RANKL signaling drives skeletal muscle into the oxidative profile.

The bone-muscle unit refers to the reciprocal regulation between bone and muscle by mechanical interaction and tissue communication via soluble factors. The receptor activator of NF-κB ligand (RANKL) stimulation induces mitochondrial biogenesis and increases the oxidative capacity in osteoclasts and adipocytes. RANKL may bind to the membrane bound receptor activator of NF-κB (RANK) or to osteoprotegerin (OPG), a decoy receptor that inhibits RANK-RANKL activation. RANK is highly expressed in skeletal muscle, but the contribution of RANKL to healthy skeletal muscle fiber remains elusive. Here we show that RANKL stimulation in C2C12-derived myotubes induced activation of mitochondrial biogenesis pathways as detected by RNA-seq and western blot. RANKL expanded the mitochondrial reticulum, as shown by mitochondrial DNA quantification and MitoTracker staining, and boosted the spare respiratory capacity. Using MEK and MAPK inhibitors, we found that RANKL signals via ERK and p38 to induce mitochondrial biogenesis. The soleus from OPG-/- and OPG+/- mice showed higher respiratory rates compared to C57BL6/J wild-type (WT) mice, which correlates with high serum RANKL levels. RANKL infusion using a mini-osmotic pump in WT mice increased the number of mitochondria, boosted the respiratory rate, increased succinate dehydrogenase (SDH) activity in skeletal muscle, and improved the fatigue resistance of gastrocnemius. Therefore, our findings reveal a new role of RANKL as an osteokine-like protein that impacts muscle fiber metabolism.

Bone modeling and remodeling are processes intricately related to bone health regulated by the RANKL system. The RANKL (receptor activator of NF-κB ligand) is a protein essential for bone resorption. RANKL activates RANK (receptor activator of NFκB) in the cell membrane of osteoclasts and can also bind to OPG (osteoprotegerin), which acts as a soluble decoy receptor. Therefore, the levels of RANKL and OPG determine the degree of osteoclast activation and bone resorption. Bone and muscle mechanically interact for movement as bone is a lever for skeletal muscle to exert force. They also communicate via soluble factors that reciprocally regulate their function. Skeletal muscle fibers express RANK, but the role of RANKL signaling in healthy myotubes was still unknown. Here, we propose that RANKL regulates muscle metabolism by inducing mitochondrial biogenesis. We show that RANKL increases mitochondrial area in myotubes and the expression of mitochondrial markers, boosting the spare respiratory capacity. In mice knockout for OPG, which shows high levels of RANKL and unopposed RANK-RANKL stimulation, we found higher respiratory rates than in the wild-type mice. We also infused a low dose of RANKL in wild-type mice, which is around ten times lower than the dose to induce osteoporosis, and found increased mitochondrial number and higher respiratory rates in soleus. In the gastrocnemius, we also observed increased phosphorylative respiration and improved resistance to fatigue compared to mice treated with the vehicle solution. Our findings indicate that RANKL regulates both bone and muscle under physiological conditions by inducing mitochondrial biogenesis and oxidative metabolism in skeletal muscle fibers.

Physical Exercise and Tumor Energy Metabolism.

Evidence supports the antitumoral effects of physical activity, either in experimental animal models or humans. However, the biological mechanisms by which physical exercise modulates tumoral development are still unclear. An important feature of the tumor cells is the altered energy metabolism, often associated with definitions of tumor aggressiveness. Nevertheless, exercise can cause global metabolic changes in the body, as well as modulate tumor metabolism. Here we specifically discuss the metabolic changes found in tumors and how exercise can contribute to anti-tumoral effects by modulating the mitochondrial function, and tricarboxylic acid cycle-related metabolites of cancer cells. The effect of physical exercise on tumor metabolism is a new possibility for comprehension of cancer biology and developing therapies focused on tumor energy metabolism.

One-Week High-Intensity Interval Training Increases Hippocampal Plasticity and Mitochondrial Content without Changes in Redox State.

Evidence suggests that physical exercise has effects on neuronal plasticity as well as overall brain health. This effect has been linked to exercise capacity in modulating the antioxidant status, when the oxidative stress is usually linked to the neuronal damage. Although high-intensity interval training (HIIT) is the training-trend worldwide, its effect on brain function is still unclear. Thus, we aimed to assess the neuroplasticity, mitochondrial, and redox status after one-week HIIT training. Male (C57Bl/6) mice were assigned to non-trained or HIIT groups. The HIIT protocol consisted of three days with short bouts at 130% of maximum speed (Vmax), intercalated with moderate-intensity continuous exercise sessions of 30 min at 60% Vmax. The mass spectrometry analyses showed that one-week of HIIT increased minichromosome maintenance complex component 2 (MCM2), brain derived neutrophic factor (BDNF), doublecortin (DCX) and voltage-dependent anion-selective channel protein 2 (VDAC), and decreased mitochondrial superoxide dismutase 2 (SOD 2) in the hippocampus. In addition, one-week of HIIT promoted no changes in H2O2 production and carbonylated protein concentration in the hippocampus as well as in superoxide anion production in the dentate gyrus. In conclusion, our one-week HIIT protocol increased neuroplasticity and mitochondrial content regardless of changes in redox status, adding new insights into the neuronal modulation induced by new training models.

Moderate Exercise Modulates Tumor Metabolism of Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) stands out for its aggressiveness and accelerated rate of proliferation. Evidence shows that exercise may exert antitumorigenic effects, but the biochemical mechanisms underlying them remain unclear. Our objective was to evaluate the ability of exercise to modulate tumor growth and energy metabolism in an experimental TNBC model. Female BALB/c mice were sedentary or trained for 12 weeks and inoculated with 1 × 104 4T1 cells in the eighth week. Analyzes of macronutrient oxidation, mitochondrial respiration, and expression of genes related to cell metabolism were performed. The results showed that the trained group had a smaller tumor mass and the mitochondria in the tumors presented lower respiratory rates in the state of maximum electron transport capacity. Additionally, the tumors of the exercised group showed a higher expression of genes related to tumor suppressors, while the genes linked with cellular growth were similar between groups. Furthermore, the training modulated the corporal macronutrient oxidation to almost exclusive carbohydrate oxidation, while the sedentary condition metabolized both carbohydrate and lipids. Therefore, the exercise reduced tumor growth, with an impact on mitochondrial and macronutrient metabolism. Our results shed light on the understanding of the antitumorigenic effects of physical exercise, particularly regarding the metabolic transformations in TNBC.

HSP-Target of Therapeutic Agents in Sepsis Treatment.

Sepsis is a syndrome characterized by a dysregulated inflammatory response, cellular stress, and organ injury. Sepsis is the main cause of death in intensive care units worldwide, creating need for research and new therapeutic strategies. Heat shock protein (HSP) analyses have recently been developed in the context of sepsis. HSPs have a cytoprotection role in stress conditions, signal to immune cells, and activate the inflammatory response. Hence, HSP analyses have become an important focus in sepsis research, including the investigation of HSPs targeted by therapeutic agents used in sepsis treatment. Many therapeutic agents have been tested, and their HSP modulation showed promising results. Nonetheless, the heterogeneity in experimental designs and the diversity in therapeutic agents used make it difficult to understand their efficacy in sepsis treatment. Therefore, future investigations should include the analysis of parameters related to the early and late immune response in sepsis, HSP localization (intra or extracellular), and time to the onset of treatment after sepsis. They also should consider the differences in experimental sepsis models. In this review, we present the main results of studies on therapeutic agents in targeting HSPs in sepsis treatment. We also discuss limitations and possibilities for future investigations regarding HSP modulators.

Exercício físico aeróbico de intensidade moderada reduz a velocidade de crescimento e modula o metabolismo energético tumoral em modelo experimental de câncer de mama triplo-negativo / Moderate-intensity aerobic physical exercise reduces tumor growth velocity and modulates tumor energy metabolism in the experimental model of triple-negative breast cancer

O câncer de mama ocupa o primeiro lugar em mortalidade dentre todos os tipos de câncer. O subtipo triplo-negativo (triple-negative breast cancer - TNBC) representa 15-20% de todos os tipos de câncer de mama com alta prevalência em mulheres pré-menopausa e destaca-se pelo seu grande tamanho tumoral e agressividade no estabelecimento de metástases, com impacto direto na redução da sobrevida dos pacientes. Apesar das evidências sobre os efeitos anti-tumorigênicos do exercício físico, tanto na prevenção como durante a carcinogênese, é comum que pacientes alterem sua rotina após o diagnóstico de câncer, frequentemente reduzindo as atividades físicas durante e após o tratamento. Em adição, os mecanismos pelos quais o exercício físico exerce papel anti-tumoral são pouco compreendidos. O objetivo deste estudo foi avaliar os efeitos do exercício físico aeróbico moderado em modelo experimental de câncer de mama de tipo triplo-negativo, com ênfase na modulação do metabolismo energético tumoral. Foram utilizados camundongos fêmeas BALB/c em desenho experimental de 12 semanas, cuja inoculação de 1x104 células 4T1 foi realizada após 8 semanas de treinamento. Após protocolo de exercício aeróbico moderado em esteira, foram realizadas análises do metabolismo mitocondrial tumoral, composição lipídica e expressão de genes relacionados à bioenergética e proliferação celular. Os resultados mostraram que o exercício aeróbico moderado reduziu 54,5% do volume e 42% da massa tumoral de animais que foram treinados antes e após a inoculação tumoral. Animais treinados apresentaram fosforilação oxidativa mais próxima ao seu limite máximo respiratório e menor respiração mitocondrial no tecido tumoral quando comparados ao grupo sedentário. O treinamento ocasionou redução no conteúdo de ácido fosfatídico e fosfatidilcolina. Enquanto a análise de expressão relativa de mRNA demonstrou aumento na expressão de genes relacionados à via metabólica glicolítica, como Hif1a, Glut-1, HKII, Ldha e Pdk, além dos supressores tumorais p53 e Lats2. Nossos resultados sugerem que a redução na velocidade de crescimento tumoral proporcionada pelo exercício físico aeróbico de carga moderada seja devida, pelo menos em parte, à modulação do metabolismo energético tumoral. Em conjunto, os dados do nosso estudo abrem novas perspectivas para a identificação de vias metabólicas sensíveis ao exercício físico, permitindo o melhor o entendimento de seus efeitos antitumorigênicos

Breast cancer ranks first in mortality among all types of cancer. The triple-negative breast cancer (TNBC) accounts for 15-20% of all types of breast cancer with a high prevalence in premenopausal women and is notable for its large tumor size and aggressiveness in the establishment of metastasis, with a direct impact on the reduction of patients' survival. Altough evidence highlight the anti-tumorigenic effects of physical exercise both on the prevention as well as during carcinogenesis, patients commonly change their routine after cancer diagnostic, usually reducing physical activity during and after treatment. Moreover, the mechanisms underlying the anti-tumor role of physical exercise remain poorly understood. The objective of this study was to evaluate the effects of moderate aerobic physical exercise in an experimental model of triple-negative breast cancer, with emphasis on the modulation of tumor energy metabolism. Female BALB / c mice were used in a 12-week experimental design, whose inoculation of 1x104 4T1 cells was performed after 8 weeks of training. After the protocol of moderate aerobic exercise was carried out on the treadmill, analyzes of mitochondrial tumor metabolism, lipid content and qPCR of genes related to bioenergetics and tumorigenic process were performed. The results showed that moderate aerobic exercise reduced 54.5% of the volume and 42% the tumor mass of animals trained before and after tumor inoculation. Trained animals showed oxidative phosphorylation closest to the maximum respiratory limit and lower mitochondrial respiration in tumor tissue when compared to the sedentary group. The training resulted in a reduction in the content of phosphatidic acid and phosphatidylcholine. In the trained group, relative mRNA quantification analysis showed increased expression of genes related to the glycolytic metabolic pathway, such as Hif1a, Glut-1, HKII, Ldha, and Pdk, as well as of the tumor suppressors p53 and Lats2. Our results suggest that the reduction in tumor growth velocity provided by moderate-intensity aerobic physical exercise is due, at least in part, to the modulation of tumor energy metabolism. Together, data from our study open new perspectives for the identification of metabolic pathways sensitive to exercise, allowing better understanding of its anti-tumorigenic effects