Role of pancreatic beta-cells in the process of beta-cell death

Pancreas transplants from small donors: are the outcomes acceptable? A retrospective study

Despite good organ quality, pancreata from extremely small pediatric donors (<30 kg) are generally avoided by many centers because of concerns of reduced islet cell mass and early technical failure. Therefore, we sought to compare the outcomes of small pancreas grafts (<30 kg) to those from higher weight donors from transplants performed between 1994 and 2015 (n = 1183). A total of 33 pancreata were from donors' ≤30 kg (3%), with a mean weight of 23.8 kg and mean age of 7.8 years. Patient survival was similar at 1, 5, and 10 years between recipients of ≤30 and >30 kg donors (≤30 kg: 96.8%, 86.8%, and 78.1% vs. >30 kg: 96.8%, 89.5%, and 79.1%, P = 0.5). Pancreas graft survival at 1, 5, and 10 years was also similar, ≤30 kg: 93.9%, 73.2%, and 61.0% vs. >30 kg: 87%, 73.3%, and 58.3% (P = 0.7). This graft survival pattern was also seen when comparing pancreata from ≤20 kg donors to those from >20 to 30 kg. Cause of graft loss, and metabolic and physiologic outcomes did not differ between the groups. After assessing the impact of donor weight as a continuous variable and calculating recipient-to-donor weight ratio (RDWR), we observed no effect of donor weight on patient and graft outcomes.

ER stress and the decline and fall of pancreatic beta cells in type 1 diabetes

Components of the unfolded protein response (UPR) modulate beta cell inflammation and death in early type 1 diabetes (T1D). The UPR is a mechanism by which cells react to the accumulation of misfolded proteins in the endoplasmic reticulum (ER). It aims to restore cellular homeostasis, but in case of chronic or overwhelming ER stress the persistent activation of the UPR triggers apoptosis, contributing to the loss of beta cells in both T1D and type 2 diabetes. It remains to be determined how and why the transition from 'physiological' to 'pathological' UPR takes place. A key component of the UPR is the ER transmembrane protein IRE1α (inositol-requiring enzyme 1α). IRE1α activity is modulated by both intra-ER signals and by the formation of protein complexes at its cytosolic domain. The amplitude and duration of IRE1α signaling is critical for the transition between the adaptive and cell death programs, with particular relevance for the activation of the pro-apoptotic c-Jun N-terminal kinase (JNK) in beta cells. In the present review we discuss the available information on IRE1α-regulating proteins in beta cells and their downstream targets, and the important differences observed between cytokine-induced UPR in human and rodent beta cells.

Involvement of long non-coding RNAs in beta cell failure at the onset of type 1 diabetes in NOD mice

AIMS/HYPOTHESIS

Exposure of pancreatic beta cells to cytokines released by islet-infiltrating immune cells induces alterations in gene expression, leading to impaired insulin secretion and apoptosis in the initial phases of type 1 diabetes. Long non-coding RNAs (lncRNAs) are a new class of transcripts participating in the development of many diseases. As little is known about their role in insulin-secreting cells, this study aimed to evaluate their contribution to beta cell dysfunction.

METHODS

The expression of lncRNAs was determined by microarray in the MIN6 beta cell line exposed to proinflammatory cytokines. The changes induced by cytokines were further assessed by real-time PCR in islets of control and NOD mice. The involvement of selected lncRNAs modified by cytokines was assessed after their overexpression in MIN6 cells and primary islet cells.

RESULTS

MIN6 cells were found to express a large number of lncRNAs, many of which were modified by cytokine treatment. The changes in the level of selected lncRNAs were confirmed in mouse islets and an increase in these lncRNAs was also seen in prediabetic NOD mice. Overexpression of these lncRNAs in MIN6 and mouse islet cells, either alone or in combination with cytokines, favoured beta cell apoptosis without affecting insulin production or secretion. Furthermore, overexpression of lncRNA-1 promoted nuclear translocation of nuclear factor of κ light polypeptide gene enhancer in B cells 1 (NF-κB).

CONCLUSIONS/INTERPRETATION

Our study shows that lncRNAs are modulated during the development of type 1 diabetes in NOD mice, and that their overexpression sensitises beta cells to apoptosis, probably contributing to their failure during the initial phases of the disease.

Alternative Medicine in Diabetes - Role of Angiogenesis, Oxidative Stress, and Chronic Inflammation

Diabetes is a chronic metabolic disorder that is characterized by hyperglycemia due to lack of or resistance to insulin. Patients with diabetes are frequently afflicted with ischemic vascular disease and impaired wound healing. Type 2 diabetes is known to accelerate atherosclerotic processes, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. Herbal medicines and naturally occurring substances may positively affect diabetes management, and could thus be utilized as cost-effective means of supporting treatment in developing countries. Natural treatments have been used in these countries for a long time to treat diabetes. The present review analyses the features of aberrant angiogenesis, abnormalities in growth factors, oxidative stress, and metabolic derangements relevant to diabetes, and how herbal substances and their active chemical constituents may counteract these events. Evidence for possible biochemical effectiveness and limitations of herbal medicines are given, as well as details regarding the role of cytokines and nitric oxide.

Diabetes in the young - a global view and worldwide estimates of numbers of children with type 1 diabetes

This paper describes the methodology, results and limitations of the 2013 International Diabetes Federation (IDF) Atlas (6th edition) estimates of the worldwide numbers of prevalent cases of type 1 diabetes in children (<15 years). The majority of relevant information in the published literature is in the form of incidence rates derived from registers of newly diagnosed cases. Studies were graded on quality criteria and, if no information was available in the published literature, extrapolation was used to assign a country the rate from an adjacent country with similar characteristics. Prevalence rates were then derived from these incidence rates and applied to United Nations 2012 Revision population estimates for 2013 for each country to obtain estimates of the number of prevalent cases. Data availability was highest for the countries in Europe (76%) and lowest for the countries in sub-Saharan Africa (8%). The prevalence estimates indicate that there are almost 500,000 children aged under 15 years with type 1 diabetes worldwide, the largest numbers being in Europe (129,000) and North America (108,700). Countries with the highest estimated numbers of new cases annually were the United States (13,000), India (10,900) and Brazil (5000). Compared with the prevalence estimates made in previous editions of the IDF Diabetes Atlas, the numbers have increased in most of the IDF Regions, often reflecting the incidence rate increases that have been well-documented in many countries. Monogenic diabetes is increasingly being recognised among those with clinical features of type 1 or type 2 diabetes as genetic studies become available, but population-based data on incidence and prevalence show wide variation due to lack of standardisation in the studies. Similarly, studies on type 2 diabetes in childhood suggest increased incidence and prevalence in many countries, especially in Indigenous peoples and ethnic minorities, but detailed population-based studies remain limited.

Therapy: Immunotherapy for T1DM--targeting innate immunity

Moran et al report two trials of antagonism of the pro-inflammatory cytokine, IL-1, assessing the monoclonal antibody canakinumab and the IL-1 antagonist, anakinra in new-onset Type 1 Diabetes (T1D). The studies both showed that, although relatively safe, there was no efficacy in terms of halting decline in beta cell function. Is this the end of the line for targeting IL-1 in T1D?

Targeted expression of islet neogenesis associated protein to beta cells enhances glucose tolerance and confers resistance to streptozotocin-induced hyperglycemia

Islet neogenesis associated protein (INGAP) stimulates experimental pancreatic islet growth, as evidenced by elevated markers of beta cell mass, in rodents, dogs and primates. Previous analyses of mice that have a transgenic expression of INGAP targeted to the exocrine pancreas have indicated additional biological activity attributed to INGAP. In this study we report on mice with a targeted expression of INGAP to the islet beta cell. The beta cell transgenic mice (IP-INGAP) showed enhanced normalization of blood glucose during IPGTT. Further, IP-INGAP mice had a significant delay in development of hyperglycemia following a diabetogenic dose of streptozotocin. INGAP conferred beta cell protection and enhanced islet function. Analysis of oxidative stress genes in IP-INGAP mice revealed a decrease in islet expression of the NADPH oxidase, NOX1, in both basal state and in response to pro-inflammatory cytokine stimulation. These data are consistent with a pleiotropic role for INGAP and reveal new pathways to target in the discovery of improved diabetic therapies.

Insulin increases H2O2-induced pancreatic beta cell death

Insulin resistance results, in part, from impaired insulin signaling in insulin target tissues. Consequently, increased levels of insulin are necessary to control plasma glucose levels. The effects of elevated insulin levels on pancreatic beta (β) cell function, however, are unclear. In this study, we investigated the possibility that insulin may influence survival of pancreatic β cells. Studies were conducted on RINm, RINm5F and Min-6 pancreatic β-cells. Cell death was induced by treatment with H(2)O(2), and was estimated by measurements of LDH levels, viability assay (Cell-Titer Blue), propidium iodide staining and FACS analysis, and mitochondrial membrane potential (JC-1). In addition, levels of cleaved caspase-3 and caspase activity were determined. Treatment with H(2)O(2) increased cell death; this effect was increased by simultaneous treatment of cells with insulin. Insulin treatment alone caused a slight increase in cell death. Inhibition of caspase-3 reduced the effect of insulin to increase H(2)O(2)-induced cell death. Insulin increased ROS production by pancreatic β cells and increased the effect of H(2)O(2). These effects were increased by inhibition of IR signaling, indicative of an effect independent of the IR cascade. We conclude that elevated levels of insulin may act to exacerbate cell death induced by H(2)O(2) and, perhaps, other inducers of apoptosis.

Involvement of microRNAs in the cytotoxic effects exerted by proinflammatory cytokines on pancreatic beta-cells

OBJECTIVE

Pancreatic beta-cells exposed to proinflammatory cytokines display alterations in gene expression resulting in defective insulin secretion and apoptosis. MicroRNAs are small noncoding RNAs emerging as key regulators of gene expression. Here, we evaluated the contribution of microRNAs to cytokine-mediated beta-cell cytotoxicity.

RESEARCH DESIGN AND METHODS

We used global microarray profiling and real-time PCR analysis to detect changes in microRNA expression in beta-cells exposed to cytokines and in islets of pre-diabetic NOD mice. We assessed the involvement of the microRNAs affected in cytokine-mediated beta-cell failure by modifying their expression in insulin-secreting MIN6 cells.

RESULTS

We found that IL-1beta and TNF-alpha induce the expression of miR-21, miR-34a, and miR-146a both in MIN6 cells and human pancreatic islets. We further show an increase of these microRNAs in islets of NOD mice during development of pre-diabetic insulitis. Blocking miR-21, miR-34a, or miR-146a function using antisense molecules did not restore insulin-promoter activity but prevented the reduction in glucose-induced insulin secretion observed upon IL-1beta exposure. Moreover, anti-miR-34a and anti-miR-146a treatment protected MIN6 cells from cytokine-triggered cell death.

CONCLUSIONS

Our data identify miR-21, miR-34a, and miR-146a as novel players in beta-cell failure elicited in vitro and in vivo by proinflammatory cytokines, notably during the development of peri-insulitis that precedes overt diabetes in NOD mice.

The nucleosome binding protein HMGN3 modulates the transcription profile of pancreatic beta cells and affects insulin secretion

Improper glucose-stimulated insulin secretion from pancreatic beta cells is a major factor in the onset of type 2 diabetes. We now report that HMGN3, a nuclear protein that binds to nucleosomes and affects chromatin function, is highly expressed in beta cells and that in mice, loss of HMGN3 impairs glucose-stimulated insulin secretion and leads to a diabetic phenotype. In pancreatic beta cells, loss of HMGN3 affects the transcription of several genes involved in glucose-stimulated insulin secretion, including that of the Glut2 glucose transporter. Chromatin immunoprecipitation reveals that HMGN3 and the transcription factor PDX1 mutually reinforce their specific binding to the chromatin in the promoter of the Glut2 gene, thereby regulating GLUT2 protein levels in pancreatic islets and in beta cells. Our results identify a new regulator of glucose homeostasis and demonstrate a link between the activity of a nucleosome binding structural protein and the regulation of insulin secretion.

Androgen receptor: a new player associated with apoptosis and proliferation of pancreatic beta-cell in type 1 diabetes mellitus

Androgen receptor (AR) mediates a wide range of cellular processes, such as proliferation, differentiation and apoptosis. Here we sought to identify whether AR was located in pancreatic beta-cells and investigate its functions in type 1 diabetes induced by multiple low doses of streptozotocin. Double/triple immunofluorescence, Western blot and semi-quantitative RT-PCR were carried out to determine variances of AR expression in beta-cells and correlation between AR and apoptosis/proliferation of beta-cells with progress of diabetes. In addition, in vitro primary beta-cells from control mice were cultured for 3 days or 6 days with compound stimulation in order to further identify effect of AR on beta-cell apoptosis and proliferation. AR expression in beta-cells peaked in control and 1-day diabetic mice, gradually and significantly decreased, even disappeared in diabetic mice with progress of diabetes. TUNEL-positive beta-cells were concomitant with overexpression of AR, and Ki67-positive beta-cells showed extremely weak, even negative AR staining. In vitro, AR could mediate beta-cell apoptosis, and AR antagonist flutamide contributed to beta-cell proliferation. In conclusion, AR is abundantly expressed in pancreatic beta-cell cytoplasm of control mice. With progress of type 1 diabetes, decrement of AR expression in diabetic mice contributes to prohibit beta-cells from apoptosis, and is strongly associated with beta-cell proliferation.

Pancreatic duct cells in human islet cell preparations are a source of angiogenic cytokines interleukin-8 and vascular endothelial growth factor

OBJECTIVE

Engraftment and function of human islet cell implants is considered to be dependent on their rapid and adequate revascularization. Studies with rodent islet grafts have shown that vascular endothelial growth factor (VEGF) expression by beta-cells can promote this process. The present work examines whether human islet preparations produce VEGF as well as interleukin (IL)-8, another angiogenic protein, and assesses the role of contaminating duct cells in VEGF and IL-8-mediated angiogenesis.

RESEARCH DESIGN AND METHODS

Human islet and pancreatic duct cell preparations are compared for their respective expression and production of VEGF and IL-8 during culture as well as following transplantation in nonobese diabetic (NOD)/scid mice. The associated angiogenic effects are measured in an in vitro aortic ring assay and in an in vivo chick embryo chorioallantoic membrane assay.

RESULTS

Cultured pancreatic duct cells expressed 3- and 10-fold more VEGF and IL-8, respectively, than cultured human islet endocrine cells and released both proteins at angiogenic levels. The angiogenic effect of purified duct cells was higher than that of purified endocrine islet cells and was completely blocked by a combination of IL-8 and VEGF antibodies. Human duct cell implants under the kidney capsule of NOD/scid mice expressed higher levels of IL-8 and VEGF than human islet cell implants and induced circulating IL-8 and VEGF levels during the first day posttransplantation.

CONCLUSIONS

Human duct cell-released IL-8 and VEGF may help revascularization of currently used human islet cell grafts. Further work should examine whether and when this effect can prevail over other inflammatory and immune influences of this cell type.

Mutated ATP synthase induces oxidative stress and impaired insulin secretion in beta-cells of female BHE/cdb rats

BACKGROUND

Adenosine triphosphate (ATP) is a critical determinant of beta-cell insulin secretion in response to glucose. BHE/cdb rats have a mutation in ATP synthase that limits ATP production, yet develop mild diabetes only with ageing. We investigated the cellular basis for reduced insulin secretion and compensatory mechanisms that mitigate the effects of the ATP synthase mutation.

METHODS

In vitro beta-cell function in isolated islets and expression of key regulatory genes was compared with in vivo oral glucose tolerance and insulin sensitivity in BHE/cdb and control rats.

RESULTS

BHE/cdb rat islets had reduced responsiveness to glucose stimulation and ATP content was 35% lower than in control islets. Oral glucose tolerance was impaired at both 21 and 43 weeks of age because of a reduction in glucose-stimulated insulin secretion (GSIS). An increase in inducible nitric oxide synthase (INOS, 3-fold) and manganese superoxide dismutase (MnSOD, 1.6-fold), detection of nitrotyrosine, beta-cell apoptosis, and nucleocytoplasmic translocation of pancreas duodenum homeobox-1 (PDX-1) in beta-cells indicated increased oxygen radical formation. However, BHE/cdb rats partially compensated for low glucose responsiveness by increasing the number of small islets and beta-cell hypertrophy. There was also an increase in the proportion of mature insulin relative to proinsulin (PI) detected within beta-cell granules. Increased activation of AMP-dependent kinase (AMPK)-regulated pathways was consistent with increased oxidative stress and with induction of apoptosis and reduction of preproinsulin gene transcription.

CONCLUSIONS

The findings are consistent with impaired but partially compensated mechanisms of insulin secretion early in life, but progressive non-compensated impairments due to oxidative stress occurs by age 43 weeks.

N-acetylcysteine derivative inhibits CD40-dependent proinflammatory properties of human pancreatic duct cells

OBJECTIVES

We recently observed that duct cells constitutively express CD40, a membrane molecule whose engagement results in duct cell activation and proinflammatory cytokine secretion. This observation suggests a potential role of this pathway in the pathogenesis of type 1 diabetes, islet graft rejection, or acute pancreatitis. In this article, we investigated whether a salt derivative of N-acetyl-L-cysteine, Nacystelyn, could modulate CD40 expression on duct cells and the response of activated duct cells to CD40 engagement.

METHODS

We assessed the effects of Nacystelyn on CD40 expression and function in human caucasian pancreatic adenocarcinoma, ATCC n degrees THB-80 (CAPAN-2) cells, a human pancreatic duct cell line. CD40 expression was analyzed by flow cytometry. To assess CAPAN-2 cell responses to CD40 engagement, we looked at nuclear factor-kappaB transcription factor activation using enzyme-linked immunosorbent assay and electrophoretic mobility shift assay and cytokine mRNA levels by quantitative real-time reverse transcriptase polymerase chain reaction.

RESULTS

We observed that Nacystelyn dose-dependently inhibited CD40 expression on CAPAN-2 cells as well as CD40-induced nuclear factor kappaB activation and proinflammatory cytokines up-regulation.

CONCLUSIONS

Our data suggest that Nacystelyn could be considered as a useful tool to prevent immune and inflammatory responses in pancreatic disorders by interfering with the CD40 pathway in pancreatic duct cells.

Role of uncoupling protein UCP2 in cell-mediated immunity: how macrophage-mediated insulitis is accelerated in a model of autoimmune diabetes

Infiltration of inflammatory cells into pancreatic islets of Langerhans and selective destruction of insulin-secreting beta-cells are characteristics of type 1 diabetes. Uncoupling protein 2 (UCP2) is a mitochondrial protein expressed in immune cells. UCP2 controls macrophage activation by modulating the production of mitochondrial reactive oxygen species (ROS) and MAPK signaling. We investigated the role of UCP2 on immune cell activity in type 1 diabetes in Ucp2-deficient mice. Using the model of multiple low-dose streptozotocin (STZ)-induced diabetes, we found that autoimmune diabetes was strongly accelerated in Ucp2-KO mice, compared with Ucp2-WT mice with increased intraislet lymphocytic infiltration. Macrophages from STZ-treated Ucp2-KO mice had increased IL-1beta and nitric oxide (NO) production, compared with WT macrophages. Moreover, more macrophages were recruited in islets of STZ-treated Ucp2-KO mice, compared with Ucp2-WT mice. This finding also was accompanied by increased NO/ROS-induced damage. Altogether, our data show that inflammation is stronger in Ucp2-KO mice and islets, leading to the exacerbated disease in these mice. Our results highlight the mitochondrial protein UCP2 as a new player in autoimmune diabetes.

Neuropeptides of the islets of Langerhans: a peptidomics study

Neuropeptides from the endocrine pancreas (the islets of Langerhans) play an important role in the regulation of blood glucose levels. Therefore, our aim is to identify the "peptidome" (the in vivo peptide profile at a certain time) of the pancreatic islets, which is beneficial for medical progress related to the treatment of diabetes. So far, there are few neuropeptides isolated and sequenced from the endocrine pancreas and mainly in situ hybridisation and immunocytochemical techniques have been used to demonstrate the occurrence of peptides in the pancreas. These techniques do not allow for unequivocal identification of peptides. In contrary, mass spectrometry identifies peptides unambiguously. We have analysed the peptidome of the islets using peptidomics, i.e. a combination of liquid chromatography, mass spectrometry and bioinformatics. We are able to identify the peptidome of islets extracts. We not only confirm the presence of peptides with a well-known effect on blood glucose levels, but also identify new peptides, which are unknown to affect blood glucose levels.

Glucose-induced release of nitric oxide from mouse pancreatic islets as detected with nitric oxide-selective glass microelectrodes

Nitric oxide (NO) is believed to play an important role in pancreatic islet physiology and pathophysiology. Research in this area has been hampered, however, by the use of indirect methods to measure islet NO. To investigate the role of NO in islet function, we positioned NO-sensitive, recessed-tip microelectrodes in close proximity to individual islets and monitored oxidation current to detect subnanomolar NO in the bath. NO release from islets consisted of a series of rapid bursts lasting several seconds and/or slow oscillations with a period of approximately 100-300 s. Average baseline NO near the islets in 2.8 mM glucose was 524+/-59 nM (n=12). Raising glucose from 2.8 to 11.1 mM augmented NO release by 429+/-133 nM (n=12, P<0.05), an effect blocked by the NO synthase inhibitor L-NAME (n=3). We also observed that glucose-stimulated increases in NO release were contemporaneous with changes in NAD(P)H and O2 but occurred well before increases in calcium associated with glucose-stimulated insulin secretion. In summary, we demonstrate that NO release from islets is oscillatory and rapidly augmented by glucose, suggesting that NO release occurs early following an increase in glucose metabolism and may contribute to the stimulated insulin secretion triggered by suprathreshold glucose.

Investigation of the age-at-onset heterogeneity in type 1 diabetes through mathematical modeling

The heterogeneity between young- and adult-onset type 1 diabetes (T1D) is well known, but not well understood. We approach this question through mathematical formulation and analysis of the dynamic interactions between the immune cells and the pancreatic islet beta-cells that lead to the beta-cell destruction. Utilizing the perturbation expansion method we investigate the dynamic stability of our system under fast and slow beta-cell turnover limits. We find that if autoimmunity is initiated when the turnover is slow (adult age), a stable steady state can exist with reduced number of beta-cells, where the beta-cell regeneration balances the ongoing autoimmune destruction. This implies that a slow disease process is possible. In contrast, if autoimmunity occurs when the beta-cell turnover is rapid (young age), such a stable state will never be attained and the destruction will progress unabated, leading to an acute disease onset. The major findings of our model are consistent with clinical observations, and it offers an explanation for the dynamic and phenotypic heterogeneity between young- and adult-onset T1D. More importantly, the model analyses point out that pathways regulating beta-cell turnover can be new targets to interfere with the disease process of T1D.

Can we slow the rising incidence of childhood-onset autoimmune diabetes? The overload hypothesis

Overload of the beta cell, mediated by a variety of mechanisms, may sensitise it to immune damage and apoptosis, and thus accelerate ongoing autoimmune processes leading to its destruction. Environmental risk determinants that may exert such overload effects include insulin resistance due to excess fat cell accumulation, and increased insulin requirement due to a high growth rate, physical stress (infection, inflammation) or psychological stress. The increasing incidence of childhood diabetes, and the shift to younger age at onset, is unlikely to be driven by environmental risk factors that have been associated with initiation of autoimmunity, e.g. virus infections or early infant feeding. Risk factors that may accelerate beta cell destruction have shown a steady increase in the population, and are more plausible causes of such a pattern of change. Child growth, weight and birthweight are well-established estimates of community wealth and increase in most countries of Europe. Overfeeding of children early in life leads to both accelerated growth and weight, and even a moderate excess of child growth, not necessarily associated with obesity, is associated with risk of type 1 diabetes. New, safe and effective immune-modulating drugs for possible arrest of the autoimmune process may become available in time, but in the interim these accelerating factors may be targeted. Public health programmes for pregnant mothers and young families, aiming at changing overfeeding and the sedentary lifestyle of the children would be preferable to other alternatives. Interventions such as these would be safe and could potentially influence future risks of type 1 and type 2 diabetes and other major threats to adult health.

Effects of overexpression of pancreatic derived factor (FAM3B) in isolated mouse islets and insulin-secreting betaTC3 cells

PANcreatic DERived factor (PANDER, FAM3B) is a recently discovered islet-specific cytokine. We have previously shown that, in vitro, truncated recombinant PANDER isoforms (20 and 21 kDa) are cytotoxic to beta-cell lines but the effects of full-length PANDER on islet biology remain unclear. In this study, we used adenovirus (Ad-PANDER) to overexpress full-length cDNA of PANDER in islets and betaTC3 cells. BetaTC3 cells were infected with Ad-PANDER or control vector. After 48 h, cell viability was significantly decreased as evaluated by MTT assay. The number of dead cells was significantly increased as indicated by the fluorescent intensity of the propidium iodide-stained cells (160 +/- 13 vs. control 100 +/- 7%, P = 0.001). Flow cytometric Tunel assay showed that overexpressing PANDER induced a significant fourfold increase in beta-cell apoptosis (19.4 +/- 6.3 vs. control 4.1 +/- 0.8%, P < 0.05). There was a significant increase in the number of annexin V-positive (apoptotic) cells and propidium iodide-positive (dead) cells in mouse islets infected with Ad-PANDER compared with control cells infected with Ad-LacZ. Addition of 4 nM recombinant PANDER protein to betaTC3 cells or infection of Ad-PANDER did not affect Akt and STAT1 phosphorylation, Bcl-2, Fas, and NF-kappaB protein levels. However, activation of caspase-3 was observed in betaTC3 and islets infected with Ad-PANDER. Overexpression of PANDER in mouse islets or addition of recombinant PANDER decreased insulin secretion induced by carbachol plus glucose or high potassium but not that by glucose alone. Culture with recombinant PANDER did not affect glucose-induced NAD(P)H elevation in mouse islets. In conclusion, Ad-PANDER infection is as effective as truncated recombinant PANDER to induce betaTC3 cell and mouse islet apoptosis.

Association between endocrine pancreas and ductal system. More than an epiphenomenon of endocrine differentiation and development?

Traditional histological descriptions of the pancreas distinguish between the exocrine and the endocrine pancreas, as if they were two functionally distinct glands. This view has been proven incorrect and can be considered obsolete. Interactions between acinar and islet tissues have been well established through numerous studies that reveal the existence of anatomical and functional relationships between these compartments of the gland. Less attention, however, has traditionally been paid to the relationships occurring between the endocrine pancreas and the ductal system. Associations between islet tissue and ducts are considered by most researchers as only a transient epiphenomenon of endocrine development. This article reviews the evidence that has emerged in the last 10 years demonstrating the existence of stable, close, and systematic relationships between these two pancreatic compartments. Functional and pathophysiological implications are considered, and the existence of an "acinar-duct-islet" axis is put forward. The pancreas appears at present to be an integrated organ composed of three functionally related components of well-orchestrated endocrine and exocrine physiological responses.

Toxin-based selection of insulin-producing cells with improved defense properties for islet cell transplantation

Insulin-producing pancreatic beta-cells are known to be extremely susceptible to destruction, primarily by autoimmune mechanisms, infectious agents, and by chemical toxins that cause overt type I diabetes. As development of highly protected insulin-producing cells would be important for successful cell therapy of diabetic patients, gene transfection technique was utilized by several investigators in order to improve the defense properties of transplanted cells. In this article, we summarize other approaches based on a selection strategy that has been developed in our laboratory and by other research groups that engineer pancreatic beta-cells to provide protection against diabetogenic toxins (streptozotocin and alloxan), oxidative stress and cytokines. Selection strategies based on acute repeated or long-term continuous treatment of cell lines with cytotoxic agents have resulted in the selection of highly resistant cell subpopulations. We discuss possible involvement of different expression of cytoprotective genes in the selection of cell subpopulations, which demonstrate a broad spectrum of resistance. Importantly, toxin-based selection did not impair functional activity of the cells as it was shown in vitro. In addition, selected cells preserved their improved metabolic characteristics following encapsulation in alginate and subsequent implantation in diabetic animals. Identifying the mechanisms through which cell defense properties act will help clarify the process responsible for beta-cell regeneration in type I diabetes patients. Such knowledge might be useful in developing strategies focusing on the regeneration of beta-cell resistant populations.

Heterogeneity in distribution of amyloid-positive islets in type-2 diabetic patients

Amyloid-containing (A+) islets are characteristic for type-2 diabetes (T2D), but their abundance seems variable among patients. It is unclear whether the distribution of A+ islets follows a certain pattern or occurs randomly throughout the pancreatic organ. We investigated the topography of A+ islets in eight pancreata of T2D patients and eight sex- and age-matched non-diabetic subjects. Transversal sections of head, body and tail segments were stained with synaptophysin combined with Congo red to map/quantify islet tissue and amyloid. In the eight T2D pancreata, the overall percentage of A+ islets varied from 4% to 85%. Further analysis in body and tail indicated that peripheral regions exhibited higher percentages of A+ islets than central regions (averages of, respectively, 30% and 17%, P<0.05). Non-diabetic control pancreata also exhibited A+ islets, albeit at a 25-fold lower frequency; a tendency towards higher percentage of A+ islets in peripheral versus central regions was also observed. The higher percentage A+ islets in peripheral regions was associated with a higher density and relative islet over exocrine surface area. These observations on heterogeneity in abundance and distribution of A+ islets need consideration when sampling tissue for studies on human islet amyloidosis. The present methodology allows us to further investigate the susceptibility to amyloidosis of islets in peripheral regions of the pancreas.

Identification of Key β Cell Gene Signaling Pathways Involved in Type 1 Diabetes

In type 1 diabetes, beta cells die through a process of immune-mediated apoptosis. To better understand this process, it has been accepted practice to study beta cell or islet apoptosis in vitro in response to a range of immune stimuli, such as interferon gamma, interleukin-1, nitric oxide or free radicals. In particular, much use has been made of immortalized beta cell lines for such studies, although it is not clear to what extent the behavior of these cell lines might mimic the behavior of normal beta cells in vivo, or freshly isolated beta cells ex vivo. To address this question we compared the gene expression of freshly isolated NOD islets in the presence or absence of insulitis, with previously published data examining either islet or beta cell gene or protein expression in a range of different species and contexts. There was a high correlation between beta cell genes found be to be expressed by mouse and rat islets, by either gene expression or proteomic analysis. There was also a surprisingly high correlation between beta cell genes found be to be expressed by islets exposed to insulitis in vivo and islets stimulated with IFN-gamma and IL-1beta in vitro, suggesting that these two cytokines as produced by the islet infiltrate are important for priming beta cells in vivo. There was a much lower correlation when gene expression was compared between fresh beta cells and beta cell lines, consistent with the view that beta cell lines are very poorly representative of real beta cells. Hence, any results obtained using beta cell lines should be interpreted with great caution when extrapolating to the behavior of real beta cells.

Superior long-term results of simultaneous pancreas-kidney transplantation from pediatric donors

The shortage of cadaveric donors for simultaneous pancreas-kidney transplantation has prompted the use of cadaveric organs from pediatric donors. The long-term outcome and its impact on overall long-term survival are unknown. A total of 680 recipients receiving cadaver Simultaneous pancreas-kidney (SPK) transplantation from pediatric and adult donors between July 1986 and September 2001 were analyzed and compared. Ten-year kidney and pancreas graft survival for SPK transplantation from donors aged <18 years (n = 142) were 80% and 72%, respectively, compared to 61% pancreas and kidney graft survival from donors > or =18 years of age (n = 538; p = 0.03 and 0.05, respectively). Five years post-transplant, blood glucose, HbA1c and creatinine clearance were significantly better in recipients from pediatric donors (85.3 +/- 13 mg/dL, 5.5 +/- 3.5% and 65.6 +/- 16 mL/min, respectively), compared to recipients from adult donors (95.1 +/- 29 mg/dL, 5.9 +/- 3.5% and 58.3 +/- 17 mL/min; p = 0.001, 0.01 and 0.002, respectively). Causes of graft failure for kidney and pancreas transplants were similar between the two groups. No statistically significant difference was observed in patient survival between recipients from pediatric donors compared to adult donors (85% vs. 76%, p = 0.29). When recipients of SPK from pediatric donors were stratified according to age (3-11 years and 12-17 years) and compared, no difference in kidney or pancreas graft survival was observed (kidney 76.4% vs. 81.3%, p = 0.15; pancreas 75% vs. 76%, p = 0.10, respectively). Pediatric donors represent a valuable source of organs, providing excellent short- and long-term outcomes. Wide utilization of pediatric organs will substantially increase the donor pool.

Autocrine regulation of single pancreatic beta-cell survival

Function and survival of cells depend in part on the presence of growth factors. We explored the autocrine regulation of insulin and nerve growth factor (NGF) on single adult rat pancreatic beta-cell survival and hormone secretion. When NGF or insulin signaling were blocked in culture media, cell survival decreased compared with control cells, with apoptosis being the main mechanism of cell death. To further explore the role of glucose in beta-cell survival, we cultured the cells for 16 h in 2.6 mmol/l glucose and observed that nearly 17% of the cells developed apoptosis; this effect was partially prevented by NGF and almost completely inhibited by insulin treatment. A high K+ concentration had the same effect, suggesting that insulin and NGF secretion by the cells was responsible for the survival effects and not glucose per se. Blocking NGF signaling with an NGF antibody or with K252a reduced insulin biosynthesis and secretion in the cells that survived the treatment. Moreover, the functional beta-cell subpopulation with a higher insulin secretion rate is more susceptible to K252a. These results further indicate that NGF and insulin play important autoregulatory roles in pancreatic beta-cell survival and function and strongly suggest the need to explore new focuses in diabetes treatment.

Parallel manifestation of insulin resistance and beta cell decompensation is compatible with a common defect in Type 2 diabetes

AIMS/HYPOTHESIS

The aim of the study was to evaluate the relationship between insulin sensitivity, beta cell function and glucose tolerance, and its dependence on variants in the newly identified Type 2 diabetes susceptibility gene, calpain-10 ( CAPN10).

METHODS

We studied 203 men of the same age but with varying degrees of glucose tolerance. These men participated in (i) an oral glucose tolerance test, (ii) a euglycaemic clamp combined with indirect calorimetry and infusion of [3-(3)H]-glucose and (iii) a stepwise assessment of acute insulin response to arginine (AIR) at three different glucose concentrations (fasting, 14 and 28 mmol/l).

RESULTS

There was a linear increase in NEFA levels ( p<0.0005) and WHR ( p<0.0005) and decrease in glucose uptake due to a reduction in glucose storage over the entire range of glucose tolerance ( r=-0.404; p<0.005). No increase in endogenous glucose production (EGP) was seen until patients had manifest diabetes. However, when EGP was expressed relative to fasting insulin concentrations, there was a linear deterioration of basal hepatic insulin sensitivity ( r=-0.514; p<0.005). The AIR followed a bell-shaped curve with an initial rise and subsequent decrease. However, AIR adjusted for insulin sensitivity (disposition index) showed a linear decrease with increasing glucose concentrations ( r=-0.563; p<0.001) starting already in subjects with normal glucose tolerance. There was an inverse correlation between increase in WHR and NEFA and peripheral as well as hepatic insulin sensitivity. Subjects with the genotype combination of CAPN10 consisting of SNP44 TT and SNP43 GG genotypes had significantly lower insulin-stimulated glucose uptake than carriers of the other genotype combinations (5.3+/-0.4 vs 7.2+/-0.4 mg.ffm kg(-1).min(-1).mU.l(-1); p<0.005).

CONCLUSIONS/INTERPRETATION

We conclude that the pre-diabetic state is characterised by a similar linear deterioration of peripheral and hepatic insulin sensitivity as beta cell function and that variants in the CAPN10 gene modify this relationship. These findings are compatible with a common defect in muscle, liver and beta cells in the pathogenesis of Type 2 diabetes.

CD40 expression on human pancreatic duct cells: role in nuclear factor-kappa B activation and production of pro-inflammatory cytokines

AIMS/HYPOTHESIS

Human pancreatic duct cells are closely associated with islet beta cells, and contaminate islet suspensions transplanted in Type 1 diabetes mellitus patients. Activated duct cells produce cytotoxic mediators and possibly contribute to the pathogenesis of Type 1 diabetes mellitus or islet graft rejection. As CD40 transduces activation signals involved in inflammatory and immune disorders, we investigated CD40 expression on duct cells and their response to CD40 engagement.

METHODS

CD40 expression on human pancreatic duct cells was analysed by flow cytometry and immunohistochemical analyses. To assess the function of CD40 expression on duct cells, activation of the transcription factor nuclear factor-kappa B was determined using electrophoretic mobility shift assay and ELISA. Cytokine mRNA levels were quantified by real-time RT-PCR, and protein levels by Luminex technology.

RESULTS

Isolated human pancreatic duct cells and Capan-2 cell lines were found to express constitutively CD40. The expression of CD40 on duct cells was confirmed in vivo on human normal and pathological pancreatic specimens. CD40 ligation on Capan-2 cells induced rapid nuclear factor-kappa B activation, and supershift assays demonstrated that p50/p65 heterodimers and p50/p50 homodimers were present in the activated complexes in the nucleus. This activation was accompanied by tumour necrosis factor-a and interleukin-1beta mRNA accumulation. Tumour necrosis factor-alpha protein secretion was confirmed in CD40-activated Capan-2 cells and in isolated human pancreatic duct cells.

CONCLUSIONS/INTERPRETATION

Interaction between activated T lymphocytes expressing CD40 ligand and duct cells expressing CD40 may contribute to the immune responses involved in Type 1 diabetes mellitus and islet graft rejection. Interfering with CD40-mediated duct cell activation could alleviate beta cell damage of immune origin.

Nitric oxide-induced carbonylation of Bcl-2, GAPDH and ANT precedes apoptotic events in insulin-secreting RINm5F cells

Generation of high levels of nitric oxide (NO) following induction of NOS2 by interleukin-1 beta (IL-1beta) triggers beta cell apoptosis in insulin-secreting RINm5F cells. Mitochondrial and nuclear events such as downregulation of the antiapoptotic protein Bcl-2, activation of the pore responsible for the permeability transition (PT) and DNA fragmentation are involved in the process. We report in the present paper that exposure of insulin-producing RINm5F cells to NO donors and to IL-1beta leads to oxidative carbonylation of both Bcl-2 and the adenine nucleotide translocator (ANT) component of the mitochondrial PT pore. When the effect of endogenous generation of high concentrations of NO following exposure of cells to IL-1beta was studied, carbonylation of Bcl-2 preceded downregulation of the protein. Overexpression of Mn-SOD decreases substantially the extent of Bcl-2 carbonylation in SIN-1-exposed cells. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) inhibition, carbonylation and translocation from cytoplasm to nucleus and DNA fragmentation were also induced by DETA/NO exposure. DETA/NO-induced carbonylation of Bcl-2 and ANT proteins takes place 6 h before apoptotic release of histone-associated DNA to cytoplasm. Time course studies also reveal a close parallel between GAPDH translocation to nucleus and carbonylation. Inhibitors of lipooxidation end products formation such as piridoxamine (PM) and aminoguanidine (AG) block NO-triggered carbonylation of Bcl-2, ANT and GAPDH, prevent NO-induced GAPDH enzyme inhibition and nuclear translocation and DNA fragmentation. Our results support the notion that the oxidative carbonylation of proteins plays a role in the control of NO-induced apoptosis.

Involvement of advanced lipooxidation end products (ALEs) and protein oxidation in the apoptotic actions of nitric oxide in insulin secreting RINm5F cells

We have explored the impact of nitric oxide (NO) exposure on oxidation damage of lipids, and proteins, and the contribution of this type of damage to the activation of the apoptotic program in insulin secreting RINm5F cells. Exposure of cells to NO donors and to interleukin-1 beta (IL-1beta) led to generation of lipooxidation products such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Addition of superoxide dismutase (SOD) and catalase (Cat) to cells decreased by 50% MDA and 4-HNE production induced by IL-1beta. Over-expression of Mn-SOD in cells conferred a remarkable decrease (75%) in IL-1beta-induced lipid peroxidation. These data suggest that peroxynitrite (ONOO(-)) mediates peroxidative damage to lipids in this cell system. Inhibitors of advanced lipooxidation end products (ALEs) formation such as aminoguanidine (AG) and pyridoxamine (PM) prevented partially apoptotic events triggered by NO such as DNA fragmentation, caspase-3 activation and cytochrome c release from mitochondria. These findings indicate that ALEs are involved in NO-induced apoptosis. In fact, NO-induced carbonylation of PARP protein preceded its apoptotic degradation and inhibitors of ALEs formation prevented both events. We thus propose that carbonylation of proteins is instrumental in linking NO-dependent lipid oxidation and apoptosis in this cell system.

Glucose-dependent insulinotropic polypeptide promotes beta-(INS-1) cell survival via cyclic adenosine monophosphate-mediated caspase-3 inhibition and regulation of p38 mitogen-activated protein kinase

The incretin glucose-dependent insulinotropic polypeptide (GIP) is a major regulator of postprandial insulin secretion in mammals. Recent studies in our laboratory, and others have suggested that GIP is a potent stimulus for protein kinase activation, including the MAPK (ERK1/2) module. Based on these studies, we hypothesized that GIP could regulate cell fate and sought to examine the underlying mechanisms involved in GIP stimulation of cell survival. GIP potentiated glucose-induced beta-(INS-1)-cell growth to levels comparable with GH and GLP-1 while promoting cell survival in the face of serum and glucose-deprivation or treatment with wortmannin or streptozotocin. In the absence of GIP, 50% of cells died after 48 h of serum and glucose withdrawal, whereas 91 +/- 10% of cells remained viable in the presence of GIP [n = 3, P < 0.05; EC50 of 1.24 +/- 0.48 nm GIP (n = 4)]. Effects of GIP on cell survival and inhibition of caspase-3 were mimicked by forskolin, but pharmacological experiments excluded roles for MAPK kinase (Mek)1/2, phosphatidylinositol 3-kinase, protein kinase A, Epac, and Rap 1. Survival effects of GIP were ablated by the inhibitor SB202190, indicating a role for p38 MAPK. Furthermore, caspase-3 activity was also regulated by p38 MAPK, with a lesser role for Mek1/2, based on RNA interference studies. We propose that GIP is able to reverse caspase-3 activation via inhibition of long-term p38 MAPK phosphorylation in response to glucose deprivation (+/-wortmannin). Intriguingly, these findings contrasted with short-term phosphorylation of MKK3/6-->p38 MAPK-->ATF-2 by GIP. Thus, these data suggest that GIP is able to regulate INS-1 cell survival by dynamic control of p38 MAPK phosphorylation via cAMP signaling and lend further support to the notion that GIP regulation of MAPK signaling is critical for its regulation of cell fate.

Necrosis is the predominant type of islet cell death during development of insulin-dependent diabetes mellitus in BB rats

Several reports propose that apoptosis of pancreatic beta cells may play a central role in the pathogenesis of both spontaneous and induced insulin-dependent diabetes mellitus (IDDM) in animal models. Whether apoptosis is a major cell death pathway during diabetes development, however, is highly controversial. The aim of this study was to examine the mode of islet cell death in prediabetic diabetes-prone (dp) BB rats, which spontaneously develop diabetes and serve as an animal model for human IDDM. In addition we investigated the cell death pathway of islet cells treated with the widely used diabetogenic compound streptozotocin or with nitric oxide (NO), which during IDDM development has been found to be present in inflamed islets in high concentrations because of the expression of inducible NO synthase. Islets of prediabetic BBdp rats were analyzed for DNA strand breaks and screened by electron microscopy. The mode of islet cell death in vitro after treatment with cytotoxic concentrations of streptozotocin or of NO was investigated using different methods including morphologic analysis by electron microscopy, detection of DNA strand breaks, poly(ADP-ribose) polymerase cleavage, and annexin V staining. Although cells with DNA stand breaks-often accepted as a proof for apoptosis-could be identified, we did not find apoptosis-specific features during islet cell death. Instead we observed massive necrosis as evidenced by disrupted plasma membranes and spilled-out cellular constituents in vitro as well as during disease manifestation in BBdp rats. These results may have serious consequences with regard to the treatment of humans to prevent the development of IDDM.

The development of insulitis and the kallikrein-kinin system

Data derived from animals and humans suggest that the onset of diabetes is associated with hemodynamic changes in the renal circulation leading to increased renal plasma flow (RPF), glomerular capillary hyperfusion, and an increased glomerular transcapillary hydraulic pressure gradient. The duration of diabetes is one of the most important factors in predicting the development of diabetic nephropathy. On the other hand, diabetic nephropathy has been associated with the degree of hyperglycemia; thus, hyperglycemia may therefore contribute to alterations in structure and function of the kidney. In the present paper, we investigated early alterations of renal function in C57BL/KSJ mdb male mice that were injected with sub-diabetogenic doses of STZ. Urinary protein excretion (UPE) increased significantly at 12 and 18-20 days after STZ with a glucose level of 4-6 mm/l; the progressive increase of glycemia was followed by a progressive increase of UPE. In a similar way, urinary nitrite (NO2-) was also significantly increased. Urinary kallikrein excretion started to increase at a level of 4-6 mmol/l blood glucose concentration (BGC) 8 days after administration of STZ, and kidney vascular permeability also increased following the increment of BGC. These results confirm the presence of early modifications of renal function prior to the clinical detection of diabetic hyperglycemia.

Increased expression of antioxidant and antiapoptotic genes in islets that may contribute to beta-cell survival during chronic hyperglycemia

Hypertrophy is one mechanism of pancreatic beta-cell growth and is seen as an important compensatory response to insulin resistance. We hypothesized that the induction of protective genes contributes to the survival of enlarged (hypertrophied) beta-cells. Here, we evaluated changes in stress gene expression that accompany beta-cell hypertrophy in islets from hyperglycemic rats 4 weeks after partial pancreatectomy (Px). A variety of protective genes were upregulated, with markedly increased expression of the antioxidant genes heme oxygenase-1 and glutathione peroxidase and the antiapoptotic gene A20. Cu/Zn-superoxide dismutase (SOD) and Mn-SOD were modestly induced, and Bcl-2 was modestly reduced; however, several other stress genes (catalase, heat shock protein 70, and p53) were unaltered. The increases in mRNA levels corresponded to the degree of hyperglycemia and were reversed in Px rats by 2-week treatment with phlorizin (treatment that normalized hyperglycemia), strongly suggesting the specificity of hyperglycemia in eliciting the response. Hyperglycemia in Px rats also led to activation of nuclear factor-kappaB in islets. The profound change in beta-cell phenotype of hyperglycemic Px rats resulted in a reduced sensitivity to the beta-cell toxin streptozotocin. Sensitivity to the toxin was restored, along with the beta-cell phenotype, in islets from phlorizin-treated Px rats. Furthermore, beta-cells of Px rats were not vulnerable to apoptosis when further challenged in vivo with dexamethasone, which increases insulin resistance. In conclusion, beta-cell adaptation to chronic hyperglycemia and, hence, increased insulin demand is accompanied by the induction of protective stress genes that may contribute to the survival of hypertrophied beta-cells.

Specific expression of Bax-omega in pancreatic beta-cells is down-regulated by cytokines before the onset of apoptosis

Cytokines have been implicated in the process of pancreatic beta-cell destruction that leads to type 1 diabetes. This study investigates the beta-cell expression of pro- and antiapoptotic proteins from the Bcl-2 family and their variation during cytokine-mediated apoptosis. Exposure of rat beta-cells to the combination of IL-1beta plus interferon-gamma causes a time-dependent increase in apoptotic cells starting after 3 d (<10% on d 3 and 28 +/- 2% on d 7). This effect was preceded by a marked down-regulation of two antiapoptotic proteins, Bcl-2 and Bax-omega (respectively reduced by 60% and 80% after 3 d), whereas no changes occurred in the expression of Bcl-x(L) and the proapoptotic protein Bax-alpha. No apoptosis or down-regulation of Bcl-2 and Bax-omega proteins was observed with individual cytokines or in the presence of N-methyl-L-arginine, an inhibitor of nitric oxide synthase. The lowered Bcl-2 protein content was associated with a decrease in Bcl-2 mRNA, which was initiated after 24 h of exposure. In MIN6 cells, the cytokine-induced suppression of Bcl-2- and Bax-omega, and apoptosis, occurred within 24 h. Primary rat beta-cells exhibited a higher expression of Bax-omega than MIN6 cells or than other rat cell types. These data suggest that suppression of the antiapoptotic proteins Bcl-2 and Bax-omega mediates cytokine-induced apoptosis of beta-cells. The beta-cell-specific expression of Bax-omega makes this protein a possible effector in the protection of this cell type against apoptosis.