RESUMEN
Lipo-chitooligosaccharides (LCOs) are signaling molecules produced by rhizobial bacteria that trigger the nodulation process in legumes, and by some fungi that also establish symbiotic relationships with plants, notably the arbuscular and ecto mycorrhizal fungi. Here, we show that many other fungi also produce LCOs. We tested 59 species representing most fungal phyla, and found that 53 species produce LCOs that can be detected by functional assays and/or by mass spectroscopy. LCO treatment affects spore germination, branching of hyphae, pseudohyphal growth, and transcription in non-symbiotic fungi from the Ascomycete and Basidiomycete phyla. Our findings suggest that LCO production is common among fungi, and LCOs may function as signals regulating fungal growth and development.
Asunto(s)
Quitina/análogos & derivados , Quitina/metabolismo , Hongos/crecimiento & desarrollo , Hongos/metabolismo , Transducción de Señal/fisiología , Ascomicetos/crecimiento & desarrollo , Basidiomycota/crecimiento & desarrollo , Quitosano , Ecología , Ácidos Grasos/metabolismo , Micorrizas/fisiología , Oligosacáridos , Rhizobium/metabolismo , Esporas Fúngicas/crecimiento & desarrollo , Simbiosis/fisiologíaRESUMEN
Impaired adipose tissue insulin signalling is a critical feature of insulin resistance. Here we identify a pathway linking the lipolytic enzyme hormone-sensitive lipase (HSL) to insulin action via the glucose-responsive transcription factor ChREBP and its target, the fatty acid elongase ELOVL6. Genetic inhibition of HSL in human adipocytes and mouse adipose tissue results in enhanced insulin sensitivity and induction of ELOVL6. ELOVL6 promotes an increase in phospholipid oleic acid, which modifies plasma membrane fluidity and enhances insulin signalling. HSL deficiency-mediated effects are suppressed by gene silencing of ChREBP and ELOVL6. Mechanistically, physical interaction between HSL, independent of lipase activity, and the isoform activated by glucose metabolism ChREBPα impairs ChREBPα translocation into the nucleus and induction of ChREBPß, the isoform with high transcriptional activity that is strongly associated with whole-body insulin sensitivity. Targeting the HSL-ChREBP interaction may allow therapeutic strategies for the restoration of insulin sensitivity.
Asunto(s)
Adipocitos/metabolismo , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/metabolismo , Resistencia a la Insulina , Insulina/metabolismo , Esterol Esterasa/metabolismo , Tejido Adiposo/metabolismo , Animales , Biomarcadores , Elongasas de Ácidos Grasos/genética , Elongasas de Ácidos Grasos/metabolismo , Expresión Génica , Glucosa/metabolismo , Resistencia a la Insulina/genética , Fluidez de la Membrana/genética , Ratones , Ratones Transgénicos , Mapeo de Interacción de Proteínas , Mapas de Interacción de Proteínas , Transducción de SeñalRESUMEN
Robust associations between low plasma level of natriuretic peptides (NP) and increased risk of type 2 diabetes (T2D) have been recently reported in humans. Adipose tissue (AT) is a known target of NP. However it is unknown whether NP signalling in human AT relates to insulin sensitivity and modulates glucose metabolism. We here show in two European cohorts that the NP receptor guanylyl cyclase-A (GC-A) expression in subcutaneous AT was down-regulated as a function of obesity grade while adipose NP clearance receptor (NPRC) was up-regulated. Adipose GC-A mRNA level was down-regulated in prediabetes and T2D, and negatively correlated with HOMA-IR and fasting blood glucose. We show for the first time that NP promote glucose uptake in a dose-dependent manner. This effect is reduced in adipocytes of obese individuals. NP activate mammalian target of rapamycin complex 1/2 (mTORC1/2) and Akt signalling. These effects were totally abrogated by inhibition of cGMP-dependent protein kinase and mTORC1/2 by rapamycin. We further show that NP treatment favoured glucose oxidation and de novo lipogenesis independently of significant gene regulation. Collectively, our data support a role for NP in blood glucose control and insulin sensitivity by increasing glucose uptake in human adipocytes. This effect is partly blunted in obesity.
Asunto(s)
Adipocitos/efectos de los fármacos , Adipocitos/metabolismo , GMP Cíclico/metabolismo , Glucosa/metabolismo , Péptidos Natriuréticos/farmacología , Tejido Adiposo/metabolismo , Biomarcadores , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Regulación de la Expresión Génica , Humanos , Resistencia a la Insulina , Modelos Biológicos , Obesidad/genética , Obesidad/metabolismo , Proteínas Proto-Oncogénicas c-akt , Receptores del Factor Natriurético Atrial/genética , Receptores del Factor Natriurético Atrial/metabolismo , Transducción de Señal , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
An efficient regiospecific total synthesis of several branched fatty acyl hydroxyl-fatty acids (FAHFA) has been achieved from available terminal alkenes and alkynes. The key steps feature a boron trifluoride mediated epoxide ring opening with acetylide carbanions, followed by hydrogenation of the alkyne function. The carboxylic acid of the hydroxylated chains is introduced at the last step of the synthesis to allow the esterification of the branched hydroxyl group by fatty acids beforehand. The chemical syntheses of a "linear" FAHFA and a branched FAHFA analog containing a Z-olefin in the hydroxyl-fatty acid chain are also reported. A LC-MS/MS method has been developed. Several reversed phase columns were compared. Regioisomers were separated.
RESUMEN
AIMS/HYPOTHESIS: Activation of macrophages by fatty acids (FAs) is a potential mechanism linking obesity to adipose tissue (AT) inflammation and insulin resistance. Here, we investigated the effects of FAs released during adipocyte lipolysis on AT macrophages (ATMs). METHODS: Human THP-1 macrophages were treated with media from human multipotent adipose-derived stem (hMADS) adipocytes stimulated with lipolytic drugs. Macrophages were also treated with mixtures of FAs and an inhibitor of Toll-like receptor 4, since this receptor is activated by saturated FAs. Levels of mRNA and the secretion of inflammation-related molecules were measured in macrophages. FA composition was determined in adipocytes, conditioned media and macrophages. The effect of chronic inhibition or acute activation of fat cell lipolysis on ATM response was investigated in vivo in mice. RESULTS: Whereas palmitic acid alone activates THP-1, conditioned media from hMADS adipocyte lipolysis had no effect on IL, chemokine and cytokine gene expression, and secretion by macrophages. Mixtures of FAs representing de novo lipogenesis or habitual dietary conditions also had no effect. FAs derived from adipocyte lipolysis were taken up by macrophages and stored as triacylglycerol droplets. In vivo, chronic treatment with an antilipolytic drug did not modify gene expression and number of ATMs in mice with intact or defective Tlr4. Stimulation of adipocyte lipolysis increased storage of neutral lipids by macrophages without change in number and phenotype. CONCLUSIONS/INTERPRETATION: Our data suggest that adipocyte lipolysis does not activate inflammatory pathways in ATMs, which instead may act as scavengers of FAs.
Asunto(s)
Adipocitos/metabolismo , Tejido Adiposo/metabolismo , Ácidos Grasos/metabolismo , Lipólisis/fisiología , Macrófagos/metabolismo , Triglicéridos/metabolismo , Adipocitos/citología , Tejido Adiposo/citología , Agonistas de Receptores Adrenérgicos beta 3/farmacología , Animales , Línea Celular , Dioxoles/farmacología , Ácidos Grasos/farmacología , Humanos , Inflamación/metabolismo , Macrófagos/citología , Macrófagos/efectos de los fármacos , Masculino , Ratones , Ratones Noqueados , Ácido Palmítico/farmacología , Células Madre/citología , Células Madre/metabolismo , Receptor Toll-Like 4/antagonistas & inhibidores , Receptor Toll-Like 4/genética , Receptor Toll-Like 4/metabolismoRESUMEN
Adipose tissue fibrosis development blocks adipocyte hypertrophy and favors ectopic lipid accumulation. Here, we show that adipose tissue fibrosis is associated with obesity and insulin resistance in humans and mice. Kinetic studies in C3H mice fed a high-fat diet show activation of macrophages and progression of fibrosis along with adipocyte metabolic dysfunction and death. Adipose tissue fibrosis is attenuated by macrophage depletion. Impairment of Toll-like receptor 4 signaling protects mice from obesity-induced fibrosis. The presence of a functional Toll-like receptor 4 on adipose tissue hematopoietic cells is necessary for the initiation of adipose tissue fibrosis. Continuous low-dose infusion of the Toll-like receptor 4 ligand, lipopolysaccharide, promotes adipose tissue fibrosis. Ex vivo, lipopolysaccharide-mediated induction of fibrosis is prevented by antibodies against the profibrotic factor TGFß1. Together, these results indicate that obesity and endotoxemia favor the development of adipose tissue fibrosis, a condition associated with insulin resistance, through immune cell Toll-like receptor 4.
Asunto(s)
Tejido Adiposo/patología , Endotoxemia/metabolismo , Obesidad/metabolismo , Receptor Toll-Like 4/metabolismo , Adipocitos/metabolismo , Adipocitos/patología , Tejido Adiposo/metabolismo , Animales , Dieta Alta en Grasa , Modelos Animales de Enfermedad , Endotoxemia/patología , Fibrosis , Humanos , Inflamación/metabolismo , Inflamación/patología , Resistencia a la Insulina/fisiología , Lipopolisacáridos/farmacología , Ratones , Ratones Endogámicos C3H , Obesidad/patología , Transducción de Señal , Receptor Toll-Like 4/genéticaRESUMEN
We examined the effects of chronic TNFalpha and dibutyryl-cAMP (Db-cAMP) pre-treatment on the lipolytic machinery of human hMADS adipocytes. TNFalpha decreased adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) protein content and triglycerides (TG)-hydrolase activity but increased basal lipolysis due to a marked reduction in perilipin (PLIN) protein content. Conversely, Db-cAMP increased ATGL and HSL protein content but prevented PLIN phosphorylation, the net result being accentuated basal lipolysis. In forskolin-stimulated conditions, TNFalpha and Db-cAMP pre-treatment decreased stimulated TG-hydrolase activity and impaired PLIN phosphorylation. Together, this resulted in a severely attenuated response to forskolin-stimulated lipolysis.
Asunto(s)
Adipocitos/efectos de los fármacos , AMP Cíclico/farmacología , Lipasa/análisis , Lipólisis/efectos de los fármacos , Fosfoproteínas/análisis , Esterol Esterasa/análisis , Factor de Necrosis Tumoral alfa/farmacología , Adipocitos/química , Adipocitos/metabolismo , Proteínas Portadoras , Colforsina/farmacología , Humanos , Perilipina-1 , Fosforilación/efectos de los fármacosRESUMEN
Lipolysis is the catabolic pathway by which triglycerides are hydrolyzed into fatty acids. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) have the capacity to hydrolyze in vitro the first ester bond of triglycerides, but their respective contributions to whole cell lipolysis in human adipocytes is unclear. Here, we have investigated the roles of HSL, ATGL, and its coactivator CGI-58 in basal and forskolin-stimulated lipolysis in a human white adipocyte model, the hMADS cells. The hMADS adipocytes express the various components of fatty acid metabolism and show lipolytic capacity similar to primary cultured adipocytes. We show that lipolysis and fatty acid esterification are tightly coupled except in conditions of stimulated lipolysis. Immunocytochemistry experiments revealed that acute forskolin treatment promotes HSL translocation from the cytosol to small lipid droplets and redistribution of ATGL from the cytosol and large lipid droplets to small lipid droplets, resulting in enriched colocalization of the two lipases. HSL or ATGL overexpression resulted in increased triglyceride-specific hydrolase capacity, but only ATGL overexpression increased whole cell lipolysis. HSL silencing had no effect on basal lipolysis and only partially reduced forskolin-stimulated lipolysis. Conversely, silencing of ATGL or CGI-58 significantly reduced basal lipolysis and essentially abolished forskolin-stimulated lipolysis. Altogether, these results suggest that ATGL/CGI-58 acts independently of HSL and precedes its action in the sequential hydrolysis of triglycerides in human hMADS adipocytes.
Asunto(s)
Adipocitos/enzimología , Metabolismo Energético/fisiología , Lipasa/metabolismo , Lipólisis/fisiología , Esterol Esterasa/metabolismo , 1-Acilglicerol-3-Fosfato O-Aciltransferasa , Adipocitos/citología , Adipocitos/efectos de los fármacos , Células Cultivadas , Colforsina/farmacología , Citosol/enzimología , Esterificación/fisiología , Ácidos Grasos/metabolismo , Proteínas Fluorescentes Verdes/genética , Humanos , Hidrólisis , Lipasa/genética , ARN Interferente Pequeño , Esterol Esterasa/genéticaRESUMEN
OBJECTIVE: The purpose of this work was to determine the pattern of genes regulated by peroxisome proliferator-activated receptor (PPAR) gamma coactivator 1 alpha (PGC-1 alpha) in human adipocytes and the involvement of PPARalpha and PPARgamma in PGC-1 alpha transcriptional action. RESEARCH DESIGN AND METHODS: Primary cultures of human adipocytes were transduced with a PGC-1 alpha adenovirus and treated with PPARgamma and PPARalpha agonists. Variation in gene expression was assessed using pangenomic microarrays and quantitative RT-PCR. To investigate glycerol kinase (GyK), a target of PGC-1 alpha, we measured enzymatic activity and glycerol incorporation into triglycerides. In vivo studies were performed on wild-type and PPARalpha(-/-) mice. The GyK promoter was studied using chromatin immunoprecipitation and promoter reporter gene assays. RESULTS: Among the large number of genes regulated by PGC-1 alpha independently of PPARgamma, new targets involved in metabolism included the gene encoding GyK. The induction of GyK by PGC-1 alpha was observed at the levels of mRNA, enzymatic activity, and glycerol incorporation into triglycerides. PPARalpha was also upregulated by PGC-1 alpha. Its activation led to an increase in GyK expression and activity. PPARalpha was shown to bind and activate the GyK promoter. Experiments in mice confirmed the role of PGC-1 alpha and PPARalpha in the regulation of GyK in vivo. CONCLUSIONS: This work uncovers novel pathways regulated by PGC-1 alpha and reveals that PPARalpha controls gene expression in human white adipocytes. The induction of GyK by PGC-1 alpha and PPARalpha may promote a futile cycle of triglyceride hydrolysis and fatty acid reesterification.
Asunto(s)
Adipocitos/fisiología , Regulación Enzimológica de la Expresión Génica , Glicerol Quinasa/genética , Péptidos y Proteínas de Señalización Intracelular/metabolismo , PPAR alfa/genética , PPAR gamma/genética , PPAR gamma/fisiología , Regulación de la Expresión Génica , Glicerol Quinasa/metabolismo , Humanos , Coactivadores de Receptor Nuclear , PPAR alfa/fisiologíaRESUMEN
A strong induction of semicarbazide-sensitive amine oxidase (SSAO) has previously been reported during murine preadipocyte lineage differentiation but it remains unknown whether this emergence also occurs during adipogenesis in man. Our aim was to compare SSAO and monoamine oxidase (MAO) expression during in vitro differentiation of human preadipocytes and in adipose and stroma-vascular fractions of human fat depots. A human preadipocyte cell strain from a patient with Simpson-Golabi-Behmel syndrome was first used to follow amine oxidase expression during in vitro differentiation. Then, human preadipocytes isolated from subcutaneous adipose tissues were cultured under conditions promoting ex vivo adipose differentiation and tested for MAO and SSAO expression. Lastly, human adipose tissue was separated into mature adipocyte and stroma-vascular fractions for analyses of MAO and SSAO at mRNA, protein and activity levels. Both SSAO and MAO were increased from undifferentiated preadipocytes to lipid-laden cells in all the models: 3T3-F442A and 3T3-L1 murine lineages, human SGBS cell strain or human preadipocytes in primary culture. In human subcutaneous adipose tissue, the adipocyte-enriched fraction exhibited seven-fold higher amine oxidase activity and contained three- to seven-fold higher levels of mRNAs encoded by MAO-A, MAO-B, AOC3 and AOC2 genes than the stroma-vascular fraction. MAO-A and AOC3 genes accounted for the majority of their respective MAO and SSAO activities in human adipose tissue. Most of the SSAO and MAO found in adipose tissue originated from mature adipocytes. Although the mechanism and role of adipogenesis-related increase in amine oxidase expression remain to be established, the resulting elevated levels of amine oxidase activities found in human adipocytes may be of potential interest for therapeutic intervention in obesity.
Asunto(s)
Adipocitos/enzimología , Adipogénesis , Amina Oxidasa (conteniendo Cobre)/metabolismo , Monoaminooxidasa/metabolismo , Células 3T3 , Células 3T3-L1 , Adipocitos/metabolismo , Adulto , Amina Oxidasa (conteniendo Cobre)/genética , Animales , Diferenciación Celular/genética , Linaje de la Célula , Femenino , Humanos , Lactante , Ratones , Persona de Mediana Edad , Monoaminooxidasa/genética , ARN Mensajero/metabolismoRESUMEN
Obesity, i.e. an excess of white adipose tissue (WAT), predisposes to the development of type 2 diabetes and cardiovascular disease. Brown adipose tissue is present in rodents but not in adult humans. It expresses uncoupling protein 1 (UCP1) that allows dissipation of energy as heat. Peroxisome proliferator-activated receptor gamma (PPAR gamma) and PPAR gamma coactivator 1 alpha (PGC-1 alpha) activate mouse UCP1 gene transcription. We show here that human PGC-1 alpha induced the activation of the human UCP1 promoter by PPAR gamma. Adenovirus-mediated expression of human PGC-1 alpha increased the expression of UCP1, respiratory chain proteins, and fatty acid oxidation enzymes in human subcutaneous white adipocytes. Changes in the expression of other genes were also consistent with brown adipocyte mRNA expression profile. PGC-1 alpha increased the palmitate oxidation rate by fat cells. Human white adipocytes can therefore acquire typical features of brown fat cells. The PPAR gamma agonist rosiglitazone potentiated the effect of PGC-1 alpha on UCP1 expression and fatty acid oxidation. Hence, PGC-1 alpha is able to direct human WAT PPAR gamma toward a transcriptional program linked to energy dissipation. However, the response of typical white adipocyte targets to rosiglitazone treatment was not altered by PGC-1 alpha. UCP1 mRNA induction was shown in vivo by injection of the PGC-1 alpha adenovirus in mouse white fat. Alteration of energy balance through an increased utilization of fat in WAT may be a conceivable strategy for the treatment of obesity.