Endurance exercise attenuates cardiotoxicity induced by androgen deprivation and doxorubicin

The Beneficial Role of Physical Exercise on Anthracyclines Induced Cardiotoxicity in Breast Cancer Patients

The increase in breast cancer (BC) survival has determined a growing survivor population that seems to develop several comorbidities and, specifically, treatment-induced cardiovascular disease (CVD), especially those patients treated with anthracyclines. Indeed, it is known that these compounds act through the induction of supraphysiological production of reactive oxygen species (ROS), which appear to be central mediators of numerous direct and indirect cardiac adverse consequences. Evidence suggests that physical exercise (PE) practised before, during or after BC treatments could represent a viable non-pharmacological strategy as it increases heart tolerance against many cardiotoxic agents, and therefore improves several functional, subclinical, and clinical parameters. At molecular level, the cardioprotective effects are mainly associated with an exercise-induced increase of stress response proteins (HSP60 and HSP70) and antioxidant (SOD activity, GSH), as well as a decrease in lipid peroxidation, and pro-apoptotic proteins such as Bax, Bax-to-Bcl-2 ratio. Moreover, this protection can potentially be explained by a preservation of myosin heavy chain (MHC) isoform distribution. Despite this knowledge, it is not clear which type of exercise should be suggested in BC patient undergoing anthracycline treatment. This highlights the lack of special guidelines on how affected patients should be managed more efficiently. This review offers a general framework for the role of anthracyclines in the physio-pathological mechanisms of cardiotoxicity and the potential protective role of PE. Finally, potential exercise-based strategies are discussed on the basis of scientific findings.

Efficacy of Physical Exercise to Offset Anthracycline-Induced Cardiotoxicity: A Systematic Review and Meta-Analysis of Clinical and Preclinical Studies

Background

Physical exercise is an intervention that might protect against doxorubicin‐induced cardiotoxicity. In this meta‐analysis and systematic review, we aimed to estimate the effect of exercise on doxorubicin‐induced cardiotoxicity and to evaluate mechanisms underlying exercise‐mediated cardioprotection using (pre)clinical evidence.

Methods and Results

We conducted a systematic search in PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases. Cochrane's and Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) risk‐of‐bias tools were used to assess the validity of human and animal studies, respectively. Cardiotoxicity outcomes reported by ≥3 studies were pooled and structured around the type of exercise intervention. Forty articles were included, of which 3 were clinical studies. Overall, in humans (sample sizes ranging from 24 to 61), results were indicative of exercise‐mediated cardioprotection, yet they were not sufficient to establish whether physical exercise protects against doxorubicin‐induced cardiotoxicity. In animal studies (n=37), a pooled analysis demonstrated that forced exercise interventions significantly mitigated in vivo and ex vivo doxorubicin‐induced cardiotoxicity compared with nonexercised controls. Similar yet slightly smaller effects were found for voluntary exercise interventions. We identified oxidative stress and related pathways, and less doxorubicin accumulation as mechanisms underlying exercise‐induced cardioprotection, of which the latter could act as an overarching mechanism.

Conclusions

Animal studies indicate that various exercise interventions can protect against doxorubicin‐induced cardiotoxicity in rodents. Less doxorubicin accumulation in cardiac tissue could be a key underlying mechanism. Given the preclinical evidence and limited availability of clinical data, larger and methodologically rigorous clinical studies are needed to clarify the role of physical exercise in preventing cardiotoxicity in patients with cancer.

Registration

URL: https://www.crd.york.ac.uk/prospero; Unique identifier: CRD42019118218.

Consideration of Sex as a Biological Variable in the Development of Doxorubicin Myotoxicity and the Efficacy of Exercise as a Therapeutic Intervention

Doxorubicin (DOX) is an anthracycline antibiotic used to treat a wide variety of hematological and solid tumor cancers. While DOX is highly effective at reducing tumor burden, its clinical use is limited by the development of adverse effects to both cardiac and skeletal muscle. The detrimental effects of DOX to muscle tissue are associated with the increased incidence of heart failure, dyspnea, exercise intolerance, and reduced quality of life, which have been reported in both patients actively receiving chemotherapy and cancer survivors. A variety of factors elevate the probability of DOX-related morbidity in patients; however, the role of sex as a biological variable to calculate patient risk remains unclear. Uncertainty regarding sexual dimorphism in the presentation of DOX myotoxicity stems from inadequate study design to address this issue. Currently, the majority of clinical data on DOX myotoxicity come from studies where the ratio of males to females is unbalanced, one sex is omitted, and/or the patient cohort include a broad age range. Furthermore, lack of consensus on standard outcome measures, difficulties in long-term evaluation of patient outcomes, and other confounding factors (i.e., cancer type, drug combinations, adjuvant therapies, etc.) preclude a definitive answer as to whether differences exist in the incidence of DOX myotoxicity between sexes. This review summarizes the current clinical and preclinical literature relevant to sex differences in the incidence and severity of DOX myotoxicity, the proposed mechanisms for DOX sexual dimorphism, and the potential for exercise training to serve as an effective therapeutic countermeasure to preserve muscle strength and function in males and females.

Exercise Protects against Cancer-induced Cardiac Cachexia

Cancer has been shown to negatively stimulate autophagy, leading to a decline in cardiac function. Although exercise is cardioprotective, its influence over autophagy-mediated tumor growth and cardiac function are not well defined.

PURPOSE

This study aimed to determine the effect of exercise on tumor morphology and cardiac function.

METHODS

Fisher 344 rats (n = 28) were assigned to one of four groups: 1) sedentary non-tumor bearing (SED), 2) sedentary tumor bearing (SED + T), 3) wheel run non-tumor bearing (WR), or 4) wheel run tumor bearing (WR + T). Rats remained sedentary or exercised for 6 wk. At week 4, rats in tumor groups were inoculated with MatBIII tumor cells. At week 6, cardiac function was measured.

RESULTS

SED + T animals exhibited significantly lower left ventricular developed pressure when compared with SED, WR, and WR + T (P < 0.05). This coincided with a significant increase in cardiac autophagy (increased LC3-II) in SED + T animals when compared with SED, WR, and WR + T (P < 0.05). Furthermore, SED + T hearts showed a significant increase in β-myosin heavy chain expression versus nontumor groups (P < 0.05). Tumor mass was significantly larger (P < 0.001) in SED + T animals when compared with WR + T animals, which was accompanied by a significant increase in tumor LC3-II protein expression (P < 0.05).

CONCLUSION

Nonexercised tumor-bearing rats showed severe cardiac dysfunction and excessive, maladaptive autophagy in the heart and tumors. Voluntary exercise preserved cardiac function and attenuated the autophagic response in heart and tumor tissues. This preservation may be related to the reduced tumor growth in aerobically exercised rats, to the improved regulation of autophagy by exercise, or both.

Sex steroids in relation to cardiac structure and function in men

The prevalence of testosterone substitution as well as of androgen deprivation therapy in men is increasing. This review aims to summarise available knowledge of the effects of sex steroids on cardiac structure and function in men. MEDLINE was searched through PubMed. Original studies, systematic reviews and meta-analyses, and relevant citations were screened. A short-term hormonal intervention study in healthy young men with respect to echocardiographic parameters of structure and function was performed. Preclinical research provides sufficient evidence for the heart as a substrate for sex hormones. In animals, administration of oestradiol appears to have beneficial effects on cardiac structure and function, whereas administration of testosterone to noncastrated animals adversely affects cardiac function. However, the effects of sex steroids on cardiac function and structure appear more heterogeneous in human observational studies while comparative, prospective studies in humans are lacking. It is concluded that although effects of testosterone substitution as well as of androgen deprivation on cardiac structure and function can be expected based on pre-clinical research, there exists an important knowledge gap of the effects of hormonal intervention in men. As such, there is a need to address this question in future prospective intervention trials.

Effects of Chronic Endurance Exercise on Doxorubicin-Induced Thymic Damage

The use of prior exercise training has shown promise in minimizing doxorubicin (DOX)-induced physical impairments. The purpose of this study was to compare changes in thymus mass, thymocyte (T-cell) number, and tissue peroxidation following chronic endurance exercise and DOX treatment in the rat. The thymus mass, number of viable T-cells, and levels of malondialdehyde and 4-hydroxyalkenals (MDA+4-HAE) were compared 3 days post-injection between rats assigned to the following treatment conditions: (a) 10 weeks of endurance training, followed by a saline injection 24 hours after the last training session (TM+SAL); (b) treadmill training as above, followed by a single, bolus 10-mg/kg injection of DOX (TM+10); (c) treadmill training with 12.5 mg/kg of DOX (TM+12.5); (d) sedentary (without exercise) and a saline injection (SED+SAL); (e) sedentary with 10 mg/kg of DOX (SED+10); and (f) sedentary with 12.5 mg/kg (SED+12.5). Thymic mass and T-cell numbers significantly decreased following DOX injections. TM rats exhibited significantly less lipid peroxidation compared with paired-dose SED groups. TM+10 did not significantly differ from SED+SAL in thymic levels of lipid peroxidation. We conclude that chronic endurance exercise decreases levels of lipid peroxidation in the thymus seen with acute DOX treatment.

Exercise training does not affect anthracycline antitumor efficacy while attenuating cardiac dysfunction

Highly effective anthracyclines, like doxorubicin (DOX), have limited clinical use due to protracted cardiotoxic effects. While exercise is known to be cardioprotective, it is unclear whether exercise compromises chemotherapy treatment efficacy. To determine the effect of exercise training on DOX antitumor efficacy as well as DOX-induced cardiotoxicity, female Fisher 344 rats were randomly assigned to sedentary + saline (SED+SAL), SED+DOX, wheel run exercise training + SAL (WR+SAL), or WR+DOX. On week 11, animals were inoculated with 1×10(6) MatBIII tumor cells. Once tumors reached ∼1 cm in diameter, animals were treated with 12 mg/kg of DOX or SAL. Animals were killed 1, 3, or 5 days following treatment. Tumor growth and cardiac function were measured at each interval. DOX accumulation and multidrug resistance protein (MRP) expression were quantified in tumor and heart tissue. No significant difference (P > 0.05) existed between DOX-treated SED and WR groups for tumor measurements. Exercise preserved cardiac function up to 5 days following DOX treatment. Exercise reduced ventricular DOX accumulation and upregulated ventricular MPR1 and MPR2. In contrast, no differences were observed in DOX accumulation or MRP expression in tumors of SED and WR animals. Endurance exercise had no effect on DOX antitumor efficacy as evidenced by a definitive DOX-induced reduction in tumor growth in both the SED and WR groups. Although exercise did not affect the antitumor efficacy of DOX, it still provided protection against cardiac dysfunction. These effects may be mediated by the degree of DOX tissue accumulation secondary to the regulation of MRP expression.