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Xu C, Li H, Tang CK. Sterol carrier protein 2 in lipid metabolism and non-alcoholic fatty liver disease: Pathophysiology, molecular biology, and potential clinical implications. Metabolism 2022; 131:155180. [PMID: 35311663 DOI: 10.1016/j.metabol.2022.155180] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 02/03/2022] [Accepted: 03/13/2022] [Indexed: 11/29/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is considered as the most common chronic liver disease and has become a rapidly global public health problem. Sterol carrier protein 2 (SCP-2), also called non-specific lipid-transfer protein, is predominantly expressed by the liver. SCP-2 plays a key role in intracellular lipid transport and metabolism. SCP-2 has been closely implicated in the development of NAFLD-related metabolic disorders, such as obesity, atherosclerosis, Type 2 diabetes mellitus (T2DM), and gallstones. Recent studies indicate that SCP-2 plays a beneficial role in NAFLD by regulating cholesterol-, endocannabinoid-, and fatty acid-related aspects of lipid metabolism. Hence, in this paper, we summarize the latest findings about the roles of SCP-2 in hepatic steatosis and further describe its molecular function in the pathogenesis of NAFLD.
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Affiliation(s)
- Can Xu
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, The First Affiliated Hospital of University of South China, Department of Cardiology, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, PR China
| | - Heng Li
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, The First Affiliated Hospital of University of South China, Department of Cardiology, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, PR China.
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, The First Affiliated Hospital of University of South China, Department of Cardiology, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, PR China.
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2
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Xu C, Li H, Tang CK. Sterol Carrier Protein 2: A promising target in the pathogenesis of atherosclerosis. Genes Dis 2022; 10:457-467. [DOI: 10.1016/j.gendis.2021.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 11/21/2021] [Accepted: 12/01/2021] [Indexed: 10/19/2022] Open
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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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He H, Wang J, Yannie PJ, Kakiyama G, Korzun WJ, Ghosh S. Sterol carrier protein-2 deficiency attenuates diet-induced dyslipidemia and atherosclerosis in mice. J Biol Chem 2018; 293:9223-9231. [PMID: 29700117 DOI: 10.1074/jbc.ra118.002290] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/25/2018] [Indexed: 01/05/2023] Open
Abstract
Intracellular cholesterol transport proteins move cholesterol to different subcellular compartments and thereby regulate its final metabolic fate. In hepatocytes, for example, delivery of high-density lipoprotein (HDL)-associated cholesterol for bile acid synthesis or secretion into bile facilitates cholesterol elimination from the body (anti-atherogenic effect), whereas delivery for esterification and subsequent incorporation into apolipoprotein B-containing atherogenic lipoproteins (e.g. very-low-density lipoprotein (VLDL)) enhances cholesterol secretion into the systemic circulation (pro-atherogenic effect). Intracellular cholesterol transport proteins such as sterol carrier protein-2 (SCP2) should, therefore, play a role in regulating these pro- or anti-atherosclerotic processes. Here, we sought to evaluate the effects of SCP2 deficiency on the development of diet-induced atherosclerosis. We generated LDLR-/- mice deficient in SCP2/SCPx (LS) and examined the effects of this deficiency on Western diet-induced atherosclerosis. SCP2/SCPx deficiency attenuated atherosclerosis in LS mice by >80% and significantly reduced plasma cholesterol and triglyceride levels. Investigation of the likely underlying mechanisms revealed a significant reduction in intestinal cholesterol absorption (given as an oral gavage) in SCP2/SCPx-deficient mice. Consistently, siRNA-mediated knockdown of SCP2 in intestinal cells significantly reduced cholesterol uptake. Furthermore, hepatic triglyceride/VLDL secretion from the liver or hepatocytes isolated from SCP2/SCPx-deficient mice was significantly reduced. These results indicate an important regulatory role for SCP2 deficiency in attenuating diet-induced atherosclerosis by limiting intestinal cholesterol absorption and decreasing hepatic triglyceride/VLDL secretion. These findings suggest targeted inhibition of SCP2 as a potential therapeutic strategy to reduce Western diet-induced dyslipidemia and atherosclerosis.
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Affiliation(s)
| | - Jing Wang
- From the Departments of Internal Medicine and
| | - Paul J Yannie
- the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - Genta Kakiyama
- the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - William J Korzun
- Clinical and Laboratory Sciences, Virginia Commonwealth University (VCU) Medical Center, Richmond, Virginia 23298 and
| | - Shobha Ghosh
- From the Departments of Internal Medicine and .,the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
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Milligan S, Martin GG, Landrock D, McIntosh AL, Mackie JT, Schroeder F, Kier AB. Ablating both Fabp1 and Scp2/Scpx (TKO) induces hepatic phospholipid and cholesterol accumulation in high fat-fed mice. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:323-338. [PMID: 29307784 DOI: 10.1016/j.bbalip.2017.12.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 12/13/2017] [Accepted: 12/31/2017] [Indexed: 01/16/2023]
Abstract
Although singly ablating Fabp1 or Scp2/Scpx genes may exacerbate the impact of high fat diet (HFD) on whole body phenotype and non-alcoholic fatty liver disease (NAFLD), concomitant upregulation of the non-ablated gene, preference for ad libitum fed HFD, and sex differences complicate interpretation. Therefore, these issues were addressed in male and female mice ablated in both genes (Fabp1/Scp2/Scpx null or TKO) and pair-fed HFD. Wild-type (WT) males gained more body weight as fat tissue mass (FTM) and exhibited higher hepatic lipid accumulation than WT females. The greater hepatic lipid accumulation in WT males was associated with higher hepatic expression of enzymes in glyceride synthesis, higher hepatic bile acids, and upregulation of transporters involved in hepatic reuptake of serum bile acids. While TKO had little effect on whole body phenotype and hepatic bile acid accumulation in either sex, TKO increased hepatic accumulation of lipids in both, specifically phospholipid and cholesteryl esters in males and females and free cholesterol in females. TKO-induced increases in glycerides were attributed not only to complete loss of FABP1, SCP2 and SCPx, but also in part to sex-dependent upregulation of hepatic lipogenic enzymes. These data with WT and TKO mice pair-fed HFD indicate that: i) Sex significantly impacted the ability of HFD to increase body weight, induce hepatic lipid accumulation and increase hepatic bile acids; and ii) TKO exacerbated the HFD ability to induce hepatic lipid accumulation, regardless of sex, but did not significantly alter whole body phenotype in either sex.
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Affiliation(s)
- Sherrelle Milligan
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Gregory G Martin
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Avery L McIntosh
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - John T Mackie
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
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Landrock D, Milligan S, Martin GG, McIntosh AL, Landrock KK, Schroeder F, Kier AB. Effect of Fabp1/Scp-2/Scp-x Ablation on Whole Body and Hepatic Phenotype of Phytol-Fed Male Mice. Lipids 2017; 52:385-397. [PMID: 28382456 PMCID: PMC5500168 DOI: 10.1007/s11745-017-4249-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 03/28/2017] [Indexed: 11/29/2022]
Abstract
Liver fatty acid binding protein (Fabp1) and sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x) genes encode proteins that enhance hepatic uptake, cytosolic transport, and peroxisomal oxidation of toxic branched-chain fatty acids derived from dietary phytol. Since male wild-type (WT) mice express markedly higher levels of these proteins than females, the impact of ablating both genes (TKO) was examined in phytol-fed males. In WT males, high phytol diet alone had little impact on whole body weight and did not alter the proportion of lean tissue mass (LTM) versus fat tissue mass (FTM). TKO conferred on dietary phytol the ability to induce weight loss as well as reduce liver weight, FTM, and even more so LTM. Concomitantly TKO induced hepatic lipid accumulation, preferentially threefold increased phospholipid (PL) at the expense of decreased triacylglycerol (TG) and total cholesterol. Increased PL was associated with upregulation of membrane fatty acid transport/translocase proteins (FATP 2,4), cytosolic fatty acid/fatty acyl-CoA binding proteins (FABP2, ACBP), and the rate limiting enzyme in PL synthesis (Gpam). Decreased TG and cholesterol levels were not attributable to altered levels in respective synthetic enzymes or nuclear receptors. These data suggest that the higher level of Fabp1 and Scp2/Scpx gene products in WT males was protective against deleterious effects of dietary phytol, but TKO significantly exacerbated phytol effects in males.
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Affiliation(s)
- Danilo Landrock
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA
| | - Sherrelle Milligan
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA
| | - Gregory G Martin
- Department of Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Kerstin K Landrock
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA.
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Milligan S, Martin GG, Landrock D, McIntosh AL, Mackie JT, Schroeder F, Kier AB. Impact of dietary phytol on lipid metabolism in SCP2/SCPX/L-FABP null mice. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:291-304. [PMID: 27940000 PMCID: PMC5266609 DOI: 10.1016/j.bbalip.2016.12.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/15/2016] [Accepted: 12/04/2016] [Indexed: 12/20/2022]
Abstract
In vitro studies suggest that liver fatty acid binding protein (L-FABP) and sterol carrier protein-2/sterol carrier protein-x (SCP2/SCPx) gene products facilitate uptake and metabolism and detoxification of dietary-derived phytol in mammals. However, concomitant upregulation of L-FABP in SCP2/SCPx null mice complicates interpretation of their physiological phenotype. Therefore, the impact of ablating both the L-FABP gene and SCP2/SCPx gene (L-FABP/SCP2/SCPx null or TKO) was examined in phytol-fed female wild-type (WT) and TKO mice. TKO increased hepatic total lipid accumulation, primarily phospholipid, by mechanisms involving increased hepatic levels of proteins in the phospholipid synthetic pathway. Concomitantly, TKO reduced expression of proteins in targeting fatty acids towards the triacylglycerol synthetic pathway. Increased hepatic lipid accumulation was not associated with any concomitant upregulation of membrane fatty acid transport/translocase proteins involved in fatty acid uptake (FATP2, FATP4, FATP5 or GOT) or cytosolic proteins involved in fatty acid intracellular targeting (ACBP). In addition, TKO exacerbated dietary phytol-induced whole body weight loss, especially lean tissue mass. Since individually ablating SCPx or SCP2/SCPx elicited concomitant upregulation of L-FABP, these findings with TKO mice help to resolve the contributions of SCP2/SCPx gene ablation on dietary phytol-induced whole body and hepatic lipid phenotype independent of concomitant upregulation of L-FABP.
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Affiliation(s)
- Sherrelle Milligan
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Gregory G Martin
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Danilo Landrock
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Avery L McIntosh
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - John T Mackie
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
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Schroeder F, McIntosh AL, Martin GG, Huang H, Landrock D, Chung S, Landrock KK, Dangott LJ, Li S, Kaczocha M, Murphy EJ, Atshaves BP, Kier AB. Fatty Acid Binding Protein-1 (FABP1) and the Human FABP1 T94A Variant: Roles in the Endocannabinoid System and Dyslipidemias. Lipids 2016; 51:655-76. [PMID: 27117865 PMCID: PMC5408584 DOI: 10.1007/s11745-016-4155-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 01/01/2023]
Abstract
The first discovered member of the mammalian FABP family, liver fatty acid binding protein (FABP1, L-FABP), occurs at high cytosolic concentration in liver, intestine, and in the case of humans also in kidney. While the rat FABP1 is well studied, the extent these findings translate to human FABP1 is not clear-especially in view of recent studies showing that endocannabinoids and cannabinoids represent novel rat FABP1 ligands and FABP1 gene ablation impacts the hepatic endocannabinoid system, known to be involved in non-alcoholic fatty liver (NAFLD) development. Although not detectable in brain, FABP1 ablation nevertheless also impacts brain endocannabinoids. Despite overall tertiary structure similarity, human FABP1 differs significantly from rat FABP1 in secondary structure, much larger ligand binding cavity, and affinities/specificities for some ligands. Moreover, while both mouse and human FABP1 mediate ligand induction of peroxisome proliferator activated receptor-α (PPARα), they differ markedly in pattern of genes induced. This is critically important because a highly prevalent human single nucleotide polymorphism (SNP) (26-38 % minor allele frequency and 8.3 ± 1.9 % homozygous) results in a FABP1 T94A substitution that further accentuates these species differences. The human FABP1 T94A variant is associated with altered body mass index (BMI), clinical dyslipidemias (elevated plasma triglycerides and LDL cholesterol), atherothrombotic cerebral infarction, and non-alcoholic fatty liver disease (NAFLD). Resolving human FABP1 and the T94A variant's impact on the endocannabinoid and cannabinoid system is an exciting challenge due to the importance of this system in hepatic lipid accumulation as well as behavior, pain, inflammation, and satiety.
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Affiliation(s)
- Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA.
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Sarah Chung
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Kerstin K Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Lawrence J Dangott
- Department of Biochemistry and Biophysics, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Shengrong Li
- Avanti Polar Lipids, 700 Industrial Park Dr., Alabaster, AL, 35007-9105, USA
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Eric J Murphy
- Department of Pharmacology, Physiology, and Therapeutics and Chemistry, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Barbara P Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
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