METRNL and diabetic kidney disease: The Western blot and qRT-PCR findings for mouse kidney tissues indicated that the expression of TNF-α, TGF-β1, TGF-R1, pSmad2, pSmad3, and α-SMA proteins was increased in the DKD, Metrnl-/-, and Metrnl+/+ groups compared to the NC + NS group (P < 0.05).