Depletion of gut microbiota induces skeletal muscle atrophy by FXR-FGF15/19 signalling.
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ABSTRACT:
SUBMITTER: Qiu Y
PROVIDER: S-EPMC8018554 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BACKGROUND: Myoblasts undergo major changes in their plasma membrane during the initial steps of skeletal muscle differentiation, including major alterations in the distribution of cholesterol. Cholesterol is involved in crucial membrane functions, such as fluidity, and permeability, and in the organization of specialized membrane microdomains (or lipid rafts). We have previously shown that alterations in cholesterol levels in myoblasts induce changes in proliferation and differentiation, which involves activation of Wnt/beta-catenin signaling pathway. In this study we used methyl-?-cyclodextrin (MbCD) to extract cholesterol from the membrane of chick skeletal muscle cells grown in culture. Using Ion Torrent-based sequencing, we compared the transcriptome of untreated and MbCD treated cells. Our aim was to define the genes that are expressed in these two conditions and relate their expression to cellular functions. RESULTS: Over 5.7 million sequences were obtained, representing 671.38 Mb of information. mRNA transcriptome profiling of myogenic cells after cholesterol depletion revealed alterations in transcripts involved in the regulation of apoptosis, focal adhesion, phagosome, tight junction, cell cycle, lysosome, adherens junctions, gap junctions, p53 signaling pathway, endocytosis, autophagy and actin cytoskeleton. Lim domain only protein 7 mRNA was found to be the highest up-regulated feature after cholesterol depletion. CONCLUSIONS: This is the first study on the effects of membrane cholesterol depletion in mRNA expression in myogenic cells. Our data shows that alterations in the availability of plasma membrane cholesterol lead to transcriptional changes in myogenic cells. The knowledge of the genes involved in the cellular response to cholesterol depletion could contribute to our understanding of skeletal muscle differentiation.
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Project description:BackgroundA therapeutic approach for the treatment of glucocorticoid-induced skeletal muscle atrophy should be based on the knowledge of the molecular mechanisms determining the unbalance between anabolic and catabolic processes and how to re-establish this balance. Here, we investigated whether the obestatin/GPR39 system, an autocrine signalling system acting on myogenesis and with anabolic effects on the skeletal muscle, could protect against chronic glucocorticoid-induced muscle atrophy.MethodsIn this study, we used an in vivo model of muscle atrophy induced by the synthetic glucocorticoid dexamethasone to examine the liaison molecules that define the interaction between the glucocorticoid receptor and the obestatin/GPR39 systems. The findings were extended to in vitro effects on human atrophy using human KM155C25 myotubes.ResultsKLF15 and FoxO transcription factors were identified as direct targets of obestatin signalling in the control of proteostasis in skeletal muscle. The KLF15-triggered gene expression program, including atrogenes and FoxOs, was regulated via KLF15 ubiquitination by the E3 ubiquitin ligase NEDD4. Additionally, a specific pattern of FoxO post-translational modification, including FoxO4 phosphorylation by Akt pathway, was critical in the regulation of the ubiquitin-proteasome system. The functional cooperativity between Akt and NEDD4 in the regulation of FoxO and KLF15 provides integrated cues to counteract muscle proteostasis and re-establish protein synthesis.ConclusionsThe effective control of FoxO activity in response to glucocorticoid is critical to counteract muscle-related pathologies. These results highlight the potential of the obestatin/GPR39 system to fine-tune the effects of glucocorticoids on skeletal muscle wasting.
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Project description:The master posttranscriptional regulator HuR promotes muscle fiber formation in cultured muscle cells. However, its impact on muscle physiology and function in vivo is still unclear. Here, we show that muscle-specific HuR knockout (muHuR-KO) mice have high exercise endurance that is associated with enhanced oxygen consumption and carbon dioxide production. muHuR-KO mice exhibit a significant increase in the proportion of oxidative type I fibers in several skeletal muscles. HuR mediates these effects by collaborating with the mRNA decay factor KSRP to destabilize the PGC-1α mRNA. The type I fiber-enriched phenotype of muHuR-KO mice protects against cancer cachexia-induced muscle loss. Therefore, our study uncovers that under normal conditions HuR modulates muscle fiber type specification by promoting the formation of glycolytic type II fibers. We also provide a proof-of-principle that HuR expression can be targeted therapeutically in skeletal muscles to combat cancer-induced muscle wasting.
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Project description:Gut microbiota is recognized as a strong determinant of host physiology including fat metabolism and can transfer obesity-associated phenotypes from donors to recipients. However, the relationship between gut microbiota and intramuscular fat (IMF) is still largely unknown. Obese Jinhua pigs (JP) have better meat quality that is associated with higher IMF content than lean Landrace pigs (LP). The present study was conducted to test the contribution of gut microbiota to IMF properties by transplanting fecal microbiota of adult JP and LP to antibiotics-treated mice. Similar to JP donors, the mice receiving JP's microbiota (JM) had elevated lipid and triglyceride levels and the lipoprotein lipase activity, as well as reduced mRNA level of angiopoietin-like 4 (ANGPTL4) in the gastrocnemius muscles, compared to those in mice receiving LP's microbiota (LM). High-throughput 16S rRNA sequencing confirmed that transplantation of JP and LP feces differently reconstructed the gut microbiota in both jejunum and colon of mouse recipients. In colonic samples, we observed an elevated ratio of Firmicutes to Bacteroidetes and increased abundance of genus Romboutsia in JM, which were positively correlated with obesity. Furthermore, the abundance of Akkermansia decreased in JM, which is positively correlated with lean. Colonic concentrations of acetate (P = 0.047) and butyrate (P = 0.014) were significantly lower in JM than in LM, and consistently, the terminal genes for butyrate synthesis, butyryl CoA: acetate CoA transferase were less abundant in colonic microbiota of JM. Taken together, these gut microbiota of obese JP intrinsically promotes IMF accumulation and can transfer the properties to mouse recipients. Manipulation of intestinal microbiota will, therefore, have the potential to improve the meat quality and flavor of pigs and even to ameliorate the metabolic syndrome in human.
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Project description:BackgroundRepetition of the onset of aspiration pneumonia in aged patients is common and causes chronic inflammation. The inflammation induces proinflammatory cytokine production and atrophy in the muscles. The proinflammatory cytokines induce muscle proteolysis by activating calpains and caspase-3, followed by further degradation by the ubiquitin-proteasome system. Autophagy is another pathway of muscle atrophy. However, little is known about the relationship between aspiration pneumonia and muscle. For swallowing muscles, it is not clear whether they produce cytokines. The main objective of this study was to determine whether aspiration pneumonia induces muscle atrophy in the respiratory (the diaphragm), skeletal (the tibialis anterior, TA), and swallowing (the tongue) systems, and their possible mechanisms.MethodsWe employed a mouse aspiration pneumonia model and computed tomography (CT) scans of aged pneumonia patients. To induce aspiration pneumonia, mice were inoculated with low dose pepsin and lipopolysaccharide solution intra-nasally 5 days a week. The diaphragm, TA, and tongue were isolated, and total RNA, proteins, and frozen sections were stored. Quantitative real-time polymerase chain reaction determined the expression levels of proinflammatory cytokines, muscle E3 ubiquitin ligases, and autophagy related genes. Western blot analysis determined the activation of the muscle proteolysis pathway. Frozen sections determined the presence of muscle atrophy. CT scans were used to evaluate the muscle atrophy in aged aspiration pneumonia patients.ResultsThe aspiration challenge enhanced the expression levels of proinflammatory cytokines in the diaphragm, TA, and tongue. Among muscle proteolysis pathways, the aspiration challenge activated caspase-3 in all the three muscles examined, whereas calpains were activated in the diaphragm and the TA but not in the tongue. Activation of the ubiquitin-proteasome system was detected in all the three muscles examined. The aspiration challenge activated autophagy in the TA and the tongue, whereas weak or little activation was detected in the diaphragm. The aspiration challenge resulted in a greater proportion of smaller myofibers than in controls in the diaphragm, TA, and tongue, suggesting muscle atrophy. CT scans clearly showed that aspiration pneumonia was followed by muscle atrophy in aged patients.ConclusionsAspiration pneumonia induced muscle atrophy in the respiratory, skeletal, and swallowing systems in a preclinical animal model and in human patients. Diaphragmatic atrophy may weaken the force of cough to expectorate sputum or mis-swallowed contents. Skeletal muscle atrophy may cause secondary sarcopenia. The atrophy of swallowing muscles may weaken the swallowing function. Thus, muscle atrophy could become a new therapeutic target of aspiration pneumonia.
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Project description:RationaleSkeletal muscle wasting with accompanying cachexia is a life threatening complication in congestive heart failure. The molecular mechanisms are imperfectly understood, although an activated renin-angiotensin aldosterone system has been implicated. Angiotensin (Ang) II induces skeletal muscle atrophy in part by increased muscle-enriched E3 ubiquitin ligase muscle RING-finger-1 (MuRF1) expression, which may involve protein kinase D1 (PKD1).ObjectiveTo elucidate the molecular mechanism of Ang II-induced skeletal muscle wasting.Methods and resultsA cDNA expression screen identified the lysosomal hydrolase-coordinating transcription factor EB (TFEB) as novel regulator of the human MuRF1 promoter. TFEB played a key role in regulating Ang II-induced skeletal muscle atrophy by transcriptional control of MuRF1 via conserved E-box elements. Inhibiting TFEB with small interfering RNA prevented Ang II-induced MuRF1 expression and atrophy. The histone deacetylase-5 (HDAC5), which was directly bound to and colocalized with TFEB, inhibited TFEB-induced MuRF1 expression. The inhibition of TFEB by HDAC5 was reversed by PKD1, which was associated with HDAC5 and mediated its nuclear export. Mice lacking PKD1 in skeletal myocytes were resistant to Ang II-induced muscle wasting.ConclusionWe propose that elevated Ang II serum concentrations, as occur in patients with congestive heart failure, could activate the PKD1/HDAC5/TFEB/MuRF1 pathway to induce skeletal muscle wasting.
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