Glucocorticoid Regulates the Synthesis of Porcine Muscle Protein through m6A Modified Amino Acid Transporter SLC7A7

The occurrence of stress is unavoidable in the process of livestock production, and prolonged stress will cause the decrease of livestock productivity. The stress response is mainly regulated by the hypothalamic-pituitary-adrenal axis (HPA axis), which produces a large amount of stress hormones, namely glucocorticoids (GCs), and generates a severe impact on the energy metabolism of the animal body. It is reported that m6A modification plays an important role in the regulation of stress response and also participates in the process of muscle growth and development. In this study, we explored the effect of GCs on the protein synthesis procession of porcine skeletal muscle cells (PSCs). We prove that dexamethasone affects the expression of SLC7A7, a main amino acid transporter for protein synthesis by affecting the level of m6A modification in PSCs. In addition, we find that SLC7A7 affects the level of PSC protein synthesis by regulating the conduction of the mTOR signaling pathway, which indicates that the reduction of SLC7A7 expression may alleviate the level of protein synthesis under stress conditions.

Greater Reduction of Blood Pressure with Exercise Intervention Than Standard Care After Recent Ischaemic Atroke: A Randomized Clinical Trial

Context and Objectives: Ischaemic stroke (IS) causes disability and uses massive public health resources. Cumulative disability from recurrence may be reduced with cardiometabolic risk reduction strategies e.g., lowering blood pressure (BP). We hypothesized that intensive exercise plus best available care in adults with recent IS improves fitness, glucose metabolism, muscle protein synthesis in paretic limbs compared to controls. BP changes were compared between intervention (INT) and controls (CON). Research Design and Setting: A randomised, interventional clinical trial conducted in Jamaican adults subjects: We investigate 103 adults with recent IS and residual weakness. Forty-nine subjects (24 women: mean age 61.5; 25 men: mean age 63.8) received task-oriented exercise training (TEXT) plus best available care. Fifty-four subjects (23 women: mean age 60.2; 31 men: mean age 61.3) received best care, including exercise advice. Measurements: We measured baseline, 3-month and 6-month BP. Results: After recent IS, TEXT plus best available care reduced systolic BP by 21 mmHg and diastolic by 12 mmHg compared to controls, independent of medication adherence, body composition; stroke severity. Men in the TEXT group had increased lean mass (P < 0.007), VO2 max (P = 0.03); 6-minute walk distance (P = 0.003). Leg press on paretic (P = 0.004) and non-paretic (P < 0.001) increased with TEXT vs CON over 6 months, in both sexes (P-values for sex difference > 0.2). Time-to-chair-rise decreased in both sexes who received intervention vs controls (P <0.04) Conclusions: TEXT results in significant blood pressure reduction in adults with recent ischaemic stroke and residual weakness when compared with best available medical care only.

Fish muscle hydrolysate obtained using largemouth bass Micropterus salmoides digestive enzymes improves largemouth bass performance in its larval stages

The present study utilized digestives tracts from adult largemouth bass (LMB) to hydrolyze Bighead carp muscle and obtain an optimal profile of muscle protein hydrolysates that would be easily assimilated within the primitive digestive tract of larval LMB. Specifically, muscle protein source was digested for the larva using the fully developed digestive system of the same species. The objectives of this study were: 1) to develop an optimal in vitro methodology for carp muscle hydrolysis using LMB endogenous digestive enzymes, and 2) to evaluate the effect of dietary inclusion of the carp muscle protein hydrolysate on LMB growth, survival, occurrence of skeletal deformities, and whole-body free amino acid composition. The study found that the in vitro hydrolysis method using carp intact muscle and LMB digestive tracts incubated at both acid and alkaline pH (to mimic digestive process of LMB) yielded a wide range of low molecular weight fractions (peptides), as opposed to the non-hydrolyzed muscle protein or muscle treated only with acid pH or alkaline pH without enzymes from LMB digestive tracts, which were comprised of large molecular weight fractions (polypeptides above 150 kDa). Overall, the dietary inclusion of the carp muscle hydrolysate improved growth performance of larval LMB in terms of final average weight, weight gain, DGC, SGR, and body length after 21 days of feeding compared to fish that received the diet based on non-hydrolyzed carp muscle. The study also found that hydrolysate-based feed significantly reduced skeletal deformities. The positive growth performance presented by fish in the hydrolysate-fed group possibly resulted from matching the specific requirements of the larvae with respect to their digestive organ development, levels of digestive enzymes present in the gut, and nutritional requirements.

Relationship of smoking with COVID-19 and its adverse effects

There is a direct relationship between COVID-19 and smoking. This relationship has detrimental consequences for smoking and COVID-19 on body physiology. Smoking causes disc herniation, lungs diseases, heart illness, lipid profile changes, muscle protein synthesis declines, head, neck, and gastric cancers, cerebral inflammation, weight loss and obesity. The smoking habit of pregnant women leads to miscarriage, poor foetal growth, and low lipid and protein levels in breast milk. In males, it also reduces semen ejaculation and seminal vesicle volume. The treatment is based on quitting the smoking. Preventive measures such as a healthy diet and regular exercise can help to mitigate the negative consequences of smoking. In addition, smoking has been recognised as a major factor in COVID-19 transmission. Tobacco smokers are at increased risk of serious COVID-19 infection due to poor lung function, cross-infection, and vulnerable hygiene behaviors. People who have smoked in the past are thought to be more susceptible than non-smokers to have more severe COVID-19 illness symptoms. COVID-19 is more common among smokers than nonsmokers. Current smokers are five times more likely to have influenza infection than non-smokers. Smoking has been identified as one of the risk factors linked to infection and death.

Regulation of Myostatin on the Growth and Development of Skeletal Muscle

Myostatin (MSTN), a member of the transforming growth factor-β superfamily, can negatively regulate the growth and development of skeletal muscle by autocrine or paracrine signaling. Mutation of the myostatin gene under artificial or natural conditions can lead to a significant increase in muscle quality and produce a double-muscle phenotype. Here, we review the similarities and differences between myostatin and other members of the transforming growth factor-β superfamily and the mechanisms of myostatin self-regulation. In addition, we focus extensively on the regulation of myostatin functions involved in myogenic differentiation, myofiber type conversion, and skeletal muscle protein synthesis and degradation. Also, we summarize the induction of reactive oxygen species generation and oxidative stress by myostatin in skeletal muscle. This review of recent insights into the function of myostatin will provide reference information for future studies of myostatin-regulated skeletal muscle formation and may have relevance to agricultural fields of study.

Fermented Antler Recovers Stamina, Muscle Strength and Muscle Mass in Middle-Aged Mice

In a previous study, we found that Lactobacillus curvatus HY7602-fermented antler (FA) improved exercise endurance by increasement of muscle mass and strength in a young mouse model. In this study, we investigated the effect of FA on recovery of muscle mass and strength in aging-induced muscle loss. We have used a middle-aged model in which muscle decline begins in many mammalian species. All mice performed treadmill exercise and forced swimming, and measured muscle grip strength. Then, calf muscle weight and histological analysis, blood biomarker and gene expression in soleus muscle tissue were measured. Muscle strength and forced swimming time were significantly increased in the FA-intake groups compared to controls. The levels of muscle and liver damage-related indicators (ATL, ALP, LDH and CK) and muscle endurance, fatigue and exercise performance-related indicators (lactate and creatinine) were significantly improved by FA supplementation. In addition, FA regulates genes related to muscle protein degradation (Atrogin-1 and MuRF1) and muscle fiber synthesis (MyoD and Myf5), resulting in increased muscle mass, and fiber diameter and area values. The Bax/Bcl-2 ratio, related to apoptosis in skeletal muscle was significantly decreased. These results demonstrate that FA improves exercise performance with ameliorating blood biomarkers and also increases muscle mass and muscle strength by inhibiting muscle proteolysis and promoting muscle synthesis in a middle-aged mouse.

The Effect of Cancer Cachexia Progression on the Feeding Regulation of Skeletal Muscle Protein Turnover

Cancer cachexia is defined as the unintentional loss of skeletal muscle mass with or without fat loss that cannot be reversed by conventional nutritional support. Cachexia occurs in ~20% of cancer patients. More specifically, 50% of lung cancer patients, the most common cancer worldwide, develop cachexia. Cachexia occurs most often in lung and gastrointestinal cancers, whereas breast and prostate have the lowest rate of cachexia. Cancer-induced cachexia disrupts skeletal muscle protein turnover (decreasing protein synthesis and increasing protein degradation). Skeletal muscle’s capacity for protein synthesis is highly sensitive to local and systemic stimuli that are controlled by mTORC1 and AMPK signaling. During cachexia, altered protein turnover is thought to occur through suppressed anabolic signaling via mTORC1, coinciding with the chronic activation of AMPK. While progress has been made in understanding some of the mechanisms underlying the suppressed anabolic signaling in cachectic muscle, gaps still remain in our understanding of muscle’s ability to respond to anabolic stimulus prior to cachexia development. The purpose of this study was to determine if cachexia progression disrupts the feeding regulation of AMPK signaling and if gp130 signaling and muscle contraction could regulate this process. Specific aim 1 examined the feeding regulation of skeletal muscle protein synthesis in pre-cachectic tumor bearing mice. Feeding increased muscle protein synthesis, while lowering AMPK signaling in pre-cachectic tumor bearing mice. Importantly, pre-cachectic tumor bearing mice have overall suppressed muscle protein synthesis independent of the fast or fed condition. Muscle specific AMPK loss was sufficient to improve the fasting suppression of muscle mTORC1 and protein synthesis in pre-cachectic tumor bearing mice. Specific aim 2 examined if muscle gp130 signaling regulates the feeding regulation of AMPK during cancer cachexia progression. Muscle gp130 loss lowered the fasting induction of AMPK in pre-cachectic tumor bearing mice without improving protein synthesis. Muscle gp130 loss did not alter the feeding regulation of muscle Akt/mTORC1 signaling and protein synthesis. Specific Aim 3 examined if an acute bout of muscle contractions could improve the muscle protein synthesis response to feeding during the progression of cachexia. Pre-cachectic tumor bearing mice exhibit suppressed protein synthesis in response low frequency electrical stimulation, and the inability to synergistically induce protein synthesis in response to feeding and contraction. In summary, pre-cachectic tumor bearing mice have lowered Akt/mTORC1 signaling and protein synthesis. Feeding can induce Akt/mTORC1 and protein synthesis and AMPK regulates the fasting suppression of protein synthesis in pre-cachectic tumor bearing mice. While gp130 loss reduces AMPK it is not sufficient to improve protein synthesis in pre-cachectic tumor bearing mice. The added protein synthesis response to feeding and contraction is blunted in pre-cachectic tumor bearing mice. These findings provide novel insight into the regulation of Akt/mTORC1 signaling and protein synthesis in response to feeding. Additionally, these studies highlight gp130’s regulation of AMPK prior to cachexia development, and the blunted anabolic muscle response to feeding and contraction in pre-cachectic tumor bearing mice. By understanding these intracellular signaling processes and perturbations prior to cachexia development, we will be able to elucidate potential therapeutic targets and treatment options to manipulate and prevent cancer cachexia.

Temporal Changes in Key Signal Transduction Pathways Mediating Muscle Protein Synthesis with Adaptive and Maladaptive Right Ventricular Hypertrophy in Pulmonary Arterial Hypertension

BackgroundPulmonary Arterial Hypertension (PAH) is a progressive cardiopulmonary disease and is characterized by occlusive remodeling of pulmonary arterioles and increased pulmonary vascular resistance. With the onset of PAH, the right ventricle (RV) of the heart adapts to the increased afterload pressure by undergoing adaptive hypertrophic remodeling to maintain adequate blood flow. However, for unknown reasons, maladaptive influences ensue, resulting in impaired RV function with progressive decompensation and right heart failure. Using a rodent model of PAH, we evaluated key signaling pathways mediating cardiac muscle protein synthesis in the RV during the adaptive hypertrophy phase, with preserved right heart function, and the decompensated maladaptive phase, in which right heart failure (RHF) was clinically present.MethodsMale Sprague-Dawley rats were injected subcutaneously with 60mg/kg Monocrotaline (MCT) and RV function was assessed by echocardiography during PAH disease progression. RV tissue was collected during the adaptive and maladaptive phases of PAH and cell signaling pathways involved in survival, hypertrophy, and autophagy, as well as fibrosis and vascularization, were probed using qPCR, Western blotting and histology. Statistical analysis was performed using ANOVA to compare differences between the independent groups and Student-Newman-Keuls test was used to compare differences within independent groups.ResultsAnalysis of protein and gene expression changes in PAH animals identified three key signaling pathways involved in the shift toward maladaptive right heart failure: i) PI3K/Akt/mTOR; ii) GSK-3; iii) MAPK/ERK, as well as IGF-1 regulation. During adaptive hypertrophy, significant increments of phosphorylated proteins in the three signaling pathways were observed with increases in RV fibrosis and decreased capillarity found. In the maladaptive phase, mTORC1 and its downstream effector p-70S6K were significantly activated, contributing to the decreased LC3-I/II ratio, a marker of autophagy inhibition. Additionally, p27, a cyclin-dependent kinase (CDK) inhibitor, which has been recently implicated in regulating mTOR activity to inhibit autophagy and promote heart failure was significantly downregulated. ConclusionWe propose that autophagy inhibition in conjunction with other maladaptive processes reported in the decompensated RV muscle contributes to the genesis of overt RHF in PAH and that a continuum of changes characterizes the adaptive and maladaptive phases in the RV muscle.

Ingestion of an ample amount of meat substitute based upon a lysine-enriched, plant-based protein blend stimulates postprandial muscle protein synthesis to a similar extent as an isonitrogenous amount of chicken in healthy, young men

Plant-based proteins are considered to be less effective in their capacity to stimulate muscle protein synthesis when compared with animal-based protein sources, likely due to differences in amino acid contents. We compared the postprandial muscle protein synthetic response following the ingestion of a lysine-enriched plant-based protein product with an isonitrogenous amount of chicken. Twenty-four men (age: 24±5 y; BMI: 22.9±2.6 kg·m−2) participated in this parallel, double-blind, randomised controlled trial and consumed 40 g protein as a lysine-enriched wheat and chickpea protein product (Plant, n=12) or chicken breast fillet (Chicken, n=12). Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were applied while repeated blood and muscle samples were collected over a 5h postprandial period to assess plasma amino acid responses, muscle protein synthesis rates, and muscle anabolic signalling responses. Postprandial plasma leucine and essential amino acid concentrations were higher following Chicken (P<0.001), while plasma lysine concentrations were higher throughout in Plant (P<0.001). Total plasma amino acid concentrations did not differ between interventions (P=0.181). Ingestion of both Plant and Chicken increased muscle protein synthesis rates from post-absorptive: 0.031±0.011 and 0.031±0.013 to postprandial: 0.046±0.010 and 0.055±0.015%∙h−1, respectively (P-time<0.001), with no differences between Plant and Chicken (P-interaction=0.068). Ingestion of 40 g protein in the form of a lysine-enriched plant-based protein product increases muscle protein synthesis rates to a similar extent as an isonitrogenous amount of chicken in healthy, young men. Plant-based protein products sold as meat replacers may be as effective as animal-based protein sources to stimulate postprandial muscle protein synthesis rates in healthy, young individuals.

Pea Proteins Have Anabolic Effects Comparable to Milk Proteins on Whole Body Protein Retention and Muscle Protein Metabolism in Old Rats

Plant proteins are attracting rising interest due to their pro-health benefits and environmental sustainability. However, little is known about the nutritional value of pea proteins when consumed by older people. Herein, we evaluated the digestibility and nutritional efficiency of pea proteins compared to casein and whey proteins in old rats. Thirty 20-month-old male Wistar rats were assigned to an isoproteic and isocaloric diet containing either casein (CAS), soluble milk protein (WHEY) or Pisane™ pea protein isolate for 16 weeks. The three proteins had a similar effect on nitrogen balance, true digestibility and net protein utilization in old rats, which means that different protein sources did not alter body composition, tissue weight, skeletal muscle protein synthesis or degradation. Muscle mitochondrial activity, inflammation status and insulin resistance were similar between the three groups. In conclusion, old rats used pea protein with the same efficiency as casein or whey proteins, due to its high digestibility and amino acid composition. Using these plant-based proteins could help older people diversify their protein sources and more easily achieve nutritional intake recommendations.