抄録
Recent advances and future perspectives in the health beneficial peptides derived from food proteins related to the ameliorative effect on cholesterol metabolism are described. The hypocholesterolemic milk peptides, soybean peptides, meat peptides, egg peptides, royal jelly peptides or fish peptides are mainly described in this chapter.
For example, lactostatin (IIAEK) is the first identified hypocholesterolemic pentapeptide derived from bovine milk β-lactoglobulin in rats by our group. Lactostatin inhibits intestinal cholesterol absorption in Caco-2 cells (model for human intestine) and rats accompanying a hypocholesterolemia. Lactostatin activates cholesterol 7a-hydroxylase (CYP7A1) gene expression of the rate-limiting enzyme for cholesterol degradation through a new regulatory pathway in the calcium-channel-related MAPK signaling in HepG2 cells (model for human liver). The effects of a crude type of soy protein hydrolysate with bound phospholipids (CSPHP) on cholesterol metabolism were compared with the effects of soy protein hydrolysate with bound phospholipids (SPHP), soy protein peptic hydrolysate (SPH) and casein. Serum and liver cholesterol levels were significantly decreased with CSPHP, SPHP and SPH feeding compared with casein feeding. Daily intake of only 3 g CSPHP for 3 months reduced both serum total cholesterol and LDL cholesterol levels of the hypercholesterolemic patients.
Soystatin (VAWWMY), with a high taurocholate binding activity derived from soybean glycinin, is the first identified inhibitory peptide of intestinal cholesterol absorption in rats. By an exhaustive screening by peptide array, soystatin could enhance its hypocholesterolemic activity. The peptide array technology will be able to promote progress in peptide research.
The cattle heart protein hydrolysate (HPH) ameliorates hypercholesterolemia accompanied by the suppression of cholesterol absorption in rats and Caco-2 cells. The cattle heart protein hydrolysate ultra-filtrate (HPHU, MW < ca. 1,000 Da peptides fraction) derived from HPH imparts a stronger hypocholesterolemic activity than HPH in rats.
To identify the hypocholesterolemic peptide derived from egg white protein (ovalbumin), CYP7A1 activated peptide has been screened. CYP7A1 mRNA levels significantly increased by GLWEK compared with the control. GLWEK, which we named ovocholestin, was identified as a CYP7A1 activated peptide derived from ovalbumin in HepG2 cells.
The cholesterol-lowering action induced by MRJP1 (Major Royal Jelly Protein) occurs because MRJP1 interacts with bile acids inducing a significant increase in fecal bile acid excretion and a tendency to increase fecal cholesterol excretion and also enhance the hepatic cholesterol catabolism. We have identified, for the first time, a novel hypocholesterolemic protein, MRJP1, in RJ.
