Identification and mechanistic insights into immunomodulatory peptides from soft-shelled turtle hydrolysates

The soft-shelled turtle (Pelodiscus sinensis) is prized for its nutritional and medicinal properties and represents an excellent source of bioactive peptides. This study elucidates the immunomodulatory mechanisms of peptides from soft-shelled turtle. Peptide sequences were virtually screened against Toll-like receptors targets, including TLR4/MD2. Subsequent validation in cellular and zebrafish models identified two potent anti-inflammatory peptides, P1 (PGPSGLIGPA) and P7 (PASAPAPAPA). Both peptides exhibited strong TLR4/MD2 binding and significantly suppressed LPS-induced production of nitric oxide, TNF-α, and IL-6 in macrophages. Transcriptomic analysis revealed that P1 primarily modulates the NF-κB pathway, whereas P7 influences neuroinflammation-associated pathways. Furthermore, using an in vitro gut simulation model, we demonstrated their prebiotic-like potential. Both peptides counteracted dysbiosis-induced elevations in propionate and butyrate, with P7 additionally enhancing microbial alpha diversity. These findings provide the first evidence for the dual immunomodulatory and microbiota-regulating functions of these specific turtle-derived peptides, highlighting their promise as functional food ingredients.