Effects of fish collagen on hairless mice skin photoaging induced by ultraviolet irradiation via regulation of the TGF- β signaling pathway

Collagen is a popular supplement and an essential protein associated with the preservation of skin firmness. Here, effects of fish collagen administration on skin aging symptoms and gut microbiota composition were investigated using ultraviolet (UV) B-irradiated SKH-1 hairless mice. Eight weeks of high-dose fish collagen administration significantly improved skin moisture and wrinkle parameters. Histopathological and molecular analyses revealed that fish collagen affected reactive oxygen species (ROS) and cytokine production, and the expression of genes related to extracellular matrix (ECM) homeostasis and significantly improved the epidermal thickness and collagen content. Additionally, collagen increased intracellular signaling process-related transforming growth fac-tor-beta (TGF-β) and TGF-β receptor levels and Smad phosphorylation. Furthermore, collagen administration significantly changed the abundance of Limosilactobacillus, Akkermansia, and Ruminococcus at the genus level. Collectively, fish collagen regulated ECM homeostasis, ROS and cytokine production, and the gut microbiota composition to increase skin health, including the reduction of skin wrinkles.