In response to various extrinsic and intrinsic factors, such as a sedentary lifestyle, obesity, hyperglycaemia, oxidative and ER stress and genetic and epigenetic reprogramming, the activation of inflammatory signalling pathways, such as the Jun N-terminal kinase (JNK) and nuclear factor-κ B (NF-κB) pathways, induces the constitutive production of inflammatory mediators. The gene discussed is MAPK8; the disease is obesity due to melanocortin 4 receptor deficiency.