Although the mechanisms underlying muscle atrophy have been clarified, those governing the rates of muscle protein synthesis and degradation are not fully understood. The present study focused on 3-methylhistidine as a measure of the rate of protein degradation rate in skeletal muscle using the samples from urine, plasma, isolated muscles tissue and cultured cells. Ingestion of leucine or lysine suppressed protein degradation in skeletal muscle of rats, and these amino acids were found to down-regulate autophagy through Akt. The effects of lysine were also demonstrated in Senescence Accelerated Mouse Prone (SAMP) 8, a mouse model of sarcopenia in aging. Thus, ingestion of the amino acids can modulate the degradation as well as synthesis of muscle protein, and could be applied for suppression of muscle atrophy related to under-nutrition, diseases and aging.

We have identified, for the first time, a novel hypocholesterolemic pentapeptide (lactostatin: IIAEK) derived from bovine milk β-lactoglobulin in rats. Lactostatin activates expression of the gene for cholesterol 7α-hydroxylase (CYP7A1) , the rate-limiting enzyme for cholesterol degradation, through a new regulatory pathway involving calcium-channel-related MAPK signaling in HepG2 cells. The novel soy protein hydrolysate with bound phospholipids exerts an excellent hypocholesterolemic effect in patients with hypercholesterolemia. Soystatin (VAWWMY) , derived from soybean glycinin, is the first inhibitory peptide of intestinal cholesterol absorption in rats to have been identified. The peptide array is able to enhance the hypocholesterolemic activity of soystatin. Cattle heart protein hydrolysate or rice bran protein ameliorates hypercholesterolemia accompanied by suppression of cholesterol absorption in rats. GLWEK (ovocholestin) was identified as a CYP7A1 activated peptide derived from ovalbumin in HepG2 cells. We have identified, for the first time, a novel hypocholesterolemic protein, MRJP (Major Royal Jelly Protein) 1 in RJ or C-phycocyanin in Spirulina platensis. Our study has contributed to the development of a food for specified health use containing S-methyl-L-cysteine sulfoxide exerting a hypocholesterolemic action. Epigallocatechin gallate induces up-regulation of the LDL receptor accompanied by a reduction of atherogenic PCSK9 via the annexin A2-independent pathway.

Alkaline phosphatase (ALP) hydrolyzes monophosphate esters. Intestinal ALP is localized in the small intestine, and has been suggested to be associated with dietary factors, but the physiological function of intestinal ALP has remained elusive. In this study, we investigated the influence of vitamin D on ALP expression in Caco-2 cells, which differentiate into human intestinal epithelial-like cells. The cells were incubated for 14 days after reaching confluency, and specific concentrations of 1,25(OH)₂D₃ (0, 10, and 100 nM) were added. It was found that the ALP activities and intensities of human intestinal ALP gene expression in the 1,25(OH)₂D₃-treated groups (100 nM) were significantly higher than in the control group (0 nM) on days 3, 5, and 7. The intensities of sucrase-isomaltase gene expression in Caco-2 cells were not enhanced by 1,25(OH)₂D₃. The present study has thus demonstrated that expression of intestinal ALP is enhanced by 1,25(OH)₂D₃, and these results will provide useful data for clarifying the novel physiological functions of vitamin D through regulation of human intestinal ALP activity.