Phenomenological Muscle Constitutive Model With Actin-Titin Binding for Simulating Active Stretching.

The force produced by a muscle depends on its contractile history, yet human movement simulations typically employ muscle models that define the force-length relationship from measurements of fiber force during isometric contractions. In these muscle models, the total force-length curve can have a negative slope at fiber lengths greater than the fiber length at which peak isometric force is produced. This region of negative stiffness can cause numerical instability in simulations. Experiments have found that the steady-state force in a muscle fiber following active stretching is greater than the force produced during a purely isometric contraction. This behavior is called residual force enhancement. We present a constitutive model that exhibits force enhancement, implemented as a hyperelastic material in the febio finite element software. There is no consensus on the mechanisms responsible for force enhancement; we adopt the assumption that the passive fiber force depends on the sarcomere length at the instant that the muscle is activated above a threshold. We demonstrate the numerical stability of our model using an eigenvalue analysis and by simulating a muscle whose fibers are of different lengths. We then use a three-dimensional muscle geometry to verify the effect of force enhancement on the development of stress and the distribution of fiber lengths. Our proposed muscle material model is one of the few models available that exhibits force enhancement and is suitable for simulations of active lengthening. We provide our implementation in febio so that others can reproduce and extend our results.

Tensile force impairs lip muscle regeneration under the regulation of interleukin-10.

BACKGROUND: Orbicularis oris muscle, the crucial muscle in speaking, facial expression and aesthetics, is considered the driving force for optimal lip repair. Impaired muscle regeneration remains the main culprit for unsatisfactory surgical outcomes. However, there is a lack of study on how different surgical manipulations affect lip muscle regeneration, limiting efforts to seek effective interventions. METHODS: In this study, we established a rat lip surgery model where the orbicularis oris muscle was injured by manipulations including dissection, transection and stretch. The effect of each technique on muscle regeneration was examined by histological analysis of myogenesis and fibrogenesis. The impact of tensile force was further investigated by the in vitro application of mechanical strain on cultured myoblasts. Transcriptome profiling of muscle satellite cells from different surgical groups was performed to figure out the key factors mediating muscle fibrosis, followed by therapeutic intervention to improve muscle regeneration after lip surgeries. RESULTS: Evaluation of lip muscle regeneration till 56 days after injury revealed that the stretch group resulted in the most severe muscle fibrosis (n = 6, fibrotic area 48.9% in the stretch group, P < 0.001, and 25.1% in the dissection group, P < 0.001). There was the lowest number of Pax7-positive nuclei at Days 3 and 7 in the stretch group (n = 6, P < 0.001, P < 0.001), indicating impaired satellite cell expansion. Myogenesis was impaired in both the transection and stretch groups, as evidenced by the delayed peak of centrally nucleated myofibers and embryonic MyHC. Meanwhile, the stretch group had the highest percentage of Pdgfra+ fibro-adipogenic progenitors infiltrated area at Days 3, 7 and 14 (n = 6, P = 0.003, P = 0.006, P = 0.037). Cultured rat lip muscle myoblasts exhibited impaired myotube formation and fusion capacity when exposed to a high magnitude (ε = 2688 µ strain) of mechanical strain (n = 3, P = 0.014, P = 0.023). RNA-seq analysis of satellite cells isolated from different surgical groups demonstrated that interleukin-10 was the key regulator in muscle fibrosis. Administration of recombinant human Wnt7a, which can inhibit the expression of interleukin-10 in cultured satellite cells (n = 3, P = 0.041), exerted an ameliorating effect on orbicularis oris muscle fibrosis after stretching injury in surgical lip repair. CONCLUSIONS: Tensile force proved to be the most detrimental manoeuvre for post-operative lip muscle regeneration, despite its critical role in correcting lip and nose deformities. Adjunctive biotherapies to regulate the interleukin-10-mediated inflammatory process could facilitate lip muscle regeneration under conditions of high surgical tensile force.

Prenatal and progressive coenzyme Q10 administration to mitigate muscle dysfunction in mitochondrial disease.

BACKGROUND: ADCK genes encode aarF domain-containing mitochondrial kinases involved in coenzyme Q (CoQ) biosynthesis and regulation. Haploinsufficiency of ADCK2 in humans leads to adult-onset physical incapacity with reduced mitochondrial CoQ levels in skeletal muscle, resulting in mitochondrial myopathy and alterations in fatty acid ß-oxidation. The sole current treatment for CoQ deficiencies is oral administration of CoQ10, which causes only partial recovery with postnatal treatment, underscoring the importance of early diagnosis for successful intervention. METHODS: We used Adck2 heterozygous mice to examine the influence of this gene on muscle structure, function and regeneration throughout development, growth and ageing. This investigation involved techniques including immunohistochemistry, analysis of CoQ levels, mitochondrial respiratory content, muscle transcriptome analysis and functional tests. RESULTS: We demonstrated that Adck2 heterozygous mice exhibit defects from embryonic development, particularly in skeletal muscle (1102 genes deregulated). Adck2 heterozygous embryos were 7% smaller in size and displayed signs of delayed development. Prenatal administration of CoQ10 could mitigate these embryonic defects. Heterozygous Adck2 mice also showed a decrease in myogenic cell differentiation, with more severe consequences in 'aged' mice (41.63% smaller) (P < 0.01). Consequently, heterozygous Adck2 mice displayed accelerated muscle wasting associated with ageing in muscle structure (P < 0.05), muscle function (less grip strength capacity) (P < 0.001) and muscle mitochondrial respiration (P < 0.001). Furthermore, progressive CoQ10 administration conferred protective effects on mitochondrial function (P < 0.0001) and skeletal muscle (P < 0.05). CONCLUSIONS: Our work uncovered novel aspects of CoQ deficiencies, revealing defects during embryonic development in mammals for the first time. Additionally, we identified the gradual establishment and progression of the deleterious Adck2 mouse phenotype. Importantly, CoQ10 supplementation demonstrated a protective effect when initiated during development.

[Knockout of Hsp70 Genes Modulates Age-Related Transcriptomic Changes in Leg Muscles and Reduces the Locomotion Speed and Lifespan of Drosophila melanogaster].

This study investigated the effect of knockout of six Hsp70 genes (orthologues of the mammalian genes Hspa1a, Hspa1b, Hspa2, and Hspa8) on age-related changes in gene expression in the legs of Drosophila melanogaster, which contain predominantly skeletal muscle bundles. For this, the leg transcriptomic profile was examined in males of the w^(1118) control strain and the Hsp70^(-) strain on the 7th, 23rd and 47th days of life. In w^(1118) flies, an age-related decrease in the locomotion (climbing) speed (a marker of functional state and endurance) was accompanied by a pronounced change in the transcriptomic profile of the leg skeletal muscles, which is conservative in nature. In Hsp70^(-) flies, the median lifespan was shorter and the locomotion speed was significantly lower compared to the control; at the same time, complex changes in the age-related dynamics of the skeletal muscle transcriptome were observed. Mass spectrometry-based quantitative proteomics showed that 47-day-old Hsp70^(-) flies, compared with w^(1118) flies, demonstrated multidirectional changes in the contents of key enzymes of glucose metabolism and fat oxidation (glycolysis, pentose phosphate pathway, Krebs cycle, beta-oxidation, and oxidative phosphorylation). Such dysregulation may be associated with a compensatory increase in the expression of other genes encoding chaperones (small Hsp, Hsp40, 60, and 70), which regulate specific sets of target proteins. Taken together, our data show that knockout of six Hsp70 genes slightly reduced the median lifespan of flies, but significantly reduced the locomotion speed, which may be associated with complex changes in the transcriptome of the leg skeletal muscles and with multidirectional changes in the contents of key enzymes of energy metabolism.

Bidirectional association between perioperative skeletal muscle and subcutaneous fat in colorectal cancer patients and their prognostic significance.

Introduction: Low skeletal muscle mass and high adipose tissue coexist across the body weight spectrum and independently predict the survival ratio of colorectal cancer (CRC) patients. This combination may lead to a mutually exacerbating vicious cycle. Tumor-associated metabolic conditions primarily affect subcutaneous adipose tissue, but the nature and direction of its relationship with skeletal muscle are unclear. This study aims to examine the bidirectional causal relationship between skeletal muscle index (SMI) and subcutaneous fat index (SFI) during the perioperative period in CRC patients; as well as to validate the association between perioperative SMI, SFI, and CRC prognosis. Methods: This population-based retrospective cohort study included patients with stage I-III colorectal cancer who underwent radical resection at the Third Affiliated Hospital of Kunming Medical University between September 2012 and February 2019. Based on inclusion and exclusion criteria, 1,448 patients were analyzed. Preoperative (P1), 2 months postoperative (P2), and 5 months postoperative (P3) CT scans were collected to evaluate the skeletal muscle index (SMI; muscle area at the third lumbar vertebra divided by height squared) and subcutaneous fat index (SFI; subcutaneous fat area at the third lumbar vertebra divided by height squared). A random intercept cross-lagged panel model (RI-CLPM) was used to examine the intra-individual relationship between SMI and SFI, and Cox regression was employed to assess the association between SMI, SFI, recurrence-free survival (RFS), and overall survival (OS). Results: The median age at diagnosis was 59.00 years (IQR: 51.00-66.00), and 587 patients (40.54%) were female. RI-CLPM analysis revealed a negative correlation between SFI and subsequent SMI at the individual level: P1-P2 (ß = -0.372, p = 0.038) and P2-P3 (ß = -0.363, p = 0.001). SMI and SFI showed a negative correlation during P1-P2 (ß = -0.363, p = 0.001) but a positive correlation during P2-P3 (ß = 0.357, p = 0.006). No significant correlation was found between the random intercepts of SFI and SMI at the between-person level (r = 0.157, p = 0.603). The Cox proportional hazards multivariate regression model identified that patients with elevated SFI had poorer recurrence-free survival (HR, 1.24; 95% CI: 1.00-1.55). Compared to patients with normal preoperative SMI and SFI, those with low SMI or high SFI had poorer recurrence-free survival (HR, 1.26; 95% CI: 1.03-1.55) and overall survival (HR, 1.39; 95% CI: 1.04-1.87). However, no significant association between SMI and SFI and the prognosis of colorectal cancer patients was observed postoperatively. Conclusion: In CRC patients, preoperative muscle loss leads to postoperative fat accumulation, exacerbating muscle loss in a feedback loop. Elevated preoperative SFI predicts poorer survival outcomes. Monitoring SMI and SFI is crucial as prognostic indicators, despite non-significant postoperative associations. Further research is needed to improve patient outcomes.

A review of porcine skeletal muscle plasticity and implications for genetic improvement of carcass and meat quality.

Skeletal muscle is characterized by a remarkable plasticity to adapt to stimuli such as contractile activity, loading conditions, substrate supply or environmental factors. The existing knowledge of muscle plasticity along with developed genetic and genomic technologies, have enabled creating animal breeding strategies and allowed for implementing agriculturally successful porcine genetic improvement programs. The primary focus of this review paper is on pig skeletal muscle plasticity as it relates to genetic improvement of desirable carcass composition and pork quality traits. Biological constraints between practically realized breeding objectives, pig skeletal muscle biology, and pork quality are also discussed. Future applications of genetic and genomic technologies and plausible focus on new breeding objectives enhancing pork production sustainability are proposed as well.

Skeletal muscle-derived exosomes selectively coated miRNAs and participate in myoblast proliferation and differentiation mediated by miR-4331-3p.

The phenotypic characteristics and meat quality of skeletal muscles are collectively determined by muscle cells and their intricate interactions with the extracellular microenvironment. In this study, we evaluated muscle fiber phenotypes in the longissimus dorsi (HC-L) and psoas major (HC-P) of Hechuan black pigs. The results revealed significant differences in muscle fiber diameter, density, and type (P < 0.05). Subsequently, co-culture experiments with myoblasts demonstrated that skeletal muscle-derived exosomes (SKM-Exos) promoted myoblast proliferation and differentiation with P-Exo exhibiting superior efficacy in promoting the augmentation of MyHCIIa fiber. Furthermore, SKM-Exos are inherently heterogeneous, and the micro RNAs (miRNAs) present in SKM-Exos are selectively coated. Notably, the expression of miR-4331-3p was significantly higher in SKM-Exos than in the corresponding skeletal muscles. The expression of miR-4331-3p was significantly elevated in the SKM-Exos of HC-L compared to that of HC-P, and it interacted with differentially expressed genes between HC-L and HC-P. Moreover, miR-4331-3p enhanced myoblast proliferation and inhibited differentiation. Our findings offer valuable insights into the molecular processes that contribute to meat formation, including intricate cellular interactions.

Mechanical Stimulation and Aligned Poly(ε-caprolactone)-Gelatin Electrospun Scaffolds Promote Skeletal Muscle Regeneration.

The current treatments to restore skeletal muscle defects present several injuries. The creation of scaffolds and implant that allow the regeneration of this tissue is a solution that is reaching the researchers' interest. To achieve this, electrospinning is a useful technique to manufacture scaffolds with nanofibers with different orientation. In this work, polycaprolactone and gelatin solutions were tested to fabricate electrospun scaffolds with two degrees of alignment between their fibers: random and aligned. These scaffolds can be seeded with myoblast C2C12 and then stimulated with a mechanical bioreactor that mimics the physiological conditions of the tissue. Cell viability as well as cytoskeletal morphology and functionality was measured. Myotubes in aligned scaffolds (9.84 ± 1.15 µm) were thinner than in random scaffolds (11.55 ± 3.39 µm; P = 0.001). Mechanical stimulation increased the width of myotubes (12.92 ± 3.29 µm; P < 0.001), nuclear fusion (95.73 ± 1.05%; P = 0.004), and actin density (80.13 ± 13.52%; P = 0.017) in aligned scaffolds regarding the control. Moreover, both scaffolds showed high myotube contractility, which was increased in mechanically stimulated aligned scaffolds. These scaffolds were also electrostimulated at different frequencies and they showed promising results. In general, mechanically stimulated aligned scaffolds allow the regeneration of skeletal muscle, increasing viability, fiber thickness, alignment, nuclear fusion, nuclear differentiation, and functionality.

Diagnostic and evaluative efficiency of 68Ga-FAPI-04 in skeletal muscle injury.

BACKGROUND: Skeletal muscles are vital for daily function, yet assessing their injuries remain challenging. We aimed to elucidate the effectiveness of 68Ga-FAPI-04 in evaluating skeletal muscle remodeling. RESULTS: C2C12 cells were subjected to graded H2O2 stimulation in vitro, revealing an initial rise and subsequent decline in fibroblast activation protein (FAP) expression as H2O2 concentration increased. In vivo, a murine triceps surae injury model was created using various solutions to simulate normal repair, mild repair failure, and severe repair failure. Assessments were conducted on days 1, 3, 7, and 14 using PET, MRI, and ultrasound. With 68Ga-FAPI-04, the normal and mild repair failure groups showed significantly higher SUVmax and T/B ratios on day 1 compared to the severe repair failure group. These values gradually decreased in the normal repair group, becoming negligible after day 7. MRI results for the normal repair group showed low to moderate signal intensity by day 7. A clinical study retrospectively evaluated post-hip arthroplasty patient images at intervals of 1 month, 2-3 months, 5-6 months, and over 7 months. In these patients, 18F-FDG SUVmax and volume remained relatively stable over time, while 68Ga-FAPI-04 SUVmax initially increased, then decreased, with a consistent reduction in volume. CONCLUSION: In skeletal muscle injuries, FAP demonstrates a distinctive mechanism of action, and 68Ga-FAPI-04, in comparison to other tests, more precisely captures alterations in lesion site uptake intensity and volume. TRIAL REGISTRATION: Trial registration: ChiCTR2000041204. Registered 22 December 2020, https://www.chictr.org.cn/showproj.html?proj=66211.

PHARMACOLOGICAL INHIBITION REVEALS PARTICIPATION OF THE ENDOCYTIC COMPARTMENT IN POSITIVE FEEDBACK IL-6 SECRETION IN HUMAN SKELETAL MYOTUBES.

IL-6 is an important cytokine involved in metabolic, immunological, and cell-fate responses. It is released upon stimulation by skeletal muscle cells through partially characterized mechanisms. In some cell types, IL-6 has been reported to activate a positive feedback loop involving endocytic vesicles, but evidence is mostly based on transcription and signal transduction mechanisms and is very scarce in muscle cells. Our aim was to directly demonstrate the presence of positive feedback in the ATP-induced release of IL-6 into the supernatant of human skeletal muscle cultures. The total release (production) of IL-6 was reduced for higher volumes of supernatant, when the secreted IL-6 molecules are more diluted, and enhanced when the supernatant volume was lower. In addition, secretion was impaired both by tocilizumab, a blocker of human IL-6 receptors, and by the soluble form of the receptor. The secretion in response to ATP was also inhibited by treatment with the endocytosis inhibitor dynasore, and by disruption of the acidic gradient of the endocytic compartment using different methods (chloroquine, NH4Cl or monensin). IL-6 secretion was also impaired by NED-19, a specific inhibitor of the two pore channels receptor mediating Ca2+ release from the endolysosomal compartment. IL-6 and ATP increased IL-6 mRNA levels, an effect blocked by tocilizumab. Altogether, our results demonstrate that ATP-secreted IL-6 activates a positive loop based on IL-6 receptors, endocytosis, two pore channels and IL-6 transcription. Given the importance of muscle IL-6 as a systemic regulator and as an inflammatory mediator, our study can help to understand muscle pathophysiology.

Single-nucleus transcriptional profiling reveals TCF7L2 as a key regulator in adipogenesis in goat skeletal muscle development.

Intramuscular adipogenesis plays an important role in muscle development, which determines the quality of goat meat. However, its underlying cellular and molecular mechanisms remain poorly understood. In this study, we provided detailed cellular atlases of goat longissimus dorsi during muscle development at single-nucleus resolution, and identified the subpopulations of fibroblasts/fibro-adipogenic progenitors (FAPs) and muscle satellite cell (MuSC), as well as the differentiation trajectory of FAPs subpopulations. Cellular ligand-receptor interaction analysis revealed enriched BMP and IGF pathways implicated in within-tissue crosstalk centered around FAPs. Through single-nucleus gene regulatory network analysis and in vitro interference verification, we found that TCF7L2 was a critical transcriptional factor (TF) in early adipogenesis in skeletal muscle. Overall, our work reveals the cellular intricacies and diversity of goat longissimus dorsi during muscle development, implementing insights into the critical roles of BMP, IGF pathways and TCF7L2 TF in intramuscular adipogenesis.

Site-specific skeletal muscle mass and functional prognosis in geriatric stroke patients.

BACKGROUND: Evidence is scarce regarding prognostic value of site-specific muscle mass in geriatric stroke survivors. We aim to assess the association between four measures of muscle mass, namely the skeletal muscle mass index of the limbs (SMI), upper limb SMI (USMI), lower limb SMI (LSMI), and trunk muscle mass index (TMI), and the functional prognosis in stroke patients. METHODS: This study conducted a retrospective cohort analysis involving post-acute stroke inpatients. Muscle mass data were obtained through bioelectrical impedance analysis and computed by dividing each muscle mass by the square of the height. The study outcomes included the Functional Independence Measure (FIM) motor at discharge and FIM-motor gain. Multiple regression analysis was conducted to assess the association between SMI, USMI, LSMI, and TMI with outcomes, while adjusting for confounding factors. RESULTS: A total of 701 patients (mean age 72.8 years, 374 males) were analyzed. As a result, LSMI (ß = 0.089, P = 0.003) and SMI (ß = 0.083, P = 0.008) were significantly associated in the FIM-motor at discharge, with LSMI showing a stronger association. USMI (ß = 0.019, P = 0.521) and TMI (ß = 0.035, P = 0.231) showed no significant association. LSMI (ß = 0.124, P = 0.003) and SMI (ß = 0.116, P = 0.008) were significantly associated with FIM-motor gain; however, USMI (ß = 0.027, P = 0.521) and TMI (ß = 0.049, P = 0.231) showed no significant association with FIM-motor gain. CONCLUSIONS: Differential associations were observed between site-specific muscle mass and functional prognosis in post-stroke patients. Among these, lower limb muscle mass was most strongly associated with activities of daily living (ADL) recovery.

Reduced muscle mass is an important part of Global Leadership Initiative on Malnutrition criteria in nutritional diagnosis of hepatocellular carcinoma.

BACKGROUND: The Global Leadership Initiative on Malnutrition criteria (GLIM) was established to build a global consensus on the diagnostic criteria for malnutrition. The study aimed to assess the prevalence of the malnutrition diagnosed by GLIM criteria for patients with hepatocellular carcinoma (HCC), and to determine the role of the reduced muscle mass defined by CT scans in the GLIM criteria. METHODS: This cohort research was conducted on adult cirrhotic patients with HCC. The risk of malnutrition was screened by Nutritional Risk Screening 2002 (NRS-2002), and malnutrition was diagnosed by GLIM criteria. The third lumbar vertebrae (L3-SMI) were used to represent the muscle mass in GLIM criteria. The variables associated with overall mortality were assessed by multivariate Cox regression analyses. RESULTS: The incidence of malnutrition diagnosed by GLIM criteria was 49.7% (179/360) in patients with HCC. If reduced muscle mass was not included in GLIM criteria, the prevalence of malnutrition was 31.7% (114/360). GLIM-defined malnutrition (HR = 1.979, 95%CI 1.019-3.841, P = 0.044) was independently associated with overall mortality in patients with HCC. However, the GLIM-defined malnutrition (without muscle mass) was not associated with overall mortality (HR = 0.863, 95%CI 0.399-1.867, P = 0.709). CONCLUSIONS: Skeletal muscle mass is an integral component of the GLIM criteria for patients with HCC. The malnutrition is common in patients with HCC, and malnourishment is associated with higher overall mortality. GLIM criteria are recommended to assess the nutritional status of hospitalized patients with HCC, which is recommended and can be used as the basis for nutritional interventions.

Appendicular skeletal muscle mass is associated with metabolic dysfunction-associated steatotic liver disease severity in young men: a cross-sectional and longitudinal study.

BACKGROUND AND AIM: Although appendicular skeletal muscle mass (ASM) has been linked to the severity of hepatic steatosis, investigations of its correlation among younger age groups are lacking. We aimed to elucidate the role of ASM in determining the severity of metabolic dysfunction-associated steatotic liver disease (MASLD) in younger patients. METHODS: Retrospective data were collected from patients younger than 35 years who visited the Armed Forces Goyang Hospital between June 2022 and February 2024. Steatosis presence was determined by a controlled attenuation parameter score ≥ 250 dB/m, and significant fibrosis was identified with liver stiffness measurement > 8.0 kPa. ASM was measured using multifrequency bioelectrical impedance analysis (InBody 620). RESULTS: Of 910 participants, 630 were diagnosed with MASLD. Patients with MASLD had lower ASM/fat mass (ASM/F) (1.02 vs. 1.91; p < 0.001), ASM/body mass index (BMI) (0.91 vs. 1.04/m2; p < 0.001), and ASM/body weight (ASM/W) (29.5% vs. 33.8%; p < 0.001) than non-MASLD patients. Additionally, ASM/F, ASM/BMI, and ASM/W significantly decreased with worsening steatosis severity and were notably lower in patients with significant fibrosis. Among 107 patients with MASLD who underwent two examinations with a median interval of 6.0 months, those with increased ASM/F showed a higher proportion of steatosis regression and a lower proportion of steatosis worsening than those with decreased ASM/F (steatosis regression, 43.1% vs. 22.9%; worsening, 11.1% vs. 28.6%; p = 0.031). All three ASM indices were significant factors in steatosis regression during the study period. CONCLUSIONS: ASM is associated with the severity of steatosis and significant fibrosis in MASLD in young adults < 35 years.

Differential gene expression in neonatal calf muscle tissues from Hanwoo cows overfed during mid to late pregnancy period.

Maternal nutrition significantly influences fetal development and postnatal outcomes. This study investigates the impact of maternal overfeeding during mid to late pregnancy on gene expression in the round and sirloin muscles of Hanwoo neonatal calves. Eight cows were assigned to either a control group receiving standard nutrition (100%) or a treated group receiving overnutrition (150%). After birth, tissue samples from the round and sirloin muscles of neonatal calves were collected and subjected to RNA sequencing to assess differentially expressed genes (DEGs). RNA sequencing identified 43 DEGs in round muscle and 15 in sirloin muscle, involving genes related to myogenesis, adipogenesis, and energy regulation. Key genes, including PPARGC1A, THBS1, CD44, JUND, CNN1, ENAH, and RUNX1, were predominantly downregulated. Gene ontology (GO) enrichment analyses revealed terms associated with muscle development, such as "biological regulation," "cellular process," and "response to stimulus." Protein-protein interaction networks highlighted complex interactions among DEGs. Random Forest analysis identified ARC, SLC1A5, and GNPTAB as influential genes for distinguishing between control and treated groups. Overall, maternal overnutrition during mid-to-late pregnancy results in the downregulation of genes involved in muscle development and energy metabolism in neonatal Hanwoo calves. These findings provide insights into the molecular effects of maternal nutrition on muscle development.

Low muscle strength rather than low muscle mass is associated with cardiovascular autonomic neuropathy in patients with type 2 diabetes.

Several studies have investigated whether sarcopenia is associated with diabetic microvascular complications, but very few have examined associations between sarcopenia and cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes mellitus (T2DM). Therefore, we investigated associations of muscle strength (handgrip strength [HGS]) and mass (appendicular skeletal muscle mass index [ASMI]) and CAN in patients with T2DM. We enrolled 342 patients in this retrospective, cross-sectional study. Cardiovascular reflex tests were used to assess CAN according to Ewing's protocol. Relative HGS was determined after normalizing absolute HGS to body weight (HGS/body weight [kg]). We defined low HGS and low ASMI according to a consensus report of the Asian Group for Sarcopenia. Logistic regression analyses were carried out to assess the associations between relative HGS or ASMI quartiles and the presence of CAN in patients with T2DM. The prevalence rates of CAN, low HGS, and low ASMI in the study subjects were 34.8%, 17.3%, and 18.7%, respectively. Low HGS was significantly more prevalent in patients with CAN than those without CAN (23.5% vs. 13.9%, p = 0.025). The CAN scores were significantly and negatively correlated with relative HGS but not with ASMI. Relative HGS was negative correlated with age, glycated hemoglobin, fasting plasma glucose, hsCRP, body mass index, and HOMA-IR and positively correlated with ASMI. The prevalence of CAN gradually increased with decreasing quartile of relative HGS (28.4% in Q4, 31.8% in Q3, 34.2% in Q2, and 45.3% in Q1, p = 0.02 for trend). Multivariable-adjusted prevalence ratios (PRs) for CAN, determined by comparing the first, second, and third quartiles with the fourth quartile of relative HGS, were 4.4 with a 95% confidence interval (95% CI) of [1.1 to 17.3]), 2.3 (95% CI [0.8 to 6.9]), and 1.2 (95% CI [0.4 to 3.7]), respectively. The prevalence of CAN and the PRs (95% [CI]) for CAN based on ASMI were not statistically significant. Our findings suggest that low muscle strength rather than low muscle mass was significantly associated with the presence of CAN. Therefore, HGS testing could help identify patients who would benefit from screening for earlier diagnosis of CAN.

Effects and mechanisms of supramaximal high-intensity interval training on extrapulmonary manifestations in people with and without chronic obstructive pulmonary disease (COPD-HIIT): study protocol for a multi-centre, randomized controlled trial.

BACKGROUND: Beyond being a pulmonary disease, chronic obstructive pulmonary disease (COPD) presents with extrapulmonary manifestations including reduced cognitive, cardiovascular, and muscle function. While exercise training is the cornerstone in the non-pharmacological treatment of COPD, there is a need for new exercise training methods due to suboptimal adaptations when following traditional exercise guidelines, often applying moderate-intensity continuous training (MICT). In people with COPD, short-duration high-intensity interval training (HIIT) holds the potential to induce a more optimal stimulus for training adaptations while circumventing the ventilatory burden often associated with MICT in people with COPD. We aim to determine the effects of supramaximal HIIT and MICT on extrapulmonary manifestations in people with COPD compared to matched healthy controls. METHODS: COPD-HIIT is a prospective, multi-centre, randomized, controlled trial with blinded assessors and data analysts, employing a parallel-group designed trial. In phase 1, we will investigate the effects and mechanisms of a 12-week intervention of supramaximal HIIT compared to MICT in people with COPD (n = 92) and matched healthy controls (n = 70). Participants will perform watt-based cycling two to three times weekly. In phase 2, we will determine how exercise training and inflammation impact the trajectories of neurodegeneration, in people with COPD, over 24 months. In addition to the 92 participants with COPD performing HIIT or MICT, a usual care group (n = 46) is included in phase 2. In both phases, the primary outcomes are a change from baseline in cognitive function, cardiorespiratory fitness, and muscle power. Key secondary outcomes include change from baseline exercise tolerance, brain structure, and function measured by MRI, neuroinflammation measured by PET/CT, systemic inflammation, and intramuscular adaptations. Feasibility of the interventions will be comprehensively investigated. DISCUSSION: The COPD-HIIT trial will determine the effects of supramaximal HIIT compared to MICT in people with COPD and healthy controls. We will provide evidence for a novel exercise modality that might overcome the barriers associated with MICT in people with COPD. We will also shed light on the impact of exercise at different intensities to reduce neurodegeneration. The goal of the COPD-HIIT trial is to improve the treatment of extrapulmonary manifestations of the disease. TRIAL REGISTRATION: Clinicaltrials.gov: NCT06068322. Prospectively registered on 2023-09-28.

Interactions between muscle volume and body mass index on brain structure in the UK Biobank.

Background: Low skeletal muscle volume may increase dementia risk through mechanisms affecting brain structure. However, it is unclear whether this relationship exists outside of sarcopenia and/or varies by other factors. We aimed to study the interplay between skeletal muscle volume and factors, such as age, sex, and body mass index (BMI), in explaining brain structure at midlife in a cohort without sarcopenia. Methods: We used abdominal and brain magnetic resonance imaging (MRI) data from a population-based cohort enrolled in the UK Biobank. The following measures were derived: thigh fat-free muscle volume (FFMV), total brain volume (TBV), gray matter volume (GMV), white matter volume (WMV), total hippocampal volume (THV), and white matter hyperintensity volume (WMHV). Participants below sex-based grip strength thresholds suggesting probable sarcopenia were excluded. Linear regression analysis was used to study the interaction or mediation effects of age, sex, and BMI on the associations between FFMV and brain volumes. Results: Data were available for 20,353 participants (median age 64 years, 53% female). We found interactions between thigh FFMV, BMI, and age (all p < 0.05). Greater thigh FFMV was associated with better brain volumes in those aged <64 years with normal (TBV: ß = 2.0 ml/L, p = 0.004; GMV: ß = 0.8 ml/L, p = 0.04; WMV: ß = 1.1 ml/L, p = 0.006; WMHV: ß = -0.2 ml/L, p = 3.7 × 10-5) or low BMI (TBV: ß = 21.2 ml/L, p = 0.003; WMV: ß = 13.3 ml/L, p = 0.002, WMHV: ß = -1.1 ml/L, p = 0.04). Conclusion: Greater thigh muscle volume correlates with better brain volumes at midlife in people without sarcopenia, but this relationship weakens with greater age and BMI. Further study is required to investigate the underlying mechanisms to understand which components of body composition are potentially modifiable risk factors for dementia.

Distinct muscle regenerative capacity of human induced pluripotent stem cell-derived mesenchymal stromal cells in Ullrich congenital muscular dystrophy model mice.

BACKGROUND: Ullrich congenital muscular dystrophy (UCMD) is caused by a deficiency in type 6 collagen (COL6) due to mutations in COL6A1, COL6A2, or COL6A3. COL6 deficiency alters the extracellular matrix structure and biomechanical properties, leading to mitochondrial defects and impaired muscle regeneration. Therefore, mesenchymal stromal cells (MSCs) that secrete COL6 have attracted attention as potential therapeutic targets. Various tissue-derived MSCs exert therapeutic effects in various diseases. However, no reports have compared the effects of MSCs of different origins on UCMD pathology. METHODS: To evaluate which MSC population has the highest therapeutic efficacy for UCMD, in vivo (transplantation of MSCs to Col6a1-KO/NSG mice) and in vitro experiments (muscle stem cell [MuSCs] co-culture with MSCs) were conducted using adipose tissue-derived MSCs, bone marrow-derived MSCs, and xeno-free-induced iPSC-derived MSCs (XF-iMSCs). RESULTS: In transplantation experiments on Col6a1-KO/NSG mice, the group transplanted with XF-iMSCs showed significantly enhanced muscle fiber regeneration compared to the other groups 1 week after transplantation. At 12 weeks after transplantation, only the XF-iMSCs transplantation group showed a significantly larger muscle fiber diameter than the other groups without inducing fibrosis, which was observed in the other transplantation groups. Similarly, in co-culture experiments, XF-iMSCs were found to more effectively promote the fusion and differentiation of MuSCs derived from Col6a1-KO/NSG mice than the other primary MSCs investigated in this study. Additionally, in vitro knockdown and supplementation experiments suggested that the IGF2 secreted by XF-iMSCs promoted MuSC differentiation. CONCLUSION: XF-iMSCs are promising candidates for promoting muscle regeneration while avoiding fibrosis, offering a safer and more effective therapeutic approach for UCMD than other potential therapies.

Association of Perioperative Skeletal Muscle Index Change With Outcome in Colorectal Cancer Patients.

BACKGROUND: The association between perioperative changes in the skeletal muscle index (SMI) and colorectal cancer (CRC) outcomes remains unclear. We aim to explore perioperative change patterns of SMI and evaluate their effects on long-term outcomes in CRC patients. METHODS: This retrospective cohort study included Stage I-III CRC patients who underwent curative resection between 2012 and 2019. SMI at the third lumbar vertebra level was calculated using computed tomography scans. Optimal cut-off values for SMI were defined separately for males and females and classified as high or low preoperatively and at 3, 6, 9 and 12 months postoperatively. SMI status was further categorized into different perioperative SMI change patterns: highpre-highpost, highpre-lowpost, lowpre-highpost and lowpre-lowpost. The association with recurrence-free survival (RFS) and overall survival (OS) was examined using Cox proportional hazards models. RESULTS: A total of 2222 patients (median [interquartile range] age, 60.00 [51.00-68.00] years; 1302 (58.60%) men; 222 (9.99%) with preoperative low SMI) were evaluated. During a median follow-up of 60 months, 375 patients (16.88%) died, and 617 patients (27.77%) experienced a recurrence. Multivariate Cox model analysis showed that, compared to patients with highpre-highpost, those with highpre-lowpost (HR = 3.32, 95% CI: 1.60-6.51; HR = 2.54, 95% CI: 1.03-6.26; HR = 2.93, 95% CI: 1.19-7.19, all p < 0.05) had significantly worse RFS and OS (HR = 4.07, 95% CI: 1.55-10.69; HR = 4.78, 95% CI: 1.40-16.29; HR = 9.69, 95% CI: 2.53-37.05, all p < 0.05), at postoperative 6, 9 and 12 months, respectively. Patients with lowpre-lowpost were an independent prognostic factor for worse OS at postoperative 12 months (HR = 3.20, 95% CI: 1.06-9.71, p = 0.040). Patients with lowpre-highpost had similar risk of RFS compared to those with highpre-highpost at postoperative 3, 6 and 12 months (HR = 1.49, 95% CI: 0.75-2.98; HR = 1.05, 95% CI: 0.45-2.43; HR = 1.36, 95% CI: 0.31-6.06, all p > 0.05) and similar risk of OS at postoperative 3, 6, 9 and 12 months (all p > 0.05). CONCLUSIONS: Patients with a high preoperative SMI that decline postoperatively have poor RFS and OS. Consistently low SMI also correlates with worse OS. Patients with low SMI but increased after resection are not an indicator of better prognosis. Routine measurement of postoperative, rather than preoperative, SMI is warranted. Patients with low SMI are at an increased risk for recurrence and death, especially within the first year after surgery.