Identification of Molecular Mechanisms by which NASH-derived Inflammation alters Hepatic Lipid Metabolism

Obesity and the metabolic syndrome, caused by high caloric intake combined with a sedentary lifestyle, are currently reaching pandemic dimensions worldwide. The hepatic consequence is an imbalance in fatty acid homeostasis, which results in hepatic lipid accumulation, a critical characteristic of non-alcoholic fatty liver disease (NAFLD). NAFLD can progress towards non-alcoholic steatohepatitis (NASH) which can ultimately lead to NASH-driven hepatocellular carcinoma (HCC). Chronic inflammation and inflammatory cytokines, derived from activated immune cells, strongly affect hepatic fatty acid metabolism and are implicated in NASH and NASH-derived HCC. However, underlying molecular mechanisms and signalling pathways are not known in detail yet.

To investigate the influence of NASH-derived inflammatory cytokines on hepatic fatty acid metabolism and to study molecular mechanisms as well as involved signalling pathways, we used several in vitro, ex vivo and in vivo experimental set-ups including fluorescence- and radioactive-labelling of lipids to focus on changes in fatty acid – uptake, de novo synthesis, storage and secretion.

Based on this, we developed a method for spatial single-cell metabolomics using MALDI-imaging and fluorescence microscopy of cell monolayers which provides metabolic profiles, fluorescence read-out and morphological features of individual cells in their native spatial context. This allows for single-cell analysis of the molecular composition of lipid droplets in hepatocytes stimulated with different NASH-derived cytokines. Thereby, we could determine single-cell molecular trends of fatty acid and cytokine treated hepatocytes. This novel method enables us to identify novel molecular mechanism and critical biological processes involved in NASH and NASH-driven HCC.