Hepatoprotective effects of the branched-chain fatty acids 12-methylmyristic and 13-methylmyristic against palmitate-induced lipotoxicity.

Dysregulated metabolism of saturated fatty acids (SFAs) in the liver is a hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD), contributing to lipotoxicity and insulin resistance in hepatocytes. While SFAs such as palmitic acid (PA) and myristic acid (MA) are altered in patients with obesity and MASLD, the role of branched-chain fatty acids (BCFAs) remains less well defined. This study aimed to evaluate hepatic BCFAs signatures in MASLD and their effects in in vitro models of PA-induced lipotoxicity. Hepatic BCFAs levels were evaluated in 91 patients with severe obesity using GC-MS. The effects of PA, MA, and specific BCFAs (13-methylmyristic acid (13-MMA) and 12-methylmyristic acid (12-MMA)) were tested in HepG2 cells and in patient-derived human liver organoids (HLOs) by assessing cell viability and CK-18 release. Endoplasmic reticulum (ER) stress markers expression was measured by RT-qPCR. Results showed that hepatic BCFAs were significantly altered in patients with MASLD, particularly 12-MMA and 13-MMA. Furthermore, 12-MMA/MA and 13-MMA/MA ratios were reduced in the presence of MASLD, negatively correlating with histopathological features. In both HepG2 cells and HLOs, PA induced cytotoxicity and CK-18 release, whereas co-incubation with 12-MMA and 13-MMA, but not MA, mitigated cell death and reduced CK-18 levels. Furthermore, BCFAs alleviated ER stress marker expression in PA-treated HepG2 cells. Our findings suggest that both 12-MMA and 13-MMA may exert a hepatoprotective effect against PA-lipotoxicity in human hepatic cell models, highlighting the potential relevance of BCFAs in mitigating liver damage associated with MASLD.