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Kalnytska O, Qvist P, Kunz S, Conrad T, Willnow TE, Schmidt V. SORCS2 activity in pancreatic α-cells safeguards insulin granule formation and release from glucose-stressed β-cells. iScience 2024; 27:108725. [PMID: 38226160 PMCID: PMC10788290 DOI: 10.1016/j.isci.2023.108725] [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: 06/09/2023] [Revised: 09/18/2023] [Accepted: 12/11/2023] [Indexed: 01/17/2024] Open
Abstract
Sorting receptor SORCS2 is a stress-response factor protecting neurons from acute insults, such as during epilepsy. SORCS2 is also expressed in the pancreas, yet its action in this tissue remains unknown. Combining metabolic studies in SORCS2-deficient mice with ex vivo functional analyses and single-cell transcriptomics of pancreatic tissues, we identified a role for SORCS2 in protective stress response in pancreatic islets, essential to sustain insulin release. We show that SORCS2 is predominantly expressed in islet alpha cells. Loss of expression coincides with inability of these cells to produce osteopontin, a secreted factor that facilitates insulin release from stressed beta cells. In line with diminished osteopontin levels, beta cells in SORCS2-deficient islets show gene expression patterns indicative of aggravated cell stress, and exhibit defects in insulin granule maturation and a blunted glucose response. These findings corroborate a function for SORCS2 in protective stress response that extends to metabolism.
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Affiliation(s)
- Oleksandra Kalnytska
- Molecular Cardiovascular Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
- Charité – Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Per Qvist
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | - Séverine Kunz
- Technology Platform for Electron Microscopy, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
| | - Thomas Conrad
- Genomics Technology Platform, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 10115 Berlin, Germany
| | - Thomas E. Willnow
- Molecular Cardiovascular Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
- Charité – Universitätsmedizin Berlin, 10117 Berlin, Germany
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | - Vanessa Schmidt
- Molecular Cardiovascular Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
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Endocrine role of bone in the regulation of energy metabolism. Bone Res 2021; 9:25. [PMID: 34016950 PMCID: PMC8137703 DOI: 10.1038/s41413-021-00142-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 12/20/2020] [Accepted: 01/12/2021] [Indexed: 02/06/2023] Open
Abstract
Bone mainly functions as a supportive framework for the whole body and is the major regulator of calcium homeostasis and hematopoietic function. Recently, an increasing number of studies have characterized the significance of bone as an endocrine organ, suggesting that bone-derived factors regulate local bone metabolism and metabolic functions. In addition, these factors can regulate global energy homeostasis by altering insulin sensitivity, feeding behavior, and adipocyte commitment. These findings may provide a new pathological mechanism for related metabolic diseases or be used in the diagnosis, treatment, and prevention of metabolic diseases such as osteoporosis, obesity, and diabetes mellitus. In this review, we summarize the regulatory effect of bone and bone-derived factors on energy metabolism and discuss directions for future research.
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Caserza L, Casula M, Elia E, Bonaventura A, Liberale L, Bertolotto M, Artom N, Minetti S, Contini P, Verzola D, Pontremoli R, Viazzi F, Viviani GL, Bertolini S, Pende A, Pisciotta L, Montecucco F, Carbone F. Serum osteopontin predicts glycaemic profile improvement in metabolic syndrome: A pilot study. Eur J Clin Invest 2021; 51:e13403. [PMID: 32918277 DOI: 10.1111/eci.13403] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 08/06/2020] [Accepted: 08/15/2020] [Indexed: 12/27/2022]
Abstract
Prediabetes is often observed in patients with Metabolic Syndrome (MetS) and might be associated with metabolic and inflammatory alterations. Here, we investigated whether the inflammatory molecule osteopontin (OPN) might have a prognostic impact in a cohort of MetS patients (n = 85) with baseline normal glycaemia or impaired fasting glucose (IFG) over one year of recommended pharmacological treatments and Mediterranean diet. Patients were then followed up for 12 months with intermediate evaluation after 6 months. At all time points, anthropometric and clinical data were recorded, alongside with haematological and biochemical profiles, including serum concentrations of OPN. As expected, Mediterranean diet improves glycaemic profile in patients with IFG. Baseline serum OPN failed to be associated with baseline anthropometric or biochemical variables. At baseline, higher levels of OPN were shown in patients with IFG as compared to normal glycaemia. Two distinct subgroups of patients in whom OPN decreased or remained stable/increased at follow-up were identified. When higher serum OPN levels were observed at baseline, greater reduction was observed at 1-year follow-up. Reduction in circulating OPN levels was associated with metabolic improvement in terms of blood pressure, LDL-c, HDL-c, and glycaemia. At both univariate and adjusted logistic regression analyses, serum OPN emerged as an independent predictor of glycaemic profile improvement at 1-year follow-up (adjOR 1.05 [1.00-1.10]; P = .041). In conclusion, pharmacological and dietetic interventions improved glycaemic profile in patients with MetS. In particular, glycaemic improvement was demonstrated in patients who also reduce circulating OPN levels. Higher OPN levels at baseline predict normalization of glycaemic profile.
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Affiliation(s)
- Lara Caserza
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, Genoa, Italy
| | - Matteo Casula
- Division of Cardiology, Department of Internal Medicine, Turin, Italy
| | - Edorado Elia
- Division of Cardiology, Department of Internal Medicine, Turin, Italy
| | - Aldo Bonaventura
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, Genoa, Italy.,Department of Internal Medicine, Division of Cardiology, Pauley Heart Center, Virginia Commonwealth University, Richmond, VA, USA
| | - Luca Liberale
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, Genoa, Italy.,Center for Molecular Cardiology, University of Zürich, Switzerland
| | - Maria Bertolotto
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, Genoa, Italy
| | - Nathan Artom
- Department of Internal Medicine, Ospedale S. Paolo di Savona, Savona, Italy
| | - Silvia Minetti
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, Genoa, Italy
| | - Paola Contini
- Department of Internal Medicine, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino Genoa, Genoa, Italy
| | - Daniela Verzola
- Department of Internal Medicine, University of Genoa, Genoa, Italy
| | - Roberto Pontremoli
- Department of Internal Medicine, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino Genoa, Genoa, Italy
| | - Franesca Viazzi
- Department of Internal Medicine, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino Genoa, Genoa, Italy
| | | | | | - Aldo Pende
- Department of Internal Medicine, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino Genoa, Genoa, Italy
| | - Livia Pisciotta
- Department of Internal Medicine, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino Genoa, Genoa, Italy
| | - Fabrizio Montecucco
- IRCCS Ospedale Policlinico San Martino Genoa - Italian Cardiovascular Network, Italy.,Department of Internal Medicine and Centre of Excellence for Biomedical Research (CEBR), First Clinic of Internal Medicine, University of Genoa, Genoa, Italy
| | - Federico Carbone
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino Genoa - Italian Cardiovascular Network, Italy
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Melanitou E. Investigation of type 1 diabetes in NOD mice knockout for the osteopontin gene. Gene 2020; 753:144785. [PMID: 32445922 DOI: 10.1016/j.gene.2020.144785] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 05/07/2020] [Accepted: 05/15/2020] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Type 1 diabetes onset is preceded by a pre-inflammatory stage leading to insulitis and followed by targeted destruction of the insulin-producing beta cells of the pancreas. Osteopontin (OPN) is a secreted phosphoprotein with cytokine properties, implicated in many physiological and pathological processes, including infection and autoimmunity. We have previously identified up-regulated osteopontin transcripts in the pancreatic lymph nodes of the NOD (Non-Obese Diabetic) mouse at the pre-diabetic stages. Investigating the underlined disease initiating mechanisms may well contribute to the development of novel preventive therapies. Our aim was to construct opn null mice in a NOD autoimmune-prone genetic background and address the pathogenic or protective role of the osteopontin molecule in the early stages of type 1 diabetes. METHODS We generated opn null mutant mice in a NOD genetic background by serial backcrossing to the existing C57BL/6 opn knockout strain. The presence of opn wild type or null alleles in the congenic lines was evaluated by PCR amplification. We used NOD opn-null mice to assess the phenotypic evolution of type 1 diabetes. The presence of OPN in the serum was evaluated by ELISA and by immunostaining on the mouse tissues. The primary gene structure of the NOD opn encoding gene and protein sequences were compared to the known alleles of other mouse strains. Evaluation of Single Nucleotide Polymorphisms (SNPs) variation between opn alleles of the opn gene is reported. RESULTS In the absence of OPN, type 1 diabetes is accelerated, suggesting a protective role of this cytokine on the insulin-producing cells of the pancreatic islets. Conversely, in the presence of the opn gene, an increase of the OPN protein in the serum of young NOD mice indicates that this molecule might be involved in the immune regulatory events taking place at early stages, prior to disease onset. Our data support that OPN acts as a positive regulator of the early islet autoimmune damage, possibly by a shift of the steady-state of T1D pathogenesis. We report that the OPN protein structure of the NOD/ShiLtJ strain corresponds to the a-type allele of the osteopontin gene. Comparative analysis of the single nucleotide polymorphisms between the a-type and b-type alleles indicates that the majority of variations are within the non-coding regions of the gene. CONCLUSIONS The construction of opn null mice in an autoimmune genetic background (NOD.B6.Cg-spp1-/-) provides important tools for the study of the implication of the OPN in type 1 diabetes, offering the possibility to address the significance of this molecule as an early marker of the disease and as a therapeutic agent in preclinical studies.
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Affiliation(s)
- Evie Melanitou
- Department of Parasites and Insect Vectors, Institut Pasteur, 25-28 rue du Dr Roux, 75724 Paris, Cedex 15, France.
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Dickerson MT, Vierra NC, Milian SC, Dadi PK, Jacobson DA. Osteopontin activates the diabetes-associated potassium channel TALK-1 in pancreatic β-cells. PLoS One 2017; 12:e0175069. [PMID: 28403169 PMCID: PMC5389796 DOI: 10.1371/journal.pone.0175069] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 03/20/2017] [Indexed: 12/17/2022] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) relies on β-cell Ca2+ influx, which is modulated by the two-pore-domain K+ (K2P) channel, TALK-1. A gain-of-function polymorphism in KCNK16, the gene encoding TALK-1, increases risk for developing type-2 diabetes. While TALK-1 serves an important role in modulating GSIS, the regulatory mechanism(s) that control β-cell TALK-1 channels are unknown. Therefore, we employed a membrane-specific yeast two-hybrid (MYTH) assay to identify TALK-1-interacting proteins in human islets, which will assist in determining signaling modalities that modulate TALK-1 function. Twenty-one proteins from a human islet cDNA library interacted with TALK-1. Some of these interactions increased TALK-1 activity, including intracellular osteopontin (iOPN). Intracellular OPN is highly expressed in β-cells and is upregulated under pre-diabetic conditions to help maintain normal β-cell function; however, the functional role of iOPN in β-cells is poorly understood. We found that iOPN colocalized with TALK-1 in pancreatic sections and coimmunoprecipitated with human islet TALK-1 channels. As human β-cells express two K+ channel-forming variants of TALK-1, regulation of these TALK-1 variants by iOPN was assessed. At physiological voltages iOPN activated TALK-1 transcript variant 3 channels but not TALK-1 transcript variant 2 channels. Activation of TALK-1 channels by iOPN also hyperpolarized resting membrane potential (Vm) in HEK293 cells and in primary mouse β-cells. Intracellular OPN was also knocked down in β-cells to test its effect on β-cell TALK-1 channel activity. Reducing β-cell iOPN significantly decreased TALK-1 K+ currents and increased glucose-stimulated Ca2+ influx. Importantly, iOPN did not affect the function of other K2P channels or alter Ca2+ influx into TALK-1 deficient β-cells. These results reveal the first protein interactions with the TALK-1 channel and found that an interaction with iOPN increased β-cell TALK-1 K+ currents. The TALK-1/iOPN complex caused Vm hyperpolarization and reduced β-cell glucose-stimulated Ca2+ influx, which is predicted to inhibit GSIS.
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Affiliation(s)
- Matthew T. Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Nicholas C. Vierra
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Sarah C. Milian
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Prasanna K. Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - David A. Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
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