Low aerobic capacity in McArdle disease: A role for mitochondrial network impairment?

BACKGROUND: McArdle disease is caused by myophosphorylase deficiency and results in complete inability for muscle glycogen breakdown. A hallmark of this condition is muscle oxidation impairment (e.g., low peak oxygen uptake (VO2peak)), a phenomenon traditionally attributed to reduced glycolytic flux and Krebs cycle anaplerosis. Here we hypothesized an additional role for muscle mitochondrial network alterations associated with massive intracellular glycogen accumulation. METHODS: We analyzed in depth mitochondrial characteristics-content, biogenesis, ultrastructure-and network integrity in skeletal-muscle from McArdle/control mice and two patients. We also determined VO2peak in patients (both sexes, N = 145) and healthy controls (N = 133). RESULTS: Besides corroborating very poor VO2peak values in patients and impairment in muscle glycolytic flux, we found that, in McArdle muscle: (a) damaged fibers are likely those with a higher mitochondrial and glycogen content, which show major disruption of the three main cytoskeleton components-actin microfilaments, microtubules and intermediate filaments-thereby contributing to mitochondrial network disruption in skeletal muscle fibers; (b) there was an altered subcellular localization of mitochondrial fission/fusion proteins and of the sarcoplasmic reticulum protein calsequestrin-with subsequent alteration in mitochondrial dynamics/function; impairment in mitochondrial content/biogenesis; and (c) several OXPHOS-related complex proteins/activities were also affected. CONCLUSIONS: In McArdle disease, severe muscle oxidative capacity impairment could also be explained by a disruption of the mitochondrial network, at least in those fibers with a higher capacity for glycogen accumulation. Our findings might pave the way for future research addressing the potential involvement of mitochondrial network alterations in the pathophysiology of other glycogenoses.

Validity of the Physical Activity Questionnaires IPAQ-SF and GPAQ for Cancer Survivors: Insights from a Spanish Cohort.

Regular physical activity (PA) decreases mortality risk in survivors of breast and colorectal cancer. Such impacts of exercise have prompted initiatives designed both to promote and adequately monitor PA in cancer survivors. This study examines the validity of 2 widely used self-report methods for PA determination, the International Physical Activity Questionnaire short version (IPAQ-SF) and Global Physical Activity Questionnaire (GPAQ). Both instruments were compared with the triaxial accelerometry (Actigraph) method as an objective reference standard. Study participants were 204 cancer survivors (both sexes, aged 18-79 years). Compared with accelerometry, both questionnaires significantly overestimated PA levels (across all intensities) and underestimated physical inactivity levels. No differences were detected between the 2 questionnaires except for a shorter inactivity time estimated by GPAQ (p=0.001). The Bland and Altman method confirmed that both questionnaires overestimated all PA levels. Receiver operating characteristic (ROC) analysis classified IPAQ and GPAQ as fair and poor predictors, respectively, of the proportions of survivors fulfilling international PA recommendations (≥150 min·week-1 of moderate-vigorous PA). IPAQ-SF showed a higher sensitivity but lower specificity than GPAQ. Our data do not support the use of IPAQ-SF or GPAQ to determine PA or inactivity levels in cancer survivors.

Response rate to the treatment of Waldenström macroglobulinemia: A meta-analysis of the results of clinical trials.

Waldenström macroglobulinemia (WM) is a malignant lymphoproliferative disorder characterized by the presence of a high level of serum monoclonal IgM and a lymphoplasmacytic infiltrate in the bone marrow. This meta-analysis sought to assess the effectiveness of the different treatments for WM tested in published trials using the response rate (RR) as the main outcome measure. Forty-six articles (1409 patients) identified were entered in a variable effects model meta-analysis of proportions (rates and sample sizes). A greater response to treatment was produced in patients treated with a combination of 2+ drugs (RR=73%; 95%CI: 62, 83; p<0.01) than in those receiving monotherapy with rituximab (RR=44%; 95%CI: 34, 55; p<0.01) or a purine analogue [61% (95%CI: 43, 78; p<0.01) for cladribine and 53% (95%CI: 34, 72; p<0.01) for fludarabine]. The combination rituximab+cladribine emerged as particularly effective (RR=87%; 95%CI: 78, 94; p<0.01), slightly more effective than rituximab+bortezomib/dexamethasone (RR=84%; 95%CI: 79, 88; p<0.01) and rituximab+cyclophosphamide/dexamethasone [RR=81% (95%CI: 72, 88; p<0.01)]. Our results are in overall agreement with treatment recommendations from the seventh International Workshops on WM. Our findings are limited by the fact that we could not analyze progression-free survival (PFS). More phase II/III trials are needed to corroborate promising recent findings with bendamustine and carfilzomib and further research are needed to standardize recommendations based on maximum treatment efficacy combined with lowest toxicity, differentiation between first vs second line treatment, or long-term follow up after treatment.

Assessment of resting energy expenditure in pediatric mitochondrial diseases with indirect calorimetry.

BACKGROUND & AIMS: Mitochondrial diseases (MD) are the most frequent inborn errors of metabolism. In affected tissues, MD can alter cellular oxygen consumption rate leading to potential decreases in whole-body resting energy expenditure (REE), but data on pediatric children are absent. We determined, using indirect calorimetry (IC), whole-body oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and REE in pediatric patients with MD and healthy controls. Another goal was to assess the accuracy of available predictive equations for REE estimation in this patient population. METHODS: IC data were obtained under fasting and resting conditions in 20 MD patients and 27 age and gender-matched healthy peers. We determined the agreement between REE measured with IC and REE estimated with Schofield weight and FAO/WHO/UNU equations. RESULTS: Mean values of VO2, VCO2 (mL·min-1·kg-1) or RQ did not differ significantly between patients and controls (P = 0.085, P = 0.055 and P = 0.626 respectively). Accordingly, no significant differences (P = 0.086) were found for REE (kcal·day-1 kg-1) either. On the other hand, although we found no significant differences between IC-measured REE and Schofield or FAO/WHO/UNU-estimated REE, Bland-Altman analysis revealed wide limits of agreement and there were some important individual differences between IC and equation-derived REE. CONCLUSIONS: VO2, VCO2, RQ and REE are not significantly altered in pediatric patients with MD compared with healthy controls. The energy demands of pediatric patients with MD should be determined based on IC data in order to provide the best possible personalized nutritional management for these children.

Physical function and quality of life in patients with chronic GvHD: a summary of preclinical and clinical studies and a call for exercise intervention trials in patients.

Allogeneic hematopoietic stem cell transplant, to reconstitute the hematopoietic and immune status of patients undergoing myeloablative therapy for hematologic disorders, has been of great benefit in minimizing or eradicating disease and extending survival. Patients who undergo allogeneic hematopoietic stem cell transplant (allo-HSCT) are subject to many comorbidities among which the most significant, affecting quality of life (QoL) and survival, are acute GvHD (aGvHD) and chronic GvHD (cGvHD), resulting from donor lymphocytes reacting to and damaging host tissues. Physical activity and exercise have clearly been shown, in both children and adults, to enhance fitness, improve symptomatology and QoL, reduce disease progression and extend survival for many diseases including malignancies. In some cases, vigorous exercise has been shown to be equal to or more effective than pharmacologic therapy. This review addresses how cGvHD affects patients' physical function and physical domain of QoL, and the potential benefits of exercise interventions along with recommendations for relevant research and evaluation targeted at incorporating this strategy as soon as possible after allo-HSCT and ideally, as soon as possible upon diagnosis of the condition leading to allo-HSCT.

Resistance training does not have an effect on cognition or related serum biomarkers in nonagenarians: a randomized controlled trial.

The aim of this randomized controlled trial was to determine the effects of 8-week exercise-intervention on cognition and related serum biochemical markers in nonagenarians. We also studied the effects of a 4-week training cessation ('detraining') period on our study variables. Participants were randomly allocated to a standard-care (control) or intervention (exercise) group [n=20 (16 women)/group]. The intervention focused on supervised, light-to-moderate-intensity aerobic and resistance exercises (mainly leg press), and included 3 weekly sessions. Cognitive status was determined by the mini-mental state examination and geriatric depression scale. We analysed proteins with reported relation with mechanisms behind cognition changes such as serum levels of angiotensin converting enzyme, amyloid-precursor protein, epidermal growth factor, brain-derived neural factor and tumor necrosis factor. No significant change (P>0.05) in any of the variables studied was found following the exercise intervention compared with the standard-care group. Similarly, no significant changes (P>0.05) were observed following the detraining period compared with the standard-care group. Overall changes after the exercise intervention in serum biomarkers were not associated with changes in functional capacity and cognitive measures. An 8-week exercise intervention focusing on resistance exercises neither benefits cognitive function nor affects the levels of the serum proteins analysed in nonagenarians.

Effects of allopurinol on exercise-induced muscle damage: new therapeutic approaches?

Intensive muscular activity can trigger oxidative stress, and free radicals may hence be generated by working skeletal muscle. The role of the enzyme xanthine oxidase as a generating source of free radicals is well documented and therefore is involved in the skeletal muscle damage as well as in the potential transient cardiovascular damage induced by high-intensity physical exercise. Allopurinol is a purine hypoxanthine-based structural analog and a well-known inhibitor of xanthine oxidase. The administration of the xanthine oxidase inhibitor allopurinol may hence be regarded as promising, safe, and an economic strategy to decrease transient skeletal muscle damage (as well as heart damage, when occurring) in top-level athletes when administered before a competition or a particularly high-intensity training session. Although continuous administration of allopurinol in high-level athletes is not recommended due to its possible role in hampering training-induced adaptations, the drug might be useful in non-athletes. Exertional rhabdomyolysis is the most common form of rhabdomyolysis and affects individuals participating in a type of intense exercise to which they are not accustomed. This condition can cause exercise-related myoglobinuria, thus increasing the risk of acute renal failure and is also associated with sickle cell trait. In this manuscript, we have reviewed the recent evidence about the effects of allopurinol on exercise-induced muscle damage. More research is needed to determine whether allopurinol may be useful for preventing not only exertional rhabdomyolysis and acute renal damage but also skeletal muscle wasting in critical illness as well as in immobilized, bedridden, sarcopenic or cachectic patients.

ACTN3 genotype in Spanish elite swimmers: no "heterozygous advantage".

The aim of the present case-control study was to examine the association of the ACTN3 R577X genotype with elite swimming status. We compared a group of Spanish (Caucasian) elite swimmers (n = 88) with other cohorts of the same ethnic origin, i.e., nonathletic controls (n = 343) and other types of athletes who are in both end-points of the sports performance continuum, i.e., world-class power (n = 119) and endurance male athletes (n = 154). Swimmers had a lower odds ratio (OR) of having the RX genotype [1.815, 95% confidence intervals (CI): 0.899-3.664] compared with nonathletic controls, yet the association did not reach statistical significance (P = 0.096). Endurance athletes had greater OR of having the XX genotype (OR: 2.88, 95% CI: 1.162-7.135, P = 0.022), or the RX+XX genotype (OR: 1.903, 95% CI: 1.015-3.567, P = 0.045) compared with swimmers. No other association was found. In summary, we did not observe an association between the ACTN3 R577X polymorphism and elite swimmer's status, suggesting that any influence of this polymorphism is not of sufficient magnitude as to significantly influence elite swimming performance, at least in Spanish athletes.

Exercise training and cytokines in breast cancer survivors.

The purpose of this randomized controlled trial was to determine the effects of an 8-week (aerobic+strength) exercise training program (3 sessions/week) on the circulating cytokine levels of breast cancer survivors. We randomly allocated 16 female survivors of breast cancer (mean±SD age: 50±5 years) to an intervention or usual care (control) group (N=8 in each group). The intervention group followed an 8-week exercise program consisting of 3 sessions/week (session duration: 90 min). We measured the levels of the following cytokines before and after the intervention: beta-NGF, CTACK, eotaxin, FGF basic, G-CSF, gmCSFα, HGF, ICAM1, IFNα2, IFNγ, IL1α, IL1ß, IL1ra, IL2, IL2ra, IL3, IL4, IL6, IL7, IL8, IL9, IL10, IL12, IL13, IL15, IL16, IL17, IL18, IP10, LIF, MCS-F, MIP1α, MIP1ß, MIF, MCP1, MCP3, MIG, PDGF bb, SCF, SCGFß, SDF1α, TRAIL, TNFα, TNFß, VCAM1, and VEGF. We only observed a significant interaction (group*time) effect for CTACK ( P=0.016), with mean values remaining stable in the intervention group but increasing over time in controls. The intervention program did not induce a significant decrease in the main breast cancer-related cytokines such as IL6 and IL8. A combined (aerobic+strength) 8-week exercise training intervention did not induce major changes in the basal cytokine levels of breast cancer survivors.

GNB3 C825T Polymorphism and elite athletic status: A replication study with two ethnic groups.

We aimed to replicate the original findings by Eynon et al. showing an association between the T allele of the GNB3 C825T polymorphism and elite endurance athletic status, in larger cohorts and in other ethnicities. We compared allelic and genotypic frequencies of the GNB3 C825T polymorphism among non-athletic controls (N=340), elite endurance athletes (N=174), and power athletes (N=134). The population sample included participants from 2 different ethnic/geographic backgrounds (Israel and Spain). We observed no significant differences in genotypic and allelic frequencies between countries or groups (all P>0.1). The odds ratio (OR) of being an endurance athlete if the subject had a T allele was 0.841 (95%CI: 0.638-1.110) compared to the control group and 1.047 (95% CI: 0.751-1.461) compared to the power group. Our findings support the need to corroborate genotype:phenotype associations in the field of sports genetics with the largest possible population samples, including populations of different ethnic backgrounds.