Exercise training can induce cardiac autophagy at end-stage chronic conditions: Insights from a graft-versus-host-disease mouse model

Chronic graft-versus-host disease (cGVHD) is a frequent cause of morbimortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and severely compromises patients' physical capacity. Despite the aggressive nature of the disease, aerobic exercise training can positively impact survival as well as clinical and functional parameters. We analyzed potential mechanisms underlying the recently reported cardiac function improvement in an exercise-trained cGVHD murine model receiving lethal total body irradiation and immunosuppressant treatment (Fiuza-Luces et al., 2013. Med Sci Sports Exerc 45, 1703-1711). We hypothesized that a cellular quality-control mechanism that is receiving growing attention in biomedicine, autophagy, was involved in such improvement. Our results suggest that exercise training elicits a positive autophagic adaptation in the myocardium that may help preserve cardiac function even at the end-stage of a devastating disease like cGVHD. These preliminary findings might provide new insights into the cardiac exercise benefits in chronic/debilitating conditions.

Anti-inflammatory effect of exercise training in subjects with type 2 diabetes and the metabolic syndrome is dependent on exercise modalities and independent of weight loss

We investigated the effect of different exercise modalities on high sensitivity-C reactive protein (hs-CRP) and other inflammatory markers in patients with type 2 diabetes and the metabolic syndrome. Eighty-two patients were randomized into 4 groups: sedentary control (A); receiving counseling to perform low-intensity physical activity (B); performing prescribed and supervised high-intensity aerobic (C) or aerobic + resistance (D) exercise (with the same caloric expenditure) for 12 months. Evaluation of leisure-time physical activity and assessment of physical fitness, cardiovascular risk factors and inflammatory biomarkers was performed at baseline and every 3 months. Volume of physical activity increased and HbA1c decreased in Groups B–D. VO2max, HOMA-IR index, HDL-cholesterol, waist circumference and albuminuria improved in Groups C and D, whereas strength and flexibility improved only in Group D. Levels of hs-CRP decreased in all three exercising groups, but the reduction was significant only in Groups C and D, and particularly in Group D. Changes in VO2max and the exercise modalities were strong predictors of hs-CRP reduction, independent of body weight. Leptin, resistin and interleukin-6 decreased, whereas adiponectin increased in Groups C and D. Interleukin-1β, tumor necrosis factor-α and interferon-γ decreased, whereas anti-inflammatory interleukin-4 and 10 increased only in Group D. In conclusion, physical exercise in type 2 diabetic patients with the metabolic syndrome is associated with a significant reduction of hs-CRP and other inflammatory and insulin resistance biomarkers, independent of weight loss. Long-term high-intensity (preferably mixed) training, in addition to daytime physical activity, is required to obtain a significant anti-inflammatory effect.

Exercise for the management of type 2 diabetes: A review of the evidence

The aim is to critically review the more relevant evidence on the interrelationships between exercise and metabolic outcomes. The research questions addressed in the recent specific literature with the most relevant randomized controlled trials, meta-analysis and cohort studies are presented in three domains: aerobic exercise, resistance exercise, combined aerobic and resistance exercise. From this review appear that the effects of aerobic exercise are well established, and interventions with more vigorous aerobic exercise programs resulted in greater reductions in HbA1c, greater increase in VO2max and greater increase in insulin sensitivity. Considering the available evidence, it appears that resistance training could be an effective intervention to help glycemic control, especially considering that the effects of this form of intervention are comparable with what reported with aerobic exercise. Less studies have investigated whether combined resistance and aerobic training offers a synergistic and incremental effect on glycemic control; however, from the available evidences appear that combined exercise training seems to determine additional change in HbA1c that can be seen significant if compared with aerobic training alone and resistance training alone.

Active paraplegics are protected against exercise-induced oxidative damage through the induction of antioxidant enzymes

Exercise improves functional capacity in spinal cord injury (SCI). However, exhaustive exercise, especially when sporadic, is linked to the production of reactive oxygen species that may have a detrimental effect on SCI. We aimed to study the effect of a single bout of exhaustive exercise on systemic oxidative stress parameters and on the expression of antioxidant enzymes in individuals with paraplegia. The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia. Sixteen paraplegic subjects were submitted to a graded exercise test (GET) until volitional exhaustion. They were divided into active or non-active groups. Blood samples were drawn immediately, 1 and 2 h after the GET. We determined plasma malondialdehyde (MDA) and protein carbonylation as markers of oxidative damage. Antioxidant gene expression (catalase and glutathione peroxidase-GPx) was determined in peripheral blood mononuclear cells. We found a significant increase in plasma MDA and protein carbonyls immediately after the GET (P<0.05). This increment correlated significantly with the lactate levels. Active paraplegics showed lower levels of exercise-induced oxidative damage (P<0.05) and higher exercise-induced catalase (P<0.01) and GPx (P<0.05) gene expression after the GET. These results suggest that exercise training may be useful in SCI patients to develop systemic antioxidant defenses that may protect them against exercise-induced oxidative damage.

Muscle signaling in exercise intolerance: Insights from the McArdle mouse model

We recently generated a knock-in mouse model (PYGM p.R50X/p.R50X) of McArdle disease (myophosphorylase deficiency). One mechanistic approach to unveil the molecular alterations caused by myophosphorylase deficiency, which is arguably the paradigm of 'exercise intolerance', is to compare the skeletal-muscle tissue of McArdle, heterozygous, and healthy (wild type (wt)) mice. We analyzed in quadriceps muscle of p.R50X/p.R50X (n=4), p.R50X/wt (n=6) and wt/wt mice (n=5) (all male, 8 wk-old) molecular markers of energy-sensing pathways, oxidative phosphorylation (OXPHOS) and autophagy/proteasome systems, oxidative damage and sarcoplamic reticulum (SR) Ca handling. We found a significant group effect for total AMPK (tAMPK) and ratio of phosphorylated (pAMPK)/tAMPK (P=0.012 and 0.033), with higher mean values in p.R50X/p.R50X mice vs. the other two groups. The absence of massive accumulation of ubiquitinated proteins, autophagosomes or lysosomes in p.R50X/p.R50X mice suggested no major alterations in autophagy/proteasome systems. Citrate synthase activity was lower in p.R50X/p.R50X mice vs. the other two groups (P=0.036) but no statistical effect existed for respiratory chain complexes. We found higher levels of 4-hydroxy-2-nonenal-modified proteins in p.R50X/p.R50X and p.R50X/wt mice compared with the wt/wt group (P=0.011). Sarco(endo)plasmic reticulum ATPase 1 (SERCA1) levels detected at 110kDa tended to be higher in p.R50X/p.R50X and p.R50X/wt mice compared with wt/wt animals (P=0.076), but their enzyme activity was normal. We also found an accumulation of phosphorylated SERCA1 in p.R50X/p.R50X animals. Myophosphorylase deficiency causes alterations in sensory energetic pathways together with some evidence of oxidative damage and alterations in Ca handling but with no major alterations in OXPHOS capacity or autophagy/ubiquitination pathways, which suggests that the muscle tissue of patients is likely to adapt overall favorably to exercise training interventions.

Exercise intervention in pediatric patients with solid tumors: The PAPEC trial

The randomized controlled trial ‘Physical Activity in Pediatric Cancer’ (PAPEC) determined the effects of an in-hospital exercise intervention combining aerobic and muscle strength training on pediatric cancer patients with solid tumors undergoing neoadjuvant chemotherapy. Methods. Participants were allocated to an exercise (n=24, 17 boys; mean±SEM age 10±1y) or control group (n=25, 18 boys; 11±1y). Training included three sessions/week for 19±2 weeks. Participants were assessed at treatment initiation, termination, and two months after end-treatment. The primary endpoint was muscle strength (as assessed by upper and lower-body five-repetition-maximum (5RM) tests). Secondary endpoints included cardiorespiratory fitness, functional capacity during daily life activities, physical activity, body mass and body mass index, and quality of life. Results. Most sessions were performed in the hospital’s gymnasium. Adherence to the program averaged 68±4% and no major adverse events or health issues were noted. A significant interaction (group*time) effect was found for all 5RM tests. Performance significantly increased after training (leg press: 40% (95% CI=15–41 kg); bench press: 24% (95% CI=6–14 kg); lateral row 25% (95%CI=6–15 kg)), whereas an opposite trend was found in controls. Two-month post values tended to be higher than baseline for leg (P=0.017) and bench press (P=0.014). In contrast, no significant interaction effect was found for any of the secondary endpoints. Conclusion. An in-hospital exercise program for pediatric cancer patients with solid tumors undergoing neoadjuvant treatment increases muscle strength despite the aggressiveness of such therapy. Key words: Cancer, exercise, muscle strength, fitness, quality of life.

Analysis of the aerobic-anaerobic transition in elite cyclists during incremental exercise with the use of electromyography

To investigate the validity and reliability of surface electromyography (EMG) as a new non-invasive determinant of the metabolic response to incremental exercise in elite cyclists. The relation between EMG activity and other more conventional methods for analysing the aerobic-anaerobic transition such as blood lactate measurements (lactate threshold (LT) and onset of blood lactate accumulation (OBLA)) and ventilatory parameters (ventilatory thresholds 1 and 2 (VT1 and VT2)) was studied.Twenty eight elite road cyclists (age 24 (4) years; VO2MAX 69.9 (6.4) ml/kg/min; values mean (SD)) were selected as subjects. Each of them performed a ramp protocol (starting at 0 W, with increases of 5 W every 12 seconds) on a cycle ergometer (validity study). In addition, 15 of them performed the same test twice (reliability study). During the tests, data on gas exchange and blood lactate levels were collected to determine VT1, VT2, LT, and OBLA. The root mean squares of EMG signals (rms-EMG) were recorded from both the vastus lateralis and the rectus femoris at each intensity using surface electrodes. Results - A two threshold response was detected in the rms-EMG recordings from both muscles in 90% of subjects, with two breakpoints, EMG(T1) and EMG(T2), at around 60-70% and 80-90% of VO2MAX respectively. The results of the reliability study showed no significant differences (p > 0.05) between mean values of EMG(T1) and EMG(T2) obtained in both tests. Furthermore, no significant differences (p > 0.05) existed between mean values of EMG(T1), in the vastus lateralis and rectus femoris, and VT1 and LT (62.8 (14.5) and 69.0 (6.2) and 64.6 (6.4) and 68.7 (8.2)% of VO2MAX respectively), or between mean values of EMG(T2), in the vastus lateralis and rectus femoris, and VT2 and OBLA (86.9 (9.0) and 88.0 (6.2) and 84.6 (6.5) and 87.7 (6.4)% of VO2MAX respectively). Rms-EMG may be a useful complementary non-invasive method for analysing the aerobic-anaerobic transition (ventilatory and lactate thresholds) in elite cyclists.