Identification of mitochondria-related hub genes in sarcopenia and functional regulation of MFG-E8 on ROS-mediated mitochondrial dysfunction and cell cycle arrest

Sarcopenia has high prevalence in the elderly population, but the genes and pathways related to aging in elderly patients with sarcopenia are poorly understood. Milk fat globule epidermal growth factor 8 (MFG-E8) is a peripheral membrane glycoprotein isolated from the milk fat globule membrane (MFGM). It has been found to exhibit various nutritional effects, including antibacterial, anti-cancer, anti-oxidant, anti-sarcopenia, and improving brain development and cognitive effects. This study aimed to investigate key differentially expressed genes (DEGs) and pathways associated with the progression of sarcopenia using bioinformatics analysis and in vitro myoblast experiment. The gene expression profiles of GSE8479 and GSE9676, which includes 40 young normal samples and 55 elderly samples, were downloaded from the Gene Expression Omnibus Database (GEO). Over 3253 DEGs were identified in the young and elderly samples (adjusted p value <0.05). A total of 213 co-expressed significantly DEGs were identified with Venn diagrams, including 82 up-regulated DEGs and 131 down-regulated DEGs. Based on the analysis of Gene Ontology (GO), protein-protein interaction (PPI) networks and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, 10 hub genes screened by our study have been proved to play a role in regulating the occurrence and development of aging-related sarcopenia mainly via metabolic pathways, Huntington's disease, Parkinson's disease, oxidative phosphorylation and non-alcoholic fatty liver disease pathways. To further verify the protective effect of MFG-E8 on oxidative stress injured myoblasts, the cell cycle distribution, cell viability and reactive oxygen species (ROS) production were measured. The protein and mRNA levels of Akt, extracellular regulated protein kinases (ERK), p21Cip1, p27Kip1, cyclin D1, cyclin E1, cyclin-dependent kinase (CDK) 2 and 4 were quantified using qRT-PCR and western blot analysis. The results indicated that MFG-E8 has potential anti-sarcopenia effects by promoting ERK and Akt activation-mediated cell proliferation and cell cycle progression in myoblasts.