FN1 and obesity due to melanocortin 4 receptor deficiency: Adipose tissue (AT) is a connective tissue in which cells are embedded in a dense extracellular matrix (ECM) composed of structural proteins (collagens, elastin) and adhesion proteins (fibronectin, proteoglycans and so on), which ensure its mechanical stability, strength and elasticity.3 Obesity is associated with profound remodelling of AT's ECM that can lead to the establishment of fibrosis.4 Together with chronic inflammation, macrophage infiltration and adipocyte hypertrophy, these changes characterise AT dysfunction of obesity and insulin resistance.