Alterations in hepatic amino acid metabolism related to MASLD in individuals with obesity.

Deregulation of amino acid (AA) metabolism has been reported in several pathological conditions, including metabolic diseases (e.g., obesity and diabetes), cardiovascular diseases, and cancer. However, the role of alterations in AA levels in chronic liver disorders such as metabolic dysfunction-associated steatotic liver disease (MASLD) remains largely unexplored. In this study we aimed to evaluate the hepatic AA composition in patients with different stages of MASLD, and their relationship with MASLD-related risk factors. A case-control study was conducted in 40 patients with obesity undergoing bariatric surgery at Virgen de la Arrixaca University Hospital (Murcia, Spain), where MASLD diagnosis was confirmed by histological analysis of liver biopsies, and hepatic AA levels were measured using ultra-performance liquid chromatography high-resolution time-of-flight mass spectrometry. Our results revealed that the hepatic AA profile was significantly altered in patients with MASLD. More specifically, comparison between MASLD patients revealed a significant increase in hepatic levels of arginine, glycine and cystine in MASH samples compared to steatotic livers. In addition, hepatic concentrations of arginine, lysine and cystine positively correlated with histopathological diagnosis and other MASLD-related parameters, including transaminases and CK-18 levels. These findings suggest that alterations in certain hepatic AA levels such as arginine, lysine, glycine and cystine in MASLD patients could have translational relevance in understanding the onset of this disease.