Dietary OPL-rich structured lipid modulates the nutritional characteristics of developing muscle and is associated with lipid and amino acid metabolic changes in juvenile largemouth bass.

1-Oleoyl-2-palmitoyl-3-linoleoylglycerol (OPL) is a representative sn-2 palmitate-containing triacylglycerol (TAG) relevant to human milk fat and early-life lipid nutrition. However, whether dietary OPL-rich structured lipid affects developing muscle nutritional characteristics and associated metabolic features remains unclear. In this study, juvenile largemouth bass were used as a developmental model to compare dietary OPL-rich oil with a mixed oil (MO), which had a similar total fatty acid composition but a lower sn-2 palmitate content. Dietary OPL-rich structured lipid significantly increased muscle crude protein content, muscle fiber area percentage, the proportion of larger-diameter fibers, springiness and cohesiveness. Untargeted metabolomics identified candidate metabolites with nominal differences, including higher abundances of DHA, linoleyl carnitine, LysoPE(18:0/0:0), L-phenylalanine, anserine and adenine, and lower abundances of β-leucine, linoleic acid and inosinic acid in the OPL group compared with the MO group. These metabolites were mapped to pathways including D-amino acid metabolism, histidine metabolism, β-alanine metabolism, biosynthesis of unsaturated fatty acids, phenylalanine, tyrosine and tryptophan biosynthesis, and linoleic acid metabolism. Targeted amino acid profiling further showed that dietary OPL-rich structured lipid increased total amino acids and essential amino acids in developing muscle. Overall, dietary OPL-rich structured lipid improved nutritional characteristics of developing muscle in juvenile largemouth bass, accompanied by changes in lipid, amino acid, dipeptide and nucleotide metabolism. These findings support further evaluation of OPL-rich structured lipids enriched in sn-2 palmitate as functional lipid ingredients for early-life nutrition.