Response Of Islets Research Articles

Islet Preconditioning via Multimodal Microfluidic Modulation of Intermittent Hypoxia

Simultaneous stimulation of ex vivo pancreatic islets with dynamic oxygen and glucose is a critical technique for studying how hypoxia alters glucose-stimulated response, especially in transplant environments. Standard techniques using a hypoxic chamber cannot provide both oxygen and glucose modulations, while monitoring stimulus-secretion coupling factors in real-time. Using novel microfluidic device with integrated glucose and oxygen modulations, we quantified hypoxic impairment of islet response by calcium influx, mitochondrial potentials, and insulin secretion. Glucose-induced calcium response magnitude and phase were suppressed by hypoxia, while mitochondrial hyperpolarization and insulin secretion decreased in coordination. More importantly, hypoxic response was improved by preconditioning islets to intermittent hypoxia (IH, 1 min/1 min 5-21% cycling for 1 h), translating to improved insulin secretion. Moreover, blocking mitochondrial K(ATP) channels removed preconditioning benefits of IH, similar to mechanisms in preconditioned cardiomyocytes. Additionally, the multimodal device can be applied to a variety of dynamic oxygen-metabolic studies in other ex vivo tissues.

Severe Maternal Hyperglycemia Exacerbates the Development of Insulin Resistance and Fatty Liver in the Offspring on High Fat Diet

Background. Adverse maternal environments may predispose the offspring to metabolic syndrome in adulthoods, but the underlying mechanism has not been fully understood. Methods. Maternal hyperglycemia was induced by streptozotocin (STZ) injection while control (CON) rats received citrate buffer. Litters were adjusted to eight pups per dam and then weaned to standard diet. Since 13 weeks old, a subset of offspring from STZ and CON dams were switched to high fat diet (HFD) for another 13 weeks. Glucose and insulin tolerance tests (GTT and ITT) and insulin secretion assay were performed; serum levels of lipids and leptin were measured. Hepatic fat accumulation and islet area were evaluated through haematoxylin and eosin staining. Results. STZ offspring exhibited lower survival rate, lower birth weights, and growth inhibition which persisted throughout the study. STZ offspring on HFD showed more severe impairment in GTT and ITT, and more profound hepatic steatosis and more severe hyperlipidemia compared with CON-HFD rats. Conclusions. Offspring from diabetic dams would be prone to exhibit low birth weight and postnatal growth inhibition, but could maintain normal glucose tolerance and insulin sensitivity. HFD accelerates development of insulin resistance in the offspring of diabetic dams mainly via a compensatory response of islets.

Quantitative Imaging of Electron Transfer Flavoprotein Autofluorescence Reveals Lipid Partitioning Dynamics in Pancreatic Islets

Pancreatic islet beta-cells are sensitive to plasma nutrients in the body. Excess levels of glucose and fatty acids lead to glucolipotoxicity, resulting in declined beta-cell function and survival - a major component of type 2 diabetes mellitus (T2DM). Despite significant knowledge of glucose-stimulated insulin secretion, the effect of fatty acids remains uncertain. Here we show a novel way to measure a response from fatty acids in ex vivo pancreatic islets using quantitative autofluorescence imaging of a Complex II flavin, electron transfer flavoprotein (ETF). Together with two-photon imaging of NAD(P)H and our previously reported lipoamide dehydrogenase (LipDH) autofluorescence, we found that the electron transport chain is nutrient supply-driven and dominated by Complex I rather than Complex II. These data are consistent with beta-cells being predominantly glucose responsive. Furthermore, we found an oxidized ETF redox response in the presence of excess glucose-stimulation, suggesting a shift in lipid partitioning from fatty acid oxidization to synthesis above 10 mM glucose. Our results demonstrate that ETF autofluorescence can in part be used as readout of islet response to fat. Overall, we anticipate our ETF imaging platform to be a starting point for more sophisticated biological studies that will explore mechanisms of mitochondrial dysfunction in T2DM.

Erratum to: Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes

Erratum to: Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes

Advanced glycation end products downregulate glucokinase in mice

Glucokinase, the enzyme that catalyses the conversion of glucose to G-6-P, plays a key role in glucose metabolism. AGEs are implicated in diabetic complications. A previous study reported that AGEs decreased β-cell function through inhibition of cytochrome c oxidase and adenosine triphosphate synthesis. This study investigated the effects of AGEs on glucokinase and islet function. Six-month-old male C57BL6 mice were divided into bovine serum albumin (BSA) and AGE-BSA groups. BSA (200 µg/g) and AGE-BSA (60 U/g) were administered intraperitoneally twice daily. After 2 weeks, serum AGE levels were measured, oral glucose tolerance test was performed, and insulin levels during the oral glucose tolerance test were determined. Glucokinase protein expression level and activity were measured in pancreatic islets. We observed that the normal mice (C57/BL6) treated for 2 weeks with AGE-BSA showed impaired glucose tolerance and decrease in acute insulin release. Glucokinase activity in islets from the AGE-BSA-treated mice was significantly inhibited and accompanied by blunted response of islets to high glucose stimulation. Moreover, in vitro experiments showed that glucokinase protein expression was decreased, its activity was inhibited, and islet function was decreased. GKA partially restored glucokinase activity and islet function caused by AGEs. We concluded that AGEs inhibited glucokinase activity, leading to islet dysfunction in mouse pancreatic islets.

Excessive Food Intake, Obesity and Inflammation Process in Zucker fa/fa Rat Pancreatic Islets

Inappropriate food intake-related obesity and more importantly, visceral adiposity, are major risk factors for the onset of type 2 diabetes. Evidence is emerging that nutriment-induced β-cell dysfunction could be related to indirect induction of a state of low grade inflammation. Our aim was to study whether hyperphagia associated obesity could promote an inflammatory response in pancreatic islets leading to ß-cell dysfunction. In the hyperphagic obese insulin resistant male Zucker rat, we measured the level of circulating pro-inflammatory cytokines and estimated their production as well as the expression of their receptors in pancreatic tissue and β-cells. Our main findings concern intra-islet pro-inflammatory cytokines from fa/fa rats: IL-1β, IL-6 and TNFα expressions were increased; IL-1R1 was also over-expressed with a cellular redistribution also observed for IL-6R. To get insight into the mechanisms involved in phenotypic alterations, abArrays were used to determine the expression profile of proteins implicated in different membrane receptors signaling, apoptosis and cell cycle pathways. Despite JNK overexpression, cell viability was unaffected probably because of decreases in cleaved caspase3 as well as in SMAC/DIABLO and APP, involved in the induction and amplification of apoptosis. Concerning β-cell proliferation, decreases in important cell cycle regulators (Cyclin D1, p35) and increased expression of SMAD4 probably contribute to counteract and restrain hyperplasia in fa/fa rat islets. Finally and probably as a result of IL-1β and IL-1R1 increased expressions with sub-cellular redistribution of the receptor, islets from fa/fa rats were found more sensitive to both stimulating and inhibitory concentrations of the cytokine; this confers some physiopathological relevance to a possible autocrine regulation of β-cell function by IL-1β. These results support the hypothesis that pancreatic islets from prediabetic fa/fa rats undergo an inflammatory process. That the latter could contribute to β-cell hyperactivity/proliferation and possibly lead to progressive β-cell failure in these animals, deserves further investigations.

The Sequential Combination of a JNK Inhibitor and Simvastatin Protects Porcine Islets from Peritransplant Apoptosis and Inflammation

Intraductal administration of a c-Jun NH(2)-terminal kinase (JNK) inhibitor enhances islet viability. However, its role in reducing the inflammatory response in islets is unknown. It is also unknown whether a JNK inhibitor could act in synergy with statins. We examined if the sequential combination of a JNK inhibitor and simvastatin would reduce islet inflammation and improve islet viability. We performed porcine islet isolation with or without intraductal administration of SP600125, a JNK inhibitor. This was followed by culture medium supplementation with either nicotinamide alone or nicotinamide plus simvastatin. We assessed the viability of islets by flow cytometry, islet loss during overnight culture, graft function in NOD/SCID mice, and expression of inflammation-related genes in islets. The sequential combination of a JNK inhibitor and simvastatin increased the β-cell viability index of porcine islets cultured overnight (p = 0.015) as well as islet viability as assessed by a DNA binding dye staining (p = 0.011). The combination of a JNK inhibitor and simvastatin significantly increased the islet survival rate (p = 0.027) when the histomorphometry of donor pancreas indicated a large islet proportion of greater than 50.55%. When we transplanted the same islet mass per recipient for each group, there was no difference in overall islet graft function. Intraductal administration of JNK inhibitor significantly suppressed mRNA expression levels of interleukin-1β (IL-1β), interferon-γ, tumor necrosis factor-α, IL-6, IL-8, and macrophage chemoattractant protein-1. It also decreased the concentration of IL-1β (p = 0.040) and IL-8 (p = 0.023) in the culture supernatant. In conclusion, the sequential combination of a JNK inhibitor and simvastatin protected porcine islets from peritransplant apoptosis. Inhibition of JNK reduced the inflammatory response and could be considered an alternative target for suppression of porcine islet inflammation.

Incretin Hormone and Insulin Responses to OralVersusIntravenous Lipid Administration in Humans

The incretin effect is responsible for the higher insulin response to oral glucose than to iv glucose at matching glucose levels. It is not known whether this effect is restricted to glucose only. The aim of the study was to examine whether insulin and incretin hormone responses are higher after oral vs. iv challenge of a lipid emulsion with matching triglyceride levels in humans. A lipid emulsion (Intralipid) was administered orally (3 ml/kg) or iv (variable infusion rates to match triglyceride levels after oral ingestion) in healthy lean males (n = 12) at a University Clinical Research Unit. Samples were collected during 300 min. We measured the suprabasal area under the curve for insulin, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and the insulin secretory rate based on C-peptide levels by deconvolution. Triglyceride levels increased similarly after oral and iv lipid; also, glucose and free fatty acid levels were similar in the two tests. Oral lipid elicited a clear insulin and C-peptide response, whereas no insulin or C-peptide responses were observed during iv lipid. Total and intact GIP and GLP-1 levels both increased after oral lipid administration but were not significantly altered after iv lipid. At matching triglyceride levels and with no difference in glucose and free fatty acid levels, oral lipid ingestion but not iv lipid infusion elicits a clear insulin response in association with increased GIP and GLP-1 concentrations. This may suggest that the incretin hormones also contribute to the islet response to noncarbohydrate nutrients.

The liver receptor homolog-1 (LRH-1) is expressed in human islets and protects β-cells against stress-induced apoptosis

Liver receptor homolog (LRH-1) is an orphan nuclear receptor (NR5A2) that regulates cholesterol homeostasis and cell plasticity in endodermal-derived tissues. Estrogen increases LRH-1 expression conveying cell protection and proliferation. Independently, estrogen also protects isolated human islets against cytokine-induced apoptosis. Herein, we demonstrate that LRH-1 is expressed in islets, including β-cells, and that transcript levels are modulated by 17β-estradiol through the estrogen receptor (ER)α but not ERβ signaling pathway. Repression of LRH-1 by siRNA abrogated the protective effect conveyed by estrogen on rat islets against cytokines. Adenoviral-mediated overexpression of LRH-1 in human islets did not alter proliferation but conferred protection against cytokines and streptozotocin-induced apoptosis. Expression levels of the cell cycle genes cyclin D1 and cyclin E1 as well as the antiapoptotic gene bcl-xl were unaltered in LRH-1 expressing islets. In contrast, the steroidogenic enzymes CYP11A1 and CYP11B1 involved in glucocorticoid biosynthesis were both stimulated in transduced islets. In parallel, graded overexpression of LRH-1 dose-dependently impaired glucose-induced insulin secretion. Our results demonstrate the crucial role of the estrogen target gene nr5a2 in protecting human islets against-stressed-induced apoptosis. We postulate that this effect is mediated through increased glucocorticoid production that blunts the pro-inflammatory response of islets.

Lack of plasma albumin enhances glucose tolerance and insulin secretion

Congenital analbuminemic individuals and rats (NAR) present several metabolic abnormalities, such as hypertriglyceridemia and plasma free fatty acids (FFA) deficiency. We aimed at studying glucose homeostasis and insulin secretion in these dyslipidemic NAR. Measurements of plasma biochemical variables, insulin levels, isolated islet insulin secretion and glucose homeostasis tests were performed in female NAR and age‐matched controls (SDR, Sprague‐Dawley rats). Plasma glucose levels were similar in fed and fasted NAR and SDR. However, insulinemia was higher in fed NAR than in SDR (P ≤ 0.05). NAR showed increased glucose tolerance compared to SDR (P ≤ 0.05). This enhanced glucose tolerance was associated with higher insulinemia after the glucose load, and with similar insulin sensitivity between groups. Compared to SDR, isolated islets from NAR secreted more insulin in response to glucose and leucine. Despite similar liver glycogen content in fully fed condition, NAR had lower glycogen content (40% of control) after 6‐h fasting. The injection of pyruvate (gluconeogenic substrate) elicited a faster rise in glycemia in NAR than in SDR. In conclusion, NAR display enhanced glucose tolerance, insulin secretion, and gluconeogenesis rate. The higher glucose tolerance is attributed to enhanced islet responsiveness to secretagogues, while peripheral insulin sensitivity is not altered.

Resveratrol Potentiates Glucose-stimulated Insulin Secretion in INS-1E β-Cells and Human Islets through a SIRT1-dependent Mechanism

Resveratrol, a polyphenol compound, is known for its effects on energy homeostasis. With properties of energy sensors mediating effects of calorie restriction, sirtuins are targets of resveratrol. The mammalian sirtuin homolog SIRT1 is a protein deacetylase playing a role in glucose metabolism and islet function. Here, we investigated the effects of resveratrol and possible link with SIRT1 in β-cells. Insulinoma INS-1E cells and human islets were cultured with resveratrol before analyzing their physiological responses. Treatment of INS-1E cells for 24 h with 25 μM resveratrol resulted in marked potentiation of glucose-stimulated insulin secretion. This effect was associated with elevated glycolytic flux, resulting in increased glucose oxidation, ATP generation, and mitochondrial oxygen consumption. Such changes correlated with up-regulation of key genes for β-cell function, i.e. Glut2, glucokinase, Pdx-1, Hnf-1α, and Tfam. In human islets, chronic resveratrol treatment similarly increased both the glucose secretory response and expression of the same set of genes, eventually restoring the glucose response in islets obtained from one type 2 diabetic donor. Overexpression of Sirt1 in INS-1E cells potentiated resveratrol effects on insulin secretion. Conversely, inhibition of SIRT1 achieved either by expression of an inactive mutant or by using the EX-527 inhibitor, both abolished resveratrol effects on glucose responses. Treatment of INS-1E cells with EX-527 also prevented resveratrol-induced up-regulation of Glut2, glucokinase, Pdx-1, and Tfam. Resveratrol markedly enhanced the glucose response of INS-1E cells and human islets, even after removal of the compound from the medium. These effects were mediated by and fully dependent on active SIRT1, defining a new role for SIRT1 in the regulation of insulin secretion.

Defects in beta cell Ca2+ signalling, glucose metabolism and insulin secretion in a murine model of KATP channel-induced neonatal diabetes mellitus

Mutations that render ATP-sensitive potassium (K(ATP)) channels insensitive to ATP inhibition cause neonatal diabetes mellitus. In mice, these mutations cause insulin secretion to be lost initially and, as the disease progresses, beta cell mass and insulin content also disappear. We investigated whether defects in calcium signalling alone are sufficient to explain short-term and long-term islet dysfunction. We examined the metabolic, electrical and insulin secretion response in islets from mice that become diabetic after induction of ATP-insensitive Kir6.2 expression. To separate direct effects of K(ATP) overactivity on beta cell function from indirect effects of prolonged hyperglycaemia, normal glycaemia was maintained by protective exogenous islet transplantation. In endogenous islets from protected animals, glucose-dependent elevations of intracellular free-calcium activity ([Ca(2+)](i)) were severely blunted. Insulin content of these islets was normal, and sulfonylureas and KCl stimulated increased [Ca(2+)](i). In the absence of transplant protection, [Ca(2+)](i) responses were similar, but glucose metabolism and redox state were dramatically altered; sulfonylurea- and KCl-stimulated insulin secretion was also lost, because of systemic effects induced by long-term hyperglycaemia and/or hypoinsulinaemia. In both cases, [Ca(2+)](i) dynamics were synchronous across the islet. After reduction of gap-junction coupling, glucose-dependent [Ca(2+)](i) and insulin secretion was partially restored, indicating that excitability of weakly expressing cells is suppressed by cells expressing mutants, via gap-junctions. The primary defect in K(ATP)-induced neonatal diabetes mellitus is failure of glucose metabolism to elevate [Ca(2+)](i), which suppresses insulin secretion and mildly alters islet glucose metabolism. Loss of insulin content and mitochondrial dysfunction are secondary to the long-term hyperglycaemia and/or hypoinsulinaemia that result from the absence of glucose-dependent insulin secretion.

A Prenylated Flavan from Broussonetia kazinoki Prevents Cytokine-Induced .BETA.-Cell Death through Suppression of Nuclear Factor-.KAPPA.B Activity

The generation of nitric oxide (NO) via inducible NO synthase (iNOS) and reactive oxygen species plays a key role in cytokine-mediated pancreatic β-cell damage. Oxidative stress due to reactive oxygen species activates the nuclear factor-κB (NF-κB) transcription factor, which regulates iNOS expression. In this regard, suppression of the NF-κB pathway is a novel strategy for protecting β-cells from damage. This study was performed to explore the effects of kazinol U, a prenylated flavan from Broussonetia kazinoki, on the NF-κB activation pathway in interleukin-1β (IL-1β)- and interferon-γ (IFN-γ)-treated β-cells. The cytotoxic effects of cytokines were completely abolished when RINm5F cells or islets were pretreated with kazinol U. Kazinol U inhibited the nuclear translocation and DNA binding of NF-κB subunits, which correlated with the inhibitory effects on IκB kinase (IKK) phosphorylation and IκBα degradation. In addition, kazinol U suppressed NO and hydrogen peroxide production and apoptotic cell death by cytokines in RINm5F cells. The protective effects of kazinol U were further demonstrated by normal insulin secretion of cytokine-treated islets in response to glucose. Taken together, these results suggest that using kazinol U to block the NF-κB pathway in pancreatic β-cells reduces cell damage. Therefore, kazinol U may have therapeutic value in delaying pancreatic β-cell destruction in type 1 diabetes.

The endoplasmic reticulum stress response in the pancreatic β‐cell

Eukaryotic cells respond to stress in the endoplasmic reticulum (ER) resulting from insufficient protein folding capacity or altered ER homeostasis by activating the unfolded protein response (UPR). In mammalian cells the UPR is mediated by at least three ER-localized sensors/transducers, and the cellular response and susceptibility to ER stress is likely to be cell-type specific to some degree. Here, we review the response of pancreatic β-cells or islets to ER stress induced by pharmacological agents, misfolded insulin expression, excessive nutrient exposure and in animal models of type 2 diabetes. This review highlights the particular importance of PERK-mediated translational control and the transcriptional response in pancreatic β-cells and how these relate to the highly specialized function of β-cells, namely glucose-regulated insulin secretion and production. We examine how chronic ER stress may prematurely 'age' the β-cell or cause its genetic reprogramming to either reduce its ability to mount a cell survival response to ER stress, or impair normal function. Both could contribute to β-cell failure in diabetes. We also explore the therapeutic potential of targeting the UPR to preserve β-cell function.

In this issue

In this issue

Mechanisms of insulin secretion in malnutrition: modulation by amino acids in rodent models

Protein restriction at early stages of life reduces β-cell volume, number of insulin-containing granules, insulin content and release by pancreatic islets in response to glucose and other secretagogues, abnormalities similar to those seen in type 2 diabetes. Amino acids are capable to directly modulate insulin secretion and/or contribute to the maintenance of β-cell function, resulting in an improvement of insulin release. Animal models of protein malnutrition have provided important insights into the adaptive mechanisms involved in insulin secretion in malnutrition. In this review, we discuss studies focusing on the modulation of insulin secretion by amino acids, specially leucine and taurine, in rodent models of protein malnutrition. Leucine supplementation increases insulin secretion by pancreatic islets in malnourished mice. This effect is at least in part due to increase in the expression of proteins involved in the secretion process, and the activation of the PI3K/PKB/mTOR pathway seems also to contribute. Mice supplemented with taurine have increased insulin content and secretion as well as increased expression of genes essential for β-cell functionality. The knowledge of the mechanisms through which amino acids act on pancreatic β-cells to stimulate insulin secretion is of interest for clinical medicine. It can reveal new targets for the development of drugs toward the treatment of endocrine diseases, in special type 2 diabetes.

R-spondin-1 Is a Novel β-Cell Growth Factor and Insulin Secretagogue

R-spondin-1 (Rspo1) is an intestinal growth factor known to exert its effects through activation of the canonical Wnt (cWnt) signaling pathway and subsequent expression of cWnt target genes. We have detected Rspo1 mRNA in murine islets and the murine MIN6 and betaTC beta-cell lines, and Rspo1 protein in MIN6 beta-cells. Rspo1 activated cWnt signaling in MIN6 beta-cells by increasing nuclear beta-catenin and c-myc, a cWnt target gene. Rspo1 also induced insulin mRNA expression in MIN6 cells. Analysis of MIN6 and mouse beta-cell proliferation by [(3)H]thymidine and BrdU incorporation, respectively, revealed that Rspo1 stimulated cell growth. Incubation of MIN6 and mouse beta-cells with cytokines (IL1beta/TNFalpha/interferon-gamma) significantly increased cellular apoptosis; this increase was abolished by pretreatment with Rspo1. Rspo1 also stimulated insulin secretion in a glucose-independent fashion. We further demonstrated that the glucagon-like peptide-1 receptor agonist, exendin4 (EX4), stimulated Rspo1 mRNA transcript levels in MIN6 cells in a glucose-, time-, dose-, and PI3-kinase-dependent fashion. This effect was not limited to this beta-cell line, as similar time-dependent increases in Rspo1 were also observed in the betaTC beta-cell line and mouse islets in response to EX4 treatment. Together, these studies demonstrate that Rspo1 is a novel beta-cell growth factor and insulin secretagogue that is regulated by EX4. These findings suggest that Rspo1 and the cWnt signaling pathway may serve as a novel target to enhance beta-cell growth and function in patients with type 2 diabetes.

Mixed Lineage Kinase-3 Stabilizes and Functionally Cooperates with TRIBBLES-3 to Compromise Mitochondrial Integrity in Cytokine-induced Death of Pancreatic Beta Cells

Mixed lineage kinases (MLKs) have been implicated in cytokine signaling as well as in cell death pathways. Our studies show that MLK3 is activated in leukocyte-infiltrated islets of non-obese diabetic mice and that MLK3 activation compromises mitochondrial integrity and induces apoptosis of beta cells. Using an ex vivo model of islet-splenocyte co-culture, we show that MLK3 mediates its effects via the pseudokinase TRB3, a mammalian homolog of Drosophila Tribbles. TRB3 expression strongly coincided with conformational change and mitochondrial translocation of BAX. Mechanistically, MLK3 directly interacted with and stabilized TRB3, resulting in inhibition of Akt, a strong suppressor of BAX translocation and mitochondrial membrane permeabilization. Accordingly, attenuation of MLK3 or TRB3 expression each prevented cytokine-induced BAX conformational change and attenuated the progression to apoptosis. We conclude that MLKs compromise mitochondrial integrity and suppress cellular survival mechanisms via TRB3-dependent inhibition of Akt.

Revisiting an old acquaintance: role for eIF5A in diabetes

Dysfunction of pancreatic islet beta cells underlies both type 1 and type 2 diabetes and appears to result in part from the local release of proinflammatory cytokines. An improved understanding of the mechanisms that mediate islet responsiveness to proinflammatory cytokines may therefore expand our knowledge of the role of cytokine signaling in the development of diabetes, providing potential new targets for the development of therapeutics to protect pancreatic islets from inflammation. In this issue of the JCI, Maier and colleagues identify eukaryotic translation initiation factor 5A (eIF5A) as a critical regulator of the inflammatory response in mouse pancreatic islets. I believe these data provide new and important insights into the regulatory pathways that contribute to the development of diabetes and deepen our understanding of the function of the, so far, rather enigmatic cellular protein eIF5A.

Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes

Beta cell failure is a crucial component in the pathogenesis of type 2 diabetes. One of the proposed mechanisms of beta cell failure is local inflammation, but the presence of pancreatic islet inflammation in type 2 diabetes and the mechanisms involved remain under debate. Chemokine and cytokine expression was studied by microarray analysis of laser-capture microdissected islets from pancreases obtained from ten non-diabetic and ten type 2 diabetic donors, and by real-time PCR of human islets exposed to oleate or palmitate at 6 or 28 mmol/l glucose. The cellular source of the chemokines was analysed by immunofluorescence of pancreatic sections from individuals without diabetes and with type 2 diabetes. Microarray analysis of laser-capture microdissected beta cells showed increased chemokine and cytokine expression in type 2 diabetes compared with non-diabetic controls. The inflammatory response in type 2 diabetes was mimicked by exposure of non-diabetic human islets to palmitate, but not to oleate or high glucose, leading to the induction of IL-1beta, TNF-alpha, IL-6, IL-8, chemokine (C-X-C motif) ligand 1 (CXCL1) and chemokine (C-C motif) ligand 2 (CCL2). Interference with IL-1beta signalling abolished palmitate-induced cytokine and chemokine expression but failed to prevent lipotoxic human islet cell death. Palmitate activated nuclear factor kappaB (NF-kappaB) in human pancreatic beta and non-beta cells, and chemically induced endoplasmic reticulum stress caused cytokine expression and NF-kappaB activation similar to that occurring with palmitate. Saturated-fatty-acid-induced NF-kappaB activation and endoplasmic reticulum stress may contribute to IL-1beta production and mild islet inflammation in type 2 diabetes. This inflammatory process does not contribute to lipotoxicity ex vivo, but may lead to local chemokine release.