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Korbecki J, Bosiacki M, Pilarczyk M, Gąssowska-Dobrowolska M, Jarmużek P, Szućko-Kociuba I, Kulik-Sajewicz J, Chlubek D, Baranowska-Bosiacka I. Phospholipid Acyltransferases: Characterization and Involvement of the Enzymes in Metabolic and Cancer Diseases. Cancers (Basel) 2024; 16:2115. [PMID: 38893234 PMCID: PMC11171337 DOI: 10.3390/cancers16112115] [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: 04/15/2024] [Revised: 05/23/2024] [Accepted: 05/28/2024] [Indexed: 06/21/2024] Open
Abstract
This review delves into the enzymatic processes governing the initial stages of glycerophospholipid (phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine) and triacylglycerol synthesis. The key enzymes under scrutiny include GPAT and AGPAT. Additionally, as most AGPATs exhibit LPLAT activity, enzymes participating in the Lands cycle with similar functions are also covered. The review begins by discussing the properties of these enzymes, emphasizing their specificity in enzymatic reactions, notably the incorporation of polyunsaturated fatty acids (PUFAs) such as arachidonic acid and docosahexaenoic acid (DHA) into phospholipids. The paper sheds light on the intricate involvement of these enzymes in various diseases, including obesity, insulin resistance, and cancer. To underscore the relevance of these enzymes in cancer processes, a bioinformatics analysis was conducted. The expression levels of the described enzymes were correlated with the overall survival of patients across 33 different types of cancer using the GEPIA portal. This review further explores the potential therapeutic implications of inhibiting these enzymes in the treatment of metabolic diseases and cancer. By elucidating the intricate enzymatic pathways involved in lipid synthesis and their impact on various pathological conditions, this paper contributes to a comprehensive understanding of these processes and their potential as therapeutic targets.
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Affiliation(s)
- Jan Korbecki
- Department of Anatomy and Histology, Collegium Medicum, University of Zielona Góra, Zyty 28, 65-046 Zielona Góra, Poland;
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland; (M.B.); (D.C.)
| | - Mateusz Bosiacki
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland; (M.B.); (D.C.)
| | - Maciej Pilarczyk
- Department of Nervous System Diseases, Neurosurgery Center University Hospital in Zielona Góra, Collegium Medicum, University of Zielona Gora, 65-417 Zielona Góra, Poland; (M.P.); (P.J.)
| | - Magdalena Gąssowska-Dobrowolska
- Department of Cellular Signalling, Mossakowski Medical Research Institute, Polish Academy of Sciences, Pawińskiego 5, 02-106 Warsaw, Poland;
| | - Paweł Jarmużek
- Department of Nervous System Diseases, Neurosurgery Center University Hospital in Zielona Góra, Collegium Medicum, University of Zielona Gora, 65-417 Zielona Góra, Poland; (M.P.); (P.J.)
| | | | - Justyna Kulik-Sajewicz
- Department of Conservative Dentistry and Endodontics, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland;
| | - Dariusz Chlubek
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland; (M.B.); (D.C.)
| | - Irena Baranowska-Bosiacka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland; (M.B.); (D.C.)
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Smith KR, Wang W, Miller MR, Boucher M, Reynold JE, Daurio NA, Li D, Hirenallur-Shanthappa D, Ahn Y, Beebe DA, Kelly KL, Ross TT, Bence KK, Wan M. GPAT1 Deficiency in Mice Modulates NASH Progression in a Model-Dependent Manner. Cell Mol Gastroenterol Hepatol 2023; 17:279-291. [PMID: 37844795 PMCID: PMC10829521 DOI: 10.1016/j.jcmgh.2023.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/11/2023] [Accepted: 10/11/2023] [Indexed: 10/18/2023]
Abstract
BACKGROUND & AIMS Nonalcoholic fatty liver disease (NAFLD), and its more severe form, nonalcoholic steatohepatitis (NASH), is the leading cause for liver failure and liver cancer. Although the etiology is likely multifactorial, genes involved in regulating lipid metabolism are enriched in human NAFLD genome-wide association studies (GWAS), pointing to dysregulated lipid metabolism as a major pathogenic factor. Glycerol-3-phosphate acyltransferase 1 (GPAT1), encoded by GPAM, converts acyl-CoAs and glycerol-3-phosphate into lysophosphatidic acid and has been shown to regulate lipid accumulation in the liver. However, its role in mediating the progression from NAFLD to NASH has not been explored. METHODS GPAT1-deficient mice were generated and challenged with diets inducing hepatic steatosis and NASH. Effects of GPAT1 deficiency on lipid and systemic metabolic end points were evaluated. RESULTS Ablating GPAT1 globally or specifically in mouse hepatocytes reduced hepatic steatosis in the context of diet-induced or genetic obesity. Interestingly, blunting of progression from NAFLD to NASH in global GPAT1 knockout (KO) mice was model dependent. GPAT1 KO mice were protected from choline deficient, amino acid defined high-fat diet-induced NASH development, but not from the high fat, high carbohydrate, and high cholesterol diet-induced NASH. CONCLUSIONS Our preclinical data support the notion that lipid metabolism pathways regulated by GPAT1 in hepatocytes play an essential role in NASH progression, albeit in a model-dependent manner.
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Affiliation(s)
- Kathleen R Smith
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Wenshan Wang
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Melissa R Miller
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Magalie Boucher
- WRDM Drug Safety, Research and Development, Pfizer Inc, Groton, Connecticut
| | - Jessica E Reynold
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Natalie A Daurio
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Dongmei Li
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | | | - Youngwook Ahn
- WRDM Target Sciences, Pfizer Inc, Cambridge, Massachusetts
| | - David A Beebe
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Kenneth L Kelly
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Trenton T Ross
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Kendra K Bence
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Min Wan
- WRDM Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts.
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3
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Chen H, Zhu C, Zhou X. Effects of Lead and Cadmium Combined Heavy Metals on Liver Function and Lipid Metabolism in Mice. Biol Trace Elem Res 2023; 201:2864-2876. [PMID: 35994140 DOI: 10.1007/s12011-022-03390-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Accepted: 08/10/2022] [Indexed: 11/02/2022]
Abstract
Although a large number of studies have been conducted on lead (Pb) and cadmium (Cd) exposure individually, information regarding the toxicity of combined Pb and Cd exposure is relatively limited. The present study aims to investigate the toxicity of Pb-Cd combination exposure and the corresponding mechanism. A heavy metal exposure model was established in mice by subcutaneous intragastric administration of Pb-Cd (50:1) for 35 days. Body weight, diet, hair state, mental state, liver index, haematological index, biochemical indicators and pathological section analysis were used to comprehensively evaluate toxicity. Then, classical oxidative stress indexes and lipidomics techniques were used to explore the potential mechanism. The results showed that Pb-Cd caused the mice to have low appetite, poor spirit, significantly reduced activity, slow weight gain and irritated or drying hair. Pb-Cd also caused liver enlargement, significantly increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) enzyme activities, and resulted in pathological changes to the liver. Prolonged Pb-Cd exposure led to significantly increased thrombocyte haematocrit (PCT), white blood cell (WBC), platelet (PLT) and monocyte (MON) counts and decreased red blood cell (RBC), haemoglobin (HGB), haematocrit (HCT) and lymphocyte (LYM) counts. Pb-Cd increased oxidative stress by increasing the activity of superoxide dismutase (SOD) and lactate dehydrogenase (LDH) and the content of malondialdehyde (MDA). Finally, Pb-Cd triggered lipid metabolism disorders by regulating linoleic acid, sphingolipid and glycerolipid metabolism.
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Affiliation(s)
- Huaguo Chen
- Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, China.
- Guizhou Engineering Laboratory for Quality Control & Evaluation Technology of Medicine, Guizhou Normal University, Guiyang, 550001, China.
| | - Chengxiang Zhu
- Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, China
- Guizhou Engineering Laboratory for Quality Control & Evaluation Technology of Medicine, Guizhou Normal University, Guiyang, 550001, China
| | - Xin Zhou
- Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, China.
- Guizhou Engineering Laboratory for Quality Control & Evaluation Technology of Medicine, Guizhou Normal University, Guiyang, 550001, China.
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Structural basis of the acyl-transfer mechanism of human GPAT1. Nat Struct Mol Biol 2023; 30:22-30. [PMID: 36522428 DOI: 10.1038/s41594-022-00884-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 10/31/2022] [Indexed: 12/23/2022]
Abstract
Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. Hepatic expression of GPAT1 is linked to liver fat accumulation and the severity of nonalcoholic fatty liver diseases. Here we present the cryo-EM structures of human GPAT1 in substrate analog-bound and product-bound states. The structures reveal an N-terminal acyltransferase domain that harbors important catalytic motifs and a tightly associated C-terminal domain that is critical for proper protein folding. Unexpectedly, GPAT1 has no transmembrane regions as previously proposed but instead associates with the membrane via an amphipathic surface patch and an N-terminal loop-helix region that contains a mitochondrial-targeting signal. Combined structural, computational and functional studies uncover a hydrophobic pathway within GPAT1 for lipid trafficking. The results presented herein lay a framework for rational inhibitor development for GPAT1.
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Abstract
Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the general population. Energy metabolism disturbance is one of the early abnormalities in CVDs, such as coronary heart disease, diabetic cardiomyopathy, and heart failure. To explore the role of myocardial energy homeostasis disturbance in CVDs, it is important to understand myocardial metabolism in the normal heart and their function in the complex pathophysiology of CVDs. In this article, we summarized lipid metabolism/lipotoxicity and glucose metabolism/insulin resistance in the heart, focused on the metabolic regulation during neonatal and ageing heart, proposed potential metabolic mechanisms for cardiac regeneration and degeneration. We provided an overview of emerging molecular network among cardiac proliferation, regeneration, and metabolic disturbance. These novel targets promise a new era for the treatment of CVDs.
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Affiliation(s)
- Lu-Yun WANG
- Division of Cardiology, Tongji Hospital, Tongji Medical College and Hubei Key Laboratory of Genetics and Molecular Mechanisms of Cardiologic Disorders, Huazhong University of Science and Technology, Wuhan, China
| | - Chen CHEN
- Division of Cardiology, Tongji Hospital, Tongji Medical College and Hubei Key Laboratory of Genetics and Molecular Mechanisms of Cardiologic Disorders, Huazhong University of Science and Technology, Wuhan, China
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Zhou J, Zhang Y, Wu J, Qiao M, Xu Z, Peng X, Mei S. Proteomic and lipidomic analyses reveal saturated fatty acids, phosphatidylinositol, phosphatidylserine, and associated proteins contributing to intramuscular fat deposition. J Proteomics 2021; 241:104235. [PMID: 33894376 DOI: 10.1016/j.jprot.2021.104235] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 04/05/2021] [Accepted: 04/09/2021] [Indexed: 12/15/2022]
Abstract
Intramuscular fat (IMF) content is an important factor in porcine meat quality. Previous studies have screened multiple candidate genes related to IMF deposition, but the lipids that affect IMF deposition and their lipid-protein network remain unknown. In this study, we performed proteomic and lipidomic analyses of the longissimus dorsi (LD) muscle from high-IMF (IMFH) and low-IMF (IMF-L) groups of Xidu black pigs. Eighty-eight proteins and 143 lipids were differentially abundant between the groups. The differentially abundant proteins were found to be involved in cholesterol metabolism, the PPAR signaling pathway, and ferroptosis. The triacylglycerols (TAGs) upregulated in the IMF-H group were mainly shown to be synthesized by saturated fatty acids (SFAs), while the downregulated TAGs were mainly synthesized by polyunsaturated fatty acids (PUFAs). All differentially abundant phosphatidylinositols (PIs) and phosphatidylserines (PSs) were found to be upregulated in the IMF-H group. A correlation analysis of the proteomic and lipidomic revealed candidate proteins (APOA4, VDAC3, PRNP, CTSB, GSPT1) related to TAG, PI, and PS lipids. These results revealed differences in proteins and lipids between the IMF-H and IMF-L groups, which represent new candidate proteins and lipids that should be investigated to determine the molecular mechanisms controlling IMF deposition in pigs. SIGNIFICANCE: Intramuscular fat (IMF) is a key factor affecting meat quality, and meat with a higher IMF content can have a better flavor. In this study, proteomic results show that the ferroptosis pathway, including the PRNP, VDAC3 and CP proteins, affects IMF deposition. Lipid composition is the key factor affecting IMF deposition, but there are few reports on this. In this study, through lipidomic analysis, we suggest that saturated fatty acid (SFA), phosphatidylinositol (PI), and phosphatidylserine (PS) may contribute to IMF deposition. A correlation analysis reveals the potential regulatory network between lipids and proteins. This study clarifies the difference in protein and lipid compositions in longissimus dorsi (LD) muscle with high and low IMF contents. This information suggests that it would be beneficial to increase the intramuscular fat content of pork not only from a genetic perspective but also from a nutritional perspective.
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Affiliation(s)
- Jiawei Zhou
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China
| | - Yu Zhang
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China
| | - Junjing Wu
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China
| | - Mu Qiao
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China
| | - Zhong Xu
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China
| | - Xianwen Peng
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China
| | - Shuqi Mei
- Institute of Animal Science and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; Hubei Key Lab for Animal Embryo Engineering and Molecular Breeding, Wuhan 430064, China.
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Kappelt F, Du Ma X, Abou Hasna B, Kornke JM, Maniak M. Phospholipids containing ether-bound hydrocarbon-chains are essential for efficient phagocytosis and neutral lipids of the ester-type perturb development in Dictyostelium. Biol Open 2020; 9:9/7/bio052126. [PMID: 32675052 PMCID: PMC7375469 DOI: 10.1242/bio.052126] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Lipids are the building blocks for cellular membranes; they provide signalling molecules for membrane dynamics and serve as energy stores. One path of their synthesis is initiated by glycerol-3-phosphate acyltransferase (GPAT), which in Dictyostelium resides on the endoplasmic reticulum. When an excess of fatty acids is present, it redistributes to storage organelles, the lipid droplets. Mutants, where the GPAT was eliminated by homologous recombination, produce fewer lipid droplets and are almost devoid of triacylglycerols (TAG), rendering them more resistant to cell death and cell loss in the developmental stages preceding fruiting body formation. The enzyme most closely related to GPAT is called FARAT, because it combines a fatty acyl-reductase (FAR) and an acyltransferase (AT) domain in its sequence. The protein is confined to the lumen of the peroxisome, where it transfers a fatty acid to dihydroxyacetone-phosphate initiating the synthesis of ether lipids, later completed at the endoplasmic reticulum. A mutant lacking FARAT produces lipid droplets that are devoid of the storage lipid monoalkyl-diacyl-glycerol (MDG), but the efficiency of spore formation in the developmental cycle is largely unaltered. Instead, these mutants are strongly impaired in phagocytosis of yeast particles, which is attributed to reduced synthesis of membrane phospholipids containing ether-linked chains.
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Affiliation(s)
| | - Xiaoli Du Ma
- Zellbiologie, Universität Kassel, D-34109 Kassel, Germany
| | | | | | - Markus Maniak
- Zellbiologie, Universität Kassel, D-34109 Kassel, Germany
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Hodson L, Gunn PJ. The regulation of hepatic fatty acid synthesis and partitioning: the effect of nutritional state. Nat Rev Endocrinol 2019; 15:689-700. [PMID: 31554932 DOI: 10.1038/s41574-019-0256-9] [Citation(s) in RCA: 147] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is an increasing global public health burden. NAFLD is strongly associated with type 2 diabetes mellitus, obesity and cardiovascular disease and begins with intrahepatic triacylglycerol accumulation. Under healthy conditions, the liver regulates lipid metabolism to meet systemic energy needs in the fed and fasted states. The processes of fatty acid uptake, fatty acid synthesis and the intracellular partitioning of fatty acids into storage, oxidation and secretion pathways are tightly regulated. When one or more of these processes becomes dysregulated, excess lipid accumulation can occur. Although genetic and environmental factors have been implicated in the development of NAFLD, it remains unclear why an imbalance in these pathways begins. The regulation of fatty acid partitioning occurs at several points, including during triacylglycerol synthesis, lipid droplet formation and lipolysis. These processes are influenced by enzyme function, intake of dietary fats and sugars and whole-body metabolism, and are further affected by the presence of obesity or insulin resistance. Insight into how the liver controls fatty acid metabolism in health and how these processes might be affected in disease would offer the potential for new therapeutic treatments for NAFLD to be developed.
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Affiliation(s)
- Leanne Hodson
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Headington, Oxford, UK.
- Oxford NIHR Biomedical Research Centre, Churchill Hospital, Headington, Oxford, UK.
| | - Pippa J Gunn
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Headington, Oxford, UK
- Oxford NIHR Biomedical Research Centre, Churchill Hospital, Headington, Oxford, UK
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9
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Sowton AP, Griffin JL, Murray AJ. Metabolic Profiling of the Diabetic Heart: Toward a Richer Picture. Front Physiol 2019; 10:639. [PMID: 31214041 PMCID: PMC6555155 DOI: 10.3389/fphys.2019.00639] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 05/06/2019] [Indexed: 01/20/2023] Open
Abstract
The increasing global prevalence of diabetes has been accompanied by a rise in diabetes-related conditions. This includes diabetic cardiomyopathy (DbCM), a progressive form of heart disease that occurs with both insulin-dependent (type-1) and insulin-independent (type-2) diabetes and arises in the absence of hypertension or coronary artery disease. Over time, DbCM can develop into overt heart failure. Like other forms of cardiomyopathy, DbCM is accompanied by alterations in metabolism which could lead to further progression of the pathology, with metabolic derangement postulated to precede functional changes in the diabetic heart. Moreover in the case of type-2 diabetes, underlying insulin resistance is likely to prevent the canonical substrate switch of the failing heart away from fatty acid oxidation toward increased use of glycolysis. Analytical chemistry techniques, collectively known as metabolomics, are useful tools for investigating the condition. In this article, we provide a comprehensive review of those studies that have employed metabolomic techniques, namely chromatography, mass spectrometry and nuclear magnetic resonance spectroscopy, to profile metabolic remodeling in the diabetic heart of human patients and animal models. These studies collectively demonstrate that glycolysis and glucose oxidation are suppressed in the diabetic myocardium and highlight a complex picture regarding lipid metabolism. The diabetic heart typically shows an increased reliance on fatty acid oxidation, yet triacylglycerols and other lipids accumulate in the diabetic myocardium indicating probable lipotoxicity. The application of lipidomic techniques to the diabetic heart has identified specific lipid species that become enriched and which may in turn act as plasma-borne biomarkers for the condition. Metabolomics is proving to be a powerful approach, allowing a much richer analysis of the metabolic alterations that occur in the diabetic heart. Careful physiological interpretation of metabolomic results will now be key in order to establish which aspects of the metabolic derangement are causal to the progression of DbCM and might form the basis for novel therapeutic intervention.
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Affiliation(s)
- Alice P. Sowton
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Julian L. Griffin
- Department of Biochemistry and Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
| | - Andrew J. Murray
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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10
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Lee J, Ridgway ND. Substrate channeling in the glycerol-3-phosphate pathway regulates the synthesis, storage and secretion of glycerolipids. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158438. [PMID: 30959116 DOI: 10.1016/j.bbalip.2019.03.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 01/16/2023]
Abstract
The successive acylation of glycerol-3-phosphate (G3P) by glycerol-3-phosphate acyltransferases and acylglycerol-3-phosphate acyltransferases produces phosphatidic acid (PA), a precursor for CDP-diacylglycerol-dependent phospholipid synthesis. PA is further dephosphorylated by LIPINs to produce diacylglycerol (DG), a substrate for the synthesis of triglyceride (TG) by DG acyltransferases and a precursor for phospholipid synthesis via the CDP-choline and CDP-ethanolamine (Kennedy) pathways. The channeling of fatty acids into TG for storage in lipid droplets and secretion in lipoproteins or phospholipids for membrane biogenesis is dependent on isoform expression, activity and localization of G3P pathway enzymes, as well as dietary and hormonal and tissue-specific factors. Here, we review the mechanisms that control partitioning of substrates into lipid products of the G3P pathway.
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Affiliation(s)
- Jonghwa Lee
- Atlantic Research Center, Depts. of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Neale D Ridgway
- Atlantic Research Center, Depts. of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.
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11
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Zhu XG, Nicholson Puthenveedu S, Shen Y, La K, Ozlu C, Wang T, Klompstra D, Gultekin Y, Chi J, Fidelin J, Peng T, Molina H, Hang HC, Min W, Birsoy K. CHP1 Regulates Compartmentalized Glycerolipid Synthesis by Activating GPAT4. Mol Cell 2019; 74:45-58.e7. [PMID: 30846317 DOI: 10.1016/j.molcel.2019.01.037] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 11/26/2018] [Accepted: 01/25/2019] [Indexed: 01/10/2023]
Abstract
Cells require a constant supply of fatty acids to survive and proliferate. Fatty acids incorporate into membrane and storage glycerolipids through a series of endoplasmic reticulum (ER) enzymes, but how these enzymes are regulated is not well understood. Here, using a combination of CRISPR-based genetic screens and unbiased lipidomics, we identified calcineurin B homologous protein 1 (CHP1) as a major regulator of ER glycerolipid synthesis. Loss of CHP1 severely reduces fatty acid incorporation and storage in mammalian cells and invertebrates. Mechanistically, CHP1 binds and activates GPAT4, which catalyzes the initial rate-limiting step in glycerolipid synthesis. GPAT4 activity requires CHP1 to be N-myristoylated, forming a key molecular interface between the two proteins. Interestingly, upon CHP1 loss, the peroxisomal enzyme, GNPAT, partially compensates for the loss of ER lipid synthesis, enabling cell proliferation. Thus, our work identifies a conserved regulator of glycerolipid metabolism and reveals plasticity in lipid synthesis of proliferating cells.
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Affiliation(s)
- Xiphias Ge Zhu
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Shirony Nicholson Puthenveedu
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA; Institute of Pathology, Medical University of Graz, Auenbruggerplatz 25, Graz 8036, Austria
| | - Yihui Shen
- Department of Chemistry and Kavli Institute for Brain Science, Columbia University, New York, NY 10027, USA
| | - Konnor La
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Can Ozlu
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Tim Wang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Diana Klompstra
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Yetis Gultekin
- Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Jingyi Chi
- Laboratory of Molecular Metabolism, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Justine Fidelin
- The Proteomics Resource Center, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Tao Peng
- Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Henrik Molina
- The Proteomics Resource Center, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Howard C Hang
- Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Wei Min
- Department of Chemistry and Kavli Institute for Brain Science, Columbia University, New York, NY 10027, USA
| | - Kıvanç Birsoy
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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12
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Update on glycerol-3-phosphate acyltransferases: the roles in the development of insulin resistance. Nutr Diabetes 2018; 8:34. [PMID: 29799006 PMCID: PMC5968029 DOI: 10.1038/s41387-018-0045-x] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 05/03/2018] [Accepted: 05/06/2018] [Indexed: 01/16/2023] Open
Abstract
Glycerol-3-phosphate acyltransferase (GPAT) is the rate-limiting enzyme in the de novo pathway of glycerolipid synthesis. It catalyzes the conversion of glycerol-3-phosphate and long-chain acyl-CoA to lysophosphatidic acid. In mammals, four isoforms of GPATs have been identified based on subcellular localization, substrate preferences, and NEM sensitivity, and they have been classified into two groups, one including GPAT1 and GPAT2, which are localized in the mitochondrial outer membrane, and the other including GPAT3 and GPAT4, which are localized in the endoplasmic reticulum membrane. GPATs play a pivotal role in the regulation of triglyceride and phospholipid synthesis. Through gain-of-function and loss-of-function experiments, it has been confirmed that GPATs play a critical role in the development of obesity, hepatic steatosis, and insulin resistance. In line with this, the role of GPATs in metabolism was supported by studies using a GPAT inhibitor, FSG67. Additionally, the functional characteristics of GPATs and the relation between three isoforms (GPAT1, 3, and 4) and insulin resistance has been described in this review.
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AIDA Selectively Mediates Downregulation of Fat Synthesis Enzymes by ERAD to Retard Intestinal Fat Absorption and Prevent Obesity. Cell Metab 2018; 27:843-853.e6. [PMID: 29617643 DOI: 10.1016/j.cmet.2018.02.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/05/2017] [Accepted: 02/21/2018] [Indexed: 01/24/2023]
Abstract
The efficiency of intestinal absorption of dietary fat constitutes a primary determinant accounting for individual vulnerability to obesity. However, how fat absorption is controlled and contributes to obesity remains unclear. Here, we show that inhibition of endoplasmic-reticulum-associated degradation (ERAD) increases the abundance of triacylglycerol synthesis enzymes and fat absorption in small intestine. The C2-domain protein AIDA acts as an essential factor for the E3-ligase HRD1 of ERAD to downregulate rate-limiting acyltransferases GPAT3, MOGAT2, and DGAT2. Aida-/- mice, when grown in a thermal-neutral condition or fed high-fat diet, display increased intestinal fatty acid re-esterification, circulating and tissue triacylglycerol, accompanied with severely increased adiposity without enhancement of adipogenesis. Intestine-specific knockout of Aida largely phenocopies its whole-body knockout, strongly indicating that increased intestinal TAG synthesis is a primary impetus to obesity. The AIDA-mediated ERAD system may thus represent an anti-thrifty mechanism impinging on the enzymes for intestinal fat absorption and systemic fat storage.
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Wang H, Airola MV, Reue K. How lipid droplets "TAG" along: Glycerolipid synthetic enzymes and lipid storage. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1131-1145. [PMID: 28642195 PMCID: PMC5688854 DOI: 10.1016/j.bbalip.2017.06.010] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 06/15/2017] [Accepted: 06/15/2017] [Indexed: 02/06/2023]
Abstract
Triacylglycerols (TAG) serve as the predominant form of energy storage in mammalian cells, and TAG synthesis influences conditions such as obesity, fatty liver, and insulin resistance. In most tissues, the glycerol 3-phosphate pathway enzymes are responsible for TAG synthesis, and the regulation and function of these enzymes is therefore important for metabolic homeostasis. Here we review the sites and regulation of glycerol-3-phosphate acyltransferase (GPAT), acylglycerol-3-phosphate acyltransferase (AGPAT), lipin phosphatidic acid phosphatase (PAP), and diacylglycerol acyltransferase (DGAT) enzyme action. We highlight the critical roles that these enzymes play in human health by reviewing Mendelian disorders that result from mutation in the corresponding genes. We also summarize the valuable insights that genetically engineered mouse models have provided into the cellular and physiological roles of GPATs, AGPATs, lipins and DGATs. Finally, we comment on the status and feasibility of therapeutic approaches to metabolic disease that target enzymes of the glycerol 3-phosphate pathway. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Huan Wang
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
| | - Michael V Airola
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Karen Reue
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States; Molecular Biology Institute, University of California, Los Angeles, CA, United States.
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15
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Alrob OA, Khatib S, Naser SA. MicroRNAs 33, 122, and 208: a potential novel targets in the treatment of obesity, diabetes, and heart-related diseases. J Physiol Biochem 2016; 73:307-314. [PMID: 27966196 DOI: 10.1007/s13105-016-0543-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 12/06/2016] [Indexed: 12/17/2022]
Abstract
Despite decades of research, obesity and diabetes remain major health problems in the USA and worldwide. Among the many complications associated with diabetes is an increased risk of cardiovascular diseases, including myocardial infarction and heart failure. Recently, microRNAs have emerged as important players in heart disease and energy regulation. However, little work has investigated the role of microRNAs in cardiac energy regulation. Both human and animal studies have reported a significant increase in circulating free fatty acids and triacylglycerol, increased cardiac reliance on fatty acid oxidation, and subsequent decrease in glucose oxidation which all contributes to insulin resistance and lipotoxicity seen in obesity and diabetes. Importantly, MED13 was initially identified as a negative regulator of lipid accumulation in Drosophilia. Various metabolic genes were downregulated in MED13 transgenic heart, including sterol regulatory element-binding protein. Moreover, miR-33 and miR-122 have recently revealed as key regulators of lipid metabolism. In this review, we will focus on the role of microRNAs in regulation of cardiac and total body energy metabolism. We will also discuss the pharmacological and non-pharmacological interventions that target microRNAs for the treatment of obesity and diabetes.
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Affiliation(s)
- Osama Abo Alrob
- Faculty of Pharmacy, Yarmouk University, P.O Box 566, Irbid, 21163, Jordan.
| | - Said Khatib
- Faculty of Medicine, Jordan University of Science and Technology, Irbid, Jordan
| | - Saleh A Naser
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
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16
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Keenan KA, Grove TJ, Oldham CA, O'Brien KM. Characterization of mitochondrial glycerol-3-phosphate acyltransferase in notothenioid fishes. Comp Biochem Physiol B Biochem Mol Biol 2016; 204:9-26. [PMID: 27836743 DOI: 10.1016/j.cbpb.2016.11.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 10/27/2016] [Accepted: 11/03/2016] [Indexed: 10/20/2022]
Abstract
Hearts of Antarctic icefishes (suborder Notothenioidei, family Channichthyidae) have higher densities of mitochondria, and mitochondria have higher densities of phospholipids, compared to red-blooded notothenioids. Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the rate-limiting step in glycerolipid biosynthesis. There are four isoforms of GPAT in vertebrates; GPAT1 and GPAT2 are localized to the outer mitochondrial membrane, whereas GPAT3 and GPAT4 are localized to the endoplasmic reticulum membrane. We hypothesized that transcript levels of GPAT1 and/or GPAT2 would mirror densities of mitochondrial phospholipids and be higher in the icefish Chaenocephalus aceratus compared to the red-blooded species Notothenia coriiceps. Transcript levels of GPAT1 were quantified in heart ventricles and liver using qRT-PCR. Additionally, GPAT1 cDNA was sequenced in the Antarctic notothenioids, C. aceratus and N. coriiceps, and in the sub-Antarctic notothenioid, Eleginops maclovinus, to identify amino acid substitutions that may maintain GPAT1 function at cold temperature. Transcript levels of GPAT1 were higher in liver compared to heart ventricles but were not significantly different between the two species. In contrast, transcripts of GPAT2 were only detected in ventricle where they were 6.6-fold higher in C. aceratus compared to N. coriiceps. These data suggest GPAT1 may be more important for synthesizing triacylglycerol, whereas GPAT2 may regulate synthesis of phospholipids. GPAT1 amino acid sequences are highly conserved among the three notothenioids with 97.9-98.7% identity. Four amino acid substitutions within the cytosolic region of Antarctic notothenioid GPAT1 may maintain conformational changes necessary for binding and catalysis at cold temperature.
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Affiliation(s)
- Kelly A Keenan
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States
| | - Theresa J Grove
- Department of Biology, Valdosta State University, Valdosta, GA 31698, United States
| | - Corey A Oldham
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States
| | - Kristin M O'Brien
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States.
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17
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Keenan K, Hoffman M, Dullen K, O'Brien KM. Molecular drivers of mitochondrial membrane proliferation in response to cold acclimation in threespine stickleback. Comp Biochem Physiol A Mol Integr Physiol 2016; 203:109-114. [PMID: 27613226 DOI: 10.1016/j.cbpa.2016.09.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/01/2016] [Accepted: 09/01/2016] [Indexed: 10/21/2022]
Abstract
Little is known about how the synthesis of mitochondrial phospholipids is integrated into mitochondrial biogenesis in fish or mammals. Glycerol-3-phosphate acyltransferase (GPAT; EC 2.3.1.15) catalyzes the addition of fatty acyl CoA to the sn-1 position of glycerol-3-phosphate, in what is considered the rate-limiting step in phospholipid biosynthesis. Previous studies have shown that mitochondrial volume density increases in oxidative skeletal muscle but not liver of Gasterosteus aculeatus (threespine stickleback) in response to cold acclimation. We hypothesized that maximal activity of GPAT would increase in oxidative skeletal muscle but not liver during cold acclimation, coinciding with mitochondrial biogenesis. GPAT activity was measured in liver and oxidative skeletal (pectoral adductor) muscle of threespine stickleback acclimated to 8°C or 20°C. In addition, mRNA levels of enzymes involved in phospholipid synthesis, including cytidine diphosphodiacylglycerol synthase-1 (CDS1), CDS2, GPAT1, GPAT2 and 1-acylglycerol 3-phosphate acyltransferase-2 (AGPAT2), were quantified in liver and pectoral muscle of stickleback harvested during cold acclimation. GPAT activity and transcript levels of AGPAT2 increased in response to cold acclimation in pectoral muscle but not liver. Transcript levels of GPAT1 increased in liver but not pectoral muscle. Overall our results suggest that the activity of GPAT, and possibly AGPAT as well, increase during cold acclimation and may contribute to mitochondrial phospholipid biosynthesis required for mitochondrial biogenesis.
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Affiliation(s)
- Kelly Keenan
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States
| | - Megan Hoffman
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States
| | - Kristin Dullen
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States
| | - Kristin M O'Brien
- University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States.
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18
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Gonzalez-Baro MR, Coleman RA. Mitochondrial acyltransferases and glycerophospholipid metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:49-55. [PMID: 27377347 DOI: 10.1016/j.bbalip.2016.06.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 06/23/2016] [Accepted: 06/28/2016] [Indexed: 12/14/2022]
Abstract
Our understanding of the synthesis and remodeling of mitochondrial phospholipids remains incomplete. Two isoforms of glycerol-3-phosphate acyltransferase (GPAT1 and 2) and two isoforms of acylglycerol-3-phosphate acyltransferase (AGPAT4 and 5) are located on the outer mitochondrial membrane, suggesting that both lysophosphatidic acid and phosphatidic acid are synthesized in situ for de novo glycerolipid biosynthesis. However, it is believed that the phosphatidic acid substrate for cardiolipin and phosphatidylethanolamine biosynthesis is produced at the endoplasmic reticulum whereas the phosphatidic acid synthesized in the mitochondria must be transferred to the endoplasmic reticulum before it undergoes additional steps to form the mature phospholipids that are trafficked back to the mitochondria. It is unclear whether mitochondrial phospholipids are remodeled by mitochondrial acyltransferases or whether lysophospholipids must return to the endoplasmic reticulum or to the mitochondrial associated membrane for reesterification. In this review we will focus on the few glycerolipid acyltransferases that are known to be mitochondrial. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.
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Affiliation(s)
- Maria R Gonzalez-Baro
- Instituto de Investigaciones Bioquımicas de La Plata, CONICET, Facultad de Ciencias Medicas, Universidad Nacional de La Plata, La Plata 1900, Argentina
| | - Rosalind A Coleman
- Department of Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA.
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19
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Dolinsky VW, Cole LK, Sparagna GC, Hatch GM. Cardiac mitochondrial energy metabolism in heart failure: Role of cardiolipin and sirtuins. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1544-54. [PMID: 26972373 DOI: 10.1016/j.bbalip.2016.03.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 03/03/2016] [Accepted: 03/04/2016] [Indexed: 01/19/2023]
Abstract
Mitochondrial oxidation of fatty acids accounts for the majority of cardiac ATP production in the heart. Fatty acid utilization by cardiac mitochondria is controlled at the level of fatty acid uptake, lipid synthesis, mobilization and mitochondrial import and oxidation. Consequently defective mitochondrial function appears to be central to the development of heart failure. Cardiolipin is a key mitochondrial phospholipid required for the activity of the electron transport chain. In heart failure, loss of cardiolipin and tetralinoleoylcardiolipin helps to fuel the generation of excessive reactive oxygen species that are a by-product of inefficient mitochondrial electron transport chain complexes I and III. In this vicious cycle, reactive oxygen species generate lipid peroxides and may, in turn, cause oxidation of cardiolipin catalyzed by cytochrome c leading to cardiomyocyte apoptosis. Hence, preservation of cardiolipin and mitochondrial function may be keys to the prevention of heart failure development. In this review, we summarize cardiac energy metabolism and the important role that fatty acid uptake and metabolism play in this process and how defects in these result in heart failure. We highlight the key role that cardiolipin and sirtuins play in cardiac mitochondrial β-oxidation. In addition, we review the potential of pharmacological modulation of cardiolipin through the polyphenolic molecule resveratrol as a sirtuin-activator in attenuating mitochondrial dysfunction. Finally, we provide novel experimental evidence that resveratrol treatment increases cardiolipin in isolated H9c2 cardiac myocytes and tetralinoleoylcardiolipin in the heart of the spontaneously hypertensive rat and hypothesize that this leads to improvement in mitochondrial function. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.
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Affiliation(s)
- Vernon W Dolinsky
- Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Children's Hospital Research Institute of Manitoba (CHRIM), Canada
| | - Laura K Cole
- Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Children's Hospital Research Institute of Manitoba (CHRIM), Canada
| | - Genevieve C Sparagna
- Department of Medicine, Division of Cardiology, University of Colorado Denver Anschutz Medical Campus, Aurora, CO, USA
| | - Grant M Hatch
- Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Children's Hospital Research Institute of Manitoba (CHRIM), Canada; Department of Biochemistry and Medical Genetics, Faculty of Health Sciences, Center for Research and Treatment of Atherosclerosis, University of Manitoba, Winnipeg, Manitoba, Canada.
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20
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Lipid metabolism and signaling in cardiac lipotoxicity. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1513-24. [PMID: 26924249 DOI: 10.1016/j.bbalip.2016.02.016] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 02/19/2016] [Accepted: 02/19/2016] [Indexed: 01/01/2023]
Abstract
The heart balances uptake, metabolism and oxidation of fatty acids (FAs) to maintain ATP production, membrane biosynthesis and lipid signaling. Under conditions where FA uptake outpaces FA oxidation and FA sequestration as triacylglycerols in lipid droplets, toxic FA metabolites such as ceramides, diacylglycerols, long-chain acyl-CoAs, and acylcarnitines can accumulate in cardiomyocytes and cause cardiomyopathy. Moreover, studies using mutant mice have shown that dysregulation of enzymes involved in triacylglycerol, phospholipid, and sphingolipid metabolism in the heart can lead to the excess deposition of toxic lipid species that adversely affect cardiomyocyte function. This review summarizes our current understanding of lipid uptake, metabolism and signaling pathways that have been implicated in the development of lipotoxic cardiomyopathy under conditions including obesity, diabetes, aging, and myocardial ischemia-reperfusion. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.
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21
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Heier C, Haemmerle G. Fat in the heart: The enzymatic machinery regulating cardiac triacylglycerol metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1500-12. [PMID: 26924251 DOI: 10.1016/j.bbalip.2016.02.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 02/17/2016] [Accepted: 02/19/2016] [Indexed: 01/22/2023]
Abstract
The heart predominantly utilizes fatty acids (FAs) as energy substrate. FAs that enter cardiomyocytes can be activated and directly oxidized within mitochondria (and peroxisomes) or they can be esterified and intracellularly deposited as triacylglycerol (TAG) often simply referred to as fat. An increase in cardiac TAG can be a signature of the diseased heart and may implicate a minor role of TAG synthesis and breakdown in normal cardiac energy metabolism. Often overlooked, the heart has an extremely high TAG turnover and the transient deposition of FAs within the cardiac TAG pool critically determines the availability of FAs as energy substrate and signaling molecules. We herein review the recent literature regarding the enzymes and co-regulators involved in cardiomyocyte TAG synthesis and catabolism and discuss the interconnection of these metabolic pathways in the normal and diseased heart. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.
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Affiliation(s)
- Christoph Heier
- Institute of Molecular Biosciences, University of Graz, Austria
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22
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Nduhirabandi F, Lamont K, Albertyn Z, Opie LH, Lecour S. Role of toll-like receptor 4 in melatonin-induced cardioprotection. J Pineal Res 2016; 60:39-47. [PMID: 26465095 DOI: 10.1111/jpi.12286] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 10/08/2015] [Indexed: 12/19/2022]
Abstract
Melatonin protects the heart against myocardial ischemia/reperfusion injury via the activation of the survivor activating factor enhancement (SAFE) pathway which involves tumor necrosis factor alpha (TNFα) and the signal transducer and activator of transcription 3 (STAT3). Toll-like receptor 4 (TLR4) plays a crucial role in myocardial ischemia/reperfusion injury and activates TNFα. In this study, we investigated whether melatonin may target TLR4 to activate the SAFE pathway. Isolated hearts from rats or mice were subjected to ischemia/reperfusion injury. Melatonin (75 ng/L) and/or TAK242 (a specific inhibitor of TLR4 signaling, 500 nm) were administered to the rat hearts before the induction of ischemia. Pre-ischemic myocardial STAT3 was evaluated by Western blotting. Lipopolysaccharide (LPS, a stimulator of TLR4) was administered to wild type, TNFα receptor 2 knockout or cardiomyocyte-specific STAT3-deficient mice (2.8 mg/kg, i.p) 45 min before the heart isolation. Myocardial infarct size was measured as an endpoint. Compared to the control, administration of melatonin reduced myocardial infarct size (34.7 ± 2.8% versus 62.6 ± 2.7%, P < 0.01). This protective effect was abolished in the presence of TAK242 (49.2 ± 6.5%). Melatonin administered alone increased the pre-ischemic activation of mitochondrial STAT3, and this effect was attenuated with TAK242. Furthermore, stimulation of TLR4 with LPS pretreatment to mice reduced myocardial infarct size of the hearts isolated from wild-type animals but failed to protect the hearts isolated from TNFα receptor 2-knockout mice or cardiomyocyte-specific STAT3-deficient mice (P < 0.001). Taken together, these data suggest that cardioprotection induced by melatonin is mediated by TLR4 to activate the SAFE pathway.
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Affiliation(s)
- Frederic Nduhirabandi
- Cardioprotection Group, Hatter Institute for Cardiovascular Research in Africa and South African Medical Research Council Inter-University Cape Heart Group, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Kim Lamont
- Cardioprotection Group, Hatter Institute for Cardiovascular Research in Africa and South African Medical Research Council Inter-University Cape Heart Group, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Zulfah Albertyn
- Cardioprotection Group, Hatter Institute for Cardiovascular Research in Africa and South African Medical Research Council Inter-University Cape Heart Group, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Lionel H Opie
- Cardioprotection Group, Hatter Institute for Cardiovascular Research in Africa and South African Medical Research Council Inter-University Cape Heart Group, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Sandrine Lecour
- Cardioprotection Group, Hatter Institute for Cardiovascular Research in Africa and South African Medical Research Council Inter-University Cape Heart Group, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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23
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Khatun I, Clark RW, Vera NB, Kou K, Erion DM, Coskran T, Bobrowski WF, Okerberg C, Goodwin B. Characterization of a Novel Intestinal Glycerol-3-phosphate Acyltransferase Pathway and Its Role in Lipid Homeostasis. J Biol Chem 2015; 291:2602-15. [PMID: 26644473 DOI: 10.1074/jbc.m115.683359] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Indexed: 01/01/2023] Open
Abstract
Dietary triglycerides (TG) are absorbed by the enterocytes of the small intestine after luminal hydrolysis into monacylglycerol and fatty acids. Before secretion on chylomicrons, these lipids are reesterified into TG, primarily through the monoacylglycerol pathway. However, targeted deletion of the primary murine monoacylglycerol acyltransferase does not quantitatively affect lipid absorption, suggesting the existence of alternative pathways. Therefore, we investigated the role of the glycerol 3-phosphate pathway in dietary lipid absorption. The expression of glycerol-3-phosphate acyltransferase (GPAT3) was examined throughout the small intestine. To evaluate the role for GPAT3 in lipid absorption, mice harboring a disrupted GPAT3 gene (Gpat3(-/-)) were subjected to an oral lipid challenge and fed a Western-type diet to characterize the role in lipid and cholesterol homeostasis. Additional mechanistic studies were performed in primary enterocytes. GPAT3 was abundantly expressed in the apical surface of enterocytes in the small intestine. After an oral lipid bolus, Gpat3(-/-) mice exhibited attenuated plasma TG excursion and accumulated lipid in the enterocytes. Electron microscopy studies revealed a lack of lipids in the lamina propria and intercellular space in Gpat3(-/-) mice. Gpat3(-/-) enterocytes displayed a compensatory increase in the synthesis of phospholipid and cholesteryl ester. When fed a Western-type diet, hepatic TG and cholesteryl ester accumulation was significantly higher in Gpat3(-/-) mice compared with the wild-type mice accompanied by elevated levels of alanine aminotransferase, a marker of liver injury. Dysregulation of bile acid metabolism was also evident in Gpat3-null mice. These studies identify GPAT3 as a novel enzyme involved in intestinal lipid metabolism.
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Affiliation(s)
- Irani Khatun
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Ronald W Clark
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Nicholas B Vera
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Kou Kou
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Derek M Erion
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Timothy Coskran
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Walter F Bobrowski
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Carlin Okerberg
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Bryan Goodwin
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
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24
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Kelly-Laubscher RF, King JC, Hacking D, Somers S, Hastie S, Stewart T, Imamdin A, Maarman G, Pedretti S, Lecour S. Cardiac preconditioning with sphingosine-1-phosphate requires activation of signal transducer and activator of transcription-3. Cardiovasc J Afr 2015; 25:118-23. [PMID: 25000441 PMCID: PMC4120131 DOI: 10.5830/cvja-2014-016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 03/31/2014] [Indexed: 02/05/2023] Open
Abstract
Aims Sphingosine-1-phosphate (S1P) is a cardioprotective agent. Signal transducer and activator of transcription 3 (STAT-3) is a key mediator of many cardioprotective agents. We aimed to explore whether STAT-3 is a key mediator in S1P-induced preconditioning. Methods Langendorff-perfused hearts from Wistar rats and wild-type or cardiomyocyte-specific STAT-3 knockout mice were pre-treated with S1P (10 nmol/l), with or without the STAT-3 pathway inhibitor AG490, before an ischaemia–reperfusion insult. Triphenyltetrazolium chloride and Evans blue staining were used for the determination of infarct size. Western blot analysis was carried out on the S1P pre-treated hearts for detection of cytosolic, nuclear and mitochondrial phosphorylated and total STAT-3 proteins. Results Pre-treatment with S1P decreased the infarct size in isolated rat (5 ± 3% vs control 26 ± 8%, p < 0.01) and wild-type mouse hearts (13 ± 1% vs control 33 ± 3%, p < 0.05). This protective effect was abolished in the rat hearts pre-treated with AG490 (30 ± 10%, p = ns vs control) and in the hearts from STAT-3 knockout mice (35 ± 4% vs control 30 ± 3%, p = ns). Levels of phosphorylated STAT-3 were significantly increased in both the nuclear (p < 0.05 vs control) and mitochondrial (p < 0.05 vs control) fractions in the S1P pre-treated hearts, but remained unchanged in the cytosolic fraction (p = ns vs control). Conclusion These novel results demonstrate that pharmacological preconditioning with S1P in the isolated heart is mediated by activation of mitochondrial and nuclear STAT-3, therefore suggesting that S1P may be a novel therapeutic target to modulate mitochondrial and nuclear function in cardiovascular disease in order to protect the heart against ischaemia–reperfusion.
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Affiliation(s)
- Roisin F Kelly-Laubscher
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Jonathan C King
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Damian Hacking
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Sarin Somers
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Samantha Hastie
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Tessa Stewart
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Aqeela Imamdin
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Gerald Maarman
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Sarah Pedretti
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
| | - Sandrine Lecour
- Hatter Institute for Cardiovascular Research in Africa, Chris Barnard Building, Medical School Campus, University of Cape Town, Cape Town, South Africa
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Kan CFK, Singh AB, Dong B, Shende VR, Liu J. PPARδ activation induces hepatic long-chain acyl-CoA synthetase 4 expression in vivo and in vitro. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:577-87. [PMID: 25645621 DOI: 10.1016/j.bbalip.2015.01.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 01/07/2015] [Accepted: 01/14/2015] [Indexed: 12/29/2022]
Abstract
The arachidonic acid preferred long-chain acyl-CoA synthetase 4 (ACSL4) is a key enzyme for fatty acid metabolism in various metabolic tissues. In this study, we utilized hamsters fed a normal chow diet, a high-fat diet or a high cholesterol and high fat diet (HCHFD) as animal models to explore novel transcriptional regulatory mechanisms for ACSL4 expression under hyperlipidemic conditions. Through cloning hamster ACSL4 homolog and tissue profiling ACSL4 mRNA and protein expressions we observed a selective upregulation of ACSL4 in testis and liver of HCHFD fed animals. Examination of transcriptional activators of the ACSL family revealed an increased hepatic expression of PPARδ but not PPARα in HCHFD fed hamsters. To explore a role of PPARδ in dietary cholesterol-mediated upregulation of ACSL4, we administered a PPARδ specific agonist L165041 to normolipidemic and dyslipidemic hamsters. We observed significant increases of hepatic ACSL4 mRNA and protein levels in all L165041-treated hamsters as compared to control animals. The induction of ACSL4 expression by L165041 in liver tissue in vivo was recapitulated in human primary hepatocytes and hepatocytes isolated from hamster and mouse. Moreover, employing the approach of adenovirus-mediated gene knockdown, we showed that depletion of PPARδ in hamster hepatocytes specifically reduced ACSL4 expression. Finally, utilizing HepG2 as a model system, we demonstrate that PPARδ activation leads to increased ACSL4 promoter activity, mRNA and protein expression, and consequently higher arachidonoyl-CoA synthetase activity. Taken together, we have discovered a novel PPARδ-mediated regulatory mechanism for ACSL4 expression in liver tissue and cultured hepatic cells.
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Affiliation(s)
- Chin Fung Kelvin Kan
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, United States
| | - Amar Bahadur Singh
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, United States
| | - Bin Dong
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, United States
| | - Vikram Ravindra Shende
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, United States; Department of Medicine, Stanford University, Stanford, CA 94305, United States
| | - Jingwen Liu
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, United States.
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26
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Polymorphisms in lipogenic genes and milk fatty acid composition in Holstein dairy cattle. Genomics 2014; 104:572-81. [DOI: 10.1016/j.ygeno.2014.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 09/15/2014] [Accepted: 10/01/2014] [Indexed: 12/30/2022]
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Ramírez E, Klett-Mingo M, Ares-Carrasco S, Picatoste B, Ferrarini A, Rupérez FJ, Caro-Vadillo A, Barbas C, Egido J, Tuñón J, Lorenzo Ó. Eplerenone attenuated cardiac steatosis, apoptosis and diastolic dysfunction in experimental type-II diabetes. Cardiovasc Diabetol 2013; 12:172. [PMID: 24261558 PMCID: PMC4222723 DOI: 10.1186/1475-2840-12-172] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 11/09/2013] [Indexed: 12/26/2022] Open
Abstract
Background Cardiac steatosis and apoptosis are key processes in diabetic cardiomyopathy, but the underlying mechanisms have not been elucidated, leading to a lack of effective therapy. The mineralocorticoid receptor blocker, eplerenone, has demonstrated anti-fibrotic actions in the diabetic heart. However, its effects on the fatty-acid accumulation and apoptotic responses have not been revealed. Methods Non-hypertensive Zucker Diabetic Fatty (ZDF) rats received eplerenone (25 mg/kg) or vehicle. Zucker Lean (ZL) rats were used as control (n = 10, each group). After 16 weeks, cardiac structure and function was examined, and plasma and hearts were isolated for biochemical and histological approaches. Cultured cardiomyocytes were used for in vitro assays to determine the direct effects of eplerenone on high fatty acid and high glucose exposed cells. Results In contrast to ZL, ZDF rats exhibited hyperglycemia, hyperlipidemia, insulin-resistance, cardiac steatosis and diastolic dysfunction. The ZDF myocardium also showed increased mitochondrial oxidation and apoptosis. Importantly, eplerenone mitigated these events without altering hyperglycemia. In cultured cardiomyocytes, high-concentrations of palmitate stimulated the fatty-acid uptake (in detriment of glucose assimilation), accumulation of lipid metabolites, mitochondrial dysfunction, and apoptosis. Interestingly, fatty-acid uptake, ceramides formation and apoptosis were also significantly ameliorated by eplerenone. Conclusions By blocking mineralocorticoid receptors, eplerenone may attenuate cardiac steatosis and apoptosis, and subsequent remodelling and diastolic dysfunction in obese/type-II diabetic rats.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Óscar Lorenzo
- Cardiovascular Pathology laboratory, IIS-Fundación Jiménez Díaz, Autónoma University, Av, Reyes Católicos 2, Madrid 28040 Spain.
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28
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Mejia EM, Nguyen H, Hatch GM. Mammalian cardiolipin biosynthesis. Chem Phys Lipids 2013; 179:11-6. [PMID: 24144810 DOI: 10.1016/j.chemphyslip.2013.10.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 09/28/2013] [Accepted: 10/02/2013] [Indexed: 12/22/2022]
Abstract
Cardiolipin is a major phospholipid in mitochondria and is involved in the generation of cellular energy in the form of ATP. In mammalian and eukaryotic cells it is synthesized via the cytidine-5'-diphosphate-1,2-diacyl-sn-glycerol phosphate pathway. This brief review will describe some of the more recent studies on mammalian cardiolipin biosynthesis and provide an overview of regulation of cardiolipin biosynthesis. In addition, the important role that this key phospholipid plays in disease processes including heart failure, diabetes, thyroid hormone disease and the genetic disease Barth Syndrome will be discussed.
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Affiliation(s)
- Edgard M Mejia
- Department of Pharmacology and Therapeutics, Center for Research and Treatment of Atherosclerosis, University of Manitoba, DREAM Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
| | - Hieu Nguyen
- Department of Pharmacology and Therapeutics, Center for Research and Treatment of Atherosclerosis, University of Manitoba, DREAM Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
| | - Grant M Hatch
- Department of Pharmacology and Therapeutics, Center for Research and Treatment of Atherosclerosis, University of Manitoba, DREAM Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada; Department of Biochemistry and Medical Genetics, Center for Research and Treatment of Atherosclerosis, University of Manitoba, DREAM Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada.
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29
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Palomer X, Salvadó L, Barroso E, Vázquez-Carrera M. An overview of the crosstalk between inflammatory processes and metabolic dysregulation during diabetic cardiomyopathy. Int J Cardiol 2013; 168:3160-72. [PMID: 23932046 DOI: 10.1016/j.ijcard.2013.07.150] [Citation(s) in RCA: 209] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 07/15/2013] [Indexed: 10/26/2022]
Abstract
Metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus are all linked to cardiovascular diseases such as cardiac hypertrophy and heart failure. Diabetic cardiomyopathy in particular, is characterized by structural and functional alterations in the heart muscle of people with diabetes that finally lead to heart failure, and which is not directly attributable to coronary artery disease or hypertension. Several mechanisms have been involved in the pathogenesis of diabetic cardiomyopathy, such as alterations in myocardial energy metabolism and calcium signaling. Metabolic disturbances during diabetic cardiomyopathy are characterized by increased lipid oxidation, intramyocardial triglyceride accumulation, and reduced glucose utilization. Overall changes result in enhanced oxidative stress, mitochondrial dysfunction and apoptosis of the cardiomyocytes. On the other hand, the progression of heart failure and cardiac hypertrophy usually entails a local rise in cytokines in cardiac cells and the activation of the proinflammatory transcription factor nuclear factor (NF)-κB. Interestingly, increasing evidences are arising in the recent years that point to a potential link between chronic low-grade inflammation in the heart and metabolic dysregulation. Therefore, in this review we summarize recent new insights into the crosstalk between inflammatory processes and metabolic dysregulation in the failing heart during diabetes, paying special attention to the role of NF-κB and peroxisome proliferator activated receptors (PPARs). In addition, we briefly describe the role of the AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1) and other pathways regulating cardiac energy metabolism, as well as their relationship with diabetic cardiomyopathy.
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Affiliation(s)
- Xavier Palomer
- Department of Pharmacology and Therapeutic Chemistry, IBUB (Institut de Biomedicina de la Universitat de Barcelona), Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Faculty of Pharmacy, University of Barcelona, Diagonal 643, Barcelona E-08028, Spain
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Wendel AA, Cooper DE, Ilkayeva OR, Muoio DM, Coleman RA. Glycerol-3-phosphate acyltransferase (GPAT)-1, but not GPAT4, incorporates newly synthesized fatty acids into triacylglycerol and diminishes fatty acid oxidation. J Biol Chem 2013; 288:27299-27306. [PMID: 23908354 DOI: 10.1074/jbc.m113.485219] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Four glycerol-3-phosphate acyltransferase (GPAT) isoforms, each encoded by a separate gene, catalyze the initial step in glycerolipid synthesis; in liver, the major isoforms are GPAT1 and GPAT4. To determine whether each of these hepatic isoforms performs a unique function in the metabolism of fatty acid, we measured the incorporation of de novo synthesized fatty acid or exogenous fatty acid into complex lipids in primary mouse hepatocytes from control, Gpat1(-/-), and Gpat4(-/-) mice. Although hepatocytes from each genotype incorporated a similar amount of exogenous fatty acid into triacylglycerol (TAG), only control and Gpat4(-/-) hepatocytes were able to incorporate de novo synthesized fatty acid into TAG. When compared with controls, Gpat1(-/-) hepatocytes oxidized twice as much exogenous fatty acid. To confirm these findings and to assess hepatic β-oxidation metabolites, we measured acylcarnitines in liver from mice after a 24-h fast and after a 24-h fast followed by 48 h of refeeding with a high sucrose diet to promote lipogenesis. Confirming the in vitro findings, the hepatic content of long-chain acylcarnitine in fasted Gpat1(-/-) mice was 3-fold higher than in controls. When compared with control and Gpat4(-/-) mice, after the fasting-refeeding protocol, Gpat1(-/-) hepatic TAG was depleted, and long-chain acylcarnitine content was 3.5-fold higher. Taken together, these data demonstrate that GPAT1, but not GPAT4, is required to incorporate de novo synthesized fatty acids into TAG and to divert them away from oxidation.
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Affiliation(s)
- Angela A Wendel
- Department of Nutrition, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Daniel E Cooper
- Department of Nutrition, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Olga R Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center and Departments of Medicine and Pharmacology and Cancer Biology, Duke University, Durham, North Carolina 27704
| | - Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center and Departments of Medicine and Pharmacology and Cancer Biology, Duke University, Durham, North Carolina 27704
| | - Rosalind A Coleman
- Department of Nutrition, University of North Carolina, Chapel Hill, North Carolina 27599.
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Lagace TA, Ridgway ND. The role of phospholipids in the biological activity and structure of the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2499-510. [PMID: 23711956 DOI: 10.1016/j.bbamcr.2013.05.018] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 05/09/2013] [Accepted: 05/15/2013] [Indexed: 01/22/2023]
Abstract
The endoplasmic reticulum (ER) is an interconnected network of tubular and planar membranes that supports the synthesis and export of proteins, carbohydrates and lipids. Phospholipids, in particular phosphatidylcholine (PC), are synthesized in the ER where they have essential functions including provision of membranes required for protein synthesis and export, cholesterol homeostasis, and triacylglycerol storage and secretion. Coordination of these biological processes is essential, as highlighted by findings that link phospholipid metabolism in the ER with perturbations in lipid storage/secretion and stress responses, ultimately contributing to obesity/diabetes, atherosclerosis and neurological disorders. Phospholipid synthesis is not uniformly distributed in the ER but is localized at membrane interfaces or contact zones with other organelles, and in dynamic, proliferating ER membranes. The topology of phospholipid synthesis is an important consideration when establishing the etiology of diseases that arise from ER dysfunction. This review will highlight our current understanding of the contribution of phospholipid synthesis to proper ER function, and how alterations contribute to aberrant stress responses and disease. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Affiliation(s)
- Thomas A Lagace
- University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
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32
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Nanthirudjanar T, Furumoto H, Hirata T, Sugawara T. Oxidized eicosapentaenoic acids more potently reduce LXRα-induced cellular triacylglycerol via suppression of SREBP-1c, PGC-1β and GPA than its intact form. Lipids Health Dis 2013; 12:73. [PMID: 23680128 PMCID: PMC3680052 DOI: 10.1186/1476-511x-12-73] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 05/13/2013] [Indexed: 11/19/2022] Open
Abstract
Dietary polyunsaturated fatty acids (PUFA), especially eicosapentaenoic acid (EPA), improve lipid metabolism and contribute to the prevention of vascular diseases such as atherosclerosis. However, EPA in the diet is easily oxidized at room temperature and several types of oxidized EPA (OEPA) derivatives are generated. To compare the efficiencies of OEPAs on lipid metabolism with EPA, human hepatocellular liver carcinoma cell line (HepG2) was treated with EPA or OEPAs and their effects on lipid metabolism related genes were studied. OEPAs more potently suppressed the expression of sterol-responsive element-binding protein (SREBP)-1c, a major transcription factor that activates the expression of lipogenic genes, and its downstream target genes than did EPA under conditions of lipid synthesis enhanced by T0901317, a synthetic liver X receptor (LXR) agonist. Furthermore, PGC-1β, a coactivator of both LXRα and SREBP-1, was markedly down-regulated by OEPAs compared with EPA. The treatment of OEPAs also significantly down-regulated the expression of glycerol-3-phosphate acyltransferase (GPA), the initiating enzyme in triacylglycerol (TG) synthesis, more than EPA. Therefore, the advantageous effects of OEPAs on cardiovascular diseases might be due to their SREBP-1c, PGC-1β and GPA mediated ameliorating effects.
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Affiliation(s)
- Tharnath Nanthirudjanar
- Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
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33
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Frias MA, Pedretti S, Hacking D, Somers S, Lacerda L, Opie LH, James RW, Lecour S. HDL protects against ischemia reperfusion injury by preserving mitochondrial integrity. Atherosclerosis 2013; 228:110-6. [PMID: 23497785 DOI: 10.1016/j.atherosclerosis.2013.02.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 01/15/2013] [Accepted: 02/04/2013] [Indexed: 11/20/2022]
Abstract
OBJECTIVE High density lipoproteins (HDL) protect against ischemia reperfusion injury (IRI). However the precise mechanisms are not clearly understood. The novel intrinsic prosurvival signaling pathway named survivor activating factor enhancement (SAFE) path involves the activation of tumor necrosis factor (TNF) alpha and signal transducer and activator of transcription 3 (STAT3). SAFE plays a crucial role in cardioprotection against IRI. We propose that HDL protect against IRI via activation of the SAFE pathway and modulation of the mitochondrial permeability transition pore (mPTP) opening. METHODS AND RESULTS Isolated mouse hearts were subjected to global ischemia (35 min) followed by reperfusion (45 min). HDL were given during the first 7 min of reperfusion. In control hearts, the post-reperfusion infarct size was 41.3 ± 2.3%. Addition of HDL during reperfusion reduced the infarct size in a dose-dependent manner (HDL 200 μg protein/ml: 25.5 ± 1.6%, p < 0.001 vs. control). This protective effect was absent in TNF deficient mice (TNF-KO) or cardiomyocyte-STAT3 deficient mice (STAT3-KO). Similarly, HDL, given as a preconditioning stimulus, improved cell survival and inhibited mPTP opening in isolated cardiomyocytes subjected to simulated ischemia. These protective responses were inhibited in cardiomyocytes from TNF-KO and STAT3-KO mice. CONCLUSION Our data demonstrate that HDL protect against IRI by inhibition of mPTP opening, an effect mediated via activation of the SAFE pathway.
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Affiliation(s)
- Miguel A Frias
- Division of Endocrinology, University Hospital Geneva, Geneva, Switzerland.
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34
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Kok BPC, Brindley DN. Myocardial fatty acid metabolism and lipotoxicity in the setting of insulin resistance. Heart Fail Clin 2012; 8:643-61. [PMID: 22999246 DOI: 10.1016/j.hfc.2012.06.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Management of diabetes and insulin resistance in the setting of cardiovascular disease has become an important issue in an increasingly obese society. Besides the development of hypertension and buildup of atherosclerotic plaques, the derangement of fatty acid and lipid metabolism in the heart plays an important role in promoting cardiac dysfunction and oxidative stress. This review discusses the mechanisms by which metabolic inflexibility in the use of fatty acids as the preferred cardiac substrate in diabetes produces detrimental effects on mechanical efficiency, mitochondrial function, and recovery from ischemia. Lipid accumulation and the consequences of toxic lipid metabolites are also discussed.
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Affiliation(s)
- Bernard P C Kok
- Signal Transduction Research Group, Department of Biochemistry, School of Translational Medicine, University of Alberta, 11207 87th Avenue, Edmonton, Alberta, Canada
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35
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Myocardial triacylglycerol metabolism. J Mol Cell Cardiol 2012; 55:101-10. [PMID: 22789525 DOI: 10.1016/j.yjmcc.2012.06.018] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 06/22/2012] [Accepted: 06/28/2012] [Indexed: 11/22/2022]
Abstract
Myocardial triacylglycerol (TAG) constitutes a highly dynamic fatty acid (FA) storage pool that can be used for an energy reserve in the cardiomyocyte. However, derangements in myocardial TAG metabolism and accumulation are commonly associated with cardiac disease, suggesting an important role of intramyocardial TAG turnover in the regulation of cardiac function. In cardiomyocytes, TAG is synthesized by acyltransferases and phosphatases at the sarcoplasmic reticulum and mitochondrial membrane and then packaged into cytosolic lipid droplets for temporary storage or into lipoproteins for secretion. A complex interplay among lipases, lipase regulatory proteins, and lipid droplet scaffold proteins leads to the controlled release of FAs from the cardiac TAG pool for subsequent mitochondrial β-oxidation and energy production. With the identification and characterization of proteins involved in myocardial TAG metabolism as well as the identification of the importance of cardiac TAG turnover, it is now evident that adequate regulation of myocardial TAG metabolism is critical for both cardiac energy metabolism and function. In this article, we review the current understanding of myocardial TAG metabolism and discuss the potential role of myocardial TAG turnover in cardiac health and disease. This article is part of a Special Issue entitled "Focus on Cardiac Metabolism".
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36
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Abstract
The heart has both the greatest caloric needs and the most robust oxidation of fatty acids (FAs). Under pathological conditions such as obesity and type 2 diabetes, cardiac uptake and oxidation are not balanced and hearts accumulate lipid potentially leading to cardiac lipotoxicity. We will first review the pathways utilized by the heart to acquire FAs from the circulation and to store triglyceride intracellularly. Then we will describe mouse models in which excess lipid accumulation causes heart dysfunction and experiments performed to alleviate this toxicity. Finally, the known relationships between heart lipid metabolism and dysfunction in humans will be summarized.
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Affiliation(s)
- Ira J Goldberg
- Department of Medicine, Columbia University, New York, NY 10032, USA.
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37
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Membrane topology of murine glycerol-3-phosphate acyltransferase 2. Biochem Biophys Res Commun 2012; 418:506-11. [DOI: 10.1016/j.bbrc.2012.01.055] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 01/11/2012] [Indexed: 10/14/2022]
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Coleman RA, Mashek DG. Mammalian triacylglycerol metabolism: synthesis, lipolysis, and signaling. Chem Rev 2011; 111:6359-86. [PMID: 21627334 PMCID: PMC3181269 DOI: 10.1021/cr100404w] [Citation(s) in RCA: 206] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Rosalind A Coleman
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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39
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van de Weijer T, Schrauwen-Hinderling VB, Schrauwen P. Lipotoxicity in type 2 diabetic cardiomyopathy. Cardiovasc Res 2011; 92:10-8. [PMID: 21803867 DOI: 10.1093/cvr/cvr212] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
As obesity and type 2 diabetes are becoming an epidemic in westernized countries, the incidence and prevalence of obesity- and diabetes-related co-morbidities are increasing. In type 2 diabetes ectopic lipid accumulation in the heart has been associated with cardiac dysfunction and apoptosis, a process termed lipotoxicity. Since cardiovascular diseases are the main cause of death in diabetic patients, diagnosis and treatment become increasingly important. Although ischaemic heart disease is a major problem in diabetes, non-ischaemic heart disease (better known as diabetic cardiomyopathy) becomes increasingly important with respect to the impairment of cardiac function and mortality in type 2 diabetes. The underlying aetiology of diabetic cardiomyopathy is incompletely understood but is beginning to be elucidated. Various mechanisms have been proposed that may lead to lipotoxicity. Therefore, this review will focus on the mechanisms of cardiac lipid accumulation and its relation to the development of cardiomyopathy.
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Affiliation(s)
- Tineke van de Weijer
- Department of Human Biology, Maastricht University Medical Centre, PO Box 616, 6200 MD Maastricht, The Netherlands
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40
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Kuhajda FP, Aja S, Tu Y, Han WF, Medghalchi SM, El Meskini R, Landree LE, Peterson JM, Daniels K, Wong K, Wydysh EA, Townsend CA, Ronnett GV. Pharmacological glycerol-3-phosphate acyltransferase inhibition decreases food intake and adiposity and increases insulin sensitivity in diet-induced obesity. Am J Physiol Regul Integr Comp Physiol 2011; 301:R116-30. [PMID: 21490364 DOI: 10.1152/ajpregu.00147.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Storage of excess calories as triglycerides is central to obesity and its associated disorders. Glycerol-3-phosphate acyltransferases (GPATs) catalyze the initial step in acylglyceride syntheses, including triglyceride synthesis. We utilized a novel small-molecule GPAT inhibitor, FSG67, to investigate metabolic consequences of systemic pharmacological GPAT inhibition in lean and diet-induced obese (DIO) mice. FSG67 administered intraperitoneally decreased body weight and energy intake, without producing conditioned taste aversion. Daily FSG67 (5 mg/kg, 15.3 μmol/kg) produced gradual 12% weight loss in DIO mice beyond that due to transient 9- to 10-day hypophagia (6% weight loss in pair-fed controls). Continued FSG67 maintained the weight loss despite return to baseline energy intake. Weight was lost specifically from fat mass. Indirect calorimetry showed partial protection by FSG67 against decreased rates of oxygen consumption seen with hypophagia. Despite low respiratory exchange ratio due to a high-fat diet, FSG67-treated mice showed further decreased respiratory exchange ratio, beyond pair-fed controls, indicating enhanced fat oxidation. Chronic FSG67 increased glucose tolerance and insulin sensitivity in DIO mice. Chronic FSG67 decreased gene expression for lipogenic enzymes in white adipose tissue and liver and decreased lipid accumulation in white adipose, brown adipose, and liver tissues without signs of damage. RT-PCR showed decreased gene expression for orexigenic hypothalamic neuropeptides AgRP or NPY after acute and chronic systemic FSG67. FSG67 given intracerebroventricularly (100 and 320 nmol icv) produced 24-h weight loss and feeding suppression, indicating contributions from direct central nervous system sites of action. Together, these data point to GPAT as a new potential therapeutic target for the management of obesity and its comorbidities.
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Affiliation(s)
- Francis P Kuhajda
- Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, 855 N. Wolfe St., Baltimore, MD 21205, USA
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Bu SY, Mashek DG. Hepatic long-chain acyl-CoA synthetase 5 mediates fatty acid channeling between anabolic and catabolic pathways. J Lipid Res 2010; 51:3270-80. [PMID: 20798351 DOI: 10.1194/jlr.m009407] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Long-chain acyl-CoA synthetases (ACSLs) and fatty acid transport proteins (FATPs) activate fatty acids (FAs) to acyl-CoAs prior to their downstream metabolism. Of numerous ACSL and FATP isoforms, ACSL5 is expressed predominantly in tissues with high rates of triacylglycerol (TAG) synthesis, suggesting it may have an anabolic role in lipid metabolism. To characterize the role of ACSL5 in hepatic energy metabolism, we used small interference RNA (siRNA) to knock down ACSL5 in rat primary hepatocytes. Compared with cells transfected with control siRNA, suppression of ACSL5 expression significantly decreased FA-induced lipid droplet formation. These findings were further extended with metabolic labeling studies showing that ACSL5 knockdown resulted in decreased [1-(14)C]oleic acid or acetic acid incorporation into intracellular TAG, phospholipids, and cholesterol esters without altering FA uptake or lipogenic gene expression. ACSL5 knockdown also decreased hepatic TAG secretion proportionate to the observed decrease in neutral lipid synthesis. ACSL5 knockdown did not alter lipid turnover or mediate the effects of insulin on lipid metabolism. Hepatocytes treated with ACSL5 siRNA had increased rates of FA oxidation without changing PPAR-α activity and target gene expression. These results suggest that ACSL5 activates and channels FAs toward anabolic pathways and, therefore, is an important branch point in hepatic FA metabolism.
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Affiliation(s)
- So Young Bu
- Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA
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Lu B, Jiang YJ, Kim P, Moser A, Elias PM, Grunfeld C, Feingold KR. Expression and regulation of GPAT isoforms in cultured human keratinocytes and rodent epidermis. J Lipid Res 2010; 51:3207-16. [PMID: 20719759 DOI: 10.1194/jlr.m007054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Phospholipids are required for epidermal lamellar body formation. Glycerol 3-phosphate acyltransferases (GPATs) catalyze the initial step in the biosynthesis of glycerolipids. Little is known about the expression and regulation of GPATs in epidermis/keratinocytes. Here, we demonstrate that GPAT 1, 3, and 4 are expressed in epidermis/keratinocytes, whereas GPAT2 is not detected. In mouse epidermis, GPAT 3 and 4 are mainly localized to the upper layers whereas GPAT1 is found in both the upper and lower layers. GPAT1 and 3 mRNA increase during fetal rat epidermal development. No change in GPAT expression was observed in adult mice following acute permeability barrier disruption. Calcium-induced human keratinocyte differentiation increased GPAT3 mRNA whereas both GPAT1 and 4 mRNA levels decreased. In parallel, total GPAT activity increased 2-fold in differentiated keratinocytes attributable to an increase in N-ethylmaleimide (NEM) sensitive GPAT activity localized to microsomes with little change in NEM resistant activity, consistent with an increase in GPAT3. Furthermore, PPARγ or PPARδ activators increased GPAT3 mRNA, microsomal GPAT activity, and glycerol lipid synthesis without affecting the expression of GPAT1 or 4. Finally, both PPARγ and PPARδ activators increased GPAT3 mRNA via increasing its transcription. Thus, multiple isoforms of GPAT are expressed and differentially regulated in epidermis/keratinocytes.
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Affiliation(s)
- Biao Lu
- Department of R&D, System Biosciences, Mountain View, CA 94043, USA
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Brindley DN, Kok BPC, Kienesberger PC, Lehner R, Dyck JRB. Shedding light on the enigma of myocardial lipotoxicity: the involvement of known and putative regulators of fatty acid storage and mobilization. Am J Physiol Endocrinol Metab 2010; 298:E897-908. [PMID: 20103741 DOI: 10.1152/ajpendo.00509.2009] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Excessive fatty acid (FA) uptake by cardiac myocytes is often associated with adverse changes in cardiac function. This is especially evident in diabetic individuals, where increased intramyocardial triacylglycerol (TG) resulting from the exposure to high levels of circulating FA has been proposed to be a major contributor to diabetic cardiomyopathy. At present, our knowledge of how the heart regulates FA storage in TG and the hydrolysis of this TG is limited. This review concentrates on what is known about TG turnover within the heart and how this is likely to be regulated by extrapolating results from other tissues. We also assess the evidence as to whether increased TG accumulation protects against FA-induced lipotoxicity through limiting the accumulations of ceramides and diacylglycerols versus whether it is a maladaptive response that contributes to cardiac dysfunction.
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Affiliation(s)
- David N Brindley
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.
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Shan D, Li JL, Wu L, Li D, Hurov J, Tobin JF, Gimeno RE, Cao J. GPAT3 and GPAT4 are regulated by insulin-stimulated phosphorylation and play distinct roles in adipogenesis. J Lipid Res 2010; 51:1971-81. [PMID: 20181984 DOI: 10.1194/jlr.m006304] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Acyl-CoA:glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first step during de novo synthesis of glycerolipids. Mammals have at least four GPAT isoforms. Here we report the further characterization of the two recently identified microsomal GPAT3 and GPAT4. Both enzymes are highly expressed in adipose tissues. However, while GPAT3 is highly (approximately 60-fold) induced during adipocyte differentiation, GPAT4 induction is only modest (approximately 5-fold), leading to a lower abundance of GPAT4 mRNA in adipocytes. While overexpression of GPAT3 and GPAT4 in either insect or mammalian cells results in a comparable increase of GPAT activity, shRNA-mediated knockdown of GPAT3, but not GPAT4, in 3T3-L1 adipocytes led to a significant decrease in GPAT activity, a profound inhibition of lipid accumulation, and a lack of expression of several adipogenic markers during adipocyte differentiation. These data suggest that GPAT3 may encode the major GPAT isoform in adipocytes and play an important role in adipogenesis. Furthermore, we have shown that both GPAT3 and GPAT4 are phosphorylated by insulin at Ser and Thr residues, leading to increased GPAT activity that is sensitive to wortmannin. Our results reveal a link between the lipogenic effects of insulin and microsomal GPAT3 and GPAT4, implying their importance in glycerolipid biosynthesis.
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Affiliation(s)
- Dandan Shan
- Biocorrection Research Unit, Pfizer, Cambridge, MA 02140, USA
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Li LO, Hu YF, Wang L, Mitchell M, Berger A, Coleman RA. Early hepatic insulin resistance in mice: a metabolomics analysis. Mol Endocrinol 2010; 24:657-66. [PMID: 20150186 DOI: 10.1210/me.2009-0152] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
When fed with a high-fat safflower oil diet for 3 wk, wild-type mice develop hepatic insulin resistance, whereas mice lacking glycerol-3-phosphate acyltransferase-1 retain insulin sensitivity. We examined early changes in the development of insulin resistance via liver and plasma metabolome analyses that compared wild-type and glycerol-3-phosphate acyltransferase-deficient mice fed with either a low-fat or the safflower oil diet for 3 wk. We reasoned that diet-induced changes in metabolites that occurred only in the wild-type mice would reflect those metabolites that were specifically related to hepatic insulin resistance. Of the identifiable metabolites (from 322 metabolites) in liver, wild-type mice fed with the high-fat diet had increases in urea cycle intermediates, consistent with increased deamination of amino acids used for gluconeogenesis. Also increased were stearoylglycerol, gluconate, glucarate, 2-deoxyuridine, and pantothenate. Decreases were observed in S-adenosylhomocysteine, lactate, the bile acid taurocholate, and 1,5-anhydroglucitol, a previously identified marker of short-term glycemic control. Of the identifiable metabolites (from 258 metabolites) in plasma, wild-type mice fed with the high-fat diet had increases in plasma stearate and two pyrimidine-related metabolites, whereas decreases were found in plasma bradykinin, alpha-ketoglutarate, taurocholate, and the tryptophan metabolite, kynurenine. This study identified metabolites previously not known to be associated with insulin resistance and points to the utility of metabolomics analysis in identifying unrecognized biochemical pathways that may be important in understanding the pathophysiology of diabetes.
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Affiliation(s)
- Lei O Li
- Department of Nutrition, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Wendel AA, Lewin TM, Coleman RA. Glycerol-3-phosphate acyltransferases: rate limiting enzymes of triacylglycerol biosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1791:501-6. [PMID: 19038363 PMCID: PMC2737689 DOI: 10.1016/j.bbalip.2008.10.010] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 10/08/2008] [Accepted: 10/28/2008] [Indexed: 12/24/2022]
Abstract
Four homologous isoforms of glycerol-3-phosphate acyltransferase (GPAT), each the product of a separate gene, catalyze the synthesis of lysophosphatidic acid from glycerol-3-phosphate and long-chain acyl-CoA. This step initiates the synthesis of all the glycerolipids and evidence from gain-of-function and loss-of-function studies in mice and in cell culture strongly suggests that each isoform contributes to the synthesis of triacylglycerol. Much work remains to fully delineate the regulation of each GPAT isoform and its individual role in triacylglycerol synthesis.
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Affiliation(s)
- Angela A Wendel
- Department of Nutrition, CB# 7461, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Karlsson EA, Wang S, Shi Q, Coleman RA, Beck MA. Glycerol-3-phosphate acyltransferase 1 is essential for the immune response to infection with coxsackievirus B3 in mice. J Nutr 2009; 139:779-83. [PMID: 19193813 PMCID: PMC2666367 DOI: 10.3945/jn.108.101683] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Livers and hearts from mice deficient in glycerol-3-phosphate acyltransferase 1 (GPAT1; Gpat1(-/-)) have a decreased content of glycerolipid intermediates and triacylglycerol, an altered composition of liver phospholipids, and elevated markers of oxidative stress. Compared with control C57BL/6 mice, infection of Gpat1(-/-) mice with coxsackievirus B3 (CVB3) resulted in higher mortality, an approximately 50% increase in heart pathology, a significant increase in liver viral titers, and a 100-fold increase in heart viral titers. Moreover, heart mRNA levels for proinflammatory cytokines tumor necrosis factor-alpha, interleukin (IL)-6, and IL-1B were increased in the Gpat1(-/-) mice. Loss of Gpat1 also resulted in dysregulation of specific immune cells. Splenic dendritic cells from Gpat1(-/-) mice were fully capable of stimulating T cells from control mice; however, splenic T cells from Gpat1(-/-) mice were defective in their response to CVB3 antigen. Our data indicate that a lack of GPAT1 activity affects both innate and adaptive immune mechanisms. Innate mechanisms may be affected by altered membrane composition or host redox status, whereas the adaptive response may require GPAT1 activity itself.
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Affiliation(s)
- Erik A Karlsson
- Department of Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA
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48
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Yen CLE, Stone SJ, Koliwad S, Harris C, Farese RV. Thematic review series: glycerolipids. DGAT enzymes and triacylglycerol biosynthesis. J Lipid Res 2008; 49:2283-301. [PMID: 18757836 PMCID: PMC3837458 DOI: 10.1194/jlr.r800018-jlr200] [Citation(s) in RCA: 759] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 08/29/2008] [Indexed: 12/18/2022] Open
Abstract
Triacylglycerols (triglycerides) (TGs) are the major storage molecules of metabolic energy and FAs in most living organisms. Excessive accumulation of TGs, however, is associated with human diseases, such as obesity, diabetes mellitus, and steatohepatitis. The final and the only committed step in the biosynthesis of TGs is catalyzed by acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes. The genes encoding two DGAT enzymes, DGAT1 and DGAT2, were identified in the past decade, and the use of molecular tools, including mice deficient in either enzyme, has shed light on their functions. Although DGAT enzymes are involved in TG synthesis, they have distinct protein sequences and differ in their biochemical, cellular, and physiological functions. Both enzymes may be useful as therapeutic targets for diseases. Here we review the current knowledge of DGAT enzymes, focusing on new advances since the cloning of their genes, including possible roles in human health and diseases.
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Affiliation(s)
- Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI
53706
| | - Scot J. Stone
- Department of Biochemistry, University of Saskatchewan, Saskatoon,
Saskatchewan, Canada
| | - Suneil Koliwad
- Gladstone Institute of Cardiovascular Disease, University of California, San
Francisco, San Francisco, CA 94141
- Cardiovascular Research Institute, University of California, San
Francisco, San Francisco, CA 94141
- Department of Medicine, University of California, San Francisco,
San Francisco, CA 94141
| | - Charles Harris
- Gladstone Institute of Cardiovascular Disease, University of California, San
Francisco, San Francisco, CA 94141
- Cardiovascular Research Institute, University of California, San
Francisco, San Francisco, CA 94141
- Department of Medicine, University of California, San Francisco,
San Francisco, CA 94141
| | - Robert V. Farese
- Gladstone Institute of Cardiovascular Disease, University of California, San
Francisco, San Francisco, CA 94141
- Cardiovascular Research Institute, University of California, San
Francisco, San Francisco, CA 94141
- Department of Medicine, University of California, San Francisco,
San Francisco, CA 94141
- Department of Biochemistry and Biophysics, University of
California, San Francisco, San Francisco, CA 94141
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Gimeno RE, Cao J. Thematic review series: glycerolipids. Mammalian glycerol-3-phosphate acyltransferases: new genes for an old activity. J Lipid Res 2008; 49:2079-88. [PMID: 18658143 DOI: 10.1194/jlr.r800013-jlr200] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Glycerol-3-phosphate acyltransferases (GPATs; EC2.3.1.15) catalyze the first step in the de novo synthesis of neutral lipids (triglycerides) and glycerophospholipids. The existence of multiple enzyme isoforms with GPAT activity was predicted many years ago when GPAT activities with distinct kinetic profiles and sensitivity to inhibitors were characterized in two subcellular compartments, mitochondria and microsomes. We now know that mammals have at least four GPAT isoforms with distinct tissue distribution and function. GPAT1 is the major mitochondrial GPAT isoform and is characterized by its resistance to sulfhydryl-modifying reagents, such as N-ethylmaleimide (NEM). GPAT2 is a minor NEM-sensitive mitochondrial isoform. The activity referred to as microsomal GPAT is encoded by two closely related genes, GPAT3 and GPAT4. GPAT isoforms are important regulators of cellular triglyceride and phospholipid content, and may channel fatty acids toward particular metabolic fates. Overexpression and knock-out studies suggest that GPAT isoforms can play important roles in the development of hepatic steatosis, insulin resistance, and obesity; GPAT isoforms are also important for lactation. This review summarizes the current state of knowledge on mammalian GPAT isoforms.
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Affiliation(s)
- Ruth E Gimeno
- Cardiovascular and Metabolic Diseases, Wyeth Research, Cambridge, MA 02140, USA.
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