The Interplay Between Cellular Senescence and Lipid Metabolism in the Progression of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD).

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), is now recognized as the leading cause of chronic liver disease worldwide. MASLD spans a spectrum ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH) and is linked to progressive fibrosis and ultimately hepatocellular carcinoma (HCC). Growing evidence implicates cellular senescence (CS) and lipid droplets (LDs) as key drivers of disease progression, although their interaction remains poorly characterized. This review provides an integrative and stage-dependent synthesis of current mechanistic insights into how bidirectional crosstalk between CS and LD regulation shapes the transition from steatosis to MASH. Senescent hepatocytes display altered lipid metabolism, including upregulation of receptors such as cluster of differentiation (CD) 36, enhancing lipid uptake to meet increased energy demands. Initially, elevated free fatty acid influx can activate peroxisome-proliferator-activated receptor alpha (PPARα), promoting fatty acid oxidation (FAO) as a compensatory response. Over time, persistent CS under steatotic conditions leads to mitochondrial dysfunction and suppression of fatty acid oxidation (FAO), while the senescence-associated secretory phenotype (SASP), largely driven by nuclear factor-kappa B (NF-κB) signaling, promotes chronic hepatic inflammation. By framing LDs as active modulators of senescence-associated signaling rather than passive lipid stores, this review highlights how disruption of senescence-lipid feedback loops may represent a disease-modifying opportunity in MASLD progression.