Combined analysis of lncRNA and mRNA emphasizes the potential role of tryptophan-mediated regulation of muscle development in weaned piglets by lncRNA.

Pork is an important high-value protein source that fulfills the nutritional requirements for normal growth development, repair, and metabolism. Tryptophan (Trp), a crucial amino acid for piglet growth performance and muscle development, has an essential yet unclear regulatory mechanism. To investigate the biological basis of Trp regulation of piglet muscle development and identify the related regulatory pathways, we studied 20 weaned piglets. The piglets were divided into control (CON, 0.14% Trp) and high Trp (HT, 0.35% Trp) groups. They were fed with different Trp concentrations for 28 days, after which we collected the longissimus dorsi (LD) muscle for histomorphometric analysis and RNA extraction. Our results showed that the HT diet significantly increased the average daily weight gain, myocyte number, and muscle fiber density in weaned piglets. We then analyzed the differentially expressed (DE) genes in the LD muscle through RNA sequencing (RNA-seq). We identified 253 lncRNAs and 1055 mRNAs mainly involved in myoblast proliferation and myofiber formation, particularly through the FoxO and AMPK signaling pathways and metabolism. Further analysis of the DE lncRNA targeting relationship and construction of a protein-protein interaction (PPI) network resulted in the discovery of a novel lncRNA, XLOC_021675 or FRPMD, and elucidated its role in regulating piglet muscle development. Finally, we confirmed the RNA-seq results by reverse transcription polymerase chain reaction (RT-PCR). This study provides valuable insights into the regulatory mechanism of lncRNA-mediated Trp regulation of muscle development in weaned piglets offering a theoretical basis for optimizing piglet dietary ratios and enhancing pork production.