Antioxidative peptides that inhibit myeloperoxidase (MPO) enzyme activity can effectively defend against oxidative stress damage. The antioxidant peptides from tuna protein were produced using alcalase hydrolysis and purified by ultrafiltration and Sephadex G-15, and the fractions with the highest free radicals scavenging ability and oxygen radical absorbance capacity (ORAC) values were sequenced using HPLC–MS/MS. Fifty-five peptide sequences were identified, 53 of which were successfully docked into MPO. The representative peptide ACGSDGK had better antioxidant activity and inhibition of MPO chlorination and peroxidation than the reference peptide hLF1-11. The docking model further showed intense molecular interactions between ACGSDGK and MPO, including hydrogen bonds, charge, and salt bridge interactions, which occluded the active site and blocked the catalytic activity of MPO. These results suggested that the antioxidant peptide ACGSDGK has the potential to inhibit oxidative stress and alleviate inflammation in vivo because of its inhibitory effect on the MPO enzyme.

In the present study, the antidiabetic properties of Trachinotus ovatus protein hydrolysates (TOH) in streptozotocin-induced diabetic mice were investigated, and peptides with α-amylase (AAM) and dipeptidyl peptidase IV (DPP-IV) inhibitory activities were identified and screened. The results showed that TOH alleviated body weight loss, polyphagia, blood glucose elevation and insulin secretion decline in diabetic mice. After 4 weeks of TOH administration, random blood glucose (RBG) decreased significantly. The TOH groups showed a dose-dependent reduction in fasting blood glucose (FBG), especially in the high-dose TOH group, which reduced FBG by 58% versus the effect of metformin. Moreover, TOH exerted a remarkable protective effect on hepatorenal function, as evidenced by increased superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) and decreased serum urea levels. Histopathological studies confirmed that TOH can significantly protect the kidney and pancreas from histological changes, which was of great benefit for ensuring the normal secretion of insulin and preventing the occurrence of complications such as diabetic nephropathy. Two fractions with higher inhibitory activity against AAM and DPP-IV, F4 and F6, were obtained from the ultrafiltration of TOH-2 (≤3 kDa). A total of 19 potentially active peptides from F4 and 3 potentially active peptides from F6 were screened by LC‒MS/MS combined with bioinformatic analysis. These peptides are small molecular peptides composed of 2-6 amino acids, rich in characteristic amino acids such as proline, arginine, phenylalanine and asparagine, and contain high proportions of peptides (68% for F4, 67% for F6) with hydrophobicity ≥50%. They offer potent antidiabetic potential and could potentially bind to the active sites in the internal cavities of the target enzymes AAM and DPP-IV. In summary, this study revealed for the first time the antidiabetic effects of protein hydrolysates of Trachinotus ovatus and their derived peptides, which are promising natural ingredients with the potential to be used for the treatment or prevention of diabetes.

In the present work, analysis of the hypolipidemic properties of Trachinotus ovatus protein hydrolysates (TOPHs) and identification of peptides with bile acid-binding activity were performed. Hydrolysates prepared by trypsin digestion exhibited the highest in vitro bile acid-binding capacities compared with hydrolysates prepared with the other four proteases and were mainly composed of small peptides and amino acids with molecular weights <3 kDa, accounting for 77.30%. Among the five ultra-filtration fractions of TOPHs, TOPHs-5 (<3 kDa) exhibited the highest in vitro bile acid-binding capacity, which was equivalent to 77.97% of cholestyramine at the same concentration. A total of 68 peptides were identified from TOPHs-5 by LC-ESI-Q-TOF-MS/MS and 9 of them had hydrophobicity of more than 60%. These highly hydrophobic peptides might be associated with the bile acid-binding activity of TOPHs-5. In vivo experiments indicated that the TOPHs could effectively reduce total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and the atherogenic index (AI), while they could evidently increase the high-density lipoprotein cholesterol (HDL-C) content. Furthermore, TOPHs exerted a marked protective effect on hepatorenal function, as evidenced by decreased levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatinine (CREA). Histopathological studies confirmed that TOPHs evidently protected the liver from histological alterations. In summary, for the first time, hypolipidemic effects and subsequential identification were obtained from TOPHs, which are promising natural ingredients that could potentially be employed in the management of hyperlipidemia.

The G. lemaneiformis polysaccharide GP90 potentiates chemotherapy sensitivity by targeting the transferrin receptor and SLC7A11/Gpx4 pathway to induce ferroptosis.