Background: Satellite cells (SCs) are critical to skeletal muscle regeneration. Inactivation of SCs is linked to skeletal muscle loss. Transferrin receptor 1 (Tfr1) is associated with muscular dysfunction as muscle‐specific deletion of Tfr1 results in growth retardation, metabolic disorder, and lethality, shedding light on the importance of Tfr1 in muscle physiology. However, its physiological function regarding skeletal muscle ageing and regeneration remains unexplored. Methods: RNA sequencing is applied to skeletal muscles of different ages to identify Tfr1 associated to skeletal muscle ageing. Mice with conditional SC ablation of Tfr1 were generated. Between Tfr1 ^SC/WT and Tfr1 ^SC/KO ( n = 6–8 mice per group), cardiotoxin was intramuscularly injected, and transverse abdominal muscle was dissected, weighted, and cryosectioned, followed by immunostaining, haematoxylin and eosin staining, and Masson staining. These phenotypical analyses were followed with functional analysis such as flow cytometry, tread mill, Prussian blue staining, and transmission electron microscopy to identify pathological pathways that contribute to regeneration defects. Results: By comparing gene expression between young (2 weeks old, n = 3) and aged (80 weeks old, n = 3) mice among four types of muscles, we identified that Tfr1 expression is declined in muscles of aged mice (~80% reduction, P < 0.005), so as to its protein level in SCs of aged mice. From in vivo and ex vivo experiments, Tfr1 deletion in SCs results in an irreversible depletion of SCs (~60% reduction, P < 0.005) and cell‐autonomous defect in SC proliferation and differentiation, leading to skeletal muscle regeneration impairment, followed by labile iron accumulation, lipogenesis, and decreased Gpx4 and Nrf2 protein levels leading to reactive oxygen species scavenger defects. These abnormal phenomena including iron accumulation, activation of unsaturated fatty acid biosynthesis, and lipid peroxidation are orchestrated with the occurrence of ferroptosis in skeletal muscle. Ferroptosis further exacerbates SC proliferation and skeletal muscle regeneration. Ferrostatin‐1, a ferroptosis inhibitor, could not rescue ferroptosis. However, intramuscular administration of lentivirus‐expressing Tfr1 could partially reduce labile iron accumulation, decrease lipogenesis, and promote skeletal muscle regeneration. Most importantly, declined Tfr1 but increased Slc39a14 protein level on cellular membrane contributes to labile iron accumulation in skeletal muscle of aged rodents (~80 weeks old), leading to activation of ferroptosis in aged skeletal muscle. This is inhibited by ferrostatin‐1 to improve running time ( P = 0.0257) and distance ( P = 0.0248). Conclusions: Satellite cell‐specific deletion of Tfr1 impairs skeletal muscle regeneration with activation of ferroptosis. This phenomenon is recapitulated in skeletal muscle of aged rodents and human sarcopenia. Our study provides mechanistic information for developing novel therapeutic strategies against muscular ageing and diseases.

Clarifying mechanisms underlying the ecological succession of gut microbiota is a central theme of gut ecology. Under experimental manipulations of zebrafish hatching and rearing environments, we test our core hypothesis that the host development will overwhelm environmental dispersal in governing fish gut microbial community succession due to host genetics, immunology, and gut nutrient niches. We find that zebrafish developmental stage substantially explains the gut microbial community succession, whereas the environmental effects do not significantly affect the gut microbiota succession from larvae to adult fish. The gut microbiotas of zebrafish are clearly separated according to fish developmental stages, and the degree of homogeneous selection governing gut microbiota succession is increasing with host development. This study advances our mechanistic understanding of the gut microbiota assembly and succession by integrating the host and environmental effects, which also provides new insights into the gut ecology of other aquatic animals.

Insomnia is a type of sleep disorder which is associated with various diseases’ development and progression, such as obesity, type II diabetes and cardiovascular diseases. Recent investigation of the gut-brain axis enhances our understanding of the role of the gut microbiota in brain-related diseases. However, whether the gut microbiota is associated with insomnia remains unknown. In the present investigation, leveraging the 16S rDNA amplicon sequencing of V3-V4 region and the novel bioinformatic analysis, it was demonstrated that between insomnia and healthy populations, the composition, diversity and metabolic function of the gut microbiota are significantly changed. Other than these, redundancy analysis, co-occurrence analysis and PICRUSt underpin the gut taxa composition, signaling pathways, and metabolic functions perturbed by insomnia disorder. Moreover, random forest together with cross-validation identified two signature bacteria, which could be used to distinguish the insomnia patients from the healthy population. Furthermore, based on the relative abundance and clinical sleep parameter, we constructed a prediction model utilizing artificial neural network (ANN) for auxiliary diagnosis of insomnia disorder. Overall, the aforementioned study provides a comprehensive understanding of the link between the gut microbiota and insomnia disorder.

Nonalcoholic steatohepatitis (NASH) is a key step in the progression of nonalcoholic fatty liver (NAFL) to cirrhosis. However, the molecular mechanisms of the NAFL-to-NASH transition are largely unknown. Here, we identify methyltransferase like 3 (METTL3) as a key negative regulator of NASH pathogenesis. Hepatocyte-specific deletion of Mettl3 drives NAFL-to-NASH progression by increasing CD36-mediated hepatic free fatty acid uptake and CCL2-induced inflammation, which is due to increased chromatin accessibility in the promoter region of Cd36 and Ccl2. Antibody blockade of CD36 and CCL2 ameliorates NASH progression in hepatic Mettl3 knockout mice. Hepatic overexpression of Mettl3 protects against NASH progression by inhibiting the expression of CD36 and CCL2. Mechanistically, METTL3 directly binds to the promoters of the Cd36 and Ccl2 genes and recruits HDAC1/2 to induce deacetylation of H3K9 and H3K27 in their promoters, thus suppressing Cd36 and Ccl2 transcription. Furthermore, METTL3 is translocated from the nucleus to the cytosol in NASH, which is associated with CDK9-mediated phosphorylation of METTL3. Our data reveal a mechanism by which METTL3 negatively regulates hepatic Cd36 and Ccl2 gene transcription via a histone modification pathway for protection against NASH progression.

The diagnosis of endometriosis is typically delayed by years for the unexclusive symptom and the traumatic diagnostic method. Several studies have demonstrated that gut microbiota and cervical mucus potentially can be used as auxiliary diagnostic biomarkers. However, none of the previous studies has compared the robustness of endometriosis classifiers based on microbiota of different body sites or demonstrated the correlation among microbiota of gut, cervical mucus, and peritoneal fluid of endometriosis, searching for alternative diagnostic approaches. Herein, we enrolled 41 women (control, n = 20; endometriosis, n = 21) and collected 122 well-matched samples, derived from feces, cervical mucus, and peritoneal fluid, to explore the nature of microbiome of endometriosis patients. Our results indicated that microbial composition is remarkably distinguished between three body sites, with 19 overlapped taxa. Moreover, endometriosis patients harbor distinct microbial communities versus control group especially in feces and peritoneal fluid, with increased abundance of pathogens in peritoneal fluid and depletion of protective microbes in feces. Particularly, genera of Ruminococcus and Pseudomonas were identified as potential biomarkers in gut and peritoneal fluid, respectively. Furthermore, novel endometriosis classifiers were constructed based on taxa selected by a robust machine learning method. These results demonstrated that gut microbiota exceeds cervical microbiota in diagnosing endometriosis. Collectively, this study reveals important insights into the microbial profiling in different body sites of endometriosis, which warrant future exploration into the role of microbiota in endometriosis and highlighted values on gut microbiota in early diagnosis of endometriosis.

Maintaining glucose and lipid homeostasis is crucial for health, with dysregulation leading to metabolic diseases such as type 2 diabetes mellitus (T2DM) and metabolic dysfunction–associated fatty liver disease (MAFLD). This study identifies alkylation repair homolog protein 5 (ALKBH5), an RNA N ⁶ -methyladenosine (m ⁶ A) demethylase, as a major regulator in metabolic disease. ALKBH5 is up-regulated in the liver during obesity and also phosphorylated by protein kinase A, causing its translocation to the cytosol. Hepatocyte-specific deletion of Alkbh5 reduces glucose and lipids by inhibiting the glucagon receptor (GCGR) and mammalian target of rapamycin complex 1 (mTORC1) signaling pathways. Targeted knockdown of hepatic Alkbh5 reverses T2DM and MAFLD in diabetic mice, highlighting its therapeutic potential. This study unveils a regulatory mechanism wherein ALKBH5 orchestrates glucose and lipid homeostasis by integrating the GCGR and mTORC1 pathways, providing insight into the regulation of metabolic diseases.