Dietary Glycine and Methyl Donors Remodel Gut Microbiota to Enhance Collagen Synthesis in Sea Cucumber ().

Collagen content is a primary indicator of quality traits in aquatic animals, with dietary supplementation currently being the main approach to enhance collagen levels. However, the pathways by which food-derived components mediate host collagen synthesis via the gut microbiota remain unclear. This study investigated the regulatory role of gut microbiota in collagen synthesis within the body wall of the sea cucumber () under dietary supplementation. The results showed that the groups supplemented with 0.60% choline (DJ), 0.50% betaine (TC), and 2.75% glycine (G) significantly increased the collagen content in the sea cucumber body wall by 8.82%, 21.28%, and 22.13%, respectively, compared to the control group (NC). The composition and metabolic function of the sea cucumber gut microbiota were altered by dietary supplementation. The dominant gut microbiota in the supplemented group were , , , and , which possess capabilities in amino acid metabolism and the decomposition of organic carbon and nitrogen sources. In addition, metabolic pathways such as amino acid metabolism, carbohydrate metabolism, energy metabolism, and nucleotide metabolism were significantly enriched. Glycine and other key collagen precursors exhibited significantly elevated levels in the gut of supplemented sea cucumbers. Research indicates that dietary supplementation with choline, betaine, and glycine modulates the composition and function of the gut microbiota in sea cucumbers. This supplementation also promotes the accumulation of collagen precursors and influences collagen content in the body wall. The objective of this study is to provide a theoretical basis to enhance the quality and efficiency of the sea cucumber aquaculture industry.