Pentapeptide IIAEK ameliorates cholesterol metabolism via the suppression of intestinal cholesterol absorption in mice.

Dietary protein-derived peptides are effective in improving dyslipidemia and hypercholesterolemia. We previously identified a novel cholesterol-lowering pentapeptide IIAEK from milk beta-lactoglobulin. However, it remains unclear whether IIAEK affects the micellar solubility of cholesterol and the bile acid-binding ability to lower cholesterol. Moreover, there is no direct evidence that IIAEK inhibits intestinal cholesterol absorption and affects hepatic cholesterol and fecal steroid excretion in vivo. Herein, we showed that IIAEK did not affect the micellar solubility of cholesterol and the bile acid-binding ability. However, we found that IIAEK decreased serum and liver cholesterol levels and increased fecal steroid excretion in mice. Interestingly, IIAEK markedly suppressed the intestinal absorption of [3H]-cholesterol in mice. In conclusion, we found that IIAEK ameliorated cholesterol metabolism by suppressing intestinal cholesterol absorption without affecting in vitro micellar solubility of cholesterol and the bile acid-binding ability in mice.

The physiological blood concentration of phenylalanine-proline can ameliorate cholesterol metabolism in HepG2 cells.

We have previously reported that the dipeptide Phe-Pro affects lipid metabolism in vivo and in vitro, but very little is known regarding the mechanism of action of Phe-Pro after it is absorbed by the intestines via PepT1. In this study, we administered a single oral dose of Phe-Pro to rats and quantified its concentration in the portal plasma using LC-TOF/MS analysis. Additionally, the physiological blood concentration of Phe-Pro was added to the lipid accumulation model of HepG2 cells to decrease intracellular cholesterol and increase the expression of CYP7A1 and PPARα mRNA levels. Moreover, we analyzed the binding of PPARα and Phe-Pro using AlphaFold2. We found that Phe-Pro is a ligand for PPARα. To the best of our knowledge, this is the first study that shows Phe-Pro to be present in the portal plasma. We found for the first time that Phe-Pro ameliorated cholesterol metabolism in HepG2 cells.