Musclin is an activity-stimulated myokine that enhances physical endurance.

Exercise remains the most effective way to promote physical and metabolic wellbeing, but molecular mechanisms underlying exercise tolerance and its plasticity are only partially understood. In this study we identify musclin-a peptide with high homology to natriuretic peptides (NP)-as an exercise-responsive myokine that acts to enhance exercise capacity in mice. We use human primary myoblast culture and in vivo murine models to establish that the activity-related production of musclin is driven by Ca(2+)-dependent activation of Akt1 and the release of musclin-encoding gene (Ostn) transcription from forkhead box O1 transcription factor inhibition. Disruption of Ostn and elimination of musclin secretion in mice results in reduced exercise tolerance that can be rescued by treatment with recombinant musclin. Reduced exercise capacity in mice with disrupted musclin signaling is associated with a trend toward lower levels of plasma atrial NP (ANP) and significantly smaller levels of cyclic guanosine monophosphate (cGMP) and peroxisome proliferator-activated receptor gamma coactivator 1-α in skeletal muscles after exposure to exercise. Furthermore, in agreement with the established musclin ability to interact with NP clearance receptors, but not with NP guanyl cyclase-coupled signaling receptors, we demonstrate that musclin enhances cGMP production in cultured myoblasts only when applied together with ANP. Elimination of the activity-related musclin-dependent boost of ANP/cGMP signaling results in significantly lower maximum aerobic capacity, mitochondrial protein content, respiratory complex protein expression, and succinate dehydrogenase activity in skeletal muscles. Together, these data indicate that musclin enhances physical endurance by promoting mitochondrial biogenesis.

Impact of Musculoskeletal Limitations on Cardiac Rehabilitation Participation.

Background: To help clarify a potential barrier to cardiac rehabilitation (CR) participation we sought to examine the association between musculoskeletal limitations (MSLs) and CR enrollment and participation. Methods: Consecutive CR eligible individuals hospitalized for a cardiac event (myocardial infarction, percutaneous coronary intervention, and/or coronary artery bypass graft) between the months of November 2007 and May 2008, were asked to complete a mailed survey within 2 weeks after hospital discharge, assessing demographic factors, Patient Health Questionnaire (PHQ-9), participation in CR and MSLs through a validated MSLs screening tool. CR enrollment rates were compared between patients with and without MSLs. Results: Three hundred and twenty-one (37%) of patients contacted responded to our survey, including 228 males (71%), with a mean age 68 ± 10.8 years, of whom 98% were Caucasian. Eighty-two percent of responders reported a musculoskeletal disorder at the time of hospital discharge. Arthritis was the most frequent diagnosis (45%). Muscle or joint pain sufficient to limit the ability to do moderate exercise was reported in 52% of the respondents. Problems with balance affected 37%, of whom 45% reported a fall within the previous year. No significant difference in CR enrollment was observed in respondents with and without MSLs [OR = 0.98, 95% CI (0.88-1.09), p = 0.750]. Similar results were found when severity and number of MSLs were taken into account. However, we found that when compared to those without MSLs, the presence of MSLs was associated with lower CR participation (OR = 0.80, 95%, CI: 0.65-0.97, p = 0.0252). Conclusion: Despite a high prevalence of MSLs among CR-eligible patients, we found no association between MSLs and CR enrollment. However, patients with MSLs attended significantly fewer CR sessions as compared to patients without them. CR programs should consider providing additional support and interventions to patients with MSLs in order to optimize their adherence to prescribed CR sessions.

Cardiac Rehabilitation for Women: A Systematic Review of Barriers and Solutions.

Cardiac rehabilitation (CR) services improve various clinical outcomes in patients with cardiovascular disease, but such services are underutilized, particularly in women. The aim of this study was to identify evidence-based barriers and solutions for CR participation in women. A literature search was carried out using PubMed, EMBASE, Cochrane, OVID/Medline, and CINAHL to identify studies that have assessed barriers and/or solutions to CR participation. Titles and abstracts were screened, and then the full-text of articles that met study criteria were reviewed. We identified 24 studies that studied barriers to CR participation in women and 31 studies that assessed the impact of various interventions to improve CR referral, enrollment, and/or completion of CR in women. Patient-level barriers included lower education level, multiple comorbid conditions, non-English native language, lack of social support, and high burden of family responsibilities. We found support for the use of automatic referral and assisted enrollment to improve CR participation. A small number of studies suggest that incentive-based strategies, as well as home-based programs, may contribute to improving CR attendance and completion rates. A systematic approach to CR referral, including automatic CR referral, may help overcome barriers to CR referral in women and should be implemented in clinical practice. However, more studies are needed to help identify the best methods to improve CR attendance and completion of CR rates in women.

Regenerative Therapy Prevents Heart Failure Progression in Dyssynchronous Nonischemic Narrow QRS Cardiomyopathy.

BACKGROUND: Cardiac resynchronization therapy using bi-ventricular pacing is proven effective in the management of heart failure (HF) with a wide QRS-complex. In the absence of QRS prolongation, however, device-based resynchronization is reported unsuitable. As an alternative, the present study tests a regenerative cell-based approach in the setting of narrow QRS-complex HF. METHODS AND RESULTS: Progressive cardiac dyssynchrony was provoked in a chronic transgenic model of stress-triggered dilated cardiomyopathy. In contrast to rampant end-stage disease afflicting untreated cohorts, stem cell intervention early in disease, characterized by mechanical dyssynchrony and a narrow QRS-complex, aborted progressive dyssynchronous HF and prevented QRS widening. Stem cell-treated hearts acquired coordinated ventricular contraction and relaxation supporting systolic and diastolic performance. Rescue of contractile dynamics was underpinned by a halted left ventricular dilatation, limited hypertrophy, and reduced fibrosis. Reverse remodeling reflected a restored cardiomyopathic proteome, enforced at systems level through correction of the pathological molecular landscape and nullified adverse cardiac outcomes. Cell therapy of a dyssynchrony-prone cardiomyopathic cohort translated prospectively into improved exercise capacity and prolonged survivorship. CONCLUSIONS: In narrow QRS HF, a regenerative approach demonstrated functional and structural benefit, introducing the prospect of device-autonomous resynchronization therapy for refractory disease.

Singing paraplegia: a distinctive manifestation of a spinal dural arteriovenous fistula.

The unique case of a baritone with a spinal dural arteriovenous fistula (SDAVF) causing recurrent, acute paraplegia during singing is described. This case underscores the presence of impaired venous drainage in these lesions and the high level of clinical suspicion required for their diagnosis in patients with any myelopathy.

Regenerative principles enrich cardiac rehabilitation practice.

Cardiovascular morbidity imposes a high degree of disability and mortality, with limited therapeutic options available in end-stage disease. Integral to standard of care, cardiac rehabilitation aims on improving quality-of-life and prolonging survival. The recent advent of regenerative technologies paves the way for a transformative era in rehabilitation medicine whereby, beyond controlling risk factors and disease progression, the prospect of curative solutions is increasingly tangible. To date, the spectrum of clinical experience in cardiac regenerative medicine relies on stem cell-based therapies delivered to the diseased myocardium either acutely/subacutely, after a coronary event, or in the setting of chronic heart failure. Application of autologous/allogeneic stem cell platforms has established safety and feasibility, with encouraging signals of efficacy. Newer protocols aim to purify cell populations in an attempt to eliminate nonregenerative and enrich for regenerative cell types before use. Most advanced technologies have been developed to isolate resident cell populations directly from the heart or, alternatively, condition cells from noncardiac sources to attain a disease-targeted lineage-specified phenotype for optimized outcome. Because a multiplicity of cell-based technologies has undergone phase I/II evaluation, pivotal trials are currently underway in larger patient populations. Translation of regenerative principles into clinical practice will increasingly involve rehabilitation providers across the continuum of patient care. Regenerative rehabilitation is thus an emerging multidisciplinary field, full of opportunities and ready to be explored.

Inpatient rehabilitation outcomes for patients receiving left ventricular assist device.

OBJECTIVE: The aim of this study was to evaluate outcomes of patients participating in inpatient rehabilitation program after left ventricular assist device (LVAD) implantation. DESIGN: Medical records of 94 patients who received LVADs between January 1, 2008, and June 30, 2010, at the Mayo Clinic in Rochester, MN, were retrospectively reviewed for demographic data, and inpatient rehabilitation functional outcomes were measured by the Functional Independence Measure scale. RESULTS: After successful implantation of LVAD, the patients were either discharged directly home from acute care (44%) or admitted to inpatient rehabilitation (56%). The patients admitted to inpatient rehabilitation were older than those discharged home. They were also more medically complex and more likely to have the LVAD placed as destination therapy. At discharge, significant improvement occurred in 17 of the 18 activities evaluated by the Functional Independence Measure scale. The mean total Functional Independence Measure scale score at admission was 77.1 compared with a score of 95.2 at discharge (P < 0.0001). CONCLUSIONS: Approximately half of the patients who received LVAD therapy were admitted in the inpatient rehabilitation. After the implantation of LVAD and inpatient rehabilitation, significant functional improvements were observed. Further studies addressing the role of inpatient rehabilitation for LVAD patients are warranted.

Mechanical dyssynchrony precedes QRS widening in ATP-sensitive K⁺ channel-deficient dilated cardiomyopathy.

BACKGROUND: Contractile discordance exacerbates cardiac dysfunction, aggravating heart failure outcome. Dissecting the genesis of mechanical dyssynchrony would enable an early diagnosis before advanced disease. METHODS AND RESULTS: High-resolution speckle-tracking echocardiography was applied in a knockout murine surrogate of adult-onset human cardiomyopathy caused by mutations in cardioprotective ATP-sensitive K(+) (K(ATP)) channels. Preceding the established criteria of cardiac dyssynchrony, multiparametric speckle-based strain resolved nascent erosion of dysfunctional regions within cardiomyopathic ventricles of the K(ATP) channel-null mutant exposed to hemodynamic stress. Not observed in wild-type counterparts, intraventricular disparity in wall motion, validated by the degree, direction, and delay of myocardial speckle patterns, unmasked the disease substrate from asymptomatic to overt heart failure. Mechanical dyssynchrony preceded widening of the QRS complex and exercise intolerance and progressed into global myocardial discoordination and decompensated cardiac pump function, precipitating a low output syndrome. CONCLUSIONS: The present study, with the use of high-resolution imaging, prospectively resolved the origin and extent of intraventricular motion disparity in a K(ATP) channel-knockout model of dilated cardiomyopathy. Mechanical dyssynchrony established as an early marker of cardiomyopathic disease offers novel insight into the pathodynamics of dyssynchronous heart failure.

Improving cardiac rehabilitation attendance and completion through quality improvement activities and a motivational program.

PURPOSE: Recent studies have demonstrated that patients who attend more cardiac rehabilitation (CR) sessions have lower subsequent mortality rates than those who attend fewer sessions. METHODS: We analyzed the impact of several phased-in policy and process changes implemented to increase patient participation in CR. In March 2010, our CR program changed from a policy of individualizing the recommended number of CR sessions per patient to a policy that recommended all 36 CR sessions. In October 2010, we introduced a 7-minute video describing the benefits of CR. In August 2011, we introduced a motivational program that rewarded patients after every sixth CR session. The number of CR sessions attended was determined through review of billing records. Enrollment and completion were defined as attending ≥1 session and ≥30 sessions, respectively. RESULTS: We identified 1103 patients sequentially enrolled in CR between May 2009 and January 2012. Overall, the median number of sessions per patient improved from 12 to 20 (P < .001). Completion rate improved from 14% to 39% (P < .001). The motivational program increased attendance by a median of 3 sessions per patient (P = .04), but this effect was limited to local CR participants. Financial analysis suggested that for every $100 spent on motivational rewards, patients attended an additional 6.6 (95% CI, -1 to 14) sessions of CR. CONCLUSIONS: Quality improvement activities significantly increased CR participation. Wide implementation of such programs may favorably impact patient participation in CR and potentially decrease the rate of subsequent cardiac events.

Exercise in cardiovascular diseases.

Analysis of extensive data has shown that exercise training provides significant impact on prevention and modification of cardiovascular diseases and mortality. In general, exercise recommendations for patients with cardiovascular diseases are based on individual aerobic capacity and comorbidities. Patients with acute syndromes benefit from participating in a cardiac rehabilitation program, whereas patients with chronic syndromes benefit from a life-long home-based program. In general, exercise prescription should involve aerobic activities in combination with resistance, flexibility, and balance exercises. This review will discuss an exercise prescription for patients with coronary artery disease, heart failure, and after heart transplantation. Detailed precautions for particular groups of patients will be discussed.

Prevalence of musculoskeletal and balance disorders in patients enrolled in phase II cardiac rehabilitation.

PURPOSE: To determine the prevalence of musculoskeletal, neurological, and balance problems in patients enrolled in early outpatient (phase II) cardiac rehabilitation. METHODS: Data were assessed retrospectively for 284 consecutive patients who attended the phase II Mayo Clinic Cardiac Rehabilitation program from April 2005 to August 2006. All participants completed a questionnaire that identified the presence of musculoskeletal pain, history of falls, joint replacements, osteoporosis, neurological disorders, and difficulties in performing activities of daily living. Balance assessment was evaluated using the single leg stance and the tandem gait tests. RESULTS: Of the total study population (mean age, 62.1 +/- 12.3 years), 25% reported musculoskeletal pain. A significantly higher prevalence of pain was noted in women than men (37% vs 20%, P = .004) and in those > 65 years than those < or = 65 years (35% vs 17%, P = .001). Back (29%), knee (17%), and hip (8%) pain were the most common symptoms, in order of decreasing frequency. Pain was worse with any activity in 32% of participants while 16% of participants had worsening at night. An abnormality in balance was present in 58% of the study participants and was significantly more common in women (71%) and those > 65 years (83%). Falls or gait instability or both were reported by 11% of participants. CONCLUSION: Musculoskeletal and balance limitations are common in persons enrolled in early outpatient cardiac rehabilitation, particularly in women and patients > 65 years. Cardiac rehabilitation programs should screen patients for musculoskeletal limitations and incorporate adaptations for treatment strategies of such patients.

Microtubule destabilization and nuclear entry are sequential steps leading to toxicity in Huntington's disease.

There has been a longstanding debate regarding the role of proteolysis in Huntington's disease. The toxic peptide theory posits that N-terminal cleavage fragments of mutant Huntington's disease protein [mutant huntingtin (mhtt)] enter the nucleus to cause transcriptional dysfunction. However, recent data suggest a second model in which proteolysis of full-length mhtt is inhibited. Importantly, the two competing theories differ with respect to subcellular distribution of mhtt at initiation of toxicity: nuclear if cleaved and cytoplasmic in the absence of cleavage. Using quantitative single-cell analysis and time-lapse imaging, we show here that transcriptional dysfunction is "downstream" of cytoplasmic dysfunction. Primary and reversible toxic events involve destabilization of microtubules mediated by full-length mhtt before cleavage. Restoration of microtubule structure by taxol inhibits nuclear entry and increases cell survival.