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Jacobo-Piqueras N, Theiner T, Geisler SM, Tuluc P. Molecular mechanism responsible for sex differences in electrical activity of mouse pancreatic β cells. JCI Insight 2024; 9:e171609. [PMID: 38358819 PMCID: PMC11063940 DOI: 10.1172/jci.insight.171609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 02/08/2024] [Indexed: 02/17/2024] Open
Abstract
In humans, type 2 diabetes mellitus shows a higher prevalence in men compared with women, a phenotype that has been attributed to a lower peripheral insulin sensitivity in men. Whether sex-specific differences in pancreatic β cell function also contribute is largely unknown. Here, we characterized the electrophysiological properties of β cells in intact male and female mouse islets. Elevation of glucose concentration above 5 mM triggered an electrical activity with a similar glucose dependence in β cells of both sexes. However, female β cells had a more depolarized membrane potential and increased firing frequency compared with males. The higher membrane depolarization in female β cells was caused by approximately 50% smaller Kv2.1 K+ currents compared with males but otherwise unchanged KATP, large-conductance and small-conductance Ca2+-activated K+ channels, and background TASK1/TALK1 K+ current densities. In female β cells, the higher depolarization caused a membrane potential-dependent inactivation of the voltage-gated Ca2+ channels (CaV), resulting in reduced Ca2+ entry. Nevertheless, this reduced Ca2+ influx was offset by a higher action potential firing frequency. Because exocytosis of insulin granules does not show a sex-specific difference, we conclude that the higher electrical activity promotes insulin release in females, improving glucose tolerance.
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Chedid P, Sokhn ES. Prevalence of type 2 diabetes (T2D) in Lebanon: association with inflammatory and infectious clinical markers. BMC Public Health 2023; 23:2523. [PMID: 38104079 PMCID: PMC10725583 DOI: 10.1186/s12889-023-17328-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 11/24/2023] [Indexed: 12/19/2023] Open
Abstract
BACKGROUND Diabetes is a growing health concern in the Middle East, particularly in countries with high rates of obesity and unhealthy lifestyles. Therefore, this study aimed to determine the prevalence of type 2 diabetes (T2D) in Lebanon and its association with clinical markers of inflammation and infection. METHODS This cross-sectional study examined retrospectively the medical laboratory record of 4093 patients from all Lebanese regions. Prevalence of T2D and its association with age, gender, calcium, vitamin D (VitD), neutrophils-to-lymphocytes ratio (NLR), and C-reactive protein (CRP) were determined. The prevalence of infection in a subpopulation of 712 patients tested from blood, body fluid, sputum, swab, tissue, and urine samples and its etiology was also assessed. RESULTS Overall, 17% (n = 690) of our participants had T2D, and the mean HbA1c was 5.9% ± 1.2. Age, gender, triglycerides, NLR, and calcemia were significantly associated with T2D. The prevalence of infections in a subgroup of 712 patients was 11.1% (n = 79). Urinary tract infections (UTIs) caused by Escherichia coli (E. coli) were the most common cause of infection, with the highest prevalence in the pre-diabetic group. Serum CRP level was significantly higher in the diabetic group than the pre-diabetic and control groups. Diabetic patients also presented a significantly higher percentage of NLR > 3 compared to the pre-diabetic and control groups. CONCLUSION The prevalence of T2D is increasing in the Lebanese population compared to prior reports. These results should be considered to guide effective public health preventive strategies.
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Affiliation(s)
- Pia Chedid
- Molecular Testing Laboratory, Medical Laboratory Department, Faculty of Health Sciences, Beirut Arab University, Beirut, Lebanon
| | - Elie Salem Sokhn
- Molecular Testing Laboratory, Medical Laboratory Department, Faculty of Health Sciences, Beirut Arab University, Beirut, Lebanon.
- Laboratory Department, Lebanese Hospital-Geitaoui University Medical Center, Beirut, Lebanon.
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Becker A, Wardas B, Salah H, Amini M, Fecher-Trost C, Sen Q, Martus D, Beck A, Philipp SE, Flockerzi V, Belkacemi A. Cavβ3 Regulates Ca 2+ Signaling and Insulin Expression in Pancreatic β-Cells in a Cell-Autonomous Manner. Diabetes 2021; 70:2532-2544. [PMID: 34426509 PMCID: PMC8564405 DOI: 10.2337/db21-0078] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 08/12/2021] [Indexed: 11/13/2022]
Abstract
Voltage-gated Ca2+ (Cav) channels consist of a pore-forming Cavα1 subunit and auxiliary Cavα2-δ and Cavβ subunits. In fibroblasts, Cavβ3, independent of its role as a Cav subunit, reduces the sensitivity to low concentrations of inositol-1,4,5-trisphosphate (IP3). Similarly, Cavβ3 could affect cytosolic calcium concentration ([Ca2 +]) in pancreatic β-cells. In this study, we deleted the Cavβ3-encoding gene Cacnb3 in insulin-secreting rat β-(Ins-1) cells using CRISPR/Cas9. These cells were used as controls to investigate the role of Cavβ3 on Ca2+ signaling, glucose-induced insulin secretion (GIIS), Cav channel activity, and gene expression in wild-type cells in which Cavβ3 and the IP3 receptor were coimmunoprecipitated. Transcript and protein profiling revealed significantly increased levels of insulin transcription factor Mafa, CaMKIV, proprotein convertase subtilisin/kexin type-1, and nitric oxide synthase-1 in Cavβ3-knockout cells. In the absence of Cavβ3, Cav currents were not altered. In contrast, CREB activity, the amount of MAFA protein and GIIS, the extent of IP3-dependent Ca2+ release and the frequency of Ca2+ oscillations were increased. These processes were decreased by the Cavβ3 protein in a concentration-dependent manner. Our study shows that Cavβ3 interacts with the IP3 receptor in isolated β-cells, controls IP3-dependent Ca2+-signaling independently of Cav channel functions, and thereby regulates insulin expression and its glucose-dependent release in a cell-autonomous manner.
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Affiliation(s)
- Alexander Becker
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Barbara Wardas
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Houssein Salah
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Maryam Amini
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Claudia Fecher-Trost
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Qiao Sen
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Damian Martus
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Andreas Beck
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Stephan E Philipp
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Veit Flockerzi
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
| | - Anouar Belkacemi
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Präklinisches Zentrum für Molekulare Signalverarbeitung der Universität des Saarlandes, Homburg, Germany
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Thompson B, Satin LS. Beta-Cell Ion Channels and Their Role in Regulating Insulin Secretion. Compr Physiol 2021; 11:1-21. [PMID: 34636409 PMCID: PMC8935893 DOI: 10.1002/cphy.c210004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Beta cells of the pancreatic islet express many different types of ion channels. These channels reside in the β-cell plasma membrane as well as subcellular organelles and their coordinated activity and sensitivity to metabolism regulate glucose-dependent insulin secretion. Here, we review the molecular nature, expression patterns, and functional roles of many β-cell channels, with an eye toward explaining the ionic basis of glucose-induced insulin secretion. Our primary focus is on KATP and voltage-gated Ca2+ channels as these primarily regulate insulin secretion; other channels in our view primarily help to sculpt the electrical patterns generated by activated β-cells or indirectly regulate metabolism. Lastly, we discuss why understanding the physiological roles played by ion channels is important for understanding the secretory defects that occur in type 2 diabetes. © 2021 American Physiological Society. Compr Physiol 11:1-21, 2021.
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Alegría KG, Gaona RC, Terranova MV, Hernández EA. Insulin resistance indexes of grazing cows and mineral or vitamin supplementation under tropical conditions. Open Vet J 2021; 11:587-597. [PMID: 35070853 PMCID: PMC8770180 DOI: 10.5455/ovj.2021.v11.i4.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 10/15/2021] [Indexed: 11/03/2022] Open
Abstract
Background During the transition period in dairy cows, metabolic changes occur, many of which are related to energy metabolism, which causes metabolic diseases or productive alterations. Aim The objective of the present work was to evaluate two mineral and vitamin supplementations related to metabolic regulation mechanisms associated with insulin during the transition period and the first phase of lactation in grazing cows under tropical conditions through metabolic indicators and insulin resistance indexes. Methods Twenty-one animals were distributed in three groups: control (CTR), iodine supplementation (SUPP-1), and mixed mineral and vitamin supplementation (SUPP-2). The experimental period was from day 30 prepartum to day 45 postpartum. Evaluation of the body condition score and the blood samples' collection by coccygeal venipuncture was carried out for serum analysis of metabolites, such as beta-hydroxybutyrate (BHB), glucose, and non-esterified fatty acids (NEFA), and hormones, such as insulin, thyroxine, triiodothyronine, and cortisol. Variables related to energy and hormone metabolism were analyzed. Four proposed indexes were calculated to identify insulin resistance: Homeostasis Model Assessment (HOMA), Quantitative Insulin Sensitivity Check Index (QUICKI), Revised Quantitative Insulin Sensitivity Check Index, and QUICKI-BHB. Through linear regression, the effect of metabolites and hormones on the indexes of insulin resistance studied was estimated. Results The groups with supplementation did not show significant changes in the mobilization of body reserves, NEFA, or triiodothyronine for interaction between treatments and periods. HOMA and QUICKI indexes used to estimate insulin resistance showed an inverse correlation (-0.97; p<0.001), and a greater capacity of linear adjustment to estimate the evaluated metabolites. Conclusion The indexes' values of insulin sensitivity in the present work constitute a starting point in tropical dairy cows to characterize insulin resistance and metabolic alterations. Vitamins and mineral supplementation did not show a positive effect on the metabolism of dairy cows during the transition period and the first phase of lactation in the study.
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Affiliation(s)
| | - Rómulo Campos Gaona
- Departamento de Ciencia Animal, Facultad de Ciencias Agropecuarias, Universidad Nacional de Colombia, sede Palmira, Colombia
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The Association between Branched-Chain Amino Acids (BCAAs) and Cardiometabolic Risk Factors in Middle-Aged Caucasian Women Stratified According to Glycemic Status. Nutrients 2021; 13:nu13103307. [PMID: 34684308 PMCID: PMC8538048 DOI: 10.3390/nu13103307] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 09/17/2021] [Accepted: 09/19/2021] [Indexed: 02/07/2023] Open
Abstract
We examined the glycemic status-stratified relationships between total serum branched-chain amino acid (BCAA) concentrations and cardiometabolic risk factors in middle-aged Caucasian women. The study included 349 women divided into 2 subgroups: a normoglycemic group (NG, n = 184) and a dysglycemic group (DG, n = 165). Blood samples, anthropometric parameters, and blood pressure were measured. HOMA-IR, albumin-corrected calcium (CCa), and fatty liver index (FLI) were calculated. BCAA concentrations were higher in the women with dysglycemia. BCAAs moderately correlated with BMI and FLI in the NG group and with BMI, FLI, total calcium (TCa), CCa, HbA1c, TG/HDL-C, and HDL-C in the DG group. After adjusting for age and BMI, correlations for TCa, CCa, HbA1c, HDL-C, and TG/HDL-C remained significant. The coexistence of increased BCAAs with dysglycemic status was associated with markedly higher concentrations of TCa, CCa, HbA1c, and TG, which were not observed in the DG women with low level of BCAAs. Multiple regression showed that TCa or CCa, age and BCAAs were significantly associated with HbA1c independently of BMI only in the DG group. We conclude that dysglycemia in particular predisposes women to a significant relationship between total BCAAs and circulating calcium and HbA1c, and that these relationships are independent of BMI and may reflect the pathophysiological calcium-dependent mechanisms connecting BCAAs with metabolic disturbances.
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Neumaier F, Alpdogan S, Hescheler J, Schneider T. Zn2+-induced changes in Cav2.3 channel function: An electrophysiological and modeling study. J Gen Physiol 2021; 152:151872. [PMID: 32559275 PMCID: PMC7478874 DOI: 10.1085/jgp.202012585] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/30/2020] [Accepted: 05/19/2020] [Indexed: 01/25/2023] Open
Abstract
Loosely bound Zn2+ ions are increasingly recognized as potential modulators of synaptic plasticity and neuronal excitability under normal and pathophysiological conditions. Cav2.3 voltage-gated Ca2+ channels are among the most sensitive targets of Zn2+ and are therefore likely to be involved in the neuromodulatory actions of endogenous Zn2+. Although histidine residues on the external side of domain I have been implicated in the effects on Cav2.3 channel gating, the exact mechanisms involved in channel modulation remain incompletely understood. Here, we use a combination of electrophysiological recordings, modification of histidine residues, and computational modeling to analyze Zn2+-induced changes in Cav2.3 channel function. Our most important findings are that multiple high- and low-affinity mechanisms contribute to the net Zn2+ action, that Zn2+ can either inhibit or stimulate Ca2+ influx through Cav2.3 channels depending on resting membrane potential, and that Zn2+ effects may persist for some time even after cessation of the Zn2+ signal. Computer simulations show that (1) most salient features of Cav2.3 channel gating in the absence of trace metals can be reproduced by an obligatory model in which activation of two voltage sensors is necessary to open the pore; and (2) most, but not all, of the effects of Zn2+ can be accounted for by assuming that Zn2+ binding to a first site is associated with an electrostatic modification and mechanical slowing of one of the voltage sensors, whereas Zn2+ binding to a second, lower-affinity site blocks the channel and modifies the opening and closing transitions. While still far from complete, our model provides a first quantitative framework for understanding Zn2+ effects on Cav2.3 channel function and a step toward the application of computational approaches for predicting the complex actions of Zn2+ on neuronal excitability.
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Affiliation(s)
- Felix Neumaier
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
| | - Serdar Alpdogan
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
| | - Jürgen Hescheler
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
| | - Toni Schneider
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
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8
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Tuluc P, Theiner T, Jacobo-Piqueras N, Geisler SM. Role of High Voltage-Gated Ca 2+ Channel Subunits in Pancreatic β-Cell Insulin Release. From Structure to Function. Cells 2021; 10:2004. [PMID: 34440773 PMCID: PMC8393260 DOI: 10.3390/cells10082004] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/27/2021] [Accepted: 08/03/2021] [Indexed: 02/07/2023] Open
Abstract
The pancreatic islets of Langerhans secrete several hormones critical for glucose homeostasis. The β-cells, the major cellular component of the pancreatic islets, secrete insulin, the only hormone capable of lowering the plasma glucose concentration. The counter-regulatory hormone glucagon is secreted by the α-cells while δ-cells secrete somatostatin that via paracrine mechanisms regulates the α- and β-cell activity. These three peptide hormones are packed into secretory granules that are released through exocytosis following a local increase in intracellular Ca2+ concentration. The high voltage-gated Ca2+ channels (HVCCs) occupy a central role in pancreatic hormone release both as a source of Ca2+ required for excitation-secretion coupling as well as a scaffold for the release machinery. HVCCs are multi-protein complexes composed of the main pore-forming transmembrane α1 and the auxiliary intracellular β, extracellular α2δ, and transmembrane γ subunits. Here, we review the current understanding regarding the role of all HVCC subunits expressed in pancreatic β-cell on electrical activity, excitation-secretion coupling, and β-cell mass. The evidence we review was obtained from many seminal studies employing pharmacological approaches as well as genetically modified mouse models. The significance for diabetes in humans is discussed in the context of genetic variations in the genes encoding for the HVCC subunits.
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Affiliation(s)
- Petronel Tuluc
- Centre for Molecular Biosciences, Department of Pharmacology and Toxicology, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria; (T.T.); (N.J.-P.); (S.M.G.)
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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Neumaier F, Schneider T, Albanna W. Ca v2.3 channel function and Zn 2+-induced modulation: potential mechanisms and (patho)physiological relevance. Channels (Austin) 2020; 14:362-379. [PMID: 33079629 PMCID: PMC7583514 DOI: 10.1080/19336950.2020.1829842] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Voltage-gated calcium channels (VGCCs) are critical for Ca2+ influx into all types of excitable cells, but their exact function is still poorly understood. Recent reconstruction of homology models for all human VGCCs at atomic resolution provides the opportunity for a structure-based discussion of VGCC function and novel insights into the mechanisms underlying Ca2+ selective flux through these channels. In the present review, we use these data as a basis to examine the structure, function, and Zn2+-induced modulation of Cav2.3 VGCCs, which mediate native R-type currents and belong to the most enigmatic members of the family. Their unique sensitivity to Zn2+ and the existence of multiple mechanisms of Zn2+ action strongly argue for a role of these channels in the modulatory action of endogenous loosely bound Zn2+, pools of which have been detected in a number of neuronal, endocrine, and reproductive tissues. Following a description of the different mechanisms by which Zn2+ has been shown or is thought to alter the function of these channels, we discuss their potential (patho)physiological relevance, taking into account what is known about the magnitude and function of extracellular Zn2+ signals in different tissues. While still far from complete, the picture that emerges is one where Cav2.3 channel expression parallels the occurrence of loosely bound Zn2+ pools in different tissues and where these channels may serve to translate physiological Zn2+ signals into changes of electrical activity and/or intracellular Ca2+ levels.
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Affiliation(s)
- Felix Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5) , Jülich, Germany.,University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging , Cologne, Germany
| | - Toni Schneider
- Institute of Neurophysiology , Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Walid Albanna
- Department of Neurosurgery, RWTH Aachen University , Aachen, Germany
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Circulating calcium levels and the risk of type 2 diabetes: a systematic review and meta-analysis. Br J Nutr 2020; 122:376-387. [PMID: 31208474 DOI: 10.1017/s0007114519001430] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Abnormal Ca homeostasis has been associated with impaired glucose metabolism. However, the epidemiological evidence is controversial. We aimed to assess the association between circulating Ca levels and the risk of type 2 diabetes mellitus (T2DM) or abnormal glucose homeostasis through conducting a systematic review and meta-analysis. Eligible studies were identified by searching electronic database (PubMed, Embase and Google Scholar) and related references with de novo results from primary studies up to December 2018. A random-effects meta-analysis was performed to estimate the weighted relative risks (RR) and 95 % CI for the associations. The search yielded twenty eligible publications with eight cohort studies identified for the meta-analysis, which included a total of 89 165 participants. Comparing the highest with the lowest category of albumin-adjusted serum Ca, the pooled RR was 1·14 (95 % CI 1·05, 1·24) for T2DM (n 51 489). Similarly, serum total Ca was associated with incident T2DM (RR 1·25; 95 % CI 1·10, 1·42) (n 64 502). Additionally, the adjusted RR for 1 mg/dl increments in albumin-adjusted serum Ca or serum total Ca levels was 1·16 (95 % CI 1·07, 1·27) and 1·19 (95 % CI 1·11, 1·28), respectively. The observed associations remained with the inclusion of a cohort study with ionised Ca as the exposure. However, data pooled from neither case-control (n 4) nor cross-sectional (n 8) studies manifested a significant correlation between circulating Ca and glucose homeostasis. In conclusion, accumulated data from the cohort studies suggest that higher circulating Ca levels are associated with an augmented risk of T2DM.
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12
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Thurmond DC, Gaisano HY. Recent Insights into Beta-cell Exocytosis in Type 2 Diabetes. J Mol Biol 2020; 432:1310-1325. [PMID: 31863749 PMCID: PMC8061716 DOI: 10.1016/j.jmb.2019.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 11/26/2019] [Accepted: 12/05/2019] [Indexed: 01/26/2023]
Abstract
As one of the leading causes of morbidity and mortality worldwide, diabetes affects an estimated 422 million adults, and it is expected to continue expanding such that by 2050, 30% of the U.S. population will become diabetic within their lifetime. Out of the estimated 422 million people currently afflicted with diabetes worldwide, about 5% have type 1 diabetes (T1D), while the remaining ~95% of diabetics have type 2 diabetes (T2D). Type 1 diabetes results from the autoimmune-mediated destruction of functional β-cell mass, whereas T2D results from combinatorial defects in functional β-cell mass plus peripheral glucose uptake. Both types of diabetes are now believed to be preceded by β-cell dysfunction. T2D is increasingly associated with numerous reports of deficiencies in the exocytosis proteins that regulate insulin release from β-cells, specifically the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. SNARE protein's functionality is further regulated by a variety of accessory factors such as Sec1/Munc18 (SM), double C2-domain proteins (DOC2), and additional interacting proteins at the cell surface that influence the fidelity of insulin release. As new evidence emerges about the detailed mechanisms of exocytosis, new questions and controversies have come to light. This emerging information is also contributing to dialogue in the islet biology field focused on how to correct the defects in insulin exocytosis. Herein we present a balanced review of the role of exocytosis proteins in T2D, with thoughts on novel strategies to protect functional β-cell mass.
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Affiliation(s)
- Debbie C Thurmond
- Department of Molecular and Cellular Endocrinology, Beckman Research Institute of City of Hope, CA, USA.
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13
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Simons C, Benkert J, Deuter N, Poetschke C, Pongs O, Schneider T, Duda J, Liss B. NCS-1 Deficiency Affects mRNA Levels of Genes Involved in Regulation of ATP Synthesis and Mitochondrial Stress in Highly Vulnerable Substantia nigra Dopaminergic Neurons. Front Mol Neurosci 2019; 12:252. [PMID: 31827421 PMCID: PMC6890851 DOI: 10.3389/fnmol.2019.00252] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 09/27/2019] [Indexed: 12/20/2022] Open
Abstract
Neuronal Ca2+ sensor proteins (NCS) transduce changes in Ca2+ homeostasis into altered signaling and neuronal function. NCS-1 activity has emerged as important for neuronal viability and pathophysiology. The progressive degeneration of dopaminergic (DA) neurons, particularly within the Substantia nigra (SN), is the hallmark of Parkinson's disease (PD), causing its motor symptoms. The activity-related Ca2+ homeostasis of SN DA neurons, mitochondrial dysfunction, and metabolic stress promote neurodegeneration and PD. In contrast, NCS-1 in general has neuroprotective effects. The underlying mechanisms are unclear. We analyzed transcriptional changes in SN DA neurons upon NCS-1 loss by combining UV-laser microdissection and RT-qPCR-approaches to compare expression levels of a panel of PD and/or Ca2+-stress related genes from wildtype and NCS-1 KO mice. In NCS-1 KO, we detected significantly lower mRNA levels of mitochondrially coded ND1, a subunit of the respiratory chain, and of the neuron-specific enolase ENO2, a glycolytic enzyme. We also detected lower levels of the mitochondrial uncoupling proteins UCP4 and UCP5, the PARK7 gene product DJ-1, and the voltage-gated Ca2+ channel Cav2.3 in SN DA neurons from NCS-1 KO. Transcripts of other analyzed uncoupling proteins (UCPs), mitochondrial Ca2+ transporters, PARK genes, and ion channels were not altered. As Cav channels are linked to regulation of gene expression, metabolic stress and degeneration of SN DA neurons in PD, we analyzed Cav2.3 KO mice, to address if the transcriptional changes in NCS-1 KO were also present in Cav.2.3 KO, and thus probably correlated with lower Cav2.3 transcripts. However, in SN DA neurons from Cav2.3 KO mice, ND1 mRNA as well as genomic DNA levels were elevated, while ENO2, UCP4, UCP5, and DJ-1 transcript levels were not altered. In conclusion, our data indicate a possible novel function of NCS-1 in regulating gene transcription or stabilization of mRNAs in SN DA neurons. Although we do not provide functional data, our findings at the transcript level could point to impaired ATP production (lower ND1 and ENO2) and elevated metabolic stress (lower UCP4, UCP5, and DJ-1 levels) in SN DA neurons from NCS-1 KO mice. We speculate that NCS-1 is involved in stimulating ATP synthesis, while at the same time controlling mitochondrial metabolic stress, and in this way could protect SN DA neurons from degeneration.
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Affiliation(s)
- Carsten Simons
- Institute of Applied Physiology, University of Ulm, Ulm, Germany
| | - Julia Benkert
- Institute of Applied Physiology, University of Ulm, Ulm, Germany
| | - Nora Deuter
- Institute of Applied Physiology, University of Ulm, Ulm, Germany
| | | | - Olaf Pongs
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, University of the Saarland, Homburg, Germany
| | - Toni Schneider
- Institute of Neurophysiology, University of Cologne, Cologne, Germany
| | - Johanna Duda
- Institute of Applied Physiology, University of Ulm, Ulm, Germany
| | - Birgit Liss
- Institute of Applied Physiology, University of Ulm, Ulm, Germany.,New College, University of Oxford, Oxford, United Kingdom
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14
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Sarmiento BE, Santos Menezes LF, Schwartz EF. Insulin Release Mechanism Modulated by Toxins Isolated from Animal Venoms: From Basic Research to Drug Development Prospects. Molecules 2019; 24:E1846. [PMID: 31091684 PMCID: PMC6571724 DOI: 10.3390/molecules24101846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/23/2019] [Accepted: 05/09/2019] [Indexed: 12/12/2022] Open
Abstract
Venom from mammals, amphibians, snakes, arachnids, sea anemones and insects provides diverse sources of peptides with different potential medical applications. Several of these peptides have already been converted into drugs and some are still in the clinical phase. Diabetes type 2 is one of the diseases with the highest mortality rate worldwide, requiring specific attention. Diverse drugs are available (e.g., Sulfonylureas) for effective treatment, but with several adverse secondary effects, most of them related to the low specificity of these compounds to the target. In this context, the search for specific and high-affinity compounds for the management of this metabolic disease is growing. Toxins isolated from animal venom have high specificity and affinity for different molecular targets, of which the most important are ion channels. This review will present an overview about the electrical activity of the ion channels present in pancreatic β cells that are involved in the insulin secretion process, in addition to the diversity of peptides that can interact and modulate the electrical activity of pancreatic β cells. The importance of prospecting bioactive peptides for therapeutic use is also reinforced.
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Affiliation(s)
- Beatriz Elena Sarmiento
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Luis Felipe Santos Menezes
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Elisabeth F Schwartz
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
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15
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Luan C, Ye Y, Singh T, Barghouth M, Eliasson L, Artner I, Zhang E, Renström E. The calcium channel subunit gamma-4 is regulated by MafA and necessary for pancreatic beta-cell specification. Commun Biol 2019; 2:106. [PMID: 30911681 PMCID: PMC6420573 DOI: 10.1038/s42003-019-0351-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 02/08/2019] [Indexed: 12/22/2022] Open
Abstract
Voltage-gated Ca2+ (CaV) channels trigger glucose-induced insulin secretion in pancreatic beta-cell and their dysfunction increases diabetes risk. These heteromeric complexes include the main subunit alpha1, and the accessory ones, including subunit gamma that remains unexplored. Here, we demonstrate that CaV gamma subunit 4 (CaVγ4) is downregulated in islets from human donors with diabetes, diabetic Goto-Kakizaki (GK) rats, as well as under conditions of gluco-/lipotoxic stress. Reduction of CaVγ4 expression results in decreased expression of L-type CaV1.2 and CaV1.3, thereby suppressing voltage-gated Ca2+ entry and glucose stimulated insulin exocytosis. The most important finding is that CaVγ4 expression is controlled by the transcription factor responsible for beta-cell specification, MafA, as verified by chromatin immunoprecipitation and experiments in beta-cell specific MafA knockout mice (MafA Δβcell ). Taken together, these findings suggest that CaVγ4 is necessary for maintaining a functional differentiated beta-cell phenotype. Treatment aiming at restoring CaVγ4 may help to restore beta-cell function in diabetes.
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Affiliation(s)
- Cheng Luan
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
| | - Yingying Ye
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
| | - Tania Singh
- Stem Cell Center, Department of Laboratory Medicine, Lund University, 221 85 Lund, Sweden
| | - Mohammad Barghouth
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
| | - Lena Eliasson
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
| | - Isabella Artner
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
- Stem Cell Center, Department of Laboratory Medicine, Lund University, 221 85 Lund, Sweden
| | - Enming Zhang
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
| | - Erik Renström
- Lund University Diabetes Center, Department of Clinical Sciences Malmö, Lund University, 202 13 Malmö, Sweden
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16
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Abstract
Diabetes develops due to deficient functional β cell mass, insulin resistance, or both. Yet, various challenges in understanding the mechanisms underlying diabetes development in vivo remain to be overcome owing to the lack of appropriate intravital imaging technologies. To meet these challenges, we have exploited the anterior chamber of the eye (ACE) as a novel imaging site to understand diabetes basics and clinics in vivo. We have developed a technology platform transplanting pancreatic islets into the ACE where they later on can be imaged non-invasively for long time. It turns out that the ACE serves as an optimal imaging site and provides implanted islets with an oxygen-rich milieu and an immune-privileged niche where they undergo optimal engraftment, rich vascularization and dense innervation, preserve organotypic features and live with satisfactory viability and functionality. The ACE technology has led to a series of significant observations. It enables in vivo microscopy of islet cytoarchitecture, function and viability in the physiological context and intravital imaging of a variety of pathological events such as autoimmune insulitis, defects in β cell function and mass and insulin resistance during diabetes development in a real-time manner. Furthermore, application of the ACE technology in humanized mice and non-human primates verifies translational and clinical values of the technology. In this article, we describe the ACE technology in detail, review accumulated knowledge gained by means of the ACE technology and delineate prospective avenues for the ACE technology.
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17
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Rodriguez R, Lee A, Mathis KW, Broome HJ, Thorwald M, Martinez B, Nakano D, Nishiyama A, Ryan MJ, Ortiz RM. Angiotensin receptor and tumor necrosis factor-α activation contributes to glucose intolerance independent of systolic blood pressure in obese rats. Am J Physiol Renal Physiol 2018; 315:F1081-F1090. [PMID: 29993275 DOI: 10.1152/ajprenal.00156.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Pathological activation of the renin-angiotensin system and inflammation are associated with hypertension and the development of metabolic syndrome (MetS). The contributions of angiotensin receptor type 1 (AT1) activation, independent of blood pressure, and inflammation to glucose intolerance and renal damage are not well defined. Using a rat model of MetS, we hypothesized that the onset of glucose intolerance is primarily mediated by AT1 activation and inflammation independent of elevated systolic blood pressure (SBP). To address this hypothesis, we measured changes in SBP, adiposity, plasma glucose and triglyceride levels, and glucose tolerance in six groups of rats: 1) lean, strain control Long-Evans Tokushima Otsuka (LETO; n = 5), 2) obese Otsuka Long-Evans Tokushima Fatty (OLETF; n = 8), 3) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg; n = 8), 4) OLETF + tumor necrosis factor-α (TNF-α) inhibitor (ETAN; 1.25 mg etanercept/kg; n = 6), 5) OLETF + TNF-α inhibitor + angiotensin receptor blocker (ETAN+ARB; 1.25 mg etanercept/kg + 10 mg olmesartan/kg; n = 6), and 6) OLETF + calcium channel blocker (CCB; 5 mg amlodipine/kg; n = 7). ARB and ETAN+ARB were most effective at decreasing SBP in OLETF, and ETAN did not offer any additional reduction. Glucose tolerance improved in ARB, ETAN, and ETAN+ARB compared with OLETF, whereas CCB had no detectable effect. Furthermore, all treatments reduced adiposity, whereas ETAN alone normalized urinary albumin excretion. These results suggest that AT1 activation and inflammation are primary factors in the development of glucose intolerance in a setting of MetS and that the associated increase in SBP is primarily mediated by AT1 activation.
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Affiliation(s)
- Ruben Rodriguez
- Department of Molecular and Cellular Biology, University of California, Merced, California
| | - Andrew Lee
- Department of Molecular and Cellular Biology, University of California, Merced, California
| | - Keisa W Mathis
- Department of Physiology and Anatomy, University of North Texas Health Science Center , Fort Worth, Texas
| | - Hanna J Broome
- Department of Biological Sciences, Mississippi College , Clinton, Mississippi
| | - Max Thorwald
- Department of Molecular and Cellular Biology, University of California, Merced, California
| | - Bridget Martinez
- Department of Molecular and Cellular Biology, University of California, Merced, California.,School of Medicine, St. George's University , St. George's , Grenada.,Department of Physics and Engineering, Los Alamos National Laboratory , Los Alamos, New Mexico
| | - Daisuke Nakano
- Department of Pharmacology, Faculty of Medicine, Kagawa University , Takamatsu , Japan
| | - Akira Nishiyama
- Department of Pharmacology, Faculty of Medicine, Kagawa University , Takamatsu , Japan
| | - Michael J Ryan
- Department of Physiology and Biophysics, University of Mississippi Medical Center , Jackson, Mississippi.,G.V. (Sonny) Montgomery Veterans Affairs Medical Center , Jackson, Mississippi
| | - Rudy M Ortiz
- Department of Molecular and Cellular Biology, University of California, Merced, California
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18
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Chemical genetic-based phenotypic screen reveals novel regulators of gluconeogenesis in human primary hepatocytes. NPJ Genom Med 2018; 3:20. [PMID: 30131871 PMCID: PMC6093908 DOI: 10.1038/s41525-018-0062-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 07/10/2018] [Accepted: 07/18/2018] [Indexed: 01/28/2023] Open
Abstract
Insulin resistance is a pathophysiological hallmark of type 2 diabetes and nonalcoholic fatty liver disease. Under the condition of fat accumulation in the liver, suppression of hepatic glucose production by insulin is diminished. In order to gain deeper understanding of dysregulation of glucose production in metabolic diseases, in the present study, we performed an unbiased phenotypic screening in primary human hepatocytes to discover novel mechanisms that regulate gluconeogenesis in the presence of insulin. To optimize phenotypic screening process, we used a chemical genetic screening approach by building a small-molecule library with prior knowledge of activity-based protein profiling. The “positive hits” result from the screen will be small molecules with known protein targets. This makes downstream deconvolution process (i.e., determining the relevant biological targets) less time-consuming. To unbiasedly decipher the molecular targets, we developed a novel statistical method and discovered a set of genes, including DDR3 and CACNA1E that suppressed gluconeogenesis in human hepatocytes. Further investigation, including transcriptional profiling and gene network analysis, was performed to understand the molecular functions of DRD3 and CACNA1E in human hepatocytes. A high-throughput screening protocol helped identify two novel genes involved in sugar metabolism that could be druggable targets for treating type 2 diabetes. Haiqing Hua and colleagues from the Lilly China Research and Development Center, a division of Eli Lilly & Company in Shanghai, evaluated the ability of human liver cells to produce glucose when exposed to a library of more than 1500 small-molecule drugs with known molecular targets. The researchers distinguished a set of genes that, when inhibited, dramatically suppressed glucose production. Two of these genes had not previously been implicated in liver function. The researchers began to dissect that molecular function through studies of gene expression and gene network analysis. The results demonstrate a way to combine chemical genetics and phenotypic screening to identify novel drug targets, revealing two for diabetes.
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19
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Govil M, Mukhopadhyay N, Weeks DE, Feingold E, Shaffer JR, Levy SM, Vieira AR, Slayton RL, McNeil DW, Weyant RJ, Crout RJ, Marazita ML. Novel caries loci in children and adults implicated by genome-wide analysis of families. BMC Oral Health 2018; 18:98. [PMID: 29859070 PMCID: PMC5984765 DOI: 10.1186/s12903-018-0559-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 05/22/2018] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Dental caries is a common chronic disease among children and adults alike, posing a substantial health burden. Caries is affected by multiple genetic and environmental factors, and prior studies have found that a substantial proportion of caries susceptibility is genetically inherited. METHODS To identify such genetic factors, we conducted a genome-wide linkage scan in 464 extended families with 2616 individuals from Iowa, Pennsylvania and West Virginia for three dental caries phenotypes: (1) PRIM: dichotomized as zero versus one or more affected primary teeth, (2) QTOT1: age-adjusted quantitative caries measure for both primary and permanent dentitions including pre-cavitated lesions, and (3) QTOT2: age-adjusted quantitative caries excluding pre-cavitated lesions. Genotyping was conducted for approximately 600,000 SNPs on an Illumina platform, pruned to 127,511 uncorrelated SNPs for the analyses reported here. RESULTS Multipoint non-parametric linkage analyses generated peak LOD scores exceeding 2.0 for eight genomic regions, but no LOD scores above 3.0 were observed. The maximum LOD score for each of the three traits was 2.90 at 1q25.3 for PRIM, 2.38 at 6q25.3 for QTOT1, and 2.76 at 5q23.3 for QTOT2. Some overlap in linkage regions was observed among the phenotypes. Genes with a potential role in dental caries in the eight chromosomal regions include CACNA1E, LAMC2, ALMS1, STAMBP, GXYLT2, SLC12A2, MEGF10, TMEM181, ARID1B, and, as well as genes in several immune gene families. Our results are also concordant with previous findings from association analyses on chromosomes 11 and 19. CONCLUSIONS These multipoint linkage results provide evidence in favor of novel chromosomal regions, while also supporting earlier association findings for these data. Understanding the genetic etiology of dental caries will allow designing personalized treatment plans based on an individual's genetic risk of disease.
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Affiliation(s)
- Manika Govil
- Center for Craniofacial and Dental Genetics, Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, Suite 500 Bridgeside Point, 100 Technology Drive, Pittsburgh, PA 15219 USA
| | - Nandita Mukhopadhyay
- Center for Craniofacial and Dental Genetics, Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, Suite 500 Bridgeside Point, 100 Technology Drive, Pittsburgh, PA 15219 USA
| | - Daniel E. Weeks
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
- Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
| | - Eleanor Feingold
- Center for Craniofacial and Dental Genetics, Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, Suite 500 Bridgeside Point, 100 Technology Drive, Pittsburgh, PA 15219 USA
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
- Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
| | - John R. Shaffer
- Center for Craniofacial and Dental Genetics, Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, Suite 500 Bridgeside Point, 100 Technology Drive, Pittsburgh, PA 15219 USA
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
| | - Steven M. Levy
- Department of Preventive and Community Dentistry, University of Iowa College of Dentistry, Iowa City, IA USA
- Department of Epidemiology, University of Iowa College of Public Health, Iowa City, IA USA
| | - Alexandre R. Vieira
- Center for Craniofacial and Dental Genetics, Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, Suite 500 Bridgeside Point, 100 Technology Drive, Pittsburgh, PA 15219 USA
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
| | - Rebecca L. Slayton
- Department of Pediatric Dentistry, School of Dentistry, University of Washington, Seattle, WA USA
| | - Daniel W. McNeil
- Dental Practice and Rural Health, West Virginia University School of Dentistry, Morgantown, WV USA
- Department of Psychology, Eberly College of Arts and Sciences, West Virginia University, Morgantown, WV USA
| | - Robert J. Weyant
- Department of Dental Public Health and Information Management, School of Dental Medicine, University of Pittsburgh, Pittsburgh, PA USA
| | - Richard J. Crout
- Department of Periodontics, West Virginia University School of Dentistry, Morgantown, WV USA
| | - Mary L. Marazita
- Center for Craniofacial and Dental Genetics, Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, Suite 500 Bridgeside Point, 100 Technology Drive, Pittsburgh, PA 15219 USA
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA USA
- Clinical and Translational Science Institute, and Department of Psychiatry, School of Medicine, University of Pittsburgh, Pittsburgh, PA USA
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20
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Schneider T, Alpdogan S, Hescheler J, Neumaier F. In vitro and in vivo phosphorylation of the Ca v2.3 voltage-gated R-type calcium channel. Channels (Austin) 2018; 12:326-334. [PMID: 30165790 PMCID: PMC6986797 DOI: 10.1080/19336950.2018.1516984] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 08/20/2018] [Accepted: 08/22/2018] [Indexed: 02/07/2023] Open
Abstract
During the recording of whole cell currents from stably transfected HEK-293 cells, the decline of currents carried by the recombinant human Cav2.3+β3 channel subunits is related to adenosine triphosphate (ATP) depletion after rupture of the cells. It reduces the number of functional channels and leads to a progressive shift of voltage-dependent gating to more negative potentials (Neumaier F., et al., 2018). Both effects can be counteracted by hydrolysable ATP, whose protective action is almost completely prevented by inhibition of serine/threonine but not tyrosine or lipid kinases. These findings indicate that ATP promotes phosphorylation of either the channel or an associated protein, whereas dephosphorylation during cell dialysis results in run-down. Protein phosphorylation is required for Cav2.3 channel function and could directly influence the normal features of current carried by these channels. Therefore, results from in vitro and in vivo phosphorylation of Cav2.3 are summarized to come closer to a functional analysis of structural variations in Cav2.3 splice variants.
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Affiliation(s)
- T. Schneider
- Center of Physiology and Pathophysiology, Institute of Neurophysiology, Cologne, Germany
| | - S. Alpdogan
- Center of Physiology and Pathophysiology, Institute of Neurophysiology, Cologne, Germany
| | - J. Hescheler
- Center of Physiology and Pathophysiology, Institute of Neurophysiology, Cologne, Germany
| | - F. Neumaier
- Center of Physiology and Pathophysiology, Institute of Neurophysiology, Cologne, Germany
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21
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Abstract
Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations. Individuals with CF have seen significant increases in life expectancy in the last 60 years. As a result, previously rare complications are now coming to light. The most common of these is cystic fibrosis-related diabetes (CFRD), which affects 40-50% of CF adults. CFRD significantly impacts the pulmonary function and longevity of CF patients, yet a lack of consensus on the best methods to diagnose and treat CFRD remains. We begin by reviewing our understanding of the pathogenesis of CFRD, as emerging evidence shows the cystic fibrosis transmembrane conductance regulator (CFTR) also has important roles in the release of insulin and glucagon and in the protection of β cells from oxidative stress. We then discuss how current recommended methods of CFRD diagnosis are not appropriate, as continuous glucose monitoring becomes more effective, practical, and cost-effective. Finally, we evaluate emerging treatments which have narrowed the mortality gap within the CF patient group. In the future, pharmacological potentiators and correctors directly targeting CFTR show huge promise for both CFRD and the wider CF patient groups.
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Affiliation(s)
- Kayani Kayani
- Faculty of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Raihan Mohammed
- Faculty of Medicine, University of Cambridge, Cambridge, United Kingdom
- *Correspondence: Raihan Mohammed,
| | - Hasan Mohiaddin
- Faculty of Medicine, Imperial College London, London, United Kingdom
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22
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Skelin Klemen M, Dolenšek J, Slak Rupnik M, Stožer A. The triggering pathway to insulin secretion: Functional similarities and differences between the human and the mouse β cells and their translational relevance. Islets 2017; 9:109-139. [PMID: 28662366 PMCID: PMC5710702 DOI: 10.1080/19382014.2017.1342022] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In β cells, stimulation by metabolic, hormonal, neuronal, and pharmacological factors is coupled to secretion of insulin through different intracellular signaling pathways. Our knowledge about the molecular machinery supporting these pathways and the patterns of signals it generates comes mostly from rodent models, especially the laboratory mouse. The increased availability of human islets for research during the last few decades has yielded new insights into the specifics in signaling pathways leading to insulin secretion in humans. In this review, we follow the most central triggering pathway to insulin secretion from its very beginning when glucose enters the β cell to the calcium oscillations it produces to trigger fusion of insulin containing granules with the plasma membrane. Along the way, we describe the crucial building blocks that contribute to the flow of information and focus on their functional role in mice and humans and on their translational implications.
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Affiliation(s)
- Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Marjan Slak Rupnik
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
- Institute of Physiology; Center for Physiology and Pharmacology; Medical University of Vienna; Vienna, Austria
| | - Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
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23
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Villar-Pazos S, Martinez-Pinna J, Castellano-Muñoz M, Alonso-Magdalena P, Marroqui L, Quesada I, Gustafsson JA, Nadal A. Molecular mechanisms involved in the non-monotonic effect of bisphenol-a on ca2+ entry in mouse pancreatic β-cells. Sci Rep 2017; 7:11770. [PMID: 28924161 PMCID: PMC5603522 DOI: 10.1038/s41598-017-11995-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 08/29/2017] [Indexed: 12/16/2022] Open
Abstract
In regulatory toxicology, the dose-response relationship is a key element towards fulfilling safety assessments and satisfying regulatory authorities. Conventionally, the larger the dose, the greater the response, following the dogma “the dose makes the poison”. Many endocrine disrupting chemicals, including bisphenol-A (BPA), induce non-monotonic dose response (NMDR) relationships, which are unconventional and have tremendous implications in risk assessment. Although several molecular mechanisms have been proposed to explain NMDR relationships, they are largely undemonstrated. Using mouse pancreatic β-cells from wild-type and oestrogen receptor ERβ−/− mice, we found that exposure to increasing doses of BPA affected Ca2+ entry in an NMDR manner. Low doses decreased plasma membrane Ca2+ currents after downregulation of Cav2.3 ion channel expression, in a process involving ERβ. High doses decreased Ca2+ currents through an ERβ-mediated mechanism and simultaneously increased Ca2+ currents via oestrogen receptor ERα. The outcome of both molecular mechanisms explains the NMDR relationship between BPA and Ca2+ entry in β-cells.
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Affiliation(s)
- Sabrina Villar-Pazos
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Institute of Bioenginering, Miguel Hernández University of Elche, Elche, Alicante, Spain
| | - Juan Martinez-Pinna
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Manuel Castellano-Muñoz
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Institute of Bioenginering, Miguel Hernández University of Elche, Elche, Alicante, Spain
| | - Paloma Alonso-Magdalena
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Institute of Bioenginering, Miguel Hernández University of Elche, Elche, Alicante, Spain
| | - Laura Marroqui
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Institute of Bioenginering, Miguel Hernández University of Elche, Elche, Alicante, Spain
| | - Ivan Quesada
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Institute of Bioenginering, Miguel Hernández University of Elche, Elche, Alicante, Spain
| | - Jan-Ake Gustafsson
- Department of Cell Biology and Biochemistry, Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, Texas, USA.,Department of Biosciences and Nutrition, Karolinska Institut, Huddinge, Sweden
| | - Angel Nadal
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Institute of Bioenginering, Miguel Hernández University of Elche, Elche, Alicante, Spain.
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Mastrolia V, Flucher SM, Obermair GJ, Drach M, Hofer H, Renström E, Schwartz A, Striessnig J, Flucher BE, Tuluc P. Loss of α 2δ-1 Calcium Channel Subunit Function Increases the Susceptibility for Diabetes. Diabetes 2017; 66:897-907. [PMID: 28115397 PMCID: PMC7360433 DOI: 10.2337/db16-0336] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 01/18/2017] [Indexed: 11/13/2022]
Abstract
Reduced pancreatic β-cell function or mass is the critical problem in developing diabetes. Insulin release from β-cells depends on Ca2+ influx through high voltage-gated Ca2+ channels (HVCCs). Ca2+ influx also regulates insulin synthesis and insulin granule priming and contributes to β-cell electrical activity. The HVCCs are multisubunit protein complexes composed of a pore-forming α1 and auxiliary β and α2δ subunits. α2δ is a key regulator of membrane incorporation and function of HVCCs. Here we show that genetic deletion of α2δ-1, the dominant α2δ subunit in pancreatic islets, results in glucose intolerance and diabetes without affecting insulin sensitivity. Lack of the α2δ-1 subunit reduces the Ca2+ currents through all HVCC isoforms expressed in β-cells equally in male and female mice. The reduced Ca2+ influx alters the kinetics and amplitude of the global Ca2+ response to glucose in pancreatic islets and significantly reduces insulin release in both sexes. The progression of diabetes in males is aggravated by a selective loss of β-cell mass, while a stronger basal insulin release alleviates the diabetes symptoms in most α2δ-1-/- female mice. Together, these findings demonstrate that the loss of the Ca2+ channel α2δ-1 subunit function increases the susceptibility for developing diabetes in a sex-dependent manner.
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Affiliation(s)
- Vincenzo Mastrolia
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
| | - Sylvia M Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Mathias Drach
- Department of General Pathology, Medical University Innsbruck, Innsbruck, Austria
| | - Helene Hofer
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Erik Renström
- Department of Clinical Sciences Malmö, Lund University, Lund, Sweden
| | - Arnold Schwartz
- College of Medicine, University of Cincinnati, Cincinnati, OH
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
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25
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Wormuth C, Lundt A, Henseler C, Müller R, Broich K, Papazoglou A, Weiergräber M. Review: Ca v2.3 R-type Voltage-Gated Ca 2+ Channels - Functional Implications in Convulsive and Non-convulsive Seizure Activity. Open Neurol J 2016; 10:99-126. [PMID: 27843503 PMCID: PMC5080872 DOI: 10.2174/1874205x01610010099] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 05/16/2016] [Accepted: 06/24/2016] [Indexed: 11/22/2022] Open
Abstract
Background: Researchers have gained substantial insight into mechanisms of synaptic transmission, hyperexcitability, excitotoxicity and neurodegeneration within the last decades. Voltage-gated Ca2+ channels are of central relevance in these processes. In particular, they are key elements in the etiopathogenesis of numerous seizure types and epilepsies. Earlier studies predominantly targeted on Cav2.1 P/Q-type and Cav3.2 T-type Ca2+ channels relevant for absence epileptogenesis. Recent findings bring other channels entities more into focus such as the Cav2.3 R-type Ca2+ channel which exhibits an intriguing role in ictogenesis and seizure propagation. Cav2.3 R-type voltage gated Ca2+ channels (VGCC) emerged to be important factors in the pathogenesis of absence epilepsy, human juvenile myoclonic epilepsy (JME), and cellular epileptiform activity, e.g. in CA1 neurons. They also serve as potential target for various antiepileptic drugs, such as lamotrigine and topiramate. Objective: This review provides a summary of structure, function and pharmacology of VGCCs and their fundamental role in cellular Ca2+ homeostasis. We elaborate the unique modulatory properties of Cav2.3 R-type Ca2+ channels and point to recent findings in the proictogenic and proneuroapoptotic role of Cav2.3 R-type VGCCs in generalized convulsive tonic–clonic and complex-partial hippocampal seizures and its role in non-convulsive absence like seizure activity. Conclusion: Development of novel Cav2.3 specific modulators can be effective in the pharmacological treatment of epilepsies and other neurological disorders.
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Affiliation(s)
- Carola Wormuth
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Andreas Lundt
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Christina Henseler
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Ralf Müller
- Department of Psychiatry and Psychotherapy, University of Cologne, Faculty of Medicine, Cologne, Germany
| | - Karl Broich
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Anna Papazoglou
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Marco Weiergräber
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
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26
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Dolai S, Xie L, Zhu D, Liang T, Qin T, Xie H, Kang Y, Chapman ER, Gaisano HY. Synaptotagmin-7 Functions to Replenish Insulin Granules for Exocytosis in Human Islet β-Cells. Diabetes 2016; 65:1962-76. [PMID: 27207520 PMCID: PMC5384637 DOI: 10.2337/db15-1436] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 04/16/2016] [Indexed: 12/13/2022]
Abstract
Synaptotagmin (Syt)-7, a major component of the exocytotic machinery in neurons, is also the major Syt in rodent pancreatic β-cells shown to mediate glucose-stimulated insulin secretion (GSIS). However, Syt-7's precise exocytotic actions in β-cells remain unknown. We show that Syt-7 is abundant in human β-cells. Adenovirus-short hairpin RNA knockdown (KD) of Syt-7 in human islets reduced first- and second-phase GSIS attributed to the reduction of exocytosis of predocked and newcomer insulin secretory granules (SGs). Glucose stimulation expectedly induced Syt-7 association in a Ca(2+)-dependent manner with syntaxin-3 and syntaxin-1A soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes known to mediate exocytosis of newcomer and predocked SGs, respectively. However, Syt-7-KD did not disrupt SNARE complex assembly. Instead, electron microscopy analysis showed that Syt-7-KD reduced the recruitment of SGs to the plasma membrane after glucose-stimulated depletion, which could not be rescued by glucagon-like peptide 1 pretreatment. To assess the possibility that this new action of Syt-7 on SG recruitment may involve calmodulin (CaM), pretreatment of islets with CaM blocker calmidazolium showed effects very similar to those of Syt-7-KD. Syt-7 therefore plays a novel more dominant function in the replenishment of releasable SG pools in human β-cells than its previously purported role in exocytotic fusion per se.
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Affiliation(s)
- Subhankar Dolai
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Li Xie
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Dan Zhu
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tairan Qin
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Huanli Xie
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Edwin R Chapman
- Department of Neuroscience, Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI
| | - Herbert Y Gaisano
- Department of Medicine, University of Toronto, Toronto, ON, Canada Department of Physiology, University of Toronto, Toronto, ON, Canada
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27
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Xie L, Dolai S, Kang Y, Liang T, Xie H, Qin T, Yang L, Chen L, Gaisano HY. Syntaxin-3 Binds and Regulates Both R- and L-Type Calcium Channels in Insulin-Secreting INS-1 832/13 Cells. PLoS One 2016; 11:e0147862. [PMID: 26848587 PMCID: PMC4743851 DOI: 10.1371/journal.pone.0147862] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 01/08/2016] [Indexed: 12/23/2022] Open
Abstract
Syntaxin (Syn)-1A mediates exocytosis of predocked insulin-containing secretory granules (SGs) during first-phase glucose-stimulated insulin secretion (GSIS) in part via its interaction with plasma membrane (PM)-bound L-type voltage-gated calcium channels (Cav). In contrast, Syn-3 mediates exocytosis of newcomer SGs that accounts for second-phase GSIS. We now hypothesize that the newcomer SG Syn-3 preferentially binds and modulates R-type Cav opening, which was postulated to mediate second-phase GSIS. Indeed, glucose-stimulation of pancreatic islet β-cell line INS-1 induced a predominant increase in interaction between Syn-3 and Cavα1 pore-forming subunits of R-type Cav2.3 and to lesser extent L-type Cavs, while confirming the preferential interactions between Syn-1A with L-type (Cav1.2, Cav1.3) Cavs. Consistently, direct binding studies employing heterologous HEK cells confirmed that Syn-3 preferentially binds Cav2.3, whereas Syn-1A prefers L-type Cavs. We then used siRNA knockdown (KD) of Syn-3 in INS-1 to study the endogenous modulatory actions of Syn-3 on Cav channels. Syn-3 KD enhanced Ca2+ currents by 46% attributed mostly to R- and L-type Cavs. Interestingly, while the transmembrane domain of Syn-1A is the putative functional domain modulating Cav activity, it is the cytoplasmic domain of Syn-3 that appears to modulate Cav activity. We conclude that Syn-3 may mimic Syn-1A in the ability to bind and modulate Cavs, but preferring Cav2.3 to perhaps participate in triggering fusion of newcomer insulin SGs during second-phase GSIS.
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Affiliation(s)
- Li Xie
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Subhankar Dolai
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Youhou Kang
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tao Liang
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Huanli Xie
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tairan Qin
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Lu Yang
- Institute of Molecular Medicine, Peking University, Beijing, China
| | - Liangyi Chen
- Institute of Molecular Medicine, Peking University, Beijing, China
| | - Herbert Y. Gaisano
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
- * E-mail:
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Anastasiou V, Ninou E, Alexopoulou D, Stertmann J, Müller A, Dahl A, Solimena M, Speier S, Serafimidis I, Gavalas A. Aldehyde dehydrogenase activity is necessary for beta cell development and functionality in mice. Diabetologia 2016; 59:139-150. [PMID: 26518685 PMCID: PMC4670456 DOI: 10.1007/s00125-015-3784-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 09/22/2015] [Indexed: 12/14/2022]
Abstract
AIMS/HYPOTHESIS Pancreatic beta cells maintain glucose homeostasis and beta cell dysfunction is a major risk factor in developing diabetes. Therefore, understanding the developmental regulatory networks that define a fully functional beta cell is important for elucidating the genetic origins of the disease. Aldehyde dehydrogenase activity has been associated with stem/progenitor cells and we have previously shown that Aldh1b1 is specifically expressed in pancreas progenitor pools. Here we address the hypothesis that Aldh1b1 may regulate the timing of the appearance and eventual functionality of beta cells. METHODS We generated an Aldh1b1-knockout mouse line (Aldh1b1 (tm1lacZ)) and used this to study pancreatic development, beta cell functionality and glucose homeostasis in the absence of Aldh1b1 function. RESULTS Differentiation in the developing pancreas of Aldh1b1 (tm1lacZ) null mice was accelerated. Transcriptome analyses of newborn and adult islets showed misregulation of key beta cell transcription factors and genes crucial for beta cell function. Functional analyses showed that glucose-stimulated insulin secretion was severely compromised in islets isolated from null mice. Several key features of beta cell functionality were affected, including control of oxidative stress, glucose sensing, stimulus-coupling secretion and secretory granule biogenesis. As a result of beta cell dysfunction, homozygous mice developed glucose intolerance and age-dependent hyperglycaemia. CONCLUSIONS/INTERPRETATION These findings show that Aldh1b1 influences the timing of the transition from the pancreas endocrine progenitor to the committed beta cell and demonstrate that changes in the timing of this transition lead to beta cell dysfunction and thus constitute a diabetes risk factor later in life. Gene Expression Omnibus (GEO) accession: GSE58025.
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Affiliation(s)
- Vivian Anastasiou
- Paul Langerhans Institute Dresden of Helmholtz Center Munich at the University Clinic Carl Gustav Carus of TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
- DZD - German Centre for Diabetes Research, Germany
| | - Elpiniki Ninou
- Developmental Biology Laboratory, Biomedical Research Foundation of the Academy of Athens, Soranou Ephessiou 4, Athens, 11527, Greece
| | - Dimitra Alexopoulou
- Deep Sequencing Group SFB655, BIOTEChnology Center (BioZ), TU Dresden, Dresden, Germany
| | - Julia Stertmann
- Paul Langerhans Institute Dresden of Helmholtz Center Munich at the University Clinic Carl Gustav Carus of TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
- DZD - German Centre for Diabetes Research, Germany
- DFG-Center for Regenerative Therapies Dresden (CRTD), Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Andreas Müller
- Paul Langerhans Institute Dresden of Helmholtz Center Munich at the University Clinic Carl Gustav Carus of TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
- DZD - German Centre for Diabetes Research, Germany
| | - Andreas Dahl
- Deep Sequencing Group SFB655, BIOTEChnology Center (BioZ), TU Dresden, Dresden, Germany
| | - Michele Solimena
- Paul Langerhans Institute Dresden of Helmholtz Center Munich at the University Clinic Carl Gustav Carus of TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
- DZD - German Centre for Diabetes Research, Germany
| | - Stephan Speier
- Paul Langerhans Institute Dresden of Helmholtz Center Munich at the University Clinic Carl Gustav Carus of TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
- DZD - German Centre for Diabetes Research, Germany
- DFG-Center for Regenerative Therapies Dresden (CRTD), Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Ioannis Serafimidis
- Developmental Biology Laboratory, Biomedical Research Foundation of the Academy of Athens, Soranou Ephessiou 4, Athens, 11527, Greece.
| | - Anthony Gavalas
- Paul Langerhans Institute Dresden of Helmholtz Center Munich at the University Clinic Carl Gustav Carus of TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany.
- DZD - German Centre for Diabetes Research, Germany, .
- Developmental Biology Laboratory, Biomedical Research Foundation of the Academy of Athens, Soranou Ephessiou 4, Athens, 11527, Greece.
- DFG-Center for Regenerative Therapies Dresden (CRTD), Faculty of Medicine, TU Dresden, Dresden, Germany.
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29
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Brereton MF, Vergari E, Zhang Q, Clark A. Alpha-, Delta- and PP-cells: Are They the Architectural Cornerstones of Islet Structure and Co-ordination? J Histochem Cytochem 2015. [PMID: 26216135 DOI: 10.1369/0022155415583535] [Citation(s) in RCA: 121] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Islet non-β-cells, the α- δ- and pancreatic polypeptide cells (PP-cells), are important components of islet architecture and intercellular communication. In α-cells, glucagon is found in electron-dense granules; granule exocytosis is calcium-dependent via P/Q-type Ca(2+)-channels, which may be clustered at designated cell membrane sites. Somatostatin-containing δ-cells are neuron-like, creating a network for intra-islet communication. Somatostatin 1-28 and 1-14 have a short bioactive half-life, suggesting inhibitory action via paracrine signaling. PP-cells are the most infrequent islet cell type. The embryologically separate ventral pancreas anlage contains PP-rich islets that are morphologically diffuse and α-cell deficient. Tissue samples taken from the head region are unlikely to be representative of the whole pancreas. PP has anorexic effects on gastro-intestinal function and alters insulin and glucagon secretion. Islet architecture is disrupted in rodent diabetic models, diabetic primates and human Type 1 and Type 2 diabetes, with an increased α-cell population and relocation of non-β-cells to central areas of the islet. In diabetes, the transdifferentiation of non-β-cells, with changes in hormone content, suggests plasticity of islet cells but cellular function may be compromised. Understanding how diabetes-related disordered islet structure influences intra-islet cellular communication could clarify how non-β-cells contribute to the control of islet function.
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Affiliation(s)
- Melissa F Brereton
- Department of Physiology, Anatomy and Genetics, University of Oxford, United Kingdom. (MFB)
| | - Elisa Vergari
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, United Kingdom. (EV, QZ, AC)
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, United Kingdom. (EV, QZ, AC)
| | - Anne Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, United Kingdom. (EV, QZ, AC)
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30
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Fan HQ, He W, Xu KF, Wang ZX, Xu XY, Chen H. FTO Inhibits Insulin Secretion and Promotes NF-κB Activation through Positively Regulating ROS Production in Pancreatic β cells. PLoS One 2015; 10:e0127705. [PMID: 26018652 PMCID: PMC4446323 DOI: 10.1371/journal.pone.0127705] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 04/17/2015] [Indexed: 11/25/2022] Open
Abstract
FTO (Fat mass and obesity-associated) is associated with increased risk of obesity and type 2 diabetes incurrence. Pancreas islet β cells dysfunction and insulin resistance are major causes of type 2 diabetes. However, whether FTO plays an important functional role in pancreatic β cells as well as the related molecular mechanism is still unclear. In the present study, the tissue expression profile of FTO was firstly determined using quantitative PCR and western blot. FTO is widely expressed in various tissues and presented with relative high expression in pancreas tissue, especially in endocrine pancreas. FTO overexpression in MIN6 cells achieved by lentivirus delivery significantly inhibits insulin secretion in the presence of glucose stimulus as well as KCl. FTO silence has no effect on insulin secretion of MIN6 cells. However, FTO overexpression doesn’t affect the transcription of insulin gene. Furthermore, reactive oxygen species (ROS) production and NF-κB activation are significantly promoted by FTO overexpression. Inhibition of intracellular ROS production by N-acetyl-L-cysteine (NAC) can alleviate NF-κB activation and restore the insulin secretion mediated by FTO overexpression. A whole transcript-microarray is employed to analyze the differential gene expression mediated by FTO overexpression. The genes which are modulated by FTO are involved in many important biological pathways such as G-protein coupled receptor signaling and NF-κB signaling. Therefore, our study indicates that FTO may contribute to pancreas islet β cells dysfunction and the inhibition of FTO activity is a potential target for the treatment of diabetes.
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Affiliation(s)
- Hong-Qi Fan
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
- * E-mail:
| | - Wei He
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Kuan-Feng Xu
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Zhi-Xiao Wang
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Xin-Yu Xu
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Heng Chen
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
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Piccand J, Strasser P, Hodson DJ, Meunier A, Ye T, Keime C, Birling MC, Rutter GA, Gradwohl G. Rfx6 maintains the functional identity of adult pancreatic β cells. Cell Rep 2014; 9:2219-32. [PMID: 25497096 PMCID: PMC4542305 DOI: 10.1016/j.celrep.2014.11.033] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/27/2014] [Accepted: 11/20/2014] [Indexed: 01/09/2023] Open
Abstract
Increasing evidence suggests that loss of β cell characteristics may cause insulin secretory deficiency in diabetes, but the underlying mechanisms remain unclear. Here, we show that Rfx6, whose mutation leads to neonatal diabetes in humans, is essential to maintain key features of functionally mature β cells in mice. Rfx6 loss in adult β cells leads to glucose intolerance, impaired β cell glucose sensing, and defective insulin secretion. This is associated with reduced expression of core components of the insulin secretion pathway, including glucokinase, the Abcc8/SUR1 subunit of KATP channels and voltage-gated Ca(2+) channels, which are direct targets of Rfx6. Moreover, Rfx6 contributes to the silencing of the vast majority of "disallowed" genes, a group usually specifically repressed in adult β cells, and thus to the maintenance of β cell maturity. These findings raise the possibility that changes in Rfx6 expression or activity may contribute to β cell failure in humans.
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Affiliation(s)
- Julie Piccand
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U964, Centre National de Recherche Scientifique UMR7104, Université de Strasbourg, Illkirch 67404, France
| | - Perrine Strasser
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U964, Centre National de Recherche Scientifique UMR7104, Université de Strasbourg, Illkirch 67404, France
| | - David J Hodson
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Hammersmith Hospital, du Cane Road, London W12 0NN, UK
| | - Aline Meunier
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U964, Centre National de Recherche Scientifique UMR7104, Université de Strasbourg, Illkirch 67404, France
| | - Tao Ye
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U964, Centre National de Recherche Scientifique UMR7104, Université de Strasbourg, Illkirch 67404, France
| | - Céline Keime
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U964, Centre National de Recherche Scientifique UMR7104, Université de Strasbourg, Illkirch 67404, France
| | | | - Guy A Rutter
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Hammersmith Hospital, du Cane Road, London W12 0NN, UK
| | - Gérard Gradwohl
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U964, Centre National de Recherche Scientifique UMR7104, Université de Strasbourg, Illkirch 67404, France.
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Rajagopal S, Fields BL, Kamatchi GL. Contribution of protein kinase Cα in the stimulation of insulin by the down-regulation of Cavβ subunits. Endocrine 2014; 47:463-71. [PMID: 24452871 PMCID: PMC4176602 DOI: 10.1007/s12020-013-0149-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/14/2013] [Indexed: 12/23/2022]
Abstract
Voltage-gated calcium (Cav) channels and protein kinase C (PKC) isozymes are involved in insulin secretion. In addition, Cavβ, one of the auxiliary subunits of Cav channels, also regulates the secretion of insulin as knockout of Cavβ3 (β3(-/-)) subunits in mice led to efficient glucose homeostasis and increased insulin levels. We examined whether other types of Cavβ subunits also have similar properties. In this regard, we used small interfering RNA (siRNA) of these subunits (20 μg each) to down-regulate them and examined blood glucose, serum insulin and PKC translocation in isolated pancreatic β cells of mice. While the down-regulation of Cavβ2 and β3 subunits increased serum insulin levels and caused efficient glucose homeostasis, the down-regulation of Cavβ1 and β4 subunits failed to affect both these parameters. Examination of PKC isozymes in the pancreatic β-cells of Cavβ2- or β3 siRNA-injected mice showed that three PKC isozymes, viz., PKC α, βII and θ, translocated to the membrane. This suggests that when present, Cavβ2 and β3 subunits inhibited PKC activation. Among these three isozymes, only PKCα siRNA inhibited insulin and increased glucose concentrations. It is possible that the activation of PKCs βII and θ is not sufficient for the release of insulin and PKCα is the mediator of insulin secretion under the control of Cavβ subunits. Since Cavβ subunits are present intracellularly, it is possible that they (1) inhibited the translocation of PKC isozymes to the membrane and (2) decreased the interaction between Cav channels and PKC isozymes and thus the secretion of insulin.
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Affiliation(s)
- Senthilkumar Rajagopal
- Department of Zoology, Nizam College, Osmania University, Hyderabad, 500001, Andhra Pradesh, India
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33
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Yang SN, Shi Y, Yang G, Li Y, Yu J, Berggren PO. Ionic mechanisms in pancreatic β cell signaling. Cell Mol Life Sci 2014; 71:4149-77. [PMID: 25052376 PMCID: PMC11113777 DOI: 10.1007/s00018-014-1680-6] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 07/03/2014] [Accepted: 07/10/2014] [Indexed: 01/07/2023]
Abstract
The function and survival of pancreatic β cells critically rely on complex electrical signaling systems composed of a series of ionic events, namely fluxes of K(+), Na(+), Ca(2+) and Cl(-) across the β cell membranes. These electrical signaling systems not only sense events occurring in the extracellular space and intracellular milieu of pancreatic islet cells, but also control different β cell activities, most notably glucose-stimulated insulin secretion. Three major ion fluxes including K(+) efflux through ATP-sensitive K(+) (KATP) channels, the voltage-gated Ca(2+) (CaV) channel-mediated Ca(2+) influx and K(+) efflux through voltage-gated K(+) (KV) channels operate in the β cell. These ion fluxes set the resting membrane potential and the shape, rate and pattern of firing of action potentials under different metabolic conditions. The KATP channel-mediated K(+) efflux determines the resting membrane potential and keeps the excitability of the β cell at low levels. Ca(2+) influx through CaV1 channels, a major type of β cell CaV channels, causes the upstroke or depolarization phase of the action potential and regulates a wide range of β cell functions including the most elementary β cell function, insulin secretion. K(+) efflux mediated by KV2.1 delayed rectifier K(+) channels, a predominant form of β cell KV channels, brings about the downstroke or repolarization phase of the action potential, which acts as a brake for insulin secretion owing to shutting down the CaV channel-mediated Ca(2+) entry. These three ion channel-mediated ion fluxes are the most important ionic events in β cell signaling. This review concisely discusses various ionic mechanisms in β cell signaling and highlights KATP channel-, CaV1 channel- and KV2.1 channel-mediated ion fluxes.
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Affiliation(s)
- Shao-Nian Yang
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, SE-171 76, Stockholm, Sweden,
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Guo JH, Chen H, Ruan YC, Zhang XL, Zhang XH, Fok KL, Tsang LL, Yu MK, Huang WQ, Sun X, Chung YW, Jiang X, Sohma Y, Chan HC. Glucose-induced electrical activities and insulin secretion in pancreatic islet β-cells are modulated by CFTR. Nat Commun 2014; 5:4420. [PMID: 25025956 PMCID: PMC4104438 DOI: 10.1038/ncomms5420] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 06/17/2014] [Indexed: 01/08/2023] Open
Abstract
The cause of insulin insufficiency remains unknown in many diabetic cases. Up to 50% adult patients with cystic fibrosis (CF), a disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), develop CF-related diabetes (CFRD) with most patients exhibiting insulin insufficiency. Here we show that CFTR is a regulator of glucose-dependent electrical acitivities and insulin secretion in β-cells. We demonstrate that glucose elicited whole-cell currents, membrane depolarization, electrical bursts or action potentials, Ca(2+) oscillations and insulin secretion are abolished or reduced by inhibitors or knockdown of CFTR in primary mouse β-cells or RINm5F β-cell line, or significantly attenuated in CFTR mutant (DF508) mice compared with wild-type mice. VX-809, a newly discovered corrector of DF508 mutation, successfully rescues the defects in DF508 β-cells. Our results reveal a role of CFTR in glucose-induced electrical activities and insulin secretion in β-cells, shed light on the pathogenesis of CFRD and possibly other idiopathic diabetes, and present a potential treatment strategy.
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Affiliation(s)
- Jing Hui Guo
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Hui Chen
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Ye Chun Ruan
- 1] Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China [2] Sichuan University-The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education of China, West China Second University Hospital, Sichuan University, Chengdu 610041, China [3] Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Xue Lian Zhang
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Xiao Hu Zhang
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Kin Lam Fok
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Lai Ling Tsang
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Mei Kuen Yu
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Wen Qing Huang
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Xiao Sun
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Yiu Wa Chung
- Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Xiaohua Jiang
- 1] Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China [2] Sichuan University-The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education of China, West China Second University Hospital, Sichuan University, Chengdu 610041, China [3] Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yoshiro Sohma
- Department of Pharmacology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Hsiao Chang Chan
- 1] Epithelial Cell Biology Research Center, Key Laboratory of Regenerative Medicine of Ministry of Education of China, CUHK-SJTU Joint Center for Human Reproduction and Related Disease, Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China [2] Sichuan University-The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education of China, West China Second University Hospital, Sichuan University, Chengdu 610041, China [3] Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
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Reinbothe TM, Safi F, Axelsson AS, Mollet IG, Rosengren AH. Optogenetic control of insulin secretion in intact pancreatic islets with β-cell-specific expression of Channelrhodopsin-2. Islets 2014; 6:e28095. [PMID: 25483880 PMCID: PMC4593566 DOI: 10.4161/isl.28095] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Insulin is secreted from the pancreatic β-cells in response to elevated glucose. In intact islets the capacity for insulin release is determined by a complex interplay between different cell types. This has made it difficult to specifically assess the role of β-cell defects to the insulin secretory impairment in type 2 diabetes. Here we describe a new approach, based on optogenetics, that enables specific investigation of β-cells in intact islets. We used transgenic mice expressing the light-sensitive cation channel Channelrhodopsin-2 (ChR2) under control of the insulin promoter. Glucose tolerance in vivo was assessed using intraperitoneal glucose tolerance tests, and glucose-induced insulin release was measured from static batch incubations. ChR2 localization was determined by fluorescence confocal microscopy. The effect of ChR2 stimulation with blue LED light was assessed using Ca(2+) imaging and static islet incubations. Light stimulation of islets from transgenic ChR2 mice triggered prompt increases in intracellular Ca(2+). Moreover, light stimulation enhanced insulin secretion in batch-incubated islets at low and intermediate but not at high glucose concentrations. Glucagon release was not affected. Beta-cells from mice rendered diabetic on a high-fat diet exhibited a 3.5-fold increase in light-induced Ca(2+) influx compared with mice on a control diet. Furthermore, light enhanced insulin release also at high glucose in these mice, suggesting that high-fat feeding leads to a compensatory potentiation of the Ca(2+) response in β-cells. The results demonstrate the usefulness and versatility of optogenetics for studying mechanisms of perturbed hormone secretion in diabetes with high time-resolution and cell-specificity.
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Meier JJ, Bonadonna RC. Role of reduced β-cell mass versus impaired β-cell function in the pathogenesis of type 2 diabetes. Diabetes Care 2013; 36 Suppl 2:S113-9. [PMID: 23882035 PMCID: PMC3920783 DOI: 10.2337/dcs13-2008] [Citation(s) in RCA: 170] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Juris J Meier
- Division of Diabetology and Gastrointestinal Endocrinology, St. Josef-Hospital, Ruhr-University of Bochum, Bochum, Germany.
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Xie L, Zhu D, Kang Y, Liang T, He Y, Gaisano HY. Exocyst sec5 regulates exocytosis of newcomer insulin granules underlying biphasic insulin secretion. PLoS One 2013; 8:e67561. [PMID: 23844030 PMCID: PMC3699660 DOI: 10.1371/journal.pone.0067561] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 05/20/2013] [Indexed: 11/24/2022] Open
Abstract
The exocyst complex subunit Sec5 is a downstream effector of RalA-GTPase which promotes RalA-exocyst interactions and exocyst assembly, serving to tether secretory granules to docking sites on the plasma membrane. We recently reported that RalA regulates biphasic insulin secretion in pancreatic islet β cells in part by tethering insulin secretory granules to Ca2+ channels to assist excitosome assembly. Here, we assessed β cell exocytosis by patch clamp membrane capacitance measurement and total internal reflection fluorescence microscopy to investigate the role of Sec5 in regulating insulin secretion. Sec5 is present in human and rodent islet β cells, localized to insulin granules. Sec5 protein depletion in rat INS-1 cells inhibited depolarization-induced release of primed insulin granules from both readily-releasable pool and mobilization from the reserve pool. This reduction in insulin exocytosis was attributed mainly to reduction in recruitment and exocytosis of newcomer insulin granules that undergo minimal docking time at the plasma membrane, but which encompassed a larger portion of biphasic glucose stimulated insulin secretion. Sec5 protein knockdown had little effect on predocked granules, unless vigorously stimulated by KCl depolarization. Taken together, newcomer insulin granules in β cells are more sensitive than predocked granules to Sec5 regulation.
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Affiliation(s)
- Li Xie
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Dan Zhu
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Yu He
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Herbert Y. Gaisano
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Buda P, Reinbothe T, Nagaraj V, Mahdi T, Luan C, Tang Y, Axelsson AS, Li D, Rosengren AH, Renström E, Zhang E. Eukaryotic translation initiation factor 3 subunit e controls intracellular calcium homeostasis by regulation of cav1.2 surface expression. PLoS One 2013; 8:e64462. [PMID: 23737983 PMCID: PMC3667822 DOI: 10.1371/journal.pone.0064462] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 04/15/2013] [Indexed: 01/09/2023] Open
Abstract
Inappropriate surface expression of voltage-gated Ca2+channels (CaV) in pancreatic ß-cells may contribute to the development of type 2 diabetes. First, failure to increase intracellular Ca2+ concentrations at the sites of exocytosis impedes insulin release. Furthermore, excessive Ca2+ influx may trigger cytotoxic effects. The regulation of surface expression of CaV channels in the pancreatic β-cells remains unknown. Here, we used real-time 3D confocal and TIRFM imaging, immunocytochemistry, cellular fractionation, immunoprecipitation and electrophysiology to study trafficking of L-type CaV1.2 channels upon β-cell stimulation. We found decreased surface expression of CaV1.2 and a corresponding reduction in L-type whole-cell Ca2+ currents in insulin-secreting INS-1 832/13 cells upon protracted (15–30 min) stimulation. This internalization occurs by clathrin-dependent endocytosis and could be prevented by microtubule or dynamin inhibitors. eIF3e (Eukaryotic translation initiation factor 3 subunit E) is part of the protein translation initiation complex, but its effect on translation are modest and effects in ion channel trafficking have been suggested. The factor interacted with CaV1.2 and regulated CaV1.2 traffic bidirectionally. eIF3e silencing impaired CaV1.2 internalization, which resulted in an increased intracellular Ca2+ load upon stimulation. These findings provide a mechanism for regulation of L-type CaV channel surface expression with consequences for β-cell calcium homeostasis, which will affect pancreatic β-cell function and insulin production.
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Affiliation(s)
- Pawel Buda
- Lund University Diabetes Center, Malmö, Sweden
| | | | | | - Taman Mahdi
- Lund University Diabetes Center, Malmö, Sweden
| | - Cheng Luan
- Lund University Diabetes Center, Malmö, Sweden
| | - Yunzhao Tang
- Lund University Diabetes Center, Malmö, Sweden
- Key Lab of Hormones and Development, Ministry of Health, and Metabolic Diseases Hospital, Tianjin Medical University, Tianjin, China
| | | | - Daiqing Li
- Key Lab of Hormones and Development, Ministry of Health, and Metabolic Diseases Hospital, Tianjin Medical University, Tianjin, China
| | | | - Erik Renström
- Lund University Diabetes Center, Malmö, Sweden
- * E-mail: (ER); (EZ)
| | - Enming Zhang
- Lund University Diabetes Center, Malmö, Sweden
- * E-mail: (ER); (EZ)
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Schneider T, Dibué M, Hescheler J. How "Pharmacoresistant" is Cav2.3, the Major Component of Voltage-Gated R-type Ca2+ Channels? Pharmaceuticals (Basel) 2013; 6:759-76. [PMID: 24276260 PMCID: PMC3816731 DOI: 10.3390/ph6060759] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 12/04/2022] Open
Abstract
Membrane-bound voltage-gated Ca2+ channels (VGCCs) are targets for specific signaling complexes, which regulate important processes like gene expression, neurotransmitter release and neuronal excitability. It is becoming increasingly evident that the so called “resistant” (R-type) VGCC Cav2.3 is critical in several physiologic and pathophysiologic processes in the central nervous system, vascular system and in endocrine systems. However its eponymous attribute of pharmacologic inertness initially made in depth investigation of the channel difficult. Although the identification of SNX-482 as a fairly specific inhibitor of Cav2.3 in the nanomolar range has enabled insights into the channels properties, availability of other pharmacologic modulators of Cav2.3 with different chemical, physical and biological properties are of great importance for future investigations. Therefore the literature was screened systematically for molecules that modulate Cav2.3 VGCCs.
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Affiliation(s)
- Toni Schneider
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
- Authors to whom correspondence should be addressed; E-Mails: (T.S.); (M.D.); Tel.: +49-221-478-69446 (T.S.); Fax: +49-221-478-6965 (T.S.)
| | - Maxine Dibué
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, Duesseldorf D-40225, Germany & Center of Molecular Medicine, Cologne D-50931, Germany
- Authors to whom correspondence should be addressed; E-Mails: (T.S.); (M.D.); Tel.: +49-221-478-69446 (T.S.); Fax: +49-221-478-6965 (T.S.)
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
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Tang G, Zhang L, Yang G, Wu L, Wang R. Hydrogen sulfide-induced inhibition of L-type Ca2+ channels and insulin secretion in mouse pancreatic beta cells. Diabetologia 2013; 56:533-41. [PMID: 23275972 DOI: 10.1007/s00125-012-2806-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 11/29/2012] [Indexed: 10/27/2022]
Abstract
AIMS/HYPOTHESIS L-type voltage-dependent Ca(2+) channels (VDCCs) in pancreatic beta cells play a critical role in regulating insulin secretion. The gasotransmitter H(2)S is mostly generated from L-cysteine in pancreatic beta cells by cystathionine γ-lyase (CSE) and has been reported to inhibit insulin release by opening ATP-sensitive K(+) channels. However, whether and how H(2)S affects VDCCs in beta cells is unknown. METHODS The whole-cell patch-clamp technique was used to record VDCCs in beta cells from Cse (also known as Cth)-knockout (KO) and wild-type (WT) mice. Insulin secretion from pancreatic islets and endogenous H(2)S production in pancreas were measured. RESULTS The H(2)S donor NaHS reversibly decreased L-type VDCC current density in a concentration-dependent fashion in WT pancreatic beta cells, and the current density was further inhibited by nifedipine. Furthermore, NaHS inhibited the channel recovery from depolarisation-induced inactivation, but did not shift the current-voltage (I-V) relationship. ACS67, another H(2)S donor, also inhibited L-type VDCCs in beta cells. Inhibiting CSE activity with DL-propargylglycine increased the basal L-channel activity of beta cells from WT mice, but not that of beta cells from Cse-KO mice. Beta cells from Cse-KO mice displayed higher L-type VDCC density than those from WT mice. Insulin secretion from pancreatic islets was elevated in Cse-KO mice compared with WT mice. NaHS dose-dependently inhibited glucose-stimulated insulin secretion, which was further inhibited by nifedipine. Bay K-8644 increased glucose-stimulated insulin secretion, but this was counteracted by NaHS and nifedipine. CONCLUSIONS/INTERPRETATION Exogenous and endogenous H(2)S inhibit L-type VDCC activity and pancreatic insulin secretion, constituting a novel mechanism for the regulation of insulin secretion by the CSE/H(2)S system.
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Affiliation(s)
- G Tang
- Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada
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Abstract
Pancreatic β-cell dysfunction plays an important role in the pathogenesis of both type 1 and type 2 diabetes. Insulin, which is produced in β-cells, is a critical regulator of metabolism. Insulin is synthesized as preproinsulin and processed to proinsulin. Proinsulin is then converted to insulin and C-peptide and stored in secretary granules awaiting release on demand. Insulin synthesis is regulated at both the transcriptional and translational level. The cis-acting sequences within the 5' flanking region and trans-activators including paired box gene 6 (PAX6), pancreatic and duodenal homeobox- 1(PDX-1), MafA, and β-2/Neurogenic differentiation 1 (NeuroD1) regulate insulin transcription, while the stability of preproinsulin mRNA and its untranslated regions control protein translation. Insulin secretion involves a sequence of events in β-cells that lead to fusion of secretory granules with the plasma membrane. Insulin is secreted primarily in response to glucose, while other nutrients such as free fatty acids and amino acids can augment glucose-induced insulin secretion. In addition, various hormones, such as melatonin, estrogen, leptin, growth hormone, and glucagon like peptide-1 also regulate insulin secretion. Thus, the β-cell is a metabolic hub in the body, connecting nutrient metabolism and the endocrine system. Although an increase in intracellular [Ca2+] is the primary insulin secretary signal, cAMP signaling- dependent mechanisms are also critical in the regulation of insulin secretion. This article reviews current knowledge on how β-cells synthesize and secrete insulin. In addition, this review presents evidence that genetic and environmental factors can lead to hyperglycemia, dyslipidemia, inflammation, and autoimmunity, resulting in β-cell dysfunction, thereby triggering the pathogenesis of diabetes.
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Affiliation(s)
- Zhuo Fu
- Department of Human Nutrition, Foods and Exercise, Virginia Tech, Blacksburg, VA 24061, USA
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Fu Z, Gilbert ER, Liu D. Regulation of insulin synthesis and secretion and pancreatic Beta-cell dysfunction in diabetes. Curr Diabetes Rev 2013; 9:25-53. [PMID: 22974359 PMCID: PMC3934755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 09/11/2012] [Accepted: 09/11/2012] [Indexed: 11/11/2023]
Abstract
Pancreatic β-cell dysfunction plays an important role in the pathogenesis of both type 1 and type 2 diabetes. Insulin, which is produced in β-cells, is a critical regulator of metabolism. Insulin is synthesized as preproinsulin and processed to proinsulin. Proinsulin is then converted to insulin and C-peptide and stored in secretary granules awaiting release on demand. Insulin synthesis is regulated at both the transcriptional and translational level. The cis-acting sequences within the 5' flanking region and trans-activators including paired box gene 6 (PAX6), pancreatic and duodenal homeobox- 1(PDX-1), MafA, and β-2/Neurogenic differentiation 1 (NeuroD1) regulate insulin transcription, while the stability of preproinsulin mRNA and its untranslated regions control protein translation. Insulin secretion involves a sequence of events in β-cells that lead to fusion of secretory granules with the plasma membrane. Insulin is secreted primarily in response to glucose, while other nutrients such as free fatty acids and amino acids can augment glucose-induced insulin secretion. In addition, various hormones, such as melatonin, estrogen, leptin, growth hormone, and glucagon like peptide-1 also regulate insulin secretion. Thus, the β-cell is a metabolic hub in the body, connecting nutrient metabolism and the endocrine system. Although an increase in intracellular [Ca2+] is the primary insulin secretary signal, cAMP signaling- dependent mechanisms are also critical in the regulation of insulin secretion. This article reviews current knowledge on how β-cells synthesize and secrete insulin. In addition, this review presents evidence that genetic and environmental factors can lead to hyperglycemia, dyslipidemia, inflammation, and autoimmunity, resulting in β-cell dysfunction, thereby triggering the pathogenesis of diabetes.
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Affiliation(s)
- Zhuo Fu
- Department of Human Nutrition, Foods and Exercise, Virginia Tech, Blacksburg, VA 24061, USA
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The mitochondrial Na+/Ca2+ exchanger upregulates glucose dependent Ca2+ signalling linked to insulin secretion. PLoS One 2012; 7:e46649. [PMID: 23056385 PMCID: PMC3466326 DOI: 10.1371/journal.pone.0046649] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 09/03/2012] [Indexed: 11/25/2022] Open
Abstract
Mitochondria mediate dual metabolic and Ca2+ shuttling activities. While the former is required for Ca2+ signalling linked to insulin secretion, the role of the latter in β cell function has not been well understood, primarily because the molecular identity of the mitochondrial Ca2+ transporters were elusive and the selectivity of their inhibitors was questionable. This study focuses on NCLX, the recently discovered mitochondrial Na+/Ca2+ exchanger that is linked to Ca2+ signalling in MIN6 and primary β cells. Suppression either of NCLX expression, using a siRNA construct (siNCLX) or of its activity, by a dominant negative construct (dnNCLX), enhanced mitochondrial Ca2+ influx and blocked efflux induced by glucose or by cell depolarization. In addition, NCLX regulated basal, but not glucose-dependent changes, in metabolic rate, mitochondrial membrane potential and mitochondrial resting Ca2+. Importantly, NCLX controlled the rate and amplitude of cytosolic Ca2+ changes induced by depolarization or high glucose, indicating that NCLX is a critical and rate limiting component in the cross talk between mitochondrial and plasma membrane Ca2+ signalling. Finally, knockdown of NCLX expression was followed by a delay in glucose-dependent insulin secretion. These findings suggest that the mitochondrial Na+/Ca2+ exchanger, NCLX, shapes glucose-dependent mitochondrial and cytosolic Ca2+ signals thereby regulating the temporal pattern of insulin secretion in β cells.
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Al-Daghri NM, Alkharfy KM, Al-Othman A, El-Kholie E, Moharram O, Alokail MS, Al-Saleh Y, Sabico S, Kumar S, Chrousos GP. Vitamin D supplementation as an adjuvant therapy for patients with T2DM: an 18-month prospective interventional study. Cardiovasc Diabetol 2012; 11:85. [PMID: 22809461 PMCID: PMC3461474 DOI: 10.1186/1475-2840-11-85] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Accepted: 07/18/2012] [Indexed: 12/19/2022] Open
Abstract
Background Vitamin D deficiency has been associated with impaired human insulin action, suggesting a role in the pathogenesis of diabetes mellitus type 2 (T2DM). In this prospective interventional study we investigated the effects of vitamin D3 supplementation on the metabolic profiles of Saudi T2DM subjects pre- and post-vitamin D supplementation over an 18-month period. Methods T2DM Saudi subjects (men, N = 34: Age: 56.6 ± 8.7 yr, BMI, 29.1 ± 3.3 kg/m2; women, N = 58: Age: 51.2 ± 10.6 yr, BMI 34.3 ± 4.9 kg/m2;) were recruited and given 2000 IU vitamin D3 daily for 18 months. Anthropometrics and fasting blood were collected (0, 6, 12, 18 months) to monitor serum 25-hydroxyvitamin D using specific ELISA, and to determine metabolic profiles by standard methods. Results In all subjects there was a significant increase in mean 25-hydroxyvitamin D levels from baseline (32.2 ± 1.5 nmol/L) to 18 months (54.7 ± 1.5 nmol/L; p < 0.001), as well as serum calcium (baseline = 2.3 ± 0.23 mmol/L vs. 18 months = 2.6 ± 0.1 mmol/L; p = 0.003). A significant decrease in LDL- (baseline = 4.4 ± 0.8 mmol/L vs. 18 months = 3.6 ± 0.8 mmol/L, p < 0.001] and total cholesterol (baseline = 5.4 ± 0.2 mmol/L vs. 18 months = 4.9 ± 0.3 mmol/L, p < 0.001) were noted, as well as a significant improvement in HOMA-β function ( p = 0.002). Majority of the improvements elicited were more prominent in women than men. Conclusion In the Saudi T2DM population receiving oral Vitamin D3 supplementation (2000 IU/day), circulating 25-hydroxyvitamin D levels remained below normal 18 months after the onset of treatment. Yet, this “suboptimal” supplementation significantly improved lipid profile with a favorable change in HDL/LDL ratio, and HOMA-β function, which were more pronounced in T2DM females.
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Affiliation(s)
- Nasser M Al-Daghri
- Biomarkers Research Program, Biochemistry Department, College of Science, King Saud University, PO Box, 2455, Riyadh, 11451, Kingdom of Saudi Arabia.
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Gunton JE, Sisavanh M, Stokes RA, Satin J, Satin LS, Zhang M, Liu SM, Cai W, Cheng K, Cooney GJ, Laybutt DR, So T, Molero JC, Grey ST, Andres DA, Rolph MS, Mackay CR. Mice deficient in GEM GTPase show abnormal glucose homeostasis due to defects in beta-cell calcium handling. PLoS One 2012; 7:e39462. [PMID: 22761801 PMCID: PMC3386271 DOI: 10.1371/journal.pone.0039462] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/21/2012] [Indexed: 11/29/2022] Open
Abstract
Aims and Hypothesis Glucose-stimulated insulin secretion from beta-cells is a tightly regulated process that requires calcium flux to trigger exocytosis of insulin-containing vesicles. Regulation of calcium handling in beta-cells remains incompletely understood. Gem, a member of the RGK (Rad/Gem/Kir) family regulates calcium channel handling in other cell types, and Gem over-expression inhibits insulin release in insulin-secreting Min6 cells. The aim of this study was to explore the role of Gem in insulin secretion. We hypothesised that Gem may regulate insulin secretion and thus affect glucose tolerance in vivo. Methods Gem-deficient mice were generated and their metabolic phenotype characterised by in vivo testing of glucose tolerance, insulin tolerance and insulin secretion. Calcium flux was measured in isolated islets. Results Gem-deficient mice were glucose intolerant and had impaired glucose stimulated insulin secretion. Furthermore, the islets of Gem-deficient mice exhibited decreased free calcium responses to glucose and the calcium oscillations seen upon glucose stimulation were smaller in amplitude and had a reduced frequency. Conclusions These results suggest that Gem plays an important role in normal beta-cell function by regulation of calcium signalling.
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Affiliation(s)
- Jenny E Gunton
- Diabetes and Transcription Factors Group, Garvan Institute of Medical Research, Sydney, Australia.
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Conotoxins that confer therapeutic possibilities. Mar Drugs 2012; 10:1244-1265. [PMID: 22822370 PMCID: PMC3397437 DOI: 10.3390/md10061244] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/24/2012] [Accepted: 05/24/2012] [Indexed: 12/19/2022] Open
Abstract
Cone snails produce a distinctive repertoire of venom peptides that are used both as a defense mechanism and also to facilitate the immobilization and digestion of prey. These peptides target a wide variety of voltage- and ligand-gated ion channels, which make them an invaluable resource for studying the properties of these ion channels in normal and diseased states, as well as being a collection of compounds of potential pharmacological use in their own right. Examples include the United States Food and Drug Administration (FDA) approved pharmaceutical drug, Ziconotide (Prialt®; Elan Pharmaceuticals, Inc.) that is the synthetic equivalent of the naturally occurring ω-conotoxin MVIIA, whilst several other conotoxins are currently being used as standard research tools and screened as potential therapeutic drugs in pre-clinical or clinical trials. These developments highlight the importance of driving conotoxin-related research. A PubMed query from 1 January 2007 to 31 August 2011 combined with hand-curation of the retrieved articles allowed for the collation of 98 recently identified conotoxins with therapeutic potential which are selectively discussed in this review. Protein sequence similarity analysis tentatively assigned uncharacterized conotoxins to predicted functional classes. Furthermore, conotoxin therapeutic potential for neurodegenerative disorders (NDD) was also inferred.
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Goehring I, Gerencser AA, Schmidt S, Brand MD, Mulder H, Nicholls DG. Plasma membrane potential oscillations in insulin secreting Ins-1 832/13 cells do not require glycolysis and are not initiated by fluctuations in mitochondrial bioenergetics. J Biol Chem 2012; 287:15706-17. [PMID: 22418435 DOI: 10.1074/jbc.m111.314567] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oscillations in plasma membrane potential play a central role in glucose-induced insulin secretion from pancreatic β-cells and related insulinoma cell lines. We have employed a novel fluorescent plasma membrane potential (Δψ(p)) indicator in combination with indicators of cytoplasmic free Ca(2+) ([Ca(2+)](c)), mitochondrial membrane potential (Δψ(m)), matrix ATP concentration, and NAD(P)H fluorescence to investigate the role of mitochondria in the generation of plasma membrane potential oscillations in clonal INS-1 832/13 β-cells. Elevated glucose caused oscillations in plasma membrane potential and cytoplasmic free Ca(2+) concentration over the same concentration range required for insulin release, although considerable cell-to-cell heterogeneity was observed. Exogenous pyruvate was as effective as glucose in inducing oscillations, both in the presence and absence of 2.8 mM glucose. Increased glucose and pyruvate each produced a concentration-dependent mitochondrial hyperpolarization. The causal relationships between pairs of parameters (Δψ(p) and [Ca(2+)](c), Δψ(p) and NAD(P)H, matrix ATP and [Ca(2+)](c), and Δψ(m) and [Ca(2+)](c)) were investigated at single cell level. It is concluded that, in these β-cells, depolarizing oscillations in Δψ(p) are not initiated by mitochondrial bioenergetic changes. Instead, regardless of substrate, it appears that the mitochondria may simply be required to exceed a critical bioenergetic threshold to allow release of insulin. Once this threshold is exceeded, an autonomous Δψ(p) oscillatory mechanism is initiated.
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Trombetta M, Bonetti S, Boselli M, Turrini F, Malerba G, Trabetti E, Pignatti P, Bonora E, Bonadonna RC. CACNA1E variants affect beta cell function in patients with newly diagnosed type 2 diabetes. the Verona newly diagnosed type 2 diabetes study (VNDS) 3. PLoS One 2012; 7:e32755. [PMID: 22427875 PMCID: PMC3302892 DOI: 10.1371/journal.pone.0032755] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 01/30/2012] [Indexed: 11/23/2022] Open
Abstract
Background Genetic variability of the major subunit (CACNA1E) of the voltage-dependent Ca2+ channel CaV2.3 is associated to risk of type 2 diabetes, insulin resistance and impaired insulin secretion in nondiabetic subjects. The aim of the study was to test whether CACNA1E common variability affects beta cell function and/or insulin sensitivity in patients with newly diagnosed type 2 diabetes. Methodology/Principal Findings In 595 GAD-negative, drug naïve patients (mean±SD; age: 58.5±10.2 yrs; BMI: 29.9±5 kg/m2, HbA1c: 7.0±1.3) with newly diagnosed type 2 diabetes we: 1. genotyped 10 tag SNPs in CACNA1E region reportedly covering ∼93% of CACNA1E common variability: rs558994, rs679931, rs2184945, rs10797728, rs3905011, rs12071300, rs175338, rs3753737, rs2253388 and rs4652679; 2. assessed clinical phenotypes, insulin sensitivity by the euglycemic insulin clamp and beta cell function by state-of-art modelling of glucose/C-peptide curves during OGTT. Five CACNA1E tag SNPs (rs10797728, rs175338, rs2184945, rs3905011 and rs4652679) were associated with specific aspects of beta cell function (p<0.05−0.01). Both major alleles of rs2184945 and rs3905011 were each (p<0.01 and p<0.005, respectively) associated to reduced proportional control with a demonstrable additive effect (p<0.005). In contrast, only the major allele of rs2253388 was related weakly to more severe insulin resistance (p<0.05). Conclusions/Significance In patients with newly diagnosed type 2 diabetes CACNA1E common variability is strongly associated to beta cell function. Genotyping CACNA1E might be of help to infer the beta cell functional phenotype and to select a personalized treatment.
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Affiliation(s)
- Maddalena Trombetta
- Department of Medicine, University of Verona, Verona, Italy
- Azienda Ospedaliera Universitaria Integrata di Verona, Verona, Italy
| | - Sara Bonetti
- Department of Medicine, University of Verona, Verona, Italy
- * E-mail: (SB); (RCB)
| | | | | | - Giovanni Malerba
- Department of Life and Reproduction Sciences, University of Verona, Verona, Italy
| | - Elisabetta Trabetti
- Department of Life and Reproduction Sciences, University of Verona, Verona, Italy
| | - PierFranco Pignatti
- Department of Life and Reproduction Sciences, University of Verona, Verona, Italy
| | - Enzo Bonora
- Department of Medicine, University of Verona, Verona, Italy
- Azienda Ospedaliera Universitaria Integrata di Verona, Verona, Italy
| | - Riccardo C. Bonadonna
- Department of Medicine, University of Verona, Verona, Italy
- Azienda Ospedaliera Universitaria Integrata di Verona, Verona, Italy
- * E-mail: (SB); (RCB)
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Misler S, Gillis KD. Modes of exocytosis and electrogenesis underlying canine biphasic insulin secretion. Front Biosci (Elite Ed) 2012. [PMID: 22201903 DOI: 10.2741/408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Biphasic insulin secretion in response to glucose consists of a transient first phase followed by a progressive second phase. It is a well described feature of whole perfused pancreases as well as isolated pancreatic islets of Langerhans. Applying to single cell assays of exocytosis (capacitance monitoring and amperometry) to single canine Beta-cells we have examined the time courses of granule exocytosis in response to voltage-clamp depolarizations that mimic two modes of glucose-induced electrical activity, and then compared these to biphasic insulin secretion. Action potentials evoked in short trains at frequencies similar those recorded during first phase insulin secretion trigger phasic exocytosis from a small pool of insulin granules that are likely docked near voltage-activated Ca²⁺ channels. In contrast, prolonged voltage-clamp pulses mimicking plateau depolarizations occur during second phase insulin secretion and trigger tonic or continuous exocytosis. Comparing the latter results with ones obtained using photorelease of caged Ca²⁺ in other insulin-secreting cells, we suggest that tonic exocytosis likely results from granule release from a highly Ca²⁺-sensitive pool of insulin granules, likely located further from Ca²⁺ channels. Both phasic and tonic modes of exocytosis are enhanced by glucose, via its metabolism. Hence, in canine Beta-cells we propose that two distinct modes of exocytosis, tuned to two types of electrical activity, may underlay biphasic insulin secretion.
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Affiliation(s)
- Stanley Misler
- Department of Medicine, Washington University School of Medicine, St. Louis MO 63110, USA.
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Regulation of calcium in pancreatic α- and β-cells in health and disease. Cell Calcium 2011; 51:300-8. [PMID: 22177710 PMCID: PMC3334273 DOI: 10.1016/j.ceca.2011.11.006] [Citation(s) in RCA: 169] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 11/10/2011] [Accepted: 11/17/2011] [Indexed: 12/15/2022]
Abstract
The glucoregulatory hormones insulin and glucagon are released from the β- and α-cells of the pancreatic islets. In both cell types, secretion is secondary to firing of action potentials, Ca2+-influx via voltage-gated Ca2+-channels, elevation of [Ca2+]i and initiation of Ca2+-dependent exocytosis. Here we discuss the mechanisms that underlie the reciprocal regulation of insulin and glucagon secretion by changes in plasma glucose, the roles played by different types of voltage-gated Ca2+-channel present in α- and β-cells and the modulation of hormone secretion by Ca2+-dependent and -independent processes. We also consider how subtle changes in Ca2+-signalling may have profound impact on β-cell performance and increase risk of developing type-2 diabetes.
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