Exercise preserves physical fitness during aging through AMPK and mitochondrial dynamics.

Exercise is a nonpharmacological intervention that improves health during aging and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise transiently alters mitochondrial functionality and metabolism. Mitochondrial fission and fusion are critical effectors of mitochondrial plasticity, which allows a fine-tuned regulation of organelle connectiveness, size, and function. Here we have investigated the role of mitochondrial dynamics during exercise in the model organism Caenorhabditis elegans. We show that in body-wall muscle, a single exercise session induces a cycle of mitochondrial fragmentation followed by fusion after a recovery period, and that daily exercise sessions delay the mitochondrial fragmentation and physical fitness decline that occur with aging. Maintenance of proper mitochondrial dynamics is essential for physical fitness, its enhancement by exercise training, and exercise-induced remodeling of the proteome. Surprisingly, among the long-lived genotypes we analyzed (isp-1,nuo-6, daf-2, eat-2, and CA-AAK-2), constitutive activation of AMP-activated protein kinase (AMPK) uniquely preserves physical fitness during aging, a benefit that is abolished by impairment of mitochondrial fission or fusion. AMPK is also required for physical fitness to be enhanced by exercise, with our findings together suggesting that exercise may enhance muscle function through AMPK regulation of mitochondrial dynamics. Our results indicate that mitochondrial connectivity and the mitochondrial dynamics cycle are essential for maintaining physical fitness and exercise responsiveness during aging and suggest that AMPK activation may recapitulate some exercise benefits. Targeting mechanisms to optimize mitochondrial fission and fusion, as well as AMPK activation, may represent promising strategies for promoting muscle function during aging.

Histidine dipeptides are key regulators of excitation-contraction coupling in cardiac muscle: Evidence from a novel CARNS1 knockout rat model.

Histidine-containing dipeptides (HCDs) are abundantly expressed in striated muscles. Although important properties have been ascribed to HCDs, including H+ buffering, regulation of Ca2+ transients and protection against oxidative stress, it remains unknown whether they play relevant functions in vivo. To investigate the in vivo roles of HCDs, we developed the first carnosine synthase knockout (CARNS1-/-) rat strain to investigate the impact of an absence of HCDs on skeletal and cardiac muscle function. Male wild-type (WT) and knockout rats (4 months-old) were used. Skeletal muscle function was assessed by an exercise tolerance test, contractile function in situ and muscle buffering capacity in vitro. Cardiac function was assessed in vivo by echocardiography and cardiac electrical activity by electrocardiography. Cardiomyocyte contractile function was assessed in isolated cardiomyocytes by measuring sarcomere contractility, along with the determination of Ca2+ transient. Markers of oxidative stress, mitochondrial function and expression of proteins were also evaluated in cardiac muscle. Animals were supplemented with carnosine (1.8% in drinking water for 12 weeks) in an attempt to rescue tissue HCDs levels and function. CARNS1-/- resulted in the complete absence of carnosine and anserine, but it did not affect exercise capacity, skeletal muscle force production, fatigability or buffering capacity in vitro, indicating that these are not essential for pH regulation and function in skeletal muscle. In cardiac muscle, however, CARNS1-/- resulted in a significant impairment of contractile function, which was confirmed both in vivo and ex vivo in isolated sarcomeres. Impaired systolic and diastolic dysfunction were accompanied by reduced intracellular Ca2+ peaks and slowed Ca2+ removal, but not by increased markers of oxidative stress or impaired mitochondrial respiration. No relevant increases in muscle carnosine content were observed after carnosine supplementation. Results show that a primary function of HCDs in cardiac muscle is the regulation of Ca2+ handling and excitation-contraction coupling.

Cardioprotection induced by a brief exposure to acetaldehyde: role of aldehyde dehydrogenase 2.

Aims: We previously demonstrated that acute ethanol administration protects the heart from ischaemia/reperfusion (I/R) injury thorough activation of aldehyde dehydrogenase 2 (ALDH2). Here, we characterized the role of acetaldehyde, an intermediate product from ethanol metabolism, and its metabolizing enzyme, ALDH2, in an ex vivo model of cardiac I/R injury. Methods and results: We used a combination of homozygous knock-in mice (ALDH2*2), carrying the human inactivating point mutation ALDH2 (E487K), and a direct activator of ALDH2, Alda-1, to investigate the cardiac effect of acetaldehyde. The ALDH2*2 mice have impaired acetaldehyde clearance, recapitulating the human phenotype. Yet, we found a similar infarct size in wild type (WT) and ALDH2*2 mice. Similar to ethanol-induced preconditioning, pre-treatment with 50 µM acetaldehyde increased ALDH2 activity and reduced cardiac injury in hearts of WT mice without affecting cardiac acetaldehyde levels. However, acetaldehyde pre-treatment of hearts of ALDH2*2 mice resulted in a three-fold increase in cardiac acetaldehyde levels and exacerbated I/R injury. Therefore, exogenous acetaldehyde appears to have a bimodal effect in I/R, depending on the ALDH2 genotype. Further supporting an ALDH2 role in cardiac preconditioning, pharmacological ALDH2 inhibition abolished ethanol-induced cardioprotection in hearts of WT mice, whereas a selective activator, Alda-1, protected ALDH2*2 against ethanol-induced cardiotoxicity. Finally, either genetic or pharmacological inhibition of ALDH2 mitigated ischaemic preconditioning. Conclusion: Taken together, our findings suggest that low levels of acetaldehyde are cardioprotective whereas high levels are damaging in an ex vivo model of I/R injury and that ALDH2 is a major, but not the only, regulator of cardiac acetaldehyde levels and protection from I/R.

Increased clearance of reactive aldehydes and damaged proteins in hypertension-induced compensated cardiac hypertrophy: impact of exercise training.

BACKGROUND: We previously reported that exercise training (ET) facilitates the clearance of damaged proteins in heart failure. Here, we characterized the impact of ET on cardiac protein quality control during compensated ventricular hypertrophy in spontaneously hypertensive rats (SHR). METHODS AND RESULTS: SHR were randomly assigned into sedentary and swimming-trained groups. Sedentary SHR displayed cardiac hypertrophy with preserved ventricular function compared to normotensive rats, characterizing a compensated cardiac hypertrophy. Hypertensive rats presented signs of cardiac oxidative stress, depicted by increased lipid peroxidation. However, these changes were not followed by accumulation of lipid peroxidation-generated reactive aldehydes and damaged proteins. This scenario was explained, at least in part, by the increased catalytic activity of both aldehyde dehydrogenase 2 (ALDH2) and proteasome. Of interest, ET exacerbated cardiac hypertrophy, improved ventricular function, induced resting bradycardia, and decreased blood pressure in SHR. These changes were accompanied by reduced cardiac oxidative stress and a consequent decrease in ALDH2 and proteasome activities, without affecting small chaperones levels and apoptosis in SHR. CONCLUSION: Increased cardiac ALDH2 and proteasomal activities counteract the deleterious effect of excessive oxidative stress in hypertension-induced compensated cardiac hypertrophy in rats. ET has a positive effect in reducing cardiac oxidative stress without affecting protein quality control.

M-protein is down-regulated in cardiac hypertrophy driven by thyroid hormone in rats.

Although it is well known that the thyroid hormone (T3) is an important positive regulator of cardiac function over a short term and that it also promotes deleterious effects over a long term, the molecular mechanisms for such effects are not yet well understood. Because most alterations in cardiac function are associated with changes in sarcomeric machinery, the present work was undertaken to find novel sarcomeric hot spots driven by T3 in the heart. A microarray analysis indicated that the M-band is a major hot spot, and the structural sarcomeric gene coding for the M-protein is severely down-regulated by T3. Real-time quantitative PCR-based measurements confirmed that T3 (1, 5, 50, and 100 physiological doses for 2 days) sharply decreased the M-protein gene and protein expression in vivo in a dose-dependent manner. Furthermore, the M-protein gene expression was elevated 3.4-fold in hypothyroid rats. Accordingly, T3 was able to rapidly and strongly reduce the M-protein gene expression in neonatal cardiomyocytes. Deletions at the M-protein promoter and bioinformatics approach suggested an area responsive to T3, which was confirmed by chromatin immunoprecipitation assay. Functional assays in cultured neonatal cardiomyocytes revealed that depletion of M-protein (by small interfering RNA) drives a severe decrease in speed of contraction. Interestingly, mRNA and protein levels of other M-band components, myomesin and embryonic-heart myomesin, were not altered by T3. We concluded that the M-protein expression is strongly and rapidly repressed by T3 in cardiomyocytes, which represents an important aspect for the basis of T3-dependent sarcomeric deleterious effects in the heart.

Acute inhibition of excessive mitochondrial fission after myocardial infarction prevents long-term cardiac dysfunction.

BACKGROUND: Ischemia and reperfusion (IR) injury remains a major cause of morbidity and mortality and multiple molecular and cellular pathways have been implicated in this injury. We determined whether acute inhibition of excessive mitochondrial fission at the onset of reperfusion improves mitochondrial dysfunction and cardiac contractility postmyocardial infarction in rats. METHODS AND RESULTS: We used a selective inhibitor of the fission machinery, P110, which we have recently designed. P110 treatment inhibited the interaction of fission proteins Fis1/Drp1, decreased mitochondrial fission, and improved bioenergetics in three different rat models of IR, including primary cardiomyocytes, ex vivo heart model, and an in vivo myocardial infarction model. Drp1 transiently bound to the mitochondria following IR injury and P110 treatment blocked this Drp1 mitochondrial association. Compared with control treatment, P110 (1 µmol/L) decreased infarct size by 28 ± 2% and increased adenosine triphosphate levels by 70+1% after IR relative to control IR in the ex vivo model. Intraperitoneal injection of P110 (0.5 mg/kg) at the onset of reperfusion in an in vivo model resulted in improved mitochondrial oxygen consumption by 68% when measured 3 weeks after ischemic injury, improved cardiac fractional shortening by 35%, reduced mitochondrial H2O2 uncoupling state by 70%, and improved overall mitochondrial functions. CONCLUSIONS: Together, we show that excessive mitochondrial fission at reperfusion contributes to long-term cardiac dysfunction in rats and that acute inhibition of excessive mitochondrial fission at the onset of reperfusion is sufficient to result in long-term benefits as evidenced by inhibiting cardiac dysfunction 3 weeks after acute myocardial infarction.

Fisiologia do Exercício para alunos de graduação: uso de estratégias de ensino baseadas na metodologia dialética / Exercise Physiology for undergraduates: the use of teaching strategies basead on the dialectical method

A metodologia dialética propõe um ensino de dupla mão (professor-aluno) que provoque a aprendizagem por meio de tarefas contínuas dos sujeitos. Para isso, o professor assume o papel de mediador e dirige as diferentes atividades. Nesse contexto, a Fisiologia do Exercício é uma disciplina academicamente orientada que está inserida em um ambiente dinâmico, e a utilização de estratégias de ensino se faz necessária para otimizar a apropriação do conhecimento de forma ativa, além de contribuir para a maior autonomia dos estudantes universitários. Portanto, o objetivo do presente estudo foi o de utilizar diferentes estratégias de ensinagem por meio de atividades propostas aos alunos na disciplina de Fisiologia da Atividade Motora I da Escola de Educação Física e Esporte da Universidade de São Paulo e correlacionar o desempenho do aluno com a sua participação nessas atividades propostas. Nossos principais achados demonstram correlações significativas e positivas entre a presença nas aulas e o desempenho nas avaliações (p < 0,0001; r = 0,84), bem como entre a realização das atividades propostas e o desempenho nas avaliações (p < 0,0001; r = 0,69). Em conjunto, esses dados sugerem que a utilização de diferentes estratégias de ensinagem baseadas na metodologia dialética com a ativa participação dos alunos é essencial para um bom rendimento acadêmico, sendo altamente recomendada para o ensino da Fisiologia do Exercício...

The dialectic method proposes a two-way teaching (teacher-student) that causes learning through ongoing task of the subjects. For this, the teacher assumes the role of mediator and directs several activities. In line with the above, Exercise Physiology is an academically oriented discipline undergoing in a dynamic environment, and the use of different teaching strategies is needed to optimize the appropriation of knowledge in an active way and contribute to the greater autonomy of university students. Therefore, the aim of this study was apply different strategies in the course entitled "Physiology of the Motor Activity I" at School of Physical Education and Sport of University of Sao Paulo and assess a correlation between students participation and students performance. We used teaching strategies such as exposition and dialogue classes, practical classes, conversations with experts, directed study, study of scientific texts, concept mapping, case study and study of the environment in order to optimize the appropriation of the concepts of exercise physiology with emphasis on neuromuscular and cardiovascular physiology exercise. Our main findings show significant and positive correlations between the presence in classes and the performance evaluations (p < 0.0001, r = 0.84) as well as between the tasks proposed and the performance evaluations (p < 0.0001; r = 0.69). Altogether, these data suggest that using different teaching strategies based on the dialectic method associated with the participation of students is essential for a good academic performance in Exercise Physiology...

Mitocondriopatia na insufuciência cardíaca: efeitos do treinamento físico aeróbico / Mitochondriopathy in heart failure: effects of endurance training

A insuficiência cardíaca é uma síndrome de mau prognóstico, caracterizada por disfunçao cardíaca associada à intolerância aos esforços, retenção de fluído e redução de longividade. Recentemente, os conhecimentos sobre a fisiopatoplogia da insuficiência cardíaca estabeleceram que, além dos distúrbios hemodinâmicos e neuro-humorais associados à síndrome, alterações mitocondriais (denominadas mitocondriopatias) podem ser nocivas ao tecido cardíaco. Prejuízos no metabolismo energético mitocondrial, com consequente aumento no estresse oxidativo seguido de morte celular programada, são caracteristicas presentes na insuficiência cardíaca. Além disso, alterações na dinâmica mitocondrial, representada por um desequilíbrio entre os processos de fusão e fissão da organela, contribuem para o agravamento da síndrome, uma vez que esses eventos estão relacionados à manutenção da viabilidade celular. Uma importante estratégia não farmacológica utilizada no tratamento da insuficiência cardíaca é o treinamento físico aeróbico, que, além de contribuir para a melhora da função ventricular, com consequente aumento da tolerância aos esforços e na qualidade de vida desses pacientes, promove importantes adaptações mitocondriais no tecido cardíaco, destacando-se o aumento dos complexos respiratórios mitocondriais e a redução na produção de espécies reativas de oxigênio. Nesse artigo de revisão. será abordada a importância da biologia mitocondrial no contexto cardíaco, retratando aspectos funcionais e morfológicos da organela, bem como sua contribuição para o agravamento da insuficiência cardíaca. Será, também, abordado o papel do treinamento físico aeróbico na reversão da mitocondriopatia observada na síndrome.

Heart failure is a clinical syndrome of poor prognosis characterized by cardiac dysfunction, exercise intolerance, lung edema and reduced longevity. Over the last decades, the knowledge regarding heart failure pathophysiology has established that in addition to hemodynamic and neurohumoral disorders, mitochondrial dysfunctions (called mitochondriopathy) can be deleterious to the heart. Impairment of mitochondrial energy metabolism, with consequent increase in oxidative stress and programmed cell death, is associated to cardiac deterioration in both human failing hearts and heart failure animal models. In addition, changes in mitochondrial dynamic, characterizated by an imbalance between the fusion and fisson processes of the organelle, contribute to the worsening of the pathology, since these events are related to the maintenance of cell viability. Endurance training has been recognized as an important adjuvant in the treatment of heart failure since it improves patient outcomes and quality of life. However, the mechanisms underlying exercise-induced beneficial effect on heart failure are not completely understood. In this review, we describe specific exercise training-mediated changes in mitochondrial function and morphology that contributes to better heart failure prognosis, including improved mitochondrial respiration, reduced oxidative stress and increased mitochondrial fussion.