1
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Zhang L, Wu M, Zhang J, Liu T, Fu S, Wang Y, Xu Z. The pivotal role of glucose transporter 1 in diabetic kidney disease. Life Sci 2024; 353:122932. [PMID: 39067659 DOI: 10.1016/j.lfs.2024.122932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 07/12/2024] [Accepted: 07/20/2024] [Indexed: 07/30/2024]
Abstract
Diabetes mellitus (DM) is a significant public health problem. Diabetic kidney disease (DKD) is the most common complication of DM, and its incidence has been increasing with the increasing prevalence of DM. Given the association between DKD and mortality in patients with DM, DKD is a significant burden on public health resources. Despite its significance in DM progression, the pathogenesis of DKD remains unclear. Aberrant glucose uptake by cells is an important pathophysiological mechanism underlying DKD renal injury. Glucose is transported across the bilayer cell membrane by a glucose transporter (GLUT) located on the cell membrane. Multiple GLUT proteins have been identified in the kidney, and GLUT1 is one of the most abundantly expressed isoforms. GLUT1 is a crucial regulator of intracellular glucose metabolism and plays a key pathological role in the phenotypic changes in DKD mesangial cells. In an attempt to understand the pathogenesis of DKD better, we here present a review of studies on the role of GLUT1 in the development and progression of DKD.
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Affiliation(s)
- Li Zhang
- Department of Nephrology, The First Hospital of Jilin University, Changchun, 130021, China
| | - Meiyan Wu
- Department of Nephrology, The First Hospital of Jilin University, Changchun, 130021, China
| | - Jizhou Zhang
- Department of Biochemistry, College of Basic Medical Sciences, Jilin University, Changchun 130021, China
| | - Tingting Liu
- Department of Nephrology, The First Hospital of Jilin University, Changchun, 130021, China
| | - Shaojie Fu
- Department of Nephrology, The First Hospital of Jilin University, Changchun, 130021, China
| | - Yue Wang
- Department of Nephrology, The First Hospital of Jilin University, Changchun, 130021, China
| | - Zhonggao Xu
- Department of Nephrology, The First Hospital of Jilin University, Changchun, 130021, China.
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2
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Liu L, Zhao D, Wang G, He Q, Song Y, Jiang Y, Xia Q, Zhao P. Adaptive Changes in Detoxification Metabolism and Transmembrane Transport of Bombyx mori Malpighian Tubules to Artificial Diet. Int J Mol Sci 2023; 24:9949. [PMID: 37373097 DOI: 10.3390/ijms24129949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 05/30/2023] [Accepted: 06/01/2023] [Indexed: 06/29/2023] Open
Abstract
The high adaptability of insects to food sources has contributed to their ranking among the most abundant and diverse species on Earth. However, the molecular mechanisms underlying the rapid adaptation of insects to different foods remain unclear. We explored the changes in gene expression and metabolic composition of the Malpighian tubules as an important metabolic excretion and detoxification organ in silkworms (Bombyx mori) fed mulberry leaf and artificial diets. A total of 2436 differentially expressed genes (DEGs) and 245 differential metabolites were identified between groups, with the majority of DEGs associated with metabolic detoxification, transmembrane transport, and mitochondrial function. Detoxification enzymes, such as cytochrome P450 (CYP), glutathione-S-transferase (GST), and UDP-glycosyltransferase, and ABC and SLC transporters of endogenous and exogenous solutes were more abundant in the artificial diet group. Enzyme activity assays confirmed increased CYP and GST activity in the Malpighian tubules of the artificial diet-fed group. Metabolome analysis showed increased contents of secondary metabolites, terpenoids, flavonoids, alkaloids, organic acids, lipids, and food additives in the artificial diet group. Our findings highlight the important role of the Malpighian tubules in adaptation to different foods and provide guidance for further optimization of artificial diets to improve silkworm breeding.
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Affiliation(s)
- Lijing Liu
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Dongchao Zhao
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Genhong Wang
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Qingxiu He
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Yuwei Song
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Yulu Jiang
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Qingyou Xia
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
| | - Ping Zhao
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing 400715, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing 400715, China
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3
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Zha D, Wu X. Nutrient sensing, signaling transduction, and autophagy in podocyte injury: implications for kidney disease. J Nephrol 2023; 36:17-29. [PMID: 35704261 DOI: 10.1007/s40620-022-01365-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 03/05/2022] [Indexed: 02/07/2023]
Abstract
Podocytes are terminally differentiated epithelial cells of the renal glomerular tuft and these highly specialized cells are essential for the integrity of the slit diaphragm. The biological function of podocytes is primarily based on a complex ramified structure that requires sufficient nutrients and a large supply of energy in support of their unique structure and function in the glomeruli. Of note, the dysregulation of nutrient signaling and energy metabolic pathways in podocytes has been associated with a range of kidney diseases i.e., diabetic nephropathy. Therefore, nutrient-related and energy metabolic signaling pathways are critical to maintaining podocyte homeostasis and the pathogenesis of podocyte injury. Recently, a growing body of evidence has indicated that nutrient starvation induces autophagy, which suggests crosstalk between nutritional signaling with the modulation of autophagy for podocytes to adapt to nutrient deprivation. In this review, the current knowledge and advancement in the understanding of nutrient sensing, signaling, and autophagy in the podocyte biology, injury, and pathogenesis of kidney diseases is summarized. Based on the existing findings, the implications and perspective to target these signaling pathways and autophagy in podocytes during the development of novel preventive and therapeutic strategies in patients with podocyte injury-associated kidney diseases are discussed.
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Affiliation(s)
- Dongqing Zha
- Division of Nephrology, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan, 430070, Hubei, China
| | - Xiaoyan Wu
- Division of Nephrology, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan, 430070, Hubei, China.
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Audzeyenka I, Bierżyńska A, Lay AC. Podocyte Bioenergetics in the Development of Diabetic Nephropathy: The Role of Mitochondria. Endocrinology 2022; 163:6429716. [PMID: 34791124 PMCID: PMC8660556 DOI: 10.1210/endocr/bqab234] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Indexed: 01/11/2023]
Abstract
Diabetic nephropathy (DN) is the leading cause of kidney failure, with an increasing incidence worldwide. Mitochondrial dysfunction is known to occur in DN and has been implicated in the underlying pathogenesis of disease. These complex organelles have an array of important cellular functions and involvement in signaling pathways, and understanding the intricacies of these responses in health, as well as how they are damaged in disease, is likely to highlight novel therapeutic avenues. A key cell type damaged early in DN is the podocyte, and increasing studies have focused on investigating the role of mitochondria in podocyte injury. This review will summarize what is known about podocyte mitochondrial dynamics in DN, with a particular focus on bioenergetic pathways, highlighting key studies in this field and potential opportunities to target, enhance or protect podocyte mitochondrial function in the treatment of DN.
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Affiliation(s)
- Irena Audzeyenka
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdańsk, Poland
- Department of Molecular Biotechnology, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland
- Correspondence: Irena Audzeyenka, PhD, Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Wita Stwosza St. 63, 80-308 Gdansk, Poland.
| | - Agnieszka Bierżyńska
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
| | - Abigail C Lay
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
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Sędzikowska A, Szablewski L. Human Glucose Transporters in Renal Glucose Homeostasis. Int J Mol Sci 2021; 22:13522. [PMID: 34948317 PMCID: PMC8708129 DOI: 10.3390/ijms222413522] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/26/2022] Open
Abstract
The kidney plays an important role in glucose homeostasis by releasing glucose into the blood stream to prevent hypoglycemia. It is also responsible for the filtration and subsequent reabsorption or excretion of glucose. As glucose is hydrophilic and soluble in water, it is unable to pass through the lipid bilayer on its own; therefore, transport takes place using carrier proteins localized to the plasma membrane. Both sodium-independent glucose transporters (GLUT proteins) and sodium-dependent glucose transporters (SGLT proteins) are expressed in kidney tissue, and mutations of the genes coding for these glucose transporters lead to renal disorders and diseases, including renal cancers. In addition, several diseases may disturb the expression and/or function of renal glucose transporters. The aim of this review is to describe the role of the kidney in glucose homeostasis and the contribution of glucose transporters in renal physiology and renal diseases.
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Affiliation(s)
| | - Leszek Szablewski
- Chair and Department of General Biology and Parasitology, Medical University of Warsaw, Chalubinskiego 5, 02-004 Warsaw, Poland;
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Rogacka D. Insulin resistance in glomerular podocytes: Potential mechanisms of induction. Arch Biochem Biophys 2021; 710:109005. [PMID: 34371008 DOI: 10.1016/j.abb.2021.109005] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 07/19/2021] [Accepted: 08/05/2021] [Indexed: 01/15/2023]
Abstract
Glomerular podocytes are a target for the actions of insulin. Accumulating evidence indicates that exposure to nutrient overload induces insulin resistance in these cells, manifested by abolition of the stimulatory effect of insulin on glucose uptake. Numerous recent studies have investigated potential mechanisms of the induction of insulin resistance in podocytes. High glucose concentrations stimulated reactive oxygen species production through NADPH oxidase activation, decreased adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, and reduced deacetylase sirtuin 1 (SIRT1) protein levels and activity. Calcium signaling involving transient receptor potential cation channel C, member 6 (TRPC6) also was demonstrated to play an essential role in the regulation of insulin-dependent signaling and glucose uptake in podocytes. Furthermore, podocytes exposed to diabetic environment, with elevated insulin levels become insulin resistant as a result of degradation of insulin receptor (IR), resulting in attenuation of insulin signaling responsiveness. Also elevated levels of palmitic acid appear to be an important factor and contributor to podocytes insulin resistance. This review summarizes cellular and molecular alterations that contribute to the development of insulin resistance in glomerular podocytes.
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Affiliation(s)
- Dorota Rogacka
- Mossakowski Medical Research Institute, Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Wita Stwosza 63, 80-308, Gdansk, Poland; University of Gdansk, Faculty of Chemistry, Department of Molecular Biotechnology, Wita Stwosza 63, 80-308, Gdansk, Poland.
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7
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Rogacka D, Piwkowska A. Beneficial effects of metformin on glomerular podocytes in diabetes. Biochem Pharmacol 2021; 192:114687. [PMID: 34274355 DOI: 10.1016/j.bcp.2021.114687] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/12/2021] [Accepted: 07/13/2021] [Indexed: 01/15/2023]
Abstract
Podocytes and their foot processes form an important cellular layer of the glomerular barrier involved in regulating glomerular permeability. Disturbances in podocyte function play a central role in the development of proteinuria in diabetic nephropathy. The retraction of podocyte foot processes forming a slit diaphragm is a common feature of proteinuria. Metformin is an oral antidiabetic agent of the biguanide class that is widely recommended for the treatment of high blood glucose in patients with type 2 diabetes mellitus. In addition to lowering glucose, several recent studies have reported potential beneficial effects of metformin on diabetic kidney function. Furthermore, a key molecule of the antidiabetic mechanism of action of metformin is adenosine 5'-monophospate-activated protein kinase (AMPK), as the metformin-induced activation of AMPK is well documented. The present review summarizes current knowledge on the protective effects of metformin against pathological changes in podocytes that are induced by hyperglycemia.
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Affiliation(s)
- Dorota Rogacka
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute Polish Academy of Sciences, Wita Stwosza 63, Gdansk 80-308, Poland; Department of Molecular Biotechnology, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdansk 80-308, Poland
| | - Agnieszka Piwkowska
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute Polish Academy of Sciences, Wita Stwosza 63, Gdansk 80-308, Poland; Department of Molecular Biotechnology, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdansk 80-308, Poland.
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8
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Lepa C, Hoppe S, Stöber A, Skryabin BV, Sievers LK, Heitplatz B, Ciarimboli G, Neugebauer U, Lindenmeyer MT, Cohen CD, Drexler HC, Boor P, Weide T, Pavenstädt H, George B. TrkC Is Essential for Nephron Function and Trans-Activates Igf1R Signaling. J Am Soc Nephrol 2021; 32:357-374. [PMID: 33380522 PMCID: PMC8054883 DOI: 10.1681/asn.2020040424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 11/03/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Injury to kidney podocytes often results in chronic glomerular disease and consecutive nephron malfunction. For most glomerular diseases, targeted therapies are lacking. Thus, it is important to identify novel signaling pathways contributing to glomerular disease. Neurotrophic tyrosine kinase receptor 3 (TrkC) is expressed in podocytes and the protein transmits signals to the podocyte actin cytoskeleton. METHODS Nephron-specific TrkC knockout (TrkC-KO) and nephron-specific TrkC-overexpressing (TrkC-OE) mice were generated to dissect the role of TrkC in nephron development and maintenance. RESULTS Both TrkC-KO and TrkC-OE mice exhibited enlarged glomeruli, mesangial proliferation, basement membrane thickening, albuminuria, podocyte loss, and aspects of FSGS during aging. Igf1 receptor (Igf1R)-associated gene expression was dysregulated in TrkC-KO mouse glomeruli. Phosphoproteins associated with insulin, erb-b2 receptor tyrosine kinase (Erbb), and Toll-like receptor signaling were enriched in lysates of podocytes treated with the TrkC ligand neurotrophin-3 (Nt-3). Activation of TrkC by Nt-3 resulted in phosphorylation of the Igf1R on activating tyrosine residues in podocytes. Igf1R phosphorylation was increased in TrkC-OE mouse kidneys while it was decreased in TrkC-KO kidneys. Furthermore, TrkC expression was elevated in glomerular tissue of patients with diabetic kidney disease compared with control glomerular tissue. CONCLUSIONS Our results show that TrkC is essential for maintaining glomerular integrity. Furthermore, TrkC modulates Igf-related signaling in podocytes.
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Affiliation(s)
- Carolin Lepa
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Sascha Hoppe
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Antje Stöber
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Boris V. Skryabin
- Medical Faculty, Core Facility Transgenic Animal and Genetic Engineering Models (TRAM), Westfälische-Wilhelms-University, Münster, Germany
| | | | - Barbara Heitplatz
- Gerhard-Domagk Institute for Pathology, University Hospital Münster, Münster, Germany
| | | | - Ute Neugebauer
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Maja T. Lindenmeyer
- III. Medizinische Klinik und Poliklinik, University Hospital Hamburg-Eppendorf, Germany
| | - Clemens D. Cohen
- Klinik für Nieren-, Hochdruck- und Rheumaerkrankungen, München Klinik Harlaching, Germany
| | - Hannes C.A. Drexler
- Mass Spectrometry Unit, Max Planck Institute for Molecular Biomedicine, Münster, Germany
| | - Peter Boor
- Institute of Pathology and Department of Nephrology, University Hospital Aachen, Rheinisch-Westfälische Technische Hochschule Aachen, Aachen, Germany
| | - Thomas Weide
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | | | - Britta George
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
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9
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Mohammadi E, Behnam B, Mohammadinejad R, Guest PC, Simental-Mendía LE, Sahebkar A. Antidiabetic Properties of Curcumin: Insights on New Mechanisms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1291:151-164. [PMID: 34331689 DOI: 10.1007/978-3-030-56153-6_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Plant extracts have been used to treat a wide range of human diseases. Curcumin, a bioactive polyphenol derived from Curcuma longa L., exhibits therapeutic effects against diabetes while only negligible adverse effects have been observed. Antioxidant and anti-inflammatory properties of curcumin are the main and well-recognized pharmacological effects that might explain its antidiabetic effects. Additionally, curcumin may regulate novel signaling molecules and enzymes involved in the pathophysiology of diabetes, including glucagon-like peptide-1, dipeptidyl peptidase-4, glucose transporters, alpha-glycosidase, alpha-amylase, and peroxisome proliferator-activated receptor gamma (PPARγ). Recent findings from in vitro and in vivo studies on novel signaling pathways involved in the potential beneficial effects of curcumin for the treatment of diabetes are discussed in this review.
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Affiliation(s)
- Elahe Mohammadi
- Student Research Committee, School of Pharmacy, Kerman University of Medical Sciences, Kerman, Iran
| | - Behzad Behnam
- Herbal and Traditional Medicines Research Center, Kerman University of Medical Sciences, Kerman, Iran. .,Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran. .,Pharmaceutical Sciences and Cosmetic Products Research Center, Kerman University of Medical Sciences, Kerman, Iran.
| | - Reza Mohammadinejad
- Herbal and Traditional Medicines Research Center, Kerman University of Medical Sciences, Kerman, Iran
| | - Paul C Guest
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, Brazil
| | | | - Amirhossein Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran. .,Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. .,Polish Mother's Memorial Hospital Research Institute (PMMHRI), Lodz, Poland. .,Halal Research Center of IRI, FDA, Tehran, Iran.
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10
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Rogacka D, Audzeyenka I, Piwkowska A. Regulation of podocytes function by AMP-activated protein kinase. Arch Biochem Biophys 2020; 692:108541. [PMID: 32781053 DOI: 10.1016/j.abb.2020.108541] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/23/2020] [Accepted: 08/06/2020] [Indexed: 01/08/2023]
Abstract
Podocytes are unique, highly specialized, terminally differentiated cells that form an essential, integral part of the glomerular filter. These cells limit the outside border of the glomerular basement membrane, forming a tight barrier that prevents significant protein loss from the capillary space. The slit diaphragm formed by podocytes is crucial for maintaining glomerular integrity and function. They are the target of injury in many glomerular diseases, including hypertension and diabetes mellitus. Accumulating studies have revealed that AMP-activated protein kinase (AMPK), an essential cellular energy sensor, might play a fundamental role in regulating podocyte metabolism and function. AMPK participates in insulin signaling, therefore controls glucose uptake and podocytes insulin sensitivity. It is also involved in insulin-dependent cytoskeleton reorganization in podocytes, mediating glomerular albumin permeability. AMPK plays an important role in the regulation of autophagy/apoptosis processes, which influence podocytes viability. The present review aimed to highlight the molecular mechanisms associated with AMPK that are involved in the regulation of podocyte function in health and disease states.
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Affiliation(s)
- Dorota Rogacka
- Mossakowski Medical Research Centre Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Wita Stwosza 63, 80-308, Gdansk, Poland; University of Gdansk, Faculty of Chemistry, Department of Molecular Biotechnology, Wita Stwosza 63, 80-308, Gdansk, Poland.
| | - Irena Audzeyenka
- Mossakowski Medical Research Centre Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Wita Stwosza 63, 80-308, Gdansk, Poland; University of Gdansk, Faculty of Chemistry, Department of Molecular Biotechnology, Wita Stwosza 63, 80-308, Gdansk, Poland.
| | - Agnieszka Piwkowska
- Mossakowski Medical Research Centre Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Wita Stwosza 63, 80-308, Gdansk, Poland; University of Gdansk, Faculty of Chemistry, Department of Molecular Biotechnology, Wita Stwosza 63, 80-308, Gdansk, Poland.
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11
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Mitrofanova A, Sosa MA, Fornoni A. Lipid mediators of insulin signaling in diabetic kidney disease. Am J Physiol Renal Physiol 2019; 317:F1241-F1252. [PMID: 31545927 PMCID: PMC6879940 DOI: 10.1152/ajprenal.00379.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/19/2019] [Accepted: 09/19/2019] [Indexed: 12/30/2022] Open
Abstract
Diabetic kidney disease (DKD) affects ∼40% of patients with diabetes and is associated with high mortality rates. Among different cellular targets in DKD, podocytes, highly specialized epithelial cells of the glomerular filtration barrier, are injured in the early stages of DKD. Both clinical and experimental data support the role of preserved insulin signaling as a major contributor to podocyte function and survival. However, little is known about the key modulators of podocyte insulin signaling. This review summarizes the novel knowledge that intracellular lipids such as cholesterol and sphingolipids are major determinants of podocyte insulin signaling. In particular, the implications of these lipids on DKD development, progression, and treatment will be addressed.
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Affiliation(s)
- Alla Mitrofanova
- Katz Family Division of Nephrology and Hypertension, Department of Medicine, Miller School of Medicine, University of Miami, Miami, Florida
- Peggy and Harold Katz Family Drug Discovery Center, Miller School of Medicine, University of Miami, Miami, Florida
- Department of Surgery, Miller School of Medicine, University of Miami, Miami, Florida
| | - Marie Anne Sosa
- Katz Family Division of Nephrology and Hypertension, Department of Medicine, Miller School of Medicine, University of Miami, Miami, Florida
| | - Alessia Fornoni
- Katz Family Division of Nephrology and Hypertension, Department of Medicine, Miller School of Medicine, University of Miami, Miami, Florida
- Peggy and Harold Katz Family Drug Discovery Center, Miller School of Medicine, University of Miami, Miami, Florida
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12
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Abstract
Finding new therapeutic targets of glomerulosclerosis treatment is an ongoing quest. Due to a living environment of various stresses and pathological stimuli, podocytes are prone to injuries; moreover, as a cell without proliferative potential, loss of podocytes is vital in the pathogenesis of glomerulosclerosis. Thus, sufficient understanding of factors and underlying mechanisms of podocyte injury facilitates the advancement of treating and prevention of glomerulosclerosis. The clinical symptom of podocyte injury is proteinuria, sometimes with loss of kidney functions progressing to glomerulosclerosis. Injury-induced changes in podocyte physiology and function are actually not a simple passive process, but a complex interaction of proteins that comprise the anatomical structure of podocytes at molecular levels. This chapter lists several aspects of podocyte injuries along with potential mechanisms, including glucose and lipid metabolism disorder, hypertension, RAS activation, micro-inflammation, immune disorder, and other factors. These aspects are not technically separated items, but intertwined with each other in the pathogenesis of podocyte injuries.
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13
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Spires D, Manis AD, Staruschenko A. Ion channels and transporters in diabetic kidney disease. CURRENT TOPICS IN MEMBRANES 2019; 83:353-396. [PMID: 31196609 PMCID: PMC6815098 DOI: 10.1016/bs.ctm.2019.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Type 1 and 2 diabetes mellitus are major medical epidemics affecting millions of patients worldwide. Diabetes mellitus is the leading cause of diabetic kidney disease (DKD), which is the most common cause of end-stage renal disease (ESRD). DKD is associated with significant changes in renal hemodynamics and electrolyte transport. Alterations in renal ion transport triggered by pathophysiological conditions in diabetes can exacerbate hypertension, accelerate renal injury, and are integral to the development of DKD. Renal ion transporters and electrolyte homeostasis play a fundamental role in functional changes and injury to the kidney during DKD. With the large number of ion transporters involved in DKD, understanding the roles of individual transporters as well as the complex cascades through which they interact is essential in the development of effective treatments for patients suffering from this disease. This chapter aims to gather current knowledge of the major renal ion transporters with altered expression and activity under diabetic conditions, and provide a comprehensive overview of their interactions and collective functions in DKD.
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Affiliation(s)
- Denisha Spires
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Anna D Manis
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States; Clement J. Zablocki VA Medical Center, Milwaukee, WI, United States.
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Wasik AA, Lehtonen S. Glucose Transporters in Diabetic Kidney Disease-Friends or Foes? Front Endocrinol (Lausanne) 2018; 9:155. [PMID: 29686650 PMCID: PMC5900043 DOI: 10.3389/fendo.2018.00155] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 03/22/2018] [Indexed: 12/16/2022] Open
Abstract
Diabetic kidney disease (DKD) is a major microvascular complication of diabetes and a common cause of end-stage renal disease worldwide. DKD manifests as an increased urinary protein excretion (albuminuria). Multiple studies have shown that insulin resistance correlates with the development of albuminuria in non-diabetic and diabetic patients. There is also accumulating evidence that glomerular epithelial cells or podocytes are insulin sensitive and that insulin signaling in podocytes is essential for maintaining normal kidney function. At the cellular level, the mechanisms leading to the development of insulin resistance include mutations in the insulin receptor gene, impairments in the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway, or perturbations in the trafficking of glucose transporters (GLUTs), which mediate the uptake of glucose into cells. Podocytes express several GLUTs, including GLUT1, GLUT2, GLUT3, GLUT4, and GLUT8. Of these, the most studied ones are GLUT1 and GLUT4, both shown to be insulin responsive in podocytes. In the basal state, GLUT4 is preferentially located in perinuclear and cytosolic vesicular structures and to a lesser extent at the plasma membrane. After insulin stimulation, GLUT4 is sorted into GLUT4-containing vesicles (GCVs) that translocate to the plasma membrane. GCV trafficking consists of several steps, including approaching of the GCVs to the plasma membrane, tethering, and docking, after which the lipid bilayers of the GCVs and the plasma membrane fuse, delivering GLUT4 to the cell surface for glucose uptake into the cell. Studies have revealed novel molecular regulators of the GLUT trafficking in podocytes and unraveled unexpected roles for GLUT1 and GLUT4 in the development of DKD, summarized in this review. These findings pave the way for better understanding of the mechanistic pathways associated with the development and progression of DKD and aid in the development of new treatments for this devastating disease.
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Lay AC, Coward RJM. The Evolving Importance of Insulin Signaling in Podocyte Health and Disease. Front Endocrinol (Lausanne) 2018; 9:693. [PMID: 30524379 PMCID: PMC6258712 DOI: 10.3389/fendo.2018.00693] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/05/2018] [Indexed: 12/17/2022] Open
Abstract
Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide, occuring in approximately one-third of diabetic patients. One of the earliest hallmarks of DKD is albuminuria, often occurring following disruptions to the glomerular filtration barrier. Podocytes are highly specialized cells with a central role in filtration barrier maintenance; hence, podocyte dysfunction is a major cause of albuminuria in many settings, including DKD. Numerous studies over the last decade have highlighted the importance of intact podocyte insulin responses in the maintenance of podocyte function. This review summarizes our current perspectives on podocyte insulin signaling, highlighting evidence to support the notion that dysregulated podocyte insulin responses contribute toward podocyte damage, particularly during the pathogenesis of DKD.
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Maria Z, Campolo AR, Scherlag BJ, Ritchey JW, Lacombe VA. Dysregulation of insulin-sensitive glucose transporters during insulin resistance-induced atrial fibrillation. Biochim Biophys Acta Mol Basis Dis 2017; 1864:987-996. [PMID: 29291943 DOI: 10.1016/j.bbadis.2017.12.038] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/29/2017] [Accepted: 12/23/2017] [Indexed: 11/18/2022]
Abstract
Diabetes has been identified as major risk factor for atrial fibrillation (AF). Although glucose and insulin disturbances during diabetes may affect atrial function, little is known about the potential pathogenic role of glucose metabolism during AF. Glucose transport into the cell via glucose transporters (GLUTs) is the rate-limiting step of glucose utilization. Although GLUT4 is the major isoform, GLUT8 has emerged as a novel insulin-sensitive cardiac isoform. We hypothesized that atrial glucose homeostasis will be impaired during insulin resistance-induced AF. AF was induced by transesophageal atrial pacing in healthy mice and following a long-term high-fat-diet-induced insulin resistance. Active cell surface GLUT content was measured using the biotinylated photolabeling assay in the intact perfused heart. Atrial fibrosis, advanced glycation end products (AGEs) and glycogen were measured in the atria using histological analyses. Animals fed a high-fat-diet were obese and mildly hyperglycemic, and developed insulin resistance compared to controls. Insulin-resistant (IR) animals demonstrated an increased vulnerability to induced AF, as well as spontaneous AF. Insulin-stimulated translocation of GLUT4 and GLUT8 was down-regulated in the atria of IR animals, as well as their total protein expression. We also reported the absence of fibrosis, glycogen and AGE accumulation in the atria of IR animals. In the absence of structural remodeling and atrial fibrosis, these data suggest that insulin signaling dysregulation, resulting in impaired glucose transport in the atria, could provide a metabolic arrhythmogenic substrate and be a novel early pathogenic factor of AF.
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Affiliation(s)
- Zahra Maria
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, USA; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Allison R Campolo
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, USA; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Benjamin J Scherlag
- Department of Internal Medicine, University of Oklahoma, Oklahoma City, OK, USA
| | - Jerry W Ritchey
- Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK, USA
| | - Véronique A Lacombe
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, USA; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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17
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Insulin signaling: implications for podocyte biology in diabetic kidney disease. Curr Opin Nephrol Hypertens 2015; 24:104-10. [PMID: 25415617 DOI: 10.1097/mnh.0000000000000078] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE OF REVIEW Several key elements of the insulin signaling cascade contribute to podocyte function and survival. While it was initially thought that the consequences of altered insulin signaling to podocyte function was strictly related to altered glucose uptake, it has become clear that upstream signaling events involved in cell survival, lipid metabolism or nutrient sensing and modulated by insulin are strong independent contributors to podocyte function. RECENT FINDINGS Akt2, the major isoform of Akt activated following cellular insulin stimulation, protects against the progression of renal disease in nephron-deficient mice, and podocyte-specific deletion of Akt2 results in a more rapid progression of experimental glomerular disease. In diabetes, podocyte mammalian target of rapamycin activation clearly contributes to podocyte injury and regulated autophagy. Furthermore, podocyte-specific glucose transporter type 4 (GLUT4) deficiency protects podocytes by preventing mammalian target of rapamycin signaling independently of glucose uptake. Finally, intracellular lipids have been recently recognized as major modulators of podocyte insulin signaling and as a new therapeutic target. SUMMARY The identification of new contributors to podocyte insulin signaling is of extreme translational value as it may lead to new drug development strategies for diabetic kidney disease, as well as for other proteinuric kidney diseases.
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18
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Involvement of the AMPK–PTEN pathway in insulin resistance induced by high glucose in cultured rat podocytes. Int J Biochem Cell Biol 2014; 51:120-30. [DOI: 10.1016/j.biocel.2014.04.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 03/28/2014] [Accepted: 04/09/2014] [Indexed: 11/17/2022]
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Beckerman P, Susztak K. Sweet debate: fructose versus glucose in diabetic kidney disease. J Am Soc Nephrol 2014; 25:2386-8. [PMID: 24876119 DOI: 10.1681/asn.2014050433] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Pazit Beckerman
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Katalin Susztak
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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Guzman J, Jauregui AN, Merscher-Gomez S, Maiguel D, Muresan C, Mitrofanova A, Diez-Sampedro A, Szust J, Yoo TH, Villarreal R, Pedigo C, Molano RD, Johnson K, Kahn B, Hartleben B, Huber TB, Saha J, Burke GW, Abel ED, Brosius FC, Fornoni A. Podocyte-specific GLUT4-deficient mice have fewer and larger podocytes and are protected from diabetic nephropathy. Diabetes 2014; 63:701-14. [PMID: 24101677 PMCID: PMC3900538 DOI: 10.2337/db13-0752] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Podocytes are a major component of the glomerular filtration barrier, and their ability to sense insulin is essential to prevent proteinuria. Here we identify the insulin downstream effector GLUT4 as a key modulator of podocyte function in diabetic nephropathy (DN). Mice with a podocyte-specific deletion of GLUT4 (G4 KO) did not develop albuminuria despite having larger and fewer podocytes than wild-type (WT) mice. Glomeruli from G4 KO mice were protected from diabetes-induced hypertrophy, mesangial expansion, and albuminuria and failed to activate the mammalian target of rapamycin (mTOR) pathway. In order to investigate whether the protection observed in G4 KO mice was due to the failure to activate mTOR, we used three independent in vivo experiments. G4 KO mice did not develop lipopolysaccharide-induced albuminuria, which requires mTOR activation. On the contrary, G4 KO mice as well as WT mice treated with the mTOR inhibitor rapamycin developed worse adriamycin-induced nephropathy than WT mice, consistent with the fact that adriamycin toxicity is augmented by mTOR inhibition. In summary, GLUT4 deficiency in podocytes affects podocyte nutrient sensing, results in fewer and larger cells, and protects mice from the development of DN. This is the first evidence that podocyte hypertrophy concomitant with podocytopenia may be associated with protection from proteinuria.
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Affiliation(s)
- Johanna Guzman
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
| | - Alexandra N. Jauregui
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Sandra Merscher-Gomez
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
| | - Dony Maiguel
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Cristina Muresan
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
| | - Alla Mitrofanova
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
| | - Ana Diez-Sampedro
- Department of Physiology, Miller School of Medicine, University of Miami, Miami, FL
| | - Joel Szust
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Tae-Hyun Yoo
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
- Department of Surgery, Miller School of Medicine, University of Miami, Miami, FL
| | - Rodrigo Villarreal
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
| | - Christopher Pedigo
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
| | - R. Damaris Molano
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Kevin Johnson
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Barbara Kahn
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | | | - Tobias B. Huber
- Division of Nephrology, Freiburg University, Freiburg, Germany
| | - Jharna Saha
- Division of Nephrology, University of Michigan, Ann Arbor, MI
| | - George W. Burke
- Department of Surgery, Miller School of Medicine, University of Miami, Miami, FL
| | - E. Dale Abel
- Division of Endocrinology, Metabolism and Diabetes and Program in Molecular Medicine, University of Utah, Salt Lake City, UT
| | | | - Alessia Fornoni
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
- Department of Medicine, Division of Nephrology and Hypertension, Miller School of Medicine, University of Miami, Miami, FL
- Corresponding author: Alessia Fornoni,
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Imasawa T, Rossignol R. Podocyte energy metabolism and glomerular diseases. Int J Biochem Cell Biol 2013; 45:2109-18. [PMID: 23806869 DOI: 10.1016/j.biocel.2013.06.013] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 06/10/2013] [Accepted: 06/14/2013] [Indexed: 11/16/2022]
Abstract
Mitochondria are crucial organelles that produce and deliver adenosine triphosphate (ATP), by which all cellular processes are driven. Although the mechanisms that control mitochondrial biogenesis, function and dynamics are complex process and vary among different cell types, recent studies provided many new discoveries in this field. Podocyte injury is a crucial step in the development of a large number of glomerular diseases. Glomerular podocytes are unique cells with complex foot processes that cover the outer layer of the glomerular basement membrane, and are the principle cells composing filtration barriers of glomerular capillaries. Little is known on the modalities and the regulation of podocyte's energetics as well as the type of energy substrate primarily used for their activity, recent studies revealed that dysfunction of energy transduction in podocytes may underlie the podocyte injury associated with numerous glomerular diseases. We herein review and discuss the importance of a fine regulation of energy metabolism in podocytes for maintaining their cellular structure and related kidney function. In the future, understanding these mechanisms will open up new areas of treatment for glomerular diseases.
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22
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Tönjes A, Kovacs P. SGLT2: a potential target for the pharmacogenetics of Type 2 diabetes? Pharmacogenomics 2013; 14:825-33. [DOI: 10.2217/pgs.13.61] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The kidney has attracted the attention of diabetologists as an organ involved in the regulation of glucose homeostasis not only by gluconeogenesis, but also by renal glucose excretion. Sodium–glucose cotransporters (SGLTs), particularly SGLT2, are responsible for reabsorption of up to 99% of the filtered glucose. SGLT2 is coded by the SLC5A2 gene, which maps on chromosome 16. Pharmacological reduction of tubular glucose reabsorption results in improved glycemic control in Type 2 diabetic patients. Since the SGLTs reabsorb most of the filtered glucose (90%), it is not surprising that mutations in SLC5A2 cause familial renal glucosuria. A recent study pointed out a possible role of common genetic variation in SLC5A2 in the control of glucose homeostasis. SLC5A2 polymorphisms might therefore represent potential candidates for pharmacogenomic studies targeting the impact of these variants on the efficacy of antidiabetic treatment that is based on inhibition of SGLT2 activity.
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Affiliation(s)
- Anke Tönjes
- University of Leipzig, Medical Department, Liebigstraße 21, 04103 Leipzig, Germany
- Leipzig University Medical Center, IFB Adiposity Diseases, Leipzig, Germany
| | - Peter Kovacs
- Leipzig University Medical Center, IFB Adiposity Diseases, Leipzig, Germany
- University of Leipzig, Medical Department, Liebigstraße 21, 04103 Leipzig, Germany
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23
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Yan K, Ito N, Nakajo A, Kurayama R, Fukuhara D, Nishibori Y, Kudo A, Akimoto Y, Takenaka H. The struggle for energy in podocytes leads to nephrotic syndrome. Cell Cycle 2012; 11:1504-11. [PMID: 22433955 DOI: 10.4161/cc.19825] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Podocytes are terminally differentiated post-mitotic cells similar to neurons, and their damage leads to nephrotic syndrome, which is characterized by massive proteinuria associated with generalized edema. A recent functional genetic approach has identified the pathological relevance of several mutated proteins in glomerular podocytes to the mechanism of proteinuria in hereditary nephrotic syndrome. In contrast, the pathophysiology of acquired primary nephrotic syndrome, including minimal change disease, is still largely unknown. We recently demonstrated the possible linkage of an energy-consuming process in glomerular podocytes to the mechanism of proteinuria. Puromycin aminonucleoside nephrosis, a rat model of minimal change disease, revealed the activation of the unfolded protein response (UPR) in glomerular podocytes to be a cause of proteinuria. The pretreatment of puromycin aminonucleoside rat podocytes and cultured podocytes with the mammalian target of rapamycin (mTOR) inhibitor everolimus further revealed that mTOR complex 1 consumed energy, which was followed by UPR activation. In this paper, we will review nutritional transporters to summarize the energy uptake process in podocytes and review the involvement of the UPR in the pathogenesis of glomerular diseases. We will also present additional data that reveal how mTOR complex 1 acts upstream of the UPR. Finally, we will discuss the potential significance of targeting the energy metabolism of podocytes to develop new therapeutic interventions for acquired nephrotic syndrome.
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Affiliation(s)
- Kunimasa Yan
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
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24
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Stieger N, Worthmann K, Schiffer M. The role of metabolic and haemodynamic factors in podocyte injury in diabetes. Diabetes Metab Res Rev 2011; 27:207-15. [PMID: 21309047 DOI: 10.1002/dmrr.1164] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Podocyte loss is a common feature in human diabetes as well as in experimental diabetes in rodents. Almost all components of the diabetic milieu lead to serious podocyte stress, driving the cells towards cell cycle arrest and hypertrophy, detachment and apoptosis. Common pathway components induced by high glucose and advanced glycation end-products are reactive oxygen species, cyclin-dependent kinases (p27(Kip1)) and transforming growth factor-beta. In addition, mechanical stresses by stretch or shear forces, insulin deficiency or insulin resistance are independent components resulting in podocyte apoptosis and detachment. In this review, we discuss the common pathways leading to podocyte death as well as novel pathways and concepts of podocyte dedifferentiation and detachment that influence the progression of diabetic glomerulopathy.
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Affiliation(s)
- Nicole Stieger
- Division of Nephrology, Department of Medicine, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover, Germany
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25
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Rogacka D, Piwkowska A, Jankowski M, Kocbuch K, Dominiczak MH, Stępiński JK, Angielski S. Expression of GFAT1 and OGT in podocytes: Transport of glucosamine and the implications for glucose uptake into these cells. J Cell Physiol 2010; 225:577-84. [DOI: 10.1002/jcp.22242] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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26
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Zhang H, Schin M, Saha J, Burke K, Holzman LB, Filipiak W, Saunders T, Xiang M, Heilig CW, Brosius FC. Podocyte-specific overexpression of GLUT1 surprisingly reduces mesangial matrix expansion in diabetic nephropathy in mice. Am J Physiol Renal Physiol 2010; 299:F91-8. [PMID: 20375116 DOI: 10.1152/ajprenal.00021.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Increased expression of the facilitative glucose transporter, GLUT1, leads to glomerulopathy that resembles diabetic nephropathy, whereas prevention of enhanced GLUT1 expression retards nephropathy. While many of the GLUT1-mediated effects are likely due to mesangial cell effects, we hypothesized that increased GLUT1 expression in podocytes also contributes to the progression of diabetic nephropathy. Therefore, we generated two podocyte-specific GLUT1 transgenic mouse lines (driven by a podocin promoter) on a db/m C57BLKS background. Progeny of the two founders were used to generate diabetic db/db and control db/m littermate mice. Immunoblots of glomerular lysates showed that transgenic mice had a 3.5-fold (line 1) and 2.1-fold (line 2) increase in GLUT1 content compared with wild-type mice. Both lines showed similar increases in fasting blood glucose and body weights at 24 wk of age compared with wild-type mice. Mesangial index (percent PAS-positive material in the mesangial tuft) increased 88% (line 1) and 75% (line 2) in the wild-type diabetic mice but only 48% (line 1) and 39% (line 2) in the diabetic transgenic mice (P < 0.05, transgenic vs. wild-type mice). This reduction in mesangial expansion was accompanied by a reduction in fibronectin accumulation, and vascular endothelial growth factor (VEGF) levels increased only half as much in the transgenic diabetic mice as in wild-type diabetic mice. Levels of nephrin, neph1, CD2AP, podocin, and GLUT4 were not significantly different in transgenic compared with wild-type mice. Taken together, increased podocyte GLUT1 expression in diabetic mice does not contribute to early diabetic nephropathy; surprisingly, it protects against mesangial expansion and fibronectin accumulation possibly by blunting podocyte VEGF increases.
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Affiliation(s)
- Hongyu Zhang
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-0680, USA
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27
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Aschenbach JR, Steglich K, Gäbel G, Honscha KU. Expression of mRNA for glucose transport proteins in jejunum, liver, kidney and skeletal muscle of pigs. J Physiol Biochem 2010; 65:251-66. [PMID: 20119820 DOI: 10.1007/bf03180578] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Indexed: 01/12/2023]
Abstract
Although pigs are adapted to starch-rich diets and have high turnover rates of glucose, very scarce information is available on the molecular basis of glucose transport. Therefore, the present study attempted a systematic screening for the presence of mRNA of glucose transport proteins in main organs of glucose absorption, production and conservation. From the members of the solute carrier family SLC5A (sodium glucose cotransporter), the porcine jejunum was positive for SGLT1 and SGLT3, but also contained detectable levels of SGLT5. Liver contained SGLT1, SGLT5, traces of SGLT3 and, in one of five pigs, SGLT2. Kidney contained SGLT1, SGLT2, SGLT3, SGLT5 and hardly detectable levels of SGLT4. Skeletal muscle showed weak signals for SGLT3 and SGLT5. Screening for members of the SLC2A family (facilitated glucose transporter) in intestine revealed the presence of mRNA for GLUT1, GLUT2, GLUT5, GLUT7 and GLUT8, while GLUT3, GLUT4, GLUT10 and GLUT11 were also detectable. The liver contained GLUT1, GLUT2 and GLUT8 mRNA, while GLUT3, GLUT4, GLUT5, GLUT10 and GLUT11 were poorly detectable. The kidney was positive for GLUT1, GLUT2, GLUT5, GLUT8 and GLUT11, but traces of GLUT3, GLUT4 and GLUT10 could also be detected. Skeletal muscle had the strongest signal for GLUT4, while GLUT1, GLUT3, GLUT5, GLUT8, GLUT10 and GLUT11 showed weak signals. A total of 12 unique partial cDNA sequences were submitted to GenBank. In conclusion, this study provides molecular insight into the organ-specific expression of glucose transporters in pigs and thus sheds light on the way of glucose handling in this omnivorous species.
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Affiliation(s)
- J R Aschenbach
- Institute of Veterinary Physiology, University of Leipzig, An den Tierkliniken 7, D-04103 Leipzig, Germany.
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28
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Lewko B, Stepinski J. Hyperglycemia and mechanical stress: Targeting the renal podocyte. J Cell Physiol 2009; 221:288-95. [DOI: 10.1002/jcp.21856] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Lennon R, Welsh G, Singh A, Satchell S, Coward R, Tavaré J, Mathieson P, Saleem M. Rosiglitazone enhances glucose uptake in glomerular podocytes using the glucose transporter GLUT1. Diabetologia 2009; 52:1944-52. [PMID: 19533082 PMCID: PMC7614273 DOI: 10.1007/s00125-009-1423-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Accepted: 05/14/2009] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Peroxisome proliferator-activated receptor (PPAR) gamma agonists are used increasingly in the treatment of type 2 diabetes. In the context of renal disease, PPARgamma agonists reduce microalbuminuria in diabetic nephropathy; however, the mechanisms underlying this effect are unknown. Glomerular podocytes are newly characterised insulin-sensitive cells and there is good evidence that they are targeted in diabetic nephropathy. In this study we investigated the functional and molecular effects of the PPARgamma agonist rosiglitazone on human podocytes. METHODS Conditionally immortalised human podocytes were cultured with rosiglitazone and functional effects were measured with glucose-uptake assays. The effect of rosiglitazone on glucose uptake was also measured in 3T3-L1 adipocytes, nephrin-deficient podocytes, human glomerular endothelial cells, proximal tubular cells and podocytes treated with the NEFA palmitate. The role of the glucose transporter GLUT1 was investigated with immunofluorescence and small interfering RNA knockdown and the plasma membrane expression of GLUT1 was determined with bis-mannose photolabelling. RESULTS Rosiglitazone significantly increased glucose uptake in wild-type podocytes and this was associated with translocation of GLUT1 to the plasma membrane. This effect was blocked with GLUT1 small interfering RNA. Nephrin-deficient podocytes, glomerular endothelial cells and proximal tubular cells did not increase glucose uptake in response to either insulin or rosiglitazone. Furthermore, rosiglitazone significantly increased basal and insulin-stimulated glucose uptake when podocytes were treated with the NEFA palmitate. CONCLUSIONS/INTERPRETATION In conclusion, rosiglitazone has a direct and protective effect on glucose uptake in wild-type human podocytes. This represents a novel mechanism by which PPARgamma agonists may improve podocyte function in diabetic nephropathy.
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Affiliation(s)
- R. Lennon
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
| | - G.I. Welsh
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
| | - A. Singh
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
| | - S.C. Satchell
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
| | - R.J. Coward
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
| | - J.M. Tavaré
- Department of Biochemistry, University of Bristol, Bristol, UK
| | - P.W. Mathieson
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
| | - M.A. Saleem
- Academic and Children’s Renal Unit, Paul O’Gorman Lifeline Centre, University of Bristol, Southmead Hospital, Bristol BS10 5NB, UK
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McNamara DB, Murthy SN, Fonseca AN, Desouza CV, Kadowitz PJ, Fonseca VA. Animal models of catheter-induced intimal hyperplasia in type 1 and type 2 diabetes and the effects of pharmacologic intervention. Can J Physiol Pharmacol 2009; 87:37-50. [PMID: 19142214 DOI: 10.1139/y08-098] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Diabetes is a complex disorder characterized by impaired insulin formation, release or action (insulin resistance), elevated blood glucose, and multiple long-term complications. It is a common endocrine disorder of humans and is associated with abnormalities of carbohydrate and lipid metabolism. There are two forms of diabetes, classified as type 1 and type 2. In type 1 diabetes, hyperglycemia is due to an absolute lack of insulin, whereas in type 2 diabetes, hyperglycemia is due to a relative lack of insulin and insulin resistance. More than 90% of people with diabetes have type 2 with varied degrees of insulin resistance. Insulin resistance is often associated with impaired insulin secretion, and hyperglycemia is a common feature in both types of diabetes, but failure to make a distinction between the types of diabetes in different animal models has led to confusion in the literature. This is particularly true in relation to cardiovascular disease in the presence of diabetes and especially the response to vascular injury, in which there are major differences between the two types of diabetes. Animal models do not completely mimic the clinical disease seen in humans. Animal models are at best analogies of the pathologic process they are designed to represent. The focus of this review is an analysis of intimal hyperplasia following catheter-induced vascular injury, including factors that may complicate comparisons between different animal models or between in vitro and in vivo studies. We examine the variables, pitfalls, and caveats that follow from the manner of induction of the injury and the diabetic state of the animal. The efficacy of selected antidiabetic drugs in inhibiting the development of the hyperplastic response is also discussed.
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Affiliation(s)
- D B McNamara
- Department of Pharmacology, Tulane University Health Sciences Center, 1430 Tulane Avenue - SL 83, New Orleans, LA 70112, USA.
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Romero A, Gomez O, Terrado J, Mesonero JE. Expression of GLUT8 in mouse intestine: Identification of alternative spliced variants. J Cell Biochem 2009; 106:1068-78. [DOI: 10.1002/jcb.22090] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Suketa Y. [Expression and regulation of renal sodium-cotransporters and -antiporters, and related-transport proteins]. YAKUGAKU ZASSHI 2008; 128:901-17. [PMID: 18520136 DOI: 10.1248/yakushi.128.901] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The authors' researches have been focused on pathogenic, physiological and biochemical mechanisms in hypertension and diabetes. Studies on hypertension were performed using salt-sensitive hypertensive Dahl rats as compared with the corresponding normotensive rats. Especially, implication with mobilization of electrolytes such as sodium, potassium, calcium and magnesium in hypertension gave rise to provocative to the author. Furthermore, complications of diabetes with hypertension were themes for the authors' researches. Thus, sodium-dependent glucose transport has been studied on sodium-dependent glucose transporters such as SGLT1 and SGLT2 using cell lines of porcelain renal cell, LLC-PK(1), and murine renal cell, NRK-52E. Relationship between magnesium mobilization and NO in hypertension has been explored using renal epithelial cell-lines and salt-sensitive hypertensive Dahl rats in the latter half of the author's research life.
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Affiliation(s)
- Yasunobu Suketa
- Department of Pharmacy, Chiba Institute of Science Faculty of Pharmacy, 3 Shiomi-cho, Choshi City, Japan.
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Wilson-O'Brien AL, Dehaan CL, Rogers S. Mitogen-stimulated and rapamycin-sensitive glucose transporter 12 targeting and functional glucose transport in renal epithelial cells. Endocrinology 2008; 149:917-24. [PMID: 18039784 DOI: 10.1210/en.2007-0985] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We hypothesized that glucose transporter 12 (GLUT12) is involved in regulation of glucose flux in distal renal tubules in response to elevated glucose. We used the Madin-Darby canine kidney polarized epithelial cell model and neutralizing antibodies to analyze GLUT12 targeting and directional GLUT12-mediated glucose transport. At physiological glucose concentrations, GLUT12 was localized to a perinuclear position. High glucose and serum treatment resulted in GLUT12 localization to the apical membrane. This mitogen-stimulated targeting of GLUT12 was inhibited by rapamycin, the specific inhibitor of mammalian target of rapamycin (mTOR). The functional role of GLUT12 was also examined. We constructed a GLUT12 cDNA containing a c-Myc epitope tag in the fifth exofacial loop. Assays of glucose transport at the apical membrane were performed using Transwell filters. By comparing transport assays in the presence of neutralizing anti-c-Myc monoclonal antibody, we specifically measured GLUT12-mediated glucose transport at the apical surface. GLUT12-mediated glucose transport was mitogen dependent and rapamycin sensitive. Our results implicate mTOR signaling in a novel pathway of glucose transporter protein targeting and glucose transport. Activity of the mTOR pathway has been associated with diabetic kidney disease. Our results provide evidence for a link between GLUT12 protein trafficking, glucose transport and signaling molecules central to the control of metabolic disease processes.
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Affiliation(s)
- Amy L Wilson-O'Brien
- The University of Melbourne, Department of Medicine, St. Vincent's Hospital, Melbourne, Fitzroy, Victoria 3065, Australia
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Schaan BD, Machado UF, Rogers S, Kelly DJ. Glucose transporters in animal models of diabetes and hypertension. Am J Physiol Renal Physiol 2006; 291:F702-3; author reply F703-4. [PMID: 16622180 DOI: 10.1152/ajprenal.00065.2006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal tubular glucose reabsorption is mediated by facilitative glucose transporter (GLUT) proteins and energy-dependent sodium glucose luminal transporters. Glucose transport in the diabetic kidney is upregulated and has been implicated in the pathogenesis of progressive diabetic nephropathy. Hyperglycemia, hypertension, and activation of the renin-angiotensin system are believed important in the development of the disease. The present study examines the renal expression of the facilitative glucose transporters GLUT1 and GLUT12 in rat models of diabetic nephropathy. Sprague-Dawley and transgenic (mRen-2)27 rats received either streptozotocin-induced diabetes or vehicle. GLUT12 expression and localization were determined by immunohistochemistry, immunoblotting, in situ hybridization, and confocal immunofluorescence. GLUT1 immunolabeling was detected on the basolateral membrane throughout the nephron. GLUT12 was localized to the distal tubules and collecting ducts. A significant increase in GLUT12 immunolabeling was measured in Ren-2 controls and Ren-2 diabetic animals compared with Sprague-Dawley controls. GLUT12 expression was higher in Ren-2 diabetic compared with Sprague-Dawley diabetic rats. Long-term diabetes resulted in significant increases in GLUT1 levels in the renal proximal tubules and expression was higher in Ren-2 diabetic than Sprague-Dawley diabetic rats. GLUT12 protein was localized to the cytoplasm and to the apical membrane of human and rat distal tubules and collecting ducts. The apical localization of GLUT12 in the distal tubules and collecting ducts suggests that it could contribute to additional glucose reabsorption in the late nephron. Levels of both GLUT1 and GLUT12 are elevated in animal models of hypertension and diabetic nephropathy.
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Gómez O, Romero A, Terrado J, Mesonero JE. Differential expression of glucose transporter GLUT8 during mouse spermatogenesis. Reproduction 2006; 131:63-70. [PMID: 16388010 DOI: 10.1530/rep.1.00750] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
GLUT8 is a facilitative glucose transporter expressed at high levels in the testis. In this study, we analyzed the GLUT8 expression in mouse testis during spermatogenesis by RT–PCR, Western blot and immunohistochemistry methods. Our results show that GLUT8 expression is limited to spermatids and spermatozoa in the testis. Expression begins when round spermatids are formed at postnatal day 24. The expression persists throughout spermiogenesis, and it is also detected in spermatozoa, but it is absent in more immature germ cells, Sertoli cells and interstitial tissue. GLUT8 immunoreactivity is always restricted to the acrosomic system in a manner that matches the acrosome system formation. The GLUT8 expression is mainly associated with the acrosomic membrane in the acrosome, although significant immunoreactivity is also found inside the acrosomic lumen. The specific GLUT8 location suggests that this transporter plays a pivotal role in the fuel supply of spermatozoa, and in the traffic of sugars during the capacitation and fertilization processes.
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Affiliation(s)
- Olga Gómez
- Department of Medicine and Animal Surgery, Experimental Sciences and Health Faculty, Cardenal Herrera- CEU University, E-46113-Moncada, Valencia, Spain
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Linden KC, DeHaan CL, Zhang Y, Glowacka S, Cox AJ, Kelly DJ, Rogers S. Renal expression and localization of the facilitative glucose transporters GLUT1 and GLUT12 in animal models of hypertension and diabetic nephropathy. Am J Physiol Renal Physiol 2006; 290:F205-13. [PMID: 16091581 DOI: 10.1152/ajprenal.00237.2004] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal tubular glucose reabsorption is mediated by facilitative glucose transporter (GLUT) proteins and energy-dependent sodium glucose luminal transporters. Glucose transport in the diabetic kidney is upregulated and has been implicated in the pathogenesis of progressive diabetic nephropathy. Hyperglycemia, hypertension, and activation of the renin-angiotensin system are believed important in the development of the disease. The present study examines the renal expression of the facilitative glucose transporters GLUT1 and GLUT12 in rat models of diabetic nephropathy. Sprague-Dawley and transgenic (mRen-2)27 rats received either streptozotocin-induced diabetes or vehicle. GLUT12 expression and localization were determined by immunohistochemistry, immunoblotting, in situ hybridization, and confocal immunofluorescence. GLUT1 immunolabeling was detected on the basolateral membrane throughout the nephron. GLUT12 was localized to the distal tubules and collecting ducts. A significant increase in GLUT12 immunolabeling was measured in Ren-2 controls and Ren-2 diabetic animals compared with Sprague-Dawley controls. GLUT12 expression was higher in Ren-2 diabetic compared with Sprague-Dawley diabetic rats. Long-term diabetes resulted in significant increases in GLUT1 levels in the renal proximal tubules and expression was higher in Ren-2 diabetic than Sprague-Dawley diabetic rats. GLUT12 protein was localized to the cytoplasm and to the apical membrane of human and rat distal tubules and collecting ducts. The apical localization of GLUT12 in the distal tubules and collecting ducts suggests that it could contribute to additional glucose reabsorption in the late nephron. Levels of both GLUT1 and GLUT12 are elevated in animal models of hypertension and diabetic nephropathy.
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Affiliation(s)
- Kelly C Linden
- Dept. of Medicine, The Univ. of Melbourne, St. Vincent's Hospital Melbourne, Victoria Parade, Fitzroy, Victoria 3065, Australia
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Keembiyehetty C, Augustin R, Carayannopoulos MO, Steer S, Manolescu A, Cheeseman CI, Moley KH. Mouse glucose transporter 9 splice variants are expressed in adult liver and kidney and are up-regulated in diabetes. Mol Endocrinol 2005; 20:686-97. [PMID: 16293642 DOI: 10.1210/me.2005-0010] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A novel glucose transporter (GLUT), mouse GLUT9 (mGLUT9), was recently cloned from mouse 7-d embryonic cDNA. Several splice variants of mGLUT9 were described, two of which were cloned (mGLUT9a and mGLUT9a Delta 209-316). This study describes the cloning and characterization of another splice variant, mGLUT9b. Cloned from adult liver, mGLUT9b is identical to mGLUT9a except at the amino terminus. Based on analysis of the genomic structure, the different amino termini result from alternative transcriptional/translational start sites. Expression and localization of these two mGLUT9 splice variants were examined in control and diabetic adult mouse tissues and in cell lines. RT-PCR analysis demonstrated expression of mGLUT9a in several tissues whereas mGLUT9b was observed primarily in liver and kidney. Using a mGLUT9-specific antibody, Western blot analysis of total membrane fractions from liver and kidney detected a single, wide band, migrating at approximately 55 kDa. This band shifted to a lower molecular mass when deglycosylated with peptide-N-glycosidase F. Both forms were present in liver and kidney. Immunohistochemical localization demonstrated basolateral distribution of mGLUT9 in liver hepatocytes and the expression of mGLUT9 in specific tubules in the outer cortex of the kidney. To investigate the alternative amino termini, mGLUT9a and mGLUT9b were overexpressed in kidney epithelium cell lines. Subcellular fractions localized both forms to the plasma membrane. Immunofluorescent staining of polarized Madin Darby canine kidney cells overexpressing mGLUT9 depicted a basolateral distribution for both splice variants. Finally, mGLUT9 protein expression was significantly increased in the kidney and liver from streptozotocin-induced diabetic mice compared with nondiabetic animals.
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Affiliation(s)
- Chithra Keembiyehetty
- Washington University School of Medicine, Department of Obstetrics/Gynelcology, Box 8064, St. Louis, Missouri 63110, USA
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