Overnutrition is a risk factor for metabolic diseases such as nonalcoholic fatty liver disease (NAFLD), insulin resistance, and cancer. Macrophages play a crucial role in regulating tissue homeostasis, however, the mechanisms by which metabolic overload affects macrophage function across tissues remains incompletely understood. We hypothesise that distinct macrophage-derived signals drive metaflammation in tissues through paracrine action on neighbouring cells and infiltrating immune cells. Due to technical limitations in studying macrophage-derived signals in vivo comprehensively, however, few of these signals have been discovered and studied mechanistically.

In this project, we will develop mass spectrometry-based proteomics methods, including cell type-specific labelling, to dissect macrophage-derived signals in vivo with mass spectrometry (MS)-based proteomics. Building on MS and computational methods we have established recently for the characterization of cell-to-cell communication, we will generate a comprehensive intercellular signalling network during high-fat diet (HFD) in mouse tissues with a focus on the liver, which plays a central role in managing metabolic signalling. We will complement our proteomics approaches with whole tissue and single cell analysis to identify altered intercellular signalling proteins and communication pathways between macrophages and tissue-resident as well as infiltrating immune cells. We will test the functional relevance of discovered common and tissue-specific single intercellular signalling proteins as well as pathways for pathology through interference with antibodies or recombinant proteins as in vitro and in vivo. Together, this project will generate a system-level view on paracrine macrophage signals in tissues and provide the basis for new hypotheses to target macrophages in order to attenuate or revert metaflammatory conditions.