FN1 and obesity due to melanocortin 4 receptor deficiency: Fibronectin, which in this report was decreased in cats with obesity, is a 500–600 kDa multifunctional glycoprotein that plays a major role in cell adhesion, growth, migration, and differentiation, and it is important for processes such as cell morphology, adipogenesis, and insulin signaling of adipocytes in vitro [34].