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Evidences suggest that the homeostasis of gut microbiota is among the most important factors for maintaining the physical and mental health of the host. Among the multiple factors affecting the homeostasis of gut microbiota, diet is one of the decisive factors. Bioactive peptides derived from protein hydrolyzed by protease or fermented by microorganism have many physiological activities that their parent proteins do not have. Currently, bioactive peptides attract more and more attention due to their bidirectional interaction with gut microbes. It has been reported that some bioactive peptides could alter the composition of gut microbiota by influencing the intestinal microenvironment. Meanwhile, quite a few bioactive peptides that are released by gut microbes or intestinal cells could resist the pathogenic bacteria to sustain the homeostasis of gut microbiota. In this review, some exogenous bioactive peptides derived from food and some endogenous bioactive peptides released from intestinal cells or microbes were discussed to summary their effects on the modulation of gut microbiota. This review is expected to provide new ideas for related research, and as well to promote the application of bioactive peptides in the fields of food and medicine.

In this study, papain and alcalase were used to generate antioxidant peptides from yak bone protein. The antioxidant activities of hydrolysates in vitro were evaluated by 2,2′-azinobios-(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity, total reducing power, ferrous ion chelating ability and hydroxyl radical scavenging activity. The hydrolysates generated by alcalase possessed the best antioxidant activity among unhydrolyzed protein and samples treated by papain, but the antioxidant activity decreased after simulated gastrointestinal digestion in vitro. The products of simulated gastrointestinal digestion were separated by ultrafiltration and high performance liquid chromatography, and the amino acid sequences of peptides were identified by mass spectrometry. The digestion sites within peptides were predicted by a bioinformatics strategy, and ten peptides were selected for synthesis. Among 10 synthetic peptides, Gly-Phe-Hyp-Gly-Ala-Asp-Gly-Val-Ala, Gly-Gly-Pro-Gln-Gly-Pro-Arg and Gly-Ser-Gln-Gly-Ser-Gln-Gly-Pro-Ala possessed strong antioxidant activities, among which Gly-Phe-Hyp-Gly-Ala-Asp-Gly-Val-Ala had a significant cytoprotective effect in Caco-2 cells under oxidative stress induced by H2O2, which reduced the formation of reactive oxygen species and malondialdehyde, and improved the activity of antioxidant enzymes in cells. These results showed that yak bone peptides exhibited strong antioxidant activity and have a potential value as a new type of natural antioxidant.

Dipeptidyl peptidase IV (DPP-IV) inhibitors have become a new choice to treat diabetes. Here, we studied the DPP-IV inhibitory activity of protein hydrolysates from common carp (Cyprinus carpio) roe. The molecular weight distribution and simulated gastrointestinal digestive stability of hydrolysates produced by four enzymes were analyzed. Papain-generated hydrolysate showed the highest DPP-IV inhibition and effective gastrointestinal stability. New effective peptide sequences from papain hydrolysates were identified using liquid chromatography-tandem mass spectrometry. The bioactivity of IPNVAVD, which was identified from papain hydrolysate (IC50 value of 777.35 ± 5.50 μM), was investigated by Caco-2 and HepG2 cell models. We found that the DPP-IV inhibition by papain hydrolysate was not attenuated after simulated gastrointestinal digestion. In addition, IPNVAVD significantly inhibited the DPP-IV secreted by Caco-2 cells with no cytotoxicity. It also promoted glucose uptake in insulin-resistant HepG2 cells. Transport experiments showed that IPNVAVD could be absorbed intactly by the Caco-2 cell monolayer. Protein hydrolysates from common carp roe inhibited DPP-IV effectively, and they may have potential as functional ingredients in food for diabetic patients.

In this study, papain and alcalase were used to generate antioxidant peptides from yak bone protein. The antioxidant activities of hydrolysates in vitro were evaluated by 2,2′-azinobios-(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity, total reducing power, ferrous ion chelating ability and hydroxyl radical scavenging activity. The hydrolysates generated by alcalase possessed the best antioxidant activity among unhydrolyzed protein and samples treated by papain, but the antioxidant activity decreased after simulated gastrointestinal digestion in vitro. The products of simulated gastrointestinal digestion were separated by ultrafiltration and high performance liquid chromatography, and the amino acid sequences of peptides were identified by mass spectrometry. The digestion sites within peptides were predicted by a bioinformatics strategy, and ten peptides were selected for synthesis. Among 10 synthetic peptides, Gly-Phe-Hyp-Gly-Ala-Asp-Gly-Val-Ala, Gly-Gly-Pro-Gln-Gly-Pro-Arg and Gly-Ser-Gln-Gly-Ser-Gln-Gly-Pro-Ala possessed strong antioxidant activities, among which Gly-Phe-Hyp-Gly-Ala-Asp-Gly-Val-Ala had a significant cytoprotective effect in Caco-2 cells under oxidative stress induced by H(2)O(2), which reduced the formation of reactive oxygen species and malondialdehyde, and improved the activity of antioxidant enzymes in cells. These results showed that yak bone peptides exhibited strong antioxidant activity and have a potential value as a new type of natural antioxidant.

In current study, novel antioxidant and ACE inhibitory peptides were screened from Arthrospira platensis protein hydrolysates (APH) generated by six different proteases, respectively. The purification steps including ultrafiltration membrane and chromatography were guided by ABTS radical scavenging activity (ARSA), hydroxyl radical scavenging activity (HRSA), ferrous ion chelation activity (FICA) and ACE inhibitory activity. A novel antioxidant peptide VTAGLVGGGAGK, which exhibited highest ARSA, HRSA and FICA with EC50 value of 1.08 mg/mL 1.35 mg/mL and 1.24 mg/mL, respectively, was identified from alcalase-APH. Meanwhile, a novel ACE inhibitory peptide PTGNPLSP with the highest ACE inhibitory activity (IC50 = 1.54 mg/mL) was identified from trypsin-APH. Both VTAGLVGGGAGK and PTGNPLSP had strong stability under thermal processing (25–100 °C) and diverse pH conditions (pH 3–11). In addition, the PTGNPLSP was more stable than VTAGLVGGGAGK during in vitro gastrointestinal digestion. Our findings will provide new knowledge for the development of novel natural antioxidants and ACE inhibitors as well as the high-value utilization of Arthrospira platensis protein.

The objective was to identify peptides with ACE inhibitory activity generated from honeybee pupae hydrolysates. In addition, we simulated gastrointestinal digestion and predicted the potential cleavage sites of the identified peptides. Peptides derived from honeybee pupae were cleaved in silico by pepsin, trypsin, and chymotrypsin using the PeptideCutter tool of ExPASy. Honeybee pupae were hydrolyzed using four different proteases (Alcalase, neutrase, trypsin, and papain), and their ACE inhibitory activity and distribution of molecular weights were determined. The neutrase hydrolysates showed the highest ACE inhibitory activity. Then, the hydrolysates were isolated and purified using ultrafiltration, gel filtration chromatography, and reversed-phased high performance liquid chromatography. Three novel ACE inhibitory peptides were identified by LC–MS/MS, AVFPSIVGR, PPVLVFV, and PGKVHIT, which exhibited the most potent ACE inhibitory activity, with IC50 values of 6.64, 47.7859, and 223.869 µM, respectively. In simulated in silico gastrointestinal digestion, peptides AVPFSIVGR and PGKVHIT had the position of cleavage sites by pepsin, chymotrypsin and trypsin, and PPVLVFV was cleaved by pepsin and chymotrypsin. We hope these results support the application of honeybee pupa hydrolysates as functional ingredients in foods and pharmaceuticals.

Unregulated oxidative reactions occur in human body or food system can cause harmful effects both on food quality and human health. This study aimed to develop novel antioxidant peptides from silver carp muscle hydrolysate after simulated gastrointestinal digestion and transepithelial transport. Results showed that alcalase- and papain-induced hydrolysates had higher antioxidant activities before and after in vitro gastrointestinal digestion. Fractions with molecular weight1 kDa from these two digestive products (named A-GID-1 and P-GID-1) exhibited the greatest antioxidant capacity, which was ascribed to the large proportion of low-molecular peptides and hydrophobic amino acids. After transepithelial transport analysis, a total of ten peptides were identified from the RP-HPLC fractions with the highest antioxidant activity from both P-GID-1 and A-GID-1 permeates. Among them, LVPVAVF exhibited the highest DPPH radical scavenging and reactive oxygen species (ROS) inhibitory activity. Our findings will provide new knowledge for the development of novel natural antioxidants and the high-value utilization of silver carp protein.

In this study, a twelve-week intervention was conducted to investigate the anti-obesity effects of yak bone collagen hydrolysates (YBCH) on mice with a high-fat diet. The obesity-associated phenotypes of mice were detected and the feces of mice were jointly analyzed by 16S rRNA gene sequencing and untargeted metabolomics. Results indicated that supplementation with YBCH could ameliorate the obesity-associated phenotypes of mice, especially with the medium dose (MD) and high dose (HD) of YBCH. Compared with the high-fat diet control (HC) group, the ratio of Firmicutes and Bacteroidetes in the fecal microbiota of the low dose (LD), MD, and HD groups was separately decreased by 29.83 %, 70.85 %, and 75.70 %. Lachnospiraceae and Muribaculaceae were the key bacteria for the YBCH intervention, which might be attributed to their different substrate preferences. The joint analysis of the 16S rRNA gene sequencing and untargeted metabolomics suggested that the anti-obesity effects of YBCH might be achieved by up-regulating the arginine and proline metabolism and down-regulating the aromatic amino acids metabolism via the gut microbiota.

Diabetes and hypertension are increasing threats to human health, which could be improved by inhibiting dipeptidyl peptidase IV (DPP-IV) and angiotensin-converting enzyme (ACE), respectively. Herein, we used five different enzymes to hydrolyze silver carp (Hypophthalmichthys molitrix) muscle protein. Among all treatments, the Neutrase-generated hydrolysate that was purified by a three-step isolation and then was identified using liquid chromatography–tandem mass spectrometry resulted in the most potent DPP-IV inhibitory activity and relatively high ACE inhibitory activity. The identified peptide Ala-Ala-Leu-Glu-Gln-Thr-Glu-Arg was the most effective at inhibiting DPP-IV with a half-maximal inhibitory concentration (IC50) value of 647.02 ± 4.30 µM. Leu-Leu-Asp-Leu-Gly-Val-Pro showed the highest ACE inhibitory activity with an IC50 value of 329.33 ± 15.53 µM. Lys-Ala-Val-Gly-Glu-Pro-Pro-Leu-Phe exhibited the dual inhibition against both DPP-IV and ACE with IC50 values of 1,317.39 ± 20.93 µM and 726.01 ± 8.69 µM, respectively. Interestingly, it seemed that the majority of peptides which were responsible for inhibiting DPP-IV were different from the ones which caused the inhibition of ACE.

Dipeptidyl peptidase-IV (DPP-IV) is a serine exo-peptidase that can inactivate incretins by removing N-terminal dipeptides. Currently, inhibiting the DPP-IV activity is a common treatment for type 2 diabetes (T2D). The goal of this study is to investigate whether IADHFL, a novel DPP-IV inhibitory peptide identified from bighead carp (Hypophthalmichthys nobilis), has the potential to modulate T2D. IADHFL remained stable after simulated gastrointestinal digestion and significantly decreased the activity and expression of both soluble and membrane-bound DPP-IV after 24 h and 48 h of treatment. Intact peptide absorption was observed, but a percentage of the peptide was degraded while passing through a monolayer of Caco-2 cells. In addition, a double-layered cell model showed that the peptide could increase insulin secretion from INS-1 cells after glucose treatments of 2.8 mM and 16.7 mM. Finally, IADHFL could regulate the expression levels of genes associated with insulin secretion and T2D in INS-1 cells.

Yak (Bos grunniens) bone is rich in collagen but there is no knowledge about immunomodulatory effects. The immunomodulatory effects of yak bone hydrolysates (YBHs) obtained by digesting 0.5 h with papain were explored on BALB/c mice in this study. The percentage of small molecular weight (

In the paper, we discuss the properties of Cowan and Mecke's Markov chain P in general form. We give some criteria for determining whether the chain P is transient, recurrent null or recurrent non-null, and for the chain P to have invariant measures.