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Li YQ, Zhang LY, Zhao YC, Xu F, Hu ZY, Wu QH, Li WH, Li YN. Vascular endothelial growth factor B improves impaired glucose tolerance through insulin-mediated inhibition of glucagon secretion. World J Diabetes 2023; 14:1643-1658. [DOI: 10.4239/wjd.v14.i11.1643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 07/11/2023] [Accepted: 09/06/2023] [Indexed: 11/14/2023] Open
Abstract
BACKGROUND Impaired glucose tolerance (IGT) is a homeostatic state between euglycemia and hyperglycemia and is considered an early high-risk state of diabetes. When IGT occurs, insulin sensitivity decreases, causing a reduction in insulin secretion and an increase in glucagon secretion. Recently, vascular endothelial growth factor B (VEGFB) has been demonstrated to play a positive role in improving glucose metabolism and insulin sensitivity. Therefore, we constructed a mouse model of IGT through high-fat diet feeding and speculated that VEGFB can regulate hyperglycemia in IGT by influencing insulin-mediated glucagon secretion, thus contributing to the prevention and cure of prediabetes.
AIM To explore the potential molecular mechanism and regulatory effects of VEGFB on insulin-mediated glucagon in mice with IGT.
METHODS We conducted in vivo experiments through systematic VEGFB knockout and pancreatic-specific VEGFB overexpression. Insulin and glucagon secretions were detected via enzyme-linked immunosorbent assay, and the protein expression of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) was determined using western blot. Further, mRNA expression of forkhead box protein O1, phosphoenolpyruvate carboxykinase, and glucose-6 phosphatase was detected via quantitative polymerase chain reaction, and the correlation between the expression of proteins was analyzed via bioinformatics.
RESULTS In mice with IGT and VEGFB knockout, glucagon secretion increased, and the protein expression of PI3K/AKT decreased dramatically. Further, in mice with VEGFB overexpression, glucagon levels declined, with the activation of the PI3K/AKT signaling pathway.
CONCLUSION VEGFB/vascular endothelial growth factor receptor 1 can promote insulin-mediated glucagon secretion by activating the PI3K/AKT signaling pathway to regulate glucose metabolism disorders in mice with IGT.
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Affiliation(s)
- Yu-Qi Li
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264000, Shandong Province, China
| | - Lu-Yang Zhang
- Department of Rheumatology and Immunology, Yantaishan Hospital, Yantai 264000, Shandong Province, China
| | - Yu-Chi Zhao
- Department of Surgery, Yantaishan Hospital, Yantai 264000, Shandong Province, China
| | - Fang Xu
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264000, Shandong Province, China
| | - Zhi-Yong Hu
- School of Public Health and Management, Binzhou Medical University, Yantai 264000, Shandong Province, China
| | - Qi-Hao Wu
- The First School of Clinical Medicine, Binzhou Medical University, Yantai 264000, Shandong Province, China
| | - Wen-Hao Li
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264000, Shandong Province, China
| | - Ya-Nuo Li
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264000, Shandong Province, China
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Abstract
Incretin hormones (glucose-dependent insulinotropic polypeptide [GIP] and glucagon-like peptide-1 [GLP-1]) play a role in the pathophysiology of type 2 diabetes. Along with their derivatives they have shown therapeutic success in type 2 diabetes, with the potential for further improvements in glycaemic, cardiorenal and body weight-related outcomes. In type 2 diabetes, the incretin effect (greater insulin secretory response after oral glucose than with 'isoglycaemic' i.v. glucose, i.e. with an identical glycaemic stimulus) is markedly reduced or absent. This appears to be because of a reduced ability of GIP to stimulate insulin secretion, related either to an overall impairment of beta cell function or to specific defects in the GIP signalling pathway. It is likely that a reduced incretin effect impacts on postprandial glycaemic excursions and, thus, may play a role in the deterioration of glycaemic control. In contrast, the insulinotropic potency of GLP-1 appears to be much less impaired, such that exogenous GLP-1 can stimulate insulin secretion, suppress glucagon secretion and reduce plasma glucose concentrations in the fasting and postprandial states. This has led to the development of incretin-based glucose-lowering medications (selective GLP-1 receptor agonists or, more recently, co-agonists, e.g. that stimulate GIP and GLP-1 receptors). Tirzepatide (a GIP/GLP-1 receptor co-agonist), for example, reduces HbA1c and body weight in individuals with type 2 diabetes more effectively than selective GLP-1 receptor agonists (e.g. semaglutide). The mechanisms by which GIP receptor agonism may contribute to better glycaemic control and weight loss after long-term exposure to tirzepatide are a matter of active research and may change the pessimistic view that developed after the disappointing lack of insulinotropic activity in people with type 2 diabetes when exposed to GIP in short-term experiments. Future medications that stimulate incretin hormone and other receptors simultaneously may have the potential to further increase the ability to control plasma glucose concentrations and induce weight loss.
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Affiliation(s)
- Michael A Nauck
- Diabetes, Endocrinology, Metabolism Section, Medical Department I, Katholisches Klinikum Bochum, St. Josef Hospital, Ruhr-University Bochum, Bochum, Germany.
- Institute for Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Greifswald, Germany.
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), München Neuherberg, Germany
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Knuth ER, Foster HR, Jin E, Merrins MJ. Leucine suppresses glucagon secretion from pancreatic islets by directly modulating α-cell cAMP. bioRxiv 2023:2023.07.31.551113. [PMID: 37577685 PMCID: PMC10418066 DOI: 10.1101/2023.07.31.551113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Objective Pancreatic islets are nutrient sensors that regulate organismal blood glucose homeostasis. Glucagon release from the pancreatic α-cell is important under fasted, fed, and hypoglycemic conditions, yet metabolic regulation of α-cells remains poorly understood. Here, we identified a previously unexplored role for physiological levels of leucine, which is classically regarded as a β-cell fuel, in the intrinsic regulation of α-cell glucagon release. Methods GcgCreERT:CAMPER and GcgCreERT:GCaMP6s mice were generated to perform dynamic, high-throughput functional measurements of α-cell cAMP and Ca2+ within the intact islet. Islet perifusion assays were used for simultaneous, time-resolved measurements of glucagon and insulin release from mouse and human islets. The effects of leucine were compared with glucose and the mitochondrial fuels 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH, non-metabolized leucine analog that activates glutamate dehydrogenase), α-ketoisocaproate (KIC, leucine metabolite), and methyl-succinate (complex II fuel). CYN154806 (Sstr2 antagonist), diazoxide (KATP activator, which prevents Ca2+-dependent exocytosis from α, β, and δ-cells), and dispersed α-cells were used to inhibit islet paracrine signaling and identify α-cell intrinsic effects. Results Mimicking the effect of glucose, leucine strongly suppressed amino acid-stimulated glucagon secretion. Mechanistically, leucine dose-dependently reduced α-cell cAMP at physiological concentrations, with an IC50 of 57, 440, and 1162 μM at 2, 6, and 10 mM glucose, without affecting α-cell Ca2+. Leucine also reduced α-cell cAMP in islets treated with Sstr2 antagonist or diazoxide, as well as dispersed α-cells, indicating an α-cell intrinsic effect. The effect of leucine was matched by KIC and the glutamate dehydrogenase activator BCH, but not methyl-succinate, indicating a dependence on mitochondrial anaplerosis. Glucose, which stimulates anaplerosis via pyruvate carboxylase, had the same suppressive effect on α-cell cAMP but with lower potency. Similarly to mouse islets, leucine suppressed glucagon secretion from human islets under hypoglycemic conditions. Conclusions These findings highlight an important role for physiological levels of leucine in the metabolic regulation of α-cell cAMP and glucagon secretion. Leucine functions primarily through an α-cell intrinsic effect that is dependent on glutamate dehydrogenase, in addition to the well-established α-cell regulation by β/δ-cell paracrine signaling. Our results suggest that mitochondrial anaplerosis-cataplerosis facilitates the glucagonostatic effect of both leucine and glucose, which cooperatively suppress α-cell tone by reducing cAMP.
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Affiliation(s)
- Emily R. Knuth
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Hannah R. Foster
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Erli Jin
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Matthew J. Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
- William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
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Chen X, Merovci A, DeFronzo RA, Tripathy D. Chronic physiologic hyperglycemia impairs insulin-mediated suppression of plasma glucagon concentration in healthy humans. Metabolism 2023; 142:155512. [PMID: 36746320 DOI: 10.1016/j.metabol.2023.155512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 01/22/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023]
Abstract
BACKGROUND AND AIMS Hyperglucagonemia is a characteristic feature of type 2 diabetes mellitus (T2DM). We examined the effect of chronic (48-72 h) physiologic increase (+50 mg/dl) in plasma glucose concentration on suppression of plasma glucagon concentration by insulin and by hyperglycemia in normal glucose tolerance (NGT) individuals. MATERIALS AND METHODS Study One: 16 NGT subjects received OGTT and 3-step hyperinsulinemic (10, 20, 40 mU/m2·min) euglycemic clamp before and after 48 hour glucose infusion to increase plasma glucose by ~50 mg/dl. Study Two: 20 NGT subjects received OGTT and 2-step hyperglycemic (+125 and + 300 mg/dl) clamp before and after 72 hour glucose infusion. Plasma insulin, C-peptide and glucagon concentrations were measured during OGTT, euglycemic hyperinsulinemic and hyperglycemic clamps. Ratio of plasma glucagon/insulin was used as an index of insulin-mediated suppression of glucagon secretion. RESULTS During all 3 insulin clamp steps (Study 1), plasma glucagon concentration was increased compared to baseline study, and plasma glucagon/insulin ratio was significantly reduced by 24 % (p < 0.05). The rate of insulin-stimulated glucose disposal was inversely correlated with plasma glucagon/insulin ratio (r = -0.44, p < 0.05) and with glucagon AUC (r = -0.48, p < 0.05). During the 2-step hyperglycemic clamp (Study 2) plasma glucagon was similar before and after 72 h of glucose infusion; however, glucagon/insulin ratio was significantly reduced (p < 0.05). Incremental area under plasma insulin curve during the first (r = -0.74, p < 0.001) and second (r = -0.85, p < 0.001) hyperglycemic clamp steps was strongly and inversely correlated with plasma glucagon/insulin ratio. CONCLUSION Sustained (48-72 h) physiologic hyperglycemia (+50 mg/dl) caused whole body insulin resistance and impaired insulin-mediated suppression of glucagon secretion, suggesting a role for glucotoxicity in development of hyperglucagonemia in T2DM.
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Affiliation(s)
- Xi Chen
- Department of Medicine, Diabetes Division, University of Texas Health Science Center, San Antonio, TX, USA
| | - Aurora Merovci
- Department of Medicine, Diabetes Division, University of Texas Health Science Center, San Antonio, TX, USA
| | - Ralph A DeFronzo
- Department of Medicine, Diabetes Division, University of Texas Health Science Center, San Antonio, TX, USA; Audie L. Murphy VA Hospital, South Texas Veterans Heath Care System, San Antonio, TX, USA
| | - Devjit Tripathy
- Department of Medicine, Diabetes Division, University of Texas Health Science Center, San Antonio, TX, USA; Audie L. Murphy VA Hospital, South Texas Veterans Heath Care System, San Antonio, TX, USA.
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Huang W, Xie C, Wewer Albrechtsen NJ, Jones KL, Horowitz M, Rayner CK, Wu T. The 'early' postprandial glucagon response is related to the rate of gastric emptying in type 2 diabetes. Peptides 2023; 161:170941. [PMID: 36623554 DOI: 10.1016/j.peptides.2023.170941] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/15/2022] [Accepted: 01/02/2023] [Indexed: 01/09/2023]
Abstract
Gastric emptying (GE) is a major determinant of the postprandial glycemic and insulinemic responses in health and type 2 diabetes (T2D). However, the effect of GE on the postprandial glucagon response, which is characteristically augmented in T2D, is unknown. This study examined the relationship between plasma glucagon and GE of a standardized mixed meal in individuals with well-controlled T2D. 89 individuals with T2D (HbA1c 6.6 ± 0.1%) consumed a mashed potato meal labeled with 100 µL 13C-octanoic acid between 0 and 5 min. Venous blood was sampled frequently over 4 h for measurements of blood glucose and plasma glucagon. The gastric half-emptying time (T50) was calculated by quantification of 13C in the breath. Blood glucose peaked at t = 90 min after the meal. Plasma glucagon increased to a peak at t = 30 min and then decreased to a nadir at t = 180 min. The T50 was 68.3 ± 1.6 min. The incremental area under the plasma glucagon curve between t = 0-30 min (glucagon iAUC0-30 min) was related inversely to the T50 (r = -0.23, P = 0.029), while the increase in blood glucose at t = 30 min was related directly to the plasma glucagon iAUC0-30 min (r = 0.25, P = 0.018). Accordingly, individuals with relatively faster GE exhibited higher postprandial glucagon and glucose levels (ANOVA: P<0.01 for each). In well-controlled T2D, the early postprandial glucagon response to a mixed meal is related to the rate of GE, and predictive of the initial glycemic response. These observations suggest that a reduction in plasma glucagon may contribute to the effect of dietary and pharmacological strategies which reduce postprandial glycemia in T2D by slowing GE.
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Affiliation(s)
- Weikun Huang
- Centre for Research Excellence in Translating Nutritional Sciences to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide 5000, Australia
| | - Cong Xie
- Centre for Research Excellence in Translating Nutritional Sciences to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide 5000, Australia
| | | | - Karen L Jones
- Centre for Research Excellence in Translating Nutritional Sciences to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide 5000, Australia
| | - Michael Horowitz
- Centre for Research Excellence in Translating Nutritional Sciences to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide 5000, Australia; Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide 5000, Australia
| | - Christopher K Rayner
- Centre for Research Excellence in Translating Nutritional Sciences to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide 5000, Australia; Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, Australia
| | - Tongzhi Wu
- Centre for Research Excellence in Translating Nutritional Sciences to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide 5000, Australia.
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Asadi F, Dhanvantari S. Misrouting of glucagon and stathmin-2 towards lysosomal system of α-cells in glucagon hypersecretion of diabetes. Islets 2022; 14:40-57. [PMID: 34923907 PMCID: PMC8726656 DOI: 10.1080/19382014.2021.2011550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Glucagon hypersecretion from the pancreatic α-cell is a characteristic sign of diabetes, which exacerbates fasting hyperglycemia. Thus, targeting glucagon secretion from α-cells may be a promising approach for combating hyperglucagonemia. We have recently identified stathmin-2 as an α-cell protein that regulates glucagon secretion by directing glucagon toward the endolysosomal system in αTC1-6 cells. We hypothesized that disruption of Stmn2-mediated trafficking of glucagon to the endolysosomes in diabetes contributes to hyperglucagonemia. In isolated islets from male mice treated with streptozotocin (STZ), glucagon secretion and cellular content were augmented, but cellular Stmn2 levels were reduced (p < .01), as measured by both ELISA and immunofluorescence intensity. Using confocal immunofluorescence microscopy, the colocalization of glucagon and Stmn2 in Lamp2A+ lysosomes was dramatically reduced (p < .001) in islets from diabetic mice, and the colocalization of Stmn2, but not glucagon, with the late endosome marker, Rab7, significantly (p < .01) increased. Further studies were conducted in αTC1-6 cells cultured in media containing high glucose (16.7 mM) for 2 weeks to mimic glucagon hypersecretion of diabetes. Surprisingly, treatment of αTC1-6 cells with the lysosomal inhibitor bafilomycin A1 reduced K+-induced glucagon secretion, suggesting that high glucose may induce glucagon secretion from another lysosomal compartment. Both glucagon and Stmn2 co-localized with Lamp1, which marks secretory lysosomes, in cells cultured in high glucose. We propose that, in addition to enhanced trafficking and secretion through the regulated secretory pathway, the hyperglucagonemia of diabetes may also be due to re-routing of glucagon from the degradative Lamp2A+ lysosome toward the secretory Lamp1+ lysosome.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Metabolism & Diabetes and Imaging Programs, Lawson Health Research Institute, London, ON, Canada
- CONTACT Savita Dhanvantari Lawson Health Research Institute, PO Box 5777, Stn B, London, ONN6A 4V2, Canada
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Lei H, Liu J, Wang W, Yang X, Feng Z, Zang P, Lu B, Shao J. Association between osteocalcin, a pivotal marker of bone metabolism, and secretory function of islet beta cells and alpha cells in Chinese patients with type 2 diabetes mellitus: an observational study. Diabetol Metab Syndr 2022; 14:160. [PMID: 36307866 PMCID: PMC9615358 DOI: 10.1186/s13098-022-00932-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 10/13/2022] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Several recent studies have found that Osteocalcin (OCN), a multifunctional protein secreted exclusively by osteoblasts, is beneficial to glucose metabolism and type 2 diabetes mellitus (T2DM). However, the effects of OCN on islets function especially islet ɑ cells function in patients with type 2 diabetes mellitus characterized by a bi-hormonal disease are still unclear. The purpose of this cross-sectional study was to investigate the relationship between serum OCN and the secretion of islet β cells and ɑ cells in Chinese patients with type 2 diabetes mellitus. METHODS 204 patients with T2DM were enrolled. Blood glucose (FBG, PBG0.5h, PBG1h, PBG2h, PBG3h), insulin (FINS, INS0.5h, INS1h, INS2h, INS3h), C-peptide (FCP, CP0.5h, CP1h, CP2h, CP3h), and glucagon (GLA0, GLA0.5 h, GLA1h, GLA2h, GLA3h) levels were measured on 0 h, 0.5 h, 1 h, 2 h, and 3 h after a 100 g standard bread meal load. Early postprandial secretion function of islet β cells was calculated as Δcp0.5h = CP0.5-FCP. The patients were divided into low, medium and high groups (T1, T2 and T3) according to tertiles of OCN. Comparison of parameters among three groups was studied. Correlation analysis confirmed the relationship between OCN and pancreatic secretion. Multiple regression analysis showed independent contributors to pancreatic secretion. MAIN RESULTS FBG, and PBG2h were the lowest while Δcp0.5h was the highest in the highest tertile group (respectively, p < 0.05). INS3h, area under the curve of insulin (AUCins3h) in T3 Group were significantly lower than T1 Group (respectively, p < 0.05). GLA1h in T3 group was lower than T1 group (p < 0.05), and GLA0.5 h in T3 group was lower than T2 and T1 groups (p < 0.05). Correlation analysis showed OCN was inversely correlated with Homeostatic model of insulin resistance (HOMA-IR), INS3h, AUCins3h (p < 0.05), and was still inversely correlated with FCP, GLA0.5 h, GLA1h, area under the curve of glucagon (AUCgla3h) (respectively, p < 0.05) after adjustment for body mass index (BMI) and alanine aminotransferase (ALT). The multiple regression analysis showed that OCN was independent contributor to Δcp0.5h, GLA0.5h and GLA1h (respectively, p < 0.05). CONCLUSIONS Higher serum OCN level is closely related to better blood glucose control, higher insulin sensitivity, increased early-phase insulin secretion of islet β cells and appropriate inhibition of postprandial glucagon secretion of islet ɑ cells in adult patients with type 2 diabetes mellitus.
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Affiliation(s)
- Haiyan Lei
- Department of Endocrinology, Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 East Zhongshan Road, Nanjing, 210002, Jiangsu, People's Republic of China
| | - Jun Liu
- Department of Endocrinology, Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 East Zhongshan Road, Nanjing, 210002, Jiangsu, People's Republic of China
| | - Wei Wang
- Department of Endocrinology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, 210002, People's Republic of China
| | - Xinyi Yang
- Department of Endocrinology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, 210002, People's Republic of China
| | - Zhouqin Feng
- Department of Endocrinology, Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 East Zhongshan Road, Nanjing, 210002, Jiangsu, People's Republic of China
| | - Pu Zang
- Department of Endocrinology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, 210002, People's Republic of China
| | - Bin Lu
- Department of Endocrinology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, 210002, People's Republic of China.
| | - Jiaqing Shao
- Department of Endocrinology, Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 East Zhongshan Road, Nanjing, 210002, Jiangsu, People's Republic of China.
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Wierup N, Abels M, Shcherbina L, Lindqvist A. The role of CART in islet biology. Peptides 2022; 149:170708. [PMID: 34896575 DOI: 10.1016/j.peptides.2021.170708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 12/03/2021] [Accepted: 12/03/2021] [Indexed: 10/19/2022]
Abstract
Cocaine- and amphetamine-regulated transcript (CART) is mostly known for its appetite regulating effects in the central nervous system. However, CART is also highly expressed in the peripheral nervous system as well as in certain endocrine cells. Our group has dedicated more than 20 years to understand the role of CART in the pancreatic islets and in this review we summarize what is known to date about CART expression and function in the islets. CART is expressed in both islet cells and nerve fibers innervating the islets. Large species differences are at hand and CART expression is highly dynamic and increased during development, as well as in Type 2 Diabetes and certain endocrine tumors. In the human islets CART is expressed in alpha cells and beta cells and the expression is increased in T2D patients. CART increases insulin secretion, reduces glucagon secretion, and protects against beta cell death by reducing apoptosis and increasing proliferation. It is still not fully understood how CART mediates its effects or which receptors that are involved. Nevertheless, CART is endowed with several properties that are beneficial in a T2D perspective. Many of the described effects of CART resemble those of GLP-1, and interestingly CART has been found to potentiate some of the effects of GLP-1, paving the way for CART-based treatments in combination with GLP-1-based drugs.
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Affiliation(s)
- Nils Wierup
- Lund University Diabetes Centre, Malmö, Sweden.
| | - Mia Abels
- Lund University Diabetes Centre, Malmö, Sweden
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Sokolowska P, Zukowski K, Janikiewicz J, Jastrzebska E, Dobrzyn A, Brzozka Z. Islet-on-a-chip: Biomimetic micropillar-based microfluidic system for three-dimensional pancreatic islet cell culture. Biosens Bioelectron 2021; 183:113215. [PMID: 33845292 DOI: 10.1016/j.bios.2021.113215] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/15/2021] [Accepted: 03/28/2021] [Indexed: 12/14/2022]
Abstract
Type 2 diabetes is currently one of the most common metabolic diseases, affecting all ages worldwide. As the incidence of type 2 diabetes increases, a growing number of studies focus on islets of Langerhans. A three-dimensional research model that maps islet morphology and maintains hormonal balance in vivo is still needed. In this work, we present an Islet-on-a-chip system, specifically a micropillar-based microfluidic platform for three-dimensional pancreatic islet cell culture and analysis. The microfluidic system consisted of two culture chambers that were equipped with 15 circular microtraps each, which were built with seven round micropillars each. Micropillars in the structure of microtraps supported cell aggregation by limiting the growth surface and minimizing wall shear stress, thereby ensuring proper medium diffusion and optimal culture conditions for cell aggregates. Our system is compatible with microwell plate readers and confocal laser scanning microscopes. Because of optimization of the immunostaining method, the appropriate cell distribution and high viability and proliferation up to 72 h of culture were confirmed. Enzyme-linked immunosorbent assays were performed to measure insulin and glucagon secretion after stimulation with different glucose concentrations. To our knowledge, this is the first Lab-on-a-chip system which enables the formation and three-dimensional culture of cell aggregates composed of commercially available α and β pancreatic islet cells. The specific composition and arrangement of cells in the obtained model corresponds to the arrangement of the cells in rodent pancreatic islets in vivo. This Islet-on-a-chip system may be utilized to test pathogenic effectors and future therapeutic agents.
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Affiliation(s)
- Patrycja Sokolowska
- Medical Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Poland; Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Kamil Zukowski
- Centre for Advanced Materials and Technologies CEZAMAT, Warsaw University of Technology, Poland
| | - Justyna Janikiewicz
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Elzbieta Jastrzebska
- Medical Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Poland
| | - Agnieszka Dobrzyn
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Zbigniew Brzozka
- Medical Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Poland.
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Zaborska KE, Dadi PK, Dickerson MT, Nakhe AY, Thorson AS, Schaub CM, Graff SM, Stanley JE, Kondapavuluru RS, Denton JS, Jacobson DA. Lactate activation of α-cell K ATP channels inhibits glucagon secretion by hyperpolarizing the membrane potential and reducing Ca 2+ entry. Mol Metab 2020; 42:101056. [PMID: 32736089 PMCID: PMC7479281 DOI: 10.1016/j.molmet.2020.101056] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/17/2020] [Accepted: 07/24/2020] [Indexed: 12/20/2022] Open
Abstract
Objective Elevations in pancreatic α-cell intracellular Ca2+ ([Ca2+]i) lead to glucagon (GCG) secretion. Although glucose inhibits GCG secretion, how lactate and pyruvate control α-cell Ca2+ handling is unknown. Lactate enters cells through monocarboxylate transporters (MCTs) and is also produced during glycolysis by lactate dehydrogenase A (LDHA), an enzyme expressed in α-cells. As lactate activates ATP-sensitive K+ (KATP) channels in cardiomyocytes, lactate may also modulate α-cell KATP. Therefore, this study investigated how lactate signaling controls α-cell Ca2+ handling and GCG secretion. Methods Mouse and human islets were used in combination with confocal microscopy, electrophysiology, GCG immunoassays, and fluorescent thallium flux assays to assess α-cell Ca2+ handling, Vm, KATP currents, and GCG secretion. Results Lactate-inhibited mouse (75 ± 25%) and human (47 ± 9%) α-cell [Ca2+]i fluctuations only under low-glucose conditions (1 mM) but had no effect on β- or δ-cells [Ca2+]i. Glyburide inhibition of KATP channels restored α-cell [Ca2+]i fluctuations in the presence of lactate. Lactate transport into α-cells via MCTs hyperpolarized mouse (14 ± 1 mV) and human (12 ± 1 mV) α-cell Vm and activated KATP channels. Interestingly, pyruvate showed a similar KATP activation profile and α-cell [Ca2+]i inhibition as lactate. Lactate-induced inhibition of α-cell [Ca2+]i influx resulted in reduced GCG secretion in mouse (62 ± 6%) and human (43 ± 13%) islets. Conclusions These data demonstrate for the first time that lactate entry into α-cells through MCTs results in KATP activation, Vm hyperpolarization, reduced [Ca2+]i, and inhibition of GCG secretion. Thus, taken together, these data indicate that lactate either within α-cells and/or elevated in serum could serve as important modulators of α-cell function. Lactate reduces islet α-cell Ca2+ entry under low glucose conditions. Lactate does not alter β- or δ-cell Ca2+ handling under low glucose conditions. Lactate enters islet α-cells through monocarboxylate transporters. Lactate hyperpolarizes islet α-cell membrane potential by activating KATP channels. Lactate reduces mouse and human islet glucagon secretion.
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Affiliation(s)
- Karolina E Zaborska
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew T Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Arya Y Nakhe
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Ariel S Thorson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Charles M Schaub
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Sarah M Graff
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Jade E Stanley
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Roy S Kondapavuluru
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Jerod S Denton
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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11
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Kuhre RE, Ghiasi SM, Adriaenssens AE, Wewer Albrechtsen NJ, Andersen DB, Aivazidis A, Chen L, Mandrup-Poulsen T, Ørskov C, Gribble FM, Reimann F, Wierup N, Tyrberg B, Holst JJ. No direct effect of SGLT2 activity on glucagon secretion. Diabetologia 2019; 62:1011-1023. [PMID: 30903205 PMCID: PMC7212061 DOI: 10.1007/s00125-019-4849-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Accepted: 02/12/2019] [Indexed: 02/03/2023]
Abstract
AIMS/HYPOTHESIS Sodium-glucose cotransporter (SGLT) 2 inhibitors constitute a new class of glucose-lowering drugs, but they increase glucagon secretion, which may counteract their glucose-lowering effect. Previous studies using static incubation of isolated human islets or the glucagon-secreting cell line α-TC1 suggested that this results from direct inhibition of alpha cell SGLT1/2-activity. The aim of this study was to test whether the effects of SGLT2 on glucagon secretion demonstrated in vitro could be reproduced in a more physiological setting. METHODS We explored the effect of SGLT2 activity on glucagon secretion using isolated perfused rat pancreas, a physiological model for glucagon secretion. Furthermore, we investigated Slc5a2 (the gene encoding SGLT2) expression in rat islets as well as in mouse and human islets and in mouse and human alpha, beta and delta cells to test for potential inter-species variations. SGLT2 protein content was also investigated in mouse, rat and human islets. RESULTS Glucagon output decreased three- to fivefold within minutes of shifting from low (3.5 mmol/l) to high (10 mmol/l) glucose (4.0 ± 0.5 pmol/15 min vs 1.3 ± 0.3 pmol/15 min, p < 0.05). The output was unaffected by inhibition of SGLT1/2 with dapagliflozin or phloridzin or by addition of the SGLT1/2 substrate α-methylglucopyranoside, whether at low or high glucose concentrations (p = 0.29-0.99). Insulin and somatostatin secretion (potential paracrine regulators) was also unaffected. Slc5a2 expression and SGLT2 protein were marginal or below detection limit in rat, mouse and human islets and in mouse and human alpha, beta and delta cells. CONCLUSIONS/INTERPRETATION Our combined data show that increased plasma glucagon during SGLT2 inhibitor treatment is unlikely to result from direct inhibition of SGLT2 in alpha cells, but instead may occur downstream of their blood glucose-lowering effects.
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Affiliation(s)
- Rune E Kuhre
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark
- Novo Nordisk Foundation Centre for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Seyed M Ghiasi
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Alice E Adriaenssens
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Nicolai J Wewer Albrechtsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark
- Novo Nordisk Foundation Centre for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
| | - Daniel B Andersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark
- Novo Nordisk Foundation Centre for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alexander Aivazidis
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Lihua Chen
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Thomas Mandrup-Poulsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark
| | - Cathrine Ørskov
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark
| | - Fiona M Gribble
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Frank Reimann
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Nils Wierup
- Department of Experimental Medical Science, Faculty of Medicine, Lund University Diabetes Centre, Lund, Sweden
| | - Björn Tyrberg
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Jens J Holst
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Panum Institute, Blegdamsvej 3B, DK-2200, Copenhagen N, Denmark.
- Novo Nordisk Foundation Centre for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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12
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Murata M, Adachi H, Nakade T, Oshima S. Glucagon secretion determined by the RIA method is lower in patients with low left ventricular ejection fraction: The new glass study. Diabetes Res Clin Pract 2018; 144:260-269. [PMID: 30213772 DOI: 10.1016/j.diabres.2018.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 08/06/2018] [Accepted: 09/03/2018] [Indexed: 10/28/2022]
Abstract
AIMS We investigated the glucagon levels in patients with heart failure (HF), using long oral glucose tolerance test (OGTT). METHODS In this prospective observational study, we enrolled 30 undiagnosed diabetes patients (age 69 ± 10 years, 70% males, HbA1c 43 mmol/mol). A 4-h OGTT was performed. Glucose, insulin, and glucagon (radioimmunoassay [RIA] and sandwich ELISA [S-W] methods) were evaluated during 4-h. We compared glucagon levels between HF and non-HF patients. RESULTS There were 11 HF and 19 non-HF patients. In patients with HF, glucagon (S-W) during 4-h was lower than in patients without HF, with no significant difference. The area under the curve (AUC) of glucagon (RIA) during 4-h was significantly lower among HF patients. Moreover, in patients with reduced left ventricular ejection fraction (LVEF) (<40%), AUC glucagon (RIA) was significantly lower than in patients with non-reduced EF (≥40%). However, there was no difference in glucagon values between the high E/e' (≥13.0) and low E/e' (<13.0) groups. CONCLUSIONS Although glucagon (S-W) showed no significant difference in patients with and without HF, especially reduced LVEF, glucagon (RIA) secretion was significantly lower in HF patients than in patients without HF. It is suggested that low glucagon secretion might be correlated with low EF.
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Affiliation(s)
- Makoto Murata
- Gunma Prefectural Cardiovascular Center, Department of Cardiology, 3-12 Kameizumimachi, Maebashi, Gunma 371-0004, Japan.
| | - Hitoshi Adachi
- Gunma Prefectural Cardiovascular Center, Department of Cardiology, 3-12 Kameizumimachi, Maebashi, Gunma 371-0004, Japan.
| | - Taishuke Nakade
- Gunma Prefectural Cardiovascular Center, Department of Cardiology, 3-12 Kameizumimachi, Maebashi, Gunma 371-0004, Japan.
| | - Shigeru Oshima
- Gunma Prefectural Cardiovascular Center, Department of Cardiology, 3-12 Kameizumimachi, Maebashi, Gunma 371-0004, Japan.
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13
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Watabe K, Yokawa S, Inoh Y, Suzuki T, Furuno T. Decreased intracellular granule movement and glucagon secretion in pancreatic α cells attached to superior cervical ganglion neurites. Mol Cell Biochem 2018; 446:83-89. [PMID: 29318457 DOI: 10.1007/s11010-018-3275-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 01/04/2018] [Indexed: 11/25/2022]
Abstract
Autonomic neurons innervate pancreatic islets of Langerhans and participate in the maintenance of blood glucose concentrations by controlling hormone levels through attachment with islet cells. We previously found that stimulated superior cervical ganglia (SCG) could induce Ca2+ oscillation in α cells via neuropeptide substance P using an in vitro co-culture model. In this study, we studied the effect of SCG neurite adhesion on intracellular secretory granule movement and glucagon secretion in α cells stimulated by low glucose concentration. Spinning disk microscopic analysis revealed that the mean velocity of intracellular granules was significantly lower in α cells attached to SCG neurites than that in those without neurites under low (2 mM), middle (10 mM), and high (20 mM) glucose concentrations. Stimulation by a low (2 mM) glucose concentration significantly increased glucagon secretion in α cells lacking neurites but not in those bound to neurites. These results suggest that adhesion to SCG neurites decreases low glucose-induced glucagon secretion in pancreatic α cells by attenuating intracellular granule movement activity.
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Affiliation(s)
- Kiyoto Watabe
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
| | - Satoru Yokawa
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
| | - Yoshikazu Inoh
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
| | - Takahiro Suzuki
- School of Dentistry, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
| | - Tadahide Furuno
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan.
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14
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Cao T, Zhang X, Yang D, Wang YQ, Qiao ZD, Huang JM, Zhang P. Antioxidant effects of epigallocatechin-3-gallate on the aTC1-6 pancreatic alpha cell line. Biochem Biophys Res Commun 2017; 495:693-699. [PMID: 29117537 DOI: 10.1016/j.bbrc.2017.11.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 11/02/2017] [Indexed: 01/20/2023]
Abstract
Hypoglycemia is a major barrier to achieving stable metabolic control in patients with diabetes which is a serious clinical concern. With progression of diabetes, the ability of pancreatic α-cells which respond to hypoglycemia becomes impaired; However, it is not clear whether the dysfunctional responses of α-cells during hypoglycemia are related with oxidative stress. In the present study, we investigated whether epigallocatechin-3-gallate (EGCG) has antioxidant potential on pancreatic alpha TC1-6 (αTC1-6) cell lines and protect the normal function of α-cells from H2O2 induced oxidative stress. ROS production, cell viability, glucagon secretion, and cell apoptosis were assessed. EGCG reduced ROS production and cell apoptosis, while restored cell viability and glucagon secretion within a particular concentration range. Moreover, EGCG activated Akt signaling and inhibited P38 as well as JNK mitogen-activated protein kinase (MAPK) pathway. Taken together, EGCG prevented αTC1-6 cells from H2O2 induced oxidative stress, restored dysfunction of glucagon secretion and inhibited cell apoptosis via the activation of Akt signaling and suppression of P38 and JNK pathway. These results provide rationale for combining the conventional anti-hyperglycemia therapy and antioxidant therapy in order to avert hypoglycemia in clinical treatment of diabetes.
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Affiliation(s)
- Ting Cao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Xiong Zhang
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Dan Yang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Yue-Qian Wang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Zheng-Dong Qiao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Jian-Ming Huang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
| | - Peng Zhang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China; Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
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15
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Abstract
PURPOSE OF REVIEW Hyperglucagonemia contributes significantly to hyperglycemia in type 2 diabetes and suppressed glucagon levels may increase the risk of hypoglycemia. Here, we give a brief overview of glucagon physiology and the role of glucagon in the pathophysiology of type 2 diabetes and provide insights into how antidiabetic drugs influence glucagon secretion as well as a perspective on the future of glucagon-targeting drugs. RECENT FINDINGS Several older as well as recent investigations have evaluated the effect of antidiabetic agents on glucagon secretion to understand how glucagon may be involved in the drugs' efficacy and safety profiles. Based on these findings, modulation of glucagon secretion seems to play a hitherto underestimated role in the efficacy and safety of several glucose-lowering drugs. Numerous drugs currently available to diabetologists are capable of altering glucagon secretion: metformin, sulfonylurea compounds, insulin, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, sodium-glucose cotransporter 2 inhibitors and amylin mimetics. Their diverse effects on glucagon secretion are of importance for their individual efficacy and safety profiles. Understanding how these drugs interact with glucagon secretion may help to optimize treatment.
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Affiliation(s)
- Magnus F Grøndahl
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Damien J Keating
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
| | - Tina Vilsbøll
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical sciences, University of Copenhagen, Copenhagen, Denmark
- Steno Diabetes Center Copenhagen, University of Copenhagen, Gentofte, Denmark
| | - Filip K Knop
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.
- Department of Clinical Medicine, Faculty of Health and Medical sciences, University of Copenhagen, Copenhagen, Denmark.
- Novo Nordisk Foundation Center for Metabolic Research, Faculty of Health and Medical sciences, University of Copenhagen, Copenhagen, Denmark.
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16
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Abstract
AIMS/HYPOTHESIS Glucagon-like peptide-1 (GLP-1) receptor agonists are currently used for the treatment of type 2 diabetes. Their main mechanism of action is enhancement of glucose-induced insulin secretion (from increased beta cell glucose sensitivity) and inhibition of glucagon secretion. The latter has been demonstrated to account for about half of their blood glucose-lowering activity. Whereas the effect of GLP-1 on insulin secretion is clearly dependent on ambient glucose concentrations and has been described in detail, the mechanism responsible for the inhibitory effect of GLP-1 on glucagon secretion is heavily debated. Glucagon inhibition is also said to be glucose-dependent, although it is unclear what is meant by this. We hypothesise here that GLP-1 does not inhibit glucagon secretion during hypoglycaemia because the inhibition depends on somatostatin secretion, which in turn is dependent on glucose levels. METHODS We used the perfused mouse pancreas model to investigate this hypothesis. RESULTS We found that, in this model, GLP-1 was able to significantly inhibit glucagon secretion from pancreatic alpha cells at all glucose levels tested: 6.0, 1.5 and 0.5 mmol/l (-27.0%, -37.1%, and -23.6%, respectively), and the decrease in glucagon secretion was invariably accompanied by an increase in somatostatin secretion (+286.8%, +158.7%, and +118.8%, respectively). Specific blockade of somatostatin receptor 2 increased glucagon secretion (+118.8% at 1.5 mmol/l glucose and +162.9% at 6.0 mmol/l glucose) and completely eliminated the inhibitory effect of GLP-1. CONCLUSIONS/INTERPRETATION We have shown here that the glucagon-lowering effect of GLP-1 is entirely mediated through the paracrine actions of somatostatin in the perfused mouse pancreas. However, in this model, the inhibitory effect of GLP-1 was preserved at hypoglycaemic levels, leaving unanswered the question of how this is avoided in vivo in individuals treated with GLP-1 receptor agonists.
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Affiliation(s)
- Anne Ørgaard
- Novo Nordisk Foundation Center for Basic Metabolic Research, Translational Metabolic Physiology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- University of Copenhagen, Department of Biomedical Sciences, Faculty of Health Sciences, Blegdamsvej 3B, Bldg 12.2, 2200, Copenhagen N, Denmark
| | - Jens J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research, Translational Metabolic Physiology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
- University of Copenhagen, Department of Biomedical Sciences, Faculty of Health Sciences, Blegdamsvej 3B, Bldg 12.2, 2200, Copenhagen N, Denmark.
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17
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Lazo-de-la-Vega-Monroy ML, Larrieta E, Tixi-Verdugo W, Ramírez-Mondragón R, Hernández-Araiza I, German MS, Fernandez-Mejia C. Effects of dietary biotin supplementation on glucagon production, secretion, and action. Nutrition 2017; 43-44:47-53. [PMID: 28935144 DOI: 10.1016/j.nut.2017.06.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 05/27/2017] [Accepted: 06/04/2017] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Despite increasing evidence that pharmacologic concentrations of biotin modify glucose metabolism, to our knowledge there have not been any studies addressing the effects of biotin supplementation on glucagon production and secretion, considering glucagon is one of the major hormones in maintaining glucose homeostasis. The aim of this study was to investigate the effects of dietary biotin supplementation on glucagon expression, secretion, and action. METHODS Male BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet (1.76 or 97.7 mg biotin/kg diet) for 8 wk postweaning. Glucagon gene mRNA expression was measured by the real-time polymerase chain reaction. Glucagon secretion was assessed in isolated islets and by glucagon concentration in plasma. Glucagon action was evaluated by glucagon tolerance tests, phosphoenolpyruvate carboxykinase (Pck1) mRNA expression, and glycogen degradation. RESULTS Compared with the control group, glucagon mRNA and secretion were increased from the islets of the biotin-supplemented group. Fasting plasma glucagon levels were higher, but no differences between the groups were observed in nonfasting glucagon levels. Despite the elevated fasting glucagon levels, no differences were found in fasting blood glucose concentrations, fasting/fasting-refeeding glucagon tolerance tests, glycogen content and degradation, or mRNA expression of the hepatic gluconeogenic rate-limiting enzyme, Pck1. CONCLUSIONS These results demonstrated that dietary biotin supplementation increased glucagon expression and secretion without affecting fasting blood glucose concentrations or glucagon tolerance and provided new insights into the effect of biotin supplementation on glucagon production and action.
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Affiliation(s)
- Maria-Luisa Lazo-de-la-Vega-Monroy
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico; Division of Health Sciences, Department of Medical Sciences, University of Guanajuato, Guanajuato, Mexico
| | - Elena Larrieta
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico; Department of Gastroentrology, Salvador Zubirán National Institute of Health Sciences and Nutrition, Mexico City, Mexico
| | - Wilma Tixi-Verdugo
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico
| | - Rafael Ramírez-Mondragón
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico
| | - Ileana Hernández-Araiza
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico
| | - Michael S German
- Diabetes Center/Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, California, USA
| | - Cristina Fernandez-Mejia
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico.
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18
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Cao T, Yang D, Zhang X, Wang Y, Qiao Z, Gao L, Liang Y, Yu B, Zhang P. FAM3D inhibits glucagon secretion via MKP1-dependent suppression of ERK1/2 signaling. Cell Biol Toxicol 2017; 33:457-466. [PMID: 28247283 DOI: 10.1007/s10565-017-9387-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 02/13/2017] [Indexed: 12/28/2022]
Abstract
Dysregulated glucagon secretion is a hallmark of type 2 diabetes (T2D). To date, few effective therapeutic agents target on deranged glucagon secretion. Family with sequence similarity 3 member D (FAM3D) is a novel gut-derived cytokine-like protein, and its secretion timing is contrary to that of glucagon. However, the roles of FAM3D in metabolic disorder and its biological functions are largely unknown. In the present study, we investigated whether FAM3D modulates glucagon production in mouse pancreatic alpha TC1 clone 6 (αTC1-6) cells. Glucagon secretion, prohormone convertase 2 (PC2) activity, and mitogen-activated protein kinase (MAPK) pathway were assessed. Exogenous FAM3D inhibited glucagon secretion, PC2 activity, as well as extracellular-regulated protein kinase 1/2 (ERK1/2) signaling and induced MAPK phosphatase 1 (MKP1) expression. Moreover, knockdown of MKP1 and inhibition of ERK1/2 abolished and potentiated the inhibitory effect of FAM3D on glucagon secretion, respectively. Taken together, FAM3D inhibits glucagon secretion via MKP1-dependent suppression of ERK1/2 signaling. These results provide rationale for developing the therapeutic potential of FAM3D for dysregulated glucagon secretion and T2D.
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Affiliation(s)
- Ting Cao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Dan Yang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Xiong Zhang
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Yueqian Wang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Zhengdong Qiao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Lili Gao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Yongjun Liang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Bo Yu
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
| | - Peng Zhang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China.
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
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19
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Dalgaard LT, Eliasson L. An 'alpha-beta' of pancreatic islet microribonucleotides. Int J Biochem Cell Biol 2017; 88:208-219. [PMID: 28122254 DOI: 10.1016/j.biocel.2017.01.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 01/16/2017] [Accepted: 01/18/2017] [Indexed: 11/17/2022]
Abstract
MicroRNAs (miRNAs) are cellular, short, non-coding ribonucleotides acting as endogenous posttranscriptional repressors following incorporation in the RNA-induced silencing complex. Despite being chemically and mechanistically very similar, miRNAs exert a multitude of different cellular effects by acting on mRNA species, whose gene-products partake in a wide array of processes. Here, the aim was to review the knowledge of miRNA expression and action in the islet of Langerhans. We have focused on: 1) physiological consequences of islet or beta cell specific inhibition of miRNA processing, 2) mechanisms regulating processing of miRNAs in islet cells, 3) presence and function of miRNAs in alpha versus beta cells - the two main cell types of islets, and 4) miRNA mediators of beta cell decompensation. It is clear that miRNAs regulate pancreatic islet development, maturation, and function in vivo. Moreover, processing of miRNAs appears to be altered by obesity, diabetes, and aging. A number of miRNAs (such as miR-7, miR-21, miR-29, miR-34a, miR-212/miR-132, miR-184, miR-200 and miR-375) are involved in mediating beta cell dysfunction and/or compensation induced by hyperglycemia, oxidative stress, cytotoxic cytokines, and in rodent models of fetal metabolic programming prediabetes and overt diabetes. Studies of human type 2 diabetic islets underline that these miRNA families could have important roles also in human type 2 diabetes. Furthermore, there is a genuine gap of knowledge regarding miRNA expression and function in pancreatic alpha cells. Progress in this area would be enhanced by improved in vitro alpha cell models and better tools for islet cell sorting.
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Affiliation(s)
| | - Lena Eliasson
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, CRC, SUS, Malmö, Sweden.
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20
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Wang Y, Han C, Zhu W, Wu Z, Liu Y, Chen L. An optical method to evaluate both mass and functional competence of pancreatic α- and β-cells. J Cell Sci 2016; 129:2462-71. [PMID: 27173492 DOI: 10.1242/jcs.184523] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 04/28/2016] [Indexed: 01/09/2023] Open
Abstract
Imbalanced glucagon and insulin release leads to the onset of type 2 diabetes. To pinpoint the underlying primary driving force, here we have developed a fast, non-biased optical method to measure ratios of pancreatic α- and β-cell mass and function simultaneously. We firstly label both primary α- and β-cells with the red fluorescent probe ZinRhodaLactam-1 (ZRL1), and then highlight α-cells by selectively quenching the ZRL1 signal from β-cells. Based on the signals before and after quenching, we calculate the ratio of the α-cell to β-cell mass within live islets, which we found matched the results from immunohistochemistry. From the same islets, glucagon and insulin release capability can be concomitantly measured. Thus, we were able to measure the ratio of α-cell to β-cell mass and their function in wild-type and diabetic Lepr(db)/Lepr(db) (denoted db/db) mice at different ages. We find that the initial glucose intolerance that appears in 10-week-old db/db mice is associated with further expansion of α-cell mass prior to deterioration in functional β-cell mass. Our method is extendable to studies of islet mass and function in other type 2 diabetes animal models, which shall benefit mechanistic studies of imbalanced hormone secretion during type 2 diabetes progression.
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Affiliation(s)
- Yi Wang
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China
| | - Chengsheng Han
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China
| | - Wenzhen Zhu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China
| | - Zhengxing Wu
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yanmei Liu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China
| | - Liangyi Chen
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China
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21
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Sun G, da Silva Xavier G, Gorman T, Priest C, Solomou A, Hodson DJ, Foretz M, Viollet B, Herrera PL, Parker H, Reimann F, Gribble FM, Migrenne S, Magnan C, Marley A, Rutter GA. LKB1 and AMPKα1 are required in pancreatic alpha cells for the normal regulation of glucagon secretion and responses to hypoglycemia. Mol Metab 2015; 4:277-86. [PMID: 25830091 DOI: 10.1016/j.molmet.2015.01.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 01/14/2015] [Accepted: 01/17/2015] [Indexed: 10/24/2022] Open
Abstract
AIMS/HYPOTHESIS Glucagon release from pancreatic alpha cells is required for normal glucose homoeostasis and is dysregulated in both Type 1 and Type 2 diabetes. The tumour suppressor LKB1 (STK11) and the downstream kinase AMP-activated protein kinase (AMPK), modulate cellular metabolism and growth, and AMPK is an important target of the anti-hyperglycaemic agent metformin. While LKB1 and AMPK have emerged recently as regulators of beta cell mass and insulin secretion, the role of these enzymes in the control of glucagon production in vivo is unclear. METHODS Here, we ablated LKB1 (αLKB1KO), or the catalytic alpha subunits of AMPK (αAMPKdKO, -α1KO, -α2KO), selectively in ∼45% of alpha cells in mice by deleting the corresponding flox'd alleles with a preproglucagon promoter (PPG) Cre. RESULTS Blood glucose levels in male αLKB1KO mice were lower during intraperitoneal glucose, aminoimidazole carboxamide ribonucleotide (AICAR) or arginine tolerance tests, and glucose infusion rates were increased in hypoglycemic clamps (p < 0.01). αLKB1KO mice also displayed impaired hypoglycemia-induced glucagon release. Glucose infusion rates were also elevated (p < 0.001) in αAMPKα1 null mice, and hypoglycemia-induced plasma glucagon increases tended to be lower (p = 0.06). Glucagon secretion from isolated islets was sensitized to the inhibitory action of glucose in αLKB1KO, αAMPKdKO, and -α1KO, but not -α2KO islets. CONCLUSIONS/INTERPRETATION An LKB1-dependent signalling cassette, involving but not restricted to AMPKα1, is required in pancreatic alpha cells for the control of glucagon release by glucose.
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Affiliation(s)
- Gao Sun
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | - Gabriela da Silva Xavier
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | | | | | - Antonia Solomou
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | - David J Hodson
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | - Marc Foretz
- Inserm, U1016, Institut Cochin, Paris, France ; CNRS, UMR8104, Paris, France ; Université Paris Descartes, Sorbonne Paris cité, Paris, France
| | - Benoit Viollet
- Inserm, U1016, Institut Cochin, Paris, France ; CNRS, UMR8104, Paris, France ; Université Paris Descartes, Sorbonne Paris cité, Paris, France
| | - Pedro-Luis Herrera
- Department of Genetic Medicine & Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Helen Parker
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK
| | - Frank Reimann
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK
| | - Fiona M Gribble
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK
| | - Stephanie Migrenne
- University Paris Diderot-Paris 7-Unit of Functional and Adaptive Biology (BFA) EAC 7059C NRS, France
| | - Christophe Magnan
- University Paris Diderot-Paris 7-Unit of Functional and Adaptive Biology (BFA) EAC 7059C NRS, France
| | | | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
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22
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Nakamura T, Yoshikawa T, Naganuma F, Mohsen A, Iida T, Miura Y, Sugawara A, Yanai K. Role of histamine H3 receptor in glucagon-secreting αTC1.6 cells. FEBS Open Bio 2014; 5:36-41. [PMID: 25685663 PMCID: PMC4309840 DOI: 10.1016/j.fob.2014.12.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 12/08/2014] [Accepted: 12/09/2014] [Indexed: 12/14/2022] Open
Abstract
Histamine H3 receptor is expressed in pancreatic α-cells. Histamine H3 receptor negatively regulates glucagon secretion from αTC1.6 cells. Immepip, a selective H3 receptor agonist, decreases serum glucagon concentration in rats.
Pancreatic α-cells secrete glucagon to maintain energy homeostasis. Although histamine has an important role in energy homeostasis, the expression and function of histamine receptors in pancreatic α-cells remains unknown. We found that the histamine H3 receptor (H3R) was expressed in mouse pancreatic α-cells and αTC1.6 cells, a mouse pancreatic α-cell line. H3R inhibited glucagon secretion from αTC1.6 cells by inhibiting an increase in intracellular Ca2+ concentration. We also found that immepip, a selective H3R agonist, decreased serum glucagon concentration in rats. These results suggest that H3R modulates glucagon secretion from pancreatic α-cells.
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Affiliation(s)
- Tadaho Nakamura
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Takeo Yoshikawa
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Fumito Naganuma
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Attayeb Mohsen
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Tomomitsu Iida
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Yamato Miura
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Akira Sugawara
- Department of Molecular Endocrinology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Kazuhiko Yanai
- Department of Pharmacology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
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23
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Aragón F, Karaca M, Novials A, Maldonado R, Maechler P, Rubí B. Pancreatic polypeptide regulates glucagon release through PPYR1 receptors expressed in mouse and human alpha-cells. Biochim Biophys Acta Gen Subj 2014; 1850:343-51. [PMID: 25445712 DOI: 10.1016/j.bbagen.2014.11.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 11/01/2014] [Accepted: 11/04/2014] [Indexed: 12/24/2022]
Abstract
BACKGROUND Plasma levels of pancreatic polypeptide (PP) rise upon food intake. Although other pancreatic islet hormones, such as insulin and glucagon, have been extensively investigated, PP secretion and actions are still poorly understood. METHODS The release of PP upon glucose stimulation and the effects of PP on glucagon and insulin secretion were analyzed in isolated pancreatic islets. Expression of PP receptor (PPYR1) was investigated by immunoblotting, quantitative RT-PCR on sorted pancreatic islet cells, and immunohistochemistry. RESULTS In isolated mouse pancreatic islets, glucose stimulation increased PP release, while insulin secretion was up and glucagon release was down. Direct exposure of islets to PP inhibited glucagon release. In mouse islets, PPYR1 protein was observed by immunoblotting and quantitative RT-PCR revealed PPYR1 expression in the FACS-enriched glucagon alpha-cell fraction. Immunohistochemistry on pancreatic sections showed the presence of PPYR1 in alpha-cells of both mouse and human islets, while the receptor was absent in other islet cell types and exocrine pancreas. CONCLUSIONS Glucose stimulates PP secretion and PP inhibits glucagon release in mouse pancreatic islets. PP receptors are present in alpha-cells of mouse and human pancreatic islets. GENERAL SIGNIFICANCE These data demonstrate glucose-regulated secretion of PP and its effects on glucagon release through PPYR1 receptors expressed by alpha-cells.
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Affiliation(s)
- F Aragón
- Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Parc de Recerca Biomèdica de Barcelona (PRBB), Barcelona, Spain
| | - M Karaca
- Department of Cell Physiology and Metabolism, Geneva University Medical Center, Geneva, Switzerland
| | - A Novials
- Diabetes Research Laboratory. IDIBAPS (Institut Investigacions Biomèdiques August Pi i Sunyer), CIBERDEM, Barcelona, Spain
| | - R Maldonado
- Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Parc de Recerca Biomèdica de Barcelona (PRBB), Barcelona, Spain
| | - P Maechler
- Department of Cell Physiology and Metabolism, Geneva University Medical Center, Geneva, Switzerland.
| | - B Rubí
- Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Parc de Recerca Biomèdica de Barcelona (PRBB), Barcelona, Spain.
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Abstract
During recent years, dipeptidyl peptidase‐4 (DPP‐4) inhibition has been included in the clinical management of type 2 diabetes, both as monotherapy and as add‐on to several other therapies. DPP‐4 inhibition prevents the inactivation of the incretin hormones, glucose‐dependent insulinotropic polypeptide (GIP) and glucagon‐like peptide‐1 (GLP‐1). This results in stimulation of insulin secretion and inhibition of glucagon secretion, and there is also a potential β‐cell preservation effect, as judged from rodent studies; that is, it might target the key islet dysfunction in the disease. In type 2 diabetes. This reduces 24‐h glucose levels and reduces HbA1c by ≈ 0.8–1.1% from baseline levels of 7.7–8.5%. DPP‐4 inhibition is safe, with a very low risk for adverse events including hypoglycemia, and it prevents weight gain. The present review summarizes the studies on the influence of DPP‐4 inhibition on islet function. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00184.x, 2012)
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Affiliation(s)
- Bo Ahrén
- Department of Clinical Sciences, Division of Medicine, Lund University, Lund, Sweden
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25
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Abstract
Glucagon secreted by pancreatic α-cells is the major hyperglycemic hormone correcting acute hypoglycaemia (glucose counterregulation). In diabetes the glucagon response to hypoglycaemia becomes compromised and chronic hyperglucagonemia appears. There is increasing awareness that glucagon excess may underlie important manifestations of diabetes. However opinions differ widely how glucose controls glucagon secretion. The autonomous nervous system plays an important role in the glucagon response to hypoglycaemia. But it is clear that glucose controls glucagon secretion also by mechanisms involving direct effects on α-cells or indirect effects via paracrine factors released from non-α-cells within the pancreatic islets. The present review discusses these mechanisms and argues that different regulatory processes are involved in a glucose concentration-dependent manner. Direct glucose effects on the α-cell and autocrine mechanisms are probably most significant for the glucagon response to hypoglycaemia. During hyperglycaemia, when secretion from β- and δ-cells is stimulated, paracrine inhibitory factors generate pulsatile glucagon release in opposite phase to pulsatile release of insulin and somatostatin. High concentrations of glucose have also stimulatory effects on glucagon secretion that tend to balance and even exceed the inhibitory influence. The latter actions might underlie the paradoxical hyperglucagonemia that aggravates hyperglycaemia in persons with diabetes.
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Affiliation(s)
- Erik Gylfe
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, SE-751 23, Uppsala, Sweden.
| | - Patrick Gilon
- Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
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