Vitamin D Switches BAF Complexes to Protect β Cells.
Wei Zong,Yoshihara Eiji,He Nanhai,Hah Nasun,Fan Weiwei,Pinto Antonio F M,Huddy Timothy,Wang Yuhao,Ross Brittany,Estepa Gabriela,Dai Yang,Ding Ning,Sherman Mara H,Fang Sungsoon,Zhao Xuan,Liddle Christopher,Atkins Annette R,Yu Ruth T,Downes Michael,Evans Ronald M
A primary cause of disease progression in type 2 diabetes (T2D) is β cell dysfunction due to inflammatory stress and insulin resistance. However, preventing β cell exhaustion under diabetic conditions is a major therapeutic challenge. Here, we identify the vitamin D receptor (VDR) as a key modulator of inflammation and β cell survival. Alternative recognition of an acetylated lysine in VDR by bromodomain proteins BRD7 and BRD9 directs association to PBAF and BAF chromatin remodeling complexes, respectively. Mechanistically, ligand promotes VDR association with PBAF to effect genome-wide changes in chromatin accessibility and enhancer landscape, resulting in an anti-inflammatory response. Importantly, pharmacological inhibition of BRD9 promotes PBAF-VDR association to restore β cell function and ameliorate hyperglycemia in murine T2D models. These studies reveal an unrecognized VDR-dependent transcriptional program underpinning β cell survival and identifies the VDR:PBAF/BAF association as a potential therapeutic target for T2D.
Effect of CAPE-pNO against type 2 diabetes mellitus via the AMPK/GLUT4/ GSK3β/PPARα pathway in HFD/STZ-induced diabetic mice.
Li Sai,Huang Qin,Zhang Liwen,Qiao Xufang,Zhang Yanyan,Tang Fashu,Li Zhubo
European journal of pharmacology
CAPE-pNO, a para-nitro derivative of caffeic acid phenethyl ester (CAPE), has been proved to exert stronger effects on diabetic complications in diabetic mice. The present study aimed at probing into the effect and potential mechanism of CAPE-pNO in type 2 diabetes mellitus (T2DM) compared with CAPE on model animal. Diabetic model was established by feeding one month of high-fat-diet (HFD) before injection of 40 mg/kg streptozotocin (STZ) for five days, and the normal diet mice were set as control group. Model mice were treated by CAPE-pNO for one month again, the levels of blood glucose, blood lipid and blood insulin significantly decreased. In addition, the myocardial enzymes (creatine Kinase and lactate dehydrogenase) and liver transaminase (aspartate aminotransferase and alanine aminotransferase) activities decreased. Furthermore, CAPE-pNO could alleviate pancreatic damage, myocardial injury and hepatic steatosis caused by diabetes mellitus, and significantly improved the islet mass, β cell survival and the hepatic glycogen content. Besides, CAPE-pNO enhanced the expression of phosphorylation-AMP-activated protein kinas (p-AMPK) (Thr172), GLUT4, peroxisome proliferator-activated receptor-α (PPARα) and p-Akt (Ser473), and inhibited the expression of glycogen synthase kinase 3β (GSK3β) and p-JNK (Thr183/Tyr185) in liver. All of those effects are better than CAPE generally. It suggested that CAPE-pNO ameliorated type 2 diabetes mellitus by effectively protecting islet β cell and improving the insulin resistance via the AMPK/GLUT4/GSK3β/PPARα pathway.
An Zebrafish Model for Interrogating ROS-Mediated Pancreatic -Cell Injury, Response, and Prevention.
Kulkarni Abhishek A,Conteh Abass M,Sorrell Cody A,Mirmira Anjali,Tersey Sarah A,Mirmira Raghavendra G,Linnemann Amelia K,Anderson Ryan M
Oxidative medicine and cellular longevity
It is well known that a chronic state of elevated reactive oxygen species (ROS) in pancreatic -cells impairs their ability to release insulin in response to elevated plasma glucose. Moreover, at its extreme, unmitigated ROS drives regulated cell death. This dysfunctional state of ROS buildup can result both from genetic predisposition and environmental factors such as obesity and overnutrition. Importantly, excessive ROS buildup may underlie metabolic pathologies such as type 2 diabetes mellitus. The ability to monitor ROS dynamics in -cells in situ and to manipulate it via genetic, pharmacological, and environmental means would accelerate the development of novel therapeutics that could abate this pathology. Currently, there is a lack of models with these attributes that are available to the field. In this study, we use a zebrafish model to demonstrate that ROS can be generated in a -cell-specific manner using a hybrid chemical genetic approach. Using a transgenic nitroreductase-expressing zebrafish line, , treated with the prodrug metronidazole (MTZ), we found that ROS is rapidly and explicitly generated in -cells. Furthermore, the level of ROS generated was proportional to the dosage of prodrug added to the system. At high doses of MTZ, caspase 3 was rapidly cleaved, -cells underwent regulated cell death, and macrophages were recruited to the islet to phagocytose the debris. Based on our findings, we propose a model for the mechanism of NTR/MTZ action in transgenic eukaryotic cells and demonstrate the robust utility of this system to model ROS-related disease pathology.
PAR2 regulates regeneration, transdifferentiation, and death.
Piran Ron,Lee Seung-Hee,Kuss Pia,Hao Ergeng,Newlin Robbin,Millán José Luis,Levine Fred
Cell death & disease
Understanding the mechanisms by which cells sense and respond to injury is central to developing therapies to enhance tissue regeneration. Previously, we showed that pancreatic injury consisting of acinar cell damage+β-cell ablation led to islet cell transdifferentiation. Here, we report that the molecular mechanism for this requires activating protease-activated receptor-2 (PAR2), a G-protein-coupled receptor. PAR2 modulation was sufficient to induce islet cell transdifferentiation in the absence of β-cells. Its expression was modulated in an islet cell type-specific manner in murine and human type 1 diabetes (T1D). In addition to transdifferentiation, PAR2 regulated β-cell apoptosis in pancreatitis. PAR2's role in regeneration is broad, as mice lacking PAR2 had marked phenotypes in response to injury in the liver and in digit regeneration following amputation. These studies provide a pharmacologically relevant target to induce tissue regeneration in a number of diseases, including T1D.
Sonodynamic therapy inhibits palmitate-induced beta cell dysfunction via PINK1/Parkin-dependent mitophagy.
Guo Tian,Liu Tianyang,Sun Yun,Liu Xianna,Xiong Rongguo,Li He,Li Zhitao,Zhang Zhiguo,Tian Zhen,Tian Ye
Cell death & disease
In type 2 diabetes mellitus (T2DM), the overload of glucose and lipids can promote oxidative stress and inflammatory responses and contribute to the failure of beta cells. However, therapies that can modulate the function of beta cells and thus prevent their failure have not been well explored. In this study, beta cell injury model was established with palmitic acid (PA) to simulate the lipotoxicity (high-fat diet) found in T2DM. Sonodynamic therapy (SDT), a novel physicochemical treatment, was applied to treat injured beta cells. We found that SDT had specific effects on mitochondria and induced transient large amount of mitochondrial reactive oxygen species (ROS) production in beta cells. SDT also improved the morphology and function of abnormal mitochondria, inhibited inflammatory response and reduced beta cell dysfunction. The improvement of mitochondria was mediated by PINK1/Parkin-dependent mitophagy. Additionally, SDT rescued the transcription of PINK1 mRNA which was blocked by PA treatment, thus providing abundant PINK1 for mitophagy. Moreover, SDT also increased insulin secretion from beta cells. The protective effects of SDT were abrogated when mitophagy was inhibited by cyclosporin A (CsA). In summary, SDT potently inhibits lipotoxicity-induced beta cell failure via PINK1/Parkin-dependent mitophagy, providing theoretical guidance for T2DM treatment in aspects of islet protection.
Anthocyanins from Chinese bayberry extract activate transcription factor Nrf2 in β cells and negatively regulate oxidative stress-induced autophagy.
Zhang Bo,Buya Miranbieke,Qin Wenjie,Sun Chongde,Cai Haolei,Xie Qiuping,Xu Bing,Wu Yulian
Journal of agricultural and food chemistry
Islet replacement is a promising cure for insulin-dependent diabetes but is limited by a massive early cell death following transplantation. Overburden oxidative stress is one of the major factors causing cell damage. We have shown previously that anthocyanins in Chinese bayberry extract protected β cells (INS-1) from hydrogen peroxide (H₂O₂)-induced apoptosis and decreased grafts' apoptosis after transplantation partially through heme oxygenase-1 (HO-1) up-regulation. In the present study, we observed that H₂O₂ stimulation induced autophagy in β cells. Inhibition of autophagy increased cell viability and decreased cell death. Anthocyanin pretreatment attenuated oxidative stress-mediated autophagic cell death. Anthocyanins activated antioxidant transcription factor Nrf2 in INS-1 cells, and Nrf2/HO-1 negatively regulated autophagy process. Furthermore, we here demonstrate that autophagy also took place in β cell grafts during the early post-transplantation phase. β Cells pretreated with anthocyanins displayed decreased extent of autophagy after transplantation. Taken together, these findings further supported the conclusion that anthocyanins could serve as a protective agent of β cells and suggested that autophagy might play a role in β cells during transplantation.
Leea macrophylla root extract upregulates the mRNA expression for antioxidative enzymes and repairs the necrosis of pancreatic β-cell and kidney tissues in fructose-fed Type 2 diabetic rats.
Mawa Jannatul,Rahman Md Atiar,Hashem M A,Juwel Hosen Md
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie
This research investigated the functional food effect of Leea macrophylla (Roxb.) ex Hornem root extract on pancreatic necrosis in Streptozotocin-induced type-2 diabetes. Prior to animal intervention, Leea macrophylla root extract (LMR) was subjected to GC-MS analysis. Across a three-week intervention of fructose-fed albino model with LMR50, LMR100 and LMR200, the fluid & food intake, body weight changes, weekly blood glucose concentrations and oral glucose tolerance (OGT) were recorded. The animals were sacrificed after intervention and serum was analyzed for insulin, ALT, AST, LDH, CK-MB, creatinine, uric acid and lipid profile and liver section was used for glycogen estimation. Changes of pancreas and kidney architecture were evaluated by histopathology. Relative mRNA for superoxide dismutase 1 (SOD1), glutathione peroxidase (GPx) and catalase (CAT) were quantitated using assay kits. Results showed that fluid and food intake, weekly blood glucose level, ALT, AST, LDH, CK-MB level were significantly (p < 0.05) decreased in LMR50 group. Conversely, the glucose tolerance ability, liver glycogen level, serum insulin, organ weight and pancreatic morphology were improved significantly in this group. Diameter of islet of Langerhans (μm), area occupied by β-cell/ islet of Langerhans (μm) and number of β-cells/islet of Langerhans were amazingly improved to the NC animals. Expressions of mRNA for SOD1 and CAT from liver tissue have been found to be increased multifold while GPx was remained unchanged. The data suggests that L. macrophylla root extract could be very potential as functional food to modulate pancreatic action.
Salvianolic acid B inhibits the amyloid formation of human islet amyloid polypeptide and protects pancreatic beta-cells against cytotoxicity.
Cheng Biao,Gong Hao,Li Xiaochao,Sun Yue,Chen Hong,Zhang Xin,Wu Qian,Zheng Ling,Huang Kun
The misfolding of human islet amyloid polypeptide (hIAPP) is regarded as one of the causative factors of type 2 diabetes mellitus (T2DM). Salvia miltiorrhiza (Danshen), one of the most commonly used of traditional Chinese medicines, is often used in Compound Recipes for treating diabetes, however with unclear mechanisms. Since salvianolic acid B (SalB) is the most abundant bioactive ingredient of salvia miltiorrhiza water-extract. In this study, we tested whether SalB has any effect on the amyloidogenicity of hIAPP. Our results clearly suggest that SalB can significantly inhibit the formation of hIAPP amyloid and disaggregate hIAPP fibrils. Furthermore, photo-crosslinking based oligomerization studies suggest SalB significantly suppresses the toxic oligomerization of hIAPP monomers. Cytotoxicity protection effects on pancreatic INS-1 cells by SalB were also observed using MTT-based assays, potentially due to the inhibition on the membrane disruption effects and attenuated mitochondria impairment induced by hIAPP. These results provide evidence that SalB may further be studied on the possible pharmacological treatment for T2DM.
Selenium-enriched Spirulina protects INS-1E pancreatic beta cells from human islet amyloid polypeptide-induced apoptosis through suppression of ROS-mediated mitochondrial dysfunction and PI3/AKT pathway.
Li Xiao-Ling,Wong Yum-Shing,Xu Gang,Chan Juliana C N
European journal of nutrition
PURPOSE:Human islet amyloid polypeptide (hIAPP) aggregation is linked to loss of pancreatic beta cells in type 2 diabetes, in part due to oxidative stress. Currently, little is known about the effects of selenium-enriched Spirulina on beta cells with the presence of hIAPP. In this study, INS-1E rat insulinoma cells were used as a model to evaluate in vitro protective effects of Se-enriched Spirulina extract (Se-SE) against hIAPP-induced cell death, as well as the underlying mechanisms. METHODS:Flow cytometric analysis was used to evaluate cell apoptosis, mitochondrial membrane potential (ΔΨm) and ROS generation. Caspase activity was measured using a fluorometric method. Western blotting was applied to detect protein expression. RESULTS:Our results showed that exposure of INS-1E cells to hIAPP resulted in cell viability loss, LDH release and appearance of sub-G peak. However, cytotoxicity of hIAPP was significantly attenuated by co-treatment with Se-SE. Se-SE also inhibited hIAPP-induced activation of caspase-3, -8 and -9. Additionally, hIAPP-induced accumulation of ROS and superoxide was suppressed by co-treatment with Se-SE. Moreover, Se-SE was able to prevent hIAPP-induced depletion of ΔΨm and intracellular ATP, reduction in mitochondrial mass, changes in the expression of Bcl-2 family members, release of mitochondrial apoptogenic factors. Furthermore, hIAPP-mediated AKT inhibition was restored by co-treatment with Se-SE. CONCLUSION:Our results showed that Se-SE protects INS-1E cells from hIAPP-induced cell death through preventing ROS overproduction, mitochondrial dysfunction and modulating PI3K/AKT pathway.
Centaurium erythraea extract improves survival and functionality of pancreatic beta-cells in diabetes through multiple routes of action.
Đorđević Miloš,Grdović Nevena,Mihailović Mirjana,Arambašić Jovanović Jelena,Uskoković Aleksandra,Rajić Jovana,Sinadinović Marija,Tolić Anja,Mišić Danijela,Šiler Branislav,Poznanović Goran,Vidaković Melita,Dinić Svetlana
Journal of ethnopharmacology
ETHNOPHARMACOLOGICAL RELEVANCE:Centaurium erythraea Rafn (CE) is used as a traditional medicinal plant in Serbia to treat different ailments due to its antidiabetic, antipyretic, antiflatulent and detoxification effects. AIM OF THE STUDY:Elucidation of the mechanisms that underlie the antioxidant and pro-survival effects of the CE extract (CEE) in beta-cells and pancreatic islets from streptozotocin (STZ)-treated diabetic rats. MATERIAL AND METHODS:Diabetes was induced in rats by multiple applications of low doses of STZ (40 mg/kg intraperitoneally (i.p.), for five consecutive days). CEE (100 mg/kg) was administered orally, in the pre-treated group for two weeks before diabetes induction, during the treatments with STZ and for four weeks after diabetes onset, and in the post-treatment group for four weeks after diabetes induction. The impact of CEE on diabetic islets was estimated by histological and immunohistochemical examination of the pancreas. Molecular mechanisms of the effects of CEE were also analyzed in insulinoma Rin-5F cells treated with STZ (12 mM) and CEE (0.25 mg/mL). Oxidative stress was evaluated by assessing the levels of DNA damage, lipid peroxidation, protein S-glutathionylation and enzymatic activities and expression of CAT, MnSOD, CuZnSOD, GPx and GR in beta-cells. The presence and activities of the redox-sensitive and islet-enriched regulatory proteins were also analyzed. RESULTS:Treatment with CEE ameliorated the insulin level and glycemic control in STZ-induced diabetic rats by improving the structural and functional properties of pancreatic islets through multiple routes of action. The disturbance of islet morphology and islet cell contents in diabetes was reduced by the CEE treatment and was associated with a protective effect of CEE on the levels of insulin, GLUT-2 and p-Akt in diabetic islets. The antioxidant effect of CEE on STZ-treated beta-cells was displayed as reduced DNA damage, lipid peroxidation, protein S-glutathionylation and alleviation of STZ-induced disruption in MnSOD, CuZnSOD and CAT enzyme activities. The oxidative stress-induced disturbance of the transcriptional regulation of CAT, MnSOD, CuZnSOD, GPx and GR enzymes in beta-cells was improved after the CEE treatment, and was observed as readjustment of the presence and activities of redox-sensitive NFκB-p65, FOXO3A, Sp1 and Nrf-2 transcription factors. The observed CEE-mediated induction of proliferative and pro-survival pathways and insulin expression/secretion after STZ-induced oxidative stress in beta-cells could be partially attributed to a fine-tuned modulation of the activities of pro-survival Akt, ERK and p38 kinases and islet-enriched Pdx-1 and MafA regulatory factors. CONCLUSIONS:The results of this study provide evidence that CEE improves the structural and functional properties of pancreatic beta-cells by correcting the endogenous antioxidant regulatory mechanisms and by promoting proliferative and pro-survival pathways in beta-cells.
Reduced Insulin Production Relieves Endoplasmic Reticulum Stress and Induces β Cell Proliferation.
Szabat Marta,Page Melissa M,Panzhinskiy Evgeniy,Skovsø Søs,Mojibian Majid,Fernandez-Tajes Juan,Bruin Jennifer E,Bround Michael J,Lee Jason T C,Xu Eric E,Taghizadeh Farnaz,O'Dwyer Shannon,van de Bunt Martijn,Moon Kyung-Mee,Sinha Sunita,Han Jun,Fan Yong,Lynn Francis C,Trucco Massimo,Borchers Christoph H,Foster Leonard J,Nislow Corey,Kieffer Timothy J,Johnson James D
Pancreatic β cells are mostly post-mitotic, but it is unclear what locks them in this state. Perturbations including uncontrolled hyperglycemia can drive β cells into more pliable states with reduced cellular insulin levels, increased β cell proliferation, and hormone mis-expression, but it is unknown whether reduced insulin production itself plays a role. Here, we define the effects of ∼50% reduced insulin production in Ins1(-/-):Ins2(f/f):Pdx1Cre(ERT):mTmG mice prior to robust hyperglycemia. Transcriptome, proteome, and network analysis revealed alleviation of chronic endoplasmic reticulum (ER) stress, indicated by reduced Ddit3, Trib3, and Atf4 expression; reduced Xbp1 splicing; and reduced phospho-eIF2α. This state was associated with hyper-phosphorylation of Akt, which is negatively regulated by Trib3, and with cyclinD1 upregulation. Remarkably, β cell proliferation was increased 2-fold after reduced insulin production independently of hyperglycemia. Eventually, recombined cells mis-expressed glucagon in the hyperglycemic state. We conclude that the normally high rate of insulin production suppresses β cell proliferation in a cell-autonomous manner.
VMP1-related autophagy induced by a fructose-rich diet in β-cells: its prevention by incretins.
Maiztegui Bárbara,Boggio Verónica,Román Carolina L,Flores Luis E,Zotto Héctor Del,Ropolo Alejandro,Grasso Daniel,Vaccaro María I,Gagliardino Juan J
Clinical science (London, England : 1979)
The aim of the present study was to demonstrate the role of autophagy and incretins in the fructose-induced alteration of β-cell mass and function. Normal Wistar rats were fed (3 weeks) with a commercial diet without (C) or with 10% fructose in drinking water (F) alone or plus sitagliptin (CS and FS) or exendin-4 (CE and FE). Serum levels of metabolic/endocrine parameters, β-cell mass, morphology/ultrastructure and apoptosis, vacuole membrane protein 1 (VMP1) expression and glucose-stimulated insulin secretion (GSIS) were studied. Complementary to this, islets isolated from normal rats were cultured (3 days) without (C) or with F and F + exendin-4 or chloroquine. Expression of autophagy-related proteins [VMP1 and microtubule-associated protein light chain 3 (LC3)], apoptotic/antiapoptotic markers (caspase-3 and Bcl-2), GSIS and insulin mRNA levels were measured. F rats developed impaired glucose tolerance (IGT) and a significant increase in plasma triacylglycerols, thiobarbituric acid-reactive substances, insulin levels, homoeostasis model assessment (HOMA) for insulin resistance (HOMA-IR) and β-cell function (HOMA-β) indices. A significant reduction in β-cell mass was associated with an increased apoptotic rate and morphological/ultrastructural changes indicative of autophagic activity. All these changes were prevented by either sitagliptin or exendin-4. In cultured islets, F significantly enhanced insulin mRNA and GSIS, decreased Bcl-2 mRNA levels and increased caspase-3 expression. Chloroquine reduced these changes, suggesting the participation of autophagy in this process. Indeed, F induced the increase of both VMP1 expression and LC3-II, suggesting that VMP1-related autophagy is activated in injured β-cells. Exendin-4 prevented islet-cell damage and autophagy development. VMP1-related autophagy is a reactive process against F-induced islet dysfunction, being prevented by exendin-4 treatment. This knowledge could help in the use of autophagy as a potential target for preventing progression from IGT to type 2 diabetes mellitus.
Glucagon is essential for alpha cell transdifferentiation and beta cell neogenesis.
Ye Lihua,Robertson Morgan A,Hesselson Daniel,Stainier Didier Y R,Anderson Ryan M
Development (Cambridge, England)
The interconversion of cell lineages via transdifferentiation is an adaptive mode of tissue regeneration and an appealing therapeutic target. However, its clinical exploitation is contingent upon the discovery of contextual regulators of cell fate acquisition and maintenance. In murine models of diabetes, glucagon-secreting alpha cells transdifferentiate into insulin-secreting beta cells following targeted beta cell depletion, regenerating the form and function of the pancreatic islet. However, the molecular triggers of this mode of regeneration are unknown. Here, using lineage-tracing assays in a transgenic zebrafish model of beta cell ablation, we demonstrate conserved plasticity of alpha cells during islet regeneration. In addition, we show that glucagon expression is upregulated after injury. Through gene knockdown and rescue approaches, we also find that peptides derived from the glucagon gene are necessary for alpha-to-beta cell fate switching. Importantly, whereas beta cell neogenesis was stimulated by glucose, alpha-to-beta cell conversion was not, suggesting that transdifferentiation is not mediated by glucagon/GLP-1 control of hepatic glucose production. Overall, this study supports the hypothesis that alpha cells are an endogenous reservoir of potential new beta cells. It further reveals that glucagon plays an important role in maintaining endocrine cell homeostasis through feedback mechanisms that govern cell fate stability.
Proteasomal degradation of the histone acetyl transferase p300 contributes to beta-cell injury in a diabetes environment.
Ruiz Lucie,Gurlo Tatyana,Ravier Magalie A,Wojtusciszyn Anne,Mathieu Julia,Brown Matthew R,Broca Christophe,Bertrand Gyslaine,Butler Peter C,Matveyenko Aleksey V,Dalle Stéphane,Costes Safia
Cell death & disease
In type 2 diabetes, amyloid oligomers, chronic hyperglycemia, lipotoxicity, and pro-inflammatory cytokines are detrimental to beta-cells, causing apoptosis and impaired insulin secretion. The histone acetyl transferase p300, involved in remodeling of chromatin structure by epigenetic mechanisms, is a key ubiquitous activator of the transcriptional machinery. In this study, we report that loss of p300 acetyl transferase activity and expression leads to beta-cell apoptosis, and most importantly, that stress situations known to be associated with diabetes alter p300 levels and functional integrity. We found that proteasomal degradation is the mechanism subserving p300 loss in beta-cells exposed to hyperglycemia or pro-inflammatory cytokines. We also report that melatonin, a hormone produced in the pineal gland and known to play key roles in beta-cell health, preserves p300 levels altered by these toxic conditions. Collectively, these data imply an important role for p300 in the pathophysiology of diabetes.
Ets-1 as an early response gene against hypoxia-induced apoptosis in pancreatic β-cells.
Qiao N,Xu C,Zhu Y-X,Cao Y,Liu D-C,Han X
Cell death & disease
Hypoxia complicates islet isolation for transplantation and may contribute to pancreatic β-cell failure in type 2 diabetes. Pancreatic β-cells are susceptible to hypoxia-induced apoptosis. Severe hypoxic conditions during the immediate post-transplantation period are a main non-immune factor leading to β-cell death and islet graft failure. In this study, we identified the transcription factor Ets-1 (v-ets erythroblastosis virus E26 oncogene homolog 1) as an early response gene against hypoxia-induced apoptosis in pancreatic β-cells. Hypoxia regulates Ets-1 at multiple levels according to the degree of β-cell oxygen deprivation. Moderate hypoxia promotes Ets-1 gene transcription, whereas severe hypoxia promotes its transactivation activity, as well as its ubiquitin-proteasome mediated degradation. This degradation causes a relative insufficiency of Ets-1 activity, and limits the transactivation effect of Ets-1 on downstream hypoxic-inducible genes and its anti-apoptotic function. Overexpression of ectopic Ets-1 in MIN6 and INS-1 cells protects them from severe hypoxia-induced apoptosis in a mitochondria-dependent manner, confirming that a sufficient amount of Ets-1 activity is critical for protection of pancreatic β-cells against hypoxic injury. Targeting Ets-1 expression may be a useful strategy for islet graft protection during the immediate post-transplantation period.
Androgen excess in pancreatic β cells and neurons predisposes female mice to type 2 diabetes.
Navarro Guadalupe,Allard Camille,Morford Jamie J,Xu Weiwei,Liu Suhuan,Molinas Adrien Jr,Butcher Sierra M,Fine Nicholas Hf,Blandino-Rosano Manuel,Sure Venkata N,Yu Sangho,Zhang Rui,Münzberg Heike,Jacobson David A,Katakam Prasad V,Hodson David J,Bernal-Mizrachi Ernesto,Zsombok Andrea,Mauvais-Jarvis Franck
Androgen excess predisposes women to type 2 diabetes (T2D), but the mechanism of this is poorly understood. We report that female mice fed a Western diet and exposed to chronic androgen excess using dihydrotestosterone (DHT) exhibit hyperinsulinemia and insulin resistance associated with secondary pancreatic β cell failure, leading to hyperglycemia. These abnormalities are not observed in mice lacking the androgen receptor (AR) in β cells and partially in neurons of the mediobasal hypothalamus (MBH) as well as in mice lacking AR selectively in neurons. Accordingly, i.c.v. infusion of DHT produces hyperinsulinemia and insulin resistance in female WT mice. We observe that acute DHT produces insulin hypersecretion in response to glucose in cultured female mouse and human pancreatic islets in an AR-dependent manner via a cAMP- and mTOR-dependent pathway. Acute DHT exposure increases mitochondrial respiration and oxygen consumption in female cultured islets. As a result, chronic DHT exposure in vivo promotes islet oxidative damage and susceptibility to additional stress induced by streptozotocin via AR in β cells. This study suggests that excess androgen predisposes female mice to T2D following AR activation in neurons, producing peripheral insulin resistance, and in pancreatic β cells, promoting insulin hypersecretion, oxidative injury, and secondary β cell failure.
Islet neuropeptide Y receptors are functionally conserved and novel targets for the preservation of beta-cell mass.
Franklin Zara J,Tsakmaki Anastasia,Fonseca Pedro Patricia,King Aileen J,Huang Guo Cai,Amjad Sakeena,Persaud Shanta J,Bewick Gavin A
Diabetes, obesity & metabolism
AIMS:Two unmet therapeutic strategies for diabetes treatment are prevention of beta-cell death and stimulation of beta-cell replication. Our aim was to characterize the role of neuropeptide Y receptors in the control of beta-cell mass. MATERIALS AND METHODS:We used endogenous and selective agonists of the NPY receptor system to explore its role in the prevention of beta-cell apoptosis and proliferation in islets isolated from both mouse and human donors. We further explored the intra-cellular signalling cascades involved, using chemical inhibitors of key signalling pathways. As proof of principle we designed a long-acting analogue of [Leu Pro ]-NPY, an agonist of the islet-expressed Y receptors, to determine if targeting this system could preserve beta-cell mass in vivo. RESULTS:Our data reveal that NPY Y1, 4 and 5 receptor activation engages a generalized and powerful anti-apoptotic pathway that protects mouse and human islets from damage. These anti-apoptotic effects were dependent on stimulating a Gαi-PLC-PKC signalling cascade, which prevented cytokine-induced NFkB signalling. NPY receptor activation functionally protected islets by restoring glucose responsiveness following chemically induced injury in both species. NPY receptor activation attenuated beta-cell apoptosis, preserved functional beta-cell mass and attenuated the hyperglycaemic phenotype in a low-dose streptozotocin model of diabetes. CONCLUSION:Taken together, our observations identify the islet Y receptors as promising targets for the preservation of beta-cell mass. As such, targeting these receptors could help to maintain beta-cell mass in both type 1 and type 2 diabetes, and may also be useful for improving islet transplantation outcomes.
Sources of beta cells inside the pancreas.
De Groef Sofie,Staels Willem,Van Gassen Naomi,Lemper Marie,Yuchi Yixing,Sojoodi Mozhdeh,Bussche Leen,Heremans Yves,Leuckx Gunter,De Leu Nico,Van de Casteele Mark,Baeyens Luc,Heimberg Harry
The generation of beta(-like) cells to compensate for their absolute or relative shortage in type 1 and type 2 diabetes is an obvious therapeutic strategy. Patients first received grafts of donor islet cells over 25 years ago, but this procedure has not become routine in clinical practice because of a donor cell shortage and (auto)immune problems. Transplantation of differentiated embryonic and induced pluripotent stem cells may overcome some but not all the current limitations. Reprogramming exocrine cells towards functional beta(-like) cells would offer an alternative abundant and autologous source of beta(-like) cells. This review focuses on work by our research group towards achieving such a source of cells. It summarises a presentation given at the 'Can we make a better beta cell?' symposium at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Amin Ardestani and Kathrin Maedler, DOI: 10.1007/s00125-016-3892-9 , and by Heiko Lickert and colleagues, DOI: 10.1007/s00125-016-3949-9 ) and a commentary by the Session Chair, Shanta Persaud (DOI: 10.1007/s00125-016-3870-2 ).
MicroRNAs 106b and 222 Improve Hyperglycemia in a Mouse Model of Insulin-Deficient Diabetes via Pancreatic β-Cell Proliferation.
Tsukita Sohei,Yamada Tetsuya,Takahashi Kei,Munakata Yuichiro,Hosaka Shinichiro,Takahashi Hironobu,Gao Junhong,Shirai Yuta,Kodama Shinjiro,Asai Yoichiro,Sugisawa Takashi,Chiba Yumiko,Kaneko Keizo,Uno Kenji,Sawada Shojiro,Imai Junta,Katagiri Hideki
Major symptoms of diabetes mellitus manifest, once pancreatic β-cell numbers have become inadequate. Although natural regeneration of β-cells after injury is very limited, bone marrow (BM) transplantation (BMT) promotes their regeneration through undetermined mechanism(s) involving inter-cellular (BM cell-to-β-cell) crosstalk. We found that two microRNAs (miRNAs) contribute to BMT-induced β-cell regeneration. Screening murine miRNAs in serum exosomes after BMT revealed 42 miRNAs to be increased. Two of these miRNAs (miR-106b-5p and miR-222-3p) were shown to be secreted by BM cells and increased in pancreatic islet cells after BMT. Treatment with the corresponding anti-miRNAs inhibited BMT-induced β-cell regeneration. Furthermore, intravenous administration of the corresponding miRNA mimics promoted post-injury β-cell proliferation through Cip/Kip family down-regulation, thereby ameliorating hyperglycemia in mice with insulin-deficient diabetes. Thus, these identified miRNAs may lead to the development of therapeutic strategies for diabetes.
Variability in endocrine cell identity in patients with chronic pancreatitis undergoing islet autotransplantation.
Beamish Christine A,Gaber A Osama,Afshar Solmaz F,Fraga Daniel W,Hamilton Dale J,Sabek Omaima M
American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons
Beta-cell dedifferentiation as shown by cellular colocalization of insulin with glucagon and/or vimentin, and decreased expression of MAFA and/or urocortin3 has been suggested to contribute to metabolic decompensation in type 2 diabetes, and was recently described postimplantation in islet allotransplant patients. Dysglycaemia and diabetes mellitus are often encountered preoperatively in patients undergoing pancreatectomy and islet autotransplantation (PIAT). In this series of case reports, we document variation in islet phenotypic identity in three patients with chronic pancreatitis (CP) without diabetes or significant insulin resistance who subsequently underwent PIAT. Pancreas histology was examined using colocalization of endocrine hormones, mesenchymal and pan-endocrine markers in islets, and the relative expression of MAFA and urocortin3 in insulin-expressing cells as compared to that of nondiabetic and type 2 diabetic donors. We present results of pre- and posttransplant clinical metabolic testing. Varying degrees of islet-cell dedifferentiation are identified in nondiabetic patients with CP at the time of PIAT, and may need further investigation.
Proinflammatory Cytokines Induce Endocrine Differentiation in Pancreatic Ductal Cells via STAT3-Dependent NGN3 Activation.
Valdez Ivan Achel,Dirice Ercument,Gupta Manoj K,Shirakawa Jun,Teo Adrian Kee Keong,Kulkarni Rohit N
A major goal of diabetes research is to develop strategies that replenish pancreatic insulin-producing beta cells. One emerging strategy is to harness pancreatic plasticity-the ability of pancreatic cells to undergo cellular interconversions-a phenomenon implicated in physiological stress and pancreatic injury. Here, we investigate the effects of inflammatory cytokine stress on the differentiation potential of ductal cells in a human cell line, in mouse ductal cells by pancreatic intraductal injection, and during the progression of autoimmune diabetes in the non-obese diabetic (NOD) mouse model. We find that inflammatory cytokine insults stimulate epithelial-to-mesenchymal transition (EMT) as well as the endocrine program in human pancreatic ductal cells via STAT3-dependent NGN3 activation. Furthermore, we show that inflammatory cytokines activate ductal-to-endocrine cell reprogramming in vivo independent of hyperglycemic stress. Together, our findings provide evidence that inflammatory cytokines direct ductal-to-endocrine cell differentiation, with implications for beta cell regeneration.
Harnessing CXCL12 signaling to protect and preserve functional β-cell mass and for cell replacement in type 1 diabetes.
Alagpulinsa David A,Cao Jenny J L,Sobell Don,Poznansky Mark C
Pharmacology & therapeutics
Type 1 diabetes (T1D) is a complex multifactorial disease characterized by autoimmune destruction of insulin-producing pancreatic β cells. Our understanding of the pathogenic mechanisms and natural history of T1D has evolved significantly over the past two decades; we can efficiently predict high-risk individuals, early diagnose the disease and stage progression. Fortuitously, novel in vitro differentiation protocols for generating functional β-like cells from human pluripotent stem cells have been developed. These advances provide a definitive roadmap to implement realistic preventive and β-cell replacement therapies in T1D. Immunoprotection and preservation of functional β-cell mass are a sine qua non for the success of these interventions. The chemokine, stromal cell-derived factor-1alpha, known as CXCL12-α, is an attractive therapeutic target molecule in this context. CXCL12-α signaling promotes β-cell development, survival and regeneration and can mediate local immunomodulation in the pancreatic islets. Interestingly, CXCL12-α is robustly expressed in maturing insulin-producing β cells and in adult β cells during periods of injury and regeneration. However, under normal physiological settings, CXCL12-α is repressed in terminally differentiated mature β cells and islets. Here, we provide a comprehensive overview of the role of CXCL12-α signaling in β-cell biology, physiology and immune regulation. We discuss CXCL12-α signaling mechanisms that could be harnessed to modulate β-cell autoimmunity, protect and preserve functional β-cell mass and for cell replacement therapy in T1D.
TCF1 links GIPR signaling to the control of beta cell function and survival.
Campbell Jonathan E,Ussher John R,Mulvihill Erin E,Kolic Jelena,Baggio Laurie L,Cao Xiemen,Liu Yu,Lamont Benjamin J,Morii Tsukasa,Streutker Catherine J,Tamarina Natalia,Philipson Louis H,Wrana Jeffrey L,MacDonald Patrick E,Drucker Daniel J
The glucagon-like peptide-1 (GLP-1) receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor transduce nutrient-stimulated signals to control beta cell function. Although the GLP-1 receptor (GLP-1R) is a validated drug target for diabetes, the importance of the GIP receptor (GIPR) for the function of beta cells remains uncertain. We demonstrate that mice with selective ablation of GIPR in beta cells (MIP-Cre:Gipr(Flox/Flox); Gipr(-/-βCell)) exhibit lower levels of meal-stimulated insulin secretion, decreased expansion of adipose tissue mass and preservation of insulin sensitivity when compared to MIP-Cre controls. Beta cells from Gipr(-/-βCell) mice display greater sensitivity to apoptosis and markedly lower islet expression of T cell-specific transcription factor-1 (TCF1, encoded by Tcf7), a protein not previously characterized in beta cells. GIP, but not GLP-1, promotes beta cell Tcf7 expression via a cyclic adenosine monophosphate (cAMP)-independent and extracellular signal-regulated kinase (ERK)-dependent pathway. Tcf7 (in mice) or TCF7 (in humans) levels are lower in islets taken from diabetic mice and in humans with type 2 diabetes; knockdown of TCF7 in human and mouse islets impairs the cytoprotective responsiveness to GIP and enhances the magnitude of apoptotic injury, whereas restoring TCF1 levels in beta cells from Gipr(-/-βCell) mice lowers the number of apoptotic cells compared to that seen in MIP-Cre controls. Tcf7(-/-) mice show impaired insulin secretion, deterioration of glucose tolerance with either aging and/or high-fat feeding and increased sensitivity to beta cell injury relative to wild-type (WT) controls. Hence the GIPR-TCF1 axis represents a potential therapeutic target for preserving both the function and survival of vulnerable, diabetic beta cells.
Minireview: Emerging Concepts in Islet Macrophage Biology in Type 2 Diabetes.
Morris David L
Molecular endocrinology (Baltimore, Md.)
Chronic systemic inflammation is a hallmark feature of obesity and type 2 diabetes. Both resident and recruited islet macrophages contribute to the proinflammatory milieu of the diabetic islet. However, macrophages also appear to be critical for β-cell formation during development and support β-cell replication in experimental models of pancreas regeneration. In light of these findings, perhaps macrophages in the islet need to be viewed more as a fulcrum where deleterious inflammatory activation is balanced with beneficial tissue repair processes. Undoubtedly, defining the factors that contribute to the ontogeny, heterogeneity, and functionality of macrophages in normal, diseased, and regenerating islets will be necessary to determine whether that fulcrum can be moved to preserve functional β-cell mass in persons with diabetes. The intent of this review is to introduce the reader to emerging concepts of islet macrophage biology that may challenge the perception that macrophage accumulation in islets is merely a pathological feature of type 2 diabetes.
Systematic single-cell analysis provides new insights into heterogeneity and plasticity of the pancreas.
Tritschler Sophie,Theis Fabian J,Lickert Heiko,Böttcher Anika
BACKGROUND:Diabetes mellitus is characterized by loss or dysfunction of insulin-producing β-cells in the pancreas, resulting in failure of blood glucose regulation and devastating secondary complications. Thus, β-cells are currently the prime target for cell-replacement and regenerative therapy. Triggering endogenous repair is a promising strategy to restore β-cell mass and normoglycemia in diabetic patients. Potential strategies include targeting specific β-cell subpopulations to increase proliferation or maturation. Alternatively, transdifferentiation of pancreatic islet cells (e.g. α- or δ-cells), extra-islet cells (acinar and ductal cells), hepatocytes, or intestinal cells into insulin-producing cells might improve glycemic control. To this end, it is crucial to systematically characterize and unravel the transcriptional program of all pancreatic cell types at the molecular level in homeostasis and disease. Furthermore, it is necessary to better determine the underlying mechanisms of β-cell maturation, maintenance, and dysfunction in diabetes, to identify and molecularly profile endocrine subpopulations with regenerative potential, and to translate the findings from mice to man. Recent approaches in single-cell biology started to illuminate heterogeneity and plasticity in the pancreas that might be targeted for β-cell regeneration in diabetic patients. SCOPE OF REVIEW:This review discusses recent literature on single-cell analysis including single-cell RNA sequencing, single-cell mass cytometry, and flow cytometry of pancreatic cell types in the context of mechanisms of endogenous β-cell regeneration. We discuss new findings on the regulation of postnatal β-cell proliferation and maturation. We highlight how single-cell analysis recapitulates described principles of functional β-cell heterogeneity in animal models and adds new knowledge on the extent of β-cell heterogeneity in humans as well as its role in homeostasis and disease. Furthermore, we summarize the findings on cell subpopulations with regenerative potential that might enable the formation of new β-cells in diseased state. Finally, we review new data on the transcriptional program and function of rare pancreatic cell types and their implication in diabetes. MAJOR CONCLUSION:Novel, single-cell technologies offer high molecular resolution of cellular heterogeneity within the pancreas and provide information on processes and factors that govern β-cell homeostasis, proliferation, and maturation. Eventually, these technologies might lead to the characterization of cells with regenerative potential and unravel disease-associated changes in gene expression to identify cellular and molecular targets for therapy.
Transgenic expression of Hsc70 in pancreatic islets enhances autoimmune diabetes in response to beta cell damage.
Alam Masih-ul,Harken Julie A,Knorn Anna-Maria,Elford Alisha R,Wigmore Kip,Ohashi Pamela S,Millar Douglas G
Journal of immunology (Baltimore, Md. : 1950)
Inflammation following tissue damage promotes lymphocyte recruitment, tissue remodeling, and wound healing while maintaining self tolerance. Endogenous signals associated with tissue damage and cell death have been proposed to initiate and instruct immune responses following injury. In this study, we have examined the effects of elevated levels of a candidate endogenous danger signal, heat shock cognate protein 70 (hsc70), on stimulation of inflammation and autoimmunity following cell damage. We find that damage to pancreatic beta cells expressing additional cytosolic hsc70 leads to an increased incidence of diabetes in a transgenic mouse model. Steady-state levels of activated APC and T cell populations in the draining lymph node were enhanced, which further increased following streptozotocin-induced beta cell death. In addition, proinflammatory serum cytokines, and lymphocyte recruitment were increased in hsc70 transgenic mice. Islet Ag-specific T cells underwent a greater extent of proliferation in the lymph nodes of mice expressing hsc70 following beta cell damage, suggesting elevated Ag presentation following release of Ag in the presence of hsc70. These findings suggest that an elevated content of hsc70 in cells undergoing necrotic or apoptotic cell death can increase the extent of sterile inflammation and increase the susceptibility to autoimmunity.
Activation of the GLP-1 receptor signalling pathway: a relevant strategy to repair a deficient beta-cell mass.
Portha Bernard,Tourrel-Cuzin Cécile,Movassat Jamileh
Experimental diabetes research
Recent preclinical studies in rodent models of diabetes suggest that exogenous GLP-1R agonists and DPP-4 inhibitors have the ability to increase islet mass and preserve beta-cell function, by immediate reactivation of beta-cell glucose competence, as well as enhanced beta-cell proliferation and neogenesis and promotion of beta-cell survival. These effects have tremendous implication in the treatment of T2D because they directly address one of the basic defects in T2D, that is, beta-cell failure. In human diabetes, however, evidence that the GLP-1-based drugs alter the course of beta-cell function remains to be found. Several questions surrounding the risks and benefits of GLP-1-based therapy for the diabetic beta-cell mass are discussed in this review and require further investigation.
HDAC7 is overexpressed in human diabetic islets and impairs insulin secretion in rat islets and clonal beta cells.
Daneshpajooh Mahboubeh,Bacos Karl,Bysani Madhusudhan,Bagge Annika,Ottosson Laakso Emilia,Vikman Petter,Eliasson Lena,Mulder Hindrik,Ling Charlotte
AIMS/HYPOTHESIS:Pancreatic beta cell dysfunction is a prerequisite for the development of type 2 diabetes. Histone deacetylases (HDACs) may affect pancreatic endocrine function and glucose homeostasis through alterations in gene regulation. Our aim was to investigate the role of HDAC7 in human and rat pancreatic islets and clonal INS-1 beta cells (INS-1 832/13). METHODS:To explore the role of HDAC7 in pancreatic islets and clonal beta cells, we used RNA sequencing, mitochondrial functional analyses, microarray techniques, and HDAC inhibitors MC1568 and trichostatin A. RESULTS:Using RNA sequencing, we found increased HDAC7 expression in human pancreatic islets from type 2 diabetic compared with non-diabetic donors. HDAC7 expression correlated negatively with insulin secretion in human islets. To mimic the situation in type 2 diabetic islets, we overexpressed Hdac7 in rat islets and clonal beta cells. In both, Hdac7 overexpression resulted in impaired glucose-stimulated insulin secretion. Furthermore, it reduced insulin content, mitochondrial respiration and cellular ATP levels in clonal beta cells. Overexpression of Hdac7 also led to changes in the genome-wide gene expression pattern, including increased expression of Tcf7l2 and decreased expression of gene sets regulating DNA replication and repair as well as nucleotide metabolism. In accordance, Hdac7 overexpression reduced the number of beta cells owing to enhanced apoptosis. Finally, we found that inhibiting HDAC7 activity with pharmacological inhibitors or small interfering RNA-mediated knockdown restored glucose-stimulated insulin secretion in beta cells that were overexpressing Hdac7. CONCLUSIONS/INTERPRETATION:Taken together, these results indicate that increased HDAC7 levels caused beta cell dysfunction and may thereby contribute to defects seen in type 2 diabetic islets. Our study supports HDAC7 inhibitors as a therapeutic option for the treatment of type 2 diabetes.
Long-term persistence and development of induced pancreatic beta cells generated by lineage conversion of acinar cells.
Li Weida,Cavelti-Weder Claudia,Zhang Yingying,Zhang Yinying,Clement Kendell,Donovan Scott,Gonzalez Gabriel,Zhu Jiang,Stemann Marianne,Xu Ke,Hashimoto Tatsu,Yamada Takatsugu,Nakanishi Mio,Zhang Yuemei,Zeng Samuel,Gifford David,Meissner Alexander,Weir Gordon,Zhou Qiao
Direct lineage conversion is a promising approach to generate therapeutically important cell types for disease modeling and tissue repair. However, the survival and function of lineage-reprogrammed cells in vivo over the long term has not been examined. Here, using an improved method for in vivo conversion of adult mouse pancreatic acinar cells toward beta cells, we show that induced beta cells persist for up to 13 months (the length of the experiment), form pancreatic islet-like structures and support normoglycemia in diabetic mice. Detailed molecular analyses of induced beta cells over 7 months reveal that global DNA methylation changes occur within 10 d, whereas the transcriptional network evolves over 2 months to resemble that of endogenous beta cells and remains stable thereafter. Progressive gain of beta-cell function occurs over 7 months, as measured by glucose-regulated insulin release and suppression of hyperglycemia. These studies demonstrate that lineage-reprogrammed cells persist for >1 year and undergo epigenetic, transcriptional, anatomical and functional development toward a beta-cell phenotype.
Bone marrow mesenchymal stem cells promote the repair of islets from diabetic mice through paracrine actions.
Gao Xiaodong,Song Lujun,Shen Kuntang,Wang Hongshan,Qian Mengjia,Niu Weixin,Qin Xinyu
Molecular and cellular endocrinology
Transplantation of bone marrow mesenchymal stem cells (MSCs) has been shown to effectively lower blood glucose levels in diabetic individuals, but the mechanism has not been adequately explained. We hypothesized that MSCs exert beneficial paracrine actions on the injured islets by releasing biologically active factors. To prove our hypothesis, we tested the cytoprotective effect of conditioned medium from cultured MSCs on isolated islets exposed to STZ in vitro and on mice islets after the experimental induction of diabetes in vivo. We assessed islet regeneration in the presence of conditioned medium and explored the possible mechanisms involved. Transplantation of MSCs can ameliorate hyperglycemia in diabetic mice by promoting the regeneration of β cells. Both β cell replication and islet progenitors differentiation contribute to β cell regeneration. MSC transplantation resulted in increases in pAkt and pErk expression by islets in vivo. Treatment with MSC-CM promoted islet cell proliferation and resulted in increases in pAkt and pErk expression by islets in vitro. The MSC-CM-mediated induction of β cell proliferation was completely blocked by the PI3K/Akt inhibitor LY294002 but not by the MEK/Erk inhibitor PD98059. Together, these data suggest that the PI3K/Akt signal pathway plays a critical role in β cell proliferation after MSC transplantation.
Maternal microchimerism: increased in the insulin positive compartment of type 1 diabetes pancreas but not in infiltrating immune cells or replicating islet cells.
Ye Jody,Vives-Pi Marta,Gillespie Kathleen M
BACKGROUND:Maternal microchimeric cells (MMc) transfer across the placenta during pregnancy. Increased levels of MMc have been observed in several autoimmune diseases including type 1 diabetes but their role is unknown. It has been suggested that MMc are 1) effector cells of the immune response, 2) targets of the autoimmune response or 3) play a role in tissue repair. The aim of this study was to define the cellular phenotype of MMc in control (n = 14) and type 1 diabetes pancreas (n = 8). METHODS:Using sex chromosome-based fluorescence in-situ hybridization, MMc were identified in male pancreas and their phenotype determined by concomitant immunofluorescence. RESULTS:In normal pancreas, MMc positive for endocrine, exocrine, duct and acinar markers were identified suggesting that these cells are derived from maternal progenitors. Increased frequencies of MMc were observed in type 1 diabetes pancreas (p = 0.03) with particular enrichment in the insulin positive fraction (p = 0.01). MMc did not contribute to infiltrating immune cells or Ki67+ islet cell populations in type 1 diabetes. CONCLUSION:These studies provide support for the hypothesis that MMc in human pancreas are derived from pancreatic precursors. Increased frequencies of MMc beta cells may contribute to the initiation of autoimmunity or to tissue repair but do not infiltrate islets in type 1 diabetes.
Sirtuin 6 regulates glucose-stimulated insulin secretion in mouse pancreatic beta cells.
Xiong Xiwen,Wang Gaihong,Tao Rongya,Wu Pengfei,Kono Tatsuyoshi,Li Kevin,Ding Wen-Xing,Tong Xin,Tersey Sarah A,Harris Robert A,Mirmira Raghavendra G,Evans-Molina Carmella,Dong X Charlie
AIMS/HYPOTHESIS:Sirtuin 6 (SIRT6) has been implicated in ageing, DNA repair and metabolism; however, its function in pancreatic beta cells is unclear. The aim of this study is to elucidate the role of SIRT6 in pancreatic beta cells. METHODS:To investigate the function of SIRT6 in pancreatic beta cells, we performed Sirt6 gene knockdown in MIN6 cells and generated pancreatic- and beta cell-specific Sirt6 knockout mice. Islet morphology and glucose-stimulated insulin secretion (GSIS) were analysed. Glycolysis and oxygen consumption rates in SIRT6-deficient beta cells were measured. Cytosolic calcium was monitored using the Fura-2-AM fluorescent probe (Invitrogen, Grand Island, NY, USA). Mitochondria were analysed by immunoblots and electron microscopy. RESULTS:Sirt6 knockdown in MIN6 beta cells led to a significant decrease in GSIS. Pancreatic beta cell Sirt6 knockout mice showed a ~50% decrease in GSIS. The knockout mouse islets had lower ATP levels compared with the wild-type controls. Mitochondrial oxygen consumption rates were significantly decreased in the SIRT6-deficient beta cells. Cytosolic calcium dynamics in response to glucose or potassium chloride were attenuated in the Sirt6 knockout islets. Numbers of damaged mitochondria were increased and mitochondrial complex levels were decreased in the SIRT6-deficient islets. CONCLUSIONS/INTERPRETATION:These data suggest that SIRT6 is important for GSIS from pancreatic beta cells and activation of SIRT6 may be useful to improve insulin secretion in diabetes.
IAPP toxicity activates HIF1α/PFKFB3 signaling delaying β-cell loss at the expense of β-cell function.
Montemurro Chiara,Nomoto Hiroshi,Pei Lina,Parekh Vishal S,Vongbunyong Kenny E,Vadrevu Suryakiran,Gurlo Tatyana,Butler Alexandra E,Subramaniam Rohan,Ritou Eleni,Shirihai Orian S,Satin Leslie S,Butler Peter C,Tudzarova Slavica
The islet in type 2 diabetes (T2D) is characterized by amyloid deposits derived from islet amyloid polypeptide (IAPP), a protein co-expressed with insulin by β-cells. In common with amyloidogenic proteins implicated in neurodegeneration, human IAPP (hIAPP) forms membrane permeant toxic oligomers implicated in misfolded protein stress. Here, we establish that hIAPP misfolded protein stress activates HIF1α/PFKFB3 signaling, this increases glycolysis disengaged from oxidative phosphorylation with mitochondrial fragmentation and perinuclear clustering, considered a protective posture against increased cytosolic Ca characteristic of toxic oligomer stress. In contrast to tissues with the capacity to regenerate, β-cells in adult humans are minimally replicative, and therefore fail to execute the second pro-regenerative phase of the HIF1α/PFKFB3 injury pathway. Instead, β-cells in T2D remain trapped in the pro-survival first phase of the HIF1α injury repair response with metabolism and the mitochondrial network adapted to slow the rate of cell attrition at the expense of β-cell function.
Dual Role of Nitric Oxide in Regulating the Response of β Cells to DNA Damage.
Oleson Bryndon J,Corbett John A
Antioxidants & redox signaling
SIGNIFICANCE:Cytokines released in and around pancreatic islets during islet inflammation are believed to contribute to impaired β cell function and β cell death during the development of diabetes. Nitric oxide, produced by β cells in response to cytokine exposure, controls many of the responses of β cells during islet inflammation. Recent Advances: Although nitric oxide has been shown to inhibit insulin secretion and oxidative metabolism and induce DNA damage in β cells, it also activates protective pathways that promote recovery of insulin secretion and oxidative metabolism and repair of damaged DNA. Recent studies have identified a novel role for nitric oxide in selectively regulating the DNA damage response in β cells. CRITICAL ISSUES:Does nitric oxide mediate cytokine-induced β cell damage, or is nitric oxide produced by β cells in response to cytokines to protect β cells from damage? FUTURE DIRECTIONS:β cells appear to be the only islet endocrine cell type capable of responding to proinflammatory cytokines with the production of nitric oxide, and these terminally differentiated cells have a limited capacity to regenerate. It is likely that there is a physiological purpose for this response, and understanding this could open new areas of study regarding the loss of functional β cell mass during diabetes development.
A novel bioelectronic glucose sensor to process distinct electrical activities of pancreatic beta-cells.
Nguyen Quang Vinh,Caro Anton,Raoux Matthieu,Quotb Adam,Floderer Jean-Baptiste,Bornat Yannick,Renaud Sylvie,Lang Jochen
Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference
Glucose sensors have improved and facilitated therapy for type 1 diabetes. However, they are still not capable to sense all physiological signals and to act in a closed-loop. Pancreatic β-cells have been shaped during evolution as biological sensors and offer the advantage to integrate all physiological signals in addition to glucose. Moreover, biosensors based on these cells may also serve for non-invasive and continuous long-term characterization of β-cells, drug research, tissue engineering and pre-transplantation quality control. β-cells alter their electrical activity upon exposure to glucose and physiological hormones and we have used these properties to design a biosensor. To this end signals were recorded extracellularly from islet cells kept on multi-electrode arrays. Slow and rapid oscillations were observed, both modulated by glucose. Especially slow oscillations are very robust and have an excellent signal/noise ratio. Signal processing functions were designed to separate the two activities to extract and analyze relevant parameters. These parameters correlate very well with either increasing or decreasing glucose concentrations. An electronic device is under construction, based on an embedded FPGA capable of processing multiple channels in parallel. In the future, such a device shall be used as a portable real-time biosensor regulating insulin delivery from a pump.
Ginseng extract reduces tacrolimus-induced oxidative stress by modulating autophagy in pancreatic beta cells.
Lim Sun Woo,Jin Long,Luo Kang,Jin Jian,Yang Chul Woo
Laboratory investigation; a journal of technical methods and pathology
We previously reported that long-term treatment with a calcineurin inhibitor impairs autophagy process in pancreatic beta cells. This study investigated the effect of Korean red ginseng extract (KRGE) on autophagy modulated by oxidative stress. In mice with tacrolimus (Tac)-induced diabetes mellitus, KRGE alleviated islet dysfunction and decreased oxidative stress and autophagic vacuoles. In vitro, KRGE decreased autophagosome formation and attenuated lysosomal degradation, accompanied by improved beta cell viability and insulin secretion. Addition of 3-methyladenine (3-MA), an inhibitor of autophagosomes, to KRGE further improved cell viability and insulin secretion, and bafilomycin A (BA), an inhibitor of lysosomal function, reduced the effects of KRGE. At the subcellular level, Tac caused mitochondrial dysfunction (impaired mitochondrial oxygen consumption, ATP production, and increased reactive oxygen species production). But KRGE improved these parameters. The effect of KRGE on mitochondrial function enhanced by 3-MA but decreased by BA, suggesting a causal relationship between KRGE effect and autophagy modulation in Tac-induced mitochondrial dysfunction. These findings indicate that KRGE modulates autophagy favorably by reducing Tac-induced oxidative stress, and this effect is closely associated with improvement of mitochondrial function.