Studio dei meccanismi cellulari influenzati da iperglicemia e infiammazione nell’obesità e nel diabete di tipo 2

Insulin resistance represents a central pathogenic feature of metabolic diseases and is tightly linked to chronic low-grade inflammation. While inflammatory cytokines are well established contributors to impaired insulin action, the molecular mechanisms through which inflammatory signalling integrates with metabolic dysfunction remain incompletely understood. In particular, the contribution of chemokine systems, traditionally studied in immune cell recruitment, to insulin resistance in metabolically active tissues is still poorly defined. This PhD thesis investigates the role of the chemokine receptors CXCR1 and CXCR2 in inflammation-driven insulin resistance, focusing on their functional involvement in the disruption of insulin signalling and cellular metabolism. Using two complementary in vitro models, differentiated 3T3-L1 adipocytes and FL83B hepatocyte-like cells, insulin resistance was induced by exposure to TNF-α, mimicking chronic inflammatory stress associated with metabolic disease. A combined transcriptional, biochemical and functional approach was employed to provide an integrated characterization of molecular signalling defects and metabolic alterations. Across both cellular models, TNF- α induced a profound impairment of the canonical insulin signalling cascade. Early and consistent reductions in IRS1 and IRS2 expression compromised signal transmission from the insulin receptor to downstream effectors, an effect further reinforced by the activation of stress-responsive kinases, particularly JNK. These proximal defects resulted in a marked attenuation of insulin- stimulated Akt phosphorylation, providing a mechanistic basis for impaired glucose handling. Functionally, these signalling alterations translated into reduced GLUT4 expression and translocation in adipocytes, decreased GLUT2 abundance in hepatocytes, and a significant reduction in insulin-stimulated glucose uptake. Beyond glucose metabolism, inflammatory stress profoundly altered cellular energy homeostasis. Both adipocytes and hepatocytes exhibited mitochondrial dysfunction, characterized by reduced basal respiration, diminished ATP production and impaired maximal respiratory capacity. These bioenergetic defects were associated with metabolic inflexibility, altered glycogen storage and, in hepatocytes, increased intracellular lipid accumulation and lipotoxic features, highlighting the integration of mitochondrial dysfunction and lipid dysregulation in insulin-resistant states. A central finding of this work is the identification of CXCR1 and CXCR2, together with their ligand CXCL1, as consistently upregulated components of the inflammatory response in insulin-resistant cells. The coordinated induction of receptors and ligand in both adipocytes and hepatocytes suggests the establishment of an autocrine/paracrine chemokine axis that actively sustains inflammatory and metabolic dysfunction. Importantly, pharmacological inhibition of CXCR1 and CXCR2 using Ladarixin partially restored insulin signalling, improved glucose uptake, enhanced mitochondrial bioenergetic performance and attenuated lipid dysregulation in both cellular models. Overall, this thesis demonstrates that inflammation-driven insulin resistance arises from the integration of signalling defects, stress pathway activation, mitochondrial dysfunction and altered substrate metabolism, and identifies the CXCR1/2 chemokine axis as a functional molecular link between inflammation and metabolic disease. By delineating the contribution of CXCR1 and CXCR2 to insulin resistance, this work provides a strong experimental foundation for considering chemokine receptor targeting as a potential therapeutic strategy to restore metabolic homeostasis in inflammatory metabolic disorders.