PROBLEM TO BE SOLVED: To provide an active ingredient of treatment and/or preventive medicine for diabetes associated with a selenium-containing protein, particularly type 2 diabetes mellitus.SOLUTION: The invention provides an antibody which epitopes a specific region of selenoprotein P which is a glycoprotein of 69 kDa (362 amino acids) biosynthesized mainly by a liver (within the 204th to 261st amino acid sequences, preferably the 204th to 254th amino acid sequences, more preferably the 204th to 217th amino acid sequences). The antibody has at least one structure selected from immunoglobulin, F(ab), Fab, Fv, scFv, tetra body, and mini body. The antibody inhibits incorporation of selenoprotein P into the cell, and suppresses increased gluthatione peroxidase in intracellular, and is useful as the treatment and/or preventive agent of diabetes, particularly type 2 diabetes mellitus.
