MAPK1 and chronic kidney disease: In the higher dose of the KP-13-treated CKD group, both the pERK/ERK ratio and pERK2 level showed a significant increase (*p < 0.05), and the pERK1 level tended to increase (p = 0.063) compared to the sham-operated group (Fig. 7D, E, F, and G, Figures S6 and S7).