scholarly journals AKAP79/150 coordinates leptin-induced PKA activation to regulate KATP channel trafficking in pancreatic β-cells

2020 ◽  
Author(s):  
Veronica A. Cochrane ◽  
Zhongying Yang ◽  
Mark Dell’Acqua ◽  
Show-Ling Shyng
Keyword(s):  
Cell Function ◽  
Β Cells ◽  
Β Cell ◽  
Signaling Mechanism ◽  
Channel Trafficking ◽  
Protein Phosphatase 2B ◽  
Anchoring Protein ◽  
Β Cell Function ◽  
Glucose Stimulated Insulin Secretion

AbstractThe adipocyte hormone leptin regulates glucose homeostasis both centrally and peripherally. A key peripheral target is the pancreatic β-cell, which secretes insulin upon glucose stimulation. Leptin suppresses glucose-stimulated insulin secretion by promoting trafficking of KATP channels to the β-cell surface, which increases K+ conductance and causes β-cell hyperpolarization. Here we investigate the signaling mechanism underlying leptin-induced KATP channel translocation with a focus on protein kinase A (PKA). Using FRET-based PKA activity reporters, we show that leptin increases PKA activity at the cell membrane via a signaling pathway involving NMDA receptors, CaMKKβ and AMPK. Genetic knockdown and rescue experiments reveal that leptin activation of PKA requires tethering of PKA to the membrane-targeted PKA-anchoring protein AKAP79/150. Interestingly, disrupting protein phosphatase 2B (PP2B) anchoring to AKAP79/150, known to elevate basal PKA signaling, increases surface KATP channels. Our findings uncover a novel role of AKAP79/150 in coordinating leptin and PKA signaling to regulate β-cell function.

scholarly journals Emerging role of testosterone in pancreatic β cell function and insulin secretion

2019 ◽  
Vol 240 (3) ◽  
pp. R97-R105 ◽  
Author(s):  
Weiwei Xu ◽  
Jamie Morford ◽  
Franck Mauvais-Jarvis
Keyword(s):  
Insulin Secretion ◽  
Metabolic Regulation ◽  
Cell Function ◽  
Visceral Obesity ◽  
Β Cells ◽  
Β Cell ◽  
Β Cell Function ◽  
Glucagon Like Peptide 1 ◽  
Glucose Stimulated Insulin Secretion

One of the most sexually dimorphic aspects of metabolic regulation is the bidirectional modulation of glucose homeostasis by testosterone in male and females. Severe testosterone deficiency predisposes men to type 2 diabetes (T2D), while in contrast, androgen excess predisposes women to hyperglycemia. The role of androgen deficiency and excess in promoting visceral obesity and insulin resistance in men and women respectively is well established. However, although it is established that hyperglycemia requires β cell dysfunction to develop, the role of testosterone in β cell function is less understood. This review discusses recent evidence that the androgen receptor (AR) is present in male and female β cells. In males, testosterone action on AR in β cells enhances glucose-stimulated insulin secretion by potentiating the insulinotropic action of glucagon-like peptide-1. In females, excess testosterone action via AR in β cells promotes insulin hypersecretion leading to oxidative injury, which in turn predisposes to T2D.

scholarly journals Pericytes contribute to the islet basement membranes to promote beta-cell gene expression

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lina Sakhneny ◽  
Alona Epshtein ◽  
Limor Landsman
Keyword(s):  
Gene Expression ◽  
Cell Function ◽  
Basement Membranes ◽  
Cell Physiology ◽  
Β Cells ◽  
Β Cell ◽  
Cell Clustering ◽  
Β Cell Function ◽  
Cell Gene Expression ◽  
Glucose Stimulated Insulin Secretion

Abstractβ-Cells depend on the islet basement membrane (BM). While some islet BM components are produced by endothelial cells (ECs), the source of others remains unknown. Pancreatic pericytes directly support β-cells through mostly unidentified secreted factors. Thus, we hypothesized that pericytes regulate β-cells through the production of BM components. Here, we show that pericytes produce multiple components of the mouse pancreatic and islet interstitial and BM matrices. Several of the pericyte-produced ECM components were previously implicated in β-cell physiology, including collagen IV, laminins, proteoglycans, fibronectin, nidogen, and hyaluronan. Compared to ECs, pancreatic pericytes produce significantly higher levels of α2 and α4 laminin chains, which constitute the peri-islet and vascular BM. We further found that the pericytic laminin isoforms differentially regulate mouse β-cells. Whereas α2 laminins promoted islet cell clustering, they did not affect gene expression. In contrast, culturing on Laminin-421 induced the expression of β-cell genes, including Ins1, MafA, and Glut2, and significantly improved glucose-stimulated insulin secretion. Thus, alongside ECs, pericytes are a significant source of the islet BM, which is essential for proper β-cell function.

scholarly journals The Role of Thioredoxin/Peroxiredoxin in the β-Cell Defense Against Oxidative Damage

2021 ◽  
Vol 12 ◽  
Author(s):  
Jennifer S. Stancill ◽  
John A. Corbett
Keyword(s):  
Oxidative Stress ◽  
Oxidative Damage ◽  
Cell Function ◽  
Cell Damage ◽  
Thioredoxin Reductase ◽  
Β Cells ◽  
Β Cell ◽  
Cell Defense ◽  
Β Cell Function

Oxidative stress is hypothesized to play a role in pancreatic β-cell damage, potentially contributing to β-cell dysfunction and death in both type 1 and type 2 diabetes. Oxidative stress arises when naturally occurring reactive oxygen species (ROS) are produced at levels that overwhelm the antioxidant capacity of the cell. ROS, including superoxide and hydrogen peroxide, are primarily produced by electron leak during mitochondrial oxidative metabolism. Additionally, peroxynitrite, an oxidant generated by the reaction of superoxide and nitric oxide, may also cause β-cell damage during autoimmune destruction of these cells. β-cells are thought to be susceptible to oxidative damage based on reports that they express low levels of antioxidant enzymes compared to other tissues. Furthermore, markers of oxidative damage are observed in islets from diabetic rodent models and human patients. However, recent studies have demonstrated high expression of various isoforms of peroxiredoxins, thioredoxin, and thioredoxin reductase in β-cells and have provided experimental evidence supporting a role for these enzymes in promoting β-cell function and survival in response to a variety of oxidative stressors. This mini-review will focus on the mechanism by which thioredoxins and peroxiredoxins detoxify ROS and on the protective roles of these enzymes in β-cells. Additionally, we speculate about the role of this antioxidant system in promoting insulin secretion.

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

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.

scholarly journals Role of the Rho-ROCK (Rho-Associated Kinase) Signaling Pathway in the Regulation of Pancreatic β-Cell Function

Endocrinology ◽  
2008 ◽  
Vol 150 (5) ◽  
pp. 2072-2079 ◽  
Author(s):  
Eva Hammar ◽  
Alejandra Tomas ◽  
Domenico Bosco ◽  
Philippe A. Halban
Keyword(s):  
Extracellular Matrix ◽  
Insulin Secretion ◽  
Actin Cytoskeleton ◽  
Cell Function ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Β Cell Function ◽  
Glucose Stimulated Insulin Secretion ◽  
And Function

Extracellular matrix has a beneficial impact on β-cell spreading and function, but the underlying signaling pathways have yet to be fully elucidated. In other cell types, Rho, a well-characterized member of the family of Rho GTPases, and its effector Rho-associated kinase (ROCK), play an important role as downstream mediators of outside in signaling from extracellular matrix. Therefore, a possible role of the Rho-ROCK pathway in β-cell spreading, actin cytoskeleton dynamics, and function was investigated. Rho was inhibited using a new cell-permeable version of C3 transferase, whereas the activity of ROCK was repressed using the specific ROCK inhibitors H-1152 and Y-27632. Inhibition of Rho and of ROCK increased spreading and improved both short-term and prolonged glucose-stimulated insulin secretion but had no impact on basal secretion. Inhibition of this pathway led to a depolymerization of the actin cytoskeleton. Furthermore, the impact of the inhibition of ROCK on stimulated insulin secretion was acute and reversible, suggesting that rapid signaling such as phosphorylation is involved. Finally, quantification of the activity of RhoA indicated that the extracellular matrix represses RhoA activity. Overall these results show for the first time that the Rho-ROCK signaling pathway contributes to the stabilization of the actin cytoskeleton and inhibits glucose-stimulated insulin secretion in primary pancreatic β-cells. Furthermore, they indicate that inhibition of this pathway might be one of the mechanisms by which the extracellular matrix exerts its beneficial effects on pancreatic β-cell function.

scholarly journals A Putative Prohibitin-Calcium Nexus in β-Cell Mitochondria and Diabetes

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Gaurav Verma ◽  
Aparna Dixit ◽  
Craig S. Nunemaker
Keyword(s):  
Cell Function ◽  
Mitochondrial Protein ◽  
Active Role ◽  
Targeted Drugs ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Β Cell Function ◽  
Significant Attention

The role of mitochondria in apoptosis is well known; however, the mechanisms linking mitochondria to the proapoptotic effects of proinflammatory cytokines, hyperglycemia, and glucolipotoxicity are not completely understood. Complex Ca2+ signaling has emerged as a critical contributor to these proapoptotic effects and has gained significant attention in regulating the signaling processes of mitochondria. In pancreatic β-cells, Ca2+ plays an active role in β-cell function and survival. Prohibitin (PHB), a mitochondrial chaperone, is actively involved in maintaining the architecture of mitochondria. However, its possible interaction with Ca2+-activated signaling pathways has not been explored. The present review aims to examine potential crosstalk between Ca2+ signaling and PHB function in pancreatic β-cells. Moreover, this review will focus on the effects of cytokines and glucolipotoxicity on Ca2+ signaling and its possible interaction with PHB. Improved understanding of this important mitochondrial protein may aid in the design of more targeted drugs to identify specific pathways involved with stress-induced dysfunction in the β-cell.

scholarly journals AMP-activated protein kinase agonist dose dependently improves function and reduces apoptosis in glucotoxic β-cells without changing triglyceride levels

2008 ◽  
Vol 41 (3) ◽  
pp. 187-194 ◽  
Author(s):  
Hanna K Nyblom ◽  
Ernest Sargsyan ◽  
Peter Bergsten
Keyword(s):  
Protein Kinase ◽  
Cell Function ◽  
Β Cells ◽  
Β Cell ◽  
Downstream Target ◽  
Homologous Protein ◽  
Prolonged Culture ◽  
Β Cell Function ◽  
Glucose Stimulated Insulin Secretion ◽  
Amp Activated Protein Kinase

Prolonged hyperglycaemia leads to impaired glucose-stimulated insulin secretion (GSIS) and apoptosis in insulin-producing β-cells. The detrimental effects have been connected with glucose-induced lipid accumulation in the β-cell. AMP-activated protein kinase (AMPK) agonist, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), promotes utilization of nutrient stores for energy production. It was tested how impaired GSIS and elevated apoptosis observed in insulinoma (INS)-1E cells after prolonged culture at 27 mM glucose were affected by the inclusion of 0.3 or 1 mM AICAR during culture. Glucose-induced impairment of insulin release was reverted by the inclusion of 0.3 but not 1 mM AICAR, which did not affect insulin content. The glucose-induced rise in triglyceride (TG) content observed in the cells cultured at 27 mM glucose was not altered by the inclusion of either 0.3 or 1 mM AICAR. Inclusion of 1 but not 0.3 mM AICAR during culture induced phosphorylation of AMPK and its downstream target acyl-CoA carboxylase. Phosphorylation was paralleled by reduced number of apoptotic cells and lowered expression of pro-apoptotic C/EBP homologous protein (CHOP). In conclusion, AICAR dose dependently improves β-cell function and reduces apoptosis in β-cells exposed to prolonged hyperglycaemia without changing TG levels.

scholarly journals The pathogenetic role of β-cell mitochondria in type 2 diabetes

2018 ◽  
Vol 236 (3) ◽  
pp. R145-R159 ◽  
Author(s):  
Malin Fex ◽  
Lisa M Nicholas ◽  
Neelanjan Vishnu ◽  
Anya Medina ◽  
Vladimir V Sharoyko ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Mitochondrial Dysfunction ◽  
Translational Regulation ◽  
Cell Function ◽  
Rare Condition ◽  
Β Cells ◽  
Β Cell ◽  
Β Cell Function

Mitochondrial metabolism is a major determinant of insulin secretion from pancreatic β-cells. Type 2 diabetes evolves when β-cells fail to release appropriate amounts of insulin in response to glucose. This results in hyperglycemia and metabolic dysregulation. Evidence has recently been mounting that mitochondrial dysfunction plays an important role in these processes. Monogenic dysfunction of mitochondria is a rare condition but causes a type 2 diabetes-like syndrome owing to β-cell failure. Here, we describe novel advances in research on mitochondrial dysfunction in the β-cell in type 2 diabetes, with a focus on human studies. Relevant studies in animal and cell models of the disease are described. Transcriptional and translational regulation in mitochondria are particularly emphasized. The role of metabolic enzymes and pathways and their impact on β-cell function in type 2 diabetes pathophysiology are discussed. The role of genetic variation in mitochondrial function leading to type 2 diabetes is highlighted. We argue that alterations in mitochondria may be a culprit in the pathogenetic processes culminating in type 2 diabetes.

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