The novel angiotensin-I-converting enzyme inhibitory peptides from Scomber japonicus muscle protein hydrolysates: QSAR-based screening, molecular docking, kinetic and stability studies.

Food-derived angiotensin-converting enzyme-inhibitory (ACE-I) peptides have attracted extensive attention. Herein, the ACE-I peptides from Scomber japonicus muscle hydrolysates were screened, and their mechanisms of action and inhibition stability were explored. The quantitative structure-activity relationship (QSAR) model based on 5z-scale metrics was developed to rapidly screen for ACE-I peptides. Two novel potential ACE-I peptides (LTPFT, PLITT) were predicted through this model coupled with in silico screening, of which PLITT had the highest activity (IC50: 48.73 ± 7.59 µM). PLITT inhibited ACE activity with a mixture of non-competitive and competitive mechanisms, and this inhibition mainly contributed to the hydrogen bonding based on molecular docking study. PLITT is stable under high temperatures, pH, glucose, and NaCl. The zinc ions (Zn2+) and copper ions (Cu2+) enhanced ACE-I activity. The study suggests that the QSAR model is effective in rapidly screening for ACE-I inhibitors, and PLITT can be supplemented in foods to lower blood pressure.

Physicochemical characterization and antioxidant effects of green microalga Chlorella pyrenoidosa polysaccharide by regulation of microRNAs and gut microbiota in Caenorhabditis elegans.

A novel polysaccharide from Chlorella pyrenoidosa (CPP) was separated and purified with the average molecular weight 15.8 kDa. It was composed of seven monosaccharides including mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose. FT-IR and NMR spectra analysis further revealed that CPP was an acidic polysaccharide consisting of ß-L-Arap-(1→, →2)-α-L-Rhap-(1→, ß-D-GlcpA-(1→, →4)-α-D-GalpA-(1→, →6)-ß-D-Glcp-(1→, →3)-ß-D-Manp-(1→, and →3, 6)-ß-D-Galp-(1→. The CPP treatment could effectively prolong lifespan of Caenorhabditis elegans under the oxidative stress conditions and inhibit the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) as well as enhancing the level of superoxide dismutase (SOD). It could up-regulate the expressions of Daf-16 and Skn-1 genes via declining miR-48-3p, miR-48-5p, and miR-51-5p translocation. Moreover, 16S rRNA sequencing revealed that the CPP-enriched Faecalibacterium, Haemophilus, Vibrio, and Shewanella were strongly correlated with SOD, MDA, apoptosis, and ROS. These results indicated that CPP may be considered as a desired ingredient on regulating the aging and oxidative diseases.

Anti-fatigue property of the oyster polypeptide fraction and its effect on gut microbiota in mice.

We aimed to evaluate the anti-fatigue effects of the oyster polypeptide (OP) fraction and its regulatory effect on the gut microbiota in mice. Our exhaustive swimming experiment showed that the swimming time of the low-, middle- and high-dose groups of the OP fraction was increased by 1.82, 2.18 and 2.44 times compared with the control group, respectively. Besides, the liver glycogen levels of the three groups were increased by 19.3%, 42.02% and 65.07%, while the lactate levels were decreased by 18.85%, 21.18% and 28.74%, respectively. Moreover, administration of the OP fraction upregulated the expressions of PEPCK and AMPK, but downregulated the TNF-α expression. Correlation analysis between the gut microbiota and fatigue-related biochemical indicators showed that Faecalibacterium, Desulfovibri and Intestinibacter were negatively correlated with the swimming time, blood lactate, blood urea nitrogen, liver glycogen and muscle glycogen, while Yaniella and Romboutsia were positively correlated. Therefore, the OP fraction had anti-fatigue effects, and could regulate the abundance of gut microbiota and maintain its balance.