Our group has identified lactostatin (IIAEK) as the first documented hypocholesterolemic pentapeptide derived from bovine milk β-lactoglobulin that exerts an effect in rats. Lactostatin activates expression of the gene for cholesterol 7α-hydroxylase (CYP7A1), which is the rate-limiting enzyme for cholesterol degradation via a newly characterized regulatory pathway for calcium channel-related MAPK signaling in HepG2 cells. The novel soy protein hydrolysate with bound phospholipids exhibits an excellent hypocholesterolemic action in hypercholesterolemic patients. Soystatin (VAWWMY), derived from soybean glycinin, is the first peptide identified to inhibit intestinal cholesterol absorption in rats. The hypocholesterolemic activity of soystatin could be enhanced by peptide array. We have also discovered a novel cholesterol metabolism-improving dipeptide FP derived from bovine heart protein. FP acts as a ligand for the peroxisome proliferator-activated receptor and acts by improving cholesterol metabolism through PepT1. A novel cholesterol metabolism-improving tripeptide, RPR, derived from protamine exhibited effects against obesity and non-alcoholic fatty liver. In order to further develop cholesterol metabolism-improving peptide research, human trials, clarification of the molecular-level mechanism of action (including target molecule identification) and commercialization will be necessary.

Secretion of the gastrointestinal hormone glucagon-like peptide-1 (GLP-1) primarily increases after meals, exerting various physiological functions, including alleviation of postprandial hyperglycemia through promotion of insulin secretion. In animal studies we have demonstrated that various dietary proteins and peptides are able to lower glycemic responses through promotion of GLP-1 secretion. Furthermore, through the use of a GLP-1-producing cell line and a dipeptide library, we have discovered 11 new active peptides, the sequence Trp-Tyr being particularly potent for stimulating GLP-1 secretion. Dietary protein intake strongly induces postprandial thermogenesis. In rats and mice, the increase of rectal temperature (core body temperature) after oral protein administration was abolished by inhibition or knockout of the GLP-1 receptor. These findings suggest a novel physiological role for GLP-1 in the induction of postprandial thermogenesis by dietary protein. In this review, we focus on the GLP-1 secretion-promoting effects of dietary peptides, and introduce a newly discovered physiological function of GLP-1.

So far, for commercialization of bioactive peptides (BPs), they have been separated and concentrated via many laborious steps from edible protein hydrolysate obtained though optimized enzymatic reactions. We have developed a method involving heat-treated silica gel (HTSG) for simple and selective separation of BPs with specific physicochemical properties. HTSG is able to adsorb hydrophobic peptides under acidic conditions and basic peptides under alkaline conditions. For example, bitter peptides with basic and hydrophobic characteristics can be easily removed from protein hydrolysates by HTSG absorbance. In this article, we report that bile acid micelle disruption peptides, which suppress cholesterol intake, can be selected from edible protein hydrolysate and selectively concentrated by adsorption/desorption with HTSG.

Cognitive dysfunction is a serious and worldwide social issue that reduces quality of life. Despite extensive research, appropriate for ameliorating cognitive dysfunction have not yet been developed. Signs of the Alzheimer's disease may become apparent 10‐20 years before a definitive clinical diagnosis, and these are due to impairment of the acetylcholine nerve system due to amyloid β accumulation in the brain. Thus far, some human and animal studies have reported that intake of certain peptides can delay the onset of dementia. However, few evidential in vivo studies have shown that peptides can be transported across the blood-brain barrier (BBB) in intact form. In this review, we discuss BBB-transportable peptides and their potential to improve amyloid β-induced memory dysfunction.

The objectives of this study were to conduct dietary assessments using the “Japanese Food Guide Spinning Top for Pregnancy and Lactation” (Food Guide hereafter) and examine the validity of this tool. The number of servings and energy intake were calculated using the dietary record (DR) and Food Frequency Questionnaire (FFQ). Next, compliance scores were calculated to quantify and evaluate the degree of compliance of women who were either pregnant or lactating, with the number of servings and energy intake recommended in the Food Guide. The validity of the Food Guide was then determined. The correlation coefficient for total compliance scores was r = 0.316 for early pregnancy and r = 0.439 for late pregnancy. Cross-tabulation among the tertiles of total compliance scores showed that 74 women (38.1%) in early pregnancy and 71 women (46.4%) in middle-to-late pregnancy were classified in the same category. The results of the correlation coefficients, and the category agreement of compliance scores for the Food Guide, calculated from DR and FFQ, confirmed the value of the Food Guide as an index for comprehensive evaluation of the diet of pregnant Japanese women.