Fig. 2

IIAEK-induced regulation of duodenal, jejunal, and hepatic mRNA levels of key genes related to cholesterol metabolism was absent in IAP-knockout (IAP-KO) (Akp3^-/-) mice. Seven-week-old wild-type (WT) and IAP-knockout (IAP-KO) (Akp3^-/-) mice were orally administered the pentapeptide IIAEK (Ile-Ile-Ala-Glu-Lys) (600 mg/kg B.W./d) once a day for 14 d. After fasting for 8 h, the duodenum, jejunum, and liver were collected from the mice. (a–e) Total RNA was collected from the duodenum, jejunum, and liver of mice. Real-time quantitative PCR was performed to the mRNA level of (a) duodenal Akp3 mRNA level, (b) jejunal Akp3 mRNA level, (c, d) duodenal and jejunal mRNA levels of key genes associated with cholesterol metabolism (Abca1, Abcg5, Abcg8, Cd36, Hmgcr, Mttp, Npc1l1, Scarb1, Soat2, and Srebf2), and (e) Liver mRNA levels of key genes associated with cholesterol metabolism (Abca1, Abcg5, Abcg8, Cd36, Cyp7a1, Fxr, Hmgcr, Ldlr, Mttp, Npc1l1, Scarb1, Soat2, and Srebf2). (f–h) Western blot analyses were performed to measure the hepatic protein levels of NPC1L1 and CYP7A1. Original blots are presented in Supplementary Fig. 2. (a, b) n = 7 mice in WT, Control group (WT, Control); n = 8 mice in WT, IIAEK group (WT, IIAEK), IAP-KO, Control group (IAP-KO, Control), and IAP-KO, IIAEK group (IAP-KO, IIAEK); (c–h) n = 6 mice per group. Data are presented as the mean ± standard error of the mean (SEM). Statistical significance was calculated using a one-way ANOVA with Tukey’s post-hoc test. Asterisks indicate significant differences between the experimental groups (* p < 0.05, ** p < 0.01).