C5 and diabetic kidney disease: Increased complement activation promotes the production of complement end products anaphylatoxins C3a and C5a, which activate G-protein-coupled receptors, C3aR and C5aR1, leading to overproduction of reactive oxygen species (ROS) and inflammatory cytokines, thereby resulting in inflammation in DKD (Tan et al., 2022; Wang P. et al., 2021).