RESUMO
Obesity significantly decreases life expectancy and increases the incidence of age-related dysfunctions, including ß-cell dysregulation leading to inadequate insulin secretion. Here, we show that diluted plasma from obese human donors acutely impairs ß-cell integrity and insulin secretion relative to plasma from lean subjects. Similar results were observed with diluted sera from obese rats fed ad libitum, when compared to sera from lean, calorically restricted, animals. The damaging effects of obese circulating factors on ß-cells occurs in the absence of nutrient overload, and mechanistically involves mitochondrial dysfunction, limiting glucose-supported oxidative phosphorylation and ATP production. We demonstrate that increased levels of adiponectin, as found in lean plasma, are the protective characteristic preserving ß-cell function; indeed, sera from adiponectin knockout mice limits ß-cell metabolic fluxes relative to controls. Furthermore, oxidative phosphorylation and glucose-sensitive insulin secretion, which are completely abrogated in the absence of this hormone, are restored by the presence of adiponectin alone, surprisingly even in the absence of other serological components, for both the insulin-secreting INS1 cell line and primary islets. The addition of adiponectin to cells treated with plasma from obese donors completely restored ß-cell functional integrity, indicating the lack of this hormone was causative of the dysfunction. Overall, our results demonstrate that low circulating adiponectin is a key damaging element for ß-cells, and suggest strong therapeutic potential for the modulation of the adiponectin signaling pathway in the prevention of age-related ß-cell dysfunction.
Assuntos
Resistência à Insulina , Células Secretoras de Insulina , Camundongos , Humanos , Ratos , Animais , Adiponectina/metabolismo , Secreção de Insulina , Insulina/metabolismo , Obesidade/metabolismo , Células Secretoras de Insulina/metabolismo , Glucose/metabolismo , Resistência à Insulina/fisiologiaRESUMO
Caloric restriction (CR) prevents obesity and increases resilience against pathological stimuli in laboratory rodents. At the mitochondrial level, protection promoted by CR in the brain and liver is related to higher Ca2+ uptake rates and capacities, avoiding Ca2+-induced mitochondrial permeability transition. Dietary restriction has also been shown to increase kidney resistance against damaging stimuli; if these effects are related to similar mitochondrial adaptations has not been uncovered. Here, we characterized changes in mitochondrial function in response to 6 mo of CR in rats and measured bioenergetic parameters, redox balance, and Ca2+ homeostasis. CR promoted an increase in succinate-supported mitochondrial oxygen consumption rates. Although CR prevents mitochondrial reactive oxygen species production in many tissues, in kidney, we found that mitochondrial H2O2 release was enhanced in a succinate-dependent manner. Surprisingly, and opposite to the effects observed in the brain and liver, mitochondria from CR animals were more prone to Ca2+-induced mitochondrial permeability transition, in a manner reversed by the antioxidant dithiothreitol. CR mitochondria also displayed higher Ca2+ uptake rates, which were not accompanied by changes in Ca2+ efflux rates or related to altered inner mitochondrial membrane potentials or amounts of the mitochondrial Ca2+ uniporter. Instead, increased mitochondrial Ca2+ uptake rates in CR kidneys correlated with loss of mitochondrial Ca2+ uptake protein 2 (MICU2), a mitochondrial Ca2+ uniporter modulator. Interestingly, MICU2 is also modulated by CR in the liver, suggesting that it has a broader diet-sensitive regulatory role controlling mitochondrial Ca2+ homeostasis. Together, our results highlight the organ-specific bioenergetic, redox, and ionic transport results of CR, with some unexpected deleterious effects in the kidney.NEW & NOTEWORTHY Prevention of obesity through caloric restriction (CR) is well known to protect many tissues but has been poorly studied in kidneys. Here, we determined the effects of long-term CR in rat kidney mitochondria, which are central players in energy metabolism and aging. Surprisingly, we found that the diet increased mitochondrial reactive oxygen production and permeability transition. This suggests that the kidneys respond differently to restricted diets and may be more susceptible under CR.
Assuntos
Restrição Calórica , Peróxido de Hidrogênio , Animais , Peróxido de Hidrogênio/metabolismo , Rim/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Obesidade/metabolismo , Ratos , Succinatos/metabolismoRESUMO
Caloric restriction (CR) is widely known to increase life span and resistance to different types of injuries in several organisms. We have previously shown that mitochondria from livers or brains of CR animals exhibit higher calcium uptake rates and lower sensitivity to calcium-induced mitochondrial permeability transition (mPT), an event related to the resilient phenotype exhibited by these organs. Given the importance of calcium in metabolic control and cell homeostasis, we aimed here to uncover possible changes in mitochondrial calcium handling, redox balance and bioenergetics in cardiac and skeletal muscle mitochondria in response to six months of CR. Unexpectedly, we found that CR does not alter the susceptibility to mPT in muscle (cardiac or skeletal), nor calcium uptake rates. Despite the lack in changes in calcium transport properties, CR consistently decreased respiration in the presence of ATP synthesis in heart and soleus muscle. In heart, such changes were accompanied by a decrease in respiration in the absence of ATP synthesis, lower maximal respiratory rates and a reduced rate of hydrogen peroxide release. Hydrogen peroxide release was unaltered by CR in skeletal muscle. No changes were observed in inner membrane potentials and respiratory control ratios. Together, these results highlight the tissue-specific bioenergetic and ion transport effects induced by CR, demonstrating that resilience against calcium-induced mPT is not present in all tissues.
Assuntos
Restrição Calórica/normas , Metabolismo Energético/fisiologia , Músculo Esquelético/imunologia , Miocárdio/imunologia , Animais , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
Microglial activation by oleate and palmitate differentially modulates brain inflammatory status. However, the metabolic reprogramming supporting these reactive phenotypes remains unknown. Employing real-time metabolic measurements and lipidomic analysis, we show that both fatty acids promote microglial oxidative metabolism, while lipopolysaccharide (LPS) enhances glycolytic rates. Interestingly, oleate treatment was followed by enrichment in storage lipids bound to polyunsaturated fatty acids (PUFA), in parallel with protection against oxidative imbalance. Palmitate, in turn, induced a distinct lipid distribution defined by PUFA linked to membrane phospholipids, which are more susceptible to lipid peroxidation and inflammatory signaling cascades. This distribution was mirrored by LPS treatment, which led to a strong pro-inflammatory phenotype in microglia. Thus, although both oleate and palmitate preserve mitochondrial function, a contrasting lipid distribution supports differences in fatty acid-induced neuroinflammation. These data reinforce the concept that reactive microglial profiles are achieved by stimulus-evoked remodeling in cell metabolism.
Assuntos
Encéfalo/patologia , Microglia/metabolismo , Mitocôndrias/metabolismo , Ácido Oleico/metabolismo , Palmitatos/metabolismo , Animais , Linhagem Celular , Glicólise/fisiologia , Inflamação/patologia , Peroxidação de Lipídeos/fisiologia , Lipopolissacarídeos/farmacologia , Lipídeos de Membrana/metabolismo , Camundongos , Microglia/citologia , Neuroimunomodulação/fisiologia , Oxirredução , Fosforilação OxidativaRESUMO
Obesity-derived inflammation and metabolic dysfunction has been related to the activity of the inducible nitric oxide synthase (iNOS). To understand the interrelation between metabolism, obesity and NO., we evaluated the effects of obesity-induced NO. signaling on liver mitochondrial function. We used mouse strains containing mitochondrial nicotinamide transhydrogenase activity, while prior studies involved a spontaneous mutant of this enzyme, and are, therefore, more prone to oxidative imbalance. Wild-type and iNOS knockout mice were fed a high fat diet for 2, 4 or 8 weeks. iNOS knockout did not protect against diet-induced metabolic changes. However, the diet decreased fatty-acid oxidation capacity in liver mitochondria at 4 weeks in both wild-type and knockout groups; this was recovered at 8 weeks. Interestingly, other mitochondrial functional parameters were unchanged, despite significant modifications in insulin resistance in wild type and iNOS knockout animals. Overall, we found two surprising features of obesity-induced metabolic dysfunction: (i) iNOS does not have an essential role in obesity-induced insulin resistance under all experimental conditions and (ii) liver mitochondria are resilient to functional changes in obesity-induced metabolic dysfunction.
Assuntos
Resistência à Insulina/fisiologia , Fígado/metabolismo , Fígado/fisiologia , Mitocôndrias Hepáticas/metabolismo , Mitocôndrias Hepáticas/fisiologia , Óxido Nítrico Sintase Tipo II/metabolismo , Animais , Dieta Hiperlipídica , Metabolismo dos Lipídeos/fisiologia , Masculino , Doenças Metabólicas/metabolismo , Doenças Metabólicas/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/metabolismo , Obesidade/fisiopatologiaRESUMO
Blastocladiella emersonii is an early diverging fungus of the phylum Blastocladiomycota. During the life cycle of the fungus, mitochondrial morphology changes significantly, from a fragmented form in sessile vegetative cells to a fused network in motile zoospores. In this study, we visualize these morphological changes using a mitochondrial fluorescent probe and show that the respiratory capacity in zoospores is much higher than in vegetative cells, suggesting that mitochondrial morphology could be related to the differences in oxygen consumption. While studying the respiratory chain of the fungus, we observed an antimycin A and cyanide-insensitive, salicylhydroxamic (SHAM)-sensitive respiratory activity, indicative of a mitochondrial alternative oxidase (AOX) activity. The presence of AOX was confirmed by the finding of a B. emersonii cDNA encoding a putative AOX, and by detection of AOX protein in immunoblots. Inhibition of AOX activity by SHAM was found to significantly alter the capacity of the fungus to grow and sporulate, indicating that AOX participates in life cycle control in B. emersonii.
Assuntos
Blastocladiella/crescimento & desenvolvimento , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Proteínas Mitocondriais/metabolismo , Oxirredutases/metabolismo , Proteínas de Plantas/metabolismo , Esporos Fúngicos/crescimento & desenvolvimento , Transporte de Elétrons , Oxirredução , Oxigênio/metabolismoRESUMO
Calorie restriction is a dietary intervention known to improve redox state, glucose tolerance, and animal life span. Other interventions have been adopted as study models for caloric restriction, including nonsupplemented food restriction and intermittent, every-other-day feedings. We compared the short- and long-term effects of these interventions to ad libitum protocols and found that, although all restricted diets decrease body weight, intermittent feeding did not decrease intra-abdominal adiposity. Short-term calorie restriction and intermittent feeding presented similar results relative to glucose tolerance. Surprisingly, long-term intermittent feeding promoted glucose intolerance, without a loss in insulin receptor phosphorylation. Intermittent feeding substantially increased insulin receptor nitration in both intra-abdominal adipose tissue and muscle, a modification associated with receptor inactivation. All restricted diets enhanced nitric oxide synthase levels in the insulin-responsive adipose tissue and skeletal muscle. However, whereas calorie restriction improved tissue redox state, food restriction and intermittent feedings did not. In fact, long-term intermittent feeding resulted in largely enhanced tissue release of oxidants. Overall, our results show that restricted diets are significantly different in their effects on glucose tolerance and redox state when adopted long-term. Furthermore, we show that intermittent feeding can lead to oxidative insulin receptor inactivation and glucose intolerance.
Assuntos
Restrição Calórica/métodos , Dieta Redutora/métodos , Gordura Intra-Abdominal/metabolismo , Músculo Esquelético/metabolismo , Obesidade/dietoterapia , Receptor de Insulina/metabolismo , Adiposidade , Animais , Western Blotting , Peso Corporal , Glucose/metabolismo , Intolerância à Glucose/metabolismo , Humanos , Insulina/metabolismo , Proteínas Substratos do Receptor de Insulina/análise , Proteínas Substratos do Receptor de Insulina/biossíntese , Masculino , Óxido Nítrico Sintase/análise , Óxido Nítrico Sintase/biossíntese , Nitrocompostos , Obesidade/metabolismo , Oxirredução , Ratos , Ratos Sprague-Dawley , Receptor de Insulina/antagonistas & inibidoresRESUMO
Mild mitochondrial uncoupling, or the reduction of the efficiency of energy conversion without compromising intracellular high energy phosphate levels, is a protective therapeutic strategy under many laboratory conditions. Here we discuss these conditions, which include both cell and animal models of ischemia reperfusion and complications associated with the metabolic syndrome. We also discuss drugs that promote mild mitochondrial uncoupling and naturally occurring mild mitochondrial uncoupling pathways involving free fatty acid cycling and K(+) transport.
Assuntos
Síndrome Metabólica/complicações , Mitocôndrias/efeitos dos fármacos , Traumatismo por Reperfusão/fisiopatologia , Animais , Modelos Animais de Doenças , Ácidos Graxos não Esterificados/metabolismo , Humanos , Canais Iônicos/metabolismo , Transporte de Íons , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Potássio/metabolismo , Proteína Desacopladora 1RESUMO
Caloric restriction is the most effective non-genetic intervention to enhance lifespan known to date. A major research interest has been the development of therapeutic strategies capable of promoting the beneficial results of this dietary regimen. In this sense, we propose that compounds that decrease the efficiency of energy conversion, such as mitochondrial uncouplers, can be caloric restriction mimetics. Treatment of mice with low doses of the protonophore 2,4-dinitrophenol promotes enhanced tissue respiratory rates, improved serological glucose, triglyceride and insulin levels, decrease of reactive oxygen species levels and tissue DNA and protein oxidation, as well as reduced body weight. Importantly, 2,4-dinitrophenol-treated animals also presented enhanced longevity. Our results demonstrate that mild mitochondrial uncoupling is a highly effective in vivo antioxidant strategy, and describe the first therapeutic intervention capable of effectively reproducing the physiological, metabolic and lifespan effects of caloric restriction in healthy mammals.