Examples of genes upregulated by AD also included ceramide synthases CERS1 and CERS2, S1P lyase SGPL1, or serine palmitoyltransferase catalytic subunit SPTLC2, while the acid ceramidase ASAH1, ceramide kinase CERK, or—less obviously—CERS6 were reduced [131, 149]. Here, SGPL1 is linked to Alzheimer disease.