江草 愛

Imidazole dipeptides (ID) are abundant in skeletal muscle and the brain and have various functions, such as antioxidant, pH-buffering, metal-ion chelation. However, the physiological significance of ID has not been fully elucidated. In this study, we orally administered ID to conventional carnosine synthase gene-deficient mice (Carns-KO mice) to investigate the pharmacokinetics. Carnosine or anserine was administered at a dose of 500 mg (∼2 mmol) per kilogram of mouse body weight, and ID contents in the tissues were measured. No ID were detected in untreated Carns-KO mice. In the ID treatment groups, the ID concentrations in the tissues increased in a time-dependent manner in the gastrocnemius muscle, soleus muscle, and cerebrum after ID administration. Our findings suggest that the Carns-KO mice are a valuable animal model for directly evaluating the effects of dietary ID and for elucidating the physiological functions of oral ID administration.

Carnosine and anserine are abundant peptides found in the skeletal muscle and nervous system in many vertebrates. Several in vitro and in vivo studies have demonstrate that exogenously administered carnosine improves exercise performance. Furthermore, carnosine is an antioxidant and antifatigue supplement. However, the physiological functions of endogenous carnosine and its related histidine-containing dipeptides in a living organism remain unclear. We aimed to clarify the physiological roles of endogenous carnosine by investigating the characteristics of carnosine synthase gene-deficient mice and the effects of carnosine on skeletal muscle protein metabolism. We discovered that carnosine and anserine were undetectable in the skeletal muscle of carnosine synthase knockout mice. We also quantified protein gene expression and enzyme levels in muscle protein metabolism. Gene and protein levels of the muscle protein synthesizer insulin-like growth factor-1 (IGF-1) and the degrading enzyme cathepsin B were markedly lower in carnosine synthase gene-deficient mice than those in wild-type mice. The amount of 3-methylhistidine (a marker for muscle proteolysis) in forced exercise and the weight of the gastrocnemius muscle were considerably lower in carnosine synthase gene-deficient mice than in wild-type mice. Consequently, we showed that carnosine deficiency affects weight maintenance and protein metabolism in skeletal muscle, suggesting that carnosine regulates skeletal muscle protein metabolism.

Isocitrate dehydrogenase 1 (IDH1) mutations are common in gliomas, acute myeloid leukemia, and chondrosarcoma. The mutation 'hotspot' is a single arginine residue, R132. The R132H mutant of IDH1 produces the 2-hydroxyglutarate (2-HG) carcinogen from α-ketoglutarate (α-KG). The reduction of α-KG induces the accumulation of hypoxia-inducible factor-1α subunit (HIF-1α) in the cytosol, which is a predisposing factor for carcinogenesis. R132H is the most common IDH1 mutation in humans, but mutations at the R132 residue can also occur in tumor tissues of dogs. The current study reported the discovery of a novel Tyr208Cys (Y208C) mutation in canine IDH1 (cIDH1), which was isolated from 2 of 45 canine chondrosarcoma cases. As the genomic DNA isolated from chondrosarcoma tissue was mutated, but that isolated from blood was not, Y208C mutations were considered to be spontaneous somatic mutations. The isocitrate dehydrogenase activity of the Y208C mutant was attenuated compared with that of wild-type (WT) cIDH1, but the attenuation of Y208C was less intense than that of the R132H mutation. The induction of HIF-1α response element activity and cell retention of HIF-1α were not increased by Y208C overexpression. In silico and cell biological analysis of IDH1 dimerization revealed that the Y208C mutation, but not the R132H mutation, attenuated binding activity with WT cIDH1. These data suggested that the attenuation of dimerization by the Y208C mutation may cause tumorigenesis through different mechanisms other than via 2-HG production by the IDH1 R132 mutation.

Carnosine (β-alanyl-l-histidine) is an imidazole dipeptide present at high concentrations in skeletal muscles, where it plays a beneficial role. However, oral intake of carnosine or β-alanine to increase skeletal muscle carnosine levels has disadvantages such as low efficiency and side effects. Therefore, we proposed homocarnosine (γ-aminobutyryl-l-histidine) as a novel alternative imidazole peptide for skeletal muscle based on its structural similarity to carnosine. To induce endogenous homocarnosine synthesis in skeletal muscles, mice were fed a basal diet mixed with 0, 0.5, 2, or 5% γ-aminobutyric acid (GABA) for 6 weeks. As expected, in the control group (0% GABA), GABA and homocarnosine were present in trace concentrations. Skeletal muscle homocarnosine levels were significantly increased in the 2% and 5% GABA intake groups (tenfold, P < 0.01 and 53-fold, P < 0.01; respectively) relative to those of the control group, whereas 0.5% GABA intake induced no such effect. GABA intake had no effect on the levels of carnosine, anserine, and β-alanine. Vigabatrin (inhibitor of GABA transaminase (GABA-T)) administration to mice receiving 2% GABA intake for 2 weeks led to GABA-T inhibition in the liver. Subsequently, a 43-fold increase in circulating GABA levels and a tendency increase in skeletal muscle homocarnosine levels were observed. Therefore, skeletal muscle homocarnosine synthesis can be induced by supplying its substrate GABA in tissues. As GABA availability is tightly regulated by GABA-T via GABA degradation, inhibitors of GABA or β-alanine degradation could be novel potential interventions for increasing skeletal muscle imidazole dipeptides.

This research was carried on in order to examine the role of umami compounds and fats in the sensation of “koku attributes” and to identify the aroma compounds contributing to the characteristic aroma in pork sausages. Sensory analyses showed that the addition of umami compounds to sausage mix enhanced the intensity of retronasal aroma sensation, the complexity of flavor, the lingeringness of taste, and the intensity of umami of sausage. Then, sensory analyses also showed that addition of fat to sausage mix enhanced the mouthfulness and lingeringness of flavor as well as the intensity of umami taste in pork sausage. This result indicates that fat enhances the effect of “koku attribute” through the lingeringness of flavor. GC/MS analyses of aroma compounds released from pork sausages containing different amounts of fat have shown that β-pinene, 3-carene, D-limonene, octanal, nonanal, caryophyllene, and methyl eugenol were identified in all these sausages. The amounts these aroma compounds released from sausage have been shown to decrease by addition of fat into sausage, indicating that fat was able to hold aroma compounds in sausages. From these results, the lingeringness effect of aroma sensation in “koku attribute” of sausage was shown to be enhanced by addition of fat.

We examined the influence of taste compounds on retronasal aroma sensation using a model chicken soup. The aroma intensity of a reconstituted flavour solution from which glutamic acid (Glu), inosine 5'-monophosphate (IMP), or phosphate was omitted was significantly lower (p &lt; 0.05) than that of the model soup. The aroma intensity of 0.4% NaCl solution containing the aroma chicken model (ACM) with added Glu and IMP was significantly higher (p &lt; 0.05) than that of 0.4% NaCl solution containing only ACM. The quantitative analyses showed that adding monosodium glutamate (MSG) to aqueous aroma solution containing only ACM enhanced the intensity of retronasal aroma sensation by 2.5-folds with increasing MSG concentration from 0% to 0.3%. Sensation intensity using an umami solution with added MSG and IMP was significantly higher than that with only MSG when the MSG concentration was 0.05%, 0.075%, or 0.1%. However, it plateaued when MSG concentration was beyond 0.3%. (C) 2015 Elsevier Ltd. All rights reserved.

We aimed to examine the substance in a precipitate of heat-treated onion concentrate (HOC) that contributes to a sensation of lingering of aroma, a koku attribute induced by the sensing of richness and persistence in terms of taste, aroma and texture. Adding precipitate, separated from HOC, to consomme enhanced the lingering sensation of aroma in the consomme more than adding the supernatant from HOC. After the precipitate was washed with hot water and ethanol its enhancing effect disappeared. Analysis of the HOC precipitate showed that it contained phytosterols, such as beta-sitosterol and stigmasterol. Tests of binding to aroma compounds showed that both sterols, as well as the washed precipitate, were able to bind methyl propyl disulfide and N-hexanal. Thus phytosterols in the HOC precipitate seemed to bind and hold the aroma compounds and gradually release them, inducing a lingering sensation of aroma under the koku concept during consumption. (C) 2015 Elsevier Ltd. All rights reserved.

Analysis of the quality of highly marbled beef during dry aging for 60 days after slaughter showed that the changes in some qualities differed from those of conventional meat. The tenderness of these meats did not change during aging for 50 days but then gradually increased until day 60. The juiciness of these meats, as determined by sensory evaluation, did not change during aging for 60 days, except for a decrease on day 20. The umami intensity of these meats in the sensory evaluation and the value calculated by Glu and IMP quantification were highest on day 40. This high umami intensity was induced by the synergistic effect of umami compounds such as Glu and IMP. These results for tenderness, juiciness, umami intensity, and flavor intensity suggested that the best duration of dry aging for highly marbled beef was 40 days. (C) 2015 Elsevier Ltd. All rights reserved.

「こく」は，現在，おいしさと同義語で使用されている場合が多い．しかし，「こく」は，味，香り，食感，色，艶と同様に，それぞれの食べ物が有する特性の一つであり，おいしさを決める要因である．「こく」には強弱が存在し，それぞれの食べ物に適した「こく」の強さでおいしさが付与される．「こく」は，食べ物の持つ味，香り，食感による複数の刺激から形成される複雑さによる特性である．これらの複数の刺激は，その食べ物の特徴を決める味わいのベースとなる部分であり，さらに持続性や広がりが付与されたときに「こく」が感じられる．このベース部分からできる味わいに持続性や広がりを与えることができる重要な成分として，現在，うま味物質と油脂が挙げられる．このうち，うま味物質は，味や香りからなる風味質を強くすると同時に広がりや持続性を与える．また，油脂は香気成分を保持することで，「こく」の特性である持続性を与えることができることがわかってきた．

The porcine myofibrillar protein hydrolysate obtained by a papain treatment showed antioxidative activity in a system of linolenic acid peroxidation induced by Fe2+. The five peptides, DSGVT, IEAEGE,DAQEKLE, EELDNALN, and VPSIDDQEELM, have been characterized as antioxidative peptides (Saiga et al., J. Agric. Food Chem., 51, 3661-3667 (2003)). These peptides were synthesized and their antioxidative activity evaluated. The antioxidative activity of four peptides, excluding DSGVT, was confirmed by their addition at 0.1% to the peroxidation system. To clarify the mechanism for the antioxidative activity of these peptides, their short peptides with amino acid deletions at The C- or N-termini were synthesized. The antioxidative activity gradually decreased with decreasing peptide length. Replacing the charged amino acids in these peptide sequences with Ala also affected their antioxidative activity. We hypothesize that the anions from acidic amino acids and the cations from iron interacted with each other and inactivated the prooxidant, Fe (II).

We examined the effects of vitamin B_1 (B_1) and fat added to a feed on their accumulation and glucose- and lipid-metabolism in the porcine liver. B_1 content in the livers of pigs fed a feed supplemented with 15 ppm B_1-supplemented feed (B+ group) was significantly higher than that in the livers of pigs fed the usual dosage of 1.5 ppm B_1 (Control group). B_1 content in the livers of pigs given a feed with 1.5 ppm B_1 plus 3% fat (F+ group) or a feed with 15 ppm B_1 plus 3% fat (B+F+ group) was significantly higher than that in pigs given a feed with 15 ppm B_1 (B+ group) or controls. The liver fat content in the B+F+ group was lower than that in the B+ group. Analysis of liver mRNA levels showed that gene expression of β-oxidation-related proteins increased in B_1-supplemented groups. Glycolytic pathway- and TCA cycle-related gene expression levels were also increased with fat supplementation. These results indicated that, in pigs with co-supplementation of high dose of B_1 and fat, glucose and lipid metabolism was enhanced in the liver.

ブタ大動脈よりエラスチンの酵素加水分解ペプチド（エラスチンペプチド）を調製し，その摂取が皮膚にもたらす影響について検討した．生後7週の雄ヘアレスマウスにエラスチンペプチドなどの試料を経口投与し，63日間の飼育を行った．皮膚老化モデルとして光老化モデルを採用し，週3回の頻度で紫外線を照射した．照射52日目および55日目にエラスチンペプチドとコラーゲンペプチドを混合投与した群およびコラーゲンペプチド投与群において，皮膚水分量が照射対照群に比べて有意に上昇し，エラスチンペプチドの単独投与群において上昇傾向が認められた．エラスチンペプチドやコラーゲンペプチドの単独投与に比べ，皮膚中の存在比やそれに近い比での混合投与による相乗効果が得られ，光老化に対する皮膚症状の改善が認められた．つまり，エラスチンペプチドがコラーゲンペプチドの摂取による皮膚水分量の上昇効果を増強することが示唆された．

Chicken collagen hydrolysate was given to 15 mildly hypertensive subjects for 4 weeks. Blood pressure was significantly decreased by 11.8 mmHg (P < 0.01). A reduction in plasma renin activity was observed in blood test after intake. A colony assay of endothelial progenitor cells in blood samples from non-smokers revealed an approximately 30% increase in the number of colonies.

In this study, we investigated the concentration of food derived-peptides in blood following oral intake of chicken collagen hydrolysate (chicken-collagen octa peptides; C-COP) and measured the angiotensin-converting enzyme (ACE) inhibitory activity of these peptides. Healthy volunteers ingested the C-COP solution (25 g/60 kg body weight) after fasting for 12 h. The peptide-formed hydroxyproline (Hyp) significantly increased and reached maximum levels (91.1 mu M) 2 h after consumption. Pro-Hyp, Leu-Hyp, Pro-Hyp-Gly, Phe-Gly, Ala-Hyp, Hyp-Gly, Glu-Hyp-Gly, Ala-Hyp-Gly and Ser-Hyp-Gly were detected in human blood, possessing ACE-inhibitory activity of them, Ala-Hyp (IC50: 0.177 mM) had the strongest ACE inhibitory activity. Thus, C-COP appears to absorb with the peptides by enzymatic digestion in blood, thereby inhibiting ACE, suggesting that food-derived collagen peptides are related to antihypertensive effects.

In this study, collagen extracted from chicken legs (which are the yellow keratin parts containing a nail) was hydrolyzed with various enzymes, and the angiotensin I-converting enzyme (ACE)-inhibitory activity of each hydrolysate was determined. The hydrolysate by treatment with an Aspergillus species-derived enzyme had the highest activity (IC50 = 260 mu g/mL). The fraction of this hydrolysate obtained by ultrafiltration with a molecular-weight cutoff of 3000 Da (low fraction) had a stronger activity (IC50 = 130 mu g/mL) than the fractionated one. This fraction was further fractionated by HPLC, and the peptides in the fraction with high ACE-inhibitory activity were identified. The amino acid sequences of the four peptides were identified using a protein sequencer. These peptides were synthesized to confirm their ACE-inhibitory activities; this showed that peptides with a Gly-Ala-Hyp-Gly-Leu-Hyp-Gly-Pro sequence had the highest activity (IC50 = 29 mu M). When the low fraction was administered to spontaneous hypertensive rats, a decrease in their blood pressure was observed after 2 h of administration, and a significant decrease in blood pressure (-50 mmHg) was observed after 6 h. Moreover, long-term administration studies indicated that the low fraction showed a significant suppression of increased blood pressure.

Royal jelly peptides (RJPx) isolated from hydrolysates of water-soluble royal jelly proteins prepared with protease P exhibited significantly stronger hydroxyl radical-scavenging activity (p &lt; 0.001), and antioxidant activity against lipid peroxidation (LPO, p &lt; 0.001), than did water-soluble royal jelly protein (WSRJP) in vitro. We also investigated the in vivo antioxidant activity of RJPx against ferric nitrilotri acetate (Fe-NTA)-induced LPO. Male Wistar rats were divided into a control group (Group C), an Fe-NTA group (Group Fe), and an Fe-NTA with RJPx group (Group Fe + R). Rats in Group Fe + R were fed RJPx (2 g/kg body weight) daily for 5 wk. Fe-NTA (8 mg Fe/kg body weight) was then intraperitoneally injected, and serum lipid levels were examined 2 h later. Serum total cholesterol (TC) levels were lower (p &lt; 0.05) while low-density lipoprotein (LDL) and LPO were significantly higher (p &lt; 0.01) in Group Fe than in Group C. TC (p &lt; 0.05) and LPO levels (P &lt; 0.01) were lower in Group Fe+R than in Group Fe. Our data suggest that RJPx may inhibit LPO both in vitro and in vivo.

We studied the antihypertensive effect of an octapeptide (Gly-Ala-Hyp-Gly-Leu-Hyp-Gly-Pro), which is derived from chicken collagen hydrolysates and has strong angiotensin I-converting enzyme (ACE)inhibitory activity, on spontaneously hypertensive rats (SHRs). 6 h after a single oral administration of the octapeptide (4.5 mg/kg SHR body weight), the systolic blood pressure was significantly reduced. The octapeptide was not digested by digestive enzymes from the epithelia of the porcine small intestines in vitro. These results suggest that this ACE-inhibitory peptide is absorbed by SHRs in the peptide: form and that it lowers blood pressure.

Royal jelly (RJ) has several physiological effects and is widely used in commercial medical products and health foods. We examined the effects of RJ supplementation on serum lipoprotein metabolism in humans. Fifteen volunteers were divided into an RJ intake group (n= 7) and a control group (n= 8). The RJ group took 6 g per day for 4 wk. Their serum total cholesterol (TC) and serum low-density lipoprotcin (LDL) decreased significantly compared with those of the control group (p &lt; 0.05). There were no significant differences in serum high-density lipoprotein (HDL) or triglyceride concentrations. Moreover, the relationship between the serum cholesterol and lipoprotein levels was investigated. Among the lipoprotein fractions. small very-low-density lipoprotein was decreased (p &lt; 0.05) after RJ intake. Our results suggest that dietary RJ decreases TC and LDL by lowering small VLDL levels.

In a previous study, we isolated the inhibitory peptide (P4 peptide, Gly-Phe-Hyp-Gly-Thr-Hyp-Gly-Leu-Hyp-Gly-Phe) for angiotensin I-converting enzyme (ACE) from chicken breast muscle extract possessing hypotensive activity for spontaneously hypertensive rats (SHRs). This study was performed to elucidate the peptide's action mechanisms of inhibiting ACE. Intravenous administration of synthetic P4 peptide resulted in significant drops in the blood pressures of SHRs. As Dixon plots indicate, the P4 peptide showed high affinity toward ACE (K-i = 11.48 mu M) and only 10% of the total amount of the P4 peptide was decomposed. The analyses of the relationship between the ACE inhibitory activity and structure of the P4 peptide clarified that Hyp-Gly-Leu-Hyp-Gly-Phe showed a stronger activity (IC50 = 10 mu M) than the P4 peptide (IC50 = 46 mu M). When Phe at the C-terminus of the P4 peptide was deleted, IC50 changed to 25000 mu M, indicating that Phe at the C-terminus of the peptide is very important for ACE inhibitory activity.

Hydrolysates obtained from porcine myofibrillar proteins by protease treatment (papain or actinase E) exhibited high antioxidant activity in a linolenic acid peroxidation system induced by Fe2+. Hydrolysates produced by both papain and actinase E showed higher activities at pH 7.1 than at pH 5.4. The antioxidant activity of the papain hydrolysate was almost the same as that of vitamin E at pH 7.0. These hydrolysates possessed 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and chelating activity toward metal ions. Antioxiclant pepticles were separated from the papain hydrolysate by ion exchange chromatography. The acidic fraction obtained by this method exhibited higher activity than the neutral or basic fractions. Antioxidant pepticles in the acidic fraction were isolated by highperformance liquid chromatography on an ODS column and shown to possess the structures DSGVT, IEAEGE, DAQEKLE, EELDNALN, and VPSIDDQEELM. The DAQEKLE pepticle showed the highest activity among these peptides.

The blood pressure of spontaneously hypertensive rats (SHRs) decreased after oral administration of an extract prepared from chicken breast muscle, falling maximally to 50 mmHg lower than before. This effect continued for at least 4 h after administration. The peptides possessing hypotensive activity in the chicken extract were examined by measuring the inhibitory activity (IC50) against angiotensin I-converting enzyme (ACE). The inhibitory activity of the chicken extract was 1060 mg%, whereas the activity of the extract treated with an Aspergillus protease and gastric proteases (trypsin, chymotrypsin, and intestinal juice) became stronger, reaching 1.1 mg%. Peptides in this hydrolysate of the extract were isolated by HPLC on a reversed-phase column, and their N-terminal sequences were analyzed. Three peptides possessed a common sequence, Gly-X-X-Gly-X-X-Gly-X-X, which was homologous with that of collagen. The peptide Gly-Phe-Hyp-Gly-Thr-Hyp-Gly-Leu-Hyp-Gly-Phe showed the strongest inhibitory activity (IC50 = 42 muM).

Hydrolysates obtained from porcine myofibrillar proteins by protease treatment (actinase E or papain) exhibited high antioxidative activity in the linolenic acid peroxidation system induced by Fe2+. Antioxidative peptides were isolated from papain hydrolysate by using ion-exchange chromatographies and HPLC. An acidic fraction obtained by chromatography exhibited the higher activity than neutral and basic fractions. Antioxidant peptides in the acidic fraction were isolated on HPLC by ODS column. They possessed the structures, DSGVT, IEAEGE, AEFAES, EELDNALN and VPSIDDQEELM. A peptide, AEFAES showed the highest activity among these peptides.

Protein hydrolysates obtained by treatment with papain, trypsin, chymotrypsin and actinase all exhibited inhibitory activity (IC50: 3.4-41.8 mg%) toward angiotensin-converting enzyme (ACE) (EC 3.4.15.1). In particular, the protein hydrolysate obtained by treatment with papain showed the highest inhibitory activity (3.7-5.3 mg%). The ACE inhibitory activity of the gluten hydrolysate obtained with actinase was mainly due to peptides of less than 500 Da in molecular mass. On the other hand, the ACE inhibitory activity of the myofibrillar protein hydrolysate obtained with papain was due to peptides of both less and more than 500 Da in molecular mass. The blood pressure of spontaneously hypertensive rats (SHR) administered the myofibrillar protein hydrolysate was significantly reduced at 2 h after administration. The blood pressure of SHR was also reduced at 2 h after administration of the gluten hydrolysate, and this effect continued until 6 h. These hydrolysates may potentially be useful as antihypertensive food materials.