Among the possible SCZ pathways, the serotonergic pathways may have a role in T2D as well.87, 88 Inhibition of peripheral serotonin synthesis reduces obesity and metabolic dysfunction,87 while increased expression of 5-HT2C receptors in pancreatic beta cells may inhibit insulin secretion.88 The dopaminergic and serotoninergic pathway interact; mutant mice over-expressing DR2D receptors in the striatum, exhibit both decreased willingness to work for reward, as well as upregulation of 5-HT2C receptors, which may lead to impaired insulin secretion.89 This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.