scholarly journals RhoG-Rac1 Signaling Pathway Mediates Metabolic Dysfunction of the Pancreatic Beta-Cells Under Chronic Hyperglycemic Conditions.

2021 ◽  
Vol 55 (2) ◽  
pp. 180-192
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
G Proteins ◽  
Pancreatic Beta Cells ◽  
Caspase 3 ◽  
Metabolic Stress ◽  
Nuclear Fraction ◽  
Metabolic Dysfunction ◽  
Islet Beta Cell ◽  
Sustained Activation

BACKGROUND/AIMS: Published evidence suggests regulatory roles for small G proteins (Cdc42 and Rac1) in glucose-stimulated insulin secretion (GSIS) from pancreatic beta-cells. More recent evidence suggests novel roles for these G proteins, specifically Rac1, in the induction of metabolic dysfunction of the islet beta-cell under the duress of a variety of stress conditions. However, potential upstream regulators of sustained activation of Rac1 have not been identified in the beta-cell. Recent studies in other cell types have identified RhoG, a small G protein, as an upstream regulator of Rac1 under specific experimental conditions. Herein, we examined putative roles for RhoG in islet beta-cell dysregulation induced by glucotoxic conditions. METHODS: Expression of RhoG or GDIγ was suppressed by siRNA transfection using the DharmaFect1 reagent. Subcellular fractions were isolated using NE-PER Nuclear and Cytoplasmic Extraction Reagent kit. The degree of activation of Rac1 was assessed using a pull-down assay kit. Extent of cell death was quantified using a Cell Death Detection ELISAplus kit. RESULTS: RhoG is expressed in human islets, rat islets, and clonal INS-1 832/13 cells. siRNA-RhoG markedly attenuated sustained activation of Rac1 and caspase-3 in INS-1 832/13 cells exposed to hyperglycemic conditions (20 mM; 24 hours). In a manner akin to Rac1, which has been shown to translocate to the nuclear fraction to induce beta-cell dysfunction under metabolic stress, a significant increase in the association of RhoG with the nuclear fraction was observed in beta-cells under the duress of metabolic stress. Interestingly, GDIγ, a known regulator of RhoG, remained associated with non-nuclear fraction under conditions RhoG and Rac1 translocated to the membrane. Lastly, siRNA-RhoG modestly attenuated pancreatic beta-cell demise induced by high glucose exposure conditions, but such an effect was not statistically significant. CONCLUSION: Based on these data we conclude that RhoG-Rac1 signaling module plays critical regulatory roles in promoting mitochondrial dysfunction (caspase-3 activation) of the islet beta cell under metabolic stress.

scholarly journals Emulsified isoflurane alleviates rat islet beta cell RIN-m5F apoptosis induced by glucose via inhibiting endoplasmic reticulum stress

2019 ◽  
Author(s):  
Wenyan Dong ◽  
Zhenkun Yang ◽  
Jingjing Zhao ◽  
Jie Sun ◽  
Min Yao ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Beta Cell ◽  
Beta Cells ◽  
Western Blotting ◽  
High Glucose ◽  
Caspase 3 ◽  
Control Group ◽  
Group Culture ◽  
Islet Beta Cell

Abstract Background Diabetes mellitus (DM) is a critical disease that considered a detriment to the health of people all over the world. Endoplasmic reticulum stress (ERS) is the response cause by endoplasmic reticulum misfolded and unfolded protein aggregation, which induces cell apoptosis. Our previous work showed that EIso could alleviate ERS in lung reperfusion injury. This study aimed to elucidate whether Emulsified isoflurane (EIso) could alleviate apoptosis induced by glucose in rat islet beta cell RIN-m5F via inhibiting ERS. Methods RIN-m5F cells were divided into five groups: Control group, cultured in 0.1M glucose for 24h (0.1G group), culture in 0.3M glucose for 24h (0.3G group), culture in 0.3M glucose with 57uM EIso for 24h (0.3G+57E group), and culture in 0.3M glucose with 76uM EIso for 24h (0.3G+76E group). First, the cellular proliferation was measured by MTT assay, and the level of insulin secretion was measured with ELISA kit. Second, the expression of Bax and Bcl-2 were detected by Western blotting. The level of caspase-3 activity was assessed by colorimetric method. Finally, the CHOP and GRP78 expression were detected by Western blotting. The level of ATF6, Xbp1 and eIF2α mRNA were assessed by qRT-PCR after treated with EIso for 24h. Results High glucose induced significant loss of RIN-m5F cell viability, and stimulated the secretion of insulin; EIso improved the survival and protected the function of RIN-m5F. Compare to 0.3G group, treatment with EIso inhibited the activity of caspase-3, decreased the expression of Bax and increased the expression of Bcl-2. The expression of CHOP and GRP78 were inhibited by EIso at 24 h after treatment, and decrement of CHOP and GRP78 expression were correlated with EIso concentration. The level of ATF6, Xbp1 and eIF2α mRNA of RIN-m5F were enhanced culture with high glucose, but only eIF2α mRNA was decreased by EIso treatment. Conclusion High glucose induces rat islet beta cell RIN-m5F apoptosis and aggravates the function of beta cells. EIso protects beta cells from glucose-induced apoptosis, and anti-apoptosis is mediated, at least in part, by inhibiting ERS.

Tetraethylammonium modifies gap junctions between pancreatic beta-cells

1981 ◽  
Vol 240 (3) ◽  
pp. C116-C120 ◽  
Author(s):  
M. S. Sheppard ◽  
P. Meda
Keyword(s):  
Beta Cell ◽  
Gap Junctions ◽  
Beta Cells ◽  
Insulin Release ◽  
Pancreatic Beta Cells ◽  
Freeze Fracture ◽  
Potassium Conductance ◽  
Median Number ◽  
Rat Islets Of Langerhans ◽  
Gap Junctional

Gap junctions between pancreatic beta-cells were quantitatively assessed in freeze-fracture replicas of isolated rat islets of Langerhans incubated for 90 min with or without the potassium conductance blocker tetraethylammonium (TEA). The results show that TEA increases the median number of particles per beta-cell gap junction but not the frequency of gap junctions at both nonstimulating and threshold-stimulating concentrations of glucose. TEA increased the relative gap junctional area at both concentrations of glucose. TEA had no effect on insulin release at a basal concentration of glucose but potentiated that release at the threshold glucose level. Thus TEA modifies beta-cell gap junctions independently of its effect on insulin release. However, the junctional changes observed were greater when insulin release was also elevated.

scholarly journals Multi-Organ Crosstalk with Endocrine Pancreas: A Focus on How Gut Microbiota Shapes Pancreatic Beta-Cells

Biomolecules ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 104
Author(s):  
Elisa Fernández-Millán ◽  
Carlos Guillén
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Cell Biology ◽  
Pancreatic Beta Cells ◽  
Metabolic Diseases ◽  
Cell Function ◽  
Cell Mass ◽  
Beta Cell Mass ◽  
Short Chain Fatty Acids

Type 2 diabetes (T2D) results from impaired beta-cell function and insufficient beta-cell mass compensation in the setting of insulin resistance. Current therapeutic strategies focus their efforts on promoting the maintenance of functional beta-cell mass to ensure appropriate glycemic control. Thus, understanding how beta-cells communicate with metabolic and non-metabolic tissues provides a novel area for investigation and implicates the importance of inter-organ communication in the pathology of metabolic diseases such as T2D. In this review, we provide an overview of secreted factors from diverse organs and tissues that have been shown to impact beta-cell biology. Specifically, we discuss experimental and clinical evidence in support for a role of gut to beta-cell crosstalk, paying particular attention to bacteria-derived factors including short-chain fatty acids, lipopolysaccharide, and factors contained within extracellular vesicles that influence the function and/or the survival of beta cells under normal or diabetogenic conditions.

scholarly journals Bergenin protects pancreatic beta cells against cytokine-induced apoptosis in INS-1E cells

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0241349
Author(s):  
Sajid Ali Rajput ◽  
Munazza Raza Mirza ◽  
M. Iqbal Choudhary
Keyword(s):  
Insulin Secretion ◽  
Beta Cell ◽  
Beta Cells ◽  
Proinflammatory Cytokines ◽  
Cell Apoptosis ◽  
Pancreatic Beta Cells ◽  
Cell Function ◽  
Beta Cell Apoptosis ◽  
Atp Levels ◽  
Induced Apoptosis

Beta cell apoptosis induced by proinflammatory cytokines is one of the hallmarks of diabetes. Small molecules which can inhibit the cytokine-induced apoptosis could lead to new drug candidates that can be used in combination with existing therapeutic interventions against diabetes. The current study evaluated several effects of bergenin, an isocoumarin derivative, in beta cells in the presence of cytokines. These included (i) increase in beta cell viability (by measuring cellular ATP levels) (ii) suppression of beta cell apoptosis (by measuring caspase activity), (iii) improvement in beta cell function (by measuring glucose-stimulated insulin secretion), and (iv) improvement of beta cells mitochondrial physiological functions. The experiments were carried out using rat beta INS-1E cell line in the presence or absence of bergenin and a cocktail of proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha, and interferon- gamma) for 48 hr. Bergenin significantly inhibited beta cell apoptosis, as inferred from the reduction in the caspase-3 activity (IC50 = 7.29 ± 2.45 μM), and concurrently increased cellular ATP Levels (EC50 = 1.97 ± 0.47 μM). Bergenin also significantly enhanced insulin secretion (EC50 = 6.73 ± 2.15 μM) in INS-1E cells, presumably because of the decreased nitric oxide production (IC50 = 6.82 ± 2.83 μM). Bergenin restored mitochondrial membrane potential (EC50 = 2.27 ± 0.83 μM), decreased ROS production (IC50 = 14.63 ± 3.18 μM), and improved mitochondrial dehydrogenase activity (EC50 = 1.39 ± 0.62 μM). This study shows for the first time that bergenin protected beta cells from cytokine-induced apoptosis and restored insulin secretory function by virtue of its anti-inflammatory, antioxidant and anti-apoptotic properties. To sum up, the above mentioned data highlight bergenin as a promising anti-apoptotic agent in the context of diabetes.

scholarly journals Glucose controls co-translation of structurally related mRNAs via the mTOR and eIF2 pathways in human pancreatic beta cells

2021 ◽  
Author(s):  
Manuel Bulfoni ◽  
Costas Bouyioukos ◽  
Albatoul Zakaria ◽  
Fabienne Nigon ◽  
Roberta Rapone ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Synthesis ◽  
Beta Cell ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Gene Expression Regulation ◽  
Human Cells ◽  
Rodent Models ◽  
Polysome Profiling ◽  
Acute Increase

ABSTRACTPancreatic beta cell response to glucose is critical for the maintenance of normoglycemia. A strong transcriptional response was classically described in rodent models but, interestingly, not in human cells. In this study, we exposed human pancreatic beta cells to an increased concentration of glucose and analysed at a global level the mRNAs steady state levels and their translationalability. Polysome profiling analysis showed an early acute increase in protein synthesis and a specific translation regulation of more than 400 mRNAs, independently of their transcriptional regulation. We clustered the co-regulated mRNAs according to their behaviour in translation in response to glucose and discovered common structural and sequence mRNA features. Among them mTOR- and eIF2-sensitive elements have a predominant role to increase mostly the translation of mRNAs encoding for proteins of the translational machinery. Furthermore, we show that mTOR and eIF2α pathways are independently regulated in response to glucose, participating to a translational reshaping to adapt beta cell metabolism. The early acute increase in the translation machinery components prepare the beta cell for further protein demand due to glucose-mediated metabolism changes.AUTHOR SUMMARYAdaptation and response to glucose of pancreatic beta cells is critical for the maintenance of normoglycemia. Its deregulation is associated to Diabetic Mellitus (DM), a significant public health concern worldwide with an increased incidence of morbidity and mortality. Despite extensive research in rodent models, gene expression regulation in response to glucose remains largely unexplored in human cells. In our work, we have tackled this question by exposing human EndoC-BH1 cells to high glucose concentration. Using polysome profiling, the gold standard technique to analyse cellular translation activity, we observed a global protein synthesis increase, independent from transcription activity. Among the specific differentially translated mRNAs, we found transcripts coding for ribosomal proteins, allowing the cell machinery to be engaged in a metabolic response to glucose. Therefore, the regulation in response to glucose occurs mainly at the translational level in human cells, and not at the transcriptional level as described in the classically used rodent models.Furthermore, by comparing the features of the differentially translated mRNAs, and classifying them according to their translational response, we show that the early response to glucose occurs through the coupling of mRNA structure and sequence features impacting translation and regulation of specific signalling pathways. Collectively, our results support a new paradigm of gene expression regulation on the translation level in human beta cells.

scholarly journals Update on the Protective Molecular Pathways Improving Pancreatic Beta-Cell Dysfunction

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Alessandra Puddu ◽  
Roberta Sanguineti ◽  
François Mach ◽  
Franco Dallegri ◽  
Giorgio Luciano Viviani ◽  
...  
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Cell Function ◽  
Pancreatic Beta Cell ◽  
Cell Mass ◽  
Beta Cell Mass ◽  
Beta Cell Dysfunction ◽  
Molecular Pathways ◽  
Cell Dysfunction

The primary function of pancreatic beta-cells is to produce and release insulin in response to increment in extracellular glucose concentrations, thus maintaining glucose homeostasis. Deficient beta-cell function can have profound metabolic consequences, leading to the development of hyperglycemia and, ultimately, diabetes mellitus. Therefore, strategies targeting the maintenance of the normal function and protecting pancreatic beta-cells from injury or death might be crucial in the treatment of diabetes. This narrative review will update evidence from the recently identified molecular regulators preserving beta-cell mass and function recovery in order to suggest potential therapeutic targets against diabetes. This review will also highlight the relevance for novel molecular pathways potentially improving beta-cell dysfunction.

scholarly journals High dose of histone deacetylase inhibitors affects insulin secretory mechanism of pancreatic beta cell line

2018 ◽  
Vol 52 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Eiji Yamato
Keyword(s):  
Insulin Secretion ◽  
Beta Cell ◽  
Cell Line ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Pancreatic Beta Cell ◽  
High Dose ◽  
Min6 Cells ◽  
Beta Cell Line ◽  
High Doses

Abstract Objective. Histone deacytylase inhibitors (HDACis) inhibit the deacetylation of the lysine residue of proteins, including histones, and regulate the transcription of a variety of genes. Recently, HDACis have been used clinically as anti-cancer drugs and possible anti-diabetic drugs. Even though HDACis have been proven to protect the cytokine-induced damage of pancreatic beta cells, evidence also shows that high doses of HDACis are cytotoxic. In the present study, we, therefore, investigated the eff ect of HDACis on insulin secretion in a pancreatic beta cell line. Methods. Pancreatic beta cells MIN6 were treated with selected HDACis (trichostatin A, TSA; valproic acid, VPA; and sodium butyrate, NaB) in medium supplemented with 25 mM glucose and 13% heat-inactivated fetal bovine serum (FBS) for indicated time intervals. Protein expression of Pdx1 and Mafa in MIN6 cells was demonstrated by immunohistochemistry and immunocytochemistry, expression of Pdx1 and Mafa genes was measured by quantitative RT-PCR method. Insulin release from MIN6 cells and insulin cell content were estimated by ELISA kit. Superoxide production in MIN6 cells was measured using a Total ROS/Superoxide Detection System. Results. TSA, VPA, and NaB inhibited the expression of Pdx1 and Mafa genes and their products. TSA treatment led to beta cell malfunction, characterized by enhanced insulin secretion at 3 and 9 mM glucose, but impaired insulin secretion at 15 and 25 mM glucose. Th us, TSA induced dysregulation of the insulin secretion mechanism. TSA also enhanced reactive oxygen species production in pancreatic beta cells. Conclusions. Our results showed that HDACis caused failure to suppress insulin secretion at low glucose concentrations and enhance insulin secretion at high glucose concentrations. In other words, when these HDACis are used clinically, high doses of HDACis may cause hypoglycemia in the fasting state and hyperglycemia in the fed state. When using HDACis, physicians should, therefore, be aware of the capacity of these drugs to modulate the insulin secretory capacity of pancreatic beta cells.

scholarly journals Disruption of Beta-Cell Mitochondrial Networks by the Orphan Nuclear Receptor Nor1/Nr4a3

Cells ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 168 ◽  
Author(s):  
Anne-Françoise Close ◽  
Nidheesh Dadheech ◽  
Hélène Lemieux ◽  
Qian Wang ◽  
Jean Buteau
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Nuclear Receptor ◽  
Pancreatic Beta Cells ◽  
Orphan Nuclear Receptor ◽  
Atp Production ◽  
Human Beta Cells ◽  
Glucose Stimulated Insulin Secretion ◽  
Mitochondrial Networks

Nor1, the third member of the Nr4a subfamily of nuclear receptor, is garnering increased interest in view of its role in the regulation of glucose homeostasis. Our previous study highlighted a proapoptotic role of Nor1 in pancreatic beta cells and showed that Nor1 expression was increased in islets isolated from type 2 diabetic individuals, suggesting that Nor1 could mediate the deterioration of islet function in type 2 diabetes. However, the mechanism remains incompletely understood. We herein investigated the subcellular localization of Nor1 in INS832/13 cells and dispersed human beta cells. We also examined the consequences of Nor1 overexpression on mitochondrial function and morphology. Our results show that, surprisingly, Nor1 is mostly cytoplasmic in beta cells and undergoes mitochondrial translocation upon activation by proinflammatory cytokines. Mitochondrial localization of Nor1 reduced glucose oxidation, lowered ATP production rates, and inhibited glucose-stimulated insulin secretion. Western blot and microscopy images revealed that Nor1 could provoke mitochondrial fragmentation via mitophagy. Our study unveils a new mode of action for Nor1, which affects beta-cell viability and function by disrupting mitochondrial networks.

scholarly journals Augmented mitochondrial energy metabolism is an early response to chronic glucose stress in human pancreatic beta cells

Diabetologia ◽  
2020 ◽  
Vol 63 (12) ◽  
pp. 2628-2640
Author(s):  
Isabelle Chareyron ◽  
Stefan Christen ◽  
Sofia Moco ◽  
Armand Valsesia ◽  
Steve Lassueur ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Beta Cell ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Cell Function ◽  
Blood Glucose Control ◽  
Calcium Signalling ◽  
Cytosolic Calcium ◽  
Metabolic Changes ◽  
Mitochondrial Energy Metabolism

Abstract Aims/hypothesis In islets from individuals with type 2 diabetes and in islets exposed to chronic elevated glucose, mitochondrial energy metabolism is impaired. Here, we studied early metabolic changes and mitochondrial adaptations in human beta cells during chronic glucose stress. Methods Respiration and cytosolic ATP changes were measured in human islet cell clusters after culture for 4 days in 11.1 mmol/l glucose. Metabolomics was applied to analyse intracellular metabolite changes as a result of glucose stress conditions. Alterations in beta cell function were followed using insulin secretion assays or cytosolic calcium signalling after expression of the calcium probe YC3.6 specifically in beta cells of islet clusters. Results At early stages of glucose stress, mitochondrial energy metabolism was augmented in contrast to the previously described mitochondrial dysfunction in beta cells from islets of diabetic donors. Following chronic glucose stress, mitochondrial respiration increased (by 52.4%, p < 0.001) and, as a consequence, the cytosolic ATP/ADP ratio in resting human pancreatic islet cells was elevated (by 27.8%, p < 0.05). Because of mitochondrial overactivation in the resting state, nutrient-induced beta cell activation was reduced. In addition, chronic glucose stress caused metabolic adaptations that resulted in the accumulation of intermediates of the glycolytic pathway, the pentose phosphate pathway and the TCA cycle; the most strongly augmented metabolite was glycerol 3-phosphate. The changes in metabolites observed are likely to be due to the inability of mitochondria to cope with continuous nutrient oversupply. To protect beta cells from chronic glucose stress, we inhibited mitochondrial pyruvate transport. Metabolite concentrations were partially normalised and the mitochondrial respiratory response to nutrients was markedly improved. Furthermore, stimulus–secretion coupling as assessed by cytosolic calcium signalling, was restored. Conclusion/interpretation We propose that metabolic changes and associated mitochondrial overactivation are early adaptations to glucose stress, and may reflect what happens as a result of poor blood glucose control. Inhibition of mitochondrial pyruvate transport reduces mitochondrial nutrient overload and allows beta cells to recover from chronic glucose stress.

Sign in / Sign up

Export Citation Format

Share Document