In particular, betulinic acid treatment has been shown to attenuate renal fibrosis in the CKD rat model by inhibiting levels of pro-fibrotic protein such as TGF-β, connective tissue growth factor (CTGF), fibronectin, collagen type I, and hydroxyproline, as well as enhancing renal structure and function (Figure 5) [255]. Here, TGFB1 is linked to chronic kidney disease.