GSK3B and chronic kidney disease: These are elevated in patients beginning with the early stages of CKD, and their levels vary in patients at the same stage of CKD (refs. 23–26 and Supplemental Table 2) because their levels are influenced by dietary intake of Trp and processing by intestinal microbiome, etc. ECs expressing LS were exposed to these solutes at concentrations observed in CKD patients in the absence (Wnt-off phase) or presence of lithium chloride, a known inhibitor of GSK-3β and Wnt activator (Wnt-on phase; refs. 27, 28 and Supplemental Figure 7A).