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Mei X, Li Y, Zhang X, Zhai X, Yang Y, Li Z, Li L. Maternal Phlorizin Intake Protects Offspring from Maternal Obesity-Induced Metabolic Disorders in Mice via Targeting Gut Microbiota to Activate the SCFA-GPR43 Pathway. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:4703-4725. [PMID: 38349207 DOI: 10.1021/acs.jafc.3c06370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
Maternal obesity increases the risk of obesity and metabolic disorders (MDs) in offspring, which can be mediated by the gut microbiota. Phlorizin (PHZ) can improve gut dysbiosis and positively affect host health; however, its transgenerational metabolic benefits remain largely unclear. This study aimed to investigate the potential of maternal PHZ intake in attenuating the adverse impacts of a maternal high-fat diet on obesity-related MDs in dams and offspring. The results showed that maternal PHZ reduced HFD-induced body weight gain and fat accumulation and improved glucose intolerance and abnormal lipid profiles in both dams and offspring. PHZ improved gut dysbiosis by promoting expansion of SCFA-producing bacteria, Akkermansia and Blautia, while inhibiting LPS-producing and pro-inflammatory bacteria, resulting in significantly increased fecal SCFAs, especially butyric acid, and reduced serum lipopolysaccharide levels and intestinal inflammation. PHZ also promoted intestinal GLP-1/2 secretion and intestinal development and enhanced gut barrier function by activating G protein-coupled receptor 43 (GPR43) in the offspring. Antibiotic-treated mice receiving FMT from PHZ-regulated offspring could attenuate MDs induced by receiving FMT from HFD offspring through the gut microbiota to activate the GPR43 pathway. It can be regarded as a promising functional food ingredient for preventing intergenerational transmission of MDs and breaking the obesity cycle.
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Affiliation(s)
- Xueran Mei
- Department of Obstetrics, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen 518020, China
- Post-Doctoral Scientific Research Station of Clinical Medicine, Jinan University, Guangzhou 510632, China
- Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China
| | - Yi Li
- Graduate School of Biomedical Engineering, Faculty of Engineering, University of New South Wales, Sydney 2052, Australia
- ARC Centre of Excellence for Nanoscale Biophotonics, University of New South Wales, Sydney 2052, Australia
| | - Xiaoyu Zhang
- College of Life Sciences, Sichuan Normal University, Chengdu 610101, China
| | - Xiwen Zhai
- Graduate School of Biomedical Engineering, Faculty of Engineering, University of New South Wales, Sydney 2052, Australia
- ARC Centre of Excellence for Nanoscale Biophotonics, University of New South Wales, Sydney 2052, Australia
| | - Yi Yang
- Department of Obstetrics, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen 518020, China
- Post-Doctoral Scientific Research Station of Clinical Medicine, Jinan University, Guangzhou 510632, China
| | - Zhengjuan Li
- Department of Obstetrics, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen 518020, China
- Post-Doctoral Scientific Research Station of Clinical Medicine, Jinan University, Guangzhou 510632, China
- Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China
| | - Liping Li
- Department of Obstetrics, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen 518020, China
- Post-Doctoral Scientific Research Station of Clinical Medicine, Jinan University, Guangzhou 510632, China
- Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China
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López-Soldado I, Guinovart JJ, Duran J. Increasing hepatic glycogen moderates the diabetic phenotype in insulin-deficient Akita mice. J Biol Chem 2021; 296:100498. [PMID: 33667544 PMCID: PMC8027280 DOI: 10.1016/j.jbc.2021.100498] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/23/2021] [Accepted: 03/01/2021] [Indexed: 12/14/2022] Open
Abstract
Hepatic glycogen metabolism is impaired in diabetes. We previously demonstrated that strategies to increase liver glycogen content in a high-fat-diet mouse model of obesity and insulin resistance led to a reduction in food intake and ameliorated obesity and glucose tolerance. These effects were accompanied by a decrease in insulin levels, but whether this decrease contributed to the phenotype observed in this animal was unclear. Here we sought to evaluate this aspect directly, by examining the long-term effects of increasing liver glycogen in an animal model of insulin-deficient and monogenic diabetes, namely the Akita mouse, which is characterized by reduced insulin production. We crossed Akita mice with animals overexpressing protein targeting to glycogen (PTG) in the liver to generate Akita mice with increased liver glycogen content (Akita-PTGOE). Akita-PTGOE animals showed lower glycemia, lower food intake, and decreased water consumption and urine output compared with Akita mice. Furthermore, Akita-PTGOE mice showed a restoration of the hepatic energy state and a normalization of gluconeogenesis and glycolysis back to nondiabetic levels. Moreover, hepatic lipogenesis, which is reduced in Akita mice, was reverted in Akita-PTGOE animals. These results demonstrate that strategies to increase liver glycogen content lead to the long-term reduction of the diabetic phenotype, independently of circulating insulin.
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Affiliation(s)
- Iliana López-Soldado
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain.
| | - Joan J Guinovart
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain; Department of Biochemistry and Molecular Biomedicine, University of Barcelona, Barcelona, Spain
| | - Jordi Duran
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
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Al-Oanzi ZH, Fountana S, Moonira T, Tudhope SJ, Petrie JL, Alshawi A, Patman G, Arden C, Reeves HL, Agius L. Opposite effects of a glucokinase activator and metformin on glucose-regulated gene expression in hepatocytes. Diabetes Obes Metab 2017; 19:1078-1087. [PMID: 28206714 DOI: 10.1111/dom.12910] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 02/10/2017] [Accepted: 02/11/2017] [Indexed: 01/19/2023]
Abstract
AIM Small molecule activators of glucokinase (GKAs) have been explored extensively as potential anti-hyperglycaemic drugs for type 2 diabetes (T2D). Several GKAs were remarkably effective in lowering blood glucose during early therapy but then lost their glycaemic efficacy chronically during clinical trials. MATERIALS AND METHODS We used rat hepatocytes to test the hypothesis that GKAs raise hepatocyte glucose 6-phosphate (G6P, the glucokinase product) and down-stream metabolites with consequent repression of the liver glucokinase gene ( Gck). We compared a GKA with metformin, the most widely prescribed drug for T2D. RESULTS Treatment of hepatocytes with 25 mM glucose raised cell G6P, concomitantly with Gck repression and induction of G6pc (glucose 6-phosphatase) and Pklr (pyruvate kinase). A GKA mimicked high glucose by raising G6P and fructose-2,6-bisphosphate, a regulatory metabolite, causing a left-shift in glucose responsiveness on gene regulation. Fructose, like the GKA, repressed Gck but modestly induced G6pc. 2-Deoxyglucose, which is phosphorylated by glucokinase but not further metabolized caused Gck repression but not G6pc induction, implicating the glucokinase product in Gck repression. Metformin counteracted the effect of high glucose on the elevated G6P and fructose 2,6-bisphosphate and on Gck repression, recruitment of Mlx-ChREBP to the G6pc and Pklr promoters and induction of these genes. CONCLUSIONS Elevation in hepatocyte G6P and downstream metabolites, with consequent liver Gck repression, is a potential contributing mechanism to the loss of GKA efficacy during chronic therapy. Cell metformin loads within the therapeutic range attenuate the effect of high glucose on G6P and on glucose-regulated gene expression.
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Affiliation(s)
- Ziad H Al-Oanzi
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
- Medical Laboratory Science, Aljouf University, Sakaka, Saudi Arabia
| | - Sophia Fountana
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
| | - Tabassum Moonira
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
| | - Susan J Tudhope
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
| | - John L Petrie
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
| | - Ahmed Alshawi
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
| | - Gillian Patman
- Northern Institute for Cancer Research, Newcastle University, Newcastle-upon-Tyne, UK
| | - Catherine Arden
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
| | - Helen L Reeves
- Northern Institute for Cancer Research, Newcastle University, Newcastle-upon-Tyne, UK
| | - Loranne Agius
- Institute of Cellular Medicine and Ageing and Health, Newcastle University, Newcastle upon Tyne, UK
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Mei X, Zhang X, Wang Z, Gao Z, Liu G, Hu H, Zou L, Li X. Insulin Sensitivity-Enhancing Activity of Phlorizin Is Associated with Lipopolysaccharide Decrease and Gut Microbiota Changes in Obese and Type 2 Diabetes (db/db) Mice. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:7502-7511. [PMID: 27635781 DOI: 10.1021/acs.jafc.6b03474] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Phlorizin exists in a number of fruits and foods and exhibits many bioactivities. The mechanism of its antidiabetic effect has been known as it can competitively inhibit sodium-glucose symporters (SGLTs). However, phlorizin has a wide range of two-phase metabolism in systemic circulation and shows poor oral bioavailability. An alternative mechanism may involve gut microbiota in intestine. Sixteen obese mice with type 2 diabetes (db/db) and eight age-matched control mice (db/+) were divided into three groups: diabetic group treated with phlorizin (DMT group), vehicle-treated diabetic group (DM group), and normal control group (CC group). Phlorizin was given in normal saline solution by intragastric administration for 10 weeks. After the last treatment course, body weight, energy intake, serum lipopolysaccharides (LPS), insulin resistance, and fecal short-chain fatty acids (SCFAs) were compared. 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) and quantitative PCR were used to determine the changes in microbiome composition. Coadministration of phlorizin significantly prevented metabolic syndrome by decreasing weight gain, energy intake, serum lipopolysaccharides, and insulin resistance, and the fecal level of total SCFAs was dramatically increased, especially butyric acid. DGGE and quantitative PCR demonstrated that phlorizin coadministration increased the gut microbial diversity and the growth of Akkermansia muciniphila and Prevotella. Meanwhile, the gut microbiota structure of db/db mice after phlorizin treatment was improved and approached the normal group. The mechanism of the hypoglycemic action of phlorizin is associated with LPS decrease and gut microbiota changes; briefly, it acts in the intestine to modify gut microbial community structure, resulting in lower LPS load in the host and higher SCFAs producing beneficial bacteria.
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Affiliation(s)
- Xueran Mei
- College of Life Sciences, Sichuan Normal University , Longquan, Chengdu 610101, China
- Metabonomics Synergy Innovation Laboratory, School of Medicine and Nursing, Chengdu University , Longquan, Chengdu 610106, China
| | - Xiaoyu Zhang
- College of Life Sciences, Sichuan Normal University , Longquan, Chengdu 610101, China
| | - Zhanguo Wang
- Metabonomics Synergy Innovation Laboratory, School of Medicine and Nursing, Chengdu University , Longquan, Chengdu 610106, China
| | - Ziyang Gao
- College of Life Sciences, Sichuan Normal University , Longquan, Chengdu 610101, China
| | - Gang Liu
- College of Life Sciences, Sichuan Normal University , Longquan, Chengdu 610101, China
| | - Huiling Hu
- School of Pharmacy, Chengdu University of Traditional Chinese Medicine , Wenjiang, Chengdu 610730, China
| | - Liang Zou
- Metabonomics Synergy Innovation Laboratory, School of Medicine and Nursing, Chengdu University , Longquan, Chengdu 610106, China
| | - Xueli Li
- College of Life Sciences, Sichuan Normal University , Longquan, Chengdu 610101, China
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Affiliation(s)
- Loranne Agius
- Institutes of Cellular Medicine and Ageing and Health, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH United Kingdom;
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Pulsatile Hyperglycaemia Induces Vascular Oxidative Stress and GLUT 1 Expression More Potently than Sustained Hyperglycaemia in Rats on High Fat Diet. PLoS One 2016; 11:e0147412. [PMID: 26790104 PMCID: PMC4720376 DOI: 10.1371/journal.pone.0147412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 01/04/2016] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION Pulsatile hyperglycaemia resulting in oxidative stress may play an important role in the development of macrovascular complications. We investigated the effects of sustained vs. pulsatile hyperglycaemia in insulin resistant rats on markers of oxidative stress, enzyme expression and glucose metabolism in liver and aorta. We hypothesized that liver's ability to regulate the glucose homeostasis under varying states of hyperglycaemia may indirectly affect oxidative stress status in aorta despite the amount of glucose challenged with. METHODS Animals were infused with sustained high (SHG), low (SLG), pulsatile (PLG) glucose or saline (VEH) for 96 h. Oxidative stress status and key regulators of glucose metabolism in liver and aorta were investigated. RESULTS Similar response in plasma lipid oxidation was observed in PLG as in SHG. Likewise, in aorta, PLG and SHG displayed increased expression of glucose transporter 1 (GLUT1), gp-91PHOX and super oxide dismutase (SOD), while only the PLG group showed increased accumulation of oxidative stress and oxidised low density lipoprotein (oxLDL) in aorta. CONCLUSION Pulsatile hyperglycaemia induced relatively higher levels of oxidative stress systemically and in aorta in particular than overt sustained hyperglycaemia thus supporting the clinical observations that pulsatile hyperglycaemia is an independent risk factor for diabetes related macrovascular complications.
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Zheng J, Shen N, Wang S, Zhao G. Oat beta-glucan ameliorates insulin resistance in mice fed on high-fat and high-fructose diet. Food Nutr Res 2013; 57:22754. [PMID: 24371433 PMCID: PMC3871839 DOI: 10.3402/fnr.v57i0.22754] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 10/17/2013] [Accepted: 11/08/2013] [Indexed: 11/26/2022] Open
Abstract
Methods This study sought to evaluate the impact of oat beta-glucan on insulin resistance in mice fed on high-fat and high-fructose diet with fructose (10%, w/v) added in drinking water for 10 weeks. Results The results showed that supplementation with oat beta-glucan could significantly reduce the insulin resistance both in low-dose (200 mg/kg−1 body weight) and high-dose (500 mg/kg−1 body weight) groups, but the high-dose group showed a more significant improvement in insulin resistance (P<0.01) compared with model control (MC) group along with significant improvement in hepatic glycogen level, oral glucose, and insulin tolerance. Moreover, hepatic glucokinase activity was markedly enhanced both in low-dose and high-dose groups compared with that of MC group (P<0.05). Conclusion These results suggested that supplementation of oat beta-glucan alleviated insulin resistance and the effect was dose dependent.
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Affiliation(s)
- Jie Zheng
- College of Food Science, Southwest University, Chongqing, China ; Department of Chemistry and Chemical Engineering, Chongqing University, Chongqing, China
| | - Nanhui Shen
- Department of Chemistry and Chemical Engineering, Chongqing University, Chongqing, China
| | - Shuanghui Wang
- Department of Chemistry and Chemical Engineering, Chongqing University, Chongqing, China
| | - Guohua Zhao
- College of Food Science, Southwest University, Chongqing, China
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Ecklonia cava Inhibits Glucose Absorption and Stimulates Insulin Secretion in Streptozotocin-Induced Diabetic Mice. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:439294. [PMID: 22645628 PMCID: PMC3356976 DOI: 10.1155/2012/439294] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 02/20/2012] [Indexed: 12/16/2022]
Abstract
Aims of study. Present study investigated the effect of Ecklonia cava (EC) on intestinal glucose uptake and insulin secretion. Materials and methods. Intestinal Na+-dependent glucose uptake (SGU) and Na+-dependent glucose transporter 1 (SGLT1) protein expression was determined using brush border membrane vesicles (BBMVs). Glucose-induced insulin secretion was examined in pancreatic β-islet cells. The antihyperglycemic effects of EC, SGU, and SGLT1 expression were determined in streptozotocin (STZ)-induced diabetic mice. Results. Methanol extract of EC markedly inhibited intestinal SGU of BBMV with the IC50 value of 345 μg/mL. SGLT1 protein expression was dose dependently down regulated with EC treatment. Furthermore, insulinotrophic effect of EC extract was observed at high glucose media in isolated pancreatic β-islet cells in vitro. We next conducted the antihyperglycemic effect of EC in STZ-diabetic mice. EC supplementation markedly suppressed SGU and SGLT1 abundance in BBMV from STZ mice. Furthermore, plasma insulin level was increased by EC treatment in diabetic mice. As a result, EC supplementation improved postprandial glucose regulation, assessed by oral glucose tolerance test, in diabetic mice. Conclusion. These results suggest that EC play a role in controlling dietary glucose absorption at the intestine and insulinotrophic action at the pancreas contributing blood glucose homeostasis in diabetic condition.
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Kim HK, Baek SS, Cho HY. Inhibitory Effect of Pomegranate on Intestinal Sodium Dependent Glucose Uptake. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2012; 39:1015-27. [DOI: 10.1142/s0192415x11009378] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Intestinal glucose uptake is mainly performed by its specific transporters, SGLT1 and GLUTs expressed in the intestinal epithelial cells. By using Caco -2 cells and 2-NBDG, we observed that intestinal glucose uptake was markedly inhibited by pomegranate (Punica granatum L, PG) among 200 screened edible Korean plants. The effects of the PG extract on Na +-dependent glucose uptake were further evaluated using brush border membrane vesicles (BBMV) obtained from the mouse small intestine. PG inhibited Na +-dependent glucose uptake with the IC50 value of 424 μg/ml. The SGLT1 protein expression was dose dependently down regulated with PG treatment in Caco -2 cells. We next assessed the antihyperglycemic effect of PG in streptozotocin (STZ)-induced diabetic mice. Administration of PG (800 mg/kg) to STZ mice for four weeks improved postprandial glucose regulation. Furthermore, elevated Na +-dependent glucose uptake by BBMV isolated from STZ mice was normalized by PG treratment. These results suggest that PG could play a role in controlling the dietary glucose absorption at the intestinal tract by decreasing SGLT1 expression, and may contribute to blood glucose homeostasis in the diabetic condition.
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Affiliation(s)
- Hye Kyung Kim
- Department of Food and Biotechnology, Hanseo University, Seosan 356-706, Republic of Korea
| | - Soon-Sun Baek
- Ginseng Research Institute, R&D Headquarters, Korea Ginseng Corporation, Daejeon 305-345, Republic of Korea
| | - Hong-Yon Cho
- Department of Food and Biotechnology, Korea University, Jochiwon 339-700, Republic of Korea
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Arden C, Petrie JL, Tudhope SJ, Al-Oanzi Z, Claydon AJ, Beynon RJ, Towle HC, Agius L. Elevated glucose represses liver glucokinase and induces its regulatory protein to safeguard hepatic phosphate homeostasis. Diabetes 2011; 60:3110-20. [PMID: 22013014 PMCID: PMC3219956 DOI: 10.2337/db11-0061] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE The induction of hepatic glucose 6-phosphatase (G6pc) by glucose presents a paradox of glucose-induced glucose intolerance. We tested whether glucose regulation of liver gene expression is geared toward intracellular homeostasis. RESEARCH DESIGN AND METHODS The effect of glucose-induced accumulation of phosphorylated intermediates on expression of glucokinase (Gck) and its regulator Gckr was determined in hepatocytes. Cell ATP and uric acid production were measured as indices of cell phosphate homeostasis. RESULTS Accumulation of phosphorylated intermediates in hepatocytes incubated at elevated glucose induced rapid and inverse changes in Gck (repression) and Gckr (induction) mRNA concomitantly with induction of G6pc, but had slower effects on the Gckr-to-Gck protein ratio. Dynamic metabolic labeling in mice and liver proteome analysis confirmed that Gckr and Gck are low-turnover proteins. Involvement of Max-like protein X in glucose-mediated Gck-repression was confirmed by chromatin immunoprecipitation analysis. Elevation of the Gck-to-Gckr ratio in hepatocytes was associated with glucose-dependent ATP depletion and elevated urate production confirming compromised phosphate homeostasis. CONCLUSIONS The lowering by glucose of the Gck-to-Gckr ratio provides a potential explanation for the impaired hepatic glucose uptake in diabetes. Elevated uric acid production at an elevated Gck-to-Gckr ratio supports a role for glucose regulation of gene expression in hepatic phosphate homeostasis.
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Affiliation(s)
- Catherine Arden
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - John L. Petrie
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - Susan J. Tudhope
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - Ziad Al-Oanzi
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
- Department of Laboratory Medicine, Al-Jouf University, Sakaka, Saudi Arabia
| | - Amy J. Claydon
- Protein Function Group, Institute of Integrative Biology, University of Liverpool, Liverpool, U.K
| | - Robert J. Beynon
- Protein Function Group, Institute of Integrative Biology, University of Liverpool, Liverpool, U.K
| | - Howard C. Towle
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Loranne Agius
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
- Corresponding author: Loranne Agius,
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Gestational diabetes affects postnatal development of transport and enzyme functions in rat intestine. Mol Cell Biochem 2011; 361:71-7. [PMID: 21964563 DOI: 10.1007/s11010-011-1090-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 09/16/2011] [Indexed: 10/17/2022]
Abstract
The effect of alloxan-induced gestational diabetes on the postnatal development of brush border disaccharidases and D-glucose transport in rat intestine was studied. Pups born to diabetic mothers showed 92-22% increase in blood sugar levels compared with the controls. Western blot and RT-PCR analyses revealed that the activities of brush border sucrase, lactase and Sodium Glucose Co-transporter 1 (SGLT1) correlates with protein and mRNA levels in intestine of pups born to diabetic rat mothers after 5-45 days of birth. Intestinal histology in pups born to diabetic mothers at day 10 and 45 after birth showed distorted cellular organization of mucosa with a decrease in the number of secretary goblet cells and regression of tubular mass. These findings suggest that the genetic switch in utero regulates the postnatal expression of enzyme and transport functions in intestine of pups born to diabetic rat mothers. This may influence the growth and development of offsprings later in life.
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Gnoni GV, Giudetti AM, Mercuri E, Damiano F, Stanca E, Priore P, Siculella L. Reduced activity and expression of mitochondrial citrate carrier in streptozotocin-induced diabetic rats. Endocrinology 2010; 151:1551-9. [PMID: 20203153 DOI: 10.1210/en.2009-1352] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Citrate carrier (CiC), an integral protein of the mitochondrial inner membrane, plays an important role in hepatic intermediary metabolism, supplying the cytosol with acetyl-coenzyme A for fatty acid and cholesterol synthesis. Here, the effect of streptozotocin-induced diabetes on CiC activity and expression in rat liver was investigated. The rate of citrate transport was reduced by about 35% in mitochondria from diabetic vs. control rats. Kinetic studies in mitochondria from diabetic rats showed a reduction in maximum velocity and almost unchanged Michaelis-Menten constant of the CiC protein. Mitochondrial phospholipid amount was not significantly affected, whereas an increase in the cholesterol content and in the cholesterol/phospholipid ratio was observed. To thoroughly investigate the mechanism responsible for the reduced CiC activity in the diabetic state, molecular studies were performed. Ribonuclease protection assays and Western blotting analysis indicated that both hepatic CiC mRNA accumulation and protein level decreased similarly to the CiC activity. The reduced mRNA level and the lower content of the mitochondrial CiC protein, might account for the decline of CiC activity in diabetic animals. To discriminate between the role played by hyperglycemia from that of hypoinsulinemia in the reduction of CiC activity and expression, studies were conducted administrating phlorizin or insulin to streptozotocin-diabetic rats. Our data indicated that both insulin and glucose affect CiC activity and expression in diabetic rats, although they act at different regulatory steps.
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Affiliation(s)
- Gabriele V Gnoni
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Laboratorio di Biochimica, Università del Salento, Via Provinciale Lecce-Monteroni, 73100 Lecce, Italy.
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Abstract
Conversion of glucose into glycogen is a major pathway that contributes to the removal of glucose from the portal vein by the liver in the postprandial state. It is regulated in part by the increase in blood-glucose concentration in the portal vein, which activates glucokinase, the first enzyme in the pathway, causing an increase in the concentration of glucose 6-P (glucose 6-phosphate), which modulates the phosphorylation state of downstream enzymes by acting synergistically with other allosteric effectors. Glucokinase is regulated by a hierarchy of transcriptional and post-transcriptional mechanisms that are only partially understood. In the fasted state, glucokinase is in part sequestered in the nucleus in an inactive state, complexed to a specific regulatory protein, GKRP (glucokinase regulatory protein). This reserve pool is rapidly mobilized to the cytoplasm in the postprandial state in response to an elevated concentration of glucose. The translocation of glucokinase between the nucleus and cytoplasm is modulated by various metabolic and hormonal conditions. The elevated glucose 6-P concentration, consequent to glucokinase activation, has a synergistic effect with glucose in promoting dephosphorylation (inactivation) of glycogen phosphorylase and inducing dephosphorylation (activation) of glycogen synthase. The latter involves both a direct ligand-induced conformational change and depletion of the phosphorylated form of glycogen phosphorylase, which is a potent allosteric inhibitor of glycogen synthase phosphatase activity associated with the glycogen-targeting protein, GL [hepatic glycogen-targeting subunit of PP-1 (protein phosphatase-1) encoded by PPP1R3B]. Defects in both the activation of glucokinase and in the dephosphorylation of glycogen phosphorylase are potential contributing factors to the dysregulation of hepatic glucose metabolism in Type 2 diabetes.
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Abstract
Type-2 diabetes is associated with impaired glucose clearance by the liver in the postprandial state, and with elevated glucose production in the post-absorptive state. New targets within the liver are currently being investigated for development of antihyperglycaemic drugs for type-2 diabetes. They include glucokinase, which catalyses the first step in glucose metabolism, the glucagon receptor, and enzymes of gluconeogenesis and/or glycogenolysis such as glucose 6-phosphatase, fructose 1,6-bisphosphatase and glycogen phosphorylase. Preclinical studies with candidate drugs on animal models or cell-based assays suggest that these targets have the potential for pharmacological glycaemic control. Data from clinical studies is awaited. Further work is required for better understanding of the implications of targeting these sites in terms of possible side-effects or tachyphylaxis. The advantage of combined targeting of two or more sites within the liver for minimizing side-effects and tachyphylaxis caused by single-site targeting is discussed.
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Affiliation(s)
- Loranne Agius
- Institute of Cellular Medicine, School of Clinical Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
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Cho YR, Kim HJ, Park SY, Ko HJ, Hong EG, Higashimori T, Zhang Z, Jung DY, Ola MS, Lanoue KF, Leiter EH, Kim JK. Hyperglycemia, maturity-onset obesity, and insulin resistance in NONcNZO10/LtJ males, a new mouse model of type 2 diabetes. Am J Physiol Endocrinol Metab 2007; 293:E327-36. [PMID: 17616608 DOI: 10.1152/ajpendo.00376.2006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
As a new mouse model of obesity-induced diabetes generated by combining quantitative trait loci from New Zealand Obese (NZO/HlLt) and Nonobese Nondiabetic (NON/LtJ) mice, NONcNZO10/LtJ (RCS10) male mice developed type 2 diabetes characterized by maturity onset obesity, hyperglycemia, and insulin resistance. To metabolically profile the progression to diabetes in preobese and obese states, a 2-h hyperinsulinemic euglycemic clamp was performed and organ-specific changes in insulin action were assessed in awake RCS10 and NON/LtJ (control) males at 8 and 13 wk of age. Prior to development of obesity and attendant increases in hepatic lipid content, 8-wk-old RCS10 mice developed insulin resistance in liver and skeletal muscle due to significant decreases in insulin-stimulated glucose uptake and GLUT4 expression in muscle. Transition to an obese and hyperglycemic state by 13 wk of age exacerbated insulin resistance in skeletal muscle, liver, and heart associated with organ-specific increases in lipid content. Thus, this polygenic mouse model of type 2 diabetes, wherein plasma insulin is only modestly elevated and obesity develops with maturity yet insulin action and glucose metabolism in skeletal muscle and liver are reduced at an early prediabetic age, should provide new insights into the etiology of type 2 diabetes.
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Affiliation(s)
- You-Ree Cho
- Department of Internal Medicine, Section of Endocrinology and Metabolism, Yale University School of Medicine, New Haven, Connecticut, USA
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16
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Jung UJ, Lee MK, Park YB, Kang MA, Choi MS. Effect of citrus flavonoids on lipid metabolism and glucose-regulating enzyme mRNA levels in type-2 diabetic mice. Int J Biochem Cell Biol 2006; 38:1134-45. [PMID: 16427799 DOI: 10.1016/j.biocel.2005.12.002] [Citation(s) in RCA: 272] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 11/28/2005] [Accepted: 12/08/2005] [Indexed: 01/31/2023]
Abstract
Flavonoids have been identified as the antidiabetic components in a number of traditional ethnic remedies. However, the mechanisms whereby these compounds exert their hypoglycemic and hypolipidemic action in type-2 diabetes have rarely been investigated. Therefore, this study investigated the effect of the flavonoids hesperidin and naringin on glucose and lipid regulation in C57BL/KsJ-db/db mice. Hesperidin and naringin both significantly increased the glucokinase mRNA level, while naringin also lowered the mRNA expression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase in the liver. In addition, the hepatic glucose transporter 2 protein expression was significantly reduced, while the expression of adipocyte glucose transporter 4 and hepatic and adipocyte peroxisome proliferator-activated receptor gamma were elevated in the hesperidin and naringin groups when compared with the control group. Furthermore, hesperidin and naringin effectively lowered the plasma free fatty acid and plasma and hepatic triglyceride levels, and simultaneously reduced the hepatic fatty acid oxidation and carnitine palmitoyl transferase activity. These changes were seemingly attributable to a suppression of the hepatic fatty acid synthase, glucose-6-phosphate dehydrogenase, and phosphatidate phosphohydrolase activities and an increase in the fecal triglycerides. The two flavonoids also led to a decrease in the plasma and hepatic cholesterol levels that may have been partly due to the decreased hepatic 3-hydroxy-3-methylglutaryl-coenzyme (HMG-CoA) reductase and acyl CoA: cholesterol acyltransferase (ACAT) activities and increased fecal cholesterol. Consequently, the current results suggest that hesperidin and naringin are beneficial for improving hyperlipidemia and hyperglycemia in type-2 diabetic animals by partly regulating the fatty acid and cholesterol metabolism and affecting the gene expression of glucose-regulating enzymes.
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Affiliation(s)
- Un Ju Jung
- Department of Food Science and Nutrition, Kyungpook National University, 1370 San-Kyuk Dong Puk-Ku, 702-701 Daegu, Republic of Korea
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17
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Wu C, Okar DA, Stoeckman AK, Peng LJ, Herrera AH, Herrera JE, Towle HC, Lange AJ. A potential role for fructose-2,6-bisphosphate in the stimulation of hepatic glucokinase gene expression. Endocrinology 2004; 145:650-8. [PMID: 14617577 DOI: 10.1210/en.2003-1290] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effects of fructose-2,6-bisphosphate (F-2,6-P(2)) on hepatic glucokinase (GK) and glucose-6-phosphatase (G-6-Pase) gene expression were investigated in streptozotocin-treated mice, which exhibited undetectable levels of insulin. Hepatic F-2,6-P(2) levels were manipulated by adenovirus-mediated overexpression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Streptozotocin treatment alone or with infusion of control adenovirus leads to a dramatic decrease in hepatic F-2,6-P(2) content compared with normal nondiabetic mice. This is accompanied by a 14-fold decrease in GK and a 3-fold increase in G-6-Pase protein levels, consistent with a diabetic phenotype. Streptozotocin-treated mice that were infused with adenovirus-overexpressing an engineered 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase with high kinase activity and little bisphosphatase activity showed high levels of hepatic F-2,6-P(2). Surprisingly, these mice had a 13-fold increase in GK protein and a 2-fold decrease in G-6-Pase protein compared with diabetic controls. The restoration of GK is associated with increases in the phosphorylation of Akt upon increasing hepatic F-2,6-P(2) content. Moreover, the changes in levels of F-2,6-P(2) and Akt phosphorylation revealed a pattern similar to that of streptozotocin mice treated with insulin, indicating that increasing hepatic content of F-2,6-P(2) mimics the action of insulin. Because G-6-Pase gene expression was down-regulated only after the restoration of euglycemia, the effect of F-2,6-P(2) was indirect. Also, the lowering of blood glucose by high F-2,6-P(2) was associated with an increase in hepatic nuclear factor 1-alpha protein, a transcription factor involved in G-6-Pase gene expression. In conclusion, F-2,6-P(2) can stimulate hepatic GK gene expression in an insulin-independent manner and can secondarily affect G-6-Pase gene expression by lowering the level of plasma glucose.
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Affiliation(s)
- Chaodong Wu
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Medical School, 321 Church Street SE, Minneapolis, MN 55455, USA
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18
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Abstract
The liver is mainly responsible for maintaining normal concentrations of blood glucose by its ability to store glucose as glycogen and to produce glucose from glycogen breakdown or gluconeogenic precursors. During the last decade, new techniques have made it possible to gain further insight into the turnover of hepatic glucose and glycogen in humans. Hepatic glycogen varies from approximately 200 to approximately 450 mM between overnight fasted and postprandial conditions. Patients with type-1 diabetes (T1DM), type 2 diabetes (T2DM) or partial agenesis of the pancreas exhibit increased endogenous glucose production and synthesize only 25-45% of hepatic glycogen compared with non-diabetic humans. This defect can be partly restored in T1DM by combined long- and short-term optimized treatment with insulin. In T2DM, increased gluconeogenesis was identified as the main cause of elevated glucose production and fasting hyperglycaemia. These patients also exhibit augmented intracellular lipid accumulation which could hint at a link between deranged glucose and lipid metabolism in insulin-resistant states.
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Affiliation(s)
- Michael Roden
- Division of Endocrinology and Metabolism, Department of Internal Medicine III, University of Vienna Medical School, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
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19
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Iozzo P, Hallsten K, Oikonen V, Virtanen KA, Parkkola R, Kemppainen J, Solin O, Lonnqvist F, Ferrannini E, Knuuti J, Nuutila P. Effects of metformin and rosiglitazone monotherapy on insulin-mediated hepatic glucose uptake and their relation to visceral fat in type 2 diabetes. Diabetes Care 2003; 26:2069-74. [PMID: 12832315 DOI: 10.2337/diacare.26.7.2069] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Impaired insulin-mediated hepatic glucose uptake (HGU) has been implicated in the hyperglycemia of type 2 diabetes. We examined the effects of metformin (2 g/day) and rosiglitazone (8 mg/day) monotherapy on HGU and its relation to subcutaneous fat, visceral fat (VF), and whole-body insulin-mediated glucose metabolism in type 2 diabetic patients. RESEARCH DESIGN AND METHODS Glucose uptake was measured before and after 26 weeks of treatment using positron emission tomography with [(18)F]2-fluoro-2-deoxyglucose during euglycemic hyperinsulinemia; fat depots were quantified by magnetic resonance imaging. RESULTS Fasting plasma glucose levels were significantly decreased after either rosiglitazone (-0.9 +/- 0.5 mmol/l) or metformin treatment (-1.1 +/- 0.5 mmol/l) in comparison with placebo; only metformin was associated with weight loss (P < 0.02 vs. placebo). When controlling for the latter, the placebo-subtracted change in whole-body glucose uptake averaged -1 +/- 4 micromol x min(-1) x kg(-1) in metformin-treated patients (NS) and +9 +/- 3 micromol x min(-1) x kg(-1) in rosiglitazone-treated patients (P = 0.01). Both rosiglitazone and metformin treatment were associated with an increase in HGU; versus placebo, the change reached statistical significance when controlling for sex (placebo-subtracted values = +0.008 +/- 0.004 micromol x min(-1) x kg(-1) x pmol/l(-1), P < 0.03, for metformin; and +0.007 +/- 0.004, P < 0.07, for rosiglitazone). After treatment with either drug, insulin-mediated VF glucose uptake (VFGU) was higher than with placebo. In the whole dataset, changes in HGU were negatively related to changes in HbA(1c) (r = 0.43, P = 0.01) and positively associated with changes in VFGU (r = 0.48, P < 0.01). CONCLUSIONS We conclude that both metformin and rosiglitazone monotherapy increase HGU in type 2 diabetes; direct drug actions, better glycemic control, and enhanced VF insulin sensitivity are likely determinants of this phenomenon.
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Affiliation(s)
- Patricia Iozzo
- Turku PET Centre, Department of Nuclear Medicine, University of Turku, Turku, Finland.
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Hsieh MC, Wu CH, Chen CL, Chen HC, Chang CC, Shin SJ. High blood glucose and osmolality, but not high urinary glucose and osmolality, affect neuronal nitric oxide synthase expression in diabetic rat kidney. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2003; 141:200-9. [PMID: 12624601 DOI: 10.1067/mlc.2003.21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We recently demonstrated that neuronal nitric oxide synthase (nNOS) messenger RNA (mRNA) is markedly increased in the kidneys of diabetic rats and water-deprived rats. It can be inferred that high plasma glucose and osmolality and high renal tubular glucose and osmolality are somehow involving in renal NOS synthesis in diabetic rats. Phlorizin, a competitive inhibitor of glucose transport in the proximal tubule, causes renal glycosuria in nondiabetic rats and reverses hyperglycemia in diabetic rats. To further investigate whether high plasma glucose and osmolality or high renal tubular glucose and osmolality influence renal NOS synthesis in diabetic rats, we measured nNOS mRNA levels in phlorizin-treated normal and diabetic rats. Neuronal NOS mRNA expression in the kidneys was not significantly different between normal rats and phlorizin-treated normal rats with high urinary glucose and osmolality. The phlorizin-treated diabetic rats showed a significant decrease in the ratio of nNOS to beta-actin mRNA compared with diabetic rats. On linear-regression analysis, plasma glucose was strongly positively correlated with nNOS mRNA expression in the cortex, outer medulla, and inner medulla (r(2) =.378, r(2) =.680, and r(2) =.445, respectively) of rat kidneys. Neither urine glucose concentration nor urine osmolality was correlated with nNOS mRNA expression in rat kidneys. In conclusion, our results indicate that nNOS mRNA expression in the kidneys of diabetic rats is directly affected by high blood glucose/osmolality but not by high urinary glucose or osmolality.
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Affiliation(s)
- Ming-Chia Hsieh
- Department of Internal Medicine, Kaohsiung Medical University, Taiwan
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21
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Hawkins M, Gabriely I, Wozniak R, Reddy K, Rossetti L, Shamoon H. Glycemic control determines hepatic and peripheral glucose effectiveness in type 2 diabetic subjects. Diabetes 2002; 51:2179-89. [PMID: 12086948 DOI: 10.2337/diabetes.51.7.2179] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucose effectiveness is impaired in type 2 diabetes. We hypothesize that chronic hyperglycemia and hyperlipidemia contribute importantly to this defect. To test this hypothesis, we compared the effect of acute hyperglycemia on glucose turnover in type 2 diabetic subjects in good control (GC) (n = 14, age 51.7 +/- 3.7 years, BMI 28.4 +/- 1.0 kg/ m(2), HbA(1c) 5.9 +/- 0.2%) and poor control (PC) (n = 10, age 50.0 +/- 2.5 years, BMI 27.9 +/- 1.5 kg/m(2), HbA(1c) 9.9 +/- 0.6%) with age- and weight-matched nondiabetic subjects (ND) (n = 11, age 47.0 +/- 4.4 years, BMI 28.5 +/- 1.0 kg/m(2), HbA(1c) 5.1 +/- 0.2%). Fixed hormonal conditions were attained by infusing somatostatin for 6 h with replacement of basal insulin, glucagon, and growth hormone. Glucose fluxes ([3-(3)H]glucose) were compared during euglycemic (5 mmol/l, t = 180-240 min) and hyperglycemic (Hy) (10 mmol/l, t = 300-360 min, variable glucose infusion) clamp intervals. Acute hyperglycemia suppressed hepatic glucose production (GP) by 43% and increased peripheral glucose uptake (GU) by 86% in the ND subjects. Conversely, GP failed to suppress (-7%) and GU was suboptimally increased (+34%) in response to Hy in the PC group. However, optimal glycemic control was associated with normal glucose effectiveness in GC subjects (GP -38%, GU +72%; P > 0.05 for GC vs. ND). To determine whether short-term correction of hyperglycemia and/or hyperlipidemia is sufficient to reverse the impairment in glucose effectiveness, five PC subjects were restudied after 72 h of normoglycemia ( approximately 100 mg/dl; variable insulin infusions). These subjects regained normal effectiveness of glucose to suppress GP and stimulate GU and in response to Hy (GP -47%, GU + 71%; P > 0.05 vs. baseline studies). Thus, chronic hyperglycemia and/or hyperlipidemia contribute to impaired effectiveness of glucose in regulating glucose fluxes in type 2 diabetes and hence to worsening of the overall metabolic condition. Short-term normalization of plasma glucose might break the vicious cycle of impaired glucose effectiveness in type 2 diabetes.
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Affiliation(s)
- Meredith Hawkins
- Division of Endocrinology and Diabetes Research and Training Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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22
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Hawkins M, Gabriely I, Wozniak R, Vilcu C, Shamoon H, Rossetti L. Fructose improves the ability of hyperglycemia per se to regulate glucose production in type 2 diabetes. Diabetes 2002; 51:606-14. [PMID: 11872657 DOI: 10.2337/diabetes.51.3.606] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The ability of hyperglycemia per se to suppress endogenous glucose production (GP) is blunted in type 2 diabetes. This could be due in part to decreased glucose-induced flux through glucokinase (GK). Because fructose activates hepatic GK, we examined whether catalytic amounts of fructose could restore inhibition of GP by hyperglycemia in humans with type 2 diabetes. Glucose fluxes ([3-(3)H]glucose) were measured during euglycemia (5 mmol/l) and after abrupt onset of hyperglycemia (10 mmol/l; variable dextrose infusion) under fixed hormonal conditions (somatostatin infusion for 6 h with basal insulin/glucagon/growth hormone replacement). A total of 10 subjects with moderately controlled type 2 diabetes and 7 age- and BMI-matched nondiabetic subjects were studied on up to three separate occasions under the following conditions: without fructose (F(-)) or with infusion of fructose at two dosages: 0.6 mg/kg center dot min (low F) and 1.8 mg/kg center dot min (high F). Although GP failed to decrease in response to hyperglycemia in type 2 diabetes, the coinfusion of both doses of fructose was associated with comparable decreases in GP in response to hyperglycemia (low F = -27%, high F = -33%; P < 0.01 vs. F(-) at both dosages), which approached the 44% decline in GP observed without fructose in the nondiabetic subjects. GP responses to hyperglycemia were not altered by the addition of fructose in the nondiabetic group (low F = -47%, high F = -42%; P > 0.05 vs. F(-)). Thus, the administration of small amounts of fructose to type 2 diabetic subjects partially corrected the regulation of GP by hyperglycemia per se, yet did not affect this regulation in the nondiabetic subjects. This suggests that the liver's inability to respond to hyperglycemia in type 2 diabetes, likely caused by impaired GK activity, contributes substantially to the increased GP in these individuals.
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Affiliation(s)
- Meredith Hawkins
- Division of Endocrinology and Diabetes Research and Training Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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23
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Bischof MG, Bernroider E, Krssak M, Krebs M, Stingl H, Nowotny P, Yu C, Shulman GI, Waldhäusl W, Roden M. Hepatic glycogen metabolism in type 1 diabetes after long-term near normoglycemia. Diabetes 2002; 51:49-54. [PMID: 11756322 DOI: 10.2337/diabetes.51.1.49] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We tested the impact of long-term near normoglycemia (HbA(1c) <7% for >1 year) on glycogen metabolism in seven type 1 diabetic and seven matched nondiabetic subjects after a mixed meal. Glycemic profiles (6.2 +/- 0.10 vs. 5.9 +/- 0.07 mmol/l; P < 0.05) of diabetic patients were approximated to that of nondiabetic subjects by variable insulin infusion. Rates of hepatic glycogen synthesis and breakdown were calculated from the glycogen concentration time curves between 7:30 P.M. and 8:00 A.M. using in vivo (13)C nuclear magnetic resonance spectroscopy. Glucose production was determined with D-[6,6-(2)H(2)]glucose, and the hepatic uridine-diphosphate glucose pool was sampled with acetaminophen. Glycogen synthesis and breakdown as well as glucose production were identical in diabetic and healthy subjects: 7.3 +/- 0.9 vs. 7.1 +/- 0.7, 4.2 +/- 0.5 vs. 3.8 +/- 0.3, and 8.7 +/- 0.5 vs. 8.4 +/- 0.7 micromol x kg(-1) x min(-1), respectively. Although portal vein insulin concentrations were doubled, the flux through the indirect pathway of glycogen synthesis remained higher in type 1 diabetic subjects: approximately 70 vs. approximately 50%; P < 0.05. In conclusion, combined long- and short-term intensified insulin substitution normalizes rates of hepatic glycogen synthesis but not the contribution of gluconeogenesis to glycogen synthesis in type 1 diabetes.
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Affiliation(s)
- Martin G Bischof
- Division of Endocrinology and Metabolism, Department of Internal Medicine III, University of Vienna Medical School, Vienna, Austria
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Abstract
Obesity is a major cause of health complaints in western developed countries. Problems ranging from apnea to joint pain have been associated with excess weight. Many factors have been attributed to the epidemic of obesity including sedentary lifestyle, high-fat diets and consumption of large amounts of processed foods. Pharmacies and health-food store shelves abound with a vast selection of products promoted for weight-loss. Some of these have made headlines recently for the damaging effect they have on such things as cardiac valvular function. Unfortunately, others will probably follow and original data is presented on potentially dangerous natural products. Alternatives are presented and discussed below. These natural alternatives include such things as digestive enzyme inhibitors (e.g. L-arabinose, hibiscus tea, marine algae, Nomame Herba, etc), anorexics (e.g. monoterpenes such as d-limonene and perillyl alcohol), glucose-uptake inhibitors (e.g. phlorizin), and probiotics as adjuvants. These all-natural products are presented as some possible alternatives to those that could be potentially lethal and are not meant as the only options.
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Affiliation(s)
- M A Brudnak
- MAK Wood Inc, Grafton, Wisconsin 53024-9439, USA.
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25
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Kim JK, Zisman A, Fillmore JJ, Peroni OD, Kotani K, Perret P, Zong H, Dong J, Kahn CR, Kahn BB, Shulman GI. Glucose toxicity and the development of diabetes in mice with muscle-specific inactivation of GLUT4. J Clin Invest 2001; 108:153-60. [PMID: 11435467 PMCID: PMC353719 DOI: 10.1172/jci10294] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Using cre/loxP gene targeting, transgenic mice with muscle-specific inactivation of the GLUT4 gene (muscle GLUT4 KO) were generated and shown to develop a diabetes phenotype. To determine the mechanism, we examined insulin-stimulated glucose uptake and metabolism during hyperinsulinemic-euglycemic clamp in control and muscle GLUT4 KO mice before and after development of diabetes. Insulin-stimulated whole body glucose uptake was decreased by 55% in muscle GLUT4 KO mice, an effect that could be attributed to a 92% decrease in insulin-stimulated muscle glucose uptake. Surprisingly, insulin's ability to stimulate adipose tissue glucose uptake and suppress hepatic glucose production was significantly impaired in muscle GLUT4 KO mice. To address whether these latter changes were caused by glucose toxicity, we treated muscle GLUT4 KO mice with phloridzin to prevent hyperglycemia and found that insulin-stimulated whole body and skeletal muscle glucose uptake were decreased substantially, whereas insulin-stimulated glucose uptake in adipose tissue and suppression of hepatic glucose production were normal after phloridzin treatment. In conclusion, these findings demonstrate that a primary defect in muscle glucose transport can lead to secondary defects in insulin action in adipose tissue and liver due to glucose toxicity. These secondary defects contribute to insulin resistance and to the development of diabetes.
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Affiliation(s)
- J K Kim
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536-8012, USA
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26
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Cam MC, Brownsey RW, McNeill JH. Mechanisms of vanadium action: insulin-mimetic or insulin-enhancing agent? Can J Physiol Pharmacol 2001. [PMID: 11077984 DOI: 10.1139/y00-053] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The demonstration that the trace element vanadium has insulin-like properties in isolated cells and tissues and in vivo has generated considerable enthusiasm for its potential therapeutic value in human diabetes. However, the mechanisms by which vanadium induces its metabolic effects in vivo remain poorly understood, and whether vanadium directly mimics or rather enhances insulin effects is considered in this review. It is clear that vanadium treatment results in the correction of several diabetes-related abnormalities in carbohydrate and lipid metabolism, and in gene expression. However, many of these in vivo insulin-like effects can be ascribed to the reversal of defects that are secondary to hyperglycemia. The observations that the glucose-lowering effect of vanadium depends on the presence of endogenous insulin whereas metabolic homeostasis in control animals appears not to be affected, suggest that vanadium does not act completely independently in vivo, but augments tissue sensitivity to low levels of plasma insulin. Another crucial consideration is one of dose-dependency in that insulin-like effects of vanadium in isolated cells are often demonstrated at high concentrations that are not normally achieved by chronic treatment in vivo and may induce toxic side effects. In addition, vanadium appears to be selective for specific actions of insulin in some tissues while failing to influence others. As the intracellular active forms of vanadium are not precisely defined, the site(s) of action of vanadium in metabolic and signal transduction pathways is still unknown. In this review, we therefore examine the evidence for and against the concept that vanadium is truly an insulin-mimetic agent at low concentrations in vivo. In considering the effects of vanadium on carbohydrate and lipid metabolism, we conclude that vanadium acts not globally, but selectively and by enhancing, rather than by mimicking the effects of insulin in vivo.
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Affiliation(s)
- M C Cam
- Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The University of British Columbia,Vancouver, Canada
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27
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Chiu KC, Chuang LM, Yoon C, Saad MF. Hepatic glucokinase promoter polymorphism is associated with hepatic insulin resistance in Asian Indians. BMC Genet 2000; 1:2. [PMID: 11112984 PMCID: PMC29078 DOI: 10.1186/1471-2156-1-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2000] [Accepted: 11/16/2000] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The role of glucokinase (GCK) in the pathogenesis of maturity-onset diabetes of the young is well established. However, its role in the common form of type 2 diabetes is far from convincing. We investigated the role of the G-to-A polymorphism in the hepatic GCK promoter on insulin sensitivity and beta cell function in 63 normotensive Asian Indians with normal glucose tolerance. As proposed by Matsuda and DeFronzo, hepatic insulin sensitivity (ISIH) and total body insulin sensitivity (ISIM) were estimated from the oral glucose tolerance test. Beta cell function was estimated using %B from the Homeostasis Model Assessment and insulingenic index (dI/dG). RESULT We identified 38 GG, 24 GA, and one AA subjects. The AA subject was pooled with the GA subjects during the analysis. No difference was noted in the demographic features between the two genotypic groups (GG vs. GA/AA). Compared to the GG group, the GA/AA group had a lower ISIH (p=0.002), a lower ISIM (p=0.009), a higher %B (p=0.014), and a higher dI/dG (p=0.030). Multivariate analysis revealed that this polymorphism is an independent determinant for ISIH (p=0.019) and along with age, waist-hip ratio, gender, and diastolic blood pressure accounted for 51.5% of the variation of ISIH. However, this polymorphism was a weak, but independent determinant for ISIM (p=0.089) and %B (p=0.083). Furthermore, it had no independent effect on dI/dG (p=0.135). CONCLUSIONS These data suggest that the G-to-A polymorphism in the hepatic GCK promoter is associated with hepatic insulin resistance in Asian Indians.
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Affiliation(s)
- Ken C Chiu
- Division of Endocrinology, Diabetes and Hypertension (KCC, CY, MFS), Department of Medicine, University of California, Los Angeles, School of Medicine, Los Angeles, California, USA; Department of Internal Medicine and Graduate Institute of Clinical Medicine (LMC), National Taiwan University Hospital, Taipei, Taiwan
| | - Lee-Ming Chuang
- Division of Endocrinology, Diabetes and Hypertension (KCC, CY, MFS), Department of Medicine, University of California, Los Angeles, School of Medicine, Los Angeles, California, USA; Department of Internal Medicine and Graduate Institute of Clinical Medicine (LMC), National Taiwan University Hospital, Taipei, Taiwan
| | - Carol Yoon
- Division of Endocrinology, Diabetes and Hypertension (KCC, CY, MFS), Department of Medicine, University of California, Los Angeles, School of Medicine, Los Angeles, California, USA; Department of Internal Medicine and Graduate Institute of Clinical Medicine (LMC), National Taiwan University Hospital, Taipei, Taiwan
| | - Mohammad F Saad
- Division of Endocrinology, Diabetes and Hypertension (KCC, CY, MFS), Department of Medicine, University of California, Los Angeles, School of Medicine, Los Angeles, California, USA; Department of Internal Medicine and Graduate Institute of Clinical Medicine (LMC), National Taiwan University Hospital, Taipei, Taiwan
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Lieth E, LaNoue KF, Antonetti DA, Ratz M. Diabetes reduces glutamate oxidation and glutamine synthesis in the retina. The Penn State Retina Research Group. Exp Eye Res 2000; 70:723-30. [PMID: 10843776 DOI: 10.1006/exer.2000.0840] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Retinas of diabetic individuals develop early functional changes measurable by electrophysiological and psychometric testing. Using a rat model of diabetes, we previously identified diabetes-induced alterations in metabolism of the neurotransmitter glutamate which may ultimately lead to accumulation of glutamate in the retina (Diabetes, 47: 815, 1998). We therefore investigated the function of enzymes that mediate the synthesis and breakdown of glutamate in retinas from rats made diabetic by injection of streptozotocin. De novo synthesis of nitrogen-containing amino acids including glutamate, glutamine and aspartate was assessed by measuring the rate of carbon fixation in freshly dissected retinas, and was unchanged by diabetes. In contrast, the oxidation of glutamate was significantly reduced in retinas from diabetic rats (62%, P < 0.05). Furthermore, diabetic retinas were less susceptible to inhibition of glutamate oxidation by the transaminase inhibitor aminoxyacetate (80%, N.S.), compared to the significant decrease seen in control rats (61%, P < 0.001). The activity and content of glutamine synthetase were also significantly reduced in retinas from rats diabetic for 2-6 months [range of 48% (P < 0.005) to 83% (P < 0.05) compared to control]. The activity of glutamine synthetase was normalized by acute injections of insulin, but not by reducing blood sugar levels with injections of phlorizin. These results indicate two enzymatic abnormalities in the glutamate metabolism pathway in the retina during diabetes: transamination to alpha-ketoglutarate and amination to glutamine. The reduced flux through these pathways may be associated with the accumulation of glutamate. These results are also consistent with the possibility that some of the glial changes in the retina during diabetes may be caused by hypoinsulinemia rather than hyperglycemia.
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Affiliation(s)
- E Lieth
- Department of Neuroscience and Anatomy, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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Nawano M, Oku A, Ueta K, Umebayashi I, Ishirahara T, Arakawa K, Saito A, Anai M, Kikuchi M, Asano T. Hyperglycemia contributes insulin resistance in hepatic and adipose tissue but not skeletal muscle of ZDF rats. Am J Physiol Endocrinol Metab 2000; 278:E535-43. [PMID: 10710509 DOI: 10.1152/ajpendo.2000.278.3.e535] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine the contribution of hyperglycemia to the insulin resistance in various insulin-sensitive tissues of Zucker diabetic fatty (ZDF) rats, T-1095, an oral sodium-dependent glucose transporter (SGLT) inhibitor, was administered by being mixed into food. Long-term treatment with T-1095 lowered both fed and fasting blood glucose levels to near normal ranges. A hyperinsulinemic euglycemic clamp study that was performed after 4 wk of T-1095 treatment demonstrated partial recovery of the reduced glucose infusion rate (GIR) in the T-1095-treated group. In the livers of T-1095-treated ZDF rats, hepatic glucose production rate (HGP) and glucose utilization rate (GUR) showed marked recovery, with almost complete normalization of reduced glucokinase/glucose-6-phosphatase (G-6-Pase) activities ratio. In adipose tissues, decreased GUR was also shown to be significantly improved with a normalization of insulin-induced GLUT-4 translocation. In contrast, in skeletal muscles, the reduced GUR was not significantly improved in response to amelioration of hyperglycemia by T-1095 treatment. These results suggest that the contribution of hyperglycemia to insulin resistance in ZDF rats is very high in the liver and considerably elevated in adipose tissues, although it is very low in skeletal muscle.
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Affiliation(s)
- M Nawano
- Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan
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30
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Tsujihara K, Hongu M, Saito K, Kawanishi H, Kuriyama K, Matsumoto M, Oku A, Ueta K, Tsuda M, Saito A. Na(+)-glucose cotransporter (SGLT) inhibitors as antidiabetic agents. 4. Synthesis and pharmacological properties of 4'-dehydroxyphlorizin derivatives substituted on the B ring. J Med Chem 1999; 42:5311-24. [PMID: 10639275 DOI: 10.1021/jm990175n] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In our studies of Na(+)-glucose cotransporter (SGLT) inhibitors as antidiabetic agents, a series of novel 4'-dehydroxyphlorizin derivatives substituted on the B ring was prepared and their effects on urinary glucose excretion were evaluated in rats. Introduction of only a small alkyl group at the 4'-position increased the activity, and 3-(benzo¿bfuran-5-yl)-2',6'-dihydroxy-4'-methylpropiophenone 2'-O-beta-D-glucopyranoside (4) showed the most potent effect. To overcome hydrolysis of compound 4 by beta-glucosidase in the digestive tract, the OH groups on the glucose moiety of compound 4 were modified. Three prodrugs (5, 42, and 55) were more potent than the parent compound 4 by oral administration, and finally 3-(benzo¿bfuran-5-yl)-2',6'-dihydroxy-4'-methylpropiophenone 2'-O-(6-O-methoxycarbonyl-beta-D-glucopyranoside) (5) was selected as a new promising candidate. Compound 5 was metabolized mainly by liver esterase to the active form (4), which was about 10 times more potent than 5 in inhibiting SGLT. In oral glucose tolerance test in db/db mice, compound 5 dose-dependently suppressed the elevation of glucose levels. Single administration of 5 reduced hyperglycemia concurrently with increase of glucose excretion into urine in diabetic KK-A(y) mice. Furthermore, compound 5 suppressed the elevation of blood glucose levels but did not lower it below the normal level even in fasted conditions in KK-A(y) mice. Additionally, long-term treatment with 5 dose-dependently reduced hyperglycemia and HbA1c in KK-A(y) mice. These pharmacological data strongly suggest that compound 5 has a therapeutic potential in the treatment of NIDDM.
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Affiliation(s)
- K Tsujihara
- Discovery Research Laboratory, Tanabe Seiyaku Company, Ltd., 2-2-50, Kawagishi, Toda, Saitama 335-8505, Japan
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31
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Reul BA, Amin SS, Buchet JP, Ongemba LN, Crans DC, Brichard SM. Effects of vanadium complexes with organic ligands on glucose metabolism: a comparison study in diabetic rats. Br J Pharmacol 1999; 126:467-77. [PMID: 10077240 PMCID: PMC1565819 DOI: 10.1038/sj.bjp.0702311] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Vanadium compounds can mimic actions of insulin through alternative signalling pathways. The effects of three organic vanadium compounds were studied in non-ketotic, streptozotocin-diabetic rats: vanadyl acetylacetonate (VAc), vanadyl 3-ethylacetylacetonate (VEt), and bis(maltolato)oxovanadium (VM). A simple inorganic vanadium salt, vanadyl sulphate (VS) was also studied. 2. Oral administration of the three organic vanadium compounds (125 mg vanadium element 1(-1) in drinking fluids) for up to 3 months induced a faster and larger fall in glycemia (VAc being the most potent) than VS. Glucosuria and tolerance to a glucose load were improved accordingly. 3. Activities and mRNA levels of key glycolytic enzymes (glucokinase and L-type pyruvate kinase) which are suppressed in the diabetic liver, were restored by vanadium treatment. The organic forms showed greater efficacy than VS, especially VAc. 4. VAc rats exhibited the highest levels of plasma or tissue vanadium, most likely due to a greater intestinal absorption. However, VAc retained its potency when given as a single i.p. injection to diabetic rats. Moreover, there was no relationship between plasma or tissue vanadium levels and any parameters of glucose homeostasis and hepatic glucose metabolism. Thus, these data suggest that differences in potency between compounds are due to differences in their insulin-like properties. 5. There was no marked toxicity observed on hepatic or renal function. However, diarrhoea occurred in 50% of rats chronically treated with VS, but not in those receiving the organic compounds. 6. In conclusion, organic vanadium compounds, in particular VAc, correct the hyperglycemia and impaired hepatic glycolysis of diabetic rats more safely and potently than VS. This is not simply due to improved intestinal absorption, indicating more potent insulin-like properties.
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Affiliation(s)
- B A Reul
- Endocrinology and Metabolism Unit, UCL 5530 AV Hippocrate 55, Brussels, Belgium
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Burcelin R, Mrejen C, Decaux JF, De Mouzon SH, Girard J, Charron MJ. In vivo and in vitro regulation of hepatic glucagon receptor mRNA concentration by glucose metabolism. J Biol Chem 1998; 273:8088-93. [PMID: 9525910 DOI: 10.1074/jbc.273.14.8088] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have recently cloned the murine glucagon receptor (GR) gene and shown that it is expressed mainly in liver. In this organ, the glucagon-GR system is involved in the control of glucose metabolism as it initiates a cascade of events leading to release of glucose into the blood stream, which is a main feature in several physiological and pathological conditions. To better define the metabolic regulators of GR expression in liver we analyzed GR mRNA concentration in physiological conditions associating various glucose metabolic pathways in vivo and in vitro in the rat and in the mouse. First, we report that the concentration of the GR mRNA progressively increased from the first day of life to the adult stage. This effect was abolished when newborn rodents were fasted. Second, under conditions where intrahepatic glucose metabolism was active such as during fasting, diabetes, and hyperglycemic clamp, the concentration of GR mRNA increased independent of the origin of the pathway that generated the glucose flux. These effects were blunted when hyperglycemia was corrected by phlorizin treatment of diabetic rats or not sustained during euglycemic clamp. In accordance with these observations, we demonstrated that the glycolytic substrates glucose, mannose, and fructose, as well as the gluconeognic substrates glycerol and dihydroxyacetone, increased the concentration of GR mRNA in primary cultures of hepatocytes from fed rats. Glucagon blunted the effect of glucose without being dominant. The stimulatory effect of those substrates was not mimicked by the nonmetabolizable carbohydrate L-glucose or the glucokinase inhibitor glucosamine or when hepatocytes were isolated from starved rats. In addition, inhibitors of gluconeogenesis and lipolysis could decrease the concentration of GR mRNA from hepatocytes of starved rats. Combined, these data strongly suggest that glucose flux in the glycolytic and gluconeogenic pathways at the level of triose intermediates could control expression of GR mRNA and participate in controlling its own metabolism.
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Affiliation(s)
- R Burcelin
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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34
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Takenoshita M, Yamaji R, Inui H, Miyatake K, Nakano Y. Suppressive effect of insulin on the synthesis of sucrase-isomaltase complex in small intestinal epithelial cells, and abnormal increase in the complex under diabetic conditions. Biochem J 1998; 329 ( Pt 3):597-600. [PMID: 9445387 PMCID: PMC1219081 DOI: 10.1042/bj3290597] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An abnormally high level of the sucrase-isomaltase (SI) complex in the small intestine of rats with streptozotocin-induced insulin-dependent diabetes mellitus (IDDM) was normalized in 11 h by the administration of insulin, in addition to normalization of the blood glucose level. Phlorizin, an inhibitor of renal glucose reabsorption, also caused normalization of the blood glucose level in the IDDM rats; however, the level of the SI complex was barely changed. When mucosa explants were cultured in a medium, the SI complex synthesized during the cultivation was accumulated as its precursor protein without maturation, owing to the absence of pancreatic proteases, and the amount of the precursor protein that accumulated in the explants was decreased by the addition of insulin into the medium. Further, the mRNA level of the SI complex in the explants incubated with insulin was obviously lower than that in the absence of insulin. These results indicate that insulin has a suppressive effect on the synthesis of the SI complex, presumably by decreasing the transcriptional level of the gene encoding the complex, in small-intestinal epithelial cells. Thus the synthesis of the SI complex might exceed normal levels in the epithelial cells as a direct result of the depletion of insulin under IDDM conditions.
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Affiliation(s)
- M Takenoshita
- Department of Applied Biological Chemistry, Osaka Prefecture University, Japan
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35
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Wakisaka M, Yoshinari M, Yamamoto M, Nakamura S, Asano T, Himeno T, Ichikawa K, Doi Y, Fujishima M. Na+-dependent glucose uptake and collagen synthesis by cultured bovine retinal pericytes. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1362:87-96. [PMID: 9434103 DOI: 10.1016/s0925-4439(97)00071-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study was performed to clarify the presence of sodium-dependent glucose uptake and its role in the synthesis of type IV and type VI collagen by cultured bovine retinal pericytes. The glucose uptake by retinal pericytes and retinal endothelial cells was measured using 3H-D-glucose in the presence or absence of sodium. Glucose uptake in the presence of sodium was twice as high as that observed in the presence of phlorizin and sodium or in the absence of sodium. Sodium-dependent glucose uptake was observed at different sodium concentrations, and its half-maximal stimulation occurred at 48 mM. These findings were not observed in retinal endothelial cells. Levels of type IV and type VI collagen produced by retinal pericytes were significantly increased at glucose concentrations higher than 20 mM. Phlorizin decreased both collagen synthesis and glucose consumption by retinal pericytes incubated with 30 mM of glucose to the levels observed with 5 mM of glucose. These data suggest that sodium-dependent glucose uptake is present in retinal pericytes and that excessive glucose entry into the cell is an important factor for overproduction of collagen. Phlorizin normalized the synthesis of type IV and type VI collagen with decreasing glucose consumption under high glucose conditions.
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Affiliation(s)
- M Wakisaka
- Second Department of Internal Medicine, Kyushu University, Fukuoka City, Japan
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36
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Rencurel F, Waeber G, Bonny C, Antoine B, Maulard P, Girard J, Leturque A. cAMP prevents the glucose-mediated stimulation of GLUT2 gene transcription in hepatocytes. Biochem J 1997; 322 ( Pt 2):441-8. [PMID: 9065761 PMCID: PMC1218210 DOI: 10.1042/bj3220441] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glucose homoeostasis necessitates the presence in the liver of the high Km glucose transporter GLUT2. In hepatocytes, we and others have demonstrated that glucose stimulates GLUT2 gene expression in vivo and in vitro. This effect is transcriptionally regulated and requires glucose metabolism within the hepatocytes. In this report, we further characterized the cis-elements of the murine GLUT2 promoter, which confers glucose responsiveness on a reporter gene coding the chloramphenicol acetyl transferase (CAT) gene. 5'-Deletions of the murine GLUT2 promoter linked to the CAT reporter gene were transfected into a GLUT2 expressing hepatoma cell line (mhAT3F) and into primary cultured rat hepatocytes, and subsequently incubated at low and high glucose concentrations. Glucose stimulates gene transcription in a manner similar to that observed for the endogenous GLUT2 mRNA in both cell types; the -1308 to -212 bp region of the promoter contains the glucose-responsive elements. Furthermore, the -1308 to -338 bp region of the promoter contains repressor elements when tested in an heterologous thymidine kinase promoter. The glucose-induced GLUT2 mRNA accumulation was decreased by dibutyryl-cAMP both in mhAT3F cells and in primary hepatocytes. A putative cAMP-responsive element (CRE) is localized at the -1074/-1068 bp region of the promoter. The inhibitory effect of cAMP on GLUT2 gene expression was observed in hepatocytes transfected with constructs containing this CRE (-1308/+49 bp fragment), as well as with constructs not containing the consensus CRE (-312/+49 bp fragment). This suggests that the inhibitory effect of cAMP is not mediated by the putative binding site located in the repressor fragment of the GLUT2 promoter. Taken together, these data demonstrate that the elements conferring glucose and cAMP responsiveness on the GLUT2 gene are located within the -312/+49 region of the promoter.
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Affiliation(s)
- F Rencurel
- Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, C.N.R.S. UPR 1511, Meudon-Bellevue, France
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37
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Rencurel F, Waeber G, Antoine B, Rocchiccioli F, Maulard P, Girard J, Leturque A. Requirement of glucose metabolism for regulation of glucose transporter type 2 (GLUT2) gene expression in liver. Biochem J 1996; 314 ( Pt 3):903-9. [PMID: 8615787 PMCID: PMC1217142 DOI: 10.1042/bj3140903] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Previous studies have shown that glucose increases the glucose transporter (GLUT2) mRNA expression in the liver in vivo and in vitro. Here we report an analysis of the effects of glucose metabolism on GLUT2 gene expression. GLUT2 mRNA accumulation by glucose was not due to stabilization of its transcript but rather was a direct effect on gene transcription. A proximal fragment of the 5' regulatory region of the mouse GLUT2 gene linked to a reporter gene was transiently transfected into liver GLUT2-expressing cells. Glucose stimulated reporter gene expression in these cells, suggesting that glucose-responsive elements were included within the proximal region of the promoter. A dose-dependent effect of glucose on GLUT2 expression was observed over 10 mM glucose irrespective of the hexokinase isozyme (glucokinase K(m) 16 mM; hexokinase I K(m) 0.01 mM) present in the cell type used. This suggests that the correlation between extracellular glucose and GLUT2 mRNA concentrations is simply a reflection of an activation of glucose metabolism. The mediators and the mechanism responsible for this response remain to be determined. In conclusion, glucose metabolism is required for the proper induction of the GLUT2 gene in the liver and this effect is transcriptionally regulated.
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Affiliation(s)
- F Rencurel
- Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, Meudon, France
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Ozcelikay AT, Becker DJ, Ongemba LN, Pottier AM, Henquin JC, Brichard SM. Improvement of glucose and lipid metabolism in diabetic rats treated with molybdate. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:E344-52. [PMID: 8779958 DOI: 10.1152/ajpendo.1996.270.2.e344] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Molybdenum mimics certain insulin actions in vitro. We have investigated the effects of oral administration of Na2MoO4 (Mo) for 8 wk on carbohydrate and lipid metabolism in streptozotocin-diabetic rats. Mo decreased hyperglycemia and glucosuria by 75% and corrected the elevation of plasma nonesterified fatty acids. Tolerance to glucose loads was improved, and glycogen stores were replenished. These effects were not due to a rise of insulinemia. In liver, Mo restored the blunted mRNA and activity of glucokinase and pyruvate kinase and decreased to normal phosphoenolpyruvate carboxykinase values. Finally, Mo totally reversed the low expression and activity of acetyl-CoA carboxylase and fatty acid synthase in liver, but not in white adipose tissue. In conclusion, Mo exerts a marked blood glucose-lowering effect in diabetic rats by an insulin-like action. This effect results in part from a restoration of hepatic glucose metabolism and is associated with a tissue-specific correction of lipogenic enzyme gene expression, both processes being essentially mediated by reversal of impaired pretranslational regulatory mechanisms. These observations raise new therapeutic perspectives in diabetes, particularly in the insulin-resistant condition.
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Affiliation(s)
- A T Ozcelikay
- Endocrinology and Metabolism Unit, Faculty of Medicine, University of Louvain, Brussels, Belgium
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39
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Becker DJ, Reul B, Ozcelikay AT, Buchet JP, Henquin JC, Brichard SM. Oral selenate improves glucose homeostasis and partly reverses abnormal expression of liver glycolytic and gluconeogenic enzymes in diabetic rats. Diabetologia 1996; 39:3-11. [PMID: 8720597 DOI: 10.1007/bf00400407] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Selenium is a trace element that exerts certain insulin-like actions in vitro. In this study, we evaluated its in vivo effects on the glucose homeostasis of rats made diabetic and insulin-deficient by streptozotocin. Na2SeO4 was administered ad libitum in drinking water and/or food for 10 weeks. The elevated plasma glucose levels (approximately 25 mmol/l) and glucosuria (approximately 85 mmol/day) of untreated rats were decreased by 50 and 80%, respectively, by selenate treatment. The beneficial effect of selenate was also evident during oral and intravenous glucose tolerance tests: the integrated glucose responses were decreased by 40-50% as compared to those in untreated rats. These effects were not due to an increase in plasma insulin levels. Compared to non-diabetic rats, pancreatic insulin reserves were reduced by more than 90% in treated and untreated diabetic rats. The hepatic activities and mRNA levels of two key glycolytic enzymes, glucokinase and L-type pyruvate kinase were blunted in diabetic rats. They increased approximately two- to threefold after selenate treatment, to reach 40-75% of the values in non-diabetic rats. In contrast, elevated activity and mRNA levels of the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, were reduced by 40-65% after selenate administration. Since selenate induced a moderate decrease in body weight due to an anorexigenic effect, we checked that there was no improvement of glucose homeostasis or hepatic glucose metabolism in an additional group of calorie-restricted diabetic rats, which was weight-matched with the selenate group. In addition, no obvious toxic side-effects on the kidney or liver were observed in the rats receiving selenate. In conclusion, selenate induces a sustained improvement of glucose homeostasis in streptozotocin-diabetic rats by an insulin-like action, which involves partial correction of altered pretranslational regulatory mechanisms in liver metabolism.
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Affiliation(s)
- D J Becker
- Endocrinology and Metabolism Unit, University of Louvain, Brussels, Belgium
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Brichard SM. Effects of vanadate on the expression of genes involved in fuel homeostasis in animal models of Type I and Type II diabetes. Mol Cell Biochem 1995; 153:121-4. [PMID: 8927026 DOI: 10.1007/bf01075926] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Vanadium is a trace element that has raised increasing interest in diabetology since the discovery of its insulin-like properties in vitro and in vivo. This brief article reviews the most recent data concerning the beneficial effects of vanadium compounds on fuel homeostasis in animal models of insulinopenic (Type I) or insulin-resistant (Type II) diabetes. These studies open obvious therapeutic possibilities in diabetes, and more particularly, in states of insulin resistance.
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Affiliation(s)
- S M Brichard
- Faculty of Medicine, University of Louvain, Brussels, Belgium
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Brichard SM, Ongemba LN, Girard J, Henquin JC. Tissue-specific correction of lipogenic enzyme gene expression in diabetic rats given vanadate. Diabetologia 1994; 37:1065-72. [PMID: 7867878 DOI: 10.1007/bf00418369] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Vanadium is a potent insulinomimetic agent. In vivo, its blood glucose lowering action in insulin-deficient diabetic rats is associated with corrected expression of genes involved in hepatic glucose metabolism. In this study, we investigated whether vanadate treatment also reverses the impaired expression of genes coding for key enzymes of lipogenesis in diabetic liver and white adipose tissue. Oral administration of vanadate to streptozotocin-rats caused a 55% fall in plasma glucose levels after feeding without modifying low insulinaemia. It also partially corrected the low thyroid hormone concentrations. In untreated diabetic animals, hepatic mRNA levels of acetyl-CoA carboxylase and fatty acid synthase were reduced by more than 80 and 90%, respectively, in close correlation with changes in enzyme activities. Three weeks of vanadate treatment totally restored acetyl-CoA carboxylase mRNA and partially restored fatty acid synthase mRNA (71% of control levels). The activities of both lipogenic enzymes were increased 3.5 to 4-fold, to reach 45 to 65% of control values. By contrast, in white adipose tissue, vanadate modified neither expression nor activity of both lipogenic enzymes, which remained blunted (< 10% of control levels). In conclusion, vanadate treatment partially restores the activities of two key lipogenic enzymes in liver, but not in white adipose tissue, of diabetic rats. This correction results from a reversal of impaired pre-translational regulatory mechanisms possibly mediated by an improvement of thyroid function and a selective restoration of liver glycolytic flux.
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Affiliation(s)
- S M Brichard
- Unité d'Endocrinologie et Métabolisme, University of Louvain, Faculty of Medicine, Brussels, Belgium
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Mick GJ, Hingre K, Benedict M, McCormick KL. Persistence of disturbed adipocyte metabolism in streptozocin-induced diabetic rats despite near-euglycemia with phlorizin. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1226:315-22. [PMID: 8054363 DOI: 10.1016/0925-4439(94)90043-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
It is widely accepted that hyperglycemia per se incites and perpetuates the diabetic state by adverse effects on beta cell insulin secretion and peripheral insulin action. Examination of the latter locus has revealed glucose-related abnormalities in facilitated glucose transport. Beyond the plasma membrane, however, there is scant data examining whether hyperglycemia influences important intracellular metabolic events. We recently described a sizable reduction in post-transport, in situ metabolism in permeabilized fat cells from streptozocin-induced diabetic rats. Of importance, the diabetes-related deficit was entirely ameliorated by insulin therapy. In this study we examined whether hyperglycemia per se contributes to this altered intracellular metabolic effect. By infusing phlorizin, near euglycemia was achieved for at least four days in streptozocin-induced diabetic rats. The phlorizin-treated diabetic rats had improved (intact cell) rates of insulin-stimulated 2-deoxyglucose uptake. Despite this, permeabilized fat cell studies revealed no improvement or deterioration in diabetic intracellular metabolism as measured by both the oxidation of [6-14C]glucose-6-phosphate via the citric acid cycle or its incorporation into triglyceride. We conclude that hypoinsulinemia, and not hyperglycemia, mediates the disturbance in porous diabetic adipocyte cellular metabolism.
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Affiliation(s)
- G J Mick
- Medical College of Wisconsin, Department of Pediatrics, MACC Fund Research Center, Milwaukee 53226
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