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Lu J, Zhao RX, Xiong FR, Zhu JJ, Shi TT, Zhang YC, Peng GX, Yang JK. All-potassium channel CRISPR screening reveals a lysine-specific pathway of insulin secretion. Mol Metab 2024; 80:101885. [PMID: 38246588 PMCID: PMC10847698 DOI: 10.1016/j.molmet.2024.101885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 01/04/2024] [Accepted: 01/12/2024] [Indexed: 01/23/2024] Open
Abstract
OBJECTIVE Genome-scale CRISPR-Cas9 knockout coupled with single-cell RNA sequencing (scRNA-seq) has been used to identify function-related genes. However, this method may knock out too many genes, leading to low efficiency in finding genes of interest. Insulin secretion is controlled by several electrophysiological events, including fluxes of KATP depolarization and K+ repolarization. It is well known that glucose stimulates insulin secretion from pancreatic β-cells, mainly via the KATP depolarization channel, but whether other nutrients directly regulate the repolarization K+ channel to promote insulin secretion is unknown. METHODS We used a system involving CRISPR-Cas9-mediated knockout of all 83 K+ channels and scRNA-seq in a pancreatic β cell line to identify genes associated with insulin secretion. RESULTS The expression levels of insulin genes were significantly increased after all-K+ channel knockout. Furthermore, Kcnb1 and Kcnh6 were the two most important repolarization K+ channels for the increase in high-glucose-dependent insulin secretion that occurred upon application of specific inhibitors of the channels. Kcnh6 currents, but not Kcnb1 currents, were reduced by one of the amino acids, lysine, in both transfected cells, primary cells and mice with β-cell-specific deletion of Kcnh6. CONCLUSIONS Our function-related CRISPR screen with scRNA-seq identifies Kcnh6 as a lysine-specific channel.
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Affiliation(s)
- Jing Lu
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Laboratory for Clinical Medicine, Capital Medical University, Beijing 100069, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China
| | - Ru-Xuan Zhao
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Laboratory for Clinical Medicine, Capital Medical University, Beijing 100069, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China
| | - Feng-Ran Xiong
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Laboratory for Clinical Medicine, Capital Medical University, Beijing 100069, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China
| | - Juan-Juan Zhu
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Laboratory for Clinical Medicine, Capital Medical University, Beijing 100069, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China
| | - Ting-Ting Shi
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China
| | - Ying-Chao Zhang
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China
| | - Gong-Xin Peng
- Center for Bioinformatics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100740, China
| | - Jin-Kui Yang
- Department of Endocrinology, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Laboratory for Clinical Medicine, Capital Medical University, Beijing 100069, China; Beijing Key Laboratory of Diabetes Research and Care, Beijing 100730, China.
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Benjamin JS, Culpepper CB, Brown LD, Wesolowski SR, Jonker SS, Davis MA, Limesand SW, Wilkening RB, Hay WW, Rozance PJ. Chronic anemic hypoxemia attenuates glucose-stimulated insulin secretion in fetal sheep. Am J Physiol Regul Integr Comp Physiol 2017; 312:R492-R500. [PMID: 28100476 PMCID: PMC5407078 DOI: 10.1152/ajpregu.00484.2016] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 01/04/2017] [Accepted: 01/11/2017] [Indexed: 01/15/2023]
Abstract
Fetal insulin secretion is inhibited by acute hypoxemia. The relationship between prolonged hypoxemia and insulin secretion, however, is less well defined. To test the hypothesis that prolonged fetal hypoxemia impairs insulin secretion, studies were performed in sheep fetuses that were bled to anemic conditions for 9 ± 0 days (anemic, n = 19) and compared with control fetuses (n = 15). Arterial hematocrit and oxygen content were 34% and 52% lower, respectively, in anemic vs. control fetuses (P < 0.0001). Plasma glucose concentrations were 21% higher in the anemic group (P < 0.05). Plasma norepinephrine and cortisol concentrations increased 70% in the anemic group (P < 0.05). Glucose-, arginine-, and leucine-stimulated insulin secretion all were lower (P < 0.05) in anemic fetuses. No differences in pancreatic islet size or β-cell mass were found. In vitro, isolated islets from anemic fetuses secreted insulin in response to glucose and leucine as well as control fetal islets. These findings indicate a functional islet defect in anemic fetuses, which likely involves direct effects of low oxygen and/or increased norepinephrine on insulin release. In pregnancies complicated by chronic fetal hypoxemia, increasing fetal oxygen concentrations may improve insulin secretion.
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Affiliation(s)
- Joshua S Benjamin
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Christine B Culpepper
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Laura D Brown
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado.,Center for Women's Health Research, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Stephanie R Wesolowski
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado.,Center for Women's Health Research, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Sonnet S Jonker
- Knight Cardiovascular Institute Center for Developmental Health, Oregon Health & Science University, Portland, Oregon; and
| | - Melissa A Davis
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Sean W Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Randall B Wilkening
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - William W Hay
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Paul J Rozance
- Perinatal Research Center, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado; .,Center for Women's Health Research, University of Colorado Denver School of Medicine, Aurora, Colorado
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Advanced physiological roles of guanidinoacetic acid. Eur J Nutr 2015; 54:1211-5. [DOI: 10.1007/s00394-015-1050-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 09/16/2015] [Indexed: 02/04/2023]
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An alternative mechanism for guanidinoacetic acid to affect methylation cycle. Med Hypotheses 2014; 83:847-8. [PMID: 25468046 DOI: 10.1016/j.mehy.2014.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 11/02/2014] [Indexed: 11/22/2022]
Abstract
Guanidinoacetic acid (also known as glycocyamine; GAA) is an endogenous substance which occurs in humans and plays a central role in the biosynthesis of creatine. The formation of creatine from GAA consumes methyl groups, and increases production of homocysteine. GAA may have the potential to stimulate insulin secretion. Insulin reduces plasma homocysteine and raises methyl group supply. It is possible that the ability of GAA to trigger the insulin secretion modulates methyl group metabolism, and comparatively counterbalance for the direct effect of GAA on increased methylation demand. Possible insulinotropic effect of GAA may contribute to total in vivo methylation demand during biotransformation.
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Jellyman JK, Valenzuela OA, Allen VL, Holdstock NB, Fowden AL. Sex‐associated differences in pancreatic β cell function in healthy preweaning pony foals. Equine Vet J 2014; 46:722-8. [DOI: 10.1111/evj.12230] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 01/04/2014] [Indexed: 01/06/2023]
Affiliation(s)
- J. K. Jellyman
- Department of Physiology Development and Neuroscience University of Cambridge UK
| | - O. A. Valenzuela
- Department of Physiology Development and Neuroscience University of Cambridge UK
| | - V. L. Allen
- Department of Physiology Development and Neuroscience University of Cambridge UK
| | | | - A. L. Fowden
- Department of Physiology Development and Neuroscience University of Cambridge UK
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6
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Ebaid H, Ahmed OM, Mahmoud AM, Ahmed RR. Limiting prolonged inflammation during proliferation and remodeling phases of wound healing in streptozotocin-induced diabetic rats supplemented with camel undenatured whey protein. BMC Immunol 2013; 14:31. [PMID: 23883360 PMCID: PMC3729579 DOI: 10.1186/1471-2172-14-31] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Accepted: 07/03/2013] [Indexed: 12/18/2022] Open
Abstract
Background Impaired diabetic wound healing occurs as a consequence of excessive reactive oxygen species (ROS) and inflammatory cytokine production. We previously found that whey protein (WP) was able to normally regulate the ROS and inflammatory cytokines during the inflammatory phase (first day) in streptozotocin (STZ)-diabetic wound healing. This study was designed to assess the effect of WP on metabolic status, the inflammation and anti-inflammation response, oxidative stress and the antioxidant defense system during different phases of the wound healing process in diabetic rats. WP at a dosage of 100 mg/kg of body weight, dissolved in 1% CMC, was orally administered daily to wounded normal (non-diabetic) and STZ-induced diabetic rats for 8 days starting from the 1st day after wounding. Results The data revealed that WP enhanced wound closure and was associated with an increase in serum insulin levels in diabetic rats and an alleviation of hyperglycemic and hyperlipidemic states in diabetic animals. The increase in insulin levels as a result of WP administration is associated with a marked multiplication of β-cells in the core of islets of Langerhans. WP induced a reduction in serum TNF-α, IL-1β and IL-6 levels and an increase in IL-10 levels, especially on the 4th day after wounding and treatment. WP also suppressed hepatic lipid peroxidation and stimulated the antioxidant defense system by increasing the level of glutathione and the activity of glutathione-S-transferase, glutathione peroxidase and superoxide dismutase (SOD) in wounded diabetic rats. Conclusions WP was observed to enhance wound closure by improving the diabetic condition, limiting prolonged inflammation, suppressing oxidative stress and elevating the antioxidant defense system in diabetic rats.
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Affiliation(s)
- Hossam Ebaid
- Department of Zoology, College of Science, King Saud University, PO Box 2455, Riyadh, 11451, Saudi Arabia.
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7
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Lavezzi JR, Thorn SR, O'Meara MC, LoTurco D, Brown LD, Hay WW, Rozance PJ. Increased fetal insulin concentrations for one week fail to improve insulin secretion or β-cell mass in fetal sheep with chronically reduced glucose supply. Am J Physiol Regul Integr Comp Physiol 2012; 304:R50-8. [PMID: 23135788 DOI: 10.1152/ajpregu.00413.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Maternal undernutrition during pregnancy and placental insufficiency are characterized by impaired development of fetal pancreatic β-cells. Prolonged reduced glucose supply to the fetus is a feature of both. It is unknown if reduced glucose supply, independent of other complications of maternal undernutrition and placental insufficiency, would cause similar β-cell defects. Therefore, we measured fetal insulin secretion and β-cell mass following prolonged reduced fetal glucose supply in sheep. We also tested whether restoring physiological insulin concentrations would correct any β-cell defects. Pregnant sheep received either a direct saline infusion (CON = control, n = 5) or an insulin infusion (HG = hypoglycemic, n = 5) for 8 wk in late gestation (75 to 134 days) to decrease maternal glucose concentrations and reduce fetal glucose supply. A separate group of HG fetuses also received a direct fetal insulin infusion for the final week of the study with a dextrose infusion to prevent a further fall in glucose concentration [hypoglycemic + insulin (HG+I), n = 4]. Maximum glucose-stimulated insulin concentrations were 45% lower in HG fetuses compared with CON fetuses. β-Cell, pancreatic, and fetal mass were 50%, 37%, and 40% lower in HG compared with CON fetuses, respectively (P < 0.05). Insulin secretion and β-cell mass did not improve in the HG+I fetuses. These results indicate that chronically reduced fetal glucose supply is sufficient to reduce pancreatic insulin secretion in response to glucose, primarily due to reduced pancreatic and β-cell mass, and is not correctable with insulin.
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Affiliation(s)
- Jinny R Lavezzi
- Perinatal Research Center, Section of Neonatology, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, USA
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8
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Abstract
Insulin secretion from pancreatic β cells is controlled by nutrients, hormones, and neurotransmitters. Unlike the latter, which work through classic receptors, glucose and most other nutrients do not interact with membrane receptors but must be metabolized by β cells to induce insulin secretion. Studies have revealed the presence of umami and sweet taste receptors and their downstream effectors in β cells. That the receptors are functional was established by the effects of fructose and artificial sweeteners, which induced signals similar to those produced in taste buds of the tongue. These signals mediated an increase in insulin secretion in the presence of glucose. However, the physiological implications of these pathways in insulin secretion are unclear because of the large differences between plasma concentrations of fructose or sweeteners and their effective concentrations in vitro.
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Affiliation(s)
- Jean-Claude Henquin
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, Avenue Hippocrate 55, B-1200 Brussels, Belgium.
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9
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Tan B, Li X, Yin Y, Wu Z, Liu C, Tekwe CD, Wu G. Regulatory roles for L-arginine in reducing white adipose tissue. FRONT BIOSCI-LANDMRK 2012; 17:2237-46. [PMID: 22652774 PMCID: PMC3422877 DOI: 10.2741/4047] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
As the nitrogenous precursor of nitric oxide, L-arginine regulates multiple metabolic pathways involved in the metabolism of fatty acids, glucose, amino acids, and proteins through cell signaling and gene expression. Specifically, arginine stimulates lipolysis and the expression of key genes responsible for activation of fatty acid oxidation to CO2 and water. The underlying mechanisms involve increases in the expression of peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1 alpha), mitochondrial biogenesis, and the growth of brown adipose tissue growth. Furthermore, arginine regulates adipocyte-muscle crosstalk and energy partitioning via the secretion of cytokines and hormones. In addition, arginine enhances AMP-activated protein kinase (AMPK) expression and activity, thereby modulating lipid metabolism and energy balance toward the loss of triacylglycerols. Growing evidence shows that dietary supplementation with arginine effectively reduces white adipose tissue in Zucker diabetic fatty rats, diet-induced obese rats, growing-finishing pigs, and obese patients with type II diabetes. Thus, arginine can be used to prevent and treat adiposity and the associated metabolic syndrome.
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Affiliation(s)
- Bi’e Tan
- Research Center of Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan, China 410125
| | - Xinguo Li
- Hunan Institute of Animal Husbandry and Veterinary Medicine, Changsha, Hunan, China 410131
| | - Yulong Yin
- Research Center of Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan, China 410125
| | - Zhenlong Wu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193
| | - Chuang Liu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193
| | - Carmen D. Tekwe
- Department of Statistics, Texas A and M University, College Station, TX, USA 77843-3143
| | - Guoyao Wu
- Research Center of Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan, China 410125
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193
- Department of Animal Science, Texas A&M University, College Station, TX, USA 77843-2471
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10
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Walker JN, Ramracheya R, Zhang Q, Johnson PRV, Braun M, Rorsman P. Regulation of glucagon secretion by glucose: paracrine, intrinsic or both? Diabetes Obes Metab 2011; 13 Suppl 1:95-105. [PMID: 21824262 DOI: 10.1111/j.1463-1326.2011.01450.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Glucagon secretion is regulated by glucose but the mechanisms involved remain hotly debated. Both intrinsic (within the α-cell itself) and paracrine (mediated by factors released β- and/or δ-cells) have been postulated. Glucagon secretion is maximally suppressed by glucose concentrations that do not affect insulin and somatostatin secretion, a finding that highlights the significance of intrinsic regulation of glucagon secretion. Experiments on islets from mice lacking functional ATP-sensitive potassium channels (K(ATP)-channels) indicate that these channels are critical to the α-cell's capacity to sense changes in extracellular glucose. Here, we review recent data on the intrinsic and paracrine regulation of glucagon secretion in human pancreatic islets. We propose that glucose-induced closure of the K(ATP)-channels, via membrane depolarization, culminates in reduced electrical activity and glucagon secretion by voltage-dependent inactivation of the ion channels involved in action potential firing. We further demonstrate that glucagon secretion measured in islets isolated from donors with type-2 diabetes is reduced at low glucose and that glucose stimulates rather than inhibits secretion in these islets. We finally discuss the relative significance of paracrine and intrinsic regulation in the fed and fasted states and propose a unifying model for the regulation of glucagon secretion that incorporates both modes of control.
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Affiliation(s)
- J N Walker
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LJ, UK
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YASUDA K, TAKASHIMA S, TAKAGI M, NISHII N, OHBA Y, KITAGAWA H. Insulin Responses to Administrations of Amino Acids and Fatty Acids in Healthy Cats. J Vet Med Sci 2011; 73:1281-6. [DOI: 10.1292/jvms.10-0414] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Kyoji YASUDA
- Department of Veterinary Clinical Veterinary Medicine, United Graduate School of Veterinary Science, Gifu University
| | - Satoshi TAKASHIMA
- Department of Veterinary Clinical Veterinary Medicine, United Graduate School of Veterinary Science, Gifu University
| | - Mitsuru TAKAGI
- Department of Veterinary Clinical Veterinary Medicine, United Graduate School of Veterinary Science, Gifu University
| | - Naohito NISHII
- Laboratory of Veterinary Pharmacotherapeutics, Faculty of Agriculture, Tottori University
| | - Yasunori OHBA
- Department of Veterinary Clinical Veterinary Medicine, United Graduate School of Veterinary Science, Gifu University
- Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University
| | - Hitoshi KITAGAWA
- Department of Veterinary Clinical Veterinary Medicine, United Graduate School of Veterinary Science, Gifu University
- Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University
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12
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Brown LD, Green AS, Limesand SW, Rozance PJ. Maternal amino acid supplementation for intrauterine growth restriction. Front Biosci (Schol Ed) 2011; 3:428-44. [PMID: 21196387 DOI: 10.2741/s162] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Maternal dietary protein supplementation to improve fetal growth has been considered as an option to prevent or treat intrauterine growth restriction. However, in contrast to balanced dietary supplementation, adverse perinatal outcomes in pregnant women who received high amounts of dietary protein supplementation have been observed. The responsible mechanisms for these adverse outcomes are unknown. This review will discuss relevant human and animal data to provide the background necessary for the development of explanatory hypotheses and ultimately for the development therapeutic interventions during pregnancy to improve fetal growth. Relevant aspects of fetal amino acid metabolism during normal pregnancy and those pregnancies affected by IUGR will be discussed. In addition, data from animal experiments which have attempted to determine mechanisms to explain the adverse responses identified in the human trials will be presented. Finally, we will suggest new avenues for investigation into how amino acid supplementation might be used safely to treat and/or prevent IUGR.
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Affiliation(s)
- Laura D Brown
- Department of Pediatrics, University of Colorado Denver; Aurora, CO 80045, USA
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Functional alterations in endocrine pancreas of rats with different degrees of dexamethasone-induced insulin resistance. Pancreas 2008; 36:284-93. [PMID: 18362843 DOI: 10.1097/mpa.0b013e31815ba826] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES We have analyzed the peripheral insulin and glucose sensitivity in vivo, and islet function ex vivo in rats with different degrees of insulin resistance induced by dexamethasone (DEX). METHODS Dexamethasone, in the concentrations of 0.1 (DEX 0.1), 0.5 (DEX 0.5), and 1.0 mg/kg body weight (DEX 1.0) was administered daily, intraperitoneally, to adult Wistar rats for 5 days, whereas controls received saline. RESULTS Dexamethasone treatment induced peripheral insulin resistance in a dose-dependent manner. At the end of the treatment, only DEX 1.0 rats showed significant increase of postabsorptive blood glucose and serum triglycerides, and nonesterified fatty acids levels. Incubation of pancreatic islets in increasing glucose concentrations (2.8-22 mM) led to an augmented insulin secretion in all DEX-treated rats. Leucine, carbachol, and high KCl concentrations induced the insulin release in DEX 0.5 and DEX 1.0, whereas arginine augmented secretion in all DEX-treated groups. CONCLUSIONS We demonstrate that in DEX 0.5 and, especially in DEX 0.1 groups, but not in DEX 1.0, the adaptations that occurred in the endocrine pancreas are able to counteract metabolic disorders (glucose intolerance and dyslipidemia). These animal models seem to be interesting approaches for the study of degrees of subjacent effects that may mediate type 2 diabetes (DEX 1.0) and islet function alterations, without collateral effects (DEX 0.1 and DEX 0.5).
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Rozance PJ, Limesand SW, Zerbe GO, Hay WW. Chronic fetal hypoglycemia inhibits the later steps of stimulus-secretion coupling in pancreatic beta-cells. Am J Physiol Endocrinol Metab 2007; 292:E1256-64. [PMID: 17213478 DOI: 10.1152/ajpendo.00265.2006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We measured the impact of chronic late gestation hypoglycemia on pancreatic islet structure and function to determine the cause of decreased insulin secretion in this sheep model of fetal nutrient deprivation. Late gestation hypoglycemia did not decrease pancreas weight, insulin content, beta-cell area, beta-cell mass, or islet size. The pancreatic islet isolation procedure selected a group of islets that were larger and had an increased proportion of beta-cells compared with islets measured in pancreatic sections, but there were no morphologic differences between islets isolated from control and hypoglycemic fetuses. The rates of glucose-stimulated pancreatic islet glucose utilization (126.2 +/- 25.3 pmol glucose.islet(-1).h(-1), hypoglycemic, vs. 93.5 +/- 5.5 pmol glucose.islet(-1).h(-1), control, P = 0.47) and oxidation (10.5 +/- 1.7 pmol glucose.islet(-1).h(-1), hypoglycemic, vs. 10.6 +/- 1.6 pmol glucose.islet(-1).h(-1), control) were not different in hypoglycemic fetuses compared with control fetuses. Chronic late gestation hypoglycemia decreased insulin secretion in isolated pancreatic islets by almost 70% in response to direct nonnutrient membrane depolarization and in response to increased extracellular calcium entry. beta-Cell ultrastructure was abnormal with markedly distended rough endoplasmic reticulum in three of the seven hypoglycemic fetuses studied, but in vitro analysis of hypoglycemic control islets showed no evidence that these changes represented endoplasmic reticulum stress, as measured by transcription of glucose regulatory protein-78 and processing of X-box binding protein-1. In conclusion, these studies show that chronic hypoglycemia in late gestation decreases insulin secretion by inhibiting the later steps of stimulus-secretion coupling after glucose metabolism, membrane depolarization, and calcium entry.
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Affiliation(s)
- Paul J Rozance
- Perinatal Research Center, University of Colorado Health Sciences Center, Aurora, Colorado 80045, USA.
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15
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Nilsson M, Holst JJ, Björck IM. Metabolic effects of amino acid mixtures and whey protein in healthy subjects: studies using glucose-equivalent drinks. Am J Clin Nutr 2007; 85:996-1004. [PMID: 17413098 DOI: 10.1093/ajcn/85.4.996] [Citation(s) in RCA: 251] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Milk protein, in particular the whey fraction, has been shown to display insulinotrophic properties in healthy persons and persons with type 2 diabetes. In parallel to the hyperinsulinemia, a pronounced postprandial rise of certain amino acids and of glucose-dependent insulinotrophic polypeptide (GIP) was observed in plasma. OBJECTIVE The objective of the study was to determine to what extent the insulinotrophic properties of whey could be simulated by specific amino acid mixtures. DESIGN Twelve healthy volunteers were served drinks consisting of pure glucose (reference drink) or glucose supplemented with free amino acids or whey proteins (test drinks). RESULTS A test drink with the branched-chain amino acids isoleucine, leucine, and valine resulted in significantly higher insulin responses than did the glucose reference. A drink containing glucose and leucine, isoleucine, valine, lysine, and threonine mimicked the glycemic and insulinemic responses seen after whey ingestion. With consumption of this drink, the glucose area under the curve (AUC) was 44% smaller (P < 0.05) and the insulin AUC was 31% larger (NS) than with consumption of the reference drink. With consumption of the whey drink, the AUCs were 56% smaller (glucose; P < 0.05) and 60% larger (insulin; P < 0.05), respectively, than with the reference drink. The whey drink was accompanied by an 80% greater GIP response (P < 0.05), whereas the drinks containing free amino acids did not significantly affect GIP secretion. CONCLUSION A mixture of leucine, isoleucine, valine, lysine, and threonine resulted in glycemic and insulinemic responses closely mimicking those seen after whey ingestion in the absence of an additional effect of GIP and glucagon-like peptide 1.
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Affiliation(s)
- Mikael Nilsson
- Division of Applied Nutrition and Food Chemistry, Lund University, Lund, Sweden.
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Kang HC, Bae YH. Polymeric gene transfection on insulin-secreting cells: sulfonylurea receptor-mediation and transfection medium effect. Pharm Res 2007; 23:1797-808. [PMID: 16850268 DOI: 10.1007/s11095-006-9027-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 04/05/2006] [Indexed: 12/21/2022]
Abstract
PURPOSE In vitro transfection of secreting cells is regarded as one strategy for improved cell engineering/ transplantation. Insulin-secreting insulinoma cell lines or pancreatic beta-cells could be genetically engineered using designed polymeric vectors which are safer than viral vectors. This study investigates the effects of the constituents in transfection media on polymeric transfection. METHODS Polyplexes conjugated with sulfonylurea (SU) were evaluated under different transfection conditions for gene transfection and their effects on cytotoxicity and insulin secretion. Several components in transfection media specifically associated with the insulin secretion pathway were amino acids, vitamins, Ca2+ and K+. The interactions of the polyplexes with insulin were monitored by surface charge and particle size to monitor how insulin as a protein influences transfection. RESULTS For an insulin-secreting cell line (RINm5F), polyplexes in Ca2+--containing KRH medium (Ca2+(+)KRH) enhanced transfection and did not cause damage to biological functions. When adding amino acids, vitamins, or K+ or depleting Ca2+ from Ca2+(+)KRH, poly(L-lysine)/DNA complexes showed a greater reduction in transfection than SU receptor (SUR)-targeting polyplexes (SU-polyplex). Positively charged polyplexes interacted with insulin, developing a negative surface charge, and these interactions may cause a decrease in transfection. CONCLUSION The findings suggest that in vitro and ex vivo polymeric transfection of insulin-secreting cells can be modulated and enhanced by adjusting the transfection conditions.
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Affiliation(s)
- Han Chang Kang
- Department of Pharmaceutics and Pharmaceutical Chemistry, The University of Utah, 421 Wakara Way, Suite 318, Salt Lake City, Utah 84108, USA
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Rozance PJ, Limesand SW, Hay WW. Decreased nutrient-stimulated insulin secretion in chronically hypoglycemic late-gestation fetal sheep is due to an intrinsic islet defect. Am J Physiol Endocrinol Metab 2006; 291:E404-11. [PMID: 16569758 DOI: 10.1152/ajpendo.00643.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We measured in vivo and in vitro nutrient-stimulated insulin secretion in late gestation fetal sheep to determine whether an intrinsic islet defect is responsible for decreased glucose-stimulated insulin secretion (GSIS) in response to chronic hypoglycemia. Control fetuses responded to both leucine and lysine infusions with increased arterial plasma insulin concentrations (average increase: 0.13 +/- 0.05 ng/ml leucine; 0.99 +/- 0.26 ng/ml lysine). In vivo lysine-stimulated insulin secretion was decreased by chronic (0.37 +/- 0.18 ng/ml) and acute (0.27 +/- 0.19 ng/ml) hypoglycemia. Leucine did not stimulate insulin secretion following acute hypoglycemia but was preserved with chronic hypoglycemia (0.12 +/- 0.09 ng/ml). Isolated pancreatic islets from chronically hypoglycemic fetuses had normal insulin and DNA content but decreased fractional insulin release when stimulated with glucose, leucine, arginine, or lysine. Isolated islets from control fetuses responded to all nutrients. Therefore, chronic late gestation hypoglycemia causes defective in vitro nutrient-regulated insulin secretion that is at least partly responsible for diminished in vivo GSIS. Chronic hypoglycemia is a feature of human intrauterine growth restriction (IUGR) and might lead to an islet defect that is responsible for the decreased insulin secretion patterns seen in human IUGR fetuses and low-birth-weight human infants.
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Affiliation(s)
- Paul J Rozance
- Perinatal Research Center, University of Colorado Health Sciences Center, Aurora, CO 80045, USA.
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18
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Ishiyama N, Ravier MA, Henquin JC. Dual mechanism of the potentiation by glucose of insulin secretion induced by arginine and tolbutamide in mouse islets. Am J Physiol Endocrinol Metab 2006; 290:E540-9. [PMID: 16249257 DOI: 10.1152/ajpendo.00032.2005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucose induces insulin secretion (IS) and also potentiates the insulin-releasing action of secretagogues such as arginine and sulfonylureas. This potentiating effect is known to be impaired in type 2 diabetic patients, but its cellular mechanisms are unclear. IS and cytosolic Ca(2+) concentration ([Ca(2+)](i)) were measured in mouse islets during perifusion with 3-15 mmol/l glucose (G3-G15, respectively) and pulse or stepwise stimulation with 1-10 mmol/l arginine or 5-250 micromol/l tolbutamide. In G3, arginine induced small increases in [Ca(2+)](i) but no IS. G7 alone only slightly increased [Ca(2+)](i) and IS but markedly potentiated arginine effects on [Ca(2+)](i), which resulted in significant IS (already at 1 mmol/l). For each arginine concentration, both responses further increased at G10 and G15, but the relative change was distinctly larger for IS than [Ca(2+)](i). At all glucose concentrations, tolbutamide dose dependently increased [Ca(2+)](i) and IS with thresholds of 25 micromol/l for [Ca(2+)](i) and 100 micromol/l for IS at G3 and of 5 micromol/l for both at G7 and above. Between G7 and G15, the effect of tolbutamide on [Ca(2+)](i) increased only slightly, whereas that on IS was strongly potentiated. The linear relationship between IS and [Ca(2+)](i) at increasing arginine or tolbutamide concentrations became steeper as the glucose concentration was raised. Thus glucose augmented more the effect of each agent on IS than that on [Ca(2+)](i). In conclusion, glucose potentiation of arginine- or tolbutamide-induced IS involves increases in both the rise of [Ca(2+)](i) and the action of Ca(2+) on exocytosis. This dual mechanism must be borne in mind to interpret the alterations of the potentiating action of glucose in type 2 diabetic patients.
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Affiliation(s)
- Nobuyoshi Ishiyama
- Unité d'Endocrinologie et Métabolisme, University of Louvain Faculty of Medicine, Brussels, Belgium
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Kuntz E, Broca C, Komurasaki T, Kaltenbacher MC, Gross R, Pinget M, Damgé C. Effect of epiregulin on pancreatic beta cell growth and insulin secretion. Growth Factors 2005; 23:285-93. [PMID: 16338791 DOI: 10.1080/08977190500233367] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The aim of this study was to determine whether epiregulin, a novel member of EGF-related growth factor family, was able to affect proliferation and secretory function of rat insulinoma INS-1E and RINm5F cell lines. A 24 h treatment with epiregulin resulted in a stimulation of INS-1E and RINm5F cells proliferation; this effect was completely blocked in the presence of an anti-epiregulin antibody which did not affect basal DNA synthesis in the absence of added ligand. In acute experiments, epiregulin was able to potentiate insulin release in the presence of glucose or arginine, in the two cell lines. Finally, in the two cell lines expressing ErbB receptors, we demonstrated that only EGFR/ErbB1 was activated by epiregulin. Thus, epiregulin appears as a new growth and insulinotropic factor in pancreatic beta cell lines.
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Affiliation(s)
- Emmanuelle Kuntz
- European Centre for the Study of Diabetes, Faculty of Medicine, Strasbourg, France
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20
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Limesand SW, Hay WW. Adaptation of ovine fetal pancreatic insulin secretion to chronic hypoglycaemia and euglycaemic correction. J Physiol 2003; 547:95-105. [PMID: 12562941 PMCID: PMC2342612 DOI: 10.1113/jphysiol.2002.026831] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Fetal pancreatic adaptations to relative hypoglycaemia, a characteristic of intra-uterine growth restriction, may limit pancreatic beta-cell capacity to produce and/or secrete insulin. The objective of this study was to measure beta-cell responsiveness in hypoglycaemic (H) fetal sheep and ascertain whether a 5 day euglycaemic recovery period would restore insulin secretion capacity. Glucose-stimulated insulin secretion (GSIS) was measured in euglycaemic (E) control fetuses, fetuses made hypoglycaemic for 14 days, and in a subset of 14-day hypoglycaemic fetuses returned to euglycaemia for 5 days (R fetuses). Hypoglycaemia significantly decreased plasma insulin concentrations in H (0.13 +/- 0.01 ng ml(-1)) and R fetuses (0.11 +/- 0.01 ng ml(-1)); insulin concentrations returned to euglycaemic control values (0.30 +/- 0.01 ng ml(-1)) in R fetuses (0.29 +/- 0.04 ng ml(-1)) during their euglycaemic recovery period. Mean steady-state plasma insulin concentration during the GSIS study was reduced in H fetuses (0.40 +/- 0.07 vs. 0.92 +/- 0.10 ng ml(-1) in E), but increased (P < 0.05) in R fetuses (0.73 +/- 0.10 ng ml(-1)) to concentrations not different from those in the E group. Nonlinear modelling of GSIS showed that response time was greater (P < 0.01) in both H (15.6 +/- 2.8 min) and R (15.4 +/- 1.5 min) than in E fetuses (6.3 +/- 1.1 min). In addition, insulin secretion responsiveness to arginine was reduced by hypoglycaemia (0.98 +/- 0.11 ng ml(-1) in H vs. 1.82 +/- 0.17 ng ml(-1) in E, P < 0.05) and did not recover (1.21 +/- 0.15 ng ml(-1) in R, P < 0.05 vs. E). Thus, a 5 day euglycaemic recovery period from chronic hypoglycaemia reestablished GSIS to normal levels, but there was a persistent reduction of beta-cell responsiveness to glucose and arginine. We conclude that programming of pancreatic insulin secretion responsiveness can occur in response to fetal glucose deprivation, indicating a possible mechanism for establishing, in fetal life, a predisposition to type 2 diabetes.
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Affiliation(s)
- Sean W Limesand
- Perinatal Research Center, Division of Perinatal Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA
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21
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Xuan S, Kitamura T, Nakae J, Politi K, Kido Y, Fisher PE, Morroni M, Cinti S, White MF, Herrera PL, Accili D, Efstratiadis A. Defective insulin secretion in pancreatic beta cells lacking type 1 IGF receptor. J Clin Invest 2002. [PMID: 12370279 DOI: 10.1172/jci200215276] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023] Open
Abstract
Defective insulin secretion is a feature of type 2 diabetes that results from inadequate compensatory increase of beta cell mass and impaired glucose-dependent insulin release. beta cell proliferation and secretion are thought to be regulated by signaling through receptor tyrosine kinases. In this regard, we sought to examine the potential proliferative and/or antiapoptotic role of IGFs in beta cells by tissue-specific conditional mutagenesis ablating type 1 IGF receptor (IGF1R) signaling. Unexpectedly, lack of functional IGF1R did not affect beta cell mass, but resulted in age-dependent impairment of glucose tolerance, associated with a decrease of glucose- and arginine-dependent insulin release. These observations reveal a requirement of IGF1R-mediated signaling for insulin secretion.
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Affiliation(s)
- Shouhong Xuan
- Department of Genetics and Development, College of Physicians & Surgeons, Columbia University, New York, New York, USA
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22
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Xuan S, Kitamura T, Nakae J, Politi K, Kido Y, Fisher PE, Morroni M, Cinti S, White MF, Herrera PL, Accili D, Efstratiadis A. Defective insulin secretion in pancreatic β cells lacking type 1 IGF receptor. J Clin Invest 2002. [PMID: 12370279 DOI: 10.1172/jci0215276] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Shouhong Xuan
- Department of Genetics and Development, College of Physicians & Surgeons, Columbia University, New York, New York, USA
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23
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Xuan S, Kitamura T, Nakae J, Politi K, Kido Y, Fisher PE, Morroni M, Cinti S, White MF, Herrera PL, Accili D, Efstratiadis A. Defective insulin secretion in pancreatic beta cells lacking type 1 IGF receptor. J Clin Invest 2002; 110:1011-9. [PMID: 12370279 PMCID: PMC151144 DOI: 10.1172/jci15276] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Defective insulin secretion is a feature of type 2 diabetes that results from inadequate compensatory increase of beta cell mass and impaired glucose-dependent insulin release. beta cell proliferation and secretion are thought to be regulated by signaling through receptor tyrosine kinases. In this regard, we sought to examine the potential proliferative and/or antiapoptotic role of IGFs in beta cells by tissue-specific conditional mutagenesis ablating type 1 IGF receptor (IGF1R) signaling. Unexpectedly, lack of functional IGF1R did not affect beta cell mass, but resulted in age-dependent impairment of glucose tolerance, associated with a decrease of glucose- and arginine-dependent insulin release. These observations reveal a requirement of IGF1R-mediated signaling for insulin secretion.
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Affiliation(s)
- Shouhong Xuan
- Department of Genetics and Development, College of Physicians & Surgeons, Columbia University, New York, New York, USA
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24
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Cherif H, Reusens B, Dahri S, Remacle C. A protein-restricted diet during pregnancy alters in vitro insulin secretion from islets of fetal Wistar rats. J Nutr 2001; 131:1555-9. [PMID: 11340115 DOI: 10.1093/jn/131.5.1555] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Previous studies indicate that insulin secretion from the fetuses of dams fed a low protein (LP) diet is reduced in response to leucine or arginine. The aim of this study was to locate the defect in the insulin secretion pathway induced by a LP diet during gestation. The effects of various secretagogues acting at different levels of the insulin secretion cascade were investigated in vitro in fetal islets from dams fed either a normal or a LP diet during pregnancy. Insulin content, insulin secretion and the cAMP content were then measured. Although insulin content of LP islets did not differ from that of control islets, insulin secretion from LP fetal islets was reduced when challenged by amino acids or cAMP enhancers. This reduction did not appear to be related solely to an altered islet cAMP content. An impairment of insulin secretion remained after stimulation of fetal LP islets with either metabolic or nonmetabolic secretagogues. The insulin secretion by LP islets was restored to normal, however, with barium or cytochalasin-B. These findings demonstrate that an in utero isocaloric LP diet impairs insulin secretion of the fetus. This alteration is located at the exocytosis step in the insulin secretion cascade and not in the insulin pool of the beta cell.
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Affiliation(s)
- H Cherif
- Laboratory of Cell Biology Department of Biology, WHO Collaborating Center, Université Catholique de Louvain, 1348, Louvain-la-Neuve, Belgium
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25
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Abstract
Stimulation of insulin release by glucose is widely thought to be coupled to a decrease in the activity of ATP-sensitive K+ channels (KATP channels) that is caused by a decreased concentration of free ADP. To date, most other investigators have reported only on total cellular ADP concentrations, even though only a small fraction of all ADP is free and only the free ADP affects KATP channels. We tested the hypothesis that amino acids elicit insulin release via a decrease in the activity of KATP channels owing to a decrease in the level of free ADP. We estimated the concentration of free ADP in betaHC9 hyperplastic insulin-secreting cells based on the cell diameter and on luminometric measurements of ATP, phosphocreatine, and total creatine. The concentration of free ADP fell exponentially as the concentration of glucose increased. A physiological mixture of amino acids greatly stimulated insulin release at 0-30 mmol/l glucose but affected the concentration of free ADP only to a minor degree and significantly so only at < or = 2 mmol/l glucose. In the presence of 2-deoxyglucose and NaN3, amino acids were unable to stimulate insulin release. When KATP channels were held open with diazoxide (and the plasma membrane partially depolarized with high extracellular KCl), amino acids still stimulated insulin release. We conclude that amino acid-induced insulin release depends on two components: a yet-unknown amino acid sensor and KATP channels, which serve to attenuate hormone release when cellular energy stores are low. We propose that glucose-induced insulin release may be regulated similarly by two components: glucokinase and KATP channels.
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Affiliation(s)
- P Ronner
- Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University College of Medicine, Philadelphia, Pennsylvania 19107-5541, USA.
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26
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Sener A, Best LC, Yates AP, Kadiata MM, Olivares E, Louchami K, Jijakli H, Ladrière L, Malaisse WJ. Stimulus-secretion coupling of arginine-induced insulin release: comparison between the cationic amino acid and its methyl ester. Endocrine 2000; 13:329-40. [PMID: 11216645 DOI: 10.1385/endo:13:3:329] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2000] [Accepted: 07/03/2000] [Indexed: 12/22/2022]
Abstract
The role currently ascribed to the accumulation of L-arginine in the pancreatic islet B-cell as a determinant of its insulinotropic action was reevaluated by comparing the uptake and the metabolic, ionic, electric, and secretory effects of the cationic amino acid with those of its more positively charged methyl ester in rat pancreatic islets. The response to L-arginine methyl ester differed from that evoked by the unesterified amino acid by a lower uptake and oxidation, lack of inhibitory action on D-glucose metabolism, more severe inhibition of the catabolism of endogenous L-glutamine, inhibition of 45Ca net uptake, decrease in both 86Rb outflow from prelabeled islets perifused at normal extracellular Ca2+ concentration and 45Ca efflux from prelabeled islets perifused in the absence of extracellular Ca2+, and delayed and lesser insulinotropic action. These findings reinforce the view that the carrier-mediated entry of L-arginine into the islet B-cells, with resulting depolarization of the plasma membrane, represents the essential mechanism for stimulation of insulin release by this cationic amino acid.
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Affiliation(s)
- A Sener
- Laboratory, of Experimental Medicine, Brussels Free University, Belgium
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27
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Sone H, Ito M, Shimizu M, Sasaki Y, Komai M, Furukawa Y. Characteristics of the biotin enhancement of glucose-induced insulin release in pancreatic islets of the rat. Biosci Biotechnol Biochem 2000; 64:550-4. [PMID: 10803952 DOI: 10.1271/bbb.64.550] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Perifused isolated rat islets were used to show that biotin plus 16.5 mM glucose evoked more insulin secretion than 16.5 mM glucose alone. Whether or not this reinforcement of glucose-induced insulin secretion by biotin is unique was studied by using perifused islets stimulated with 16.5 mM glucose plus 100 microM of one of various components of the vitamin B group. No effect of any of these vitamins was found on glucose-induced insulin secretion. These results indicate that biotin is unique among the members of the vitamin B group in enhancing glucose-induced insulin secretion. Static incubation experiments showed that biotin did not potentiate insulin release when the islets were incubated with an experimental solution containing either no or 2.8 mM glucose. The addition of biotin to 27.7 mM glucose, which is the maximal concentration for stimulating insulin release, did not significantly enhance the effect of the glucose on insulin release (although it did at 16.5 mM glucose). These findings indicate that biotin, by itself, does not stimulate insulin secretion, and does not enhance glucose-induced insulin secretion beyond the ability of glucose itself to stimulate insulin secretion.
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Affiliation(s)
- H Sone
- Department of Applied Biological Chemistry, Faculty of Agriculture, Tohoku University, Sendai, Japan
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28
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Matthews DR, Boland O. The stimulation of insulin secretion in non-insulin-dependent diabetic patients by amino acids and gliclazide in the basal and hyperglycemic state. Metabolism 1997; 46:5-9. [PMID: 9439551 DOI: 10.1016/s0026-0495(97)90309-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Sulfonylureas stimulate insulin secretion as their predominant contribution toward decreasing blood glucose in diabetic patients. We studied eight gliclazide-treated, non-insulin-dependent diabetic patients on two occasions with a protocol of basal observation for 30 minutes, a 60-minute infusion of randomized leucine or arginine, and a further 90-minute hyperglycemic clamp. Basal glucose was the same on both occasions (mean, 7.82 mmol/L for leucine v 7.79 for arginine, P = NS), and glucose levels declined to 7.50 and 7.25 mmol/L, respectively, by 30 minutes. After leucine infusion, the decline of glucose continued, but stabilized or reversed with arginine such that by the end of the infusions, glucose levels were 6.63 +/- 0.69 mmol/L for leucine and 7.62 +/- 0.67 for arginine (P < .02). Arginine caused a sharp increase in insulin secretion (from 17.8 mU/L to 43.8 mU/L in 6 minutes) at the onset of the infusion, and thereafter insulin secretion was not significantly different throughout either the amino acid or hyperglycemic clamp periods (mean, 42.1 v 44.7 mU/L, respectively, P = NS). By contrast, the leucine infusion caused little acute change in secretion, but augmented it with time from the basal period (17.2 mU/L) to the end of the infusion (29.4 mU/L). During the hyperglycemic clamp period, there was significant further augmentation of insulin secretion, increasing to 81.6 +/- 16 mU/L at the end of the study. Leucine significantly augmented insulin secretion compared with arginine (81.6 +/- 16 v 54.0 +/- 8.4 mU/L, respectively, P < .002). These data suggest that leucine is a better priming agent for sulfonylurea than arginine. Additive effects on insulin secretion may allow the use of combinations of branched chain amino acids (BCAAs) and sulfonylureas to augment insulin secretion in the presence of hyperglycemia.
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Affiliation(s)
- D R Matthews
- Oxford Diabetes and Endocrinology Centre, Radcliffe Infirmary National Health Service Trust, Oxford, UK
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Nakata M, Yada T, Nakagawa S, Kobayashi K, Maruyama I. Citrulline-argininosuccinate-arginine cycle coupled to Ca2+-signaling in rat pancreatic beta-cells. Biochem Biophys Res Commun 1997; 235:619-24. [PMID: 9207208 DOI: 10.1006/bbrc.1997.6854] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pancreatic beta-cells possess nitric oxide (NO) synthases (NOSs) which synthesize NO and L-citrulline from L-arginine. The present study was designed to explore the mechanism of citrulline and arginine metabolism in beta-cells and its possible coupling to beta-cell functions. The enzymes involved in citrulline-arginine metabolism, argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), and NOS were expressed in rat islets and insulinoma HIT T15 cells. In the presence of stimulatory glucose, L-citrulline and L-argininosuccinate at physiological concentrations (0.1-1 mM) increased cytosolic Ca2+ concentration ([Ca2+]i) in rat beta-cells. The citrulline-induced [Ca2+]i increase was inhibited by a NOS inhibitor, N(G)-monomethyl-L-arginine (NMMA). L-citrulline also stimulated NO production in HIT cells, which was inhibited by NMMA. In conclusion, L-citrulline is metabolized by ASS-ASL-NOS cycle to produce NO, which in turn increases [Ca2+]i in beta-cells.
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Affiliation(s)
- M Nakata
- Department of Laboratory Medicine, Faculty of Medicine, Kagoshima University, Japan
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30
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Smith PA, Sakura H, Coles B, Gummerson N, Proks P, Ashcroft FM. Electrogenic arginine transport mediates stimulus-secretion coupling in mouse pancreatic beta-cells. J Physiol 1997; 499 ( Pt 3):625-35. [PMID: 9130159 PMCID: PMC1159281 DOI: 10.1113/jphysiol.1997.sp021955] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. We have investigated the mechanism by which L-arginine stimulates membrane depolarization, an increase of intracellular calcium ([Ca2+]i) and insulin secretion in pancreatic beta-cells. 2. L-Arginine failed to affect beta-cell metabolism, as monitored by NAD(P)H autofluorescence. 3. L-Arginine produced a dose-dependent increase in [Ca2+]i, which was dependent on membrane depolarization and extracellular calcium. 4. The cationic amino acids L-ornithine, L-lysine, L-homoarginine (which is not metabolized) and NG-monomethyl-L-arginine (L-NMMA, a nitric oxide synthase inhibitor) produced [Ca2+]i responses similar to that produced by L-arginine. The neutral nitric oxide synthase inhibitors NG-nitro-L-arginine (L-NNA) and N omega-monomethyl-L-arginine (L-NAME) also increased [Ca2+]i. D-Arginine was ineffective. 5. L-Arginine did not affect whole-cell Ca2+ currents or ATP-sensitive K+ currents, but produced an inward current that was carried by the amino acid. 6. The reverse transcriptase-polymerase chain reaction demonstrated the presence of messenger RNA for the murine cationic amino acid transporters mCAT2A and mCAT2B within the beta-cell. 7. L-Arginine did not affect beta-cell exocytosis as assayed by changes in cell capacitance. 8. Our data suggest that L-arginine elevates [Ca2+]i and stimulates insulin secretion as a consequence of its electrogenic transport into the beta-cell. This uptake is mediated by the mCAT2A transporter.
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Affiliation(s)
- P A Smith
- University Laboratory of Physiology, Oxford, UK
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31
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Carver TD, Anderson SM, Aldoretta PW, Hay WW. Effect of low-level basal plus marked "pulsatile" hyperglycemia on insulin secretion in fetal sheep. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:E865-71. [PMID: 8944673 DOI: 10.1152/ajpendo.1996.271.5.e865] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We compared fetal glucose- and arginine-stimulated insulin secretion (delta I, pM) among four groups of pregnant sheep after 10-11 days of different maternal glycemic patterns: 1) control, euglycemic; 2) low-level basal plus "pulsatile" hyperglycemic (PHG group); 3) markedly hyperglycemic (HG) group); 4) markedly hypoglycemic (LG group). Mean delta I during a hyperglycemic clamp was greatest in the PHG group (190 +/- 28 pM, P < 0.01) and least in the HG (64 +/- 13 pM, P < 0.05) and LG groups (68 +/- 15 pM, P < 0.05) compared with the control group (126 +/- 18 pM). After an arginine bolus, insulin concentration was greater in the PHG group at two of four sampling times over 30 min compared with the control group and at all times compared with the HG and LG groups. The trend in mean delta I over the postarginine sampling period (PHG 1,092 +/- 114 pM; control 921 +/- 86 pM; HG897 +/- 117 pM; LG831 +/- 57 pM) was in the same direction as for glucose and was significant (P < 0.05). Thus glucose-stimulated fetal insulin secretion is regulated by the duration and pattern, as well as the magnitude, of maternal and fetal hyperglycemia; this regulation may also extend to insulin-secretion capacity.
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Affiliation(s)
- T D Carver
- Division of Perinatal Medicine, University of Colorado School of Medicine, Denver 80262, USA
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32
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Drews G, Debuyser A, Henquin JC. Significance of membrane repolarization and cyclic AMP changes in mouse pancreatic B-cells for the inhibition of insulin release by galanin. Mol Cell Endocrinol 1994; 105:97-102. [PMID: 7529734 DOI: 10.1016/0303-7207(94)90040-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
It is unclear whether the inhibition of insulin release by galanin is entirely explained by an interference with the secretory process at a step distal to the rise of cytoplasmic Ca2+ and to the action of second messengers in pancreatic B-cells. In this study, normal mouse islets were used to assess the functional significance of the effects of galanin on other signalling pathways. In the presence of 15 mM glucose, galanin caused a small repolarization of the B-cell membrane and a sustained decrease in the Ca(2+)-dependent electrical activity. These changes were largely prevented by tolbutamide and by arginine. Under these conditions the concentration-dependence curve of galanin inhibition of insulin release was shifted to the right. The IC50 was increased 4-5-fold from a control value of 1.8 nM in the presence of glucose alone. This was not the case when insulin release was increased by cytochalasin B, an agent that acts on the filamentous cell web. We also evaluated the role of the changes in cAMP. To bypass the inhibition of adenylate cyclase produced by galanin, the islets were provided with exogenous, membrane permeant cAMP. When 10 mM glucose and 0.25 mM dibutyryl cAMP were combined, control insulin release was similar to that produced by 15 mM glucose alone. Neither the repolarization of the membrane nor the inhibition of insulin release by galanin were affected. A higher concentration of dibutyryl cAMP (0.5 mM) depolarized the B-cell membrane in the presence of 15 mM glucose and partially antagonized the effects of galanin on membrane potential and insulin release.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G Drews
- Unité d'Endocrinologie et Métabolisme, University of Louvain Faculty of Medicine, Brussels, Belgium
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33
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Gu XH, Kurose T, Kato S, Masuda K, Tsuda K, Ishida H, Seino Y. Suppressive effect of GABA on insulin secretion from the pancreatic beta-cells in the rat. Life Sci 1993; 52:687-94. [PMID: 8445998 DOI: 10.1016/0024-3205(93)90229-v] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In order to investigate a possible role of GABA in the regulation of insulin secretion, we have studied the effect of GABA on insulin secretion from the isolated perfused rat pancreas in vitro and on the changes in the cytoplasmic Ca2+ of Beta-cells from the isolated rat islets. When glucose is present, GABA caused a dose dependent inhibition of the first phase of arginine-induced insulin secretion during the range of 10-1000 microM, but GABA did not affect arginine-induced insulin secretion in the absence of glucose. GABA inhibited not only the first phase but also the second phase of glucose-induced insulin secretion. A GABAB-receptor agonist, baclofen, also inhibited both phases of insulin secretion induced by 16.7 mM glucose. Furthermore, GABA inhibited the rise in cytoplasmic Ca2+ of Beta-cells in response to 16.7 mM glucose. These studies indicate that GABA decreases Beta cell secretory activity mainly in response to glucose. These inhibitory effects of GABA on insulin secretion may be mediated through GABAB-receptor and the inhibition of the rise in cytoplasmic Ca2+.
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Affiliation(s)
- X H Gu
- Department of Metabolism and Clinical Nutrition, Kyoto University Faculty of Medicine, Japan
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34
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Abstract
Northern-blot analysis was used to demonstrate that an increase in extracellular glucose concentration increased the content of preproinsulin mRNA 2.3-fold in the beta-cell line HIT T15. A probe for the constitutively expressed glyceraldehyde-3-phosphate dehydrogenase was used as a control. Mannoheptulose blocked this effect of glucose. A stimulatory effect on preproinsulin mRNA levels was also observed in response to mannose and to 4-methyl-2-oxopentanoate. However, galactose and arginine were ineffective. Glucagon, forskolin and dibutyryl cyclic AMP also elicited an increase in HIT-cell preproinsulin mRNA. The ability of the 5' upstream region of the preproinsulin gene to mediate the effect of glucose and other metabolites on transcription was studied by using a bacterial reporter gene technique. HIT cells were transfected with a plasmid, pOK1, containing the upstream region of the rat insulin-1 gene (-345 to +1) linked to chloramphenicol acetyltransferase (CAT). Co-transfection with a plasmid pRSV beta-gal containing beta-galactosidase driven by the Rous sarcoma virus promoter was used as a control for the efficiency of transfection; expression of CAT activity in transfected HIT cells was normalized by reference to expression of beta-galactosidase. Glucose caused a dose-dependent increase in expression of CAT activity, with a half-maximal effect at 5.5 mM and a maximum response of 4-fold. Mannoheptulose blocked this effect of glucose. Other metabolites (mannose, 4-methyl-2-oxopentanoate and leucine plus glutamine) were also able to increase insulin promoter-driven CAT expression, but galactose and arginine were ineffective. The stimulatory effect of glucose on CAT expression was not blocked by verapamil and was inhibited by increasing extracellular Ca2+ from 0.4 to 5 mM. Both dibutyryl cyclic AMP and forskolin caused an increase in insulin promoter-driven gene expression in the presence of 1 mM-glucose, but neither agent further increased the level of expression occurring in the presence of a maximally stimulating glucose concentration. The phorbol ester phorbol 12-myristate 13-acetate (PMA) also increased insulin promoter-driven CAT expression in the presence of 1 mM-, but not 11 mM-glucose. Staurosporine blocked the stimulatory effect not only of PMA but also of glucose and of dibutyryl cyclic AMP. We conclude that the 5' upstream region of the insulin gene contains sequences responsible for mediating the stimulatory effect of glucose on insulin-gene transcription.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- S Goodison
- Nuffield Department of Clinical Biochemistry, John Radcliffe Hospital, Headington, Oxford, U.K
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35
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Ghigo E, Maccario M, Arvat E, Valetto MR, Valente F, Nicolosi M, Mazza E, Martina V, Cocchi D, Camanni F. Interactions of galanin and arginine on growth hormone, prolactin, and insulin secretion in man. Metabolism 1992; 41:85-9. [PMID: 1371576 DOI: 10.1016/0026-0495(92)90195-g] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Galanin (GAL), a 29 amino acid neuropeptide, is known to increase both basal and growth hormone-releasing hormone (GHRH)-induced growth hormone (GH) secretion while not significantly increasing prolactin (PRL) secretion in man. GAL is also endowed with an inhibiting effect on glucose-stimulated insulin release in animals, but not in man. We studied the effect of GAL (80 pmol/kg/min infused over 60 minutes) on the arginine- (ARG, 30 g infused over 30 minutes) stimulated GH, PRL, insulin, and C-peptide secretion in eight healthy volunteers (age, 20 to 30 years). GAL induced an increase of GH (GAL v saline, area under curve [AUC], mean +/- SEM: 316.5 +/- 73.9 v 93.2 +/- 20.9 micrograms/L/h, P less than .05), but failed to modify both PRL and insulin secretion. GAL enhanced the ARG-induced stimulation of both GH (1,634.1 +/- 293.1 v 566.9 +/- 144.0 micrograms/L/h, P less than .02) and PRL secretion (1,541.9 +/- 248.8 v 1,023.8 +/- 158.7 micrograms/L/h, P less than .02). On the contrary, GAL blunted the ARG-stimulated insulin (816.3 +/- 87.7 v 1,322.7 +/- 240.9 mU/L/h, P less than .05), as well as C-peptide secretion (105.1 +/- 9.8 v 132.8 +/- 17.3 micrograms/L/h, P less than .02). ARG administration induced a transient increase of glucose levels (P less than .01 v baseline) followed by a significant decrease (P less than .05 v baseline). This latter effect was prevented by the coadministration of GAL. In conclusion, these results show that in man GAL potentiates the GH response to ARG, suggesting that these drugs act at the hypothalamic level, at least in part, via different mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E Ghigo
- Department of Clinical Pathophysiology, University of Turin, Italy
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36
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Debuyser A, Drews G, Henquin JC. Adrenaline inhibition of insulin release: role of the repolarization of the B cell membrane. Pflugers Arch 1991; 419:131-7. [PMID: 1961683 DOI: 10.1007/bf00372998] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Activation of alpha 2-adrenergic receptors affects several signalling pathways in pancreatic B cells. However, since adrenaline can inhibit insulin release by interfering with a late step of the secretory process, the functional significance of the earlier effects is unclear. In this study, normal mouse islets were used to determine whether the repolarization of the B cell membrane caused by adrenaline contributes to the inhibition of insulin release. The decrease in 86Rb efflux and the repolarization of the B cell membrane produced by adrenaline were attenuated by tolbutamide, which depolarizes by blocking ATP-sensitive K+ channels, and by arginine, which depolarizes because of its transport in a charged form. It is also known that adrenaline does not affect the membrane potential and 86Rb efflux in B cells depolarized by high K+. These three depolarizing conditions similarly shifted to the right the concentration dependence of adrenaline inhibition of insulin release: the effect of 1 nM and 10 nM adrenaline was reduced, but high concentrations of adrenaline still inhibited insulin release nearly completely under all conditions. In contrast, increasing insulin release by cytochalasin B did not alter the inhibitory potency of adrenaline. It is concluded that the repolarization of the B cell membrane and the ensuing decrease in Ca2+ influx play a significant role in the inhibition of insulin release by low concentrations of adrenaline. When high concentrations are used, a more distal effect becomes predominant.
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Affiliation(s)
- A Debuyser
- Unité de Diabétologie et Nutrition, University of Louvain, Faculty of Medicine, Brussels, Belgium
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37
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Sandler S, Eizirik DL, Svensson C, Strandell E, Welsh M, Welsh N. Biochemical and molecular actions of interleukin-1 on pancreatic beta-cells. Autoimmunity 1991; 10:241-53. [PMID: 1836745 DOI: 10.3109/08916939109001895] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- S Sandler
- Department of Medical Cell Biology, Uppsala University, Sweden
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38
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Malaisse WJ, Plasman PO, Blachier F, Herchuelz A, Sener A. Stimulus-secretion coupling of arginine-induced insulin release: significance of changes in extracellular and intracellular pH. Cell Biochem Funct 1991; 9:1-7. [PMID: 1712259 DOI: 10.1002/cbf.290090102] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The possible relevance of changes in extracellular and/or intracellular pH to the insulinotropic action of L-arginine and L-homoarginine was investigated in rat pancreatic islets. A rise in extracellular pH from 7.0 to 7.4 and 7.8 augmented the secretory response to these cationic amino acids whilst failing to affect the uptake of L-arginine by islet cells and whilst decreasing the release of insulin evoked by D-glucose. Under these conditions, a qualified dissociation was also observed between secretory data and 45Ca net uptake. Moreover, at high extracellular pH, the homoarginine-induced increase in 86Rb outflow from prelabelled islets rapidly faded out, despite sustained stimulation of insulin release. The cationic amino acids failed to affect the intracellular pH of islet cells, whether in the absence or presence of D-glucose and whether at normal or abnormal extracellular pH. These findings argue against the view that the secretory response to L-arginine would be related to either a change in cytosolic pH or the accumulation of this positively charged amino acid in the beta-cell. Nevertheless, they suggest that the yet unidentified target for L-arginine and its non-metabolized analogue in islet cells displays pH-dependency with optimal responsiveness at alkaline pH.
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Affiliation(s)
- W J Malaisse
- Laboratory Experimental Medicine, Brussels Free University, Belgium
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39
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Tung P, Pai G, Johnson DG, Punzalan R, Levin SR. Relationships between adenylate cyclase and Na+, K(+)-ATPase in rat pancreatic islets. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39683-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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40
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Stimulus-secretion coupling of arginine-induced insulin release. Resistance of arginine- and ornithine-stimulated glucagon and insulin release to D,L-alpha-difluoromethylornithine. Biochem Pharmacol 1990; 39:537-47. [PMID: 2407245 DOI: 10.1016/0006-2952(90)90061-o] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In the isolated perfused rat pancreas, D,L-difluoromethylornithine, tested at a concentration of 3 mmol/L, failed to affect the release of glucagon and insulin caused, over 15 min stimulation, by either L-arginine or L-ornithine (2.0, 5.0 or 10.0 mmol/L) in the presence of either 3.3 or 5.6 mmol/L D-glucose. The inhibition of ornithine decarboxylase also failed to affect the release of glucagon provoked by either L-leucine (2 or 3 mmol/L) or L-glutamine (2 mmol/L) and the secretion of insulin stimulated by a rise in glucose concentration from 5.6 to 10.6 mmol/L. These data are interpreted to suggest that the rapid generation of polyamines from either L-arginine or L-ornithine does not play any significant role in the immediate glucagonotropic and insulinotropic action of these cationic amino acids.
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41
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Malaisse WJ, Blachier F, Mourtada A, Camara J, Albor A, Valverde I, Sener A. Stimulus-secretion coupling of arginine-induced insulin release: metabolism of L-arginine and L-ornithine in tumoral islet cells. Mol Cell Endocrinol 1989; 67:81-91. [PMID: 2558931 DOI: 10.1016/0303-7207(89)90233-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The metabolism of L-arginine and L-ornithine was examined in tumoral islet cells of the RINm5F line and compared to the situation previously characterized in normal rat islets. The maximal velocity of arginase in cell homogenates, as well as either the production of 14C-urea or the steady-state content of 14C-labelled ornithine in intact cells exposed to L-[U-14C]arginine were about one order of magnitude lower in tumoral than normal islet cells. The activity of ornithine-glutamate transaminase was similar in both cell types, and this coincided with a comparable rate of 14C-labelled L-glutamate generation by intact cells exposed to L-[1-14C]ornithine. Despite a comparable cell content in 14C-labelled ornithine of normal and tumoral cells exposed to exogenous ornithine, the rate of di- and polyamine generation was about one order of magnitude higher in tumoral than normal islet cells, this coinciding with a much higher activity of ornithine decarboxylase in RINm5F cell than islet homogenates.
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Affiliation(s)
- W J Malaisse
- Laboratory of Experimental Medicine, Brussels Free University, Belgium
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42
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Blachier F, Leclercq-Meyer V, Marchand J, Woussen-Colle MC, Mathias PC, Sener A, Malaisse WJ. Stimulus-secretion coupling of arginine-induced insulin release. Functional response of islets to L-arginine and L-ornithine. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 1013:144-51. [PMID: 2504287 DOI: 10.1016/0167-4889(89)90042-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
L-Arginine and L-ornithine stimulate insulin release from pancreatic islets exposed to D-glucose. This coincides with an increased outflow of 86Rb and 45Ca from prelabelled islets and an increased net uptake of 45Ca by the islets. In the presence of D-glucose, L-lysine stimulates insulin secretion to the same extent as L-arginine or L-ornithine, but the hormonal release is not further enhanced by combinations of these cationic amino acids. L-Arginine or L-ornithine failed to enhance insulin release evoked by either L-leucine or 2-ketoisocaproate. The inhibitor of ornithine decarboxylase D,L-alpha-difluoromethyl ornithine failed to affect the metabolism and insulinotropic action of D-glucose in pancreatic islets, and only caused a partial inhibition of the secretory response to either L-arginine or L-ornithine. The latter amino acids inhibited modestly but significantly D-glucose utilization and oxidation by pancreatic islets. These and complementary findings suggest that the secretory response to L-arginine and L-ornithine is not attributable to any major change in the overall oxidative catabolism of nutrients, but involves mainly a biophysical component, such as the depolarization of the plasma membrane by these cationic amino acids.
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Affiliation(s)
- F Blachier
- Laboratory of Experimental Medicine, Brussels Free University, Belgium
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43
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Malaisse WJ, Blachier F, Mourtada A, Camara J, Albor A, Valverde I, Sener A. Stimulus-secretion coupling of arginine-induced insulin release. Metabolism of L-arginine and L-ornithine in pancreatic islets. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 1013:133-43. [PMID: 2669974 DOI: 10.1016/0167-4889(89)90041-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Exogenous L-arginine and L-ornithine rapidly accumulate in rat pancreatic islets. L-Arginine is converted to L-ornithine and urea. Endogenous or exogenous L-ornithine generates di- and polyamines, the putrescine turnover being faster than that of spermidine and spermine. However, the major pathway for L-ornithine metabolism consists of its transamination to L-glutamaldehyde and further conversion to L-glutamate. The amines and L-glutamate derived from exogenous L-ornithine are incorporated into islet proteins at the intervention of transglutaminase and cycloheximide-sensitive biosynthetic processes, respectively. These findings suggest the hypothesis that the insulinotropic action of L-arginine and L-ornithine could somehow be related to the metabolism of these cationic amino acids in islet cells.
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Affiliation(s)
- W J Malaisse
- Laboratory of Experimental Medicine, Brussels Free University, Belgium
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44
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Ashcroft FM, Rorsman P. Electrophysiology of the pancreatic beta-cell. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1989; 54:87-143. [PMID: 2484976 DOI: 10.1016/0079-6107(89)90013-8] [Citation(s) in RCA: 772] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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45
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Bozem M, Henquin JC. Glucose modulation of spike activity independently from changes in slow waves of membrane potential in mouse B-cells. Pflugers Arch 1988; 413:147-52. [PMID: 3064046 DOI: 10.1007/bf00582524] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In mouse B-cells glucose induces a typical electrical activity consisting of slow waves of the membrane potential with spikes superimposed on the plateau. As the concentration of glucose is raised the number of spikes per minute increases. However, this increase could simply be due to the concomitant lengthening of the slow waves. We thus investigated whether glucose can influence spike activity when no slow waves occur. Persistent depolarization to the plateau potential was achieved at 3 mM glucose by tolbutamide or at 10 mM glucose by low Ca2+, by arginine or by ouabain. Under all these conditions, raising the concentration of glucose increased the spike frequency without changing the plateau potential. Similar effects were produced by tolbutamide which does not affect B-cell metabolism but directly blocks K+-ATP channels. The spike frequency could also be increased by arginine, which, however, consistently depolarized the membrane. In conclusion, spike activity in B-cells can be influenced by glucose independently from changes in slow wave duration. This indicates that some K+-ATP channels, a target for both glucose and tolbutamide, are still open when the membrane is depolarized at the plateau, or that these two agents share another yet unidentified target involved in spike generation.
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Affiliation(s)
- M Bozem
- I. Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Federal Republic of Germany
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46
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Gylfe E. Nutrient secretagogues induce bimodal early changes in cytoplasmic calcium of insulin-releasing ob/ob mouse beta-cells. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68305-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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47
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Patzelt C. Differential inhibitory action of cationic amino acids on protein synthesis in pancreatic rat islets. Diabetologia 1988; 31:241-6. [PMID: 3133268 DOI: 10.1007/bf00290592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The effect of cationic amino acids, i.e. L-arginine and L-lysine, on protein synthesis in isolated rat islets of Langerhans has been investigated. Except for prosomatostatin, the formation of islet proteins is strongly depressed by these amino acids. This effect can be demonstrated within a few minutes and is rapidly reversible. For proglucagon, efficient concentrations of arginine are in the range of 1 to 10 mmol/l. The sensitivity of proinsulin formation to arginine is glucose-dependent: at 2.5 mmol/l, inhibitory concentrations of arginine are 10-fold lower than in the case of proglucagon. High glucose (20 mmol/l) almost completely protects proinsulin synthesis from this inhibition. The proteolytic conversion steps in hormonal precursor processing are not influenced by cationic amino acids as studied in intact islets and in a cell-free translational system. It is concluded that arginine and lysine inhibit protein synthesis in islet cells at the translational level. The release of these amino acids by prohormone conversion may exert a feed-back control on proinsulin formation that is modulated by glucose.
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Affiliation(s)
- C Patzelt
- Department of Physiological Chemistry, University of Würzburg, FRG
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48
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Hermans MP, Schmeer W, Henquin JC. The permissive effect of glucose, tolbutamide and high K+ on arginine stimulation of insulin release in isolated mouse islets. Diabetologia 1987; 30:659-65. [PMID: 3308605 DOI: 10.1007/bf00277325] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mouse islets were used to study how glucose modulates arginine stimulation of insulin release. At 3 mmol/l glucose, arginine (20 mmol/l) decreased the resting membrane potential of B cells by about 10 mV, but did not evoke electrical activity. This depolarisation was accompanied by a slight but rapid acceleration of 86Rb+ efflux and 45Ca2+ influx. However, 45Ca2+ efflux and insulin release increased only weakly and belatedly. When the membrane was depolarised by threshold (7 mmol/l) or stimulatory (10-15 mmol/l) concentrations of glucose, arginine rapidly induced or augmented electrical activity, markedly accelerated 86Rb+ efflux, 45Ca2+ influx and efflux, and triggered a strong and fast increase in insulin release. When glucose-induced depolarisation of the B-cell membrane was prevented by diazoxide, arginine lost all effects but those produced at low glucose. However, the delayed increase in release still exhibited some glucose-dependency. In contrast, depolarisation by tolbutamide, at low glucose, largely mimicked the permissive effect of high glucose. Depolarisation by high K+ also amplified arginine stimulation of insulin release, but did not accelerate it as did glucose or tolbutamide. Omission of extracellular Ca2+ abolished the releasing effect of arginine under all conditions. The results thus show that the permissive action of glucose mainly results from its ability to depolarise the B-cell membrane. It enables the small depolarisation by arginine itself to activate Ca channels more rapidly and efficiently. Changes in the metabolic state of B cells may also contribute to this permissive action by increasing the efficacy of the initiating signal triggered by arginine.
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Affiliation(s)
- M P Hermans
- Unité de Diabétologie et Nutrition, University of Louvain, Faculty of Medicine, Brussels, Belgium
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49
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Ashcroft FM, Ashcroft SJ, Harrison DE. Effects of 2-ketoisocaproate on insulin release and single potassium channel activity in dispersed rat pancreatic beta-cells. J Physiol 1987; 385:517-29. [PMID: 2443671 PMCID: PMC1192358 DOI: 10.1113/jphysiol.1987.sp016505] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
1. The effects of the insulin secretagogue 2-ketoisocaproate, and of arginine, on insulin release, intracellular adenosine triphosphate (ATP) concentration and the activity of single K channels in cell-attached membrane patches have been studied in primary cultures of beta-cells from adult rat islets of Langerhans. 2. Insulin secretion was significantly increased by 2-ketoisocaproate (20 mM). The time course of this release was biphasic. Arginine (20 mM) did not stimulate insulin secretion. 3. In the absence of 2-ketoisocaproate (or arginine), two kinds of K channel were regularly observed in cell-attached membrane patches held at the cell resting potential: a channel of approximately 20 pS conductance and a channel of 50 pS conductance ([K]o = 140 mM, room temperature). 4. Addition of 2-ketoisocaproate (20 mM) to the bath suppressed the activity of the 50 pS channel and initiated action potentials. Arginine (20 mM) was without effect. 5. The intracellular concentration of ATP was increased significantly by 2-ketoisocaproate (20 mM) but not by arginine (20 mM). 6. It is suggested that, like glucose, 2-ketoisocaproate depolarizes the beta-cell and mediates insulin secretion by reducing the open probability of the 50 pS K channel. The results are also consistent with the idea that both secretagogues inhibit this channel by increasing the cytoplasmic concentration of ATP.
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50
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Sgambato S, Paolisso G, Passariello N, Varricchio M, D'Onofrio F. Effect of sparteine sulphate upon basal and nutrient-induced insulin and glucagon secretion in normal man. Eur J Clin Pharmacol 1987; 32:477-80. [PMID: 3305040 DOI: 10.1007/bf00637673] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Infusion of a therapeutic dose of sparteine sulphate, increased the basal plasma insulin level and lowered plasma glucose. When an intravenous glucose tolerance test was performed with the infusion, the total insulin AUC was significantly larger than in absence of sparteine (2025 vs 1464 microU/ml X min), plasma glucose levels were lower and improved glucose utilization was observed (kg:1.55 vs 1.39%). In the presence of arginine, sparteine sulphate stimulated both beta and alpha cells, increasing both the total insulin (1907 vs 1516 microU/ml X min p less than 0.02) and total glucagon AUCs (7616 +/- 654 vs 6789 +/- 707 pg/ml X min p less than 0.01). Thus, sparteine sulphate increased both basal and nutrient-induced insulin and glucagon secretion in normal man.
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