RESUMO
The future of healthcare for cardiovascular diseases holds immense promise, not only based in new discoveries in cardiac metabolism but also in translating them to solutions for critical challenges faced by society. Here, ten scientists share their insights, shedding light on the future that lies ahead for this field.
Assuntos
Doenças Cardiovasculares , Humanos , Doenças Cardiovasculares/metabolismo , Doenças Cardiovasculares/terapia , Pesquisa Translacional Biomédica , AnimaisRESUMO
Normal energy metabolism is characterized by periodic shifts in glucose and fat oxidation, as the mitochondrial machinery responsible for carbon combustion switches freely between alternative fuels according to physiological and nutritional circumstances. These transitions in fuel choice are orchestrated by an intricate network of metabolic and cell signaling events that enable exquisite crosstalk and cooperation between competing substrates to maintain energy and glucose homeostasis. By contrast, obesity-related cardiometabolic diseases are increasingly recognized as disorders of metabolic inflexibility, in which nutrient overload and heightened substrate competition result in mitochondrial indecision, impaired fuel switching, and energy dysregulation. This Perspective offers a speculative view on the molecular origins and pathophysiological consequences of metabolic inflexibility.
Assuntos
Metabolismo Energético , Síndrome Metabólica/metabolismo , Mitocôndrias/metabolismo , Animais , Respiração Celular , Dieta , Glucose/metabolismo , Humanos , Resistência à Insulina , Modelos BiológicosRESUMO
Differences in chromatin organization are key to the multiplicity of cell states that arise from a single genetic background, yet the landscapes of in vivo tissues remain largely uncharted. Here, we mapped chromatin genome-wide in a large and diverse collection of human tissues and stem cells. The maps yield unprecedented annotations of functional genomic elements and their regulation across developmental stages, lineages, and cellular environments. They also reveal global features of the epigenome, related to nuclear architecture, that also vary across cellular phenotypes. Specifically, developmental specification is accompanied by progressive chromatin restriction as the default state transitions from dynamic remodeling to generalized compaction. Exposure to serum in vitro triggers a distinct transition that involves de novo establishment of domains with features of constitutive heterochromatin. We describe how these global chromatin state transitions relate to chromosome and nuclear architecture, and discuss their implications for lineage fidelity, cellular senescence, and reprogramming.
Assuntos
Montagem e Desmontagem da Cromatina , Cromatina/metabolismo , Epigênese Genética , Interação Gene-Ambiente , Estudo de Associação Genômica Ampla , Núcleo Celular , Senescência Celular , Células-Tronco Embrionárias/metabolismo , Regulação da Expressão Gênica , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Especificidade de ÓrgãosRESUMO
RATIONALE: Circumstantial evidence links the development of heart failure to posttranslational modifications of mitochondrial proteins, including lysine acetylation (Kac). Nonetheless, direct evidence that Kac compromises mitochondrial performance remains sparse. OBJECTIVE: This study sought to explore the premise that mitochondrial Kac contributes to heart failure by disrupting oxidative metabolism. METHODS AND RESULTS: A DKO (dual knockout) mouse line with deficiencies in CrAT (carnitine acetyltransferase) and Sirt3 (sirtuin 3)-enzymes that oppose Kac by buffering the acetyl group pool and catalyzing lysine deacetylation, respectively-was developed to model extreme mitochondrial Kac in cardiac muscle, as confirmed by quantitative acetyl-proteomics. The resulting impact on mitochondrial bioenergetics was evaluated using a respiratory diagnostics platform that permits comprehensive assessment of mitochondrial function and energy transduction. Susceptibility of DKO mice to heart failure was investigated using transaortic constriction as a model of cardiac pressure overload. The mitochondrial acetyl-lysine landscape of DKO hearts was elevated well beyond that observed in response to pressure overload or Sirt3 deficiency alone. Relative changes in the abundance of specific acetylated lysine peptides measured in DKO versus Sirt3 KO hearts were strongly correlated. A proteomics comparison across multiple settings of hyperacetylation revealed ≈86% overlap between the populations of Kac peptides affected by the DKO manipulation as compared with experimental heart failure. Despite the severity of cardiac Kac in DKO mice relative to other conditions, deep phenotyping of mitochondrial function revealed a surprisingly normal bioenergetics profile. Thus, of the >120 mitochondrial energy fluxes evaluated, including substrate-specific dehydrogenase activities, respiratory responses, redox charge, mitochondrial membrane potential, and electron leak, we found minimal evidence of oxidative insufficiencies. Similarly, DKO hearts were not more vulnerable to dysfunction caused by transaortic constriction-induced pressure overload. CONCLUSIONS: The findings challenge the premise that hyperacetylation per se threatens metabolic resilience in the myocardium by causing broad-ranging disruption to mitochondrial oxidative machinery.
Assuntos
Insuficiência Cardíaca/metabolismo , Mitocôndrias Cardíacas/metabolismo , Proteínas Mitocondriais/metabolismo , Miócitos Cardíacos/metabolismo , Proteoma , Acetilação , Animais , Carnitina O-Acetiltransferase/deficiência , Carnitina O-Acetiltransferase/genética , Modelos Animais de Doenças , Metabolismo Energético , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/fisiopatologia , Lisina , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Estresse Oxidativo , Processamento de Proteína Pós-Traducional , Proteômica , Sirtuína 3/deficiência , Sirtuína 3/genéticaRESUMO
Lipid metabolism is tightly controlled by the nutritional state of the organism. Nutrient-rich conditions increase lipogenesis, whereas nutrient deprivation promotes fat oxidation. In this study, we identify the mitochondrial sirtuin, SIRT4, as a regulator of lipid homeostasis. SIRT4 is active in nutrient-replete conditions to repress fatty acid oxidation while promoting lipid anabolism. SIRT4 deacetylates and inhibits malonyl CoA decarboxylase (MCD), an enzyme that produces acetyl CoA from malonyl CoA. Malonyl CoA provides the carbon skeleton for lipogenesis and also inhibits fat oxidation. Mice lacking SIRT4 display elevated MCD activity and decreased malonyl CoA in skeletal muscle and white adipose tissue. Consequently, SIRT4 KO mice display deregulated lipid metabolism, leading to increased exercise tolerance and protection against diet-induced obesity. In sum, this work elucidates SIRT4 as an important regulator of lipid homeostasis, identifies MCD as a SIRT4 target, and deepens our understanding of the malonyl CoA regulatory axis.
Assuntos
Carboxiliases/metabolismo , Metabolismo dos Lipídeos , Proteínas Mitocondriais/metabolismo , Sirtuínas/metabolismo , Acetilação , Tecido Adiposo Branco/metabolismo , Animais , Dieta , Ácidos Graxos/metabolismo , Metabolismo dos Lipídeos/genética , Lipídeos/biossíntese , Masculino , Camundongos , Camundongos Knockout , Proteínas Mitocondriais/genética , Obesidade/etiologia , Obesidade/metabolismo , Oxirredução , Sirtuínas/genéticaRESUMO
Genetic manipulation via transgene overexpression, RNAi, or Cas9-based methods is central to biomedical research. Unfortunately, use of these tools is often limited by vector options. We have created a modular platform (pMVP) that allows a gene of interest to be studied in the context of an array of promoters, epitope tags, conditional expression modalities, and fluorescent reporters, packaged in 35 custom destination vectors, including adenovirus, lentivirus, PiggyBac transposon, and Sleeping Beauty transposon, in aggregate >108,000 vector permutations. We also used pMVP to build an epigenetic engineering platform, pMAGIC, that packages multiple gRNAs and either Sa-dCas9 or x-dCas9(3.7) fused to one of five epigenetic modifiers. Importantly, via its compatibility with adenoviral vectors, pMAGIC uniquely enables use of dCas9/LSD1 fusions to interrogate enhancers within primary cells. To demonstrate this, we used pMAGIC to target Sa-dCas9/LSD1 and modify the epigenetic status of a conserved enhancer, resulting in altered expression of the homeobox transcription factor PDX1 and its target genes in pancreatic islets and insulinoma cells. In sum, the pMVP and pMAGIC systems empower researchers to rapidly generate purpose-built, customized vectors for manipulation of gene expression, including via targeted epigenetic modification of regulatory elements in a broad range of disease-relevant cell types.
Assuntos
Sistemas CRISPR-Cas/genética , Engenharia Genética/métodos , Vetores Genéticos/genética , Proteínas de Homeodomínio/genética , Transativadores/genética , Transgenes/genética , Adenoviridae/genética , Animais , Elementos de DNA Transponíveis/genética , Elementos Facilitadores Genéticos/genética , Epigenômica/métodos , Edição de Genes/métodos , Regulação da Expressão Gênica/genética , Células HEK293 , Histona Desmetilases/genética , Humanos , Insulinoma/metabolismo , Ilhotas Pancreáticas/metabolismo , Lentivirus/genética , Camundongos , Regiões Promotoras Genéticas/genética , RNA Guia de Cinetoplastídeos/genética , RatosRESUMO
Nearly unlimited supplies of energy-dense foods and technologies that encourage sedentary behaviour have introduced a new threat to the survival of our species: obesity and its co-morbidities. Foremost among the co-morbidities is type 2 diabetes, which is projected to afflict 300 million people worldwide by 2020. Compliance with lifestyle modifications such as reduced caloric intake and increased physical activity has proved to be difficult for the general population, meaning that pharmacological intervention may be the only recourse for some. This epidemiological reality heightens the urgency for gaining a deeper understanding of the processes that cause metabolic failure of key tissues and organ systems in type 2 diabetes, as reviewed here.
Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Resistência à Insulina/fisiologia , Células Secretoras de Insulina/patologia , Animais , Diabetes Mellitus Tipo 2/genética , Glucose/metabolismo , Humanos , Insulina/metabolismo , Transdução de SinaisRESUMO
Insulin resistance is a major risk factor for many diseases. However, its underlying mechanism remains unclear in part because it is triggered by a complex relationship between multiple factors, including genes and the environment. Here, we used metabolomics combined with computational methods to identify factors that classified insulin resistance across individual mice derived from three different mouse strains fed two different diets. Three inbred ILSXISS strains were fed high-fat or chow diets and subjected to metabolic phenotyping and metabolomics analysis of skeletal muscle. There was significant metabolic heterogeneity between strains, diets, and individual animals. Distinct metabolites were changed with insulin resistance, diet, and between strains. Computational analysis revealed 113 metabolites that were correlated with metabolic phenotypes. Using these 113 metabolites, combined with machine learning to segregate mice based on insulin sensitivity, we identified C22:1-CoA, C2-carnitine, and C16-ceramide as the best classifiers. Strikingly, when these three metabolites were combined into one signature, they classified mice based on insulin sensitivity more accurately than each metabolite on its own or other published metabolic signatures. Furthermore, C22:1-CoA was 2.3-fold higher in insulin-resistant mice and correlated significantly with insulin resistance. We have identified a metabolomic signature composed of three functionally unrelated metabolites that accurately predicts whole-body insulin sensitivity across three mouse strains. These data indicate the power of simultaneous analysis of individual, genetic, and environmental variance in mice for identifying novel factors that accurately predict metabolic phenotypes like whole-body insulin sensitivity.
Assuntos
Biologia Computacional/métodos , Dieta , Resistência à Insulina/fisiologia , Metaboloma , Metabolômica/métodos , Animais , Masculino , Camundongos , Camundongos EndogâmicosRESUMO
High concentrations of propionate and its metabolites are found in several diseases that are often associated with the development of cardiac dysfunction, such as obesity, diabetes, propionic acidemia, and methylmalonic acidemia. In the present work, we employed a stable isotope-based metabolic flux approach to understand propionate-mediated perturbation of cardiac energy metabolism. Propionate led to accumulation of propionyl-CoA (increased by ~101-fold) and methylmalonyl-CoA (increased by 36-fold). This accumulation caused significant mitochondrial CoA trapping and inhibited fatty acid oxidation. The reduced energy contribution from fatty acid oxidation was associated with increased glucose oxidation. The enhanced anaplerosis of propionate and CoA trapping altered the pool sizes of tricarboxylic acid cycle (TCA) metabolites. In addition to being an anaplerotic substrate, the accumulation of proprionate-derived malate increased the recycling of malate to pyruvate and acetyl-CoA, which can enter the TCA for energy production. Supplementation of 3 mM l-carnitine did not relieve CoA trapping and did not reverse the propionate-mediated fuel switch. This is due to new findings that the heart appears to lack the specific enzyme catalyzing the conversion of short-chain (C3 and C4) dicarboxylyl-CoAs to dicarboxylylcarnitines. The discovery of this work warrants further investigation on the relevance of dicarboxylylcarnitines, especially C3 and C4 dicarboxylylcarnitines, in cardiac conditions such as heart failure.
Assuntos
Carnitina/farmacologia , Coenzima A/metabolismo , Metabolismo Energético/efeitos dos fármacos , Coração/efeitos dos fármacos , Miocárdio/metabolismo , Propionatos/metabolismo , Acetilcoenzima A/metabolismo , Acil Coenzima A/metabolismo , Animais , Ciclo do Ácido Cítrico/efeitos dos fármacos , Ciclo do Ácido Cítrico/fisiologia , Metabolismo Energético/fisiologia , Ácidos Graxos/metabolismo , Glucose/metabolismo , Preparação de Coração Isolado , Fígado/metabolismo , Malatos/metabolismo , Masculino , Análise do Fluxo Metabólico , Mitocôndrias Cardíacas/efeitos dos fármacos , Mitocôndrias Cardíacas/metabolismo , Oxirredução/efeitos dos fármacos , Ácido Pirúvico/metabolismo , RatosRESUMO
In order to propagate a solid tumor, cancer cells must adapt to and survive under various tumor microenvironment (TME) stresses, such as hypoxia or lactic acidosis. To systematically identify genes that modulate cancer cell survival under stresses, we performed genome-wide shRNA screens under hypoxia or lactic acidosis. We discovered that genetic depletion of acetyl-CoA carboxylase (ACACA or ACC1) or ATP citrate lyase (ACLY) protected cancer cells from hypoxia-induced apoptosis. Additionally, the loss of ACLY or ACC1 reduced levels and activities of the oncogenic transcription factor ETV4. Silencing ETV4 also protected cells from hypoxia-induced apoptosis and led to remarkably similar transcriptional responses as with silenced ACLY or ACC1, including an anti-apoptotic program. Metabolomic analysis found that while α-ketoglutarate levels decrease under hypoxia in control cells, α-ketoglutarate is paradoxically increased under hypoxia when ACC1 or ACLY are depleted. Supplementation with α-ketoglutarate rescued the hypoxia-induced apoptosis and recapitulated the decreased expression and activity of ETV4, likely via an epigenetic mechanism. Therefore, ACC1 and ACLY regulate the levels of ETV4 under hypoxia via increased α-ketoglutarate. These results reveal that the ACC1/ACLY-α-ketoglutarate-ETV4 axis is a novel means by which metabolic states regulate transcriptional output for life vs. death decisions under hypoxia. Since many lipogenic inhibitors are under investigation as cancer therapeutics, our findings suggest that the use of these inhibitors will need to be carefully considered with respect to oncogenic drivers, tumor hypoxia, progression and dormancy. More broadly, our screen provides a framework for studying additional tumor cell stress-adaption mechanisms in the future.
Assuntos
ATP Citrato (pro-S)-Liase/genética , Acetil-CoA Carboxilase/genética , Proteínas E1A de Adenovirus/genética , Neoplasias/genética , Proteínas Proto-Oncogênicas/genética , ATP Citrato (pro-S)-Liase/antagonistas & inibidores , Acetil-CoA Carboxilase/antagonistas & inibidores , Proteínas E1A de Adenovirus/biossíntese , Apoptose/genética , Hipóxia Celular/genética , Linhagem Celular Tumoral , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Ácidos Cetoglutáricos/metabolismo , Ácidos Cetoglutáricos/farmacologia , Neoplasias/patologia , Proteínas Proto-Oncogênicas/biossíntese , Proteínas Proto-Oncogênicas c-ets , Microambiente Tumoral/genéticaRESUMO
Levels of certain circulating short-chain dicarboxylacylcarnitine (SCDA), long-chain dicarboxylacylcarnitine (LCDA) and medium chain acylcarnitine (MCA) metabolites are heritable and predict cardiovascular disease (CVD) events. Little is known about the biological pathways that influence levels of most of these metabolites. Here, we analyzed genetics, epigenetics, and transcriptomics with metabolomics in samples from a large CVD cohort to identify novel genetic markers for CVD and to better understand the role of metabolites in CVD pathogenesis. Using genomewide association in the CATHGEN cohort (N = 1490), we observed associations of several metabolites with genetic loci. Our strongest findings were for SCDA metabolite levels with variants in genes that regulate components of endoplasmic reticulum (ER) stress (USP3, HERC1, STIM1, SEL1L, FBXO25, SUGT1) These findings were validated in a second cohort of CATHGEN subjects (N = 2022, combined p = 8.4x10-6-2.3x10-10). Importantly, variants in these genes independently predicted CVD events. Association of genomewide methylation profiles with SCDA metabolites identified two ER stress genes as differentially methylated (BRSK2 and HOOK2). Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm. Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP. Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.
Assuntos
Doenças Cardiovasculares/genética , Metabolômica , Complexo de Endopeptidases do Proteassoma/genética , Locos de Características Quantitativas , Ubiquitina/genética , Doenças Cardiovasculares/patologia , Carnitina/análogos & derivados , Carnitina/metabolismo , Metilação de DNA , Estresse do Retículo Endoplasmático/genética , Humanos , Polimorfismo de Nucleotídeo Único , Fatores de RiscoRESUMO
BACKGROUND: Significant evidence indicates that the failing heart is energy starved. During the development of heart failure, the capacity of the heart to utilize fatty acids, the chief fuel, is diminished. Identification of alternate pathways for myocardial fuel oxidation could unveil novel strategies to treat heart failure. METHODS AND RESULTS: Quantitative mitochondrial proteomics was used to identify energy metabolic derangements that occur during the development of cardiac hypertrophy and heart failure in well-defined mouse models. As expected, the amounts of proteins involved in fatty acid utilization were downregulated in myocardial samples from the failing heart. Conversely, expression of ß-hydroxybutyrate dehydrogenase 1, a key enzyme in the ketone oxidation pathway, was increased in the heart failure samples. Studies of relative oxidation in an isolated heart preparation using ex vivo nuclear magnetic resonance combined with targeted quantitative myocardial metabolomic profiling using mass spectrometry revealed that the hypertrophied and failing heart shifts to oxidizing ketone bodies as a fuel source in the context of reduced capacity to oxidize fatty acids. Distinct myocardial metabolomic signatures of ketone oxidation were identified. CONCLUSIONS: These results indicate that the hypertrophied and failing heart shifts to ketone bodies as a significant fuel source for oxidative ATP production. Specific metabolite biosignatures of in vivo cardiac ketone utilization were identified. Future studies aimed at determining whether this fuel shift is adaptive or maladaptive could unveil new therapeutic strategies for heart failure.
Assuntos
Dieta Cetogênica/métodos , Ácidos Graxos/metabolismo , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/patologia , Corpos Cetônicos/metabolismo , Animais , Feminino , Perfilação da Expressão Gênica/métodos , Insuficiência Cardíaca/dietoterapia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Metabolic assay buffers often omit bicarbonate, which is susceptible to alkalinisation in an open environment. Here, we assessed the effect of including bicarbonate in respirometry experiments. By supplementing HEPES-buffered media with low concentrations of bicarbonate, we found increased respiration in adipocytes and hepatocytes, but not myotubes. This was observed across multiple respirometry platforms and was independent of effects on enhanced insulin sensitivity, pH drift, or mitochondrial function. Permeabilised cell experiments suggest that bicarbonate increases substrate availability, likely by acting as a cofactor for carboxylase enzymes. This emphasises the importance of buffer choice in experimental biology.
Assuntos
Adipócitos/efeitos dos fármacos , Bicarbonatos/farmacologia , Respiração Celular/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Células 3T3-L1 , Adipócitos/metabolismo , Animais , Carbono-Carbono Ligases/metabolismo , Células Cultivadas , Hepatócitos/metabolismo , Camundongos , Relação Estrutura-AtividadeRESUMO
Mitochondrial biology is the sum of diverse phenomena from molecular profiles to physiological functions. A mechanistic understanding of mitochondria in disease development, and hence the future prospect of clinical translations, relies on a systems-level integration of expertise from multiple fields of investigation. Upon the successful conclusion of a recent National Institutes of Health, National Heart, Lung, and Blood Institute initiative on integrative mitochondrial biology in cardiovascular diseases, we reflect on the accomplishments made possible by this unique interdisciplinary collaboration effort and exciting new fronts on the study of these remarkable organelles.
Assuntos
Programas Governamentais/organização & administração , Cardiopatias/fisiopatologia , Mitocôndrias Cardíacas/fisiologia , Miócitos Cardíacos/fisiologia , National Heart, Lung, and Blood Institute (U.S.)/organização & administração , Comportamento Cooperativo , Previsões , Cardiopatias/metabolismo , Cardiopatias/terapia , Humanos , Comunicação Interdisciplinar , Invenções , Computação em Informática Médica , Modelos Cardiovasculares , Miócitos Cardíacos/ultraestrutura , Avaliação de Programas e Projetos de Saúde , Biologia de Sistemas , Terapias em Estudo , Pesquisa Translacional Biomédica , Estados Unidos , UniversidadesRESUMO
In many forms of cardiomyopathy, alterations in energy substrate metabolism play a key role in disease pathogenesis. Stable isotope tracing in rodent heart perfusion systems can be used to determine cardiac metabolic fluxes, namely those relative fluxes that contribute to pyruvate, the acetyl-CoA pool, and pyruvate anaplerosis, which are critical to cardiac homeostasis. Methods have previously been developed to interrogate these relative fluxes using isotopomer enrichments of measured metabolites and algebraic equations to determine a predefined metabolic flux model. However, this approach is exquisitely sensitive to measurement error, thus precluding accurate relative flux parameter determination. In this study, we applied a novel mathematical approach to determine relative cardiac metabolic fluxes using 13C-metabolic flux analysis (13C-MFA) aided by multiple tracer experiments and integrated data analysis. Using 13C-MFA, we validated a metabolic network model to explain myocardial energy substrate metabolism. Four different 13C-labeled substrates were queried (i.e., glucose, lactate, pyruvate, and oleate) based on a previously published study. We integrated the analysis of the complete set of isotopomer data gathered from these mouse heart perfusion experiments into a single comprehensive network model that delineates substrate contributions to both pyruvate and acetyl-CoA pools at a greater resolution than that offered by traditional methods using algebraic equations. To our knowledge, this is the first rigorous application of 13C-MFA to interrogate data from multiple tracer experiments in the perfused heart. We anticipate that this approach can be used widely to study energy substrate metabolism in this and other similar biological systems.
Assuntos
Glucose/metabolismo , Ácido Láctico/metabolismo , Análise do Fluxo Metabólico , Miocárdio/metabolismo , Ácido Oleico/metabolismo , Ácido Pirúvico/metabolismo , Acetilcoenzima A/metabolismo , Animais , Isótopos de Carbono , Metabolismo Energético , Preparação de Coração Isolado , Masculino , Redes e Vias Metabólicas , Camundongos , Modelos Biológicos , Modelos CardiovascularesRESUMO
The purpose of this study was to determine if plasma acylcarnitine (AC) profiling is altered under hyperinsulinemic conditions as part of the aging process. Fifteen young, lean (19-29 years) and fifteen middle-to older-aged (57-82 years) individuals underwent a 2-hr euglycemic-hyperinsulinemic clamp. Plasma samples were obtained at baseline, 20 min, 50 min, and 120 min for analysis of AC species and amino acids. Skeletal muscle biopsies were performed after 60 min of insulin-stimulation for analysis of acetyl-CoA carboxylase (ACC) phosphorylation. Insulin infusion decreased the majority of plasma short-, medium-, and long-chain (SC, MC, and LC, respectively) AC. However, during the initial 50 min, a number of MC and LC AC species (C10, C10:1, C12:1, C14, C16, C16:1, C18) remained elevated in aged individuals compared to their younger counterparts indicating a lag in responsiveness. Additionally, the insulin-induced decline in skeletal muscle ACC phosphorylation was blunted in the aged compared to young individuals (-24% vs. -56%, P < 0.05). These data suggest that a desensitization to insulin during aging, possibly at the level of skeletal muscle ACC phosphorylation, results in a diminished ability to transition to glucose oxidation indicative of metabolic inflexibility.
Assuntos
Envelhecimento/sangue , Carnitina/análogos & derivados , Insulina/sangue , Acetil-CoA Carboxilase/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/metabolismo , Aminoácidos/sangue , Carnitina/sangue , Carnitina/química , Feminino , Glucose/metabolismo , Técnica Clamp de Glucose , Humanos , Insulina/administração & dosagem , Resistência à Insulina , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/enzimologia , Oxirredução , Fosforilação , Adulto JovemRESUMO
RATIONALE: Increasing evidence has shown that proper control of mitochondrial dynamics (fusion and fission) is required for high-capacity ATP production in the heart. Transcriptional coactivators, peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1) α and PGC-1ß, have been shown to regulate mitochondrial biogenesis in the heart at the time of birth. The function of PGC-1 coactivators in the heart after birth has been incompletely understood. OBJECTIVE: Our aim was to assess the role of PGC-1 coactivators during postnatal cardiac development and in adult hearts in mice. METHODS AND RESULTS: Conditional gene targeting was used in mice to explore the role of PGC-1 coactivators during postnatal cardiac development and in adult hearts. Marked mitochondrial structural derangements were observed in hearts of PGC-1α/ß-deficient mice during postnatal growth, including fragmentation and elongation, associated with the development of a lethal cardiomyopathy. The expression of genes involved in mitochondrial fusion (Mfn1, Opa1) and fission (Drp1, Fis1) was altered in the hearts of PGC-1α/ß-deficient mice. PGC-lα was shown to directly regulate Mfn1 gene transcription by coactivating the estrogen-related receptor α on a conserved DNA element. Surprisingly, PGC-1α/ß deficiency in the adult heart did not result in evidence of abnormal mitochondrial dynamics or heart failure. However, transcriptional profiling demonstrated that PGC-1 coactivators are required for high-level expression of nuclear- and mitochondrial-encoded genes involved in mitochondrial dynamics and energy transduction in the adult heart. CONCLUSIONS: These results reveal distinct developmental stage-specific programs involved in cardiac mitochondrial dynamics.
Assuntos
Cardiomiopatias/metabolismo , Coração/crescimento & desenvolvimento , Mitocôndrias Cardíacas/metabolismo , Fatores de Transcrição/metabolismo , Fatores Etários , Animais , Cardiomiopatias/genética , Progressão da Doença , Metabolismo Energético/fisiologia , Receptor alfa de Estrogênio/metabolismo , Feminino , GTP Fosfo-Hidrolases/genética , Regulação da Expressão Gênica no Desenvolvimento , Masculino , Camundongos , Camundongos Knockout , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fatores de Transcrição/genéticaRESUMO
Cellular proteins rely on reversible redox reactions to establish and maintain biological structure and function. How redox catabolic (NAD+/NADH) and anabolic (NADP+/NADPH) processes integrate during metabolism to maintain cellular redox homoeostasis, however, is unknown. The present work identifies a continuously cycling mitochondrial membrane potential (ΔΨm)-dependent redox circuit between the pyruvate dehydrogenase complex (PDHC) and nicotinamide nucleotide transhydrogenase (NNT). PDHC is shown to produce H2O2 in relation to reducing pressure within the complex. The H2O2 produced, however, is effectively masked by a continuously cycling redox circuit that links, via glutathione/thioredoxin, to NNT, which catalyses the regeneration of NADPH from NADH at the expense of ΔΨm. The net effect is an automatic fine-tuning of NNT-mediated energy expenditure to metabolic balance at the level of PDHC. In mitochondria, genetic or pharmacological disruptions in the PDHC-NNT redox circuit negate counterbalance changes in energy expenditure. At the whole animal level, mice lacking functional NNT (C57BL/6J) are characterized by lower energy-expenditure rates, consistent with their well-known susceptibility to diet-induced obesity. These findings suggest the integration of redox sensing of metabolic balance with compensatory changes in energy expenditure provides a potential mechanism by which cellular redox homoeostasis is maintained and body weight is defended during periods of positive and negative energy balance.
Assuntos
Peróxido de Hidrogênio/metabolismo , Potencial da Membrana Mitocondrial/fisiologia , Mitocôndrias Musculares/enzimologia , NADP Trans-Hidrogenase Específica para A ou B/metabolismo , NADP/metabolismo , Complexo Piruvato Desidrogenase/metabolismo , Animais , Inibidores Enzimáticos/farmacologia , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Camundongos , Mitocôndrias Musculares/genética , Proteínas Mitocondriais/antagonistas & inibidores , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , NADP/genética , NADP Trans-Hidrogenase Específica para A ou B/antagonistas & inibidores , NADP Trans-Hidrogenase Específica para A ou B/genética , Oxirredução/efeitos dos fármacos , Complexo Piruvato Desidrogenase/antagonistas & inibidores , Complexo Piruvato Desidrogenase/genéticaRESUMO
Palmitic acid (PA) is associated with higher blood concentrations of medium-chain acylcarnitines (MCACs), and we hypothesized that PA may inhibit progression of FA ß-oxidation. Using a cross-over design, 17 adults were fed high PA (HPA) and low PA/high oleic acid (HOA) diets, each for 3 weeks. The [1-(13)C]PA and [13-(13)C]PA tracers were administered with food in random order with each diet, and we assessed PA oxidation (PA OX) and serum AC concentration to determine whether a higher PA intake promoted incomplete PA OX. Dietary PA was completely oxidized during the HOA diet, but only about 40% was oxidized during the HPA diet. The [13-(13)C]PA/[1-(13)C]PA ratio of PA OX had an approximate value of 1.0 for either diet, but the ratio of the serum concentrations of MCACs to long-chain ACs (LCACs) was significantly higher during the HPA diet. Thus, direct measurement of PA OX did not confirm that the HPA diet caused incomplete PA OX, despite the modest, but statistically significant, increase in the ratio of MCACs to LCACs in blood.
Assuntos
Carnitina/análogos & derivados , Dieta , Ácidos Graxos/sangue , Palmitatos/administração & dosagem , Adolescente , Adulto , Composição Corporal/efeitos dos fármacos , Carnitina/sangue , Citocinas/metabolismo , Gorduras na Dieta/administração & dosagem , Feminino , Humanos , Imunidade Inata/efeitos dos fármacos , Peroxidação de Lipídeos/genética , Masculino , Ácido Oleico/administração & dosagem , Palmitatos/sangueRESUMO
Thioredoxin-interacting protein (TXNIP) is an α-arrestin family member involved in redox sensing and metabolic control. Growing evidence links TXNIP to mitochondrial function, but the molecular nature of this relationship has remained poorly defined. Herein, we employed targeted metabolomics and comprehensive bioenergetic analyses to evaluate oxidative metabolism and respiratory kinetics in mouse models of total body (TKO) and skeletal muscle-specific (TXNIP(SKM-/-)) Txnip deficiency. Compared with littermate controls, both TKO and TXNIP(SKM-/-) mice had reduced exercise tolerance in association with muscle-specific impairments in substrate oxidation. Oxidative insufficiencies in TXNIP null muscles were not due to perturbations in mitochondrial mass, the electron transport chain, or emission of reactive oxygen species. Instead, metabolic profiling analyses led to the discovery that TXNIP deficiency causes marked deficits in enzymes required for catabolism of branched chain amino acids, ketones, and lactate, along with more modest reductions in enzymes of ß-oxidation and the tricarboxylic acid cycle. The decrements in enzyme activity were accompanied by comparable deficits in protein abundance without changes in mRNA expression, implying dysregulation of protein synthesis or stability. Considering that TXNIP expression increases in response to starvation, diabetes, and exercise, these findings point to a novel role for TXNIP in coordinating mitochondrial fuel switching in response to nutrient availability.