1
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Kajani S, Laker RC, Ratkova E, Will S, Rhodes CJ. Hepatic glucagon action: beyond glucose mobilization. Physiol Rev 2024; 104:1021-1060. [PMID: 38300523 DOI: 10.1152/physrev.00028.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 01/10/2024] [Accepted: 01/11/2024] [Indexed: 02/02/2024] Open
Abstract
Glucagon's ability to promote hepatic glucose production has been known for over a century, with initial observations touting this hormone as a diabetogenic agent. However, glucagon receptor agonism [when balanced with an incretin, including glucagon-like peptide 1 (GLP-1) to dampen glucose excursions] is now being developed as a promising therapeutic target in the treatment of metabolic diseases, like metabolic dysfunction-associated steatotic disease/metabolic dysfunction-associated steatohepatitis (MASLD/MASH), and may also have benefit for obesity and chronic kidney disease. Conventionally regarded as the opposing tag-team partner of the anabolic mediator insulin, glucagon is gradually emerging as more than just a "catabolic hormone." Glucagon action on glucose homeostasis within the liver has been well characterized. However, growing evidence, in part thanks to new and sensitive "omics" technologies, has implicated glucagon as more than just a "glucose liberator." Elucidation of glucagon's capacity to increase fatty acid oxidation while attenuating endogenous lipid synthesis speaks to the dichotomous nature of the hormone. Furthermore, glucagon action is not limited to just glucose homeostasis and lipid metabolism, as traditionally reported. Glucagon plays key regulatory roles in hepatic amino acid and ketone body metabolism, as well as mitochondrial turnover and function, indicating broader glucagon signaling consequences for metabolic homeostasis mediated by the liver. Here we examine the broadening role of glucagon signaling within the hepatocyte and question the current dogma, to appreciate glucagon as more than just that "catabolic hormone."
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Affiliation(s)
- Sarina Kajani
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Rhianna C Laker
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Ekaterina Ratkova
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Mölndal, Sweden
| | - Sarah Will
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Christopher J Rhodes
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
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2
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Wang C, Yang F, Zeng W, Chen X, Qiu Z, Wang Q, Meng Y, Zheng G, Hu J. Vine tea total flavonoids activate the AMPK/mTOR pathway to amelioration hepatic steatosis in mice fed a high-fat diet. J Food Sci 2024; 89:3019-3036. [PMID: 38517018 DOI: 10.1111/1750-3841.17025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 02/07/2024] [Accepted: 02/22/2024] [Indexed: 03/23/2024]
Abstract
Vine tea (Ampelopsis grossedentata), a traditional Chinese tea, is rich in flavonoids with various biological activities. Our study found that Vine tea total flavonoids (TFs) treatment reduced the body mass and blood lipid levels and improved the hepatic tissue morphology in mice fed the high-fat diet (HFD). In vivo, TF treatment activated the hepatic adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway, initiated autophagy, and regulated the expression levels of proteins for lipid metabolism in those HFD-fed mice. In vitro, TF treatment dramatically reduced the lipid droplets and triacylglycerol content in HepG2 and L02 cells treated with oleic acid (OA). These were associated with the activation of the AMPK/mTOR pathway and autophagy initiation in OA-treated hepatocytes. This phenotype was abolished in the presence of 3-methyladenine, an autophagy inhibitor. Our results indicated that the TF activation of AMPK/mTOR leads to the stimulation of autophagy and a decrease in the buildup of intracellular lipids in hepatocytes, showing the potential of TF as a therapeutic agent for nonalcoholic fatty liver disease. PRACTICAL APPLICATION: Vine tea, a tea drink, has been consumed by Chinese folk for over a thousand years. The result of this study will provide evidence that vine tea total flavonoids have potential use as a functional material for the prevention and amelioration of nonalcoholic fatty liver disease.
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Affiliation(s)
- Chuting Wang
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
- Hubei Shizhen Laboratory, Wuhan, Hubei, People's Republic of China
| | - Fang Yang
- School of Laboratory Medicine, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
| | - Wei Zeng
- Respiratory, The First People's Hospital of Jingzhou, Jingzhou, Hubei, People's Republic of China
| | - Xin Chen
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
| | - Zhenpeng Qiu
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
| | - Qi Wang
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
| | - Yan Meng
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
| | - Guohua Zheng
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
| | - Junjie Hu
- College of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, People's Republic of China
- Center of Traditional Chinese Medicine Modernization for Liver Diseases, Hubei University of Traditional Chinese Medicine, Wuhan, Hubei, People's Republic of China
- Hubei Shizhen Laboratory, Wuhan, Hubei, People's Republic of China
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3
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Colaço-Gaspar M, Hofer P, Oberer M, Zechner R. PNPLA-mediated lipid hydrolysis and transacylation - At the intersection of catabolism and anabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2024; 1869:159410. [PMID: 37951382 DOI: 10.1016/j.bbalip.2023.159410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/24/2023] [Accepted: 10/30/2023] [Indexed: 11/14/2023]
Abstract
Patatin-like phospholipase domain containing proteins (PNPLAs) play diverse roles in lipid metabolism. In this review, we focus on the enzymatic properties and predicted 3D structures of PNPLA1-5. PNPLA2-4 exert both catabolic and anabolic functions. Whereas PNPLA1 is predominantly expressed in the epidermis and involved in sphingolipid biosynthesis, PNPLA2 and 4 are ubiquitously expressed and exhibit several enzymatic activities, including hydrolysis and transacylation of various (glycero-)lipid species. This review summarizes known biological roles for PNPLA-mediated hydrolysis and transacylation reactions and highlights open questions concerning their physiological function.
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Affiliation(s)
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria; BioTechMed-Graz, 8010 Graz, Austria.
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria; BioTechMed-Graz, 8010 Graz, Austria.
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4
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Kulminskaya N, Rodriguez Gamez CF, Hofer P, Cerk IK, Dubey N, Viertlmayr R, Sagmeister T, Pavkov-Keller T, Zechner R, Oberer M. Unmasking crucial residues in adipose triglyceride lipase for coactivation with comparative gene identification-58. J Lipid Res 2024; 65:100491. [PMID: 38135254 PMCID: PMC10828586 DOI: 10.1016/j.jlr.2023.100491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 12/04/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023] Open
Abstract
Lipolysis is an essential metabolic process that releases unesterified fatty acids from neutral lipid stores to maintain energy homeostasis in living organisms. Adipose triglyceride lipase (ATGL) plays a key role in intracellular lipolysis and can be coactivated upon interaction with the protein comparative gene identification-58 (CGI-58). The underlying molecular mechanism of ATGL stimulation by CGI-58 is incompletely understood. Based on analysis of evolutionary conservation, we used site directed mutagenesis to study a C-terminally truncated variant and full-length mouse ATGL providing insights in the protein coactivation on a per-residue level. We identified the region from residues N209-N215 in ATGL as essential for coactivation by CGI-58. ATGL variants with amino acids exchanges in this region were still able to hydrolyze triacylglycerol at the basal level and to interact with CGI-58, yet could not be activated by CGI-58. Our studies also demonstrate that full-length mouse ATGL showed higher tolerance to specific single amino acid exchanges in the N209-N215 region upon CGI-58 coactivation compared to C-terminally truncated ATGL variants. The region is either directly involved in protein-protein interaction or essential for conformational changes required in the coactivation process. Three-dimensional models of the ATGL/CGI-58 complex with the artificial intelligence software AlphaFold demonstrated that a large surface area is involved in the protein-protein interaction. Mapping important amino acids for coactivation of both proteins, ATGL and CGI-58, onto the 3D model of the complex locates these essential amino acids at the predicted ATGL/CGI-58 interface thus strongly corroborating the significance of these residues in CGI-58-mediated coactivation of ATGL.
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Affiliation(s)
| | | | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Ines Kathrin Cerk
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Noopur Dubey
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Roland Viertlmayr
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Theo Sagmeister
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Tea Pavkov-Keller
- Institute of Molecular Biosciences, University of Graz, Graz, Austria; BioTechMed Graz, Graz, Austria; BioHealth Field of Excellence, University of Graz, Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria; BioTechMed Graz, Graz, Austria; BioHealth Field of Excellence, University of Graz, Graz, Austria
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria; BioTechMed Graz, Graz, Austria; BioHealth Field of Excellence, University of Graz, Graz, Austria.
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5
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Eliaš J, Fellner K, Hofer P, Oberer M, Schreiber R, Zechner R. The Potential Roles of Transacylation in Intracellular Lipolysis and Related Qssa Approximations. Bull Math Biol 2023; 85:82. [PMID: 37544001 PMCID: PMC10404580 DOI: 10.1007/s11538-023-01188-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Accepted: 07/19/2023] [Indexed: 08/08/2023]
Abstract
Fatty acids (FAs) are crucial energy metabolites, signalling molecules, and membrane building blocks for a wide range of organisms. Adipose triglyceride lipase (ATGL) is the first and presumingly most crucial regulator of FA release from triacylglycerols (TGs) stored within cytosolic lipid droplets. However, besides the function of releasing FAs by hydrolysing TGs into diacylglycerols (DGs), ATGL also promotes the transacylation reaction of two DG molecules into one TG and one monoacylglycerol molecule. To date, it is unknown whether DG transacylation is a coincidental byproduct of ATGL-mediated lipolysis or whether it is physiologically relevant. Experimental evidence is scarce since both, hydrolysis and transacylation, rely on the same active site of ATGL and always occur in parallel in an ensemble of molecules. This paper illustrates the potential roles of transacylation. It shows that, depending on the kinetic parameters but also on the state of the hydrolytic machinery, transacylation can increase or decrease downstream products up to 80% respectively 30%. We provide an extensive asymptotic analysis including quasi-steady-state approximations (QSSA) with higher order correction terms and provide numerical simulation. We also argue that when assessing the validity of QSSAs one should include parameter sensitivity derivatives. Our results suggest that the transacylation function of ATGL is of biological relevance by providing feedback options and altogether stability to the lipolytic machinery in adipocytes.
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Affiliation(s)
- Ján Eliaš
- Boehringer Ingelheim RCV GmbH & Co KG, Dr. Boehringer-Gasse 5-11, 1121 Vienna, Austria
- Institute of Mathematics and Scientific Computing, University of Graz, Heinrichstraße 36, 8010 Graz, Austria
| | - Klemens Fellner
- Institute of Mathematics and Scientific Computing, University of Graz, Heinrichstraße 36, 8010 Graz, Austria
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria
- BioTechMed Graz, 8010 Graz, Austria
- BioHealth Field of Excellence, University of Graz, 8010 Graz, Austria
| | - Renate Schreiber
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria
- BioHealth Field of Excellence, University of Graz, 8010 Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria
- BioTechMed Graz, 8010 Graz, Austria
- BioHealth Field of Excellence, University of Graz, 8010 Graz, Austria
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6
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Lulić AM, Katalinić M. The PNPLA family of enzymes: characterisation and biological role. Arh Hig Rada Toksikol 2023; 74:75-89. [PMID: 37357879 PMCID: PMC10291501 DOI: 10.2478/aiht-2023-74-3723] [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: 02/01/2023] [Revised: 02/01/2023] [Accepted: 05/01/2023] [Indexed: 06/27/2023] Open
Abstract
This paper brings a brief review of the human patatin-like phospholipase domain-containing protein (PNPLA) family. Even though it consists of only nine members, their physiological roles and mechanisms of their catalytic activity are not fully understood. However, the results of a number of knock-out and gain- or loss-of-function research models suggest that these enzymes have an important role in maintaining the homeostasis and integrity of organelle membranes, in cell growth, signalling, cell death, and the metabolism of lipids such as triacylglycerol, phospholipids, ceramides, and retinyl esters. Research has also revealed a connection between PNPLA family member mutations or irregular catalytic activity and the development of various diseases. Here we summarise important findings published so far and discuss their structure, localisation in the cell, distribution in the tissues, specificity for substrates, and their potential physiological role, especially in view of their potential as drug targets.
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Affiliation(s)
- Ana-Marija Lulić
- Institute for Medical Research and Occupational Health, Biochemistry and Organic Analytical Chemistry Unit, Zagreb, Croatia
| | - Maja Katalinić
- Institute for Medical Research and Occupational Health, Biochemistry and Organic Analytical Chemistry Unit, Zagreb, Croatia
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7
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Meyer JM, Boeglin WE, Brash AR. Recombinant PNPLA1 catalyzes the synthesis of acylceramides and acyl acids with selective incorporation of linoleic acid. J Lipid Res 2023; 64:100379. [PMID: 37087101 PMCID: PMC10209018 DOI: 10.1016/j.jlr.2023.100379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 04/17/2023] [Accepted: 04/18/2023] [Indexed: 04/24/2023] Open
Abstract
Loss-of-function mutations in patatin-like phospholipase domain-containing protein 1 (PNPLA1) cause autosomal recessive congenital ichthyosis, and altered PNPLA1 activity is implicated in the pathogenesis of atopic dermatitis and other common skin diseases. To examine the hypothesis that PNPLA1 catalyzes the synthesis of acylceramides and acyl acids, we expressed and partially purified a soluble, truncated form of PNPLA1 in Escherichia coli, (PNPLA1trun) along with the related protein PNPLA2 (ATGL, adipose triglyceride lipase) and coactivator CGI-58. Liposomal substrates were incubated with recombinant enzymes for 0.5-24 h and products analyzed by HPLC-UV and LC-MS. Using trilinolein or dilinolein substrates, PNPLA1trun, like ATGLtrun, catalyzed lipolysis and acyltransferase reactions with 2-30% conversion into linoleic acid, monolinolein, and trilinolein. CGI-58 enhanced ATGL-catalyzed lipolysis as previously reported, but transacylase activity was not enhanced with ATGL or PNPLA1. In matching the proposed activity in vivo, PNPLA1 catalyzed acyl transfer from trilinolein and dilinolein donors to omega-hydroxy ceramide, omega-hydroxy glucosylceramide, and omega-hydroxy acid acceptors to form acylceramide, glucosyl-acylceramide, and acyl acid, respectively, albeit with only ∼0.05% conversion of the substrates. Notably, in experiments comparing dilinolein vs. diolein acyl donors, PNPLA1 transferred linoleate with 3:1 selectivity over oleate into acylceramide. These results support the role for PNPLA1 in the synthesis of acylceramides and acyl acids in epidermis and suggest that the enrichment of these lipids with linoleic acid could result from the substrate selectivity of PNPLA1.
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Affiliation(s)
- Jason M Meyer
- Department of Dermatology, Vanderbilt University Medical Center, Nashville, TN, USA; Dermatology Service, Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN, USA.
| | - William E Boeglin
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Alan R Brash
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA.
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8
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Rajan S, Hofer P, Christiano A, Stevenson M, Ragolia L, Villa-Cuesta E, Fried SK, Lau R, Braithwaite C, Zechner R, Schwartz GJ, Hussain MM. Microsomal triglyceride transfer protein regulates intracellular lipolysis in adipocytes independent of its lipid transfer activity. Metabolism 2022; 137:155331. [PMID: 36228741 DOI: 10.1016/j.metabol.2022.155331] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/21/2022] [Accepted: 10/06/2022] [Indexed: 11/22/2022]
Abstract
BACKGROUND The triglyceride (TG) transfer activity of microsomal triglyceride transfer protein (MTP) is essential for lipoprotein assembly in the liver and intestine; however, its function in adipose tissue, which does not assemble lipoproteins, is unknown. Here we have elucidated the function of MTP in adipocytes. APPROACH AND RESULTS We demonstrated that MTP is present on lipid droplets in human adipocytes. Adipose-specific MTP deficient (A-Mttp-/-) male and female mice fed an obesogenic diet gained less weight than Mttpf/f mice, had less fat mass, smaller adipocytes and were insulin sensitive. A-Mttp-/- mice showed higher energy expenditure than Mttpf/f mice. During a cold challenge, A-Mttp-/- mice maintained higher body temperature by mobilizing more fatty acids. Biochemical studies indicated that MTP deficiency de-repressed adipose triglyceride lipase (ATGL) activity and increased TG lipolysis. Both wild type MTP and mutant MTP deficient in TG transfer activity interacted with and inhibited ATGL activity. Thus, the TG transfer activity of MTP is not required for ATGL inhibition. C-terminally truncated ATGL that retains its lipase activity interacted less efficiently than full-length ATGL. CONCLUSION Our findings demonstrate that adipose-specific MTP deficiency increases ATGL-mediated TG lipolysis and enhances energy expenditure, thereby resisting diet-induced obesity. We speculate that the regulatory function of MTP involving protein-protein interactions might have evolved before the acquisition of TG transfer activity in vertebrates. Adipose-specific inhibition of MTP-ATGL interactions may ameliorate obesity while avoiding the adverse effects associated with inhibition of the lipid transfer activity of MTP.
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Affiliation(s)
- Sujith Rajan
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Amanda Christiano
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Matthew Stevenson
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Louis Ragolia
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Eugenia Villa-Cuesta
- Department of Biology, College of Arts and Science, Adelphi University, Garden City, NY 11530, United States of America
| | - Susan K Fried
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - Raymond Lau
- Department of Surgery, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Collin Braithwaite
- Department of Surgery, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria; BioTechMed-Graz, Austria; BioHealth Field of Excellence, University of Graz, Graz, Austria
| | - Gary J Schwartz
- Department of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, United States of America.
| | - M Mahmood Hussain
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America; Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY, United States of America.
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Patel R, Santoro A, Hofer P, Tan D, Oberer M, Nelson AT, Konduri S, Siegel D, Zechner R, Saghatelian A, Kahn BB. ATGL is a biosynthetic enzyme for fatty acid esters of hydroxy fatty acids. Nature 2022; 606:968-975. [PMID: 35676490 PMCID: PMC9242854 DOI: 10.1038/s41586-022-04787-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 04/21/2022] [Indexed: 12/16/2022]
Abstract
Branched fatty acid (FA) esters of hydroxy FAs (HFAs; FAHFAs) are recently discovered lipids that are conserved from yeast to mammals1,2. A subfamily, palmitic acid esters of hydroxy stearic acids (PAHSAs), are anti-inflammatory and anti-diabetic1,3. Humans and mice with insulin resistance have lower PAHSA levels in subcutaneous adipose tissue and serum1. PAHSA administration improves glucose tolerance and insulin sensitivity and reduces inflammation in obesity, diabetes and immune-mediated diseases1,4-7. The enzyme(s) responsible for FAHFA biosynthesis in vivo remains unknown. Here we identified adipose triglyceride lipase (ATGL, also known as patatin-like phospholipase domain containing 2 (PNPLA2)) as a candidate biosynthetic enzyme for FAHFAs using chemical biology and proteomics. We discovered that recombinant ATGL uses a transacylation reaction that esterifies an HFA with a FA from triglyceride (TG) or diglyceride to produce FAHFAs. Overexpression of wild-type, but not catalytically dead, ATGL increases FAHFA biosynthesis. Chemical inhibition of ATGL or genetic deletion of Atgl inhibits FAHFA biosynthesis and reduces the levels of FAHFA and FAHFA-TG. Levels of endogenous and nascent FAHFAs and FAHFA-TGs are 80-90 per cent lower in adipose tissue of mice in which Atgl is knocked out specifically in the adipose tissue. Increasing TG levels by upregulating diacylglycerol acyltransferase (DGAT) activity promotes FAHFA biosynthesis, and decreasing DGAT activity inhibits it, reinforcing TGs as FAHFA precursors. ATGL biosynthetic transacylase activity is present in human adipose tissue underscoring its potential clinical relevance. In summary, we discovered the first, to our knowledge, biosynthetic enzyme that catalyses the formation of the FAHFA ester bond in mammals. Whereas ATGL lipase activity is well known, our data establish a paradigm shift demonstrating that ATGL transacylase activity is biologically important.
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Affiliation(s)
- Rucha Patel
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Anna Santoro
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Dan Tan
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Andrew T Nelson
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego, La Jolla, CA, USA
| | - Srihari Konduri
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego, La Jolla, CA, USA
| | - Dionicio Siegel
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego, La Jolla, CA, USA
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Alan Saghatelian
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Barbara B Kahn
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
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10
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Riegler-Berket L, Wechselberger L, Cerk IK, Padmanabha Das KM, Viertlmayr R, Kulminskaya N, Rodriguez Gamez CF, Schweiger M, Zechner R, Zimmermann R, Oberer M. Residues of the minimal sequence of G0S2 collectively contribute to ATGL inhibition while C-and N-terminal extensions promote binding to ATGL. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159105. [PMID: 35026402 DOI: 10.1016/j.bbalip.2021.159105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 11/29/2021] [Accepted: 12/17/2021] [Indexed: 11/25/2022]
Abstract
The protein encoded by the G0/G1 switch gene 2 (G0S2) is a potent inhibitor of adipose triglyceride lipase (ATGL) and thus an important regulator of intracellular lipolysis. Since dysfunction of lipolysis is associated with metabolic diseases including diabetes and obesity, inhibition of ATGL is considered a therapeutic strategy. G0S2 interacts with ATGL's patatin-domain to mediate non-competitive inhibition, however atomic details of the inhibition mechanism are incompletely understood. Sequences of G0S2 from higher organisms show a highly conserved N-terminal part, including a hydrophobic region covering amino acids 27 to 42. We show that predicted G0S2 orthologs from platypus, chicken and Japanese rice-fish are able to inhibit human and mouse ATGL, emphasizing the contribution of conserved amino acid to ATGL inhibition. Our site directed mutagenesis and truncation studies give insights in the protein-protein interaction on a per-residue level. We determine that the minimal sequence required for ATGL inhibition ranges from amino acids 20 to 44. Residues Y27, V28, G30, A34 G37, V39 or L42 within this sequence play a substantial role in ATGL inhibition. Furthermore, we show that unspecific interactions of the N-terminal part (amino acids 20-27) of the minimal sequence facilitate the interaction to ATGL. Our studies also demonstrate that full-length G0S2 shows higher tolerance to specific single amino acid exchanges in the hydrophobic region due to the stronger contributions of unspecific interactions. However, exchanges of more than one amino-acid in the hydrophobic region also result in the loss of function as ATGL inhibitor even in the full-length protein.
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Affiliation(s)
- L Riegler-Berket
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - L Wechselberger
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - I K Cerk
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - K M Padmanabha Das
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - R Viertlmayr
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - N Kulminskaya
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | | | - M Schweiger
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria
| | - R Zechner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria; BioHealth Field of Excellence, University of Graz, 8010 Graz, Austria
| | - R Zimmermann
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria; BioHealth Field of Excellence, University of Graz, 8010 Graz, Austria
| | - M Oberer
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria; BioHealth Field of Excellence, University of Graz, 8010 Graz, Austria.
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Li HY, Peng ZG. Targeting lipophagy as a potential therapeutic strategy for nonalcoholic fatty liver disease. Biochem Pharmacol 2022; 197:114933. [PMID: 35093393 DOI: 10.1016/j.bcp.2022.114933] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/04/2022] [Accepted: 01/21/2022] [Indexed: 02/09/2023]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is becoming an increasingly serious disease worldwide. Unfortunately, no specific drug has been approved to treat NAFLD. Accumulating evidence suggests that lipotoxicity, which is induced by an excess of intracellular triacylglycerols (TAGs), is a potential mechanism underlying the ill-defined progression of NAFLD. Under physiological conditions, a balance is maintained between TAGs and free fatty acids (FFAs) in the liver. TAGs are catabolized to FFAs through neutral lipolysis and/or lipophagy, while FFAs can be anabolized to TAGs through an esterification reaction. However, in the livers of patients with NAFLD, lipophagy appears to fail. Reversing this abnormal state through several lipophagic molecules (mTORC1, AMPK, PLIN, etc.) facilitates NAFLD amelioration; therefore, restoring failed lipophagy may be a highly efficient therapeutic strategy for NAFLD. Here, we outline the lipophagy phases with the relevant important proteins and discuss the roles of lipophagy in the progression of NAFLD. Additionally, the potential candidate drugs with therapeutic value targeting these proteins are discussed to show novel strategies for future treatment of NAFLD.
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Affiliation(s)
- Hong-Ying Li
- CAMS Key Laboratory of Antiviral Drug Research, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Zong-Gen Peng
- CAMS Key Laboratory of Antiviral Drug Research, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China; Key Laboratory of Biotechnology of Antibiotics, The National Health and Family Planning Commission (NHFPC), Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
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