Anti-Photoaging Effect of Pinctada martensii Hydrolysates on Ultraviolet B-Irradiated Nude Mice Skin

Pinctada martensii is a marine resource with potential for bioactive peptide development, but its anti-photoaging properties remain underexplored. In this study, Pinctada martensii meat hydrolysates (PME) were prepared by enzymatic hydrolysis, and their anti-photoaging effects were evaluated in an in vivo ultraviolet-B (UVB)-irradiated nude mouse model. The results showed that PME markedly ameliorated UVB-induced skin damage. UVB increased epidermal thickness from 21.60 μm in the Control to 47.50 μm in the Model, and PME reduced epidermal thickness to 22.46 μm. Dermal collagen content decreased from 64.58% in the Control to 26.22% in the Model and was restored to 52.75% by PME. UVB upregulated matrix metalloproteinases-1 (MMP-1), MMP-3 and MMP-9 by approximately 2.20-, 1.93- and 3.09-fold relative to the Control, and PME suppressed these matrix metalloproteinases (MMPs) by approximately 61%, 65% and 52%, respectively. Extracellular signal-regulated kinase (ERK) expression increased to 1.41-fold in the Model and was reduced to about 1.05-fold after PME treatment, suggesting inhibition of collagen degradation-related pathways. Untargeted serum metabolomics identified 205 differential metabolites between the Model and the Control, and PME shifted metabolite profiles toward those of the Control. Total short-chain fatty acids (SCFAs) decreased from 868.69 μmol/g in the Control to 301.34 μmol/g in the Model and increased to approximately 562 μmol/g after PME treatment, accompanied by modulation of the gut microbiota including recovery of Lachnospiraceae members, indicating involvement of the gut-skin axis. These findings support the potential of Pinctada martensii meat as a source for developing novel functional foods targeting skin photoaging.