In this context, the downregulated protein ADCY8, upregulated protein KNG1, and serum sphingolipids (d18:1/18:0) have been associated with the nervous and immune systems, with studies indicating that cerebrospinal fluid levels of KNG1 can serve as a marker for cognitive deficits in Parkinson’s disease [27]. This evidence concerns the gene ADCY8 and Parkinson disease.