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He X, Gao F, Hou J, Li T, Tan J, Wang C, Liu X, Wang M, Liu H, Chen Y, Yu Z, Yang M. Metformin inhibits MAPK signaling and rescues pancreatic aquaporin 7 expression to induce insulin secretion in type 2 diabetes mellitus. J Biol Chem 2021; 297:101002. [PMID: 34303707 PMCID: PMC8374641 DOI: 10.1016/j.jbc.2021.101002] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 07/15/2021] [Accepted: 07/21/2021] [Indexed: 02/07/2023] Open
Abstract
Metformin is the first-line antidiabetic agent for type 2 diabetes mellitus (T2DM) treatment. Although accumulated evidence has shed light on the consequences of metformin action, the precise mechanisms of its action, especially in the pancreas, are not fully understood. Aquaporin 7 (AQP7) acts as a critical regulator of intraislet glycerol content, which is necessary for insulin production and secretion. The aim of this study was to investigate the effects of different doses of metformin on AQP7 expression and explore the possible mechanism of its protective effects in the pancreatic islets. We used an in vivo model of high-fat diet in streptozocin-induced diabetic rats and an in vitro model of rat pancreatic β-cells (INS-1 cells) damaged by hyperglycemia and hyperlipidemia. Our data showed that AQP7 expression levels were decreased, whereas p38 and JNK mitogen-activated protein kinases (MAPKs) were activated in vivo and in vitro in response to hyperglycemia and hyperlipidemia. T2DM rats treated with metformin demonstrated a reduction in blood glucose levels and increased regeneration of pancreatic β-cells. In addition, metformin upregulated AQP7 expression as well as inhibited activation of p38 and JNK MAPKs both in vivo and in vitro. Overexpression of AQP7 increased glycerol influx into INS-1 cells, whereas inhibition of AQP7 reduced glycerol influx, thereby decreasing subsequent insulin secretion. Our findings demonstrate a new mechanism by which metformin suppresses the p38 and JNK pathways, thereby upregulating pancreatic AQP7 expression and promoting glycerol influx into pancreatic β-cells and subsequent insulin secretion in T2DM.
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Affiliation(s)
- Xueting He
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Fei Gao
- Department of Urology, The First Affiliated Hospital, Chongqing Medical University, Chongqing, People's Republic of China
| | - Jiaojiao Hou
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Tingjie Li
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Jiang Tan
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Chunyu Wang
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Xiaoyan Liu
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Maoqi Wang
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Hui Liu
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Yuqin Chen
- Institute of Neuroscience, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China
| | - Zhuoyuan Yu
- Department of Urology, The First Affiliated Hospital, Chongqing Medical University, Chongqing, People's Republic of China
| | - Mei Yang
- Department of Anatomy, College of Basic Medicine, Chongqing Medical University, Chongqing, People's Republic of China.
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Panicker N, Coutman M, Lawlor-O’Neill C, Kahl RGS, Roselli S, Verrills NM. Ppp2r2a Knockout Mice Reveal That Protein Phosphatase 2A Regulatory Subunit, PP2A-B55α, Is an Essential Regulator of Neuronal and Epidermal Embryonic Development. Front Cell Dev Biol 2020; 8:358. [PMID: 32582689 PMCID: PMC7290052 DOI: 10.3389/fcell.2020.00358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 04/22/2020] [Indexed: 12/13/2022] Open
Abstract
The serine/threonine protein phosphatase 2A (PP2A) is a master regulator of the complex cellular signaling that occurs during all stages of mammalian development. PP2A is composed of a catalytic, a structural, and regulatory subunit, for which there are multiple isoforms. The association of specific regulatory subunits determines substrate specificity and localization of phosphatase activity, however, the precise role of each regulatory subunit in development is not known. Here we report the generation of the first knockout mouse for the Ppp2r2a gene, encoding the PP2A-B55α regulatory subunit, using CRISPR/Cas9. Heterozygous animals developed and grew as normal, however, homozygous knockout mice were not viable. Analysis of embryos at different developmental stages found a normal Mendelian ratio of Ppp2r2a-/- embryos at embryonic day (E) 10.5 (25%), but reduced Ppp2r2a-/- embryos at E14.5 (18%), and further reduced at E18.5 (10%). No live Ppp2r2a-/- pups were observed at birth. Ppp2r2a-/- embryos were significantly smaller than wild-type or heterozygous littermates and displayed a variety of neural defects such as exencephaly, spina bifida, and cranial vault collapse, as well as syndactyly and severe epidermal defects; all processes driven by growth and differentiation of the ectoderm. Ppp2r2a-/- embryos had incomplete epidermal barrier acquisition, associated with thin, poorly differentiated stratified epithelium with weak attachment to the underlying dermis. The basal keratinocytes in Ppp2r2a-/- embryos were highly disorganized, with reduced immunolabeling of integrins and basement membrane proteins, suggesting impaired focal adhesion and hemidesmosome assembly. The spinous and granular layers were thinner in the Ppp2r2a-/- embryos, with aberrant expression of adherens and tight junction associated proteins. The overlying stratum corneum was either absent or incomplete. Thus PP2A-B55α is an essential regulator of epidermal stratification, and is essential for ectodermal development during embryogenesis.
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Affiliation(s)
- Nikita Panicker
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Priority Research Centre for Cancer Research, Innovation and Translation, University of Newcastle, Callaghan, NSW, Australia
- Hunter Cancer Research Alliance, Hunter Medical Research Institute, New Lambton, NSW, Australia
| | - Melody Coutman
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Priority Research Centre for Cancer Research, Innovation and Translation, University of Newcastle, Callaghan, NSW, Australia
- Hunter Cancer Research Alliance, Hunter Medical Research Institute, New Lambton, NSW, Australia
| | - Charley Lawlor-O’Neill
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Priority Research Centre for Cancer Research, Innovation and Translation, University of Newcastle, Callaghan, NSW, Australia
- Hunter Cancer Research Alliance, Hunter Medical Research Institute, New Lambton, NSW, Australia
| | - Richard G. S. Kahl
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Priority Research Centre for Cancer Research, Innovation and Translation, University of Newcastle, Callaghan, NSW, Australia
- Hunter Cancer Research Alliance, Hunter Medical Research Institute, New Lambton, NSW, Australia
| | - Séverine Roselli
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Priority Research Centre for Cancer Research, Innovation and Translation, University of Newcastle, Callaghan, NSW, Australia
- Hunter Cancer Research Alliance, Hunter Medical Research Institute, New Lambton, NSW, Australia
| | - Nicole M. Verrills
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, Priority Research Centre for Cancer Research, Innovation and Translation, University of Newcastle, Callaghan, NSW, Australia
- Hunter Cancer Research Alliance, Hunter Medical Research Institute, New Lambton, NSW, Australia
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