In vivo Imaging β-cell Function Reveals Two Waves of β-cell Maturation

AbstractThe insulin-secreting cells generated from stem cells in vitro are less glucose responsive than primary β-cells. To search for the missing ingredients that are needed for β-cell maturation, we have longitudinally monitored function of every β-cell in Tg (ins:Rcamp1.07) zebrafish embryos with a newly-invented two-photon light-sheet microscope. We have shown that β-cell maturation begins from the islet mantle and propagates to the islet core during the hatching period, coordinated by the islet vascularization. Lower concentration of glucose is optimal to initiate β-cell maturation, while increased glucose delivery to every cell through microcirculation is required for functional boosting of the β-cells. Both the initiation and the boosting of β-cell maturation demands activation of calcineurin/NFAT by glucose. Calcineurin activator combined with glucose promotes mouse neonatal β-cells cultured in vitro to mature to a functional state similar to adult β-cells, suggesting a new strategy for improving stem cell-derived β-like cell function in vitro.

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The HDAC Inhibitor Butyrate Impairs β Cell Function and Activates the Disallowed Gene Hexokinase I

International Journal of Molecular Sciences ◽

10.3390/ijms222413330 ◽

2021 ◽

Vol 22 (24) ◽

pp. 13330

Author(s):

Stephanie Bridgeman ◽

Gaewyn Ellison ◽

Philip Newsholme ◽

Cyril Mamotte

Keyword(s):

Insulin Secretion ◽

Low Dose ◽

Cell Function ◽

High Dose ◽

Hdac Inhibition ◽

Β Cells ◽

Β Cell ◽

Β Cell Function

Histone deacetylase (HDAC) inhibitors such as butyrate have been reported to reduce diabetes risk and protect insulin-secreting pancreatic β cells in animal models. However, studies on insulin-secreting cells in vitro have found that butyrate treatment resulted in impaired or inappropriate insulin secretion. Our study explores the effects of butyrate on insulin secretion by BRIN BD-11 rat pancreatic β cells and examined effects on the expression of genes implicated in β cell function. Robust HDAC inhibition with 5 mM butyrate or trichostatin A for 24 h in β cells decreased basal insulin secretion and content, as well as insulin secretion in response to acute stimulation. Treatment with butyrate also increased expression of the disallowed gene hexokinase I, possibly explaining the impairment to insulin secretion, and of TXNIP, which may increase oxidative stress and β cell apoptosis. In contrast to robust HDAC inhibition (>70% after 24 h), low-dose and acute high-dose treatment with butyrate enhanced nutrient-stimulated insulin secretion. In conclusion, although protective effects of HDAC inhibition have been observed in vivo, potent HDAC inhibition impairs β cell function in vitro. The chronic low dose and acute high dose butyrate treatments may be more reflective of in vivo effects.

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Inhibition of Small Maf Function in Pancreatic β-Cells Improves Glucose Tolerance Through the Enhancement of Insulin Gene Transcription and Insulin Secretion

Endocrinology ◽

10.1210/en.2014-1906 ◽

2015 ◽

Vol 156 (10) ◽

pp. 3570-3580 ◽

Cited By ~ 9

Author(s):

Hiroshi Nomoto ◽

Takuma Kondo ◽

Hideaki Miyoshi ◽

Akinobu Nakamura ◽

Yoko Hida ◽

...

Keyword(s):

Insulin Secretion ◽

Glucose Tolerance ◽

High Fat Diet ◽

Cell Function ◽

High Fat ◽

Β Cells ◽

Β Cell ◽

Β Cell Function

The large-Maf transcription factor v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (MafA) has been found to be crucial for insulin transcription and synthesis and for pancreatic β-cell function and maturation. However, insights about the effects of small Maf factors on β-cells are limited. Our goal was to elucidate the function of small-Maf factors on β-cells using an animal model of endogenous small-Maf dysfunction. Transgenic (Tg) mice with β-cell-specific expression of dominant-negative MafK (DN-MafK) experiments, which can suppress the function of all endogenous small-Mafs, were fed a high-fat diet, and their in vivo phenotypes were evaluated. Phenotypic analysis, glucose tolerance tests, morphologic examination of β-cells, and islet experiments were performed. DN-MafK-expressed MIN6 cells were also used for in vitro analysis. The results showed that DN-MafK expression inhibited endogenous small-Maf binding to insulin promoter while increasing MafA binding. DN-MafK Tg mice under high-fat diet conditions showed improved glucose metabolism compared with control mice via incremental insulin secretion, without causing changes in insulin sensitivity or MafA expression. Moreover, up-regulation of insulin and glucokinase gene expression was observed both in vivo and in vitro under DN-MafK expression. We concluded that endogenous small-Maf factors negatively regulates β-cell function by competing for MafA binding, and thus, the inhibition of small-Maf activity can improve β-cell function.

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In vivo imaging of β-cell function reveals glucose-mediated heterogeneity of β-cell functional development

eLife ◽

10.7554/elife.41540 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 8

Author(s):

Jia Zhao ◽

Weijian Zong ◽

Yiwen Zhao ◽

Dongzhou Gou ◽

Shenghui Liang ◽

...

Keyword(s):

Insulin Secretion ◽

In Vivo Imaging ◽

Cell Function ◽

Β Cells ◽

Β Cell ◽

Functional Development ◽

Β Cell Function ◽

Glucose Stimulated Insulin Secretion

How pancreatic β-cells acquire function in vivo is a long-standing mystery due to the lack of technology to visualize β-cell function in living animals. Here, we applied a high-resolution two-photon light-sheet microscope for the first in vivo imaging of Ca2+activity of every β-cell in Tg (ins:Rcamp1.07) zebrafish. We reveal that the heterogeneity of β-cell functional development in vivo occurred as two waves propagating from the islet mantle to the core, coordinated by islet vascularization. Increasing amounts of glucose induced functional acquisition and enhancement of β-cells via activating calcineurin/nuclear factor of activated T-cells (NFAT) signaling. Conserved in mammalians, calcineurin/NFAT prompted high-glucose-stimulated insulin secretion of neonatal mouse islets cultured in vitro. However, the reduction in low-glucose-stimulated insulin secretion was dependent on optimal glucose but independent of calcineurin/NFAT. Thus, combination of optimal glucose and calcineurin activation represents a previously unexplored strategy for promoting functional maturation of stem cell-derived β-like cells in vitro.

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Perilipin2 down-regulation in β cells impairs insulin secretion under nutritional stress and damages mitochondria

10.1101/2020.10.01.322974 ◽

2020 ◽

Author(s):

Akansha Mishra ◽

Siming Liu ◽

Joseph Promes ◽

Mikako Harata ◽

William Sivitz ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Islet Cells ◽

Cell Metabolism ◽

Nutritional Stress ◽

Β Cells ◽

Β Cell ◽

Down Regulation

Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in β cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was down-regulated in mouse β cells, INS1 cells, and human islet cells. β cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells have an important role in preserving insulin secretion, β cell metabolism and mitochondrial function under nutritional stress.

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Downregulation of lncRNA TUG1 Affects Apoptosis and Insulin Secretion in Mouse Pancreatic β Cells

Cellular Physiology and Biochemistry ◽

10.1159/000373999 ◽

2015 ◽

Vol 35 (5) ◽

pp. 1892-1904 ◽

Cited By ~ 68

Author(s):

Dan-dan Yin ◽

Er-bao Zhang ◽

Liang-hui You ◽

Ning Wang ◽

Lin-tao Wang ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Annexin V ◽

Pancreatic Tissue ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Lncrna Tug1

Background: Increasing evidence indicates that long noncoding RNAs (IncRNAs) perform specific biological functions in diverse processes. Recent studies have reported that IncRNAs may be involved in β cell function. The aim of this study was to characterize the role of IncRNA TUG1 in mouse pancreatic β cell functioning both in vitro and in vivo. Methods: qRT-PCR analyses were performed to detect the expression of lncRNA TUG1 in different tissues. RNAi, MTT, TUNEL and Annexin V-FITC assays and western blot, GSIS, ELISA and immunochemistry analyses were performed to detect the effect of lncRNA TUG1 on cell apoptosis and insulin secretion in vitro and in vivo. Results: lncRNA TUG1 was highly expressed in pancreatic tissue compared with other organ tissues, and expression was dynamically regulated by glucose in Nit-1 cells. Knockdown of lncRNA TUG1 expression resulted in an increased apoptosis ratio and decreased insulin secretion in β cells both in vitro and in vivo . Immunochemistry analyses suggested decreased relative islet area after treatment with lncRNA TUG1 siRNA. Conclusion: Downregulation of lncRNA TUG1 expression affected apoptosis and insulin secretion in pancreatic β cells in vitro and in vivo. lncRNA TUG1 may represent a factor that regulates the function of pancreatic β cells.

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Can Functionally Mature Islet β-Cells Be Derived from Pluripotent Stem Cells? – A Step Towards Ready-To-Use β-Cells in Type 1 Diabetes

Current Stem Cell Research & Therapy ◽

10.2174/1574888x15666200621171726 ◽

2020 ◽

Vol 15 ◽

Author(s):

Bishnu K Khand ◽

Ramesh R Bhonde

Keyword(s):

Stem Cells ◽

Type 1 Diabetes ◽

Pluripotent Stem Cells ◽

Cell Function ◽

Β Cells ◽

Β Cell ◽

Β Cell Function ◽

Glucose Stimulated Insulin Secretion

: Pluripotent Stem Cells [PSCs] are emerging as an excellent cellular source for treatment of many degenerative diseases such as diabetes, ischemic heart failure, Alzheimer’s disease. PSC-derived pancreatic islet β-cells appear to be as a promising therapy for type 1 diabetes patients with impaired β-cell function. Several protocols have been developed to derive β-cells from PSCs. However, these protocols produce β-like cells that show low glucose stimulated insulin secretion [GSIS] function and mirror GSIS profile of functionally immature neonatal β-cells. Several studies have documented a positive correlation between the sirtuins [a family of ageing-related proteins] and the GSIS function of adult β-cells. We are of the view that GSIS function of PSC-derived β-like cells could be enhanced by improving the function of sirtuins in them. Studying the sirtuin expression and activation pattern during the β-cell development and inclusion of the sirtuin activator and inhibitor cocktail [specific to a developmental stage] in the present protocols may help us derive functionally mature, ready-to-use β-cells in-vitro making them suitable for transplantation in type 1 diabetes.

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Metformin Preserves β-Cell Compensation in Insulin Secretion and Mass Expansion in Prediabetic Nile Rats

International Journal of Molecular Sciences ◽

10.3390/ijms22010421 ◽

2021 ◽

Vol 22 (1) ◽

pp. 421

Author(s):

Hui Huang ◽

Bradi R. Lorenz ◽

Paula Horn Zelmanovitz ◽

Catherine B. Chan

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Cell Mass ◽

Metformin Treatment ◽

Β Cells ◽

Β Cell ◽

Β Cell Function ◽

Glucose Output ◽

Mass Expansion

Prediabetes is a high-risk condition for type 2 diabetes (T2D). Pancreatic β-cells adapt to impaired glucose regulation in prediabetes by increasing insulin secretion and β-cell mass expansion. In people with prediabetes, metformin has been shown to prevent prediabetes conversion to diabetes. However, emerging evidence indicates that metformin has negative effects on β-cell function and survival. Our previous study established the Nile rat (NR) as a model for prediabetes, recapitulating characteristics of human β-cell compensation in function and mass expansion. In this study, we investigated the action of metformin on β-cells in vivo and in vitro. A 7-week metformin treatment improved glucose tolerance by reducing hepatic glucose output and enhancing insulin secretion. Although high-dose metformin inhibited β-cell glucose-stimulated insulin secretion in vitro, stimulation of β-cell insulin secretion was preserved in metformin-treated NRs via an indirect mechanism. Moreover, β-cells in NRs receiving metformin exhibited increased endoplasmic reticulum (ER) chaperones and alleviated apoptotic unfold protein response (UPR) without changes in the expression of cell identity genes. Additionally, metformin did not suppress β-cell mass compensation or proliferation. Taken together, despite the conflicting role indicated by in vitro studies, administration of metformin does not exert a negative effect on β-cell function or cell mass and, instead, early metformin treatment may help protect β-cells from exhaustion and decompensation.

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