Analysis of bile acid profiles and AD markers revealed that bile acid ratios, such as glycochenodeoxycholic acid (GDCA)/cholic acid (CA), taurodeoxycholic acid (TDCA)/CA, and glycocholic acid (GLCA)/chenodeoxycholic acid (CDCA), negatively correlate with Aβ1-42 levels in cerebrospinal fluid (CSF), while glycochenodeoxycholic acid (GCDCA), GLCA, and taurolithocholic acid (TLCA), positively correlate with phosphorylated tau protein [12]. The gene discussed is MAPT; the disease is Alzheimer disease.