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1.
Mol Cell ; 74(1): 32-44.e8, 2019 04 04.
Artículo en Inglés | MEDLINE | ID: mdl-30846318

RESUMEN

Excessive levels of saturated fatty acids are toxic to cells, although the basis for this lipotoxicity remains incompletely understood. Here, we analyzed the transcriptome, lipidome, and genetic interactions of human leukemia cells exposed to palmitate. Palmitate treatment increased saturated glycerolipids, accompanied by a transcriptional stress response, including upregulation of the endoplasmic reticulum (ER) stress response. A comprehensive genome-wide short hairpin RNA (shRNA) screen identified >350 genes modulating lipotoxicity. Among previously unknown genetic modifiers of lipotoxicity, depletion of RNF213, a putative ubiquitin ligase mutated in Moyamoya vascular disease, protected cells from lipotoxicity. On a broader level, integration of our comprehensive datasets revealed that changes in di-saturated glycerolipids, but not other lipid classes, are central to lipotoxicity in this model. Consistent with this, inhibition of ER-localized glycerol-3-phosphate acyltransferase activity protected from all aspects of lipotoxicity. Identification of genes modulating the response to saturated fatty acids may reveal novel therapeutic strategies for treating metabolic diseases linked to lipotoxicity.


Asunto(s)
Estrés del Retículo Endoplásmico/efectos de los fármacos , Retículo Endoplásmico/efectos de los fármacos , Glicéridos/metabolismo , Metabolismo de los Lípidos/efectos de los fármacos , Ácido Palmítico/toxicidad , Aciltransferasas/genética , Aciltransferasas/metabolismo , Adenosina Trifosfatasas/metabolismo , Retículo Endoplásmico/metabolismo , Retículo Endoplásmico/patología , Estrés del Retículo Endoplásmico/genética , Regulación Enzimológica de la Expresión Génica , Células HeLa , Células Hep G2 , Humanos , Células K562 , Metabolismo de los Lípidos/genética , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/genética , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Transcriptoma , Ubiquitina-Proteína Ligasas/metabolismo
2.
Hepatology ; 70(6): 1972-1985, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-31081165

RESUMEN

Nonalcoholic fatty liver disease (NAFLD) is characterized by excess lipid accumulation in hepatocytes and represents a huge public health problem owing to its propensity to progress to nonalcoholic steatohepatitis, fibrosis, and liver failure. The lipids stored in hepatic steatosis (HS) are primarily triglycerides (TGs) synthesized by two acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes. Either DGAT1 or DGAT2 catalyzes this reaction, and these enzymes have been suggested to differentially utilize exogenous or endogenously synthesized fatty acids, respectively. DGAT2 has been linked to storage of fatty acids from de novo lipogenesis, a process increased in NAFLD. However, whether DGAT2 is more responsible for lipid accumulation in NAFLD and progression to fibrosis is currently unknown. Also, it is unresolved whether DGAT2 can be safely inhibited as a therapy for NAFLD. Here, we induced NAFLD-like disease in mice by feeding a diet rich in fructose, saturated fat, and cholesterol and found that hepatocyte-specific Dgat2 deficiency reduced expression of de novo lipogenesis genes and lowered liver TGs by ~70%. Importantly, the reduction in steatosis was not accompanied by increased inflammation or fibrosis, and insulin and glucose metabolism were unchanged. Conclusion: This study suggests that hepatic DGAT2 deficiency successfully reduces diet-induced HS and supports development of DGAT2 inhibitors as a therapeutic strategy for treating NAFLD and preventing downstream consequences.


Asunto(s)
Diacilglicerol O-Acetiltransferasa/fisiología , Hepatitis/etiología , Hepatocitos/enzimología , Cirrosis Hepática Experimental/etiología , Enfermedad del Hígado Graso no Alcohólico/prevención & control , Animales , Diacilglicerol O-Acetiltransferasa/antagonistas & inhibidores , Diacilglicerol O-Acetiltransferasa/deficiencia , Grasas de la Dieta/administración & dosificación , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Enfermedad del Hígado Graso no Alcohólico/tratamiento farmacológico , Triglicéridos/metabolismo
3.
J Lipid Res ; 60(6): 1112-1120, 2019 06.
Artículo en Inglés | MEDLINE | ID: mdl-30936184

RESUMEN

Mammals store metabolic energy as triacylglycerols (TGs) in adipose tissue. TG synthesis is catalyzed by the evolutionarily unrelated acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes DGAT1 and DGAT2, which catalyze the same reaction and account for nearly all TG synthesis. The reasons for their convergent evolution to synthesize TGs remain unclear. Mice lacking DGAT1 are viable with reduced fat stores of TGs, whereas DGAT2 KO mice die postnatally just after birth with >90% reduction of TGs, suggesting that DGAT2 is the predominant enzyme for TG storage. To better understand the functional differences between the DGATs, we studied mice fed chow or high-fat diets lacking either enzyme in adipose tissue. Unexpectedly, mice lacking DGAT2 in adipocytes have normal TG storage and glucose metabolism on regular or high-fat diets, indicating DGAT2 is not essential for fat storage. In contrast, mice lacking DGAT1 in adipocytes have normal TG storage on a chow diet but moderately decreased body fat accompanied by glucose intolerance when challenged with a high-fat diet. The latter changes were associated with the activation of ER stress pathways. We conclude that DGAT1 and DGAT2 can largely compensate for each other for TG storage but that DGAT1 uniquely has an important role in protecting the ER from the lipotoxic effects of high-fat diets.


Asunto(s)
Adipocitos/metabolismo , Diacilglicerol O-Acetiltransferasa/metabolismo , Triglicéridos/metabolismo , Adipocitos/enzimología , Tejido Adiposo/metabolismo , Animales , Dieta Alta en Grasa/efectos adversos , Estrés del Retículo Endoplásmico/fisiología , Epidermis/metabolismo , Immunoblotting , Ratones , Ratones Endogámicos C57BL , Obesidad/enzimología , Obesidad/etiología , Obesidad/metabolismo
4.
J Lipid Res ; 58(6): 1230-1237, 2017 06.
Artículo en Inglés | MEDLINE | ID: mdl-28373485

RESUMEN

Acyl-CoA:diacylglycerol acyltransferase (DGAT)1 and DGAT2 catalyze triglyceride (TG) biosynthesis in humans. Biallelic loss-of-function mutations in human DGAT1 result in severe congenital diarrhea and protein-losing enteropathy. Additionally, pharmacologic inhibition of DGAT1 led to dose-related diarrhea in human clinical trials. Here we identify a previously unknown DGAT1 mutation in identical twins of South Asian descent. These male patients developed watery diarrhea shortly after birth, with protein-losing enteropathy and failure to thrive. Exome sequencing revealed a homozygous recessive mutation in DGAT1, c.314T>C, p.L105P. We show here that the p.L105P DGAT1 enzyme produced from the mutant allele is less abundant, resulting in partial loss of TG synthesis activity and decreased formation of lipid droplets in patient-derived primary dermal fibroblasts. Thus, in contrast with complete loss-of-function alleles of DGAT1, the p.L105P missense allele partially reduces TG synthesis activity and causes a less severe clinical phenotype. Our findings add to the growing recognition of DGAT1 deficiency as a cause of congenital diarrhea with protein-losing enteropathy and indicate that DGAT1 mutations result in a spectrum of diseases.


Asunto(s)
Diacilglicerol O-Acetiltransferasa/genética , Diarrea/congénito , Diarrea/genética , Mutación Missense , Alelos , Línea Celular Tumoral , Preescolar , Diarrea/enzimología , Femenino , Homocigoto , Humanos , Mutación con Pérdida de Función , Masculino , Embarazo
5.
J Lipid Res ; 58(1): 226-235, 2017 01.
Artículo en Inglés | MEDLINE | ID: mdl-27836991

RESUMEN

Variations in the gene LDAH (C2ORF43), which encodes lipid droplet-associated hydrolase (LDAH), are among few loci associated with human prostate cancer. Homologs of LDAH have been identified as proteins of lipid droplets (LDs). LDs are cellular organelles that store neutral lipids, such as triacylglycerols and sterol esters, as precursors for membrane components and as reservoirs of metabolic energy. LDAH is reported to hydrolyze cholesterol esters and to be important in macrophage cholesterol ester metabolism. Here, we confirm that LDAH is localized to LDs in several model systems. We generated a murine model in which Ldah is disrupted but found no evidence for a major function of LDAH in cholesterol ester or triacylglycerol metabolism in vivo, nor a role in energy or glucose metabolism. Our data suggest that LDAH is not a major cholesterol ester hydrolase, and an alternative metabolic function may be responsible for its possible effect on development of prostate cancer.


Asunto(s)
Ésteres del Colesterol/genética , Gotas Lipídicas/metabolismo , Metabolismo de los Lípidos/genética , Serina Proteasas/genética , Animales , Ésteres del Colesterol/metabolismo , Metabolismo Energético/genética , Glucosa/metabolismo , Humanos , Macrófagos/metabolismo , Masculino , Ratones , Neoplasias de la Próstata/metabolismo , Neoplasias de la Próstata/patología , Serina Proteasas/metabolismo , Triglicéridos/metabolismo
6.
Biochim Biophys Acta ; 1851(7): 937-45, 2015 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-25732851

RESUMEN

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.


Asunto(s)
Células Estrelladas Hepáticas/metabolismo , Lipasa/fisiología , Retinoides/metabolismo , Triglicéridos/metabolismo , Adipocitos/enzimología , Adipocitos/metabolismo , Animales , Células COS , Hidrolasas de Éster Carboxílico/genética , Hidrolasas de Éster Carboxílico/metabolismo , Chlorocebus aethiops , Femenino , Metabolismo de los Lípidos/genética , Ratones , Ratones Noqueados , Esterol Esterasa/genética , Esterol Esterasa/metabolismo
7.
Am J Physiol Heart Circ Physiol ; 311(6): H1392-H1408, 2016 12 01.
Artículo en Inglés | MEDLINE | ID: mdl-27694217

RESUMEN

The HDL receptor SR-BI mediates the transfer of cholesteryl esters from HDL to cells and controls HDL abundance and structure. Depending on the genetic background, loss of SR-BI causes hypercholesterolemia, anemia, reticulocytosis, splenomegaly, thrombocytopenia, female infertility, and fatal coronary heart disease (CHD). The carboxy terminus of SR-BI (505QEAKL509) must bind to the cytoplasmic adaptor PDZK1 for normal hepatic-but not steroidogenic cell-expression of SR-BI protein. To determine whether SR-BI's carboxy terminus is also required for normal protein levels in steroidogenic cells, we introduced into SR-BI's gene a 507Ala/STOP mutation that produces a truncated receptor (SR-BIΔCT). As expected, the dramatic reduction of hepatic receptor protein in SR-BIΔCT mice was similar to that in PDZK1 knockout (KO) mice. Unlike SR-BI KO females, SR-BIΔCT females were fertile. The severity of SR-BIΔCT mice's hypercholesterolemia was intermediate between those of SR-BI KO and PDZK1 KO mice. Substantially reduced levels of the receptor in adrenal cortical cells, ovarian cells, and testicular Leydig cells in SR-BIΔCT mice suggested that steroidogenic cells have an adaptor(s) functionally analogous to hepatic PDZK1. When SR-BIΔCT mice were crossed with apolipoprotein E KO mice (SR-BIΔCT/apoE KO), pathologies including hypercholesterolemia, macrocytic anemia, hepatic and splenic extramedullary hematopoiesis, massive splenomegaly, reticulocytosis, thrombocytopenia, and rapid-onset and fatal occlusive coronary arterial atherosclerosis and CHD (median age of death: 9 wk) were observed. These results provide new insights into the control of SR-BI in steroidogenic cells and establish SR-BIΔCT/apoE KO mice as a new animal model for the study of CHD.


Asunto(s)
Corteza Suprarrenal/metabolismo , Hipercolesterolemia/genética , Células Intersticiales del Testículo/metabolismo , Hígado/metabolismo , Ovario/metabolismo , Receptores Depuradores de Clase B/genética , Anemia Macrocítica/genética , Animales , Apolipoproteínas E/genética , Enfermedad de la Arteria Coronaria/genética , Enfermedad de la Arteria Coronaria/mortalidad , Enfermedad Coronaria/genética , Enfermedad Coronaria/mortalidad , Oclusión Coronaria/genética , Oclusión Coronaria/mortalidad , Femenino , Técnicas de Sustitución del Gen , Hematopoyesis Extramedular/genética , Immunoblotting , Lipoproteínas HDL/genética , Masculino , Ratones , Mutación , Reacción en Cadena de la Polimerasa , Receptores de Lipoproteína/genética , Reticulocitosis/genética , Esplenomegalia/genética , Trombocitopenia/genética , Transcriptoma
8.
J Lipid Res ; 55(7): 1465-77, 2014 07.
Artículo en Inglés | MEDLINE | ID: mdl-24868093

RESUMEN

Accurate protein inventories are essential for understanding an organelle's functions. The lipid droplet (LD) is a ubiquitous intracellular organelle with major functions in lipid storage and metabolism. LDs differ from other organelles because they are bounded by a surface monolayer, presenting unique features for protein targeting to LDs. Many proteins of varied functions have been found in purified LD fractions by proteomics. While these studies have become increasingly sensitive, it is often unclear which of the identified proteins are specific to LDs. Here we used protein correlation profiling to identify 35 proteins that specifically enrich with LD fractions of Saccharomyces cerevisiae Of these candidates, 30 fluorophore-tagged proteins localize to LDs by microscopy, including six proteins, several with human orthologs linked to diseases, which we newly identify as LD proteins (Cab5, Rer2, Say1, Tsc10, YKL047W, and YPR147C). Two of these proteins, Say1, a sterol deacetylase, and Rer2, a cis-isoprenyl transferase, are enzymes involved in sterol and polyprenol metabolism, respectively, and we show their activities are present in LD fractions. Our results provide a highly specific list of yeast LD proteins and reveal that the vast majority of these proteins are involved in lipid metabolism.


Asunto(s)
Dolicoles/biosíntesis , Gotas Lipídicas/metabolismo , Metabolismo de los Lípidos/fisiología , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Esteroles/metabolismo , Acetilación , Dolicoles/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética
9.
J Lipid Res ; 54(8): 2185-2194, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23740967

RESUMEN

We showed earlier that nutritional stress like starvation or high-fat diet resulted in phenotypic changes in the lipidomes of hepatocyte lipid droplets (LDs), representative for the pathophysiological status of the mouse model. Here we extend our former study by adding genetic stress due to knockout (KO) of adipocyte triglyceride lipase (ATGL), the rate limiting enzyme in LD lipolysis. An intervention trial for 6 weeks with male wild-type (WT) and ATGL-KO mice was carried out; both genotypes were fed lab chow or were exposed to short-time starvation. Isolated LDs were analyzed by LC-MS/MS. Triacylglycerol, diacylglycerol, and phosphatidylcholine lipidomes, in that order, provided the best phenotypic signatures characteristic for respective stresses applied to the animals. This was evidenced at lipid species level by principal component analysis, calculation of average values for chain-lengths and numbers of double bonds, and by visualization in heat maps. Structural backgrounds for analyses and metabolic relationships were elaborated at lipid molecular species level. Relating our lipidomic data to nonalcoholic fatty liver diseases of nutritional and genetic etiologies with or without accompanying insulin resistance, phenotypic distinction in hepatocyte LDs dependent on insulin status emerged. Taken together, lipidomes of hepatocyte LDs are sensitive responders to nutritional and genetic stress.


Asunto(s)
Daño del ADN , Hepatocitos/metabolismo , Lipasa/deficiencia , Lípidos , Animales , Eliminación de Gen , Hepatocitos/química , Lipasa/genética , Metabolismo de los Lípidos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Tamaño de la Partícula
10.
Elife ; 122023 10 02.
Artículo en Inglés | MEDLINE | ID: mdl-37782317

RESUMEN

Triglycerides (TGs) in adipocytes provide the major stores of metabolic energy in the body. Optimal amounts of TG stores are desirable as insufficient capacity to store TG, as in lipodystrophy, or exceeding the capacity for storage, as in obesity, results in metabolic disease. We hypothesized that mice lacking TG storage in adipocytes would result in excess TG storage in cell types other than adipocytes and severe lipotoxicity accompanied by metabolic disease. To test this hypothesis, we selectively deleted both TG synthesis enzymes, DGAT1 and DGAT2, in adipocytes (ADGAT DKO mice). As expected with depleted energy stores, ADGAT DKO mice did not tolerate fasting well and, with prolonged fasting, entered torpor. However, ADGAT DKO mice were unexpectedly otherwise metabolically healthy and did not accumulate TGs ectopically or develop associated metabolic perturbations, even when fed a high-fat diet. The favorable metabolic phenotype resulted from activation of energy expenditure, in part via BAT (brown adipose tissue) activation and beiging of white adipose tissue. Thus, the ADGAT DKO mice provide a fascinating new model to study the coupling of metabolic energy storage to energy expenditure.


Asunto(s)
Adipocitos , Obesidad , Animales , Ratones , Tejido Adiposo Pardo , Dieta Alta en Grasa/efectos adversos , Triglicéridos
11.
J Lipid Res ; 53(10): 2141-2152, 2012 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-22872753

RESUMEN

Liver steatosis can be induced by fasting or high-fat diet. We investigated by lipidomic analysis whether such metabolic states are reflected in the lipidome of hepatocyte lipid droplets (LDs) from mice fed normal chow diet (FED), fasted (FAS), or fed a high-fat diet (HFD). LC-MS/MS at levels of lipid species profiles and of lipid molecular species uncovered a FAS phenotype of LD enriched in triacylglycerol (TG) molecular species with very long-chain (VLC)-PUFA residues and an HFD phenotype with less unsaturated TG species in addition to characteristic lipid marker species. Nutritional stress did not result in dramatic structural alterations in diacylglycerol (DG) and phospholipid (PL) classes. Moreover, molecular species of bulk TG and of DG indicated concomitant de novo TG synthesis and lipase-catalyzed degradation to be active in LDs. DG species with VLC-PUFA residues would be preferred precursors for phosphatidylcholine (PC) species, the others for TG molecular species. In addition, molecular species of PL classes fitted the hepatocyte Kennedy and phosphatidylethanolamine methyltransferase pathways. We demonstrate that lipidomic analysis of LDs enables phenotyping of nutritional stress. TG species are best suited for such phenotyping, whereas structural analysis of TG, DG, and PL molecular species provides metabolic insights.


Asunto(s)
Hepatocitos/metabolismo , Lípidos/análisis , Hígado/metabolismo , Estrés Fisiológico , Animales , Dieta Alta en Grasa , Diglicéridos/metabolismo , Ayuno , Hepatocitos/química , Lipasa/metabolismo , Hígado/química , Ratones , Fosfatidilcolinas/metabolismo , Fosfatidiletanolamina N-Metiltransferasa/metabolismo , Triglicéridos/metabolismo
12.
Bioinformatics ; 27(4): 572-7, 2011 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-21169379

RESUMEN

MOTIVATION: The accurate measurement of the lipidome permits insights into physiological and pathological processes. Of the present high-throughput technologies, LC-MS especially bears potential of monitoring quantitative changes in hundreds of lipids simultaneously. In order to extract valuable information from huge amount of mass spectrometry data, the aid of automated, reliable, highly sensitive and specific analysis algorithms is indispensable. RESULTS: We present here a novel approach for the quantitation of lipids in LC-MS data. The new algorithm obtains its analytical power by two major innovations: (i) a 3D algorithm that confines the peak borders in m/z and time direction and (ii) the use of the theoretical isotopic distribution of an analyte as selection/exclusion criterion. The algorithm is integrated in the Lipid Data Analyzer (LDA) application which additionally provides standardization, a statistics module for results analysis, a batch mode for unattended analysis of several runs and a 3D viewer for the manual verification. The statistics module offers sample grouping, tests between sample groups and export functionalities, where the results are visualized by heat maps and bar charts. The presented algorithm has been applied to data from a controlled experiment and to biological data, containing analytes distributed over an intensity range of 10(6). Our approach shows improved sensitivity and an extremely high positive predictive value compared with existing methods. Consequently, the novel algorithm, integrated in a user-friendly application, is a valuable improvement in the high-throughput analysis of the lipidome. IMPLEMENTATION AND AVAILABILITY: The Java application is freely available for non-commercial users at http://genome.tugraz.at/lda. Raw data associated with this manuscript may be downloaded from ProteomeCommons.org Tranche using the following hash: ZBh3nS5bXk6I/Vn32tB5Vh0qnMpVIW71HByFFQqM0RmdF4/4Hcn H3Wggh9kU2teYVOtM1JWwHIeMHqSS/bc2yYNFmyUAAAAAAACl DQ ==


Asunto(s)
Algoritmos , Cromatografía Liquida/métodos , Lípidos/análisis , Espectrometría de Masas/métodos , Animales , Hepatocitos/química , Masculino , Ratones , Ratones Endogámicos C57BL , Valor Predictivo de las Pruebas , Sensibilidad y Especificidad , Programas Informáticos
13.
Lipids ; 57(3): 183-195, 2022 05.
Artículo en Inglés | MEDLINE | ID: mdl-35318678

RESUMEN

1-O-Acylceramides (1-OACs) have a fatty acid esterified to the 1-hydroxyl of the sphingosine head group of the ceramide, and recently we identified these lipids as natural components of human and mouse epidermis. Here we show epidermal 1-OACs arise shortly before birth during the establishment of the water permeability barrier in mice. Fractionation of human epidermis indicates 1-OACs concentrate in the stratum corneum. During in vitro maturation into reconstructed human epidermis, human keratinocytes dramatically increase 1-OAC levels indicating they are one source of epidermal 1-OACs. In search of potential enzymes responsible for 1-OAC synthesis in vivo, we analyzed mutant mice with deficiencies of ceramide synthases (Cers2, Cers3, or Cers4), diacylglycerol acyltransferases (Dgat1 or Dgat2), elongase of very long fatty acids 3 (Elovl3), lecithin cholesterol acyltransferase (Lcat), stearoyl-CoA desaturase 1 (Scd1), or acidic ceramidase (Asah1). Overall levels of 1-OACs did not decrease in any mouse model. In Cers3 and Dgat2-deficient epidermis they even increased in correlation with deficient skin barrier function. Dagt2 deficiency reshapes 1-OAC synthesis with an increase in 1-OACs with N-linked non-hydroxylated fatty acids and a 60% decrease compared to control in levels of 1-OACs with N-linked hydroxylated palmitate. As none of the single enzyme deficiencies we examined resulted in a lack of 1-OACs, we conclude that either there is functional redundancy in forming 1-OAC and more than one enzyme is involved, and/or an unknown acyltransferase of the epidermis performs the final step of 1-OAC synthesis, the implications of which are discussed.


Asunto(s)
Epidermis , Agua , Animales , Ceramidas , Ácidos Grasos , Queratinocitos , Ratones , Permeabilidad , Esfingosina N-Aciltransferasa
14.
Dev Cell ; 57(3): 387-397.e4, 2022 02 07.
Artículo en Inglés | MEDLINE | ID: mdl-35134345

RESUMEN

Lipid droplets (LDs) are organelles of cellular lipid storage with fundamental roles in energy metabolism and cell membrane homeostasis. There has been an explosion of research into the biology of LDs, in part due to their relevance in diseases of lipid storage, such as atherosclerosis, obesity, type 2 diabetes, and hepatic steatosis. Consequently, there is an increasing need for a resource that combines datasets from systematic analyses of LD biology. Here, we integrate high-confidence, systematically generated human, mouse, and fly data from studies on LDs in the framework of an online platform named the "Lipid Droplet Knowledge Portal" (https://lipiddroplet.org/). This scalable and interactive portal includes comprehensive datasets, across a variety of cell types, for LD biology, including transcriptional profiles of induced lipid storage, organellar proteomics, genome-wide screen phenotypes, and ties to human genetics. This resource is a powerful platform that can be utilized to identify determinants of lipid storage.


Asunto(s)
Bases de Datos como Asunto , Gotas Lipídicas/metabolismo , Animales , Ésteres del Colesterol/metabolismo , Minería de Datos , Genoma , Humanos , Inflamación/patología , Metabolismo de los Lípidos , Hígado/metabolismo , Masculino , Ratones Endogámicos C57BL , Fenotipo , Fosforilación , Interferencia de ARN
15.
J Lipid Res ; 52(12): 2314-2322, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-21960706

RESUMEN

This work aims to combine chromatographic retention, high mass resolution and accuracy, MS/MS spectra, and a package for automated identification and quantitation of lipid species in one platform for lipidomic analysis. The instrumental setup elaborated comprises reversed-phase HPLC coupled to a Fourier transform ion cyclotron resonance mass spectrometer (LTQ-FT), and Lipid Data Analyzer (LDA) software. Data analysis for lipid species quantification in this platform is based on retention time, mass resolution of 200,000, and mass accuracy below 2 ppm. In addition, automatically generated MS/MS spectra provide structural information at molecular level. This LC/MS technology allows analyzing complex biological samples in a quantitative manner as shown here paradigmatically for murine lipid droplets having a huge surplus of triacylglycerol species. Chromatographic preseparation of the bulk lipid class alleviates the problem of ion suppression of lipid species from other classes. Extension of 1D to 2D chromatography is possible, yet time consuming. The platform affords unambiguous detection of lipid species as low as 0.1‰ within major lipid classes. Taken together, a novel lipidomic LC/MS platform based on chromatographic retention, high mass resolution and accuracy, MS/MS analysis, and quantitation software enables analysis of complex samples as demonstrated for lipid droplets.


Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Ciclotrones , Lípidos/análisis , Lípidos/química , Espectrometría de Masas en Tándem/métodos , Animales , Cromatografía de Fase Inversa , Ratones , Ratones Endogámicos C57BL , Reproducibilidad de los Resultados , Espectrometría de Masas en Tándem/instrumentación , Factores de Tiempo
16.
Biol Open ; 10(3)2021 03 03.
Artículo en Inglés | MEDLINE | ID: mdl-33593792

RESUMEN

Phosphatidylethanolamine is an abundant component of most cellular membranes whose physical and chemical properties modulate multiple aspects of organelle membrane dynamics. An evolutionarily ancient mechanism for producing phosphatidylethanolamine is to decarboxylate phosphatidylserine and the enzyme catalyzing this reaction, phosphatidylserine decarboxylase, localizes to the inner membrane of the mitochondrion. We characterize a second form of phosphatidylserine decarboxylase, termed PISD-LD, that is generated by alternative splicing of PISD pre-mRNA and localizes to lipid droplets and to mitochondria. Sub-cellular targeting is controlled by a common segment of PISD-LD that is distinct from the catalytic domain and is regulated by nutritional state. Growth conditions that promote neutral lipid storage in lipid droplets favors targeting to lipid droplets, while targeting to mitochondria is favored by conditions that promote consumption of lipid droplets. Depletion of both forms of phosphatidylserine decarboxylase impairs triacylglycerol synthesis when cells are challenged with free fatty acid, indicating a crucial role phosphatidylserine decarboxylase in neutral lipid storage. The results reveal a previously unappreciated role for phosphatidylserine decarboxylase in lipid droplet biogenesis.


Asunto(s)
Carboxiliasas/metabolismo , Gotas Lipídicas/metabolismo , Metabolismo de los Lípidos , Fosfatidilserinas/metabolismo , Empalme Alternativo , Secuencia de Aminoácidos , Biomarcadores , Carboxiliasas/química , Carboxiliasas/genética , Cromatografía en Capa Delgada , Ácidos Grasos , Perfilación de la Expresión Génica , Células HeLa , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Mitocondrias/genética , Mitocondrias/metabolismo , Imagen Molecular , Señales de Clasificación de Proteína , Imagen de Lapso de Tiempo
17.
Cell Rep ; 33(5): 108348, 2020 11 03.
Artículo en Inglés | MEDLINE | ID: mdl-33147469

RESUMEN

Brown adipocytes store metabolic energy as triglycerides (TGs) in lipid droplets (LDs). Fatty acids released from brown adipocyte LDs by lipolysis are thought to activate and fuel UCP1-mediated thermogenesis. Here, we test this hypothesis by preventing fatty acid storage in murine brown adipocytes through brown adipose tissue (BAT)-specific deletions of the TG synthesis enzymes DGAT1 and DGAT2 (BA-DGAT KO). Despite the absence of TGs in brown adipocytes, BAT is functional, and BA-DGAT-KO mice maintain euthermia during acute or chronic cold exposure. As apparent adaptations to the lack of TG, brown adipocytes of BA-DGAT-KO mice appear to use circulating glucose and fatty acids, and stored glycogen, to fuel thermogenesis. Moreover, BA-DGAT-KO mice are resistant to diet-induced glucose intolerance, likely because of increased glucose disposal by BAT. We conclude that TGs in BAT are dispensable for its contribution to cold-induced thermogenesis, at least when other fuel sources are available.


Asunto(s)
Tejido Adiposo Pardo/metabolismo , Frío , Gotas Lipídicas/metabolismo , Termogénesis , Adaptación Fisiológica , Adipocitos Beige/metabolismo , Adipocitos Marrones/metabolismo , Animales , Diacilglicerol O-Acetiltransferasa/deficiencia , Diacilglicerol O-Acetiltransferasa/metabolismo , Dieta Alta en Grasa , Intolerancia a la Glucosa/patología , Ratones Noqueados , Triglicéridos/metabolismo
18.
Artículo en Inglés | MEDLINE | ID: mdl-32474112

RESUMEN

Except for epidermis and liver, little is known about endogenous expression of 1-O-acylceramides (1-OACs) in mammalian tissue. Therefore, we screened several organs (brain, lung, liver, spleen, lymph nodes, heart, kidney, thymus, small intestine, and colon) from mice for the presence of 1-OACs by LC-MS2. In most organs, low levels of about 0.25-1.3 pmol 1-OACs/mg wet weight were recorded. Higher levels were detected in liver, small and large intestines, with about 4-13 pmol 1-OACs/mg wet weight. 1-OACs were esterified mainly with palmitic, stearic, or oleic acids. Esterification with saturated very long-chain fatty acids, as in epidermis, was not observed. Western-type diet induced 3-fold increased 1-OAC levels in mice livers while ceramides were unaltered. In a mouse model of Farber disease with a decrease of acid ceramidase activity, we observed a strong, up to 50-fold increase of 1-OACs in lung, thymus, and spleen. In contrast, 1-OAC levels were reduced 0.54-fold in liver. Only in lung 1-OAC levels correlated to changes in ceramide levels - indicating tissue-specific mechanisms of regulation. Glucosylceramide synthase deficiency in liver did not cause changes in 1-OAC or ceramide levels, whereas increased ceramide levels in glucosylceramide synthase-deficient small intestine caused an increase in 1-OAC levels. Deficiency of Dgat1 in mice resulted in a reduction of 1-OACs to 30% in colon, but not in small intestine and liver, going along with constant free ceramides levels. From these data, we conclude that Dgat1 as well as lysosomal lipid metabolism contribute in vivo to homeostatic 1-OAC levels in an organ-specific manner.


Asunto(s)
Ceramidas/metabolismo , Diacilglicerol O-Acetiltransferasa/metabolismo , Lipogranulomatosis de Farber/metabolismo , Metabolismo de los Lípidos , Animales , Encéfalo/metabolismo , Colon/metabolismo , Intestino Delgado/metabolismo , Riñón/metabolismo , Hígado/metabolismo , Pulmón/metabolismo , Ganglios Linfáticos/metabolismo , Masculino , Ratones Endogámicos C57BL , Miocardio/metabolismo , Bazo/metabolismo , Timo/metabolismo
19.
Cell Metab ; 26(2): 407-418.e3, 2017 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-28768178

RESUMEN

Triglyceride (TG) storage in adipose tissue provides the major reservoir for metabolic energy in mammals. During lipolysis, fatty acids (FAs) are hydrolyzed from adipocyte TG stores and transported to other tissues for fuel. For unclear reasons, a large portion of hydrolyzed FAs in adipocytes is re-esterified to TGs in a "futile," ATP-consuming, energy dissipating cycle. Here we show that FA re-esterification during adipocyte lipolysis is mediated by DGAT1, an ER-localized DGAT enzyme. Surprisingly, this re-esterification cycle does not preserve TG mass but instead functions to protect the ER from lipotoxic stress and related consequences, such as adipose tissue inflammation. Our data reveal an important role for DGAT activity and TG synthesis generally in averting ER stress and lipotoxicity, with specifically DGAT1 performing this function during stimulated lipolysis in adipocytes.


Asunto(s)
Adipocitos/metabolismo , Diacilglicerol O-Acetiltransferasa/metabolismo , Estrés del Retículo Endoplásmico , Lipólisis , Triglicéridos/biosíntesis , Células 3T3-L1 , Animales , Retículo Endoplásmico/enzimología , Humanos , Ratones
20.
Elife ; 52016 Aug 26.
Artículo en Inglés | MEDLINE | ID: mdl-27564575

RESUMEN

How proteins control the biogenesis of cellular lipid droplets (LDs) is poorly understood. Using Drosophila and human cells, we show here that seipin, an ER protein implicated in LD biology, mediates a discrete step in LD formation-the conversion of small, nascent LDs to larger, mature LDs. Seipin forms discrete and dynamic foci in the ER that interact with nascent LDs to enable their growth. In the absence of seipin, numerous small, nascent LDs accumulate near the ER and most often fail to grow. Those that do grow prematurely acquire lipid synthesis enzymes and undergo expansion, eventually leading to the giant LDs characteristic of seipin deficiency. Our studies identify a discrete step of LD formation, namely the conversion of nascent LDs to mature LDs, and define a molecular role for seipin in this process, most likely by acting at ER-LD contact sites to enable lipid transfer to nascent LDs.

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