A Novel Mri-Method Allows a Rapid and Robust Assessment of Muscle Quantity and Quality in Hemodialysis Patients.

BackgroundSarcopenia is a prevalent condition in patients on maintenance hemodialysis and associates with mortality. Research using magnetic resonance imaging (MRI) has demonstrated the importance of a proper body size-adjustment in the assessment of muscle mass, and that a muscle composition assessment including measurements of both muscle volume and fat infiltration improves the prediction of comorbidity and survival related to sarcopenia. Such combined muscle composition assessment has not previously been performed in hemodialysis patients.MethodsEleven hemodialysis patients were scanned using whole-body fat and water separated MRI and followed regarding survival and comorbidity for five years. Muscle composition was assessed using AMRA® Researcher. Using data from 9615 UK Biobank participants, sex and BMI-matched muscle volume z-scores and sex-adjusted muscle fat infiltration values were calculated for each patient. These measurements were then used for the calculation of a combined muscle score. Resulting three muscle measurements were associated with survival and comorbidity index.ResultsSix patients exhibited low muscle volume (muscle volume z-score <25th percentile (population wide)), and six patients presented with high muscle fat infiltration (>75th percentile (population wide)). During a 68-months follow-up, five patients died, four were transplanted and two remained on hemodialysis treatment. The combined muscle score was significantly associated with comorbidity index (p<0.05) and was highly predictive of survival (AUROC 0.97).ConclusionsThe combined assessment including both body size-adjusted muscle volume and muscle fat infiltration can be used to analyze muscle composition in hemodialysis patients. MRI based muscle composition assessment reflected comorbidity and predicted survival in hemodialysis patients.

Do skeletal muscle composition and gene expression as well as acute exercise-induced serum adaptations in older adults depend on fitness status?

Background Inactive physical behavior among the elderly is one risk factor for cardiovascular disease, immobility and increased all-cause mortality. We aimed to answer the question whether or not circulating and skeletal muscle biomarkers are differentially expressed depending on fitness status in a group of elderly individuals. Methods Twenty-eight elderly individuals (73.36 ± 5.46 years) participated in this exploratory study after participating as part of the multinational SITLESS-clinical trial (implementation of self-management and exercise programs over 16 weeks). A cardiopulmonary exercise test (CPX) and resting skeletal muscle biopsy were performed to determine individual physiological performance capacity. Participants were categorized into a high physical fitness group (HPF) and a low physical fitness group (LPF) depending on peak oxygen uptake (VO2peak). Serum blood samples were taken before (pre) and after (post) CPX and were examined regarding serum BDNF, HSP70, Kynurenine, Irisin and Il-6 concentrations. Skeletal muscle tissue was analyzed by silver staining to determine the myosin heavy chain (MyHC) composition and selected genes by qRT-PCR. Results HPF showed lower body weight and body fat, while skeletal muscle mass and oxygen uptake at the first ventilatory threshold (VO2T1) did not differ between groups. There were positive associations between VO2peak and VO2VT1 in HPF and LPF. MyHC isoform quantification revealed no differences between groups. qRT-PCR showed higher expression of BDNF and BRCA1 in LPF skeletal muscle while there were no differences in other examined genes regarding energy metabolism. Basal serum concentrations of Irisin were higher in HPF compared to LPF with a trend towards higher values in BDNF and HSP70 in HPF. Increases in Il-6 in both groups were observed post. Conclusions Although no association between muscle composition/VO2peak with fitness status in older people was detected, higher basal Irisin serum levels in HPF revealed slightly beneficial molecular serum and muscle adaptations. Trial registration ClinicalTrials.gov, NCT02629666. Registered 19 November 2015.

Quantitative MRI and Clinical Assessment of Muscle Function in Adults With Cerebral Palsy

Aim: To relate quantitative magnetic resonance imaging (MRI) of ankle plantar flexor muscles to clinical functional tests in adults with cerebral palsy (CP) and neurologically intact (NI) adults.Methods: Eleven adults with CP (aged 41 ± 12, GMFCS level I-II) and 11 NI adults (aged 35 ± 10) participated in this case-control study. We used MRI to assess muscle volume and composition of the triceps surae muscles. We quantified muscle function as maximal voluntary plantarflexion (MVC) torque and countermovement jump (CMJ) height.Results: Compared to NI adults, the MRI intramuscular fat fraction estimate was significantly higher and MRI muscle volume and functional abilities (MVC and CMJ) significantly lower in adults with CP. In NI adults, but not adults with CP, MRI muscle volume correlated significantly with MVC and CMJ. In adults with CP, the estimate of intramuscular fat levels correlated significantly with jump height in a CMJ.Discussion: This study shows reduced muscle volume and altered muscle composition in adults with CP. Muscle composition appears to provide a better marker than muscle volume of reduced muscle function and impaired performance in this population. Measurements of muscle composition could be used in the assessment of neuromuscular impairments and in the determination of rehabilitation protocols in individuals with neurological disorders.