Integrated Multi-Omics Profiling reveals MASH-Driven Metabolic Dysregulation and Highlights Perilipin-2 (PLIN2) as a Biomarker of Disease Severity

The rising prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) represents a major public health concern and it is strongly associated with comorbidities such as type 2 diabetes (T2D) and obesity; individuals with T2D and obesity have a higher risk of developing MASLD and its progressive form, MASH. The gold standard for diagnosis of MASH is liver biopsy; however, this procedure is invasive, costly and scoring is subjective. In this context, the development of non-invasive tests (NITs) is needed. Advances in omics techniques, in particular metabolomics and lipidomics, offer new opportunities to better understand metabolic alterations and to identify new biomarkers for diagnosis, monitoring and therapeutic targeting. The aims of this thesis were: (1) to characterize the metabolomic and lipidomic profiles of individuals with MASH, obesity and T2D to identify metabolites capable of discriminating those at-risk MASH; (2) to determine whether the expression of Perilipin-2 (PLIN2), a lipid droplet-associated protein, in monocytes is associated with a distinct metabolomic/lipidomic signature; (3) to evaluate whether bariatric surgery leads to greater improvements in metabolomic/lipidomic profiles compared with intensive lifestyle modification (ILM) after 3 years. Metabolomics and lipidomics revealed that individuals with MASH and obesity exhibit metabolic alterations. Specifically, they showed higher levels of branched-chain amino acids (BCAAs), aromatic amino acids (AAAs), TCA cycle intermediates and altered lipid metabolism characterized by higher concentration of triglycerides (TAGs), diglycerides (DAGs), ceramides (CER) and sphingomyelins (SM) compared to subjects without MASH and obesity. Obesity emerged as the primary driver of these alterations, whereas T2D status did not significantly influence them. Eleven metabolites and lipids were identified as predictors of at-risk-MASH. PLIN2 expression in monocytes mirrored this altered metabolism, being increased in subjects with MASH and obesity, with no significant differences due to T2D. PLIN2 was also correlated with clinical variables and metabolites even after adjustment for clinical parameters. In this population, PLIN2 alone and PLIN2 combined with ALT showed a better discriminatory performance for identifying individuals at-risk MASH compared with FIB-4. Given that obesity is a major determinant of MASH, weight loss interventions are essential. Bariatric surgery (BS) is one of the most widely used treatments for weight loss and is also effective for T2D remission. After three years, individuals who underwent BS showed significant improvements in clinical variables, liver histology and metabolomic/lipidomic profiles compared to those who followed intensive lifestyle modification (ILM). Notably, improvements were observed in BMI, glycemic control, lipid and energy metabolism, bringing them closer to individuals without MASH and obesity. In conclusion, individuals with MASH and obesity showed an altered metabolism primarily driven by obesity. PLIN2 may serve as a useful biomarker for identifying metabolic impairment and, together with clinical variables, for distinguishing individuals at-risk MASH. BS leads to more pronounced metabolic improvements than ILM, aligning the metabolic profiles more closely to subjects without obesity and MASH.