(A) Representative EM image of cardiac left ventricle tissue from Long–Evans Tokushima Otsuka (LETO), Otsuka Long–Evans Tokushima Fatty (OLETF), and OLETF/BH4 rats. (B) EM images of cardiac left ventricle tissue from WT, db/db, and db/db-BH4 mice. (C, D) Quantification of damaged mitochondrial proportion in hearts from LETO, OLETF, and OLETF/BH4 rats (C) and WT, db/db, and db/db-BH4 mice (n = 5/group). (C) *P < 0.05 versus LETO; #P < 0.05 versus OLETF. (D) *P < 0.05 versus WT; #P < 0.05 versus db/db.