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Kong L, Yang J, Yang H, Xu B, Yang T, Liu W. Research advances on CaMKs-mediated neurodevelopmental injury. Arch Toxicol 2024:10.1007/s00204-024-03865-5. [PMID: 39292234 DOI: 10.1007/s00204-024-03865-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2024] [Accepted: 09/09/2024] [Indexed: 09/19/2024]
Abstract
Calcium/calmodulin-dependent protein kinases (CaMKs) are important proteins in the calcium signaling cascade response pathway, which can broadly regulate biological functions in vivo. Multifunctional CaMKs play key roles in neural development, including neuronal circuit building, synaptic plasticity establishment, and neurotrophic factor secretion. Currently, four familial proteins, calcium/calmodulin-dependent protein kinase I (CaMKI), calcium/calmodulin-dependent protein kinase II (CaMKII), eukaryotic elongation factor 2 kinase (eEF2K, popularly known as CaMKIII) and calcium/calmodulin-dependent protein kinase IV (CaMKIV), are thought to have been the most extensively studied during neurodevelopment. Although their spatial structures are extremely similar, as well as the initial starting point of activation, both require the activation of calcium and calmodulin (CaM) complexes to be involved in the process, and the phosphorylation sites and modes of each member are different. Furthermore, due to the high structural similarity of CaMKs, their members may play synergistic roles in the regulation of neural development, but different CaMKs also have their own means of regulating neural development. In this review, we first describe the visualized protein structural forms of CaMKI, CaMKII, eEF2K and CaMKIV, and then describe the functions of each kinase in neurodevelopment. After that, we focus on four main mechanisms of neurodevelopmental damage caused by CaMKs: CaMKI/ERK/CREB pathway inhibition leading to dendritic spine structural damage; Ca2+/CaM/CaMKII through induction of mitochondrial kinetic disorders leading to neurodevelopmental damage; CaMKIII/eEF2 hyperphosphorylation affects the establishment of synaptic plasticity; and CaMKIV/JNK/NF-κB through induction of an inflammatory response leading to neurodevelopmental damage. In conclusion, we briefly discuss the pathophysiological significance of aberrant CaMK family expression in neurodevelopmental disorders, as well as the protective effects of conventional CaMKII and CaMKIII antagonists against neurodevelopmental injury.
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Affiliation(s)
- Lingxu Kong
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention, China Medical University, Ministry of Education, Shenyang, China
- Department of Environmental and Occupational Health, School of Public Health, China Medical University, Shenyang, 110122, China
| | - Jing Yang
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention, China Medical University, Ministry of Education, Shenyang, China
- Department of Environmental and Occupational Health, School of Public Health, China Medical University, Shenyang, 110122, China
| | - Huajie Yang
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention, China Medical University, Ministry of Education, Shenyang, China
- Department of Environmental and Occupational Health, School of Public Health, China Medical University, Shenyang, 110122, China
| | - Bin Xu
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention, China Medical University, Ministry of Education, Shenyang, China
- Department of Environmental and Occupational Health, School of Public Health, China Medical University, Shenyang, 110122, China
| | - Tianyao Yang
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention, China Medical University, Ministry of Education, Shenyang, China.
- Department of Environmental and Occupational Health, School of Public Health, China Medical University, Shenyang, 110122, China.
| | - Wei Liu
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention, China Medical University, Ministry of Education, Shenyang, China.
- Department of Environmental and Occupational Health, School of Public Health, China Medical University, Shenyang, 110122, China.
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Molecular Mechanisms Underlying Ca2+/Calmodulin-Dependent Protein Kinase Kinase Signal Transduction. Int J Mol Sci 2022; 23:ijms231911025. [PMID: 36232320 PMCID: PMC9570080 DOI: 10.3390/ijms231911025] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/16/2022] [Accepted: 09/16/2022] [Indexed: 12/03/2022] Open
Abstract
Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) is the activating kinase for multiple downstream kinases, including CaM-kinase I (CaMKI), CaM-kinase IV (CaMKIV), protein kinase B (PKB/Akt), and 5′AMP-kinase (AMPK), through the phosphorylation of their activation-loop Thr residues in response to increasing the intracellular Ca2+ concentration, as CaMKK itself is a Ca2+/CaM-dependent enzyme. The CaMKK-mediated kinase cascade plays important roles in a number of Ca2+-dependent pathways, such as neuronal morphogenesis and plasticity, transcriptional activation, autophagy, and metabolic regulation, as well as in pathophysiological pathways, including cancer progression, metabolic syndrome, and mental disorders. This review focuses on the molecular mechanism underlying CaMKK-mediated signal transduction in normal and pathophysiological conditions. We summarize the current knowledge of the structural, functional, and physiological properties of the regulatory kinase, CaMKK, and the development and application of its pharmacological inhibitors.
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Ibata T, Lyu J, Imachi H, Fukunaga K, Sato S, Kobayashi T, Saheki T, Yoshimura T, Murao K. Effects of 2-Methoxyestradiol, a Main Metabolite of Estradiol on Hepatic ABCA1 Expression in HepG2 Cells. Nutrients 2022; 14:nu14020288. [PMID: 35057469 PMCID: PMC8779252 DOI: 10.3390/nu14020288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 02/04/2023] Open
Abstract
ATP-binding cassette transporter A1 (ABCA1) is a key regulator of lipid efflux, and the absence of ABCA1 induces hepatic lipid accumulation, which is one of the major causes of fatty liver. 2-Methoxyestradiol (2-ME2) has been demonstrated to protect against fatty liver. In this study, we investigated the effects of 2-ME2 on the hepatic lipid content and ABCA1 expression. We found that 2-ME2 dose-dependently increased ABCA1 expression, and therefore, the lipid content was significantly decreased in HepG2 cells. 2-ME2 enhanced the ABCA1 promoter activity; however, this effect was reduced after the inhibition of the PI3K pathway. The overexpression of Akt or p110 induced ABCA1 promoter activity, while dominant-negative Akt diminished the ability of 2-ME2 on ABCA1 promoter activity. Further, 2-ME2 stimulated the rapid phosphorylation of Akt and FoxO1 and reduced the nuclear accumulation of FoxO1. Chromatin immunoprecipitation confirmed that FoxO1 bonded to the ABCA1 promoter region. The binding was reduced by 2-ME2, which facilitated ABCA1 gene transcription. Furthermore, mutating FoxO1-binding sites in the ABCA1 promoter region or treatment with FoxO1-specific siRNA disrupted the effect of 2-ME2 on ABCA1 expression. All of our results demonstrated that 2-ME2 might upregulate ABCA1 expression via the PI3K/Akt/FoxO1 pathway, which thus reduces the lipid content in hepatocytes.
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Affiliation(s)
- Tomohiro Ibata
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Jingya Lyu
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
- Department of Physiology, School of Medicine, Jinan University, 601 Huangpu Avenue West, Tianhe District, Guangzhou 510632, China
| | - Hitomi Imachi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Kensaku Fukunaga
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Seisuke Sato
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Toshihiro Kobayashi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Takanobu Saheki
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Takafumi Yoshimura
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
| | - Koji Murao
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho 761-0793, Kagawa, Japan; (T.I.); (J.L.); (H.I.); (K.F.); (S.S.); (T.K.); (T.S.); (T.Y.)
- Correspondence:
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Zhou X, Guo W, Yin H, Chen J, Ma L, Yang Q, Zhao Y, Li S, Liu W, Li H. Whole Exome Sequencing Study in a Family with Type 2 Diabetes Mellitus. Int J Gen Med 2021; 14:8217-8229. [PMID: 34815695 PMCID: PMC8605871 DOI: 10.2147/ijgm.s335090] [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: 08/19/2021] [Accepted: 10/01/2021] [Indexed: 12/25/2022] Open
Abstract
Background Type 2 diabetes mellitus (T2DM) is characterized by β cell decline in the pancreas and insulin resistance. This study aimed to investigate the possible pathogenic gene mutation sites of T2DM patients using whole exome sequencing. Materials and Methods We recruited a Chinese family with 3-generation history of diabetes. The whole blood genomic DNA of seven members of the family was extracted and sent for whole exome sequencing. Biological information was analyzed with in silico prediction methods, including significance analysis of single nucleotide polymorphism (SNP)/Indel site, and analysis of specific SNP/Indel proteins and their potential mechanisms. Results Six out of seven members of the family were diagnosed with diabetes. All DNA samples (23 kb) met quality requirements of library construction. Clean reads of each sample demonstrated high Q20 and Q30 (>80%), indicating good sequencing quality of sequencing data. A total of 130,693 SNPs and 15,928 Indels were found in DNA samples. A total of 22 significant SNPs and Indel mutation sites located on 19 genes were obtained, including ZCCHC3, SYN2, RPL14, SRRD, AMD1, CAMKK2, ZNF787, RNF157, NPIPB15, ALG3, KIAA0040, MAST2, ESRRA, C8orf58, PNLIPRP1, DACH1, MACC1, CAPN9 and DMKN. An rs2305205 mutation of PNLIPRP1 gene and an rs778701848 mutation of CAMKK2 gene may be associated with the pathogenesis of T2DM in this family. Conclusion Exons of these diabetic patients demonstrated an rs2305205 mutation in PNLIPRP1 gene and an rs778701848 mutation in CAMKK2 gene. These two mutations might promote T2DM occurrence through reducing sensitivity of peripheral tissue to insulin and reducing insulin secretion.
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Affiliation(s)
- Xiaowei Zhou
- Department of Diabetes, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Weichang Guo
- Department of Physical Education, Kunming Medical University, Kunming, People's Republic of China
| | - Hejia Yin
- Department of Diabetes, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Jie Chen
- Department of Diabetes, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Liju Ma
- Department of Clinical Laboratory, First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Qiuping Yang
- Department of Geriatrics, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Yan Zhao
- Department of Diabetes, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Shaoyou Li
- Department of NHC Key Laboratory of Drug Addiction Medicine, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Weijun Liu
- Department of Diabetes, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
| | - Huifang Li
- Department of Diabetes, The First Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China
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Li R, Sun X, Li P, Li W, Zhao L, Zhu L, Zhu S. GLP-1-Induced AMPK Activation Inhibits PARP-1 and Promotes LXR-Mediated ABCA1 Expression to Protect Pancreatic β-Cells Against Cholesterol-Induced Toxicity Through Cholesterol Efflux. Front Cell Dev Biol 2021; 9:646113. [PMID: 34307343 PMCID: PMC8292745 DOI: 10.3389/fcell.2021.646113] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 06/09/2021] [Indexed: 12/11/2022] Open
Abstract
T2DM (Type 2 diabetes) is a complex, chronic disease characterized as insulin resistance and islet β-cell dysfunction. Bariatric surgeries such as Roux-en-Y gastric bypass (RYGB) surgery and laparoscopic sleeve gastrectomy (LSG) have become part of a critical treatment regimen in the treatment of obesity and T2DM. Moreover, GLP-1 increase following bariatric surgery has been regarded as a significant event in bariatric surgery-induced remission of T2DM. In this study, a high concentration cholesterol-induced lipotoxicity was observed in INS-1 cells, including inhibited cell viability and insulin secretion. Enhanced cell apoptosis and inhibited cholesterol efflux from INS-1 cells; meanwhile, ABCA1 protein level was decreased by cholesterol stimulation. Cholesterol-induced toxicity and ABCA1 downregulation were attenuated by GLP-1 agonist EX-4. GLP-1 induced AMPK phosphorylation during the protection against cholesterol-induced toxicity. Under cholesterol stimulation, GLP-1-induced AMPK activation inhibited PARP-1 activity, therefore attenuating cholesterol-induced toxicity in INS-1 cells. In INS-1 cells, PARP-1 directly interacted with LXR, leading to the poly(ADP-ribosyl)ation of LXRα and downregulation of LXR-mediated ABCA1 expression. In the STZ-induced T2DM model in rats, RYGB surgery or EX-4 treatment improved the glucose metabolism and lipid metabolism in rats through GLP-1 inhibition of PARP-1 activity. In conclusion, GLP-1 inhibits PARP-1 to protect islet β cell function against cholesterol-induced toxicity in vitro and in vivo through enhancing cholesterol efflux. GLP-1-induced AMPK and LXR-mediated ABCA1 expression are involved in GLP-1 protective effects.
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Affiliation(s)
- Rao Li
- Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Xulong Sun
- Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Pengzhou Li
- Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Weizheng Li
- Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Lei Zhao
- Department of General Surgery, First Affiliated Hospital of University of South China, Hengyang, China
| | - Liyong Zhu
- Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Shaihong Zhu
- Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, China
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Liu J, Yang R, Meng H, Zhou T, He Q. In vitro treatment of 3 T3-L1 adipocytes with recombinant Calcium/calmodulin-dependent Protein Kinase IV (CaMKIV) limits ER stress and improves insulin sensitivity through inhibition of autophagy via the mTOR/CREB signaling pathway. BMC Endocr Disord 2020; 20:104. [PMID: 32660483 PMCID: PMC7359471 DOI: 10.1186/s12902-020-00589-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 07/07/2020] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Recently, CaMKIV has been identified as a potential regulator of skeletal muscle glucose metabolism, it can also affect insulin gene expression in pancreas. However, its effects on adipose insulin resistance have yet to be explored. Autophagy has been shown as a potential therapeutic target for ER (endoplasmic reticulum) stress and insulin resistance. The purpose of this study is to investigate the effects of CaMKIV on ER stress, autophagic function and insulin signaling in tunicamycin-treated adipocytes. METHODS In this study, mature 3 T3-L1 adipocytes were treated with tunicamycin to induce ER stress. Tunicamycin-treated 3 T3-L1 adipocytes were treated with recombinant CaMKIV in the presence or absence of targeted-siRNA mediated down-regulation of CREB and mTOR. The ER stress markers, autophagy activation, mTOR/CREB signaling and insulin sensitivity were analyzed by western blotting or electron microscopy. RESULTS Treatment with CaMKIV significantly reversed tunicamycin-induced expression of p-PERK, cleaved-ATF6, Atg7 and LC3II. It also reduced p62 expression. In addition, levels of p-Akt and p-IRS-1 were increased. Moreover, CaMKIV inhibited activated ER stress and insulin resistance in Atg7 siRNA transfected adipocytes. However, the protective effects of CaMKIV on ER stress, insulin signaling, and autophagy function were nullified by suppression of mTOR or CREB in tunicamycin-treated adipocytes. CONCLUSION This study proves recombinant CaMKIV inhibits tunicamycin-induced ER stress and insulin resistance by regulating autophagy. The protective effect of CaMKIV in adipocytes is affected at least partly through mTOR/CREB signaling. Our finding may offer novel opportunities for treating obesity and type 2 diabetes.
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Affiliation(s)
- Jiali Liu
- Department of Clinical Laboratory, Xi'an Jiaotong University Second Affiliated Hospital, 157 West 5 Road, Xi'an, 710004, Shaanxi, China
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Ruihua Yang
- Department of Clinical Laboratory, Xi'an Jiaotong University Second Affiliated Hospital, 157 West 5 Road, Xi'an, 710004, Shaanxi, China
| | - Hao Meng
- Department of Clinical Laboratory, Xi'an Jiaotong University Second Affiliated Hospital, 157 West 5 Road, Xi'an, 710004, Shaanxi, China
| | - Ting Zhou
- Department of Clinical Laboratory, Xi'an Jiaotong University Second Affiliated Hospital, 157 West 5 Road, Xi'an, 710004, Shaanxi, China
| | - Qian He
- Department of Clinical Laboratory, Xi'an Jiaotong University Second Affiliated Hospital, 157 West 5 Road, Xi'an, 710004, Shaanxi, China.
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Lyu J, Imachi H, Fukunaga K, Sato S, Kobayashi T, Dong T, Saheki T, Matsumoto M, Iwama H, Zhang H, Murao K. Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes. Mol Metab 2020; 34:16-26. [PMID: 32180556 PMCID: PMC6997505 DOI: 10.1016/j.molmet.2019.12.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 12/25/2019] [Accepted: 12/30/2019] [Indexed: 12/17/2022] Open
Abstract
Objective Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) influences hepatic cholesterol transportation. Accumulation of hepatic cholesterol leads to fatty liver disease, which is improved by glucagon-like peptide 1 (GLP-1) in diabetes. Therefore, we analyzed the molecular mechanism in the regulation of hepatic ABCA1 by GLP-1 analogue exendin-4. Methods Hepatic ABCA1 expression and transcription were checked by western blotting, real-time polymerase chain reaction (PCR), and luciferase assay in HepG2 cells. Chromatin immunoprecipitation (ChIP) and site-directed mutagenesis were employed to determine transcriptional regulation of the ABCA1 gene. Prolactin regulatory element-binding (PREB)-transgenic mice were generated to access the effect of exendin-4 on improving lipid accumulation caused by a high-fat diet (HFD). Results Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca2+/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo, exendin-4 or overexpression of PREB increased hepatic ABCA1 expression and decreased hepatic lipid accumulation and high plasma cholesterol caused by a HFD. Conclusions Our data shows that exendin-4 stimulates hepatic ABCA1 expression and decreases lipid accumulation by the CaMKK/CaMKIV/PREB pathway, suggesting that ABCA1 and PREB might be the therapeutic targets in fatty liver disease. The GLP-1R agonist exendin-4 suppressed lipid accumulation by upregulating ABCA1 expression in hepatocytes. Exendin-4 regulated the expression and transcription of hepatic ABCA1 via the CaMKK/CaMKIV/PREB pathway. Overexpression of PREB or exendin-4 protected mouse liver from fatty liver by upregulation of ABCA1.
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Affiliation(s)
- Jingya Lyu
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan; Department of Cell Biology, Jiangsu Key Laboratory of Stem Cell Research, Medical College of Soochow University, Ren Ai Road 199, Suzhou, 215123, China.
| | - Hitomi Imachi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Kensaku Fukunaga
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Seisuke Sato
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Toshihiro Kobayashi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Tao Dong
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Takanobu Saheki
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Mari Matsumoto
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Hisakazu Iwama
- Life Science Research Center, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Huanxiang Zhang
- Department of Cell Biology, Jiangsu Key Laboratory of Stem Cell Research, Medical College of Soochow University, Ren Ai Road 199, Suzhou, 215123, China
| | - Koji Murao
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
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Regulation of Multifunctional Calcium/Calmodulin Stimulated Protein Kinases by Molecular Targeting. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:649-679. [PMID: 31646529 DOI: 10.1007/978-3-030-12457-1_26] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Multifunctional calcium/calmodulin-stimulated protein kinases control a broad range of cellular functions in a multitude of cell types. This family of kinases contain several structural similarities and all are regulated by phosphorylation, which either activates, inhibits or modulates their kinase activity. As these protein kinases are widely or ubiquitously expressed, and yet regulate a broad range of different cellular functions, additional levels of regulation exist that control these cell-specific functions. Of particular importance for this specificity of function for multifunctional kinases is the expression of specific binding proteins that mediate molecular targeting. These molecular targeting mechanisms allow pools of kinase in different cells, or parts of a cell, to respond differently to activation and produce different functional outcomes.
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Coppola T, Beraud-Dufour S, Lebrun P, Blondeau N. Bridging the Gap Between Diabetes and Stroke in Search of High Clinical Relevance Therapeutic Targets. Neuromolecular Med 2019; 21:432-444. [PMID: 31489567 DOI: 10.1007/s12017-019-08563-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 08/13/2019] [Indexed: 12/20/2022]
Abstract
Diabetes affects more than 425 million people worldwide, a scale approaching pandemic proportion. Diabetes represents a major risk factor for stroke, and therefore is actively addressed for stroke prevention. However, how diabetes affects stroke severity has not yet been extensively considered, which is surprising given the evident but understudied common mechanistic features of both pathologies. The increase in number of diabetic people, incidence of stroke in the presence of this specific risk factor, and the exacerbation of ischemic brain damage in diabetic conditions (at least in animal models) warrants the need to integrate this comorbidity in preclinical studies of brain ischemia to develop novel therapeutic approaches. Therefore, a better understanding of the commonalties involved in the course of both diseases would offer the promise of discovering novel neuroprotective pathways that would be more appropriated to clinical scenarios. In this article, we will review the relevant mechanisms that have been identified as common traits of both pathologies and that could be, to our knowledge, potential targets in both pathologies.
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Affiliation(s)
- Thierry Coppola
- Université Côte d'Azur, CNRS, IPMC, 660 route des Lucioles, 06560, Valbonne, France.
| | - Sophie Beraud-Dufour
- Université Côte d'Azur, CNRS, IPMC, 660 route des Lucioles, 06560, Valbonne, France
| | - Patricia Lebrun
- Université Côte d'Azur, CNRS, IPMC, 660 route des Lucioles, 06560, Valbonne, France
| | - Nicolas Blondeau
- Université Côte d'Azur, CNRS, IPMC, 660 route des Lucioles, 06560, Valbonne, France.
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Chitooligosaccharide Biguanide Repairs Islet β‐Cell Dysfunction by Activating the IRS‐2/PI3K/Akt Signaling Pathway in Type 2 Diabetic Rats. ADVANCED THERAPEUTICS 2019. [DOI: 10.1002/adtp.201800136] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Leem J, Shim HM, Cho H, Park JH. Octanoic acid potentiates glucose-stimulated insulin secretion and expression of glucokinase through the olfactory receptor in pancreatic β-cells. Biochem Biophys Res Commun 2018; 503:278-284. [PMID: 29885841 DOI: 10.1016/j.bbrc.2018.06.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 06/07/2018] [Indexed: 12/30/2022]
Abstract
Olfactory receptors (ORs) are G protein-coupled receptors that mediate olfactory chemosensation, leading to the perception of smell. ORs are expressed in many tissues, but their functions are largely unknown. Here, we show that the olfactory receptor Olfr15 is highly and selectively expressed in both mouse pancreatic β-cells and MIN6 cells. In addition, octanoic acid (OA), a medium-chain fatty acid, potentiates glucose-stimulated insulin secretion (GSIS). The OA-induced enhancement of GSIS was inhibited by Olfr15 knockdown. Treatment with a PLC inhibitor or an Ins(1,4,5)P3 receptor (IP3R) antagonist also blocked the OA-induced enhancement of GSIS. These results suggest that OA potentiates GSIS via Olfr15 though the PLC-IP3 pathway. Furthermore, long-term treatment with OA increased cellular glucose uptake in MIN6 cells by up-regulating the expression of glucokinase (GK). Moreover, this process was blocked by an IP3R antagonist and a Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) inhibitor. Similarly, OA stimulated GK promoter activity, while either Olfr15 or CaMKIV knockdown blocked the stimulatory effect of OA on GK promoter activity. These results suggest that long-term treatment of OA induces GK promoter activity via Olfr15 through the IP3-CaMKK/CaMKIV pathway. In islets from type 2 diabetic mice, the expression level of Olfr15 and the OA-induced enhancement of GSIS were strongly reduced. Collectively, our results highlight the crucial role of the olfactory receptor Olfr15 in potentiating GSIS in pancreatic β-cells, suggesting that Olfr15 may be an important therapeutic target in type 2 diabetes.
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Affiliation(s)
- Jaechan Leem
- Department of Immunology, School of Medicine, Catholic University of Daegu, Daegu, 42472, South Korea
| | - Hae-Min Shim
- Department of Physiology, School of Medicine, Keimyung University, Daegu, 42601, South Korea
| | - Hochan Cho
- Division of Endocrinology, Department of Internal Medicine, Keimyung University Dongsan Medical Center, Daegu, 41931, South Korea
| | - Jae-Hyung Park
- Department of Physiology, School of Medicine, Keimyung University, Daegu, 42601, South Korea; Institute for Medical Science, Keimyung University, Daegu, 42601, South Korea.
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12
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Arden C. A role for Glucagon-Like Peptide-1 in the regulation of β-cell autophagy. Peptides 2018; 100:85-93. [PMID: 29412836 DOI: 10.1016/j.peptides.2017.12.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 12/04/2017] [Accepted: 12/04/2017] [Indexed: 12/11/2022]
Abstract
Autophagy is a highly conserved intracellular recycling pathway that serves to recycle damaged organelles/proteins or superfluous nutrients during times of nutritional stress to provide energy to maintain intracellular homeostasis and sustain core metabolic functions. Under these conditions, autophagy functions as a cell survival mechanism but impairment of this pathway can lead to pro-death stimuli. Due to their role in synthesising and secreting insulin, pancreatic β-cells have a high requirement for robust degradation pathways. Recent research suggests that functional autophagy is required to maintain β-cell survival and function in response to high fat diet suggesting a pro-survival role. However, a role for autophagy has also been implicated in the pathogenesis of type 2 diabetes. Thus, the pro-survival vs pro-death role of autophagy in regulating β-cell mass requires discussion. Emerging evidence suggests that Glucagon-Like Peptide-1 (GLP-1) may exert beneficial effects on glucose homeostasis via autophagy-dependent pathways both in pancreatic β-cells and in other cell types. The aim of the current review is to: i) summarise the literature surrounding β-cell autophagy and its pro-death vs pro-survival role in regulating β-cell mass; ii) review the literature describing the impact of GLP-1 on β-cell autophagy and in other cell types; iii) discuss the potential underlying mechanisms.
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Affiliation(s)
- Catherine Arden
- Institute of Cellular Medicine, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
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13
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Lyu J, Imachi H, Yoshimoto T, Fukunaga K, Sato S, Ibata T, Kobayashi T, Dong T, Yonezaki K, Yamaji N, Kikuchi F, Iwama H, Ishikawa R, Haba R, Sugiyama Y, Zhang H, Murao K. Thyroid stimulating hormone stimulates the expression of glucose transporter 2 via its receptor in pancreatic β cell line, INS-1 cells. Sci Rep 2018; 8:1986. [PMID: 29386586 PMCID: PMC5792451 DOI: 10.1038/s41598-018-20449-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 01/17/2018] [Indexed: 12/30/2022] Open
Abstract
Thyroid stimulating hormone (TSH) stimulates the secretion of thyroid hormones by binding the TSH receptor (TSHR). TSHR is well-known to be expressed in thyroid tissue, excepting it, TSHR has also been expressed in many other tissues. In this study, we have examined the expression of TSHR in rat pancreatic islets and evaluated the role of TSH in regulating pancreas-specific gene expression. TSHR was confirmed to be expressed in rodent pancreatic islets and its cell line, INS-1 cells. TSH directly affected the glucose uptake in INS cells by up-regulating the expression of GLUT2, and furthermore this process was blocked by SB203580, the specific inhibitor of the p38 MAPK signaling pathway. Similarly, TSH stimulated GLUT2 promoter activity, while both a dominant-negative p38MAPK α isoform (p38MAPK α-DN) and the specific inhibitor for p38MAPK α abolished the stimulatory effect of TSH on GLUT2 promoter activity. Finally, INS-1 cells treated with TSH showed increased protein level of glucokinase and enhanced glucose-stimulated insulin secretion. Together, these results confirm that TSHR is expressed in INS-1 cells and rat pancreatic islets, and suggest that activation of the p38MAPK α might be required for TSH-induced GLUT2 gene transcription in pancreatic β cells.
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Affiliation(s)
- Jingya Lyu
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan.,Department of Cell Biology, Medical College of Soochow University, Jiangsu Key Laboratory of Stem Cell Research, Ren Ai Road 199, Suzhou Industrial Park, Suzhou, 215123, China
| | - Hitomi Imachi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Takuo Yoshimoto
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Kensaku Fukunaga
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Seisuke Sato
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Tomohiro Ibata
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Toshihiro Kobayashi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Tao Dong
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Kazuko Yonezaki
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Nao Yamaji
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Fumi Kikuchi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Hisakazu Iwama
- Life Science Research Center, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Ryou Ishikawa
- Department of Diagnostic Pathology, Kagawa University Hospital, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Reiji Haba
- Department of Diagnostic Pathology, Kagawa University Hospital, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan
| | - Yasunori Sugiyama
- Department of Life Sciences, Faculty of Agriculture, Kagawa University, 2393, Miki-cho, Kita-gun, Kagawa, 761-0795, Japan
| | - Huanxiang Zhang
- Department of Cell Biology, Medical College of Soochow University, Jiangsu Key Laboratory of Stem Cell Research, Ren Ai Road 199, Suzhou Industrial Park, Suzhou, 215123, China.
| | - Koji Murao
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan.
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14
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Mukherjee S, Sheng W, Sun R, Janssen LJ. Ca2+/calmodulin-dependent protein kinase IIβ and IIδ mediate TGFβ-induced transduction of fibronectin and collagen in human pulmonary fibroblasts. Am J Physiol Lung Cell Mol Physiol 2017; 312:L510-L519. [DOI: 10.1152/ajplung.00084.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 01/19/2017] [Accepted: 01/20/2017] [Indexed: 12/20/2022] Open
Abstract
It is now clear that in addition to activating several complex kinase pathways (Smad, MAP kinase, PI3 kinase), TGFβ also acts by elevating cytosolic Ca2+ concentration within human pulmonary fibroblasts. Ca2+/calmodulin-dependent protein kinase II (CamK II) is also known to regulate gene expression in fibroblasts. In this study, we examined the interactions between calcium signaling, activation of CamK and other kinases, and extracellular matrix (ECM) gene expression. Human pulmonary fibroblasts were cultured and stimulated with artificially generated Ca2+ pulses in the absence of TGFβ, or with TGFβ (1 nM) or vehicle in the presence of various blockers of Ca2+ signaling. PCR and Western blotting were used to measure gene expression and protein levels, respectively. We found that Ca2+ pulses in the absence of TGFβ increased ECM gene expression in a pulse frequency-dependent manner, and that blocking Ca2+ signaling and the CamK II pathway significantly reduced TGFβ-mediated ECM gene expression, without having any effects on other kinase pathways (Smad, PI3 kinase, or MAP kinase). We also found that TGFβ elevated the expression of CamK IIβ and CamK IIδ, while siRNA silencing of those two subtypes significantly reduced TGFβ-mediated expression of collagen A1 and fibronectin 1. Our data suggest that TGFβ induces the expression of CamK IIβ and CamK IIδ, which in turn are activated by TGFβ-evoked Ca2+ waves in a frequency-dependent manner, leading to increased expression of ECM proteins.
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Affiliation(s)
- Subhendu Mukherjee
- Firestone Institute for Respiratory Health, St. Joseph’s Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Wei Sheng
- Firestone Institute for Respiratory Health, St. Joseph’s Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Rui Sun
- Firestone Institute for Respiratory Health, St. Joseph’s Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Luke J. Janssen
- Firestone Institute for Respiratory Health, St. Joseph’s Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
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15
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Schernthaner-Reiter MH, Schernthaner G. Combination therapy of SGLT2 inhibitors with incretin-based therapies for the treatment of type 2 diabetes mellitus: Effects and mechanisms of action. Expert Rev Endocrinol Metab 2016; 11:281-296. [PMID: 30058933 DOI: 10.1586/17446651.2016.1151783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is a growing health problem worldwide; its pathogenesis is multifactorial and its progressive nature often necessitates a combination therapy with multiple antihyperglycemic agents. Sodium glucose cotransporter 2 (SGLT2) inhibitors and the incretin-based therapies - dipeptidyl peptidase 4(DPP-4) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists - were introduced for the treatment of T2DM within the last decade. Evidence of the beneficial effects of these antihyperglycemic agents on micro- and macrovascular complications have started to emerge, which will become important in individualizing different combinations of antihyperglycemic agents to different patient populations. We review here the mechanisms of action, glycemic and cardiovascular effects of SGLT2 inhibitors and incretin-based therapies and their combination in the treatment of T2DM.
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Affiliation(s)
- Marie Helene Schernthaner-Reiter
- a Clinical Division of Endocrinology and Metabolism, Department of Internal Medicine III , Medical University of Vienna , Vienna , Austria
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16
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Song Z, Wang H, Zhu L, Han M, Gao Y, Du Y, Wen Y. Curcumin improves high glucose-induced INS-1 cell insulin resistance via activation of insulin signaling. Food Funct 2016; 6:461-9. [PMID: 25474544 DOI: 10.1039/c4fo00608a] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Curcumin is a yellow pigment isolated from Corcuma longan. This research investigates the improvement of curcumin on INS-1 cells with insulin resistance induced by high glucose. INS-1 cells were treated with high glucose (30 mmol L(-1)) for 48 h. Subsequently, the medium was replaced with curcumin for 24 h. Curcumin effectively increased insulin gene expression and glucose stimulated insulin secretion (GSIS) in a dose-dependent manner. Furthermore, the molecular mechanism of curcumin-induced insulin expression and secretion in high glucose-induced INS-1 cells was investigated in this study. Curcumin increased the expression of glucose transporter 2 (GLUT2) and phosphorylation of insulin receptor (IR), insulin receptor substrate-1 (IRS1), phosphatidylinositol-3-kinase (PI3K) and AKT in the INS-1 cells. Moreover, curcumin stimulation increased the expression of PDX-1 and GCK. This investigation suggests that curcumin prevented high glucose-reduced insulin expression and secretion through activation of the PI3K/Akt/GLUT2 pathway in INS-1 cells.
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Affiliation(s)
- Zhenfeng Song
- Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, 157 Baojian Road, Nangang District, 150086, Harbin, People's Republic of China.
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17
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Janssen LJ, Mukherjee S, Ask K. Calcium Homeostasis and Ionic Mechanisms in Pulmonary Fibroblasts. Am J Respir Cell Mol Biol 2015; 53:135-48. [PMID: 25785898 DOI: 10.1165/rcmb.2014-0269tr] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Fibroblasts are key cellular mediators of many chronic interstitial lung diseases, including idiopathic pulmonary fibrosis, scleroderma, sarcoidosis, drug-induced interstitial lung disease, and interstitial lung disease in connective tissue disease. A great deal of effort has been expended to understand the signaling mechanisms underlying the various cellular functions of fibroblasts. Recently, it has been shown that Ca(2+) oscillations play a central role in the regulation of gene expression in human pulmonary fibroblasts. However, the mechanisms whereby cytosolic [Ca(2+)] are regulated and [Ca(2+)] oscillations transduced are both poorly understood. In this review, we present the general concepts of [Ca(2+)] homeostasis, of ionic mechanisms responsible for various Ca(2+) fluxes, and of regulation of gene expression by [Ca(2+)]. In each case, we then also summarize the original findings that pertain specifically to pulmonary fibroblasts. From these data, we propose an overall signaling cascade by which excitation of the fibroblasts triggers pulsatile release of internally sequestered Ca(2+), which, in turn, activates membrane conductances, including voltage-dependent Ca(2+) influx pathways. Collectively, these events produce recurring Ca(2+) oscillations, the frequency of which is transduced by Ca(2+)-dependent transcription factors, which, in turn, orchestrate a variety of cellular events, including proliferation, synthesis/secretion of extracellular matrix proteins, autoactivation (production of transforming growth factor-β), and transformation into myofibroblasts. That unifying hypothesis, in turn, allows us to highlight several specific cellular targets and therapeutic intervention strategies aimed at controlling unwanted pulmonary fibrosis. The relationships between Ca(2+) signaling events and the unfolded protein response and apoptosis are also explored.
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Affiliation(s)
- Luke J Janssen
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, and Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Subhendu Mukherjee
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, and Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Kjetil Ask
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, and Department of Medicine, McMaster University, Hamilton, Ontario, Canada
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18
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Dhanesha N, Joharapurkar A, Shah G, Kshirsagar S, Patel V, Patel K, Bahekar R, Jain M. Treatment with exendin-4 improves the antidiabetic efficacy and reverses hepatic steatosis in glucokinase activator treated db/db mice. Eur J Pharmacol 2013; 714:188-92. [PMID: 23810686 DOI: 10.1016/j.ejphar.2013.06.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 05/29/2013] [Accepted: 06/08/2013] [Indexed: 01/27/2023]
Abstract
The glucokinase activators improve the fasting as well as postprandial glucose control and are important investigational drugs for the treatment of diabetes. However, recent studies have implicated that continuous activation of glucokinase with a small molecule activator can increase hepatic triglycerides and the long term glucose control is not achieved. In this study, we investigated the effect of combination of glucokinase activator (GKA, Piragliatin) with GLP-1 receptor agonist exendin-4 (Ex-4) in male db/db mice. Twelve weeks combination treatment in the db/db mice resulted in a significant decrease in body weight gain, food consumption, random glucose and %HbA1c. The decrease in serum glucose and %HbA1c in combination group was more profound and significantly different than that of individual treatment (GKA or Ex-4) group. GKA treatment increased hepatic triglycerides, whereas combination of Ex-4 with GKA attenuated hepatic steatosis. The combination of GKA with Ex-4 reduced the hepatic lipid accumulation, improved the insulin sensitivity, and reduced hepatic glucose production in db/db mice. Overall, our data indicate that combination of GKA and GLP-1 receptor agonist Ex-4 improves glucose homeostasis, shows antiobesity activity, without causing harmful side effects like fatty liver.
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Affiliation(s)
- Nirav Dhanesha
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H. No. 8A, Moraiya, Ahmedabad 382210, India
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19
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Patel V, Joharapurkar A, Gandhi T, Patel K, Dhanesha N, Kshirsagar S, Dhote V, Detroja J, Bahekar R, Jain M. Omeprazole improves the anti-obesity and antidiabetic effects of exendin-4 in db/db mice (-4 db/db)*. J Diabetes 2013; 5:163-71. [PMID: 22830490 DOI: 10.1111/j.1753-0407.2012.00227.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND In addition to its glucoregulatory actions, exendin-4, a stable glucagon-like peptide-1 receptor agonist, exhibits protective effects in the pancreas and anti-obesity effects. Suitable combination treatment with other anti-obesity or pancreas protective agents would be an effective approach to optimize these additional effects. In the present study, we investigated the effects of the addition of omeprazole, a proton pump inhibitor, to exendin-4 in db/db mice, an experimental model of obesity and type 2 diabetes. METHODS The effects repeated dose treatment for 14 days with exendin-4 (8 μg/kg, s.c.) and omeprazole (30 mg/kg, s.c.) on glycemic control, food intake, and body weight were determined in obese and hyperglycemic db/db mice. The effects of these treatments on plasma gastrin, ghrelin, and leptin levels were determined, along with effects on nausea-like symptoms. The pancreatic effects of the repeated dose treatment were assessed by measuring %HbA1c in the circulation as well as pancreatic insulin and glucagon content and glucokinase activity. RESULTS Combination treatment resulted in significant decreases in plasma leptin and ghrelin levels after repeated dosing. Omeprazole improved the anorectic and body weight-lowering effects and reversed the inhibitory effect of exendin-4 on gastrin levels after repeated dose treatment. The 14-day combination treatment significantly reduced glucose excursion and improved insulin levels, with a concomitant decrease in %HbA1c levels. It also improved glucokinase activity and pancreatic insulin content, with a significant decrease in glucagon content. CONCLUSIONS Combined treatment with omeprazole with exendin-4 reduces food intake and body weight gain, most likely through changes in plasma ghrelin and leptin levels, and improves pancreatic insulin and glucagon content by improving glucokinase activity.
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Affiliation(s)
- Vishal Patel
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Moraiya, Ahmedabad Anand Pharmacy College, Anand, Gujarat, India
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20
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Puddu A, Sanguineti R, Mach F, Dallegri F, Viviani GL, Montecucco F. Update on the protective molecular pathways improving pancreatic beta-cell dysfunction. Mediators Inflamm 2013; 2013:750540. [PMID: 23737653 PMCID: PMC3659509 DOI: 10.1155/2013/750540] [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: 02/05/2013] [Accepted: 04/10/2013] [Indexed: 12/16/2022] Open
Abstract
The primary function of pancreatic beta-cells is to produce and release insulin in response to increment in extracellular glucose concentrations, thus maintaining glucose homeostasis. Deficient beta-cell function can have profound metabolic consequences, leading to the development of hyperglycemia and, ultimately, diabetes mellitus. Therefore, strategies targeting the maintenance of the normal function and protecting pancreatic beta-cells from injury or death might be crucial in the treatment of diabetes. This narrative review will update evidence from the recently identified molecular regulators preserving beta-cell mass and function recovery in order to suggest potential therapeutic targets against diabetes. This review will also highlight the relevance for novel molecular pathways potentially improving beta-cell dysfunction.
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Affiliation(s)
- Alessandra Puddu
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Roberta Sanguineti
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - François Mach
- Division of Cardiology, Geneva University Hospitals, Faculty of Medicine, Foundation for Medical Researches, Avenue de la Roseraie 64, 1211 Geneva 4, Switzerland
| | - Franco Dallegri
- First Medical Clinic, Laboratory of Phagocyte Physiopathology and Inflammation, Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Giorgio Luciano Viviani
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Fabrizio Montecucco
- Division of Cardiology, Geneva University Hospitals, Faculty of Medicine, Foundation for Medical Researches, Avenue de la Roseraie 64, 1211 Geneva 4, Switzerland
- First Medical Clinic, Laboratory of Phagocyte Physiopathology and Inflammation, Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
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Dhanesha N, Joharapurkar A, Shah G, Dhote V, Kshirsagar S, Bahekar R, Jain M. Exendin-4 ameliorates diabetic symptoms through activation of glucokinase. J Diabetes 2012; 4:369-77. [PMID: 22356440 DOI: 10.1111/j.1753-0407.2012.00193.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Glucagon-like peptide-1 (GLP-1) and its stable analogue exendin-4 maintain glucose homeostasis by modulating insulin secretion from pancreatic β-cells and controlling hepatic glucose output. Glucokinase (GK), by catalysing the first step in glycolysis, plays an important role in glucose-stimulated insulin secretion and hepatic glucose metabolism. In the present study, we investigated the effects of exendin-4 on GK in high fat-fed and alloxan-treated diabetic mice. METHODS The effects of alloxan (5, 10 and 20 μmol/L) on insulin release from isolated murine islets, as well as glycogen synthesis by isolated murine hepatocytes, were assessed. The effects of exendin-4 (10 nmol/kg, twice daily for 4 weeks) were assessed in high fat-fed, alloxan (50 mg/kg, i.v.)-treated C57 mice. Glucokinase activity was assessed in the same model. RESULTS Pretreatment with exendin-4 attenuated alloxan-induced decreases in insulin release and glycogen synthesis in islets and hepatocytes. The alloxan-induced decrease in the GK activity in islets and hepatocytes was also ameliorated by exendin-4 treatment. Pretreatment with the GLP-1 receptor antagonist exendin-9 (100 nmol/L) blocked the effects of exendin-4 on the liver and pancreas. Treatment of high-fat fed, alloxan-treated diabetic mice with exendin-4 (10 nmol/L, i.p.) reduced the severity of diabetic symptoms. Specifically, exendin-4 treatment reduced serum glucose by 50% and %HbA1c by 24% compared with control and significantly decreased HOMA-IR by 39% and increased HOMA-β by 150%. In addition, exendin-4 treatment significantly reduced body weight by 6.8% and serum triglycerides by 35%. CONCLUSIONS The results indicate that glucose-stimulated insulin release and glycogen synthesis are decreased by alloxan due to reduced GK activity. These findings provide further insight into the mechanism by which exendin-4 regulates glucose homeostasis.
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Affiliation(s)
- Nirav Dhanesha
- Department of Pharmacology and Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Ahmedabad, India
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22
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Hong SW, Lee J, Park SE, Rhee EJ, Park CY, Oh KW, Park SW, Lee WY. Repression of sterol regulatory element-binding protein 1-c is involved in the protective effects of exendin-4 in pancreatic β-cell line. Mol Cell Endocrinol 2012; 362:242-52. [PMID: 22820130 DOI: 10.1016/j.mce.2012.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 06/06/2012] [Accepted: 07/10/2012] [Indexed: 02/07/2023]
Abstract
Exendin-4 (Ex-4), a long-acting agonist of glucagon-like peptide-1 receptor, is a novel anti-diabetic drug that prevents β-cells against various toxicities. However, the mechanism and molecules mediating the protection procession of Ex-4 are not fully understood. We investigated the protective effect of Ex-4 against lipotoxicity, mediated by a repression of sterol regulatory element-binding protein (SREBP)-1c, a regulator of genes expression involved in fat and cholesterol synthesis. To observe the effect of Ex-4, we evaluated glucose-stimulated insulin secretion (GSIS) and apoptosis in the MIN6 pancreatic β-cell line, which were cultured in DMEM medium containing 500 μM palmitate, with or without 10 nM Ex-4. We also examined the roles of SREBP-1c in lipotoxicity model by knockdown with si-RNA. Treatment with Ex-4 improved insulin secretion and survival as well as reduced SREBP-1c expression and activity in palmitate-treated MIN6 cells. This improvement was accompanied with an upregulation of PI3K/Akt signaling pathway, and LY294.002, a specific inhibitor of PI3 kinase, abrogated effects of Ex-4 on insulin secretion. Moreover, SREBP-1c in nuclei was increased by the inhibition of PI3 kinase. Lipotoxic effects of palmitate in the insulin secretion and apoptosis were significantly prevented by SREBP-1 knockdown. In conclusion, Ex-4 protects β-cell against palmitate-induced β-cell dysfunction and apoptosis, by inhibiting SREBP-1c expression and activity through the PI3K/Akt signaling pathway.
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Affiliation(s)
- Seok-Woo Hong
- Institute of Medical Research, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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Park JH, Kim SJ, Park SH, Son DG, Bae JH, Kim HK, Han J, Song DK. Glucagon-like peptide-1 enhances glucokinase activity in pancreatic β-cells through the association of Epac2 with Rim2 and Rab3A. Endocrinology 2012; 153:574-82. [PMID: 22147008 DOI: 10.1210/en.2011-0259] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Glucokinase (GK), which phosphorylates D-glucose, is a major glucose sensor in β-cells for glucose-stimulated insulin secretion (GSIS) and is a promising new drug target for type 2 diabetes (T2D). In T2D, pancreatic β-cells exhibit defective glucose sensitivity, which leads to impaired GSIS. Although glucagon-like peptide-1-(7-36)-amide (GLP-1) is known to enhance β-cell glucose sensitivity, the effect of GLP-1 on GK activity is still unknown. The present study demonstrated that GLP-1 pretreatment for 30 min significantly enhanced GK activity in a glucose-dependent manner, with a lower Michaelis-Menten constant (K(m)) but unchanged maximal velocity (V(max)). Thus, GLP-1 acutely enhanced cellular glucose uptake, mitochondrial membrane potential, and cellular ATP levels in response to glucose in rat INS-1 and native β-cells. This effect of GLP-1 occurred via its G protein-coupled receptor pathway in a cAMP-dependent but protein kinase A-independent manner with evidence of exchange protein activated by cAMP (Epac) involvement. Silencing Epac2, interacting molecule of the small G protein Rab3 (Rim2), or Ras-associated protein Rab3A (Rab3A) significantly blocked the effect of GLP-1. These results suggested that GLP-1 can further potentiate GSIS by enhancing GK activity through the signaling of Epac2 to Rim2 and Rab3A, which is the similar pathway for GLP-1 to potentiate Ca(2+)-dependent insulin granule exocytosis. The present finding may also be an important mechanism of GLP-1 for recovery of GSIS in T2D.
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Affiliation(s)
- Jae-Hyung Park
- Department of Physiology, Keimyung University School of Medicine, Daegu 704-701, Korea
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24
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Skelding KA, Rostas JAP. The role of molecular regulation and targeting in regulating calcium/calmodulin stimulated protein kinases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:703-30. [PMID: 22453966 DOI: 10.1007/978-94-007-2888-2_31] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Calcium/calmodulin-stimulated protein kinases can be classified as one of two types - restricted or multifunctional. This family of kinases contains several structural similarities: all possess a calmodulin binding motif and an autoinhibitory region. In addition, all of the calcium/calmodulin-stimulated protein kinases examined in this chapter are regulated by phosphorylation, which either activates or inhibits their kinase activity. However, as the multifunctional calcium/calmodulin-stimulated protein kinases are ubiquitously expressed, yet regulate a broad range of cellular functions, additional levels of regulation that control these cell-specific functions must exist. These additional layers of control include gene expression, signaling pathways, and expression of binding proteins and molecular targeting. All of the multifunctional calcium/calmodulin-stimulated protein kinases examined in this chapter appear to be regulated by these additional layers of control, however, this does not appear to be the case for the restricted kinases.
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Affiliation(s)
- Kathryn A Skelding
- School of Biomedical Sciences and Pharmacy and Hunter Medical Research Institute, Faculty of Health, The University of Newcastle, University Drive, Callaghan, NSW 2308, Australia
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25
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Miyai Y, Murao K, Imachi H, Li J, Nishiuchi Y, Masugata H, Iwama H, Kushida Y, Ishida T, Haba R. Exendin-4 regulates the expression of the ATP-binding cassette transporter A1 via transcriptional factor PREB in the pancreatic β cell line. J Endocrinol Invest 2011; 34:e268-74. [PMID: 21521937 DOI: 10.3275/7683] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND PRL regulatory element-binding (PREB) protein is a transcription factor that regulates insulin promoter activity in the rat anterior pituitary. The PREB protein is expressed not only in the anterior pituitary but also in pancreatic β cells. Previously, we have reported that PREB plays an important role in glucose-mediated insulin gene expression in pancreatic β cells. The ATP-binding cassette transporter A1 (ABCA1) in pancreatic β cells influences insulin secretion and glucose homeostasis. Exendin-4 (Ex-4), a longacting agonist of the glucagon-like peptide 1, stimulates ABCA1 expression in pancreatic β cells. AIMS In this study, we examined the role played by PREB in Ex-4-induced ABCA1 expression in pancreatic β cells. MATERIAL/SUBJECTS AND METHODS PREB mRNA and protein expression were evaluated in pancreatic β cell line (INS-1 cells) treated with Ex-4 (10 nM). RESULTS Ex-4 stimulated PREB protein and mRNA expression in INS-1 cells. PREB stimulated the activity of the luciferase reporter protein that was under the control of the ABCA1 promoter. Chromatin immunoprecipitation assay showed that PREB mediates its transcriptional activity by directly binding to the ABCA1 promoter region. Finally, we used small interfering RNA to inhibit PREB expression in the cells and demonstrated that the knockdown of PREB expression attenuated the effects of Ex-4 on ABCA1 expression. CONCLUSION PREB mediates Ex-4-stimulated transcription of the ABCA1 gene in pancreatic β cells.
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Affiliation(s)
- Y Miyai
- Department of diagnostic pathology, Kagawa University, Miki-cho, Kita-gun, Kagawa, Japan
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26
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Park JH, Earm YE, Song DK. Cellular glucose availability and glucagon-like peptide-1. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:286-92. [PMID: 21907232 DOI: 10.1016/j.pbiomolbio.2011.08.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 08/22/2011] [Accepted: 08/25/2011] [Indexed: 12/25/2022]
Abstract
Glucagon-like peptide (GLP)-1 and gastric inhibitory polypeptide (GIP, glucose-dependent insulinotropic polypeptide) are produced in enteroendocrine L-cells and K-cells, respectively. They are known as incretins because they potentiate postprandial insulin secretion. Although unresponsiveness of type 2 diabetes (T2D) patients to GIP has now been reconsidered, GLP-1 mimetics and inhibitors of the GLP-1 degradation enzyme dipeptidyl peptidase (DPP)-4 have now been launched as drugs against T2D. The major roles of GLP-1 in T2D are reduction of appetite, gastric motility, glucagon secretion, enhancement of insulin secretion and β-cell survival. For insulin secretion and peripheral insulin function, GLP-1 and its mimetics sensitise β-cells to glucose; accelerate blood glucose withdrawal, in-cell glucose utilisation and glycogen synthesis in insulin-sensitive tissues; and assist in the function and survival of neurons mainly using glucose as an energy source. Taken together, GLP-1 acts to potentiate glucose availability of various cells or tissues to assist with their essential functions and/or survival. Herein, we review the signalling pathways and clinical relevance of GLP-1 in enhancing cellular glucose availability. On the basis of our recent research results, we also describe a mechanism that regulates GLP-1 for glucokinase activity. Because diabetic tissues including β-cells resist glucose, GLP-1 may be useful for treating T2D.
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Affiliation(s)
- Jae-Hyung Park
- Department of Physiology, Keimyung University School of Medicine, 2800 Dalgubeoldae-Ro, Dalseo-Gu, Daegu 704-701, Republic of Korea
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27
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Chen K, Yu X, Murao K, Imachi H, Li J, Muraoka T, Masugata H, Zhang GX, Kobayashi R, Ishida T, Tokumitsu H. Exendin-4 regulates GLUT2 expression via the CaMKK/CaMKIV pathway in a pancreatic β-cell line. Metabolism 2011; 60:579-85. [PMID: 20598720 DOI: 10.1016/j.metabol.2010.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 05/19/2010] [Accepted: 06/01/2010] [Indexed: 11/17/2022]
Abstract
The GLUT2 glucose transporter plays an important role in glucose-induced insulin secretion in pancreatic β-cells by catalyzing the uptake of glucose into the cell. In this study, we investigated whether exendin-4, a long-acting agonist of glucagon-like peptide-1, mediates stimulatory effects on GLUT2 gene expression through the Ca²+/calmodulin (CaM)-dependent protein kinase IV (CaMKIV) cascade. GLUT2 expression was examined by real-time polymerase chain reaction, Western blot analysis, and a reporter gene assay in rat insulin-secreting INS-1 cells incubated with exendin-4. An increased expression level of GLUT2 protein was noted in response to increasing concentrations of exendin-4, with maximal induction at 10 nmol/L. Real-time polymerase chain reaction analysis similarly revealed a significant increase in the amount of GLUT2 messenger RNA by 10 nmol/L exendin-4. Exendin-4 also stimulated GLUT2 promoter activity in response to increasing exendin-4 concentrations, but failed to do so in the presence of STO-609, a CaMKK inhibitor. We also investigated the effect of the constitutively active form of CaMKK (CaMKKc) on GLUT2 promoter activity. The result is consistent with the observations that CaMKKc/CaMKIV enhanced or up-regulated GLUT2 promoter activity in INS-1 cells. Furthermore, exendin-4 induction of GLUT2 protein expression was significantly suppressed in the cells knocking down the CaMKIV. In summary, activation of the CaMKK/CaMKIV cascade might be required for exendin-4-induced GLUT2 gene transcription, indicating that exendin-4 plays an important role in insulin secretion in pancreatic β-cells.
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Affiliation(s)
- Ke Chen
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe Miki-CHO, Kagawa 761-0793, Japan
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28
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Kim Chung LT, Hosaka T, Yoshida M, Harada N, Sakaue H, Sakai T, Nakaya Y. Exendin-4, a GLP-1 receptor agonist, directly induces adiponectin expression through protein kinase A pathway and prevents inflammatory adipokine expression. Biochem Biophys Res Commun 2009; 390:613-8. [PMID: 19850014 DOI: 10.1016/j.bbrc.2009.10.015] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Accepted: 10/03/2009] [Indexed: 12/12/2022]
Abstract
Exendin-4 (Ex-4) is a glucagon-like peptide-1 receptor (GLP-1R) agonist that has been used as a drug injected subcutaneously for treatment of type 2 diabetes. Many studies have revealed molecular targets of Ex-4, but its influence on adipokines has not been determined. Our study showed that Ex-4 induced secretion of adiponectin into the culture medium of 3T3-L1 adipocytes. This effect of Ex-4 is due to increased adiponectin mRNA level through the GLP-1R. Both forskolin and 3-isobutyl-1-methylxanthine (IBMX), which may finally elevate cyclic adenosine monophosphate (cAMP) concentration, prevented the induction of adiponectin expression by Ex-4. Moreover, H89, a protein kinase A inhibitor, blocked the effect of Ex-4 on adiponectin. On the other hand, Ex-4 decreased the mRNA levels of inflammatory adipokines. The results indicate that Ex-4 directly promotes adiponectin secretion via the protein kinase A pathway in 3T3-L1 adipocytes and may ameliorate insulin resistance.
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Affiliation(s)
- Le Thi Kim Chung
- Department of Nutrition and Metabolism, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan
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