| 1. |
- Mader, Theresa, et al.
(författare)
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Exercise reduces intramuscular stress and counteracts muscle weakness in mice with breast cancer
- 2022
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Ingår i: Journal of Cachexia, Sarcopenia and Muscle. - : John Wiley & Sons. - 2190-5991 .- 2190-6009. ; 13:2, s. 1151-1163
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Patients with breast cancer exhibit muscle weakness, which is associated with increased mortality risk and reduced quality of life. Muscle weakness is experienced even in the absence of loss of muscle mass in breast cancer patients, indicating intrinsic muscle dysfunction. Physical activity is correlated with reduced cancer mortality and disease recurrence. However, the molecular processes underlying breast cancer-induced muscle weakness and the beneficial effect of exercise are largely unknown.METHODS: Eight-week-old breast cancer (MMTV-PyMT, PyMT) and control (WT) mice had access to active or inactive in-cage voluntary running wheels for 4 weeks. Mice were also subjected to a treadmill test. Muscle force was measured ex vivo. Tumour markers were determined with immunohistochemistry. Mitochondrial biogenesis and function were assessed with transcriptional analyses of PGC-1α, the electron transport chain (ETC) and antioxidants superoxide dismutase (Sod) and catalase (Cat), combined with activity measurements of SOD, citrate synthase (CS) and β-hydroxyacyl-CoA-dehydrogenase (βHAD). Serum and intramuscular stress levels were evaluated by enzymatic assays, immunoblotting, and transcriptional analyses of, for example, tumour necrosis factor-α (TNF-α) and p38 mitogen-activated protein kinase (MAPK) signalling.RESULTS: PyMT mice endured shorter time and distance during the treadmill test (~30%, P < 0.05) and ex vivo force measurements revealed ~25% weaker slow-twitch soleus muscle (P < 0.001). This was independent of cancer-induced alteration of muscle size or fibre type. Inflammatory stressors in serum and muscle, including TNF-α and p38 MAPK, were higher in PyMT than in WT mice (P < 0.05). Cancer-induced decreases in ETC (P < 0.05, P < 0.01) and antioxidant gene expression were observed (P < 0.05). The exercise intervention counteracted the cancer-induced muscle weakness and was accompanied by a less aggressive, differentiated tumour phenotype, determined by increased CK8 and reduced CK14 expression (P < 0.05). In PyMT mice, the exercise intervention led to higher CS activity (P = 0.23), enhanced β-HAD and SOD activities (P < 0.05), and reduced levels of intramuscular stressors together with a normalization of the expression signature of TNFα-targets and ETC genes (P < 0.05, P < 0.01). At the same time, the exercise-induced PGC-1α expression, and CS and β-HAD activity was blunted in muscle from the PyMT mice as compared with WT mice, indicative that breast cancer interfere with transcriptional programming of mitochondria and that the molecular adaptation to exercise differs between healthy mice and those afflicted by disease.CONCLUSIONS: Four-week voluntary wheel running counteracted muscle weakness in PyMT mice which was accompanied by reduced intrinsic stress and improved mitochondrial and antioxidant profiles and activities that aligned with muscles of healthy mice.
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| 2. |
- Blackwood, Sarah J, et al.
(författare)
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Role of nitration in control of phosphorylase and glycogenolysis in mouse skeletal muscle.
- 2021
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 320:4, s. E691-E701
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorylase is one of the most carefully studied proteins in history, but knowledge of its regulation during intense muscle contraction is incomplete. Tyrosine nitration of purified preparations of skeletal muscle phosphorylase results in inactivation of the enzyme and this is prevented by antioxidants. Whether an altered redox state affects phosphorylase activity and glycogenolysis in contracting muscle is not known. Here, we investigate the role of redox state in control of phosphorylase and glycogenolysis in isolated mouse fast-twitch (extensor digitorum longus, EDL) and slow-twitch (soleus) muscle preparations during repeated contractions. Exposure of crude muscle extracts to H2O2 had little effect on phosphorylase activity. However, exposure of extracts to peroxynitrite (ONOO-), a nitrating/oxidizing agent, resulted in complete inactivation of phosphorylase (half maximal inhibition at ~200 µM ONOO-), which was fully reversed by the presence of an ONOO-scavanger, dithiothreitol (DTT). Incubation of isolated muscles with ONOO- resulted in nitration of phosphorylase and marked inhibition of glycogenolysis during repeated contractions. ONOO- also resulted in large decreases in high-energy phosphates (ATP and phosphocreatine) in the rested state and following repeated contractions. These metabolic changes were associated with decreased force production during repeated contractions (to ~60% of control). In contrast, repeated contractions did not result in nitration of phosphorylase, nor did DTT or the general antioxidant N-acetylcysteine alter glycogenolysis during repeated contractions. These findings demonstrate that ONOO- inhibits phosphorylase and glycogenolysis in living muscle under extreme conditions. However, nitration does not play a significant role in control of phosphorylase and glycogenolysis during repeated contractions.
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| 3. |
- Breznau, Nate, et al.
(författare)
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Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:44
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Tidskriftsartikel (refereegranskat)abstract
- This study explores how researchers analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each teams workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.
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| 4. |
- Lanner, Johanna, et al.
(författare)
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Running reverses tumor-induced muscle weakness in mice with breast cancer
- 2019
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Konferensbidrag (refereegranskat)abstract
- Introduction: Patients with breast cancer experience muscle dysfunction, which is a clinical challenge that is not restricted to advanced stage patients, but also observed in newly diagnosed weight-stable patients with low tumor burden. Recent data indicate that physical activity can reduce breast cancerassociated mortality, suggesting that improved muscle performance per secan have positive impact on survival. Here, the transgenic PyMT mouse model of breast cancer was used to elucidate molecular mechanisms underlying breast cancer-induced muscle impairments.Materials and Methods: PyMT mice and wildtype (WT) littermates w/wo access to an in-cage running wheel for four weeks (week 8-12). Functional readouts included Ca2+imaging; isometric force measurement on single fibers and intact fast-and slow-twitchmuscles. Intramuscular signaling was assessed using immunofluorescence, immunoblotting and enzymatic assays.Results: The specific force (i.e. force/cross-sectional area) was significantly decreased by ~ 35% in slow-twitch soleus muscles from breast cancermice as compared to WT muscles, which was the result of reduced Ca2+release and impaired myofibrillar function. There were no difference in muscle size or fiber type between the two groups. However, higher intramuscular stress (e.g. p38 activation and carbonylation (DNP)) was observed in PyMT than in WT. Intriguingly, voluntary running for four weeks reversed the weakness and PyMT soleus muscles generated similar forces as muscles of exercised WT mice. The running induced higher SOD2 expression and normalized levels of p38 and DNP.Conclusion: Intrinsic contractile dysfunction and higher intramuscular stress was present in mice with breast cancer, which was counteracted with voluntary running.
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| 5. |
- Liu, Zhengye, et al.
(författare)
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Mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force
- 2021
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Ingår i: The FASEB Journal. - : John Wiley & Sons. - 0892-6638 .- 1530-6860. ; 35:12
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Tidskriftsartikel (refereegranskat)abstract
- The hypoxia-inducible nuclear-encoded mitochondrial protein NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2 (NDUFA4L2) has been demonstrated to decrease oxidative phosphorylation and production of reactive oxygen species in neonatal cardiomyocytes, brain tissue and hypoxic domains of cancer cells. Prolonged local hypoxia can negatively affect skeletal muscle size and tissue oxidative capacity. Although skeletal muscle is a mitochondrial rich, oxygen sensitive tissue, the role of NDUFA4L2 in skeletal muscle has not previously been investigated. Here we ectopically expressed NDUFA4L2 in mouse skeletal muscles using adenovirus-mediated expression and in vivo electroporation. Moreover, femoral artery ligation (FAL) was used as a model of peripheral vascular disease to induce hind limb ischemia and muscle damage. Ectopic NDUFA4L2 expression resulted in reduced mitochondrial respiration and reactive oxygen species followed by lowered AMP, ADP, ATP, and NAD(+) levels without affecting the overall protein content of the mitochondrial electron transport chain. Furthermore, ec-topically expressed NDUFA4L2 caused a similar to 20% reduction in muscle mass that resulted in weaker muscles. The loss of muscle mass was associated with increased gene expression of atrogenes MurF1 and Mul1, and apoptotic genes caspase 3 and Bax. Finally, we showed that NDUFA4L2 was induced by FAL and that the Ndufa4l2 mRNA expression correlated with the reduced capacity of the muscle to generate force after the ischemic insult. These results show, for the first time, that mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force. Specifically, induced NDUFA4L2 reduces mitochondrial activity leading to lower levels of important intramuscular metabolites, including adenine nucleotides and NAD(+), which are hallmarks of mitochondrial dysfunction and hence shows that dysfunctional mitochondrial activity may drive muscle wasting.
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| 6. |
- Mader, Theresa
(författare)
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Functional and metabolic alterations in skeletal muscle in response to physiological and pathophysiological stressors
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Skeletal muscle performance is essential for our body’s movement as well as for the wholebody metabolism. In health and disease, skeletal muscle is exposed to various endogenous and exogenous stressors, influencing its physiological functions. In paper I, we showed that exercise performance and muscle force is affected by the stressor breast cancer, in a mouse model of breast cancer (PyMT). Mimicking the experienced muscle weakness of human breast cancer patients, PyMT mice performed poorly in a treadmill exhaustion run and their muscles produced less force than wildtype (WT) mice, although no difference in morphology, fiber type distribution or diameter was found. The muscle weakness was associated with an increase of pro-inflammatory cytokines, such as TNF-α in the skeletal muscle, activating the p38 mitogen-activated protein kinase (MAPK) stress-response pathway and decreasing the expression of mitochondrial electron transport chain (ETC) genes as well as antioxidant genes. After the mice had access to four weeks of voluntary running ad libitum, skeletal muscle force as well as the time and distance of the treadmill exhaustion run improved drastically for PyMT mice. The exercise also reduced the intramuscular stress, improved both the expression of mitochondrial ETC genes and the activity of key mitochondrial enzymes, such as citrate synthase (CS) and especially β-hydroxyacyl-CoA dehydrogenase (β-HAD) and restored the antioxidant defense system including superoxide dismutase (SOD 1,2). Additionally, we could show that the breast cancer blunted the exercise-induced expression of PPARγ coactivator-1α (Pgc-1α) in PyMT mice. Our results showed that breast cancer-induced weakness is linked to increased intramuscular stress signaling and that voluntary, moderate exercise was able to counteract the weakness in PyMT mice. Patients with breast cancer are treated with various systemic anti-cancer treatments, and while aiming to treat cancer, these treatments often cause side-effects. In paper II, we aimed to study the effect of a novel anti-tumorigenic compound (CX-5461) on the whole-body as well skeletal muscle-specific metabolism. Four weeks of CX-5461 treatment effectively reduced the breast cancer tumor in PyMT mice, but also resulted in increased food intake, energy expenditure and a higher respiratory exchange ratio (VCO2/VO2), indicative of a substrate shift towards carbohydrate utilization in both WT and PyMT mice. Moreover, basal blood glucose levels were increased, and we observed a slower glucose clearance from the blood stream in both WT and PyMT mice after CX-5461 treatment. Skeletal muscle is an important tissue involved in maintaining the body’s glucose homeostatic. In WT mice, CX-5461 treatment reduced the basal glucose uptake, whereas in PyMT mice the insulin-stimulated glucose uptake was affected in extensor digitorum longus (EDL) muscles. We found that CX-5461 not only exerts its mechanism of action, the inhibition of the RNA-Polymerase I (Pol I) pre-initiation complex, in breast cancer cells, but also directly in skeletal muscle and through that alters the glucose and fat metabolism in skeletal muscle. The results indicate that the novel drug CX-5461 affects the whole-body metabolism including elevated blood glucose levels and reduced glucose uptake into skeletal muscle, independently of the tumor development. Skeletal muscle is a highly metabolic tissue which functions can also be regulated by oxidative stress, cause by an imbalance in the endogenous oxidative and antioxidative system. In paper III, we investigated the role of the intermuscular redox state on glycogen phosphorylase activity and glycogenolysis, which supply the muscle with energy from glycogen storage during exercise. Glycogen phosphorylase was strongly inhibited by incubation with the reactive nitrogen species (RNS) peroxynitrite (ONOO-), contrary to the reactive oxygen species (ROS) H2O2 in muscle extracts. In intact muscles, ONOOincubation resulted in inhibition of glycogenolysis in resting and contracting as well as a reduction of muscle force in slow-twitch oxidative soleus (SOL) and fast-twitch glycolytic EDL muscles, despite not exerting a direct effect on phosphorylase activity. Moreover, post-translational nitrate modification was observed in EDL muscle after ONOOincubation. Incubation with two antioxidants N-acetylcysteine (NAC) and dithiothreitol (DTT) did not affect phosphorylase activity or glycogenolysis, but reduced the force of EDL and SOL muscle. These results suggest that exogenous ONOOinhibits phosphorylase activity in muscle extracts and glycogenolysis in intact contracted muscles, whereas antioxidants such as DTT and NAC only play a minor role in inducing endogenous ROS and regulate the phosphorylase activity. All results from these three studies in this thesis investigate how the performance and function of skeletal muscle can be affected by different stressors. Taken together, a better understanding of the responsible underlying molecular mechanisms, might lead to targeted therapy approaches for afflicted patients in the future.
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| 7. |
- Mader, Theresa, et al.
(författare)
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Metabolic alteration and muscle dysfunction in mice with breast cancer
- 2018
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Konferensbidrag (refereegranskat)abstract
- Breast cancer accounts for ~25% of diagnosed cancer types in woman [1]. Decreased physical fitness and muscle weakness are common complications in patients with breast cancer. In cancer, muscle weakness has traditionally been linked to muscle wasting and significant weight loss (cachexia) [2]. However, muscle weakness is present in non-cachectic, weight-stable patients with breast cancer [3]. In fact, cancer-induced muscle dysfunction is a broad clinical challenge that is not restricted to palliative or advanced stage patients, but also observed in newly diagnosed patients with low tumor burden [4]. Further, with the breast cancer treatment improving, it is important to take a look on the patients quality of life [5]. However, little is known about the features underlying breast cancer-induced muscle impairments and no drug preventing cancer-induced muscle weakness is clinically proven. Here we aim at characterizing the metabolic status and the muscle function in mice with breast cancer.The breast cancer mouse-model MMTV-PyMT (PyMT) used here, is characterized by an early onset of mammary cancer (from 5 weeks of age) and follows a similar progression pattern as the one observed in human patients [6]. Soleus muscle from PyMT mice exhibited ~30% lower specific force (kN/m2) than soleus muscle from wildtype (WT) mice (n=28-29, p ≤ 0.05, mice were 12 week old at sacrifice). There were no significant differences in muscle mass, fiber size or fiber type distribution between PyMT and WT muscle. Furthermore, there were no differences in glycogen content (μg/g muscle) in soleus muscle from PyMT and WT mice. Simultaneous measurement of numerous parameters (e.g. oxygen consumption (VO2), carbon dioxide production (VCO2), and food and water intake) was carried out using comprehensive lab animal monitoring system (CLAMS) to gain insight into the metabolic status of the mice. The mice were monitored over a week and the average respiratory exchange ratio (RER = CO2production: O2 uptake) were significantly differed between PyMT and WT mice, with mean PyMT RER of 0.95±0.01 and WT RER of 1.0±0.01 (mean data +/-SEM, n=8, p<0.001). Thus, indicative that PyMT have an altered metabolism towards fatty acid utilization.In summary, soleus muscles are weaker and the whole-body metabolism appears altered in mice with breast cancer as compared with healthy control mice. Gene and molecular analysis are currently being performed to further assess mitochondrial and glucose metabolism. Nevertheless, further studies are needed to gain insight into cancer-derived factors that contributes to skeletal muscle dysfunction and altered metabolism.1. Jemal, A., et al., Cancer statistics, 2008. CA Cancer J Clin, 2008. 58(2): p. 71-96.2. Johns, N., N.A. Stephens, and K.C. Fearon, Muscle wasting in cancer. Int J Biochem Cell Biol, 2013. 45(10): p. 2215-29.3. Klassen, O., et al., Muscle strength in breast cancer patients receiving different treatment regimes. Journal of Cachexia, Sarcopenia and Muscle, 2017. 8(2): p. 305-316.4. Villasenor, A., et al., Prevalence and prognostic effect of sarcopenia in breast cancer survivors: the HEAL Study. J Cancer Surviv, 2012. 6(4): p. 398-406.5. Perry, S., T.L. Kowalski, and C.H. Chang, Quality of life assessment in women with breast cancer: benefits, acceptability and utilization. Health Qual Life Outcomes, 2007. 5: p. 24.6. Fantozzi, A. and G. Christofori, Mouse models of breast cancer metastasis. Breast Cancer Res, 2006. 8(4): p. 212.
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