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Koepsell H. Glucose transporters in the small intestine in health and disease. Pflugers Arch 2020; 472:1207-1248. [PMID: 32829466 PMCID: PMC7462918 DOI: 10.1007/s00424-020-02439-5] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 07/11/2020] [Accepted: 07/17/2020] [Indexed: 12/23/2022]
Abstract
Absorption of monosaccharides is mainly mediated by Na+-D-glucose cotransporter SGLT1 and the facititative transporters GLUT2 and GLUT5. SGLT1 and GLUT2 are relevant for absorption of D-glucose and D-galactose while GLUT5 is relevant for D-fructose absorption. SGLT1 and GLUT5 are constantly localized in the brush border membrane (BBM) of enterocytes, whereas GLUT2 is localized in the basolateral membrane (BLM) or the BBM plus BLM at low and high luminal D-glucose concentrations, respectively. At high luminal D-glucose, the abundance SGLT1 in the BBM is increased. Hence, D-glucose absorption at low luminal glucose is mediated via SGLT1 in the BBM and GLUT2 in the BLM whereas high-capacity D-glucose absorption at high luminal glucose is mediated by SGLT1 plus GLUT2 in the BBM and GLUT2 in the BLM. The review describes functions and regulations of SGLT1, GLUT2, and GLUT5 in the small intestine including diurnal variations and carbohydrate-dependent regulations. Also, the roles of SGLT1 and GLUT2 for secretion of enterohormones are discussed. Furthermore, diseases are described that are caused by malfunctions of small intestinal monosaccharide transporters, such as glucose-galactose malabsorption, Fanconi syndrome, and fructose intolerance. Moreover, it is reported how diabetes, small intestinal inflammation, parental nutrition, bariatric surgery, and metformin treatment affect expression of monosaccharide transporters in the small intestine. Finally, food components that decrease D-glucose absorption and drugs in development that inhibit or downregulate SGLT1 in the small intestine are compiled. Models for regulations and combined functions of glucose transporters, and for interplay between D-fructose transport and metabolism, are discussed.
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Affiliation(s)
- Hermann Koepsell
- Institute for Anatomy and Cell Biology, University of Würzburg, Koellikerstr 6, 97070, Würzburg, Germany.
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2
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Nagarajan SR, Paul-Heng M, Krycer JR, Fazakerley DJ, Sharland AF, Hoy AJ. Lipid and glucose metabolism in hepatocyte cell lines and primary mouse hepatocytes: a comprehensive resource for in vitro studies of hepatic metabolism. Am J Physiol Endocrinol Metab 2019; 316:E578-E589. [PMID: 30694691 DOI: 10.1152/ajpendo.00365.2018] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The liver is a critical tissue for maintaining glucose, fatty acid, and cholesterol homeostasis. Primary hepatocytes represent the gold standard for studying the mechanisms controlling hepatic glucose, lipid, and cholesterol metabolism in vitro. However, access to primary hepatocytes can be limiting, and therefore, other immortalized hepatocyte models are commonly used. Here, we describe substrate metabolism of cultured AML12, IHH, and PH5CH8 cells, hepatocellular carcinoma-derived HepG2s, and primary mouse hepatocytes (PMH) to identify which of these cell lines most accurately phenocopy PMH basal and insulin-stimulated metabolism. Insulin-stimulated glucose metabolism in PH5CH8 cells, and to a lesser extent AML12 cells, responded most similarly to PMH. Notably, glucose incorporation in HepG2 cells were 14-fold greater than PMH. The differences in glucose metabolic activity were not explained by differential protein expression of key regulators of these pathways, for example glycogen synthase and glycogen content. In contrast, fatty acid metabolism in IHH cells was the closest to PMHs, yet insulin-responsive fatty acid metabolism in AML12 and HepG2 cells was most similar to PMH. Finally, incorporation of acetate into intracellular-free cholesterol was comparable for all cells to PMH; however, insulin-stimulated glucose conversion into lipids and the incorporation of acetate into intracellular cholesterol esters were strikingly different between PMHs and all tested cell lines. In general, AML12 cells most closely phenocopied PMH in vitro energy metabolism. However, the cell line most representative of PMHs differed depending on the mode of metabolism being investigated, and so careful consideration is needed in model selection.
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Affiliation(s)
- Shilpa R Nagarajan
- Discipline of Physiology, School of Medical Sciences & Bosch Institute, Charles Perkins Centre, Faculty of Medicine and Health, The University of Sydney , New South Wales , Australia
| | - Moumita Paul-Heng
- Discipline of Surgery, Central Clinical School & Bosch Institute, Charles Perkins Centre, Faculty of Medicine and Health, University of Sydney , New South Wales , Australia
| | - James R Krycer
- School of Life and Environmental Sciences, Charles Perkins Centre, Faculty of Science, The University of Sydney , New South Wales , Australia
| | - Daniel J Fazakerley
- School of Life and Environmental Sciences, Charles Perkins Centre, Faculty of Science, The University of Sydney , New South Wales , Australia
| | - Alexandra F Sharland
- Discipline of Surgery, Central Clinical School & Bosch Institute, Charles Perkins Centre, Faculty of Medicine and Health, University of Sydney , New South Wales , Australia
| | - Andrew J Hoy
- Discipline of Physiology, School of Medical Sciences & Bosch Institute, Charles Perkins Centre, Faculty of Medicine and Health, The University of Sydney , New South Wales , Australia
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3
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Developmental exposure to DEHP alters hepatic glucose uptake and transcriptional regulation of GLUT2 in rat male offspring. Toxicology 2018; 413:56-64. [PMID: 30597186 DOI: 10.1016/j.tox.2018.12.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/14/2018] [Accepted: 12/27/2018] [Indexed: 12/16/2022]
Abstract
Type-2-diabetes (T2D) is a long term metabolic disorder characterized by high blood glucose and insulin resistance. It has become an alarming issue globally due to tremendous increase in number of new subjects every year. Apart from the classical factors, there are few non-classical factors such as environmental pollutants, endocrine disrupting chemicals (EDCs) which also play a major role in pathogenesis of T2D. Di-(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer which is an endocrine disrupting chemical. It is used in the plastic industry to give flexibility and durability. Its widespread use resulted in constant presence in the environment and human are under high risk of exposure to this compound. There are literature available stating that DEHP has an impact on glucose homeostasis. Glucose transporter 2 (GLUT2) is a principal transporter of glucose in liver and it is a bi-directional transporter. We investigated whether DEHP exposure during gestation and lactation alters transcriptional regulation of GLUT2 and epigenetics changes in the rat F1 male offspring at adulthood. Pregnant rats were divided into three groups and administered with DEHP (10 and 100 mg /kg /day) or olive oil from gestational day (GD) 9- to postnatal day (PND) 21 through oral gavage. DEHP treated rats showed decreased glucose uptake and oxidation, decreased mRNA levels of insulin receptor (IR), GLUT2 and reduced GLUT2 protein in cytosol but unaltered level in plasma membrane. There are three main transcription factors (SREBP1c, HNF3β and HNF1α) involved in the regulation of GLUT2 gene and all these proteins were reduced in DEHP exposed groups. A weak interaction of the transcription factors (SREBP1c & HNF1α) with GLUT2 gene promoter was observed in DEHP-treated groups. Hyper- methylation of IR and GLUT2 gene promoter was observed in both the DEHP-exposed groups compared to control. The present study reveals that DEHP exposure alters transcriptional regulation of GLUT2 and imposes epigenetic alteration in IR and GLUT2 gene promoters which plays a significant role in the development of metabolic abnormality in F1 male offspring at adulthood.
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Ahn YH. A Journey to Understand Glucose Homeostasis: Starting from Rat Glucose Transporter Type 2 Promoter Cloning to Hyperglycemia. Diabetes Metab J 2018; 42:465-471. [PMID: 30398040 PMCID: PMC6300444 DOI: 10.4093/dmj.2018.0116] [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: 07/30/2018] [Accepted: 08/08/2018] [Indexed: 12/24/2022] Open
Abstract
My professional journey to understand the glucose homeostasis began in the 1990s, starting from cloning of the promoter region of glucose transporter type 2 (GLUT2) gene that led us to establish research foundation of my group. When I was a graduate student, I simply thought that hyperglycemia, a typical clinical manifestation of type 2 diabetes mellitus (T2DM), could be caused by a defect in the glucose transport system in the body. Thus, if a molecular mechanism controlling glucose transport system could be understood, treatment of T2DM could be possible. In the early 70s, hyperglycemia was thought to develop primarily due to a defect in the muscle and adipose tissue; thus, muscle/adipose tissue type glucose transporter (GLUT4) became a major research interest in the diabetology. However, glucose utilization occurs not only in muscle/adipose tissue but also in liver and brain. Thus, I was interested in the hepatic glucose transport system, where glucose storage and release are the most actively occurring.
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Affiliation(s)
- Yong Ho Ahn
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Yonsei University College of Medicine, Seoul, Korea.
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5
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Lin ST, Tu SH, Yang PS, Hsu SP, Lee WH, Ho CT, Wu CH, Lai YH, Chen MY, Chen LC. Apple Polyphenol Phloretin Inhibits Colorectal Cancer Cell Growth via Inhibition of the Type 2 Glucose Transporter and Activation of p53-Mediated Signaling. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:6826-6837. [PMID: 27538679 DOI: 10.1021/acs.jafc.6b02861] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Glucose transporters (GLUTs) are required for glucose uptake in malignant cells, and they can be used as molecular targets for cancer therapy. An RT-PCR analysis was performed to investigate the mRNA levels of 14 subtypes of GLUTs in human colorectal cancer (COLO 205 and HT-29) and normal (FHC) cells. RT-PCR (n = 27) was used to assess the differences in paired tissue samples (tumor vs normal) isolated from colorectal cancer patients. GLUT2 was detected in all tested cells. The average GLUT2 mRNA level in 12 of 27 (44.4%) cases was 2.4-fold higher in tumor compared to normal tissues (*, p = 0.027). Higher GLUT2 mRNA expression was preferentially detected in advanced-stage tumors (stage 0 vs 3 = 16.38-fold, 95% CI = 9.22-26.54-fold; *, p = 0.029). The apple polyphenol phloretin (Ph) and siRNA methods were used to inhibit GLUT2 protein expression. Ph (0-100 μM, for 24 h) induced COLO 205 cell growth cycle arrest in a p53-dependent manner, which was confirmed by pretreatment of the cells with a p53-specific dominant negative expression vector. Hepatocyte nuclear factor 6 (HNF6), which was previously reported to be a transcription factor that activates GLUT2 and p53, was also induced by Ph (0-100 μM, for 24 h). The antitumor effect of Ph (25 mg/kg or DMSO twice a week for 6 weeks) was demonstrated in vivo using BALB/c nude mice bearing COLO 205 tumor xenografts. In conclusion, targeting GLUT2 could potentially suppress colorectal tumor cell invasiveness.
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Affiliation(s)
- Sheng-Tsai Lin
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Shuang Ho Hospital , New Taipei City, Taiwan
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
| | - Shih-Hsin Tu
- TMU Taipei Cancer Center, Taipei Medical University , Taipei, Taiwan
- Department of Surgery, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
- Breast Medical Center, Taipei Medical University Hospital , Taipei, Taiwan
| | - Po-Sheng Yang
- Department of Surgery, Mackay Memorial Hospital , Taipei, Taiwan
- Department of Medicine, Mackay Medical College , New Taipei City, Taiwan
- Nursing and Management, Mackay Junior College of Medicine , Taipei, Taiwan
| | - Sung-Po Hsu
- Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
- Graduate Institue of Medical Sciences, College of Medicine, Taipei Medical University , Taipei, Taiwan
| | - Wei-Hwa Lee
- Department of Pathology, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
- Department of Pathology, Taipei Medical University-Shuang Ho Hospital , Jhonghe City, Taiwan
| | - Chi-Tang Ho
- Department of Food Science, Rutgers University , New Brunswick, New Jersey 08901, United States
| | - Chih-Hsiung Wu
- Department of Surgery, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
- Department of Surgery, En Chu Kong Hospital , New Taipei City 237, Taiwan
| | - Yu-Hsin Lai
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Shuang Ho Hospital , New Taipei City, Taiwan
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
| | - Ming-Yao Chen
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Shuang Ho Hospital , New Taipei City, Taiwan
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
| | - Li-Ching Chen
- TMU Taipei Cancer Center, Taipei Medical University , Taipei, Taiwan
- Breast Medical Center, Taipei Medical University Hospital , Taipei, Taiwan
- Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University , Taipei, Taiwan
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Yu JH, Song SJ, Kim A, Choi Y, Seok JW, Kim HJ, Lee YJ, Lee KS, Kim JW. Suppression of PPARγ-mediated monoacylglycerol O-acyltransferase 1 expression ameliorates alcoholic hepatic steatosis. Sci Rep 2016; 6:29352. [PMID: 27404390 PMCID: PMC4941543 DOI: 10.1038/srep29352] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 06/16/2016] [Indexed: 12/20/2022] Open
Abstract
Alcohol consumption is one of the major causes of hepatic steatosis, fibrosis, cirrhosis, and superimposed hepatocellular carcinoma. Ethanol metabolism alters the NAD(+)/NADH ratio, thereby suppressing the activity of sirtuin family proteins, which may affect lipid metabolism in liver cells. However, it is not clear how long-term ingestion of ethanol eventually causes lipid accumulation in liver. Here, we demonstrate that chronic ethanol ingestion activates peroxisome proliferator-activated receptor γ (PPARγ) and its target gene, monoacylglycerol O-acyltransferase 1 (MGAT1). During ethanol metabolism, a low NAD(+)/NADH ratio repressed NAD-dependent deacetylase sirtuin 1 (SIRT1) activity, concomitantly resulting in increased acetylated PPARγ with high transcriptional activity. Accordingly, SIRT1 transgenic mice exhibited a low level of acetylated PPARγ and were protected from hepatic steatosis driven by alcohol or PPARγ2 overexpression, suggesting that ethanol metabolism causes lipid accumulation through activation of PPARγ through acetylation. Among the genes induced by PPARγ upon alcohol consumption, MGAT1 has been shown to be involved in triglyceride synthesis. Thus, we tested the effect of MGAT1 knockdown in mice following ethanol consumption, and found a significant reduction in alcohol-induced hepatic lipid accumulation. These results suggest that MGAT1 may afford a promising approach to the treatment of fatty liver disease.
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Affiliation(s)
- Jung Hwan Yu
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Korea
| | - Su Jin Song
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Korea
| | - Ara Kim
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Korea
| | - Yoonjeong Choi
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Korea
| | - Jo Woon Seok
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Korea
| | - Hyo Jung Kim
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea
| | - Yoo Jeong Lee
- Division of Metabolic Disease, Center for Biomedical Sciences, National Institutes of Health, Cheongwon-gun, Chungbuk 363-951, Korea
| | - Kwan Sik Lee
- Department of Internal Medicine, Yonsei University College of Medicine, Seoul 120-752, Korea
| | - Jae-Woo Kim
- Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-752, Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Korea.,Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul 120-752, Korea
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7
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Ferulic acid regulates hepatic GLUT2 gene expression in high fat and fructose-induced type-2 diabetic adult male rat. Eur J Pharmacol 2015; 761:391-7. [DOI: 10.1016/j.ejphar.2015.04.043] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 04/20/2015] [Indexed: 11/22/2022]
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8
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Chang WC, Wu SC, Xu KD, Liao BC, Wu JF, Cheng AS. Scopoletin protects against methylglyoxal-induced hyperglycemia and insulin resistance mediated by suppression of advanced glycation endproducts (AGEs) generation and anti-glycation. Molecules 2015; 20:2786-801. [PMID: 25671364 PMCID: PMC6272799 DOI: 10.3390/molecules20022786] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 02/03/2015] [Indexed: 12/13/2022] Open
Abstract
Recently, several types of foods and drinks, including coffee, cream, and cake, have been found to result in high methylglyoxal (MG) levels in the plasma, thus causing both nutritional and health concerns. MG can be metabolized by phase-II enzymes in liver through the positive regulation of nuclear factor-erythroid 2-related factor 2 (Nrf2). In this study, we investigated the ability of scopoletin (SP) to protect against MG-induced hyperglycemia and insulin resistance. Recently, SP was shown to be a peroxisome proliferator-activated receptor-γ activator to elevate insulin sensitivity. We investigated the effects of oral administration of SP on the metabolic, biochemical, and molecular abnormalities characteristic of type 2 diabetes in MG-treated Wistar rats to understand the potential mechanism of scopoletin for diabetes protection. Our results suggested that SP activated Nrf2 by Ser40 phosphorylation, resulting in the metabolism of MG into d-lactic acid and the inhibition of AGEs generation, which reduced the accumulation of AGEs in the livers of MG-induced rats. In this manner, SP improved the results of the oral glucose tolerance test and dyslipidemia. Moreover, SP also increased the plasma translocation of glucose transporter-2 and promoted Akt phosphorylation caused by insulin treatment in MG-treated FL83B hepatocytes. In contrast, SP effectively suppressed protein tyrosine phosphatase 1B (PTP1B) expression, thereby alleviating insulin resistance. These findings suggest that SP acts as an anti-glycation and anti-diabetic agent, and thus has therapeutic potential for the prevention of diabetes.
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Affiliation(s)
- Wen-Chang Chang
- Department of Medicinal Plant Development, Yupintang Traditional Chinese Medicine Foundation, 4F., No.2, Ln. 138, Yongyuan Rd., Yonghe Dist., New Taipei City 234, Taiwan.
| | - Shinn-Chih Wu
- Department of Animal Science and Technology, National Taiwan University, 59 Roosevelt Road Section 4, Taipei 10617, Taiwan.
| | - Kun-Di Xu
- Department of Medicinal Plant Development, Yupintang Traditional Chinese Medicine Foundation, 4F., No.2, Ln. 138, Yongyuan Rd., Yonghe Dist., New Taipei City 234, Taiwan.
| | - Bo-Chieh Liao
- Department of Medicinal Plant Development, Yupintang Traditional Chinese Medicine Foundation, 4F., No.2, Ln. 138, Yongyuan Rd., Yonghe Dist., New Taipei City 234, Taiwan.
| | - Jia-Feng Wu
- Department of Medicinal Plant Development, Yupintang Traditional Chinese Medicine Foundation, 4F., No.2, Ln. 138, Yongyuan Rd., Yonghe Dist., New Taipei City 234, Taiwan.
| | - An-Sheng Cheng
- Department of Medicinal Plant Development, Yupintang Traditional Chinese Medicine Foundation, 4F., No.2, Ln. 138, Yongyuan Rd., Yonghe Dist., New Taipei City 234, Taiwan.
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9
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Holen E, Espe M, Andersen SM, Taylor R, Aksnes A, Mengesha Z, Araujo P. A co culture approach show that polyamine turnover is affected during inflammation in Atlantic salmon immune and liver cells and that arginine and LPS exerts opposite effects on p38MAPK signaling. FISH & SHELLFISH IMMUNOLOGY 2014; 37:286-298. [PMID: 24565893 DOI: 10.1016/j.fsi.2014.02.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 02/03/2014] [Accepted: 02/09/2014] [Indexed: 06/03/2023]
Abstract
This study assess which pathways and molecular processes are affected by exposing salmon head kidney cells or liver cells to arginine supplementation above the established requirements for growth support. In addition to the conventional mono cultures of liver and head kidney cells, co cultures of the two cell types were included in the experimental set up. Responses due to elevated levels of arginine were measured during inflammatory (lipopolysaccharide/LPS) and non -inflammatory conditions. LPS up regulated the genes involved in polyamine turnover; ODC (ornithine decarboxylase), SSAT (spermidine/spermine-N1-acetyltransferase) and SAMdc (S-adenosyl methionine decarboxylase) in head kidney cells when co cultured with liver cells. Regardless of treatment, liver cells in co culture up regulated ODC and down regulated SSAT when compared to liver mono cultures. This suggests that polyamines have anti-inflammatory properties and that both salmon liver cells and immune cells seem to be involved in this process. The transcription of C/EBP β/CCAAT, increased during inflammation in all cultures except for liver mono cultures. The observed up regulation of this gene may be linked to glucose transport due to the highly variable glucose concentrations found in the cell media. PPARα transcription was also increased in liver cells when receiving signals from head kidney cells. Gene transcription of Interleukin 1β (IL-1β), Interleukin-8 (IL-8), cyclooxygenase 2 (COX2) and CD83 were elevated during LPS treatment in all the head kidney cell cultures while arginine supplementation reduced IL-1β and IL-8 transcription in liver cells co cultured with head kidney cells. This is probably connected to p38MAPK signaling as arginine seem to affect p38MAPK signaling contrary to the LPS induced p38MAPK signaling, suggesting anti-inflammatory effects of arginine/arginine metabolites. This paper shows that co culturing these two cell types reveals the connection between metabolism and inflammation, suggesting different pathways and candidate biomarkers to be further explored.
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Affiliation(s)
- Elisabeth Holen
- National Institute of Nutrition and Seafood Research (NIFES), P.B. 2029 Nordnes, 5817 Bergen, Norway.
| | - Marit Espe
- National Institute of Nutrition and Seafood Research (NIFES), P.B. 2029 Nordnes, 5817 Bergen, Norway
| | - Synne M Andersen
- National Institute of Nutrition and Seafood Research (NIFES), P.B. 2029 Nordnes, 5817 Bergen, Norway
| | | | | | - Zebasil Mengesha
- National Institute of Nutrition and Seafood Research (NIFES), P.B. 2029 Nordnes, 5817 Bergen, Norway; Department of Industrial Chemistry, Bahir Dar University, P.B. 79, Bahir Dar, Ethiopia
| | - Pedro Araujo
- National Institute of Nutrition and Seafood Research (NIFES), P.B. 2029 Nordnes, 5817 Bergen, Norway
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10
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David-Silva A, Freitas HS, Okamoto MM, Sabino-Silva R, Schaan BD, Machado UF. Hepatocyte nuclear factors 1α/4α and forkhead box A2 regulate the solute carrier 2A2 (Slc2a2) gene expression in the liver and kidney of diabetic rats. Life Sci 2013; 93:805-13. [DOI: 10.1016/j.lfs.2013.10.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 09/24/2013] [Accepted: 10/10/2013] [Indexed: 10/26/2022]
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11
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Hsu WH, Lee BH, Chang YY, Hsu YW, Pan TM. A novel natural Nrf2 activator with PPARγ-agonist (monascin) attenuates the toxicity of methylglyoxal and hyperglycemia. Toxicol Appl Pharmacol 2013; 272:842-51. [DOI: 10.1016/j.taap.2013.07.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 07/11/2013] [Accepted: 07/12/2013] [Indexed: 12/22/2022]
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12
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Storey SM, McIntosh AL, Huang H, Martin GG, Landrock KK, Landrock D, Payne HR, Kier AB, Schroeder F. Loss of intracellular lipid binding proteins differentially impacts saturated fatty acid uptake and nuclear targeting in mouse hepatocytes. Am J Physiol Gastrointest Liver Physiol 2012; 303:G837-50. [PMID: 22859366 PMCID: PMC3469595 DOI: 10.1152/ajpgi.00489.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The liver expresses high levels of two proteins with high affinity for long-chain fatty acids (LCFAs): liver fatty acid binding protein (L-FABP) and sterol carrier protein-2 (SCP-2). Real-time confocal microscopy of cultured primary hepatocytes from gene-ablated (L-FABP, SCP-2/SCP-x, and L-FABP/SCP-2/SCP-x null) mice showed that the loss of L-FABP reduced cellular uptake of 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazo)-aminostearic acid (a fluorescent-saturated LCFA analog) by ∼50%. Importantly, nuclear targeting of the LCFA was enhanced when L-FABP was upregulated (SCP-2/SCP-x null) but was significantly reduced when L-FABP was ablated (L-FABP null), thus impacting LCFA nuclear targeting. These effects were not associated with a net decrease in expression of key membrane proteins involved in LCFA or glucose transport. Since hepatic LCFA uptake and metabolism are closely linked to glucose uptake, the effect of glucose on L-FABP-mediated LCFA uptake and nuclear targeting was examined. Increasing concentrations of glucose decreased cellular LCFA uptake and even more extensively decreased LCFA nuclear targeting. Loss of L-FABP exacerbated the decrease in LCFA nuclear targeting, while loss of SCP-2 reduced the glucose effect, resulting in enhanced LCFA nuclear targeting compared with control. Simply, ablation of L-FABP decreases LCFA uptake and even more extensively decreases its nuclear targeting.
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Affiliation(s)
- Stephen M. Storey
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Avery L. McIntosh
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Huan Huang
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Gregory G. Martin
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Kerstin K. Landrock
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Danilo Landrock
- 2Department of Pathobiology, Texas A & M University, College Station, Texas
| | - H. Ross Payne
- 2Department of Pathobiology, Texas A & M University, College Station, Texas
| | - Ann B. Kier
- 2Department of Pathobiology, Texas A & M University, College Station, Texas
| | - Friedhelm Schroeder
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
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Higuchi N, Kato M, Miyazaki M, Tanaka M, Kohjima M, Ito T, Nakamuta M, Enjoji M, Kotoh K, Takayanagi R. Potential role of branched-chain amino acids in glucose metabolism through the accelerated induction of the glucose-sensing apparatus in the liver. J Cell Biochem 2011; 112:30-8. [PMID: 20506195 DOI: 10.1002/jcb.22688] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Branched-chain amino acids (BCAAs) have a potential to improve glucose metabolism in cirrhotic patients; however, the contribution of liver in this process has not been clarified. To estimate the effect of BCAA on glucose metabolism in liver, we evaluated the mRNA expression levels of glucose-sensing apparatus genes in HepG2 cells and in rat liver after oral administration of BCAA. HepG2 cells were cultured in low glucose (100 mg/dl) or high glucose (400 mg/dl) in the absence or presence of BCAA. The mRNA expression levels and protein levels of GLUT2 and liver-type glucokinase (L-GK) were estimated using RT-PCR and immunoblotting. The expression levels of transcriptional factors, including SREBP-1c, ChREBP, PPAR-γm and LXRα, were estimated. The mRNA expression levels of transcriptional factors, glycogen synthase, and genes involved in gluconeogenesis were evaluated in rat liver at 3 h after the administration of BCAA. BCAA accelerated the expression of GLUT2 and L-GK in HepG2 cells in high glucose. Expression levels of ChREBP, SREBP-1c, and LXRα were also increased in this condition. BCAA administration enhanced the mRNA expression levels of L-GK, SREBP-1c, and LXRα and suppressed the expression levels of G-6-Pase in rat liver, without affecting the expression levels of glycogen synthase or serum glucose concentrations. BCAA administration enhanced the bioactivity of the glucose-sensing apparatus, probably via the activation of a transcriptional mechanism, suggesting that these amino acids may improve glucose metabolism through the accelerated utility of glucose and glucose-6-phosphate in the liver.
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Affiliation(s)
- Nobito Higuchi
- Department of Medicine and Bioregulatory Science, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan
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14
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Zhao FQ, Keating AF. Functional properties and genomics of glucose transporters. Curr Genomics 2011; 8:113-28. [PMID: 18660845 DOI: 10.2174/138920207780368187] [Citation(s) in RCA: 369] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 12/08/2006] [Accepted: 12/17/2007] [Indexed: 12/17/2022] Open
Abstract
Glucose is the major energy source for mammalian cells as well as an important substrate for protein and lipid synthesis. Mammalian cells take up glucose from extracellular fluid into the cell through two families of structurallyrelated glucose transporters. The facilitative glucose transporter family (solute carriers SLC2A, protein symbol GLUT) mediates a bidirectional and energy-independent process of glucose transport in most tissues and cells, while the NaM(+)/glucose cotransporter family (solute carriers SLC5A, protein symbol SGLT) mediates an active, Na(+)-linked transport process against an electrochemical gradient. The GLUT family consists of thirteen members (GLUT1-12 and HMIT). Phylogenetically, the members of the GLUT family are split into three classes based on protein similarities. Up to now, at least six members of the SGLT family have been cloned (SGLT1-6). In this review, we report both the genomic structure and function of each transporter as well as intra-species comparative genomic analysis of some of these transporters. The affinity for glucose and transport kinetics of each transporter differs and ranges from 0.2 to 17mM. The ability of each protein to transport alternative substrates also differs and includes substrates such as fructose and galactose. In addition, the tissue distribution pattern varies between species. There are different regulation mechanisms of these transporters. Characterization of transcriptional control of some of the gene promoters has been investigated and alternative promoter usage to generate different protein isoforms has been demonstrated. We also introduce some pathophysiological roles of these transporters in human.
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Affiliation(s)
- Feng-Qi Zhao
- Lactation and Mammary Gland Biology Group, Department of Animal Science, University of Vermont, Burlington, VT, USA
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15
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Park JM, Kim TH, Bae JS, Kim MY, Kim KS, Ahn YH. Role of resveratrol in FOXO1-mediated gluconeogenic gene expression in the liver. Biochem Biophys Res Commun 2010; 403:329-34. [PMID: 21078299 DOI: 10.1016/j.bbrc.2010.11.028] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 11/07/2010] [Indexed: 01/13/2023]
Abstract
During a state of fasting, the blood glucose level is maintained by hepatic gluconeogenesis. SIRT1 is an important metabolic regulator during nutrient deprivation and the liver-specific knockdown of SIRT1 resulted in decreased glucose production. We hypothesize that SIRT1 is responsible for the upregulation of insulin-suppressed gluconeogenic genes through the deacetylation of FOXO1. Treatment of primary cultured hepatocytes with resveratrol increased insulin-repressed PEPCK and G6Pase mRNA levels, which depend on SIRT1 activity. We found that the resveratrol treatment resulted in a decrease in the phosphorylation of Akt and FOXO1, which are independent of SIRT1 action. Fluorescence microscopy revealed that resveratrol caused the nuclear localization of FOXO1. In the nucleus, FOXO1 is deacetylated by SIRT1, which might make it more accessible to the IRE of the PEPCK and G6Pase promoter, causing an increase in their gene expression. Our results indicate that resveratrol upregulates the expression of gluconeogenic genes by attenuating insulin signaling and by deacetylating FOXO1, which are SIRT1-independent in the cytosol and SIRT1-dependent in the nucleus, respectively.
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Affiliation(s)
- Joo-Man Park
- Department of Biochemistry and Molecular Biology, Center for Chronic Metabolic Disease Research, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
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16
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Transcriptional regulation of glucose sensors in pancreatic β-cells and liver: an update. SENSORS 2010; 10:5031-53. [PMID: 22399922 PMCID: PMC3292162 DOI: 10.3390/s100505031] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 05/07/2010] [Accepted: 05/13/2010] [Indexed: 01/17/2023]
Abstract
Pancreatic β-cells and the liver play a key role in glucose homeostasis. After a meal or in a state of hyperglycemia, glucose is transported into the β-cells or hepatocytes where it is metabolized. In the β-cells, glucose is metabolized to increase the ATP:ADP ratio, resulting in the secretion of insulin stored in the vesicle. In the hepatocytes, glucose is metabolized to CO(2), fatty acids or stored as glycogen. In these cells, solute carrier family 2 (SLC2A2) and glucokinase play a key role in sensing and uptaking glucose. Dysfunction of these proteins results in the hyperglycemia which is one of the characteristics of type 2 diabetes mellitus (T2DM). Thus, studies on the molecular mechanisms of their transcriptional regulations are important in understanding pathogenesis and combating T2DM. In this paper, we will review a recent update on the progress of gene regulation of glucose sensors in the liver and β-cells.
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17
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Gragnoli C, Pierpaoli L, Piumelli N, Chiaramonte F. Linkage studies for T2D in Chop and C/EBPbeta chromosomal regions in Italians. J Cell Physiol 2008; 213:552-5. [PMID: 17620318 DOI: 10.1002/jcp.21132] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The genes causing type 2 diabetes (T2D), a complex heterogeneous disorder, differ and/or overlap in various populations. Among others there are two loci in linkage to T2D, the chromosomes 20q12-13.1 and 12q15. These two regions harbor two genes, C/EBPbeta and CHOP, which are excellent candidate genes for T2D. In fact, C/EBPbeta protein cooperates with HNF4alpha (MODY1, monogenic form of diabetes) and 1alpha (MODY3, monogenic form of diabetes). C/EBPbeta mediates suppression of insulin gene transcription in hyperglycemia and may contribute to insulin-resistance. It interacts in a complex pathway with the CHOP protein. CHOP may play a role in altered beta-cell glucose metabolism, in beta-cell apoptosis, and in lack of beta-cell replication. Thus, both C/EBPbeta and CHOP genes may independently and interactively contribute to T2D. The chromosomal regions targeting C/EBPbeta and CHOP genes have never been previously explored in T2D. We planned to identify their potential contribution to T2D in Italians. We have genotyped a group of affected siblings/families with both late- and early-onset T2D around the C/EBPbeta and the CHOP genes. We have performed non-parametric linkage analysis in the total T2D group, in the late-onset and the early-onset group, separately. We have identified a suggestive linkage to T2D in the CHOP gene locus in the early-onset T2D group (P = 0.04). We identified the linkage to T2D in the chromosome 12q15 region in the early-onset T2D families and specifically target the CHOP gene. Our next step will be the identification of CHOP gene variants, which may contribute to the linkage to T2D in Italians.
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Affiliation(s)
- Claudia Gragnoli
- Laboratory of Molecular Genetics of Monogenic and Complex Disorders, Endocrinology, Diabetes & Metabolism, Medicine and Cellular & Molecular Physiology, Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033, USA.
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18
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Takanaga H, Chaudhuri B, Frommer WB. GLUT1 and GLUT9 as major contributors to glucose influx in HepG2 cells identified by a high sensitivity intramolecular FRET glucose sensor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:1091-9. [PMID: 18177733 DOI: 10.1016/j.bbamem.2007.11.015] [Citation(s) in RCA: 241] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Revised: 10/16/2007] [Accepted: 11/26/2007] [Indexed: 11/17/2022]
Abstract
Genetically encoded FRET glucose nanosensors have proven to be useful for imaging glucose flux in HepG2 cells. However, the dynamic range of the original sensor was limited and thus it did not appear optimal for high throughput screening of siRNA populations for identifying proteins involved in regulation of sugar flux. Here we describe a hybrid approach that combines linker-shortening with fluorophore-insertion to decrease the degrees of freedom for fluorophore positioning leading to improved nanosensor dynamics. We were able to develop a novel highly sensitive FRET nanosensor that shows a 10-fold higher ratio change and dynamic range (0.05-11 mM) in vivo, permitting analyses in the physiologically relevant range. As a proof of concept that this sensor can be used to screen for proteins playing a role in sugar flux and its control, we used siRNA inhibition of GLUT family members and show that GLUT1 is the major glucose transporter in HepG2 cells and that GLUT9 contributes as well, however to a lower extent. GFP fusions suggest that GLUT1 and 9 are preferentially localized to the plasma membrane and thus can account for the transport activity. The improved sensitivity of the novel glucose nanosensor increases the reliability of in vivo glucose flux analyses, and provides a new means for the screening of siRNA collections as well as drugs using high-content screens.
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Affiliation(s)
- Hitomi Takanaga
- Carnegie Institution for Science, 260 Panama Street, Stanford CA 94305, USA
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Porter MH, Paveglio SA, Zhang JA, Olson DE, Campbell AG, Thulé PM. Host Cells Reduce Glucose Uptake and Glycogen Deposition in Response to Hepatic Insulin Gene Therapy. J Investig Med 2005; 53:201-12. [PMID: 15974246 DOI: 10.2310/6650.2005.00404] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND Hepatic insulin gene therapy (HIGT) restores weight gain and near-normal glycemia in rodent models of insulin-deficient diabetes mellitus. However, the effect of transgenic insulin on endogenous genes and recipient cell function is relatively unexplored. To investigate hepatocellular effects of transgenic insulin expression, we evaluated intermediary glucose metabolism in primary cultured hepatocytes treated with HIGT. METHODS Rat hepatocytes were transduced with adenovirus expressing a glucose-responsive human insulin transgene and cultured in high-glucose and high-insulin conditions. We determined glycogen content in cell cultures and intact liver directly. Glycogenolysis was compared using glucose production of cultured cells. Glucose uptake, oxidative, and glycolytic processing were determined by radiotracer analysis or direct end-product assessment. Quantitative real-time reverse transcriptase polymerase chain reaction was used to determine expression of glucose transporter 2 (GLUT2) and glucokinase genes. GLUT2 protein abundance was determined by Western blot analysis. RESULTS HIGT-treated hepatocytes contained significantly less glycogen than either untreated hepatocytes or those treated with an empty virus. Glucose release owing to glycogenolysis remained normal. However, HIGT treatment significantly impaired glucose uptake and processing. Metabolic synthetic processes were not generally inhibited, as indicated by enhanced beta-hydroxybutyrate secretion. While preserving cell viability, HIGT treatment diminished expression of both glucokinase and GLUT2. In HIGT-treated streptozocin-treated diabetic rats, total liver glycogen was intermediate between diabetic animals and normal controls. CONCLUSIONS These results suggest gene-specific effects in recipient hepatocytes following HIGT treatment and underscore the need for expanded studies examining host cell responses to the transfer of metabolically active transgenes.
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Affiliation(s)
- Marty H Porter
- Department of Internal Medicine and Metabolism Section, Veterans Administration Medical Center, Decatur, GA, USA
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20
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Schaan BD, Irigoyen MC, Bertoluci MC, Lima NGD, Passaglia J, Hermes E, Oliveira FR, Okamoto M, Machado UF. Increased urinary TGF-beta1 and cortical renal GLUT1 and GLUT2 levels: additive effects of hypertension and diabetes. Nephron Clin Pract 2005; 100:p43-50. [PMID: 15855808 DOI: 10.1159/000085413] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Accepted: 01/23/2005] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND/AIM Diabetes and mesangial stretch caused by hypertension increase mesangial matrix deposition which is induced by local production of transforming growth factor beta 1 (TGF-beta1). Both conditions are associated with cortical GLUT1 overexpression. We evaluated the effect of genetically determined hypertension and its association with diabetes on urinary TGF-beta1 and cortical GLUT1 and GLUT2 expression. METHODS We studied Wistar-Kyoto rats (controls, C) and spontaneously hypertensive rats (SHR), weighing approximately 210 g, 30 days after the injection of streptozotocin (diabetic, D) or citrate buffer (10 C, 9 SHR, 12 C-D and 15 SHR-D). Twenty-four-hour urine was collected for glucose, albumin, and TGF-beta1 determinations. Catheters were implanted into the femoral artery to measure the arterial blood pressure in conscious animals 1 day later. Then GLUT1 and GLUT2 protein levels (Western blotting) in renal cortex and medulla were evaluated. RESULTS The cortical GLUT1 levels were 5, 2, and 7 times higher in SHR, C-D, and SHR-D groups versus C group (p < 0.05); the GLUT2 contents were 1.5, 1.8, and 2.3 times higher in SHR, C-D and SHR-D groups versus C group (p < 0.05). The urinary TGF-beta1 level was elevated by diabetes and diabetes and hypertension, but not by hypertension alone: 1.39 +/- 0.2, 2.34 +/- 0.6, 18.2 +/- 3.2, and 28.8 +/- 7.6 ng/24 h, respectively, in C, SHR, C-D, and SHR-D groups (p < 0.05). CONCLUSIONS Diabetes, hypertension, and especially their association increase the renal cortical GLUT1 and GLUT2 levels. The magnitude of GLUT1 overexpression caused by hypertension is higher than that induced by diabetes alone. The impact on urinary TGF-beta1 occurs when diabetes and hypertension are associated, suggesting an effect that is triggered in the presence of GLUT1 overexpression and hyperglycemia.
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Affiliation(s)
- Beatriz D'Agord Schaan
- Department of Experimental Medicine, Institute of Cardiology of Rio Grande do Sul, University Foundation of Cardiology, Porto Alegre, Brazil.
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21
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Inoue Y, Inoue J, Lambert G, Yim SH, Gonzalez FJ. Disruption of hepatic C/EBPalpha results in impaired glucose tolerance and age-dependent hepatosteatosis. J Biol Chem 2004; 279:44740-8. [PMID: 15292250 DOI: 10.1074/jbc.m405177200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C/EBPalpha is highly expressed in liver and regulates many genes that are preferentially expressed in liver. Because C/EBPalpha-null mice die soon after birth, it is impossible to analyze the function of C/EBPalpha in the adult with this model. To address the function of C/EBPalpha in adult hepatocytes, liver-specific C/EBPalpha-null mice were produced using a floxed C/EBPalpha allele and the albumin-Cre transgene. Unlike whole body C/EBPalpha-null mice, mice lacking hepatic C/EBPalpha expression did not exhibit hypoglycemia, nor did they show reduced hepatic glycogen in adult. Expression of liver glycogen synthase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase remained at normal levels. However, these mice exhibited impaired glucose tolerance due in part to reduced expression of hepatic glucokinase, and hyperammonemia from reduced expression of hepatic carbamoyl phosphate synthase-I. These mice also had reduced serum cholesterol and steatotic livers that was exacerbated with aging. This phenotype could be explained by increased expression of hepatic lipoprotein lipase and reduced expression of microsomal triglyceride transfer protein, apolipoproteins B100, and A-IV. These data demonstrate that hepatic C/EBPalpha is critical for ammonia detoxification and glucose and lipid homeostasis in adult mice.
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Affiliation(s)
- Yusuke Inoue
- Laboratory of Metabolism, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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22
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Kim SY, Kim HI, Kim TH, Im SS, Park SK, Lee IK, Kim KS, Ahn YH. SREBP-1c mediates the insulin-dependent hepatic glucokinase expression. J Biol Chem 2004; 279:30823-9. [PMID: 15123649 DOI: 10.1074/jbc.m313223200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The regulation of hepatic glucose metabolism is important in glucose homeostasis, and liver glucokinase (LGK) plays a central role in this process. Hepatic glucokinase expression is known to be regulated by insulin. Recently it has been suggested that sterol regulatory element binding protein-1c (SREBP-1c) mediates the action of insulin on LGK transcription; however, the precise mechanism is not, to date, well known. In the present study, we identified two functional SREBP-1c response elements, SREa and SREb, in the rat LGK promoter. SREBP-1c could bind to these SREs and activate the LGK promoter, and insulin activated the LGK promoter in Alexander cells. The physical interaction between the protein and SREs of the LGK promoter in vivo was also confirmed. Insulin selectively increased SREBP-1c and LGK expression in primary hepatocytes. Adenoviral expression of SREBP-1c stimulated LGK expression, and the dominant negative mutant of SREBP-1c blocked the increased gene expression of LGK by insulin and SREBP-1c. A chromatin immunoprecipitation assay using primary hepatocytes showed increased binding of SREBP-1 to SREs of the LGK promoter by insulin.
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Affiliation(s)
- So-Youn Kim
- Department of Biochemistry and Molecular Biology, Yonsei University, Seoul, Korea
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Dwyer DS, Vannucci SJ, Simpson IA. Expression, regulation, and functional role of glucose transporters (GLUTs) in brain. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 51:159-88. [PMID: 12420359 DOI: 10.1016/s0074-7742(02)51005-9] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Donard S Dwyer
- Departments of Psychiatry and Pharmacology, LSU Health Sciences Center, Shreveport, Louisiana 71130, USA
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Paiva L, Binsack R, Machado UF. Chronic acarbose-feeding increases GLUT1 protein without changing intestinal glucose absorption function. Eur J Pharmacol 2002; 434:197-204. [PMID: 11779583 DOI: 10.1016/s0014-2999(01)01538-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
As alpha-glucosidase inhibitor, the antidiabetic drug acarbose reduces postprandial glucose levels by retarding the intestinal digestion of polysaccharides. However, it is unknown if acarbose also affects the expression of intestinal glucose transporters, especially the Na(+)-glucose cotransporter (SGLT1) and the glucose transporters GLUT1 and GLUT2. To unravel this question, Wistar rats received standard powdered chow either without (control) or with acarbose (40 mg acarbose/100 g chow) for 40 days. While food intake was slightly enhanced by acarbose, the drug had no influence on weight gain or plasma glucose and insulin levels. The acarbose-treatment did not alter the SGLT1 and GLUT2 gene expression in both upper and middle small intestine, whereas GLUT1 protein was increased by 75% in middle small intestine. Despite the territorial change in GLUT1 protein, the intestinal glucose absorption in an acarbose-free perfusion study was unaltered. In conclusion, the chronic use of acarbose did not alter the acarbose-free glucose absorption profile.
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Affiliation(s)
- Leonardo Paiva
- Department of Physiology and Biophysics, University of São Paulo, Av. Prof. Lineu Prestes 1524, 05508-900, São Paulo, Brazil
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25
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Cha JY, Kim H, Kim KS, Hur MW, Ahn Y. Identification of transacting factors responsible for the tissue-specific expression of human glucose transporter type 2 isoform gene. Cooperative role of hepatocyte nuclear factors 1alpha and 3beta. J Biol Chem 2000; 275:18358-65. [PMID: 10748140 DOI: 10.1074/jbc.m909536199] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated transacting factors binding to the cis-element important in tissue-specific expression of the human glucose transporter type 2 isoform (GLUT2) gene. By transient transfection assay, we determined that the 227-base pair fragment upstream of the ATG start site contained promoter activity and that the region from +87 to +132 (site C) was responsible for tissue-specific expression. DNase I footprinting and electrophoretic mobility shift assay indicated that site C contained one binding site for hepatocyte nuclear factor 1 (HNF1) and two binding sites for HNF3. The mutations at positions +101 and +103, which are considered to be critical in binding HNF1 and HNF3, resulted in a 53% decrease in promoter activity, whereas the mutation of the proximal HNF3 binding site (+115 and +117) reduced promoter activity by 28%. The mutations of these four sites resulted in marked decrease (70%) in promoter activity as well as diminished bindings of HNF1 and HNF3. A to G mutation, which causes conversion of the HNF1 and HNF3 binding sequence to the NF-Y binding site, resulted in a 22% decrease in promoter activity. We identified that both HNF1 and HNF3 function as transcriptional activators in GLUT2 gene expression. Coexpression of the pGL+74 (+74 to +301) construct with the HNF1alpha and HNF3beta expression vectors in NIH 3T3 cells showed the synergistic effect on GLUT2 promoter activity compared with the expression of HNF1alpha, HNF3beta, or a combination of HNF1beta and HNF3beta. These data suggest that HNF1alpha and HNF3beta may be the most important players in the tissue-specific expression of the human GLUT2 gene.
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Affiliation(s)
- J Y Cha
- Department of Biochemistry and Molecular Biology and the Institute of Genetic Science, Yonsei University College of Medicine, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, South Korea
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