Effects of voluntary wheel running on cardiac function and myosin heavy chain in chemically gonadectomized rats

Androgen-deprivation therapy with leuprolide increases abdominal adiposity without causing cardiac dysfunction in middle-aged male mice: effect of sildenafil

Androgen-deprivation therapy (ADT) is the primary systemic therapy for treating advanced or metastatic prostate cancer (PCa), which has improved survival outcomes in patients with PCa. However, ADT may develop metabolic and cardiovascular adverse events that impact the quality of life and lifespan in PCa survivors. The present study was designed to establish a murine model of ADT with a gonadotropin-releasing hormone (GnRH) agonist leuprolide and to investigate its effects on metabolism and cardiac function. We also examined the potential cardioprotective role of sildenafil (inhibitor of phosphodiesterase 5) under chronic ADT. Middle-aged male C57BL/6J mice received a 12-wk subcutaneous infusion via osmotic minipumps containing either saline or 18 mg/4 wk leuprolide with or without 1.3 mg/4 wk sildenafil cotreatment. Compared with saline controls, leuprolide treatment significantly reduced prostate weight and serum testosterone levels, confirming chemical castration in these mice. The ADT-induced chemical castration was not affected by sildenafil. Leuprolide significantly increased the weight of abdominal fat after 12-wk treatment without a change in total body weight, and sildenafil did not block the proadipogenic effect of leuprolide. No signs of left ventricular systolic and diastolic dysfunction were observed throughout the leuprolide treatment period. Interestingly, leuprolide treatment significantly elevated serum levels of cardiac troponin I (cTn-I), a biomarker of cardiac injury, and sildenafil did not abolish this effect. We conclude that long-term ADT with leuprolide increases abdominal adiposity and cardiac injury biomarker without cardiac contractile dysfunction. Sildenafil did not prevent ADT-associated adverse changes.

Notch1 Is Involved in Physiologic Cardiac Hypertrophy of Mice via the p38 Signaling Pathway after Voluntary Running

Appropriate exercise such as voluntary wheel-running can induce physiological cardiac hypertrophy. Notch1 plays an important role in cardiac hypertrophy; however, the experimental results are inconsistent. In this experiment, we aimed to explore the role of Notch1 in physiological cardiac hypertrophy. Twenty-nine adult male mice were randomly divided into a Notch1 heterozygous deficient control (Notch1^+/- CON) group, a Notch1 heterozygous deficient running (Notch1^+/- RUN) group, a wild type control (WT CON) group, and a wild type running (WT RUN) group. Mice in the Notch1^+/- RUN and WT RUN groups had access to voluntary wheel-running for two weeks. Next, the cardiac function of all of the mice was examined by echocardiography. The H&E staining, Masson trichrome staining, and a Western blot assay were carried out to analyze cardiac hypertrophy, cardiac fibrosis, and the expression of proteins relating to cardiac hypertrophy. After two-weeks of running, the Notch1 receptor expression was decreased in the hearts of the WT RUN group. The degree of cardiac hypertrophy in the Notch1^+/- RUN mice was lower than that of their littermate control. Compared to the Notch1^+/- CON group, Notch1 heterozygous deficiency could lead to a decrease in Beclin-1 expression and the ratio of LC3II/LC3I in the Notch1^+/- RUN group. The results suggest that Notch1 heterozygous deficiency could partly dampen the induction of autophagy. Moreover, Notch1 deficiency may lead to the inactivation of p38 and the reduction of β-catenin expression in the Notch1^+/- RUN group. In conclusion, Notch1 plays a critical role in physiologic cardiac hypertrophy through the p38 signaling pathway. Our results will help to understand the underlying mechanism of Notch1 on physiological cardiac hypertrophy.

Voluntary wheel exercise training affects locomotor muscle, but not the diaphragm in the rat

Introduction: Functional tests and training regimens intensity-controlled by an individual are used in sport practice, clinical rehabilitation, and space medicine. The model of voluntary wheel running in rats can be used to explore molecular mechanisms of such training regimens in humans. Respiratory and locomotor muscles demonstrate diverse adaptations to treadmill exercise, but the effects of voluntary exercise training on these muscle types have not been compared yet. Therefore, this work aimed at the effects of voluntary ET on rat triceps brachii and diaphragm muscles with special attention to reactive oxygen species, which regulate muscle plasticity during exercise.

Methods: Male Wistar rats were distributed into exercise trained (ET) and sedentary (Sed) groups. ET group had free access to running wheels, running activity was continuously recorded and analyzed using the original hardware/software complex. After 8 weeks, muscle protein contents were studied using Western blotting.

Results: ET rats had increased heart ventricular weights but decreased visceral/epididymal fat weights and blood triglyceride level compared to Sed. The training did not change corticosterone, testosterone, and thyroid hormone levels, but decreased TBARS content in the blood. ET rats demonstrated higher contents of OXPHOS complexes in the triceps brachii muscle, but not in the diaphragm. The content of SOD2 increased, and the contents of NOX2 and SOD3 decreased in the triceps brachii muscle of ET rats, while there were no such changes in the diaphragm.

Conclusion: Voluntary wheel running in rats is intensive enough to govern specific adaptations of muscle fibers in locomotor, but not respiratory muscle.

Sex Hormone Suppression and Physical Activity: Possible Implications for Transgender Individuals

Purpose

Transgender individuals tend to be less physically active than cisgender individuals, and the primary focus of these physical activity barriers have been psychosocial in nature. Very little attention has been given to the role that changes in the sex hormone milieu (such as that occurring during gender-affirming hormone therapy) play on physical activity. The purpose of this study was to explore the effects of sex hormone suppression using a gonadotropin-releasing hormone agonist (GnRHa) on physical activity levels and patterns.

Methods

Female and male rats received 4 weeks of sex hormone suppression using the GnRHa goserelin acetate (GA) or received a placebo as a control (CON). Animals were then allowed free access to voluntary running wheels, and activity was recorded throughout the treatment period.

Results

Female rats receiving GA (F GA) had a significantly lower total wheel running distance than female CON (F CON, 53±11 km vs. 113±28 km, respectively, p=0.042), and male rats receiving GA (M GA) had a significantly lower total wheel running distance when compared with male CON (M CON, 31±7 km vs. 69±18 km, respectively, p=0.037). Differences in daily wheel running distances were first observed at day 18 between F GA and F CON (p=0.037) and at day 2 between M GA and M CON (p=0.021).

Conclusion

Reduced sex hormone availability reduced wheel running activity in female and male rats. Understanding the role that sex hormone manipulation has on physical activity may be an important consideration in promoting physical activity in transgender individuals receiving treatments that reduce sex hormone availability.

Suppression of myofilament cross-bridge kinetic in the heart of orchidectomized rats

AIMS

The increased incidence of heart failure with reduced ejection fraction in men compared with women suggests that male sex hormones significantly impact myocardial contractile activation. This study aims to examine associations among molecular alterations, cellular modulations and in vivo cardiac contractile function upon deprivation of testicular hormones.

MAIN METHODS

Myocardial structure and functions were compared among sham-operated control and twelve-week orchidectomized (ORX) male rats with and without testosterone supplementation.

KEY FINDINGS

Echocardiography and pressure-volume relationships demonstrated a decreased left ventricular ejection fraction compared with sham-operated controls. The percentage of contractility reduction was generally similar to the decrease in tension development detected in both right ventricular trabeculae and skinned isolated left ventricular cardiomyocytes of ORX rats. Reductions in tension cost and the rate constant of tension redevelopment (k_tr) in ORX samples suggested a decrease in the rate of cross-bridge formation, reflecting a reduced number of cross-bridges. Slow cross-bridge detachment in ORX rat hearts could result from a shift of myosin heavy chain isoforms towards a slower ATPase activity β-isoform and reductions in the phosphorylation levels of cardiac troponin I and myosin binding protein-C. All the changes in the ORX rat heart, including ejection fractions and myofilament protein expression and phosphorylation, were completed attenuated by a physiological dose of testosterone.

SIGNIFICANCE

Testosterone plays a critical role in regulating the mechanical and contractile dynamics of the heart. Deprivation of male sex hormones cause the loss of normal preserved cardiac contractile function leading to a high risk of severe cardiomyopathy progression.

Testosterone suppression does not exacerbate disuse atrophy and impairs muscle recovery that is not rescued by high protein

Androgen deprivation therapy (ADT) decreases muscle mass, force, and physical activity levels, but it is unclear whether disuse atrophy and testosterone suppression are additive. Additionally, conflicting reports exist on load-mediated hypertrophy during ADT and if protein supplementation offsets these deficits. This study sought to determine the role of testosterone suppression and a high-protein diet on 1) immobilization-induced atrophy and 2) muscle regrowth during reloading. Eight-week-old male Fischer 344 rats underwent sham surgery (Sham), castration surgery (ORX), or ORX and a high-casein diet supplemented with branched-chain amino acids (BCAA) (ORX+CAS/AA) followed by 10 days of unilateral immobilization (IMM) and 0, 6, or 14 days of reloading. With IMM, body mass gains were ~8% greater than ORX and ORX+CAS/AA that increased to 15% during reloading (both P < 0.01). IMM reduced muscle mass by 11-34% (all P < 0.01) and extensor digitorum longus and soleus (SOL) force by 21% and 49% (both P < 0.01), respectively, with no group differences. During reloading, castration reduced gastrocnemius mass (~12%) at 6 days and SOL mass (~20%) and SOL force recovery (~46%) at 14 days relative to Sham (all P < 0.05). Specific force reduced castration deficits, indicating that muscle atrophy was a key contributor. IMM decreased SOL cross-sectional area by 30.3% (P < 0.001), with a trend for reduced regrowth in ORX and ORX+CAS/AA following reloading (P = 0.083). Castration did not exacerbate disuse atrophy but may impair recovery of muscle function, with no benefit from a CAS/AA diet during reloading. Examining functional outcomes in addition to muscle mass during dietary interventions provides novel insights into muscle regrowth during ADT.NEW & NOTEWORTHY Low testosterone levels during skeletal muscle disuse did not worsen declines in muscle mass and function, although hypogonadism may attenuate recovery during subsequent reloading. Diets high in casein did not improve outcomes during immobilization or reloading. Practical strategies are needed that do not compromise caloric intake yet provide effective protein doses to augment these adverse effects.

Exercise stimulates beneficial adaptations to diminish doxorubicin-induced cellular toxicity

Doxorubicin (DOX) is a highly effective antitumor agent used for the treatment of a wide range of cancers. Unfortunately, DOX treatment results in cytotoxic side effects due to its accumulation within off-target tissues. DOX-induced cellular toxicity occurs as a result of increased oxidative damage, resulting in apoptosis and cell death. While there is no standard-of-care practice to prevent DOX-induced toxicity to healthy organs, exercise has been shown to prevent cellular dysfunction when combined with DOX chemotherapy. Endurance exercise stimulates numerous biochemical adaptations that promote a healthy phenotype in several vulnerable tissues without affecting the antineoplastic properties of DOX. Therefore, for the development of an effective strategy to combat the pathological effects of DOX, it is important to determine the appropriate exercise regimen to prescribe to cancer patients receiving DOX therapy and to understand the mechanisms responsible for exercise-induced protection against DOX toxicity to noncancer cells. This review summarizes the cytotoxic effects of DOX on the heart, skeletal muscle, liver, and kidneys and discusses the current understanding of the clinical benefits of regular physical activity and the potential mechanisms mediating the positive effects of exercise on each organ system.

Regulation of PI3K and Hand2 gene on physiological hypertrophy of heart following high-intensity interval, and endurance training

Background:

Physical training signals cardiac hypertrophy through PI3K as an upstream and Hand2 gene as a downstream agent. The present study aimed to find the role of PI3K and Hand2 gene in myocardial hypertrophy following interval and endurance training (ET).

Materials and Methods:

Twenty-four adult Wistar male rats (210–250 g) randomly divided into control, sham, high-intensity interval training (HIIT), and ET group. Swimming time in ET increased incrementally 30–75 min, whereas in HIIT, load/body weight, and time/rest ratio increased within 12 weeks. Heart morphometry, including left ventricle end systolic (LVESV) and Diastolic (LVEDV) volume, LV posterior wall (LVPW), stroke volume (SV), ejection fraction (EF), fraction shortening (%FS), pure heart weight (HW) and left ventricle weight (LVW), and PI3K and Hand2 gene expression were measured.

Results:

HW and LVW were significantly more than control after ET (P < 0.05) and HIIT (P < 0.05). Both of the training groups demonstrated significantly thicker LVPW (P < 0.05), SV (P < 0.05), and %FS (P < 0.05). Furthermore, PI3K concentration and Hand2 expression significantly increased in ET (P < 0.001; P < 0.001, respectively) and HIIT (P < 0.05; P < 0.001, respectively) compared to control.

Conclusion:

It can be concluded that this training protocol caused physiological hypertrophy in both of ET and HIIT groups, whereas HIIT can be more beneficial because of shorter training time.

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.

Ovarian hormones mediate running-induced changes in high fat diet choice patterns in female rats

Physical inactivity and increased consumption of energy dense, high fat (HF) foods often leads to a state of positive energy balance. Regular exercise can facilitate the maintenance of a healthy body weight and mediate changes in dietary selection. Past studies using a two-diet choice (chow vs. HF) and voluntary wheel running paradigm found that when a novel HF diet and wheel running are simultaneously introduced, male rats show complete and persistent HF diet avoidance whereas the majority of females show HF diet avoidance for a few days, but then revert to HF diet preference. Ovariectomy (OVX) appears to decrease preference for the HF diet bringing it closer to that of males. Given that estradiol but not progesterone mediates changes in food intake and energy balance, we hypothesized that estradiol signaling is required for the reversal of HF diet avoidance in female rats. Accordingly, Experiment 1 compared the persistency of running-induced HF diet avoidance in males, sham-operated females, and OVX rats with replacement of oil vehicle, estradiol benzoate (E), progesterone (P), or both (E + P). The number of wheel running rats that either avoided or preferred the HF diet varied with hormone treatment. The reversal of HF diet avoidance in running females and OVX E + P rats occurred more rapidly and frequently than male running rats. E + P but not E or P replaced OVX wheel running rats significantly reversed HF diet avoidance. OVX oil rats avoided HF diet to the same extent as male rats for the first 11 days of diet choice and then rapidly increased HF diet intake and began preferring it. This incomplete elimination of sex differences suggests that developmental factors or androgens might play a role in sustaining running-induced HF diet avoidance. Subsequently, Experiment 2 aimed to determine the role of androgens in the persistency of running-associated HF diet avoidance with sham-operated and orchiectomized (GDX) male rats. Both intact and GDX male running rats persistently avoided the HF diet to the same extent. Taken together, these results suggest that activational effects of ovarian hormones play a role in female specific running-induced changes in diet choice patterns. Furthermore, the activational effects of androgens are not required for the expression of HF diet avoidance in males.

Cardiac adaptation to hypertension in adult female Dahl salt-sensitive rats is dependent on ovarian function, but loss of ovarian function does not predict early maladaptation

Aim of study was to examine experimentally the adult female hypertensive heart in order to determine the role of ovary function in the response of the heart to salt-dependent hypertension. Dahl salt-sensitive rats, age 12 weeks, with/without ovariectomy were fed a standard (0.3% NaCl) or high-salt diet (8%) for 16 weeks. Mean arterial blood pressure monitored noninvasively in conscious state increased significantly by high salt. Echocardiography was performed at baseline and endpoint. Heart function and molecular changes were evaluated at endpoint by left ventricle catheterization, by sirius red staining for collagen and by gene expression using quantitative RT-PCR for selected genes. At endpoint, significant concentric hypertrophy was present with high salt. Increase in relative wall thickening with high salt compared to normal diet was more pronounced with intact ovaries (0.33 ± 0.02 and 0.57 ± 0.04 vs. 0.29 ± 0.00 and 0.46 ± 0.03) as was the reduction in midwall fractional shortening (20 ± 0.6 and 14 ± 2 vs. 19 ± 0.9 and 18 ± 1). Ovariectomy increased stroke volume and decreased the ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity (E') (E/E' ratio) when compared to hearts from intact rats. High salt increased expression of collagen I and III genes and perivascular collagen in the heart slightly, but % interstitial collagen by sirius red staining remained unchanged in intact rats and decreased significantly by ovariectomy. Added volume load but not deterioration of function or structure characterized the nonfailing hypertensive heart of salt-sensitive females ovariectomized at mature age when compared to corresponding intact females.

Voluntary exercise training restores anticontractile effect of NO in coronary arteries of adult rats with antenatal/early postnatal hypothyroidism

INTRODUCTION

Our recent study showed that NO-mediated anticontractile effect of endothelium is absent in coronary arteries of adult rats, which suffered from antenatal/early postnatal hypothyroidism. This study tested the hypothesis that exercise training would improve such detrimental consequences of early thyroid deficiency.

DESIGN AND METHODS

Wistar dams received propylthiouracil (PTU, 7 ppm) in drinking water during gestation and two weeks postpartum; control dams received tap water. Six-week-old male offspring of control (CON) and PTU dams was divided into sedentary (CON-Sed, n = 12; PTU-Sed, n = 10) and trained (CON-Tr, n = 12; PTU-Tr, n = 10) groups; the latter had 24-h access to running wheels. Eight weeks later coronary arteries were studied by wire myography. Anticontractile effect of NO was assessed by the effects of NOS inhibitor L-NNA on the basal tone and contractile response to U46619. Oxidative phosphorylation complexes and eNOS were estimated by Western blotting.

RESULTS

T₃/T₄ and TSH levels (ELISA) were normalized in the progeny of PTU-treated dams at the age of 6 weeks and were not affected by training. Total running distance did not differ between CON-Tr and PTU-Tr. The contents of oxidative phosphorylation complexes were increased post-training in triceps brachii muscle from CON-Tr and PTU-Tr and in heart from PTU-Tr. Coronary arteries of PTU-Sed compared to CON-Sed demonstrated higher basal tone and contractile response to U46619, which were not further increased by L-NNA. The effects of L-NNA on the basal tone and contractile response to U46619 did not differ in CON-Tr and PTU-Tr groups, but were elevated in PTU-Tr compared to PTU-Sed group. PTU-Tr rats in comparison to PTU-Sed group had higher eNOS content in heart. Responses of coronary arteries to DEA/NO did not differ among all experimental groups.

CONCLUSIONS

Long-lasting coronary endothelial dysfunction resulted from transient thyroid deficiency during the antenatal/early postnatal period can be corrected by voluntary exercise training.

Physical training promotes similar effects to the blockade of angiotensin-converting enzyme on the cardiac morphology and function in old female rats subjected to premature ovarian failure

We investigated the effects of angiotensin-converting enzyme (ACE) inhibition and aerobic physical training on the heart of old female rats (82-wk-old) submitted to premature ovarian failure (10-wk.-old). We used different approaches: morphology and function by echocardiography, reactivity of the coronary bed and left ventricular contractibility (Langendorff Technique). Female Wistar ovariectomized (OVX) rats (n=42) were assigned to one of four groups: OVX, vehicle treated only; OVX-EM, Enalapril Maleate only (EM, 10mg·kg^-1·d^-1); OVX-T, aerobic trained only; and OVX-EMT, treated with Enalapril Maleate and aerobic trained. Both Enalapril Maleate treatment and aerobic training were done in the last 20weeks of the experimental protocol. When compared to the OVX group, the OVX-EM group showed lower values of wall thickness and left ventricular (LV) mass, lower values of coronary bed reactivity and reduced maximum response of LV contractility to dobutamine, while the OVX-T group showed lower values of LV wall thickness, increase in end-systolic volume, reduced maximum response of LV contractility to dobutamine, and left intraventricular pressure due to increased flow. The combination of treatments (EM and aerobic physical training) did not promote additional important effects on the parameters evaluated. Our results suggest similar beneficial effects of physical training and EM treatment on the morphology and cardiac function in old female rats submitted to premature ovarian failure. Although the causes of these benefits are still unknown, both treatments have promoted a decrease in cardiac contractility, and the reduced β1-adrenergic sensitivity suggests that both treatments may attenuate the sympathetic effect on the heart.

Voluntary exercise and testosterone therapy caused increase in percentage of Myh6 and expression of oxidative stress marker Cybb in left ventricles of rats

Aim: The aim of this study is to identify a possible damage to heart ventricles caused by supraphysiological doses of testosterone, voluntary physical activity or their combination.

Methods: In the 8-week long experiment, 10-12 weeks old male Wistar rats were administered testosterone depot in dose of 100 mg/kg (TES, n = 15) or vehiculum (CON, n = 12) once a week subcutaneously. Next groups injected with testosterone (SPOTES, n = 12) or vehiculum (SPO, n = 12) were running in exercise wheels ad libitum. Gene expressions in left and right ventricles of the heart were measured by quantitative reverse transcription polymerase chain reaction method.

Results:ln left ventricles of the testosterone groups, we observed a mild but significant increase in the percentage of Myh6 myosin heavy chain isoform and higher expression of NADPH oxidase subunit Cybb (*p < 0.05).

Conclusions:Testosterone affected the expression of genes related to contractile apparatus and oxidative stress in the left ventricle but not in right ventricle of the heart of rats. The observed level of physical activity did not have a compelling effect on the expression of measured genes.

Breast cancer treatment-associated cardiovascular toxicity and effects of exercise countermeasures

Advances in breast cancer treatment have improved disease-free survival and overall survival in women with early-stage breast cancer. However, these improvements may be attenuated by the adverse cardiovascular effects associated with breast cancer adjuvant therapy. Exercise may be a potential strategy to counteract these toxicities. The purpose of this paper is to provide an overview on the adverse cardiovascular effects of breast cancer therapy as well as the evidence supporting the potential cardioprotective effects of exercise training in breast cancer patients during and after treatment. We will also discuss research gaps and avenues for future research.

Regular exercise improves cardiac contractile activation by modulating MHC isoforms and SERCA activity in orchidectomized rats

Data from the trial known as Testosterone in Older Men with Mobility Limitations (TOM) has indicated an association between testosterone administration and a greater risk for adverse cardiovascular events. We therefore propose that regular exercise is a cardioprotective alternative that prevents detrimental changes in contractile activation when a deficiency in male sex hormones exists. Ten-week-old orchidectomized (ORX) rats were subjected to a 9-wk treadmill running program at moderate intensity starting 1 wk after surgery. Although exercise-induced cardiac hypertrophy was observed both in rats that underwent ORX and sham surgery, regular exercise enhanced cardiac myofilament Ca(2+) sensitivity and myosin light-chain 2 phosphorylation only in rats that underwent a sham operation. Although the rats that had sham surgery and and given exercise exhibited no change in maximum developed tension, regular running prevented the suppression of maximum active tension in the hearts of ORX rats. Regular exercise also prevented a shift in myosin heavy chain (MHC) isoforms toward β-MHC, a reduction in sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) activity, and an increase in SERCA sensitivity in the hearts of ORX rats. Neither SERCA content nor its modulating component, phospholamban (PLB), was altered by exercise in either sham-operated or ORX rats. However, decreases in the phosphorylated Thr(17) form of PLB and the phosphorylated Thr(287) form of Ca(2+)/calmodulin-dependent kinase II in the hearts of ORX rats were abolished after regular exercise. These results thus support the use of regular running as a cardioprotective alternative to testosterone replacement in hypogonadal conditions.

Aerobic physical training increases contractile response and reduces cardiac fibrosis in rats subjected to early ovarian hormone deprivation

We investigated the effects of early ovarian hormone deprivation on the heart and the role of physical training in this condition using different approaches: cardiac autonomic tone, contractility, morphology and function, and cardiac fibrosis. Female Wistar rats ( n = 48) were assigned into two groups: ovariectomized (Ovx; 10-wk-old) and control rats (Sham; 10-wk-old). Each group was further divided into two subgroups, sedentary and trained (aerobic training by swimming for 10 wk). The sedentary groups showed similar cardiac autonomic tone values; however, only the Sham group had an increase in vagal participation for the determination of the basal heart rate after physical training. The contractile responses to cardiac β-agonists of the sedentary groups were similar, including an increased response to a β1-agonist (dobutamine) observed after physical training. The Ovx sedentary group presented changes in cardiac morphology, which resulted in decreases in the ejection fraction, fractional shortening, and cardiac index compared with the Sham sedentary group. Physical training did little to alter these findings. Moreover, histology analysis showed a significant increase in cardiac fibrosis in the sedentary Ovx group, which was not observed in the trained Ovx group. We conclude that early ovarian hormone deprivation in rats impairs autonomic control, cardiac morphology, and cardiac function and increases cardiac fibrosis; however, it does not affect the contractility induced by dobutamine and salbutamol. Furthermore, this model of physical training prevented an increase in fibrosis and promoted an increase in the cardiac contractile response but had little effect on cardiac autonomic control or morphological and functional parameters.

Cardiomyopathy associated with cancer therapy

Chemotherapy-associated cardiomyopathy is a well known cardiotoxicity of contemporary cancer treatment and a cause of increasing concern for both cardiologists and oncologists. As cancer outcomes improve, cardiovascular disease has become a leading cause of morbidity and mortality among cancer survivors. Asymptomatic or symptomatic left ventricular systolic dysfunction in the setting of cardiotoxic chemotherapy is an important entity to recognize. Early diagnosis of cardiac injury through the use of novel blood-based biomarkers or noninvasive imaging modalities may allow for the initiation of cardioprotective medications or modification of chemotherapy regimen to minimize or prevent further damage. Several clinical trials are currently underway to determine the efficacy of cardioprotective medications for the prevention of chemotherapy-associated cardiomyopathy. Implementing a strategy that includes both early detection and prevention of cardiotoxicity will likely have a significant impact on the overall prognosis of cancer survivors. Continued coordination of care between cardiologists and oncologists remains critical to maximizing the oncologic benefit of cancer therapy while minimizing any early or late cardiovascular effects.

Endurance exercise attenuates cardiotoxicity induced by androgen deprivation and doxorubicin

Doxorubicin (DOX) is associated with cardiac dysfunction and irreversible testicular damage. Androgen deprivation therapy (ADT) is administered prior to DOX treatment to preserve testicular function. However, ADT may exacerbate DOX-induced cardiac dysfunction. Exercise is cardioprotective, but the effects of exercise on cardiac function during combined ADT and DOX treatment are currently unknown. In this study, male Sprague-Dawley rats were randomly assigned to experimental groups: control (CON), ADT, DOX, or ADT+DOX. Animals received ADT or control implants on days 1 and 29 of the 56-day protocol. Animals remained sedentary (SED) or engaged in treadmill endurance exercise (TM) beginning on day 1. On day 15, the animals received DOX at 1 mg·(kg body mass)(-1)·d(-1) by intraperitoneal injection for 10 consecutive days, or an equivalent volume of saline. On day 57, cardiac function was assessed in vivo and ex vivo. Animals treated with DOX alone, or with combined ADT+DOX, showed significant (P < 0.05) reductions in left ventricular developed pressure (-21% and -27%), maximal rate of pressure development (-29% and -32%), and maximal rate of pressure decline (25% and 31%), respectively when compared with the sedentary control animals. Endurance exercise training attenuated (P > 0.05) cardiac dysfunction associated with combined ADT+DOX treatment, indicating that exercise during simultaneous ADT+DOX treatment is cardioprotective.

Cardiorespiratory fitness in breast cancer patients: a call for normative values

Background

There is emerging evidence that adjuvant treatments for breast cancer negatively impact cardiorespiratory fitness (CRF) or Vo_2max, a key predictor of cardiovascular risk. Although a number of studies have measured CRF in breast cancer patients, there is currently limited data regarding expected CRF values in this patient population. Given that CRF is a poor prognostic sign and recently highlighted as a key measure to standardize by the American Heart Association, we sought to review the available literature on CRF among breast cancer patients.

Methods and Results

We identified 27 clinical trials and observational studies measuring Vo_2max in the pre– and post–adjuvant treatment setting for breast cancer. We compared Vo_2max before to Vo_2max after adjuvant therapy and compared Vo_2max in female breast cancer patients with Vo_2max in healthy controls.

Conclusions

We found that CRF was substantially lower in women with a history of breast cancer compared with healthy women and this was most pronounced among breast cancer patients in the post‐adjuvant setting. We conclude that knowledge of normative CRF values is critical to tailor appropriately timed exercise interventions in breast cancer patients susceptible to low CRF and subsequent cardiovascular risk.

Switching to a low-fat diet attenuates the intensified doxorubicin cardiotoxicity associated with high-fat feeding

PURPOSE

A high-fat diet has been shown to exacerbate the cardiotoxicity associated with the chemotherapy drug doxorubicin (DOX); however, it is unknown whether switching from a high-fat diet to a low-fat diet can attenuate the intensified DOX cardiotoxicity. The purpose of this study was to investigate the effects of a low-fat diet on DOX-induced cardiotoxicity in rats previously fed a high-fat diet.

METHODS

Male rats were randomly assigned to consume a Western diet or a low-fat diet for 6 weeks. Western diet-fed rats were then further randomized to switch to the low-fat diet (WD-LF) or continue with the Western diet (WD). One week later, WD-LF and WD received 1 mg/kg DOX per day for 10 consecutive days and continued with their diets (WD-LF + DOX, WD + DOX). LF was further randomized to receive 1 mg/kg DOX per day for 10 consecutive days (LF + DOX) or saline injections as a control (LF + SAL). Four weeks following the first injection, cardiac function was analyzed, and left ventricles were analyzed for cardiotoxicity indices.

RESULTS

When compared to LF + SAL and LF + DOX, WD + DOX exhibited an enhanced cardiotoxicity as evidenced by reduced septal wall thickness, fractional shortening, and sarco-endoplasmic reticulum Ca(2+) ATPase expression as well as increased left ventricular cavity dimensions, lipid peroxidation, and β-myosin heavy-chain expression. This exacerbated cardiotoxicity was not observed in WD-LF + DOX.

CONCLUSIONS

Switching to a low-fat diet 1 week prior to, during, and following DOX treatment attenuated the exacerbated cardiotoxicity observed in the previously Western diet-fed rats.

Effects of Aromatase Inhibition on the Physical Activity Levels of Male Mice

Increasing activity levels in an inactive population can lead to associative increases in health and well-being. Both biologic and genetic factors have been identified that alter physical activity levels in humans and rodents with an extensive early literature regarding sex steroid effects on physical activity. Currently, it is suggested that the androgens require conversion to estrogens prior to eliciting any effects on activity patterns. Recent data contradicts this assertion; thus, the purpose of this study was to evaluate the necessity of the aromatase complex in activity regulation. Wheel running was assessed in male C57BL/6J mice under various sex steroid-disrupted and aromatase-inhibited conditions. Inhibition of the aromatase complex was achieved through administration of two different aromatase inhibiting substances-letrozole and exemestane. Wheel running was unaffected by aromatase inhibition in reproductively intact and sex steroid supplemented mice. Orchidectomy significantly reduced wheel running activity. Steroid replacement recovered wheel running to pre-surgical levels; however, aromatase inhibition did not further affect wheel running levels. The recovery of wheel running in mice with androgen supplementation and the further persistence of wheel running in mice with compromised aromatase function suggests that the androgens-testosterone in particular-may directly affect wheel running patterns in male mice.

Rehabilitative exercise in a rat model of doxorubicin cardiotoxicity

The use of exercise to minimize doxorubicin (DOX)-induced cardiotoxicity is gaining attention. However, very few clinically relevant reports exist investigating the effects of exercise performed during and following DOX treatments. The purpose of this study, therefore, was to examine the effects of voluntary wheel running during and following DOX treatment using two models of late-onset DOX cardiotoxicity in the rat. Female Sprague-Dawley rats received either DOX or saline injections using one of two separate treatment regimens. These regimens involved either daily or weekly DOX injections with cumulative doses for both protocols totaling 15 mg/kg. Daily DOX injections were 1 mg/kg and lasted for 15 consecutive days while weekly DOX injections were 2.5 mg/kg and lasted for six consecutive weeks with control animals receiving matched saline injection regimens. Immediately following the initial DOX/saline injection, animals were randomly housed in cages with voluntary running wheels or standard rat cages throughout DOX/saline treatments and continued until reaching 10 weeks. Cardiac function was then assessed using echocardiography and an isolated working heart model, and myosin heavy chain (MHC) isoform distribution was assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When compared wth controls, daily DOX treatment resulted in reduced running wheel distances at weeks 2-10 (P < 0.05), and weekly DOX treatment resulted in reduced running wheel distances at weeks 2, 6 and 10 (P < 0.05). Nonetheless, wheel running during and following daily and weekly DOX dosing protected against DOX-induced cardiotoxicity by preserving maximal mitral and aortic blood flow velocities, left ventricular developed pressure and MHC isoform expression. In conclusion, the overall reduced volume of activity during and following daily and weekly DOX treatments attenuated DOX-induced cardiac dysfunction suggesting that low-volume endurance training may be an effective rehabilitative approach in minimizing DOX cardiotoxicity in cancer patients.

Dissociating behavioral, autonomic, and neuroendocrine effects of androgen steroids in animal models

Developments in behavioral assessment, autonomic and/or baseline reactivity, psychopharmacology, and genetics, have contributed significantly to the assessment of performance-enhancing drugs in animal models. Particular classes of steroid hormones: androgenic steroids are of interest. Anecdotally, the performance enhancing effects of androgens are attributed to anabolic events. However, there is a discrepancy between anecdotal evidence and investigative data. While some androgen steroids may promote muscle growth (myogenesis), effects of androgens on performance enhancement are not always seen. Indeed, some effects of androgens on performance may be attributable to their psychological and cardiovascular effects. As such, we consider androgen effects in terms of their behavioral, autonomic, and neuroendocrine components. Techniques are discussed in this chapter, some of which are well established, while others have been more recently developed to study androgen action. Androgens may be considered for their positive impact, negative consequence, or psychotropic properties. Thus, this review aims to elucidate some of the effects and/or mechanisms of androgens on behavioral, autonomic, and/or neuroendocrine assessment that may underlie their controversial performance enhancing effects.

Exercise rehabilitation in patients with cancer

Emerging evidence indicates that patients with cancer have considerable impairments in cardiorespiratory fitness, which is likely to be a result of the direct toxic effects of anticancer therapy as well as the indirect consequences secondary to therapy (for example, deconditioning). This reduced cardiorespiratory fitness is associated with heightened symptoms, functional dependence, and possibly with an increased risk of cardiovascular morbidity and mortality. Current understanding of the complex interaction between the effects of the tumour and cancer-associated therapies on the organ components that govern cardiorespiratory fitness, and the effects of exercise training on these parameters is limited; further research will be critical for further progress of exercise-based rehabilitation in the oncology setting. We assess the current evidence regarding the level, mechanisms, and clinical importance of diminished cardiorespiratory fitness in patients with cancer. The efficacy and adaptations to exercise training to prevent and/or mitigate dysfunction in conjunction with exercise prescription considerations for clinical use are also discussed.

Exercise as a potential treatment for drug abuse: evidence from preclinical studies

Epidemiological studies reveal that individuals who engage in regular aerobic exercise are less likely to use and abuse illicit drugs. Until recently, very few studies had examined the causal influences that mediate this relationship, and it was not clear whether exercise was effective at reducing substance use and abuse. In the past few years, several preclinical studies have revealed that exercise reduces drug self-administration in laboratory animals. These studies have revealed that exercise produces protective effects in procedures designed to model different transitional phases that occur during the development of, and recover from, a substance use disorder (e.g., acquisition, maintenance, escalation, and relapse/reinstatement of drug use). Moreover, recent studies have revealed several behavioral and neurobiological consequences of exercise that may be responsible for its protective effects in these assays. Collectively, these studies have provided convincing evidence to support the development of exercise-based interventions to reduce compulsive patterns of drug intake in clinical and at-risk populations.

Exercise as a beneficial adjunct therapy during Doxorubicin treatment--role of mitochondria in cardioprotection

One of the mostly used chemotherapeutic drugs is the highly effective anthracycline Doxorubicin. However, its clinical use is limited by the dose-related and cumulative cardiotoxicity and consequent dysfunction. It has been proposed that the etiology of this toxicity is related to mitochondrial dysfunction. The present review aimed to analyze the promising results regarding the effect of several types of physical exercise in cardiac tolerance of animals treated with acute and sub-chronic doses of Doxorubicin (DOX), highlighting the importance of cardiac mitochondrial-related mechanisms in the process. Physical exercise positively modulates some important cardiac defense systems to antagonize the toxic effects caused by DOX treatment, including antioxidant capacity, the overexpression of heat shock proteins and other anti-apoptotic proteins. An important role in this protective phenotype afforded by exercise should be attributed to mitochondrial plasticity, as related adaptations could be translated into improved cardiac function in the setting of the DOX cardiomyopathy.

The heart: a novel gonadotrophin-releasing hormone target

Gonadotrophin-releasing hormone (GnRH) is a hypothalamic hormone transported by the hypophyseal portal bloodstream to the pituitary gland, where it binds to GnRH receptors. However, GnRH receptors are expressed in multiple extrapituitary tissues, although their physiological relevance is not fully understood. GnRH agonists are employed extensively in steroid deprivation therapy, especially to suppress testosterone in prostate cancer. Because GnRH agonist treatment is associated with increased coronary heart disease and myocardial infarction, we investigated the impact of GnRH on cardiomyocyte contractile function. Cardiomyocytes were isolated from mouse hearts and mechanical and intracellular Ca(2+) properties were evaluated, including peak shortening amplitude (PS), time-to-PS (TPS), time-to-90% relengthening (TR(90) ), maximal velocity of shortening/relengthening (± dLdt), electrically-stimulated rise in Fura-2 fluorescence intensity (ΔFFI) and Ca(2+) decay. GnRH (1 ng/ml) increased PS, ± dL/dt, resting FFI and ΔFFI, and prolonged TPS, TR(90) and Ca(2+) decay time, whereas 1 pg/ml GnRH affected all these cardiomyocyte variables, except TPS, resting FFI and ΔFFI. A concentration of 1 fg/ml GnRH and the GnRH cleavage product, GnRH-[1-5] (300 pg/ml), had no effect on any cardiomyocyte parameter. The 1 pg/ml GnRH-elicited responses were attenuated by the GnRH receptor antagonist cetrorelix (10 μm), the protein kinase A (PKA) inhibitor H89 (1 μm) but not the protein kinase C inhibitor chelerythrine chloride (1 μm). These data revealed that GnRH is capable of regulating cardiac contractile function via a GnRH receptor/PKA-dependent mechanism. If present in the human heart, dysfunction of such a system may play an important role in cardiac pathology observed in men treated with GnRH agonists for prostate cancer.

Is there a relationship between physical performance and orchiectomy?

Bilateral orchiectomy is indicated for the treatment of patients with testicular cancer or advanced prostate tumours. The influence of hypogonadism on physical performance is still not known. The purpose of this work was to verify the effect of bilateral orchiectomy on physical performance. Sixteen rats were divided into two groups: Group 1 (Control), in which only skin incision and suture were made (n = 5) and Group 2, in which the rats were submitted to bilateral orchiectomy (n = 11). The animals ran on a treadmill at the speed of 20 m min(-1) until they were fatigued and felt once, during 10 s, when the experiment was interrupted. Time to running and weight of animals were verified. The results were compared using the Mann-Whitney test. There was no difference on time to running - minutes - (P = 0.14) and weight - grams - (P = 0.25) between the animals submitted to orchiectomy (100 ± 44 min and 359 ± 38 g) and the control Group (81 ± 40 min to run and 327 ± 25 g). Bilateral orchiectomy does not affect the physical performance of the rat.

Exercise intolerance in cancer and the role of exercise therapy to reverse dysfunction

Exercise tolerance reflects the integrative capacity of components in the oxygen cascade to supply adequate oxygen for ATP resynthesis. Conventional cancer therapies can simultaneously affect one or more components of this cascade and reduce the body's ability to deliver or utilise oxygen and substrate, leading to exercise intolerance. We propose that molecularly-targeted therapy is associated with a further, more subtle, negative effect on the components that regulate exercise limitation. We outline possible causes of exercise intolerance in patients with cancer and the role of exercise therapy to mitigate or prevent dysfunction. We also discuss possible implications for exercise-regulated gene expression for cancer biology and treatment efficacy. A better understanding of these issues might lead to more effective integration of exercise therapy to optimise the treatment and management of patients with cancer.

Effects of gonadotrophin-releasing hormone outside the hypothalamic-pituitary-reproductive axis

Gonadotrophin-releasing hormone (GnRH) is a hypothalamic decapeptide with an undisputed role as a primary regulator of gonadal function. It exerts this regulation by controlling the release of gonadotrophins. However, it is becoming apparent that GnRH may have a variety of other vital roles in normal physiology. A reconsideration of the potential widespread action that this traditional reproductive hormone exerts may lead to the generation of novel therapies and provide insight into seemingly incongruent outcomes from current treatments using GnRH analogues to combat diseases such as prostate cancer.

Effects of voluntary wheel running on goserelin acetate-induced bone degeneration

A common treatment option for many breast and prostate cancer patients is the use of a luteinizing hormone-releasing hormone agonist such as goserelin acetate (GA) which reduces sex hormone levels. This treatment, however, is associated with bone degeneration, and exercise has been suggested as a means of preventing this side effect. Little is known about the effects of low intensity, low volume exercise on GA-induced bone loss. The purpose of this study, therefore, was to investigate the effects of voluntary wheel running on bone architecture in growing male (M) and female (F) rats receiving GA treatment. Rats received an 8-week GA treatment or placebo (CON) and were either housed in cages equipped with voluntary running wheels (WR) or remained sedentary (SED) in standard cages throughout the experimental period. Following treatments, tibiae were excised and analyzed for cortical bone (cross-sectional volume, cortical volume, marrow volume, cortical thickness) and cancellous bone (bone volume/total volume, trabecular number, trabecular thickness, trabecular spacing) using micro-computed tomography. Treatment with GA resulted in a significant reduction in running wheel distances in both sexes throughout the study period (P<0.05). GA treatment had no effect on cortical bone architecture in neither sex (P>0.05). Cancellous bone degeneration, however, was observed in M and F SED+GA (P<0.05). No significant differences were observed in M WR+GA animals in bone volume/total volume, trabecular number and trabecular spacing when compared to M SED+CON (P>0.05). In F WR+GA, trabecular thickness did not differ from that of F SED+CON (P>0.05), and trabecular spacing was found to be significantly lower than F SED+GA (P<0.05). The current report indicates that 8 weeks of GA treatment promotes cancellous bone degeneration, and voluntary wheel running provides no clear osteoprotection in growing male and female rats.