NR1H4 and diabetic kidney disease: Primary BAs are transformed into secondary bile acids (SBAs) by the gut bacteria, the latter could regulate glucose metabolism and alleviate insulin resistance and improve DKD by binding to its receptor the nuclear farnesoid X receptor (FXR) and the membrane-bound Takeda G protein-coupled receptor 5 (TGR5) (Deng L. et al., 2022; Fang Q. et al., 2021; Gao et al., 2022; Ni et al., 2022; Tanase et al., 2020; Wang Y. et al., 2022).