Dual-Reporter β-Cell-Specific Male Transgenic Rats for the Analysis of β-Cell Functional Mass and Enrichment by Flow Cytometry

Abstract Mouse β-cell-specific reporter lines have played a key role in diabetes research. Although the rat provides several advantages, its use has lagged behind the mouse due to the relative paucity of genetic models. In this report we describe the generation and characterization of transgenic rats expressing a Renilla luciferase (RLuc)-enhanced yellow fluorescent protein (YFP) fusion under control of a 9-kb genomic fragment from the rat ins2 gene (RIP7-RLuc-YFP). Analysis of RLuc luminescence and YFP fluorescence revealed that reporter expression is restricted to β-cells in the adult rat. Physiological characteristics including body weight, fat and lean mass, fasting and fed glucose levels, glucose and insulin tolerance, and β-cell mass were similar between two RIP7-RLuc-YFP lines and wild-type littermates. Glucose-induced insulin secretion in isolated islets was indistinguishable from controls in one of the lines, whereas surprisingly, insulin secretion was defective in the second line. Consequently, subsequent studies were limited to the former line. We asked whether transgene activity was responsive to glucose as shown previously for the ins2 gene. Exposing islets ex vivo to high glucose (16.7 mM) or in vivo infusion of glucose for 24 hours increased luciferase activity in islets, whereas the fraction of YFP-positive β-cells after glucose infusion was unchanged. Finally, we showed that fluorescence-activated cell sorting of YFP-positive islet cells can be used to enrich for β-cells. Overall, this transgenic line will enable for the first time the application of both fluorescence and bioluminescence/luminescence-based approaches for the study of rat β-cells.

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Nrf2 Regulates β-cell Mass by Suppressing Cell Death and Promoting Proliferation

10.1101/2021.03.05.434145 ◽

2021 ◽

Author(s):

Sharon Baumel-Alterzon ◽

Liora S. Katz ◽

Gabriel Brill ◽

Clairete Jean-Pierre ◽

Yansui Li ◽

...

Keyword(s):

Cell Proliferation ◽

High Fat Diet ◽

Ex Vivo ◽

Cell Mass ◽

Conditional Knockout ◽

Diabetes Research ◽

Loss Of Function ◽

High Fat ◽

Β Cells ◽

Β Cell

SUMMARYFinding therapies that can protect and expand functional β-cell mass is a major goal of diabetes research. Here we generated β-cell-specific conditional knockout and gain-of-function mouse models and used human islet transplant experiments to examine how manipulating Nrf2 levels affects β-cell survival, proliferation and mass. Depletion of Nrf2 in β-cells resulted in decreased glucose-stimulated β-cell proliferation ex vivo and decreased adaptive β-cell proliferation and β-cell mass expansion after a high fat diet in vivo. Nrf2 protects β-cells from apoptosis after a high fat diet. Nrf2 loss-of-function decreases Pdx1 abundance and insulin content. Activating Nrf2 in a β-cell-specific manner increases β-cell proliferation and β-cell mass. Human islets transplanted under the kidney capsule of immunocompromised mice and treated systemically with CDDO-Me, an Nrf2 activator, display increased β-cell proliferation. Thus, Nrf2 regulates β-cell mass and is an exciting therapeutic target for expanding β-cell mass in diabetes.

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Ontology of the apelinergic system in mouse pancreas during pregnancy and relationship with β-cell mass

Scientific Reports ◽

10.1038/s41598-021-94725-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Brenda Strutt ◽

Sandra Szlapinski ◽

Thineesha Gnaneswaran ◽

Sarah Donegan ◽

Jessica Hill ◽

...

Keyword(s):

Cell Proliferation ◽

Insulin Secretion ◽

Glucose Transporter ◽

Cell Mass ◽

Elevated Serum ◽

Pancreatic Β Cell ◽

Β Cells ◽

Β Cell ◽

Glucose Transporter 2 ◽

Glucose Stimulated Insulin Secretion

AbstractThe apelin receptor (Aplnr) and its ligands, Apelin and Apela, contribute to metabolic control. The insulin resistance associated with pregnancy is accommodated by an expansion of pancreatic β-cell mass (BCM) and increased insulin secretion, involving the proliferation of insulin-expressing, glucose transporter 2-low (Ins+Glut2LO) progenitor cells. We examined changes in the apelinergic system during normal mouse pregnancy and in pregnancies complicated by glucose intolerance with reduced BCM. Expression of Aplnr, Apelin and Apela was quantified in Ins+Glut2LO cells isolated from mouse pancreata and found to be significantly higher than in mature β-cells by DNA microarray and qPCR. Apelin was localized to most β-cells by immunohistochemistry although Aplnr was predominantly associated with Ins+Glut2LO cells. Aplnr-staining cells increased three- to four-fold during pregnancy being maximal at gestational days (GD) 9–12 but were significantly reduced in glucose intolerant mice. Apelin-13 increased β-cell proliferation in isolated mouse islets and INS1E cells, but not glucose-stimulated insulin secretion. Glucose intolerant pregnant mice had significantly elevated serum Apelin levels at GD 9 associated with an increased presence of placental IL-6. Placental expression of the apelinergic axis remained unaltered, however. Results show that the apelinergic system is highly expressed in pancreatic β-cell progenitors and may contribute to β-cell proliferation in pregnancy.

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NEUROD1 Is Required for the Early α and β Endocrine Differentiation in the Pancreas

International Journal of Molecular Sciences ◽

10.3390/ijms22136713 ◽

2021 ◽

Vol 22 (13) ◽

pp. 6713

Author(s):

Romana Bohuslavova ◽

Ondrej Smolik ◽

Jessica Malfatti ◽

Zuzana Berkova ◽

Zaneta Novakova ◽

...

Keyword(s):

Transcription Factor ◽

Cell Fate ◽

Cell Mass ◽

Neonatal Diabetes ◽

Diabetes Research ◽

Pancreas Development ◽

Β Cells ◽

Β Cell ◽

Pancreatic Islet Cell ◽

Endocrine Differentiation

Diabetes is a metabolic disease that involves the death or dysfunction of the insulin-secreting β cells in the pancreas. Consequently, most diabetes research is aimed at understanding the molecular and cellular bases of pancreatic development, islet formation, β-cell survival, and insulin secretion. Complex interactions of signaling pathways and transcription factor networks regulate the specification, growth, and differentiation of cell types in the developing pancreas. Many of the same regulators continue to modulate gene expression and cell fate of the adult pancreas. The transcription factor NEUROD1 is essential for the maturation of β cells and the expansion of the pancreatic islet cell mass. Mutations of the Neurod1 gene cause diabetes in humans and mice. However, the different aspects of the requirement of NEUROD1 for pancreas development are not fully understood. In this study, we investigated the role of NEUROD1 during the primary and secondary transitions of mouse pancreas development. We determined that the elimination of Neurod1 impairs the expression of key transcription factors for α- and β-cell differentiation, β-cell proliferation, insulin production, and islets of Langerhans formation. These findings demonstrate that the Neurod1 deletion altered the properties of α and β endocrine cells, resulting in severe neonatal diabetes, and thus, NEUROD1 is required for proper activation of the transcriptional network and differentiation of functional α and β cells.

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Regulation of Insulin Secretion and β-Cell Mass by Activating Signal Cointegrator 2

Molecular and Cellular Biology ◽

10.1128/mcb.01412-05 ◽

2006 ◽

Vol 26 (12) ◽

pp. 4553-4563 ◽

Cited By ~ 15

Author(s):

Seon-Yong Yeom ◽

Geun Hyang Kim ◽

Chan Hee Kim ◽

Heun Don Jung ◽

So-Yeon Kim ◽

...

Keyword(s):

Insulin Secretion ◽

Endocrine Cells ◽

Potential Role ◽

Cell Mass ◽

Dominant Negative ◽

Transcriptional Coactivator ◽

Β Cells ◽

Β Cell ◽

Islet Mass

ABSTRACT Activating signal cointegrator 2 (ASC-2) is a transcriptional coactivator of many nuclear receptors (NRs) and other transcription factors and contains two NR-interacting LXXLL motifs (NR boxes). In the pancreas, ASC-2 is expressed only in the endocrine cells of the islets of Langerhans, but not in the exocrine cells. Thus, we examined the potential role of ASC-2 in insulin secretion from pancreatic β-cells. Overexpressed ASC-2 increased glucose-elicited insulin secretion, whereas insulin secretion was decreased in islets from ASC-2+/− mice. DN1 and DN2 are two dominant-negative fragments of ASC-2 that contain NR boxes 1 and 2, respectively, and block the interactions of cognate NRs with the endogenous ASC-2. Primary rat islets ectopically expressing DN1 or DN2 exhibited decreased insulin secretion. Furthermore, relative to the wild type, ASC-2+/− mice showed reduced islet mass and number, which correlated with increased apoptosis and decreased proliferation of ASC-2+/− islets. These results suggest that ASC-2 regulates insulin secretion and β-cell survival and that the regulatory role of ASC-2 in insulin secretion appears to involve, at least in part, its interaction with NRs via its two NR boxes.

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Insulin secretion in health and disease: nutrients dictate the pace

Proceedings of The Nutrition Society ◽

10.1017/s0029665115004152 ◽

2015 ◽

Vol 75 (1) ◽

pp. 19-29 ◽

Cited By ~ 9

Author(s):

Romano Regazzi ◽

Adriana Rodriguez-Trejo ◽

Cécile Jacovetti

Keyword(s):

Fatty Acids ◽

Insulin Secretion ◽

Cell Mass ◽

Insulin Biosynthesis ◽

Β Cells ◽

Β Cell ◽

Altered Expression ◽

Cell Dysfunction ◽

Dietary Nutrients ◽

Underlying Mechanisms

Insulin is a key hormone controlling metabolic homeostasis. Loss or dysfunction of pancreatic β-cells lead to the release of insufficient insulin to cover the organism needs, promoting diabetes development. Since dietary nutrients influence the activity of β-cells, their inadequate intake, absorption and/or utilisation can be detrimental. This review will highlight the physiological and pathological effects of nutrients on insulin secretion and discuss the underlying mechanisms. Glucose uptake and metabolism in β-cells trigger insulin secretion. This effect of glucose is potentiated by amino acids and fatty acids, as well as by entero-endocrine hormones and neuropeptides released by the digestive tract in response to nutrients. Glucose controls also basal and compensatory β-cell proliferation and, along with fatty acids, regulates insulin biosynthesis. If in the short-term nutrients promote β-cell activities, chronic exposure to nutrients can be detrimental to β-cells and causes reduced insulin transcription, increased basal secretion and impaired insulin release in response to stimulatory glucose concentrations, with a consequent increase in diabetes risk. Likewise, suboptimal early-life nutrition (e.g. parental high-fat or low-protein diet) causes altered β-cell mass and function in adulthood. The mechanisms mediating nutrient-induced β-cell dysfunction include transcriptional, post-transcriptional and translational modifications of genes involved in insulin biosynthesis and secretion, carbohydrate and lipid metabolism, cell differentiation, proliferation and survival. Altered expression of these genes is partly caused by changes in non-coding RNA transcripts induced by unbalanced nutrient uptake. A better understanding of the mechanisms leading to β-cell dysfunction will be critical to improve treatment and find a cure for diabetes.

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β-Cell adaptation in 60% pancreatectomy rats that preserves normoinsulinemia and normoglycemia

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.279.1.e68 ◽

2000 ◽

Vol 279 (1) ◽

pp. E68-E73 ◽

Cited By ~ 30

Author(s):

Ye Qi Liu ◽

Peter W. Nevin ◽

Jack L. Leahy

Keyword(s):

Insulin Secretion ◽

Regulatory Element ◽

Cell Mass ◽

Maximal Velocity ◽

Β Cells ◽

Β Cell ◽

Biochemical Basis ◽

Adaptive Mechanisms ◽

Sense And Respond ◽

Glucose Responsiveness

Islet β-cells are the regulatory element of the glucose homeostasis system. When functioning normally, they precisely counterbalance changes in insulin sensitivity or β-cell mass to preserve normoglycemia. This understanding seems counter to the dogma that β-cells are regulated by glycemia. We studied 60% pancreatectomy rats (Px) 4 wk postsurgery to elucidate the β-cell adaptive mechanisms. Nonfasting glycemia and insulinemia were identical in Px and sham-operated controls. There was partial regeneration of the excised β-cells in the Px rats, but it was limited in scope, with the pancreas β-cell mass reaching 55% of the shams (40% increase from the time of surgery). More consequential was a heightened glucose responsiveness of Px islets so that glucose utilization and insulin secretion per milligram of islet protein were both 80% augmented at normal levels of glycemia. Investigation of the biochemical basis showed a doubled glucokinase maximal velocity in Px islets, with no change in the glucokinase protein concentration after adjustment for the different β-cell mass in Px and sham islets. Hexokinase activity measured in islet extracts was also minimally increased, but the glucose 6-phosphate concentration and basal glucose usage of Px islets were not different from those in islets from sham-operated rats. The dominant β-cell adaptive response in the 60% Px rats was an increased catalytic activity of glucokinase. The remaining β-cells thus sense, and respond to, perceived hyperglycemia despite glycemia actually being normal. β-Cell mass and insulin secretion are both augmented so that whole pancreas insulin output, and consequently glycemia, are maintained at normal levels.

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GENETICALLY ENGINEERED PIG MODELS FOR TRANSLATIONAL DIABETES RESEARCH

Reproduction Fertility and Development ◽

10.1071/rdv25n1ab346 ◽

2013 ◽

Vol 25 (1) ◽

pp. 320 ◽

Cited By ~ 2

Author(s):

Eckhard Wolf

Keyword(s):

Mouse Models ◽

Cell Mass ◽

Physiological Age ◽

Diabetic Patients ◽

Diabetes Research ◽

Rodent Models ◽

Β Cells ◽

Β Cell ◽

Transgenic Pigs ◽

Genetic Modifications

Animal models play crucial roles for understanding disease mechanisms and for the development and evaluation of therapeutic strategies. In biomedicine, classical rodent models are most widely used for several reasons, including standardization of genetics and environment, cost efficiency, and the possibility to introduce targeted genetic modifications for the generation of tailored disease models. However, due to differences in anatomical and physiological characteristics, rodent models do not always reflect the situation of human patients sufficiently well to be predictive in terms of efficacy and safety of new therapies. In this respect, the pig has been discussed as a missing link between mouse models and human patients. As a monogastric omnivore, the pig shares many anatomical and physiological similarities with humans. Importantly, the techniques for genetic modification of pigs have been refined to a level allowing almost the same spectrum of alterations as in mouse models (Aigner et al. 2010 J. Mol. Med. (Berl.) 88, 653–664). These include inducible transgene expression systems (Klymiuk et al. 2012 FASEB J. 26, 1086–1099) as well as the introduction of targeted genetic modifications (Klymiuk et al. 2012 J. Mol. Med. (Berl.) 90, 597–608). A major focus of our laboratory is the generation, characterisation, and implementation of pig models for translational diabetes research. Transgenic pigs expressing a dominant negative receptor for the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) demonstrated a crucial role of the GIP system for the physiological age-related expansion of pancreatic β-cell mass. Moreover, this animal model shares important characteristics of type 2 diabetes mellitus: impaired incretin effect, reduced glucose tolerance and insulin secretion, and a progressive reduction of β-cell mass (Renner et al. 2010 Diabetes 59, 1228–1238). More recently, we used this model to search for metabolic biomarkers which are associated with progression in the pre-diabetic period and identified specific amino acid and lipid signatures as candidate biomarkers (Renner et al. 2012 Diabetes 61, 2166–2175). Further, we created the first pig model for permanent neonatal diabetes by expression C94Y mutant insulin in the β-cells of transgenic pigs. In addition to their use as biomedical models, pigs may also serve as organ and tissue donors for xenotransplantation. Transplantation of encapsulated porcine pancreatic islets to type 1 diabetic patients with severe unaware hypoglycemia has already entered clinical studies, but encapsulation may shorten the lifespan of the islets. Therefore, in order to overcome the rejection of pig islets by human T-cells, we generated transgenic pigs expressing the optimized CTLA-4Ig variant LEA29Y in the pancreatic β-cells. Islets from LEA29Y transgenic pigs rescued diabetes and were protected against rejection in a humanized mouse model (Klymiuk et al. 2012 Diabetes 61, 1527–1532).

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Increased alpha and beta cell mass during mouse pregnancy is not dependent on transdifferentiation

Experimental Biology and Medicine ◽

10.1177/1535370220972686 ◽

2020 ◽

pp. 153537022097268

Author(s):

Sandra K Szlapinski ◽

Jamie Bennett ◽

Brenda J Strutt ◽

David J Hill

Keyword(s):

Beta Cell ◽

Fluorescent Protein ◽

Control Diet ◽

Yellow Fluorescent Protein ◽

Pancreatic Beta Cell ◽

Cell Mass ◽

Beta Cell Mass ◽

Alpha Cell ◽

Β Cell ◽

Cell Conversion

Maternal pancreatic beta-cell mass (BCM) increases during pregnancy to compensate for relative insulin resistance. If BCM expansion is suboptimal, gestational diabetes mellitus can develop. Alpha-cell mass (ACM) also changes during pregnancy, but there is a lack of information about α-cell plasticity in pregnancy and whether α- to β-cell transdifferentiation can occur. To investigate this, we used a mouse model of gestational glucose intolerance induced by feeding low-protein (LP) diet from conception until weaning and compared pregnant female offspring to control diet-fed animals. Control and LP pancreata were collected for immunohistochemical analysis and serum glucagon levels were measured. In order to lineage trace α- to β-cell conversion, we utilized transgenic mice expressing yellow fluorescent protein behind the proglucagon gene promoter (Gcg-Cre/YFP) and collected pancreata for histology at various gestational timepoints. Alpha-cell proliferation increased significantly at gestational day (GD) 9.5 in control pregnancies resulting in an increased ACM at GD18.5, and this was significantly reduced in LP animals. Despite these changes, serum glucagon was higher in LP mice at GD18.5. Pregnant Gcg-Cre/YFP mice showed no increase in the abundance of insulin+YFP+glucagon– cells (phenotypic β-cells). A second population of insulin+YFP+glucagon+ cells was identified which also did not alter during pregnancy. However, there was an altered anatomical distribution within islets with fewer insulin+YFP+glucagon– cells but more insulin+YFP+glucagon+ cells being present in the islet mantle at GD18.5. These findings demonstrate that dynamic changes in ACM occur during normal pregnancy and were altered in glucose-intolerant pregnancies.

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β cell-specific deletion of HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase causes overt diabetes due to reduction of β cell mass and impaired insulin secretion

10.2337/figshare.12771422.v1 ◽

2020 ◽

Author(s):

Ada Admin ◽

Shoko Takei ◽

Shuichi Nagashima ◽

Akihito Takei ◽

Daisuke Yamamuro ◽

...

Keyword(s):

Insulin Secretion ◽

Coenzyme A ◽

Cell Mass ◽

Bzip Transcription Factor ◽

Β Cells ◽

Β Cell ◽

Embryonic Pancreas ◽

Endocrine Progenitors ◽

Coenzyme A Reductase

Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), statins, which are used to prevent cardiovascular diseases, are associated with a modest increase in the risk of new-onset diabetes mellitus. To investigate the role of HMGCR in the development of β cells and glucose homeostasis, we deleted Hmgcr in a β cell-specific manner by using the Cre-loxP technique. Mice lacking Hmgcr in β cells (β-KO) exhibited hypoinsulinemic hyperglycemia as early as postnatal day 9 (P9) due to decreases in both β cell mass and insulin secretion. Ki67 positive cells were reduced in β-KO mice at P9, thus β cell mass reduction was caused by proliferation disorder immediately after birth. The mRNA expression of neurogenin3 (Ngn3), which is transiently expressed in endocrine progenitors of the embryonic pancreas, was maintained despite a striking reduction in the expression of β cell-associated genes, such as insulin, Pancreatic and duodenal homeobox 1 (Pdx1) and MAF BZIP transcription factor A (Mafa) in the islets from β-KO mice. Histological analyses revealed dysmorphic islets with markedly reduced numbers of β cells, some of which were also positive for glucagon. In conclusion, HMGCR plays critical roles not only in insulin secretion but also in the development of β cells in mice.

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