Molecular docking and antihypertensive effects of a novel angiotensin-I converting enzyme inhibitory peptide from yak bone.

A novel angiotensin-converting enzyme (ACE) inhibitory peptide ser-ala-ser-val-ile-pro-val-ser-ala-val-arg-ala (SASVIPVSAVRA) was purified and identified from yak bone by Electrospray Ionization-Time of Flight-Mass Spectrometry (ESI-TOF-MS). Results in vitro showed that the peptide exhibited strong ACE inhibition activities with an IC50 of 54.22 µM. Molecular docking results showed the binding between the peptide SASVIPVSAVRA and ACE mainly driven by van der Waals forces, hydrogen bonds and metal receptor. Interestingly, the ACE inhibition activities of the peptide increased about 19% after digestion, but none of its metabolites showed stronger activity than it. The in vivo experiment showed that the antihypertensive effect of peptide SASVIPVSAVRA at dose of 30 mg/kg is nearly equal to Captopril at dose of 10 mg/kg to spontaneously hypertensive rats (SHRs). The antihypertensive effect mechanism of SASVIPVSAVRA should be further studied through plasma metabolomics and bioanalysis. Structure analysis of amino acids and peptides produced during digestion may help better understand the antihypertensive effect of peptides.

Microbiome-metabolomics insights into the feces of high-fat diet mice to reveal the anti-obesity effects of yak (Bos grunniens) bone collagen hydrolysates.

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.

Purification and characterization of antioxidant peptides from yak (Bos grunniens) bone hydrolysates and evaluation of cellular antioxidant activity.

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.

Novel antioxidant and ACE inhibitory peptide identified from Arthrospira platensis protein and stability against thermal/pH treatments and simulated gastrointestinal digestion.

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.

Purification and identification of novel antioxidant peptides from silver carp muscle hydrolysate after simulated gastrointestinal digestion and transepithelial transport.

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 weight <1 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.

Evaluating the effects of IADHFL on inhibiting DPP-IV activity and expression in Caco-2 cells and contributing to the amount of insulin released from INS-1 cells in vitro.

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.