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Xie T, Zhao LJ. Synthetic approaches and clinical application of small-molecule inhibitors of sodium-dependent glucose transporters 2 for the treatment of type 2 diabetes mellitus. Eur J Med Chem 2024; 269:116343. [PMID: 38513341 DOI: 10.1016/j.ejmech.2024.116343] [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: 01/25/2024] [Revised: 03/08/2024] [Accepted: 03/15/2024] [Indexed: 03/23/2024]
Abstract
Sodium-dependent glucose transporters 2 (SGLT2) inhibitors are a class of small-molecule drugs that have gained significant attention in recent years for their potential clinical applications in the treatment of type 2 diabetes mellitus (T2DM). These inhibitors function by obstructing the kidneys' ability to reabsorb glucose, resulting in a rise in the excretion of glucose in urine (UGE) and subsequently lowering blood glucose levels. Several SGLT2 inhibitors, such as Dapagliflozin, Canagliflozin, and Empagliflozin, have been approved by regulatory authorities and are currently available for clinical use. These inhibitors have shown notable enhancements in managing blood sugar levels, reducing body weight, and lowering blood pressure in individuals with T2DM. Additionally, they have exhibited potential advantages in decreasing the likelihood of cardiovascular incidents and renal complications among this group of patients. This review article focuses on the synthesis and clinical application of small-molecule SGLT2 inhibitors, which have provided a new therapeutic approach for the management of T2DM.
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Affiliation(s)
- Tong Xie
- First People's Hospital of Shangqiu, Henan Province, Shangqiu, 476000, China.
| | - Li-Jie Zhao
- The Rogel Cancer Center, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48109, United States.
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2
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Subramaniam M, Loewen ME. Review: A species comparison of the kinetic homogeneous and heterogeneous organization of sodium-dependent glucose transport systems along the intestine. Comp Biochem Physiol A Mol Integr Physiol 2023; 285:111492. [PMID: 37536429 DOI: 10.1016/j.cbpa.2023.111492] [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: 06/15/2023] [Revised: 07/21/2023] [Accepted: 07/31/2023] [Indexed: 08/05/2023]
Abstract
The targeted use of carbohydrates by feed and food industries to create balanced and cost-effective diets has generated a tremendous amount of research in carbohydrate digestion and absorption in different species. Specifically, this research has led us to a larger observation that identified different organizations of intestinal sodium-dependent glucose absorption across species, which has not been previously collated and reviewed. Thus, this review will compare the kinetic segregation of sodium-dependent glucose transport across the intestine of different species, which we have termed either homogeneous or heterogeneous systems. For instance, the pig follows a heterogeneous system of sodium-dependent glucose transport with a high-affinity, super-low-capacity (Ha/sLc) in the jejunum, and a high-affinity, super-high-capacity (Ha/sHc) in the ileum. This is achieved by multiple sodium-dependent glucose transporters contributing to each segment. In contrast, tilapia have a homogenous system characterized by high-affinity, high-capacity (Ha/Hc) throughout the intestine. Additionally, we are the first to report glucose transporter patterns across species presented from vertebrates to invertebrates. Finally, other kinetic transport systems are briefly covered to illustrate possible contributions/modulations to sodium-dependent glucose transporter organization. Overall, we present a new perspective on the organization of glucose absorption along the intestinal tract.
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Affiliation(s)
- Marina Subramaniam
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada
| | - Matthew E Loewen
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada.
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3
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Al Thani NA, Hasan M, Yalcin HC. Use of Animal Models for Investigating Cardioprotective Roles of SGLT2 Inhibitors. J Cardiovasc Transl Res 2023; 16:975-986. [PMID: 37052784 PMCID: PMC10615955 DOI: 10.1007/s12265-023-10379-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 03/14/2023] [Indexed: 04/14/2023]
Abstract
Sodium-glucose co-transporter 2 (SGLT2) inhibitors represent one type of new-generation type 2 diabetes (T2DM) drug treatment. The mechanism of action of an SGLT2 inhibitor (SGLT2i) in treating T2DM depends on lowering blood glucose levels effectively via increasing the glomerular excretion of glucose. A good number of randomized clinical trials revealed that SGLT2is significantly prevented heart failure (HF) and cardiovascular death in T2DM patients. Despite ongoing clinical trials in HF patients without T2DM, there have been a limited number of translational studies on the cardioprotective properties of SGLT2is. As the cellular mechanism behind the cardiac benefits of SGLT2is is still to be elucidated, animal models are used to better understand the pathways behind the cardioprotective mechanism of SGLT2i. In this review, we summarize the animal models constructed to study the cardioprotective mechanisms of SGLT2is to help deliver a more comprehensive understanding of the in vivo work that has been done in this field and to help select the most optimal animal model to use when studying the different cardioprotective effects of SGLT2is.
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Affiliation(s)
- Najlaa A Al Thani
- Research and Development Department, Barzan Holdings, P. O. Box 7178, Doha, Qatar
| | - Maram Hasan
- Biomedical Research Center, Qatar University, P. O. Box 2713, Doha, Qatar
| | - Huseyin C Yalcin
- Biomedical Research Center, Qatar University, P. O. Box 2713, Doha, Qatar.
- Department of Biomedical Science, College of Health Sciences, QU Health, Qatar University, P. O. Box 2713, Doha, Qatar.
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4
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Pruett JE, Romero DG, Yanes Cardozo LL. Obesity-associated cardiometabolic complications in polycystic ovary syndrome: The potential role of sodium-glucose cotransporter-2 inhibitors. Front Endocrinol (Lausanne) 2023; 14:951099. [PMID: 36875461 PMCID: PMC9974663 DOI: 10.3389/fendo.2023.951099] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 01/26/2023] [Indexed: 02/17/2023] Open
Abstract
Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder in reproductive-age women. PCOS is characterized by androgen excess, oligo/anovulation, and polycystic appearance of the ovaries. Women with PCOS have an increased prevalence of multiple cardiovascular risk factors such as insulin resistance, hypertension, renal injury, and obesity. Unfortunately, there is a lack of effective, evidence-based pharmacotherapeutics to target these cardiometabolic complications. Sodium-glucose cotransporter-2 (SGLT2) inhibitors provide cardiovascular protection in patients with and without type 2 diabetes mellitus. Although the exact mechanisms of how SGLT2 inhibitors confer cardiovascular protection remains unclear, numerous mechanistic hypotheses for this protection include modulation of the renin-angiotensin system and/or the sympathetic nervous system and improvement in mitochondrial function. Data from recent clinical trials and basic research show a potential role for SGLT2 inhibitors in treating obesity-associated cardiometabolic complications in PCOS. This narrative review discusses the mechanisms of the beneficial effect of SGLT2 inhibitors in cardiometabolic diseases in PCOS.
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Affiliation(s)
- Jacob E. Pruett
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, MS, United States
| | - Damian G. Romero
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, MS, United States
- Mississippi Center of Excellence in Perinatal Research, University of Mississippi Medical Center, Jackson, MS, United States
- Women’s Health Research Center, University of Mississippi Medical Center, Jackson, MS, United States
- Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, MS, United States
| | - Licy L. Yanes Cardozo
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, MS, United States
- Mississippi Center of Excellence in Perinatal Research, University of Mississippi Medical Center, Jackson, MS, United States
- Women’s Health Research Center, University of Mississippi Medical Center, Jackson, MS, United States
- Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, MS, United States
- Department of Medicine, University of Mississippi Medical Center, Jackson, MS, United States
- *Correspondence: Licy L. Yanes Cardozo,
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Alicic RZ, Neumiller JJ, Galindo RJ, Tuttle KR. Use of Glucose-Lowering Agents in Diabetes and CKD. Kidney Int Rep 2022; 7:2589-2607. [PMID: 36506243 PMCID: PMC9727535 DOI: 10.1016/j.ekir.2022.09.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 08/31/2022] [Accepted: 09/19/2022] [Indexed: 12/15/2022] Open
Abstract
Diabetes is the most common cause of kidney failure worldwide. Patients with diabetes and chronic kidney disease (CKD) are also at markedly higher risk of cardiovascular disease, particularly heart failure (HF), and death. Through the processes of gluconeogenesis and glucose reabsorption, the kidney plays a central role in glucose homeostasis. Insulin resistance is an early alteration observed in CKD, worsened by the frequent presence of hypertension, obesity, and ongoing chronic inflammation, and oxidative stress. Management of diabetes in moderate to severe CKD warrants special consideration because of changes in glucose and insulin homeostasis and altered metabolism of glucose-lowering therapies. Kidney failure and initiation of kidney replacement therapy by dialysis adds to management complexity by further limiting therapeutic options, and predisposing individuals to hypoglycemia and hyperglycemia. Glycemic goals should be individualized, considering CKD severity, presence of macrovascular and microvascular complications, and life expectancy. A general hemoglobin A1c (HbA1c) goal of approximately 7% may be appropriate in earlier stages of CKD, with more relaxed targets often appropriate in later stages. Use of sodium glucose cotransporter2 (SGLT2) inhibitors and glucagon like peptide-1 receptor agonists (GLP-1RAs) meaningfully improves kidney and heart outcomes for patients with diabetes and CKD, irrespective of HbA1c targets, and are now part of guideline-directed medical therapy in this high-risk population. Delivery of optimal care for patients with diabetes and CKD will require collaboration across health care specialties and disciplines.
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Affiliation(s)
- Radica Z. Alicic
- Providence Medical Research Center, Providence Health Care, Spokane, Washington, USA
- Department of Medicine, University of Washington School of Medicine, Spokane and Seattle, Washington, USA
- Correspondence: Radica Z. Alicic, Providence Medical Research Center, 105 West 8th Avenue, Suite 250E, Spokane, Washington 99204, USA.
| | - Joshua J. Neumiller
- Providence Medical Research Center, Providence Health Care, Spokane, Washington, USA
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington, USA
| | - Rodolfo J. Galindo
- Department of Medicine, Division of Endocrinology, Emory University School of Medicine
| | - Katherine R. Tuttle
- Providence Medical Research Center, Providence Health Care, Spokane, Washington, USA
- Department of Medicine, University of Washington School of Medicine, Spokane and Seattle, Washington, USA
- Nephrology Division, Kidney Research Institute and Institute of Translational Health Sciences, University of Washington, Spokane and Seattle, Washington, USA
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Xie L, Xiao Y, Tai S, Yang H, Zhou S, Zhou Z. Emerging Roles of Sodium Glucose Cotransporter 2 (SGLT-2) Inhibitors in Diabetic Cardiovascular Diseases: Focusing on Immunity, Inflammation and Metabolism. Front Pharmacol 2022; 13:836849. [PMID: 35295328 PMCID: PMC8920092 DOI: 10.3389/fphar.2022.836849] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/07/2022] [Indexed: 11/29/2022] Open
Abstract
Diabetes mellitus (DM) is one of the most fast evolving global issues characterized by hyperglycemia. Patients with diabetes are considered to face with higher risks of adverse cardiovascular events. Those are the main cause of mortality and disability in diabetes patients. There are novel antidiabetic agents that selectively suppress sodium-glucose cotransporter-2 (SGLT-2). They work by reducing proximal tubule glucose reabsorption. Although increasing evidence has shown that SGLT-2 inhibitors can contribute to a series of cardiovascular benefits in diabetic patients, including a reduced incidence of major adverse cardiovascular events and protection of extracardiac organs, the potential mechanisms of SGLT2 inhibitors’ cardiovascular protective effects are still not fully elucidated. Given the important role of inflammation and metabolism in diabetic cardiovascular diseases, this review is intended to rationally compile the multifactorial mechanisms of SGLT-2 inhibitors from the point of immunity, inflammation and metabolism, depicting the fundamental cellular and molecular processing of SGLT-2 inhibitors exerting regulating immunity, inflammation and metabolism. Finally, future directions and perspectives to prevent or delay cardiovascular complications in DM by SGLT-2 inhibitors are presented.
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Affiliation(s)
- Lingxiang Xie
- Key Laboratory of Diabetes Immunology, Department of Metabolism and Endocrinology, National Clinical Research Center for Metabolic Diseases, Ministry of Education, The Second Xiangya Hospital of Central South University, Changsha, China
| | - Yang Xiao
- Key Laboratory of Diabetes Immunology, Department of Metabolism and Endocrinology, National Clinical Research Center for Metabolic Diseases, Ministry of Education, The Second Xiangya Hospital of Central South University, Changsha, China
| | - Shi Tai
- Department of Cardiovascular Medicine, The Second Xiangya Hospital of Central South University, Changsha, China
| | - Huijie Yang
- Key Laboratory of Diabetes Immunology, Department of Metabolism and Endocrinology, National Clinical Research Center for Metabolic Diseases, Ministry of Education, The Second Xiangya Hospital of Central South University, Changsha, China
| | - Shenghua Zhou
- Department of Cardiovascular Medicine, The Second Xiangya Hospital of Central South University, Changsha, China
| | - Zhiguang Zhou
- Key Laboratory of Diabetes Immunology, Department of Metabolism and Endocrinology, National Clinical Research Center for Metabolic Diseases, Ministry of Education, The Second Xiangya Hospital of Central South University, Changsha, China
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7
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Matsui T. Polyphenols-absorption and occurrence in the body system. FOOD SCIENCE AND TECHNOLOGY RESEARCH 2022. [DOI: 10.3136/fstr.fstr-d-21-00264] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Toshiro Matsui
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduated School of Kyushu University
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Sharma S, Mittal A, Kumar S, Mittal A. Structural Perspectives and Advancement of SGLT2 Inhibitors for the Treatment of Type 2 Diabetes. Curr Diabetes Rev 2022; 18:e170921196601. [PMID: 34538233 DOI: 10.2174/1573399817666210917122745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 08/12/2021] [Accepted: 08/14/2021] [Indexed: 11/22/2022]
Abstract
Diabetes mellitus is an ailment that affects a large number of individuals worldwide and its pervasiveness has been predicted to increase later on. Every year, billions of dollars are spent globally on diabetes-related health care practices. Contemporary hyperglycemic therapies to rationalize Type 2 Diabetes Mellitus (T2DM) mostly involve pathways that are insulin-dependent and lack effectiveness as the pancreas' β-cell function declines more significantly. Homeostasis via kidneys emerges as a new and future strategy to minimize T2DM complications. This article covers the reabsorption of glucose mechanism in the kidneys, the functional mechanism of various Sodium- Glucose Cotransporter 2 (SGLT2) inhibitors, their structure and driving profile, and a few SGLT2 inhibitors now accessible in the market as well as those in different periods of advancement. The advantages of SGLT2 inhibitors are dose-dependent glycemic regulation changes with a significant reduction both in the concentration of HbA1c and body weight clinically and statistically. A considerable number of SGLT2 inhibitors have been approved by the FDA, while a few others, still in preliminaries, have shown interesting effects.
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Affiliation(s)
- Shivani Sharma
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Lovely Professional University, Jalandhar-Delhi G.T. Road (NH-1), Phagwara (Punjab) 144411, India
| | - Amit Mittal
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Lovely Professional University, Jalandhar-Delhi G.T. Road (NH-1), Phagwara (Punjab) 144411, India
| | - Shubham Kumar
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Lovely Professional University, Jalandhar-Delhi G.T. Road (NH-1), Phagwara (Punjab) 144411, India
- Faculty of Pharmaceutical Sciences, PCTE Group of Institutes, Campus-2, Near Baddowal Cantt. Ferozepur Road, Ludhiana-142021, India
| | - Anu Mittal
- Department of Chemistry, Guru Nanak Dev University College, Patti, Distt. Tarn Taran, India
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Abstract
Patients with type 2 diabetes mellitus (T2D) are at increased risk of cardiovascular (CV) disease. Sodium glucose cotransporter 2 (SGLT2) inhibitors, also known as gliflozins, are a class of medications used to treat T2D by preventing the reabsorption of glucose filtered through the kidney and thereby facilitating glucose excretion in the urine. Over the past 5 years, many cardiovascular outcome trials (CVOTs) have evaluated the safety and efficacy of SGLT2 inhibitors in preventing CV events. The results of 7 CVOTs have provided solid evidence that the use of SGLT2 in patients with T2D and at high CV risk significantly reduced the risk of death from CV causes. Moreover, in patient with heart failure with reduced ejection fraction, regardless of the presence or absence of T2D, SGLT2 inhibitors use significantly reduced the risk of worsening heart failure and death from CV causes. Although the exact mechanism of the cardiorenal benefit of SGLT2 inhibitors is still unknown, studies have shown that the beneficial effect of these drugs cannot be exclusively explained by their glucose lowering effect, and several possible mechanisms have been proposed. This review will explore the changing role of SGLT2 inhibitors from a diabetes drug to clinical practice guideline-supported therapy for the prevention and treatment of CV diseases, including heart failure.
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Affiliation(s)
- Reza Mohebi
- Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - James L Januzzi
- Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Baim Institute for Clinical Research, Boston, MA, USA
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10
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Anti-inflammatory Effects of Empagliflozin and Gemigliptin on LPS-Stimulated Macrophage via the IKK/NF- κB, MKK7/JNK, and JAK2/STAT1 Signalling Pathways. J Immunol Res 2021; 2021:9944880. [PMID: 34124273 PMCID: PMC8192181 DOI: 10.1155/2021/9944880] [Citation(s) in RCA: 69] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 05/06/2021] [Accepted: 05/20/2021] [Indexed: 12/13/2022] Open
Abstract
Background Sodium-glucose cotransporter 2 (SGLT2) and dipeptidyl peptidase-4 (DPP-4) inhibitors are glucose-lowering drugs whose anti-inflammatory properties have recently become useful in tackling metabolic syndromes in chronic inflammatory diseases, including diabetes and obesity. We investigated whether empagliflozin (SGLT2 inhibitor) and gemigliptin (DPP-4 inhibitor) improve inflammatory responses in macrophages, identified signalling pathways responsible for these effects, and studied whether the effects can be augmented with dual empagliflozin and gemigliptin therapy. Methods RAW 264.7 macrophages were first stimulated with lipopolysaccharide (LPS), then cotreated with empagliflozin, gemigliptin, or empagliflozin plus gemigliptin. We conducted quantitative RT-PCR (qRT-PCR) to determine the most effective anti-inflammatory doses without cytotoxicity. We performed ELISA and qRT-PCR for inflammatory cytokines and chemokines and flow cytometry for CD80, the M1 macrophage surface marker, to evaluate the anti-inflammatory effects of empagliflozin and gemigliptin. NF-κB, MAPK, and JAK2/STAT signalling pathways were examined via Western blotting to elucidate the molecular mechanisms of anti-inflammation. Results LPS-stimulated CD80+ M1 macrophages were suppressed by coincubation with empagliflozin, gemigliptin, and empagliflozin plus gemigliptin, respectively. Empagliflozin and gemigliptin (individually and combined) inhibited prostaglandin E2 (PGE2) release and COX-2, iNOS gene expression in LPS-stimulated RAW 264.7 macrophages. These three treatments also attenuated the secretion and mRNA expression of proinflammatory cytokines, such as TNF-α, IL-1β, IL-6, and IFN-γ, and proinflammatory chemokines, such as CCL3, CCL4, CCL5, and CXCL10. All of them blocked NF-κB, JNK, and STAT1/3 phosphorylation through IKKα/β, MKK4/7, and JAK2 signalling. Conclusions Our study demonstrated the anti-inflammatory effects of empagliflozin and gemigliptin via IKK/NF-κB, MKK7/JNK, and JAK2/STAT1 pathway downregulation in macrophages. In all cases, combined empagliflozin and gemigliptin treatment showed greater anti-inflammatory properties.
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Cahill T, da Silveira WA, Renaud L, Williamson T, Wang H, Chung D, Overton I, Chan SSL, Hardiman G. Induced Torpor as a Countermeasure for Low Dose Radiation Exposure in a Zebrafish Model. Cells 2021; 10:906. [PMID: 33920039 PMCID: PMC8071006 DOI: 10.3390/cells10040906] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 04/07/2021] [Accepted: 04/11/2021] [Indexed: 12/15/2022] Open
Abstract
The development of the Artemis programme with the goal of returning to the moon is spurring technology advances that will eventually take humans to Mars and herald a new era of interplanetary space travel. However, long-term space travel poses unique challenges including exposure to ionising radiation from galactic cosmic rays and potential solar particle events, exposure to microgravity and specific nutritional challenges arising from earth independent exploration. Ionising radiation is one of the major obstacles facing future space travel as it can generate oxidative stress and directly damage cellular structures such as DNA, in turn causing genomic instability, telomere shortening, extracellular-matrix remodelling and persistent inflammation. In the gastrointestinal tract (GIT) this can lead to leaky gut syndrome, perforations and motility issues, which impact GIT functionality and affect nutritional status. While current countermeasures such as shielding from the spacecraft can attenuate harmful biological effects, they produce harmful secondary particles that contribute to radiation exposure. We hypothesised that induction of a torpor-like state would confer a radioprotective effect given the evidence that hibernation extends survival times in irradiated squirrels compared to active controls. To test this hypothesis, a torpor-like state was induced in zebrafish using melatonin treatment and reduced temperature, and radiation exposure was administered twice over the course of 10 days. The protective effects of induced-torpor were assessed via RNA sequencing and qPCR of mRNA extracted from the GIT. Pathway and network analysis were performed on the transcriptomic data to characterise the genomic signatures in radiation, torpor and torpor + radiation groups. Phenotypic analyses revealed that melatonin and reduced temperature successfully induced a torpor-like state in zebrafish as shown by decreased metabolism and activity levels. Genomic analyses indicated that low dose radiation caused DNA damage and oxidative stress triggering a stress response, including steroidal signalling and changes to metabolism, and cell cycle arrest. Torpor attenuated the stress response through an increase in pro-survival signals, reduced oxidative stress via the oxygen effect and detection and removal of misfolded proteins. This proof-of-concept model provides compelling initial evidence for utilizing an induced torpor-like state as a potential countermeasure for radiation exposure.
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Affiliation(s)
- Thomas Cahill
- School of Biological Sciences & Institute for Global Food Security, Queens University Belfast, Belfast BT9 5DL, UK; (T.C.); (W.A.d.S.); (H.W.)
| | - Willian Abraham da Silveira
- School of Biological Sciences & Institute for Global Food Security, Queens University Belfast, Belfast BT9 5DL, UK; (T.C.); (W.A.d.S.); (H.W.)
| | - Ludivine Renaud
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA;
| | - Tucker Williamson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, USA; (T.W.); (S.S.L.C.)
| | - Hao Wang
- School of Biological Sciences & Institute for Global Food Security, Queens University Belfast, Belfast BT9 5DL, UK; (T.C.); (W.A.d.S.); (H.W.)
| | - Dongjun Chung
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH 43210, USA;
| | - Ian Overton
- Patrick G Johnston Centre for Cancer Research, Queen’s University Belfast, Belfast BT9 7AE, UK;
| | - Sherine S. L. Chan
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, USA; (T.W.); (S.S.L.C.)
| | - Gary Hardiman
- School of Biological Sciences & Institute for Global Food Security, Queens University Belfast, Belfast BT9 5DL, UK; (T.C.); (W.A.d.S.); (H.W.)
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA;
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Rysz J, Franczyk B, Radek M, Ciałkowska-Rysz A, Gluba-Brzózka A. Diabetes and Cardiovascular Risk in Renal Transplant Patients. Int J Mol Sci 2021; 22:3422. [PMID: 33810367 PMCID: PMC8036743 DOI: 10.3390/ijms22073422] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 03/05/2021] [Accepted: 03/08/2021] [Indexed: 02/06/2023] Open
Abstract
End-stage kidney disease (ESKD) is a main public health problem, the prevalence of which is continuously increasing worldwide. Due to adverse effects of renal replacement therapies, kidney transplantation seems to be the optimal form of therapy with significantly improved survival, quality of life and diminished overall costs compared with dialysis. However, post-transplant patients frequently suffer from post-transplant diabetes mellitus (PTDM) which an important risk factor for cardiovascular and cardiovascular-related deaths after transplantation. The management of post-transplant diabetes resembles that of diabetes in the general population as it is based on strict glycemic control as well as screening and treatment of common complications. Lifestyle interventions accompanied by the tailoring of immunosuppressive regimen may be of key importance to mitigate PTDM-associated complications in kidney transplant patients. More transplant-specific approach can include the exchange of tacrolimus with an alternative immunosuppressant (cyclosporine or mammalian target of rapamycin (mTOR) inhibitor), the decrease or cessation of corticosteroid therapy and caution in the prescribing of diuretics since they are independently connected with post-transplant diabetes. Early identification of high-risk patients for cardiovascular diseases enables timely introduction of appropriate therapeutic strategy and results in higher survival rates for patients with a transplanted kidney.
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Affiliation(s)
- Jacek Rysz
- Department of Nephrology, Hypertension and Family Medicine, Medical University of Lodz, 90-549 Lodz, Poland; (J.R.); (B.F.)
| | - Beata Franczyk
- Department of Nephrology, Hypertension and Family Medicine, Medical University of Lodz, 90-549 Lodz, Poland; (J.R.); (B.F.)
| | - Maciej Radek
- Department of Neurosurgery, Surgery of Spine and Peripheral Nerves, Medical University of Lodz, 90-549 Lodz, Poland;
| | | | - Anna Gluba-Brzózka
- Department of Nephrology, Hypertension and Family Medicine, Medical University of Lodz, 90-549 Lodz, Poland; (J.R.); (B.F.)
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Angus M, Ruben P. Voltage gated sodium channels in cancer and their potential mechanisms of action. Channels (Austin) 2019; 13:400-409. [PMID: 31510893 PMCID: PMC6768049 DOI: 10.1080/19336950.2019.1666455] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 08/30/2019] [Accepted: 09/08/2019] [Indexed: 01/22/2023] Open
Abstract
Voltage gated sodium channels (VGSC) are implicated in cancer cell invasion and metastasis. However, the mechanism by which VGSC increase cell invasiveness and probability of metastasis is still unknown. In this review we outline lesser known functions of VGSC outside of action potential propagation, and the current understanding of the effects of VGSC in cancer. Finally, we discuss possible downstream effects of VGSC activation in cancer cells. After extensive review of the literature, the most likely role of VGSC in cancer is in the invadopodia, the leading edge of metastatic cancer cells. Sodium gradients are used to drive many biological processes in the body, and invadopodia may be similar. The function of the sodium hydrogen exchanger (NHE) and sodium calcium exchanger (NCX) are driven by sodium gradients. Voltage gated calcium channels, activated by membrane depolarization, are also capable of becoming activated in response to VGSC activity. Changes to hydrogen ion exchange or calcium handling have functional consequences for invadopodia and would explain the relationship between VGSC expression and invasiveness of cancer cells.
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Affiliation(s)
- Madeline Angus
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Peter Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
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Alicic RZ, Johnson EJ, Tuttle KR. SGLT2 Inhibition for the Prevention and Treatment of Diabetic Kidney Disease: A Review. Am J Kidney Dis 2018; 72:267-277. [DOI: 10.1053/j.ajkd.2018.03.022] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/06/2018] [Indexed: 02/06/2023]
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Mühlemann M, Zdzieblo D, Friedrich A, Berger C, Otto C, Walles H, Koepsell H, Metzger M. Altered pancreatic islet morphology and function in SGLT1 knockout mice on a glucose-deficient, fat-enriched diet. Mol Metab 2018; 13:67-76. [PMID: 29859847 PMCID: PMC6026318 DOI: 10.1016/j.molmet.2018.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 05/08/2018] [Accepted: 05/15/2018] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES Glycemic control by medical treatment represents one therapeutic strategy for diabetic patients. The Na+-d-glucose cotransporter 1 (SGLT1) is currently of high interest in this context. SGLT1 is known to mediate glucose absorption and incretin secretion in the small intestine. Recently, inhibition of SGLT1 function was shown to improve postprandial hyperglycemia. In view of the lately demonstrated SGLT1 expression in pancreatic islets, we investigated if loss of SGLT1 affects islet morphology and function. METHODS Effects associated with the loss of SGLT1 on pancreatic islet (cyto) morphology and function were investigated by analyzing islets of a SGLT1 knockout mouse model, that were fed a glucose-deficient, fat-enriched diet (SGLT1-/--GDFE) to circumvent the glucose-galactose malabsorption syndrome. To distinguish diet- and Sglt1-/--dependent effects, wildtype mice on either standard chow (WT-SC) or the glucose-free, fat-enriched diet (WT-GDFE) were used as controls. Feeding a glucose-deficient, fat-enriched diet further required the analysis of intestinal SGLT1 expression and function under diet-conditions. RESULTS Consistent with literature, our data provide evidence that small intestinal SGLT1 mRNA expression and function is regulated by nutrition. In contrast, pancreatic SGLT1 mRNA levels were not affected by the applied diet, suggesting different regulatory mechanisms for SGLT1 in diverse tissues. Morphological changes such as increased islet sizes and cell numbers associated with changes in proliferation and apoptosis and alterations of the β- and α-cell population are specifically observed for pancreatic islets of SGLT1-/--GDFE mice. Glucose stimulation revealed no insulin response in SGLT1-/--GDFE mice while WT-GDFE mice displayed only a minor increase of blood insulin. Irregular glucagon responses were observed for both, SGLT1-/--GDFE and WT-GDFE mice. Further, both animal groups showed a sustained release of GLP-1 compared to WT-SC controls. CONCLUSION Loss or impairment of SGLT1 results in abnormal pancreatic islet (cyto)morphology and disturbed islet function regarding the insulin or glucagon release capacity from β- or α-cells, respectively. Consequently, our findings propose a new, additional role for SGLT1 maintaining proper islet structure and function.
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Affiliation(s)
- Markus Mühlemann
- Chair Tissue Engineering and Regenerative Medicine, University Hospital Würzburg, 97070, Würzburg, Germany
| | - Daniela Zdzieblo
- Chair Tissue Engineering and Regenerative Medicine, University Hospital Würzburg, 97070, Würzburg, Germany.
| | - Alexandra Friedrich
- Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, 97070, Würzburg, Germany
| | - Constantin Berger
- Chair Tissue Engineering and Regenerative Medicine, University Hospital Würzburg, 97070, Würzburg, Germany
| | - Christoph Otto
- Department of General Visceral Vascular and Pediatric Surgery, University Hospital Würzburg, 97070, Würzburg, Germany
| | - Heike Walles
- Chair Tissue Engineering and Regenerative Medicine, University Hospital Würzburg, 97070, Würzburg, Germany; Translational Center Regenerative Therapies (TLC-RT), Fraunhofer Institute for Silicate Research ISC, 97070, Würzburg, Germany
| | - Hermann Koepsell
- Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, 97070, Würzburg, Germany
| | - Marco Metzger
- Chair Tissue Engineering and Regenerative Medicine, University Hospital Würzburg, 97070, Würzburg, Germany; Translational Center Regenerative Therapies (TLC-RT), Fraunhofer Institute for Silicate Research ISC, 97070, Würzburg, Germany
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SLC5A1 Mutations in Saudi Arabian Patients With Congenital Glucose-Galactose Malabsorption. J Pediatr Gastroenterol Nutr 2018; 66:250-252. [PMID: 28753187 DOI: 10.1097/mpg.0000000000001694] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Congenital glucose-galactose malabsorption (cGGM) is a rare autosomal recessive disorder, caused by mutations in the SLC5A1 gene, encoding the sodium/glucose cotransporter 1, which may result in severe life-threatening osmotic diarrhea due to the accumulation of unabsorbed sugars in the intestinal lumen. If treated early with elimination of glucose and galactose from the diet, patients usually recover and develop normally. We present clinical and molecular data from 16 unrelated cGGM diagnosed Saudi patients from consanguineous families with majority of them having previous positive family history of cGGM. Sanger sequencing for the full coding regions of SLC5A1 for all patients resulted in the identification of 4 allelic variants in a homozygous state. Two mutations are novel; c.265G>A (p.G89R) and c.1304 G>A (p.G435D), and 2 have been previously reported to cause cGGM, c.765 C>G (p.C255W) and c.1136 G>A (p.R379Q). This is the first report delineating the clinical and molecular basis of cGGM in patients from this region.
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Norton L, Shannon CE, Fourcaudot M, Hu C, Wang N, Ren W, Song J, Abdul-Ghani M, DeFronzo RA, Ren J, Jia W. Sodium-glucose co-transporter (SGLT) and glucose transporter (GLUT) expression in the kidney of type 2 diabetic subjects. Diabetes Obes Metab 2017; 19:1322-1326. [PMID: 28477418 DOI: 10.1111/dom.13003] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 04/18/2017] [Accepted: 04/30/2017] [Indexed: 12/22/2022]
Abstract
The sodium-glucose co-transporters (SGLTs) are responsible for the tubular reabsorption of filtered glucose from the kidney into the bloodstream. The inhibition of SGLT2-mediated glucose reabsorption is a novel and highly effective strategy to alleviate hyperglycaemia in patients with type 2 diabetes mellitus (T2DM). However, the effectiveness of SGLT2 inhibitor therapy is diminished due, in part, to a compensatory increase in the maximum reabsorptive capacity (Tm) for glucose in patients with T2DM. We hypothesized that this increase in Tm could be explained by an increase in the tubular expression of SGLT and glucose transporters (GLUT) in these patients. To examine this, we obtained human kidney biopsy specimens from patients with or without T2DM and examined the mRNA expression of SGLTs and GLUTs. The expression of SGLT1 is markedly increased in the kidney of patients with T2DM, and SGLT1 mRNA is highly and significantly correlated with fasting and postprandial plasma glucose and HbA1c. In contrast, our data demonstrate that the levels of SGLT2 and GLUT2 mRNA are downregulated in diabetic patients, but not to a statistically significant level. These important findings are clinically significant and may have implications for the treatment of T2DM using strategies that target SGLT transporters in the kidney.
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Affiliation(s)
- Luke Norton
- Diabetes Division, University of Texas Health Science Center, San Antonio, Texas
| | | | - Marcel Fourcaudot
- Diabetes Division, University of Texas Health Science Center, San Antonio, Texas
| | - Cheng Hu
- Shanghai Diabetes Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Niansong Wang
- Shanghai Diabetes Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Wei Ren
- Shanghai Diabetes Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Jun Song
- Shanghai Diabetes Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Muhammad Abdul-Ghani
- Diabetes Division, University of Texas Health Science Center, San Antonio, Texas
| | - Ralph A DeFronzo
- Diabetes Division, University of Texas Health Science Center, San Antonio, Texas
| | - Jimmy Ren
- Janssen Pharmaceuticals Inc, Raritan, New Jersey
| | - Weiping Jia
- Shanghai Diabetes Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
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Szablewski L. Distribution of glucose transporters in renal diseases. J Biomed Sci 2017; 24:64. [PMID: 28854935 PMCID: PMC5577680 DOI: 10.1186/s12929-017-0371-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 08/23/2017] [Indexed: 02/06/2023] Open
Abstract
Kidneys play an important role in glucose homeostasis. Renal gluconeogenesis prevents hypoglycemia by releasing glucose into the blood stream. Glucose homeostasis is also due, in part, to reabsorption and excretion of hexose in the kidney.Lipid bilayer of plasma membrane is impermeable for glucose, which is hydrophilic and soluble in water. Therefore, transport of glucose across the plasma membrane depends on carrier proteins expressed in the plasma membrane. In humans, there are three families of glucose transporters: GLUT proteins, sodium-dependent glucose transporters (SGLTs) and SWEET. In kidney, only GLUTs and SGLTs protein are expressed. Mutations within genes that code these proteins lead to different renal disorders and diseases. However, diseases, not only renal, such as diabetes, may damage expression and function of renal glucose transporters.
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Affiliation(s)
- Leszek Szablewski
- Medical University of Warsaw, Chair & Department of General Biology & Parasitology, Center for Biostructure Research, 5 Chalubinskiego Str., 02-004, Warsaw, Poland.
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Yoshimoto T, Furuki T, Kobori H, Miyakawa M, Imachi H, Murao K, Nishiyama A. Effects of sodium-glucose cotransporter 2 inhibitors on urinary excretion of intact and total angiotensinogen in patients with type 2 diabetes. J Investig Med 2017; 65:1057-1061. [PMID: 28596160 PMCID: PMC5812257 DOI: 10.1136/jim-2017-000445] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2017] [Indexed: 12/26/2022]
Abstract
We conducted a descriptive case study to examine the effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors on urinary angiotensinogen excretion, which represents the function of the intrarenal renin–angiotensin system, in patients with type 2 diabetes. An SGLT2 inhibitor (canagliflozin 100 mg/day, ipragliflozin 25 mg/day, dapagliflozin 5 mg/day, luseogliflozin 2.5 mg/day or tofogliflozin 20 mg/day) was administered for 1 month (n=9). ELISA kits were used to measure both urinary intact and total angiotensinogen levels. Treatment with SGLT2 inhibitors significantly decreased hemoglobin A1c, body weight, systolic blood pressure and diastolic blood pressure (8.5±1.3 to 7.5%±1.0%, 82.5±20.2 to 80.6±20.9 kg, 143±8 to 128±14 mm Hg, 78±10 to 67±9 mm Hg, p<0.05, respectively), while urinary albumin/creatinine ratio was not significantly changed (58.6±58.9 to 29.2±60.7 mg/g, p=0.16). Both total urinary angiotensinogen/creatinine ratio and intact urinary angiotensinogen/creatinine ratio tended to decrease after administration of SGLT2 inhibitors. However, these changes were not significant (p=0.19 and p=0.08, respectively). These data suggest that treatment with SGLT2 inhibitors does not activate the intrarenal renin–angiotensin system in patients with type 2 diabetes.
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Affiliation(s)
- Takuo Yoshimoto
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, Miki - cho, Kagawa, Japan
| | - Takayuki Furuki
- Department of Medicine, Hadanoeki - Minamiguchi Clinic, Hadano, Kanagawa, Japan
| | - Hiroyuki Kobori
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Miki - cho, Kagawa, Japan
| | - Masaaki Miyakawa
- Department of Medicine, Miyakawa Clinic, Yokohama, Kanagawa, Japan
| | - Hitomi Imachi
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, Miki - cho, Kagawa, Japan
| | - Koji Murao
- Department of Endocrinology and Metabolism, Faculty of Medicine, Kagawa University, Miki - cho, Kagawa, Japan
| | - Akira Nishiyama
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Miki - cho, Kagawa, Japan
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Craig PM, Massarsky A, Moon TW. Understanding glucose uptake during methionine deprivation in incubated rainbow trout (Oncorhynchus mykiss) hepatocytes using a non-radioactive method. Comp Biochem Physiol B Biochem Mol Biol 2013; 166:23-9. [DOI: 10.1016/j.cbpb.2013.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 06/11/2013] [Accepted: 06/17/2013] [Indexed: 11/15/2022]
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Assiri A, Saeed A, Alnimri A, Ahmad S, Saeed E, Jameel S. Five Arab children with glucose-galactose malabsorption. Paediatr Int Child Health 2013; 33:108-10. [PMID: 23925285 DOI: 10.1179/2046905513y.0000000055] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Five children with glucose-galactose malabsorption (GGM) are presented. Two infants from Saudi Arabia were first-degree relatives, the third infant was unrelated and the other two were of Yemeni and Syrian origin, respectively. All the infants had chronic diarrhoea and four had failed to thrive since early infancy. All had stools positive for reducing substances, and sugar chromatography showed glucose and galactose malabsorption. Small bowel biopsies were normal in all. One infant developed gangrene of both legs as a complication of hypernatraemia and dehydration, necessitating bilateral amputation. Two infants had nephrolithiasis. All the infants responded well to fructose-based formulae. GGM should be considered in the differential diagnosis of chronic diarrhoea in infants breastfed or artificially fed from early life.
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Affiliation(s)
- Asaad Assiri
- Department of Pediatrics, Faculty of Medicine, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia.
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23
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Wright EM. Glucose transport families SLC5 and SLC50. Mol Aspects Med 2013; 34:183-96. [DOI: 10.1016/j.mam.2012.11.002] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 10/04/2012] [Indexed: 01/15/2023]
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Misra M. SGLT2 inhibitors: a promising new therapeutic option for treatment of type 2 diabetes mellitus. ACTA ACUST UNITED AC 2012; 65:317-27. [PMID: 23356840 DOI: 10.1111/j.2042-7158.2012.01574.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND Hyperglycemia is an important pathogenic component in the development of microvascular and macrovascular complications in type 2 diabetes mellitus. Inhibition of renal tubular glucose reabsorption that leads to glycosuria has been proposed as a new mechanism to attain normoglycemia and thus prevent and diminish these complications. Sodium glucose cotransporter 2 (SGLT2) has a key role in reabsorption of glucose in kidney. Competitive inhibitors of SGLT2 have been discovered and a few of them have also been advanced in clinical trials for the treatment of diabetes. OBJECTIVE To discuss the therapeutic potential of SGLT2 inhibitors currently in clinical development. KEY FINDINGS A number of preclinical and clinical studies of SGLT2 inhibitors have demonstrated a good safety profile and beneficial effects in lowering plasma glucose levels, diminishing glucotoxicity, improving glycemic control and reducing weight in diabetes. Of all the SGLT2 inhibitors, dapagliflozin is a relatively advanced compound with regards to clinical development. SUMMARY SGLT2 inhibitors are emerging as a promising therapeutic option for the treatment of diabetes. Their unique mechanism of action offers them the potential to be used in combination with other oral anti-diabetic drugs as well as with insulin.
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Affiliation(s)
- Monika Misra
- Department of Pharmacology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Uttar Pradesh, India.
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K⁺-dependent ³H-D-glucose transport by hepatopancreatic brush border membrane vesicles of a marine shrimp. J Comp Physiol B 2012; 183:61-9. [PMID: 22752676 DOI: 10.1007/s00360-012-0684-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/03/2012] [Accepted: 06/09/2012] [Indexed: 01/15/2023]
Abstract
The effects of sodium, potassium, sugar inhibitors, and membrane potential on ³H-D-glucose uptake by hepatopancreatic epithelial brush border membrane vesicles (BBMV) of the Atlantic marine shrimp, Litopenaeus setiferus, were investigated. Brush border membrane vesicles were prepared using a MgCl₂/EGTA precipitation method and uptake experiments were conducted using a high speed filtration technique. ³H-D-Glucose uptake was stimulated by both sodium and potassium and these transport rates were almost doubled in the presence of an inside-negative-induced membrane potential. Kinetics of ³H-D-glucose influx were hyperbolic functions of both external Na⁺ or K⁺, and an induced membrane potential increased influx J(max) and lowered K(m) in both salts. ³H-D-Glucose influx versus [glucose] in both Na⁺ or K⁺ media also displayed Michaelis-Menten properties that were only slightly affected by induced membrane potential. Phloridzin was a poor inhibitor of 0.5 mM ³H-D-glucose influx, requiring at least 5 mM in NaCl and 10 mM in KCl to significantly reduce hexose transport. Several sugars (D-galactose, α-methyl-D-gluco-pyranoside, unlabeled D-glucose, D-fructose, and D-mannose) were used at 75 mM as potential inhibitors of 0.1 mM ³H-D-glucose influx. Only unlabeled D-glucose, D-fructose, and D-mannose significantly (p < 0.05) reduced labeled glucose transport. An additional experiment using increasing concentrations of D-mannose (0, 10, 25, 75, and 100 mM) showed this hexose to be an effective inhibitor of 0.1 mM ³H-D-glucose uptake at concentrations of 75 mM and higher. As a whole these results suggest that ³H-D-glucose transport by hepatopancreatic BBMV occurs by a carrier system that is able to use both Na⁺ and K⁺ as drivers, is enhanced by membrane potential, is relatively refractory to phloridzin, and is only inhibited by itself, D-fructose, and D-mannose. These properties are similar to those exhibited by the mammalian SLC5A9/SGLT4 transporter, suggesting that an invertebrate analogue of this protein may occur in shrimp.
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Raja M, Puntheeranurak T, Hinterdorfer P, Kinne R. SLC5 and SLC2 transporters in epithelia-cellular role and molecular mechanisms. CURRENT TOPICS IN MEMBRANES 2012. [PMID: 23177983 DOI: 10.1016/b978-0-12-394316-3.00002-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Members of the SLC5 and SLC2 family are prominently involved in epithelial sugar transport. SGLT1 (sodium-glucose transporter) and SGLT2, as representatives of the former, mediate sodium-dependent uptake of sugars into intestinal and renal cells. GLUT2 (glucose transporter), as representative of the latter, facilitates the sodium-independent exit of sugars from cells. SGLT has played a major role in the formulation and experimental proof for the existence of sodium cotransport systems. Based on the sequence data and biochemical and biophysical analyses, the role of extramembranous loops in sugar and inhibitor binding can be delineated. Crystal structures and homology modeling of SGLT reveal that the sugar translocation involves operation of two hydrophobic gates and intermediate exofacial and endofacial occluded states of the carrier in an alternating access model. The same basic model is proposed for GLUT1. Studies on GLUT1 have pioneered the isolation of eukaryotic transporters by biochemical methods and the development of transport kinetics and transporter models. For GLUT1, results from extensive mutagenesis, cysteine substitution and accessibility studies can be incorporated into a homology model with a barrel-like structure in which accessibility to the extracellular and intracellular medium is altered by pinching movements of some of the helices. For SGLT1 and GLUT1, the extensive hydrophilic and hydrophobic interactions between sugars and binding sites of the various intramembrane helices occur and lead to different substrate specificities and inhibitor affinities of the two transporters. A complex network of regulatory steps adapts the transport activity to the needs of the body.
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Affiliation(s)
- Mobeen Raja
- Max Planck Institute of Molecular Physiology, Dortmund, Germany
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Obi IE, Sterling KM, Ahearn GA. Transepithelial D-glucose and D-fructose transport across the American lobster, Homarus americanus, intestine. ACTA ACUST UNITED AC 2011; 214:2337-44. [PMID: 21697425 DOI: 10.1242/jeb.055095] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Transepithelial transport of dietary D-glucose and d-fructose was examined in the lobster Homarus americanus intestine using D-[(3)H]glucose and D-[(3)H]fructose. Lobster intestines were mounted in a perfusion chamber to determine transepithelial mucosal to serosal (MS) and serosal to mucosal (SM) transport mechanisms of glucose and fructose. Both MS glucose and fructose transport, as functions of luminal sugar concentration, increased in a hyperbolic manner, suggesting the presence of mucosal transport proteins. Phloridizin inhibited the MS flux of glucose, but not that of fructose, suggesting the presence of a sodium-dependent (SGLT1)-like glucose co-transporter. Immunohistochemical analysis, using a goat anti-rabbit GLUT5 polyclonal antibody, revealed the localization of a brush border GLUT5-like fructose transport protein. MS fructose transport was decreased in the presence of mucosal phloretin in warm spring/summer animals, but the same effect was not observed in cold autumn/winter animals, suggesting a seasonal regulation of sugar transporters. Mucosal phloretin had no effect on MS glucose transport. Both SM glucose and SM fructose transport were decreased in the presence of increasing concentrations of serosal phloretin, providing evidence for the presence of a shared serosal GLUT2 transport protein for the two sugars. The transport of d-glucose and d-fructose across lobster intestine is similar to sugar uptake in mammalian intestine, suggesting evolutionarily conserved absorption processes for these solutes.
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Affiliation(s)
- Ijeoma E Obi
- Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA
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Abdul-Ghani MA, Norton L, Defronzo RA. Role of sodium-glucose cotransporter 2 (SGLT 2) inhibitors in the treatment of type 2 diabetes. Endocr Rev 2011; 32:515-31. [PMID: 21606218 DOI: 10.1210/er.2010-0029] [Citation(s) in RCA: 317] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Hyperglycemia plays an important role in the pathogenesis of type 2 diabetes mellitus, i.e., glucotoxicity, and it also is the major risk factor for microvascular complications. Thus, effective glycemic control will not only reduce the incidence of microvascular complications but also correct some of the metabolic abnormalities that contribute to the progression of the disease. Achieving durable tight glycemic control is challenging because of progressive β-cell failure and is hampered by increased frequency of side effects, e.g., hypoglycemia and weight gain. Most recently, inhibitors of the renal sodium-glucose cotransporter have been developed to produce glucosuria and reduce the plasma glucose concentration. These oral antidiabetic agents have the potential to improve glycemic control while avoiding hypoglycemia, to correct the glucotoxicity, and to promote weight loss. In this review, we will summarize the available data concerning the mechanism of action, efficacy, and safety of this novel antidiabetic therapeutic approach.
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Abstract
There are two classes of glucose transporters involved in glucose homeostasis in the body, the facilitated transporters or uniporters (GLUTs) and the active transporters or symporters (SGLTs). The energy for active glucose transport is provided by the sodium gradient across the cell membrane, the Na(+) glucose cotransport hypothesis first proposed in 1960 by Crane. Since the cloning of SGLT1 in 1987, there have been advances in the genetics, molecular biology, biochemistry, biophysics, and structure of SGLTs. There are 12 members of the human SGLT (SLC5) gene family, including cotransporters for sugars, anions, vitamins, and short-chain fatty acids. Here we give a personal review of these advances. The SGLTs belong to a structural class of membrane proteins from unrelated gene families of antiporters and Na(+) and H(+) symporters. This class shares a common atomic architecture and a common transport mechanism. SGLTs also function as water and urea channels, glucose sensors, and coupled-water and urea transporters. We also discuss the physiology and pathophysiology of SGLTs, e.g., glucose galactose malabsorption and familial renal glycosuria, and briefly report on targeting of SGLTs for new therapies for diabetes.
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Affiliation(s)
- Ernest M Wright
- Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California 90095-1751, USA.
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La Ferla B, Spinosa V, D'Orazio G, Palazzo M, Balsari A, Foppoli AA, Rumio C, Nicotra F. Dansyl C-Glucoside as a Novel Agent Against Endotoxic Shock. ChemMedChem 2010; 5:1677-80. [DOI: 10.1002/cmdc.201000282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Nose Y, Wood LK, Kim BE, Prohaska JR, Fry RS, Spears JW, Thiele DJ. Ctr1 is an apical copper transporter in mammalian intestinal epithelial cells in vivo that is controlled at the level of protein stability. J Biol Chem 2010; 285:32385-92. [PMID: 20699218 DOI: 10.1074/jbc.m110.143826] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Copper is an essential trace element that functions in a diverse array of biochemical processes that include mitochondrial respiration, neurotransmitter biogenesis, connective tissue maturation, and reactive oxygen chemistry. The Ctr1 protein is a high-affinity Cu(+) importer that is structurally and functionally conserved in yeast, plants, fruit flies, and humans and that, in all of these organisms, is localized to the plasma membrane and intracellular vesicles. Although intestinal epithelial cell-specific deletion of Ctr1 in mice demonstrated a critical role for Ctr1 in dietary copper absorption, some controversy exists over the localization of Ctr1 in intestinal epithelial cells in vivo. In this work, we assess the localization of Ctr1 in intestinal epithelial cells through two independent mechanisms. Using immunohistochemistry, we demonstrate that Ctr1 localizes to the apical membrane in intestinal epithelial cells of the mouse, rat, and pig. Moreover, biotinylation of intestinal luminal proteins from mice fed a control or a copper-deficient diet showed elevated levels of both total and apical membrane Ctr1 protein in response to transient dietary copper limitation. Experiments in cultured HEK293T cells demonstrated that alterations in the levels of the glycosylated form of Ctr1 in response to copper availability were a time-dependent, copper-specific posttranslational response. Taken together, these results demonstrate apical localization of Ctr1 in intestinal epithelia across three mammalian species and suggest that increased Ctr1 apical localization in response to dietary copper limitation may represent an adaptive response to homeostatically modulate Ctr1 availability at the site of intestinal copper absorption.
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Affiliation(s)
- Yasuhiro Nose
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Rawat A, Gust KA, Deng Y, Garcia-Reyero N, Quinn MJ, Johnson MS, Indest KJ, Elasri MO, Perkins EJ. From raw materials to validated system: the construction of a genomic library and microarray to interpret systemic perturbations in Northern bobwhite. Physiol Genomics 2010; 42:219-35. [PMID: 20406850 PMCID: PMC3032282 DOI: 10.1152/physiolgenomics.00022.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 04/16/2010] [Indexed: 01/02/2023] Open
Abstract
The limited availability of genomic tools and data for nonmodel species impedes computational and systems biology approaches in nonmodel organisms. Here we describe the development, functional annotation, and utilization of genomic tools for the avian wildlife species Northern bobwhite (Colinus virginianus) to determine the molecular impacts of exposure to 2,6-dinitrotoluene (2,6-DNT), a field contaminant of military concern. Massively parallel pyrosequencing of a normalized multitissue library of Northern bobwhite cDNAs yielded 71,384 unique transcripts that were annotated with gene ontology (GO), pathway information, and protein domain analysis. Comparative genome analyses with model organisms revealed functional homologies in 8,825 unique Northern bobwhite genes that are orthologous to 48% of Gallus gallus protein-coding genes. Pathway analysis and GO enrichment of genes differentially expressed in livers of birds exposed for 60 days (d) to 10 and 60 mg/kg/d 2,6-DNT revealed several impacts validated by RT-qPCR including: prostaglandin pathway-mediated inflammation, increased expression of a heme synthesis pathway in response to anemia, and a shift in energy metabolism toward protein catabolism via inhibition of control points for glucose and lipid metabolic pathways, PCK1 and PPARGC1, respectively. This research effort provides the first comprehensive annotated gene library for Northern bobwhite. Transcript expression analysis provided insights into the metabolic perturbations underlying several observed toxicological phenotypes in a 2,6-DNT exposure case study. Furthermore, the systemic impact of dinitrotoluenes on liver function appears conserved across species as PPAR signaling is similarly affected in fathead minnow liver tissue after exposure to 2,4-DNT.
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Affiliation(s)
- Arun Rawat
- Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS, USA
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Banerjee SK, Wang DW, Alzamora R, Huang XN, Pastor-Soler NM, Hallows KR, McGaffin KR, Ahmad F. SGLT1, a novel cardiac glucose transporter, mediates increased glucose uptake in PRKAG2 cardiomyopathy. J Mol Cell Cardiol 2010; 49:683-92. [PMID: 20600102 DOI: 10.1016/j.yjmcc.2010.06.003] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 06/06/2010] [Accepted: 06/09/2010] [Indexed: 01/04/2023]
Abstract
Human mutations in the gene PRKAG2 encoding the gamma2 subunit of AMP-activated protein kinase (AMPK) cause a glycogen storage cardiomyopathy. Transgenic mice (TG(T400N)) with the human T400N mutation exhibit inappropriate activation of AMPK and consequent glycogen storage in the heart. Although increased glucose uptake and activation of glycogen synthesis have been documented in PRKAG2 cardiomyopathy, the mechanism of increased glucose uptake has been uncertain. Wildtype (WT), TG(T400N), and TG(alpha2DN) (carrying a dominant negative, kinase dead alpha2 catalytic subunit of AMPK) mice were studied at ages 2-8 weeks. Cardiac mRNA expression of sodium-dependent glucose transporter 1 (SGLT1), but not facilitated-diffusion glucose transporter 1 (GLUT1) or GLUT4, was increased approximately 5- to 7-fold in TG(T400N) mice relative to WT. SGLT1 protein was similarly increased at the cardiac myocyte sarcolemma in TG(T400N) mice. Phlorizin, a specific SGLT1 inhibitor, attenuated cardiac glucose uptake in TG(T400N) mice by approximately 40%, but not in WT mice. Chronic phlorizin treatment reduced cardiac glycogen content by approximately 25% in TG(T400N) mice. AICAR, an AMPK activator, increased cardiac SGLT1 mRNA expression approximately 3-fold in WT mice. Relative to TG(T400N) mice, double transgenic (TG(T400N)/TG(alpha2DN)) mice had decreased ( approximately 50%) cardiac glucose uptake and decreased (approximately 70%) cardiac SGLT1 expression. TG(T400N) hearts had increased binding activity of the transcription factors HNF-1 and Sp1 to the promoter of the gene encoding SGLT1. Our data suggest that upregulation of cardiac SGLT1 is responsible for increased cardiac glucose uptake in the TG(T400N) mouse. Increased AMPK activity leads to upregulation of SGLT1, which in turn mediates increased cardiac glucose uptake.
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Affiliation(s)
- Sanjay K Banerjee
- Cardiovascular Institute, University of Pittsburgh, Pittsburgh, PA 15213-2582, USA
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Wang Z, Jin H, Li C, Hou Y, Mei Q, Fan D. Heat Shock Protein 72 Protects Kidney Proximal Tubule Cells From Injury Induced by Triptolide by Means of Activation of the MEK/ERK Pathway. Int J Toxicol 2009; 28:177-89. [PMID: 19546256 DOI: 10.1177/1091581809337418] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Triptolide, which has been used to treat inflammatory diseases, has also been reported to inhibit proliferation of cancer cells. However, it can cause severe nephrotoxicity, limiting its clinical use. Here, nephrotoxicity of triptolide was observed in vivo and in vitro. Heat shock protein 72 (HSP72) was upregulated during kidney injury in rats. HSP72 partially protected human kidney proximal tubule cell lines HK-2 and HKC from triptolide-induced injury. Phospho-Raf, phospho-MEK and phospho-ERK were elevated in HK-2 cells that overexpressed HSP72 after either heat shock or triptolide treatment, and downregulated when HSP72 was repressed by siRNA. The participation of the MEK/ERK1/2 pathway was confirmed by exposure of the cells to the MEK inhibitor U0126. Collectively, our results suggested that HSP72 plays a protective role by means of the MEK/ERK pathway, against triptolide-induced kidney injury.
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Affiliation(s)
- Zhipeng Wang
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Haifeng Jin
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Chen Li
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Ying Hou
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Qibing Mei
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Daiming Fan
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
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Santos A, Gonçalves P, Araújo JR, Martel F. Intestinal Permeability to Glucose after Experimental Traumatic Brain Injury: Effect of Gadopentetate Dimeglumine Administration. Basic Clin Pharmacol Toxicol 2008; 103:247-54. [DOI: 10.1111/j.1742-7843.2008.00272.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Kekuda R, Saha P, Sundaram U. Role of Sp1 and HNF1 transcription factors in SGLT1 regulation during chronic intestinal inflammation. Am J Physiol Gastrointest Liver Physiol 2008; 294:G1354-61. [PMID: 18339704 DOI: 10.1152/ajpgi.00080.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In a rabbit model of chronic intestinal inflammation, we previously demonstrated that the activity of Na-glucose cotransporter (SGLT1), SLC5A1, is inhibited. This inhibition is secondary to a decrease in the number of cotransporters, indicating that the regulation of SGLT1 during chronic inflammation is at the level of transcription. However, the regulation of SGLT1 expression and the transcription factors involved in the regulation are not yet known. In this report, we describe the cloning and characterization of rabbit SGLT1 promoter and the identification of transcription factors affected in villus cells during chronic intestinal inflammation. The promoter sequence for SGLT1 gene was identified by using the publicly available rabbit genomic sequence. Even though rabbit SGLT1 promoter did not have considerable overall homology with other mammalian SGLT1 promoters, two specificity protein 1 (Sp1) and a hepatocyte nuclear factor 1 (HNF1) binding sites were highly conserved among the species. Rabbit SGLT1 cDNA was encoded by 15 exons. Minimal promoter region determination showed that 196 nucleotides upstream of the transcription start site were sufficient for optimal promoter activity. This region encompassed two transcription factor binding sites, Sp1 and HNF1. For maximal SGLT1 promoter activity, these two transcription factor binding sites were essential, and their effect was synergistic, indicating that two separate regulatory pathways might be involved in their regulation. Using mobility shift assays, we further demonstrated that the binding of both Sp1 and HNF1 transcription factors to SGLT1 promoter regions were affected during chronic intestinal inflammation. Thus this report demonstrates that Sp1 and HNF1 transcription factors act in concert to regulate SGLT1 transcription in the chronically inflamed intestine.
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Affiliation(s)
- Ramesh Kekuda
- Section of Digestive Diseases, Dept. of Medicine, West Virginia Univ. School of Medicine, Morgantown, WV 26506, USA
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Bergeron MJ, Simonin A, Bürzle M, Hediger MA. Inherited epithelial transporter disorders--an overview. J Inherit Metab Dis 2008; 31:178-87. [PMID: 18415698 DOI: 10.1007/s10545-008-0861-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2007] [Revised: 02/12/2008] [Accepted: 02/13/2008] [Indexed: 01/11/2023]
Abstract
In the late 1990s, the identification of transporters and transporter-associated genes progressed substantially due to the development of new cloning approaches such as expression cloning and, subsequently, to the implementation of the human genome project. Since then, the role of many transporter genes in human diseases has been elucidated. In this overview, we focus on inherited disorders of epithelial transporters. In particular, we review genetic defects of the genes encoding glucose transporters (SLC2 and SLC5 families) and amino acid transporters (SLC1, SLC3, SLC6 and SLC7 families).
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Affiliation(s)
- M J Bergeron
- Institute of Biochemistry and Molecular Medicine, University of Berne, Berne, Switzerland
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Lee YJ, Lee YJ, Han HJ. Regulatory mechanisms of Na(+)/glucose cotransporters in renal proximal tubule cells. Kidney Int 2007:S27-35. [PMID: 17653207 DOI: 10.1038/sj.ki.5002383] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glucose is a key fuel and an important metabolic substrate in mammals. Renal proximal tubular cells (PTCs) not only reabsorb filtered glucose but are also believed to play a role in the glucotoxicity associated with renal pathogenesis, such as in diabetes. The proximal tubule environment is where 90% of the filtered glucose is reabsorbed by the low-affinity/high-capacity Na(+)/glucose cotransporter 2 (SGLT2) and facilitated diffusion glucose transporter 2 (GLUT2). Both active and facilitative glucose transporters have distinct distribution profiles along the proximal tubule related to their particular kinetic characteristics. A number of mechanisms contribute to the changes in the cellular functions, which occur in response to exposure to various endogenous factors. Hyperglycemia was reported to regulate the renal SGLT activities through the reactive oxygen species-nuclear factor-kappaB pathways, which suggests that the transcellular glucose uptake within the PTCs contribute to the development of diabetic-like nephropathy. Angiotensin II (ANG II) plays an important role in its development through epidermal growth factor receptor (EGFR) transactivation. Therefore, a combination of high glucose, ANG II, and EGF are involved in diabetic-like nephropathy by regulating the SGLT activity. In addition, endogenously enhanced SGLTs have a cytoprotective function. The renal proximal tubules play a major role in regulating the plasma glucose levels, and there is increasing interest in the renal glucose transporters on account of their potential implications in the treatment of various conditions including diabetes mellitus.
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Affiliation(s)
- Y J Lee
- Biotherapy Human Resources Center, College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
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Kumar A, Tyagi NK, Arevalo E, Miller KW, Kinne RKH. A proteomic study of sodium/d-glucose cotransporter 1 (SGLT1): Topology of loop 13 and coverage of other functionally important domains. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:968-74. [PMID: 17588833 DOI: 10.1016/j.bbapap.2007.05.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Revised: 05/04/2007] [Accepted: 05/08/2007] [Indexed: 11/16/2022]
Abstract
In order to obtain further information about the structure and function of human sodium/D-glucose cotransporter 1 (hSGLT1), the recombinant protein was subjected, either after reconstitution into liposomes or in its free form, to proteolysis followed by nanoscale microcapillary liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS). The peptides released from SGLT1 proteoliposomes by trypsin bead digestion represented the early N-terminal, loop 7, and loop 9, supporting topology models that place these domains on the extracellular side of the protein. Trypsin bead digestion generated, however, also a number of peptides derived from loop 13 whose topology with regard to the membrane is hitherto a point of debate. Sequence coverage was provided from amino acids 559 to 644, suggesting that loop 13 is almost completely accessible at the extravesicular face of the proteoliposomes. These results support the notion that major parts of loop 13, essential for the interaction with transport inhibitors in vivo, are located extracellularly in intact cells. In-gel trypsin, chymotrypsin, and in particular trypsin/chymotrypsin digestion of recombinant SGLT1 in combination with LC-MS/MS provide extensive sequence coverage of the protein, including domains involved in sugar and inhibitor binding and potential phosphorylation sites. These studies demonstrate that proteomic analysis combined with mass spectrometry is a useful tool to characterize regions of SGLT1 that are important for its function and regulation.
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Affiliation(s)
- Azad Kumar
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, Dortmund 44227, Germany
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40
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Puntheeranurak T, Kasch M, Xia X, Hinterdorfer P, Kinne RKH. Three surface subdomains form the vestibule of the Na+/glucose cotransporter SGLT1. J Biol Chem 2007; 282:25222-30. [PMID: 17616521 DOI: 10.1074/jbc.m704190200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A combination of biophysical and biochemical approaches was employed to probe the topology, arrangement, and function of the large surface subdomains of SGLT1 in living cells. Using atomic force microscopy on the single molecule level, Chinese hamster ovary cells overexpressing SGLT1 were probed with atomic force microscopy tips carrying antibodies against epitopes of different subdomains. Specific single molecule recognition events were observed with antibodies against loop 6-7, loop 8-9, and loop 13-14, demonstrating the extracellular orientation of these subdomains. The addition of D-glucose in Na+-containing medium decreased the binding probability of the loop 8-9 antibody, suggesting a transport-related conformational change in the region between amino acids 339 and 356. Transport studies with mutants C345A, C351A, C355A, or C361S supported a role for these amino acids in determining the affinity of SGLT1 for D-glucose. MTSET, [2-(trimethylammonium)ethyl] methanethiosulfonate and dithiothreitol inhibition patterns on alpha-methyl-glucoside uptake by COS-7 cells expressing C255A, C560A, or C608A suggested the presence of a disulfide bridge between Cys255 and Cys608. This assumption was corroborated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry showing mass differences in peptides derived from transporters biotinylated in the absence and presence of dithiothreitol. These results indicate that loop 6-7 and loop 13-14 are connected by a disulfide bridge. This bridge brings also loop 8-9 into close vicinity with the former subdomains to create a vestibule for sugar binding.
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Affiliation(s)
- Theeraporn Puntheeranurak
- Department of Biology, Faculty of Science, Mahidol University, and Center of Excellence, National Nanotechnology Center at Mahidol University, Bangkok, 10400, Thailand
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Puntheeranurak T, Wildling L, Gruber HJ, Kinne RKH, Hinterdorfer P. Ligands on the string: single-molecule AFM studies on the interaction of antibodies and substrates with the Na+-glucose co-transporter SGLT1 in living cells. J Cell Sci 2006; 119:2960-7. [PMID: 16787940 DOI: 10.1242/jcs.03035] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Atomic force microscopy (AFM) was used to probe topology, conformational changes and initial substratecarrier interactions of Na+-glucose co-transporter (SGLT1) in living cells on a single-molecule level. By scanning SGLT1-transfected Chinese hamster ovary (CHO) cells with AFM tips carrying an epitope-specific antibody directed against the extramembranous C-terminal loop 13, significant recognition events could be detected. Specificity was confirmed by the absence of events in nontransfected CHO cells and by the use of free antigen and free antibody superfusion. Thus, contrary to computer predictions on SGLT1 topology, loop 13 seems to be part of the extracellular surface of the transporter. Binding probability of the antibody decreased upon addition of phlorizin, a specific inhibitor of SGLT1, suggesting a considerable conformational change of loop 13 when the inhibitor occludes the sugar translocation pathway. Using an AFM tip carrying 1-thio-D-glucose, direct evidence could be obtained that in the presence of Na+ a sugarbinding site appears on the transporter surface. The binding site accepts the sugar residue of the glucoside phlorizin, free D-glucose, and D-galactose, but not free Lglucose and probably represents the first of several selectivity filters of the transporter. This work demonstrates the potential of AFM to study the presence and dynamics of plasma membrane transporters in intact cells on the single molecule level.
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Affiliation(s)
- Theeraporn Puntheeranurak
- Institute for Biophysics, Johannes Kepler University of Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
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42
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Raja MM, Kinne RKH. Interaction of C-Terminal Loop 13 of Sodium-Glucose Cotransporter SGLT1 with Lipid Bilayers. Biochemistry 2005; 44:9123-9. [PMID: 15966736 DOI: 10.1021/bi050323d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously shown that C-terminal loop 13 of SGLT1 acts as a major binding domain for the aglucon residues of d-glucose transport inhibitors, phlorizin (Raja, M. M., Tyagi, N. K., and Kinne, R. K. H. (2003) Phlorizin Recognition in a C-terminal Fragment of SGLT1 Studied by Tryptophan Scanning and Affinity Labeling, J. Biol. Chem. 278, 49154-49163) and alkyl glucosides (Raja, M. M., Kipp, H., and Kinne, R. K. H. (2004) C-Terminus Loop 13 of Na(+) Glucose Cotransporter SGLT1 Contains a Binding Site for Alkyl Glucosides, Biochemistry 43, 10944-10951). Topology of this loop with regard to the membrane lipids is hitherto a point of debate. Here we report on in vitro incorporation studies using fluorescence of Trp mutants of loop 13 to determine the position of various parts of the loop with the lipid bilayer. Six single Trp mutants were prepared as described in previous studies (Raja et al., 2003) and subsequently incorporated into DOPC:DOPG (60:40% molar ratio) lipid vesicles. Upon addition of the phospholipids only one mutant, R601W, exhibited no change in the fluorescence intensities, position of maxima, or acrylamide accessibility. Mutants Q581W, E621W, and L630W exhibited the most pronounced blue shifts (3-6 nm) and protection against acrylamide, suggesting a position of these segments within the lipid bilayer. This assumption was confirmed by the result that the fluorescence of only these mutants was quenched by doxyl spin membrane embedded labels in the 5- or 12-positions of the acyl side chain of phospholipids. The other parts of the peptide appear to remain outside of the lipid vesicles. Trp-591 and Trp-611 showed, although to a different extent, increase in fluorescence, blue shift of maxima, and decrease in acrylamide accessibility but no interaction with the spin-labeled phospholipids. This suggests changes in the conformation of the peptide itself. These conformation changes are probably induced by the interaction of an adjacent lysine rich region of the peptide with the negatively charged DOPG, since in the absence of this lipid no incorporation of loop 13 into the bilayer is observed. Trypsin cleavage experiments of loop 13 in proteoliposomes yield a peptide containing amino acid residues 603 to 614, confirming that this part of the loop is accessible at the extravesicular face of the membranes. The studies show that at least in the in vitro system the part of loop 13 essential for the interaction with the transport inhibitors is located extracellularly, making a similar arrangement in the intact SGLT1 probable.
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Affiliation(s)
- M Mobeen Raja
- Department of Epithelial Cell Physiology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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Abstract
The dihydrochalcone phlorizin is a natural product and dietary constituent found in a number of fruit trees. It has been used as a pharmaceutical and tool for physiology research for over 150 years. Phlorizin's principal pharmacological action is to produce renal glycosuria and block intestinal glucose absorption through inhibition of the sodium-glucose symporters located in the proximal renal tubule and mucosa of the small intestine. This review covers the role phlorizin has played in the history of diabetes mellitus and its use as an agent to understand fundamental concepts in renal physiology as well as summarizes the physiology of cellular glucose transport and the pathophysiology of renal glycosuria. It reviews the biology and pathobiology of glucose transporters and discusses the medical botany of phlorizin and the potential effects of plant flavonoids, such as phlorizin, on human metabolism. Lastly, it describes the clinical pharmacology and toxicology of phlorizin, including investigational uses of phlorizin and phlorizin analogs in the treatment of diabetes, obesity, and stress hyperglycemia.
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Affiliation(s)
- Joel R L Ehrenkranz
- Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado, USA.
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Santer R, Kinner M, Lassen CL, Schneppenheim R, Eggert P, Bald M, Brodehl J, Daschner M, Ehrich JHH, Kemper M, Li Volti S, Neuhaus T, Skovby F, Swift PGF, Schaub J, Klaerke D. Molecular analysis of the SGLT2 gene in patients with renal glucosuria. J Am Soc Nephrol 2004; 14:2873-82. [PMID: 14569097 DOI: 10.1097/01.asn.0000092790.89332.d2] [Citation(s) in RCA: 239] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The role of SGLT2 (the gene for a renal sodium-dependent glucose transporter) in renal glucosuria was evaluated. Therefore, its genomic sequence and its intron-exon organization were determined, and 23 families with index cases were analyzed for mutations. In 21 families, 21 different SGLT2 mutations were detected. Most of them were private; only a splice mutation was found in 5 families of different ethnic backgrounds, and a 12-bp deletion was found in two German families. Fourteen individuals (including the original patient with 'renal glucosuria type 0') were homozygous or compound heterozygous for an SGLT2 mutation resulting in glucosuria in the range of 14.6 to 202 g/1.73 m(2)/d (81 - 1120 mmol/1.73 m(2)/d). Some, but not all, of their heterozygous family members had an increased glucose excretion of up to 4.4 g/1.73 m(2)/d (24 mmol/1.73 m(2)/d). Likewise, in index cases with glucosuria below 10 g/1.73 m(2)/d (55 mmol/1.73 m(2)/d) an SGLT2 mutation, if present, was always detected in the heterozygous state. We conclude that SGLT2 plays an important role in renal tubular glucose reabsorption. Inheritance of renal glucosuria shows characteristics of a codominant trait with variable penetrance.
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Affiliation(s)
- René Santer
- Department of Pediatrics, University of Kiel, Kiel, Germany.
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Abstract
PURPOSE OF REVIEW The small intestinal mucosa is highly specialized for terminal digestion of nutrient polysaccharides and disaccharides and absorption of monosaccharides. However, in the case of digestive or absorptive deficiency, symptoms of carbohydrate intolerance result. Significant progress has been made toward defining the molecular genetic mechanisms responsible for several carbohydrate intolerances. RECENT FINDINGS This review summarizes monosaccharide and disaccharide intolerance conditions and recent clinical and basic science reports related to carbohydrate digestion and membrane transport. Genetic polymorphisms closely associated with lactase persistence/nonpersistence have been identified. Lactose intolerance is capable of preventing the achievement of adequate peak bone mass in susceptible young adults and may predispose to osteoporosis. Recent studies support previous reports that fructose malabsorption is associated with unexplained gastrointestinal symptoms. GLUT2 may be recruited from the basolateral to the apical membrane of enterocytes to facilitate small intestinal fructose absorption. SUMMARY Knowledge regarding the clinical aspects of and the physiologic mechanisms responsible for specific carbohydrate intolerances has allowed for improved diagnostic and treatment options and has contributed to continuing investigation of intestinal gene expression.
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Affiliation(s)
- Eric Sibley
- Stanford University School of Medicine, Stanford, California 94304, USA.
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46
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Abstract
Carbohydrates are mostly digested to glucose, fructose and galactose before absorption by the small intestine. Absorption across the brush border and basolateral membranes of enterocytes is mediated by sodium-dependent and -independent membrane proteins. Glucose and galactose transport across the brush border occurs by a Na(+)/glucose (galactose) co-transporter (SGLT1), whereas passive fructose transport is mediated by a uniporter (GLUT5). The passive exit of all three sugars out of the cell across the basolateral membrane occurs through two uniporters (GLUT2 and GLUT5). Mutations in SGLT1 cause a major defect in glucose and galactose absorption (glucose-galactose Malabsorption), but mutations in GLUT2 do not appear to disrupt glucose and galactose absorption. Studies on GLUT1 null mice and Fanconi-Bickel patients suggest that there is another exit pathway for glucose and galactose that may involve exocytosis. There are no known defects of fructose absorption.
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Affiliation(s)
- Ernest M Wright
- Departments of Physiology and Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1751, USA.
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Higashi T, Fisher SJ, Nakada K, Romain DJ, Wahl RL. Is enteral administration of fluorine-18-fluorodeoxyglucose (F-18 FDG) a palatable alternative to IV injection? Pre-clinical evaluation in normal rodents. Nucl Med Biol 2002; 29:363-73. [PMID: 11929708 DOI: 10.1016/s0969-8051(01)00312-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To establish effective methods of enteral 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) administration, the efficiency of FDG absorption in the gastrointestinal tracts following enteral administrations was evaluated using the FDG biodistribution in normal rodents, in combination with various fasting conditions and FDG diluents. The blood FDG curve using hypotonic solution showed a rapid increase, while that in iso- and hypertonic groups showed slow rises. Brain FDG uptake had a close positive correlation with blood AUC (area under curve) and an inverse relationship with the stomach contents.
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Affiliation(s)
- T Higashi
- Division of Nuclear Medicine, Department of Internal Medicine, University of Michigan Medical Center, 1500 E. Medical Center Drive, B1G 505C, Ann Arbor, MI 48109-0028, USA.
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Roll P, Massacrier A, Pereira S, Robaglia-Schlupp A, Cau P, Szepetowski P. New human sodium/glucose cotransporter gene (KST1): identification, characterization, and mutation analysis in ICCA (infantile convulsions and choreoathetosis) and BFIC (benign familial infantile convulsions) families. Gene 2002; 285:141-8. [PMID: 12039040 DOI: 10.1016/s0378-1119(02)00416-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cotransporters represent a major class of proteins that make use of ion gradients to drive active transport of substrate into cells. A new human gene, KST1, encoding a member of the sodium/glucose cotransporter family, was identified onto human chromosome 16p12-p11. This genomic region contains a major gene responsible for a syndrome of infantile convulsions and paroxysmal dyskinesia (ICCA syndrome), inherited as an autosomal dominant trait, as well as for benign familial infantile convulsions (BFIC). The entire coding sequence of the human KST1 gene was determined using a combination of methods including in silico comparison of its rabbit orthologous DNA complementary to RNA (cDNA) to the corresponding human genomic sequences, reverse transcription-polymerase chain reaction on human brain RNA, 5' and 3' rapid amplification of cDNA ends. The gene is divided into 16 exons and the predicted protein of 675 amino acids contains 14 transmembrane domains. It shares significant homology to the sodium-glucose transporter 1 cotransporter proteins. An alternatively spliced transcript resulting from the skipping of exon 6 led to a predicted protein lacking the 4th transmembrane domain. As ion transporters are good candidates for a large variety of human diseases, including paroxysmal disorders, a mutation search was performed in four families with ICCA or BFIC syndromes. No pathogenic mutation was found, although several polymorphic variants with amino acids exchanges were identified. Due to its broad expression in human tissues, the human KST1 gene could be involved in several other diseases mapped to human chromosome 16p12-p11.
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MESH Headings
- Amino Acid Sequence
- Athetosis/complications
- Athetosis/genetics
- Base Sequence
- Blotting, Northern
- Chorea/complications
- Chorea/genetics
- Cloning, Molecular
- DNA Mutational Analysis
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Epilepsy, Benign Neonatal/genetics
- Exons
- Family Health
- Gene Expression
- Genes/genetics
- Humans
- Infant
- Infant, Newborn
- Introns
- Molecular Sequence Data
- Monosaccharide Transport Proteins/genetics
- Mutation
- Phylogeny
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Seizures/complications
- Seizures/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Sodium-Glucose Transport Proteins
- Symporters
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Affiliation(s)
- Patrice Roll
- INSERM U491, Faculté de Médecine de la Timone, 27 Bd J Moulin, 13385, Marseille Cedex 5, France
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Loflin P, Lever JE. HuR binds a cyclic nucleotide-dependent, stabilizing domain in the 3' untranslated region of Na(+)/glucose cotransporter (SGLT1) mRNA. FEBS Lett 2001; 509:267-71. [PMID: 11741601 DOI: 10.1016/s0014-5793(01)03176-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Differentiation-dependent expression of the Na(+)/glucose cotransporter (SGLT1) is accompanied by a large, cAMP-dependent increase in stability of its mRNA. Stabilization is mediated by protein binding to a critical uridine-rich element (URE) in its 3' untranslated region. In the present study, we demonstrate that HuR, an RNA binding protein of the embryonic lethal abnormal vision family, binds the SGLT1 URE. HuR binding was increased after elevation of intracellular cAMP levels and was dependent on protein phosphorylation. This interaction was prevented by a substitution mutation previously shown to block cAMP-dependent reporter message stabilization. These results implicate HuR as a key mediator of cAMP-dependent SGLT1 mRNA stabilization.
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Affiliation(s)
- P Loflin
- Department of Biochemistry and Molecular Biology, University of Texas-Houston Medical School, P.O. Box 20708, Houston, TX 77225, USA
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Suzuki T, Fujikura K, Koyama H, Matsuzaki T, Takahashi Y, Takata K. The apical localization of SGLT1 glucose transporter is determined by the short amino acid sequence in its N-terminal domain. Eur J Cell Biol 2001; 80:765-74. [PMID: 11831390 DOI: 10.1078/0171-9335-00204] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
SGLT1, an isoform of Na+-dependent glucose cotransporters, is localized at the apical plasma membrane in the epithelial cells of the small intestine and the kidney, where it plays a pivotal role in the absorption and reabsorption of sugars, respectively. To search the domain responsible for the apical localization of SGLT1, we constructed an N-terminal deletion clone series of rat SGLT1 and analyzed the localization of the respective products in Madin-Darby canine kidney (MDCK) cells. The products of N-terminal deletion clones up to the 19th amino acid were localized at the apical plasma membrane, whereas the products of N-terminal 20- and 23-amino-acid deletion clones were localized along the entire plasma membrane. Since single-amino-acid mutations of either D28N or D28G in the N-terminal domain give rise to glucose/galactose malabsorption disease, we examined the localization of these mutants. The products of D28N and D28G clones were localized in the cytoplasm, showing that the aspartic acid-28 may be essential for the delivery of SGLT1 to the plasma membrane. These results suggest that a short amino acid sequence of the N-terminal domain of SGLT1 plays important roles in plasma membrane targeting and specific apical localization of the protein.
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Affiliation(s)
- T Suzuki
- Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
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