Rat Islets Of Langerhans Research Articles

The potential antioxidant effect of N-acetylcysteine on X-ray ionizing radiation-induced pancreas islet cell toxicity

PurposePrevious research has highlighted the impact of X-ray irradiation-induced organ damage, on cancer patients after radiation therapy. The ionizing radiation-induced oxidative stress causes injury to the pancreatic islet cells of Langerhans. We used histopathological, immunohistochemical, and biochemical analyses to examine α- and β-cells in the islets of Langerhans in rats undergoing whole-body x-ray ionizing radiation, a group of which was treated with NAC. Material and methodsTwenty-four male rats were randomly divided into 3 groups, one control, and two experimental groups. Group I (Control) was administered only saline solution (0.09% NaCl) by oral gavage for 7 days. Group II (IR) was administrated whole body single dose 6 Gray ionizing radiation (IR) and saline solution (0.09% NaCl) by oral gavage for 7 days. Group III (IR + NAC) was administered 300 mg/kg NAC (N-acetylcysteine) by oral gavage for 7 days, 5 days before, and 2 days after 6 Gray IR application. ResultsIn the X-ray irradiation group, we observed diffuse necrotic endocrine cells in the islets of Langerhans. In addition, we found that Caspase-3, malondialdehyde (MDA) levels increased, and insulin, glucagon, and glutathione (GSH) levels decreased in the IR group compared to the control group. In contrast, we observed a decrease in Caspase-3, and MDA levels in necrotic endocrine cells, and an increase in insulin, glucagon, and GSH levels in the IR + NAC group compared to the IR group. ConclusionThis study provides evidence for the beneficial effects of N-acetyl cysteine on islets of Langerhans cells with X-ray ionizing-radiation-induced damage in a rat model.

Blood Glucose Level, Langerhans Pancreas and Lipid Profile of Diabetic Rats After Administration of Red Betel, Ginger and Cinnamon Combination Extract.

Previous studies had reported antihyperglycemic activity in vitro, in vivo and in silico of red betel (Piper crocatum) extract, which was associated with its polyphenolic, tannins, alkaloids, and flavonoids compounds. This study aimed to determine blood glucose level, Langerhans pancreas, lipid profile and bodyweight of streptozotocin-induced diabetic rats after administrating red betel combination extract. Red betel combination extract is composed of red betel extract that was combined with ginger and cinnamon extracts. 16 male rats (Sprague Dawley) were divided randomly into two controls groups (Normal and diabetic groups; orally administered with 2 mL of aquadest for 14 days) and two extract groups (diabetic groups; orally administered with red betel combination extract 9 mL/kg BW and 13.5 mL/kg BW). Results showed that the administration of red betel combination extract for 14 days (9 mL/kg BW dosage) decreased the rat's blood glucose level up to 55.42%, which was significantly different (p < 0.05) compared to the rat's blood glucose levels on day 3. While the combination extract (dosages 9 mL/kg BW and 13.5 mL/kg BW) increased the numbers of rat Langerhans islets up to 10.9%-30.6%. The level of rat's blood high-density lipoprotein (HDL) and triglyceride levels in the diabetic control group were significantly different (p < 0.05) compared to that of the diabetic with red betel combination extract and normal groups. The treatment orally with red betel combination extract (various dosages) for 14 days suppressed the weight loss of rats by 10%-11%.

The Effect of Sleeve Gastrectomy and Omentoplasty on HOMA BETA Value and Islets of Langerhans in Rats with Type 2 Diabetes Mellitus

INTRODUCTION: WHO predicts an increase in the number of people with diabetes in Indonesia from 8.4 million in 2000 to around 21.3 million in 2030. Another marker for measuring insulin resistance is the homeostasis model assessment-insulin resistance (HOMA-IR). Bariatric surgery is the most effective therapy for patients both in terms of weight loss and improvement in obesity-related diseases such as Type-2 Diabetes Mellitus (DM). OBJECTIVE: This study aims to prove the improvement of HOMA Beta values and Diameter of the islets of Langerhans in type 2 diabetes mellitus rats that underwent Sleeve Gastrectomy and Pancreatic Omentoplasty. METHODS: This study is an experimental post-test control group design study with 18 male Sprague-Dawley rats. Samples are divided into 1 control group and 2 treatment groups (Sleeve gastrectomy and Omentoplasty). Rats’ pancreas and glucose level were measured by using HOMA IR method and Hematoxylin eosin-paraffin block method. Data of islets Langerhans were measured using ANOVA, while HOMA Beta values were measured by Mann Whitney and Kruskall Wallis test. RESULTS: HOMA Beta values in treatment Group P1 (Sleeve gastrectomy) and Group P2 (Sleeve gastrectomy + omentoplasty) are statistically different compared to control group. Islets cells of Langerhans diameter in treatment groups 1 and 2 was not statistically different compared to control group. HOMA Beta Value and Langerhans diameter was correlated moderately. CONCLUSION: Sleeve Gastrectomy and Pancreatic Omentoplasty in type 2 diabetes mellitus rats improved the HOMA Beta values and the diameter of the islets of Langerhans. KEYWORDS: Sleeve Gastrectomy; Omentoplasty; Diabetes mellitus; HOMA Beta; Langerhan's Islet

Vitamin D regulates insulin and ameliorates apoptosis and oxidative stress in pancreatic tissues of rats with streptozotocin-induced diabetes

This study was designed to evaluate the potential therapeutic efficacy of vitamin D (Vit D) in averting the harmful effects of type 2 diabetes mellitus (T2D). Forty male Wistar rats were allotted into four groups: (1) the control, (2) Vit D, (3) streptozotocin (STZ), and (4) STZ + Vit D groups. Rats co-treated with Vit D had significantly (p < 0.05) decreased levels of cortisol; proinflammatory cytokines, including interleukin-6 (IL-6); and malondialdehyde (MDA). Meanwhile, the levels of insulin significantly (p < 0.05) increased, whereas the activity of the antioxidant system, including glutathione (GSH), superoxide dismutase (SOD), catalase, and total antioxidant capacity (TAC), significantly (p < 0.05) decreased. Histopathological examination revealed the destruction of beta cells in the islets of Langerhans in rats with diabetes. Meanwhile, immunoexpression revealed an increase in the immunoreactivity of caspase-3 and endothelial nitric oxide synthase and a reduction in the immunoreactivity of insulin in rats with diabetes. In conclusion, Vit D ameliorated the harmful biochemical impact of diabetes mellitus, probably by increasing insulin secretion and sensitivity, ameliorating β-cell function, and decreasing cortisol levels; also, the anti-inflammatory effect of Vit D reduces the number of proinflammatory cytokines (e.g., IL-6) and increases the activity of the antioxidant system, such as GSH, SOD, TAC, and catalase while reducing lipid peroxidation enzymes (e.g., MDA).

Development of a pancreas-liver organ-on-chip coculture model for organ-to-organ interaction studies

Type 2 diabetes mellitus (T2DM) is a widespread chronic disease with a high prevalence of comorbidity and mortality. The exponential increase of TD2M represents an important public health challenge and leads a strong demand for the development of relevant in vitro models to improve mechanistic understanding of diabetes and identify new anti-diabetic drugs and therapies. These models involve considering the multi-organ characteristic of T2DM. The organ-on-chip technology has made it possible to connect several organs thanks to dedicated microbioreactors interconnected by microfluidic network. Here, we developed pancreas-liver coculture model in a microfluidic biochip, using rat islets of Langerhans and hepatocytes. The behavior and functionality of the model were compared to islets and hepatocytes (with/without insulin) monocultures. Compared to monoculture, the islets coculture presented high C-peptide and insulin secretions, and downregulation of Pdx1, Glut2, App, Ins1, Neurod, Neurog3 and Gcgr genes. In the hepatic compartment, the monocultures without insulin were negative to CK18 staining and displayed a weaker albumin production, compared to monoculture with insulin. The hepatocytes cocultures were highly positive to INSR, GLUT2, CK18 and CYP3A2 immunostaining and allowed to recover mRNA levels similar to monocultures with insulin. The result showed that islets could produce insulin to supplement the culture medium and recover hepatic functionality. This model illustrated the potential of organ-on-chip technology for reproducing crosstalk between liver and pancreas.

Effect of Juvenile Obesity on the Islets of Langerhans in Rat and the Possibility of Recovery at Adulthood: A Histological and Immunohistochemical Study

Background: Juvenile obesity is a serious problem that increases the risk of future development of cardiovascular disease and type 2 diabetes at adulthood through programing a metabolic dysfunction during development.Aim of the Work: to perform a biochemical, histological and immunohistochemical evaluation of the effect of juvenile obesity on the morphology, insulin expression, apoptosis and proliferation of the islets of Langerhans in albino rat and to evaluate the possibility of recovery at adulthood.Material and Methods: Twenty-one juvenile male albino rats were equally divided into 3 groups; control (fed 11% fat standard diet), high fat diet-induced obesity group (fed 45% fat diet for 8 weeks) and recovery group (fed 45% fat diet for 8 weeks then left for 4 weeks on standard diet). Animals were weighed and fasting blood glucose and serum insulin were quantified. Pancreatic specimens were processed for histological and immunohistochemical staining for detection of insulin, Bcl2 and Ki67.Results: Juvenile obesity group recorded a significant increase in total body weight and blood glucose coupling with a significant decrease in serum insulin. Histological examination revealed few shrunken islets of Langerhans with cells expressing nuclear alterations and cytoplasmic vacuolation. Peripheral mononuclear infiltration and dilated congested blood capillaries were observed. A significant decrease in the immunohistochemical expression of insulin, Bcl2 and Ki67 was recorded. While a significant improvement of all studied parameters was detected in the recovery group.Conclusion: Restoration of a normal diet in high fat diet-induced obesity in juvenile rats reinstated the abnormal glucose and insulin levels, ameliorated the altered morphology of islets of Langerhans, and upregulated the suppressed immunoexpression of insulin, Bcl2 and Ki67 in the islets at adulthood.

Estrogens counteract tributyltin-induced toxicity in the rat islets of Langerhans

BackgroundTributyltin (TBT) is known as an endocrine disruptor able to interfere with estrogen receptors (ERs) leading to toxic effects on the related endocrine pathways. TBT is an obesogen, reported to disrupt glucose homeostasis leading to diabetes. The aim of this study was to assess the influence of TBT and β-estradiol on the pancreatic islets of Langerhans in simultaneous exposures. ExperimentalPancreatic islets of 15 male rat were isolated and exposed to TBT (10 μM), β-estradiol, and TBT plus β-estradiol for 24 h. Therewith, cellular viability, oxidative stress, apoptosis, and insulin secretion markers were investigated. ResultsTBT decreased the viability and increased the apoptosis, reactive oxygen species, and insulin secretion TBT led to increased amounts of apaptosis, reactive oxygen species (ROS), and insulin secretion in pancreatic islets; however, cellular viability was reduced. Co-exposure with β-estradiol ameliorated the entire mentioned variables near to the control level. ConclusionThese results showed that β-estradiol protect pancreatic islets of Langerhans against TBT-induced toxicity by counteracting oxidative stress and apoptosis as well as insulin secretion. In this way, it is postulated that pancreatic ER pathways particularly in β-cells might be the determinant target of toxic effects of xenoestrogens like TBT. Hence, evaluation of xenoestrogens-induced ER dysfunction in the endocrine pancreas can be helpful in diabetic risk assessment of these contaminants. Pharmacological modifications of ER pathway in the β-cells seems promising for better management of diabetes.

Influence of rat bone marrow mesenchymal stem cells to rat Langerhans islets viability during co-cultivation with microst ructured collagen‑containing hydrogel

Aim. To research the rat bone marrow mesenchymal stem cells (MSC BM) effect to the viability of isolated rat OL during cultivation with microstructured collagen-containing hydrogel (BMCH).Materials and methods. Rat islets and MSC BM were isolated according to classical technique with some modifications. The experiments on the co- cultivation were carried out under standard conditions. Islet’s viability was determined by immunofluorescence staining.Results. TheOL cultivation with BMCH and MSCBM resulted in destructive changes of isletson the third day, and complete destruction of OL was observed on the seventh day. At the same time, OL cultured with BMCH remained viable for 14 days of incubation.Conclusion. Cultivation of OL with BMCH and MSC BM did not contribute to the long-term survival of the islets. Thus, there was no positive effect of MSC BM on the viability of pancreatic islets.

Gastric fundus submucosa as a site for islets transplantation: An experimental study.

BackgroundIslets of Langerhans transplantation is a promising alternative for glycemic control in patients with type 1 diabetes. The graft site is a factor that has large impact on the functioning of this transplant, and the stomach appears to be a promising location. Our objective is to describe a new experimental model for the grafting of Islets of Langerhans in rat stomachs.MethodologyIslets of Langerhans were extracted from 45 isogenic male rats of the Lewis lineage and transplanted into 9 isogenic rats of the Wistar lineage; 5 in the gastric body submucosa, and 4 in the gastric fundus submucosa. Normoglycemia was defined as two successive measurements of <250 mg/dL. No immunosuppression was used. The two groups glycemia control improvement were compared with t-student test.ResultsThe results obtained following the transplantation of the islets in 9 rats showed between 995 and 2310 islets transplanted (mean of 1367). The rats from the gastric submucosa group had a better glycemic level improvement, with a confidence equal to 83.94%.ConclusionIslets graft into the gastric fundus submucosa is a viable model with potential for adequate glycemic control. This model gives potential for new perspectives and future studies in this area.

In-vitro and in-vivo studies supporting the therapeutic potential of ZP3022 in diabetes

GLP-1-gastrin dual agonist ZP3022 has been shown to increase β-cell mass with a concomitant improvement of glycemic control in diabetic mice and rats. Here we tested the in-vitro effects of ZP3022 on β-cell proliferation, islet apoptosis and glucose-stimulated insulin secretion (GSIS) in rat islets of Langerhans. Moreover, gene expression profiling in whole pancreas from Zucker Diabetic Fatty (ZDF) rats was performed to characterize genes differently regulated by short-term treatment with ZP3022. Treatments with exendin-4, gastrin-17 alone or in combination were included in the studies. ZP3022 promoted β-cell proliferation, protected from palmitate-, but not from cytokine-induced apoptosis, and induced an increase in GSIS, demonstrating a glucose dependent insulinotropic action of ZP3022 on β-cells. The combination treatment with exendin-4 and gastrin-17 showed comparable effects on proliferation, apoptosis, and GSIS as did ZP3022. Microarray analysis revealed that ZP3022 exerted specific effects on pancreatic gene expression not observed when treating ZDF rats with either exendin-4 alone or in combination with gastrin-17. In particular MAPK signaling pathway was observed among the highest affected pathways; while also pathways related to insulin signaling and secretion were regulated by ZP3022. Moreover, rats treated with ZP3022 had a higher expression of genes encoding for the specific β-cell/endocrine cell markers, such as islet amyloid polypeptide (IAPP), protein convertase 1/3 and -2 (PC 1/3 and-2), as well as transmembrane protein 27(TMEM27) compared to vehicle treated rats. We conclude that ZP3022 may have therapeutic potential in the prevention/delay of β cell dysfunction.

The effect of ghrelin on Kiss-1 and KissR gene transcription and insulin secretion in rat islets of Langerhans and CRI-D2 cell line.

Objective(s):Ghrelin is a peptide hormone that has been shown to have numerous central and peripheral effects. The central effects including GH secretion, food intake, and energy homeostasis are partly mediated by Kiss1- KissR signaling pathway. Ghrelin and its receptor are also expressed in the pancreatic islets. Ghrelin is one of the key metabolic factors controlling insulin secretion from the islets of Langerhans. We hypothesize that the inhibitory effect of ghrelin on KiSS-1 and KissR in the islet cells may be similar to the same inhibitory effect of ghrelin in the hypothalamus.Materials and Methods:To investigate the effect of ghrelin, we isolated the islets from adult male rats by collagenase and cultured CRI-D2 cell lines. Then, we incubated them with different concentrations of ghrelin for 24 hr. After RNA extraction and cDNA synthesis from both islets and CRI-D2 cells, the relative expression of KiSS-1 and KissR was evaluated by means of real-time PCR. Furthermore, we measured the amount of insulin secreted by the islets after incubation in different concentrations of ghrelin and glucose after 1 hr. Besides, we checked the viability of the cells after 24 hr cultivation.Results:Ghrelin significantly decreased the KiSS-1 and KissR mRNA transcription in rat islets and CRI-D2 cells. Besides, Ghrelin suppressed insulin secretion from pancreatic beta cells and CRI-D2 cells.Conclusion:These findings indicate the possibility that KiSS-1 and KissR mRNA expression is mediator of ghrelin function in the islets of Langerhans.

A TRPM4 Inhibitor 9-Phenanthrol Inhibits Glucose- and Glucagon-Like Peptide 1-Induced Insulin Secretion from Rat Islets of Langerhans.

Pancreatic β-cells express several ion channels of the transient receptor potential family, which play important roles in mediating the stimulus-secretion coupling. One of these channels, the TRPM4 is a Ca2+-activated monovalent cation channel. This channel is inhibited by 9-phenanthrol, which also inhibits the TMEM16a Cl− channel, and activates the Ca2+-activated K+ channel, Kca3.1. The net effects of ion-channel modulation by 9-phenantherol on the insulin secretion remain unclear. We tested the effects of 9-phenanthrol on glucose- and GLP-1-induced insulin secretion from isolated rat islets in static incubations. When applied to the islets in the presence of 3.3 mM glucose, 9-phenanthrol caused a small increase in insulin secretion (~7% of the insulin secretion stimulated by 10 mM glucose). 10 μM 9-phenanthrol did not inhibit glucose- or GLP-1-induced insulin secretion. 20 μM and 30 μM 9-phenanthrol inhibited glucose-induced insulin secretion by ~80% and ~85%, respectively. Inhibition of the GLP-1-induced insulin secretion by 20 μM and 30 μM 9-phenanthrol was 65% and 94%, respectively. Our study shows that the major effect of 9-phenanthrol on the islets is a strong inhibition of insulin secretion, and we speculate that compounds related to 9-phenanthrol may be potentially useful in treating the pancreatogenous hyperinsulinemic hypoglycemia syndromes.

The Effect of Leptin and Adiponectin on KiSS-1 and KissR mRNA Expression in Rat Islets of Langerhans and CRI-D2 Cell Line.

Background:Leptin and adiponectin are the two key metabolic hormones secreted from adipocytes to control food intake and energy expenditure. The action of both hormones in regulation of Gonadotropin Releasing Hormone (GnRH) secretion from the hypothalamus is mediated through Kisspeptins. Kisspeptins are products of KiSS-1 gene. Leptin and adiponectin are modulators of KiSS-1 expression in the hypothalamus. These peptides have also important roles in pancreatic β-cells to control insulin synthesis and secretion and their receptors are detected in Langerhans islets. We hypothesized that leptin and adiponectin might alter KiSS-1 and Kiss Receptor mRNA expression in the islets.Objectives:The aim of this study is to investigate any modulatory effect that leptin and adiponectin may have on the expression of Kiss-1 and KiSSR gene in Langerhans islets.Materials and Methods:We isolated the islets from adult male rats by collagenase and cultured CRI-D2 cell lines to investigate the effect of leptin and adiponectin. Then, we incubated them with different concentrations of leptin and adiponectin for 24 hours. After that, RNA was extracted from the islets and CRI-D2 cells and transcripted to cDNA. KiSS-1 and KissR expression levels were evaluated by real time PCR.Results:In islet and CRI-D2 cells, leptin increased the KiSS-1 mRNA expression significantly, but adiponectin decreased it was expected.Conclusions:These findings indicated the possibility that KiSS-1 mRNA expression is a mediator of leptin and adiponectin function in the islets.

The effects of Leptin and Adiponectin on Pdx1, Foxm1, and PPARγ Transcription in Rat Islets of Langerhans

BackgroundLeptin and adiponectin are two hormones, which are released from adipocytes in order to control energy expenditure. Both hormones are also involved in glucose homeostasis through control of insulin secretion from pancreatic islets. Since Pdx1, PPARγ, and foxm1 play important roles in islets function, it is essential to understand how these genes are regulated in the islets of Langerhans.ObjectivesWe have designed an experiment to identify the effect of leptin and adiponectin treatment on Pdx1, PPARγ, and foxm1 transcription.Materials and MethodsIslets were isolated from adult male rats by collagenase and incubated with different concentrations of leptin and adiponectin for 24 hours. Next, by means of real time PCR, we evaluated the gene transcription related to a housekeeping gene. The effect of leptin and adiponectin on insulin secretion was evaluated by ELISA.ResultsLeptin decreased PPARγ transcription and insulin secretion, while adiponectin significantly increased Pdx1 and PPARγ transcription and insulin secretion in rat islets. The transcription of foxm1 did not change in the islet cells treated with leptin or adiponectin.ConclusionsThese findings indicate the possibility that Pdx1 and PPARγ transcription is a mediator of leptin and adiponectin function in control of insulin secretion and glucose homeostasis in pancreatic islets.

Gliadin Fragments and a Specific Gliadin 33-mer Peptide Close KATP Channels and Induce Insulin Secretion in INS-1E Cells and Rat Islets of Langerhans

In non-obese diabetic (NOD) mice, diabetes incidence is reduced by a gluten-free diet. Gluten peptides, such as the compound gliadin, can cross the intestinal barrier and may directly affect pancreatic beta cells. We investigated the effects of enzymatically-digested gliadin in NOD mice, INS-1E cells and rat islets. Six injections of gliadin digest in 6-week-old NOD mice did not affect diabetes development, but increased weight gain (20% increase by day 100). In INS-1E cells, incubation with gliadin digest induced a dose-dependent increase in insulin secretion, up to 2.5-fold after 24 hours. A similar effect was observed in isolated rat islets (1.6-fold increase). In INS-1E cells, diazoxide reduced the stimulatory effect of gliadin digest. Additionally, gliadin digest was shown to decrease current through KATP-channels. A specific gliadin 33-mer had a similar effect, both on current and insulin secretion. Finally, INS-1E incubation with gliadin digest potentiated palmitate-induced insulin secretion by 13% compared to controls. Our data suggest that gliadin fragments may contribute to the beta-cell hyperactivity observed prior to the development of type 1 diabetes.

The Neuregulin System of Ligands and Their Receptors in Rat Islets of Langerhans

Islet cell growth and function are affected by ligands from the epidermal growth factor (EGF) family. We describe here the expression, regional distribution, and effect on growth and secretion of insulin of a subset of these, the neuregulin (NRG) family. The expression of NRG1α, NRG1β, NRG2α, NRG2β, NRG3, and NRG4 in rat islets was determined using immunohistochemical and double immunofluorescent staining. We also report the expression of the 4 receptors and the remaining 7 ligands using immunohistochemistry. The NRG1α splice variant was expressed in β-cells and the NRG1β variant mainly in α-cells. NRG3 was also predominantly present in α-cells. Most of the members of the EGF family of ligands were also expressed, with Epigen being present at the highest levels. The rat islet-derived cell line CRI-G1 was used to study the effect of addition of EGF, NRG1β, NRG3, and NRG4 on cell growth and insulin secretion. Synthetic refolded NRG3 strongly stimulated the growth of the CRI-G1 cells, and NRG4 gave the greatest stimulation of insulin release. Different members of the NRG family are therefore potentially potent stimuli for islet cell growth and insulin release and differ in expression in α- and β-cells.

Enhanced maintenance of rat islets of Langerhans on laminin‐coated electrospun nanofibrillar matrix in vitro

Understanding the extracellular matrix (ECM) effect on pancreatic β cells is critical to optimise the derivation of functional β cells for transplantation and understand mechanisms that control islet neogenesis and glucose homeostasis. We assessed the effect of natural ECMs [collagen I, collagen IV, laminin and fibronectin (FN)] on rat islets of Langerhans' morphology, adhesion, viability, functionality and islet specific genes expression after 7 days in vitro culture. However, we could not detect a significant difference on the other parameters in these ECMs and islets interaction. To examine islets interactions, we used a synthetic three dimensional surface composed of electrospun polyamide nanofibres. Laminin-coated nanofibrillar surfaces, but not laminin or nanosurface alone, induced comparable expression of the Ins1 and Ins2 genes in adult β cells. Using a glucose challenge test, a marked response of insulin secretion by islets occurred that were cultured on laminin-coated nanofibrillar surfaces.We contend that the reestablishment of cellular interactions by the combination of nanomaterials and natural ECMs can be useful in maintaining in vitro islet functions.

The lysine deacetylase inhibitor givinostat inhibits β-cell IL-1β induced IL-1β transcription and processing

Aims: Pro-inflammatory cytokines and chemokines, in particular IL-1β, IFNγ, and CXCL10, contribute to β-cell failure and loss in DM via IL-1R, IFNγR, and TLR4 signaling. IL-1 signaling deficiency reduces diabetes incidence, islet IL-1β secretion, and hyperglycemia in animal models of diabetes. Further, IL-1R antagonism improves normoglycemia and β-cell function in type 2 diabetic patients. Inhibition of lysine deacetylases (KDACi) counteracts β-cell toxicity induced by the combination of IL-1 and IFNγ and reduces diabetes incidence in non-obese diabetic (NOD) mice. We hypothesized that KDACi breaks an autoinflammatory circuit by differentially preventing β-cell expression of the β-cell toxic inflammatory molecules IL-1β and CXCL10 induced by single cytokines. Results: CXCL10 did not induce transcription of IL-1β mRNA. IL-1β induced β-cell IL-1β mRNA and both IL-1β and IFNγ individually induced Cxcl10 mRNA transcription. Givinostat inhibited IL-1β-induced IL-1β mRNA expression in INS-1 and rat islets and IL-1β processing in INS-1 cells. Givinostat also reduced IFNγ induced Cxcl10 transcription in INS-1 cells but not in rat islets, while IL-1β induced Cxcl10 transcription was unaffected in both. Materials and Methods: INS-1 cells and rat islets of Langerhans were exposed to IL-1β, IFNγ or CXCL10 in the presence or absence of KDACi (givinostat). Cytokine and chemokine mRNA expressions were quantified by real-time qPCR, and IL-1β processing by western blotting of cell lysates. Conclusion/Interpretation: Inhibition of β-cell IL-1β expression and processing and Cxcl10 transcription contributes to the β-cell protective actions of KDACi. In vitro β-cell destructive effects of CXCL10 are not mediated via IL-1β transcription. The differential proinflammatory actions of KDACs may be attractive novel drug targets in DM.

MicroRNA-29a is up-regulated in beta-cells by glucose and decreases glucose-stimulated insulin secretion

Chronically elevated levels of glucose impair pancreatic beta-cell function while inducing beta-cell proliferation. MicroRNA-29a (miR-29a) levels are increased in several tissues in diabetic animals and mediate decreased insulin-stimulated glucose-transport of adipocytes. The aim was to investigate the impact of glucose on miR-29a levels in INS-1E beta-cells and in human islets of Langerhans and furthermore to evaluate the impact of miR-29a on beta-cell function and proliferation. Increased glucose levels up-regulated miR-29a in beta-cells and human and rat islets of Langerhans. Glucose-stimulated insulin-secretion (GSIS) of INS-1E beta-cells was decreased by forced expression of miR-29a, while depletion of endogenous miR-29a improved GSIS. Over-expression of miR-29a increased INS-1E proliferation. Thus, miR-29a up-regulation is involved in glucose-induced proliferation of beta-cells. Furthermore, as depletion of miR-29a improves beta-cell function, miR-29a is a mediator of glucose-induced beta-cell dysfunction. Glucose-induced up-regulation of miR-29a in beta-cells could be implicated in progression from impaired glucose tolerance to type 2 diabetes.

Effect of Fluoride on the Secretion of Insulin in the Rat

Sodium fluoride (CAS 7681-49-4) 5-20 micromol/L in the extracellular space inhibited insulin secretion by isolated Langerhans islets stimulated with glucose. Insulin secretion followed a negative exponential function. This phenomenon is rapidly reversible. Perfusion of pancreatic tissue (rat) in vivo with stimulatory levels of glucose revealed that 20 micromol/L fluoride in the perfusion fluid inhibited the initial and sustained phases of insulin secretion to 15% of that of controls. The stimulatory effects of the ionophore A23187, phorbol-ester and forskolin on the secretion of insulin of isolated rat Langerhans islets in vitro were inhibited by 20 micromol/L fluoride. The results suggested that fluoride affects some stage of insulin secretion situated below the cascade of events that include the participation of calmodulin, protein-kinase C and cyclic AMP.