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Azimian L, Weerasuriya NM, Munasinghe R, Song S, Lin CY, You L. Investigating the effects of Ceylon cinnamon water extract on HepG2 cells for Type 2 diabetes therapy. Cell Biochem Funct 2023; 41:254-267. [PMID: 36779418 DOI: 10.1002/cbf.3778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Revised: 01/17/2023] [Accepted: 01/17/2023] [Indexed: 02/14/2023]
Abstract
Cinnamon and its extracts have been used as herbal remedies for many ailments, including for reducing insulin resistance and diabetes complications. Type 2 diabetes mellitus (T2DM) is a rapidly growing health concern around the world. Although many drugs are available for T2DM treatment, side effects and costs can be considerable, and there is increasing interest in natural products for managing chronic health conditions. Cinnamon may decrease the expression of genes associated with T2DM risk. The purpose of this study was to evaluate the effects of cinnamon water extract (CWE) compared with metformin on T2DM-related gene expression. HepG2 human hepatoma cells, widely used in drug metabolism and hepatotoxicity studies, were treated with different concentrations of metformin or CWE for 24 or 48 h. Cell viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and glucose uptake was compared in untreated and CWE- or metformin-treated cells under high-glucose conditions. Finally, total RNA was extracted and analyzed by RNA sequencing (RNA-seq), and bioinformatics analyses were performed to compare the transcriptional effects of CWE and metformin. We found cell viability was better in cells treated with CWE than in metformin-treated cells, demonstrating that CWE was not toxic at tested doses. CWE significantly increased glucose uptake in HepG2 cells, to the same degree as metformin (1.4-fold). RNA-seq data revealed CWE and metformin both induced significantly increased (1.3- to 1.4-fold) glucose uptake gene expression compared with untreated controls. Transcriptional differences between CWE and metformin were not significant. The effects of 0.125 mg mL-1 CWE on gene expression were comparable to 1.5 mg mL-1 (9.5 mM) metformin. In addition, gene expression at 0.125 mg mL-1 CWE was comparable to 1.5 mg mL-1 (9.5 mM) metformin. Our results reveal that CWE's effects on cell viability, glucose uptake, and gene expression in HepG2 cells are comparable to those of metformin, suggesting CWE may be an effective dietary supplement for mitigating T2DM-related metabolic dysfunction.
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Affiliation(s)
- Leila Azimian
- Department of Mechanical and Industrial Engineering, The University of Toronto, Toronto, Ontario, Canada
| | | | | | - Suzie Song
- Department of Mechanical and Industrial Engineering, The University of Toronto, Toronto, Ontario, Canada
| | - Chun-Yu Lin
- Institute of Biomedical Engineering, The University of Toronto, Toronto, Ontario, Canada
| | - Lidan You
- Department of Mechanical and Industrial Engineering, The University of Toronto, Toronto, Ontario, Canada.,Institute of Biomedical Engineering, The University of Toronto, Toronto, Ontario, Canada
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2
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Yang L, Fye MA, Yang B, Tang Z, Zhang Y, Haigh S, Covington BA, Bracey K, Taraska JW, Kaverina I, Qu S, Chen W. Genome-wide CRISPR screen identified a role for commander complex mediated ITGB1 recycling in basal insulin secretion. Mol Metab 2022; 63:101541. [PMID: 35835371 PMCID: PMC9304790 DOI: 10.1016/j.molmet.2022.101541] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/30/2022] [Accepted: 07/01/2022] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVES Pancreatic beta cells secrete insulin postprandially and during fasting to maintain glucose homeostasis. Although glucose-stimulated insulin secretion (GSIS) has been extensively studied, much less is known about basal insulin secretion. Here, we performed a genome-wide CRISPR/Cas9 knockout screen to identify novel regulators of insulin secretion. METHODS To identify genes that cell autonomously regulate insulin secretion, we engineered a Cas9-expressing MIN6 subclone that permits irreversible fluorescence labeling of exocytic insulin granules. Using a fluorescence-activated cell sorting assay of exocytosis in low glucose and high glucose conditions in individual cells, we performed a genome-wide CRISPR/Cas9 knockout screen. RESULTS We identified several members of the COMMD family, a conserved family of proteins with central roles in intracellular membrane trafficking, as positive regulators of basal insulin secretion, but not GSIS. Mechanistically, we show that the Commander complex promotes insulin granules docking in basal state. This is mediated, at least in part, by its function in ITGB1 recycling. Defective ITGB1 recycling reduces its membrane distribution, the number of focal adhesions and cortical ELKS-containing complexes. CONCLUSIONS We demonstrated a previously unknown function of the Commander complex in basal insulin secretion. We showed that by ITGB1 recycling, Commander complex increases cortical adhesions, which enhances the assembly of the ELKS-containing complexes. The resulting increase in the number of insulin granules near the plasma membrane strengthens basal insulin secretion.
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Affiliation(s)
- Liu Yang
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai 200072, China; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Margret A Fye
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Bingyuan Yang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Zihan Tang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Yue Zhang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Sander Haigh
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Brittney A Covington
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Kai Bracey
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Justin W Taraska
- Biochemistry and Biophysics Center, NHLBI, NIH, Bethesda, MD 20892, USA
| | - Irina Kaverina
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Shen Qu
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai 200072, China.
| | - Wenbiao Chen
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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3
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Emfinger CH, de Klerk E, Schueler KL, Rabaglia ME, Stapleton DS, Simonett SP, Mitok KA, Wang Z, Liu X, Paulo JA, Yu Q, Cardone RL, Foster HR, Lewandowski SL, Perales JC, Kendziorski CM, Gygi SP, Kibbey RG, Keller MP, Hebrok M, Merrins MJ, Attie AD. β Cell-specific deletion of Zfp148 improves nutrient-stimulated β cell Ca2+ responses. JCI Insight 2022; 7:e154198. [PMID: 35603790 PMCID: PMC9220824 DOI: 10.1172/jci.insight.154198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 04/20/2022] [Indexed: 12/05/2022] Open
Abstract
Insulin secretion from pancreatic β cells is essential for glucose homeostasis. An insufficient response to the demand for insulin results in diabetes. We previously showed that β cell-specific deletion of Zfp148 (β-Zfp148KO) improves glucose tolerance and insulin secretion in mice. Here, we performed Ca2+ imaging of islets from β‑Zfp148KO and control mice fed both a chow and a Western-style diet. β-Zfp148KO islets demonstrated improved sensitivity and sustained Ca2+ oscillations in response to elevated glucose levels. β-Zfp148KO islets also exhibited elevated sensitivity to amino acid-induced Ca2+ influx under low glucose conditions, suggesting enhanced mitochondrial phosphoenolpyruvate-dependent (PEP-dependent), ATP-sensitive K+ channel closure, independent of glycolysis. RNA-Seq and proteomics of β-Zfp148KO islets revealed altered levels of enzymes involved in amino acid metabolism (specifically, SLC3A2, SLC7A8, GLS, GLS2, PSPH, PHGDH, and PSAT1) and intermediary metabolism (namely, GOT1 and PCK2), consistent with altered PEP cycling. In agreement with this, β-Zfp148KO islets displayed enhanced insulin secretion in response to l-glutamine and activation of glutamate dehydrogenase. Understanding pathways controlled by ZFP148 may provide promising strategies for improving β cell function that are robust to the metabolic challenge imposed by a Western diet.
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Affiliation(s)
| | | | - Kathryn L. Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Mary E. Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Donnie S. Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Shane P. Simonett
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kelly A. Mitok
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Ziyue Wang
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Durham, North Carolina, USA
| | - Xinyue Liu
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Joao A. Paulo
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Qing Yu
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Rebecca L. Cardone
- Department of Internal Medicine (Endocrinology), Yale University, New Haven, Connecticut, USA
| | - Hannah R. Foster
- Department of Medicine, Division of Endocrinology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Sophie L. Lewandowski
- Department of Medicine, Division of Endocrinology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - José C. Perales
- Department of Physiological Sciences, School of Medicine, University of Barcelona, L’Hospitalet del Llobregat, Barcelona, Spain
| | - Christina M. Kendziorski
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Steven P. Gygi
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Richard G. Kibbey
- Department of Internal Medicine (Endocrinology), Yale University, New Haven, Connecticut, USA
- Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, USA
| | - Mark P. Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | | | - Matthew J. Merrins
- Department of Medicine, Division of Endocrinology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin, USA
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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4
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Bian Y, Hou W, Chen X, Fang J, Xu N, Ruan BH. Glutamate Dehydrogenase as a Promising Target for Hyperinsulinism Hyperammonemia Syndrome Therapy. Curr Med Chem 2021; 29:2652-2672. [PMID: 34525914 DOI: 10.2174/0929867328666210825105342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 11/22/2022]
Abstract
Hyperinsulinism-hyperammonemia syndrome (HHS) is a rare disease characterized by recurrent hypoglycemia and persistent elevation of plasma ammonia, and it can lead to severe epilepsy and permanent brain damage. It has been demonstrated that functional mutations of glutamate dehydrogenase (GDH), an enzyme in the mitochondrial matrix, are responsible for the HHS. Thus, GDH has become a promising target for the small molecule therapeutic intervention of HHS. Several medicinal chemistry studies are currently aimed at GDH, however, to date, none of the compounds reported has been entered clinical trials. This perspective summarizes the progress in the discovery and development of GDH inhibitors, including the pathogenesis of HHS, potential binding sites, screening methods, and research models. Future therapeutic perspectives are offered to provide a reference for discovering potent GDH modulators and encourage additional research that will provide more comprehensive guidance for drug development.
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Affiliation(s)
- Yunfei Bian
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Wei Hou
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Xinrou Chen
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Jinzhang Fang
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Ning Xu
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Benfang Helen Ruan
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
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5
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Mathioudakis L, Bourbouli M, Daklada E, Kargatzi S, Michaelidou K, Zaganas I. Localization of Human Glutamate Dehydrogenases Provides Insights into Their Metabolic Role and Their Involvement in Disease Processes. Neurochem Res 2018; 44:170-187. [PMID: 29943084 DOI: 10.1007/s11064-018-2575-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 06/11/2018] [Accepted: 06/13/2018] [Indexed: 12/21/2022]
Abstract
Glutamate dehydrogenase (GDH) catalyzes the reversible deamination of L-glutamate to α-ketoglutarate and ammonia. In mammals, GDH contributes to important processes such as amino acid and carbohydrate metabolism, energy production, ammonia management, neurotransmitter recycling and insulin secretion. In humans, two isoforms of GDH are found, namely hGDH1 and hGDH2, with the former being ubiquitously expressed and the latter found mainly in brain, testis and kidney. These two iso-enzymes display highly divergent allosteric properties, especially concerning their basal activity, ADP activation and GTP inhibition. On the other hand, both enzymes are thought to predominantly localize in the mitochondrial matrix, even though alternative localizations have been proposed. To further study the subcellular localization of the two human iso-enzymes, we created HEK293 cell lines stably over-expressing hGDH1 and hGDH2. In these cell lines, immunofluorescence and enzymatic analyses verified the overexpression of both hGDH1 and hGDH2 iso-enzymes, whereas subcellular fractionation followed by immunoblotting showed their predominantly mitochondrial localization. Given that previous studies have only indirectly compared the subcellular localization of the two iso-enzymes, we co-expressed them tagged with different fluorescent dyes (green and red fluorescent protein for hGDH1 and hGDH2, respectively) and found them to co-localize. Despite the wealth of information related to the functional properties of hGDH1 and hGDH2 and the availability of the hGDH1 structure, there is still an ongoing debate concerning their metabolic role and their involvement in disease processes. Data on the localization of hGDHs, as the ones presented here, could contribute to better understanding of the function of these important human enzymes.
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Affiliation(s)
- Lambros Mathioudakis
- Neurology Laboratory, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Mara Bourbouli
- Neurology Laboratory, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Elisavet Daklada
- Neurology Laboratory, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Sofia Kargatzi
- Neurology Laboratory, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Kleita Michaelidou
- Neurology Laboratory, Medical School, University of Crete, Heraklion, Crete, Greece
| | - Ioannis Zaganas
- Neurology Laboratory, Medical School, University of Crete, Heraklion, Crete, Greece. .,Department of Neurology, University Hospital of Heraklion, Heraklion, Crete, Greece.
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6
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Jerzsele Á, Karancsi Z, Pászti-Gere E, Sterczer Á, Bersényi A, Fodor K, Szabó D, Vajdovich P. Effects of p.o. administered xylitol in cats. J Vet Pharmacol Ther 2018; 41:409-414. [PMID: 29430681 DOI: 10.1111/jvp.12479] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 10/30/2017] [Indexed: 01/02/2023]
Abstract
Xylitol is commonly used as sugar substitute in households. While it has numerous beneficial effects on human health, it is highly toxic to dogs. The goal of this study was to examine whether xylitol has similar deleterious effects, such as hypoglycaemia and acute hepatic failure, on cats. Our research included six healthy middle-aged cats. Xylitol was dissolved in deionized water and administered p.o. at three doses (100, 500 and 1,000 mg/kg body weight). These dosages have been considered toxic and can cause liver failure or even death in dogs. After every xylitol administration, the basic health status and the blood glucose of cats were observed regularly. Additionally, prior to and 6, 24 and 72 hr after xylitol administration, blood samples were taken to check complete blood count, clinical biochemical parameters and enzymes such as ALT, ALKP, GGT, GLDH, bile acids, BUN, creatinine, phosphate, total protein, albumin, sodium and potassium. There were no significant changes (p > .05) in any of the haematological or biochemical parameters. Blood glucose concentrations did not show any significant alterations, except at 1,000 mg/kg dose, where a mild but significant increase was observed, but it was in physiological range. Based on our results, xylitol did not induce toxic effects on cats.
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Affiliation(s)
- Á Jerzsele
- Department of Pharmacology and Toxicology, University of Veterinary Medicine, Budapest, Hungary
| | - Z Karancsi
- Department of Pharmacology and Toxicology, University of Veterinary Medicine, Budapest, Hungary
| | - E Pászti-Gere
- Department of Pharmacology and Toxicology, University of Veterinary Medicine, Budapest, Hungary
| | - Á Sterczer
- Department of Clinic of Internal Medicine, University of Veterinary Medicine, Budapest, Hungary
| | - A Bersényi
- Department of Animal Breeding, Nutrition and Laboratory Animal Science, University of Veterinary Medicine, Budapest, Hungary
| | - K Fodor
- Department of Veterinary Forensics, Law and Economics, University of Veterinary Medicine, Budapest, Hungary
| | - D Szabó
- Department of Pharmacology and Toxicology, University of Veterinary Medicine, Budapest, Hungary
| | - P Vajdovich
- Department of Clinical Pathology and Oncology, University of Veterinary Medicine, Budapest, Hungary
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7
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Wang M, Zhang X, Wang Y, Li Y, Chen Y, Zheng H, Ma F, Ma CW, Lu B, Xie Z, Liao Q. Metabonomic strategy for the detection of metabolic effects of probiotics combined with prebiotic supplementation in weaned rats. RSC Adv 2018; 8:5042-5057. [PMID: 35539530 PMCID: PMC9078034 DOI: 10.1039/c7ra12067b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/15/2018] [Indexed: 11/21/2022] Open
Abstract
The purpose of this study is to investigate the effects of probiotics combined with prebiotics (PP) supplementation on weaned rat metabolism. A metabonomic strategy employing 1H-NMR spectroscopy and multivariate data analysis was used to examine weaned rat biological responses to PP supplementation. Male Sprague-Dawley rats (post-natal day 21, PD 21) received probiotics (Lactobacillus acidophilus NCFM (L-NCFM) and Bifidobacterium lactis Bi-07 (B-LBi07), 1 : 1, 1.0 × 1011 cfu kg−1) and prebiotics (Lycium barbarum polysaccharides (LBP), Poria cocos polysaccharides (PCPs) and Lentinan, 1 : 1 : 1, 24 g kg−1) via intragastric administration for 28 consecutive days. Urine and feces were collected for analysis. Significant topographical metabolic variations were present in urine and feces. Urinary metabolites upregulated by PP treatment included alanine, N-acetylglycine, glutamine, dimethylamine, phosphorylcholine, ethylene glycol, mannitol, phenylacetylglycine and glycoate, which were related to alanine, aspartate and glutamate metabolism, and choline metabolism. Feces-derived metabolites, including caproate, valerate, butyrate, propionate, lactate, acetate, succinate, methanol, threonine and methionine, were significantly increased, which were related to short-chain fatty acid (SCFA) metabolism and TCA cycle metabolism. These results indicate that dietary PP supplementation can regulate common systemic metabolic processes, including energy metabolism, amino acid metabolism, lipid metabolism, nucleic acid metabolism, and gut microbiota-related metabolism. This study also illuminates the vital role of PP supplementation in regulating the metabolism of weaned rats. Dietary probiotic supplementation is beneficial to the growth of weaned rats by regulating the metabolism.![]()
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Affiliation(s)
- Mengxia Wang
- School of Pharmaceutical Sciences
- Guangzhou University of Chinese Medicine
- Guangzhou
- P. R. China
| | - Xiaojun Zhang
- School of Pharmaceutical Sciences
- Guangzhou University of Chinese Medicine
- Guangzhou
- P. R. China
| | | | - Yuan Li
- School of Pharmaceutical Sciences
- Guangzhou University of Chinese Medicine
- Guangzhou
- P. R. China
| | - Yongxiong Chen
- School of Pharmaceutical Sciences
- Guangzhou University of Chinese Medicine
- Guangzhou
- P. R. China
| | - Haihui Zheng
- School of Pharmaceutical Sciences (Shen Zhen)
- Sun Yat-sen University
- Guangzhou
- P. R. China
| | - Fangli Ma
- Infinitus (China) Company Ltd
- Guangzhou
- China
| | | | - Biyu Lu
- School of Pharmaceutical Sciences
- Guangzhou University of Chinese Medicine
- Guangzhou
- P. R. China
| | - Zhiyong Xie
- School of Pharmaceutical Sciences (Shen Zhen)
- Sun Yat-sen University
- Guangzhou
- P. R. China
| | - Qiongfeng Liao
- School of Pharmaceutical Sciences
- Guangzhou University of Chinese Medicine
- Guangzhou
- P. R. China
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8
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Lin X, Zhao L, Tang S, Zhou Q, Lin Q, Li X, Zheng H, Gao H. Metabolic effects of basic fibroblast growth factor in streptozotocin-induced diabetic rats: A 1H NMR-based metabolomics investigation. Sci Rep 2016; 6:36474. [PMID: 27808173 PMCID: PMC5093531 DOI: 10.1038/srep36474] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 10/14/2016] [Indexed: 12/11/2022] Open
Abstract
The fibroblast growth factors (FGFs) family shows a great potential in the treatment of diabetes, but little attention is paid to basic FGF (bFGF). In this study, to explore the metabolic effects of bFGF on diabetes, metabolic changes in serum and feces were analyzed in the normal rats, the streptozocin (STZ)-induced diabetic rats and the bFGF-treated diabetic rats using a 1H nuclear magnetic resonance (NMR)-based metabolomic approach. Interestingly, bFGF treatment significantly decreased glucose, lipid and low density lipoprotein/very low density lipoprotein (LDL/VLDL) levels in serum of diabetic rats. Moreover, bFGF treatment corrected diabetes-induced reductions in citrate, lactate, choline, glycine, creatine, histidine, phenylalanine, tyrosine and glutamine in serum. Fecal propionate was significantly increased after bFGF treatment. Correlation analysis shows that glucose, lipid and LDL/VLDL were significantly negatively correlated with energy metabolites (citrate, creatine and lactate) and amino acids (alanine, glycine, histidine, phenylalanine, tyrosine and glutamine). In addition, a weak but significant correlation was observed between fecal propionate and serum lipid (R = −0.35, P = 0.046). Based on metabolic correlation and pathway analysis, therefore, we suggest that the glucose and lipid lowering effects of bFGF in the STZ-induced diabetic rats may be achieved by activating microbial metabolism, increasing energy metabolism and correcting amino acid metabolism.
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Affiliation(s)
- Xiaodong Lin
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Liangcai Zhao
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.,Metabonomics Section of Collaborative Innovation Center of Biomedicine, Wenzhou Medical University-Wenzhou University, Wenzhou 325035, China
| | - Shengli Tang
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Qi Zhou
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Qiuting Lin
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Xiaokun Li
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.,Metabonomics Section of Collaborative Innovation Center of Biomedicine, Wenzhou Medical University-Wenzhou University, Wenzhou 325035, China
| | - Hong Zheng
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.,Metabonomics Section of Collaborative Innovation Center of Biomedicine, Wenzhou Medical University-Wenzhou University, Wenzhou 325035, China
| | - Hongchang Gao
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.,Metabonomics Section of Collaborative Innovation Center of Biomedicine, Wenzhou Medical University-Wenzhou University, Wenzhou 325035, China
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9
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Integrated, Step-Wise, Mass-Isotopomeric Flux Analysis of the TCA Cycle. Cell Metab 2015; 22:936-47. [PMID: 26411341 PMCID: PMC4635072 DOI: 10.1016/j.cmet.2015.08.021] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 06/12/2015] [Accepted: 08/25/2015] [Indexed: 11/24/2022]
Abstract
Mass isotopomer multi-ordinate spectral analysis (MIMOSA) is a step-wise flux analysis platform to measure discrete glycolytic and mitochondrial metabolic rates. Importantly, direct citrate synthesis rates were obtained by deconvolving the mass spectra generated from [U-(13)C6]-D-glucose labeling for position-specific enrichments of mitochondrial acetyl-CoA, oxaloacetate, and citrate. Comprehensive steady-state and dynamic analyses of key metabolic rates (pyruvate dehydrogenase, β-oxidation, pyruvate carboxylase, isocitrate dehydrogenase, and PEP/pyruvate cycling) were calculated from the position-specific transfer of (13)C from sequential precursors to their products. Important limitations of previous techniques were identified. In INS-1 cells, citrate synthase rates correlated with both insulin secretion and oxygen consumption. Pyruvate carboxylase rates were substantially lower than previously reported but showed the highest fold change in response to glucose stimulation. In conclusion, MIMOSA measures key metabolic rates from the precursor/product position-specific transfer of (13)C-label between metabolites and has broad applicability to any glucose-oxidizing cell.
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10
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Zhang W, Zeng T, Chen L. EdgeMarker: Identifying differentially correlated molecule pairs as edge-biomarkers. J Theor Biol 2014; 362:35-43. [PMID: 24931676 DOI: 10.1016/j.jtbi.2014.05.041] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 05/22/2014] [Accepted: 05/27/2014] [Indexed: 10/25/2022]
Abstract
Biomarker discovery is one of the major topics in translational biomedicine study based on high-throughput biological data analysis. Traditional methods focus on differentially expressed genes (or node-biomarkers) but ignore non-differentials. However, non-differentially expressed genes also play important roles in the biological processes and the rewired interactions / edges among non-differential genes may reveal fundamental difference between variable conditions. Therefore, it is necessary to identify relevant interactions or gene pairs to elucidate the molecular mechanism of complex biological phenomena, e.g. distinguish different phenotypes. To address this issue, we proposed a new method based on a new vector representation of an edge, EdgeMarker, to (1) identify edge-biomarkers, i.e. the differentially correlated molecular pairs (e.g., gene pairs) with optimal classification ability, and (2) transform the 'node expression' data in node space into the 'edge expression' data in edge space and classify the phenotype of each single sample in edge space, which generally cannot be achieved in traditional methods. Unlike the traditional methods which analyze the node space (i.e. molecular expression space) or higher dimensional space using arbitrary kernel methods, this study provides a mathematical model to explore the edge space (i.e. correlation space) for classification of a single sample. In this work, we show that the identified edge-biomarkers indeed have strong ability in distinguishing normal and disease samples even when all involved genes are not significantly differentially expressed. The analysis of human cholangiocarcinoma dataset and diabetes dataset also suggested that the identified edge-biomarkers may cast new biological insights into the pathogenesis of human complex diseases.
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Affiliation(s)
- Wanwei Zhang
- Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Tao Zeng
- Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
| | - Luonan Chen
- Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; Collaborative Research Center for Innovative Mathematical Modelling, Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan.
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11
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Han SJ, Choi SE, Yi SA, Lee SJ, Kim HJ, Kim DJ, Lee HC, Lee KW, Kang Y. β-Cell-protective effect of 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid as a glutamate dehydrogenase activator in db/db mice. J Endocrinol 2012; 212:307-15. [PMID: 22131441 DOI: 10.1530/joe-11-0340] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) is an activator of glutamate dehydrogenase (GDH), which is a mitochondrial enzyme with an important role in insulin secretion. We investigated the effect of BCH on the high-glucose (HG)-induced reduction in glucose-stimulated insulin secretion (GSIS), the HG/palmitate (PA)-induced reduction in insulin gene expression, and HG/PA-induced β-cell death. We also studied whether long-term treatment with BCH lowers blood glucose and improves β-cell integrity in db/db mice. We evaluated GSIS, insulin gene expression, and DNA fragmentation in INS-1 cells exposed to HG or HG/PA in the presence or absence of BCH. An in vivo study was performed in which 7-week-old diabetic db/db mice were treated with BCH (0.7 g/kg, n = 10) and placebo (n = 10) every other day for 6 weeks. After treatment, an intraperitoneal glucose tolerance test and immunohistological examinations were performed. Treatment with BCH blocked HG-induced GSIS inhibition and the HG/PA-induced reduction in insulin gene expression in INS-1 cells. In addition, BCH significantly reduced HG/PA-induced INS-1 cell death and phospho-JNK level. BCH treatment improved glucose tolerance and insulin secretion in db/db mice. BCH treatment also increased the ratio of insulin-positive β-cells to total islet area (P < 0.05) and reduced the percentage of β-cells expressing cleaved caspase 3 (P < 0.05). In conclusion, the GDH activator BCH improved glycemic control in db/db mice. This anti-diabetic effect may be associated with improved insulin secretion, preserved islet architecture, and reduced β-cell apoptosis.
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Affiliation(s)
- Seung Jin Han
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, San 5, Wonchon-dong, Yeongtong-gu, Suwon 443-721, South Korea
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12
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Karaca M, Frigerio F, Maechler P. From pancreatic islets to central nervous system, the importance of glutamate dehydrogenase for the control of energy homeostasis. Neurochem Int 2011; 59:510-7. [DOI: 10.1016/j.neuint.2011.03.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 03/21/2011] [Accepted: 03/23/2011] [Indexed: 11/25/2022]
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13
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Gao P, Jiao Y, Xiong Q, Wang CY, Gerling I, Gu W. Genetic and Molecular Basis of QTL of Diabetes in Mouse: Genes and Polymorphisms. Curr Genomics 2011; 9:324-37. [PMID: 19471607 PMCID: PMC2685644 DOI: 10.2174/138920208785133253] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 04/14/2008] [Accepted: 04/17/2008] [Indexed: 12/14/2022] Open
Abstract
A systematic study has been conducted of all available reports in PubMed and OMIM (Online Mendelian Inheritance in Man) to examine the genetic and molecular basis of quantitative genetic loci (QTL) of diabetes with the main focus on genes and polymorphisms. The major question is, What can the QTL tell us? Specifically, we want to know whether those genome regions differ from other regions in terms of genes relevant to diabetes. Which genes are within those QTL regions, and, among them, which genes have already been linked to diabetes? whether more polymorphisms have been associated with diabetes in the QTL regions than in the non-QTL regions. Our search revealed a total of 9038 genes from 26 type 1 diabetes QTL, which cover 667,096,006 bp of the mouse genomic sequence. On one hand, a large number of candidate genes are in each of these QTL; on the other hand, we found that some obvious candidate genes of QTL have not yet been investigated. Thus, the comprehensive search of candidate genes for known QTL may provide unexpected benefit for identifying QTL genes for diabetes.
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Affiliation(s)
- Peng Gao
- Departments of Orthopaedic Surgery, Campbell Clinic and Pathology, University of Tennessee Health Science Center, Memphis, Tennessee, USA
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14
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Zhou Y, Jetton TL, Goshorn S, Lynch CJ, She P. Transamination is required for {alpha}-ketoisocaproate but not leucine to stimulate insulin secretion. J Biol Chem 2010; 285:33718-26. [PMID: 20736162 DOI: 10.1074/jbc.m110.136846] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
It remains unclear how α-ketoisocaproate (KIC) and leucine are metabolized to stimulate insulin secretion. Mitochondrial BCATm (branched-chain aminotransferase) catalyzes reversible transamination of leucine and α-ketoglutarate to KIC and glutamate, the first step of leucine catabolism. We investigated the biochemical mechanisms of KIC and leucine-stimulated insulin secretion (KICSIS and LSIS, respectively) using BCATm(-/-) mice. In static incubation, BCATm disruption abolished insulin secretion by KIC, D,L-α-keto-β-methylvalerate, and α-ketocaproate without altering stimulation by glucose, leucine, or α-ketoglutarate. Similarly, during pancreas perfusions in BCATm(-/-) mice, glucose and arginine stimulated insulin release, whereas KICSIS was largely abolished. During islet perifusions, KIC and 2 mM glutamine caused robust dose-dependent insulin secretion in BCATm(+/+) not BCATm(-/-) islets, whereas LSIS was unaffected. Consistently, in contrast to BCATm(+/+) islets, the increases of the ATP concentration and NADPH/NADP(+) ratio in response to KIC were largely blunted in BCATm(-/-) islets. Compared with nontreated islets, the combination of KIC/glutamine (10/2 mM) did not influence α-ketoglutarate concentrations but caused 120 and 33% increases in malate in BCATm(+/+) and BCATm(-/-) islets, respectively. Although leucine oxidation and KIC transamination were blocked in BCATm(-/-) islets, KIC oxidation was unaltered. These data indicate that KICSIS requires transamination of KIC and glutamate to leucine and α-ketoglutarate, respectively. LSIS does not require leucine catabolism and may be through leucine activation of glutamate dehydrogenase. Thus, KICSIS and LSIS occur by enhancing the metabolism of glutamine/glutamate to α-ketoglutarate, which, in turn, is metabolized to produce the intracellular signals such as ATP and NADPH for insulin secretion.
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Affiliation(s)
- Yingsheng Zhou
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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Diao C, Chen S, Xiao X, Wang T, Sun X, Wang O, Song H, Zhang Y, Yu M, Zhang Q, Wang H. Two unrelated Chinese patients with hyperinsulinism /hyperammonemia (HI/HA) syndrome due to mutations in glutamate dehydrogenase gene. J Pediatr Endocrinol Metab 2010; 23:733-8. [PMID: 20857847 DOI: 10.1515/jpem.2010.23.7.733] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Hyperinsulinism/ hyperammonemia (HI/HA) syndrome is caused by excessive activity of glutamate dehydrogenase (GDH) encoded by GLUD1 gene, which oxidizes glutamate to alpha-ketoglutarate and which is a potential regulator of insulin secretion in pancreatic beta cells and of ureagenesis in the liver. So GDH is important in normal glucose homeostasis. Mutations of GDH result in HI/ HA syndrome. METHODS We have performed protein (leucine) and fat loading test on one patient. We detected the level of serum glucose, insulin and blood ammonia. Genomic DNA of the two patients and their parents is isolated from blood and the exons of GLUD1 gene are amplified by polymerase chain reaction (PCR) for direct sequencing. RESULTS The leucine diet can evocate hypoglycemia obviously. Two heterozygous mutations c.978G>A (R269H) and c.1506C>T (S445L) are identified, respectively. These are both de novo. For one patient, a better blood glucose level can be gained from leucine-restriction diet, and without diazoxide while, for the other patient, diazoxide is necessary. CONCLUSIONS The heterozygous mutations in GLUD1 gene can cause HI/HA syndrome, it is sensitive to the leucine. The diazoxide and leucine-restriction diet do well in controlling the blood glucose level.
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Affiliation(s)
- Chengming Diao
- Key Laboratory of Endocrinology, Ministry of Health, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
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Jitrapakdee S, Wutthisathapornchai A, Wallace JC, MacDonald MJ. Regulation of insulin secretion: role of mitochondrial signalling. Diabetologia 2010; 53:1019-32. [PMID: 20225132 PMCID: PMC2885902 DOI: 10.1007/s00125-010-1685-0] [Citation(s) in RCA: 220] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Accepted: 01/06/2010] [Indexed: 12/23/2022]
Abstract
Pancreatic beta cells are specialised endocrine cells that continuously sense the levels of blood sugar and other fuels and, in response, secrete insulin to maintain normal fuel homeostasis. During postprandial periods an elevated level of plasma glucose rapidly stimulates insulin secretion to decrease hepatic glucose output and promote glucose uptake into other tissues, principally muscle and adipose tissues. Beta cell mitochondria play a key role in this process, not only by providing energy in the form of ATP to support insulin secretion, but also by synthesising metabolites (anaplerosis) that can act, both intra- and extramitochondrially, as factors that couple glucose sensing to insulin granule exocytosis. ATP on its own, and possibly modulated by these coupling factors, triggers closure of the ATP-sensitive potassium channel, resulting in membrane depolarisation that increases intracellular calcium to cause insulin secretion. The metabolic imbalance caused by chronic hyperglycaemia and hyperlipidaemia severely affects mitochondrial metabolism, leading to the development of impaired glucose-induced insulin secretion in type 2 diabetes. It appears that the anaplerotic enzyme pyruvate carboxylase participates directly or indirectly in several metabolic pathways which are important for glucose-induced insulin secretion, including: the pyruvate/malate cycle, the pyruvate/citrate cycle, the pyruvate/isocitrate cycle and glutamate-dehydrogenase-catalysed alpha-ketoglutarate production. These four pathways enable 'shuttling' or 'recycling' of these intermediate(s) into and out of mitochondrion, allowing continuous production of intracellular messenger(s). The purpose of this review is to present an account of recent progress in this area of central importance in the realm of diabetes and obesity research.
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Affiliation(s)
- S Jitrapakdee
- Molecular Metabolism Research Group, Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Road, Phya-Thai, Bangkok 10400, Thailand.
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Genes and networks expressed in perioperative omental adipose tissue are correlated with weight loss from Roux-en-Y gastric bypass. Int J Obes (Lond) 2008; 32:1395-406. [PMID: 18645576 DOI: 10.1038/ijo.2008.106] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
CONTEXT Gastric bypass surgery is the most commonly performed bariatric surgical procedure in the United States. Variable weight loss following this relatively standardized intervention has been reported. To date, a method for reliable profiling of patients who will successfully sustain weight loss for the long term has not been established. In addition, the mechanisms of action in accomplishing major weight loss as well as the explanation for the variable weight loss have not been established. OBJECTIVE To examine whether gene expression in perioperative omental adipose is associated with gastric bypass-induced weight loss. DESIGN Cross-sectional study of gene expression in perisurgical omental adipose tissues taken/available at the time of operation and total excess weight loss (EWL). SUBJECTS Fifteen overweight individuals who underwent Roux-en-Y gastric bypass (RYGB) surgery at the University of California Davis Medical Center (BMI: 40.6-72.8 kg/m(2)). MEASUREMENTS Body weight before and following weight stabilization 18-42 months after surgery. Perioperative omental adipose RNA isolated from 15 subjects was hybridized to Affymetrix HG-U133A chips for 22,283 transcript expression measurements. RESULTS Downstream analysis identified a set of genes whose expression was significantly correlated with RYGB-induced weight loss. The significant individual genes include acyl-coenzyme A oxidase 1 (ACOX1), phosphodiesterase 3A cGMP-inhibited (PDE3A) and protein kinase, AMP-activated, beta 1 non-catalytic subunit (PRKAB1). Specifically, ACOX1 plays a role in fatty acid metabolism. PDE3A is involved in purine metabolism and hormone-stimulated lipolysis. PRKAB1 is involved in adipocytokine signaling pathway. Gene network analysis revealed that pathways for glycerolipid metabolism, breast cancer and apoptosis were significantly correlated with long-term weight loss. CONCLUSION This study demonstrates that RNA expression profiles from perioperative adipose tissue are associated with weight loss outcome following RYGB surgery. Our data suggest that EWL could be predicted from preoperative samples, which would allow for informed decisions about whether or not to proceed to surgery.
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Tissue specificity of mitochondrial glutamate pathways and the control of metabolic homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:965-72. [PMID: 18486589 DOI: 10.1016/j.bbabio.2008.04.031] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 04/11/2008] [Accepted: 04/22/2008] [Indexed: 11/24/2022]
Abstract
Glutamate is implicated in numerous metabolic and signalling functions that vary according to specific tissues. Glutamate metabolism is tightly controlled by activities of mitochondrial enzymes and transmembrane carriers, in particular glutamate dehydrogenase and mitochondrial glutamate carriers that have been identified in recent years. It is remarkable that, although glutamate-specific enzymes and transporters share similar properties in most tissues, their regulation varies greatly according to particular organs in order to achieve tissue specific functions. This is illustrated in this review when comparing glutamate handling in liver, brain, and pancreatic beta-cells. We describe the main cellular glutamate pathways and their specific functions in different tissues, ultimately contributing to the control of metabolic homeostasis at the organism level.
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19
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Differential expression of liver proteins in streptozotocin-induced diabetic rats in response to hypoglycemic mushroom polysaccharides. KOREAN J CHEM ENG 2008. [DOI: 10.1007/s11814-008-0054-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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20
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Choi MM, Kim EA, Yang SJ, Choi SY, Cho SW, Huh JW. Amino Acid Changes within Antenna Helix Are Responsible for Different Regulatory Preferences of Human Glutamate Dehydrogenase Isozymes. J Biol Chem 2007; 282:19510-7. [PMID: 17507377 DOI: 10.1074/jbc.m703018200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human glutamate dehydrogenase (hGDH) exists in hGDH1 (housekeeping isozyme) and in hGDH2 (nerve-specific isozyme), which differ markedly in their allosteric regulation. Because they differ in only 16 of their 505 amino acids, the regulatory preferences must arise from amino acid residues that are not common between hGDH1 and hGDH2. To our knowledge none of the mutagenesis studies on the hGDH isozymes to date have identified the amino acid residues fully responsible for the different regulatory preferences between hGDH1 and hGDH2. In this study we constructed hGDH1(hGDH2(390-448))hGDH1 (amino acid segment 390-448 of hGDH1 replaced by the corresponding hGDH2 segment) and hGDH2(hGDH1(390-448))hGDH2 (amino acid segment 390-448 of hGDH2 replaced by the corresponding hGDH1 segment) by swapping the corresponding amino acid segments in hGDH1 and hGDH2. The chimeric enzymes by reciprocal swapping resulted in double mutations in amino acid sequences at 415 and 443 residues that are not common between hGDH1 and hGDH2 and are located in the C-terminal 48-residue "antenna" helix, which is thought to be part of the regulatory domain of mammalian GDHs. Functional analyses revealed that the doubly mutated chimeric enzymes almost completely acquired most of the different regulatory preferences between hGDH1 and hGDH2 for electrophoretic mobility, heat-stability, ADP activation, palmitoyl-CoA inhibition, and l-leucine activation, except for GTP inhibition. Our results indicate that substitutions of the residues in the antenna region may be important evolutionary changes that led to the adaptation of hGDH2 to the unique metabolic needs of the nerve tissue.
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Affiliation(s)
- Myung-Min Choi
- Department of Biochemistry and Molecular Biology, University of Ulsan College of Medicine, Seoul 138-736, Korea
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Kawajiri M, Okano Y, Kuno M, Tokuhara D, Hase Y, Inada H, Tashiro F, Miyazaki JI, Yamano T. Unregulated insulin secretion by pancreatic beta cells in hyperinsulinism/hyperammonemia syndrome: role of glutamate dehydrogenase, ATP-sensitive potassium channel, and nonselective cation channel. Pediatr Res 2006; 59:359-64. [PMID: 16492972 DOI: 10.1203/01.pdr.0000198775.22719.46] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The hyperinsulinism/hyperammonemia (HI/HA) syndrome is caused by "gain of function" of glutamate dehydrogenase (GDH). Several missense mutations have been found; however, cell behaviors triggered by the excessive GDH activity have not been fully demonstrated. This study was aimed to clarify electrophysiological mechanisms underlying the dysregulated insulin secretion in pancreatic beta cells with GDH mutations. GDH kinetics and insulin secretion were measured in MIN6 cells overexpressing the G446D and L413V. Membrane potentials and channel activity were recorded under the perforated-patch configuration that preserved intracellular environments. In mutant MIN6 cells, sensitivity of GDH to guanosine triphosphate (GTP) was reduced and insulin secretion at low glucose concentrations was enhanced. The basal GDH activity was elevated in L413V bearing a mutation in the antenna-like structure. The L413V cells were depolarized without glucose, often accompanying by repetitive Ca2+ firings. The depolarization was maintained in the presence of adenosine triphosphate (ATP) and disappeared by depleting ATP, suggesting that the depolarization depended on intracellular ATP. In L413V cells, the ATP-sensitive potassium channel (K(ATP) channel) was suppressed and the nonselective cation channel (NSCC) was potentiated, while sensitivity of the channels to their specific blockers or agonists was not impaired. These data suggest that the L413V cells increase the intracellular ATP/adenosine diphosphate (ADP) ratio, which in turn causes sustained depolarization not only by closure of the K(ATP) channel, but also by opening of the NSCC. The resultant activation of the voltage-gated Ca2+ channel appears to induce hyperinsulinism. The present study provides evidence that multiple channels cooperate in unregulated insulin secretion in pancreatic beta cells of the HI/HA syndrome.
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Affiliation(s)
- Mie Kawajiri
- Deparment of Pediatrics, Osaka City University Graduate School of Medicien, Osaka, Japan
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22
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Maechler P, Carobbio S, Rubi B. In beta-cells, mitochondria integrate and generate metabolic signals controlling insulin secretion. Int J Biochem Cell Biol 2006; 38:696-709. [PMID: 16443386 DOI: 10.1016/j.biocel.2005.12.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 12/08/2005] [Accepted: 12/12/2005] [Indexed: 12/14/2022]
Abstract
Pancreatic beta-cells are unique neuroendocrine cells displaying the peculiar feature of responding to nutrients, principally glucose, as primary stimulus. This requires translation of a metabolic substrate into intracellular messengers recognized by the exocytotic machinery. Central to this signal transduction mechanism, mitochondria integrate and generate metabolic signals, thereby coupling glucose recognition to insulin secretion. In response to a glucose rise, nucleotides and metabolites are generated by mitochondria and participate, together with cytosolic calcium, to the stimulation of insulin exocytosis. This review describes the mitochondrion-dependent pathways of regulated insulin secretion. In particular, importance of cataplerotic and anaplerotic processes is discussed, with special attention to the mitochondrial enzyme glutamate dehydrogenase. Mitochondrial defects, such as mutations and reactive oxygen species production, are presented in the context of beta-cell failure in the course of type 2 diabetes.
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Affiliation(s)
- Pierre Maechler
- Department of Cell Physiology and Metabolism, University Medical Centre, Geneva, Switzerland.
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Abstract
Hereditary origin of a tumor helps toward early discovery of its mutated gene; for example, it supports the compilation of a DNA panel from index cases to identify that gene by finding mutations in it. The gene for a hereditary tumor may contribute also to common tumors. For some syndromes, such as hereditary paraganglioma, several genes can cause a similar syndrome. For other syndromes, such as multiple endocrine neoplasia 2, one gene supports variants of a syndrome. Onset usually begins earlier and in more locations with hereditary than sporadic tumors. Mono- or oligoclonal ("clonal") tumor usually implies a postnatal delay, albeit less delay than for sporadic tumor, to onset and potential for cancer. Hormone excess from a polyclonal tissue shows onset at birth and no benefit from subtotal ablation of the secreting organ. Genes can cause neoplasms through stepwise loss of function, gain of function, or combinations of these. Polyclonal hormonal excess reflects abnormal gene dosage or effect, such as activation or haploinsufficiency. Polyclonal hyperplasia can cause the main endpoint of clinical expression in some syndromes or can be a precursor to clonal progression in others. Gene discovery is usually the first step toward clarifying the molecule and pathway mutated in a syndrome. Most mutated pathways in hormone excess states are only partly understood. The bases for tissue specificity of hormone excess syndromes are usually uncertain. In a few syndromes, tissue selectivity arises from mutation in the open reading frame of a regulatory gene (CASR, TSHR) with selective expression driven by its promoter. Polyclonal excess of a hormone is usually from a defect in the sensor system for an extracellular ligand (e.g., calcium, glucose, TSH). The final connections of any of these polyclonal or clonal pathways to hormone secretion have not been identified. In many cases, monoclonal proliferation causes hormone excess, probably as a secondary consequence of accumulation of cells with coincidental hormone-secretory ability.
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Affiliation(s)
- Stephen J Marx
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases/NIH, Building 10, Room 9C-101, 10 Center Drive, MSC 1802, Bethesda, MD 20892-1802, USA.
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Miki T, Seino S. Roles of KATP channels as metabolic sensors in acute metabolic changes. J Mol Cell Cardiol 2005; 38:917-25. [PMID: 15910876 DOI: 10.1016/j.yjmcc.2004.11.019] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2004] [Revised: 06/15/2004] [Accepted: 11/12/2004] [Indexed: 11/29/2022]
Abstract
Physiological and pathophysiological roles of K(ATP) channels have been clarified recently in genetically engineered mice. The Kir6.2-containing K(ATP) channels in pancreatic ss-cells and the hypothalamus are essential in the regulation of glucose-induced insulin secretion and hypoglycemia-induced glucagon secretion, respectively, and are involved in glucose uptake in skeletal muscles, thus playing a key role in the maintenance of glucose homeostasis. Disruption of Kir6.1-containing K(ATP) channels in mice leads to spontaneous vascular spasm mimicking vasospastic (Prinzmetal) angina in humans, indicating that the Kir6.1-containing K(ATP) channels in vascular smooth muscles participate in the regulation of vascular tonus, especially in coronary arteries. Together with protective roles of K(ATP) channels against cardiac ischemia and hypoxia-induced seizure propagation, it is now clear that K(ATP) channels, as metabolic sensors, are critical in the maintenance of homeostasis against acute metabolic changes.
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Affiliation(s)
- Takashi Miki
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Chuo-ku, Japan
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Morand JPF, Macri J, Adeli K. Proteomic Profiling of Hepatic Endoplasmic Reticulum-associated Proteins in an Animal Model of Insulin Resistance and Metabolic Dyslipidemia. J Biol Chem 2005; 280:17626-33. [PMID: 15760893 DOI: 10.1074/jbc.m413343200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hepatic insulin resistance and lipoprotein overproduction are common features of the metabolic syndrome and insulin-resistant states. A fructose-fed, insulin-resistant hamster model was recently developed to investigate mechanisms linking the development of hepatic insulin resistance and overproduction of atherogenic lipoproteins. Here we report a systematic analysis of protein expression profiles in the endoplasmic reticulum (ER) fractions isolated from livers of fructose-fed hamsters with the intention of identifying new candidate proteins involved in hepatic complications of insulin resistance and lipoprotein dysregulation. We have profiled hepatic ER-associated proteins from chow-fed (control) and fructose-fed (insulin-resistant) hamsters using two-dimensional gel electrophoresis and mass spectrometry. A total of 26 large scale two-dimensional gels of hepatic ER were used to identify 34 differentially expressed hepatic ER protein spots observed to be at least 2-fold differentially expressed with fructose feeding and the onset of insulin resistance. Differentially expressed proteins were identified by matrix-assisted laser desorption ionization-quadrupole time of flight (MALDI-Q-TOF), MALDI-TOF-postsource decay, and database mining using ProteinProspector MS-fit and MS-tag or the PROWL ProFound search engine using a focused rodent or mammalian search. Hepatic ER proteins ER60, ERp46, ERp29, glutamate dehydrogenase, and TAP1 were shown to be more than 2-fold down-regulated, whereas alpha-glucosidase, P-glycoprotein, fibrinogen, protein disulfide isomerase, GRP94, and apolipoprotein E were all found to be up-regulated in the hepatic ER of the fructose-fed hamster. Seven isoforms of ER60 in the hepatic ER were all shown to be down-regulated at least 2-fold in hepatocytes from fructosefed/insulin-resistant hamsters. Implications of the differential expression of positively identified protein factors in the development of hepatic insulin resistance and lipoprotein abnormalities are discussed.
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Affiliation(s)
- Jean-Paul F Morand
- Division of Clinical Biochemistry, and Structural Biology and Biochemistry, Department of Pediatric Laboratory Medicine, Research Institute, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada
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Lehtihet M, Webb DL, Honkanen RE, Sjöholm A. Glutamate inhibits protein phosphatases and promotes insulin exocytosis in pancreatic β-cells. Biochem Biophys Res Commun 2005; 328:601-7. [PMID: 15694391 DOI: 10.1016/j.bbrc.2005.01.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Indexed: 11/24/2022]
Abstract
In human type 2 diabetes mellitus, loss of glucose-sensitive insulin secretion from the pancreatic beta-cell is an early pathogenetic event, but the mechanisms involved in glucose sensing are poorly understood. A messenger role has been postulated for L-glutamate in linking glucose stimulation to sustained insulin exocytosis in the beta-cell, but the precise nature by which L-glutamate controls insulin secretion remains elusive. Effects of L-glutamate on the activities of ser/thr protein phosphatases (PPase) and Ca(2+)-regulated insulin exocytosis in INS-1E cells were investigated. Glucose increases L-glutamate contents and promotes insulin secretion from INS-1E cells. L-glutamate also dose-dependently inhibits PPase enzyme activities analogous to the specific PPase inhibitor, okadaic acid. L-glutamate and okadaic acid directly and non-additively promote insulin exocytosis from permeabilized INS-1E cells in a Ca(2+)-independent manner. Thus, an increase in phosphorylation state, through inhibition of protein dephosphorylation by glucose-derived L-glutamate, may be a novel regulatory mechanism linking glucose sensing to sustained insulin exocytosis.
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Affiliation(s)
- Mikael Lehtihet
- Karolinska Institutet, Department of Internal Medicine, Stockholm South Hospital, SE-118 83 Stockholm, Sweden
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Yoon HY, Cho EH, Yang SJ, Lee HJ, Huh JW, Choi MM, Cho SW. Reactive amino acid residues involved in glutamate-binding of human glutamate dehydrogenase isozymes. Biochimie 2005; 86:261-7. [PMID: 15194228 DOI: 10.1016/j.biochi.2004.04.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2004] [Revised: 04/15/2004] [Accepted: 04/15/2004] [Indexed: 11/28/2022]
Abstract
In the present study, the cassette mutagenesis at several putative positions (K94, G96, K118, K130, or D172) was performed to examine the residues involved in the glutamate-binding of the human glutamate dehydrogenase isozymes (hGDH1 and hGDH2). None of the mutations tested affected the expression or stability of the proteins. There was dramatic reduction in the catalytic efficiency in mutant proteins at K94, G96, K118, or K130 site, but not at D172 site. The K(M) values for glutamate were 4-10-fold greater for the mutants at K94, G96, or K118 site than for the wild-type hGDH1 and hGDH2, whereas no differences in the K(M) values for NAD(+) were detected between the mutant and wild-type enzymes. For K130Y mutant, the K(M) value for glutamate increased 1.6-fold, whereas the catalytic efficiency (k(cat)/K(M)) showed only 2-3% of the wild-type. Therefore, the decreased catalytic efficiency of the K130 mutant mainly results from the reduced k(cat) value, suggesting a possibility that the K130Y residue may be involved in the catalysis rather than in the glutamate-binding. The D172Y mutant did not show any changes in k(cat) value and K(M) values for glutamate and NAD(+), indicating that D172Y is not directly involved in catalysis and substrates binding of the hGDH isozymes. For sensitivity to ADP activation, only the D172Y mutant showed a reduced sensitivity to ADP activation. The reduction of ADP activation in D172Y mutant was more profoundly observed in hGDH2 than in hGDH1. There were no differences in their sensitivities to GTP inhibition between the wild-type and mutant GDHs at all positions tested. Our results suggest that K94, G96, and K118 residues play an important role, although at different degrees, in the binding of glutamate to hGDH isozymes.
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Affiliation(s)
- Hye-Young Yoon
- Department of Biochemistry and Molecular Biology, University of Ulsan College of Medicine, 388-1 Poongnap-dong, Songpa-gu, Seoul 138-736, Republic of Korea
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Yang SJ, Huh JW, Hong HN, Kim TU, Cho SW. Important role of Ser443 in different thermal stability of human glutamate dehydrogenase isozymes1. FEBS Lett 2004; 562:59-64. [PMID: 15044002 DOI: 10.1016/s0014-5793(04)00183-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2004] [Revised: 02/16/2004] [Accepted: 02/16/2004] [Indexed: 10/26/2022]
Abstract
Molecular biological studies confirmed that two glutamate dehydrogenase isozymes (hGDH1 and hGDH2) of distinct genetic origin are expressed in human tissues. hGDH1 is heat-stable and expressed widely, whereas hGDH2 is heat-labile and specific for neural and testicular tissues. A selective deficiency of hGDH2 has been reported in patients with spinocerebellar ataxia. We have identified an amino acid residue involved in the different thermal stability of human GDH isozymes. At 45 degrees C (pH 7.0), heat inactivation proceeded faster for hGDH2 (half life=45 min) than for hGDH1 (half-life=310 min) in the absence of allosteric regulators. Both hGDH1 and hGDH2, however, showed much slower heat inactivation processes in the presence of 1 mM ADP or 3 mM L-Leu. Virtually most of the enzyme activity remained up to 100 min at 45 degrees C after treatment with ADP and L-Leu in combination. In contrast to ADP and L-Leu, the thermal stabilities of the hGDH isozymes were not affected by addition of substrates or coenzymes. In human GDH isozymes, the 443 site is Arg in hGDH1 and Ser in hGDH2. Replacement of Ser by Arg at the 443 site by cassette mutagenesis abolished the heat lability of hGDH2 with a similar half-life of hGDH1. The mutagenesis at several other sites (L415M, A456G, and H470R) having differences in amino acid sequence between the two GDH isozymes did not show any change in the thermal stability. These results suggest that the Ser443 residue plays an important role in the different thermal stability of human GDH isozymes.
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Affiliation(s)
- Seung-Ju Yang
- Department of Biochemistry and Molecular Biology, University of Ulsan College of Medicine, 388-1 Poongnap-2dong, Songpa-gu, Seoul 138-736, South Korea
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Carobbio S, Ishihara H, Fernandez-Pascual S, Bartley C, Martin-Del-Rio R, Maechler P. Insulin secretion profiles are modified by overexpression of glutamate dehydrogenase in pancreatic islets. Diabetologia 2004; 47:266-76. [PMID: 14689183 DOI: 10.1007/s00125-003-1306-2] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Revised: 10/27/2003] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Glutamate dehydrogenase (GDH) is a mitochondrial enzyme playing a key role in the control of insulin secretion. However, it is not known whether GDH expression levels in beta cells are rate-limiting for the secretory response to glucose. GDH also controls glutamine and glutamate oxidative metabolism, which is only weak in islets if GDH is not allosterically activated by L-leucine or (+/-)-2-aminobicyclo-[2,2,1]heptane-2-carboxylic acid (BCH). METHODS We constructed an adenovirus encoding for GDH to overexpress the enzyme in the beta-cell line INS-1E, as well as in isolated rat and mouse pancreatic islets. The secretory responses to glucose and glutamine were studied in static and perifusion experiments. Amino acid concentrations and metabolic parameters were measured in parallel. RESULTS GDH overexpression in rat islets did not change insulin release at basal or intermediate glucose (2.8 and 8.3 mmol/l respectively), but potentiated the secretory response at high glucose concentrations (16.7 mmol/l) compared to controls (+35%). Control islets exposed to 5 mmol/l glutamine at basal glucose did not increase insulin release, unless BCH was added with a resulting 2.5-fold response. In islets overexpressing GDH glutamine alone stimulated insulin secretion (2.7-fold), which was potentiated 2.2-fold by adding BCH. The secretory responses evoked by glutamine under these conditions correlated with enhanced cellular metabolism. CONCLUSIONS/INTERPRETATION GDH could be rate-limiting in glucose-induced insulin secretion, as GDH overexpression enhanced secretory responses. Moreover, GDH overexpression made islets responsive to glutamine, indicating that under physiological conditions this enzyme acts as a gatekeeper to prevent amino acids from being inappropriate efficient secretagogues.
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Affiliation(s)
- S Carobbio
- Division of Clinical Biochemistry, University Medical Center, Geneva, Switzerland
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Anno T, Uehara S, Katagiri H, Ohta Y, Ueda K, Mizuguchi H, Moriyama Y, Oka Y, Tanizawa Y. Overexpression of constitutively activated glutamate dehydrogenase induces insulin secretion through enhanced glutamate oxidation. Am J Physiol Endocrinol Metab 2004; 286:E280-5. [PMID: 14532172 DOI: 10.1152/ajpendo.00380.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glutamate dehydrogenase (GDH) catalyzes reversible oxidative deamination of l-glutamate to alpha-ketoglutarate. Enzyme activity is regulated by several allosteric effectors. Recognition of a new form of hyperinsulinemic hypoglycemia, hyperinsulinism/hyperammonemia (HI/HA) syndrome, which is caused by gain-of-function mutations in GDH, highlighted the importance of GDH in glucose homeostasis. GDH266C is a constitutively activated mutant enzyme we identified in a patient with HI/HA syndrome. By overexpressing GDH266C in MIN6 mouse insulinoma cells, we previously demonstrated unregulated elevation of GDH activity to render the cells responsive to glutamine in insulin secretion. Interestingly, at low glucose concentrations, basal insulin secretion was exaggerated in such cells. Herein, to clarify the role of GDH in the regulation of insulin secretion, we studied cellular glutamate metabolism using MIN6 cells overexpressing GDH266C (MIN6-GDH266C). Glutamine-stimulated insulin secretion was associated with increased glutamine oxidation and decreased intracellular glutamate content. Similarly, at 5 mmol/l glucose without glutamine, glutamine oxidation also increased, and glutamate content decreased with exaggerated insulin secretion. Glucose oxidation was not altered. Insulin secretion profiles from GDH266C-overexpressing isolated rat pancreatic islets were similar to those from MIN6-GDH266C, suggesting observation in MIN6 cells to be relevant in native beta-cells. These results demonstrate that, upon activation, GDH oxidizes glutamate to alpha-ketoglutarate, thereby stimulating insulin secretion by providing the TCA cycle with a substrate. No evidence was obtained supporting the hypothesis that activated GDH produced glutamate, a recently proposed second messenger of insulin secretion, by the reverse reaction, to stimulate insulin secretion.
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Affiliation(s)
- Takatoshi Anno
- Division of Molecular Analysis of Human Disorders, Department of Bio-Signal Analysis, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi 755-8505, Japan
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Katsuta H, Ozawa S, Ninomiya T, Shimoyama T, Ito E, Tanaka T, Yamaguchi S, Katahira H, Nagamatsu S, Horie M, Ishida H. Insulinotropic action of glutamate is dependent on the inhibition of ATP-sensitive potassium channel activities in MIN 6 beta cells. Biochem Biophys Res Commun 2004; 311:660-4. [PMID: 14623322 DOI: 10.1016/j.bbrc.2003.10.043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
To investigate the cellular mechanism of insulinotropic effect of glutamate in pancreatic beta cells, we utilized patch-clamp technique to monitor directly the activities of ATP-sensitive potassium channels (K(ATP) channels). Dimethylglutamate (5mM), a membrane-permeable analog of glutamate, augmented the insulin release induced by the stimulatory concentrations of glucose (p<0.05-0.01). In the cell-attached configurations, dimethylglutamate reversibly and significantly suppressed the K(ATP) channel activities (p<0.01). On the other hand, no significant effect was observed when glutamate itself was applied to the inside-out patches, whereas the prompt and reversible suppression was recorded in the case of ATP (p<0.01). These results indicate that the insulinotropic action of glutamate in beta cells could be derived from the inhibition of K(ATP) channel activities, probably due to generation of messengers via intracellular metabolism such as ATP.
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Affiliation(s)
- Hidenori Katsuta
- Third Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan
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Dunne MJ, Cosgrove KE, Shepherd RM, Aynsley-Green A, Lindley KJ. Hyperinsulinism in Infancy: From Basic Science to Clinical Disease. Physiol Rev 2004; 84:239-75. [PMID: 14715916 DOI: 10.1152/physrev.00022.2003] [Citation(s) in RCA: 185] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dunne, Mark J., Karen E. Cosgrove, Ruth M. Shepherd, Albert Aynsley-Green, and Keith J. Lindley. Hyperinsulinism in Infancy: From Basic Science to Clinical Disease. Physiol Rev 84: 239–275, 2004; 10.1152/physrev.00022.2003.—Ion channelopathies have now been described in many well-characterized cell types including neurons, myocytes, epithelial cells, and endocrine cells. However, in only a few cases has the relationship between altered ion channel function, cell biology, and clinical disease been defined. Hyperinsulinism in infancy (HI) is a rare, potentially lethal condition of the newborn and early childhood. The causes of HI are varied and numerous, but in almost all cases they share a common target protein, the ATP-sensitive K+channel. From gene defects in ion channel subunits to defects in β-cell metabolism and anaplerosis, this review describes the relationship between pathogenesis and clinical medicine. Until recently, HI was generally considered an orphan disease, but as parallel defects in ion channels, enzymes, and metabolic pathways also give rise to diabetes and impaired insulin release, the HI paradigm has wider implications for more common disorders of the endocrine pancreas and the molecular physiology of ion transport.
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Affiliation(s)
- Mark J Dunne
- Research Division of Physiology and Pharmacology, The School of Biological Sciences, University of Manchester, Manchester, United Kingdom.
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Brennan L, Corless M, Hewage C, Malthouse JPG, McClenaghan NH, Flatt PR, Newsholme P. 13C NMR analysis reveals a link between L-glutamine metabolism, D-glucose metabolism and gamma-glutamyl cycle activity in a clonal pancreatic beta-cell line. Diabetologia 2003; 46:1512-21. [PMID: 12955201 DOI: 10.1007/s00125-003-1184-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2003] [Revised: 05/26/2003] [Indexed: 10/26/2022]
Abstract
AIMS/HYPOTHESIS Pancreatic islet cells and clonal beta-cell lines can metabolise L-glutamine at high rates. The pathway of L-glutamine metabolism has traditionally been described as L-glutamine-->L-glutamate-->2-oxoglutarate-->oxidation in TCA cycle following conversion to pyruvate. Controversially, the metabolism of D-glucose to L-glutamate in beta cells is not widely accepted. However, L-glutamate has been proposed to be a stimulation-secretion coupling factor in glucose-induced insulin secretion. We aimed to investigate the metabolism of glutamine and glucose by using (13)C NMR analysis. METHODS BRIN-BD11 cells were incubated in the presence of 16.7 mmol/l [1-(13)C]glucose, 2 mmol/l [2-(13)C]L-glycine or 2 mmol/l [1,2-(13)C]glutamine in the presence or absence of other amino acids or inhibitors. After an incubation period the cellular metabolites were extracted using a PCA extract procedure. After neutralisation, the extracts were prepared for analysis using (13)C-NMR spectroscopy. RESULTS Using (13)C NMR analysis we have shown that L-glutamine could be metabolised in BRIN-BD11 cells via reactions constituting part of the gamma-glutamyl cycle producing glutathione. Moderate or high activities of the enzymes required for these pathways of metabolism including glutaminase, gamma-glutamyltransferase and gamma-glutamylcysteine synthetase were observed. We additionally report significant D-glucose metabolism to L-glutamate. Addition of the aminotransferase inhibitor, aminooxyacetate, attenuated L-glutamate production from D-glucose. CONCLUSION/INTERPRETATION We propose that L-glutamine metabolism is important in the beta cell for generation of stimulus-secretion coupling factors, precursors of glutathione synthesis and for supplying carbon for oxidation in the TCA cycle. D-glucose, under appropriate conditions, can be converted to L-glutamate via an aminotransferase catalysed step.
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Affiliation(s)
- L Brennan
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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Newsholme P, Procopio J, Lima MMR, Pithon-Curi TC, Curi R. Glutamine and glutamate--their central role in cell metabolism and function. Cell Biochem Funct 2003; 21:1-9. [PMID: 12579515 DOI: 10.1002/cbf.1003] [Citation(s) in RCA: 407] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Glucose is widely accepted as the primary nutrient for maintenance and promotion of cell function. However, we propose that the 5-carbon amino acids, glutamine and glutamate, should be considered to be equally important for maintenance and promotion of cell function. The functions of glutamine are many and include: substrate for protein synthesis, anabolic precursor for muscle growth, acid-base balance in the kidney, substrate for ureogenesis in the liver, substrate for hepatic and renal gluconeogenesis, an oxidative fuel for intestine and cells of the immune system, inter-organ nitrogen transport, precursor for neurotransmitter synthesis, precursor for nucleotide and nucleic acid synthesis and precursor for glutathione production. Many of these functions are connected to the formation of glutamate from glutamine. We propose that the unique properties regarding concentration and routes of metabolism of these amino acids allow them to be used for a diverse array of processes related to the specialized function of each of the glutamine utilizing cells. In this review we highlight the specialized aspects of glutamine/glutamate metabolism of different glutamine-utilizing cells and in each case relate key aspects of metabolism to cell function.
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Affiliation(s)
- Philip Newsholme
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland.
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Reimann F, Huopio H, Dabrowski M, Proks P, Gribble FM, Laakso M, Otonkoski T, Ashcroft FM. Characterisation of new KATP-channel mutations associated with congenital hyperinsulinism in the Finnish population. Diabetologia 2003; 46:241-9. [PMID: 12627323 DOI: 10.1007/s00125-002-1014-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2002] [Revised: 09/17/2002] [Indexed: 10/26/2022]
Abstract
AIMS/HYPOTHESIS ATP-sensitive potassium (K(ATP)) channels are crucial for the regulation of insulin secretion from pancreatic beta cells and mutations in either the Kir6.2 or SUR1 subunit of this channel can cause congenital hyperinsulinism (CHI). The aim of this study was to analyse the functional consequences of four CHI mutations (A1457T, V1550D and L1551V in SUR1, and K67N in Kir6.2) recently identified in the Finnish population. METHODS Wild type or mutant Kir6.2 and SUR1 subunits were coexpressed in Xenopus oocytes. The functional properties of the channels were examined by measuring currents in intact oocytes or giant inside-out membrane patches. Surface expression was measured by enzyme-linked immunosorbance assay, using HA-epitope-tagged subunits. RESULTS Two mutations (A1457T and V1550D) prevented trafficking of the channel to the plasma membrane. The L1551V mutation reduced surface expression 40-fold, and caused loss of MgADP and diazoxide activation. Both these factors will contribute to the lack of K(ATP) current activation observed in response to metabolic inhibition in intact oocytes. The L1551V mutation also increased the channel open probability, thereby producing a reduction in ATP-sensitivity (from 10 micro mol/l to 120 micro mol/l). The fourth mutation (K67N mutation in Kir6.2) did not affect surface expression nor alter the properties of K(ATP) channels in excised patches, but resulted in a reduced K(ATP) current amplitude in intact cells on metabolic inhibition, through an unidentified mechanism. CONCLUSION/INTERPRETATION The four CHI mutations disrupted K(ATP) channel activity by different mechanisms. Our results are discussed in relation to the CHI phenotype observed in patients with these mutations.
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Affiliation(s)
- F Reimann
- Department of Clinical Biochemistry, University of Cambridge, UK
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Newsholme P, Lima MMR, Procopio J, Pithon-Curi TC, Doi SQ, Bazotte RB, Curi R. Glutamine and glutamate as vital metabolites. Braz J Med Biol Res 2003; 36:153-63. [PMID: 12563517 DOI: 10.1590/s0100-879x2003000200002] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Glucose is widely accepted as the primary nutrient for the maintenance and promotion of cell function. This metabolite leads to production of ATP, NADPH and precursors for the synthesis of macromolecules such as nucleic acids and phospholipids. We propose that, in addition to glucose, the 5-carbon amino acids glutamine and glutamate should be considered to be equally important for maintenance and promotion of cell function. The functions of glutamine/glutamate are many, i.e., they are substrates for protein synthesis, anabolic precursors for muscle growth, they regulate acid-base balance in the kidney, they are substrates for ureagenesis in the liver and for hepatic and renal gluconeogenesis, they act as an oxidative fuel for the intestine and cells of the immune system, provide inter-organ nitrogen transport, and act as precursors of neurotransmitter synthesis, of nucleotide and nucleic acid synthesis and of glutathione production. Many of these functions are interrelated with glucose metabolism. The specialized aspects of glutamine/glutamate metabolism of different glutamine-utilizing cells are discussed in the context of glucose requirements and cell function.
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Affiliation(s)
- P Newsholme
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College of Dublin, Belfield, Dublin, Ireland
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Bertrand G, Ishiyama N, Nenquin M, Ravier MA, Henquin JC. The elevation of glutamate content and the amplification of insulin secretion in glucose-stimulated pancreatic islets are not causally related. J Biol Chem 2002; 277:32883-91. [PMID: 12087106 DOI: 10.1074/jbc.m205326200] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose increases insulin secretion by raising cytoplasmic Ca(2+) ([Ca(2+)](i)) in beta-cells (triggering pathway) and augmenting the efficacy of Ca(2+) on exocytosis (amplifying pathway). It has been suggested that glutamate formed from alpha-ketoglutarate is a messenger of the amplifying pathway (Maechler, P., and Wollheim, C. B. (1999) Nature 402, 685-689). This hypothesis was tested with mouse islets depolarized with 30 mm KCl (+ diazoxide) or with a saturating concentration of sulfonylurea. Because [Ca(2+)](i) was elevated under these conditions, insulin secretion was stimulated already in 0 mm glucose. The amplification of secretion produced by glucose was accompanied by an increase in islet glutamate. However, glutamine (0.5-2 mm) markedly augmented islet glutamate without affecting insulin secretion, whereas glucose augmented secretion without influencing glutamate levels when these were elevated by glutamine. Allosteric activation of glutamate dehydrogenase by BCH (2-amino 2-norbornane carboxylic acid) lowered islet glutamate but increased insulin secretion. Similar insulin secretion thus occurred at very different cellular glutamate levels. Glutamine did not affect islet [Ca(2+)](i) and pH(i), whereas glucose and BCH slightly raised pH(i) and either slightly decreased (30 mm KCl) or increased (tolbutamide) [Ca(2+)](i). The general dissociation between changes in islet glutamate and insulin secretion refutes a role of beta-cell glutamate in the amplification of insulin secretion by glucose.
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Affiliation(s)
- Gyslaine Bertrand
- Unité d'Endocrinologie et Métabolisme, University of Louvain Faculty of Medicine, B-1200 Brussels, Belgium
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Current literature in diabetes. Diabetes Metab Res Rev 2002; 18:245-52. [PMID: 12112943 DOI: 10.1002/dmrr.245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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