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Engin A. Lipid Storage, Lipolysis, and Lipotoxicity in Obesity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1460:97-129. [PMID: 39287850 DOI: 10.1007/978-3-031-63657-8_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/19/2024]
Abstract
The ratio of free fatty acid (FFA) turnover decreases significantly with the expansion of white adipose tissue. Adipose tissue and dietary saturated fatty acid levels significantly correlate with an increase in fat cell size and number. The G0/G1 switch gene 2 increases lipid content in adipocytes and promotes adipocyte hypertrophy through the restriction of triglyceride (triacylglycerol: TAG) turnover. Hypoxia in obese adipose tissue due to hypertrophic adipocytes results in excess deposition of extracellular matrix (ECM) components. Cluster of differentiation (CD) 44, as the main receptor of the extracellular matrix component regulates cell-cell and cell-matrix interactions including diet-induced insulin resistance. Excess TAGs, sterols, and sterol esters are surrounded by the phospholipid monolayer surface and form lipid droplets (LDs). Once LDs are formed, they grow up because of the excessive amount of intracellular FFA stored and reach a final size. The ratio of FFA turnover/lipolysis decreases significantly with increases in the degree of obesity. Dysfunctional adipose tissue is unable to expand further to store excess dietary lipids, increased fluxes of plasma FFAs lead to ectopic fatty acid deposition and lipotoxicity. Reduced neo-adipogenesis and dysfunctional lipid-overloaded adipocytes are hallmarks of hypertrophic obesity linked to insulin resistance. Obesity-associated adipocyte death exhibits feature of necrosis-like programmed cell death. Adipocyte death is a prerequisite for the transition from hypertrophic to hyperplastic obesity. Increased adipocyte number in obesity has life-long effects on white adipose tissue mass. The positive correlation between the adipose tissue volume and magnetic resonance imaging proton density fat fraction estimation is used for characterization of the obesity phenotype, as well as the risk stratification and selection of appropriate treatment strategies. In obese patients with type 2 diabetes, visceral adipocytes exposed to chronic/intermittent hyperglycemia develop a new microRNAs' (miRNAs') expression pattern. Visceral preadipocytes memorize the effect of hyperglycemia via changes in miRNAs' expression profile and contribute to the progression of diabetic phenotype. Nonsteroidal anti-inflammatory drugs, metformin, and statins can be beneficial in treating the local or systemic consequences of white adipose tissue inflammation. Rapamycin inhibits leptin-induced LD formation. Collectively, in this chapter, the concept of adipose tissue remodeling in response to adipocyte death or adipogenesis, and the complexity of LD interactions with the other cellular organelles are reviewed. Furthermore, clinical perspective of fat cell turnover in obesity is also debated.
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Affiliation(s)
- Atilla Engin
- Faculty of Medicine, Department of General Surgery, Gazi University, Besevler, Ankara, Turkey.
- Mustafa Kemal Mah. 2137. Sok. 8/14, 06520, Cankaya, Ankara, Turkey.
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Arredondo-Amador M, Zambrano C, Kulyté A, Luján J, Hu K, Sánchez de Medina F, Scheer FAJL, Arner P, Ryden M, Martínez-Augustin O, Garaulet M. Circadian Rhythms in Hormone-sensitive Lipase in Human Adipose Tissue: Relationship to Meal Timing and Fasting Duration. J Clin Endocrinol Metab 2020; 105:5877911. [PMID: 32725188 PMCID: PMC7538104 DOI: 10.1210/clinem/dgaa492] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/27/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND Fat mobilization in adipose tissue (AT) has a specific timing. However, circadian rhythms in the activity of the major enzyme responsible for fat mobilization, hormone-sensitive lipase (HSL), have not been demonstrated in humans. OBJECTIVE To analyze in a cross-sectional study whether there is an endogenous circadian rhythm in HSL activity in human AT ex vivo and whether rhythm characteristics are related to food timing or fasting duration. METHODS Abdominal AT biopsies were obtained from 18 severely obese participants (age: 46 ± 11 years; body mass index 42 ± 6 kg/m2) who underwent laparoscopic gastric bypass. Twenty-four-hour rhythms of HSL activity and LIPE (HSL transcript in humans) expression in subcutaneous AT were analyzed together with habitual food timing and night fasting duration. RESULTS HSL activity exhibited a circadian rhythm (P = .023) and reached the maximum value at circadian time 16 (CT) that corresponded to around midnight (relative local clock time. Similarly, LIPE displayed a circadian rhythm with acrophase also at night (P = .0002). Participants with longer night fasting duration >11.20 hours displayed almost double the amplitude (1.91 times) in HSL activity rhythm than those with short duration (P = .013); while habitual early diners (before 21:52 hours) had 1.60 times higher amplitude than late diners (P = .035). CONCLUSIONS Our results demonstrate circadian rhythms in HSL activity and may lead to a better understanding of the intricate relationships between food timing, fasting duration and body fat regulation.
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Affiliation(s)
- María Arredondo-Amador
- Department of Pharmacology, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Investigación Biosanitaria ibs, Granada, School of Pharmacy, University of Granada, Granada, Spain
| | - Carolina Zambrano
- Department of Physiology, Biomedical Research Institute of Murcia (IMIB)-Arrixaca, University of Murcia, Murcia, Spain
| | - Agné Kulyté
- Endocrinology Unit, Department of Medicine (H7) Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Juán Luján
- General Surgery Service, University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Kun Hu
- Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Boston, Massachusetts; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts
| | - Fermín Sánchez de Medina
- Department of Pharmacology, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Investigación Biosanitaria ibs, Granada, School of Pharmacy, University of Granada, Granada, Spain
| | - Frank A J L Scheer
- Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Boston, Massachusetts; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts
| | - Peter Arner
- Endocrinology Unit, Department of Medicine (H7) Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Mikael Ryden
- Endocrinology Unit, Department of Medicine (H7) Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Olga Martínez-Augustin
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Investigación Biosanitaria ibs, Granada, Instituto de Nutrición y Tecnología de los Alimentos José Mataix, University of Granada, Granada, Spain
| | - Marta Garaulet
- Department of Physiology, Biomedical Research Institute of Murcia (IMIB)-Arrixaca, University of Murcia, Murcia, Spain
- Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Boston, Massachusetts; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts
- Correspondence and Reprint Requests: Marta Garaulet, Department of Physiology, University of Murcia, s/n. 30100, Murcia, Spain; or Division of Sleep and Circadian Disorders, Brigham and Women’s, Boston, MA, USA. E-mail: ;
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Rogne M, Chu DT, Küntziger TM, Mylonakou MN, Collas P, Tasken K. OPA1-anchored PKA phosphorylates perilipin 1 on S522 and S497 in adipocytes differentiated from human adipose stem cells. Mol Biol Cell 2018; 29:1487-1501. [PMID: 29688805 PMCID: PMC6014102 DOI: 10.1091/mbc.e17-09-0538] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Optic atrophy 1 (OPA1) is the A-kinase anchoring protein targeting the pool of protein kinase A (PKA) responsible for perilipin 1 phosphorylation, a gatekeeper for lipolysis. However, the involvement of OPA1-bound PKA in the downstream regulation of lipolysis is unknown. Here we show up-regulation and relocation of OPA1 from mitochondria to lipid droplets during adipocytic differentiation of human adipose stem cells. We employed various biochemical and immunological approaches to demonstrate that OPA1-bound PKA phosphorylates perilipin 1 at S522 and S497 on lipolytic stimulation. We show that the first 30 amino acids of OPA1 are essential for its lipid droplet localization as is OMA1-dependent processing. Finally, our results indicate that presence of OPA1 is necessary for lipolytic phosphorylation of downstream targets. Our results show for the first time, to our knowledge, how OPA1 mediates adrenergic control of lipolysis in human adipocytes by regulating phosphorylation of perilipin 1.
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Affiliation(s)
- Marie Rogne
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, 0318 Oslo, Norway
| | - Dinh-Toi Chu
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, 0318 Oslo, Norway
| | | | - Maria-Niki Mylonakou
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, 0318 Oslo, Norway
| | - Philippe Collas
- Department of Molecular Medicine, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, 0318 Oslo, Norway.,Norewegian Center for Stem Cell Research, Department of Immunology and Transfusion Medicine, Oslo University Hospital, 0424 Oslo, Norway
| | - Kjetil Tasken
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, 0318 Oslo, Norway.,Department of Cancer Immunology, Institute of Cancer Research, Oslo University Hospital, 0424 Oslo, Norway
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Engin A. Fat Cell and Fatty Acid Turnover in Obesity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 960:135-160. [PMID: 28585198 DOI: 10.1007/978-3-319-48382-5_6] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The ratio of free fatty acid (FFA) turnover decreases significantly with the expansion of white adipose tissue. Adipose tissue and dietary saturated fatty acid levels significantly correlate with an increase in fat cell size and number. Inhibition of adipose triglyceride lipase leads to an accumulation of triglyceride, whereas inhibition of hormone-sensitive lipase leads to the accumulation of diacylglycerol. The G0/G1 switch gene 2 increases lipid content in adipocytes and promotes adipocyte hypertrophy through the restriction of triglyceride turnover. Excess triacylglycerols (TAGs), sterols and sterol esters are surrounded by the phospholipid monolayer surface and form lipid droplets. Following the release of lipid droplets from endoplasmic reticulum, cytoplasmic lipid droplets increase their volume either by local TAG synthesis or by homotypic fusion. The number and the size of lipid droplet distribution is correlated with obesity. Obesity-associated adipocyte death exhibits feature of necrosis-like programmed cell death. NOD-like receptors family pyrin domain containing 3 (NLRP3) inflammasome-dependent caspase-1 activation in hypertrophic adipocytes induces obese adipocyte death by pyroptosis. Actually adipocyte death may be a prerequisite for the transition from hypertrophic to hyperplastic obesity. Major transcriptional factors, CCAAT/enhancer-binding proteins beta and delta, play a central role in the subsequent induction of critical regulators, peroxisome-proliferator-activated receptor gamma, CCAAT/enhancer-binding protein alpha and sterol regulatory element-binding protein 1, in the transcriptional control of adipogenesis in obesity.Collectively, in this chapter the concept of adipose tissue remodeling in response to adipocyte death or adipogenesis, and the complexity of lipid droplet interactions with the other cellular organelles are reviewed. Furthermore, in addition to lipid droplet growth, the functional link between the adipocyte-specific lipid droplet-associated protein and fatty acid turn-over is also debated.
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Affiliation(s)
- Atilla Engin
- Faculty of Medicine, Department of General Surgery, Gazi University, Besevler, Ankara, Turkey. .,, Mustafa Kemal Mah. 2137. Sok. 8/14, 06520, Cankaya, Ankara, Turkey.
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Nielsen TS, Jessen N, Jørgensen JOL, Møller N, Lund S. Dissecting adipose tissue lipolysis: molecular regulation and implications for metabolic disease. J Mol Endocrinol 2014; 52:R199-222. [PMID: 24577718 DOI: 10.1530/jme-13-0277] [Citation(s) in RCA: 263] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Lipolysis is the process by which triglycerides (TGs) are hydrolyzed to free fatty acids (FFAs) and glycerol. In adipocytes, this is achieved by sequential action of adipose TG lipase (ATGL), hormone-sensitive lipase (HSL), and monoglyceride lipase. The activity in the lipolytic pathway is tightly regulated by hormonal and nutritional factors. Under conditions of negative energy balance such as fasting and exercise, stimulation of lipolysis results in a profound increase in FFA release from adipose tissue (AT). This response is crucial in order to provide the organism with a sufficient supply of substrate for oxidative metabolism. However, failure to efficiently suppress lipolysis when FFA demands are low can have serious metabolic consequences and is believed to be a key mechanism in the development of type 2 diabetes in obesity. As the discovery of ATGL in 2004, substantial progress has been made in the delineation of the remarkable complexity of the regulatory network controlling adipocyte lipolysis. Notably, regulatory mechanisms have been identified on multiple levels of the lipolytic pathway, including gene transcription and translation, post-translational modifications, intracellular localization, protein-protein interactions, and protein stability/degradation. Here, we provide an overview of the recent advances in the field of AT lipolysis with particular focus on the molecular regulation of the two main lipases, ATGL and HSL, and the intracellular and extracellular signals affecting their activity.
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Affiliation(s)
- Thomas Svava Nielsen
- The Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, DenmarkThe Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, Denmark
| | - Niels Jessen
- The Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, DenmarkThe Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, Denmark
| | - Jens Otto L Jørgensen
- The Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, Denmark
| | - Niels Møller
- The Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, Denmark
| | - Sten Lund
- The Novo Nordisk Foundation Center for Basic Metabolic ResearchSection on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 6.6.30, DK-2200 N Copenhagen, DenmarkDepartment of Endocrinology and Internal MedicineAarhus University Hospital, Nørrebrogade 44, Bldg. 3.0, 8000 Aarhus C, DenmarkDepartment of Molecular MedicineAarhus University Hospital, Brendstrupgårdsvej 100, 8200 Aarhus N, Denmark
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Badin PM, Langin D, Moro C. Dynamics of skeletal muscle lipid pools. Trends Endocrinol Metab 2013; 24:607-15. [PMID: 23988586 DOI: 10.1016/j.tem.2013.08.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 07/22/2013] [Accepted: 08/03/2013] [Indexed: 11/20/2022]
Abstract
Intramyocellular triacylglycerol (IMTG) is emerging as an important energy fuel source during muscle contraction and are adaptively increased in response to exercise, without adverse physiological effects. Paradoxically, elevated IMTG content in obese and type 2 diabetics has been linked to insulin resistance, highlighting the importance of IMTG pools in physiology and pathology. Two separate views suggest that IMTG dynamics are determinant for skeletal muscle fat oxidation, and that disruption of IMTG dynamics facilitates the accumulation of lipotoxic intermediates such as diacylglycerols and ceramides that interfere with insulin signaling. Thus, understanding the factors that control IMTG dynamics is crucial. Here we discuss recent literature describing the regulation of IMTG pools with a particular emphasis on lipases and lipid droplet (LD)-associated proteins.
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Affiliation(s)
- Pierre-Marie Badin
- Obesity Research Laboratory, Institut National de la Santé et de la Recherche Médicale (INSERM) Unité Mixte de Recherche (UMR) 1048, Institute of Metabolic and Cardiovascular Diseases (I2MC), Toulouse, France; University of Toulouse, UMR1048, Paul Sabatier University, Toulouse, France
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7
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Reactive oxygen species facilitate translocation of hormone sensitive lipase to the lipid droplet during lipolysis in human differentiated adipocytes. PLoS One 2012; 7:e34904. [PMID: 22493722 PMCID: PMC3321042 DOI: 10.1371/journal.pone.0034904] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 03/07/2012] [Indexed: 01/18/2023] Open
Abstract
In obesity, there is an increase in reactive oxygen species (ROS) within adipose tissue caused by increases in inflammation and overnutrition. Hormone sensitive lipase (HSL) is part of the canonical lipolytic pathway and critical for complete lipolysis. This study hypothesizes that ROS is a signal that integrates regulation of lipolysis by targeting HSL. Experiments were performed with human differentiated adipocytes from the subcutaneous depot. Antioxidants were employed as a tool to decrease ROS, and it was found that scavenging ROS with diphenyliodonium, N-acetyl cysteine, or resveratrol decreased lipolysis in adipocytes. HSL phosphorylation of a key serine residue, Ser552, as well as translocation of this enzyme from the cytosol to the lipid droplet upon lipolytic stimulation were both abrogated by scavenging ROS. The phosphorylation status of other serine residues on HSL were not affected. These findings are significant because they document that ROS contributes to the physiological regulation of lipolysis via an effect on translocation. Such regulation could be useful in developing new obesity therapies.
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8
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Lampidonis AD, Rogdakis E, Voutsinas GE, Stravopodis DJ. The resurgence of Hormone-Sensitive Lipase (HSL) in mammalian lipolysis. Gene 2011; 477:1-11. [PMID: 21241784 DOI: 10.1016/j.gene.2011.01.007] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 12/22/2010] [Accepted: 01/07/2011] [Indexed: 12/13/2022]
Abstract
The ability to store energy in the form of energy-dense triacylglycerol and to mobilize these stores rapidly during periods of low carbohydrate availability or throughout the strong metabolic demand is a highly conserved process, absolutely essential for survival. In the industrialized world the regulation of this pathway is viewed as an important therapeutic target for disease prevention. Adipose tissue lipolysis is a catabolic process leading to the breakdown of triacylglycerols stored in fat cells, and release of fatty acids and glycerol. Mobilization of adipose tissue fat is mediated by the MGL, HSL and ATGL, similarly functioning enzymes. ATGL initiates lipolysis followed by the actions of HSL on diacylglycerol, and MGL on monoacylglycerol. HSL is regulated by reversible phosphorylation on five critical residues. Phosphorylation alone, however, is not enough to activate HSL. Probably, conformational alterations and a translocation from the cytoplasm to lipid droplets are also involved. In accordance, Perilipin functions as a master regulator of lipolysis, protecting or exposing the triacylglycerol core of a lipid droplet to lipases. The prototype processes of hormonal lipolytic control are the β-adrenergic stimulation and suppression by insulin, both of which affect cytoplasmic cyclic AMP levels. Lipolysis in adipocytes is an important process in the management of body energy reserves. Its deregulation may contribute to the symptoms of type 2 diabetes mellitus and other pathological situations. We, herein, discuss the metabolic regulation and function of lipases mediating mammalian lipolysis with a focus on HSL, quoting newly identified members of the lipolytic proteome.
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Affiliation(s)
- Antonis D Lampidonis
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Zografou, 157 84 Athens, Greece
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Krintel C, Klint C, Lindvall H, Mörgelin M, Holm C. Quarternary structure and enzymological properties of the different hormone-sensitive lipase (HSL) isoforms. PLoS One 2010; 5:e11193. [PMID: 20567594 PMCID: PMC2887374 DOI: 10.1371/journal.pone.0011193] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Accepted: 05/26/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Hormone-sensitive lipase (HSL) is a key enzyme in the mobilization of energy in the form of fatty acids from intracellular stores of neutral lipids. The enzyme has been shown to exist in different isoforms with different molecular masses (84 kDa, 89 kDa and 117 kDa) expressed in a tissue-dependent manner, where the predominant 84 kDa form in adipocytes is the most extensively studied. METHODOLOGY/PRINCIPAL FINDINGS In this study we employed negative stain electron microscopy (EM) to analyze the quarternary structure of the different HSL isoforms. The results show that all three isoforms adopt a head-to-head homodimeric organization, where each monomer contains two structural domains. We also used enzymatic assays to show that despite the variation in the size of the N-terminal domain all three isoforms exhibit similar enzymological properties with regard to psychrotolerance and protein kinase A (PKA)-mediated phosphorylation and activation. CONCLUSIONS/SIGNIFICANCE We present the first data on the quaternary structure and domain organization of the three HSL isoforms. We conclude that despite large differences in the size of the N-terminal, non-catalytic domain all three HSL isoforms exhibit the same three-dimensional architecture. Furthermore, the three HSL isoforms are very similar with regard to two unique enzymological characteristics of HSL, i.e., cold adaptation and PKA-mediated activation.
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Affiliation(s)
- Christian Krintel
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Division of Diabetes, Metabolism and Endocrinology, Department of Molecular Biophysics, Lund University, Lund, Sweden
| | - Cecilia Klint
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Håkan Lindvall
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Matthias Mörgelin
- Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Cecilia Holm
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail:
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Wang H, Hu L, Dalen K, Dorward H, Marcinkiewicz A, Russell D, Gong D, Londos C, Yamaguchi T, Holm C, Rizzo MA, Brasaemle D, Sztalryd C. Activation of hormone-sensitive lipase requires two steps, protein phosphorylation and binding to the PAT-1 domain of lipid droplet coat proteins. J Biol Chem 2009; 284:32116-25. [PMID: 19717842 PMCID: PMC2797282 DOI: 10.1074/jbc.m109.006726] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 08/27/2009] [Indexed: 11/06/2022] Open
Abstract
Lipolysis is an important metabolic pathway controlling energy homeostasis through degradation of triglycerides stored in lipid droplets and release of fatty acids. Lipid droplets of mammalian cells are coated with one or more members of the PAT protein family, which serve important functions in regulating lipolysis. In this study, we investigate the mechanisms by which PAT family members, perilipin A, adipose differentiation-related protein (ADFP), and LSDP5, control lipolysis catalyzed by hormone-sensitive lipase (HSL), a major lipase in adipocytes and several non-adipose cells. We applied fluorescence microscopic tools to analyze proteins in situ in cultured Chinese hamster ovary cells using fluorescence recovery after photobleaching and anisotropy Forster resonance energy transfer. Fluorescence recovery after photobleaching data show that ADFP and LSDP5 exchange between lipid droplet and cytoplasmic pools, whereas perilipin A does not. Differences in protein mobility do not correlate with PAT protein-mediated control of lipolysis catalyzed by HSL or endogenous lipases. Forster resonance energy transfer and co-immunoprecipitation experiments reveal that each of the three PAT proteins bind HSL through interaction of the lipase with amino acids within the highly conserved amino-terminal PAT-1 domain. ADFP and LSDP5 bind HSL under basal conditions, whereas phosphorylation of serine residues within three amino-terminal protein kinase A consensus sequences of perilipin A is required for HSL binding and maximal lipolysis. Finally, protein kinase A-mediated phosphorylation of HSL increases lipolysis in cells expressing ADFP or LSDP5; in contrast, phosphorylation of perilipin A exerts the major control over HSL-mediated lipolysis when perilipin is the main lipid droplet protein.
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Affiliation(s)
- Hong Wang
- From the Geriatric Research, Education, and Clinical Center, Baltimore Veterans Affairs Health Care Center, and Division of Endocrinology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Liping Hu
- From the Geriatric Research, Education, and Clinical Center, Baltimore Veterans Affairs Health Care Center, and Division of Endocrinology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Knut Dalen
- the Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-8028
| | - Heidi Dorward
- the Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-8028
| | - Amy Marcinkiewicz
- the Department of Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901
| | - Deanna Russell
- the Department of Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901
| | - Dawei Gong
- the Division of Endocrinology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Constantine Londos
- the Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-8028
| | - Tomohiro Yamaguchi
- the Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori, Hyogo 678-1297, Japan
| | - Cecilia Holm
- the Department of Experimental Medical Science, Lund University, BMC C11, SE-221 84, Lund, Sweden
| | - Mark A. Rizzo
- the Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, and
| | - Dawn Brasaemle
- the Department of Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901
| | - Carole Sztalryd
- From the Geriatric Research, Education, and Clinical Center, Baltimore Veterans Affairs Health Care Center, and Division of Endocrinology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201
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Abstract
Human obesity and its complications are an increasing burden in developed and underdeveloped countries. Adipose tissue mass and the mechanisms that control it are central to elucidating the aetiology of obesity and insulin resistance. Over the past 15 years tremendous progress has been made in several avenues relating to adipose tissue. Knowledge of the lipolytic machinery has grown with the identification of new lipases, cofactors and interactions between proteins and lipids that are central to the regulation of basal and stimulated lipolysis. The dated idea of an inert lipid droplet has been appropriately revamped to that of a dynamic and highly-structured organelle that in itself offers regulatory control over lipolysis. The present review provides an overview of the numerous partners and pathways involved in adipose tissue lipolysis and their interaction under various metabolic states. Integration of these findings into whole adipose tissue metabolism and its systemic effects is also presented in the context of inflammation and insulin resistance.
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Krintel C, Mörgelin M, Logan DT, Holm C. Phosphorylation of hormone-sensitive lipase by protein kinase A in vitro promotes an increase in its hydrophobic surface area. FEBS J 2009; 276:4752-62. [PMID: 19664063 DOI: 10.1111/j.1742-4658.2009.07172.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hormone-sensitive lipase (EC 3.1.1.79; HSL) is a key enzyme in the mobilization of fatty acids from stored triacylglycerols. HSL activity is controlled by phosphorylation of at least four serines. In rat HSL, Ser563, Ser659 and Ser660 are phosphorylated by protein kinase A (PKA) in vitro as well as in vivo, and Ser660 and Ser659 have been shown to be the activity-controlling sites in vitro. The exact molecular events of PKA-mediated activation of HSL in vitro are yet to be determined, but increases in both Vmax and S0.5 seem to be involved, as recently shown for human HSL. In this study, the hydrophobic fluorescent probe 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) was found to inhibit the hydrolysis of triolein by purified recombinant rat adipocyte HSL, with a decrease in the effect of bis-ANS upon PKA phosphorylation of HSL. The interaction of HSL with bis-ANS was found to have a Kd of 1 microM in binding assays. Upon PKA phosphorylation, the interactions of HSL with both bis-ANS and the alternative probe SYPRO Orange were increased. By negative stain transmission electron microscopy, phosphorylated HSL was found to have a closer interaction with phospholipid vesicles than unphosphorylated HSL. Taken together, our results show that HSL increases its hydrophobic nature upon phosphorylation by PKA. This suggests that PKA phosphorylation induces a conformational change that increases the exposed hydrophobic surface and thereby facilitates binding of HSL to the lipid substrate.
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Affiliation(s)
- Christian Krintel
- Department of Experimental Medical Science, Division of Diabetes, Metabolism and Endocrinology, Lund University, Sweden
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Ström K, Gundersen TE, Hansson O, Lucas S, Fernandez C, Blomhoff R, Holm C. Hormone-sensitive lipase (HSL) is also a retinyl ester hydrolase: evidence from mice lacking HSL. FASEB J 2009; 23:2307-16. [PMID: 19246492 DOI: 10.1096/fj.08-120923] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Here, we investigated the importance of hormone-sensitive lipase (HSL) as a retinyl ester hydrolase (REH). REH activity was measured in vitro using recombinant HSL and retinyl palmitate. The expression of retinoic acid (RA)-regulated genes and retinoid metabolites were measured in high-fat diet fed HSL-null mice using real-time quantitative PCR and triple-stage liquid chromatography/tandem mass spectrometry, respectively. Age- and gender-matched wild-type littermates were used as controls. The REH activity of rat HSL was found to be higher than that against the hitherto best known HSL substrate, i.e., diacylglycerols. REH activity in white adipose tissue (WAT) of HSL-null mice was completely blunted and accompanied by increased levels of retinyl esters and decreased levels of retinol, retinaldehyde and all-trans RA. Accordingly, genes known to be positively regulated by RA were down-regulated in HSL-null mice, including pRb and RIP140, key factors promoting differentiation into the white over the brown adipocyte lineage. Dietary RA supplementation partly restored WAT mass and the expression of RA-regulated genes in WAT of HSL-null mice. These findings demonstrate the importance of HSL as an REH of adipose tissue and suggest that HSL via this action provides RA and other retinoids for signaling events that are crucial for adipocyte differentiation and lineage commitment.
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Affiliation(s)
- Kristoffer Ström
- Division of Diabetes, Metabolism and Endocrinology, Department of Experimental Medical Science, Lund University, BMC C11, SE-221 84 Lund, Sweden.
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Ser649 and Ser650 are the major determinants of protein kinase A-mediated activation of human hormone-sensitive lipase against lipid substrates. PLoS One 2008; 3:e3756. [PMID: 19018281 PMCID: PMC2582450 DOI: 10.1371/journal.pone.0003756] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 10/22/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Hormone-sensitive lipase (HSL) is a key enzyme in the mobilization of fatty acids from stored triacylglycerols. Its activity is regulated by reversible protein phosphorylation. In rat HSL Ser563, Ser659 and Ser660 have been shown to be phosphorylated by protein kinase A (PKA) in vitro as well as in vivo. METHODOLOGY/PRINCIPAL FINDINGS In this study we employed site-directed mutagenesis, in vitro phosphorylation and mass spectrometry to show that in vitro phosphorylation of human HSL by PKA occurs primarily on Ser649 and Ser650 (Ser659 and Ser660 in rat HSL). The wild type enzyme and four mutants were expressed in C-terminally His-tagged form in Sf9 insect cells and purified to homogeneity. HSL variants in which Ser552 and/or Ser554 were mutated to Ala or Glu retained both lipolytic and non-lipolytic activity and were phosphorylated by PKA and activated to a similar extent as the wild type enzyme. (32)P-labeling studies revealed that the bulk of the phosphorylation was on the Ser649/Ser650 site, with only a minor phosphorylation of Ser552 and Ser554. MS/MS analysis demonstrated that the peptide containing Ser649 and Ser650 was primarily phosphorylated on Ser650. The mutant lacking all four serines had severely reduced lipolytic activity, but a lesser reduction in non-lipolytic activity, had S(0.5) values for p-nitrophenol butyrate and triolein comparable to those of wild type HSL and was not phosphorylated by PKA. PKA phosphorylation of the wild type enzyme resulted in an increase in both the maximum turnover and S(0,5) using the TO substrate. CONCLUSIONS Our results demonstrate that PKA activates human HSL against lipid substrates in vitro primarily through phosphorylation of Ser649 and Ser650. In addition the results suggest that Ser649 and Ser650 are located in the vicinity of a lipid binding region and that PKA phosphorylation controls the accessibility of this region.
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Ebdrup S, Refsgaard HHF, Fledelius C, Jacobsen P. Synthesis and structure-activity relationship for a novel class of potent and selective carbamate-based inhibitors of hormone selective lipase with acute in vivo antilipolytic effects. J Med Chem 2007; 50:5449-56. [PMID: 17918819 DOI: 10.1021/jm0607653] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hormone-sensitive lipase (HSL) is an intracellular enzyme that has a central role in the regulation of fatty acid metabolism. The enzyme, therefore, is a potentially interesting pharmacological target for the treatment of insulin resistance and dyslipidemic disorders. Based on a high throughput screening, a carbamate based HSL inhibitor was identified and optimized into the selective HSL inhibitors 4-hydroxymethyl-piperidine-1-carboxylic acid 4-(5-trifluoromethylpyridin-2-yloxy)-phenyl ester (13f) and 4-hydroxy-piperidine-1-carboxylic acid 4-(5-trifluoromethylpyridin-2-yloxy)-phenyl ester (13g), with IC50 values of 110 and 500 nM, respectively. Both inhibitors were active in acute antilipolytic experiments in vivo and none of the inhibitors inhibited the cytochrome P450 (CYP) isoforms 2D6, 3A4, and 1A2.
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Affiliation(s)
- Søren Ebdrup
- Novo Nordisk A/S, Novo Nordisk Park, 2760 Måløv, Denmark.
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de Jong JC, Sørensen LG, Tornqvist H, Jacobsen P. Carbazates as potent inhibitors of hormone-sensitive lipase. Bioorg Med Chem Lett 2004; 14:1741-4. [PMID: 15026062 DOI: 10.1016/j.bmcl.2004.01.038] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2003] [Revised: 01/16/2004] [Accepted: 01/16/2004] [Indexed: 11/30/2022]
Abstract
The central role of adipose tissue hormone-sensitive lipase in regulating fatty acid metabolism makes it a potential pharmacological target for the prevention of peripheral insulin resistance in obese, prediabetic and diabetic individuals. The synthesis of a new series of carbazates is presented. Modification of the phenolic 4-position in a series of 1,2,3,4-tetrahydroisoquinoline and morpholine derived carbazates, yielded inhibitors of the catalytic activity of this enzyme with nanomolar potency.
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Affiliation(s)
- Johannes C de Jong
- Novo Nordisk A/S, Medicinal Chemistry, Novo Nordisk Park, 2760 Maaloev, Denmark
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Ebdrup S, Sørensen LG, Olsen OH, Jacobsen P. Synthesis and Structure−Activity Relationship for a Novel Class of Potent and Selective Carbamoyl-Triazole Based Inhibitors of Hormone Sensitive Lipase. J Med Chem 2003; 47:400-10. [PMID: 14711311 DOI: 10.1021/jm031004s] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The central role of the intracellular enzyme hormone-sensitive lipase (HSL) in regulating fatty acid metabolism makes it an interesting pharmacological target for the treatment of insulin resistant and dyslipidemic disorders where a decrease in delivery of fatty acids to the circulation is desirable, e.g., in individuals with type 2 diabetes, metabolic syndrome, or impaired glucose tolerance. On the basis of a lead structure from high throughput screening, we have identified a very potent type of carbamoyl-triazole inhibitors of HSL. As part of the lead optimization program, four new classes of carbamoyl-triazoles were synthesized and tested with respect to potency, efficacy and selectivity. Methyl-phenyl-carbamoyl-triazoles were identified as potent and efficacious HSL inhibitors. These compounds do not inhibit other hydrolases such as hepatic lipase, lipoprotein lipase, pancreatic lipase, and butyrylcholine esterase. However, the inhibitors 4b and 4g with IC(50) values for HSL of 0.17 and 0.25 microM, respectively, were the only inhibitors selective against acetylcholine esterase. A reversible pseudosubstrate inhibition mechanism is proposed for this class of inhibitors.
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Affiliation(s)
- Søren Ebdrup
- Novo Nordisk A/S, Novo Nordisk Park, 2760 Måløv, Denmark
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Zhang L, Wu G, Tate CG, Lookene A, Olivecrona G. Calreticulin promotes folding/dimerization of human lipoprotein lipase expressed in insect cells (sf21). J Biol Chem 2003; 278:29344-51. [PMID: 12740382 DOI: 10.1074/jbc.m300455200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipoprotein lipase (LPL) is a non-covalent, homodimeric, N-glycosylated enzyme important for metabolism of blood lipids. LPL is regulated by yet unknown post-translational events affecting the levels of active dimers. On co-expression of LPL with human molecular chaperones, we found that calreticulin had the most pronounced effects on LPL activity, but calnexin was also effective. Calreticulin caused a 9-fold increase in active LPL, amounting to about 50% of the expressed LPL protein. The total expression of LPL protein was increased less than 20%, and the secretion rates for active and inactive LPL were not significantly changed by the chaperone. Thus, the main effect was an increased specific activity of LPL both in cells and media. Chromatography on heparin-Sepharose and sucrose density gradient centrifugation demonstrated that most of the inactive LPL was monomeric and that calreticulin promoted formation of active dimers. Higher oligomers of inactive LPL were present in cell extracts, but only monomers and dimers were secreted to the medium. Interaction between LPL and calreticulin was demonstrated, and the effect of the chaperone was prevented by castanospermine, an inhibitor of N-glycan glucose trimming. Our data indicate an important role of endoplasmic reticulum-based chaperones for the folding/dimerization of LPL.
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Affiliation(s)
- Liyan Zhang
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden
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Ek I, Arner P, Rydén M, Holm C, Thörne A, Hoffstedt J, Wahrenberg H. A unique defect in the regulation of visceral fat cell lipolysis in the polycystic ovary syndrome as an early link to insulin resistance. Diabetes 2002; 51:484-92. [PMID: 11812759 DOI: 10.2337/diabetes.51.2.484] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The etiology of polycystic ovary syndrome (PCOS) is unknown. However, PCOS has a strong resemblance to the insulin resistance (metabolic) syndrome, where an increased rate of visceral fat cell lipolysis is believed to play a pathophysiological role. We hypothesized that primary defects in visceral lipolysis might also exist in PCOS. Ten young, nonobese, and otherwise healthy PCOS women were compared with 13 matched control women. In vitro lipolysis regulation and stoichiometric properties of the final step in lipolysis activation, namely the protein kinase A (PKA)-hormone sensitive lipase (HSL) complex, were investigated in isolated visceral (i.e., omental) fat cells. Body fat distribution and circulating levels of insulin, glucose, and lipids were normal in PCOS women. However, in vivo insulin sensitivity was slightly decreased (P = 0.03). Catecholamine-induced adipocyte lipolysis was markedly (i.e., about twofold) increased in PCOS women due to changes at the postreceptor level, although there was no change in the antilipolytic properties of visceral fat cells. Western blot analyses of visceral adipose tissue showed twofold increased levels of the catalytic and the regulatory Ialpha components of PKA. In contrast, the regulatory RIIbeta component of PKA was almost 50% decreased in visceral adipose tissue in PCOS women. Recent studies on genetically modified mice have shown that a similar transition in the regulatory PKA units induces an increased lipolytic response to catecholamines. Further analysis showed that the level of HSL-short, an enzymatically inactive splice form of HSL, was decreased in PCOS (P < 0.01). The altered lipolysis in PCOS is different from that observed in visceral fat cells in the insulin resistance syndrome that occurs at the level of adrenergic receptors. We concluded that increased catecholamine-induced lipolysis in visceral fat cells may be due to unique alterations in the stoichiometric properties of the adipose PKA-HSL holoenzymes. This could be an early and possibly primary lipolysis defect in PCOS.
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Affiliation(s)
- Ingvar Ek
- Department of Gynecology, Karolinska Institutet at Huddinge University Hospital, Stockholm, Sweden
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Raclot T, Holm C, Langin D. Fatty acid specificity of hormone-sensitive lipase: implication in the selective hydrolysis of triacylglycerols. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31534-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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Raclot T, Holm C, Langin D. A role for hormone-sensitive lipase in the selective mobilization of adipose tissue fatty acids. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1532:88-96. [PMID: 11420177 DOI: 10.1016/s1388-1981(01)00119-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The mobilization of fatty acids from rat and human fat cells is selective according to molecular structure, and notably carbon atom chain length. This study aimed at examining whether the release of individual fatty acids from triacylglycerols (TAG) by hormone-sensitive lipase (HSL) plays a role in the selectivity of fatty acid mobilization. Recombinant rat and human HSL were incubated with a lipid emulsion. The hydrolysis of 18 individual fatty acids, ranging in chain length from 12 to 24 carbon atoms and in unsaturation degree from 0 to 3 double bond(s), was measured by comparing the composition of non-esterified fatty acids (NEFA) to that of the original TAG. The relative hydrolysis (% in NEFA/% in TAG) differed between fatty acids, being about 5-fold and 3-fold higher for the most (18:1n-7) than for the least (24:0) readily released fatty acid by recombinant rat and human HSL, respectively. Relationships were found between the chain length of fatty acids and their relative hydrolysis. Among 12-24 carbon atom saturated fatty acids, the relative hydrolysis markedly decreased (by about 5- and 3-times for recombinant rat and human HSL, respectively) with increasing chain length. We conclude that fatty acids are selectively released from TAG by HSL according to carbon atom chain length. These data provide insight on the mechanism by which fatty acids are selectively mobilized from fat cells.
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Affiliation(s)
- T Raclot
- INSERM Unité 317, Institut Louis Bugnard, Université Paul SAbatier, Hôpital Rangueil, France.
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Osterlund T. Structure-function relationships of hormone-sensitive lipase. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:1899-907. [PMID: 11277912 DOI: 10.1046/j.1432-1327.2001.02097.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Research into the structure-function relationships of lipases and esterases has increased significantly during the past decade. Of particular importance has been the deduction of several crystal structures, providing a new basis for understanding these enzymes. The generated insights have, together with cloning and expression, aided studies on structure-function relationships of hormone-sensitive lipase (HSL). Novel phosphorylation sites have been identified in HSL, which are probably important for activation of HSL and lipolysis. Functional and structural analyses have revealed features in HSL common to lipases and esterases. In particular, the catalytic core with a catalytic triad has been unveiled. Furthermore, the investigations have given clear suggestions with regard to the identity of functional and structural domains of HSL. In the present paper, these studies on HSL structure-function relationships and short-term regulation are reviewed, and the results presented in relation to other discoveries in regulated lipolysis.
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Affiliation(s)
- T Osterlund
- Department of Biosciences at Novum, Karolinska Institute, Huddinge, Sweden.
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Holm C, Osterlund T, Laurell H, Contreras JA. Molecular mechanisms regulating hormone-sensitive lipase and lipolysis. Annu Rev Nutr 2001; 20:365-93. [PMID: 10940339 DOI: 10.1146/annurev.nutr.20.1.365] [Citation(s) in RCA: 302] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hormone-sensitive lipase, the rate-limiting enzyme of intracellular TG hydrolysis, is a major determinant of fatty acid mobilization in adipose tissue as well as other tissues. It plays a pivotal role in lipid metabolism, overall energy homeostasis, and, presumably, cellular events involving fatty acid signaling. Detailed knowledge about its structure and regulation may provide information regarding the pathogenesis of such human diseases as obesity and diabetes and may generate concepts for new treatments of these diseases. The current review summarizes the recent advances with regard to hormone-sensitive lipase structure and molecular mechanisms involved in regulating its activity and lipolysis in general. A summary of the current knowledge regarding regulation of expression, potential involvement in lipid disorders, and role in tissues other than adipose tissue is also provided.
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Affiliation(s)
- C Holm
- Department of Cell and Molecular Biology, Section for Molecular Signalling, Lund University, Lund, Sweden.
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