Trunk Skeletal Muscle Research Articles

Impact of Skeletal Muscle Mass on Physical Function and Locomotive Syndrome of Pre- and Postoperative Adult Spinal Deformity

Background: The purpose of this study is to identify the relationship between locomotive syndrome (LS) status, physical performance and limb and trunk skeletal muscle mass before and after surgery in adult spinal surgery (ASD) patients. Methods: A retrospective observational investigation of 63 consecutive patients with ASD who underwent spinal surgery was conducted. The total skeletal muscle mass of the arms and legs was considered a measure of the total appendicular skeletal muscle mass measured with whole-body dual-energy X-ray absorptiometry. All data pertaining to the physical performance tests and LS were collected preoperatively with follow-up one year postoperatively. Results: Gait speed, the one-leg standing test and the stand-up test were significantly improved one year after surgery compared to preoperative measurements. The lower extremity skeletal muscle mass predominantly influences physical function improvement including gait stride, one-leg standing and the stand-up test after ASD surgery. Conclusions: This study is the first to show that assessing lower extremity muscles prior to ASD surgery is useful in predicting postoperative recovery.

Understanding the Association Between Obesity and Obstructive Sleep Apnea Syndrome: A Case-Control Study.

Introduction Obstructive sleep apnea (OSA) represents a sleep-related impairment linked to upper airway function. The question of whether OSA drives obesity or if shared underlying factors contribute to both conditions remains unresolved. Hence, this present study aims to understand the interplay between obstructive sleep apnea syndrome (OSAS) and obesity through in-depth analysis of anthropometric data within control subjects and OSA patients. Methodology A case-control study was conducted, which included 40 cases and 40 matched healthy controls. Study participants with reported symptoms of snoring, daytime drowsiness, or both were included in the study. All the study participants underwent comprehensive anthropometric assessments such as height, weight, body mass index (BMI), neck circumference, waist circumference, hip circumference, waist-to-hip ratio, skin-fold thickness, and thickness measurements of biceps, triceps, suprailiac, and subscapular muscles. Results Within the OSA group, significant disparities emerged in mean age, waist circumference, waist-to-hip ratio, and diverse fat accumulations encompassing visceral, subcutaneous, trunk, and subcutaneous leg fat. Notably, skin-fold thickness at specific sites - biceps, triceps, subscapula, and suprailiac - demonstrated considerable augmentation relative to the control group. Furthermore, mean values associated with height, weight, BMI, neck circumference, fat percentage, subcutaneous arm fat, entire arm composition, and trunk skeletal muscle either equaled or exceeded those in the control group. However, statistical significance was not attained in these comparisons. Conclusion This investigation underscored a pronounced correlation between numerous endpoints characterizing OSA patients and markers of obesity. Consequently, addressing altered levels of obesity-linked anthropometric variables through pharmacological interventions might hold promise as a pivotal strategy for improving symptoms associated with OSA.

Gastruloids as an in vitro model of Cardiopharyngeal Mesoderm specification into skeletal and cardiac muscle lineages

Cardiopharyngeal mesoderm (CPM) contributes to the formation of the heart and head muscles. These muscles are both affected in rare congenital disorders including velocardiofacial syndrome or cardiofaciocutaneous syndrome. While the mechanisms governing CPM specification remain relatively unknown, there is a lack of an in vitro platform that would allow the differentiation of both head and heart muscles. Develop embryonic organoids from mouse embryonic stem cells (mESC), also called gastruloids, to form and specify CPM toward the cardiac and muscle lineages. Use in vitro 3D culture to develop and characterize embryonic organoid. By using single-cell RNAseq, and high-resolution imaging of single molecule FISH experiments, we confirm that the CPM is established in gastruloids, with a kinetic of gene expression that is similar to the mouse embryo. We identify different subpopulations of cardiomyocytes and skeletal muscles most likely corresponding to the different cardiac chambers and head and trunk skeletal muscles. These findings unveil the potential of mESCs-derived gastruloids to undergo CPM specification in both head and heart lineages, allowing the investigation of the mechanisms of CPM specification in development and how this could be affected in congenital disorders.

Sex- and region-specific associations of skeletal muscle mass with metabolic dysfunction-associated fatty liver disease.

Metabolic dysfunction-associated fatty liver disease (MAFLD) is known to be the most common chronic liver disease worldwide, and accumulating evidence suggests that skeletal muscle might play an important role in metabolic health. However, the association between skeletal muscle and MAFLD is poorly understood so far. Therefore, we aimed to evaluate the associations of skeletal muscle with MAFLD and significant fibrosis. A cross-sectional analysis was conducted using data obtained from the 2017-2018 US National Health and Nutrition Examination Survey. The whole-body, appendicular, and trunk skeletal muscle mass index (SMI) were assessed by dual-energy x-ray absorptiometry. MAFLD and significant fibrosis were assessed by transient elastography. Survey-weight adjusted multivariable logistic regressions were used to determine the associations. The area under the receiver operating characteristic curve (AUC) and variable importance scores from the random forest and logistic regression model were calculated to assess the predictive capability of variables and models. Of the 2065 participants, those with appendicular SMI in the highest quartile were associated with a lower risk for MAFLD in both sexes (male, OR[95%CI]: 0.46 [0.25~0.84]; female, OR[95%CI]: 0.32 [0.13~0.82]), but with a significantly different scale of the associations between sexes (P interaction = 0.037). However, females with trunk SMI in the highest quartile had an increased risk of significant fibrosis (OR[95%CI]: 7.82 [1.86~32.77]). Trunk SMI and appendicular SMI ranked the third contributor to MAFLD in random forest and logistic regression models, respectively. Taking appendicular and trunk SMI into consideration, the AUCs for MAFLD were 0.890 and 0.866 in random forest and logistic regression models, respectively. The distribution of skeletal muscle mass differently affects MAFLD and significant fibrosis in the sex groups. Higher appendicular skeletal muscle mass was associated with a lower risk of MAFLD, while the risk of significant fibrosis in females was increased with the trunk skeletal muscle mass.

Effects of truncal taping on center of gravity sway: comparison of different trunk muscle masses.

[Purpose] Taping is a therapeutic technique used to prevent and treat sporting injuries and other conditions. This study aimed to clarify how kinesio taping versus non-elastic taping of the trunk affects postural control. [Participants and Methods] Thirty-three healthy male participants were included in this study. Participants were assigned to low or high trunk skeletal muscle mass groups. Main outcomes of path length and area representing the center of gravity sway were measured using a Zebris FDM-S system in three conditions: control, kinesio taping, and non-elastic taping. Tapes were applied to the rectus abdominis, external oblique, and erector spinae muscles. The measured limb position was seated on a balance cushion. [Results] The area of the low trunk mass group differed significantly between kinesio and non-elastic taping. However, the path length of the low trunk mass group and path length and area of participants with high trunk mass did not differ significantly between groups. [Conclusion] This study’s findings indicated that two types of taping methods affected the area of gravitational sway in healthy adult males with a low trunk muscle mass.

Comparison of metabolic risk factors, physical performances, and prevalence of low back pain among categories determined by visceral adipose tissue and trunk skeletal muscle mass in middle-aged men.

The present study compared metabolic risk factors, physical performances, and musculoskeletal impairment among categories determined by visceral adipose tissue (VAT) and trunk skeletal muscle (SM) mass in middle-aged Japanese men. In total, 1026 healthy Japanese males aged between 35 and 59years were categorized into 4 groups according to the amount of VAT and SM in the trunk measured using low-dose computed tomography (LowVAT-HighSM, LowVAT-LowSM, HighVAT-HighSM, and HighVAT-LowSM). Height, body mass waist circumference, body fat, intramuscular adipose tissue (IntraMAT), subcutaneous adipose tissue, biochemical blood profiles (triglycerides, high-density lipoprotein cholesterol, fasting blood glucose, aspartate transaminase, alanine transaminase and γ-glutamyl trans peptidase), physical performances (trunk flexibility, the chair-stand test, two-step length and hand-grip strength), the prevalence of low back pain, and lifestyle habits for exercise, alcohol intake and smoking, were compared among the groups. The results showed that LowVAT-HighSM had significantly superior biochemical blood profiles and physical performances to the other groups. HighVAT-LowSM had significantly higher %IntraMAT and the prevalence of low back pain. The two-step length, which is an index of walking ability, significantly differed according to the four subject categories. These results indicate that metabolic risk factors, physical performances, and prevalence of low back pain in middle-aged Japanese men may differ among four categories determined by VAT and trunk SM.

Smyd1 is essential for myosin expression and sarcomere organization in craniofacial, extraocular, and cardiac muscles

Skeletal and cardiac muscles are striated myofibers that contain highly organized sarcomeres for muscle contraction. Recent studies revealed that Smyd1, a lysine methyltransferase, plays a key role in sarcomere assembly in heart and trunk skeletal muscles. However, Smyd1 expression and function in craniofacial muscles are not known. Here, we analyze the developmental expression and function of two smyd1 paralogous genes, smyd1a and smyd1b, in craniofacial and cardiac muscles of zebrafish embryos. Our data show that loss of smyd1a (smyd1amb5) or smyd1b (smyd1bsa15678) has no visible effects on myogenic commitment and expression of myod and myosin heavy-chain mRNA transcripts in craniofacial muscles. However, myosin heavy-chain protein accumulation and sarcomere organization are dramatically reduced in smyd1bsa15678 single mutant, and almost completely diminish in smyd1amb5; smyd1bsa15678 double mutant, but not in smyd1amb5 mutant. Similar defects are also observed in cardiac muscles of smyd1bsa15678 mutant. Defective craniofacial and cardiac muscle formation is associated with an upregulation of hsp90α1 and unc45b mRNA expression in smyd1bsa15678 and smyd1amb5; smyd1bsa15678 mutants. Together, our studies indicate that Smyd1b, but not Smyd1a, plays a key role in myosin heavy-chain protein expression and sarcomere organization in craniofacial and cardiac muscles. Loss of smyd1b results in muscle-specific stress response.

Impact of appendicular and trunk skeletal muscle mass and back extensor strength on sagittal spinal alignment in Japanese women without vertebral fracture

ObjectivesProgressive and generalized loss of skeletal muscle mass (SMM) and strength are characteristics of sarcopenia. However, the impact of appendicular and trunk SMM and back extensor strength (BES) on spinal sagittal alignment remains unclear. Herein, we investigate the relationship between these factors and spinal sagittal alignment. MethodsIn total, 202 women without vertebral fractures (median age, 66.9 years; interquartile range, 61.4–71.9 years) were analyzed at an orthopedic outpatient clinic. Pelvic incidence (PI), lumbar lordosis (LL), sagittal vertical axis (SVA), and pelvic tilt (PT) were measured on whole spine radiographs. Body mass index (BMI), appendicular and trunk relative SMM index, and BES were also evaluated. These measurements were compared between spinal sagittal alignment groups using the Mann–Whitney U test. Finally, the factors contributing to abnormal alignment were analyzed using multiple logistic regression analysis. ResultsBES was significantly lower in all abnormal sagittal alignment groups, as defined by PI-LL (≥ 10°), SVA (≥4 cm), and PT (≥20°) (all P < 0.001). On multivariate analysis, BES was a contributing factor for abnormal PI-LL (P < 0.001), SVA (P = 0.001), and PT (P < 0.001). Conversely, a decrease in appendicular and trunk relative SMM index did not statistically affect abnormal spinal sagittal alignment. ConclusionsBES was associated with changes in spinal sagittal alignment; however, SMM, which is often used for diagnosing sarcopenia, did not affect spinal sagittal alignment.

Trunk Skeletal Muscle Changes on CT with Long-Duration Spaceflight.

Astronauts exposed to microgravity for extended time are susceptible to trunk muscle atrophy, which may compromise strength and function on mission and after return. This study investigates changes in trunk skeletal muscle size and composition using computed tomography (CT) and dual-energy X-ray absorptiometry (DXA) among 16 crewmembers (1 female, 15 male) on 4-6month missions. Muscle cross-sectional area and muscle attenuation were measured using abdominal CT scans at pre-flight, post-flight return, 1year post-flight, and 2-4years post-flight. Longitudinal muscle changes were analyzed using mixed models. In six crewmembers, CT and DXA data were used to calculate subject height-normalized skeletal muscle indices. Changes in these indices were analyzed using paired t-tests and compared by imaging modality using Pearson correlations. Trunk muscle area decreased at post-flight return (-4.7 ± 1.1%, p < 0.001) and recovered to pre-flight values at 1-4years post-flight. Muscle attenuation changes were not significant. Skeletal muscle index from CT decreased (-5.2 ± 1.0%, p = 0.004) while appendicular skeletal muscle index from DXA did not change significantly. In summary, trunk muscle atrophies with long-duration microgravity exposure but recovers to pre-flight values within 1-4years. The CT measures highlight size decreases not detected with DXA, emphasizing the importance of advanced imaging modalities in assessing muscle health with spaceflight.

Validity of Extended-Field-of-View Ultrasound Imaging to Evaluate Quantity and Quality of Trunk Skeletal Muscles

This study examined the validity of extended-field-of-view (EFOV) ultrasound imaging for evaluating the quantity (cross-sectional area [CSA]) and quality (accumulation of intramuscular fat) of trunk skeletal muscles (rectus abdominis, abdominal oblique and erector spinae) using magnetic resonance imaging (MRI) as a reference. Thirty healthy young men participated in this study. Cross-sectional images of the trunk at the height of the third lumbar vertebra were acquired and compared by EFOV ultrasound imaging and MRI. No significant differences were observed in CSAs between the two methods (0.74 ≤ R2 ≤ 0.85). Echo intensities significantly correlated with MRI-derived accumulation of intramuscular fat in each skeletal muscle group. However, the correlation coefficients were relatively low (0.37 ≤ r ≤0.47; p < 0.05). These results indicate that EFOV ultrasound imaging is a reliable method for assessing trunk skeletal muscle CSA. Further research is warranted to find the optimal ultrasound setting for evaluating muscle quality.

Trunk Skeletal Muscle Mass and Phase Angle Measured by Bioelectrical Impedance Analysis are Associated with the Chance of Femoral Neck Fracture in Very Elderly People.

BackgroundThe study aimed to investigate the potential association of trunk skeletal muscle mass (tSM) and phase angle measured by bioelectrical impedance analysis (BIA) with the chance of femoral neck fractures in very elderly people.Patients and MethodsThis case-control study enrolled 78 femoral neck fracture patients aged over 75 years (29 males) and 1:2 matched healthy controls. All participants were subjected to BIA examination by specialists. tSM, the corrected values by height squared of tSM (tSMI) and phase angle were compared between fracture patients and controls. Multivariate logistic regression was performed to explore the strength of association of femoral neck fracture with tSM, tSMI, and phase angle.ResultstSM (kg) of fracture patients was significantly lower than those of controls in all participants (women: 13.49±0.42 vs 15.44±0.39, p<0.05; men: 15.30±0.71 vs 17.54±0.78, p<0.05). In the sarcopenic subgroup, fracture patients also got a lower tSM than controls (women: 12.58±0.21 vs 13.62±0.16, p<0.05; men:14.41±0.29 vs 16.07±0.21, p<0.05). The comparison of tSMI between the two groups was similar to that of tSM. Phase angle (°) at 50 kHz in fracture patients was significantly lower than that of controls in women and men (women: 3.70±0.32 vs 4.61±0.21, p<0.05; men: 3.50±0.20 vs 3.84±0.22, p<0.05). Multivariate logistic regression analysis demonstrated higher fracture chance with significantly associated decreased tSM [women: OR (95% CI): 0.78(0.67–0.91); men: 0.74(0.64–0.86)] and tSMI [women: OR (95% CI): 0.72(0.61–0.85); men: 0.69 (0.59–0.81)]. In addition, per 1° increase of phase angle in the trunk could decrease the fracture risk by 14% for women [OR (95% CI): 0.86 0.79–0.94)] and 29% for men [OR (95% CI): 0.71 (0.64–0.79)].ConclusionThis study indicates a decrease in tSM, tSMI, and phase angle measured by BIA is significantly related to the increased chance of femoral neck fracture in people aged over 75 years. Strengthening the mass and strength of trunk skeletal muscles may help reduce the risk of femoral neck fracture in elderly patients.

A cross-sectional study: Associations between sarcopenia and clinical characteristics of patients with type 2 diabetes.

Sarcopenia is a geriatric syndrome and it impairs physical function. Patients with type 2 diabetes mellitus (T2DM) are at a higher risk of sarcopenia. The purpose of this study is to explore characteristics of general information and metabolic factors of sarcopenia in patients with T2DM in the northeast of China, and provide information for the prevention and treatment of sarcopenia in clinical practice.Patients with T2DM aged ≥65 were recruited in Changchun from March 2017 to February 2018. Questionnaires of general information, physical examination, laboratory and imaging examination were conducted. The patients were assigned into sarcopenia group and non-sarcopenia group according to the diagnostic criteria proposed by Asian working group for sarcopenia (AWGS), and the differences between 2 groups were analyzed.A total of 132 participants were included in this study, of which, 38 (28.8%) were diagnosed with sarcopenia. 94 (71.2%) were with no sarcopenia. Logistic regression analysis showed that age (OR: 1.182, 95%CI: 1.038–1.346), trunk fat mass (TFM) (OR: 1.499, 95%CI: 1.146–1.960) and free thyroxine (FT4) (OR: 1.342, 95%CI: 1.102–1.635) were independent risk factors for sarcopenia. BMI (body mass index) (OR: 0.365, 95%CI: 0.236–0.661), exercise (OR: 0.016, 95%CI: 0.001–0.169), female (OR: 0.000, 95%CI: 0.00–0.012), metformin (OR: 0.159, 95%CI: 0.026–0.967) and TSM (trunk skeletal muscle mass) (OR: 0.395, 95%CI: 0.236–0.661) were protective factors for sarcopenia.Sarcopenia in patients with T2DM is associated with increased age, increased TFM and increased FT4 level. Regular exercise, female, metformin administrations, high BMI and increased TSM are associated with lower risk of sarcopenia.

Triclosan Affects Ca2+ Regulatory Module and Musculature Development in Skeletal Myocyte during Early Life Stages of Zebrafish (Danio rerio).

Advanced technologies for toxicity tests are designed to identify biomarkers with superior predictive power or end points of the complex web of biological pathways. However, the data obtained need to be fully characterized for dose-response, physiological systems, and relevance to a system or (sub) population before biological interpretation and decision making. In this study, the toxicity of triclosan (TCS) on zebrafish was selected as a case study to correlate the observed morphological effects with existing data and identify the critical events by receptor activity sensitivity analysis. Triclosan exhibited weak acute toxicity against zebrafish and significantly affected the development of trunk muscles at 0.52, 1.04, and 1.73 μM. Through receptor-mediated screening, we found that the adverse effects of TCS induce Ryanodine receptor 1 (RyR1) activity and distort Ca2+ signaling. The trunk skeletal muscle abnormalities occurred only when the dihydropyridine receptor (DHPR) was blocked, demonstrating that TCS mainly influenced the Ca2+ regulatory module associated with signaling between DHPRs and RyR1; DHPRs mainly regulated the orthograde and retrograde signaling in skeletal muscles. This unexpected result could integrate the mode of action of TCS and provide insight for high-throughput screening and toxicity prediction using zebrafish.

Levels of skeletal muscle mass and handgrip strength in adults from 10 regions of China

Objective: To describe the regional and population-related differences in skeletal muscle mass and handgrip strength across the 10 regions of China. Methods: 24 533 participants aged 38-88 years from the second resurvey of China Kadoorie Biobank were included in our analyses. Appendicular and trunk skeletal muscle mass were assessed using the bioelectrical impedance analysis (TANITA). Handgrip strength was measured using Jamar hand-held dynamometer. Low muscle mass and low muscle strength were defined as the lowest quintile of height-adjusted appendicular muscle mass or handgrip strength according to the Consensus Report of the Asian Working Group for Sarcopenia. We analyzed the mean value of absolute muscle mass, height-adjusted muscle mass, weight-adjusted muscle mass and handgrip strength. We also reported the prevalence of low muscle mass and low muscle strength. Results: The average appendicular and total skeletal muscle mass were (22.0±0.02) kg and (49.7±0.05) kg in men, which were higher than in women [(15.9±0.02) kg and (37.2±0.04) kg, respectively]. The handgrip strength was (32.6±0.06) kg in men, which was higher than (19.9±0.05) kg in women. The absolute muscle mass was higher in north area and urban region (P<0.001). The weight-adjusted muscle mass showed reverse patterns of regional difference compared with height-adjusted muscle mass. Both muscle mass and handgrip strength decreased by age (trend P<0.001), with a larger decline observed in handgrip strength. According to AWGS criteria, the proportions of low muscle mass and strength increased by age. Among participants over 80 years old, the prevalence of low muscle mass and strength were 56.2% and 74.5% in men, and 35.7% and 66.0% in women. Conclusions: Levels of skeletal muscle mass and strength varied greatly among people from 10 regions and among participants with different demographic characteristics. The prevalence of low muscle mass and strength was extremely high in elderly.

The association of back muscle strength and sarcopenia-related parameters in the patients with spinal disorders.

To evaluate the correlations between back muscle strength, trunk muscle mass, and sarcopenia-related parameters in patients with spinal disorders. This cross-sectional observational study included 230 consecutive patients with spinal disorders who visited our outpatient clinic (age range 65-92years). We measured back muscle strength, handgrip strength, gait speed, and appendicular and trunk skeletal muscle mass using bioimpedance analysis. We classified the subjects into the sarcopenia, dynapenia, or normal stages in accordance with the guidelines set by the European Working Group on Sarcopenia in Older People, and used the cutoff values reported in the guidelines set by the Asian Working Group for Sarcopenia. Back muscle strength was significantly correlated with trunk muscle mass (males: r = 0.47, P < 0.001; females: r = 0.39, P < 0.001), handgrip strength (males: r = 0.67, P < 0.001; females: r = 0.59, P < 0.001), and gait speed (males: r = 0.49, P < 0.001; females: r = 0.51, P < 0.001). The respective incidences of the sarcopenia, dynapenia, and normal stages were 16.4%, 26.7%, and 56.9% for males, and 23.7%, 50.9%, and 25.4% for females. Dynapenia was significantly more prevalent in females than in males. Back muscle strength in the normal group was significantly greater than that in the sarcopenic and dynapenic groups. Back muscle strength is significantly correlated with trunk muscle mass and sarcopenia-related parameters in patients with spinal disorders. Back muscle strength in the sarcopenic stage is significantly lesser than that in the normal stage. Although sarcopenia is a multifaceted geriatric syndrome, spinal disorders might be one of the risk factors for disease-related sarcopenia. These slides can be retrieved from Electronic Supplementary Material.

Associations between sarcopenia and degenerative lumbar scoliosis in older women

BackgroundAge-related sarcopenia can cause various forms of physical disabilities. We investigated how sarcopenia affects degenerative lumbar scoliosis (DLS) and lumbar spinal canal stenosis (LSCS).MethodsSubjects comprised 40 elderly women (mean age 74 years) with spinal disease whose chief complaints were low back pain and lower limb pain. They included 15 cases of DLS (mean 74.8 years) and 25 cases of LSCS (mean age 72.9 years).We performed whole-body dual-energy X-ray absorptiometry (DXA) to analyze body composition, including appendicular and trunk skeletal muscle mass index (SMI; lean mass (kg)/height (m)2) and bone mineral density (BMD). A diagnostic criterion for sarcopenia was an appendicular SMI <5.46. To check spinal alignment, lumbar scoliosis (LS), sagittal vertical axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), and vertebral rotational angle (VRA) were measured. Clinical symptoms were determined from the Japanese Orthopedic Association scores, low back pain visual analog scale, and Roland-Morris Disability Questionnaire (RDQ). Criteria for DLS were lumbar scoliosis >10° and a sagittal vertical axis (SVA) >50 mm. Sarcopenia prevalence, correlations between spinal alignment, BMD, and clinical symptoms with appendicular and trunk SMIs, and correlation between spinal alignment and clinical symptoms were investigated.ResultsDLS cases had significantly lower body weight, BMI, lean mass arm, and total lean mass than LSCS cases. Sarcopenia prevalence rates were 4/25 cases (16%) in LSCS and 7/15 cases (46.6%) in DLS, revealing a high prevalence in DLS. Appendicular SMIs were DLS 5.61 and LSCS 6.13 (p < 0.05), and trunk SMIs were DLS 6.91 and LSCS 7.61 (p < 0.01) showing DLS to have significantly lower values than LSCS. Spinal alignment correlations revealed the appendicular SMI was negatively correlated with PT (p < 0.05) and the trunk SMI was found to have a significant negative correlation with SVA, PT, LS, and VRA (p < 0.05). The trunk SMI was found to have a significant positive correlation with BMD (p < 0.05). As for clinical symptoms, RDQ was negatively correlated with appendicular SMI and positively correlated with PT (P < 0.05).ConclusionsSarcopenia complications were noted in 16% of LSCS patients and a much higher percentage, or 46.6%, of DLS patients. Appendicular and trunk SMIs were both lower in DLS, suggesting that sarcopenia may be involved in scoliosis. The appendicular skeletal muscle was related to posterior pelvic tilt, while the trunk muscle affected stooped posture, posterior pelvic tilt, lumbar scoliosis, and vertebral rotation. Decreases in trunk muscle mass were also associated with osteoporosis. Moreover, RDQ had a negative correlation with appendicular skeletal muscle mass and a positive correlation with PT, suggesting that sarcopenia may be associated with low back pain as a result of posterior pelvic tilt. Our research reveals for the first time how sarcopenia is involved in spinal deformations, suggesting decreases in pelvic/lumbar support structures such as trunk and appendicular muscle mass may be involved in the progression of spinal deformities and increased low back pain.

Changes in skeletal muscle and organ size after a weight-loss intervention in overweight and obese type 2 diabetic patients

Background: The effect of a weight-loss intervention on the masses of lean tissues and organs in humans is not well known.Objective: We studied the effects of a diet and exercise weight-loss intervention on skeletal muscle (SM) mass and selected organs over 2 y using MRI in overweight adults with type 2 diabetes.Design: Participants were 53 women and 39 men [mean ± SD: age 58 ± 7 y; body mass index (BMI; in kg/m2) 32 ± 3] enrolled in the Look AHEAD (Action for Health in Diabetes) trial and randomly assigned to an intensive lifestyle intervention (ILI) or diabetes support and education (DSE) on whom 2 y of data were collected. MRI-derived measurements of SM, heart, liver, kidney, spleen, and pancreas were acquired.Results: Adjusted for baseline weight, height, age, sex, and ethnicity, the ILI group weighed (mean ± SE) 6.6 ± 0.7 kg less after 1 y and 5.2 ± 0.7 kg less after 2 y, whereas the DSE group did not change significantly (−0.4 ± 0.6 and −1.0 ± 0.7 kg after 1 and 2 y, respectively; P-interaction < 0.001). Total SM decreased in both groups during year 1 (−1.4 ± 0.2 kg; P < 0.001) with appendicular SM regained during year 2. Liver and spleen masses decreased in the ILI group (−0.12 ± 0.02 and −0.006 ± 0.003 kg, respectively) but were unchanged in the DSE group (0.00 ± 0.02 and 0.004 ± 0.003 kg, respectively). Kidney mass decreased by 0.013 ± 0.003 kg (P < 0.001) over 2 y in both groups.Conclusions: Decreases in liver (in Caucasians but not African Americans) and spleen were detected after a 6.2-kg weight reduction compared with a control group. SM and kidney mass decreased in both groups. Appendicular SM was regained during the second year whereas trunk SM was not. No evidence of a disproportionate loss of high–metabolic rate organs (heart, liver, kidney, spleen) compared with SM was found.

Stem cell expression and development of trunk musculature of lesser-spotted dogfish (Scyliorhinus canicula) reveal differences between sharks and teleosts

This study compares the trunk skeletal muscle anatomy in 870- and 2900-degree-day-old lesser-spotted dogfish larvae (Scyliorhinus canicula) via haematoxylin/eosin staining as well as immunohistochemistry and Western blot analysis. The results showed poorly differentiated muscle formation in the trunk segments in the younger larvae and fully developed skeletal muscle with a division of red and white cells in the older larvae. The stem cell marker PAX7, which is present in all developmental stages of teleost fish, is only expressed in the younger dogfish. The results show the necessity of examining the skeletal muscle development in sharks to understand the evolutional changes from cartilaginous fishes to teleosts.

In vivo assessment of contractile strength distinguishes differential gene function in skeletal muscle of zebrafish larvae.

The accessible genetics and extensive skeletal musculature of the zebrafish make it a versatile and increasingly used model for studying muscle contraction. We here describe the development of an in vivo assay for measuring the contractile force of intact zebrafish at the larval stage. In addition, as proof of applicability, we have used this assay to quantify contractile strength of zebrafish larvae in a morphant model of deranged rbfox function. Average maximum tetanic (180 Hz) whole body forces produced by wild-type larvae at 2, 3, 4, and 5 days postfertilization amounted to 3.0, 7.2, 9.1, and 10.8 mN, respectively. To compare at potentially different stages of muscle development, we developed an immunohistological assay for empirically determining the cross-sectional area of larval trunk skeletal muscle to quantify muscle-specific force per cross-sectional area. At 4-5 days postfertilization, specific force amounts to ∼ 300 mN/mm(2), which is similar to fully developed adult mammalian skeletal muscle. We used these assays to measure contractile strength in zebrafish singly or doubly deficient for two rbfox paralogs, rbfox1l and rbfox2, which encode RNA-binding factors shown previously to modulate muscle function and muscle-specific splicing. We found rbfox2 morphants produce maximal tetanic forces similar to wild-type larvae, whereas rbfox1l morphants demonstrate significantly impaired function. rbfox1l/rbfox2 morphants are paralyzed, and their lack of contractile force production in our assay suggests that paralysis is a muscle-autonomous defect. These quantitative functional results allow measurement of muscle-specific phenotypes independent of neural input.

Direct Assessment of Skeletal Muscle Contractile Strength in Live Wildtype and Rbfox Morphant Zebrafish Larvae

The accessible genetics and abundant skeletal musculature of the zebrafish make it an ideal model for studies of muscle contraction. Current functional assays for quantifying the effect of experimental modification of zebrafish muscle are indirect and observational, or they underestimate contractile force. Therefore, we developed an in vivo assay for measuring muscle contractile force. As proof of concept, we have measured contractile strength of skeletal muscle in wildtype larvae and in a morphant model from 2-5 days post fertilization (dpf). Mean maximum tetanic whole-body forces produced by wildtype 2, 3, 4, and 5 dpf larvae amounted to 3.03 mN, 7.31 mN, 8.67 mN, and 10.94 mN, respectively. Mean twitch forces produced by larvae were 0.90 mN, 5.58 mN, 7.08 mN, and 9.08 mN for 2, 3, 4, and 5 dpf respectively. The morphants we have analyzed are knockdowns of two zebrafish paralogs of rbfox, rbfox1l and rbfox2, which regulate muscle-specific splicing programs. We assessed the contractile force developed during contraction and found that our assay is clearly able to differentiate between morphant phenotypes. rbfox2 morphants appear to produce maximal tetanic forces similar to wildtype larvae, while rbfox1l morphants demonstrate significantly impaired function by producing decreased forces at the same developmental time points. This supports the conclusion that rbfox1l regulates the majority of splicing events in larval skeletal muscle. rbfox1l/rbfox2 morphants are paralyzed and their lack of significant contractile force production in our assay indicated a muscle-specific defect, not just a motoneural defect, causing the characteristic paralysis. We have also developed an immunohistological assay for empirically determining the cross-sectional area of larval trunk skeletal muscle in order quantify muscle-specific force per cross-sectional area. These functional results quantify muscle-specific phenotypes sans neural input.