Lanzhou Fat-Tailed sheep (LFTS), a local characteristic sheep breed in Gansu province, China, possess tail fat with low cholesterol content and a unique aroma. This fat exhibit moisturizing, anti-inflammatory, and immunity-enhancing properties. In this study, the tail fat of LFTS was used as raw material, and three components with varying polarities were obtained via silica gel column chromatography. It was observed that HPF, the high polarity fraction of LFTS tail fat, had significant scavenging effect on DPPH, ABTS⁺, ·OH, and O₂^- radicals. Application of different polarity fractions of sheep tail fat to a whole skin defect model in mice. The results indicated that HPF, MPF, and LPF were outperformed the NT group in terms of wound healing rate, scab removal time, anti-inflammatory effects, and the promotion of collagen fibers production and remodeling. Notably, the HPF fraction reduced serum IL-1β in the mouse wound model, a pro-inflammatory cytokine associated with wound inflammation. Additionally, HPF decreased the levels of pro-inflammatory factors IL-1β and TNF-α while increasing the levels of the growth factor TGF-β1 in the skin of trauma model mice. Pathological analysis revealed that HPF accelerated the generation of hair follicles, sebaceous glands, and promoted collagen deposition and remodeling, thereby preventing scar formation. qRT-PCR and Western blot analyses of wounds and surrounding skin demonstrated that HPF upregulated the transcription and protein expression of TGF-β1 while downregulating Smad3 transcription and expression, thus enhancing wound healing.

In this experiment, HEK293 cells were induced by H₂O₂ to establish a cell model of oxidative damage, and the optimal H₂O₂ concentration and treatment time were determined. The effects of five antioxidant peptides (AFK, IEQI, FPFF, LPVPQ and RELEEL) derived from yak milk casein on the survival rate, malondialdehyde (MDA) content, antioxidant enzyme activities, reduced glutathione and oxidized glutathione contents of the damaged cells were studied, and the mechanism of action of the antioxidant peptides was explored to provide a theoretical basis for their development and application in high value-added biological products and functional foods. The results showed that these antioxidant peptides had different scavenging effects on different radical species, but they all showed a dose-effect relationship. After being treated with a final concentration of 400 μmol/L H₂O₂ for 12 h, the inhibitory rate of HEK293 cells was (46.21 ± 0.40)%. Cytotoxicity test showed that the five antioxidant peptides had no toxic or side effects on HEK-293 cells, and did not promote cell proliferation either. These antioxidant peptides could significantly reduce the contents of malondialdehyde (except LPVPQ) and oxidized glutathione in HEK293 cells damaged by oxidation, and enhance the activity of antioxidant enzymes. RELEEL at a concentration of 200 μg/mL significantly reduced MDA content to (0.062 ± 0.000) nmol/10⁴ cells and increased glutathione content to (61.17 ± 2.48) μg/10⁶ cells while maintaining high GSH/GSSG ratio of 64.93 ± 0.95. The antioxidant peptide LPVPQ at 200 μg/mL significantly reduced the content of oxidized glutathione to (0.74 ± 0.26) μg/10⁶ cells and increased the activity of superoxide dismutase (SOD) to (1.17 ± 0.02) U/10⁴ cells; the antioxidant peptide AFK at 200 μg/mL significantly enhanced catalase (CAT) activity to (0.60 ± 0.09) U/10⁴ cells. These results indicate that the antioxidant peptides derived from yak milk casein have positive effects on cells damaged by oxidation, which can provide a reference for further development of relevant products.

This study aimed to investigate the structure-function relationship of angiotensin-converting enzyme (ACE) inhibitory peptides and to elucidate the action mechanism of food-derived ACE inhibitory peptides. Based on the amino acid sequences of recently reported ACE inhibitory pentapeptides and their half-maximal inhibitory concentration (IC₅₀) values, a library of ACE inhibitory pentapeptides was generated and the structures of the ACE inhibitory pentapeptides were characterized using three amino acid descriptors, Z-scales, VHSE and SVHEHS. A partial least square (PLS) model for describing the quantitative structure-activity relationship (QSAR) of the ACE inhibitory peptides with the hydrophobic properties, steric properties, and electrical properties of amino acids as the independent variables and the lg IC₅₀ of the ACE inhibitory pentapeptides as the dependent variable was established using Matlab software. The results showed that the R² and Q² of the QSAR model based on Z-scales descriptor were 0.6411 and 0.5369, respectively, and Gln-Arg-Pro-Asn-Met showed higher ACE inhibitory activity as predicted by this model. The predicted and measured IC₅₀ were 0.0517 and (0.0400 ± 0.0083) μmol/L, respectively, and the error between them was 0.0117 μmol/L. The R² and Q² of the QSAR model based on VHSE descriptor were 0.7636 and 0.5081, respectively, and Leu-Arg-Ala-Phe-Gln exhibited better ACE inhibitory activity as predicted by this model. The predicted and measured IC₅₀ were 0.0438 and (0.0273 ± 0.0053) μmol/L, respectively, and the error between them was 0.0165 μmol/L. The R² and Q² of the QSAR model based on SVHEHS descriptor were 0.8405 and 0.4005, respectively, and Leu-Arg-Ala-Phe-Gln displayed better ACE inhibitory activity as predicted by this model. The predicted and measured IC₅₀ were 0.0055 and (0.0312 ± 0.0042) μmol/L, and the error between them was 0.0257 μmol/L. Among the three QSAR models, the one based on SVHEHS descriptor had the strongest fitting capability but weak predictive capacity, while the models based on Z-scales and VHSE descriptors could allow good QSAR analysis of the pentapeptides. Our modeling analysis showed that the activity of the ACE inhibitory peptides was negatively correlated with the hydrophobic characteristics of amino acids and positively correlated with the steric characteristics of amino acids. Molecular docking of three ACE inhibitory peptides to ACE protein (2X8J) showed that all the ACE inhibitory peptides could bind to ACE protein. This study provides a new tool for developing ACE inhibitory peptides and a theoretical basis for the development and application of food-derived ACE inhibitory peptides.