RESUMO
RATIONALE: Fatty acid oxidation is transcriptionally regulated by peroxisome proliferator-activated receptor (PPAR)α and under normal conditions accounts for 70% of cardiac ATP content. Reduced Ppara expression during sepsis and heart failure leads to reduced fatty acid oxidation and myocardial energy deficiency. Many of the transcriptional regulators of Ppara are unknown. OBJECTIVE: To determine the role of Krüppel-like factor 5 (KLF5) in transcriptional regulation of Ppara. METHODS AND RESULTS: We discovered that KLF5 activates Ppara gene expression via direct promoter binding. This is blocked in hearts of septic mice by c-Jun, which binds an overlapping site on the Ppara promoter and reduces transcription. We generated cardiac myocyte-specific Klf5 knockout mice that showed reduced expression of cardiac Ppara and its downstream fatty acid metabolism-related targets. These changes were associated with reduced cardiac fatty acid oxidation, ATP levels, increased triglyceride accumulation, and cardiac dysfunction. Diabetic mice showed parallel changes in cardiac Klf5 and Ppara expression levels. CONCLUSIONS: Cardiac myocyte KLF5 is a transcriptional regulator of Ppara and cardiac energetics.
Assuntos
Cardiomiopatia Dilatada/metabolismo , Diabetes Mellitus Experimental/metabolismo , Metabolismo Energético , Fatores de Transcrição Kruppel-Like/metabolismo , Miócitos Cardíacos/metabolismo , PPAR alfa/metabolismo , Sepse/metabolismo , Animais , Sítios de Ligação , Ligação Competitiva , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/fisiopatologia , Linhagem Celular , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/fisiopatologia , Ácidos Graxos/metabolismo , Genótipo , Fatores de Transcrição Kruppel-Like/deficiência , Fatores de Transcrição Kruppel-Like/genética , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oxirredução , PPAR alfa/genética , Fenótipo , Regiões Promotoras Genéticas , Ligação Proteica , Proteínas Proto-Oncogênicas c-jun/metabolismo , Sepse/genética , Sepse/fisiopatologia , Transdução de Sinais , Transportador 2 de Glucose-Sódio/genética , Transportador 2 de Glucose-Sódio/metabolismo , Inibidores do Transportador 2 de Sódio-Glicose , Fatores de Tempo , Transcrição Gênica , Ativação Transcricional , Transfecção , Triglicerídeos/metabolismo , Regulação para CimaRESUMO
OBJECTIVE: Diabetic hypertriglyceridemia is thought to be primarily driven by increased hepatic de novo lipogenesis. However, experiments in animal models indicated that insulin deficiency should decrease hepatic de novo lipogenesis and reduce plasma triglyceride levels. APPROACH AND RESULTS: To address the discrepancy between human data and genetically altered mouse models, we investigated whether insulin-deficient diabetic mice had triglyceride changes that resemble those in diabetic humans. Streptozotocin-induced insulin deficiency increased plasma triglyceride levels in mice. Contrary to the mouse models with impaired hepatic insulin receptor signaling, insulin deficiency did not reduce hepatic triglyceride secretion and de novo lipogenesis-related gene expression. Diabetic mice had a marked decrease in postprandial triglycerides clearance, which was associated with decreased lipoprotein lipase and peroxisome proliferator-activated receptor α mRNA levels in peripheral tissues and decreased lipoprotein lipase activity in skeletal muscle, heart, and brown adipose tissue. Diabetic heterozygous lipoprotein lipase knockout mice had markedly elevated fasting plasma triglyceride levels and prolonged postprandial triglycerides clearance. CONCLUSIONS: Insulin deficiency causes hypertriglyceridemia by decreasing peripheral lipolysis and not by an increase in hepatic triglycerides production and secretion.
Assuntos
Diabetes Mellitus Experimental/metabolismo , Hipertrigliceridemia/metabolismo , Insulina/sangue , Lipólise , Fígado/metabolismo , Estreptozocina , Triglicerídeos/sangue , Tecido Adiposo Marrom/metabolismo , Animais , Biomarcadores/sangue , Glicemia/metabolismo , Diabetes Mellitus Experimental/sangue , Diabetes Mellitus Experimental/induzido quimicamente , Diabetes Mellitus Experimental/genética , Hipertrigliceridemia/sangue , Hipertrigliceridemia/induzido quimicamente , Hipertrigliceridemia/genética , Lipogênese , Lipase Lipoproteica/deficiência , Lipase Lipoproteica/genética , Lipase Lipoproteica/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , PPAR alfa/genética , PPAR alfa/metabolismo , PPAR delta/genética , PPAR delta/metabolismo , Período Pós-Prandial , RNA Mensageiro/metabolismo , Transdução de Sinais , Fatores de TempoRESUMO
Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final step in triglyceride synthesis, the conversion of diacylglycerol (DAG) to triglyceride. Dgat1(-/-) mice exhibit a number of beneficial metabolic effects including reduced obesity and improved insulin sensitivity and no known cardiac dysfunction. In contrast, failing human hearts have severely reduced DGAT1 expression associated with accumulation of DAGs and ceramides. To test whether DGAT1 loss alone affects heart function, we created cardiomyocyte-specific DGAT1 knock-out (hDgat1(-/-)) mice. hDgat1(-/-) mouse hearts had 95% increased DAG and 85% increased ceramides compared with floxed controls. 50% of these mice died by 9 months of age. The heart failure marker brain natriuretic peptide increased 5-fold in hDgat1(-/-) hearts, and fractional shortening (FS) was reduced. This was associated with increased expression of peroxisome proliferator-activated receptor α and cluster of differentiation 36. We crossed hDgat1(-/-) mice with previously described enterocyte-specific Dgat1 knock-out mice (hiDgat1(-/-)). This corrected the early mortality, improved FS, and reduced cardiac ceramide and DAG content. Treatment of hDgat1(-/-) mice with the glucagon-like peptide 1 receptor agonist exenatide also improved FS and reduced heart DAG and ceramide content. Increased fatty acid uptake into hDgat1(-/-) hearts was normalized by exenatide. Reduced activation of protein kinase Cα (PKCα), which is increased by DAG and ceramides, paralleled the reductions in these lipids. Our mouse studies show that loss of DGAT1 reproduces the lipid abnormalities seen in severe human heart failure.
Assuntos
Insuficiência Cardíaca/sangue , Insuficiência Cardíaca/enzimologia , Lipídeos/sangue , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/patologia , Envelhecimento/patologia , Animais , Glicemia/metabolismo , Colesterol/sangue , Diacilglicerol O-Aciltransferase/antagonistas & inibidores , Diacilglicerol O-Aciltransferase/metabolismo , Inibidores Enzimáticos/farmacologia , Exenatida , Ácidos Graxos/sangue , Deleção de Genes , Regulação da Expressão Gênica/efeitos dos fármacos , Insuficiência Cardíaca/genética , Humanos , Intestinos/efeitos dos fármacos , Intestinos/patologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Miocárdio/metabolismo , Miocárdio/patologia , Miócitos Cardíacos/efeitos dos fármacos , Especificidade de Órgãos , Peptídeos/farmacologia , Fenótipo , Proteína Quinase C/metabolismo , Triglicerídeos/sangue , Peçonhas/farmacologiaRESUMO
The intestinal microbiota enhances dietary energy harvest leading to increased fat storage in adipose tissues. This effect is caused in part by the microbial suppression of intestinal epithelial expression of a circulating inhibitor of lipoprotein lipase called Angiopoietin-like 4 (Angptl4/Fiaf). To define the cis-regulatory mechanisms underlying intestine-specific and microbial control of Angptl4 transcription, we utilized the zebrafish system in which host regulatory DNA can be rapidly analyzed in a live, transparent, and gnotobiotic vertebrate. We found that zebrafish angptl4 is transcribed in multiple tissues including the liver, pancreatic islet, and intestinal epithelium, which is similar to its mammalian homologs. Zebrafish angptl4 is also specifically suppressed in the intestinal epithelium upon colonization with a microbiota. In vivo transgenic reporter assays identified discrete tissue-specific regulatory modules within angptl4 intron 3 sufficient to drive expression in the liver, pancreatic islet ß-cells, or intestinal enterocytes. Comparative sequence analyses and heterologous functional assays of angptl4 intron 3 sequences from 12 teleost fish species revealed differential evolution of the islet and intestinal regulatory modules. High-resolution functional mapping and site-directed mutagenesis defined the minimal set of regulatory sequences required for intestinal activity. Strikingly, the microbiota suppressed the transcriptional activity of the intestine-specific regulatory module similar to the endogenous angptl4 gene. These results suggest that the microbiota might regulate host intestinal Angptl4 protein expression and peripheral fat storage by suppressing the activity of an intestine-specific transcriptional enhancer. This study provides a useful paradigm for understanding how microbial signals interact with tissue-specific regulatory networks to control the activity and evolution of host gene transcription.
Assuntos
Angiopoietinas , Mucosa Intestinal/microbiologia , Sequências Reguladoras de Ácido Nucleico , Peixe-Zebra , Proteína 4 Semelhante a Angiopoietina , Angiopoietinas/genética , Angiopoietinas/metabolismo , Animais , Sequência Conservada , Evolução Molecular , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Mucosa Intestinal/embriologia , Mucosa Intestinal/metabolismo , Íntrons , Mamíferos , Mutagênese Sítio-Dirigida , Especificidade de Órgãos , Sequências Reguladoras de Ácido Nucleico/genética , Transcrição Gênica , Peixe-Zebra/embriologia , Peixe-Zebra/genética , Peixe-Zebra/microbiologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
The rodent heart accumulates TGs and lipid droplets during fasting. The sources of heart lipids could be either FFAs liberated from adipose tissue or FAs from lipoprotein-associated TGs via the action of lipoprotein lipase (LpL). Because circulating levels of FFAs increase during fasting, it has been assumed that albumin transported FFAs are the source of lipids within heart lipid droplets. We studied mice with three genetic mutations: peroxisomal proliferator-activated receptor α deficiency, cluster of differentiation 36 (CD36) deficiency, and heart-specific LpL deletion. All three genetically altered groups of mice had defective accumulation of lipid droplet TGs. Moreover, hearts from mice treated with poloxamer 407, an inhibitor of lipoprotein TG lipolysis, also failed to accumulate TGs, despite increased uptake of FFAs. TG storage did not impair maximal cardiac function as measured by stress echocardiography. Thus, LpL hydrolysis of circulating lipoproteins is required for the accumulation of lipids in the heart of fasting mice.
Assuntos
Gotículas Lipídicas/fisiologia , Lipase Lipoproteica/fisiologia , Miocárdio/metabolismo , Animais , Jejum , Hidrólise , Metabolismo dos Lipídeos , Lipoproteínas/sangue , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , PPAR alfa/genética , Perilipina-2 , Perilipina-5 , Proteínas/metabolismo , Sístole , Triglicerídeos/sangueRESUMO
Dietary carotenoids like ß-carotene are converted within the body either to retinoid, via ß-carotene-15,15'-dioxygenase (BCO1), or to ß-apo-carotenoids, via ß-carotene-9',10'-oxygenase 2. Some ß-apo-carotenoids are potent antagonists of retinoic acid receptor (RAR)-mediated transcriptional regulation, which is required to ensure normal heart development and functions. We established liquid chromatography tandem mass spectrometery methods for measuring concentrations of 10 ß-apo-carotenoids in mouse plasma, liver, and heart and assessed how these are influenced by Bco1 deficiency and ß-carotene intake. Surprisingly, Bco1(-/-) mice had an increase in heart levels of retinol, nonesterified fatty acids, and ceramides and a decrease in heart triglycerides. These lipid changes were accompanied by elevations in levels of genes important to retinoid metabolism, specifically retinol dehydrogenase 10 and retinol-binding protein 4, as well as genes involved in lipid metabolism, including peroxisome proliferator-activated receptor-γ, lipoprotein lipase, Cd36, stearoyl-CoA desaturase 1, and fatty acid synthase. We also obtained evidence of compromised heart function, as assessed by two-dimensional echocardiography, in Bco1(-/-) mice. However, the total absence of Bco1 did not substantially affect ß-apo-carotenoid concentrations in the heart. ß-Carotene administration to matched Bco1(-/-) and wild-type mice elevated total ß-apo-carotenal levels in the heart, liver, and plasma and total ß-apo-carotenoic acid levels in the liver. Thus, BCO1 modulates heart metabolism and function, possibly by altering levels of cofactors required for the actions of nuclear hormone receptors.
Assuntos
Cardiopatias/genética , Metabolismo dos Lipídeos/genética , Retinoides/metabolismo , beta-Caroteno 15,15'-Mono-Oxigenase/deficiência , beta-Caroteno 15,15'-Mono-Oxigenase/genética , Animais , Carotenoides/metabolismo , Cardiopatias/enzimologia , Cardiopatias/metabolismo , Homeostase , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Miocárdio/metabolismoRESUMO
BACKGROUND: Diabetes mellitus and obesity, which confer an increased risk of sudden cardiac death, are associated with cardiomyocyte lipid accumulation and altered cardiac electric properties, manifested by prolongation of the QRS duration and QT interval. It is difficult to distinguish the contribution of cardiomyocyte lipid accumulation from the contribution of global metabolic defects to the increased incidence of sudden death and electric abnormalities. METHODS AND RESULTS: In order to study the effects of metabolic abnormalities on arrhythmias without the complex systemic effects of diabetes mellitus and obesity, we studied transgenic mice with cardiac-specific overexpression of peroxisome proliferator-activated receptor γ 1 (PPARγ1) via the cardiac α-myosin heavy-chain promoter. The PPARγ transgenic mice develop abnormal accumulation of intracellular lipids and die as young adults before any significant reduction in systolic function. Using implantable ECG telemeters, we found that these mice have prolongation of the QRS and QT intervals and spontaneous ventricular arrhythmias, including polymorphic ventricular tachycardia and ventricular fibrillation. Isolated cardiomyocytes demonstrated prolonged action potential duration caused by reduced expression and function of the potassium channels responsible for repolarization. Short-term exposure to pioglitazone, a PPARγ agonist, had no effect on mortality or rhythm in WT mice but further exacerbated the arrhythmic phenotype and increased the mortality in the PPARγ transgenic mice. CONCLUSIONS: Our findings support an important link between PPARγ activation, cardiomyocyte lipid accumulation, ion channel remodeling, and increased cardiac mortality.
Assuntos
PPAR gama/genética , Período Refratário Eletrofisiológico/fisiologia , Taquicardia Ventricular/fisiopatologia , Fibrilação Ventricular/fisiopatologia , Potenciais de Ação/fisiologia , Animais , Cálcio/metabolismo , Conexina 43/genética , Conexina 43/metabolismo , Morte Súbita Cardíaca/epidemiologia , Modelos Animais de Doenças , Eletrocardiografia , Hipoglicemiantes/farmacologia , Incidência , Lipídeo A/metabolismo , Camundongos , Camundongos Transgênicos , Miocárdio/metabolismo , Miócitos Cardíacos/citologia , Miócitos Cardíacos/fisiologia , PPAR gama/fisiologia , Fenótipo , Pioglitazona , Potássio/metabolismo , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , Canais de Potássio de Abertura Dependente da Tensão da Membrana/fisiologia , Período Refratário Eletrofisiológico/efeitos dos fármacos , Sódio/metabolismo , Taquicardia Ventricular/genética , Taquicardia Ventricular/mortalidade , Tiazolidinedionas/farmacologia , Fibrilação Ventricular/genética , Fibrilação Ventricular/mortalidade , Remodelação Ventricular/fisiologiaRESUMO
The global obesity epidemic demands an improved understanding of the developmental and environmental factors regulating fat storage. Adipocytes serve as major sites of fat storage and as regulators of energy balance and inflammation. The optical transparency of developing zebrafish provides new opportunities to investigate mechanisms governing adipocyte biology, however zebrafish adipocytes remain uncharacterized. We have developed methods for visualizing zebrafish adipocytes in vivo by labeling neutral lipid droplets with Nile Red. Our results establish that neutral lipid droplets first accumulate in visceral adipocytes during larval stages and increase in number and distribution as zebrafish grow. We show that the cellular anatomy of zebrafish adipocytes is similar to mammalian white adipocytes and identify peroxisome-proliferator activated receptor gamma and fatty acid binding protein 11a as markers of the zebrafish adipocyte lineage. By monitoring adipocyte development prior to neutral lipid deposition, we find that the first visceral preadipocytes appear in association with the pancreas shortly after initiation of exogenous nutrition. Zebrafish reared in the absence of food fail to form visceral preadipocytes, indicating that exogenous nutrition is required for adipocyte development. These results reveal homologies between zebrafish and mammalian adipocytes and establish the zebrafish as a new model for adipocyte research.
Assuntos
Adipócitos/fisiologia , Adipogenia/fisiologia , Alimentos , Gordura Intra-Abdominal/crescimento & desenvolvimento , Lipídeos/fisiologia , Modelos Animais , Peixe-Zebra/fisiologia , Adipócitos/ultraestrutura , Animais , Composição Corporal , Distribuição da Gordura Corporal , Peso Corporal , Proteínas de Ligação a Ácido Graxo/genética , Corantes Fluorescentes , Privação de Alimentos/fisiologia , Expressão Gênica , Coração/crescimento & desenvolvimento , Sistema Hematopoético/crescimento & desenvolvimento , Gordura Intra-Abdominal/embriologia , Lipídeos/análise , Estado Nutricional , Oxazinas , PPAR gama/genética , Pâncreas/crescimento & desenvolvimento , RNA Mensageiro/análise , Imagem Corporal Total/métodos , Peixe-Zebra/anatomia & histologia , Peixe-Zebra/embriologia , Peixe-Zebra/crescimento & desenvolvimento , Proteínas de Peixe-Zebra/genéticaRESUMO
Numerous studies have connected the gut microbiome with diet-induced obesity; however, mechanistic explanations for the host-microbial interactions are needed. Perry et al. (2016) present studies suggesting that microbially produced acetate (MPA) increases post-prandial insulin release via a sequential and integrated gut, brain, and pancreatic signaling network promoting energy retention.
Assuntos
Metabolismo Energético , Trato Gastrointestinal , Acetatos , Dieta , Humanos , ObesidadeRESUMO
BACKGROUND: Obesity, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD) are serious health concerns, especially in Western populations. Antibiotic exposure and high-fat diet (HFD) are important and modifiable factors that may contribute to these diseases. METHODS: To investigate the relationship of antibiotic exposure with microbiome perturbations in a murine model of growth promotion, C57BL/6 mice received lifelong sub-therapeutic antibiotic treatment (STAT), or not (control), and were fed HFD starting at 13 weeks. To characterize microbiota changes caused by STAT, the V4 region of the 16S rRNA gene was examined from collected fecal samples and analyzed. RESULTS: In this model, which included HFD, STAT mice developed increased weight and fat mass compared to controls. Although results in males and females were not identical, insulin resistance and NAFLD were more severe in the STAT mice. Fecal microbiota from STAT mice were distinct from controls. Compared with controls, STAT exposure led to early conserved diet-independent microbiota changes indicative of an immature microbial community. Key taxa were identified as STAT-specific and several were found to be predictive of disease. Inferred network models showed topological shifts concurrent with growth promotion and suggest the presence of keystone species. CONCLUSIONS: These studies form the basis for new models of type 2 diabetes and NAFLD that involve microbiome perturbation.
Assuntos
Adiposidade , Antibacterianos/farmacologia , Dieta Hiperlipídica/efeitos adversos , Microbioma Gastrointestinal/efeitos dos fármacos , Resistência à Insulina , Hepatopatias/etiologia , Hepatopatias/metabolismo , Adiposidade/efeitos dos fármacos , Animais , Biodiversidade , Composição Corporal , Peso Corporal , Citocinas/sangue , Modelos Animais de Doenças , Metabolismo Energético/efeitos dos fármacos , Glucose/metabolismo , Homeostase/efeitos dos fármacos , Hormônios/sangue , Mediadores da Inflamação/sangue , Insulina/metabolismo , Metabolismo dos Lipídeos , Hepatopatias/microbiologia , Metagenoma , Metagenômica , Camundongos , Hepatopatia Gordurosa não Alcoólica/etiologia , Hepatopatia Gordurosa não Alcoólica/metabolismo , Hepatopatia Gordurosa não Alcoólica/microbiologia , Fenótipo , Filogenia , RNA Ribossômico 16S/genética , Fatores de TempoRESUMO
BACKGROUND: Diabetes and obesity are associated with an increased risk of arrhythmia and sudden cardiac death. Abnormal lipid accumulation is observed in cardiomyocytes of obese and diabetic patients, which may contribute to arrhythmia, but the mechanisms are poorly understood. A transgenic mouse model of cardiac lipid overload, the peroxisome proliferator-activated receptor-γ (PPARg) cardiac overexpression mouse, has long QT and increased ventricular ectopy. OBJECTIVE: The purpose of this study was to evaluate the hypothesis that the increase in ventricular ectopy during cardiac lipid overload is caused by abnormalities in calcium handling due to increased mitochondrial oxidative stress. METHODS: Ventricular myocytes were isolated from adult mouse hearts to record sparks and calcium transients. Mice were implanted with heart rhythm monitors for in vivo recordings. RESULTS: PPARg cardiomyocytes have more frequent triggered activity and increased sparks compared to control. Sparks and triggered activity are reduced by mitotempo, a mitochondrial-targeted antioxidant. This is explained by a significant increase in oxidation of RyR2. Calcium transients are increased in amplitude, and sarcoplasmic reticulum (SR) calcium stores are increased in PPARg cardiomyocytes. Computer modeling of the cardiac action potential demonstrates that long QT contributes to increased SR calcium. Mitotempo decreased ventricular ectopy in vivo. CONCLUSION: During cardiac lipid overload, mitochondrial oxidative stress causes increased SR calcium leak by oxidizing RyR2 channels. This promotes ventricular ectopy, which is significantly reduced in vivo by a mitochondrial-targeted antioxidant. These results suggest a potential role for mitochondrial-targeted antioxidants in preventing arrhythmia and sudden cardiac death in obese and diabetic patients.
Assuntos
Arritmias Cardíacas/metabolismo , Cálcio/metabolismo , Metabolismo dos Lipídeos , Mitocôndrias Cardíacas/metabolismo , Miócitos Cardíacos/metabolismo , Estresse Oxidativo , PPAR gama/biossíntese , Animais , Arritmias Cardíacas/patologia , Modelos Animais de Doenças , Líquido Intracelular/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Miócitos Cardíacos/patologiaRESUMO
In vitro studies have demonstrated a critical role for high-mobility group box 1 (HMGB1) in autophagy and the autophagic clearance of dysfunctional mitochondria, resulting in severe mitochondrial fragmentation and profound disturbances of mitochondrial respiration in HMGB1-deficient cells. Here, we investigated the effects of HMGB1 deficiency on autophagy and mitochondrial function in vivo, using conditional Hmgb1 ablation in the liver and heart. Unexpectedly, deletion of Hmgb1 in hepatocytes or cardiomyocytes, two cell types with abundant mitochondria, did not alter mitochondrial structure or function, organ function, or long-term survival. Moreover, hepatic autophagy and mitophagy occurred normally in the absence of Hmgb1, and absence of Hmgb1 did not significantly affect baseline and glucocorticoid-induced hepatic gene expression. Collectively, our findings suggest that HMGB1 is dispensable for autophagy, mitochondrial quality control, the regulation of gene expression, and organ function in the adult organism.
Assuntos
Autofagia , Proteína HMGB1/metabolismo , Mitocôndrias/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Glicemia/metabolismo , Metabolismo Energético , Expressão Gênica , Proteína HMGB1/genética , Fígado/metabolismo , Fígado/patologia , Camundongos , Camundongos Transgênicos , Miócitos Cardíacos/metabolismo , Fosforilação Oxidativa , RNA Mensageiro/metabolismoRESUMO
BACKGROUND: Cardiac dysfunction with sepsis is associated with both inflammation and reduced fatty acid oxidation. We hypothesized that energy deprivation accounts for sepsis-related cardiac dysfunction. METHODS AND RESULTS: Escherichia coli lipopolysaccharide (LPS) administered to C57BL/6 mice (wild type) induced cardiac dysfunction and reduced fatty acid oxidation and mRNA levels of peroxisome proliferator-activated receptor (PPAR)-α and its downstream targets within 6-8 hours. Transgenic mice in which cardiomyocyte-specific expression of PPARγ is driven by the α-myosin heavy chain promoter (αMHC-PPARγ) were protected from LPS-induced cardiac dysfunction. Despite a reduction in PPARα, fatty acid oxidation and associated genes were not decreased in hearts of LPS-treated αMHC-PPARγ mice. LPS treatment, however, continued to induce inflammation-related genes, such as interleukin-1α, interleukin-1ß, interleukin-6, and tumor necrosis factor-α in hearts of αMHC-PPARγ mice. Treatment of wild-type mice with LPS and the PPARγ agonist, rosiglitazone, but not the PPARα agonist (WY-14643), increased fatty acid oxidation, prevented LPS-mediated reduction of mitochondria, and treated cardiac dysfunction, as well as it improved survival, despite continued increases in the expression of cardiac inflammatory markers. CONCLUSIONS: Activation of PPARγ in LPS-treated mice prevented cardiac dysfunction and mortality, despite development of cardiac inflammation and PPARα downregulation.
Assuntos
Cardiopatias/fisiopatologia , PPAR gama/metabolismo , Sepse/complicações , Animais , Ácidos Graxos/metabolismo , Cardiopatias/mortalidade , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Miocárdio/metabolismo , PPAR gama/agonistas , Rosiglitazona , Sepse/fisiopatologia , Sepse/terapia , Tiazolidinedionas/farmacologia , Disfunção Ventricular Esquerda/fisiopatologiaRESUMO
The heart has both the greatest caloric needs and the most robust oxidation of fatty acids (FAs). Under pathological conditions such as obesity and type 2 diabetes, cardiac uptake and oxidation are not balanced and hearts accumulate lipid potentially leading to cardiac lipotoxicity. We will first review the pathways utilized by the heart to acquire FAs from the circulation and to store triglyceride intracellularly. Then we will describe mouse models in which excess lipid accumulation causes heart dysfunction and experiments performed to alleviate this toxicity. Finally, the known relationships between heart lipid metabolism and dysfunction in humans will be summarized.
Assuntos
Metabolismo dos Lipídeos , Miocárdio/metabolismo , Animais , Cardiomiopatias/etiologia , Cardiomiopatias/metabolismo , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/metabolismo , Metabolismo Energético , Ácidos Graxos/sangue , Ácidos Graxos/metabolismo , Humanos , Miocárdio/patologia , Obesidade/complicações , Obesidade/metabolismoRESUMO
Complex microbial communities reside within the intestines of humans and other vertebrates. Remarkably little is known about how these microbial consortia are established in various locations within the gut, how members of these consortia behave within their dynamic ecosystems, or what microbial factors mediate mutually beneficial host-microbial interactions. Using a gnotobiotic zebrafish-Pseudomonas aeruginosa model, we show that the transparency of this vertebrate species, coupled with methods for raising these animals under germ-free conditions can be used to monitor microbial movement and localization within the intestine in vivo and in real time. Germ-free zebrafish colonized with isogenic P. aeruginosa strains containing deletions of genes related to motility and pathogenesis revealed that loss of flagellar function results in attenuation of evolutionarily conserved host innate immune responses but not conserved nutrient responses. These results demonstrate the utility of gnotobiotic zebrafish in defining the behavior and localization of bacteria within the living vertebrate gut, identifying bacterial genes that affect these processes, and assessing the impact of these genes on host-microbial interactions.
Assuntos
Intestinos/microbiologia , Movimento , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/fisiologia , Simbiose , Peixe-Zebra/microbiologia , Animais , Flagelos/genética , Flagelos/fisiologia , Vida Livre de Germes , Intestinos/imunologia , Intestinos/ultraestrutura , Microscopia Eletrônica de Transmissão , Pseudomonas aeruginosa/imunologia , Pseudomonas aeruginosa/ultraestrutura , Simbiose/genética , Fatores de Tempo , Peixe-Zebra/imunologiaRESUMO
The metabolic syndrome is currently defined by various combinations of insulin resistance, obesity, dyslipidaemia and hypertension. The tendency for these risk factors to appear simultaneously suggests a single aetiologic basis. A low level of circulating adiponectin is associated with the appearance of each metabolic syndrome risk factor. The following review summarizes a large body of evidence that suggests a low level of circulating adiponectin represents an independent risk factor and a possible biomarker for the metabolic syndrome. An association between the metabolic syndrome and low adiponectin supports the view that the development of the metabolic syndrome may be triggered by a single underlying mechanism. Clinical studies in the future may show that a low level of circulating adiponectin is a primary biomarker for a specific cluster of metabolic syndrome risk factors rather than all the possible combinations of risk factors currently used to identify the metabolic syndrome. The significance of low circulating adiponectin in risk assessment models should ultimately be compared against insulin resistance, obesity, dyslipidaemia, hypertension and other metabolic syndrome risk factors presently under consideration. Adiponectin can be measured reliably in a clinical setting; circulating values of adiponectin do not fluctuate on a diurnal basis as much as insulin, glucose, triglycerides or cholesterol and only 2-4 microl of blood are currently needed for its measurement.
Assuntos
Adiponectina/sangue , Síndrome Metabólica/sangue , Biomarcadores/sangue , Dislipidemias/sangue , Humanos , Hipertensão/sangue , Resistência à Insulina , Síndrome Metabólica/diagnóstico , Obesidade/sangue , Fatores de RiscoRESUMO
Glucose metabolism is altered in long-lived people and mice. Although it is clear that there is an association between altered glucose metabolism and longevity, it is not known whether this link is causal or not. Our current hypothesis is that decreased fasting glucose utilization may increase longevity by reducing oxygen radical production, a potential cause of aging. We observed that whole body fasting glucose utilization was lower in the Snell dwarf, a long-lived mutant mouse. Whole body fasting glucose utilization may be reduced by a decrease in the production of circulating glucose. Our isotope labeling analysis indicated both gluconeogenesis and glycogenolysis were suppressed in Snell dwarfs. Elevated circulating adiponectin may contribute to the reduction of glucose production in Snell dwarfs. Adiponectin lowered the appearance of glucose in the media over hepatoma cells by suppressing gluconeogenesis and glycogenolysis. The suppression of glucose production by adiponectin in vitro depended on AMP-activated protein kinase, a cell mediator of fatty acid oxidation. Elevated fatty acid oxidation was indicated in Snell dwarfs by increased utilization of circulating oleic acid, reduced intracellular triglyceride content, and increased phosphorylation of acetyl-CoA carboxylase. Finally, protein carbonyl content, a marker of oxygen radical damage, was decreased in Snell dwarfs. The correlation between high glucose utilization and elevated oxygen radical production was also observed in vitro by altering the concentrations of glucose and fatty acids in the media or pharmacologic inhibition of glucose and fatty acid oxidation with 4-hydroxycyanocinnamic acid and etomoxir, respectively.