1
|
Liu J, Xia Z, Peng S, Xia J, Xu R, Wang X, Li F, Zhu W. The Important Role of Aquaglyceroporin 7 in Health and Disease. Biomolecules 2024; 14:1228. [PMID: 39456161 PMCID: PMC11505742 DOI: 10.3390/biom14101228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2024] [Revised: 09/20/2024] [Accepted: 09/26/2024] [Indexed: 10/28/2024] Open
Abstract
Aquaporins (AQPs) are highly conserved small transmembrane proteins that facilitate the transport of water and small solutes across cell membranes. Aquaglyceroporin 7 (AQP7), a significant member of the AQP family, is widely distributed throughout the body. For years, AQP7 was predominantly recognized for its role as a small-molecule transporter, facilitating the passage of small molecular substances. However, growing studies have revealed that AQP7 is also involved in the regulation of lipid synthesis, gluconeogenesis, and energy homeostasis, and it is intimately linked to a variety of diseases, such as obesity, type 2 diabetes mellitus, cardiovascular diseases, cancer, and inflammatory bowel disease. This article presents a comprehensive overview of the structure of AQP7, its regulatory mechanisms, its vital roles in both healthy and diseased states, and potential therapeutic advancements. We hope that these studies will serve as a valuable reference for the development of future treatments and diagnostic protocols targeting AQP7.
Collapse
Affiliation(s)
- Jing Liu
- School of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China; (J.L.); (Z.X.); (J.X.); (R.X.); (X.W.)
| | - Ziwei Xia
- School of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China; (J.L.); (Z.X.); (J.X.); (R.X.); (X.W.)
| | - Shuhong Peng
- Research Center for Differentiation and Development of Traditional Chinese Medicine Basic Theory, Jiangxi University of Chinese Medicine, Nanchang 330004, China;
| | - Juanjuan Xia
- School of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China; (J.L.); (Z.X.); (J.X.); (R.X.); (X.W.)
| | - Ruixiang Xu
- School of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China; (J.L.); (Z.X.); (J.X.); (R.X.); (X.W.)
| | - Xin Wang
- School of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China; (J.L.); (Z.X.); (J.X.); (R.X.); (X.W.)
| | - Fei Li
- Frontiers Science Center for Disease-Related Molecular Network, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Weifeng Zhu
- School of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China; (J.L.); (Z.X.); (J.X.); (R.X.); (X.W.)
- Key Laboratory of Modern Preparation of Traditional Chinese Medicine, Ministry of Education, Jiangxi University of Chinese Medicine, Nanchang 330004, China
| |
Collapse
|
2
|
Increased Aquaporin-7 Expression Is Associated with Changes in Rat Brown Adipose Tissue Whitening in Obesity: Impact of Cold Exposure and Bariatric Surgery. Int J Mol Sci 2023; 24:ijms24043412. [PMID: 36834823 PMCID: PMC9963055 DOI: 10.3390/ijms24043412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/24/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Glycerol is a key metabolite for lipid accumulation in insulin-sensitive tissues. We examined the role of aquaporin-7 (AQP7), the main glycerol channel in adipocytes, in the improvement of brown adipose tissue (BAT) whitening, a process whereby brown adipocytes differentiate into white-like unilocular cells, after cold exposure or bariatric surgery in male Wistar rats with diet-induced obesity (DIO) (n = 229). DIO promoted BAT whitening, evidenced by increased BAT hypertrophy, steatosis and upregulation of the lipogenic factors Pparg2, Mogat2 and Dgat1. AQP7 was detected in BAT capillary endothelial cells and brown adipocytes, and its expression was upregulated by DIO. Interestingly, AQP7 gene and protein expressions were downregulated after cold exposure (4 °C) for 1 week or one month after sleeve gastrectomy in parallel to the improvement of BAT whitening. Moreover, Aqp7 mRNA expression was positively associated with transcripts of the lipogenic factors Pparg2, Mogat2 and Dgat1 and regulated by lipogenic (ghrelin) and lipolytic (isoproterenol and leptin) signals. Together, the upregulation of AQP7 in DIO might contribute to glycerol influx used for triacylglycerol synthesis in brown adipocytes, and hence, BAT whitening. This process is reversible by cold exposure and bariatric surgery, thereby suggesting the potential of targeting BAT AQP7 as an anti-obesity therapy.
Collapse
|
3
|
Ganekal P, Vastrad B, Kavatagimath S, Vastrad C, Kotrashetti S. Bioinformatics and Next-Generation Data Analysis for Identification of Genes and Molecular Pathways Involved in Subjects with Diabetes and Obesity. MEDICINA (KAUNAS, LITHUANIA) 2023; 59:medicina59020309. [PMID: 36837510 PMCID: PMC9967176 DOI: 10.3390/medicina59020309] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/19/2023] [Accepted: 01/29/2023] [Indexed: 02/10/2023]
Abstract
Background and Objectives: A subject with diabetes and obesity is a class of the metabolic disorder. The current investigation aimed to elucidate the potential biomarker and prognostic targets in subjects with diabetes and obesity. Materials and Methods: The next-generation sequencing (NGS) data of GSE132831 was downloaded from Gene Expression Omnibus (GEO) database. Functional enrichment analysis of DEGs was conducted with ToppGene. The protein-protein interactions network, module analysis, target gene-miRNA regulatory network and target gene-TF regulatory network were constructed and analyzed. Furthermore, hub genes were validated by receiver operating characteristic (ROC) analysis. A total of 872 DEGs, including 439 up-regulated genes and 433 down-regulated genes were observed. Results: Second, functional enrichment analysis showed that these DEGs are mainly involved in the axon guidance, neutrophil degranulation, plasma membrane bounded cell projection organization and cell activation. The top ten hub genes (MYH9, FLNA, DCTN1, CLTC, ERBB2, TCF4, VIM, LRRK2, IFI16 and CAV1) could be utilized as potential diagnostic indicators for subjects with diabetes and obesity. The hub genes were validated in subjects with diabetes and obesity. Conclusion: This investigation found effective and reliable molecular biomarkers for diagnosis and prognosis by integrated bioinformatics analysis, suggesting new and key therapeutic targets for subjects with diabetes and obesity.
Collapse
Affiliation(s)
- Prashanth Ganekal
- Department of General Medicine, Basaveshwara Medical College, Chitradurga 577501, Karnataka, India
| | - Basavaraj Vastrad
- Department of Pharmaceutical Chemistry, K.L.E. College of Pharmacy, Gadag 582101, Karnataka, India
| | - Satish Kavatagimath
- Department of Pharmacognosy, K.L.E. College of Pharmacy, Belagavi 590010, Karnataka, India
| | - Chanabasayya Vastrad
- Biostatistics and Bioinformatics, Chanabasava Nilaya, Bharthinagar, Dharwad 580001, Karnataka, India
- Correspondence: ; Tel.: +91-9480073398
| | - Shivakumar Kotrashetti
- Biostatistics and Bioinformatics, Chanabasava Nilaya, Bharthinagar, Dharwad 580001, Karnataka, India
| |
Collapse
|
4
|
Calamita G, Delporte C. Aquaporins in Glandular Secretion. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:225-249. [PMID: 36717498 DOI: 10.1007/978-981-19-7415-1_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Exocrine and endocrine glands deliver their secretory product, respectively, at the surface of the target organs or within the bloodstream. The release of their products has been shown to rely on secretory mechanisms often involving aquaporins (AQPs). This chapter will provide insight into the role of AQPs in secretory glands located within the gastrointestinal tract, including salivary glands, gastric glands, duodenal Brunner's glands, liver, gallbladder, intestinal goblets cells, and pancreas, as well and in other parts of the body, including airway submucosal glands, lacrimal glands, mammary glands, and eccrine sweat glands. The involvement of AQPs in both physiological and pathophysiological conditions will also be highlighted.
Collapse
Affiliation(s)
- Giuseppe Calamita
- Department of Biosciences, Biotechnologies and Environment, University of Bari "Aldo Moro", Bari, Italy
| | - Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Faculty of Medicine, Université Libre de Bruxelles, Brussels, Belgium.
| |
Collapse
|
5
|
Wagner K, Unger L, Salman MM, Kitchen P, Bill RM, Yool AJ. Signaling Mechanisms and Pharmacological Modulators Governing Diverse Aquaporin Functions in Human Health and Disease. Int J Mol Sci 2022; 23:1388. [PMID: 35163313 PMCID: PMC8836214 DOI: 10.3390/ijms23031388] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/18/2022] [Accepted: 01/20/2022] [Indexed: 02/07/2023] Open
Abstract
The aquaporins (AQPs) are a family of small integral membrane proteins that facilitate the bidirectional transport of water across biological membranes in response to osmotic pressure gradients as well as enable the transmembrane diffusion of small neutral solutes (such as urea, glycerol, and hydrogen peroxide) and ions. AQPs are expressed throughout the human body. Here, we review their key roles in fluid homeostasis, glandular secretions, signal transduction and sensation, barrier function, immunity and inflammation, cell migration, and angiogenesis. Evidence from a wide variety of studies now supports a view of the functions of AQPs being much more complex than simply mediating the passive flow of water across biological membranes. The discovery and development of small-molecule AQP inhibitors for research use and therapeutic development will lead to new insights into the basic biology of and novel treatments for the wide range of AQP-associated disorders.
Collapse
Affiliation(s)
- Kim Wagner
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005, Australia;
| | - Lucas Unger
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK; (L.U.); (P.K.)
| | - Mootaz M. Salman
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK;
- Oxford Parkinson’s Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Philip Kitchen
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK; (L.U.); (P.K.)
| | - Roslyn M. Bill
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK; (L.U.); (P.K.)
| | - Andrea J. Yool
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005, Australia;
| |
Collapse
|
6
|
Galli M, Hameed A, Żbikowski A, Zabielski P. Aquaporins in insulin resistance and diabetes: More than channels! Redox Biol 2021; 44:102027. [PMID: 34090243 PMCID: PMC8182305 DOI: 10.1016/j.redox.2021.102027] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/09/2021] [Accepted: 05/24/2021] [Indexed: 12/12/2022] Open
Abstract
Aquaporins (AQPs) are part of the family of the integral membrane proteins. Their function is dedicated to the transport of water, glycerol, ammonia, urea, H2O2, and other small molecules across the biological membranes. Although for many years they were scarcely considered, AQPs have a relevant role in the development of many diseases. Recent discoveries suggest, that AQPs may play an important role in the process of fat accumulation and regulation of oxidative stress, two crucial aspects of insulin resistance and type-2 diabetes (T2D). Insulin resistance (IR) and T2D are multi-faceted systemic diseases with multiple connections to obesity and other comorbidities such as hypertension, dyslipidemia and metabolic syndrome. Both IR and T2D transcends different tissues and organs, creating the maze of mutual relationships between adipose fat depots, skeletal muscle, liver and other insulin-sensitive organs. AQPs with their heterogenous properties, distinctive tissue distribution and documented involvement in both the lipid metabolism and regulation of the oxidative stress appear to be feasible candidates in the search for the explanation to this third-millennium plague. A lot of research has been assigned to adipose tissue AQP7 and liver tissue AQP9, clarifying their relationship and coordinated work in the induction of hepatic insulin resistance. Novel research points also to other aquaporins, such as AQP11 which may be associated with the induction of insulin resistance and T2D through its involvement in hydrogen peroxide transport. In this review we collected recent discoveries in the field of AQP's involvement in the insulin resistance and T2D. Novel paths which connect AQPs with metabolic disorders can give new fuel to the research on obesity, insulin resistance and T2D - one of the most worrying problems of the modern society.
Collapse
Affiliation(s)
- Mauro Galli
- Department of Medical Biology, Medical University of Bialystok, 15-089, Bialystok, Poland.
| | - Ahsan Hameed
- Clinical Research Center, Medical University of Bialystok, 15-089, Bialystok, Poland.
| | - Arkadiusz Żbikowski
- Department of Medical Biology, Medical University of Bialystok, 15-089, Bialystok, Poland.
| | - Piotr Zabielski
- Department of Medical Biology, Medical University of Bialystok, 15-089, Bialystok, Poland.
| |
Collapse
|
7
|
Tardelli M, Stulnig TM. Aquaporin regulation in metabolic organs. VITAMINS AND HORMONES 2021; 112:71-93. [PMID: 32061350 DOI: 10.1016/bs.vh.2019.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aquaporins (AQPs) are a family of 13 small trans-membrane proteins, which facilitate shuttling of glycerol, water and urea. The peculiar role of AQPs in glycerol transport makes them attractive targets in metabolic organs since glycerol represents the backbone of triglyceride synthesis. Importantly, AQPs are known to be regulated by various nuclear receptors which in turn govern lipid and glucose metabolism as well as inflammatory cascades. Here, we review the role of AQPs regulation in metabolic organs exploring their physiological impact in health and disease.
Collapse
Affiliation(s)
- Matteo Tardelli
- Division of Gastroenterology and Hepatology, Joan & Sanford I. Weill Cornell Department of Medicine, Weill Cornell Medical College, New York, NY, United States; Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Thomas M Stulnig
- Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria.
| |
Collapse
|
8
|
Calamita G, Delporte C. Involvement of aquaglyceroporins in energy metabolism in health and disease. Biochimie 2021; 188:20-34. [PMID: 33689852 DOI: 10.1016/j.biochi.2021.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/23/2021] [Accepted: 03/01/2021] [Indexed: 11/27/2022]
Abstract
Aquaglyceroporins are a group of the aquaporin (AQP) family of transmembrane water channels. While AQPs facilitate the passage of water, small solutes, and gases across biological membranes, aquaglyceroporins allow passage of water, glycerol, urea and some other solutes. Thanks to their glycerol permeability, aquaglyceroporins are involved in energy homeostasis. This review provides an overview of what is currently known concerning the functional implication and control of aquaglyceroporins in tissues involved in energy metabolism, i.e. liver, adipose tissue and endocrine pancreas. The expression, role and (dys)regulation of aquaglyceroporins in disorders affecting energy metabolism, and the potential relevance of aquaglyceroporins as drug targets to treat the alterations of the energy balance is also addressed.
Collapse
Affiliation(s)
- Giuseppe Calamita
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy
| | - Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Université Libre de Bruxelles, Brussels, Belgium.
| |
Collapse
|
9
|
da Silva IV, Cardoso C, Méndez-Giménez L, Camoes SP, Frühbeck G, Rodríguez A, Miranda JP, Soveral G. Aquaporin-7 and aquaporin-12 modulate the inflammatory phenotype of endocrine pancreatic beta-cells. Arch Biochem Biophys 2020; 691:108481. [PMID: 32735865 DOI: 10.1016/j.abb.2020.108481] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 02/08/2023]
Abstract
Aquaporins (AQPs) facilitate water and glycerol movement across membranes. AQP7 is the main aquaglyceroporin in pancreatic β-cells and was proposed to play a role in insulin exocytosis. Although AQP7-null mice display adult-onset obesity, impaired insulin secretion and insulin resistance, AQP7 loss-of-function homozygous mutations in humans do not correlate with obesity nor type-2 diabetes. In addition, AQP12 is upregulated in pancreatitis. However, the implication of this isoform in endocrine pancreas inflammation is still unclear. Here, we investigated AQP7 and AQP12 involvement in cellular and inflammatory processes using RIN-m5F beta cells, a model widely used for their high insulin secretion. AQP7 and AQP12 expression were directly associated with cell proliferation, adhesion and migration. While tumor necrosis factor-alpha (TNFα)-induced inflammation impaired AQP7 expression and drastically reduced insulin secretion, lipopolysaccharides (LPS) prompted AQP7 upregulation, and both TNFα and LPS upregulated AQP12. Importantly, cells overexpressing AQP12 are more resistant to inflammation, revealing lower levels of proinflammatory markers. Altogether, these data document AQP7 involvement in insulin secretion and AQP12 implication in inflammation, highlighting their fundamental role in pancreatic β-cell function.
Collapse
Affiliation(s)
- Inês Vieira da Silva
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal; Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, 1649-003, Lisboa, Portugal
| | - Carlos Cardoso
- Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, 1649-003, Lisboa, Portugal; Clinical Chemistry Laboratory, Dr. Joaquim Chaves, 1495-068, Algés, Portugal
| | - Leire Méndez-Giménez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, 31008, Pamplona, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008, Pamplona, Spain
| | - Sérgio Povoas Camoes
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal; Department of Toxicological and Bromatological Sciences, Faculty of Pharmacy, Universidade de Lisboa, 1649-003, Lisboa, Portugal
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, 31008, Pamplona, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008, Pamplona, Spain
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, 31008, Pamplona, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008, Pamplona, Spain
| | - Joana Paiva Miranda
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal; Department of Toxicological and Bromatological Sciences, Faculty of Pharmacy, Universidade de Lisboa, 1649-003, Lisboa, Portugal.
| | - Graça Soveral
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal; Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, 1649-003, Lisboa, Portugal.
| |
Collapse
|
10
|
Aquaporin-11 Contributes to TGF-β1-Induced Endoplasmic Reticulum Stress in Human Visceral Adipocytes: Role in Obesity-Associated Inflammation. Cells 2020; 9:cells9061403. [PMID: 32512939 PMCID: PMC7349025 DOI: 10.3390/cells9061403] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 05/27/2020] [Accepted: 05/31/2020] [Indexed: 02/06/2023] Open
Abstract
Aquaporin-11 (AQP11) is expressed in human adipocytes, but its functional role remains unknown. Since AQP11 is an endoplasmic reticulum (ER)-resident protein that transports water, glycerol, and hydrogen peroxide (H2O2), we hypothesized that this superaquaporin is involved in ER stress induced by lipotoxicity and inflammation in human obesity. AQP11 expression was assessed in 67 paired visceral and subcutaneous adipose tissue samples obtained from patients with morbid obesity and normal-weight individuals. We found that obesity and obesity-associated type 2 diabetes increased (p < 0.05) AQP11 mRNA and protein in visceral adipose tissue, but not subcutaneous fat. Accordingly, AQP11 mRNA was upregulated (p < 0.05) during adipocyte differentiation and lipolysis, two biological processes altered in the obese state. Subcellular fractionation and confocal microscopy studies confirmed its presence in the ER plasma membrane of visceral adipocytes. Proinflammatory factors TNF-α, and particularly TGF-β1, downregulated (p < 0.05) AQP11 mRNA and protein expression and reinforced its subcellular distribution surrounding lipid droplets. Importantly, the AQP11 gene knockdown increased (p < 0.05) basal and TGF-β1-induced expression of the ER markers ATF4 and CHOP. Together, the downregulation of AQP11 aggravates TGF-β1-induced ER stress in visceral adipocytes. Owing to its "peroxiporin" properties, AQP11 overexpression in visceral fat might constitute a compensatory mechanism to alleviate ER stress in obesity.
Collapse
|
11
|
Aquaglyceroporins Are Differentially Expressed in Beige and White Adipocytes. Int J Mol Sci 2020; 21:ijms21020610. [PMID: 31963489 PMCID: PMC7014209 DOI: 10.3390/ijms21020610] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 01/13/2020] [Accepted: 01/15/2020] [Indexed: 12/31/2022] Open
Abstract
Browning of white adipocytes has been proposed as a powerful strategy to overcome metabolic complications, since brown adipocytes are more catabolic, expending energy as a heat form. However, the biological pathways involved in the browning process are still unclear. Aquaglyceroporins are a sub-class of aquaporin water channels that also permeate glycerol and are involved in body energy homeostasis. In the adipose tissue, aquaporin-7 (AQP7) is the most representative isoform, being crucial for white adipocyte fully differentiation and glycerol metabolism. The altered expression of AQP7 is involved in the onset of obesity and metabolic disorders. Herein, we investigated if aquaglyceroporins are implicated in beige adipocyte differentiation, similar to white cells. Thus, we optimized a protocol of murine 3T3-L1 preadipocytes browning that displayed increased beige and decreased white adipose tissue features at both gene and protein levels and evaluated aquaporin expression patterns along the differentiation process together with cellular lipid content. Our results revealed that AQP7 and aquaporin-9 (AQP9) expression was downregulated throughout beige adipocyte differentiation compared to white differentiation, which may be related to the beige physiological role of heat production from oxidative metabolism, contrasting with the anabolic/catabolic lipid metabolism requiring glycerol gateways occurring in white adipose cells.
Collapse
|
12
|
Comparative Analysis of the aquaporin Gene Family in 12 Fish Species. Animals (Basel) 2019; 9:ani9050233. [PMID: 31086002 PMCID: PMC6562760 DOI: 10.3390/ani9050233] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 05/10/2019] [Accepted: 05/11/2019] [Indexed: 01/15/2023] Open
Abstract
Simple Summary Aquaporins (Aqps) are a group of membrane proteins. In this study, 166 Aqp genes were identified in 12 fish species. Gene organization, motif distribution, recombination, and selection pressure were performed to investigate their evolutionary characteristics. In addition, expression profiles of Aqps were also examined under pathogens infection and organophosphorus pesticide stress. This study will provide a useful reference for further functional study. Abstract Aquaporins (Aqps) are a class of water channel proteins that play key roles in many physiological functions and cellular processes. Here, we analyzed 166 putative Aqp genes in 12 fish species and divided them into four groups. Gene organization and motif distribution analyses suggested potentially conserved functions in each group. Several recombination events were identified in some members, which accelerate their divergence in evolution. Furthermore, a few positive selection sites were identified, and mutations at these sites could alter the stability of Aqp proteins. In addition, expression profiles of some Aqp genes under pathogen infection and organophosphorus pesticide stress were also investigated. The result implied that several Aqp genes may affect different immune responses and osmoregulation. This study provides a comparative analysis of the fish Aqp gene family to facilitate further functional analyses.
Collapse
|
13
|
Associations between Aquaglyceroporin Gene Polymorphisms and Risk of Type 2 Diabetes Mellitus. BIOMED RESEARCH INTERNATIONAL 2018; 2018:8167538. [PMID: 30598999 PMCID: PMC6288565 DOI: 10.1155/2018/8167538] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 09/24/2018] [Indexed: 12/11/2022]
Abstract
Objectives AQP7 and AQP9 represent glycerol channel in adipose tissue and liver and have been associated with metabolic diseases. We aimed to investigate the associations between genetic variants in AQP7 and AQP9 genes and the risk of type 2 diabetes (T2DM) in Chinese population. Methods Blood samples were drawn from 400 T2DM patients and 400 age- and gender-matched controls. Genomic DNA was extracted by proteinase K digestion and phenol–chloroform extraction. Genotyping of 5 single nucleotide polymorphisms (SNPs) in AQP7 (rs2989924, rs3758269, and rs62542743) and AQP9 (rs57139208, rs16939881) was performed by the polymerase chain reaction assay with TaqMan probes. Results The subjects with rs2989924 GA+AA genotypes had 1.47-fold increased risk of T2DM (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.06-2.04), compared to those with GG genotype, and this association remained significant after adjustment for covariates (OR 1.66, 95% CI 1.07-2.57). When compared with rs3758269 CC genotype, the subjects with CT+TT genotypes had 45% decreased T2DM risk after multivariate adjustment (OR 0.55, 95% CI 0.35-0.85). The associations were evident in elder and overweight subjects and those with central obesity. No association was observed between AQP9 SNPs and T2DM risk. Conclusions AQP7 SNP rs2989924 and rs3758269 were associated with T2DM risk in Chinese Han population.
Collapse
|
14
|
Lebeck J, Søndergaard E, Nielsen S. Increased AQP7 abundance in skeletal muscle from obese men with type 2 diabetes. Am J Physiol Endocrinol Metab 2018; 315:E367-E373. [PMID: 29783856 DOI: 10.1152/ajpendo.00468.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Aquaglyceroporin 7 (AQP7) facilitates the transport of glycerol across cell membranes. In mice, fasting and refeeding regulate adipose tissue AQP7 abundance, and a role in controlling triglyceride accumulation in adipose tissue has been proposed. AQP7 is also expressed in skeletal muscle, where its function remains to be determined. Here, the abundance of AQP7 in abdominal subcutaneous adipose tissue (SAT) and skeletal muscle was evaluated in the overnight fasted and postprandial state in eight lean and eight obese men with type 2 diabetes (T2D). A biopsy from SAT and muscle was collected after an overnight fast and 2 h after ingestion of a low-fat test meal. Palmitate turnover was evaluated using a [9,10-3H] palmitate dilution technique. Tissue samples were analyzed by immunoblotting. Meal intake did not affect AQP7 expression in SAT or skeletal muscle. No association between the SAT AQP7 abundance and palmitate turnover was found. SAT AQP7 abundance was similar in lean and obese T2D men, whereas muscle AQP7 abundance was more than fourfold higher in obese T2D men. In conclusion, meal intake did not affect AQP7 protein abundance in SAT or skeletal muscle. In addition, SAT AQP7 expression does not appear to be involved in the regulation of adipose tissue lipolysis. However, in contrast to SAT AQP7, skeletal muscle AQP7 protein abundance is markedly increased in obese T2D men, potentially contributing to the excess lipid accumulation in skeletal muscle in type 2 diabetes.
Collapse
Affiliation(s)
- Janne Lebeck
- The Danish Diabetes Academy, Odense University Hospital , Odense , Denmark
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 3, Aarhus , Denmark
| | - Esben Søndergaard
- The Danish Diabetes Academy, Odense University Hospital , Odense , Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital , Aarhus , Denmark
| | - Søren Nielsen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital , Aarhus , Denmark
| |
Collapse
|
15
|
Calamita G, Perret J, Delporte C. Aquaglyceroporins: Drug Targets for Metabolic Diseases? Front Physiol 2018; 9:851. [PMID: 30042691 PMCID: PMC6048697 DOI: 10.3389/fphys.2018.00851] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 06/15/2018] [Indexed: 12/29/2022] Open
Abstract
Aquaporins (AQPs) are a family of transmembrane channel proteins facilitating the transport of water, small solutes, and gasses across biological membranes. AQPs are expressed in all tissues and ensure multiple roles under normal and pathophysiological conditions. Aquaglyceroporins are a subfamily of AQPs permeable to glycerol in addition to water and participate thereby to energy metabolism. This review focalizes on the present knowledge of the expression, regulation and physiological roles of AQPs in adipose tissue, liver and endocrine pancreas, that are involved in energy metabolism. In addition, the review aims at summarizing the involvement of AQPs in metabolic disorders, such as obesity, diabetes and liver diseases. Finally, challenges and recent advances related to pharmacological modulation of AQPs expression and function to control and treat metabolic diseases are discussed.
Collapse
Affiliation(s)
- Giuseppe Calamita
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Jason Perret
- Laboratory of Pathophysiological and Nutritional Biochemistry, Université Libre de Bruxelles, Brussels, Belgium
| | - Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Université Libre de Bruxelles, Brussels, Belgium
| |
Collapse
|
16
|
Tardelli M, Claudel T, Bruschi FV, Trauner M. Nuclear Receptor Regulation of Aquaglyceroporins in Metabolic Organs. Int J Mol Sci 2018; 19:E1777. [PMID: 29914059 PMCID: PMC6032257 DOI: 10.3390/ijms19061777] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 06/12/2018] [Accepted: 06/13/2018] [Indexed: 02/07/2023] Open
Abstract
Nuclear receptors, such as the farnesoid X receptor (FXR) and the peroxisome proliferator-activated receptors gamma and alpha (PPAR-γ, -α), are major metabolic regulators in adipose tissue and the liver, where they govern lipid, glucose, and bile acid homeostasis, as well as inflammatory cascades. Glycerol and free fatty acids are the end products of lipid droplet catabolism driven by PPARs. Aquaporins (AQPs), a family of 13 small transmembrane proteins, facilitate the shuttling of water, urea, and/or glycerol. The peculiar role of AQPs in glycerol transport makes them pivotal targets in lipid metabolism, especially considering their tissue-specific regulation by the nuclear receptors PPARγ and PPARα. Here, we review the role of nuclear receptors in the regulation of glycerol shuttling in liver and adipose tissue through the function and expression of AQPs.
Collapse
Affiliation(s)
- Matteo Tardelli
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology & Hepatology, Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
| | - Thierry Claudel
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology & Hepatology, Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
| | - Francesca Virginia Bruschi
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology & Hepatology, Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
| | - Michael Trauner
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology & Hepatology, Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
| |
Collapse
|
17
|
Méndez-Giménez L, Ezquerro S, da Silva IV, Soveral G, Frühbeck G, Rodríguez A. Pancreatic Aquaporin-7: A Novel Target for Anti-diabetic Drugs? Front Chem 2018; 6:99. [PMID: 29675407 PMCID: PMC5895657 DOI: 10.3389/fchem.2018.00099] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/20/2018] [Indexed: 12/26/2022] Open
Abstract
Aquaporins comprise a family of 13 members of water channels (AQP0-12) that facilitate a rapid transport of water across cell membranes. In some cases, these pores are also permeated by small solutes, particularly glycerol, urea or nitric oxide, among other solutes. Several aquaporins have been identified in the pancreas, an exocrine and endocrine organ that plays an essential role in the onset of insulin resistance and type 2 diabetes. The exocrine pancreas, which accounts for 90% of the total pancreas, secretes daily large volumes of a near-isotonic fluid containing digestive enzymes into the duodenum. AQP1, AQP5, and AQP8 contribute to fluid secretion especially from ductal cells, whereas AQP12 allows the proper maturation and exocytosis of secretory granules in acinar cells of the exocrine pancreas. The endocrine pancreas (10% of the total pancreatic cells) is composed by the islets of Langerhans, which are distributed in α, β, δ, ε, and pancreatic polypeptide (PP) cells that secrete glucagon, insulin, somatostatin, ghrelin and PP, respectively. AQP7, an aquaglyceroporin permeated by water and glycerol, is expressed in pancreatic β-cells and murine studies have confirmed its participation in insulin secretion, triacylglycerol synthesis and proliferation of these endocrine cells. In this regard, transgenic AQP7-knockout mice develop adult-onset obesity, hyperinsulinemia, increased intracellular triacylglycerol content and reduced β-cell mass in Langerhans islets. Moreover, we have recently reported that AQP7 upregulation in β-cells after bariatric surgery, an effective weight loss surgical procedure, contributes, in part, to the improvement of pancreatic steatosis and insulin secretion through the increase of intracytoplasmic glycerol in obese rats. Human studies remain scarce and controversial, with some rare cases of loss-of function mutations of the AQP7 gene being associated with the onset of type 2 diabetes. The present Review is focused on the role of aquaporins in the physiology and pathophysiology of the pancreas, highlighting the role of pancreatic AQP7 as a novel player in the control of β-cell function and a potential anti-diabetic-drug.
Collapse
Affiliation(s)
- Leire Méndez-Giménez
- Metabolic Research Laboratory, University of Navarra, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain
| | - Silvia Ezquerro
- Metabolic Research Laboratory, University of Navarra, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain
| | - Inês V da Silva
- Faculty of Pharmacy, Research Institute for Medicines (iMed.ULisboa), Universidade de Lisboa, Lisboa, Portugal
| | - Graça Soveral
- Faculty of Pharmacy, Research Institute for Medicines (iMed.ULisboa), Universidade de Lisboa, Lisboa, Portugal
| | - Gema Frühbeck
- Metabolic Research Laboratory, University of Navarra, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain.,Department of Endocrinology and Nutrition, Clínica Universidad de Navarra, Pamplona, Spain
| | - Amaia Rodríguez
- Metabolic Research Laboratory, University of Navarra, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain
| |
Collapse
|
18
|
Méndez-Giménez L, Becerril S, Moncada R, Valentí V, Fernández S, Ramírez B, Catalán V, Gómez-Ambrosi J, Soveral G, Malagón MM, Diéguez C, Rodríguez A, Frühbeck G. Gastric Plication Improves Glycemia Partly by Restoring the Altered Expression of Aquaglyceroporins in Adipose Tissue and the Liver in Obese Rats. Obes Surg 2018; 27:1763-1774. [PMID: 28054299 DOI: 10.1007/s11695-016-2532-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND Gastric plication is a minimally invasive bariatric surgical procedure, where the greater curvature is plicated inside the gastric lumen. Our aims were to analyze the effectiveness of gastric plication on the resolution of obesity, impaired glucose tolerance, and fatty liver in an experimental model of diet-induced obesity (DIO) and to evaluate changes in glycerol metabolism, a key substrate for adiposity and gluconeogenesis, in adipose tissue and the liver. METHODS Male Wistar DIO rats (n = 58) were subjected to surgical (sham operation and gastric plication) or dietary interventions [fed a normal diet (ND) or high-fat diet (HFD) or pair-fed to the amount of food eaten by gastric-plicated animals]. The expression of aquaglyceroporins (AQPs) in epididymal (EWAT) and subcutaneous (SCWAT) fat and the liver was analyzed by real-time PCR and Western blot. RESULTS Gastric plication did not result in a significant weight loss in DIO rats, showing a modest reduction in whole-body adiposity and hepatic steatosis. However, gastric-plicated animals exhibited an improvement in basal glycemia and glucose clearance, without changes in hepatic gluconeogenic genes. DIO was associated with an increase in glycerol, higher AQP3 and AQP7 in EWAT and SCWAT, and a decrease in hepatic AQP9. Gastric plication downregulated AQP3 in both fat depots without changes in adipose AQP7 and hepatic AQP9. CONCLUSION Gastric plication results in a modest reduction in adiposity and hepatosteatosis but restores glycemia by downregulating AQP3, which entails lower efflux of glycerol from fat, lower plasma glycerol availability, and a reduced use of glycerol as a substrate for hepatic gluconeogenesis.
Collapse
Affiliation(s)
- Leire Méndez-Giménez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain
| | - Sara Becerril
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain
| | - Rafael Moncada
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.,Department of Anesthesia, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| | - Víctor Valentí
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.,Department of Surgery, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| | - Secundino Fernández
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.,Department of Otorhinolaryngology, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| | - Beatriz Ramírez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain
| | - Victoria Catalán
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain
| | - Javier Gómez-Ambrosi
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain
| | - Graça Soveral
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - María M Malagón
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.,Department of Cell Biology, Physiology, and Immunology, Instituto Maimónides de Investigación Biomédica (IMIBIC)/Reina Sofia University Hospital/University of Córdoba, Córdoba, Spain
| | - Carlos Diéguez
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.,Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, Spain
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain. .,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Irunlarrea 1, 31008, Pamplona, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, Spain.,Department of Endocrinology and Nutrition, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| |
Collapse
|
19
|
Iena FM, Lebeck J. Implications of Aquaglyceroporin 7 in Energy Metabolism. Int J Mol Sci 2018; 19:ijms19010154. [PMID: 29300344 PMCID: PMC5796103 DOI: 10.3390/ijms19010154] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 12/29/2017] [Accepted: 12/31/2017] [Indexed: 12/14/2022] Open
Abstract
The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in carbohydrate and lipid metabolism. It is primarily stored in white adipose tissue as part of the triglyceride molecules. During states with increased lipolysis, such as fasting and diabetes, glycerol is released from adipose tissue and metabolized in other tissues. AQP7 is expressed in adipose tissue where it facilitates the efflux of glycerol, and AQP7 deficiency has been linked to increased glycerol kinase activity and triglyceride accumulation in adipose tissue, leading to obesity and secondary development of insulin resistance. However, AQP7 is also expressed in a wide range of other tissues, including kidney, muscle, pancreatic β-cells and liver, where AQP7 also holds the potential to influence whole body energy metabolism. The aim of the review is to summarize the current knowledge on AQP7 in adipose tissue, as well as AQP7 expressed in other tissues where AQP7 might play a significant role in modulating whole body energy metabolism.
Collapse
Affiliation(s)
- Francesco Maria Iena
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 3, 8000 Aarhus, Denmark.
| | - Janne Lebeck
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 3, 8000 Aarhus, Denmark.
| |
Collapse
|
20
|
Lipopolysaccharide Modifies Glycerol Permeability and Metabolism in 3T3-L1 Adipocytes. Int J Mol Sci 2017; 18:ijms18122566. [PMID: 29186031 PMCID: PMC5751169 DOI: 10.3390/ijms18122566] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 11/09/2017] [Accepted: 11/25/2017] [Indexed: 12/15/2022] Open
Abstract
Aquaglyceroporins-aquaporin membrane channels (AQP) that conduct glycerol and other small neutral solutes in addition to water-play major roles in obesity. In adipocytes, aquaglyceroporins mediate glycerol uptake and release across the plasma membrane, which are two key steps for triacylglycerols (TAGs) synthesis (lipogenesis) and hydrolysis (lipolysis). The aim of this study was to assess both glycerol permeability and metabolism in undifferentiated 3T3-L1 cells (UDCs) as well as in untreated (CTL-DCs) versus lipopolysaccharide (LPS-DCs)-treated differentiated 3T3-L1 adipocytes. Glycerol release, TAGs content and whole membrane glycerol permeability were significantly increased in DCs as compared to UDCs. Moreover, in DCs, LPS treatment significantly increased TAGs content and decreased glycerol permeability. In addition, a significant reduction in whole membrane glycerol permeability was observed in LPS-DCs as compared to CTL-DCs. The relative contributions of AQP3, AQP7 and AQP9 (facilitated diffusion), as well as that of the phospholipid bilayer (simple diffusion), to the whole membrane glycerol permeability, were estimated biophysically in UDCs, CTL-DCs and LPS-DCs, using selective AQP inhibitors. Further studies will be required to determine if modifications in either subcellular localization and/or activity of aquaglyceroporins could account for the data herein. Nevertheless, our findings provide novel insights in understanding the LPS-induced adipocyte hypertrophy that accompanies obesity.
Collapse
|
21
|
Rocha-Rodrigues S, Rodríguez A, Becerril S, Ramírez B, Gonçalves IO, Beleza J, Frühbeck G, Ascensão A, Magalhães J. Physical exercise remodels visceral adipose tissue and mitochondrial lipid metabolism in rats fed a high-fat diet. Clin Exp Pharmacol Physiol 2017; 44:386-394. [PMID: 27873387 DOI: 10.1111/1440-1681.12706] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 11/02/2016] [Accepted: 11/10/2016] [Indexed: 01/17/2023]
Abstract
We aimed to investigate the effects of two physical exercise models, voluntary physical activity (VPA) and endurance training (ET) as preventive and therapeutic strategies, respectively, on lipid accumulation regulators and mitochondrial content in VAT of rats fed a high-fat diet (HFD). Sprague-Dawley rats (6 weeks old, n=60) were assigned into sedentary and VPA groups fed isoenergetic diets: standard (S, 35 kcal% fat) or HFD (71 kcal% fat). The VPA groups had free access to wheel running during the entire protocol. After 9 weeks, half of the sedentary animals were exercised on a treadmill while maintaining the dietary treatments. The HFD induced no changes in plasma non-esterified fatty acids (NEFA) and glycerol levels and decreased oxidative phosphorylation (OXPHOS) subunit IV and increased truncated/full-length sterol regulatory element-binding transcription factor 1c (SREBP1c) ratio in epididymal white adipose tissue (eWAT). VPA decreased plasma glycerol levels, aquaglyceroporin 7 (AQP7) and increased subunit I of cytochrome c oxidase (COX) protein, in standard diet fed animals. Eight weeks of ET decreased body weight, visceral adiposity and adipocyte size and plasma NEFA and glycerol levels, as well as AQP7 protein expression in eWAT. ET increased fatty acid translocase (FAT/CD36), mitochondrial content of complexes IV and V subunits, mitochondrial biogenesis and dynamic (mitofusins and optic atrophy 1)-related proteins. Moreover, lipogenesis-related markers (SREBP1c and acetyl CoA carboxylase) were reduced after 8 weeks of ET. In conclusion, ET-induced alterations reflect a positive effect on mitochondrial function and the overall VAT metabolism of HFD-induced obese rats.
Collapse
Affiliation(s)
- Sílvia Rocha-Rodrigues
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,Obesity & Adipobiology Group, Instituto de Investigación Sanitario de Navarra (IdiSNA), Pamplona, Spain.,CIBEROBN, Instituto de Salud Carlos III, Pamplona, Spain
| | - Sara Becerril
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,Obesity & Adipobiology Group, Instituto de Investigación Sanitario de Navarra (IdiSNA), Pamplona, Spain.,CIBEROBN, Instituto de Salud Carlos III, Pamplona, Spain
| | - Beatriz Ramírez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,Obesity & Adipobiology Group, Instituto de Investigación Sanitario de Navarra (IdiSNA), Pamplona, Spain.,CIBEROBN, Instituto de Salud Carlos III, Pamplona, Spain
| | - Inês O Gonçalves
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| | - Jorge Beleza
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,Obesity & Adipobiology Group, Instituto de Investigación Sanitario de Navarra (IdiSNA), Pamplona, Spain.,CIBEROBN, Instituto de Salud Carlos III, Pamplona, Spain.,Department of Endocrinology & Nutrition, Clínica Universidad de Navarra, Pamplona, Spain
| | - António Ascensão
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| | - José Magalhães
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| |
Collapse
|
22
|
Abstract
Aquaporins (AQPs ) are expressed in most exocrine and endocrine secretory glands. Consequently, summarizing the expression and functions of AQPs in secretory glands represents a daunting task considering the important number of glands present in the body, as well as the number of mammalian AQPs - thirteen. The roles played by AQPs in secretory processes have been investigated in many secretory glands. However, despite considerable research, additional studies are clearly needed to pursue our understanding of the role played by AQPs in secretory processes. This book chapter will focus on summarizing the current knowledge on AQPs expression and function in the gastrointestinal tract , including salivary glands, gastric glands, Duodenal Brunner's gland, liver and gallbladder, intestinal goblets cells, exocrine and endocrine pancreas, as well as few other secretory glands including airway submucosal glands, lacrimal glands, mammary glands and eccrine sweat glands.
Collapse
Affiliation(s)
- Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Faculty of Medicine, Université Libre de Bruxelles, Brussels, Belgium.
| |
Collapse
|
23
|
Ram R, Morahan G. Effects of Type 1 Diabetes Risk Alleles on Immune Cell Gene Expression. Genes (Basel) 2017; 8:E167. [PMID: 28635624 PMCID: PMC5485531 DOI: 10.3390/genes8060167] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 05/17/2017] [Accepted: 06/14/2017] [Indexed: 12/12/2022] Open
Abstract
Genetic studies have identified 61 variants associated with the risk of developing Type 1 Diabetes (T1D). The functions of most of the non-HLA (Human Leukocyte Antigen) genetic variants remain unknown. We found that only 16 of these risk variants could potentially be linked to a protein-coding change. Therefore, we investigated whether these variants affected susceptibility by regulating changes in gene expression. To do so, we examined whole transcriptome profiles of 600 samples from the Type 1 Diabetes Genetics Consortium (T1DGC). These comprised four different immune cell types (Epstein-Barr virus (EBV)-transformed B cells, either basal or after stimulation; and cluster of differentiation (CD)4+ and CD8+ T cells). Many of the T1D-associated risk variants regulated expression of either neighboring (cis-) or distant (trans-) genes. In brief, 24 of the non-HLA T1D variants affected the expression of 31 nearby genes (cis) while 25 affected 38 distant genes (trans). The effects were highly significant (False Discovery Rate p < 0.001). In addition, we searched in public databases for expression effects of T1D single nucleotide polymorphisms (SNPs) in other immune cell types such as CD14+ monocytes, lipopolysaccharide (LPS) stimulated monocytes, and CD19+ B cells. In this paper, we review the (expression quantitative trait loci (eQTLs) associated with each of the 60 T1D variants and provide a summary of the genes impacted by T1D risk alleles in various immune cells. We then review the methodological steps involved in analyzing the function of genome wide association studies (GWAS)-identified variants, with emphasis on those affecting gene expression. We also discuss recent advancements in the methodologies and their advantages. We conclude by suggesting future study designs that will aid in the study of T1D risk variants.
Collapse
Affiliation(s)
- Ramesh Ram
- Centre for Diabetes Research, Harry Perkins Institute of Medical Research, Nedlands, WA 6009, Australia.
- Centre of Medical Research, University of Western Australia, Nedlands, WA 6009, Australia.
| | - Grant Morahan
- Centre for Diabetes Research, Harry Perkins Institute of Medical Research, Nedlands, WA 6009, Australia.
- Centre of Medical Research, University of Western Australia, Nedlands, WA 6009, Australia.
| |
Collapse
|
24
|
Méndez-Giménez L, Becerril S, Camões SP, da Silva IV, Rodrigues C, Moncada R, Valentí V, Catalán V, Gómez-Ambrosi J, Miranda JP, Soveral G, Frühbeck G, Rodríguez A. Role of aquaporin-7 in ghrelin- and GLP-1-induced improvement of pancreatic β-cell function after sleeve gastrectomy in obese rats. Int J Obes (Lond) 2017; 41:1394-1402. [PMID: 28584298 DOI: 10.1038/ijo.2017.135] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 05/06/2017] [Accepted: 05/25/2017] [Indexed: 01/24/2023]
Abstract
BACKGROUND/OBJECTIVES Glycerol is a key metabolite for lipid accumulation in insulin-sensitive tissues as well as for pancreatic insulin secretion. We examined the role of aquaporin-7 (AQP7), the main glycerol channel in β-cells, and AQP12, an aquaporin related to pancreatic damage, in the improvement of pancreatic function and steatosis after sleeve gastrectomy in diet-induced obese rats. SUBJECTS/METHODS Male Wistar obese rats (n=125) were subjected to surgical (sham operation and sleeve gastrectomy) or dietary (pair-fed to the amount of food eaten by sleeve-gastrectomized animals) interventions. The tissue distribution and expression of AQPs in the rat pancreas were analyzed by real-time PCR, western blotting and immunohistochemistry. The effect of ghrelin isoforms and glucagon-like peptide 1 (GLP-1) on insulin secretion, triacylglycerol (TG) accumulation and AQP expression was determined in vitro in RIN-m5F β-cells. RESULTS Sleeve gastrectomy reduced pancreatic β-cell apoptosis, steatosis and insulin secretion. Lower ghrelin and higher GLP-1 concentrations were also found after bariatric surgery. Acylated and desacyl ghrelin increased TG content, whereas GLP-1 increased insulin release in RIN-m5F β-cells. Sleeve gastrectomy was associated with an upregulation of AQP7 together with a normalization of the increased AQP12 levels in the rat pancreas. Interestingly, ghrelin and GLP-1 repressed AQP7 and AQP12 expression in RIN-m5F β-cells. AQP7 protein was negatively correlated with intracellular lipid accumulation in acylated ghrelin-treated cells and with insulin release in GLP-1-stimulated β-cells. CONCLUSIONS AQP7 upregulation in β-cells after sleeve gastrectomy contributes, in part, to the improvement of pancreatic steatosis and insulin secretion by increasing intracellular glycerol used for insulin release triggered by GLP-1 rather than for ghrelin-induced TG biosynthesis.
Collapse
Affiliation(s)
- L Méndez-Giménez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain
| | - S Becerril
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain
| | - S P Camões
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - I V da Silva
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - C Rodrigues
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - R Moncada
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain.,Department of Anesthesia, Clínica Universidad de Navarra, Pamplona, Spain
| | - V Valentí
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain.,Department of Surgery, Clínica Universidad de Navarra, Pamplona, Spain
| | - V Catalán
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain
| | - J Gómez-Ambrosi
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain
| | - J P Miranda
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - G Soveral
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - G Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain.,Department of Endocrinology &Nutrition, Clínica Universidad de Navarra, Pamplona, Spain
| | - A Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Pamplona, Spain
| |
Collapse
|
25
|
Rocha-Rodrigues S, Rodríguez A, Gonçalves IO, Moreira A, Maciel E, Santos S, Domingues MR, Frühbeck G, Ascensão A, Magalhães J. Impact of physical exercise on visceral adipose tissue fatty acid profile and inflammation in response to a high-fat diet regimen. Int J Biochem Cell Biol 2017; 87:114-124. [PMID: 28438715 DOI: 10.1016/j.biocel.2017.04.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/17/2017] [Accepted: 04/18/2017] [Indexed: 01/14/2023]
Abstract
PURPOSE Studies associate specific fatty-acids (FA) with the pathophysiology of inflammation. We aimed to analyze the impact of exercise on adipose tissue FA profile in response to a high-fat diet (HFD) and to ascertain whether these exercise-induced changes in specific FA have repercussions on obesity-related inflammation. METHODS Sprague-Dawley rats were assigned into sedentary, voluntary physical-activity (VPA) and endurance training (ET) groups fed a standard (S, 35kcal% fat) or high-fat (71kcal% fat) diets. VPA-animals had unrestricted access to wheel-running. After 9-wks, ET-animals engaged a running protocol for 8-wks, while maintained dietary treatments. The FA content in epididymal white-adipose tissue (eWAT) triglycerides was analyzed by gas-chromatography and the expression of inflammatory markers was determined using RT-qPCR, Western and slot blotting. RESULTS Eight-wks of ET reversed obesity-related anatomical features. HFD increased plasma tumor necrosis factor (TNF)-α content and eWAT monocyte chemoattractant protein (MCP)-1 protein expression. HFD decreased eWAT content of saturated FA and monounsaturated FA, while increased linoleic acid and prostaglandin E2 (PGE2) levels in eWAT. VPA decreased visceral adiposity, adipocyte size and MCP-1 in HFD-fed animals. The VPA and ET interventions diminished palmitoleic acid and increased linoleic acid in HFD-fed groups. Moreover, both interventions increased PGE2 levels in standard diet-fed groups and decreased in HFD. ET increased eWAT fatty acid desaturase 1 (FADS1) and elongase 5 (ELOVL5) protein content in both diet types. ET reduced eWAT inflammatory markers (TNF-α, IL-6), macrophage recruitment (MCP-1 and F4/80) and increased IL-10/TNF-α ratio in plasma and in eWAT in both diet types. CONCLUSIONS Exercise induced FA-specific changes independently of dietary FA composition, but only ET attenuated the inflammatory response in VAT of HFD-fed rats. Moreover, the exercise-induced FA changes did not correlate with the inflammatory response in VAT of rats submitted to HFD.
Collapse
Affiliation(s)
- Sílvia Rocha-Rodrigues
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal.
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Obesity & Adipobiology Group, Instituto de Investigación Sanitario de Navarra (IdiSNA), CIBEROBN, Instituto de Salud Carlos III, Pamplona, Spain
| | - Inês O Gonçalves
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| | - Ana Moreira
- Mass spectrometry Centre, UI-QOPNA Department of Chemistry, University of Aveiro, Aveiro, Portugal
| | - Elisabete Maciel
- Mass spectrometry Centre, UI-QOPNA Department of Chemistry, University of Aveiro, Aveiro, Portugal
| | - Sónia Santos
- CICECO, Department of Chemistry, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal
| | - Maria R Domingues
- Mass spectrometry Centre, UI-QOPNA Department of Chemistry, University of Aveiro, Aveiro, Portugal
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Obesity & Adipobiology Group, Instituto de Investigación Sanitario de Navarra (IdiSNA), CIBEROBN, Instituto de Salud Carlos III, Pamplona, Spain; Department of Endocrinology & Nutrition, Clínica Universidad de Navarra, Pamplona, Spain
| | - António Ascensão
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| | - José Magalhães
- CIAFEL - Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal
| |
Collapse
|
26
|
Wawrzkiewicz-Jałowiecka A, Kowalczyk K, Pluta D, Blukacz Ł, Madej P. The role of aquaporins in polycystic ovary syndrome - A way towards a novel drug target in PCOS. Med Hypotheses 2017; 102:23-27. [PMID: 28478824 DOI: 10.1016/j.mehy.2017.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/05/2017] [Indexed: 11/25/2022]
Abstract
Aquaporins (AQPs) are transmembrane proteins, able to transport water (and in some cases also small solutes, e. g. glycerol) through the cell membrane. There are twelve types of aquaporins (AQP1-AQP12) expressed in mammalian reproductive systems. According to literature, many diseases of the reproductive organs are correlated with changes of AQPs expression and their malfunction. That is the case in the polycystic ovary syndrome (PCOS), where dysfunctions of AQPs 7-9 and alterations in its levels occur. In this work, we postulate how AQPs are involved in PCOS-related disorders, in order to emphasize their potential therapeutic meaning as a drug target. Our research allows for a surprising inference, that genetic mutation causing malfunction and/or decreased expression of aquaporins, may be incorporated in the popular insulin-dependent hypothesis of PCOS pathogenesis. What is more, changes in AQP's expression may affect the folliculogenesis and follicular atresia in PCOS.
Collapse
Affiliation(s)
- Agata Wawrzkiewicz-Jałowiecka
- Department of Physical Chemistry and Technology of Polymers, Faculty of Chemistry, Silesian University of Technology, 44-100 Gliwice, Ks. M. Strzody 9, Poland.
| | - Karolina Kowalczyk
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| | - Dagmara Pluta
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| | - Łukasz Blukacz
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| | - Paweł Madej
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| |
Collapse
|
27
|
Tardelli M, Moreno-Viedma V, Zeyda M, Itariu BK, Langer FB, Prager G, Stulnig TM. Adiponectin regulates aquaglyceroporin expression in hepatic stellate cells altering their functional state. J Gastroenterol Hepatol 2017; 32:253-260. [PMID: 27083512 DOI: 10.1111/jgh.13415] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 04/04/2016] [Accepted: 04/08/2016] [Indexed: 12/29/2022]
Abstract
BACKGROUND AND AIM Obesity is a major risk factor for liver fibrosis and tightly associated with low levels of adiponectin. Adiponectin has antifibrogenic activity protecting from liver fibrosis, which is mainly driven by activated hepatic stellate cells (HSC). Aquaporins are transmembrane proteins that allow the movement of water and, in case of aquaglyceroporins (AQPs), of glycerol that is needed in quiescent HSC for lipogenesis. Expression of various AQPs in liver is altered by obesity; however, the mechanisms through which obesity influences HSCs activation and AQPs expression remain unclear. This study aimed to identify obesity-associated factors that are related to HSC AQPs expression activation and lipid storage. METHODS Correlations between serum adipokine levels and hepatic AQPs gene expression were analyzed from a cohort of obese patients. AQP and fibrotic gene expression was determined in a HSC line (LX2) and in a hepatocyte cell line (HepG2) after stimulation with adiponectin using quantitative real-time polymerase chain reaction. RESULTS We found that serum adiponectin significantly correlated with liver AQP3, AQP7, AQP9 gene expressions. In vitro, adiponectin induced upregulation of AQP3 gene and AQP3 protein expression in human HSCs, but not in hepatocytes, while AQP7, AQP9 remained undetectable. Accordingly, HSC stimulated with adiponectin increased glycerol uptake, lipogenic gene expression, and lipid storage while downregulating activation/fibrosis markers. CONCLUSIONS These findings demonstrate that adiponectin is a potent inhibitor of HSC activation and induces AQPs expression. Thus, low serum levels of adiponectin could be a mechanism how obesity affects the functional state of HSC, thereby contributing to obesity-associated liver fibrosis.
Collapse
Affiliation(s)
- Matteo Tardelli
- Christian Doppler-Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Veronica Moreno-Viedma
- Christian Doppler-Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Maximilian Zeyda
- Christian Doppler-Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Bianca K Itariu
- Christian Doppler-Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Felix B Langer
- Department of Surgery, Division of General Surgery, Medical University of Vienna, Vienna, Austria
| | - Gerhard Prager
- Department of Surgery, Division of General Surgery, Medical University of Vienna, Vienna, Austria
| | - Thomas M Stulnig
- Christian Doppler-Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| |
Collapse
|
28
|
Involvement of JNK/NFκB Signaling Pathways in the Lipopolysaccharide-Induced Modulation of Aquaglyceroporin Expression in 3T3-L1 Cells Differentiated into Adipocytes. Int J Mol Sci 2016; 17:ijms17101742. [PMID: 27763558 PMCID: PMC5085770 DOI: 10.3390/ijms17101742] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/11/2016] [Accepted: 10/12/2016] [Indexed: 01/26/2023] Open
Abstract
Aquaglyceroporins, belonging to the family of aquaporins (AQPs), are integral plasma membrane proteins permeable to water and glycerol that have emerged as key players in obesity. The aim of this study was to investigate the expression profile of AQPs in undifferentiated and differentiated 3T3-L1 cells and to investigate the changes in expression of aquaglyceroporins in 3T3-L1 cells differentiated into adipocytes and subjected to lipopolysaccharide (LPS) mimicking inflammation occurring during obesity. Furthermore, the study aimed at identifying the signaling cascade involved in the regulation of aquaglyceroporins expression upon LPS stimulation. 3T3-L1 cells were grown as undifferentiated cells (UDC; preadipocytes) or cells differentiated into adipocytes (DC, adipocytes). DC were incubated in the presence or absence of LPS with or without inhibitors of various protein kinases. AQPs mRNA expression levels were measured by real-time quantitative polymerase chain reaction (RT-qPCR). AQP1, AQP2, AQP3, AQP9 and AQP11 mRNA were expressed in both UDC and DC, whereas AQP4, AQP7 and AQP8 mRNA were expressed only in DC. In DC, LPS up-regulated AQP3 mRNA levels (p < 0.05) compared to control; these effects were inhibited by CLI095, SP600125 and BAY11-7082 (p < 0.05). LPS decreased both AQP7 and AQP11 mRNA levels (p < 0.01) in DC as compared to control; this decrease was inhibited by CLI095 and BAY11-7082 (p < 0.05) and additionally by SP00125 for AQP7 (p < 0.05). SB203580 had no effect on LPS-induced AQP3, AQP7 and AQP11 mRNA levels modulations. In conclusion, our results clearly show that many AQPs are expressed in murine 3T3-L1 adipocytes. Moreover, in DCs, LPS led to decreased AQP7 and AQP11 mRNA levels but to increased AQP3 mRNA levels, resulting from the Toll-like receptor 4 (TLR4)-induced activation of JNK and/or NFκB pathway.
Collapse
|
29
|
Cheung OKW, Cheng ASL. Gender Differences in Adipocyte Metabolism and Liver Cancer Progression. Front Genet 2016; 7:168. [PMID: 27703473 PMCID: PMC5029146 DOI: 10.3389/fgene.2016.00168] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/05/2016] [Indexed: 12/12/2022] Open
Abstract
Liver cancer is the third most common cancer type and the second leading cause of deaths in men. Large population studies have demonstrated remarkable gender disparities in the incidence and the cumulative risk of liver cancer. A number of emerging risk factors regarding metabolic alterations associated with obesity, diabetes and dyslipidemia have been ascribed to the progression of non-alcoholic fatty liver diseases (NAFLD) and ultimately liver cancer. The deregulation of fat metabolism derived from excessive insulin, glucose, and lipid promotes cancer-causing inflammatory signaling and oxidative stress, which eventually triggers the uncontrolled hepatocellular proliferation. This review presents the current standing on the gender differences in body fat compositions and their mechanistic linkage with the development of NAFLD-related liver cancer, with an emphasis on genetic, epigenetic and microRNA control. The potential roles of sex hormones in instructing adipocyte metabolic programs may help unravel the mechanisms underlying gender dimorphism in liver cancer and identify the metabolic targets for disease management.
Collapse
Affiliation(s)
- Otto K-W Cheung
- School of Biomedical Sciences, The Chinese University of Hong Kong Hong Kong, China
| | - Alfred S-L Cheng
- School of Biomedical Sciences, The Chinese University of Hong Kong Hong Kong, China; State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong Hong Kong, China
| |
Collapse
|
30
|
Sleeve Gastrectomy Reduces Hepatic Steatosis by Improving the Coordinated Regulation of Aquaglyceroporins in Adipose Tissue and Liver in Obese Rats. Obes Surg 2015; 25:1723-34. [PMID: 25736229 DOI: 10.1007/s11695-015-1612-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Glycerol constitutes an important metabolite for the control of lipid accumulation and glucose homeostasis. Our aim was to investigate the potential role of aquaglyceroporins, which are glycerol channels mediating glycerol efflux in adipocytes (AQP3 and AQP7) and glycerol influx (AQP9) in hepatocytes, in the improvement of adiposity and hepatic steatosis after sleeve gastrectomy in an experimental model of diet-induced obesity (DIO). METHODS Male Wistar DIO rats (n = 161) were subjected to surgical (sham operation and sleeve gastrectomy) or dietary interventions [fed ad libitum a normal diet (ND) or a high-fat diet (HFD) or pair-fed to the amount of food eaten by sleeve-gastrectomized animals]. The tissue distribution and expression of AQPs in biopsies of epididymal (EWAT) and subcutaneous (SCWAT) white adipose tissue and liver were analyzed by real-time PCR, Western blot, and immunohistochemistry. RESULTS Four weeks after surgery, DIO rats undergoing sleeve gastrectomy showed a reduction in body weight, whole-body adiposity, and hepatic steatosis. DIO was associated with a tendency towards an increase in EWAT AQP3 and SCWAT AQP7 and a decrease in hepatic AQP9. Sleeve gastrectomy downregulated AQP7 in both fat depots and upregulated AQP3 in EWAT, without changing hepatic AQP9. Aqp7 transcript levels in EWAT and SCWAT were positively associated with adiposity and glycemia, while Aqp9 mRNA was negatively correlated with markers of hepatic steatosis and insulin resistance. CONCLUSION Our results show, for the first time, that sleeve gastrectomy, a widely applied bariatric surgery procedure, restores the coordinated regulation of fat-specific AQP7 and liver-specific AQP9, thereby improving whole-body adiposity and hepatic steatosis.
Collapse
|
31
|
Laforenza U, Bottino C, Gastaldi G. Mammalian aquaglyceroporin function in metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:1-11. [PMID: 26456554 DOI: 10.1016/j.bbamem.2015.10.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 10/05/2015] [Accepted: 10/07/2015] [Indexed: 11/26/2022]
Abstract
Aquaglyceroporins are integral membrane proteins that are permeable to glycerol as well as water. The movement of glycerol from a tissue/organ to the plasma and vice versa requires the presence of different aquaglyceroporins that can regulate the entrance or the exit of glycerol across the plasma membrane. Actually, different aquaglyceroporins have been discovered in the adipose tissue, small intestine, liver, kidney, heart, skeletal muscle, endocrine pancreas and capillary endothelium, and their differential expression could be related to obesity and the type 2 diabetes. Here we describe the expression and function of different aquaglyceroporins in physiological condition and in obesity and type 2 diabetes, suggesting they are potential therapeutic targets for metabolic disorders.
Collapse
Affiliation(s)
| | - Cinzia Bottino
- Department of Molecular Medicine, University of Pavia, Italy
| | - Giulia Gastaldi
- Department of Molecular Medicine, University of Pavia, Italy
| |
Collapse
|
32
|
Leptin administration restores the altered adipose and hepatic expression of aquaglyceroporins improving the non-alcoholic fatty liver of ob/ob mice. Sci Rep 2015; 5:12067. [PMID: 26159457 PMCID: PMC4498231 DOI: 10.1038/srep12067] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 06/17/2015] [Indexed: 12/27/2022] Open
Abstract
Glycerol is an important metabolite for the control of lipid accumulation in white adipose tissue (WAT) and liver. We aimed to investigate whether exogenous administration of leptin improves features of non-alcoholic fatty liver disease (NAFLD) in leptin-deficient ob/ob mice via the regulation of AQP3 and AQP7 (glycerol channels mediating glycerol efflux in adipocytes) and AQP9 (aquaglyceroporin facilitating glycerol influx in hepatocytes). Twelve-week-old male wild type and ob/ob mice were divided in three groups as follows: control, leptin-treated (1 mg/kg/d) and pair-fed. Leptin deficiency was associated with obesity and NAFLD exhibiting an AQP3 and AQP7 increase in WAT, without changes in hepatic AQP9. Adipose Aqp3 and hepatic Aqp9 transcripts positively correlated with markers of adiposity and hepatic steatosis. Chronic leptin administration (4-weeks) was associated with improved body weight, whole-body adiposity, and hepatosteatosis of ob/ob mice and to a down-regulation of AQP3, AQP7 in WAT and an up-regulation of hepatic AQP9. Acute leptin stimulation in vitro (4-h) induced the mobilization of aquaglyceroporins towards lipid droplets (AQP3) and the plasma membrane (AQP7) in murine adipocytes. Our results show that leptin restores the coordinated regulation of fat-specific AQP7 and liver-specific AQP9, a step which might prevent lipid overaccumulation in WAT and liver in obesity.
Collapse
|
33
|
Madeira A, Moura TF, Soveral G. Aquaglyceroporins: implications in adipose biology and obesity. Cell Mol Life Sci 2015; 72:759-71. [PMID: 25359234 PMCID: PMC11113391 DOI: 10.1007/s00018-014-1773-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/07/2014] [Accepted: 10/27/2014] [Indexed: 01/19/2023]
Abstract
Aquaporins (AQPs) are membrane water/glycerol channels that are involved in many physiological processes. Their primary function is to facilitate the bidirectional transfer of water and small solutes across biological membranes in response to osmotic gradients. Aquaglyceroporins, a subset of the AQP family, are the only mammalian proteins with the ability to permeate glycerol. For a long time, AQP7 has been the only aquaglyceroporin associated with the adipose tissue, which is the major source of circulating glycerol in response to the energy demand. AQP7 dysregulation was positively correlated with obesity onset and adipocyte glycerol permeation through AQP7 was appointed as a novel regulator of adipocyte metabolism and whole-body fat mass. Recently, AQP3, AQP9, AQP10 and AQP11 were additionally identified in human adipocytes and proposed as additional glycerol pathways in these cells. This review contextualizes the importance of aquaglyceroporins in adipose tissue biology and highlights aquaglyceroporins' unique structural features which are relevant for the design of effective therapeutic compounds. We also refer to the latest advances in the identification and characterization of novel aquaporin isoforms in adipose tissue. Finally, considerations on the actual progress of aquaporin research and its implications on obesity therapy are suggested.
Collapse
Affiliation(s)
- Ana Madeira
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, Lisbon, 1649-003 Portugal
- Department of Bioquimica e Biologia Humana, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - Teresa F. Moura
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, Lisbon, 1649-003 Portugal
- FCT-UNL, 2829-516 Caparica, Portugal
| | - Graça Soveral
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, Lisbon, 1649-003 Portugal
- Department of Bioquimica e Biologia Humana, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| |
Collapse
|
34
|
Rodríguez A, Marinelli RA, Tesse A, Frühbeck G, Calamita G. Sexual Dimorphism of Adipose and Hepatic Aquaglyceroporins in Health and Metabolic Disorders. Front Endocrinol (Lausanne) 2015; 6:171. [PMID: 26594198 PMCID: PMC4633488 DOI: 10.3389/fendo.2015.00171] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 10/26/2015] [Indexed: 12/13/2022] Open
Abstract
Gender differences in the relative risk of developing metabolic complications, such as insulin resistance or non-alcoholic fatty liver disease (NAFLD), have been reported. The deregulation of glycerol metabolism partly contributes to the onset of these metabolic diseases, since glycerol constitutes a key substrate for the synthesis of triacylglycerols (TAGs) as well as for hepatic gluconeogenesis. The present mini-review covers the sex--related differences in glycerol metabolism and aquaglyceroporins (AQPs) and its impact in the control of adipose and hepatic fat accumulation as well as in whole-body glucose homeostasis. Plasma glycerol concentrations are increased in women compared to men probably due to the higher lipolytic rate and larger AQP7 amounts in visceral fat as well as the well-known sexual dimorphism in fat mass with women showing higher adiposity. AQP9 represents the primary route for glycerol uptake in hepatocytes, where glycerol is converted by the glycerol-kinase enzyme into glycerol-3-phosphate, a key substrate for de novo synthesis of glucose and TAG. In spite of showing similar hepatic AQP9 protein, women exhibit lower hepatocyte glycerol permeability than men, which might contribute to their lower prevalence of insulin resistance and NAFLD.
Collapse
Affiliation(s)
- Amaia Rodríguez
- Metabolic Research Laboratory, CIBEROBN, IdiSNA, Clínica Universidad de Navarra, Pamplona, Spain
| | - Raul A. Marinelli
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Angela Tesse
- INSERM UMR 1087/CNRS UMR 629, L’Institut du Thorax, IRS-UN, Nantes, France
| | - Gema Frühbeck
- Metabolic Research Laboratory, CIBEROBN, IdiSNA, Clínica Universidad de Navarra, Pamplona, Spain
| | - Giuseppe Calamita
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari “Aldo Moro”, Bari, Italy
- *Correspondence: Giuseppe Calamita,
| |
Collapse
|
35
|
Méndez-Giménez L, Rodríguez A, Balaguer I, Frühbeck G. Role of aquaglyceroporins and caveolins in energy and metabolic homeostasis. Mol Cell Endocrinol 2014; 397:78-92. [PMID: 25008241 DOI: 10.1016/j.mce.2014.06.017] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 06/25/2014] [Accepted: 06/26/2014] [Indexed: 12/23/2022]
Abstract
Aquaglyceroporins and caveolins are submicroscopic integral membrane proteins that are particularly abundant in many mammalian cells. Aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) encompass a subfamily of aquaporins that allow the movement of water, but also of small solutes, such as glycerol, across cell membranes. Glycerol constitutes an important metabolite as a substrate for de novo synthesis of triacylglycerols and glucose as well as an energy substrate to produce ATP via the mitochondrial oxidative phosphorylation. In this sense, the control of glycerol influx/efflux in metabolic organs by aquaglyceroporins plays a crucial role with the dysregulation of these glycerol channels being associated with metabolic diseases, such as obesity, insulin resistance, non-alcoholic fatty liver disease and cardiac hypertrophy. On the other hand, caveolae have emerged as relevant plasma membrane sensors implicated in a wide range of cellular functions, including endocytosis, apoptosis, cholesterol homeostasis, proliferation and signal transduction. Caveolae-coating proteins, namely caveolins and cavins, can act as scaffolding proteins within caveolae by concentrating signaling molecules involved in free fatty acid and cholesterol uptake, proliferation, insulin signaling or vasorelaxation, among others. The importance of caveolae in whole-body homeostasis is highlighted by the link between homozygous mutations in genes encoding caveolins and cavins with metabolic diseases, such as lipodystrophy, dyslipidemia, muscular dystrophy and insulin resistance in rodents and humans. The present review focuses on the role of aquaglyceroporins and caveolins on lipid and glucose metabolism, insulin secretion and signaling, energy production and cardiovascular homeostasis, outlining their potential relevance in the development and treatment of metabolic diseases.
Collapse
Affiliation(s)
- Leire Méndez-Giménez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Pamplona, Spain
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Pamplona, Spain.
| | - Inmaculada Balaguer
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Pamplona, Spain; Department of Endocrinology and Nutrition, Clínica Universidad de Navarra, Pamplona, Spain.
| |
Collapse
|
36
|
Guo M, Chen F, Lin T, Peng Y, Li W, Zhu X, Lin L, Chen Y. Apelin-13 decreases lipid storage in hypertrophic adipocytes in vitro through the upregulation of AQP7 expression by the PI3K signaling pathway. Med Sci Monit 2014; 20:1345-52. [PMID: 25080850 PMCID: PMC4136933 DOI: 10.12659/msm.890124] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 01/26/2014] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Adipocyte-secreted apelin contributes to decreased adiposity and to improved insulin resistance, but the mechanisms remain unknown. The present study aimed to assess if apelin-13 is an upstream signal regulation factor of aquaporin 7 (AQP7), a water-glycerol transporter present in the plasma membrane of adipocytes that plays a key role in the regulation of lipid accumulation. MATERIAL/METHODS 3T3-L1 pre-adipocytes were induced to fully differentiated adipocytes; hypertrophic adipocytes were then induced using palmitate. The effects of apelin-13 on AQP7 expression in hypertrophic adipocytes were investigated before and after treatment with LY249002, a PI3K inhibitor. Accumulation of cytoplasmic triglycerides (TG) in hypertrophic adipocytes was also determined. RESULTS We found that 0.1 mM of palmitate induced a model of hypertrophic adipocytes with a lower AQP7 expression (0.26±0.07 vs. 0.46±0.04, P<0.05). Apelin-13 100 nM or 1000 nM upregulated AQP7 mRNA expression (100 nM: 0.54±0.06 and 1000 nM: 0.58±0.09 vs. control: 0.33±0.04, both P<0.05), and decreased accumulation of cytoplasmic triglycerides in hypertrophic adipocytes. Pretreatment using 10 µM LY294002 prevented the increase in AQP7 expression observed when using apelin-13 alone (apelin-13 + LY49002: 0.38±0.03 vs. apelin-13: 0.54±0.06, P<0.05), as well as the decreased cytoplasmic TG accumulation (apelin-13 + LY294002: 3.79±0.04 µM per µg/ml vs. apelin-13: 3.32±0.08 µM per µg/ml, P<0.05). CONCLUSIONS Apelin-13 decreases lipid storage in hypertrophic adipocytes in vitro, possibly through the upregulation of AQP7 expression by the PI3K signaling pathway. Treatment using apelin-13 and AQP modulators might represent novel treatment strategies against obesity and its related complications.
Collapse
Affiliation(s)
- Mei Guo
- Department of Endocrinology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Fu Chen
- Department of Endocrinology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Tanfa Lin
- Department of Endocrinology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Yanqiang Peng
- Department of Nephrology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Weiping Li
- Department of Endocrinology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Xuxin Zhu
- Department of Endocrinology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Ling Lin
- Department of Rheumatology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
| | - Yongsong Chen
- Department of Endocrinology, First Affiliated Hospital, Shantou University Medical College, Shantou, China
- Corresponding Author: Yongsong Chen, e-mail: and Ling Lin, e-mail:
| |
Collapse
|
37
|
Abstract
In adipocytes the hydrolysis of TAG to produce fatty acids and glycerol under fasting conditions or times of elevated energy demands is tightly regulated by neuroendocrine signals, resulting in the activation of lipolytic enzymes. Among the classic regulators of lipolysis, adrenergic stimulation and the insulin-mediated control of lipid mobilisation are the best known. Initially, hormone-sensitive lipase (HSL) was thought to be the rate-limiting enzyme of the first lipolytic step, while we now know that adipocyte TAG lipase is the key enzyme for lipolysis initiation. Pivotal, previously unsuspected components have also been identified at the protective interface of the lipid droplet surface and in the signalling pathways that control lipolysis. Perilipin, comparative gene identification-58 (CGI-58) and other proteins of the lipid droplet surface are currently known to be key regulators of the lipolytic machinery, protecting or exposing the TAG core of the droplet to lipases. The neuroendocrine control of lipolysis is prototypically exerted by catecholaminergic stimulation and insulin-induced suppression, both of which affect cyclic AMP levels and hence the protein kinase A-mediated phosphorylation of HSL and perilipin. Interestingly, in recent decades adipose tissue has been shown to secrete a large number of adipokines, which exert direct effects on lipolysis, while adipocytes reportedly express a wide range of receptors for signals involved in lipid mobilisation. Recently recognised mediators of lipolysis include some adipokines, structural membrane proteins, atrial natriuretic peptides, AMP-activated protein kinase and mitogen-activated protein kinase. Lipolysis needs to be reanalysed from the broader perspective of its specific physiological or pathological context since basal or stimulated lipolytic rates occur under diverse conditions and by different mechanisms.
Collapse
|
38
|
Aquaporins in salivary glands and pancreas. Biochim Biophys Acta Gen Subj 2014; 1840:1524-32. [DOI: 10.1016/j.bbagen.2013.08.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 08/07/2013] [Accepted: 08/08/2013] [Indexed: 12/23/2022]
|
39
|
Abstract
Obesity and secondary development of type 2 diabetes (T2D) are major health care problems throughout the developed world. Accumulating evidence suggest that glycerol metabolism contributes to the pathophysiology of obesity and T2D. Glycerol is a small molecule that serves as an important intermediate between carbohydrate and lipid metabolism. It is stored primarily in adipose tissue as the backbone of triglyceride (TG) and during states of metabolic stress, such as fasting and diabetes, it is released for metabolism in other tissues. In the liver, glycerol serves as a gluconeogenic precursor and it is used for the esterification of free fatty acid into TGs. Aquaporin 7 (AQP7) in adipose tissue and AQP9 in the liver are transmembrane proteins that belong to the subset of AQPs called aquaglyceroporins. AQP7 facilitates the efflux of glycerol from adipose tissue and AQP7 deficiency has been linked to TG accumulation in adipose tissue and adult onset obesity. On the other hand, AQP9 expressed in liver facilitates the hepatic uptake of glycerol and thereby the availability of glycerol for de novo synthesis of glucose and TG that both are involved in the pathophysiology of diabetes. The aim of this review was to summarize the current knowledge on the role of the two glycerol channels in controlling glycerol metabolism in adipose tissue and liver.
Collapse
Affiliation(s)
- Janne Lebeck
- The Danish Diabetes Academy, Odense, Denmark Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 3, DK-8000 Aarhus, Denmark
| |
Collapse
|
40
|
Reduced hepatic aquaporin-9 and glycerol permeability are related to insulin resistance in non-alcoholic fatty liver disease. Int J Obes (Lond) 2013; 38:1213-20. [PMID: 24418844 DOI: 10.1038/ijo.2013.234] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 11/20/2013] [Accepted: 12/04/2013] [Indexed: 12/26/2022]
Abstract
BACKGROUND/OBJECTIVES Glycerol represents an important metabolite for the control of lipid accumulation and hepatic gluconeogenesis. We investigated whether hepatic expression and functionality of aquaporin-9 (AQP9), a channel mediating glycerol influx into hepatocytes, is impaired in non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) in the context of insulin resistance. SUBJECTS/METHODS Liver biopsies were obtained from 66 morbid obese patients undergoing bariatric surgery (66% women, mean body mass index (BMI) 46.1±1.0 kg m(-2)) with available liver echography and pathology analysis of the biopsies in this cross-sectional study. Subjects were classified according to normoglycemia (NG), impaired glucose tolerance (IGT) or type 2 diabetes (T2D). Hepatic expression of AQP9 was analyzed by real-time PCR, western blotting and immunohistochemistry, while glycerol permeability (P(gly)) was measured by stopped-flow light scattering. RESULTS AQP9 was the most abundantly (P<0.0001) expressed aquaglyceroporin in human liver (AQP9>>>AQP3>AQP7>AQP10). Obese patients with T2D showed increased plasma glycerol as well as lower P(gly) and hepatic AQP9 expression. The prevalence of NAFLD and NASH in T2D patients was 100 and 65%, respectively. Interestingly, AQP9 expression was decreased in patients with NAFLD and NASH as compared with those without hepatosteatosis, in direct relation to the degree of steatosis and lobular inflammation, being further reduced in insulin-resistant individuals. The association of AQP9 with insulin sensitivity was independent of BMI and age. Consistent with these data, fasting insulin and C-reactive protein contributed independently to 33.1% of the hepatic AQP9 mRNA expression variance after controlling for the effects of age and BMI. CONCLUSIONS AQP9 downregulation together with the subsequent reduction in hepatic glycerol permeability in insulin-resistant states emerges as a compensatory mechanism whereby the liver counteracts further triacylglycerol accumulation within its parenchyma as well as reduces hepatic gluconeogenesis in patients with NAFLD.
Collapse
|
41
|
Liver glycerol permeability and aquaporin-9 are dysregulated in a murine model of Non-Alcoholic Fatty Liver Disease. PLoS One 2013; 8:e78139. [PMID: 24205128 PMCID: PMC3813550 DOI: 10.1371/journal.pone.0078139] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 09/11/2013] [Indexed: 11/19/2022] Open
Abstract
One form of liver steatosis, namely Non-Alcoholic Fatty Liver Disease (NAFLD), is a worrisome health problem worldwide characterized by intrahepatic triacylglycerol (TG) overaccumulation. NAFLD is a common feature of metabolic syndrome being often associated with obesity, dyslipidemia and diabetes and mostly closely linked to insulin resistance. The mechanism of NAFLD pathogenesis is object of intense investigation especially regarding complex systems ultimately resulting in excessive TG deposition in hepatocytes. However, scarce is the attention about the relevance of hepatic import of glycerol, the other primary source (as glycerol-3-phosphate) of increased TG in hepatocytes. Obese leptin-deficient (ob/ob) mice, an animal model of NAFLD, were used to evaluate the functional involvement of Aquaporin-9 (AQP9), the major pathway of liver glycerol entry, in hepatosteatosis. By RT-PCR and qPCR, the level of Aqp9 mRNA in the liver of starved obese mice was comparable with the corresponding control lean littermates. By immunoblotting, the AQP9 protein at the hepatocyte sinusoidal plasma membrane of obese mice was markedly lower (33%) than lean mice, a finding fully confirmed by immunohistochemistry. By stopped-flow light scattering, the liver glycerol permeability of ob/ob mice was significantly lower (53%) than lean mice, a finding consistent with both the observed down-regulation of AQP9 protein and increased level of plasma glycerol characterizing obese mice. In summary, our results suggest implication of AQP9 in liver steatosis. The reduction of hepatocyte AQP9 and, consequently, glycerol permeability might be a defensive mechanism to counteract further fat infiltration in liver parenchyma.
Collapse
|
42
|
Cai C, Wang C, Ji W, Liu B, Kang Y, Hu Z, Jiang Z. Knockdown of hepatic aquaglyceroporin-9 alleviates high fat diet-induced non-alcoholic fatty liver disease in rats. Int Immunopharmacol 2013; 15:550-6. [PMID: 23415870 DOI: 10.1016/j.intimp.2013.01.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Revised: 01/23/2013] [Accepted: 01/25/2013] [Indexed: 12/25/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) has emerged as a common public health problem that can progress to end-stage liver disease. Although the function of aquaglyceroporin-9 (AQP9) as a glycerol channel has been proven, the mechanism of AQP9 in the development of NAFLD is poorly understood. To investigate the effect of hepatic glycerol uptake inhibition, we utilized a lentivirus-associated RNA interference technique to knock down the expression of hepatic AQP9 in high fat diet (HFD)-induced NAFLD in rodents. Male Sprague-Dawley rats were fed with a standard chow diet or HFD for 8 weeks. Rats fed a HFD were separated into 3 groups: HFD, control and transfection group, which were injected with equivalent amounts of PBS, lentivirus-scramble and lentivirus-shRNA-AQP9 through the hepatic portal vein. The results showed a remarkable decrease in the expression of AQP9 mRNA and protein in liver for the transfection group. Furthermore, less hepatic steatosis occurred when compared to the HFD and control groups after 8weeks. Our results indicate a potential role for AQP9 in the pathogenesis of hepatic steatosis.
Collapse
Affiliation(s)
- Can Cai
- Department of Gastroenterology, First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, PR China
| | | | | | | | | | | | | |
Collapse
|
43
|
Seow KM, Lin YH, Wang PH, Hwang JL, Ho LT, Juan CC. Aquaglyceroporin-7 Overexpression in Women with the Polycystic Ovary Syndrome. Gynecol Obstet Invest 2013; 75:126-31. [DOI: 10.1159/000345069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 09/27/2012] [Indexed: 11/19/2022]
|
44
|
Lebeck J, Østergård T, Rojek A, Füchtbauer EM, Lund S, Nielsen S, Praetorius J. Gender-specific effect of physical training on AQP7 protein expression in human adipose tissue. Acta Diabetol 2012; 49 Suppl 1:S215-26. [PMID: 23001483 DOI: 10.1007/s00592-012-0430-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 09/03/2012] [Indexed: 02/08/2023]
Abstract
AQP7 is a glycerol channel in adipose tissue with a suggested role in controlling the accumulation of triglycerides and secondly development of obesity and type-2 diabetes. In the present study, we aimed to test the hypotheses that (1) AQP7 is localized to the capillaries within human adipose tissue, (2) genetic predisposition to type-2 diabetes is associated with a low expression of AQP7 in abdominal subcutaneous adipose tissue (SAT) and (3) physical training increases AQP7 expression in SAT. The cellular localization of AQP7 in adipose tissue was investigated by immunohistochemistry. The relative expression of AQP7 protein in abdominal SAT was analysed before and after ending a 10-week exercise training programme in first-degree relatives to type-2 diabetic patients and control individuals. Non-obese first-degree relatives to type-2 diabetic patients (n = 20) and control (n = 11) men and women participated in this study. By this, we find that AQP7 is localized to the capillary endothelial cells within adipose tissue. We were unable to evidence a link between a low AQP7 abundance in SAT and genetic predisposition type-2 diabetes. Instead we demonstrate that physical training influences the expression of AQP7 in SAT in a gender-specific manner. Thus, women responds by increasing the abundance of AQP7 by 2.2-fold (p = 0.03) whereas in men a reduced expression is observed (p = 0.00009), resulting in a more than twofold higher abundance of AQP7 in women as compared with men. In conclusion, the adipose tissue glycerol channel, AQP7, is regulated in response to physical training in a gender-dependent manner in SAT.
Collapse
Affiliation(s)
- Janne Lebeck
- Department of Biomedicine, The Water and Salt Research Center, Health, Aarhus University, Wilhelm Meyers Allé 3, 8000 Aarhus, Denmark.
| | | | | | | | | | | | | |
Collapse
|
45
|
Maeda N. Implications of aquaglyceroporins 7 and 9 in glycerol metabolism and metabolic syndrome. Mol Aspects Med 2012; 33:665-75. [DOI: 10.1016/j.mam.2012.02.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 02/28/2012] [Accepted: 02/28/2012] [Indexed: 10/28/2022]
|
46
|
Yokoyama Y, Iguchi K, Usui S, Hirano K. AMP-activated protein kinase modulates the gene expression of aquaporin 9 via forkhead box a2. Arch Biochem Biophys 2011; 515:80-8. [PMID: 21867676 DOI: 10.1016/j.abb.2011.08.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 08/05/2011] [Accepted: 08/06/2011] [Indexed: 11/29/2022]
Abstract
Aquaporin 9 (AQP9) is permeable to glycerol, which is a source material in lipogenesis and gluconeogenesis in the liver. We investigated the transcriptional regulation of the AQP9 gene by AMP-activated protein kinase (AMPK), known as an energy sensor in cells since AMPK contributes to the metabolism of carbohydrate, lipid, and protein by regulating the expression of many enzymes and transcription factors in metabolic pathways. An AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR), was observed to suppress the expression of the AQP9 gene in HepG2 cells by promoting the phosphorylation of AMPK and AKT/PKB. Forkhead box a2 (Foxa2) was speculated to be one of the transcriptional regulators of AQP9 gene expression repressed by AICAR from the results of a reporter gene assay with a plasmid containing the promoter region of the AQP9 gene and knock-down of the Foxa2 gene by a specific siRNA. AICAR was determined to induce the phosphorylation and nuclear exclusion of Foxa2. Leptomycin B, inhibiting the binding of the nuclear exclusion signal sequence and chromosome region maintenance 1, prevented nuclear export of Foxa2 triggered by AICAR. These results suggest that the activated AMPK by AICAR causes suppression of the gene expression of AQP9 through transcriptional regulation by Foxa2.
Collapse
Affiliation(s)
- Yuichi Yokoyama
- Laboratory of Pharmaceutics, Department of Medical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, Japan
| | | | | | | |
Collapse
|
47
|
Rodríguez A, Catalán V, Gómez-Ambrosi J, Frühbeck G. Aquaglyceroporins serve as metabolic gateways in adiposity and insulin resistance control. Cell Cycle 2011; 10:1548-56. [PMID: 21502813 DOI: 10.4161/cc.10.10.15672] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) encompass a subfamily of aquaporins that allow the movement of water and other small solutes, especially glycerol, through cell membranes. Adipose tissue constitutes a major source of glycerol via AQP7. We have recently reported that, in addition to the well-known expression of AQP7 in adipose tissue, AQP3 and AQP9 are also expressed in omental and subcutaneous fat depots. Moreover, insulin and leptin act as regulators of aquaglyceroporins through the PI3K/Akt/mTOR pathway. AQP3 and AQP7 appear to facilitate glycerol efflux from adipose tissue while reducing the glycerol influx into hepatocytes via AQP9 to prevent the excessive lipid accumulation and the subsequent aggravation of hyperglycemia in human obesity. This Extra View focuses on the control of glycerol release by aquaglyceroporins in the adipose tissue and briefly discusses the importance of glycerol as a substrate for hepatic gluconeogenesis, pancreatic insulin secretion and cardiac ATP production.
Collapse
|
48
|
Rodríguez A, Catalán V, Gómez-Ambrosi J, García-Navarro S, Rotellar F, Valentí V, Silva C, Gil MJ, Salvador J, Burrell MA, Calamita G, Malagón MM, Frühbeck G. Insulin- and leptin-mediated control of aquaglyceroporins in human adipocytes and hepatocytes is mediated via the PI3K/Akt/mTOR signaling cascade. J Clin Endocrinol Metab 2011; 96:E586-97. [PMID: 21289260 DOI: 10.1210/jc.2010-1408] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Glycerol constitutes an important metabolite for the control of lipid accumulation and glucose homeostasis. The impact of obesity and obesity-associated type 2 diabetes as well as the potential regulatory role of insulin and leptin on aquaglyceroporins (AQP) 3, 7, and 9 were analyzed. RESEARCH DESIGN AND METHODS The tissue distribution and expression of AQP in biopsies of omental and sc adipose tissue as well as liver were analyzed in lean and obese Caucasian volunteers (n = 63). The effect of insulin (1, 10, and 100 nmol/liter) and leptin (0.1, 1, and 10 nmol/liter) on the expression of the glycerol channels was determined in vitro in human omental adipocytes and HepG2 hepatocytes. The translocation of AQP in response to insulin and isoproterenol was analyzed by immunocytochemistry. RESULTS In addition to the well-known expression of AQP7 in adipose tissue, AQP3 and AQP9 were also expressed in both omental and sc adipose tissue. Obese type 2 diabetes patients showed higher expression of AQP in visceral adipose tissue and lower expression of AQP7 in sc adipose tissue and hepatic AQP9. The staining of AQP9 in the plasma membrane of adipocytes was reinforced by insulin, whereas isoproterenol induced the translocation of AQP3 and AQP7 from the lipid droplets to the plasma membrane. Insulin up-regulated all AQP, whereas leptin up-regulated AQP3 and down-regulated AQP7 and AQP9 in adipocytes and hepatocytes. These effects were abrogated by both the phosphatidylinositol 3-kinase inhibitor wortmannin and the mammalian target of rapamycin inhibitor rapamycin. CONCLUSIONS Our findings show, for the first time, that insulin and leptin regulate the AQP through the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin pathway in human visceral adipocytes and hepatocytes. AQP3 and AQP7 may facilitate glycerol efflux from adipose tissue while reducing the glycerol influx into hepatocytes via AQP9 to prevent the excessive lipid accumulation and the subsequent aggravation of hyperglycemia in human obesity.
Collapse
Affiliation(s)
- Amaia Rodríguez
- Metabolic Research Laboratory, University of Navarra, 31080 Pamplona, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Tinahones FJ, Garrido-Sanchez L, Miranda M, García-Almeida JM, Macias-Gonzalez M, Ceperuelo V, Gluckmann E, Rivas-Marin J, Vendrell J, García-Fuentes E. Obesity and insulin resistance-related changes in the expression of lipogenic and lipolytic genes in morbidly obese subjects. Obes Surg 2011; 20:1559-67. [PMID: 20512427 DOI: 10.1007/s11695-010-0194-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND The storage capacity of adipose tissue may be an important factor linking obesity, insulin resistance (IR), and associated morbidities. The aim of this study was to analyze the expression of lipogenic and lipolytic genes in adipose tissue and the influence of IR. METHODS We studied the mRNA expression of peroxisome proliferator-activated receptor-γ (PPARγ) and lipogenic and lipolytic enzymes in the visceral (VAT) and subcutaneous adipose tissue (SAT) from 23 morbidly obese patients (MO; 13 with low IR and ten with high IR) and from 15 healthy, lean controls. RESULTS In the VAT and SAT from the MO, we found an increased expression of PPARγ (p = 0.001 and p = 0.022, respectively), acyl-coenzyme A (CoA)/cholesterol acyltransferase (p < 0.001 and p < 0.001), aquaporin 7 (p < 0.001 and p = 0.003), and adipose triglyceride lipase (p < 0.001 and p < 0.001) and a reduced expression of acetyl-coenzyme A carboxylase (p = 0.004 and p < 0.001), independently of the state of IR. The expression of phosphoenolpyruvate carboxykinase and acyl-CoA synthetase, however, was significantly lower in the MO with high IR (p < 0.05). Glycerol kinase (p = 0.010), hormone-sensitive lipase (p < 0.001), and perilipin (p = 0.006) were only significantly increased in VAT. Acyl-CoA synthetase (p = 0.012) and fatty acid binding protein-4 (p = 0.003) were only significantly decreased in SAT. The expression of the genes studied was only greater in the SAT than the VAT in the controls. CONCLUSION Our results show an upregulation of genes facilitating triglyceride/fatty acid cycling and a reduction in the genes involved in de novo synthesis of fatty acids in morbid obesity. The expression of some of the genes studied seems to be related with the state of IR. VAT and SAT differ metabolically and also between controls and MO.
Collapse
Affiliation(s)
- F J Tinahones
- CIBER Fisiopatología Obesidad y Nutrición, Hospital Clínico Virgen de la Victoria, Malaga, Spain
| | | | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Azlina A, Javkhlan P, Hiroshima Y, Hasegawa T, Yao C, Akamatsu T, Hosoi K. Roles of lysosomal proteolytic systems in AQP5 degradation in the submandibular gland of rats following chorda tympani parasympathetic denervation. Am J Physiol Gastrointest Liver Physiol 2010; 299:G1106-17. [PMID: 20689061 DOI: 10.1152/ajpgi.00194.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chorda tympani denervation (CTD) of rats was earlier shown to result in loss of submandibular gland (SMG) weight (at only 1 wk) and in continued reduction in aquaporin 5 (AQP5) protein expression (until 4 wk), without affecting its mRNA synthesis (Li X, Azlina A, Karabasil MR, Purwanti N, Hasegawa T, Yao C, Akamatsu T, Hosoi K. Am J Physiol Gastrointest Liver Physiol 295: G112-G123, 2008). The present study indicated that despite elevation of bax, a proapoptosis protein, by CTD, the operation also increased the level of bcl-2, an antiapoptosis protein, in the SMG. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL assay) showed no increase in the number of apoptotic cells in the SMG. CTD, however, induced strongly and transiently (at 1-3 days) the protein expression of LC3B-II, a marker protein of autophagosomes, suggesting that the reduction in the gland weight was due to onset of autophagy by CTD. Upon CTD, Lamp2, a lysosomal marker, gradually increased in amount, reaching a peak at the 14th day. Immunohistochemical analysis revealed an increase in the number of lysosome-like structures positive for both AQP5 and Lamp2 in the acinar cells of the SMG after CTD; similar changes were observed also for AQP5 and LC3Bs. These data suggest that AQP5 in the SMG entered autophagosomes and/or lysosomes for degradation upon CTD. In vitro AQP5-degrading activity was found in the SMG extracts, and such activity was shown to be increased by CTD. Inhibitor experiments implied cathepsins B and L to be candidate enzymes for this degradation under normal and CTD conditions, respectively.
Collapse
Affiliation(s)
- Ahmad Azlina
- Department of Molecular Oral Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
| | | | | | | | | | | | | |
Collapse
|