Dietary Alaska Pollack Protein Induces Acute and Sustainable Skeletal Muscle Hypertrophy in Rats.

Our previous studies suggested that Alaska pollack protein (APP) intake increases skeletal muscle mass and that it may cause a slow-to-fast shift in muscle fiber type in rats fed a high-fat diet after 56 days of feeding. In this study, we explored whether dietary APP induces acute and sustainable skeletal muscle hypertrophy in rats fed a normal-fat diet. Male 5-week-old Sprague-Dawley rats were divided into four groups and fed a purified ingredient-based high-fat diet or a purified ingredient-based normal-fat diet with casein or APP, containing the same amount of crude protein. Dietary APP significantly increased gastrocnemius muscle mass (105~110%) after 2, 7 days of feeding, regardless of dietary fat content. Rats were separated into two groups and fed a normal-fat diet with casein or APP. Dietary APP significantly increased gastrocnemius muscle mass (110%) after 56 days of feeding. Dietary APP significantly increased the cross-sectional area of the gastrocnemius skeletal muscle and collagen-rich connective tissue after 7 days of feeding. It decreased the gene expression of Mstn /Myostatin, Trim63/MuRF1, and Fbxo32/atrogin-1, but not other gene expression, such as serum IGF-1 after 7 days of feeding. No differences were observed between casein and APP groups with respect to the percentage of Type I, Type IIA, and Type IIX or IIB fibers, as determined by myosin ATPase staining after 7 days of feeding. In the similar experiment, the puromycin-labeled peptides were not different between dietary casein and APP after 2 days of feeding. These results demonstrate that APP induces acute and sustainable skeletal muscle hypertrophy in rats, regardless of dietary fat content. Dietary APP, as a daily protein source, may be an approach for maintaining or increasing muscle mass.

Mechanism of Soy Isoflavone Daidzein-Induced Female-Specific Anorectic Effect.

Epidemiological studies suggest that regular intake of soy isoflavone exerts a preventive effect on postmenopausal obesity and other forms of dysmetabolism. Estrogens inhibit eating behavior. Soy isoflavones may act as estrogen agonist in estrogen-depleted conditions, whereas they may either act as an estrogen antagonist or be ineffective in estrogen-repleted conditions. We investigated the effects of dietary soy isoflavone on food intake under various estrogen conditions using male, ovariectomized (OVX), and non-OVX female rats, and compared the effects with those of estradiol. We found that soy isoflavones reduced food intake in females specifically, regardless of whether ovariectomy had been performed, whereas subcutaneous implantation of estradiol pellet did not reduce food intake in intact female rats, but did so in OVX female and male rats. Contrary to this hypothesis, the reduction in food intake may not be caused by the estrogenic properties of soy isoflavones. It is of great interest to understand the mechanisms underlying the anorectic effects of soy isoflavones. In this non-systematic review, we summarize our recent studies that have investigated the bioactive substances of anorectic action, pharmacokinetic properties of soy isoflavones, and the modification of central and peripheral signals regulating appetite by soy isoflavones, and selected studies that were identified via database mining.

Lipid Dynamics due to Muscle Atrophy Induced by Immobilization.

Muscle atrophy refers to skeletal muscle loss and dysfunction that affects glucose and lipid metabolism. Moreover, muscle atrophy is manifested in cancer, diabetes, and obesity. In this study, we focused on lipid metabolism during muscle atrophy. We observed that the gastrocnemius muscle was associated with significant atrophy with 8 days of immobilization of hind limb joints and that muscle atrophy occurred regardless of the muscle fiber type. Further, we performed lipid analyses using thin layer chromatography, liquid chromatography-mass spectrometry, and mass spectrometry imaging. Total amounts of triacylglycerol, phosphatidylserine, and sphingomyelin were found to be increased in the immobilized muscle. Additionally, we found that specific molecular species of phosphatidylserine, phosphatidylcholine, and sphingomyelin were increased by immobilization. Furthermore, the expression of adipose triglyceride lipase and the activity of cyclooxygenase-2 were significantly reduced by atrophy. From these results, it was revealed that lipid accumulation and metabolic changes in specific fatty acids occur during disuse muscle atrophy. The present study holds implications in validating preventive treatment strategies for muscle atrophy.

Neuromodulatory peptides: Orally active anxiolytic-like and antidepressant-like peptides derived from dietary plant proteins.

Mental disorders are a severe health problem, and the number of patients is growing worldwide. Increased anxiety and decreased motivation due to excessive mental stress further accelerated the severity of the problem. Enzymatic digestion of food proteins produces bioactive peptides with various physiological functions, some of which exhibit neuromodulatory effects with oral administration. Recently, studies reported that some peptides produced from plant proteins such as soybeans, leaves, and grains exhibit emotional regulatory functions such as strong anxiolytic-like and antidepressant-like effects comparable to pharmaceuticals. Conventionally, researchers investigated bioactive peptides by fractionation of protein hydrolysates and structure-activity relationship. As a novel methodology for analyzing bioactive peptides, the information obtained by peptidomics simultaneous analysis of the digested fractions of proteins using mass spectrometry has been effectively utilized. Some small-sized peptides such as dipeptides and tripeptides released food-derived proteins show emotional regulating effects. Moreover, some middle-sized peptides produced after intestinal digestion may exhibit the emotional regulating effect via the vagus nerve, and the importance of the gut-brain axis is also focused. As the central mechanism of emotional regulation, it has been found that these plant-derived peptides regulated monoamine neurotransmitter signaling and hippocampal neurogenesis.

Prolyl-hydroxyproline, a collagen-derived dipeptide, enhances hippocampal cell proliferation, which leads to antidepressant-like effects in mice.

Depression has been a mental health issue worldwide. We previously reported that ginger-degraded collagen hydrolysate (GDCH) suppressed depression-like behavior in mice. Furthermore, prolyl-hydroxyproline (PO) and hydroxyprolyl-glycine (OG) were detected in the circulating blood after the oral administration of GDCH. In the present study, PO, but not OG, was detected in the cerebrospinal fluid of rats after the oral administration of GDCH, suggesting that PO is transported from blood to the brain. We then investigated the effects of PO and OG on the depression-like behavior of mice. The oral administration of PO significantly decreased depression-like behavior in the forced swim test. OG had no antidepressant-like effect. In addition, proline and hydroxyproline, components of PO, also had no antidepressant-like effect after their oral administration. PO significantly increased the gene expression of brain-derived neurotrophic factor and nerve growth factor in the hippocampus, and promoted the proliferation of neural progenitor cells in vivo and in vitro. PO also increased the dopamine concentration in the prefrontal cortex. Thus, PO-dependent regulation of neurotrophic function and neurotransmitter may be the mechanism for antidepressant-like behavior. Together, these results demonstrate that PO is an antidepressant bioactive peptide accompanying the proliferation of hippocampal neural progenitor cells.

Dipeptide tyrosyl-leucine exhibits antidepressant-like activity in mice.

Depression is a worldwide health problem. In the present study, we found that a dipeptide, tyrosyl leucine (Tyr-Leu, YL), administered orally, intracerebroventricularly, or intraperitoneally exhibited a potent antidepressant-like activity in the forced swim and tail suspension tests in naïve mice. YL increased the amount of cells expressing c-Fos, a marker for neuronal activity, in the dentate gyrus of the hippocampus. YL increased bromo-2'-deoxyuridine-positive cells and doublecortin expression in the dentate gyrus of the hippocampus, suggesting that YL enhanced the proliferation of hippocampal progenitor cells in vivo and in vitro. YL did not affect hippocampal mRNA and protein expression of BDNF, which is a regulatory factor of both neurogenesis and depression-like behavior. Intriguingly, YL suppressed activation of the hypothalamo-pituitary-adrenal axis by forced swim stress. Moreover, other aromatic amino acid-leucines, Phe-Leu and Trp-Leu, also exhibited antidepressant-like activities, suggesting that the structure of aromatic amino acid-leucine may be important for antidepressant activity. In addition, bovine milk casein-derived peptide, Tyr-Leu-Gly (YLG), an anxiolytic peptide, exhibited an antidepressant-like activity. Our findings demonstrate that YL exhibits an antidepressant-like effect, moderates the stress response, and induces hippocampal neuronal proliferation through a signal pathway independent of BDNF.

Orally administered milk-derived tripeptide improved cognitive decline in mice fed a high-fat diet.

The functions of the brain, which is thought of as an organ highly independent from the periphery, are often affected by the peripheral environment. Indeed, epidemiologic studies demonstrated that diabetes was a risk factor for dementia. It was also reported that the intake of dairy products, such as milk, reduces the risk of developing dementia. We found that mice on a short-term high-fat diet (HFD) for 1 wk had reduced cognitive function. Thus, using this acute model, we investigated the effects of milk-derived peptide on cognitive decline induced by HFD. Tyr-Leu-Gly (YLG), a tripeptide derived from αS1-casein, a major bovine milk protein, is released by gastrointestinal proteases. We found that orally administered YLG improved cognitive decline induced by 1-wk HFD intake in the object recognition test. YLG also improved cognitive decline in the object location test. Thus, we found that YLG improved cognitive decline induced by HFD. Next, we examined the effects of YLG on the hippocampus, a brain area essential for cognitive function. HFD intake decreased the number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells, and this decrease was improved by YLG administration. HFD intake decreased nerve growth factor (NGF) and glial cell line-derived neurotrophic factor, whereas YLG increased NGF and ciliary neurotrophic factor, suggesting that these neurotropic factors play a role in hippocampal neurogenesis after YLG administration. In conclusion, we demonstrated that 1-wk HFD reduced cognitive function. Furthermore, we found that YLG, a milk-derived tripeptide, improved cognitive decline in mice on HFD. The HFD reduced neural stem cell proliferation, and YLG improved this reduction. YLG is the first reported milk peptide to improve cognitive decline induced by HFD intake.-Nagai, A., Mizushige, T., Matsumura, S., Inoue, K., Ohinata, K. Orally administered milk-derived tripeptide improved cognitive decline in mice fed a high-fat diet.

Ginger-Degraded Collagen Hydrolysate Exhibits Antidepressant Activity in Mice.

Collagen is the most abundant protein in animals. Collagen hydrolysate has been found to have multiple functions in the skin, bones, joints, muscles, and blood vessels. Recently, it has been reported that the low molecular weight fraction of collagen hydrolysate exhibited anxiolytic activity, suggesting that collagen peptides affect brain functions. In the present study, we found that oral administration of ginger-degraded collagen hydrolysate (GDCH) significantly decreased depression-like behavior in a forced swim test, suggesting that GDCH exhibited antidepressant activity in mice. The antidepressant activity of GDCH was abolished by pre-treatment with an antagonist of the dopamine receptor, but not treatment with a serotonin receptor antagonist. GDCH significantly increased gene expression of glial cell line-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF) in the hippocampus, molecules that affect the differentiation and survival of neurons, relative to that in the control condition. Meanwhile, there were no changes in the gene expression of brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3, major factors related to depression-like behavior. We also found that GDCH exhibited antidepressant activity in corticosterone-administered mice in a model of stress. In addition, GDCH increased GDNF and CNTF expression in the stressed condition, suggesting that mechanisms of the antidepressant activity of GDCH were the same in unstressed and stressed conditions. These results imply that GDCH exhibits antidepressant activity in unstressed and stressed conditions in mice. The upregulation of neurotrophic genes in the hippocampus may contribute to the reduction of depression-like behavior via a dopamine signal pathway modulated by GDCH.

Dietary Alaska pollack protein improves skeletal muscle weight recovery after immobilization-induced atrophy in rats.

The promotion of muscle recovery after immobilization is important to preserve an optimum health status. Here, we examined the effect of dietary Alaska pollack protein (APP) on skeletal muscle weight after atrophy induced by hind limb immobilization using plaster immobilization technique. Rat left limb was casted with a wetted plaster cast under anesthesia. After 2 weeks of feeding, the cast was removed and the rats were divided into three groups, namely, a baseline group, high-fat casein diet group, and high-fat APP diet group. After 3 weeks of feeding, the skeletal muscles (soleus, extensor digitorum longus [EDL], and gastrocnemius) were sampled. The estimated weight gains of soleus, gastrocnemius, and EDL muscle in the immobilized limbs were significantly larger in the rats fed with APP diet as compared with those fed with casein diet. In soleus muscle, dietary APP increased the expression of Igf1 and Myog genes in the immobilized limbs after the recovery period.

Dietary daidzein induces accumulation of S-equol in enterohepatic circulation to far higher levels than that of daidzein in female rats with and without ovariectomy.

We previously found that daidzein decreased food intake in female rats. To understand the mechanism of anorectic action of dietary daidzein, it is necessary to determine distributions of daidzein and S-equol, a metabolite of intestinal bacterial conversion from daidzein, in the body. In the present study, we measured the concentrations of daidzein and S-equol in serum and bile in sham-operated and ovariectomized female rats fed a diet containing 150 mg/kg daidzein for 7 days. Dietary daidzein increased serum and bile concentrations of S-equol to far higher levels than those of daidzein. S-equol concentration was more than several hundred fold-higher in bile than in serum, regardless of ovariectomy. Moreover, to investigate whether accumulation of S-equol is facilitated by efficient enterohepatic circulation during continuous intake of daidzein and S-equol, female rats were fed diet containing daidzein or S-equol (both 150 mg/kg), or control diet for 1, 2, 3, or 5 days. Dietary daidzein significantly increased serum and bile concentrations of S-equol in a time-dependent manner, but not those of daidzein. These results indicated that substantial proportion of dietary daidzein was converted to S-equol, which underwent efficient enterohepatic circulation and predominantly accumulated there.

Enzymatic digest of whey protein and wheylin-1, a dipeptide released in the digest, increase insulin sensitivity in an Akt phosphorylation-dependent manner.

We investigated the effects of the enzymatic digest of ß-lactoglobulin, a major bovine milk whey protein, on glucose metabolism in KK-Ay mice, an animal model of type II diabetes. In the glucose tolerance test and insulin tolerance test (ITT), the thermolysin digest of ß-lactoglobulin decreased blood glucose levels, suggesting that it increases insulin sensitivity in diabetic KK-Ay mice. The digest also increased phosphorylation of Akt, an intracellular factor activated in response to the insulin receptor activation, in the liver and skeletal muscle. Next, we searched for a bioactive peptide present in the digest that increased the insulin sensitivity. Wheylin-1 is an anxiolytic-like dipeptide (Met-His) isolated from the thermolysin digest of ß-lactoglobulin. Wheylin-1 decreased blood glucose levels in the ITT test and increased hepatic Akt phosphorylation. Wheylin-1 also increased insulin-induced Akt phosphorylation in hepatic HepG2 cells and muscular C2C12 myotube cells. These results suggest that wheylin-1 increases insulin sensitivity in an Akt-dependent manner in vivo and in vitro. Taken together, we found that the thermolysin digest of bovine milk whey ß-lactoglobulin and wheylin-1 increase insulin sensitivity in an Akt system-dependent manner. Wheylin-1 is the first factor found that increases insulin sensitivity in association with Akt-phosphorylation.

Absorption and metabolism of orally administered collagen hydrolysates evaluated by the vascularly perfused rat intestine and liver in situ.

A number of studies have shown that oral administration of collagen hydrolysate (CH) results in the absorption of di- and tri-peptides. In order to understand the dynamics of CH absorption and metabolism, molecular profiles of hydroxyproline (Hyp) and Hyp-containing peptides (HCPs) were analyzed by in situ perfusion of rat intestine and liver. The total amount of absorbed HCPs during 1 h of perfusion was 16.6 µmol, which was significantly higher than that of free Hyp (6.6 µmol). In addition, HCPs were also reliably detected in hepatic perfusate at the level higher than free Hyp. Thus, the results demonstrated that CH is absorbed predominantly as peptides, which subsequently enter systemic circulation. Size exclusion chromatography showed that perfusates include significant amount of HCPs larger than tripeptides, leading us to analyze these peptides in detail. Mass spectrometric analysis of intestinal perfusate finally identified three CH-derived peptides, which are surprisingly large as food-derived circulating peptides. Peptide quantitation by liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed that di- and tri-peptides, which are previously identified as major peptides in circulating blood, comprise only a part of HCPs in intestinal and liver perfusate. Finally, analysis of portal vein blood revealed that the larger peptides, such as pentadecapeptide identified in this study, could be absorbed in vivo. Taken all together, this study showed that peptides which are larger than tripeptide could reach to the circulation system after administration of CH, revealing previously unknown dynamics of absorption of CH.

Fish protein hydrolysate exhibits anti-obesity activity and reduces hypothalamic neuropeptide Y and agouti-related protein mRNA expressions in rats.

Fish protein is a source of animal protein that is consumed worldwide. Although it has been reported that the intake of Alaska pollack protein (APP) reduces body fat accumulation and increases muscle weight in rats, the mechanisms underlying these effects are poorly understood. As a possibility, peptides released from APP in the gastrointestinal tract are important to the functions of APP. In the present study, we examined the effects of APP hydrolysate digested artificially with pepsin and pancreatin on white adipose tissue and skeletal muscle. We found that APP hydrolysate group shows significantly lower weight of white adipose tissue and higher weight of soleus muscle than the control group. We also found that APP hydrolysate group reduces food intake and mRNA expressions of neuropeptide Y and agouti-related protein in the hypothalamus compared with the control group. These results may imply that APP hydrolysate exhibits anti-obesity activity by the reduction of appetite and the enhancement of basal energy expenditure by skeletal muscle hypertrophy in rats. The downregulation of orexigenic gene by APP hydrolysate in the hypothalamus may contribute to the reduction of appetite. These results suggest that the effect of APP on anti-obesity and muscle hypertrophy may be induced by peptides released from APP in the gastrointestinal tract.

l-Ornithine and l-lysine stimulate gastrointestinal motility via transient receptor potential vanilloid 1.

SCOPE: The gastrointestinal (GI) tract senses and responds to intraluminal nutrients and these interactions often affect GI functions. We found that, among basic amino acids, l-ornithine (Orn) and l-lysine (Lys) stimulated but l-arginine (Arg) suppressed GI motility after oral administration (24 mmol/kg) in mice (Orn and Lys, 14.3 and 26.4% promotion; Arg, 7.7% suppression). We investigated the mechanism of the action of Orn and Lys on GI motility. METHODS AND RESULTS: Orn-induced promotion of small intestinal transit was significantly inhibited (p<0.05) by oral administration of capsazepine, a transient receptor potential vanilloid 1 (TRPV1) antagonist. Moreover, the stimulatory effect of Orn and Lys was abolished in TRPV1-knockout mice. In TRPV1-transfected HEK293 cells, Orn and Lys (10 mM) evoked Ca2+ influx, which was blocked by ruthenium red, a TRP channel antagonist. These results suggest that Orn and Lys promote GI motility via activation of TRPV1. The GI motility stimulation by Orn and Lys was also blocked by atropine, a muscarinic acetylcholine receptor (mAChR) antagonist, or NG -nitro-l-arginine methyl ester, a nitric oxide (NO) synthase inhibitor. CONCLUSION: Orally administered Orn and Lys stimulate GI motility via TRPV1, mAChR and NO synthase in mice.

Lacto-ghrestatin, a novel bovine milk-derived peptide, suppresses ghrelin secretion.

Ghrelin, an endogenous peptide isolated from the stomach, is known to stimulate food intake after peripheral administration. We found that the enzymatic digest of ß-lactoglobulin decreases ghrelin secretion from the ghrelin-producing cell line MGN3-1. The peptides present in the digest were comprehensively analyzed using the nanoLC-OrbitrapMS. Among them, we identified that the nonapeptide LIVTQTMKG, corresponding to ß-lactoglobulin(1-9), suppresses ghrelin secretion from MGN3-1 cells. We named LIVTQTMKG 'lacto-ghrestatin'. We found that lacto-ghrestatin decreases intracellular cAMP levels and mRNA expression levels of ghrelin production-related genes in MGN3-1 cells. Orally administered lacto-ghrestatin decreases plasma ghrelin levels and food intake in fasted mice. Lacto-ghrestatin is the first food-derived peptide to suppress ghrelin secretion in vitro and in vivo.

l-Ornithine stimulates growth hormone release in a manner dependent on the ghrelin system.

We found that intraduodenal administration of l-ornithine (l-Orn) stimulates growth hormone (GH) secretion in Wistar rats, and then investigated its mechanism. GH-releasing activity after intraduodenal administration of l-Orn was blocked by [d-Lys3]-GHRP-6, an antagonist of the ghrelin receptor; however, l-Orn (100 µM) has no affinity for the ghrelin receptor, suggesting that the GH-releasing activity of l-Orn is mediated via ghrelin release and activation of the ghrelin receptor. Intraduodenally administered l-Orn increased ghrelin mRNA expression in the duodenum but not in the stomach or hypothalamus. In addition, l-Orn-induced GH-releasing activity was inhibited by propranolol, an antagonist of ß-adrenergic receptor, which is known to be coupled to ghrelin release. In conclusion, intraduodenally administered l-Orn stimulates GH secretion through the sympathetic nervous and ghrelin systems.

Rational identification of a novel soy-derived anxiolytic-like undecapeptide acting via gut-brain axis after oral administration.

Here we found that the chymotryptic digest of soy ß-conglycinin, a major storage protein, exhibited anxiolytic-like effects in mice. We then searched for anxiolytic-like peptides in the digest. Based on a comprehensive peptide analysis of the chymotryptic digest by high performance liquid chromatograph connected to an LTQ Orbitrap mass spectrometer and the structure-activity relationship of known peptides, we explored anxiolytic-like peptides present in the digest. FLSSTEAQQSY, which corresponds to 323-333 of the ß-conglycinin α subunit [ßCGα(323-333)] emerged as a candidate. Oral administration of synthetic ßCGα(323-333) exhibited anxiolytic-like effects in the elevated plus-maze and open-field test in male mice. Orally administered ßCGα(323-333) exhibited anxiolytic-like effects in sham-operated control mice but not in vagotomized mice. In addition, oral administration of ßCGα(323-333) increased the expression of c-Fos, a marker of neuronal activity, in the nucleus of the solitary tract, which receives inputs from the vagus nerve. These results suggest that the anxiolytic-like effects were mediated by the vagus nerve. The anxiolytic-like effects of ßCGα(323-333) were also blocked by antagonists of the serotonin 5-HT1A, dopamine D1 and GABAA receptors. However ßCGα(323-333) had no affinity for these receptors, suggesting it stimulates the release of endogenous neurotransmitters to activate the receptors. Taken together, a soy-derived undecapeptide, ßCGα(323-333), may exhibit anxiolytic-like effects after oral administration via the vagus nerve and 5-HT1A, D1 and GABAA systems.

A novel Alaska pollack-derived peptide, which increases glucose uptake in skeletal muscle cells, lowers the blood glucose level in diabetic mice.

We found that the tryptic digest of Alaska pollack protein exhibits a glucose-lowering effect in KK-Ay mice, a type II diabetic model. We then searched for glucose-lowering peptides in the digest. Ala-Asn-Gly-Glu-Val-Ala-Gln-Trp-Arg (ANGEVAQWR) was identified from a peak of the HPLC fraction selected based on the glucose-lowering activity in an insulin resistance test using ddY mice. ANGEVAQWR (3 mg kg(-1)) decreased the blood glucose level after intraperitoneal administration. Among its fragment peptides, the C-terminal tripeptide, Gln-Trp-Arg (QWR, 1 mg kg(-1)), lowered the blood glucose level, suggesting that the C-terminal is critical for glucose-lowering activity. QWR also enhanced glucose uptake into C2C12, a mouse skeletal muscle cell line. QWR did not induce the phosphorylation of serine/threonine protein kinase B (Akt) and adenosine monophosphate-activated protein kinase (AMPK). We also demonstrated that QWR lowered the blood glucose level in NSY and KK-Ay, type II diabetic models.

Antidepressant-like effect of food-derived pyroglutamyl peptides in mice.

The N-terminal glutamine residue, exposed by enzymatic cleavage of precursor proteins, is known to be modified to a pyroglutamyl residue with a cyclic structure in not only endogenous but also food-derived peptides. We investigated the effects of wheat-derived pyroglutamyl peptides on emotional behaviors. Pyroglutamyl leucine (pyroGlu-Leu, pEL) and pyroglutamyl glutaminyl leucine (pyroGlu-Gln-Leu, pEQL) exhibited antidepressant-like activity in the tail suspension and forced swim tests in mice. pEQL exhibited more potent antidepressant-like activity than pEL after i.p. and i.c.v. administration. pEQL exhibited antidepressant-like activity at a lower dose than Gln-Gln-Leu, suggesting that pyroglutamyl peptide had more potent activity. To examine whether pyroglutamyl peptides increased hippocampus neurogenesis, associated with the effects of antidepressants, we measured 5-bromo-2'-deoxyuridine (BrdU) incorporation. pEL and pEQL increased BrdU-positive cells in the dentate gyrus of the hippocampus. Intriguingly, pEL did not increase hippocampal mRNA and protein expression of brain-derived neurotrophic factor (BDNF), which is a factor associated with both neuropoietic and antidepressive effects. Thus, pyroglutamyl peptides may enhance hippocampal neurogenesis via a pathway independent of BDNF. We also confirmed that pEL and pEQL were produced in the subtilisin digest of major wheat proteins, glutenin and gliadin, after heat treatment. pEL and pEQL are the first peptides derived from wheat proteins to be shown to exhibit an antidepressant-like activity.

Dynamics of appetite-mediated gene expression in daidzein-fed female rats in the meal-feeding method.

We previously found that daidzein decreased food intake in female rats. The present study aimed to elucidate the relationship between dynamics of appetite-mediated neuropeptides and the anorectic effect of daidzein. We examined appetite-mediated gene expression in the hypothalamus and small intestine during the 3 meals per day feeding method. Daidzein had an anorectic effect specifically at the second feeding. Neuropeptide-Y (NPY) and galanin mRNA levels in the hypothalamus were significantly higher after feeding in the control but not in the daidzein group, suggesting that daidzein attenuated the postprandial increase in NPY and galanin expression. The daidzein group had higher corticotrophin-releasing hormone (CRH) mRNA levels in the hypothalamus after feeding, and increased cholelcystokinin (CCK) mRNA levels in the small intestine, suggesting that CCK is involved in the hypothalamic regulation of this　anorectic effect. Therefore, daidzein may induce anorexia by suppressing expression of NPY and galanin and increasing expression of CRH in the hypothalamus.