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1.
Cardiovasc Res ; 2019 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-31166588

RESUMO

AIMS: Lipotoxic cardiomyopathy in diabetic and obese patients typically encompasses increased cardiac fatty acid (FA) uptake eventually surpassing the mitochondrial oxidative capacity. Lowering FA utilization via inhibition of lipolysis represents a strategy to counteract the development of lipotoxic heart dysfunction. However, defective cardiac triacylglycerol (TAG) catabolism and FA oxidation in humans (and mice) carrying mutated ATGL alleles provokes lipotoxic heart dysfunction questioning a therapeutic approach to decrease cardiac lipolysis. Interestingly, decreased lipolysis via cardiac overexpression of Perilipin 5 (Plin5), a binding partner of ATGL, is compatible with normal heart function and lifespan despite massive cardiac lipid accumulation. Herein, we decipher mechanisms that protect Plin5 transgenic mice from the development of heart dysfunction. METHODS AND RESULTS: We generated mice with cardiac-specific overexpression of Plin5 encoding a serine-155 to alanine exchange (Plin5-S155A) of the protein kinase A phosphorylation site, which has been suggested as a prerequisite to stimulate lipolysis and may play a crucial role in the preservation of heart function. Plin5-S155A mice showed a substantial increase in cardiac TAG and ceramide levels, which was comparable to mice overexpressing non-mutated Plin5. Lipid accumulation was compatible with normal heart function even under mild stress. Plin5-S155A mice showed reduced cardiac FA oxidation but normal ATP production and changes in the Plin5-S155A phosphoproteome compared to Plin5 transgenic mice. Interestingly, mitochondrial recruitment of dynamin-related protein 1 (Drp1) was markedly reduced in cardiac muscle of Plin5-S155A and Plin5 transgenic mice accompanied by decreased phosphorylation of mitochondrial fission factor, a mitochondrial receptor of Drp1. CONCLUSIONS: This study suggests that low cardiac lipolysis is associated with reduced mitochondrial fission and may represent a strategy to combat the development of lipotoxic heart dysfunction.

2.
Biochim Biophys Acta Mol Cell Biol Lipids ; 1864(4): 500-511, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30639734

RESUMO

Lysosomal acid lipase (LAL) hydrolyzes cholesteryl esters (CE) and triglycerides (TG) to generate fatty acids (FA) and cholesterol. LAL deficiency (LAL-D) in both humans and mice leads to hepatomegaly, hypercholesterolemia, and shortened life span. Despite its essential role in lysosomal neutral lipid catabolism, the cell type-specific contribution of LAL to disease progression is still elusive. To investigate the role of LAL in the liver in more detail and to exclude the contribution of LAL in macrophages, we generated hepatocyte-specific LAL-deficient mice (Liv-Lipa-/-) and fed them either chow or high fat/high cholesterol diets (HF/HCD). Comparable to systemic LAL-D, Liv-Lipa-/- mice were resistant to diet-induced obesity independent of food intake, movement, and energy expenditure. Reduced body weight gain was mainly due to reduced white adipose tissue depots. Furthermore, Liv-Lipa-/- mice exhibited improved glucose clearance during glucose and insulin tolerance tests compared to control mice. Analysis of hepatic lipid content revealed a massive reduction of TG, whereas CE concentrations were markedly increased, leading to CE crystal formation in the livers of Liv-Lipa-/- mice. Elevated plasma transaminase activities, increased pro-inflammatory cytokines and chemokines as well as hepatic macrophage infiltration indicated liver inflammation. Our data provide evidence that hepatocyte-specific LAL deficiency is sufficient to alter whole-body lipid and energy homeostasis in mice. We conclude that hepatic LAL plays a pivotal role by preventing liver damage and maintaining lipid and energy homeostasis, especially during high lipid availability.

3.
J Lipid Res ; 59(12): 2360-2367, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30361410

RESUMO

Mutations in the genes coding for patatin-like phospholipase domain-containing 1 (PNPLA1) and α/ß-hydrolase domain-containing 5 (ABHD5), also known as comparative gene identification 58, are causative for ichthyosis, a severe skin barrier disorder. Individuals with mutations in either of these genes show a defect in epidermal ω-O-acylceramide (AcylCer) biosynthesis, suggesting that PNPLA1 and ABHD5 act in the same metabolic pathway. In this report, we identified ABHD5 as a coactivator of PNPLA1 that stimulates the esterification of ω-hydroxy ceramides with linoleic acid for AcylCer biosynthesis. ABHD5 interacts with PNPLA1 and recruits the enzyme to its putative triacylglycerol substrate onto cytosolic lipid droplets. Conversely, alleles of ABHD5 carrying point mutations associated with ichthyosis in humans failed to accelerate PNPLA1-mediated AcylCer biosynthesis. Our findings establish an important biochemical function of ABHD5 in interacting with PNPLA1 to synthesize crucial epidermal lipids, emphasizing the significance of these proteins in the formation of a functional skin permeability barrier.

4.
Biochim Biophys Acta Mol Cell Biol Lipids ; 1863(10): 1285-1296, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30305245

RESUMO

Physical contacts between organelles play a pivotal role in intracellular trafficking of metabolites. Monitoring organelle interactions in living cells using fluorescence microscopy is a powerful approach to functionally assess these cellular processes. However, detailed target acquisition is typically limited due to light diffraction. Furthermore, subcellular compartments such as lipid droplets and mitochondria are highly dynamic and show significant subcellular movement. Thus, high-speed acquisition of these organelles with extended-resolution is appreciated. Here, we present an imaging informatics pipeline enabling spatial and time-resolved analysis of the dynamics and interactions of fluorescently labeled lipid droplets and mitochondria in a fibroblast cell line. The imaging concept is based on multispectral confocal laser scanning microscopy and includes high-speed resonant scanning for fast spatial acquisition of organelles. Extended-resolution is achieved by the recording of images at minimized pinhole size and by post-processing of generated data using a computational image restoration method. Computation of inter-organelle contacts is performed on basis of segmented spatial image data. We show limitations of the image restoration and segmentation part of the imaging informatics pipeline. Since both image processing methods are implemented in other related methodologies, our findings will help to identify artifacts and the false-interpretation of obtained morphometric data. As a proof-of-principle, we studied how lipid load and overexpression of PLIN5, considered to be involved in the tethering of LDs and mitochondria, affects organelle association.

5.
Artigo em Inglês | MEDLINE | ID: mdl-29883718

RESUMO

Excessive accumulation of triacylglycerol is the common denominator of a wide range of clinical pathologies of liver diseases, termed non-alcoholic fatty liver disease. Such excessive triacylglycerol deposition in the liver is also referred to as hepatic steatosis. Although liver steatosis often resolves over time, it eventually progresses to steatohepatitis, liver fibrosis and cirrhosis, with associated complications, including liver failure, hepatocellular carcinoma and ultimately death of affected individuals. From the disease etiology it is obvious that a tight regulation between lipid uptake, triacylglycerol synthesis, hydrolysis, secretion and fatty acid oxidation is required to prevent triacylglycerol deposition in the liver. In addition to triacylglycerol, also a tight control of other neutral lipid ester classes, i.e. cholesteryl esters and retinyl esters, is crucial for the maintenance of a healthy liver. Excessive cholesteryl ester accumulation is a hallmark of cholesteryl ester storage disease or Wolman disease, which is associated with premature death. The loss of hepatic vitamin A stores (retinyl ester stores of hepatic stellate cells) is incidental to the onset of liver fibrosis. Importantly, this more advanced stage of liver disease usually does not resolve but progresses to life threatening stages, i.e. liver cirrhosis and cancer. Therefore, understanding the enzymes and pathways that mobilize hepatic neutral lipid esters is crucial for the development of strategies and therapies to ameliorate pathophysiological conditions associated with derangements of hepatic neutral lipid ester stores, including liver steatosis, steatohepatitis, and fibrosis. This review highlights the physiological roles of enzymes governing the mobilization of neutral lipid esters at different sites in liver cells, including cytosolic lipid droplets, endoplasmic reticulum, and lysosomes. This article is part of a Special Issue entitled Molecular Basis of Disease: Animal models in liver disease.

6.
J Lipid Res ; 59(5): 784-794, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29599420

RESUMO

In mammals, white adipose tissue (WAT) stores and releases lipids, whereas brown adipose tissue (BAT) oxidizes lipids to fuel thermogenesis. In obese individuals, WAT undergoes profound changes; it expands, becomes dysfunctional, and develops a low-grade inflammatory state. Importantly, BAT content and activity decline in obese subjects, mainly as a result of the conversion of brown adipocytes to white-like unilocular cells. Here, we show that BAT "whitening" is induced by multiple factors, including high ambient temperature, leptin receptor deficiency, ß-adrenergic signaling impairment, and lipase deficiency, each of which is capable of inducing macrophage infiltration, brown adipocyte death, and crown-like structure (CLS) formation. Brown-to-white conversion and increased CLS formation were most marked in BAT from adipose triglyceride lipase (Atgl)-deficient mice, where, according to transmission electron microscopy, whitened brown adipocytes contained enlarged endoplasmic reticulum, cholesterol crystals, and some degenerating mitochondria, and were surrounded by an increased number of collagen fibrils. Gene expression analysis showed that BAT whitening in Atgl-deficient mice was associated to a strong inflammatory response and NLRP3 inflammasome activation. Altogether, the present findings suggest that converted enlarged brown adipocytes are highly prone to death, which, by promoting inflammation in whitened BAT, may contribute to the typical inflammatory state seen in obesity.

7.
Cell Metab ; 26(5): 753-763.e7, 2017 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-28988821

RESUMO

Fatty acids (FAs) activate and fuel UCP1-mediated non-shivering thermogenesis (NST) in brown adipose tissue (BAT). Release of FAs from intracellular fat stores by adipose triglyceride lipase (ATGL) is considered a key step in NST. Accordingly, the severe cold intolerance of global ATGL knockout (AKO) mice has been attributed to defective BAT lipolysis. Here we show that this conclusion is incorrect. We demonstrate that although the BAT-specific loss of ATGL impairs BAT lipolysis and alters BAT morphology, it does not compromise the ß3-adrenergic thermogenic response or cold-induced NST. Instead, NST depends on nutrient supply or lipolysis in white adipose tissue during fasting, suggesting that circulating energy substrates are sufficient to fuel NST. Cold intolerance in AKO mice is not caused by BAT dysfunction as previously suspected but by severe cardiomyopathy. We conclude that functional NST requires adequate substrate supply and cardiac function, but does not depend on ATGL-mediated lipolysis in BAT.


Assuntos
Tecido Adiposo Marrom/metabolismo , Temperatura Baixa , Lipase/fisiologia , Lipólise/fisiologia , Miocárdio/metabolismo , Termogênese/fisiologia , Tecido Adiposo Branco/metabolismo , Animais , Ingestão de Alimentos , Eletrocardiografia , Jejum , Lipase/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Desacopladora 1/genética , Proteína Desacopladora 1/metabolismo
8.
Nat Methods ; 14(12): 1171-1174, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29058722

RESUMO

We achieve automated and reliable annotation of lipid species and their molecular structures in high-throughput data from chromatography-coupled tandem mass spectrometry using decision rule sets embedded in Lipid Data Analyzer (LDA; http://genome.tugraz.at/lda2). Using various low- and high-resolution mass spectrometry instruments with several collision energies, we proved the method's platform independence. We propose that the software's reliability, flexibility, and ability to identify novel lipid molecular species may now render current state-of-the-art lipid libraries obsolete.


Assuntos
Cromatografia Líquida/métodos , Lipídeos/análise , Lipídeos/química , Espectrometria de Massas em Tandem/métodos , Algoritmos , Animais , Fígado/química , Camundongos , Estrutura Molecular , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
9.
J Invest Dermatol ; 137(2): 394-402, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27751867

RESUMO

Mutations in PNPLA1 have been identified as causative for autosomal recessive congenital ichthyosis in humans and dogs. So far, the underlying molecular mechanisms are unknown. In this study, we generated and characterized PNPLA1-deficient mice and found that PNPLA1 is crucial for epidermal sphingolipid synthesis. The absence of functional PNPLA1 in mice impaired the formation of omega-O-acylceramides and led to an accumulation of nonesterified omega-hydroxy-ceramides. As a consequence, PNPLA1-deficient mice lacked a functional corneocyte-bound lipid envelope leading to a severe skin barrier defect and premature death of newborn animals. Functional analyses of differentiated keratinocytes from a patient with mutated PNPLA1 demonstrated an identical defect in omega-O-acylceramide synthesis in human cells, indicating that PNPLA1 function is conserved among mammals and indispensable for normal skin physiology. Notably, topical application of epidermal lipids from wild-type onto Pnpla1-mutant mice promoted rebuilding of the corneocyte-bound lipid envelope, indicating that supplementation of ichthyotic skin with omega-O-acylceramides might be a therapeutic approach for the treatment of skin symptoms in individuals affected by omega-O-acylceramide deficiency.


Assuntos
Ceramidas/biossíntese , Lipase/fisiologia , Pele/metabolismo , Animais , Ictiose/etiologia , Lipase/deficiência , Camundongos , Camundongos Endogâmicos C57BL , Permeabilidade
10.
J Invest Dermatol ; 137(2): 403-413, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27725204

RESUMO

Adipose triglyceride lipase (ATGL) and its coactivator comparative gene identification-58 (CGI-58) are limiting in cellular triglyceride catabolism. Although ATGL deficiency is compatible with normal skin development, mice globally lacking CGI-58 die postnatally and exhibit a severe epidermal permeability barrier defect, which may originate from epidermal and/or peripheral changes in lipid and energy metabolism. Here, we show that epidermis-specific disruption of CGI-58 is sufficient to provoke a defect in the formation of a functional corneocyte lipid envelope linked to impaired ω-O-acylceramide synthesis. As a result, epidermis-specific CGI-58-deficient mice show severe skin dysfunction, arguing for a tissue autonomous cause of disease development. Defective skin permeability barrier formation in global CGI-58-deficient mice could be reversed via transgenic restoration of CGI-58 expression in differentiated but not basal keratinocytes suggesting that CGI-58 is essential for lipid metabolism in suprabasal epidermal layers. The compatibility of ATGL deficiency with normal epidermal function indicated that CGI-58 may stimulate an epidermal triglyceride lipase beyond ATGL required for the adequate provision of fatty acids as a substrate for ω-O-acylceramide synthesis. Pharmacological inhibition of ATGL enzyme activity similarly reduced triglyceride-hydrolytic activities in wild-type and CGI-58 overexpressing epidermis implicating that CGI-58 participates in ω-O-acylceramide biogenesis independent of its role as a coactivator of epidermal triglyceride catabolism.


Assuntos
1-Acilglicerol-3-Fosfato O-Aciltransferase/fisiologia , Queratinócitos/citologia , Pele/metabolismo , Animais , Diferenciação Celular , Ceramidas/biossíntese , Lipase/fisiologia , Camundongos , Pele/embriologia , Triglicerídeos/metabolismo
11.
Diabetologia ; 60(2): 296-305, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27858140

RESUMO

AIMS/HYPOTHESIS: Dysfunction of lipid metabolism in white adipose tissue can substantially interfere with health and quality of life, for example in obesity and associated metabolic diseases. Therefore, it is important to characterise pathways that regulate lipid handling in adipocytes and determine how they affect metabolic homeostasis. Components of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway are involved in adipocyte physiology and pathophysiology. However, the exact physiological importance of the STAT family member STAT5 in white adipose tissue is yet to be determined. Here, we aimed to delineate adipocyte STAT5 functions in the context of lipid metabolism in white adipose tissue. METHODS: We generated an adipocyte specific knockout of Stat5 in mice using the Adipoq-Cre recombinase transgene followed by in vivo and in vitro biochemical and molecular studies. RESULTS: Adipocyte-specific deletion of Stat5 resulted in increased adiposity, while insulin resistance and gluconeogenic capacity was decreased, indicating that glucose metabolism can be improved by interfering with adipose STAT5 function. Basal lipolysis and fasting-induced lipid mobilisation were diminished upon STAT5 deficiency, which coincided with reduced levels of the rate-limiting lipase of triacylglycerol hydrolysis, adipose triglyceride lipase (ATGL, encoded by Pnpla2) and its coactivator comparative gene identification 58 (CGI-58). In a mechanistic analysis, we identified a functional STAT5 response element within the Pnpla2 promoter, indicating that Pnpla2 is transcriptionally regulated by STAT5. CONCLUSIONS/INTERPRETATION: Our findings reveal an essential role for STAT5 in maintaining lipid homeostasis in white adipose tissue and provide a rationale for future studies into the potential of STAT5 manipulation to improve outcomes in metabolic diseases.


Assuntos
Adipócitos/metabolismo , Adiposidade/fisiologia , Fator de Transcrição STAT5/metabolismo , Células 3T3-L1 , Adiposidade/genética , Animais , Western Blotting , Imunoprecipitação da Cromatina , Ensaio de Desvio de Mobilidade Eletroforética , Feminino , Glucose/metabolismo , Resistência à Insulina/genética , Resistência à Insulina/fisiologia , Metabolismo dos Lipídeos/genética , Metabolismo dos Lipídeos/fisiologia , Mobilização Lipídica/genética , Mobilização Lipídica/fisiologia , Lipólise/genética , Lipólise/fisiologia , Masculino , Camundongos , Qualidade de Vida , Reação em Cadeia da Polimerase em Tempo Real , Fator de Transcrição STAT5/genética
12.
Nat Med ; 22(12): 1428-1438, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27841876

RESUMO

Aging is associated with an increased risk of cardiovascular disease and death. Here we show that oral supplementation of the natural polyamine spermidine extends the lifespan of mice and exerts cardioprotective effects, reducing cardiac hypertrophy and preserving diastolic function in old mice. Spermidine feeding enhanced cardiac autophagy, mitophagy and mitochondrial respiration, and it also improved the mechano-elastical properties of cardiomyocytes in vivo, coinciding with increased titin phosphorylation and suppressed subclinical inflammation. Spermidine feeding failed to provide cardioprotection in mice that lack the autophagy-related protein Atg5 in cardiomyocytes. In Dahl salt-sensitive rats that were fed a high-salt diet, a model for hypertension-induced congestive heart failure, spermidine feeding reduced systemic blood pressure, increased titin phosphorylation and prevented cardiac hypertrophy and a decline in diastolic function, thus delaying the progression to heart failure. In humans, high levels of dietary spermidine, as assessed from food questionnaires, correlated with reduced blood pressure and a lower incidence of cardiovascular disease. Our results suggest a new and feasible strategy for protection against cardiovascular disease.


Assuntos
Envelhecimento/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Coração/efeitos dos fármacos , Longevidade/efeitos dos fármacos , Mitocôndrias Cardíacas/efeitos dos fármacos , Degradação Mitocondrial/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Espermidina/farmacologia , Adulto , Idoso , Envelhecimento/imunologia , Envelhecimento/metabolismo , Animais , Proteína 5 Relacionada à Autofagia/genética , Cardiomegalia/diagnóstico por imagem , Cardiotônicos/farmacologia , Doenças Cardiovasculares/epidemiologia , Cromatografia Líquida de Alta Pressão , Conectina/efeitos dos fármacos , Conectina/metabolismo , Citocinas/efeitos dos fármacos , Citocinas/imunologia , Diástole , Dieta/estatística & dados numéricos , Ecocardiografia , Feminino , Expressão Gênica/efeitos dos fármacos , Teste de Tolerância a Glucose , Coração/diagnóstico por imagem , Insuficiência Cardíaca , Humanos , Immunoblotting , Inflamação , Masculino , Espectrometria de Massas , Camundongos , Pessoa de Meia-Idade , Mitocôndrias Cardíacas/metabolismo , Fosforilação/efeitos dos fármacos , Estudos Prospectivos , Ratos , Ratos Endogâmicos Dahl , Inquéritos e Questionários
13.
Cell Rep ; 16(4): 939-949, 2016 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-27396333

RESUMO

Adipose triglyceride lipase (ATGL) and comparative gene identification 58 (CGI-58) are critical regulators of triacylglycerol (TAG) turnover. CGI-58 is thought to regulate TAG mobilization by stimulating the enzymatic activity of ATGL. However, it is not known whether this coactivation function of CGI-58 occurs in vivo. Moreover, the phenotype of human CGI-58 mutations suggests ATGL-independent functions. Through direct comparison of mice with single or double deficiency of CGI-58 and ATGL, we show here that CGI-58 knockdown causes hepatic steatosis in both the presence and absence of ATGL. CGI-58 also regulates hepatic diacylglycerol (DAG) and inflammation in an ATGL-independent manner. Interestingly, ATGL deficiency, but not CGI-58 deficiency, results in suppression of the hepatic and adipose de novo lipogenic program. Collectively, these findings show that CGI-58 regulates hepatic neutral lipid storage and inflammation in the genetic absence of ATGL, demonstrating that mechanisms driving TAG lipolysis in hepatocytes differ significantly from those in adipocytes.


Assuntos
1-Acilglicerol-3-Fosfato O-Aciltransferase/metabolismo , Lipase/metabolismo , Fígado/metabolismo , Triglicerídeos/metabolismo , Adipócitos/metabolismo , Animais , Diglicerídeos/metabolismo , Fígado Gorduroso/metabolismo , Hepatócitos/metabolismo , Humanos , Inflamação/metabolismo , Metabolismo dos Lipídeos/fisiologia , Lipogênese/fisiologia , Lipólise/fisiologia , Masculino , Camundongos , Camundongos Knockout
14.
J Biol Chem ; 291(34): 17977-87, 2016 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-27354281

RESUMO

Lysosomal acid lipase (LAL) is essential for the clearance of endocytosed cholesteryl ester and triglyceride-rich chylomicron remnants. Humans and mice with defective or absent LAL activity accumulate large amounts of cholesteryl esters and triglycerides in multiple tissues. Although chylomicrons also contain retinyl esters (REs), a role of LAL in the clearance of endocytosed REs has not been reported. In this study, we found that murine LAL exhibits RE hydrolase activity. Pharmacological inhibition of LAL in the human hepatocyte cell line HepG2, incubated with chylomicrons, led to increased accumulation of REs in endosomal/lysosomal fractions. Furthermore, pharmacological inhibition or genetic ablation of LAL in murine liver largely reduced in vitro acid RE hydrolase activity. Interestingly, LAL-deficient mice exhibited increased RE content in the duodenum and jejunum but decreased RE content in the liver. Furthermore, LAL-deficient mice challenged with RE gavage exhibited largely reduced post-prandial circulating RE content, indicating that LAL is required for efficient nutritional vitamin A availability. In summary, our results indicate that LAL is the major acid RE hydrolase and required for functional retinoid homeostasis.


Assuntos
Hidrolases de Éster Carboxílico/metabolismo , Duodeno/enzimologia , Jejuno/enzimologia , Retinoides/metabolismo , Esterol Esterase/metabolismo , Animais , Hidrolases de Éster Carboxílico/genética , Ésteres do Colesterol/genética , Ésteres do Colesterol/metabolismo , Remanescentes de Quilomícrons/genética , Remanescentes de Quilomícrons/metabolismo , Humanos , Camundongos , Camundongos Knockout , Retinoides/genética , Esterol Esterase/genética , Triglicerídeos/genética , Triglicerídeos/metabolismo
15.
Biochim Biophys Acta ; 1861(10): 1500-12, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-26924251

RESUMO

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.


Assuntos
Metabolismo dos Lipídeos , Miocárdio/enzimologia , Miocárdio/metabolismo , Triglicerídeos/metabolismo , Animais , Doenças Cardiovasculares/metabolismo , Humanos , Lipólise , Modelos Biológicos , Miocárdio/patologia , Miocárdio/ultraestrutura
16.
Proc Natl Acad Sci U S A ; 112(45): 13850-5, 2015 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-26508640

RESUMO

Adipose triglyceride lipase (ATGL) initiates intracellular triglyceride (TG) catabolism. In humans, ATGL deficiency causes neutral lipid storage disease with myopathy (NLSDM) characterized by a systemic TG accumulation. Mice with a genetic deletion of ATGL (AKO) also accumulate TG in many tissues. However, neither NLSDM patients nor AKO mice are exceedingly obese. This phenotype is unexpected considering the importance of the enzyme for TG catabolism in white adipose tissue (WAT). In this study, we identified the counteracting mechanisms that prevent excessive obesity in the absence of ATGL. We used "healthy" AKO mice expressing ATGL exclusively in cardiomyocytes (AKO/cTg) to circumvent the cardiomyopathy and premature lethality observed in AKO mice. AKO/cTg mice were protected from high-fat diet (HFD)-induced obesity despite complete ATGL deficiency in WAT and normal adipocyte differentiation. AKO/cTg mice were highly insulin sensitive under hyperinsulinemic-euglycemic clamp conditions, eliminating insulin insensitivity as a possible protective mechanism. Instead, reduced food intake and altered signaling by peroxisome proliferator-activated receptor-gamma (PPAR-γ) and sterol regulatory element binding protein-1c in WAT accounted for the phenotype. These adaptations led to reduced lipid synthesis and storage in WAT of HFD-fed AKO/cTg mice. Treatment with the PPAR-γ agonist rosiglitazone reversed the phenotype. These results argue for the existence of an adaptive interdependence between lipolysis and lipid synthesis. Pharmacological inhibition of ATGL may prove useful to prevent HFD-induced obesity and insulin resistance.


Assuntos
Adaptação Fisiológica , Dieta Hiperlipídica , Comportamento Alimentar , Lipase/fisiologia , Lipólise , Obesidade/prevenção & controle , Animais , Lipase/genética , Camundongos , Camundongos Knockout , Obesidade/metabolismo , PPAR gama/genética , PPAR gama/metabolismo , Fenótipo
17.
J Biol Chem ; 290(30): 18438-53, 2015 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-25953897

RESUMO

The coordinated breakdown of intracellular triglyceride (TG) stores requires the exquisitely regulated interaction of lipolytic enzymes with regulatory, accessory, and scaffolding proteins. Together they form a dynamic multiprotein network designated as the "lipolysome." Adipose triglyceride lipase (Atgl) catalyzes the initiating step of TG hydrolysis and requires comparative gene identification-58 (Cgi-58) as a potent activator of enzyme activity. Here, we identify adipocyte-type fatty acid-binding protein (A-Fabp) and other members of the fatty acid-binding protein (Fabp) family as interaction partners of Cgi-58. Co-immunoprecipitation, microscale thermophoresis, and solid phase assays proved direct protein/protein interaction between A-Fabp and Cgi-58. Using nuclear magnetic resonance titration experiments and site-directed mutagenesis, we located a potential contact region on A-Fabp. In functional terms, A-Fabp stimulates Atgl-catalyzed TG hydrolysis in a Cgi-58-dependent manner. Additionally, transcriptional transactivation assays with a luciferase reporter system revealed that Fabps enhance the ability of Atgl/Cgi-58-mediated lipolysis to induce the activity of peroxisome proliferator-activated receptors. Our studies identify Fabps as crucial structural and functional components of the lipolysome.


Assuntos
1-Acilglicerol-3-Fosfato O-Aciltransferase/metabolismo , Proteínas de Ligação a Ácido Graxo/metabolismo , Lipase/metabolismo , Complexos Multiproteicos/metabolismo , Triglicerídeos/metabolismo , 1-Acilglicerol-3-Fosfato O-Aciltransferase/genética , Tecido Adiposo/metabolismo , Animais , Células COS , Cercopithecus aethiops , Proteínas de Ligação a Ácido Graxo/genética , Humanos , Ligantes , Lipase/genética , Lipólise/genética , Lipossomos/metabolismo , Camundongos , Complexos Multiproteicos/genética , Receptores Ativados por Proliferador de Peroxissomo/metabolismo , Proteólise
18.
Biochim Biophys Acta ; 1851(7): 937-45, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25732851

RESUMO

Hepatic stellate cells (HSCs) store triglycerides (TGs) and retinyl ester (RE) in cytosolic lipid droplets. RE stores are degraded following retinoid starvation or in response to pathogenic stimuli resulting in HSC activation. At present, the major enzymes catalyzing lipid degradation in HSCs are unknown. In this study, we investigated whether adipose triglyceride lipase (ATGL) is involved in RE catabolism of HSCs. Additionally, we compared the effects of ATGL deficiency and hormone-sensitive lipase (HSL) deficiency, a known RE hydrolase (REH), on RE stores in liver and adipose tissue. We show that ATGL degrades RE even in the presence of TGs, implicating that these substrates compete for ATGL binding. REH activity was stimulated and inhibited by comparative gene identification-58 and G0/G1 switch gene-2, respectively, the physiological regulators of ATGL activity. In cultured primary murine HSCs, pharmacological inhibition of ATGL, but not HSL, increased RE accumulation. In mice globally lacking ATGL or HSL, RE contents in white adipose tissue were decreased or increased, respectively, while plasma retinol and liver RE levels remained unchanged. In conclusion, our study shows that ATGL acts as REH in HSCs promoting the degradation of RE stores in addition to its established function as TG lipase. HSL is the predominant REH in adipocytes but does not affect lipid mobilization in HSCs.


Assuntos
Células Estreladas do Fígado/metabolismo , Lipase/fisiologia , Retinoides/metabolismo , Triglicerídeos/metabolismo , Adipócitos/enzimologia , Adipócitos/metabolismo , Animais , Células COS , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/metabolismo , Cercopithecus aethiops , Feminino , Metabolismo dos Lipídeos/genética , Camundongos , Camundongos Knockout , Esterol Esterase/genética , Esterol Esterase/metabolismo
19.
J Hepatol ; 63(2): 437-45, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25733154

RESUMO

BACKGROUND & AIMS: Adipose tissue (AT)-derived fatty acids (FAs) are utilized for hepatic triacylglycerol (TG) generation upon fasting. However, their potential impact as signaling molecules is not established. Herein we examined the role of exogenous AT-derived FAs in the regulation of hepatic gene expression by investigating mice with a defect in AT-derived FA supply to the liver. METHODS: Plasma FA levels, tissue TG hydrolytic activities and lipid content were determined in mice lacking the lipase co-activator comparative gene identification-58 (CGI-58) selectively in AT (CGI-58-ATko) applying standard protocols. Hepatic expression of lipases, FA oxidative genes, transcription factors, ER stress markers, hormones and cytokines were determined by qRT-PCR, Western blotting and ELISA. RESULTS: Impaired AT-derived FA supply upon fasting of CGI-58-ATko mice causes a marked defect in liver PPARα-signaling and nuclear CREBH translocation. This severely reduced the expression of respective target genes such as the ATGL inhibitor G0/G1 switch gene-2 (G0S2) and the endocrine metabolic regulator FGF21. These changes could be reversed by lipid administration and raising plasma FA levels. Impaired AT-lipolysis failed to induce hepatic G0S2 expression in fasted CGI-58-ATko mice leading to enhanced ATGL-mediated TG-breakdown strongly reducing hepatic TG deposition. On high fat diet, impaired AT-lipolysis counteracts hepatic TG accumulation and liver stress linked to improved systemic insulin sensitivity. CONCLUSIONS: AT-derived FAs are a critical regulator of hepatic fasting gene expression required for the induction of G0S2-expression in the liver to control hepatic TG-breakdown. Interfering with AT-lipolysis or hepatic G0S2 expression represents an effective strategy for the treatment of hepatic steatosis.


Assuntos
Tecido Adiposo/metabolismo , Jejum/metabolismo , Ácidos Graxos/metabolismo , Fígado Gorduroso/genética , Fatores de Crescimento de Fibroblastos/genética , Regulação da Expressão Gênica , Fígado/metabolismo , Animais , Western Blotting , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Fígado Gorduroso/metabolismo , Fígado Gorduroso/patologia , Fatores de Crescimento de Fibroblastos/biossíntese , Genes de Troca , Fígado/ultraestrutura , Camundongos , Camundongos Transgênicos , Microscopia Eletrônica , RNA/genética , Reação em Cadeia da Polimerase em Tempo Real
20.
J Biol Chem ; 290(3): 1295-306, 2015 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-25418045

RESUMO

Defective lipolysis in mice lacking adipose triglyceride lipase provokes severe cardiac steatosis and heart dysfunction, markedly shortening life span. Similarly, cardiac muscle (CM)-specific Plin5 overexpression (CM-Plin5) leads to severe triglyceride (TG) accumulation in cardiomyocytes via impairing TG breakdown. Interestingly, cardiac steatosis due to overexpression of Plin5 is compatible with normal heart function and life span indicating a more moderate impact of Plin5 overexpression on cardiac lipolysis and energy metabolism. We hypothesized that cardiac Plin5 overexpression does not constantly impair cardiac lipolysis. In line with this assumption, TG levels decreased in CM of fasted compared with nonfasted CM-Plin5 mice indicating that fasting may lead to a diminished barrier function of Plin5. Recent studies demonstrated that Plin5 is phosphorylated, and activation of adenylyl cyclase leads to phosphorylation of Plin5, suggesting that Plin5 is a substrate for PKA. Furthermore, any significance of Plin5 phosphorylation by PKA in the regulation of TG mobilization from lipid droplets (LDs) is unknown. Here, we show that the lipolytic barrier of Plin5-enriched LDs, either prepared from cardiac tissue of CM-Plin5 mice or Plin5-transfected cells, is abrogated by incubation with PKA. Notably, PKA-induced lipolysis of LDs enriched with Plin5 carrying a single mutation at serine 155 (PlinS155A) of the putative PKA phosphorylation site was substantially impaired revealing a critical role for PKA in Plin5-regulated lipolysis. The strong increase in protein levels of phosphorylated PKA in CM of Plin5 transgenic mice may partially restore fatty acid release from Plin5-enriched LDs, rendering these hearts compatible with normal heart function despite massive steatosis.


Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulação Enzimológica da Expressão Gênica , Coração/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Lipólise/genética , Proteínas Musculares/metabolismo , Animais , Células COS , Cercopithecus aethiops , Perfilação da Expressão Gênica , Teste de Tolerância a Glucose , Cardiopatias/metabolismo , Insulina/química , Metabolismo dos Lipídeos , Lipídeos/química , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mitocôndrias/metabolismo , Mutação , Fosforilação , Transfecção
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