AR cooperates with SMAD4 to maintain skeletal muscle homeostasis

Astragalus membranaceus and its monomers treat peritoneal fibrosis and related muscle atrophy through the AR/TGF-β1 pathway

Background: To anticipate the potential molecular mechanism of Astragalus membranaceus (AM) and its monomer, Calycosin, against peritoneal fibrosis (PF) and related muscle atrophy using mRNA-seq, network pharmacology, and serum pharmacochemistry. Methods: Animal tissues were examined to evaluate a CKD-PF mice model construction. mRNA sequencing was performed to find differential targets. The core target genes of AM against PF were screened through network pharmacology analysis, and CKD-PF mice models were given high- and low-dose AM to verify common genes. Serum pharmacochemistry was conducted to clarify which components of AM can enter the blood circulation, and the selected monomer was further validated through cell experiments for the effect on PF and mesothelial mesenchymal transition (MMT) of peritoneal mesothelial cells (PMCs). Results: The CKD-PF mice models were successfully constructed. A total of 31,184 genes were detected in the blank and CKD-PF groups, and 228 transcription factors had significant differences between the groups. Combined with network pharmacology analysis, a total of 228 AM-PF-related targets were identified. Androgen receptor (AR) was the remarkable transcription factor involved in regulating transforming growth factor-β1 (TGF-β1). AM may be involved in regulating the AR/TGF-β1 signaling pathway and may alleviate peritoneal dialysis-related fibrosis and muscle atrophy in CKD-PF mice. In 3% peritoneal dialysis solution-stimulated HMrSV5 cells, AR expression levels were dramatically reduced, whereas TGF-β1/p-smads expression levels were considerably increased. Conclusion: AM could ameliorate PF and related muscle atrophy via the co-target AR and modulated AR/TGF-β1 pathway. Calycosin, a monomer of AM, could partially reverse PMC MMT via the AR/TGF-β1/smads pathway. This study explored the traditional Chinese medicine theory of "same treatment for different diseases," and supplied the pharmacological evidence of "AM can treat flaccidity syndrome."

271st ENMC international workshop: Towards a unifying effort to fight Kennedy's disease. 20-22 October 2023, Hoofddorp, Netherlands

The workshop held in the Netherlands from October 20-22, 2023, united 27 scientists from academia, healthcare, and industry representing 11 countries, alongside four patient and charity representatives. Focused on Kennedy's Disease (KD), also known as spinal and bulbar muscular atrophy (SBMA), the workshop aimed to consolidate knowledge, align on clinical trial designs, and promote participative medicine for effective treatments. Discussions emphasized KD's molecular mechanisms, highlighting its status as a neuromuscular disorder with motor neuron degeneration. Strategies for therapeutic intervention, including AR activity modulation and targeting post-translational modifications, were proposed. The need for diagnostic, prognostic, and target engagement biomarkers was stressed. Challenges in patient stratification and clinical trial recruitment were acknowledged, with the International KD/SBMA Registry praised for its role. The workshop concluded with a patient-focused session, underscoring challenges in KD diagnosis and the vital support provided by patient associations.

Epitranscriptomics as a New Layer of Regulation of Gene Expression in Skeletal Muscle: Known Functions and Future Perspectives

Epitranscriptomics refers to post-transcriptional regulation of gene expression via RNA modifications and editing that affect RNA functions. Many kinds of modifications of mRNA have been described, among which are N6-methyladenosine (m6A), N1-methyladenosine (m1A), 7-methylguanosine (m7G), pseudouridine (Ψ), and 5-methylcytidine (m5C). They alter mRNA structure and consequently stability, localization and translation efficiency. Perturbation of the epitranscriptome is associated with human diseases, thus opening the opportunity for potential manipulations as a therapeutic approach. In this review, we aim to provide an overview of the functional roles of epitranscriptomic marks in the skeletal muscle system, in particular in embryonic myogenesis, muscle cell differentiation and muscle homeostasis processes. Further, we explored high-throughput epitranscriptome sequencing data to identify RNA chemical modifications in muscle-specific genes and we discuss the possible functional role and the potential therapeutic applications.

Spinal and bulbar muscular atrophy: From molecular pathogenesis to pharmacological intervention targeting skeletal muscle

The clinical characteristics of SBMA, also known as Kennedy's disease (OMIM 313200), were initially documented by Dr. H Kawahara in the 18th century and a hundred years later by Dr. W. Kennedy. SBMA is a neuromuscular disease caused by expansions of a CAG microsatellite tandem repeat in exon 1 of the androgen receptor (AR) gene located on the X chromosome. These expansions result in the production of AR with an aberrantly expanded polyglutamine (polyQ) tract. In this review, we explore recent advancements in the significance of gene expression changes in skeletal muscle and discuss how pharmacological interventions targeting this aspect of disease pathogenesis can potentially be translated into therapies for SBMA patients.

Full-Length Transcriptomes and Sex-Based Differentially Expressed Genes in the Brain and Ganglia of Giant River Prawn Macrobrachium rosenbergii

Macrobrachium rosenbergii is an important aquaculture prawn that exhibits sexual dimorphism in growth, with males growing much faster than females. However, the mechanisms controlling these complex traits are not well understood. The nervous system plays an important role in regulating life functions. In the present work, we applied PacBio RNA-seq to obtain and characterize the full-length transcriptomes of the brains and thoracic ganglia of female and male prawns, and we performed comparative transcriptome analysis of female and male prawns. A total of 159.1-Gb of subreads were obtained with an average length of 2175 bp and 93.2% completeness. A total of 84,627 high-quality unigenes were generated and annotated with functional databases. A total of 6367 transcript factors and 6287 LncRNAs were predicted. In total, 5287 and 6211 significantly differentially expressed genes (DEGs) were found in the brain and thoracic ganglion, respectively, and confirmed by qRT-PCR. Of the 435 genes associated with protein processing pathways in the endoplasmic reticula, 42 DEGs were detected, and 21/26 DEGs with upregulated expression in the male brain/thoracic ganglion. The DEGs in this pathway are regulated by multiple LncRNAs in polypeptide folding and misfolded protein degradation in the different organs and sexes of the prawn. Our results provide novel theories and insights for studying the nervous system, sexual control, and growth dimorphism.

The role of ubiquitination in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative and neuromuscular genetic disease caused by the expansion of a polyglutamine-encoding CAG tract in the androgen receptor (AR) gene. The AR is an important transcriptional regulator of the nuclear hormone receptor superfamily; its levels are regulated in many ways including by ubiquitin-dependent degradation. Ubiquitination is a post-translational modification (PTM) which plays a key role in both AR transcriptional activity and its degradation. Moreover, the ubiquitin-proteasome system (UPS) is a fundamental component of cellular functioning and has been implicated in diseases of protein misfolding and aggregation, including polyglutamine (polyQ) repeat expansion diseases such as Huntington's disease and SBMA. In this review, we discuss the details of the UPS system, its functions and regulation, and the role of AR ubiquitination and UPS components in SBMA. We also discuss aspects of the UPS that may be manipulated for therapeutic effect in SBMA.

Skeletal Muscle Pathogenesis in Polyglutamine Diseases

Polyglutamine diseases are characterized by selective dysfunction and degeneration of specific types of neurons in the central nervous system. In addition, nonneuronal cells can also be affected as a consequence of primary degeneration or due to neuronal dysfunction. Skeletal muscle is a primary site of toxicity of polyglutamine-expanded androgen receptor, but it is also affected in other polyglutamine diseases, more likely due to neuronal dysfunction and death. Nonetheless, pathological processes occurring in skeletal muscle atrophy impact the entire body metabolism, thus actively contributing to the inexorable progression towards the late and final stages of disease. Skeletal muscle atrophy is well recapitulated in animal models of polyglutamine disease. In this review, we discuss the impact and relevance of skeletal muscle in patients affected by polyglutamine diseases and we review evidence obtained in animal models and patient-derived cells modeling skeletal muscle.