RARS1 and obesity due to melanocortin 4 receptor deficiency: RXR-mediated signaling, which coordinates signaling pathways with several heterodimer binding partner nuclear receptors like PPARs, LXR and NR4A as permissive and RARs and vitamin D receptor (VDR) as non-permissive partners [4,43], is selectively augmented in various neurological diseases: obesity, diabetes and further diseases of the cardiovascular system such as atherosclerosis [1,2,5].