We examined the protective effect of tea catechin against X-ray-induced chromosomal damage using the micronucleus assay. Male ICR mice were orally administered tea catechin extract at 10-300mg/kgBW/day for 7 days, then subjected to X-ray irradiation at 0.5 Gy. The resulting chromosomal damage to bone marrow was evaluated by the micronucleus assay using peripheral blood. Tea catechin extract tended to protect the bone marrow from X-ray-induced chromosomal damage. To examine this radioprotective effect of tea catechin in more detail, human lymphoblastoid WIL2-NS cells were incubated with various concentrations of (-) -epigallocatechin3-O-gallate (EGCg), the main constituent of tea catechins, and then exposed to 0.5 Gy of X-ray radiation. The resulting chromosomal damage was evaluated by a cytokinesis-block micronucleus assay. A high dose of EGCg (10μM) protected WIL2-NS cells from X-ray-induced chromosomal damage, but a physiological dose (<1μM) did not. EGCg was markedly decomposed by X-ray irradiation, indicating a direct reaction between EGCg and X-rays. These results suggest that although tea catechin has a radioprotective effect, no such effect can be expected at a physiological dose.

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Quinoa (seeds of Chenopodium quinoa), a pseudo-cereal, has been utilized as the staple food in the Andes for many centuries. In order to popularize quinoa, quinoa was fermented with Rhizopus oligosporus to prepare quinoa-tempe (Q-tempe), and the antioxidant activities of Q-tempe and quinoa were compared. An 80% methanol extract from Q-tempe scavenged the 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical more strongly than a similar extract from quinoa. This DPPH radical scavenging activity of Q-tempe extract was unstable upon steam cooking, whereas it was improved by acidification to pH 2, which is similar level of acidity to gastric juice. To confirm the antioxidant activity of Q-tempe in vivo, rats were fed Q-tempe powder and quinoa powder. The serum and liver thiobarbituric acid-reactive substance (TBARS) values in rats fed with Q-tempe were significantly lower than those in rats fed quinoa, while hepatic glutathione peroxidase (EC 1.11.1.9) activity in rats fed Q-tempe was higher than that in rats fed quinoa. These results suggest that Q-tempe has higher antioxidant activity in vivo than quinoa.

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A placebo-controlled clinical study was undertaken to evaluate the effectiveness and most effective dose of γ-aminobutyric acid (GABA)-rich Chlorella in subjects with high-normal blood pressure and mild hypertension. Sixty adult participants (47.8±10.0 years old, mean±SD) with high-normal blood pressure or mild hypertension (systolic blood pressure: 145.3±5.9 mmHg, diastolic blood pressure: 87.7±6.5mmHg) were randomly assigned to 4 groups (15 participants per group). Participants in Groups A, B, and C ingested 2, 4, and 6g of GABA-rich Chlorella per day, respectively, and participants in Group D ingested 4g of lactose (placebo), throughout the eight-week treatment period, followed by a two-week withdrawal observation period. Systolic blood pressures in Groups B and C were significantly reduced at six and eight weeks of GABA-rich Chlorella administration in comparison with the values in the placebo group (p<0.05 and p<0.01 for Groups B and C at eight weeks). There was also a tendency for a decrease of diastolic pressure, although the differences from the control group did not reach statistical significance. Two weeks after discontinuation of GABA-rich Chlorella intake, the systolic blood pressure in Groups B and C showed a rising tendency, while no change was observed in the placebo group. No adverse events were observed, and there were no marked changes in hematological, biochemical, or urinalysis parameters during the eight-week treatment period in any of the groups. These results indicate that GABA-rich Chlorella improves blood pressure in subjects with high-normal blood pressure and mild hypertension without adverse consequences in subjective symptoms or clinical signs.

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The influences of skipping breakfast on the diurnal rhythm of salivary corticosteroids (cortisol and cortisone) in healthy humans were studied. Based on a questionnaire about dietary habits, healthy student subjects (19-22 y) were classified into two groups: Group A (18 people), those who were chosen at random from respondents who got up at about 0800h and took breakfast every day, and Group B (8 people), those who got up at about 0800h and always skipped breakfast. Saliva samples were obtained from the subjects while they maintained their usual dietary habit. Corticosteroids in the saliva were measured from the time of awakening (0800h as usual) until 1200h at intervals of 2h, and then at 1300h, 1500h and 1700h. Among the 18 subjects in Group A, 15 showed the typical diurnal rhythm, i.e., the corticosteroid peak was observed upon awakening. On the other hand, the typical rhythm was not shown in any of the subjects in Group B. Fisher's exact test indicated that this difference between the groups was significant (p=0.00011). These results suggest the dietary habit (skipping breakfast) influences the diurnal rhythm of salivary corticosteriods.

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Most in vivo cholesterol oxidation products (COP) are considered to originate from ingestion of processed foods. Although dietary COP have various deleterious activities, their functions have not been completely elucidated, and information about them is limited in comparison with in vitro data. In this study using rats, we examined the deleterious activities of COP in vivo. The absorption rate of dietary COP was approximately 35%, and dietary COP lowered hepatic cholesterol biosynthesis and catabolism, while promoting linoleic acid desaturation. These alterations of lipid metabolism by dietary COP were more marked in immature than in mature rats. Therefore, dietary COP may disturb age-related changes in lipid metabolism, and may also perturb various immune functions by affecting immunoglobulin production by lymphocytes and the release of histamine from peritoneal exudate cells. However, dietary soybean protein, soybean polysaccharides, milk whey protein, procyanidin, and catechin alleviated the deleterious effects of dietary COP. Thus, dietary COP have biologically detrimental effects on health; however, their deleterious actions may be prevented by suitable selection and combination of dietary components.

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The acute increase of protein synthesis in response to food intake is achieved in part through increases in the rate of translation of mRNA by stimulating peptide-chain initiation. The increase of translation initiation in both skeletal muscle and liver in response to food intake was not associated with any detectable change in the activity of eIF2B or in the phosphorylation state of eIF2α, both of which regulate binding of the initiator methionyl-tRNAi to the 40S ribosomal subunit. Food intake stimulated translation initiation partly through enhanced association of eIF4G with eIF4E, an event that promotes binding of mRNA to the 40S ribosomal subunit. Furthermore, this study provided evidence that the protein component of the diet (i.e., amino acids) plays an important regulatory role in the initiation of mRNA translation. Of all the amino acids, leucine appears to be the most effective in recapitulating the responses of protein synthesis and the eIF4F regulatory step produced by ingestion of a protein-containing meal. Leucine-dependent stimulation of translation initiation in vivo occurs via a rapamycin-sensitive pathway and likely involves mTOR. In addition, leucine selectively enhances the translation of mRNAs encoding ribosomal proteins in association with the S6K1 signaling pathway in the liver.

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SREBPs (Sterol Regulatory Element-binding Proteins) regulate the transcription of genes encoding proteins and enzymes involved in cholesterol or fatty acid metabolism. There exist two isoforms, SREBP-1 and -2, with 47% amino acid homology. Unlike other members of the basic helix-loop-helix leucine zipper (bHLH-Zip) family, SREBPs are synthesized as precursors bound to the ER membrane and nuclear envelope. The transcriptionally active NH₂-terminal portion including the bHLH-Zip domain is released from the membrane by two-step proteolysis. Among the SREBP family members, SREBP1 mainly regulates fatty acid metabolism and SREBP2 does cholesterol metabolism. Transcriptional regulation of SREBP2 gene expression, newly identified SREBP-responsive genes, and nuclear transport of SREBPs are discussed in this report. Furthermore, a novel mechanism by which bile acids enhance the expression of the LDL receptor gene is presented. It is noted that cholesterol, fatty acid and bile acid metabolism are coordinately regulated through the actions of the SREBPs, some nuclear receptors and signal transduction cascades.

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