α-Cell Dysfunctions and Molecular Alterations in Male Insulinopenic Diabetic Mice Are Not Completely Corrected by Insulin

Abstract Glucagon and α-cell dysfunction are critical in the development of hyperglycemia during diabetes both in humans and rodents. We hypothesized that α-cell dysfunction leading to dysregulated glucagon secretion in diabetes is due to both a lack of insulin and intrinsic defects. To characterize α-cell dysfunction in diabetes, we used glucagon-Venus transgenic male mice and induced insulinopenic hyperglycemia by streptozotocin administration leading to alterations of glucagon secretion. We investigated the in vivo impact of insulinopenic hyperglycemia on glucagon-producing cells using FACS-sorted α-cells from control and diabetic mice. We demonstrate that increased glucagonemia in diabetic mice is mainly due to increases of glucagon release and biosynthesis per cell compared with controls without changes in α-cell mass. We identified genes coding for proteins involved in glucagon biosynthesis and secretion, α-cell differentiation, and potential stress markers such as the glucagon, Arx, MafB, cMaf, Brain4, Foxa1, Foxa3, HNF4α, TCF7L2, Glut1, Sglt2, Cav2.1, Cav2.2, Nav1.7, Kir6.2/Sur1, Pten, IR, NeuroD1, GPR40, and Sumo1 genes, which were abnormally regulated in diabetic mice. Importantly, insulin treatment partially corrected α-cell function and expression of genes coding for proglucagon, or involved in glucagon secretion, glucose transport and insulin signaling but not those coding for cMAF, FOXA1, and α-cell differentiation markers as well as GPR40, NEUROD1, CAV2.1, and SUMO1. Our results indicate that insulinopenic diabetes induce marked α-cell dysfunction and molecular alteration, which are only partially corrected by in vivo insulin treatment.

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Diminished glucagon suppression after β-cell reduction is due to impaired α-cell function rather than an expansion of α-cell mass

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00315.2010 ◽

2011 ◽

Vol 300 (4) ◽

pp. E717-E723 ◽

Cited By ~ 24

Author(s):

Juris J. Meier ◽

Sandra Ueberberg ◽

Simone Korbas ◽

Stephan Schneider

Keyword(s):

Insulin Treatment ◽

Cell Function ◽

Cell Mass ◽

Glucagon Secretion ◽

Pancreatic Tissue ◽

Oral Glucose ◽

Inverse Association ◽

Β Cell ◽

Glucose Ingestion ◽

Glucagon Suppression

Impaired suppression of glucagon levels after oral glucose or meal ingestion is a hallmark of type 2 diabetes. Whether hyperglucagonemia after a β-cell loss results from a functional upregulation of glucagon secretion or an increase in α-cell mass is yet unclear. CD-1 mice were treated with streptozotocin (STZ) or saline. Pancreatic tissue was collected after 14, 21, and 28 days and examined for α- and β-cell mass and turnover. Intraperitoneal (ip) glucose tolerance tests were performed at day 28 as well as after 12 days of subcutaneous insulin treatment, and glucose, insulin, and glucagon levels were determined. STZ treatment led to fasting and post-challenge hyperglycemia ( P < 0.001 vs. controls). Insulin levels increased after glucose injection in controls ( P < 0.001) but were unchanged in STZ mice ( P = 0.36). Intraperitoneal glucose elicited a 63.1 ± 4.1% glucagon suppression in control mice ( P < 0.001), whereas the glucagon suppression was absent in STZ mice ( P = 0.47). Insulin treatment failed to normalize glucagon levels. There was a significant inverse association between insulin and glucagon levels after ip glucose ingestion ( r2 = 0.99). β-Cell mass was reduced by ∼75% in STZ mice compared with controls ( P < 0.001), whereas α-cell mass remained unchanged ( P > 0.05). α-Cell apoptosis (TUNEL) and replication (Ki67) were rather infrequently noticed, with no significant differences between the groups. These studies underline the importance of endogenous insulin for the glucose-induced suppression of glucagon secretion and suggest that the insufficient decline in glucagon levels after glucose administration in diabetes is primarily due to a functional loss of intraislet inhibition of α-cell function rather than an expansion of α-cell mass.

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Harnessing Proliferation for the Expansion of Stem Cell-Derived Pancreatic Cells: Advantages and Limitations

Frontiers in Endocrinology ◽

10.3389/fendo.2021.636182 ◽

2021 ◽

Vol 12 ◽

Cited By ~ 1

Author(s):

Amanda Oakie ◽

Maria Cristina Nostro

Keyword(s):

Stem Cell ◽

Cell Differentiation ◽

Cellular Proliferation ◽

Cell Function ◽

Cell Mass ◽

Β Cells ◽

Β Cell ◽

Pancreatic Cells

Restoring the number of glucose-responsive β-cells in patients living with diabetes is critical for achieving normoglycemia since functional β-cells are lost during the progression of both type 1 and 2 diabetes. Stem cell-derived β-cell replacement therapies offer an unprecedented opportunity to replace the lost β-cell mass, yet differentiation efficiencies and the final yield of insulin-expressing β-like cells are low when using established protocols. Driving cellular proliferation at targeted points during stem cell-derived pancreatic progenitor to β-like cell differentiation can serve as unique means to expand the final cell therapeutic product needed to restore insulin levels. Numerous studies have examined the effects of β-cell replication upon functionality, using primary islets in vitro and mouse models in vivo, yet studies that focus on proliferation in stem cell-derived pancreatic models are only just emerging in the field. This mini review will discuss the current literature on cell proliferation in pancreatic cells, with a focus on the proliferative state of stem cell-derived pancreatic progenitors and β-like cells during their differentiation and maturation. The benefits of inducing proliferation to increase the final number of β-like cells will be compared against limitations associated with driving replication, such as the blunted capacity of proliferating β-like cells to maintain optimal β-cell function. Potential strategies that may bypass the challenges induced by the up-regulation of cell cycle-associated factors during β-cell differentiation will be proposed.

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NF-κB activity during pancreas development regulates adult β-cell mass by modulating neonatal β-cell proliferation and apoptosis

Cell Death Discovery ◽

10.1038/s41420-020-00386-9 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Dror Sever ◽

Anat Hershko-Moshe ◽

Rohit Srivastava ◽

Roy Eldor ◽

Daniel Hibsher ◽

...

Keyword(s):

Cell Proliferation ◽

Developmental Stages ◽

Cell Mass ◽

Diabetes Incidence ◽

Β Cells ◽

Β Cell ◽

Cell Dysfunction ◽

Regulatory Circuit ◽

Proliferation And Apoptosis

AbstractNF-κB is a well-characterized transcription factor, widely known for its roles in inflammation and immune responses, as well as in control of cell division and apoptosis. However, its function in β-cells is still being debated, as it appears to depend on the timing and kinetics of its activation. To elucidate the temporal role of NF-κB in vivo, we have generated two transgenic mouse models, the ToIβ and NOD/ToIβ mice, in which NF-κB activation is specifically and conditionally inhibited in β-cells. In this study, we present a novel function of the canonical NF-κB pathway during murine islet β-cell development. Interestingly, inhibiting the NF-κB pathway in β-cells during embryogenesis, but not after birth, in both ToIβ and NOD/ToIβ mice, increased β-cell turnover, ultimately resulting in a reduced β-cell mass. On the NOD background, this was associated with a marked increase in insulitis and diabetes incidence. While a robust nuclear immunoreactivity of the NF-κB p65-subunit was found in neonatal β-cells, significant activation was not detected in β-cells of either adult NOD/ToIβ mice or in the pancreata of recently diagnosed adult T1D patients. Moreover, in NOD/ToIβ mice, inhibiting NF-κB post-weaning had no effect on the development of diabetes or β-cell dysfunction. In conclusion, our data point to NF-κB as an important component of the physiological regulatory circuit that controls the balance of β-cell proliferation and apoptosis in the early developmental stages of insulin-producing cells, thus modulating β-cell mass and the development of diabetes in the mouse model of T1D.

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The Role of the α Cell in the Pathogenesis of Diabetes: A World beyond the Mirror

International Journal of Molecular Sciences ◽

10.3390/ijms22179504 ◽

2021 ◽

Vol 22 (17) ◽

pp. 9504

Author(s):

María Sofía Martínez ◽

Alexander Manzano ◽

Luis Carlos Olivar ◽

Manuel Nava ◽

Juan Salazar ◽

...

Keyword(s):

Cell Function ◽

Cell Mass ◽

Glucagon Secretion ◽

Endocrine Regulation ◽

Β Cell ◽

Cell Hyperplasia ◽

Dipeptidyl Peptidase 4 ◽

Dipeptidyl Peptidase 4 Inhibitors ◽

Glucagon Like Peptide 1 ◽

Chronic Hyperglycaemia

Type 2 Diabetes Mellitus (T2DM) is one of the most prevalent chronic metabolic disorders, and insulin has been placed at the epicentre of its pathophysiological basis. However, the involvement of impaired alpha (α) cell function has been recognized as playing an essential role in several diseases, since hyperglucagonemia has been evidenced in both Type 1 and T2DM. This phenomenon has been attributed to intra-islet defects, like modifications in pancreatic α cell mass or dysfunction in glucagon’s secretion. Emerging evidence has shown that chronic hyperglycaemia provokes changes in the Langerhans’ islets cytoarchitecture, including α cell hyperplasia, pancreatic beta (β) cell dedifferentiation into glucagon-positive producing cells, and loss of paracrine and endocrine regulation due to β cell mass loss. Other abnormalities like α cell insulin resistance, sensor machinery dysfunction, or paradoxical ATP-sensitive potassium channels (KATP) opening have also been linked to glucagon hypersecretion. Recent clinical trials in phases 1 or 2 have shown new molecules with glucagon-antagonist properties with considerable effectiveness and acceptable safety profiles. Glucagon-like peptide-1 (GLP-1) agonists and Dipeptidyl Peptidase-4 inhibitors (DPP-4 inhibitors) have been shown to decrease glucagon secretion in T2DM, and their possible therapeutic role in T1DM means they are attractive as an insulin-adjuvant therapy.

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

Mediators of Inflammation ◽

10.1155/2013/750540 ◽

2013 ◽

Vol 2013 ◽

pp. 1-14 ◽

Cited By ~ 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.

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Follow-up of GK rats during prediabetes highlights increased insulin action and fat deposition despite low insulin secretion

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00501.2007 ◽

2008 ◽

Vol 294 (1) ◽

pp. E168-E175 ◽

Cited By ~ 32

Author(s):

Jamileh Movassat ◽

Danièle Bailbé ◽

Cécile Lubrano-Berthelier ◽

Françoise Picarel-Blanchot ◽

Eric Bertin ◽

...

Keyword(s):

Body Composition ◽

Insulin Secretion ◽

Insulin Sensitivity ◽

Cell Function ◽

Cell Mass ◽

The Body ◽

Whole Body ◽

Β Cell ◽

Gk Rats

The adult Goto-Kakizaki (GK) rat is characterized by impaired glucose-induced insulin secretion in vivo and in vitro, decreased β-cell mass, decreased insulin sensitivity in the liver, and moderate insulin resistance in muscles and adipose tissue. GK rats do not exhibit basal hyperglycemia during the first 3 wk after birth and therefore could be considered prediabetic during this period. Our aim was to identify the initial pathophysiological changes occurring during the prediabetes period in this model of type 2 diabetes (T2DM). To address this, we investigated β-cell function, insulin sensitivity, and body composition in normoglycemic prediabetic GK rats. Our results revealed that the in vivo secretory response of GK β-cells to glucose is markedly reduced and the whole body insulin sensitivity is increased in the prediabetic GK rats in vivo. Moreover, the body composition of suckling GK rats is altered compared with age-matched Wistar rats, with an increase of the number of adipocytes before weaning despite a decreased body weight and lean mass in the GK rats. None of these changes appeared to be due to the postnatal nutritional environment of GK pups as demonstrated by cross-fostering GK pups with nondiabetic Wistar dams. In conclusion, in the GK model of T2DM, β-cell dysfunction associated with increased insulin sensitivity and the alteration of body composition are proximal events that might contribute to the establishment of overt diabetes in adult GK rats.

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From Theory to Clinical Practice in the Use of GLP-1 Receptor Agonists and DPP-4 Inhibitors Therapy

Experimental Diabetes Research ◽

10.1155/2011/898913 ◽

2011 ◽

Vol 2011 ◽

pp. 1-8 ◽

Cited By ~ 14

Author(s):

Ilaria Dicembrini ◽

Laura Pala ◽

Carlo Maria Rotella

Keyword(s):

Cell Function ◽

Lifestyle Modification ◽

Cell Mass ◽

Beta Cell Mass ◽

Minimal Risk ◽

Dipeptidyl Peptidase 4 ◽

Receptor Agonists ◽

Dipeptidyl Peptidase 4 Inhibitors

Promoting long-term adherence to lifestyle modification and choice of antidiabetic agent with low hypoglycemia risk profile and positive weight profile could be the most effective strategy in achieving sustained glycemic control and in reducing comorbidities. From this perspective, vast interest has been generated by glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 inhibitors (DPP-4i). In this review our ten-year clinical and laboratory experience byin vitroandin vivostudies is reported. Herein, we reviewed available data on the efficacy and safety profile of GLP-1 receptor agonists and DPP-4i. The introduction of incretin hormone-based therapies represents a novel therapeutic strategy, because these drugs not only improve glycemia with minimal risk of hypoglycemia but also have other extraglycemic beneficial effects. In clinical studies, both GLP-1 receptor agonists and DPP-4i, improveβcell function indexes. All these agents showed trophic effects on beta-cell mass in animal studies. The use of these drugs is associated with positive or neucral effect on body weight and improvements in blood pressure, diabetic dyslipidemia, hepatic steazosis markets, and myocardial function. These effects have the potential to reduce the burden of cardiovascular disease, which is a major cause of mortality in patients with diabetes.

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Glucagon-like peptide-1: a major regulator of pancreatic beta-cell function

Acta Endocrinologica ◽

10.1530/eje.0.1430717 ◽

2000 ◽

pp. 717-725 ◽

Cited By ~ 96

Author(s):

R Perfetti ◽

P Merkel

Keyword(s):

Beta Cell ◽

Cell Function ◽

Pancreatic Beta Cell ◽

Cell Mass ◽

Beta Cell Mass ◽

Glucagon Secretion ◽

Insulin Biosynthesis ◽

Gut Hormone ◽

Glucagon Like Peptide ◽

Glucagon Like Peptide 1

Glucagon-like peptide-1 (GLP-1) is a gut hormone synthesized by post-translational processing in intestinal L-cells, and it is released in response to food ingestion. GLP-1 stimulates insulin secretion during hyperglycemia, suppresses glucagon secretion, stimulates (pro)-insulin biosynthesis and decreases the rate of gastric emptying and acid secretion. GLP-1 has also been shown to have a pro-satiety effect. In addition, it has been demonstrated that a long-term infusion with GLP-1, or exendin-4, a long-acting analog of human GLP-1, increases beta-cell mass in rats. In conclusion, GLP-1 appears to regulate plasma glucose levels via various and independent mechanisms. GLP-1 is an excellent candidate option for the treatment of patients with type 2 diabetes mellitus.

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Foxa1 and Foxa2 Regulate α-Cell Differentiation, Glucagon Biosynthesis, and Secretion

Endocrinology ◽

10.1210/en.2013-1843 ◽

2014 ◽

Vol 155 (10) ◽

pp. 3781-3792 ◽

Cited By ~ 22

Author(s):

Mounia Heddad Masson ◽

Caroline Poisson ◽

Audrey Guérardel ◽

Aline Mamin ◽

Jacques Philippe ◽

...

Keyword(s):

Gene Expression ◽

Cell Differentiation ◽

Target Genes ◽

Adult Mouse ◽

Glucagon Secretion ◽

Mrna Levels ◽

Forkhead Box ◽

Interfering Rna

Abstract The Forkhead box A transcription factors are major regulators of glucose homeostasis. They show both distinct and redundant roles during pancreas development and in adult mouse β-cells. In vivo ablation studies have revealed critical implications of Foxa1 on glucagon biosynthesis and requirement of Foxa2 in α-cell terminal differentiation. In order to examine the respective role of these factors in mature α-cells, we used small interfering RNA (siRNA) directed against Foxa1 and Foxa2 in rat primary pancreatic α-cells and rodent α-cell lines leading to marked decreases in Foxa1 and Foxa2 mRNA levels and proteins. Both Foxa1 and Foxa2 control glucagon gene expression specifically through the G2 element. Although we found that Foxa2 controls the expression of the glucagon, MafB, Pou3f4, Pcsk2, Nkx2.2, Kir6.2, and Sur1 genes, Foxa1 only regulates glucagon gene expression. Interestingly, the Isl1 and Gipr genes were not controlled by either Foxa1 or Foxa2 alone but by their combination. Foxa1 and Foxa2 directly activate and bind the promoter region the Nkx2.2, Kir6.2 and Sur1, Gipr, Isl1, and Pou3f4 genes. We also demonstrated that glucagon secretion is affected by the combined effects of Foxa1 and Foxa2 but not by either one alone. Our results indicate that Foxa1 and Foxa2 control glucagon biosynthesis and secretion as well as α-cell differentiation with both common and unique target genes.

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