Senescent myoblasts exhibit an altered exometabolome that is linked to senescence-associated secretory phenotype (SASP) signalling.

Cellular senescence has been implicated in the aging-related dysfunction of satellite cells, the resident muscle stem cell population primarily responsible for the repair of muscle fibres. Despite being in a state of permanent cell cycle arrest, these cells remain metabolically active and release an abundance of factors that can have detrimental effects on the cellular microenvironment. This phenomenon is known as the senescence-associated secretory phenotype (SASP), and its metabolic profile is poorly characterized in senescent muscle. In the present investigation, we examined the intracellular and extracellular metabolome of C ₂ C ₁₂ myoblasts using a bleomycin-mediated model of DNA damage-induced senescence. We also evaluated the relationship between the senescent metabolic phenotype and SASP signalling through molecular and network-based analyses. Senescent myoblasts exhibited a significantly altered extracellular metabolome ( i.e. exometabolome), including increased secretion of several aging-associated metabolites. Four of these metabolites - trimethylamine- N -oxide (TMAO), xanthine, choline, and oleic acid - were selected for individual dose-response experiments to determine if they could drive the senescence phenotype. While most of the tested metabolites did not independently alter senescence markers, oleic acid treatment of healthy myoblasts significantly upregulated the SASP genes Ccl2 , Cxcl12 , and Il33 ( p <0.05). A gene-metabolite interaction network further revealed that oleic acid was one of the most interconnected metabolites to key senescence-associated genes. Notably, oleic acid interacted with several prominent SASP genes, suggesting a potential epigenetic effect between this monounsaturated fatty acid and SASP regulation. In summary, the exometabolome, particularly oleic acid, is implicated in SASP signalling within senescent myoblasts.