, insulin secretion in PRL-treated islets was more than doubled in response to 8 mM glucose plus glucagon-like peptide 1 compared with control islets. PRL also increased protein kinase C (PKC) activity in cultured islets. When islets were cultured at an insulin secretion desensitizing concentration of glucose (11 mM) for 4 days, there was a decrease in forskolin-stimulated cAMP production. However, the presence of PRL with 11 mM glucose prevented the glucose-induced decrease in cAMP production. Insulin secretion in response to 17 mM glucose was also higher (P<0.02) in islets cultured with 11 mM glucose plus PRL compared with islets cultured with 11 mM glucose alone. Islet AC types -III, -V, and -VI mRNA levels increased relative to 18s rRNA following PRL treatment. In contrast, culture at 11 mM glucose decreased relative AC-III, -V and -VI mRNA levels by as much as 50%. Culture with PRL prevented the decrease in AC expression during islet culture with 11 mM glucose, and the mRNA levels remained similar to control islets cultured at 5.5 mM glucose. Thus, PRL not only increased islet AC expression and activity and insulin secretory responsiveness, but also protected islets from chronic glucose-induced inhibition of these β-cell activation parameters. [Copyright &y& Elsevier]

Maintenance of glucose homeostasis requires the precise regulation of hormone secretion from the endocrine pancreas. Free fatty acid receptor 4 (FFAR4/GPR120) is a G protein-coupled receptor whose activation in islets of Langerhans promotes insulin and glucagon secretion and inhibits somatostatin secretion. However, the contribution of individual islet cell types (α, β, and δ cells) to the insulinotropic and glucagonotropic effects of GPR120 remains unclear. As gpr120 mRNA is enriched in somatostatin-secreting δ cells, we hypothesized that GPR120 activation stimulates insulin and glucagon secretion via inhibition of somatostatin release. Glucose tolerance tests were performed in mice after administration of selective GPR120 agonist Compound A. Insulin, glucagon, and somatostatin secretion were measured in static incubations of isolated mouse islets in response to endogenous (ω-3 polyunsaturated fatty acids) and/or pharmacological (Compound A and AZ-13581837) GPR120 agonists. The effect of Compound A on hormone secretion was tested further in islets isolated from mice with global or somatostatin cell-specific knock-out of gpr120. Gpr120 expression was assessed in pancreatic sections by RNA in situ hybridization. Cyclic AMP (cAMP) and calcium dynamics in response to pharmacological GPR120 agonists were measured specifically in α, β, and δ cells in intact islets using cAMPER and GCaMP6 reporter mice, respectively. Acute exposure to Compound A increased glucose tolerance, circulating insulin, and glucagon levels in vivo. Endogenous and/or pharmacological GPR120 agonists reduced somatostatin secretion in isolated islets and concomitantly demonstrated dose-dependent potentiation of glucose-stimulated insulin secretion and arginine-stimulated glucagon secretion. Gpr120 was enriched in δ cells. Pharmacological GPR120 agonists reduced cAMP and calcium levels in δ cells but increased these signals in α and β cells. Compound A-mediated inhibition of somatostatin secretion was insensitive to pertussis toxin. The effect of Compound A on hormone secretion was completely absent in islets from mice with either global or somatostatin cell-specific deletion of gpr120 and partially reduced upon blockade of somatostatin receptor signaling by cyclosomatostatin. Inhibitory GPR120 signaling in δ cells contributes to both insulin and glucagon secretion in part by mitigating somatostatin release. Image 1 • Gpr120 was enriched in mouse somatostatin-secreting δ cells. • GPR120 activation in mouse δ cells inhibited cAMP generation and somatostatin release. • GPR120 activation in mouse δ cells potentiated insulin and glucagon secretion. [ABSTRACT FROM AUTHOR]

Bisphenol-S (BPS) and Bisphenol-F (BPF) are current Bisphenol-A (BPA) substitutes. Here we used pancreatic β-cells from wild type (WT) and estrogen receptor β (ERβ) knockout (BERKO) mice to investigate the effects of BPS and BPF on insulin secretion, and the expression and activity of ion channels involved in β-cell function. BPS or BPF rapidly increased insulin release and diminished ATP-sensitive K+ (K ATP) channel activity. Similarly, 48 h treatment with BPS or BPF enhanced insulin release and decreased the expression of several ion channel subunits in β-cells from WT mice, yet no effects were observed in cells from BERKO mice. PaPE-1, a ligand designed to preferentially trigger extranuclear-initiated ER pathways, mimicked the effects of bisphenols, suggesting the involvement of extranuclear-initiated ERβ pathways. Molecular dynamics simulations indicated differences in ERβ ligand-binding domain dimer stabilization and solvation free energy among different bisphenols and PaPE-1. Our data suggest a mode of action involving ERβ whose activation alters three key cellular events in β-cell, namely ion channel expression and activity, and insulin release. These results may help to improve the hazard identification of bisphenols. Image 1 • Low doses of BPS and BPF enhanced glucose-stimulated insulin secretion, a key characteristic in blood glucose homeostasis. • These effects seem to be due to changes in activity and gene expression of ion channels. • The potency of BPS was significantly higher compared to BPF. • The Estrogen Receptor (ER) β mediated bisphenols effects via an extranuclear-initiated pathway. • The ERβ extranuclear-initiated pathway may start a molecular event whose activation leads to alteration of β-cell function. [ABSTRACT FROM AUTHOR]

Elevated plasma glucagon is an early symptom of diabetes, occurring in subjects with impaired glucose regulation. Here, we explored alpha-cell function in female mice fed a high-fat diet (HFD). Female mice expressing the Ca2+ indicator GCaMP3 specifically in alpha-cells were fed a high-fat or control (CTL) diet. We then conducted in vivo phenotyping of these mice, as well as experiments on isolated (ex vivo) islets and in the in situ perfused pancreas. In HFD-fed mice, fed plasma glucagon levels were increased and glucagon secretion from isolated islets and in the perfused mouse pancreas was also elevated. In mice fed a CTL diet, increasing glucose reduced intracellular Ca2+ ([Ca2+ i) oscillation frequency and amplitude. This effect was also observed in HFD mice; however, both the frequency and amplitude of the [Ca2+ i oscillations were higher than those in CTL alpha-cells. Given that alpha-cells are under strong paracrine control from neighbouring somatostatin-secreting delta-cells, we hypothesised that this elevation of alpha-cell output was due to a lack of somatostatin (SST) secretion. Indeed, SST secretion in isolated islets from HFD-fed mice was reduced but exogenous SST also failed to suppress glucagon secretion and [Ca2+ i activity from HFD alpha-cells, in contrast to observations in CTL mice. These findings suggest that reduced delta-cell function, combined with intrinsic changes in alpha-cells including sensitivity to somatostatin, accounts for the hyperglucagonaemia in mice fed a HFD. • HFD feeding causes hyperglucagonaemia in vivo. • Glucagon is inadequately suppressed by glucose in HFD-fed mice. • Alpha-cell [Ca2+ i oscillations and glucagon output are elevated ex vivo in response to HFD feeding. • SST secretion from HFD islets is reduced. • Alpha-cells from HFD-fed mice become 'resistant' to SST. [ABSTRACT FROM AUTHOR]

Summary Type 1 diabetes (T1D) results from the autoimmune destruction of insulin-producing β cells. A comprehensive picture of the changes during T1D development is lacking due to limited sample availability, inability to sample longitudinally, and the paucity of technologies enabling comprehensive tissue profiling. Here, we analyzed 1,581 islets from 12 human donors, including eight with T1D, using imaging mass cytometry (IMC). IMC enabled simultaneous measurement of 35 biomarkers with single-cell and spatial resolution. We performed pseudotime analysis of islets through T1D progression from snapshot data to reconstruct the evolution of β cell loss and insulitis. Our analyses revealed that β cell destruction is preceded by a β cell marker loss and by recruitment of cytotoxic and helper T cells. The approaches described herein demonstrate the value of IMC for improving our understanding of T1D pathogenesis, and our data lay the foundation for hypothesis generation and follow-on experiments. Graphical Abstract Highlights • Highly multiplexed imaging of pancreas tissues from human donors with T1D • Islet evolution through T1D progression inferred from snapshot data • The phenotype of β cells is altered prior to β cell destruction • T cell recruitment depends on both disease stage and islet profile Using imaging mass cytometry of pancreas sections from human donors, Damond et al. generate a detailed marker-based timeline and find that loss of β cell markers precedes β cell destruction and that cytotoxic and helper T cells are recruited simultaneously to β cell-rich islets in type 1 diabetes. [ABSTRACT FROM AUTHOR]

Abstract: The glucose-stimulus/insulin-secretion-coupling by the pancreatic β-cell, which guarantees the maintenance of glucose homeostasis in man, is regulated by a sophisticated interplay between glucose and a plethora of additional factors. Besides other nutrients, incretins, nerval innervation, systemic growth factors as well as autocrine and paracrine regulatory loops within the islet of Langerhans modulate the function of the insulin-producing β-cell. Although the modulatory role of these factors is well appreciated, the underlying molecular mechanisms involved remain poorly understood. However, in most cases β-cell membrane receptors coupled primarily to either G-proteins or tyrosine kinases, which subsequently activate respective second messenger cascades, are involved. In the present mini-review we will discuss the role of signaling through some of these receptor-operated effector systems in the light of pancreatic β-cell signal-transduction. [Copyright &y& Elsevier]