N-Acetyl-D-mannosamine (ManNAc) is an essential precursor of N-acetylneuraminic acid (NeuAc), the specific monomer of bacterial capsular polysialic acid (PA).N-Acetyl-D-mannosamine (ManNAc) can be metabolized by GNE and GlcNAc 2-epimerase (Renin binding protein, RnBP), into ManNAc-6-phosphate and GlcNAc, respectively.?N-Acetyl-d-mannosamine (ManNAc) and its derivatives activates hypocretin (HCRT) gene expression in the orexin neurons, providing a potential model for the testing of a therapy for neural disorders[2].