INS and obesity due to melanocortin 4 receptor deficiency: Accumulation of the non-canonical NF-κB-inducing kinase (NIK) in obesity drives insulin resistance in the liver [10] and muscle [11] and impairs insulin secretion in pancreatic beta cells [12], whereas deletion of Map3k14, which encodes NIK, renders mice hypoglycaemic and improves glucose tolerance [10].