A novel insight into the key gene signature associated with the immune landscape in the progression of sarcopenia

Decoding the Impact of Theabrownin on Skeletal Muscle Function in Gestational Diabetic Offspring: Insights from Integrated Metabolome and Transcriptome Analysis

Gestational diabetes mellitus (GDM) often leads to long-term metabolic issues, including skeletal muscle dysfunction in the offspring, with traditional managements focusing solely on blood glucose regulation and not addressing muscle metabolic and structural changes. Theabrownin (TB), a polyphenol derived from Pu-erh tea, has known antioxidant and metabolic benefits, but its effects on skeletal muscle function in GDM offspring remain unclear. In this study, GDM model was induced in mice, and their offspring were treated by TB. Transcriptomic and metabolomic analyses identified key genes and metabolites involved in lipid metabolism, oxidative stress, and inflammation. TB treatment significantly improved lipid metabolism, reduced oxidative stress, and alleviated inflammation in skeletal muscle of GDM offspring. Key genes (Fabp3, Acot1, and Acot4) and metabolites (Palmitic acid, Oleic acid) were regulated by TB. Pathway analysis revealed that TB mitigates GDM-induced skeletal muscle dysfunction through modulation of the biosynthesis of unsaturated fatty acids. These findings highlight the potential of theabrownin (TB) as a therapeutic agent for improving skeletal muscle function in the offspring of GDM through modulation of lipid metabolism. Further investigation is needed to elucidate its mechanisms and evaluate long-term effects.

Characterizing the skeletal muscle immune microenvironment for sarcopenia: insights from transcriptome analysis and histological validation

Background

Sarcopenia is a condition characterized by the age-related loss of skeletal muscle mass and function. The pathogenesis of the disease is influenced by chronic low-grade inflammation. However, the specific changes in the immune landscape changes of sarcopenic muscle are not yet fully understood.

Methods

To gain insights into the immune cell composition and interactions, we combined single-nucleus RNA sequencing data, bulk RNA sequencing dataset, and comprehensive bioinformatic analyses on the skeletal muscle samples from young, aged, and sarcopenic individuals. Histological staining was then performed on skeletal muscles to validate the distribution of immune cells in clinical samples.

Results

We analyzed the transcriptomes of 101,862 single nuclei, revealing a total of 10 major cell types and 6 subclusters of immune cell types within the human skeletal muscle tissues. Notable variations were identified in the immune microenvironment between young and aged skeletal muscle. Among the immune cells from skeletal muscle microenvironment, macrophages constituted the largest fraction. A specific marker gene LYVE1 for skeletal muscle resident macrophages was further identified. Cellular subclasses included four distinct groups of resident macrophages, which play different roles in physiological or non-physiological conditions. Utilizing bulk RNA sequencing data, we observed a significant enrichment of macrophage-rich inflammation in sarcopenia.

Conclusions

Our findings demonstrate age-related changes in the composition and cross-talk of immune cells in human skeletal muscle microenvironment, which contribute to chronic inflammation in aged or sarcopenia muscle. Furthermore, macrophages emerge as a potential therapeutic target, thus advancing our understanding of the pathogenesis of sarcopenia.

Polygonatum sibiricum polysaccharide ameliorates skeletal muscle aging via mitochondria-associated membrane-mediated calcium homeostasis regulation

BACKGROUND

Sarcopenia, an age-related disease, is characterized by a gradual loss of muscle mass, strength, and function. It has been linked to abnormal organelle function in myotubes, including the mitochondria and endoplasmic reticulum (ER). Recent studies revealed that mitochondria-associated membranes (MAM), the sites connecting mitochondria and the ER, may be implicated in skeletal muscle aging. In this arena, the potential of Polygonatum sibiricum polysaccharide (PSP) emerges as a beacon of hope. PSP, with its remarkable antioxidant and anti-senescence properties, is on the cusp of a therapeutic revolution, offering a promising strategy to mitigate the impacts of sarcopenia.

PURPOSE

The objective of this research is to explore the effects of PSP on age-related muscle dysfunction and the underlying mechanisms involved both in vivo and in vitro.

METHODS

In this investigation, we used in vitro experiments using D-galactose (D-gal)-induced aging in C2C12 myotubes and in vivo experiments on aged mice. Key indices were assessed, including reactive oxygen species (ROS) levels, mitochondrial function, the expression of aging-related markers, and the key proteins of mitochondria and MAM fraction. Differentially expressed genes (DEGs) related to mitochondria and ER were identified, and bioinformatic analyses were performed to explore underlying mechanisms. Muscle mass and function were determined to evaluate the quantity and quality of skeletal muscle in vivo.

RESULTS

PSP treatment effectively mitigated oxidative stress and mitochondrial malfunction caused by D-gal in C2C12 myotubes, preserving mitochondrial fitness and reducing MAM formation. Besides, PSP attenuated D-gal-induced increases in Ca2+ concentrations intracellularly by modulating the calcium-related proteins, which were also confirmed by gene ontology (GO) analysis of DEGs. In aged mice, PSP increased muscle mass and improved grip strength, hanging time, and other parameters while reducing ROS levels and increasing antioxidant enzyme activities in skeletal muscle tissue.

CONCLUSION

PSP offers protection against age-associated muscle impairments. The proposed mechanism suggests that modulation of calcium homeostasis via regulation of the MAM results in a favorable functional outcome during skeletal muscle aging. The results of this study highlight the prospect of PSP as a curative intervention for sarcopenia and affiliated pathological conditions, warranting further investigation.