scholarly journals Small subpopulations of β-cells do not drive islet oscillatory [Ca2+] dynamics via gap junction communication

2020 ◽  
Author(s):  
JaeAnn M. Dwulet ◽  
Jennifer K. Briggs ◽  
Richard K.P. Benninger
Keyword(s):  
Blood Glucose ◽  
Gap Junction ◽  
Metabolic Activity ◽  
Oscillation Frequency ◽  
Cell Populations ◽  
Small Populations ◽  
Β Cells ◽  
Β Cell ◽  
Gap Junction Communication ◽  
Junction Coupling

AbstractThe islets of Langerhans exist as a multicellular network that is important for the regulation of blood glucose levels. The majority of cells in the islet are insulin-producing β-cells, which are excitable cells that are electrically coupled via gap junction channels. β-cells have long been known to display heterogeneous functionality. However, due to gap junction electrical coupling, β-cells show coordinated [Ca2+] oscillations when stimulated with glucose, and global quiescence when unstimulated. Small subpopulations of highly functional β-cells have been suggested to control the dynamics of [Ca2+] and insulin release across the islet. In this study, we investigated the theoretical basis of whether small subpopulations of β-cells can disproportionality control islet [Ca2+] dynamics. Using a multicellular model of the islet, we generated continuous or bimodal distributions of β-cell heterogeneity and examined how islet [Ca2+] dynamics depended on the presence of cells with increased excitability or increased oscillation frequency. We found that the islet was susceptible to marked suppression of [Ca2+] when a ∼10% population of cells with high metabolic activity was hyperpolarized; where hyperpolarizing cells with normal metabolic activity had little effect. However, when these highly metabolic cells were removed from the islet model, near normal [Ca2+] remained. Similarly, when ∼10% of cells with either the highest frequency or earliest elevations in [Ca2+] were removed from the islet, the [Ca2+] oscillation frequency remained largely unchanged. Overall these results indicate that small populations of β-cells with either increased excitability or increased frequency, or signatures of [Ca2+] dynamics that suggest such properties, are unable to disproportionately control islet-wide [Ca2+] via gap junction coupling. As such, we need to reconsider the physiological basis for such small β-cell populations or the mechanism by which they may be acting to control normal islet function.Author summaryMany biological systems can be studied using network theory. How heterogeneous cell subpopulations come together to create complex multicellular behavior is of great value in understanding function and dysfunction in tissues. The pancreatic islet of Langerhans is a highly coupled structure that is important for maintaining blood glucose homeostasis. β-cell electrical activity is coordinated via gap junction communication. The function of the insulin-producing β-cell within the islet is disrupted in diabetes. As such, to understand the causes of islet dysfunction we need to understand how different cells within the islet contribute to its overall function via gap junction coupling. Using a computational model of β-cell electrophysiology, we investigated how small highly functional β-cell populations within the islet contribute to its function. We found that when small populations with greater functionality were introduced into the islet, they displayed signatures of this enhanced functionality. However, when these cells were removed, the islet, retained near-normal function. Thus, in a highly coupled system, such as an islet, the heterogeneity of cells allows small subpopulations to be dispensable, and thus their absence is unable to disrupt the larger cellular network. These findings can be applied to other electrical systems that have heterogeneous cell populations.

scholarly journals Small subpopulations of β-cells do not drive islet oscillatory [Ca2+] dynamics via gap junction communication

2021 ◽  
Vol 17 (5) ◽  
pp. e1008948
Author(s):  
JaeAnn M. Dwulet ◽  
Jennifer K. Briggs ◽  
Richard K. P. Benninger
Keyword(s):  
Gap Junction ◽  
Metabolic Activity ◽  
Oscillation Frequency ◽  
Cell Populations ◽  
Small Populations ◽  
Β Cells ◽  
Β Cell ◽  
Physiological Basis ◽  
Gap Junction Coupling ◽  
Junction Coupling

The islets of Langerhans exist as multicellular networks that regulate blood glucose levels. The majority of cells in the islet are excitable, insulin-producing β-cells that are electrically coupled via gap junction channels. β-cells are known to display heterogeneous functionality. However, due to gap junction coupling, β-cells show coordinated [Ca2+] oscillations when stimulated with glucose, and global quiescence when unstimulated. Small subpopulations of highly functional β-cells have been suggested to control [Ca2+] dynamics across the islet. When these populations were targeted by optogenetic silencing or photoablation, [Ca2+] dynamics across the islet were largely disrupted. In this study, we investigated the theoretical basis of these experiments and how small populations can disproportionality control islet [Ca2+] dynamics. Using a multicellular islet model, we generated normal, skewed or bimodal distributions of β-cell heterogeneity. We examined how islet [Ca2+] dynamics were disrupted when cells were targeted via hyperpolarization or populations were removed; to mimic optogenetic silencing or photoablation, respectively. Targeted cell populations were chosen based on characteristics linked to functional subpopulation, including metabolic rate of glucose oxidation or [Ca2+] oscillation frequency. Islets were susceptible to marked suppression of [Ca2+] when ~10% of cells with high metabolic activity were hyperpolarized; where hyperpolarizing cells with normal metabolic activity had little effect. However, when highly metabolic cells were removed from the model, [Ca2+] oscillations remained. Similarly, when ~10% of cells with either the highest frequency or earliest elevations in [Ca2+] were removed from the islet, the [Ca2+] oscillation frequency remained largely unchanged. Overall, these results indicate small populations of β-cells with either increased metabolic activity or increased frequency are unable to disproportionately control islet-wide [Ca2+] via gap junction coupling. Therefore, we need to reconsider the physiological basis for such small β-cell populations or the mechanism by which they may be acting to control normal islet function.

scholarly journals Effect of Sago Analog Rice and Red Bean Diet to β Cells Pancreas Refinement in STZ-NA Induced Diabetic Rats

2020 ◽  
pp. 667-673
Author(s):  
Sri Budi Wahjuningsih ◽  
Haslina Haslina ◽  
Agus Tri Putranto ◽  
Mita Nurul Azkia
Keyword(s):  
Blood Glucose ◽  
Blood Glucose Level ◽  
Glucose Level ◽  
Insulin Level ◽  
Diabetic Rats ◽  
Diabetic Group ◽  
Pancreatic Β Cell ◽  
Β Cells ◽  
Β Cell ◽  
Red Bean

The study aims to determine the effect of sago analogue rice and red beans in diabetic rats to repair pancreatic β-cells. Thirty-five males Wistar rats were divided into 5 groups: normal group diet (STD), the diabetic group (STDD) with a standard feed diet, the diabetic group with mentik wangi rice (MWRD), the diabetic group with sago analogue rice (SARD) and the diabetic group with sago analogue rice with the addition of 10% red bean flour (SARKBD). All groups were analysed for dietary interventions, blood glucose level, insulin level for HOMA-β and HOMA S indices and measurement of insulin level by using IHC analysis. In addition, short-chain fatty acids (SCFA) analysis was performed in the caecum. This study showed that decreasing blood glucose level shown in SARD and RASKBD groups. The pancreatic β-cell number indicated an increase in the SARD group compares to the STDD group. The pool total of SCFA in SARD group was the highest among of all groups, as well as the acetate, propionate and butyrate pools. These results indicate that the sago analogue rice diet could repair and increase the expression of pancreatic β-cell through absorption inhibition mechanisms and by increasing insulin sensitivity and the SCFA level.

β Cell Protecting and Immunomodulatory Activities of Paecilomyces Hepiali Chen Mycelium in STZ Induced T1DM Mice

2009 ◽  
Vol 37 (02) ◽  
pp. 361-372 ◽  
Author(s):  
Ming Xiang ◽  
Jing Tang ◽  
Xiao-Lei Zou ◽  
Zeng-Yu Zhao ◽  
Yun-Yang Wang ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Insulin Level ◽  
Inflammatory Cells ◽  
Diabetic Control ◽  
Control Group ◽  
Β Cells ◽  
Β Cell ◽  
Diabetic Control Group ◽  
Paecilomyces Hepiali

The anti-hyperglycemic and immunomodulatory activities of the ethanol extract from Paecilomyces Hepiali Chen (PHC), a Chinese medicine, were investigated in streptozotocin-induced type 1 diabetic (T1DM) mice. Male Balb/c mice, which were i.p. injected with streptozotocin (STZ, 50 mg/kg, for 5 consecutive days) on Day 7, were orally administered saline (the normal control and diabetic control group), Metformin (60 mg/kg, b.w., positive group), or the extract (100 mg/kg, b.w., PHC prevention group) from Day 1 to Day 28, Mice i.p. injected with streptozotocin (STZ, 50 mg/kg, b.w.) for 5 consecutive days prior to PHC treatment (100 mg/kg, b.w.) were used as the PHC treatment group. The effects of PHC on postprandial blood glucose concentrations, plasmatic insulin levels, morphology of pancreatic β cells and CD4+ T cells proliferation after 28-day treatment were monitored. Results showed that PHC administered 6 days before STZ induction of diabetes in mice significantly decreased blood glucose level (p < 0.01). An increase of insulin level was also observed as compared to those in the diabetic control group (p < 0.01). In addition, fewer inflammatory cells infiltrated the pancreatic islet and fewer β cells death by apoptosis within the inflamed islets were observed. More importantly, the CD4+ T cell proliferation was remarkably attenuated ex vivo in mice preventively treated with PHC (p < 0.01). In comparison to the PHC prevention group, no significant hypoglycemia, changes of insulin level and β cell protection were observed in mice treated with PHC after STZ administration. Our findings demonstrated that preventive administration of PHC protected β cells from apoptosis in type 1 diabetes induced by STZ, and the underlying mechanism may be involved in suppressing CD4+ T cells reaction, reducing inflammatory cells infiltration and protecting beta cell apoptosis in pancreatic islet.

scholarly journals Development and Characteristics of Pancreatic Epsilon Cells

2019 ◽  
Vol 20 (8) ◽  
pp. 1867 ◽  
Author(s):  
Naoaki Sakata ◽  
Gumpei Yoshimatsu ◽  
Shohta Kodama
Keyword(s):  
Transcription Factors ◽  
Blood Glucose ◽  
Endocrine Cells ◽  
Current Evidence ◽  
Β Cells ◽  
Β Cell ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Ghrelin Gene ◽  
Pancreatic Endocrine Cells

Pancreatic endocrine cells expressing the ghrelin gene and producing the ghrelin hormone were first identified in 2002. These cells, named ε cells, were recognized as the fifth type of endocrine cells. Differentiation of ε cells is induced by various transcription factors, including Nk2 homeobox 2, paired box proteins Pax-4 and Pax6, and the aristaless-related homeobox. Ghrelin is generally considered to be a “hunger hormone” that stimulates the appetite and is produced mainly by the stomach. Although the population of ε cells is small in adults, they play important roles in regulating other endocrine cells, especially β cells, by releasing ghrelin. However, the roles of ghrelin in β cells are complex. Ghrelin contributes to increased blood glucose levels by suppressing insulin release from β cells and is also involved in the growth and proliferation of β cells and the prevention of β cell apoptosis. Despite increasing evidence and clarification of the mechanisms of ε cells over the last 20 years, many questions remain to be answered. In this review, we present the current evidence for the participation of ε cells in differentiation and clarify their characteristics by focusing on the roles of ghrelin.

scholarly journals Herbal constituent sequoyitol improves hyperglycemia and glucose intolerance by targeting hepatocytes, adipocytes, and β-cells

2012 ◽  
Vol 302 (8) ◽  
pp. E932-E940 ◽  
Author(s):  
Hong Shen ◽  
Mengle Shao ◽  
Kae Won Cho ◽  
Suqing Wang ◽  
Zheng Chen ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Blood Glucose ◽  
Glucose Intolerance ◽  
Insulin Signaling ◽  
Glucose Production ◽  
Water Soluble ◽  
Β Cells ◽  
Β Cell ◽  
Reduce Blood Glucose

The prevalence of insulin resistance and type 2 diabetes increases rapidly; however, treatments are limited. Various herbal extracts have been reported to reduce blood glucose in animals with either genetic or dietary type 2 diabetes; however, plant extracts are extremely complex, and leading compounds remain largely unknown. Here we show that 5- O-methyl- myo-inositol (also called sequoyitol), a herbal constituent, exerts antidiabetic effects in mice. Sequoyitol was chronically administrated into ob/ob mice either orally or subcutaneously. Both oral and subcutaneous administrations of sequoyitol decreased blood glucose, improved glucose intolerance, and enhanced insulin signaling in ob/ob mice. Sequoyitol directly enhanced insulin signaling, including phosphorylation of insulin receptor substrate-1 and Akt, in both HepG2 cells (derived from human hepatocytes) and 3T3-L1 adipocytes. In agreement, sequoyitol increased the ability of insulin to suppress glucose production in primary hepatocytes and to stimulate glucose uptake into primary adipocytes. Furthermore, sequoyitol improved insulin signaling in INS-1 cells (a rat β-cell line) and protected INS-1 cells from streptozotocin- or H2O2-induced injury. In mice with streptozotocin-induced β-cell deficiency, sequoyitol treatments increased plasma insulin levels and decreased hyperglycemia and glucose intolerance. These results indicate that sequoyitol, a natural, water-soluble small molecule, ameliorates hyperglycemia and glucose intolerance by increasing both insulin sensitivity and insulin secretion. Sequoyitol appears to directly target hepatocytes, adipocytes, and β-cells. Therefore, sequoyitol may serve as a new oral diabetes medication.

scholarly journals Glucose and NAADP trigger elementary intracellular β-cell Ca2+ signals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paula Maria Heister ◽  
Trevor Powell ◽  
Antony Galione
Keyword(s):  
Blood Glucose ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Atp Production ◽  
Insulin Granules ◽  
Intracellular Ca ◽  
Membrane Depolarisation ◽  
Stimulus Secretion Coupling

AbstractPancreatic β-cells release insulin upon a rise in blood glucose. The precise mechanisms of stimulus-secretion coupling, and its failure in Diabetes Mellitus Type 2, remain to be elucidated. The consensus model, as well as a class of currently prescribed anti-diabetic drugs, are based around the observation that glucose-evoked ATP production in β-cells leads to closure of cell membrane ATP-gated potassium (KATP) channels, plasma membrane depolarisation, Ca2+ influx, and finally the exocytosis of insulin granules. However, it has been demonstrated by the inactivation of this pathway using genetic and pharmacological means that closure of the KATP channel alone may not be sufficient to explain all β-cell responses to glucose elevation. We have previously proposed that NAADP-evoked Ca2+ release is an important step in stimulus-secretion coupling in pancreatic β-cells. Here we show using total internal reflection fluorescence (TIRF) microscopy that glucose as well as the Ca2+ mobilising messenger nicotinic acid adenine dinucleotide phosphate (NAADP), known to operate in β-cells, lead to highly localised elementary intracellular Ca2+ signals. These were found to be obscured by measurements of global Ca2+ signals and the action of powerful SERCA-based sequestration mechanisms at the endoplasmic reticulum (ER). Building on our previous work demonstrating that NAADP-evoked Ca2+ release is an important step in stimulus-secretion coupling in pancreatic β-cells, we provide here the first demonstration of elementary Ca2+ signals in response to NAADP, whose occurrence was previously suspected. Optical quantal analysis of these events reveals a unitary event amplitude equivalent to that of known elementary Ca2+ signalling events, inositol trisphosphate (IP3) receptor mediated blips, and ryanodine receptor mediated quarks. We propose that a mechanism based on these highly localised intracellular Ca2+ signalling events mediated by NAADP may initially operate in β-cells when they respond to elevations in blood glucose.

scholarly journals Caloric Restriction recovers impaired β-cell-β-cell coupling, calcium oscillation coordination and insulin secretion in prediabetic mice

2020 ◽  
Author(s):  
Maria Esméria Corezola do Amaral ◽  
Vira Kravets ◽  
JaeAnn M. Dwulet ◽  
Nikki L. Farnsworth ◽  
Robert Piscopio ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Weight Gain ◽  
Gap Junction ◽  
Caloric Restriction ◽  
Glucose Homeostasis ◽  
Fasting Glucose ◽  
Β Cell ◽  
Insulin Levels ◽  
Gap Junction Coupling ◽  
Junction Coupling

AbstractCaloric restriction has been shown to decrease the incidence of metabolic diseases such as obesity and type 2 diabetes mellitus (T2DM). The mechanisms underlying the benefits of caloric restriction involved in insulin secretion and glucose homeostasis and are not fully understood. Intercellular communication within the islets of Langerhans, mediated by Connexin36 (Cx36) gap junctions, regulates insulin secretion dynamics and glucose homeostasis. The goal of this study was to determine if caloric restriction can protect against decreases in Cx36 gap junction coupling and altered islet function induced in models of obesity and prediabetes. C57BL6 mice were fed with a high fat diet (HFD), showing indications of prediabetes after 2 months, including weight gain, insulin resistance, and elevated fasting glucose and insulin levels. Subsequently, mice were submitted to one month of 40% caloric restriction (2g/day of HFD). Mice under 40% caloric restriction showed reversal in weight gain and recovered insulin sensitivity, fasting glucose and insulin levels. In islets of mice fed the HFD, caloric restriction protected against obesity-induced decreases in gap junction coupling and preserved glucose-stimulated calcium signaling, including Ca2+ oscillation coordination and oscillation amplitude. Caloric restriction also promoted a slight increase in glucose metabolism, as measured by increased NAD(P)H autofluorescence, as well as recovering glucose-stimulated insulin secretion. We conclude that declines in Cx36 gap junction coupling that occur in obesity can be completely recovered by caloric restriction and obesity reversal, improving Ca2+ dynamics and insulin secretion regulation. This suggests a critical role for caloric restriction in the context of obesity to prevent islet dysfunction.

Generation of Pancreatic β-cells From iPSCs and their Potential for Type 1 Diabetes Mellitus Replacement Therapy and Modelling

2018 ◽  
Vol 128 (05) ◽  
pp. 339-346 ◽  
Author(s):  
Maria Csobonyeiova ◽  
Stefan Polak ◽  
Lubos Danisovic
Keyword(s):  
Type 1 Diabetes ◽  
Blood Glucose ◽  
Replacement Therapy ◽  
Cell Physiology ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
High Blood Glucose ◽  
Cell Based Therapy

AbstractDiabetes type 1 (T1D) is a common autoimmune disease characterized by permanent destruction of the insulin-secreting β-cells in pancreatic islets, resulting in a deficiency of the glucose-lowering hormone insulin and persisting high blood glucose levels. Insulin has to be replaced by regular subcutaneous injections, and blood glucose level must be monitored due to the risk of hyperglycemia. Recently, transplantation of new pancreatic β-cells into T1D patients has come to be considered one of the most potentially effective treatments for this disease. Therefore, much effort has focused on understanding the regulation of β-cells. Induced pluripotent stem cells (iPSCs) represent a valuable source for T1D modelling and cell replacement therapy because of their ability to differentiate into all cell types in vitro. Recent advances in stem cell-based therapy and gene-editing tools have enabled the generation of functionally adult pancreatic β-cells derived from iPSCs. Although animal and human pancreatic development and β-cell physiology have significant differences, animal models represent an important tool in evaluating the therapeutic potential of iPSC-derived β-cells on type 1 diabetes treatment. This review outlines the recent progress in iPSC-derived β-cell differentiation methods, disease modelling, and future perspectives.

Glucose homeostasis with infinite gain: further lessons from the Daisyworld parable?

1997 ◽  
Vol 154 (2) ◽  
pp. 187-192 ◽  
Author(s):  
J H Koeslag ◽  
P T Saunders ◽  
J A Wessels
Keyword(s):  
Blood Glucose ◽  
Blood Glucose Level ◽  
Glucose Level ◽  
Cell Activity ◽  
Β Cells ◽  
Β Cell ◽  
Set Point ◽  
Black And White ◽  
Wide Range ◽  
Glucagon And Insulin

Abstract A major unresolved physiological problem is how the rate of hepatic glucose production is increased to match the increased rate of glucose utilization during exercise without a change in arterial blood glucose level. A homeostat with such capabilities is said to have infinite gain. Daisyworld is an imaginary planet orbiting a variable star. The only life is black and white daisies. Black daisies retain heat, slightly warming the planet; white daisies cool it. When the two types of daisies grow best at slightly different temperatures, variations in solar luminosity (over a wide range) cause the ratio of white:black daisies to vary in a manner that keeps the planetary temperature constant. This model therefore achieves infinite gain by having two opposing but interdependent controllers. Here we suggest that the pancreatic islet α- and β-cells might act as black and white daisies. For the analogy to apply, glucagon and insulin must not only have opposing effects on the blood sugar concentration, but the secretion of the one has, at some quantum level, to be at the expense of the other. Electrical coupling between heterocellular groups of α- and β-cells within the pancreatic islets suggests that this might indeed be the case. α-Cell activity must, furthermore, promote secretory activity in other α-cells; similarly with β-cells. This is probably mediated via pancreastatin and γ-amino butyric acid (GABA) which are paracrinically co-secreted with glucagon and insulin, respectively. α-Cell activity spreads (at the expense of β-cell activity) when the blood glucose level is below set point, while β-cell activity progressively replaces α-cell activity above set point. At set point changes in the ratio of α:β-cell activity are inhibited. Journal of Endocrinology (1997) 154, 187–192

Glucose regulation of insulin gene expression in pancreatic β-cells

2008 ◽  
Vol 415 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Sreenath S. Andrali ◽  
Megan L. Sampley ◽  
Nathan L. Vanderford ◽  
Sabire Özcan
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Blood Glucose ◽  
Insulin Gene ◽  
Β Cells ◽  
Β Cell ◽  
Insulin Synthesis ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Insulin Gene Expression

Production and secretion of insulin from the β-cells of the pancreas is very crucial in maintaining normoglycaemia. This is achieved by tight regulation of insulin synthesis and exocytosis from the β-cells in response to changes in blood glucose levels. The synthesis of insulin is regulated by blood glucose levels at the transcriptional and post-transcriptional levels. Although many transcription factors have been implicated in the regulation of insulin gene transcription, three β-cell-specific transcriptional regulators, Pdx-1 (pancreatic and duodenal homeobox-1), NeuroD1 (neurogenic differentiation 1) and MafA (V-maf musculoaponeurotic fibrosarcoma oncogene homologue A), have been demonstrated to play a crucial role in glucose induction of insulin gene transcription and pancreatic β-cell function. These three transcription factors activate insulin gene expression in a co-ordinated and synergistic manner in response to increasing glucose levels. It has been shown that changes in glucose concentrations modulate the function of these β-cell transcription factors at multiple levels. These include changes in expression levels, subcellular localization, DNA-binding activity, transactivation capability and interaction with other proteins. Furthermore, all three transcription factors are able to induce insulin gene expression when expressed in non-β-cells, including liver and intestinal cells. The present review summarizes the recent findings on how glucose modulates the function of the β-cell transcription factors Pdx-1, NeuroD1 and MafA, and thereby tightly regulates insulin synthesis in accordance with blood glucose levels.

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