Muscle Protein Expression Research Articles

Role of pulmonary rehabilitation in extracellular matrix protein expression in vastus lateralis muscle in atrophic and nonatrophic patients with COPD.

In response to exercise-based pulmonary rehabilitation (PR), the type of muscle fibre remodelling differs between COPD patients with peripheral muscle wasting (atrophic patients with COPD) and those without wasting (nonatrophic patients with COPD). Extracellular matrix (ECM) proteins are major constituents of the cell micro-environment steering cell behaviour and regeneration. We investigated whether the composition of ECM in atrophic compared to nonatrophic patients with COPD differs in response to PR. Vastus lateralis muscle biopsies from 29 male COPD patients (mean±sem forced expiratory volume in 1 s: 43±6% predicted) classified according to their fat-free mass index as atrophic (<17 kg·m-2, n=10) or nonatrophic (≥17 kg·m-2, n=19) were analysed before and after a 10-week PR programme for myofibre distribution and size, whereas a selection of ECM molecules was quantified using ELISA and real-time PCR. In nonatrophic patients with COPD PR was associated with increased myofibre type I distribution (by 6.6±2.3%) and cross-sectional area (CSA) (by 16.4±4.8%), whereas in atrophic patients with COPD, PR induced increased myofibre type IIa distribution (by 9.6±2.8%) and CSA (by 12.1±3.2%). PR induced diverse intramuscular ECM adaptations in atrophic compared to nonatrophic patients with COPD. Accordingly, following PR there was a significant increase in protein levels of ECM biomarkers (collagen type I by 90 pg·mL-1; collagen type IV by 120 pg·mL-1; decorin by 70 pg·mL-1) only in nonatrophic patients with COPD. Conversely, post-PR, osteopontin, a protein known for its dystrophic effects, and tenacin C, a necroptosis compensatory factor facilitating muscle regeneration, were upregulated at protein levels (by 280 pg·mL-1and 40 pg·mL-1, respectively) in atrophic patients with COPD, whereas fibronectin protein levels were decreased. These findings suggest that the differential PR-induced myofibre adaptations in atrophic compared to nonatrophic patients with COPD could be associated with inadequate remodelling of the intramuscular ECM environment.

Quinine inhibits myogenic differentiation by disrupting AKT signaling pathway.

Sarcopenia is a disease characterized by decreased muscle fibers and mass. Although it mainly affects the older adults, it can also occur in various age groups as a secondary effect of medications used for treating certain diseases, such as cancer and diabetes. With population aging, sarcopenia has drawn significant attention owing to its increasing prevalence. However, its pathogenesis remains unclear, and no specific treatment is available. Natural products containing bioactive compounds have long been used as therapeutic agents and are crucial sources for drug development. However, the use of drugs derived from natural extracts is limited because of their ambiguous mechanisms of action and potential side effects. Therefore, a systematic analysis of the potential effects of using natural products is required. In this study, we investigated the effects of the antimalarial drug quinine on myogenic differentiation. Our findings revealed that quinine significantly inhibited the expression of marker genes and proteins associated with myogenic differentiation and markedly impaired muscle regeneration following injury. Furthermore, this reduction occurred when quinine selectively decreased the AKT signaling activity. Quinine reduced muscle protein and gene expression by modulating AKT signaling and inhibiting myogenic differentiation and muscle regeneration. Therefore, quinine may cause sarcopenia, and this risk should be considered when using quinine for treatment.

Aerobic exercise attenuates insulin resistance via restoring branched chain amino acids homeostasis in obese mice.

Emerging evidences suggests that the disrupted branched-chain amino acids (BCAAs) homeostasis and elevated BCAAs promote obesity-related insulin resistance (IR). Exercise improves insulin sensitivity. However, whether BCAAs plays a role in the exercise-attenuated IR remains to be fully investigated. In this study, male C57BL/6J mice were induced to become diet-induced obese (DIO) and served as subjects. The initial investigation focused on the impact of exercise on IR and BCAAs. The DIO mice were randomly assigned to either a sedentary group (CON, n = 16) or an exercise group (EX, n = 16). The EX group underwent a 12-week aerobic exercise regimen on a treadmill. After 12-week, plasma BCAAs and branched-chain keto acids (BCKAs) were measured by liquid chromatography-mass spectrometry, glucose tolerance test (GTT) and insulin tolerance test (ITT) were performed, and the expression and phosphorylation of BCAAs catabolic proteins, as well as AKT T308 in gastrocnemius muscle and liver tissues, were evaluated using western blotting. Subsequently, the study explored the role of BCAAs in enhancing IR through exercise. Mice were randomly allocated into 4 groups: sedentary group (CON, n = 8), sedentary with BCAAs supplementation group (CON+BCAA, n = 8), exercise group (EX, n = 16), and exercise with BCAAs supplementation group (EX+BCAA, n = 16). The exercise protocol was as above. Mice in the BCAAs supplemented groups received drinking water containing 2% BCAAs. After 12-week, plasma BCAAs and BCKAs were measured, GTT and ITT tests were performed, and the phosphorylation of AKT T308, as well as p70S6K T389 in gastrocnemius muscle and liver, were compared between the EX group and the EX+BCAA group. Additionally, the phosphorylation of AMPKα T172 in both tissues was measured across all four groups. 12-week aerobic exercise improved insulin sensitivity in DIO mice while inducing BCAAs catabolic protein expression in skeletal muscle and liver, and reducing the plasma BCAAs level. Importantly, BCAAs supplementation elevated the plasma level of BCAAs and counteracted the exercise-attenuated IR. In skeletal muscle and liver tissues, BCAAs supplementation impaired the exercise-improved insulin signaling without enhancing mammalian target of rapamycin activity. AMPK activity was enhanced by aerobic exercise, which was abolished by BCAAs supplementation. Aerobic exercise attenuated insulin resistance via restoring BCAAs homeostasis and AMPK activity. The impacts of BCAAs intake on the metabolic effects of exercise sheds light on the combined exercise and nutrition intervention strategy for diabetes management.

Time-series transcriptomics reveals distinctive mRNA expression dynamics associated with gene ontology specificity and protein expression in skeletal muscle after electrical stimulation-induced resistance exercise.

Resistance exercise upregulates and downregulates the expression of a wide range of genes in skeletal muscle. However, detailed analysis of mRNA dynamics such as response rates and temporal patterns of the transcriptome after resistance exercise has not been performed. We aimed to clarify the dynamics of time-series transcriptomics after resistance exercise. We used electrical stimulation-induced muscle contraction as a resistance exercise model (5 sets × 10 times of 3 s of 100-Hz electrical stimulation) on the tibialis anterior muscle of rats and measured the transcriptome in the muscle before and at 0, 1, 3, 6, and 12 h after muscle contractions by RNA sequencing. We also examined the relationship between the parameters of mRNA dynamics and the increase in protein expression at 12 h after muscle contractions. We found that the function of the upregulated genes differed after muscle contractions depending on their response rate. Genes related to muscle differentiation and response to mechanical stimulus were enriched in the sustainedly upregulated genes. Furthermore, there was a positive correlation between the magnitude of upregulated mRNA expression and the corresponding protein expression level at 12 h after muscle contractions. Although it has been theoretically suggested, this study experimentally demonstrated that the magnitude of the mRNA response after electrical stimulation-induced resistance exercise contributes to skeletal muscle adaptation via increases in protein expression. These findings suggest that mRNA expression dynamics such as response rate, a sustained upregulated expression pattern, and the magnitude of the response contribute to mechanisms underlying adaptation to resistance exercise.

Nutritional intervention to enhance recovery after arthroscopic knee surgery in adults: a randomized controlled pilot trial

BackgroundEssential amino acid (EAA) and omega-3 fatty acid ingestion independently attenuate leg skeletal muscle disuse atrophy in uninjured persons. However, no data exist regarding the effectiveness of combined EAA and omega-3 fatty acid ingestion to mitigate skeletal muscle disuse atrophy in response to anterior cruciate ligament reconstruction (ACLR) surgery. This pilot trial will explore the feasibility of recruitment and retention of ACLR outpatients from a single center across 18 months to consume either a combination of omega-3 fatty acids and EAAs, or a placebo control, for 4 weeks before and 2 weeks after surgery.MethodsThirty adult (≥ 18 years old) ACLR outpatients will be recruited for this single center, double-blind, two-arm randomized controlled feasibility pilot trial. Participants will consume either 5 g⋅day−1 of omega-3 fatty acids (fish oil) and 40 g⋅day−1 of EAAs or 5 g⋅day−1 of a control fatty acid mixture (safflower oil) and 40 g⋅day−1 of non-essential amino acids (NEAAs). Fatty acid supplements will be consumed 4 weeks before and for 2 weeks after ACLR surgery, whereas the EAAs and NEAAs will be consumed 1 week before and for 2 weeks after ACLR surgery. The primary outcomes are feasibility of recruitment and retention, with the goal to recruit 30 outpatients across 18 months and retain 22 participants upon completion of the study protocol following 12 weeks of data collection. These results will be reported using descriptive statistics, along with reasons and timepoints for study dropout. Secondary exploratory outcomes will be reported using inferential statistics for purposes of hypothesis generation and elucidation of mechanistic targets for future work; no inferences to clinical efficacy will be made. These outcomes include integrated rates of skeletal muscle protein synthesis, skeletal muscle protein content and expression of translation factors, skeletal muscle and erythrocyte phospholipid composition, and measures of skeletal muscle mass, strength, and power.ImpactThis work will set the foundation for a future randomized controlled trial powered to detect an effect of EAA + omega-3 fatty acid intake on skeletal muscle size or function in response to ACLR surgery.Trial registrationClinicalTrials.gov, NCT06233825. Registered 31 January 2024. https://clinicaltrials.gov/study/NCT06233825?term=NCT06233825&rank=1

Histological and histochemical study of effect of dietary fibre in motility of stomach in male mice.

To investigate the relationship between dietary fibres and muscularis externa layer. The experimental study was conducted at the Anatomy Department of the College of Medicine, Al- Nahrain University, Iraq, from November 2020 to April 2021, and comprised adult healthy males. They were divided randomly into experimental group A and control group B. Group A was fed high-fibre diet, and group B was fed standard pellet diet. The tissue samples were harvested at day 30 post-surgery. The stomach samplings were placed in 10% neutral formalin for 24 hours to obtain paraffin sections for routine histological and immunohistochemical staining. The protein expression in stomach's smooth muscle of each group was detected by immunohistochemical staining. Data was analysed using SPSS 24. Of the 20 mice, 10(50%) were in each of the two groups. Group A exhibited significant weight-gain compared to group B (p≤0.01). There was significant reduction in the thickness of the muscularis layer in group A compared to group B (p≤0.01). Anoctamin 1 expression in group A was significantly lower than that in group B (p≤0.01). The stress induced by an unstable fibre diet significantly affected the stomach by decreasing the muscularis layer thickness and Anoctamin 1 expression in interstitial cells of Cajal.

Effects of protein diet on expression of Anoctamin1 of Cajal cell in the nervous plexus of the stomach in male mice.

To determine the association between a protein-rich diet and the expression of anoctamin 1 in Interstitial cells of Cajal within the muscle layer of the stomach wall in male mice. The experimental study was conducted at the Anatomy Department of the College of Medicine, Al- Nahrain University, Iraq, from November 2020 to April 2021, and comprised male adult healthy male mice. They were divided randomly into two equal groups. Group A was fed a high protein diet, while control group B was fed a standard pellet diet. The tissue samples were harvested at day 30 post-surgery. The stomach samplings were placed in 10% neutral formalin for 24 hours to obtain paraffin sections for routine histological and immunohistochemical staining. The protein expression in stomach smooth muscle of each group was detected by immunohistochemical staining. Data was analysed using SPSS 24. Of the 20 mice, 10(50%) were in each of the two groups. Group A exhibited significant weight-gain compared to group B (p≤ 0.05). There was significant elevation in muscle wall thickness in group A, compared to group B (p≤0.05). Tunica muscularis of the stomach in group A significantly thickened compared to group B (p≤0.05). The expression of anoctamin 1 was significantly more intense in group A compared to group B (p≤0.01). Unbalanced food had a significant impact on the stomach, affecting the thickness of the muscularis layer and the expression of anoctamin 1 in cajal cells in the muscularis externa.

The Oldest of Old Male C57B/6J Mice Are Protected from Sarcopenic Obesity: The Possible Role of Skeletal Muscle Protein Kinase B Expression

The impact of aging on body composition and glucose metabolism is not well established in C57BL/6J mice, despite being a common pre-clinical model for aging and metabolic research. The purpose of this study was to examine the effect of advancing age on body composition, in vivo glucose metabolism, and skeletal muscle AKT expression in young (Y: 4 months old, n = 7), old (O: 17–18 months old, n = 10), and very old (VO: 26–27 month old, n = 9) male C57BL/6J mice. Body composition analysis, assessed by nuclear magnetic resonance, demonstrated O mice had a significantly greater fat mass and body fat percentage when compared to Y and VO mice. Furthermore, VO mice had a significantly greater lean body mass than both O and Y mice. We also found that the VO mice had greater AKT protein levels in skeletal muscle compared to O mice, an observation that explains a portion of the increased lean body mass in VO mice. During glucose tolerance (GT) testing, blood glucose values were significantly lower in the VO mice when compared to the Y and O mice. No age-related differences were observed in insulin tolerance (IT). We also assessed the glucose response to AMPK activation by 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR). The change in blood glucose following AICAR administration was significantly reduced in VO mice compared to Y and AG mice. Our findings indicate that lean body mass and AKT2 protein expression in muscle are significantly increased in VO mice compared to O mice. The increase in AKT2 likely plays a role in the greater lean body mass observed in the oldest of old mice. Finally, despite the increased GT, VO mice appear to be resistant to AMPK-mediated glucose uptake.

Unveils key proteins in Xinjiang goat muscle linked to post-mortem meat quality: A TMT-based proteomic analysis

An extensive proteomic analysis utilizing the tandem mass tag (TMT) method was conducted to investigate the changes in protein expression in the longissimus dorsi muscle of Xinjiang goats over various post-mortem intervals: immediately after death within 0 h, 12 h, 24 h and 48 h. The investigation carefully identified around 108 proteins that showed significant changes in expression during these intervals. Among these proteins, six were highlighted for their crucial roles in muscle growth and differentiation of muscle fibers post-mortem. These proteins, namely COL12A1, MRPL46, CTNNB1, MYH1, CAPZA1, and MYL9, have a direct effect on the meat's quality attributes, such as tenderness and color. Further discuss observed a progressive increase in the expression of proteins linked with oxidative metabolism (MSRB2, ENOX1, LOC102170282, GSTM1, and AOC3) as the post-mortem aging period extended, particularly between 24 h to 48 h. These proteins are instrumental in defining the color and flavor profiles of goat meat, underscoring the importance of precise processing and storage conditions to preserve meat quality during the critical aging phase. This enhanced understanding of protein expression dynamics offers significant implications for optimizing meat quality and provides a scientific basis for post-mortem handling practices in the goat meat industry.

A comprehensive study of CYP2E1 and its role in carcass characteristics and chemical lamb meat quality in different Indonesian sheep breeds.

The role of CYP2E1 in oxidation is essential for its effects on meat quality. This study used 200 Indonesian sheep (Ovis aries) to determine the SNP g allele frequencies. g. 50658168 T>C of CYP2E1 gene located in 3´-UTR region and their genetic association with lamb quality traits, including carcass characteristics, retail cut carcass, physicochemical lamb, fatty acid, cholesterol, flavor and odor, and mineral content. Further, the level of CYP2E1 mRNA and CYP2E1 protein expression in muscle were determined and correlated with lamb quality traits. CYP2E1 gene polymorphisms were identified using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) analysis. The CYP2E1 mRNA expression levels in phenotypically divergent sheep populations were analyzed using Quantitative Real Time-PCR (qRT-PCR). Immunohistochemistry (IHC) and hematoxylin-eosin (HE) staining analysis used three samples each in the high and low lamb quality groups based on pH value and tenderness. An association study of CYP2E1 gene polymorphisms was performed using General Linear Model (GLM) analysis. The genetic association between the CC, CT, and TT genotypes at the SNP g. 50658168 T>C CYP2E1 gene and lamb quality traits were significant (P<0.05), including carcass characteristics, retail cut carcass, fatty acid, cholesterol, flavor, and odor. Lambs with the CT genotype had a higher mRNA and protein expression in high lamb quality traits. The highest CYP2E1 protein expression was localized in the longissimus dorsi. The group sample with high lamb quality had a higher area and perimeter of muscle cells. CYP2E1 can be used as a genetic marker for selecting sheep with high meat quality.

Akt1 deficiency does not affect fiber type composition or mitochondrial protein expression in skeletal muscle of male mice.

Insulin-like growth factor-1-induced activation of ATP citrate lyase (ACLY) improves muscle mitochondrial function through an Akt-dependent mechanism. In this study, we examined whether Akt1 deficiency alters skeletal muscle fiber type and mitochondrial function by regulating ACLY-dependent signaling in male Akt1 knockout (KO) mice (12-16 weeks old). Akt1 KO mice exhibited decreased body weight and muscle wet weight, with reduced cross-sectional areas of slow- and fast-type muscle fibers. Loss of Akt1 did not affect the phosphorylation status of ACLY in skeletal muscle. The skeletal muscle fiber type and expression of mitochondrial oxidative phosphorylation complex proteins were unchanged in Akt1 KO mice compared with the wild-type control. These observations indicate that Akt1 is important for the regulation of skeletal muscle fiber size, whereas the regulation of muscle fiber type and muscle mitochondrial content occurs independently of Akt1 activity.

CaMKII protein expression and phosphorylation in human skeletal muscle by immunoblotting: Isoform specificity

Calcium (Ca2+)/calmodulin-dependent protein kinase II (CaMKII) is activated during exercise by reactive oxygen species (ROS) and Ca2+ transients initiating muscle contraction. CaMKII modulates antioxidant, inflammatory, metabolic and autophagy signalling pathways. CaMKII is coded by four homologous genes (α, β, γ, and δ). In rat skeletal muscle, δD, δA, γD, γB and βM have been described while different characterisations of human skeletal muscle CaMKII isoforms have been documented. Precisely discerning between the various isoforms is pivotal for understanding their distinctive functions and regulatory mechanisms in response to exercise and other stimuli. This study aimed to optimize the detection of the different CaMKII isoforms by western blotting using eight different CaMKII commercial antibodies in human skeletal muscle. Exercise-induced posttranslational modifications, i.e. phosphorylation and oxidations, allowed the identification of specific bands by multitargeting them with different antibodies after stripping and reprobing. The methodology proposed has confirmed the molecular weight of βM CaMKII and allows distinguishing between γ/δ and δD CaMKII isoforms. The corresponding molecular weight for the CaMKII isoforms resolved were: δD, at 54.2 ± 2.1 kDa; γ/δ, at 59.0 ± 1.2 kDa and 61.6 ± 1.3 kDa; and βM isoform, at 76.0 ± 1.8 kDa. Some tested antibodies showed high specificity for the δD, the most responsive isoform to ROS and intracellular Ca2+ transients in human skeletal muscle, while others, despite the commercial claims, failed to show such specificity.

6'-Sialyllactose Enhances Exercise Performance via Increased Muscle Mass and Strength.

Sialyllactose (SL) is a functional human milk oligosaccharide essential for immune support, brain development, intestinal maturation, and antiviral defense. However, despite its established health benefits, the effect of SL on exercise performance and muscle mass in mice remains unknown. Here, we aimed to investigate, for the first time, the effects of 6'-SL on muscle functions. Seven-week-old male C57BL/6J mice were administered 100 mg/kg 6'-SL for 12 weeks, after which exhaustive treadmill performance was conducted. Moreover, muscle strength was examined by grip strength, and muscle phenotype characteristics such as muscle mass, muscle fiber size, and muscle protein expression were also examined. The administration of 6'-SL significantly improved exhaustive treadmill performance metrics, including distance and exhaustion time. Grip strength was also increased by 6'-SL administration. Additionally, 6'-SL increased muscle mass in both the gastrocnemius (GAS) and soleus. 6'-SL administration led to an increase in the minimum Feret's diameter and the protein expression of total myosin heavy chain in the GAS muscle. In conclusion, 6'-SL administration in vivo led to increased running distance and time by increasing muscle mass and strength. These findings collectively indicate that 6'-SL is a potential agent for improving muscle health and exercise performance.

Effects of Ulmus macrocarpa Extract and Catechin 7-O-β-D-apiofuranoside on Muscle Loss and Muscle Atrophy in C2C12 Murine Skeletal Muscle Cells.

Muscle atrophy is known to be one of the symptoms leading to sarcopenia, which significantly impacts the quality of life, mortality, and morbidity. Therefore, the development of therapeutics for muscle atrophy is essential. This study focuses on addressing muscle loss and atrophy using Ulmus macrocarpa extract and its marker compound, catechin 7-O-β-D-apiofuranoside, by investigating their effects on biomarkers associated with muscle cell apoptosis. Additionally, protein and gene expression in a muscle atrophy model were examined using Western blotting and RT-PCR. Ulmus macrocarpa has been used as food or medicine due to its safety, including its roots, barks, and fruit. Catechin 7-O-β-D apiofuranoside is an indicator substance of plants of the Ulmus genus and has been reported to have various effects such as antioxidant and anti-inflammatory effects. The experimental results demonstrated that catechin glycoside and Ulmus macrocarpa extract decreased the expression of the muscle-degradation-related proteins Atrogin-1 and Muscle RING-Finger protein-1 (MuRF1) while increasing the expression of the muscle-synthesis-related proteins Myoblast determination (MyoD) and Myogenin. Gene expression confirmation experiments validated a decrease in the expression of Atrogin and MuRF1 mRNA and an increase in the expression of MyoD and Myogenin mRNA. Furthermore, an examination of muscle protein expression associated with the protein kinase B (Akt)/forkhead box O (FoxO) signaling pathway confirmed a decrease in the expression of FoxO, a regulator of muscle protein degradation. These results confirm the potential of Ulmus macrocarpa extract to inhibit muscle apoptosis, prevent muscle decomposition, and promote the development of functional materials for muscle synthesis, health-functional foods, and natural-product-derived medicines.

Sympathetic Activation Promotes Sodium Glucose Co-Transporter-1 Protein Expression in Rodent Skeletal Muscle.

The hyperactivation of the sympathetic nervous system (SNS) is linked to obesity, hypertension, and type 2 diabetes, which are characterized by elevated norepinephrine (NE) levels. Previous research has shown increased sodium-dependent glucose cotransporter 1 (SGLT1) protein levels in kidneys of hypertensive rodents, prompting investigation into the expression of SGLT1 in various tissues, such as skeletal muscle. This study aimed to assess (i) whether skeletal muscle cells and tissue express SGLT1 and SGLT2 proteins; (ii) if NE increases SGLT1 levels in skeletal muscle cells, and (iii) whether the skeletal muscle of neurogenically hypertensive mice exhibits increased SGLT1 expression. We found that (i) skeletal muscle cells and tissue are a novel source of the SGLT2 protein and that (ii) NE significantly elevated SGLT1 levels in skeletal muscle cells. As SGLT2 inhibition (SGLT2i) with Empagliflozin increased SGLT1 levels, in vivo studies with the dual inhibitor SGLT1/2i, Sotagliflozin were warranted. The treatment of neurogenically hypertensive mice using Sotagliflozin significantly reduced blood pressure. Our findings suggest that SNS activity upregulates the therapeutic target, SGLT1, in skeletal muscle, potentially worsening cardiometabolic control. As clinical trial data suggest cardiorenal benefits from SGLT2i, future studies should aim to utilize SGLT1i by itself, which may offer a therapeutic strategy for conditions with heightened SNS activity, such as hypertension, diabetes, and obesity.

Characterised intron retention profiles in muscle tissue of idiopathic inflammatory myopathy subtypes

ObjectivesIdiopathic inflammatory myopathies (IIMs) are a group of heterogeneous autoimmune diseases. Intron retention (IR) serves as an important post-transcriptional and translational regulatory mechanism. This study aims to identify changes in...

PGE2 binding to EP2 promotes ureteral stone expulsion by relaxing ureter via the cAMP-PKA pathway

BackgroundThis study investigated the relaxation effect of PGE2 on the ureter and its role in promoting calculi expulsion following calculi development.MethodsBy using immunofluorescence and Western blot, we were able to locate EP receptors in the ureter. In vitro experiments assessed the impact of PGE2, receptor antagonists, and agonists on ureteral relaxation rate. We constructed a model of ureteral calculi with flowable resin and collected ureteral tissue from postoperative side of the ureter after obstruction surgery. Western blot analysis was used to determine the protein expression levels of EP receptors and the PGE2 terminal synthase mPGES-1. Additionally, PGE2 was added to smooth muscle cells to observe downstream cAMP and PKA changes.ResultsThe expression of EP2 and EP4 proteins in ureteral smooth muscle was verified by Western blot analysis. According to immunofluorescence, EP2 was primarily found on the cell membrane, while EP4 was found in the nucleus. In vitro, PGE2 induced concentration-dependent ureteral relaxation. Maximum diastolic rate was 70.94 ± 4.57% at a concentration of 30µM. EP2 antagonists hindered this effect, while EP4 antagonists did not. Obstructed ureters exhibited elevated mPGES-1 and EP2 protein expression (P < 0.01). Smooth muscle cells treated with PGE2 displayed increased cAMP and phosphorylated PKA.ConclusionsPGE2 binding to EP2 induces ureteral relaxation through the cAMP-PKA pathway. This will provide a new theoretical basis for the development of new therapeutic approaches for the use of PGE2 in the treatment of ureteral stones.

Elevated heart rate and decreased muscle endothelial nitric oxide synthase in early development of insulin resistance.

Insulin resistance (IR) is a risk factor for the development of several major metabolic diseases. Muscle fiber composition is established early in life and is associated with insulin sensitivity. Hence, muscle fiber composition was used to identify early defects in the development of IR in healthy young individuals in the absence of clinical manifestations. Biopsies were obtained from the thigh muscle, followed by an intravenous glucose tolerance test. Indices of insulin action were calculated and cardiovascular measurements, analyses of blood and muscle were performed. Whole body insulin sensitivity (SIgalvin) was positively related to expression of type I muscle fibers (r = 0.49; P < 0.001) and negatively related to resting heart rate (HR, r = -0.39; P < 0.001), which was also negatively related to expression of type I muscle fibers (r = -0.41; P < 0.001). Muscle protein expression of endothelial nitric oxide synthase (eNOS), whose activation results in vasodilation, was measured in two subsets of subjects expressing a high percentage of type I fibers (59 ± 6%; HR = 57 ± 9 beats/min; SIgalvin = 1.8 ± 0.7 units) or low percentage of type I fibers (30 ± 6%; HR = 71 ± 11; SIgalvin = 0.8 ± 0.3 units; P < 0.001 for all variables vs. first group). eNOS expression was 1) higher in subjects with high type I expression; 2) almost twofold higher in pools of type I versus II fibers; 3) only detected in capillaries surrounding muscle fibers; and 4) linearly associated with SIgalvin. These data demonstrate that an altered function of the autonomic nervous system and a compromised capacity for vasodilation in the microvasculature occur early in the development of IR.NEW & NOTEWORTHY Insulin resistance (IR) is a risk factor for the development of several metabolic diseases. In healthy young individuals, an elevated heart rate (HR) correlates with low insulin sensitivity and high expression of type II skeletal muscle fibers, which express low levels of endothelial nitric oxide synthase (eNOS) and, hence, a limited capacity to induce vasodilation in response to insulin. Early targeting of the autonomic nervous system and microvasculature may attenuate development of diseases stemming from insulin resistance.

Inflammatory Cytokine-Induced Muscle Atrophy and Weakness Can Be Ameliorated by an Inhibition of TGF-β-Activated Kinase-1.

Chronic inflammation causes muscle wasting. Because most inflammatory cytokine signals are mediated via TGF-β-activated kinase-1 (TAK1) activation, inflammatory cytokine-induced muscle wasting may be ameliorated by the inhibition of TAK1 activity. The present study was undertaken to clarify whether TAK1 inhibition can ameliorate inflammation-induced muscle wasting. SKG/Jcl mice as an autoimmune arthritis animal model were treated with a small amount of mannan as an adjuvant to enhance the production of TNF-α and IL-1β. The increase in these inflammatory cytokines caused a reduction in muscle mass and strength along with an induction of arthritis in SKG/Jcl mice. Those changes in muscle fibers were mediated via the phosphorylation of TAK1, which activated the downstream signaling cascade via NF-κB, p38 MAPK, and ERK pathways, resulting in an increase in myostatin expression. Myostatin then reduced the expression of muscle proteins not only via a reduction in MyoD1 expression but also via an enhancement of Atrogin-1 and Murf1 expression. TAK1 inhibitor, LL-Z1640-2, prevented all the cytokine-induced changes in muscle wasting. Thus, TAK1 inhibition can be a new therapeutic target of not only joint destruction but also muscle wasting induced by inflammatory cytokines.

Relationship between Serum Concentrations and Muscular Expressions of Selenoproteins on Selenium-Supplemented Insulin Resistance Mouse Model.

Previously, insulin resistance and hepatic oxidative stress with increased expressions of glutathione peroxidase (GPx) 1 and selenoprotein P (SelP) were induced in NSY mice, a diabetic mouse model, by administrating a high fat diet (HFD) and seleno-L-methionine (SeMet) for 12 weeks. In this study we developed an analysis method for serum selenoproteins using LC-tandem mass spectrometry (LC-MS/MS) and investigated the effects of supplementary selenium on serum concentrations of selenoproteins as well as protein expression in skeletal muscle as a major insulin target tissue under the same experimental condition. The glucose area under the curves for oral glucose tolerance and insulin tolerance tests indicated that the HFD induced insulin resistance, whereas the treatment of SeMet + HFD showed insignificant promotion compared with the HFD-induced insulin resistance. Although the expressions of GPx1 in gastrocnemius and soleus were not significantly induced by supplementary SeMet nor HFD administration, the expressions of SelP in both skeletal muscles were significantly induced by the treatment of SeMet + HFD. There were also significant increases in serum concentrations of SelP by supplementary SeMet + HFD administration, whereas GPx3 was augmented by supplementary SeMet only. These results indicated that the HFD intake under the sufficient selenium status augmented the blood secretion of SelP, which may participate in the reduction of insulin sensitivity in skeletal muscles as well as liver or adipose tissues, and it is a better indicator of deterioration than GPx3 as it is a major selenoprotein in serum.