Intriguingly, SIM1 plays a crucial role in the development of the Drosophila brain, and its impairment was linked to obesity and high leptin levels in mice, although the underlying mechanisms are not entirely clear, providing further evidence of the connections between neuroendocrine signaling pathways and MetS [65,76,77]. This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.