Muscle wasting: the gut microbiota as a new therapeutic target?

Gut microbes-muscle axis in muscle function and meat quality

The concept of the gut microbes-muscle axis underscores the impact of intestinal microbiota on the muscular system, an area that is increasingly coming to light. However, current interpretations and applications of this concept remain underdeveloped. In this review, we concluded and discussed factors, such as short-chain fatty acids, amino acids, vitamins, bile acids, antibiotics, cytokines, hormones, and extracellular vesicles that mediate gut microbes-muscle crosstalk and influence the gut microbes-muscle axis. Additionally, we examined how the gut microbes-muscle axis affects muscle mass, muscle strength, muscle metabolism, as well as muscle oxidative and immune status. Furthermore, we reviewed the influence of the microbes-muscle axis on muscle fiber type transition, muscle fat deposition, and meat quality. These insights illuminate the potential mechanisms by which the gut microbes-muscle axis operates in humans and animals. Thus, this review provides a theoretical foundation for future research and offers practical guidance for its application in biomedical and livestock industries.

Training Status Influences Regulation of Muscle and PBMC TLR4 Expression and Systemic Cytokine Responses to Vigorous Endurance Exercise

INTRODUCTION

A bout of vigorous endurance exercise transiently activates Toll-like receptor 4 (TLR4) and reduces TLR4 protein expressed on peripheral blood mononuclear cells (PBMCs). Endurance training, on the other hand, reduces TLR4-mediated signaling and minimizes the physiological stress imposed by exercise. Less is known about what occurs in skeletal muscle regarding TLR4 regulation and signaling. Therefore, this study aimed to investigate the regulation of TLR4 expressed in different tissue types (PBMCs and skeletal muscle samples) between endurance-trained and untrained men following vigorous endurance exercise and determine the effect of training status on cytokine responses associated with TLR4 activation.

METHODS

Endurance-trained ( n = 7) and untrained ( n = 5) men cycled for 1 h at their respiratory compensation point, with blood and skeletal muscle samples collected pre- and 3 h post-exercise.

RESULTS

In response to vigorous exercise, untrained men experienced a decrease in inhibitor of κBα (IκBα) protein (suggesting IκB degradation and the activation of TLR4-associated transcription factor NF-κB) and TLR4 protein levels, along with a simultaneous increase in TLR4 mRNA expression in both skeletal muscle and PBMCs. Moreover, this exercise session led to elevated levels of circulating interleukin-6, tumor necrosis factor-α, and interleukin-1β. Collectively, these results suggest a heightened TLR4-mediated signaling pathway in untrained men. However, no changes in these targets were observed in endurance-trained men, possibly indicating a potential mechanism by which regular endurance training blunts systemic inflammation.

CONCLUSIONS

These findings highlight the potential of endurance training to mitigate TLR4-mediated signaling, such as systemic inflammation, and shed light on the effects of exercise on TLR4 expression in PBMCs and skeletal muscle.

The mediating role of biological age in the association between dietary index for gut microbiota and sarcopenia

Background

Dietary Index of Gut Microbiota (DI-GM) is a newly proposed comprehensive metric for assessing dietary quality in relation to gut microbiota composition. Alterations in muscle structure are closely linked to DNA methylation-based biological age assessments and individual dietary patterns. However, a systematic investigation of the interrelationships among DI-GM, biological age, and sarcopenia remains lacking. We hypothesize that consuming foods beneficial to the gut microbiota may help mitigate the risk of sarcopenia by slowing the aging process.

Methods

This study analyzed data from NHANES 2007-2018. DI-GM was calculated using two 24-hour dietary recall datasets. Sarcopenia was assessed via dual-energy X-ray absorptiometry (DXA). The association between DI-GM and sarcopenia was evaluated using multivariate logistic regression, subgroup analysis, and restricted cubic splines. This study also investigated the potential mediating effects of three biological age indicators: the Klemera-Doubal Method (KDM), PhenoAge, and Homeostatic Dysregulation (HD).

Results

An increase in DI-GM score was significantly associated with a reduced risk of sarcopenia (OR: 0.87, 95% CI: 0.82-0.94).The risk of sarcopenia was significantly lower in the highest quartile group (Q3) (OR: 0.25, 95% CI: 0.11-0.58). The three biological age-related indicators (KDM, PA, and HD) partially mediated the association between DI-GM and sarcopenia, with PhenoAge showing the highest mediation proportion at 30.6%.

Conclusion

A higher DI-GM score was significantly associated with a reduced risk of sarcopenia. PhenoAge, HD, and KDM demonstrated significant mediating effects, with PhenoAge showing the highest mediation proportion.

Probiotics and muscle health: the impact of Lactobacillus on sarcopenia through the gut-muscle axis

Sarcopenia refers to the decline in skeletal muscle mass and function. Due to its increased mortality rate and severe disability, the clinical importance of sarcopenia is becoming increasingly prominent. Although the exact cause of sarcopenia is not fully understood, the gut microbiota (GM) plays a crucial role in the pathogenesis of sarcopenia, and increasing evidence suggests that gut dysbiosis may be associated with disease development. In the past few decades, the use of probiotics has surged, few studies have explored their impact on sarcopenia prevention and treatment. Lactobacillus probiotics are commonly used for gut health and immune support, but their mechanism in sarcopenia via the gut-muscle axis remains uncertain. This review highlights the treatment challenges, GM's role in sarcopenia, and the potential of Lactobacillus as an adjunct therapy. In addition, we also discuss the possible mechanisms by which Lactobacillus affect muscle function, such as alleviating inflammatory states, clearing excessive reactive oxygen species (ROS), improving skeletal muscle metabolism, enhancing intestinal barrier function and modulating the gut microbiota and its metabolites. These mechanisms may collectively contribute to the preservation of muscle mass and function, offering a promising avenue for advancing microbial therapies for sarcopenia.

Metagenomic Analysis Identifies Sex-Related Gut Microbial Functions and Bacterial Taxa Associated With Skeletal Muscle Mass

BACKGROUND

This study aimed to explore the association between gut microbiota functional profiles and skeletal muscle mass, focusing on sex-specific differences in a population under 65 years of age.

METHODS

Stool samples from participants were analysed using metagenomic shotgun sequencing. Skeletal muscle mass and skeletal muscle mass index (SMI) were quantified (SMI [%] = total appendage muscle mass [kg]/body weight [kg] × 100) using bioelectrical impedance analysis. Participants were categorized into SMI quartiles, and associations between gut microbiota, functional profiling and SMI were assessed by sex, adjusting for age, BMI and physical activity.

RESULTS

The cohort included 1027 participants (651 men, 376 women). In men, Escherichia coli (log2 fold change 3.08, q = 0.001), Ruminococcus_B gnavus (log2 fold change 2.89, q = 0.014) and Enterocloster sp001517625 (log2 fold change 2.47, q = 0.026) were more abundant in the lowest SMI compared to the highest SMI group. In contrast, Bifidobacterium bifidum (log2 fold change 3.13, q = 0.025) showed higher levels in the second lowest SMI group in women. Microbial pathways associated with amino acid synthesis (MET-SAM-PWY: log2 fold change 0.42; METSYN-PWY: log2 fold change 0.44; SER-GLYSYN-PWY: log2 fold change 0.20; PWY-5347: log2 fold change 0.41; P4-PWY: log2 fold change 0.53), N-acetylneuraminate degradation (log2 fold change 0.43), isoprene biosynthesis (log2 fold change 0.20) and purine nucleotide degradation and salvage (PWY-6353: log2 fold change 0.42; PWY-6608: log2 fold change 0.38; PWY66-409: log2 fold change 0.52; SALVADEHYPOX-PWY: log2 fold change 0.43) were enriched in the lowest SMI in men (q < 0.10). In women, the second lowest SMI group showed enrichment in energy-related pathways, including lactic acid fermentation (ANAEROFRUCAT-PWY: log2 fold change 0.19), pentose phosphate pathway (PENTOSE-P-PWY: log2 fold change 0.30) and carbohydrate degradation (PWY-5484: log2 fold change 0.31; GLYCOLYSIS: log2 fold change 0.29; PWY-6901: log2 fold change 0.27) (q < 0.05).

CONCLUSIONS

This study highlights sex-specific differences in gut microbiota and functional pathways associated with SMI. These findings suggest that gut microbiota may play a role in muscle health and point toward microbiota-targeted strategies for maintaining muscle mass.

The Bile Acid Metabolism of Intestinal Microorganisms Mediates the Effect of Different Protein Sources on Muscle Protein Deposition in Procambarus clarkii

The most economically important trait of the Procambarus clarkii is meat quality. Protein deposition is essential in muscle growth and nutritional quality formation. The effects and potential mechanisms of feed protein sources on crustaceans' muscle protein deposition have not been elucidated. This study established an all-animal protein source (AP) and an all-plant protein source group (PP), with a feeding period of 8 weeks (four replicates per group, 45 individuals per replicate). The results demonstrated that muscle protein deposition, muscle fiber diameter, and hardness were significantly higher in the PP group (p < 0.05). The transcript levels of genes involved in protein synthesis were notably upregulated, while those of protein hydrolysis and negative regulators of myogenesis notably downregulated in PP group (p < 0.05). Furthermore, protein sources shaped differential intestinal microbiota composition and microbial metabolites profiles, as evidenced by a significant decrease in g_Bacteroides (p = 0.030), and a significant increase in taurochenodeoxycholic acid (TCDCA) in PP group (p = 0.027). A significant correlation was further established by Pearson correlation analysis between the g_Bacteroides, TCDCA, and genes involved in the MSTN-mediated protein deposition pathway (p < 0.05). In vitro anaerobic fermentation confirmed the ability of the two groups of intestinal flora to metabolically produce differential TCDCA (p = 0.038). Our results demonstrated that the 'Bacteroides-TCDCA-MSTN' axis may mediate the effects of different protein sources on muscle development and protein deposition in P. clarkii, which was anticipated to represent a novel target for the muscle quality modulation in crustaceans.

Compound Probiotics Improve Neuropathic Pain Prognosis in a Murine Model of Chronic Constriction Injury

Purpose

Compound probiotics have been reported to ameliorate imbalances in the intestinal flora that may play a critical role in neuropathic pain. This study aimed to investigate the efficacy of compound probiotic treatment on neuropathic pain.

Methods

Thirty mice were randomly divided into three groups: 1) sham group, 2) mouse with chronic constrictive injury (CCI), and 3) probiotic gavage with CCI (CCI+Prob). The degree of pain and gait recovery was assessed by Mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), and mouse footprints. The degree of atrophy of the gastrocnemius muscle was assessed by muscle weight, hematoxylin and eosin (H&E) staining. Gut microbiota were analyzed by 16S ribosomal RNA sequencing (16SrRNA).

Results

Four weeks after surgery, TWL and MWT assessment showed significant increases in the CCI+Prob group compared with the CCI group (P < 0.01). Gait analysis results as well as gastrocnemius muscle weight showed a significant improvement in the CCI+Prob group compared with the CCI group. Measurement of alpha diversity showed a significant increase in the CCI group compared with the sham group, but this increase was attenuated by probiotic intervention in the CCI+Prob group. Although the CCI group had significantly decreased levels of Akkermansia and significantly increased levels of Ruminococcaceae, probiotic treatment reversed these changes.

Conclusion

Compound probiotics treatment can improve the pain and muscle atrophy in mice with CCI-induced neuropathic pain. The improvement of symptoms is associated with changes in the composition of gut microbiota.

The effect of probiotics and casein supplementation on aerobic capacity parameters of male soccer players

BACKGROUND

In the realm of sports science, nutrition is a well-established pillar for athletes' training, performance, and post-workout recovery. However, the role of gut microbiota, often overlooked, is a novel and intriguing aspect that can significantly impact athletic performance. With this in mind, our study ventures into uncharted territory, investigating the effect of probiotic and casein supplementation on the aerobic capacity of male soccer players.

METHOD

A double-blinded and placebo-controlled study was conducted with 44 male soccer players (Age: 22.81 ± 2.76 yr, Height: 177.90 ± 6.75 cm, Weight: 67.42 ± 8.44 kg). The participants were subjected to the Bruce test in the beginning; then, they were randomly divided into four groups, each consisting of 11 people: probiotics (PRO), casein (CAS), probiotics with casein (PRO+CAS), and placebo (PLA). PRO group was given one probiotic capsule (containing strains of Lactiplantibacillus plantarum BP06, Lacticaseibacillus casei BP07, Lactobacillus acidophilus BA05, Lactobacillus delbrueckii BD08 bulgaricus, Bifidobacterium infantis BI04, Bifidobacterium longum BL03, Bifidobacterium breve BB02 and Streptococcus salivarius thermophilus BT01, with a total dose of 4.5 × 1011 CFU) during dinner, while the CAS group consumed 20 grams of casein powder 45 minutes before bed. The PRO+CAS group was given one probiotic capsule during dinner and 20 grams of casein powder 45 minutes before bed. The participants in the PLA group were given one red capsule (containing 5 grams of starch) during dinner. All participants were instructed to take the supplements only on training days, three times a week for four weeks. The maximal oxygen consumption (VO2max), Ventilatory Threshold (VT), Time-to-exhaustion (TTE), Respiratory Compensation Point (RCP), Isocapnic area Time (Time-IC), Isocapnic area oxygen consumption (VO2-IC), and Hypocapnic Hyperventilation area Time (Time-HHV), after the Bruce test were Measured. All data were analyzed using SPSS Windows software, mixed repeated measure ANOVA, and Bonferroni post hoc test at p < 0.05 level.

RESULTS

The current study's findings illustrated that, after the intervention, TTE (p = 0.01) and RCP (p = 0.01) were significantly improved in PRO+CAS compared to the PLA group. No significant difference was observed between PRO and PLA (p = 0.52), PRO and CAS (p = 0.999), PRO and PRO+CAS (p = 0.9), CAS and PLA (p = 0.65), CAS and PRO+CAS (p = 0.73) in TTE. In addition, no significant difference was observed between PRO and CAS (p = 0.999), PRO and PLA (p = 0.40), PRO and PRO+CAS (p = 0.999), CAS and PLA (p = 0.263), CAS and PRO+CAS (p = 0.999) in RCP. Time-HHV was significantly higher in PRO+CAS (p = 0.000) and CAS (p = 0.047) compared to the PLA group. However, no significant difference was observed in the Time-HHV between PRO and CAS (p = 0.999), PRO and PRO+CAS (p = 0.25), PRO and PLA (p = 0.12), and CAS and PRO+CAS (p = 0.57). Additionally, all the groups had no significant differences in VO2max, VT1, VO2-IC and Time-IC.

CONCLUSION

The findings showed that consuming probiotics and casein could relatively improve the aerobic capacity of male soccer players. Nevertheless, simultaneous consumption of probiotics and casein had a more pronounced effect on aerobic capacity indicators, especially TTE and Time-HHV.

Weizmannia coagulans BC99 Improves Strength Performance by Enhancing Protein Digestion and Regulating Skeletal Muscle Quality in College Students of Physical Education Major

Background: The dietary proteins are one of the most important factors determining health conditions in humans. The sufficient digestion and absorption of dietary proteins in the digestive tract has positive effects on performance and recovery in sportspeople and athletes. Improving protein digestibility is a strategy for maintaining health status and optimal performance in sport and exercise activities. Objectives: The aim of the present study is to verify whether Weizmannia coagulans BC 99 (BC99) can increase muscle mass and strength. Methods: This randomized double-blind, controlled trial assigned 72 male college students to receive probiotics (n = 36, 20.25 ± 1.03 years; 179.00 ± 5.94 cm; 73.55 ± 8.73 kg, protein powder with BC99) or the placebo (n = 36, 20.19 ± 0.79 years; 179.25 ± 5.16 cm; 73.61 ± 8.24 kg, protein powder) for 12 weeks. At the baseline and final stages of the study, strength tests and body composition assessment were performed. Blood and stool samples were taken at the end of the 12-week intervention, and digestive enzymatic activity of stool samples, biochemical parameters, amino acids and hormone level of plasma were analyzed. Results: BC99 administration significantly improved strength performance, skeletal muscle mass, activity of pepsin and trypsin, the concentrations of branched chain amino acids and essential amino acids, reduced activities of creatine kinase and lactic dehydrogenase and urea nitrogen (BUN) level and increased testosterone and glucagon-like peptide-1 level in male college students. Conclusions: Therefore, BC99 supplementation can be an important nutritional strategy to improve strength performance, body composition, protein digestion and body metabolism in healthy young males.

Integrated analysis of intestinal microbial community and muscle transcriptome profile in rabbits

Intestinal microbial community plays an important part in maintaining health and skeletal muscle development in livestock. This study is the first of its kind in the world. In order to better understand the relationship between gut microbiota and gene expression in skeletal muscle of rabbits, caecum contents and longissimus dorsi tissues of rabbits at 0 d (S1), 35 d (S2) and 70d (S3) were collected and subjected for 16S rRNA sequencing and transcriptome sequencing. Our results showed that, among three groups of rabbits, Firmicutes and Bacteroidetes were the dominant phyla at the phylum level, while Akmansia, Bacteroides and Ruminobacter were the dominant genera at the genus level, and the relative abundance of Akmansia and Bacteroides increased firstly and then decreased from 0 d to 70 d. By analyzing the transcriptome sequencing data, we identified 2866, 2446 and 4541 differentially expressed genes (DEGs) in S1 vs S2, S2 vs S3 and S1 vs S3 groups, respectively. Finally, we performed correlation analysis between gut microbiota and the expression levels of muscle development-related genes of rabbits at 0 d and 70 d. Compared with 0 day old rabbits, in 70 day old rabbits Acinetobacter and Cronbacter with decreased abundance, and Ruminococcaceae_UCG-014 and Ruminococcus_1 with increase abundance is beneficial to caecum health in rabbits. These results will lay a foundation for further re-searches about the relationship between caecum microflora and muscle development in rabbits.

Metagenomic and Metabolomic Analyses Reveal the Role of Gut Microbiome-Associated Metabolites in the Muscle Elasticity of the Large Yellow Croaker (Larimichthys crocea)

The large yellow croaker (LYC, Larimichthys crocea) is highly regarded for its delicious taste and unique flavor. The gut microbiota has the ability to affect the host muscle performance and elasticity by regulating nutrient metabolism. The purpose of this study is to establish the relationship between muscle quality and intestinal flora in order to provide reference for the improvement of the muscle elasticity of LYC. In this study, the intestinal contents of high muscle elasticity males (IEHM), females (IEHF), and low muscle elasticity males (IELM) and females (IELF) were collected and subjected to metagenomic and metabolomic analyses. Metagenomic sequencing results showed that the intestinal flora structures of LYCs with different muscle elasticities were significantly different. The abundance of Streptophyta in the IELM (24.63%) and IELF (29.68%) groups was significantly higher than that in the IEHM and IEHF groups. The abundance of Vibrio scophthalmi (66.66%) in the IEHF group was the highest. Based on metabolomic analysis by liquid chromatograph-mass spectrometry, 107 differentially abundant metabolites were identified between the IEHM and IELM groups, and 100 differentially abundant metabolites were identified between the IEHF and IELF groups. Based on these metabolites, a large number of enriched metabolic pathways related to muscle elasticity were identified. Significant differences in the intestinal metabolism between groups with different muscle elasticities were identified. Moreover, the model of the relationship between the intestinal flora and metabolites was constructed, and the molecular mechanism of intestinal flora regulation of the nutrient metabolism was further revealed. The results help to understand the molecular mechanism of different muscle elasticities of LYC and provide an important reference for the study of the mechanism of the effects of LYC intestinal symbiotic bacteria on muscle development, and the development and application of probiotics in LYC.

Association between Drug Therapy and Risk of Incident Frailty: A Systematic Review

Medication is a potential factor influencing frailty. However, the relationship between pharmaceutical treatments and frailty remains unclear. Therefore, we conducted the present systematic review to summarize the association between drug therapy and the risk of incident frailty in older adults. We systematically searched the MEDLINE electronic database for articles indexed between January 1, 2000, and December 31, 2021, for randomized controlled trials (RCTs) and cohort studies reporting frailty changes associated with drug therapy. A total of six RCTs and 13 cohort studies involving 211,948 participants were identified, and their treatments were categorized into six medication classes: analgesics, cardiometabolic medication, chemotherapy, central nervous system (CNS)-active medication, hormonal therapy, and nutritional supplements. While the analysis revealed that only CNS-active medications were associated with an elevated risk of frailty, other medication classes also affected frailty; however, this is not conclusively attributable to a class-wide effect.

New evidence for gut-muscle axis: Lactic acid bacteria-induced gut microbiota regulates duck meat flavor

The interaction between gut microbiota and muscles through the gut-muscle axis has received increasing attention. This study attempted to address existing research gaps by investigating the effects of gut microbiota on meat flavor. Specifically, lactic acid bacteria were administered to ducks, and the results of e-nose and e-tongue showed significantly enhanced meat flavor in the treatment group. Further analyses using GC-MS revealed an increase in 6 characteristic volatile flavor compounds, including pentanal, hexanal, heptanal, 1-octen-3-ol, 2,3-octanedione, and 2-pentylfuran. Linoleic acid was identified as the key fatty acid that influences meat flavor. Metagenomic and transcriptomic results further confirmed that cecal microbiota affects the duck meat flavor by regulating the metabolic pathways of fatty acids and amino acids, especially ACACB was related to fatty acid biosynthesis and ACAT2, ALDH1A1 with fatty acid degradation. This study sheds light on a novel approach to improving the flavor of animal-derived food.

Comprehensive Strategies for Metabolic Syndrome: How Nutrition, Dietary Polyphenols, Physical Activity, and Lifestyle Modifications Address Diabesity, Cardiovascular Diseases, and Neurodegenerative Conditions

Several hallmarks of metabolic syndrome, such as dysregulation in the glucose and lipid metabolism, endothelial dysfunction, insulin resistance, low-to-medium systemic inflammation, and intestinal microbiota dysbiosis, represent a pathological bridge between metabolic syndrome and diabesity, cardiovascular, and neurodegenerative disorders. This review aims to highlight some therapeutic strategies against metabolic syndrome involving integrative approaches to improve lifestyle and daily diet. The beneficial effects of foods containing antioxidant polyphenols, intestinal microbiota control, and physical activity were also considered. We comprehensively examined a large body of published articles involving basic, animal, and human studie, as well as recent guidelines. As a result, dietary polyphenols from natural plant-based antioxidants and adherence to the Mediterranean diet, along with physical exercise, are promising complementary therapies to delay or prevent the onset of metabolic syndrome and counteract diabesity and cardiovascular diseases, as well as to protect against neurodegenerative disorders and cognitive decline. Modulation of the intestinal microbiota reduces the risks associated with MS, improves diabetes and cardiovascular diseases (CVD), and exerts neuroprotective action. Despite several studies, the estimation of dietary polyphenol intake is inconclusive and requires further evidence. Lifestyle interventions involving physical activity and reduced calorie intake can improve metabolic outcomes.

Navigating the Intersection: Sarcopenia and Sarcopenic Obesity in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) are intricate systemic conditions that can extend beyond the gastrointestinal tract through both direct and indirect mechanisms. Sarcopenia, characterized by a reduction in muscle mass and strength, often emerges as a consequence of the clinical course of IBDs. Indeed, sarcopenia exhibits a high prevalence in Crohn's disease (52%) and ulcerative colitis (37%). While computed tomography and magnetic resonance imaging remain gold-standard methods for assessing muscle mass, ultrasound is gaining traction as a reliable, cost-effective, and widely available diagnostic method. Muscle strength serves as a key indicator of muscle function, with grip strength test emerging nowadays as the most reliable assessment method. In IBDs, sarcopenia may arise from factors such as inflammation, malnutrition, and gut dysbiosis, leading to the formulation of the 'gut-muscle axis' hypothesis. This condition determines an increased need for surgery with poorer post-surgical outcomes and a reduced response to biological treatments. Sarcopenia and its consequences lead to reduced quality of life (QoL), in addition to the already impaired QoL. Of emerging concern is sarcopenic obesity in IBDs, a challenging condition whose pathogenesis and management are still poorly understood. Resistance exercise and nutritional interventions, particularly those aimed at augmenting protein intake, have demonstrated efficacy in addressing sarcopenia in IBDs. Furthermore, anti-TNF biological therapies showed interesting outcomes in managing this condition. This review seeks to furnish a comprehensive overview of sarcopenia in IBDs, elucidating diagnostic methodologies, pathophysiological mechanisms, and clinical implications and management. Attention will also be paid to sarcopenic obesity, exploring the pathophysiology and possible treatment modalities of this condition.

Unraveling the Microbiome-Human Body Axis: A Comprehensive Examination of Therapeutic Strategies, Interactions and Implications

This review scrutinizes the intricate interplay between the microbiome and the human body, exploring its multifaceted dimensions and far-reaching implications. The human microbiome, comprising diverse microbial communities inhabiting various anatomical niches, is increasingly recognized as a critical determinant of human health and disease. Through an extensive examination of current research, this review elucidates the dynamic interactions between the microbiome and host physiology across multiple organ systems. Key topics include the establishment and maintenance of microbiota diversity, the influence of host factors on microbial composition, and the bidirectional communication pathways between microbiota and host cells. Furthermore, we delve into the functional implications of microbiome dysbiosis in disease states, emphasizing its role in shaping immune responses, metabolic processes, and neurological functions. Additionally, this review discusses emerging therapeutic strategies aimed at modulating the microbiome to restore host-microbe homeostasis and promote health. Microbiota fecal transplantation represents a groundbreaking therapeutic approach in the management of dysbiosis-related diseases, offering a promising avenue for restoring microbial balance within the gut ecosystem. This innovative therapy involves the transfer of fecal microbiota from a healthy donor to an individual suffering from dysbiosis, aiming to replenish beneficial microbial populations and mitigate pathological imbalances. By synthesizing findings from diverse fields, this review offers valuable insights into the complex relationship between the microbiome and the human body, highlighting avenues for future research and clinical interventions.

Systemic LPS Administration Stimulates the Activation of Non-Neuronal Cells in an Experimental Model of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by deficiency of the survival motor neuron (SMN) protein. Although SMA is a genetic disease, environmental factors contribute to disease progression. Common pathogen components such as lipopolysaccharides (LPS) are considered significant contributors to inflammation and have been associated with muscle atrophy, which is considered a hallmark of SMA. In this study, we used the SMNΔ7 experimental mouse model of SMA to scrutinize the effect of systemic LPS administration, a strong pro-inflammatory stimulus, on disease outcome. Systemic LPS administration promoted a reduction in SMN expression levels in CNS, peripheral lymphoid organs, and skeletal muscles. Moreover, peripheral tissues were more vulnerable to LPS-induced damage compared to CNS tissues. Furthermore, systemic LPS administration resulted in a profound increase in microglia and astrocytes with reactive phenotypes in the CNS of SMNΔ7 mice. In conclusion, we hereby show for the first time that systemic LPS administration, although it may not precipitate alterations in terms of deficits of motor functions in a mouse model of SMA, it may, however, lead to a reduction in the SMN protein expression levels in the skeletal muscles and the CNS, thus promoting synapse damage and glial cells' reactive phenotype.

A Patented Dietary Supplement (Hydroxy-Methyl-Butyrate, Carnosine, Magnesium, Butyrate, Lactoferrin) Is a Promising Therapeutic Target for Age-Related Sarcopenia through the Regulation of Gut Permeability: A Randomized Controlled Trial

Adequate diet, physical activity, and dietary supplementation with muscle-targeted food for special medical purposes (FSMP) or dietary supplement (DS) are currently considered fundamental pillars in sarcopenia treatment. The aim of this study is to evaluate the effectiveness of a DS (containing hydroxy-methyl-butyrate, carnosine, and magnesium, for its action on muscle function and protein synthesis and butyrate and lactoferrin for their contribution to the regulation of gut permeability and antioxidant/anti-inflammation activity) on muscle mass (assessed by dual X-ray absorptiometry (DXA)), muscle function (by handgrip test, chair test, short physical performance battery (SPPB) test, and walking speed test), inflammation (tumor necrosis factor-alpha (TNF-a), C-reactive protein (CRP), and visceral adipose tissue (VAT)) and gut axis (by zonulin). A total of 59 participants (age 79.7 ± 4.8 years, body mass index 20.99 ± 2.12 kg/m2) were enrolled and randomly assigned to intervention (n = 30) or placebo (n = 28). The skeletal muscle index (SMI) significantly improved in the supplemented group compared to the placebo one, +1.02 (CI 95%: -0.77; 1.26), p = 0.001; a significant reduction in VAT was observed in the intervention group, -70.91 g (-13.13; -4.70), p = 0.036. Regarding muscle function, all the tests significantly improved (p = 0.001) in the supplemented group compared to the placebo one. CRP, zonulin, and TNF-alpha significantly decreased (p = 0.001) in intervention, compared to placebo, -0.74 mg/dL (CI 95%: -1.30; -0.18), -0.30 ng/mL (CI 95%: -0.37; -0.23), -6.45 pg/mL (CI 95%: -8.71; -4.18), respectively. This DS improves muscle mass and function, and the gut muscle has emerged as a new intervention target for sarcopenia.

Longitudinal association of sleep duration with possible sarcopenia: evidence from CHARLS

OBJECTIVES

There are limited data on the relationship between sleep duration and possible sarcopenia. Hence, this study aimed to investigate the associations of sleep duration with possible sarcopenia and its defining components based on the China Health and Retirement Longitudinal Study (CHARLS).

DESIGN

A retrospective cohort study.

SETTING

This study was conducted on participants aged over 45 years applying the 2011 baseline and 2015 follow-up survey from CHARLS covering 450 villages, 150 counties and 28 provinces.

PARTICIPANTS

Data from 5036 individuals (2568 men and 2468 women) free of possible sarcopenia at baseline were analysed.

PRIMARY AND SECONDARY OUTCOME MEASURES

The dose-response relationship between sleep duration and possible sarcopenia.

RESULTS

During 4 years of follow-up, 964 (19.14%) participants developed possible sarcopenia. Compared with participants who slept 6-8 hours per night, those with shorter sleep duration (<6 hours per night) were independently associated with 22% (OR, 1.22; 95% CI, 1.04 to 1.44) increased risk of developing possible sarcopenia and 27% (OR, 1.27; 95% CI, 1.04 to 1.57) increased risk of developing low handgrip strength after controlling for potential confounders. Long sleep duration (>8 hours per night) was not significantly associated with incident possible sarcopenia. The plots of restricted cubic splines exhibited an atypical inverse J-shaped association between sleep duration and possible sarcopenia. Subgroup analysis showed a stronger association between sleep duration and possible sarcopenia in participants aged 45-59 years and composed of male populations.

CONCLUSIONS

Short sleep duration was a potential risk factor for possible sarcopenia and low handgrip strength. The improvement of sleep duration should be considered a target in early preventive and administrative strategies against the development of handgrip strength decline and further reduced the occurrence of sarcopenia.

Comprehensive evaluation of serum hepatic proteins in predicting prognosis among cancer patients with cachexia: an observational cohort study

BACKGROUND

Hepatic proteins, including albumin, prealbumin, and transferrin have been confirmed to be prognostic predictors in various cancers. This study aimed to comprehensively assess the prognostic value of these three serum markers in patients with cancer cachexia.

METHODS

This multicenter prospective cohort study included 1303 cancer cachexia patients, among whom 592 deaths occurred during a median follow-up of 20.23 months. The definition of cachexia was based on the 2011 international consensus. Concordance index (C-index) and receiver operating characteristic (ROC) curves were applied to compare the prognostic performance. The primary outcome was overall survival, which was calculated using the Kaplan-Meier method generated by log-rank test. A Cox proportional hazard regression model was used to identify independent predictors associated with survival. The secondary outcomes included 90-days mortality and quality of life (QoL).

RESULTS

C-index and ROC curves showed that albumin had the most accurate predictive capacity for survival, followed by transferrin and prealbumin. Multivariate Cox analysis confirmed that low albumin (hazard ratio [HR] = 1.51, 95% confidence interval [95%CI] = 1.28-1.80, P < 0.001), prealbumin (HR = 1.42, 95%CI = 1.19-1.69, P < 0.001), and transferrin (HR = 1.50, 95%CI = 1.25-1.80, P < 0.001) were independent risk factors for long-term survival in cancer patients with cachexia. In subgroup analysis, the prognostic value of low albumin was significant in patients with upper gastrointestinal, hepatobiliary and pancreatic, and colorectal cancers; low prealbumin was significant in colorectal cancer; and low transferrin was significant in patients with upper gastrointestinal and colorectal cancer. All three hepatic proteins were valuable as prognostic predictors for patients with advanced (Stage III and IV) cancer with cachexia. The risks of 90-days mortality and impaired QoL were higher in cachexia patients with low albumin, prealbumin, and transferrin levels.

CONCLUSION

Low albumin, prealbumin, and transferrin levels were all independent prognostic factors affecting patients with cancer cachexia, especially in patients in the advanced stages. These results highlight the value of routinely checking serum hepatic proteins in clinical practice to predict the prognosis of patients with cancer cachexia.

Pathophysiological-Based Nutritional Interventions in Cirrhotic Patients with Sarcopenic Obesity: A State-of-the-Art Narrative Review

In recent decades, following the spread of obesity, metabolic dysfunction has come to represent the leading cause of liver disease. The classical clinical presentation of the cirrhotic patient has, therefore, greatly changed, with a dramatic increase in subjects who appear overweight or obese. Due to an obesogenic lifestyle (lack of physical activity and overall malnutrition, with an excess of caloric intake together with a deficit of proteins and micronutrients), these patients frequently develop a complex clinical condition defined as sarcopenic obesity (SO). The interplay between cirrhosis and SO lies in the sharing of multiple pathogenetic mechanisms, including malnutrition/malabsorption, chronic inflammation, hyperammonemia and insulin resistance. The presence of SO worsens the outcome of cirrhotic patients, affecting overall morbidity and mortality. International nutrition and liver diseases societies strongly agree on recommending the use of food as an integral part of the healing process in the comprehensive management of these patients, including a reduction in caloric intake, protein and micronutrient supplementation and sodium restriction. Based on the pathophysiological paths shared by cirrhosis and SO, this narrative review aims to highlight the nutritional interventions currently advocated by international guidelines, as well as to provide hints on the possible role of micronutrients and nutraceuticals in the treatment of this multifaceted clinical condition.

Advancing Biomarker Discovery and Therapeutic Targets in Duchenne Muscular Dystrophy: A Comprehensive Review

Mounting evidence underscores the intricate interplay between the immune system and skeletal muscles in Duchenne muscular dystrophy (DMD), as well as during regular muscle regeneration. While immune cell infiltration into skeletal muscles stands out as a prominent feature in the disease pathophysiology, a myriad of secondary defects involving metabolic and inflammatory pathways persist, with the key players yet to be fully elucidated. Steroids, currently the sole effective therapy for delaying onset and symptom control, come with adverse side effects, limiting their widespread use. Preliminary evidence spotlighting the distinctive features of T cell profiling in DMD prompts the immuno-characterization of circulating cells. A molecular analysis of their transcriptome and secretome holds the promise of identifying a subpopulation of cells suitable as disease biomarkers. Furthermore, it provides a gateway to unraveling new pathological pathways and pinpointing potential therapeutic targets. Simultaneously, the last decade has witnessed the emergence of novel approaches. The development and equilibrium of both innate and adaptive immune systems are intricately linked to the gut microbiota. Modulating microbiota-derived metabolites could potentially exacerbate muscle damage through immune system activation. Concurrently, genome sequencing has conferred clinical utility for rare disease diagnosis since innovative methodologies have been deployed to interpret the functional consequences of genomic variations. Despite numerous genes falling short as clinical targets for MD, the exploration of Tdark genes holds promise for unearthing novel and uncharted therapeutic insights. In the quest to expedite the translation of fundamental knowledge into clinical applications, the identification of novel biomarkers and disease targets is paramount. This initiative not only advances our understanding but also paves the way for the design of innovative therapeutic strategies, contributing to enhanced care for individuals grappling with these incapacitating diseases.

Divergent mechanisms regulate TLR4 expression on peripheral blood mononuclear cells following workload-matched exercise in normoxic and hypoxic environments

Exercise in hypoxia increases immune responses compared with normoxic exercise, and while Toll-like receptor 4 (TLR4) is implicated in these responses, its regulation remains undefined. The purpose of this study was to 1) investigate TLR4 regulation during workload-matched endurance exercise in normoxic and hypoxic conditions in vivo and 2) determine the independent effects of hypoxia and muscle contractions on TLR4 expression in vitro. Eight recreationally active men cycled for 1 h at 65% of their V̇o2max in normoxia (630 mmHg) and in hypobaric hypoxia (440 mmHg). Exercise in normoxia decreased TLR4 expressed on peripheral blood mononuclear cells (PBMCs), had no effect on the expression of inhibitor of κBα (IκBα), and increased the concentration of soluble TLR4 (sTLR4) in circulation. In contrast, exercise in hypoxia decreased the expression of TLR4 and IκBα in PBMCs, and sTLR4 in circulation. Markers of physiological stress were higher during exercise in hypoxia, correlating with markers of intestinal barrier damage, circulating lipopolysaccharides (LPS), and a concurrent decrease in circulating sTLR4, suggesting heightened TLR4 activation, internalization, and degradation in response to escalating physiological strain. In vitro, both hypoxia and myotube contractions independently, and in combination, reduced TLR4 expressed on C2C12 myotubes, and these effects were dependent on hypoxia-inducible factor 1 (HIF-1). In summary, the regulation of TLR4 varies depending on the physiological stress during exercise. To our knowledge, our study provides the first evidence of exercise-induced effects on sTLR4 in vivo and highlights the essential role of HIF-1 in the reduction of TLR4 during contraction and hypoxia in vitro.NEW & NOTEWORTHY We provide the first evidence of exercise affecting soluble Toll-like receptor 4 (sTLR4), a TLR4 ligand decoy receptor. We found that the degree of exercise-induced physiological stress influences TLR4 regulation on peripheral blood mononuclear cells (PBMCs). Moderate-intensity exercise reduces PBMC TLR4 and increases circulating sTLR4. Conversely, workload-matched exercise in hypoxia induces greater physiological stress, intestinal barrier damage, circulating lipopolysaccharides, and reduces both TLR4 and sTLR4, suggesting heightened TLR4 activation, internalization, and degradation under increased strain.

Microbiome's role in musculoskeletal health through the gut-bone axis insights

The interplay between the human microbiome and the musculoskeletal system represents a burgeoning field of research with profound implications for understanding and treating musculoskeletal disorders. This review articulates the pivotal role of the microbiome in modulating bone health, highlighting the gut-bone axis as a critical nexus for potential therapeutic intervention. Through a meticulous analysis of recent clinical research, we underscore the microbiome's influence on osteoporosis, sarcopenia, osteoarthritis, and rheumatoid arthritis, delineating both the direct and indirect mechanisms by which microbiota could impact musculoskeletal integrity and function. Our investigation reveals novel insights into the microbiota's contribution to bone density regulation, hormone production, immune modulation, and nutrient absorption, laying the groundwork for innovative microbiome-based strategies in musculoskeletal disease management. Significantly, we identify the challenges hindering the translation of research into clinical practice, including the limitations of current microbial sequencing techniques and the need for standardized methodologies in microbiome studies. Furthermore, we highlight promising directions for future research, particularly in the realm of personalized medicine, where the microbiome's variability offers unique opportunities for tailored treatment approaches. This review sets a new agenda for leveraging gut microbiota in the diagnosis, prevention, and treatment of musculoskeletal conditions, marking a pivotal step toward integrating microbiome science into clinical musculoskeletal care.

Optimizing the Gut Microbiota for Individualized Performance Development in Elite Athletes

The human gut microbiota can be compared to a fingerprint due to its uniqueness, hosting trillions of living organisms. Taking a sport-centric perspective, the gut microbiota might represent a physiological system that relates to health aspects as well as individualized performance in athletes. The athletes' physiology has adapted to their exceptional lifestyle over the years, including the diversity and taxonomy of the microbiota. The gut microbiota is influenced by several physiological parameters and requires a highly individual and complex approach to unravel the linkage between performance and the microbial community. This approach has been taken in this review, highlighting the functions that the microbial community performs in sports, naming gut-centered targets, and aiming for both a healthy and sustainable athlete and performance development. With this article, we try to consider whether initiating a microbiota analysis is practicable and could add value in elite sport, and what possibilities it holds when influenced through a variety of interventions. The aim is to support enabling a well-rounded and sustainable athlete and establish a new methodology in elite sport.

Cancer Cachexia: New Insights and Future Directions

Cancer remains a major health problem and is associated with cachexia in up to 80% of cases, leading to decreased survival and quality of life. Cachexia involves complex metabolic disturbances in both protein and energy balance, muscle wasting phenomena, weight loss, systemic inflammation, overall decreased performance status, and tolerability to treatment. The clinical impact of cancer cachexia is very complex, with early detection of cachectic patients and identification of predictive biomarkers being two key factors for improving survival. Thus, a better understanding of the complexity of cancer cachexia phenomena and its main pathophysiological mechanism is much needed. Our review highlights the most important information about cancer cachexia, aiming to disseminate updated research findings about this highly deadly condition.

Composition of gut microbiota involved in alleviation of dexamethasone-induced muscle atrophy by whey protein

Skeletal muscle atrophy is a condition associated with increased morbidity and mortality. While the concept of the gut-muscle axis has been proposed, the role of gut microbiota in dexamethasone (DEX)-induced skeletal muscle atrophy remains largely unknown, limiting its clinical applications. In this study, we found that administration of DEX caused a shift in the gut microbiota of mice, characterized by an increased ratio of Firmicutes/Bacteroidota and a reduction in alpha diversity. We also identified 480 new operational taxonomic units (OTUs), while 1168 specific OTUs were lost. Our Spearman correlation analysis revealed 28 key taxonomic genera of bacteria that were positively or negatively associated with skeletal muscle strength and weight (r: -0.881 to 0.845, p < 0.05). Moreover, supplementation with whey protein reshaped the gut microbiota structure in DEX-treated mice, making it more similar to that of the control group. Importantly, we further utilized a stepwise regression model to identify two enterotypes capable of predicting skeletal muscle function and weight. Notably, Ileibacterium and Lachnospiraceae_UCG-001 played significant roles in predicting both skeletal muscle function and weight. Our findings suggest that DEX causes shifts in the gut microbiota, which can be reversed by whey protein intervention. The enterotypes identified by our stepwise regression models predict muscle function and weight, underscoring the potential role of gut microbiota in modulating muscle atrophy and emphasizing the therapeutic opportunities of microbiota-altering interventions.

The Human Microbiome and Its Role in Musculoskeletal Disorders

Musculoskeletal diseases (MSDs) are characterized as injuries and illnesses that affect the musculoskeletal system. MSDs affect every population worldwide and are associated with substantial global burden. Variations in the makeup of the gut microbiota may be related to chronic MSDs. There is growing interest in exploring potential connections between chronic MSDs and variations in the composition of gut microbiota. The human microbiota is a complex community consisting of viruses, archaea, bacteria, and eukaryotes, both inside and outside of the human body. These microorganisms play crucial roles in influencing human physiology, impacting metabolic and immunological systems in health and disease. Different body areas host specific types of microorganisms, with facultative anaerobes dominating the gastrointestinal tract (able to thrive with or without oxygen), while strict aerobes prevail in the nasal cavity, respiratory tract, and skin surfaces (requiring oxygen for development). Together with the immune system, these bacteria have coevolved throughout time, forming complex biological relationships. Changes in the microbial ecology of the gut may have a big impact on health and can help illnesses develop. These changes are frequently impacted by lifestyle choices and underlying medical disorders. The potential for safety, expenses, and efficacy of microbiota-based medicines, even with occasional delivery, has attracted interest. They are, therefore, a desirable candidate for treating MSDs that are chronic and that may have variable progression patterns. As such, the following is a narrative review to address the role of the human microbiome as it relates to MSDs.

Sarcopenia in liver cirrhosis: perspectives from epigenetics and microbiota

Sarcopenia is characterized by the loss of muscle mass and function. It is well known that sarcopenia is often associated with aging, while in recent years, sarcopenia comorbid with chronic diseases such as cirrhosis has attracted widespread attention, whose underlying molecular mechanisms remain unclear. Since cirrhosis and sarcopenia are assumed to be closely interrelated in terms of pathogenesis, this review innovatively discussed the role of epigenetic modifications and microecological dysregulation in sarcopenia in the context of liver cirrhosis. Here we illustrated the relationship between sarcopenia and cirrhosis in the aspect of epigenetics, dysbiosis, and the crosstalk between gene modifications and intestinal microecology. Furthermore, the alterations in cirrhosis patients with sarcopenia, such as inflammatory response and oxidative stress, are found to present synergistic effects in the pathways of epigenetics and dysbiosis leading to sarcopenia. This review proposes that microbiome-based therapies are promising to break the vicious cycle between epigenetic modification and dysbiosis, providing strong support for the use of intestinal microecological interventions to prevent sarcopenia in cirrhotic patients.

Evaluation and management of body composition changes in cancer patients

Wasting in cancer patients has long been recognized as a condition that adversely affects cancer patients' quality of life, treatment tolerance, and oncological outcomes. Historically, this condition was mainly evaluated by changes in body weight. However, this approach is not quite accurate because body weight is the overall change of all body compartments. Conditions such as edema and ascites can mask the severity of muscle and adipose tissue depletion. Changes in body composition assessment in cancer patients have historically been underappreciated because of the limited availability of measurement tools. As more evidence highlighting the importance of body composition has emerged, it is imperative to apply a more precise evaluation of nutritional status and a more targeted approach to provide nutritional support for cancer patients. In this review, we will discuss the modalities for evaluating body composition and how to manage body composition changes in cancer patients.

Microbes, metabolites and muscle: Is the gut-muscle axis a plausible therapeutic target in Duchenne muscular dystrophy?

NEW FINDINGS

What is the topic of this review? The contribution of gut microbial signalling to skeletal muscle maintenance and development and identification of potential therapeutic targets in progressive muscle degenerative diseases such as Duchenne muscular dystrophy. What advances does it highlight? Gut microbe-derived metabolites are multifaceted signalling molecules key to muscle function, modifying pathways contributing to skeletal muscle wasting, making them a plausible target for adjunctive therapy in muscular dystrophy.

ABSTRACT

Skeletal muscle is the largest metabolic organ making up ∼50% of body mass. Because skeletal muscle has both metabolic and endocrine properties, it can manipulate the microbial populations within the gut. In return, microbes exert considerable influence on skeletal muscle via numerous signalling pathways. Gut bacteria produce metabolites (i.e., short chain fatty acids, secondary bile acids and neurotransmitter substrates) that act as fuel sources and modulators of inflammation, influencing host muscle development, growth and maintenance. The reciprocal interactions between microbes, metabolites and muscle establish a bidirectional gut-muscle axis. The muscular dystrophies constitute a broad range of disorders with varying disabilities. In the profoundly debilitating monogenic disorder Duchenne muscular dystrophy (DMD), skeletal muscle undergoes a reduction in muscle regenerative capacity leading to progressive muscle wasting, resulting in fibrotic remodelling and adipose infiltration. The loss of respiratory muscle in DMD culminates in respiratory insufficiency and eventually premature death. The pathways contributing to aberrant muscle remodelling are potentially modulated by gut microbial metabolites, thus making them plausible targets for pre- and probiotic supplementation. Prednisone, the gold standard therapy for DMD, drives gut dysbiosis, inducing a pro-inflammatory phenotype and leaky gut barrier contributing to several of the well-known side effects associated with chronic glucocorticoid treatment. Several studies have observed that gut microbial supplementation or transplantation exerts positive effects on muscle, including mitigating the side effects of prednisone. There is growing evidence in support of the potential for an adjunctive microbiota-directed regimen designed to optimise gut-muscle axis signalling, which could alleviate muscle wasting in DMD.

Clinical features and molecular mechanism of muscle wasting in end stage renal disease

Muscle wasting in end-stage renal disease (ESRD) is an escalating issue due to the increasing global prevalence of ESRD and its significant clinical impact, including a close association with elevated mortality risk. The phenomenon of muscle wasting in ESRD, which exceeds the rate of muscle loss observed in the normal aging process, arises from multifactorial processes. This review paper aims to provide a comprehensive understanding of muscle wasting in ESRD, covering its epidemiology, underlying molecular mechanisms, and current and emerging therapeutic interventions. It delves into the assessment techniques for muscle mass and function, before exploring the intricate metabolic and molecular pathways that lead to muscle atrophy in ESRD patients. We further discuss various strategies to mitigate muscle wasting, including nutritional, pharmacological, exercise, and physical modalities intervention. This review seeks to provide a solid foundation for future research in this area, fostering a deeper understanding of muscle wasting in ESRD, and paving the way for the development of novel strategies to improve patient outcomes. [BMB Reports 2023; 56(8): 426-438].

Clinical features and molecular mechanism of muscle wasting in end stage renal disease

Muscle wasting in end-stage renal disease (ESRD) is an escalating issue due to the increasing global prevalence of ESRD and its significant clinical impact, including a close association with elevated mortality risk. The phenomenon of muscle wasting in ESRD, which exceeds the rate of muscle loss observed in the normal aging process, arises from multifactorial processes. This review paper aims to provide a comprehensive understanding of muscle wasting in ESRD, covering its epidemiology, underlying molecular mechanisms, and current and emerging therapeutic interventions. It delves into the assessment techniques for muscle mass and function, before exploring the intricate metabolic and molecular pathways that lead to muscle atrophy in ESRD patients. We further discuss various strategies to mitigate muscle wasting, including nutritional, pharmacological, exercise, and physical modalities intervention. This review seeks to provide a solid foundation for future research in this area, fostering a deeper understanding of muscle wasting in ESRD, and paving the way for the development of novel strategies to improve patient outcomes. [BMB Reports 2023; 56(8): 426-438].

The role of probiotics in tissue engineering and regenerative medicine

Tissue engineering and regenerative medicine (TERM) as an emerging field is a multidisciplinary science and combines basic sciences such as biomaterials science, biology, genetics and medical sciences to achieve functional TERM-based products to regenerate or replace damaged or diseased tissues or organs. Probiotics are useful microorganisms which have multiple effective functions on human health. They have some immunomodulatory and biocompatibility effects and improve wound healing. In this article, we describe the latest findings on probiotics and their pro-healing properties on various body systems that are useable in regenerative medicine. Therefore, this review presents a new perspective on the therapeutic potential of probiotics for TERM.

Microbiota-gut-adipose axis: butyrate-mediated the improvement effect on inflammatory response and fatty acid oxidation dysregulation attenuates obesity in sleep-restricted mice

BACKGROUND

Insufficient sleep was considered as a substantial cause of obesity. The present study further explored the mechanism whereby sleep restriction (SR)-mediated intestinal dysbiosis induced metabolic disorder and ultimately lead to obesity in mice and the improvement effect of butyrate exerting on it.

METHODS

A continuous 3 months SR mouse model with or without butyrate supplementation and fecal microbiota transplantation to explore the key role of intestinal microbiota in butyrate improving inflammatory response in inguinal white adipose tissue (iWAT) and fatty acid oxidation dysfunction in brown adipose tissue (BAT), further ameliorating SR-induced obesity.

RESULTS

SR-mediated gut microbiota dysbiosis (down-regulation in butyrate level and up-regulation in LPS level) induced intestinal permeability increase and inflammatory response in iWAT and fatty acid oxidation dysfunction in BAT, ultimately resulting in obesity. Further, we demonstrated butyrate ameliorated gut microbiota homeostasis, suppressed inflammatory response via GPR43/LPS/TLR4/MyD88/GSK-3β/β-catenin loop in iWAT and restored fatty acid oxidation function via HDAC3/PPARα/PGC-1α/UCP1/Calpain1 pathway in BAT, ultimately reversing SR-induced obesity.

CONCLUSIONS

We revealed that gut dysbiosis is a key factor for SR-induced obesity and provided a better understanding of the effects of butyrate. We further expected that reversing SR-induced obesity by improving microbiota-gut-adipose axis disorder could be a possible treatment for metabolic diseases.

Sarcopenia and Cognitive Decline in Older Adults: Targeting the Muscle-Brain Axis

Declines in physical performance and cognition are commonly observed in older adults. The geroscience paradigm posits that a set of processes and pathways shared among age-associated conditions may also serve as a molecular explanation for the complex pathophysiology of physical frailty, sarcopenia, and cognitive decline. Mitochondrial dysfunction, inflammation, metabolic alterations, declines in cellular stemness, and altered intracellular signaling have been observed in muscle aging. Neurological factors have also been included among the determinants of sarcopenia. Neuromuscular junctions (NMJs) are synapses bridging nervous and skeletal muscle systems with a relevant role in age-related musculoskeletal derangement. Patterns of circulating metabolic and neurotrophic factors have been associated with physical frailty and sarcopenia. These factors are mostly related to disarrangements in protein-to-energy conversion as well as reduced calorie and protein intake to sustain muscle mass. A link between sarcopenia and cognitive decline in older adults has also been described with a possible role for muscle-derived mediators (i.e., myokines) in mediating muscle-brain crosstalk. Herein, we discuss the main molecular mechanisms and factors involved in the muscle-brain axis and their possible implication in cognitive decline in older adults. An overview of current behavioral strategies that allegedly act on the muscle-brain axis is also provided.

An Integrated Approach to Skeletal Muscle Health in Aging

A decline in muscle mass and function represents one of the most problematic changes associated with aging, and has dramatic effects on autonomy and quality of life. Several factors contribute to the inexorable process of sarcopenia, such as mitochondrial and autophagy dysfunction, and the lack of regeneration capacity of satellite cells. The physiologic decline in muscle mass and in motoneuron functionality associated with aging is exacerbated by the sedentary lifestyle that accompanies elderly people. Regular physical activity is beneficial to most people, but the elderly need well-designed and carefully administered training programs that improve muscle mass and, consequently, both functional ability and quality of life. Aging also causes alteration in the gut microbiota composition associated with sarcopenia, and some advances in research have elucidated that interventions via the gut microbiota-muscle axis have the potential to ameliorate the sarcopenic phenotype. Several mechanisms are involved in vitamin D muscle atrophy protection, as demonstrated by the decreased muscular function related to vitamin D deficiency. Malnutrition, chronic inflammation, vitamin deficiencies, and an imbalance in the muscle-gut axis are just a few of the factors that can lead to sarcopenia. Supplementing the diet with antioxidants, polyunsaturated fatty acids, vitamins, probiotics, prebiotics, proteins, kefir, and short-chain fatty acids could be potential nutritional therapies against sarcopenia. Finally, a personalized integrated strategy to counteract sarcopenia and maintain the health of skeletal muscles is suggested in this review.

Dietary 25-hydroxycholecalciferol modulates gut microbiota and improves the growth, meat quality, and antioxidant status of growing-finishing pigs

Introduction

25-Hydroxycholecalciferol (25OHD₃) is the active metabolite of regular vitamin D₃ in vivo, which has a stronger biological activity and is more easily absorbed by the intestine than regular vitamin D₃. Our study aimed to detect the potential influences of 25OHD₃ on pork quality, antioxidant status, and intestinal microbiota of growing-finishing pigs receiving low-phosphorus (P) diet.

Methods and results

Forty pigs [initial body weight (BW): 49.42 ± 4.01 kg] were allocated into two groups including low-P diet (CON group) and low-P diet supplemented with 50 μg/kg 25OHD₃ (25OHD₃ group). The whole experiment lasted for 88 days, including phase 1 (day 1-28), phase 2 (day 29-60), and phase 3 (day 61-88). The results showed that 25OHD₃ supplementation tended to decrease feed conversion ratio in phase 3 and overall phase in comparison with the CON group. 25OHD₃ increased (p < 0.05) serum contents of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and decreased (p < 0.05) serum bone-specific alkaline phosphatase level. 25OHD₃ increased (p < 0.05) mucosal GSH-Px activity in the duodenum and ileum, and tended to increase redness value and the activities of total antioxidant capacity and SOD in longissimus dorsi. 25OHD₃ significantly upregulated the mRNA level of copper/zinc superoxide dismutase, and tended to change the mRNA levels of nuclear factor E2-related factor 2 and kelch-like ECH-associated protein 1 in longissimus dorsi. Moreover, 25OHD₃ supplementation decreased (p < 0.05) n-6/n-3 and iodine value in longissimus dorsi. For bone quality, 25OHD₃ supplementation increased (p < 0.05) calcium content, bone mineral content, and breaking strength in the metacarpal bones. Moreover, the colonic abundance of Lactobacillus was significantly higher in pigs fed with 25OHD₃, and exhibited a positive association with serum antioxidant status, pork quality, and bone characteristics.

Conclusion

Overall, the inclusion of 25OHD₃ in low P diet partly improved production performance, meat quality, antioxidant capacity, bone properties, and gut microbiota composition of growing-finishing pigs.

Pathological features of tissues and cell populations during cancer cachexia

Cancers remain among the most devastating diseases in the human population in spite of considerable advances in limiting their impact on lifespan and healthspan. The multifactorial nature of cancers, as well as the number of tissues and organs that are affected, have exposed a considerable diversity in mechanistic features that are reflected in the wide array of therapeutic strategies that have been adopted. Cachexia is manifested in a number of diseases ranging from cancers to diabetes and ageing. In the context of cancers, a majority of patients experience cachexia and succumb to death due to the indirect effects of tumorigenesis that drain the energy reserves of different organs. Considerable information is available on the pathophysiological features of cancer cachexia, however limited knowledge has been acquired on the resident stem cell populations, and their function in the context of these diseases. Here we review current knowledge on cancer cachexia and focus on how tissues and their resident stem and progenitor cell populations are individually affected.

Role of the Gut Microbiome in Skeletal Muscle Physiology and Pathophysiology

PURPOSE OF REVIEW

This review aims to summarize the recent findings about the contribution of the gut microbiome to muscle pathophysiology and discuss molecular pathways that may be involved in such process. Related findings in the context of cancer cachexia are outlined.

RECENT FINDINGS

Many bacterial metabolites have been reported to exert a beneficial or detrimental impact on muscle physiology. Most of the evidence concentrates on short-chain fatty acids (SCFAs), with an emerging role for bile acids, bacterial amino acid metabolites (bAAms), and bacterial polyphenol metabolites. Other molecular players worth considering include cytokines, hormones, lipopolysaccharides, and quorum sensing molecules. The current literature clearly establishes the ability for the gut microbiome to modulate muscle function and mass. The understanding of the mechanisms underlying this gut-muscle axis may lead to the delivery of novel therapeutic tools to tackle muscle wasting in cancer cachexia, chronic kidney disease, liver fibrosis, and age-related sarcopenia.

Targeting cancer cachexia: Molecular mechanisms and clinical study

Cancer cachexia is a complex systemic catabolism syndrome characterized by muscle wasting. It affects multiple distant organs and their crosstalk with cancer constitute cancer cachexia environment. During the occurrence and progression of cancer cachexia, interactions of aberrant organs with cancer cells or other organs in a cancer cachexia environment initiate a cascade of stress reactions and destroy multiple organs including the liver, heart, pancreas, intestine, brain, bone, and spleen in metabolism, neural, and immune homeostasis. The role of involved organs turned from inhibiting tumor growth into promoting cancer cachexia in cancer progression. In this review, we depicted the complicated relationship of cancer cachexia with the metabolism, neural, and immune homeostasis imbalance in multiple organs in a cancer cachexia environment and summarized the treatment progress in recent years. And we discussed the molecular mechanism and clinical study of cancer cachexia from the perspective of multiple organs metabolic, neurological, and immunological abnormalities. Updated understanding of cancer cachexia might facilitate the exploration of biomarkers and novel therapeutic targets of cancer cachexia.

Functional Nutrients to Ameliorate Neurogenic Muscle Atrophy

Neurogenic muscle atrophy is a debilitating condition that occurs from nerve trauma in association with diseases or during aging, leading to reduced interaction between motoneurons and skeletal fibers. Current therapeutic approaches aiming at preserving muscle mass in a scenario of decreased nervous input include physical activity and employment of drugs that slow down the progression of the condition yet provide no concrete resolution. Nutritional support appears as a precious tool, adding to the success of personalized medicine, and could thus play a relevant part in mitigating neurogenic muscle atrophy. We herein summarize the molecular pathways triggered by denervation of the skeletal muscle that could be affected by functional nutrients. In this narrative review, we examine and discuss studies pertaining to the use of functional ingredients to counteract neurogenic muscle atrophy, focusing on their preventive or curative means of action within the skeletal muscle. We reviewed experimental models of denervation in rodents and in amyotrophic lateral sclerosis, as well as that caused by aging, considering the knowledge generated with use of animal experimental models and, also, from human studies.

Sarcopenia-related gut microbial changes are associated with the risk of complications in people with cirrhosis

Background & Aims

Sarcopenia and gut dysbiosis are common in individuals with cirrhosis. However, the association between sarcopenia and microbial alterations, and the subsequent impact on cirrhotic outcomes are poorly understood. This study aimed to identify muscle-dependent microbial changes and related risks of cirrhotic complications.

Methods

From September 2018 to December 2020, 89 individuals with cirrhosis and 16 healthy volunteers were prospectively enrolled. Muscle and nutritional status, serum amino acids, and fecal microbiota were analyzed. The association between microbial signatures of sarcopenia and cirrhotic complications was investigated.

Results

A decline in muscle mass and strength were associated with gut microbial alterations in individuals with cirrhosis. The greatest microbial dissimilarity was observed between those with sarcopenia (both decline in muscle mass and strength) and those with normal-muscle status (p = 0.035). Individuals with sarcopenia had lower serum levels of alanine, valine, leucine, isoleucine, proline, tryptophan and ornithine. Besides, gut microbial functions associated with amino acid biosynthesis were significantly reduced in individuals with sarcopenia and cirrhosis. Depletion of Dialister, Ruminococcus 2, and Anaerostipes were associated with cirrhotic sarcopenia, and significantly correlated with the serum levels of amino acids. Individuals with coexistent depletion of Ruminococcus 2 and Anaerostipes developed more infectious (44.4% vs. 3.0%) and non-infectious (74.1% vs. 3.0%) complications, and more hospitalizations (54 vs. 3) than those with cirrhosis with good microbial signatures (all p <0.001). In contrast, fecal enrichment of Ruminococcus 2 and Anaerostipes independently decreased the risk of 1-year complications.

Conclusions

Sarcopenia-related fecal microbial alterations are associated with cirrhotic complications. These findings may facilitate measures to improve the outcomes of individuals with cirrhosis and sarcopenia by modifying gut microbiota.

Impact and implications

The composition and biosynthetic functions of gut microbiota are significantly changed in individuals with sarcopenic cirrhosis. Those with a sarcopenia-related poor microbial signature, in which Ruminococcus 2 and Anaerostipes were both depleted, had significantly more infectious and non-infectious complications, as well as more hospitalizations. These findings highlight the therapeutic potential of modifying the gut microbiota of individuals with sarcopenic cirrhosis to improve their clinical outcomes.

Role of brain-gut-muscle axis in human health and energy homeostasis

The interrelationship between brain, gut and skeletal muscle plays a key role in energy homeostasis of the body, and is becoming a hot topic of research. Intestinal microbial metabolites, such as short-chain fatty acids (SCFAs), bile acids (BAs) and tryptophan metabolites, communicate with the central nervous system (CNS) by binding to their receptors. In fact, there is a cross-talk between the CNS and the gut. The CNS, under the stimulation of pressure, will also affect the stability of the intestinal system, including the local intestinal transport, secretion and permeability of the intestinal system. After the gastrointestinal tract collects information about food absorption, it sends signals to the central system through vagus nerve and other channels to stimulate the secretion of brain-gut peptide and produce feeding behavior, which is also an important part of maintaining energy homeostasis. Skeletal muscle has receptors for SCFAs and BAs. Therefore, intestinal microbiota can participate in skeletal muscle energy metabolism and muscle fiber conversion through their metabolites. Skeletal muscles can also communicate with the gut system during exercise. Under the stimulation of exercise, myokines secreted by skeletal muscle causes the secretion of intestinal hormones, and these hormones can act on the central system and affect food intake. The idea of the brain-gut-muscle axis is gradually being confirmed, and at present it is important for regulating energy homeostasis, which also seems to be relevant to human health. This article focuses on the interaction of intestinal microbiota, central nervous, skeletal muscle energy metabolism, and feeding behavior regulation, which will provide new insight into the diagnostic and treatment strategies for obesity, diabetes, and other metabolic diseases.

Three Pathways of Cancer Cachexia: Inflammation, Changes in Adipose Tissue and Loss of Muscle Mass—The Role of miRNAs

According to the World Health Organization, in 2018, cancers, along with over 18 million new cases and over 9.5 million deaths remained one of the main causes of mortality globally. Cancer-cachexia, also called wasting syndrome is a complex, multifactorial disorder characterized by progressive skeletal muscle mass loss, with or without adipose tissue atrophy. It is considered as a state of cancer-related malnutrition (CRM) accompanied by inflammation, that is irreversible despite the introduction of nutritional support. Indication of markers of pre-cachectic state seems to be urgently needed. Moreover, such markers have also potential to be used in the assessment of the effects of anti-cachexia treatment, and prognosis. miRNAs are non-coding RNA molecules that are about 20–30 nucleotides long. Single miRNA has the potential to control from few dozen to several hundred different genes. Despite the fact, that the number of miRNAs keep growing. we are making steady progress in establishing regulatory targets and their physiological levels. In this review we described the current knowledge on the impact of miRNAs on processes involved in cancer cachexia development: inflammation, adipose tissue remodelling, and loss of muscle mass both in animal models and the human cohorts. The available studies suggest that miRNAs, due to their properties, e.g., the possibility of regulating even hundreds of different genes, signalling pathways, and biological processes by one molecule, but also due their stability in biological material, the fact, that the change in their level reflects the disease status or the response to the applied treatment, they have great potential to be used as valuable biomarkers in the diagnosis, treatment, and prognosis of cancer cachexia.

Eggshell membrane modulates gut microbiota to prevent murine pre-cachexia through suppression of T helper cell differentiation

BACKGROUND

Cachexia is a life-threatening condition observed in several pathologies, such as cancer or chronic diseases. Interleukin 10 (Il10) gene transfer is known to improve cachexia by downregulating Il6. Here, we used an IL10-knockout mouse model to simulate cachexia and investigate the effects of eggshell membrane (ESM), a resistant protein, on general pre-cachexia symptoms, which is particularly important for the development of cachexia therapeutics.

METHODS

Five-week-old male C57BL6/J mice were fed an AIN-93G powdered diet (WT), and 5-week-old male B6.129P2-Il10 < tm1Cgn>/J (IL10^-/- ) mice were fed either the AIN-93G diet (KO) or an 8% ESM-containing diet (KOE) for 28 weeks. The tissue weight and levels of anaemia-, blood glucose-, lipid metabolism-, and muscular and colonic inflammation-related biochemical markers were measured. Transcriptomic analysis on liver and colon mucus and proteomic analysis on skeletal muscle were performed. Ingenuity Pathway Analysis was used to identify molecular pathways and networks. Caecal short-chain fatty acids (SCFAs) were identified using HPLC, and caecal bacteria DNA were subjected to metagenomic analysis. Flow cytometry analysis was performed to measure the CD4⁺ IL17⁺ T cells in mesenteric lymph nodes.

RESULTS

The body weight, weight of gastrocnemius muscle and fat tissues, colon weight/length ratio, plasma HDL and NEFA, muscular PECAM-1 levels (P < 0.01), plasma glucose and colonic mucosal myeloperoxidase activity (P < 0.05) and T helper (Th) 17 cell abundance (P = 0.071) were improved in KOE mice over KO mice. Proteomic analysis indicated the protective role of ESM in muscle weakness and maintenance of muscle formation (>1.5-fold). Transcriptomic analysis revealed that ESM supplementation suppressed the LPS/IL1-mediated inhibition of RXR function pathway in the liver and downregulated the colonic mucosal expression of chemokines and Th cell differentiation-related markers (P < 0.01) by suppressing the upstream BATF pathway. Analysis of the intestinal microenvironment revealed that ESM supplementation ameliorated the microbial alpha diversity and the abundance of microbiota associated with the degree of inflammation (P < 0.05) and increased the level of total organic acids, particularly of SCFAs such as butyrate (2.3-fold), which could inhibit Th1 and Th17 production.

CONCLUSIONS

ESM supplementation ameliorated the chief symptoms of cachexia, including anorexia, lean fat tissue mass, skeletal muscle wasting and reduced physical function. ESM also improved colon and skeletal muscle inflammation, lipid metabolism and microbial dysbiosis. These results along with the suppressed differentiation of Th cells could be associated with the beneficial intestinal microenvironment and, subsequently, attenuation of pre-cachexia. Our findings provide insights into the potential of ESM in complementary interventions for pre-cachexia prevention.

Effects of Dietary Yeast β-Glucan Supplementation on Meat Quality, Antioxidant Capacity and Gut Microbiota of Finishing Pigs

Yeast β-glucan is a natural antioxidant and has been reported to improve growth performance of piglets, but its application in improving pork quality is limited. This study investigated the effects of dietary yeast β-glucan supplementation on meat quality, antioxidant capacity and gut microbiota of finishing pigs. In a 40-day experiment, ninety finishing pigs (Duroc × Landrace × Yorkshire, 70.47 ± 0.04 kg) were randomly allocated into five treatments including a basal diet supplemented with 0, 50, 100, 200 and 400 mg/kg yeast β-glucan. Results showed that yeast β-glucan significantly increased pH45 min (linear and quadratic, p < 0.01) and a*45 min (linear, p < 0.05), and reduced cooking loss (linear, p < 0.05) and drip loss (quadratic, p < 0.05) of meat in finishing pigs. Importantly, the 200 mg/kg group exhibited the highest values of pH45 min (p < 0.01) and the lowest values of drip loss (p < 0.05), accompanied by a decreased lactate content (p < 0.05) and glycolytic potential (p < 0.05). Dietary supplementation of 200 mg/kg yeast β-glucan markedly increased catalase (CAT) (p < 0.05), superoxide dismutase (SOD) (p < 0.05) and total antioxidant capacity (T-AOC) (p < 0.01) activities in skeletal muscle. Moreover, WPS-2 abundance was decreased significantly in colonic digesta by 200 mg/kg yeast β-glucan and exhibited a positive association with muscle lactate content and drip loss. Together, dietary 200 mg/kg yeast β-glucan supplementation effectively improved pH value and the water-holding capacity of fresh meat through reducing muscle postmortem glycolysis, increasing antioxidant capacity and altering the gut microbiota composition of finishing pigs.

Targeting the gut to prevent and counteract metabolic disorders and pathologies during aging

Impairment of gut function is one of the explanatory mechanisms of health status decline in elderly population. These impairments involve a decline in gut digestive physiology, metabolism and immune status, and associated to that, changes in composition and function of the microbiota it harbors. Continuous deteriorations are generally associated with the development of systemic dysregulations and ultimately pathologies that can worsen the initial health status of individuals. All these alterations observed at the gut level can then constitute a wide range of potential targets for development of nutritional strategies that can impact gut tissue or associated microbiota pattern. This can be key, in a preventive manner, to limit gut functionality decline, or in a curative way to help maintaining optimum nutrients bioavailability in a context on increased requirements, as frequently observed in pathological situations. The aim of this review is to give an overview on the alterations that can occur in the gut during aging and lead to the development of altered function in other tissues and organs, ultimately leading to the development of pathologies. Subsequently is discussed how nutritional strategies that target gut tissue and gut microbiota can help to avoid or delay the occurrence of aging-related pathologies.

Muscle Wasting in Chronic Kidney Disease: Mechanism and Clinical Implications—A Narrative Review

Muscle wasting, known to develop in patients with chronic kidney disease (CKD), is a deleterious consequence of numerous complications associated with deteriorated renal function. Muscle wasting in CKD mainly involves dysregulated muscle protein metabolism and impaired muscle cell regeneration. In this narrative review, we discuss the cardinal role of the insulin-like growth factor 1 and myostatin signaling pathways, which have been extensively investigated using animal and human studies, as well as the emerging concepts in microRNA- and gut microbiota-mediated regulation of muscle mass and myogenesis. To ameliorate muscle loss, therapeutic strategies, including nutritional support, exercise programs, pharmacological interventions, and physical modalities, are being increasingly developed based on advances in understanding its underlying pathophysiology.

Intestinal Microbiota Regulate Certain Meat Quality Parameters in Chicken

Growing evidence of intestinal microbiota-muscle axis provides a possibility to improve meat quality of broilers through regulating intestinal microbiota. Water-holding capacity is a crucial factor to evaluate the meat quality. High quality of water-holding capacity is usually described as a low drip-losing rate. This study aimed to explore the relationship between intestinal microbiota and water-holding capacity of muscle in broilers. According to our results, two native breeds of broilers (the Arbor Acres broilers and the Beijing-You broilers) exhibited remarkable differences in microbiota composition. However, the regular of gut bacteria compositions gradually became similar when the two breeds of broiler were raised in a same feeding environment. Therefore, this similar regular of intestinal microbiota induced similar water-holding capacity of the muscle from the two breeds. In subsequent fecal microbiota transplantation (FMT) experiments, the intestinal microbiota community of the Arbor Acres broilers was remodeling by oral gavage of bacterial suspension that was derived from the Beijing-You broilers. Then, not only body weight and abdominal fat rate were increased, but also drip loss of muscle was decreased in the Arbor Acres broilers. Additionally, muscle fiber diameter of biceps femoris muscle and expression of MyoD1 were notably enlarged. Muscle fiber diameter and related genes were deemed as important elements for water-holding capacity of muscle. Simultaneously, we screened typical intestinal bacteria in both the two native breeds of broilers by 16S rDNA sequencing. Lachnoclostridium was the only bacteria genus associated with drip-losing rate, meat fiber diameter, body weight, and abdominal fat rate.