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Type 2 Diabetes Variants Disrupt Function of SLC16A11 through Two Distinct Mechanisms.
Rusu V, Hoch E, Mercader JM, Tenen DE, Gymrek M, Hartigan CR, DeRan M, von Grotthuss M, Fontanillas P, Spooner A, Guzman G, Deik AA, Pierce KA, Dennis C, Clish CB, Carr SA, Wagner BK, Schenone M, Ng MCY, Chen BH, MEDIA Consortium, SIGMA T2D Consortium, Centeno-Cruz F, Zerrweck C, Orozco L, Altshuler DM, Schreiber SL, Florez JC, Jacobs SBR, Lander ES
(2017) Cell 170: 199-212.e20
MeSH Terms: Basigin, Cell Membrane, Chromosomes, Human, Pair 17, Diabetes Mellitus, Type 2, Gene Knockdown Techniques, Haplotypes, Hepatocytes, Heterozygote, Histone Code, Humans, Liver, Models, Molecular, Monocarboxylic Acid Transporters
Show Abstract · Added September 20, 2017
Type 2 diabetes (T2D) affects Latinos at twice the rate seen in populations of European descent. We recently identified a risk haplotype spanning SLC16A11 that explains ∼20% of the increased T2D prevalence in Mexico. Here, through genetic fine-mapping, we define a set of tightly linked variants likely to contain the causal allele(s). We show that variants on the T2D-associated haplotype have two distinct effects: (1) decreasing SLC16A11 expression in liver and (2) disrupting a key interaction with basigin, thereby reducing cell-surface localization. Both independent mechanisms reduce SLC16A11 function and suggest SLC16A11 is the causal gene at this locus. To gain insight into how SLC16A11 disruption impacts T2D risk, we demonstrate that SLC16A11 is a proton-coupled monocarboxylate transporter and that genetic perturbation of SLC16A11 induces changes in fatty acid and lipid metabolism that are associated with increased T2D risk. Our findings suggest that increasing SLC16A11 function could be therapeutically beneficial for T2D. VIDEO ABSTRACT.
Copyright © 2017 Elsevier Inc. All rights reserved.
0 Communities
1 Members
0 Resources
13 MeSH Terms
Hepatic β-arrestin 2 is essential for maintaining euglycemia.
Zhu L, Rossi M, Cui Y, Lee RJ, Sakamoto W, Perry NA, Urs NM, Caron MG, Gurevich VV, Godlewski G, Kunos G, Chen M, Chen W, Wess J
(2017) J Clin Invest 127: 2941-2945
MeSH Terms: Animals, Blood Glucose, COS Cells, Chlorocebus aethiops, Diabetes Mellitus, Type 2, Diet, High-Fat, Gene Deletion, Gene Expression Regulation, Glucagon, Hepatocytes, Homeostasis, Insulin, Liver, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Phenotype, Receptors, Glucagon, Signal Transduction, beta-Arrestin 1, beta-Arrestin 2
Show Abstract · Added March 14, 2018
An increase in hepatic glucose production (HGP) represents a key feature of type 2 diabetes. This deficiency in metabolic control of glucose production critically depends on enhanced signaling through hepatic glucagon receptors (GCGRs). Here, we have demonstrated that selective inactivation of the GPCR-associated protein β-arrestin 2 in hepatocytes of adult mice results in greatly increased hepatic GCGR signaling, leading to striking deficits in glucose homeostasis. However, hepatocyte-specific β-arrestin 2 deficiency did not affect hepatic insulin sensitivity or β-adrenergic signaling. Adult mice lacking β-arrestin 1 selectively in hepatocytes did not show any changes in glucose homeostasis. Importantly, hepatocyte-specific overexpression of β-arrestin 2 greatly reduced hepatic GCGR signaling and protected mice against the metabolic deficits caused by the consumption of a high-fat diet. Our data support the concept that strategies aimed at enhancing hepatic β-arrestin 2 activity could prove useful for suppressing HGP for therapeutic purposes.
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22 MeSH Terms
A Chimeric Egfr Protein Reporter Mouse Reveals Egfr Localization and Trafficking In Vivo.
Yang YP, Ma H, Starchenko A, Huh WJ, Li W, Hickman FE, Zhang Q, Franklin JL, Mortlock DP, Fuhrmann S, Carter BD, Ihrie RA, Coffey RJ
(2017) Cell Rep 19: 1257-1267
MeSH Terms: Adult Stem Cells, Amphiregulin, Animals, Embryo, Mammalian, ErbB Receptors, Genes, Reporter, Green Fluorescent Proteins, Hepatocytes, Intestinal Mucosa, Mice, Microscopy, Fluorescence, Protein Transport, Recombinant Proteins, Transgenes
Show Abstract · Added June 21, 2017
EGF receptor (EGFR) is a critical signaling node throughout life. However, it has not been possible to directly visualize endogenous Egfr in mice. Using CRISPR/Cas9 genome editing, we appended a fluorescent reporter to the C terminus of the Egfr. Homozygous reporter mice appear normal and EGFR signaling is intact in vitro and in vivo. We detect distinct patterns of Egfr expression in progenitor and differentiated compartments in embryonic and adult mice. Systemic delivery of EGF or amphiregulin results in markedly different patterns of Egfr internalization and trafficking in hepatocytes. In the normal intestine, Egfr localizes to the crypt rather than villus compartment, expression is higher in adjacent epithelium than in intestinal tumors, and following colonic injury expression appears in distinct cell populations in the stroma. This reporter, under control of its endogenous regulatory elements, enables in vivo monitoring of the dynamics of Egfr localization and trafficking in normal and disease states.
Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
1 Communities
5 Members
2 Resources
14 MeSH Terms
Metabolic profiles of pomalidomide in human plasma simulated with pharmacokinetic data in control and humanized-liver mice.
Shimizu M, Suemizu H, Mitsui M, Shibata N, Guengerich FP, Yamazaki H
(2017) Xenobiotica 47: 844-848
MeSH Terms: Angiogenesis Inhibitors, Animals, Cytochrome P-450 Enzyme System, Glucuronides, Hepatocytes, Humans, Liver, Metabolome, Mice, Microsomes, Liver, Thalidomide
Show Abstract · Added March 14, 2018
1. Pomalidomide has been shown to be potentially teratogenic in thalidomide-sensitive animal species such as rabbits. Screening for thalidomide analogs devoid of teratogenicity/toxicity - attributable to metabolites formed by cytochrome P450 enzymes - but having immunomodulatory properties is a strategic pathway towards development of new anticancer drugs. 2. In this study, plasma concentrations of pomalidomide, its primary 5-hydroxylated metabolite, and its glucuronide conjugate(s) were investigated in control and humanized-liver mice. Following oral administration of pomalidomide (100 mg/kg), plasma concentrations of 7-hydroxypomalidomide and 5-hydroxypomalidomide glucuronide were slightly higher in humanized-liver mice than in control mice. 3. Simulations of human plasma concentrations of pomalidomide were achieved with simplified physiologically-based pharmacokinetic models in both groups of mice in accordance with reported pomalidomide concentrations after low dose administration in humans. 4. The results indicate that pharmacokinetic profiles of pomalidomide were roughly similar between control mice and humanized-liver mice and that control and humanized-liver mice mediated pomalidomide 5-hydroxylation in vivo. Introducing one aromatic amino group into thalidomide resulted in less species differences in in vivo pharmacokinetics in control and humanized-liver mice.
0 Communities
1 Members
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11 MeSH Terms
Assessment of Protein Binding of 5-Hydroxythalidomide Bioactivated in Humanized Mice with Human P450 3A-Chromosome or Hepatocytes by Two-Dimensional Electrophoresis/Accelerator Mass Spectrometry.
Yamazaki H, Suemizu H, Kazuki Y, Oofusa K, Kuribayashi S, Shimizu M, Ninomiya S, Horie T, Shibata N, Guengerich FP
(2016) Chem Res Toxicol 29: 1279-81
MeSH Terms: Animals, Cytochrome P-450 Enzyme System, Electrophoresis, Gel, Two-Dimensional, Hepatocytes, Humans, Mass Spectrometry, Mice, Protein Binding, Thalidomide
Show Abstract · Added March 14, 2018
Bioactivation of 5-hydroxy-[carbonyl-(14)C]thalidomide, a known metabolite of thalidomide, by human artificial or native cytochrome P450 3A enzymes, and nonspecific binding in livers of mice was assessed using two-dimensional electrophoresis combined with accelerator mass spectrometry. The apparent major target proteins were liver microsomal cytochrome c oxidase subunit 6B1 and ATP synthase subunit α in mice containing humanized P450 3A genes or transplanted humanized liver. Liver cytosolic retinal dehydrogenase 1 and glutathione transferase A1 were targets in humanized mice with P450 3A and hepatocytes, respectively. 5-Hydroxythalidomide is bioactivated by human P450 3A enzymes and trapped with proteins nonspecifically in humanized mice.
0 Communities
1 Members
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9 MeSH Terms
Knockdown of triglyceride synthesis does not enhance palmitate lipotoxicity or prevent oleate-mediated rescue in rat hepatocytes.
Leamy AK, Hasenour CM, Egnatchik RA, Trenary IA, Yao CH, Patti GJ, Shiota M, Young JD
(2016) Biochim Biophys Acta 1861: 1005-1014
MeSH Terms: Animals, Apoptosis, Diacylglycerol O-Acyltransferase, Esterification, Gene Knockout Techniques, Hepatocytes, Lipid Metabolism, Lipogenesis, Oleic Acid, Oxidative Stress, Palmitic Acid, Rats, Triglycerides
Show Abstract · Added April 27, 2017
Experiments in a variety of cell types, including hepatocytes, consistently demonstrate the acutely lipotoxic effects of saturated fatty acids, such as palmitate (PA), but not unsaturated fatty acids, such as oleate (OA). PA+OA co-treatment fully prevents PA lipotoxicity through mechanisms that are not well defined but which have been previously attributed to more efficient esterification and sequestration of PA into triglycerides (TGs) when OA is abundant. However, this hypothesis has never been directly tested by experimentally modulating the relative partitioning of PA/OA between TGs and other lipid fates in hepatocytes. In this study, we found that addition of OA to PA-treated hepatocytes enhanced TG synthesis, reduced total PA uptake and PA lipid incorporation, decreased phospholipid saturation and rescued PA-induced ER stress and lipoapoptosis. Knockdown of diacylglycerol acyltransferase (DGAT), the rate-limiting step in TG synthesis, significantly reduced TG accumulation without impairing OA-mediated rescue of PA lipotoxicity. In both wild-type and DGAT-knockdown hepatocytes, OA co-treatment significantly reduced PA lipid incorporation and overall phospholipid saturation compared to PA-treated hepatocytes. These data indicate that OA's protective effects do not require increased conversion of PA into inert TGs, but instead may be due to OA's ability to compete against PA for cellular uptake and/or esterification and, thereby, normalize the composition of cellular lipids in the presence of a toxic PA load.
Copyright © 2016 Elsevier B.V. All rights reserved.
0 Communities
1 Members
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13 MeSH Terms
Human PCSK9 promotes hepatic lipogenesis and atherosclerosis development via apoE- and LDLR-mediated mechanisms.
Tavori H, Giunzioni I, Predazzi IM, Plubell D, Shivinsky A, Miles J, Devay RM, Liang H, Rashid S, Linton MF, Fazio S
(2016) Cardiovasc Res 110: 268-78
MeSH Terms: Animals, Apolipoproteins E, Atherosclerosis, Cholesterol, LDL, Hepatocytes, Humans, Lipogenesis, Liver, Mice, Inbred C57BL, Mice, Knockout, Proprotein Convertase 9, Receptors, LDL, Triglycerides
Show Abstract · Added February 3, 2017
AIMS - Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the degradation of hepatic low-density lipoprotein (LDL) receptors (LDLR), thereby, decreasing hepatocyte LDL-cholesterol (LDL-C) uptake. However, it is unknown whether PCSK9 has effects on atherogenesis that are independent of lipid changes. The present study investigated the effect of human (h) PCSK9 on plasma lipids, hepatic lipogenesis, and atherosclerotic lesion size and composition in transgenic mice expressing hPCSK9 (hPCSK9tg) on wild-type (WT), LDLR⁻/⁻, or apoE⁻/⁻ background.
METHODS AND RESULTS - hPCSK9 expression significantly increased plasma cholesterol (+91%), triglycerides (+18%), and apoB (+57%) levels only in WT mice. The increase in plasma lipids was a consequence of both decreased hepatic LDLR and increased hepatic lipid production, mediated transcriptionally and post-transcriptionally by PCSK9 and dependent on both LDLR and apoE. Despite the lack of changes in plasma lipids in mice expressing hPCSK9 and lacking LDLR (the main target for PCSK9) or apoE (a canonical ligand for the LDLR), hPCSK9 expression increased aortic lesion size in the absence of apoE (268 655 ± 97 972 µm² in hPCSK9tg/apoE⁻/⁻ vs. 189 423 ± 65 700 µm(2) in apoE⁻/⁻) but not in the absence of LDLR. Additionally, hPCSK9 accumulated in the atheroma and increased lesion Ly6C(hi) monocytes (by 21%) in apoE⁻/⁻ mice, but not in LDLR⁻/⁻ mice.
CONCLUSIONS - PCSK9 increases hepatic lipid and lipoprotein production via apoE- and LDLR-dependent mechanisms. However, hPCSK9 also accumulate in the artery wall and directly affects atherosclerosis lesion size and composition independently of such plasma lipid and lipoprotein changes. These effects of hPCSK9 are dependent on LDLR but are independent of apoE.
Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.
1 Communities
1 Members
0 Resources
13 MeSH Terms
A G Protein-biased Designer G Protein-coupled Receptor Useful for Studying the Physiological Relevance of Gq/11-dependent Signaling Pathways.
Hu J, Stern M, Gimenez LE, Wanka L, Zhu L, Rossi M, Meister J, Inoue A, Beck-Sickinger AG, Gurevich VV, Wess J
(2016) J Biol Chem 291: 7809-20
MeSH Terms: Animals, Arrestins, COS Cells, Calcium, Cells, Cultured, Chlorocebus aethiops, GTP-Binding Protein alpha Subunits, Gq-G11, Gene Knockdown Techniques, Glucose, HEK293 Cells, Hepatocytes, Humans, Mice, Inbred C57BL, Protein Interaction Mapping, Protein Interaction Maps, Receptors, G-Protein-Coupled, Signal Transduction, beta-Arrestins
Show Abstract · Added February 15, 2016
Designerreceptorsexclusivelyactivated by adesignerdrug (DREADDs) are clozapine-N-oxide-sensitive designer G protein-coupled receptors (GPCRs) that have emerged as powerful novel chemogenetic tools to study the physiological relevance of GPCR signaling pathways in specific cell types or tissues. Like endogenous GPCRs, clozapine-N-oxide-activated DREADDs do not only activate heterotrimeric G proteins but can also trigger β-arrestin-dependent (G protein-independent) signaling. To dissect the relative physiological relevance of G protein-mediatedversusβ-arrestin-mediated signaling in different cell types or physiological processes, the availability of G protein- and β-arrestin-biased DREADDs would be highly desirable. In this study, we report the development of a mutationally modified version of a non-biased DREADD derived from the M3muscarinic receptor that can activate Gq/11with high efficacy but lacks the ability to interact with β-arrestins. We also demonstrate that this novel DREADD is activein vivoand that cell type-selective expression of this new designer receptor can provide novel insights into the physiological roles of G protein (Gq/11)-dependentversusβ-arrestin-dependent signaling in hepatocytes. Thus, this novel Gq/11-biased DREADD represents a powerful new tool to study the physiological relevance of Gq/11-dependent signaling in distinct tissues and cell types, in the absence of β-arrestin-mediated cellular effects. Such studies should guide the development of novel classes of functionally biased ligands that show high efficacy in various pathophysiological conditions but display a reduced incidence of side effects.
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
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1 Members
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18 MeSH Terms
Mitochondrial metabolism mediates oxidative stress and inflammation in fatty liver.
Satapati S, Kucejova B, Duarte JA, Fletcher JA, Reynolds L, Sunny NE, He T, Nair LA, Livingston KA, Livingston K, Fu X, Merritt ME, Sherry AD, Malloy CR, Shelton JM, Lambert J, Parks EJ, Corbin I, Magnuson MA, Browning JD, Burgess SC
(2015) J Clin Invest 125: 4447-62
MeSH Terms: Animals, Hepatocytes, Humans, Inflammation, Intracellular Signaling Peptides and Proteins, Mice, Mitochondria, Liver, Non-alcoholic Fatty Liver Disease, Oxidative Stress, Phosphoenolpyruvate Carboxykinase (GTP), Rats, Rats, Wistar
Show Abstract · Added January 5, 2016
Mitochondria are critical for respiration in all tissues; however, in liver, these organelles also accommodate high-capacity anaplerotic/cataplerotic pathways that are essential to gluconeogenesis and other biosynthetic activities. During nonalcoholic fatty liver disease (NAFLD), mitochondria also produce ROS that damage hepatocytes, trigger inflammation, and contribute to insulin resistance. Here, we provide several lines of evidence indicating that induction of biosynthesis through hepatic anaplerotic/cataplerotic pathways is energetically backed by elevated oxidative metabolism and hence contributes to oxidative stress and inflammation during NAFLD. First, in murine livers, elevation of fatty acid delivery not only induced oxidative metabolism, but also amplified anaplerosis/cataplerosis and caused a proportional rise in oxidative stress and inflammation. Second, loss of anaplerosis/cataplerosis via genetic knockdown of phosphoenolpyruvate carboxykinase 1 (Pck1) prevented fatty acid-induced rise in oxidative flux, oxidative stress, and inflammation. Flux appeared to be regulated by redox state, energy charge, and metabolite concentration, which may also amplify antioxidant pathways. Third, preventing elevated oxidative metabolism with metformin also normalized hepatic anaplerosis/cataplerosis and reduced markers of inflammation. Finally, independent histological grades in human NAFLD biopsies were proportional to oxidative flux. Thus, hepatic oxidative stress and inflammation are associated with elevated oxidative metabolism during an obesogenic diet, and this link may be provoked by increased work through anabolic pathways.
1 Communities
1 Members
0 Resources
12 MeSH Terms
Loss of hepatocyte ERBB3 but not EGFR impairs hepatocarcinogenesis.
Scheving LA, Zhang X, Stevenson MC, Weintraub MA, Abbasi A, Clarke AM, Threadgill DW, Russell WE
(2015) Am J Physiol Gastrointest Liver Physiol 309: G942-54
MeSH Terms: Age Factors, Animals, Cell Proliferation, Cell Transformation, Neoplastic, Diethylnitrosamine, ErbB Receptors, Genotype, Hepatocytes, Liver Neoplasms, Liver Regeneration, Male, Mice, 129 Strain, Mice, Inbred C3H, Mice, Knockout, Phenotype, Phosphorylation, Receptor, ErbB-3, STAT3 Transcription Factor, Signal Transduction
Show Abstract · Added May 5, 2016
Epidermal growth factor receptor (EGFR) and ERBB3 have been implicated in hepatocellular carcinogenesis (HCC). However, it is not known whether altering the activity of either EGFR or ERBB3 affects HCC development. We now show that Egfr(Dsk5) mutant mice, which have a gain-of-function allele that increases basal EGFR kinase activity, develop spontaneous HCC by 10 mo of age. Their tumors show increased activation of EGFR, ERBB2, and ERBB3 as well as AKT and ERK1,2. Hepatocyte-specific models of EGFR and ERBB3 gene ablation were generated to evaluate how the loss of these genes affected tumor progression. Loss of either receptor tyrosine kinase did not alter liver development or regenerative liver growth following carbon tetrachloride injection. However, using a well-characterized model of HCC in which N-nitrosodiethylamine is injected into 14-day-old mice, we discovered that loss of hepatocellular ERBB3 but not EGFR, which occurred after tumor initiation, retarded liver tumor formation and cell proliferation. We found no evidence that this was due to increased apoptosis or diminished phosphatidylinositol-3-kinase activity in the ERBB3-null cells. However, the relative amount of phospho-STAT3 was diminished in tumors derived from these mice, suggesting that ERBB3 may promote HCC through STAT3 activation.
Copyright © 2015 the American Physiological Society.
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19 MeSH Terms