Gastrocnemius Research Articles

Pregabalin produces analgesia in males but not females in an animal model of chronic widespread muscle pain.

Pregabalin, which acts on the α2δ-1 subunit of voltage-gated calcium channels, relieves ≥50% of pain in a third of individuals with fibromyalgia. Thus far, preclinical studies of pregabalin have predominantly used male animals. The purpose of our study was to investigate potential sex differences in the analgesic efficacy of pregabalin that may contribute to disparities in human outcomes. We used a mouse model of chronic widespread muscle pain (CWP) to test the effects of pregabalin on muscle hyperalgesia, nonreflexive pain, and motor behaviors. The CWP pain model combines 2 pH 4.0 saline injections, spaced 5 days apart, into the gastrocnemius muscle and produces bilateral muscle hyperalgesia. Furthermore, we explored sex differences in the mRNA and protein expression of the α2δ-1 subunit of voltage-gated calcium channels in the dorsal horn of the spinal cord and dorsal root ganglia after development of CWP. Pregabalin fully attenuated muscle hyperalgesia bilaterally in male but not female mice with equal motor deficits produced in both sexes. In addition, using the conditioned place preference test, mice of both sexes with CWP spent significantly more time in the pregabalin-paired chamber compared with baseline, but not significantly greater than pain-free controls. Chronic widespread muscle pain produced no changes in α2δ-1 subunit mRNA or protein expression in the dorsal horn of the spinal cord or dorsal root ganglia in either sex. Overall, these findings indicate pregabalin may be more effective in treating CWP in males, but the factors leading to these differences are not fully understood.

Increased Variability in Lower Limb Muscle Activation Is Observed with Increasing Walking Speed in Fall-Risk Older Adults

This study is a cross-sectional study and aims to determine the differences in lower limb muscle activation and variability at preferred, slow, and fast walking speeds according to age and fall risk. We divided 301 participants into groups based on fall risk (fall-risk vs. non-fall-risk). We measured muscle activation and its coefficients of variation (CV) for the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius muscle (GCM) at speeds 20% slower, 20% faster, and 40% faster than the preferred speed (PS). When compared by fall risk, fall-risk older adults had significantly lower GCM activity and higher CVs of RF, BF, TA, and GCM in PS. With changes in gait speed, fall-risk older adults had significantly increased CVs of RF, BF, and GCM. Our findings provide new evidence that variability rather than muscle activity increases with walking speed in older adults at risk of falls, highlighting the importance of decreasing muscle activity variability in preventing fall risk.

Direct Anatomical Reconstruction of the Achilles Tendon and Its Application for Surgical Treatment of Acute Achilles Tendon Ruptures

Background/Objectives: Acute ruptures of the Achilles Tendon (AT) are common injuries in the active population, in particular among men aged 30 to 50. Full functional recovery after this kind of injury is long and challenging and nowadays there is no universal “gold standard” strategy when dealing with them. Methods: When it comes to surgical treatment, various techniques have been described: in case of a typical lesion at the midportion of the tendon (which is the most common type), the basic principle of surgical repair is the end-to-end suture of the tendon stumps. The AT (“calcaneal tendon” according to the International Anatomical Terminology) is the strongest tendon of the human body, it is the conjunct tendon of the two Gastrocnemii Muscles and the Soleus Muscle and has a well-recognizable twisted structure: the subtendon from the Medial Head of the Gastrocnemius attaches postero-laterally on the calcaneal tendon footprint, the subtendon from the Lateral Head of the Gastrocnemius attaches antero-laterally and the subtendon from the Soleus attaches medially, therefore creating a 90° twist of the tendon structure. Results: the twisted structure of the human AT is of central importance to its biomechanics, since it gives the tendon a higher resistance to deformation and concurs in supination of the subtalar joint during gait. Conclusions: given the abovementioned anatomical and biomechanical premises, we believe that the restoration of the subtendons anatomy can lead to a better functional recovery of the Triceps Surae—Achilles Tendon complex, therefore we recently decided to adopt for open surgical repair the Direct Anatomical Reconstruction of the Achilles Tendon, which we describe in the present article.

Muscle type-specific effects of bilateral abobotulinumtoxinA injection on muscle growth and contractile function in spastic mice.

Intramuscular injection of botulinum neurotoxin type A (BoNT-A) is commonly used to improve or maintain the joint range of motion in young children with spasticity. However, the effectiveness of BoNT-A treatment is variable and movement limitations are recurrent. Here we show long-term effects of a single, bilateral abobotulinumtoxinA (aboBoNT-A) injection in the gastrocnemius medialis and soleus muscles of wild-type and spastic (B6.Cg-Glrbspa/J with a mutation in the glycine receptor) mice at a young age (6-7 days). Specifically, we evaluated the impact of aboBoNT-A-A on gait, physical performance, and spontaneous physical behavior, as well as on contractile force characteristics, morphology, and histological phenotype of soleus and gastrocnemius muscles by comparing their results to those of saline-injected controls up to 9 weeks after the injection. The detailed time course of the study specifies the timing of the aboBoNT-A injection at 1 week, the period of behavioral studies from 4-9 weeks, and the age of the mice (10 weeks) at the time of contractile force characteristics and histology assessments. In spastic mice, aboBoNT-A injection had a minor and very specific effect on physical performance, by only modestly increasing stride length as a function of age. aboBoNT-A injection caused a reduction in the force-generating capacity and a slightly smaller physiological cross-sectional area in gastrocnemius medialis, but not in soleus. Reduced physiological cross-sectional area in aboBoNT-A-injected muscles was due to a lower number of muscle fibers, rather than reduced muscle fiber cross-sectional area. The percentage of slow-type muscle fibers and mitochondrial succinate dehydrogenase activity were increased, which was associated with an improved muscle endurance capacity. In conclusion, aboBoNT-A injection reduced the number of muscle fibers, causing muscle hypertrophy in remaining fibers and a shift towards more oxidative fibers, resulting in an improved endurance capacity and gait. This study proposed potential cellular mechanisms for the therapeutic efficacy of aboBoNT-A in spasticity.

No detectable loss of myonuclei from human muscle fibers after six weeks of immobilization following an Achilles tendon rupture.

Muscle disuse has rapid and debilitating effects on muscle mass and overall health, making it an important issue from both scientific and clinical perspectives. However, the myocellular adaptations to muscle disuse are not yet fully understood, particularly those related to the myonuclear permanence hypothesis. Therefore, in this study, we assessed fiber size, number of myonuclei, satellite cells, and capillaries in human gastrocnemius muscle after a period of immobilization following an Achilles tendon rupture. Six physically active patients (5M/1F, 43 {plus minus} 15 years) were recruited to participate after sustaining an acute unilateral Achilles tendon rupture. Muscle biopsies were obtained from the lateral part of the gastrocnemius before and after six weeks of immobilization using a plaster cast and orthosis. Muscle fiber characteristics were analyzed in tissue cross-sections and isolated single fibers using immunofluorescence and high-resolution microscopy. Immobilization did not change muscle fiber type composition nor cross-sectional area of type I or type II fibers, but muscle fiber volume tended to decline by 13% (p=0.077). After immobilization, the volume per myonucleus was significantly reduced by 20% (p=0.008). Myonuclei were not lost in response to immobilization but tended to increase in single fibers and type II fibers. No significant changes were observed for satellite cells or capillaries. Myonuclei were not lost in the gastrocnemius muscle after a prolonged period of immobilization, which may provide support to the myonuclear permanence hypothesis in human muscle. Capillaries remained stable throughout the immobilization period, whereas the response was variable for satellite cells, particularly in type II fibers.

Molecular modeling and implications of Biochanin A on ghrelin and IGF-1/myostatin signaling in radiation triggered cachexia

BackgroundCachexia, a loss of appetite and body weight as a result of systemic inflammation, considered one of the unavoidable side effects of radiation therapy. Controlling ghrelin (Ghr) levels could assist in alleviating this condition by improving appetite, promoting energy storage, and reducing cytokines’ generation. This study aimed to explore the effect of Biochanin A (BCA), a natural bioactive isoflavone, in alleviating radiation-cachexic syndrome.ResultsMolecular docking study of BCA demonstrated strong fitting with more binding interactions than megestrol acetate (MA), a commonly prescribed medication for cachexia, into Ghr active binding site. Accordingly, irradiated rats were treated with BCA or MA, with body weight monitoring. Force swimming test (FST) was carried out followed by gastrocnemius muscle weighting and histological examination. Biochemical assay of Ghr, TNF-α, insulin growth factor-1 (IGF-1), myostatin (Mst), lactate dehydrogenase (LDH), and brain serotonin (5-HT) level, were carried in order to estimate the possible action pathway of BCA. Results showed that BCA improved weight gain and histological muscle bundle arrangement. Although, BCA and MA significantly reduced serum TNF-α by 25.6% and 24.2%, respectively, only BCA maintained normal IGF-1and Mst levels, whose balance is necessary to avoid skeletal muscle loss, the main mark of cachexia. Moreover, BCA showed tissue injury mitigation with normal energy expenditure by significantly suppressing LDH (20.5%) and maintaining normal 5-HT level.ConclusionBy preserving the appropriate IGF-1 and MST metabolic balance and keeping muscle homeostasis, BCA, with its high Ghr binding interaction and anti-inflammatory properties, could have an impact on radiation cachectic syndrome.

Using muscle-tendon load limits to assess unphysiological musculoskeletal model deformation and Hill-type muscle parameter choice.

Musculoskeletal simulations are a useful tool for improving our understanding of the human body. However, the physiological validity of predicted kinematics and forces is highly dependent upon the correct calibration of muscle parameters and the structural integrity of a model's internal skeletal structure. In this study, we show how ill-tuned muscle parameters and unphysiological deformations of a model's skeletal structure can be detected by using muscle elements as sensors with which modelling and parameterization inconsistencies can be identified through muscle and tendon strain injury assessment. To illustrate our approach, two modelling issues were recreated. First, a model repositioning simulation using the THUMS AM50 occupant model version 5.03 was performed to show how internal model deformations can occur during a change of model posture. Second, the muscle material parameters of the OpenSim gait2354 model were varied to illustrate how unphysiological muscle forces can arise if material parameters are inadequately calibrated. The simulations were assessed for muscle and tendon strain injuries using previously published injury criteria and a newly developed method to determine tendon strain injury threshold values. Muscle strain injuries in the left and right musculus pronator teres were detected during the model repositioning. This straining was caused by an unphysiologically large gap (12.92 mm) that had formed in the elbow joint. Similarly, muscle and tendon strain injuries were detected in the modified right-hand musculus gastrocnemius medialis of the gait2354 model where an unphysiological reduction of the tendon slack length introduced large pre-strain of the muscle-tendon unit. The results of this work show that the proposed method can quantify the internal distortion behaviour of musculoskeletal human body models and the plausibility of Hill-type muscle parameter choice via strain injury assessment. Furthermore, we highlight possible actions to avoid the presented issues and inconsistencies in literature data concerning the material characteristics of human tendons.

Determination of qPCR reference genes suitable for normalizing gene expression in a novel model of Duchenne muscular dystrophy, the D2-mdx mouse.

Duchenne muscular dystrophy (DMD) is a X-linked neuromuscular disorder arising from mutations in the dystrophin gene, leading to a progressive muscle wasting and disability. Currently there is no universal therapy, and there is thus a strong interest in preclinical studies for finding novel treatments. The most widely used and characterized mouse model for DMD is the C57BL/10ScSn-Dmdmdx/J (BL10-mdx), but this model exhibits mild pathology and does not replicate key features of human disease. The D2.B10-Dmdmdx/J (D2-mdx) mouse is a more recent model which seems to better mimics the complex human DMD phenotype. However, the D2-mdx mouse remains less extensively characterised than its BL10-mdx counterpart. Quantitative PCR analysis of gene expression is an important tool to monitor disease progression and evaluate therapeutic efficacy, but measurements must be normalised to stably expressed reference genes, which should ideally be determined and validated empirically. We examined gene expression in the gastrocnemius (GC), diaphragm (DIA) and heart in the D2-mdx mouse, the BL10-mdx mouse, and appropriate strain-matched wild-type controls (D2-wt and BL10-wt), from 4 to 52 weeks of age, using a large panel of candidate references (ACTB, AP3D1, CSNK2A2, GAPDH, HPRT1, PAK1IP1, RPL13A, SDHA, and in the heart, also HTATSF1 and HMBS). Data was analyzed using GeNorm, Bestkeeper, deltaCt and Normfinder algorithms to identify stable references under multiple possible scenarios. We show that CSNK2A2, AP3D1 and ACTB represent strong universal reference genes in both GC and DIA, regardless of age, muscle type, strain and genotype, while HTATSF1 and SDHA are optimal for the heart. GAPDH, HPRT1 and RPL13A were conversely revealed to be poor references, showing tissue-, age- or disease-specific changes in expression. Our results illustrate the importance of determining appropriate reference genes for specific comparative scenarios, but also reconfirm that universal panels can nevertheless be identified for normalising gene expression studies in even complex pathological states.

Effects of Raised Heel Insole on Muscle Activity during ankle Sudden Inversion in Normal Adults

Raised heel insoles increase the plantar flexion angle of the ankle and cause ankle inversion sprain. The purpose of this study was to artificially create an ankle sudden inversion situation, which is a mechanical situation of actual ankle joint damage, and investigate the effect of the raised heel insole on ankle joint muscle activity. The subjects of this study were forty subjects with normal adults. The subjects performed sudden ankle inversion on the trapdoor with no raised heel insole, insole heights of 3cm, and insole heights of 7cm. The application of the raised heel insole was conducted randomly. The subjects performed the trapdoor test three times using dominant feet with a 60-second rest period between tests. This study assessed muscle activity during sudden ankle inversion three times. Raised heel insoles showed a significant decrease in Tibialis Anterior, Peroneus Longus, and Peroneus Brevis muscle activity than no raised heel insole (p<.05). Raised heel insoles showed a significant increase in Gastrocnemius muscle activity than no raised heel insole (p<.05). Raised heel insoles increase the risk of ankle sprain injury by reducing tibialis anterior and peroneus muscle activity during sudden ankle inversion.

Abstract 4137264: Subclassification of Peripheral Artery Disease Based on Muscle Force: Leg Failure with Reduced Muscle Force and Leg Failure with Preserved Muscle Force

Introduction: All claudicating patients with peripheral artery disease (PAD) exhibit leg failure, as evidenced by distinct walking impairment. However, based on a detailed evaluation of leg biomechanics, some claudicating patients maintain preserved leg muscle strength, while others demonstrate reduced strength. In this study, we aim to compare the clinical and physiological characteristics of the two groups. Methods: Fifty-four claudicating patients were categorized into two groups: leg failure with preserved muscle force (LEF-PF) versus leg failure with reduced muscle force (LEF-RF), based on the peak torque (PT) from performing maximum isometric plantar flexion contractions on a Biodex system. All patients underwent history and physical exam, measurement of leg hemodynamics, walking performance and quality of life, and gastrocnemius biopsy to evaluate the histology and biochemistry of the affected leg muscles. We used independent samples T test and chi-square test to compare the two groups. Results: LEF-PF (N=19, PT 92±15 Nm) and LEF-RF (N=35, PT 49±13 Nm) had similar demographic and comorbidity profiles. While ankle-brachial index didn't differ between the two groups, during the reactive hyperemia test, ankle pressure of LEF-RF dropped more significantly (p=0.021) upon occlusion release and took longer to recover (p=0.023). Both groups performed similarly on the Gardner Treadmill test, but LEF-PF performed better in the 6-Minute Walking test (p=0.062). LEF-PF also trended towards higher scores on the modified falls efficacy scale (p=0.056). Histologically, gastrocnemius muscle from LEF-PF had larger myofibers, while biochemically, they exhibited lower mitochondrial respiratory activity dependent on complex-II compared to LEF-RF. Conclusion: Our study presents a novel approach to understanding the physiology of claudication, focusing on the strength of the ischemic muscles. Despite comparable demographics and hemodynamics at rest, notable differences separate the two groups during stress-induced hemodynamics, walking performance, myofiber histology, and mitochondrial biochemistry. Further investigations are necessary to elucidate the underlying mechanisms behind the differences in muscle strength among patients with claudication. Such insights may enhance our understanding of PAD physiology and potentially correlate with variations in mortality rates, progression to more advanced PAD stages, and responses to different therapeutic interventions.

Abstract 4134449: Increasing Histidyl dipeptides in Skeletal Muscle Preserves Muscle Mass and Function During Heart Failure.

Background: In heart failure patients muscle wasting is a serious comorbidity. Oxidative stress and inflammatory cytokines, which cause muscle wasting, are increased in the skeletal muscle of heart failure patients. Oxidative stress leads to oxidation of lipids, generating toxic lipid peroxidation products, such as acrolein, which activates TNFa. Whether lipid peroxidation products accumulate in muscle and their removal from muscle influences muscle atrophy during heart failure has not been studied. In the muscle there are histidyl dipeptides, such as carnosine, ranging between 5-10 mM, synthesized via enzyme carnosine synthase (CARNS) that bind lipid peroxidation products. We examined whether intramuscular histidyl dipeptides influences heart failure-induced muscle wasting. Hypothesis: Histidyl dipeptides, alleviates intramuscular inflammation, preserves muscle mass and function during heart failure. Methods: Wild type (WT) and muscle-specific CARNS transgenic (Tg) mice were subjected to sham and transverse aortic constriction (TAC) surgeries. Cardiac function, muscle strength, atrophic and inflammatory markers, aldehyde modified protein, CARNS, and histidyl dipeptides were measured after 12 weeks. Results: In heart failure mice, weight of gastrocnemius (sham: 18.64 ± 1.73 vs TAC: 14.10 ± 0.90 mg, p=0.005), soleus (sham: 6.06 ± 0.82 vs TAC: 4.14 ± 0.70 mg, p=0.001), and tibialis anterior (sham:10.76 ± 1.62 vs TAC: 6.22 ± 1.83 mg, p=0.003), were decreased. Muscle strength was diminished (sham: 2.81 ± 0.36 vs TAC: 1.52 ± 0.27 N, p=0.004). Atrophic marker, atrogin1, aldehyde protein adducts and TNF-a were increased in the gastrocnemius muscle of TAC mice (~2-3-fold vs sham, p<0.05). CARNS expression and carnosine was decreased in different muscles of TAC mice (gastrocnemius; sham: 43.38 ± 20.46 vs TAC: 24.48 ± 6.49 nmoles/mg protein, p=0.03; soleus; sham: 22.04 ± 11.36 vs TAC: 11.02 ± 4.69 nmoles/mg protein, p=0.03; and tibialis; sham: 27.9 ± 11.70 vs TAC: 15.50 ± 3.48 nmoles/mg protein, p=0.01). Gastrocnemius muscle weight (WT TAC: 14.38 ± 1.08 vs Tg TAC: 17.30 ± 1.32 mg, p=0.004) and muscle strength (WT TAC: 3.06 ± 0.32 vs Tg TAC: 3.98 ± 0.41 N) were preserved, atrogin and TNFa expressions were decreased in gastrocnemius muscle of Tg TAC mice (~2-3-fold, p=0.04). Conclusion: Increasing intramuscular histidyl dipeptides alleviates muscle inflammation, preserves muscle mass, and function during heart failure.

Investigating the Effects of Shockwave and Percussion Massage Gun on Subacute Myofascial Pain in Gasterocenemious Muscle

Introduction: Myofascial pain syndrome is a common musculoskeletal injury, especially among athletes, typically treated with symptomatic invasive and non-invasive methods. This study compares the effects of massage guns and radial extracorporeal shock wave therapies on myofascial pain syndrome symptoms in amateur athletes. Materials and Methods: In this clinical trial, 45 amateur athletes (18-30 years old) were recruited, who were randomly assigned to 15-member groups of shock wave, massage gun, and control (routine treatment included electrotherapy and stretching, which was applied on three groups). After initial evaluations of the pain intensity, pain pressure threshold (PPT), isometric muscle strength, and range of motion (ROM), the patients received single-session treatment and were immediately reassessed. Results: The results showed pain relief and improved PPT following shock wave plus routine treatment (P=0.03). The control group had less pain, while pain intensity and PPT did not change. The variables were not significantly different between the groups (P=0.12). Shock wave along with routine treatment increased plantar flexion ROM (P=0.00), unlike the massage gun. Additionally, dorsiflexion ROM (P=0.63) and maximal isometric gastrocnemius muscle strength (P=0.95) remained unchanged in all groups. Conclusion: One session of massage gun therapy immediately reduced gastrocnemius muscle pain, while it failed to change PPT, maximal isometric gastrocnemius muscle strength, or dorsiflexion and plantar flexion ROM. However, shock wave therapy immediately increased plantar flexion ROM and PPT, and reduced pain intensity. These modalities led to limited changes, suggesting the need for repeated sessions and supplementary treatments.

GABA Prevents Sarcopenia by Regulation of Muscle Protein Degradation and Inflammaging in 23- to 25-Month-Old Female Mice.

Sarcopenia is the gradual decrease in skeletal muscle mass, strength and function in elderly individuals. Gamma-aminobutyric acid (GABA) is a neurotransmitter naturally produced from glutamate by the enzyme glutamic acid decarboxylase. Age-related decline in GABA is linked to age-related motor and sensory decline and seems to affect sarcopenia, yet no detailed study has been conducted. In this study, we aimed to investigate the effect of GABA on improving sarcopenia by suppressing muscle protein degradation through supplementing decreased GABA in old mice. GABA (10 or 30 mg/kg/day) was orally administered daily to young (3 months) and old (21-23 months) C57BL/6 mice for 7 weeks. The body weight and grip strength of the mice were measured weekly at the same time. After sacrificing the mice, the quadriceps and gastrocnemius muscles were excised from their hind limbs, and the spleen and serum were collected. Histological, biochemical and molecular analyses were conducted in various experiments. The administration of GABA increased muscle strength (+41%, +70% compared to the aged mouse control group, GABA at doses of 10 or 30 mg/kg/day respectively, p < 0.05) and muscle mass (quadriceps: +28%, +46%; gastrocnemius: +12%, +19%, p < 0.05) in old mice. This increase was accompanied by a cross-sectional area (CSA) increase in the quadriceps and gastrocnemius muscle (p < 0.05). The administration of GABA increased IGF-1 levels in serum (p < 0.05), leading to the activation of muscle protein synthesis. We found that GABA inhibits sarcopenia by regulating muscle protein degradation through the activation of Akt/mTOR/FoxO3a signalling pathways. GABA also regulates inflammaging, which is a hallmark of age-related muscle atrophy. There was a significant increase in the F4/80 + CD11b + total macrophage ratio in gastrocnemius and spleen, especially the M1 macrophage ratio increased in old mice. However, GABA administration was effective in suppressing M1 macrophages (gastrocnemius: -40%, - 53%; spleen: -22%, -26%, p < 0.05). Pro-inflammatory cytokines such as TNF-α and IL-6, primarily secreted by M1 macrophages, are also decreased by treatment with GABA (TNF-α: -24%, -27%; IL-6: -45%, -59%, p < 0.05). Together, this study demonstrates the importance of GABA in maintaining muscle and low-chronic inflammation during ageing. We suggest that GABA shows potential as a substance that can effectively address sarcopenia and enhance the overall lifespan and well-being of older individuals.

Dietary glycine supplementation enhances creatine availability in tissues of pigs with intrauterine growth restriction.

This study tested the hypothesis that dietary supplementation with glycine (Gly) enhances the synthesis and availability of creatine (Cr) in tissues of pigs with intrauterine growth restriction (IUGR). At weaning (21 d of age), IUGR pigs and litter mates with normal birth weights (NBW) were assigned randomly to one of two groups, namely, supplementation with 1% Gly or 1.19% L-alanine (isonitrogenous control) to a corn- and soybean meal-based diet. Blood, kidneys, liver, pancreas, jejunum, longissimus lumborum muscle (LLM), and gastrocnemius muscle (GM) were obtained from the pigs within 1wk after the feeding trial ended at 188 d of age to determine concentrations of guanidinoacetate (GAA), Cr, creatinine, and phosphocreatine (CrP). The organs were also analyzed for activities and mRNA levels for Cr-synthetic enzymes: L-arginine:glycine amidinotransferase (AGAT; forming GAA from Gly and L-arginine) and guanidinoacetate N-methyltransferase (GAMT; converting GAA and L-methionine into Cr). AGAT activity was present in the kidneys, liver, and pancreas, whereas GAMT activity was found in all the organs analyzed. AGAT and GAMT were most active per g of tissue in the kidneys and liver, respectively. Based on tissue mass, the kidneys had the greatest (P < 0.001) AGAT activity per whole organ, followed by the liver, while skeletal muscle had the greatest (P < 0.001) GAMT activity per whole organ, followed by the liver. Thus, the kidneys played a dominant role in forming GAA, whereas skeletal muscle and liver were the major sites for converting GAA into Cr. Dietary supplementation with 1% Gly enhanced AGAT activity in the kidneys and pancreas but reduced GAMT activity in the pancreas and small intestine, therefore directing GAA to the liver and skeletal muscle for Cr production. IUGR selectively reduced the concentration of Cr in LLM among all the organs studied. Except for the GM that had greater mRNA levels for GAMT in IUGR pigs, neither Gly nor IUGR affected mRNA levels for the selected genes in the tissues examined. Collectively, these novel results indicate that dietary Gly intake upregulates the Cr-synthetic pathway in swine.

Effect of foot strike patterns and angles on the biomechanics of side-step cutting.

The study aimed to determine how foot strike patterns and cutting angles affect lower extremity (LE) kinematics, kinetics, and muscle activity during side-step cutting. Twenty male college sport athletes participated in this research. Three-dimensional motion analysis featuring ground reaction force (GRF) and electromyography (EMG) of the dominant leg was used. LE kinematics, kinetics, and EMG data parameters were obtained during a 45° and 90° side-step cutting involving rearfoot strikes (RFS) and forefoot strikes (FFS). The significant foot strike pattern × angle interactions were observed for the ankle eversion range of motion (ROM) at the loading phase. Cutting of 90° had greater knee flexion ROM, knee valgus ROM, and knee varus moment compared to that of 45°. RFS cutting had greater knee flexion, hip flexion, knee valgus, knee varus moment, knee varus moment, and ankle eversion ROM. FFS cutting produced a lower vertical GRF, lateral GRF, and a loading rate. Both vastus medialis and vastus lateralis muscle activities were remarkably greater during cutting of 90° than 45°. At the loading phase, semitendinosus, biceps femoris, and the lateral head of gastrocnemius muscle activities during FFS cutting were considerably greater than those during RFS cutting. The FFS pattern can better protect the anterior cruciate ligament (ACL) and improve the flexibility of athletes by increasing the plantarflexion torque of the ankle. The injury risk also increases with the larger cutting angle. The EMG activities of semitendinosus and biceps femoris are vital for the stability of knee joint during side-step cutting, which helps reduce ACL stress during buffering.

Acute high-intensity muscle contraction moderates AChR gene expression independent of rapamycin-sensitive mTORC1 pathway in rat skeletal muscle.

The relationship between mechanistic target of rapamycin complex 1 (mTORC1) activation after resistance exercise and acetylcholine receptor (AChR) subunit gene expression remains largely unknown. Therefore, we aimed to investigate the effect of electrical stimulation-induced intense muscle contraction, which mimics acute resistance exercise, on the mRNA expression of AChR genes and the signalling pathways involved in neuromuscular junction (NMJ) maintenance, such as mTORC1 and muscle-specific kinase (MuSK). The gastrocnemius muscle of male adult Sprague-Dawley rats was isometrically exercised. Upon completion of muscle contraction, the rats were euthanized in the early (after 0, 1, 3, 6 or 24h) and late (after 48 or 72h) recovery phases and the gastrocnemius muscles were removed. Non-exercised control animals were euthanized in the basal state (control group). In the early recovery phase, Agrn gene expression increased whereas LRP4 decreased without any change in the protein and gene expression of AChR gene subunits. In the late recovery phase, Agrn, Musk, Chrnb1, Chrnd and Chrne gene expression were altered and agrin and MuSK protein expression increased. Moreover, mTORC1 and protein kinase B/Akt-histone deacetylase 4 (HDAC) were activated in the early phase but not in the late recovery phase. Furthermore, rapamycin, an inhibitor of mTORC1, did not disturb changes in AChR subunit gene expression after muscle contraction. However, rapamycin addition slightly increased AChR gene expression, while insulin did not impact it in rat L6 myotube. These results suggest that changes in the AChR subunits after muscle contraction are independent of the rapamycin-sensitive mTORC1 pathway.

A nanofibrous polycaprolactone/collagen neural guidance channel filled with sciatic allogeneic schwann cells and platelet-rich plasma for sciatic nerve repair.

Sciatic nerve damage, a common condition affecting approximately 2.8% of the US population, can lead to significant disability due to impaired nerve signal transmission, resulting in loss of sensation and motor function in the lower extremities. In this study, a neural guidance channel was developed by rolling a nanofibrous scaffold produced via electrospinning. The scaffold's microstructure, biocompatibility, biodegradation rate, porosity, mechanical properties, and hemocompatibility were evaluated. Platelet-rich plasma (PRP) activated with 30,000 allogeneic Schwann cells (SCs) was injected into the lumen of the channels following implantation into a rat model of sciatic nerve injury. Recovery of motor function, sensory function, and muscle re-innervation was assessed using the sciatic function index (SFI), hot plate latency time, and gastrocnemius muscle wet weight loss. Results showed mean hot plate latency times of Autograft: 7.03, PCL/collagen scaffolds loaded with PRP and SCs (PCLCOLPRPSCs): 8.34, polymer-only scaffolds (PCLCOL): 10.66, and untreated animals (Negative Control): 12.00. The mean SFI values at week eight were Autograft: -49.30, PCLCOLPRPSCs: -64.29, PCLCOL: -75.62, and Negative Control: -77.14. The PCLCOLPRPSCs group showed a more negative SFI compared to the Autograft group but performed better than both the PCLCOL and Negative Control groups. These findings suggest that the developed strategy enhanced sensory and functional recovery compared to the negative control and polymer-only scaffold groups.

Post-exercise hot-water immersion is not effective for ribosome biogenesis in rat skeletal muscle.

Ribosome biogenesis is an important regulator of skeletal muscle hypertrophy induced by repeated bouts of resistance exercise (RE). Hot-water immersion (HWI), a widely used post-exercise recovery strategy, activates the mechanistic target of rapamycin (mTOR) signaling, a key regulator of ribosome biogenesis in skeletal muscle. However, the effect of HWI on skeletal muscle ribosome biogenesis is not well understood. Here, we aimed to investigate the effects of HWI and post-exercise HWI on ribosome biogenesis using a rat RE model. Male Sprague-Dawley rats were randomly assigned to HWI and non-HWI groups. In both groups, the right leg was isometrically exercised using transcutaneous electrical stimulation, while the left leg was used as an internal non-RE control. Following RE, both limbs were immersed in hot water (41.2 ± 0.03℃) for 20 min under isoflurane anesthesia in the HWI group and the gastrocnemius muscles were sampled at 3 and 24 h post-exercise. HWI significantly increased mTOR signaling and c-Myc mRNA expression, whereas post-exercise HWI significantly increased transcription initiation factor-IA mRNA expression. However, neither HWI nor post-exercise HWI enhanced 45S pre-rRNA expression, ribosomal RNA, or ribosomal protein content. Additionally, HWI tended to decrease 28S rRNA and 18S rRNA content, widely used markers of ribosome content. These results suggest that HWI as a post-exercise recovery is not effective in activating ribosome biogenesis.

Therapeutic potential of omaveloxolone in counteracting muscle atrophy post-denervation: a multi-omics approach

BackgroundMuscle atrophy caused by denervation is common in neuromuscular diseases, leading to loss of muscle mass and function. However, a comprehensive understanding of the overall molecular network changes during muscle denervation atrophy is still deficient, hindering the development of effective treatments.MethodIn this study, a sciatic nerve transection model was employed in male C57BL/6 J mice to induce muscle denervation atrophy. Gastrocnemius muscles were harvested at 3 days, 2 weeks, and 4 weeks post-denervation for transcriptomic and proteomic analysis. An integrative multi-omics approach was utilized to identify key genes essential for disease progression. Targeted proteomics using PRM was then employed to validate the differential expression of central genes. Combine single-nucleus sequencing results to observe the expression levels of PRM-validated genes in different cell types within muscle tissue.Through upstream regulatory analysis, NRF2 was identified as a potential therapeutic target. The therapeutic potential of the NRF2-targeting drug Omaveloxolone was evaluated in the mouse model.ResultThis research examined the temporal alterations in transcripts and proteins during muscle atrophy subsequent to denervation. A comprehensive analysis identified 54,534 transcripts and 3,218 proteins, of which 23,282 transcripts and 1,852 proteins exhibited statistically significant changes at 3 days, 2 weeks, and 4 weeks post-denervation. Utilizing multi-omics approaches, 30 hubgenes were selected, and PRM validation confirmed significant expression variances in 23 genes. The findings highlighted the involvement of mitochondrial dysfunction, oxidative stress, and metabolic disturbances in the pathogenesis of muscle atrophy, with a pronounced impact on type II muscle fibers, particularly type IIb fibers. The potential therapeutic benefits of Omaveloxolone in mitigating oxidative stress and preserving mitochondrial morphology were confirmed, thereby presenting novel strategies for addressing muscle atrophy induced by denervation. GSEA analysis results show that Autophagy, glutathione metabolism, and PPAR signaling pathways are significantly upregulated, while inflammation-related and neurodegenerative disease-related pathways are significantly inhibited in the Omaveloxolone group.GSR expression and the GSH/GSSG ratio were significantly higher in the Omaveloxolone group compared to the control group, while MuSK expression was significantly lower than in the control group.ConclusionIn our study, we revealed the crucial role of oxidative stress, glucose metabolism, and mitochondrial dysfunction in denervation-induced muscle atrophy, identifying NRF2 as a potential therapeutic target. Omaveloxolone was shown to stabilize mitochondrial function, enhance antioxidant capacity, and protect neuromuscular junctions, thereby offering promising therapeutic potential for treating denervation-induced muscle atrophy.Graphical

A Large Calf Mass in a Patient with Rheumatoid Arthritis: Giant Pannus Filling Baker’s Cyst

Abstract Rheumatoid arthritis (RA) presents a significant challenge among autoimmune diseases, affecting millions globally with diverse clinical manifestations, primarily targeting joints and inducing inflammation, pain, and deformities. In some cases, it leads to the formation of Bakers cysts, fluid-filled bursae in the popliteal region, resulting from chronic inflammation of the synovial membrane and subsequent pannus growth. Our case, a young female patient with RA, presenting with calf mass, highlights this complex interplay. She presented with large swelling and pain in her left calf region which on high-frequency ultrasound revealed a large, well-defined heteroechoic mass lesion distending bursa between the medial head of the gastrocnemius and semimembranosus muscle, measuring 25 cm craniocaudally, without any color Doppler abnormality. Ultrasound-guided biopsy was performed to rule out the possibility of sarcoma and it revealed inflammatory changes. Final diagnosis of excessive pannus formation within the Baker’s cyst forming large mass was made, with RA identified as the underlying cause. The differential diagnosis of masses in the popliteal fossa includes synovial/meniscal/ganglion cysts, lipomas, vascular pathologies, and neoplastic conditions. High-resolution ultrasound is an important diagnostic modality for evaluating popliteal fossa masses. Magnetic resonance imaging is typically performed to assess for neoplastic causes and internal derangement of the knee. Our case of a massive pannus filling a Baker’s cyst in the context of RA emphasizes the intricate nature of the disease and its diverse clinical expressions. It is important for the radiologist to be aware of this imaging appearance for timely diagnosis and management.