Sitagliptin protects the diabetic ZDF rats against endocrine pancreas apoptotic cell death. Upper panel (A-C) - pancreas mRNA expression of Bax and bcl2 in 26 week-old ZDF rats: A significant increase (p < 0.05) in apoptotic protein Bax (A), as well as, in antiapoptotic Bcl2 (B) was observed in the untreated diabetic ZDF rats when compared with the lean control ZDF animals, resulting in an unchanged Bax/Bcl2 ratio (C). In the sitagliptin-treated diabetic rats an overexpression of the mRNA was registered for both Bax (not statically significant) and Bcl2 (p < 0.001) ensuing a reduced Bax/Bcl2 ratio (C). Middle panel (D-I) - Immunostaining of pancreas Bax and Bcl2 in 26 week-old ZDF rats: (D) The expression of Bax protein is not present in the pancreatic islet (grade 0) of a lean control rat; (E) A deeply stained islet (grade 3) revealing Bax protein expression in untreated diabetic ZDF rat; (F) The diabetic sitagliptin-treated rats displayed a light stained islet (grade 1); (G) Expression of Bcl2 protein not observed in islet (grade 0) of a lean control rat; (H) A moderately stained islet (grade 2) with Bcl2 antibody in an untreated diabetic ZDF rat; (I) An intensely stained islet (grade 3) in a diabetic sitagliptin-treated rat. Lower panel (J-L) - Quantification of protein expression: Bax protein expression in diabetic untreated rats exhibited a significant increase in relation to lean control rats; in sitagliptin-treated diabetic rats, Bax presented a trend for overexpression (J), accompanied by a significantly (p < 0.001) increased expression of Bcl2 (K), resulting in a Bax/Bcl2 ratio identical to control animals (L). Statistical comparisons between groups were performed using one-way ANOVA and the post-hoc Bonferroni test (p < 0.05, p < 0.01 and p < 0.001 for one, two or three symbols, respectively; n = 5 per group).