MAPKs are involved in various mechanisms leading to obesity, insulin resistance and diabetes, including low-level systemic inflammation; ERK1/2, JNK and p38, which are activated by a high-fat diet, promote the infiltration of monocytes/macrophages into adipose tissue, proinflammatory signalling and dysregulation of immune responses [112, 113]. The gene discussed is MAPK8; the disease is obesity due to melanocortin 4 receptor deficiency.