Sitagliptin prevents TRIB3 protein overexpression in pancreas of ZDF diabetic rats. Micrographs of TRIB3 expression by immunostaining in 26 week-old ZDF rats (A-C): (A) Lean ZDF control rat presenting unstained pancreatic islet (grade 0); (B) Untreated diabetic ZDF rat showing an intensely stained pancreatic islet (grade 3); (C) Sitagliptin-treated diabetic rat for 6 weeks displayed light staining of endocrine cells (grade 1). Exocrine pancreatic tissue presents normal constant staining for TRIB3 in all three groups. (D) Quantification of protein expression by score points: expression of TRIB3 is almost undetectable in control rats, rising very significantly (p < 0.001) in untreated diabetic ZDF rats; and declining very meaningfully (p < 0.001) in 6 weeks sitagliptin-treated diabetic treated rats. 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).