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Results: 1 to 10 of 121

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Treating Nonalcoholic Fatty Liver Disease From the Outside In?
Flynn CR
(2019) Cell Mol Gastroenterol Hepatol 7: 682-683
MeSH Terms: Animals, Hepatocytes, Intracellular Signaling Peptides and Proteins, Mice, Non-alcoholic Fatty Liver Disease, Oligonucleotides, Antisense, Protein-Serine-Threonine Kinases
Added April 15, 2019
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1 Members
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7 MeSH Terms
Glutamate-oxaloacetate transaminase activity promotes palmitate lipotoxicity in rat hepatocytes by enhancing anaplerosis and citric acid cycle flux.
Egnatchik RA, Leamy AK, Sacco SA, Cheah YE, Shiota M, Young JD
(2019) J Biol Chem 294: 3081-3090
MeSH Terms: Animals, Aspartate Aminotransferases, Cell Death, Cell Line, Citric Acid Cycle, Extracellular Space, Glutamine, Hepatocytes, Ketoglutaric Acids, Male, Oxidative Stress, Oxygen, Palmitates, Rats, Rats, Sprague-Dawley
Show Abstract · Added March 28, 2019
Hepatocyte lipotoxicity is characterized by aberrant mitochondrial metabolism, which predisposes cells to oxidative stress and apoptosis. Previously, we reported that translocation of calcium from the endoplasmic reticulum to mitochondria of palmitate-treated hepatocytes activates anaplerotic flux from glutamine to α-ketoglutarate (αKG), which subsequently enters the citric acid cycle (CAC) for oxidation. We hypothesized that increased glutamine anaplerosis fuels elevations in CAC flux and oxidative stress following palmitate treatment. To test this hypothesis, primary rat hepatocytes or immortalized H4IIEC3 rat hepatoma cells were treated with lipotoxic levels of palmitate while modulating anaplerotic pathways leading to αKG. We found that culture media supplemented with glutamine, glutamate, or dimethyl-αKG increased palmitate lipotoxicity compared with media that lacked these anaplerotic substrates. Knockdown of glutamate-oxaloacetate transaminase activity significantly reduced the lipotoxic effects of palmitate, whereas knockdown of glutamate dehydrogenase (Glud1) had no effect on palmitate lipotoxicity. C flux analysis of H4IIEC3 cells co-treated with palmitate and the pan-transaminase inhibitor aminooxyacetic acid confirmed that reductions in lipotoxic markers were associated with decreases in anaplerosis, CAC flux, and oxygen consumption. Taken together, these results demonstrate that lipotoxic palmitate treatments enhance anaplerosis in cultured rat hepatocytes, causing a shift to aberrant transaminase metabolism that fuels CAC dysregulation and oxidative stress.
© 2019 Egnatchik et al.
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15 MeSH Terms
In vitro safety pharmacology evaluation of 2-hydroxybenzylamine acetate.
Fuller JC, Pitchford LM, Morrison RD, Daniels JS, Flynn CR, Abumrad NN, Oates JA, Boutaud O, Rathmacher JA
(2018) Food Chem Toxicol 121: 541-548
MeSH Terms: Adult, Benzylamines, Blood Proteins, Cytochrome P-450 Enzyme System, ERG1 Potassium Channel, Erythrocytes, Female, Gene Expression Regulation, Enzymologic, Hepatocytes, Humans, Male, Middle Aged, Mutagenicity Tests, Salmonella typhimurium
Show Abstract · Added April 15, 2019
2-hydroxybenzylamine (2-HOBA), a compound found in buckwheat, is a potent scavenger of reactive γ-ketoaldehydes, which are increased in diseases associated with inflammation and oxidative stress. While the potential of 2-HOBA is promising, studies were needed to characterize the safety of the compound before clinical trials. In a series of experiments, the risks of 2-HOBA-mediated mutagenicity and cardio-toxicity were assessed in vitro. The effects of 2-HOBA on the mRNA expression of select cytochrome P450 (CYP) enzymes were also assessed in cryopreserved human hepatocytes. Further, the distribution and metabolism of 2-HOBA in blood were determined. Our results indicate that 2-HOBA is not cytotoxic or mutagenic in vitro and does not induce the expression of CYP1A2, CYP2B6, or CYP3A4 in human hepatocytes. The results of the hERG testing showed a low risk of cardiac QT wave prolongation. Plasma protein binding and red blood cell distribution characteristics indicate low protein binding and no preferential distribution into erythrocytes. The major metabolites identified were salicylic acid and the glycoside conjugate of 2-HOBA. Together, these findings support development of 2-HOBA as a nutritional supplement and provide important information for the design of further preclinical safety studies in animals as well as for human clinical trials with 2-HOBA.
Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.
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MeSH Terms
Hepatic Gi signaling regulates whole-body glucose homeostasis.
Rossi M, Zhu L, McMillin SM, Pydi SP, Jain S, Wang L, Cui Y, Lee RJ, Cohen AH, Kaneto H, Birnbaum MJ, Ma Y, Rotman Y, Liu J, Cyphert TJ, Finkel T, McGuinness OP, Wess J
(2018) J Clin Invest 128: 746-759
MeSH Terms: Animals, Blood Glucose, Extracellular Signal-Regulated MAP Kinases, Female, GTP-Binding Protein alpha Subunits, Gi-Go, Gene Expression Profiling, Glucagon, Gluconeogenesis, Glucose, Hepatocytes, Homeostasis, Humans, Liver, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Oxygen, Phosphatidylinositol 3-Kinases, Phosphorylation, Reactive Oxygen Species, Receptors, Glucagon, Signal Transduction
Show Abstract · Added March 14, 2018
An increase in hepatic glucose production (HGP) is a key feature of type 2 diabetes. Excessive signaling through hepatic Gs-linked glucagon receptors critically contributes to pathologically elevated HGP. Here, we tested the hypothesis that this metabolic impairment can be counteracted by enhancing hepatic Gi signaling. Specifically, we used a chemogenetic approach to selectively activate Gi-type G proteins in mouse hepatocytes in vivo. Unexpectedly, activation of hepatic Gi signaling triggered a pronounced increase in HGP and severely impaired glucose homeostasis. Moreover, increased Gi signaling stimulated glucose release in human hepatocytes. A lack of functional Gi-type G proteins in hepatocytes reduced blood glucose levels and protected mice against the metabolic deficits caused by the consumption of a high-fat diet. Additionally, we delineated a signaling cascade that links hepatic Gi signaling to ROS production, JNK activation, and a subsequent increase in HGP. Taken together, our data support the concept that drugs able to block hepatic Gi-coupled GPCRs may prove beneficial as antidiabetic drugs.
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23 MeSH Terms
Hepatocyte estrogen receptor alpha mediates estrogen action to promote reverse cholesterol transport during Western-type diet feeding.
Zhu L, Shi J, Luu TN, Neuman JC, Trefts E, Yu S, Palmisano BT, Wasserman DH, Linton MF, Stafford JM
(2018) Mol Metab 8: 106-116
MeSH Terms: Animals, Atherosclerosis, Biological Transport, Cells, Cultured, Cholesterol, Diet, Western, Estrogen Receptor alpha, Female, Hepatocytes, Insulin Resistance, Macrophages, Male, Mice, Mice, Inbred C57BL, Obesity, Sex Factors
Show Abstract · Added April 10, 2018
OBJECTIVE - Hepatocyte deletion of estrogen receptor alpha (LKO-ERα) worsens fatty liver, dyslipidemia, and insulin resistance in high-fat diet fed female mice. However, whether or not hepatocyte ERα regulates reverse cholesterol transport (RCT) in mice has not yet been reported.
METHODS AND RESULTS - Using LKO-ERα mice and wild-type (WT) littermates fed a Western-type diet, we found that deletion of hepatocyte ERα impaired in vivo RCT measured by the removal of H-cholesterol from macrophages to the liver, and subsequently to feces, in female mice but not in male mice. Deletion of hepatocyte ERα decreased the capacity of isolated HDL to efflux cholesterol from macrophages and reduced the ability of isolated hepatocytes to accept cholesterol from HDL ex vivo in both sexes. However, only in female mice, LKO-ERα increased serum cholesterol levels and increased HDL particle sizes. Deletion of hepatocyte ERα increased adiposity and worsened insulin resistance to a greater degree in female than male mice. All of the changes lead to a 5.6-fold increase in the size of early atherosclerotic lesions in female LKO-ERα mice compared to WT controls.
CONCLUSIONS - Estrogen signaling through hepatocyte ERα plays an important role in RCT and is protective against lipid retention in the artery wall during early stages of atherosclerosis in female mice fed a Western-type diet.
Published by Elsevier GmbH.
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16 MeSH Terms
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.
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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, Cercopithecus 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
4 Members
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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.
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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.
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9 MeSH Terms