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Martin GG, Landrock D, McIntosh AL, Milligan S, Landrock KK, Kier AB, Mackie J, Schroeder F. High Glucose and Liver Fatty Acid Binding Protein Gene Ablation Differentially Impact Whole Body and Liver Phenotype in High-Fat Pair-Fed Mice. Lipids 2020; 55:309-327. [PMID: 32314395 DOI: 10.1002/lipd.12238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 03/12/2020] [Accepted: 03/30/2020] [Indexed: 12/14/2022]
Abstract
Ad libitum-fed diets high in fat and carbohydrate (especially fructose) induce weight gain, obesity, and nonalcoholic fatty liver disease (NAFLD) in humans and animal models. However, interpretation is complicated since ad libitum feeding of such diets induces hyperphagia and upregulates expression of liver fatty acid binding protein (L-FABP)-a protein intimately involved in fatty acid and glucose regulation of lipid metabolism. Wild-type (WT) and L-fabp gene ablated (LKO) mice were pair-fed either high-fat diet (HFD) or high-fat/high-glucose diet (HFGD) wherein total carbohydrate was maintained constant but the proportion of glucose was increased at the expense of fructose. In LKO mice, the pair-fed HFD increased body weight and lean tissue mass (LTM) but had no effect on fat tissue mass (FTM) or hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and sterol carrier protein-2), but lower hepatic fatty acid oxidation (decreased serum β-hydroxybutyrate). LKO mice pair-fed HFGD also exhibited increased body weight; however, these mice had increased FTM, not LTM, and increased hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice also exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and acyl-CoA binding protein, but not sterol carrier protein-2), but there was no change in hepatic fatty acid oxidation (serum β-hydroxybutyrate) as compared to pair-fed WT counterparts.
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Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - John Mackie
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
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Martin GG, Seeger DR, McIntosh AL, Milligan S, Chung S, Landrock D, Dangott LJ, Golovko MY, Murphy EJ, Kier AB, Schroeder F. Sterol Carrier Protein-2/Sterol Carrier Protein-x/Fatty Acid Binding Protein-1 Ablation Impacts Response of Brain Endocannabinoid to High-Fat Diet. Lipids 2019; 54:583-601. [PMID: 31487051 DOI: 10.1002/lipd.12192] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 08/16/2019] [Accepted: 08/21/2019] [Indexed: 12/14/2022]
Abstract
Brain endocannabinoids (EC) such as arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) primarily originate from serum arachidonic acid (ARA), whose level is regulated in part by a cytosolic ARA-binding protein, that is, liver fatty acid binding protein-1 (FABP1), not expressed in the brain. Ablation of the Fabp1 gene (LKO) increases brain AEA and 2-AG by decreasing hepatic uptake of ARA to increase serum ARA, thereby increasing ARA availability for uptake by the brain. The brain also expresses sterol carrier protein-2 (SCP-2), which is also a cytosolic ARA-binding protein. To further resolve the role of SCP-2 independent of FABP1, mice ablated in the Scp-2/Scp-x gene (DKO) were crossed with mice ablated in the Fabp1 gene (LKO) mice to generate triple knock out (TKO) mice. TKO impaired the ability of LKO to increase brain AEA and 2-AG. While a high-fat diet (HFD) alone increased brain AEA, TKO impaired this effect. Overall, these TKO-induced blocks were not attributable to altered expression of brain proteins in ARA uptake, AEA/2-AG synthesis, or AEA/2-AG degrading enzymes. Instead, TKO reduced serum levels of free ARA and/or total ARA and thereby decreased ARA availability for uptake to the brain and downstream synthesis of AEA and 2-AG therein. In summary, Scp-2/Scp-x gene ablation in Fabp1 null (LKO) mice antagonized the impact of LKO and HFD on brain ARA and, subsequently, EC levels. Thus, both FABP1 and SCP-2 participate in regulating the EC system in the brain.
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Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX, 77843-4466, USA
| | - Drew R Seeger
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX, 77843-4466, USA
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4467, USA
| | - Sarah Chung
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4467, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4467, USA
| | - Lawrence J Dangott
- Protein Chemistry Laboratory, Texas A&M University, College Station, TX, 77843-2128, USA
| | - Mikhail Y Golovko
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Eric J Murphy
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX, 77843-4466, USA
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McIntosh AL, Atshaves BP, Martin GG, Landrock D, Milligan S, Landrock KK, Huang H, Storey SM, Mackie J, Schroeder F, Kier AB. Effect of liver fatty acid binding protein (L-FABP) gene ablation on lipid metabolism in high glucose diet (HGD) pair-fed mice. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:985-1004. [PMID: 30910689 PMCID: PMC6482111 DOI: 10.1016/j.bbalip.2019.03.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 03/02/2019] [Accepted: 03/21/2019] [Indexed: 01/06/2023]
Abstract
Liver fatty acid binding protein (L-FABP) is the major fatty acid binding/"chaperone" protein in hepatic cytosol. Although fatty acids can be derived from the breakdown of dietary fat and glucose, relatively little is known regarding the impact of L-FABP on phenotype in the context of high dietary glucose. Potential impact was examined in wild-type (WT) and Lfabp gene ablated (LKO) female mice fed either a control or pair-fed high glucose diet (HGD). WT mice fed HGD alone exhibited decreased whole body weight gain and weight gain/kcal food consumed-both as reduced lean tissue mass (LTM) and fat tissue mass (FTM). Conversely, LKO alone increased weight gain, lean tissue mass, and fat tissue mass while decreasing serum β-hydroxybutyrate (indicative of hepatic fatty acid oxidation)-regardless of diet. Both LKO alone and HGD alone significantly altered the serum lipoprotein profile and increased triacylglycerol (TG), but in HGD mice the LKO did not further exacerbate serum TG content. HGD had little effect on hepatic lipid composition in WT mice, but prevented the LKO-induced selective increase in hepatic phospholipid, free-cholesterol and cholesteryl-ester. Taken together, these findings suggest that high glucose diet diminished the effects of LKO on the whole body and lipid phenotype of these mice.
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Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Barbara P Atshaves
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, United States of America
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Stephen M Storey
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - John Mackie
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America.
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Martin GG, Landrock D, Dangott LJ, McIntosh AL, Kier AB, Schroeder F. Human Liver Fatty Acid Binding Protein-1 T94A Variant, Nonalcohol Fatty Liver Disease, and Hepatic Endocannabinoid System. Lipids 2019; 53:27-40. [PMID: 29488637 DOI: 10.1002/lipd.12008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 10/26/2017] [Accepted: 10/31/2017] [Indexed: 12/16/2022]
Abstract
Hepatic endocannabinoids (EC) and their major binding/"chaperone" protein (i.e., liver fatty acid binding protein-1 [FABP1]) are associated with development of nonalcoholic fatty liver (NAFLD) in animal models and humans. Since expression of the highly prevalent human FABP1 T94A variant induces serum lipid accumulation, it is important to determine its impact on hepatic lipid accumulation and the EC system. This issue was addressed in livers from human subjects expressing only wild-type (WT) FABP1 T94T (TT genotype) or T94A variant (TC or CC genotype). WT FABP1 males had lower total lipids (both neutral cholesteryl esters, triacylglycerols) and phospholipids than females. WT FABP1 males' lower lipids correlated with lower levels of the N-acylethanolamide DHEA and 2-monoacylglycerols (2-MAG) (2-OG, 2-PG). T94A expression in males increased the hepatic total lipids (triacylglycerol, cholesteryl ester), which is consistent with their higher level of CB1-potentiating 2-OG and lower antagonistic EPEA. In contrast, in females, T94A expression did not alter the total lipids, neutral lipids, or phospholipids, which is attributable to the higher cannabinoid receptor-1 (CB1) agonist arachidonoylethanolamide (AEA) and its CB1-potentiator OEA being largely offset by reduced potentiating 2-OG and increased antagonistic EPEA. Taken together, these findings indicate that T94A-induced alterations in the hepatic EC system contribute at least in part to the hepatic accumulation of lipids associated with NAFLD, especially in males.
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Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4467, USA
| | - Lawrence J Dangott
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX, 77843-4466, USA
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Huang H, McIntosh AL, Martin GG, Dangott LJ, Kier AB, Schroeder F. Structural and Functional Interaction of Δ 9-Tetrahydrocannabinol with Liver Fatty Acid Binding Protein (FABP1). Biochemistry 2018; 57:6027-6042. [PMID: 30232874 DOI: 10.1021/acs.biochem.8b00744] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Although serum Δ9-tetrahydrocannabinol (Δ9-THC) undergoes rapid hepatic clearance and metabolism, almost nothing is known regarding the mechanism(s) whereby this highly lipophilic phytocannabinoid is transported for metabolism/excretion. A novel NBD-arachidonoylethanolamide (NBD-AEA) fluorescence displacement assay showed that liver fatty acid binding protein (FABP1), the major hepatic endocannabinoid (EC) binding protein, binds the first major metabolite of Δ9-THC (Δ9-THC-OH) as well as Δ9-THC itself. Circular dichroism (CD) confirmed that not only Δ9-THC and Δ9-THC-OH but also downstream metabolites Δ9-THC-COOH and Δ9-THC-CO-glucuronide directly interact with FABP1. Δ9-THC and metabolite interaction differentially altered the FABP1 secondary structure, increasing total α-helix (all), decreasing total β-sheet (Δ9-THC-COOH, Δ9-THC-CO-glucuronide), increasing turns (Δ9-THC-OH, Δ9-THC-COOH, Δ9-THC-CO-glucuronide), and decreasing unordered structure (Δ9-THC, Δ9-THC-OH). Cultured primary hepatocytes from wild-type (WT) mice took up and converted Δ9-THC to the above metabolites. Fabp1 gene ablation (LKO) dramatically increased hepatocyte accumulation of Δ9-THC and even more so its primary metabolites Δ9-THC-OH and Δ9-THC-COOH. Concomitantly, rtPCR and Western blotting indicated that LKO significantly increased Δ9-THC's ability to regulate downstream nuclear receptor transcription of genes important in both EC ( Napepld > Daglb > Dagla, Naaa, Cnr1) and lipid ( Cpt1A > Fasn, FATP4) metabolism. Taken together, the data indicated that FABP1 may play important roles in Δ9-THC uptake and elimination as well as Δ9-THC induction of genes regulating hepatic EC levels and downstream targets in lipid metabolism.
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Affiliation(s)
- Huan Huang
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Avery L McIntosh
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Gregory G Martin
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Lawrence J Dangott
- Protein Chemistry Laboratory , Texas A&M University , College Station , Texas 77843-2128 , United States
| | - Ann B Kier
- Department of Pathobiology , Texas A&M University , College Station , Texas 77843-4467 , United States
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
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McIntosh AL, Huang H, Landrock D, Martin GG, Li S, Kier AB, Schroeder F. Impact of Fabp1 Gene Ablation on Uptake and Degradation of Endocannabinoids in Mouse Hepatocytes. Lipids 2018; 53:561-580. [PMID: 30203570 DOI: 10.1002/lipd.12071] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 06/11/2018] [Accepted: 06/15/2018] [Indexed: 12/30/2022]
Abstract
Liver fatty-acid-binding protein (FABP1, L-FABP) is the major cytosolic binding/chaperone protein for both precursor arachidonic acid (ARA) and the endocannabinoid (EC) products N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG). Although FABP1 regulates hepatic uptake and metabolism of ARA, almost nothing is known regarding FABP1's impact on AEA and 2-AG uptake, intracellular distribution, and targeting of AEA and 2-AG to degradative hepatic enzymes. In vitro assays revealed that FABP1 considerably enhanced monoacylglycerol lipase hydrolysis of 2-AG but only modestly enhanced AEA hydrolysis by fatty-acid amide hydrolase. Conversely, liquid chromatography-mass spectrometry of lipids from Fabp1 gene-ablated (LKO) hepatocytes confirmed that loss of FABP1 markedly diminished hydrolysis of 2-AG. Furthermore, the real-time imaging of novel fluorescent NBD-labeled probes (NBD-AEA, NBD-2-AG, and NBD-ARA) resolved FABP1's impact on uptake vs intracellular targeting/hydrolysis. FABP1 bound NBD-ARA with 2:1 stoichiometry analogous to ARA, but bound NBD-2-AG and NBD-AEA with 1:1 stoichiometry-apparently at different sites in FABP1's binding cavity. All three probes were taken up, but NBD-2-AG and NBD-AEA were targeted to lipid droplets. LKO reduced the uptake of NBD-ARA as expected, significantly enhanced that of NBD-AEA, but had little effect on NBD-2-AG. These data indicated that FABP1 impacts hepatocyte EC levels by binding EC and differentially impacts their intracellular hydrolysis (2-AG) and uptake (AEA).
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Affiliation(s)
- Avery L McIntosh
- Departments of Physiology and Pharmacology, Texas A&M University, 664 Raymond Stotzer Pkwy, 4466 TAMU, College Station, TX 77843-4466, USA
| | - Huan Huang
- Departments of Physiology and Pharmacology, Texas A&M University, 664 Raymond Stotzer Pkwy, 4466 TAMU, College Station, TX 77843-4466, USA
| | - Danilo Landrock
- Departments of Pathobiology, Texas A&M University, 664 Raymond Stotzer Pkwy, 4467 TAMU, College Station, TX 77843-4467, USA
| | - Gregory G Martin
- Departments of Physiology and Pharmacology, Texas A&M University, 664 Raymond Stotzer Pkwy, 4466 TAMU, College Station, TX 77843-4466, USA
| | - Shengrong Li
- Avanti Polar Lipids, 700 Industrial Park Drive, Alabaster, AL 35007-9105, USA
| | - Ann B Kier
- Departments of Pathobiology, Texas A&M University, 664 Raymond Stotzer Pkwy, 4467 TAMU, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Departments of Physiology and Pharmacology, Texas A&M University, 664 Raymond Stotzer Pkwy, 4466 TAMU, College Station, TX 77843-4466, USA
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Martin GG, Seeger DR, McIntosh AL, Chung S, Milligan S, Landrock D, Dangott LJ, Golovko MY, Murphy EJ, Kier AB, Schroeder F. Scp-2/Scp-x ablation in Fabp1 null mice differentially impacts hepatic endocannabinoid level depending on dietary fat. Arch Biochem Biophys 2018; 650:93-102. [PMID: 29763591 PMCID: PMC6033332 DOI: 10.1016/j.abb.2018.05.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 05/07/2018] [Accepted: 05/11/2018] [Indexed: 12/21/2022]
Abstract
Dysregulation of the hepatic endocannabinoid (EC) system and high fat diet (HFD) are associated with non-alcoholic fatty liver disease. Liver cytosol contains high levels of two novel endocannabinoid binding proteins-liver fatty acid binding protein (FABP1) and sterol carrier protein-2 (SCP-2). While Fabp1 gene ablation significantly increases hepatic levels of arachidonic acid (ARA)-containing EC and sex-dependent response to pair-fed high fat diet (HFD), the presence of SCP-2 complicates interpretation. These issues were addressed by ablating Scp-2/Scp-x in Fabp1 null mice (TKO). In control-fed mice, TKO increased hepatic levels of arachidonoylethanolamide (AEA) in both sexes. HFD impacted hepatic EC levels by decreasing AEA in TKO females and decreasing 2-arachidonoyl glycerol (2-AG) in WT of both sexes. Only TKO males on HFD had increased hepatic 2-AG levels. Hepatic ARA levels were decreased in control-fed TKO of both sexes. Changes in hepatic AEA/2-AG levels were not associated with altered amounts of hepatic proteins involved in AEA/2-AG synthesis or degradation. These findings suggested that ablation of the Scp-2/Scp-x gene in Fabp1 null mice exacerbated hepatic EC accumulation and antagonized the impact of HFD on hepatic EC levels-suggesting both proteins play important roles in regulating the hepatic EC system.
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Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA.
| | - Drew R Seeger
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037 USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA
| | - Sarah Chung
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, USA
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, USA
| | - Lawrence J Dangott
- Protein Chemistry Laboratory, Texas A&M University, College Station, TX 77843-2128, USA
| | - Mikhail Y Golovko
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037 USA
| | - Eric J Murphy
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037 USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA.
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McIntosh AL, Martin GG, Huang H, Landrock D, Kier AB, Schroeder F. Δ 9-Tetrahydrocannabinol induces endocannabinoid accumulation in mouse hepatocytes: antagonism by Fabp1 gene ablation. J Lipid Res 2018; 59:646-657. [PMID: 29414765 PMCID: PMC5880504 DOI: 10.1194/jlr.m082644] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/03/2018] [Indexed: 01/06/2023] Open
Abstract
Phytocannabinoids, such as Δ9-tetrahydrocannabinol (THC), bind and activate cannabinoid (CB) receptors, thereby "piggy-backing" on the same pathway's endogenous endocannabinoids (ECs). The recent discovery that liver fatty acid binding protein-1 (FABP1) is the major cytosolic "chaperone" protein with high affinity for both Δ9-THC and ECs suggests that Δ9-THC may alter hepatic EC levels. Therefore, the impact of Δ9-THC or EC treatment on the levels of endogenous ECs, such as N-arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG), was examined in cultured primary mouse hepatocytes from WT and Fabp1 gene-ablated (LKO) mice. Δ9-THC alone or 2-AG alone significantly increased AEA and especially 2-AG levels in WT hepatocytes. LKO alone markedly increased AEA and 2-AG levels. However, LKO blocked/diminished the ability of Δ9-THC to further increase both AEA and 2-AG. In contrast, LKO potentiated the ability of exogenous 2-AG to increase the hepatocyte level of AEA and 2-AG. These and other data suggest that Δ9-THC increases hepatocyte EC levels, at least in part, by upregulating endogenous AEA and 2-AG levels. This may arise from Δ9-THC competing with AEA and 2-AG binding to FABP1, thereby decreasing targeting of bound AEA and 2-AG to the degradative enzymes, fatty acid amide hydrolase and monoacylglyceride lipase, to decrease hydrolysis within hepatocytes.
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Affiliation(s)
- Avery L McIntosh
- Departments of Physiology and Pharmacology Texas A&M University, College Station, TX 77843
| | - Gregory G Martin
- Departments of Physiology and Pharmacology Texas A&M University, College Station, TX 77843
| | - Huan Huang
- Departments of Physiology and Pharmacology Texas A&M University, College Station, TX 77843
| | - Danilo Landrock
- Departments of Pathobiology, Texas A&M University, College Station, TX 77843
| | - Ann B Kier
- Departments of Pathobiology, Texas A&M University, College Station, TX 77843
| | - Friedhelm Schroeder
- Departments of Physiology and Pharmacology Texas A&M University, College Station, TX 77843.
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