B2M and diabetes mellitus: In the db/db group, 20 proteins, including known diabetes-associated proteins such as Itih2, Apoc1, Timp3, B2M, Adh1, Bhmt, Apoh, C4bpa, Ctsd, Ctsb, Lgals3 and Cyb5a, were significantly altered in both serum and kidney samples, whereas only three identical proteins (Igk-V19-17, Eif5 and Ighg1) were detected in the EMPA group (Fig. 3A).