The primary purpose of the current study was to assess the genetic diversity, runs of homozygosity (ROH) and ROH islands in a Chinese composite pig and explore hotspot regions for traces of selection. First, we estimated the length, number, and frequency of ROH in 262 Xidu black pigs using the Porcine SNP50 BeadChip and compared the estimates of inbreeding coefficients, which were calculated based on ROHs (F_ROH) and homozygosity (F_HOM). Our result shows that a total of 7,248 ROH exceeding 1Mb were detected in 262 pigs. In addition, Sus scrofa chromosome (SSC) 8 and SSC10, respectively, has the highest and lowest chromosome coverage by ROH. These results suggest that inbreeding estimation based on total ROH may be a useful method, especially for crossbreed or composite populations. We also calculated an inbreeding coefficient of 0.077 from the total ROH. Eight ROH islands were found in this study. These ROH islands harbored genes associated with fat deposition, muscular development, reproduction, ear shape, and adaptation, such as TRAF7, IGFBP7, XPO1, SLC26A8, PPARD, and OR1F1. These findings may help to understand the effects of environmental and artificial selection on the genome structure of composite pigs. Our results provide a basis for subsequent genomic selection (GS), and provides a reference for the hybrid utilization of other pig breeds.

Porcine skeletal muscle development is closely linked to meat production efficiency and quality. The accumulation of porcine intramuscular fat is influenced by the hyperplasia and hypertrophy of adipocytes within the muscle. However, the cellular profiles corresponding to the two stages of muscle development remain undetermined. Single-nucleus RNA sequencing (snRNA-seq) can elucidate cell subsets in tissues, capture gene expression at the individual cell level, and provide innovative perspectives for studying muscle and intramuscular fat formation. In this study, a total of 78,302 nuclei and 9 clusters of cells, which included fibro/adipogenic progenitor (FAP), myonuclei, adipocytes, and other cell types, of Xidu black pigs, were identified on Day 1 and Day 180. The pattern of cell clustering varied between the two developmental stages. Notably, the percentage of adipocytes in the Day 180 group was higher than in the Day 1 group (0.51% vs. 0.15%). Pseudo-time sequence analysis indicated that FAPs could differentiate into adipocytes and myonuclei cells, respectively. The THRSP gene was identified as a biomarker for swine intramuscular fat cells, and its down-regulation resulted in significant reduction in lipid droplet formation in porcine preadipocytes. Our research provides new insights into the cellular characteristics of intramuscular fat formation, which may facilitate the development of novel strategies to enhance intramuscular fat deposition and improve pork quality.

Background/Objectives: Abnormalities in lipid metabolism and endoplasmic reticulum (ER) stress are strongly associated with the development of a multitude of pathological conditions, including nonalcoholic fatty liver disease (NAFLD), diabetes mellitus, and obesity. Previous studies have indicated a potential connection between thyroid hormone responsive (THRSP) and lipid metabolism and that ER stress may participate in the synthesis of key regulators of adipogenesis. However, the specific mechanisms remain to be investigated. Methods: In this study, we explored the roles of THRSP in lipid metabolism by interfering with THRSP gene expression in mouse mesenchymal stem cells, comparing the effects on adipogenesis between control and interfered groups, and by combining transcriptomic and proteomic analysis. Results: Our results showed that the number of lipid droplets was significantly reduced after interfering with THRSP, and the expression levels of key regulators of adipogenesis, such as LPL, FABP4, PLIN1, and CIDEC, were significantly downregulated. Both transcriptomic and proteomic results showed that the differential genes (proteins) were enriched in the processes of lipolytic regulation, ER stress, cholesterol metabolism, sphingolipid metabolism, PPAR signaling pathway, and glycerophospholipid metabolism. The ER stress marker gene, ATF6, was the most significantly downregulated transcription factor. In addition, RT-qPCR validation indicated that the expression levels of PPAR signaling pathway gene SCD1; key genes of lipid droplet generation including LIPE, DGAT1, and AGPAT2; and ER stress marker gene ATF6 were significantly downregulated. Conclusions: These suggest that THRSP is involved in regulating ER stress and the PPAR signaling pathway, which is closely related to lipid synthesis and metabolism. Interfering with the expression of THRSP may be helpful in ameliorating the occurrence of diseases related to abnormalities in lipid metabolism.

Xiangyang Black (XYB) is a valuable indigenous pig breed from Hubei Province, China, known for its high meat quality, disease resistance, and adaptability

Pork serves as a significant meat commodity, with intramuscular fat (IMF) content being a critical determinant of its quality. However, the epigenetic mechanism of porcine IMF deposition is still unclear. This study integrated proteomics and lactylation profiles from the longissimus thoracis (LT) muscles of pigs with extremely high (IMF_H) and extremely low (IMF_L) IMF content to clarify the association between lactylation and porcine fat deposition. Furthermore, an intramuscular preadipocyte induction and differentiation model was conducted to elucidate the changes in lactylation during adipocyte differentiation. Finally, the regulatory role of lactylation in adipocyte differentiation was explored by modulating lactate production during the induction and differentiation of preadipocytes. Proteomic analysis revealed significantly increased expression of key lipid metabolism related proteins (FASN, APOA4, FABP4, ACLY, PLIN1) in IMF_H pig muscle tissues compared with IMF_L tissues, along with substantial activation of lipid metabolism pathways. Lactylation profiling identified 95 differential lysine sites across 56 proteins, with most showing lower lactylation levels in the IMF_H group. The integrative omics analysis revealed differences in lactylation profiles in porcine LT tissues with varying efficiencies of IMF deposition, highlighted PGK1, PKM, and PYGM as central lactylation-modified proteins in porcine fat deposition regulation. Further in vitro study proved that lactate-mediated lactylation inhibited adipogenic differentiation of porcine intramuscular preadipocytes through PPARγ signaling pathway. This study clarified the changes in the lactylation profile in porcine LT tissues with varying efficiencies of IMF deposition, and demonstrated that lactate-mediated lactylation inhibits the PPARγ signaling pathway and the adipogenic differentiation of porcine intramuscular preadipocyte. This study provided a new insight to understanding the epigenetic regulation mechanisms of lipid deposition in pigs.

Jianli pig (JL) is a representative Chinese local pig breed with a unique fruity flavor and excellent meat quality. However, the reasons for the unique fruity flavor of Jianli pork are still unclear. This study explored the potential genetic mechanisms by performing an integrative analysis of the flavoromics, lipidomics, and transcriptomics of the longissimus thoracis (LT) from JL pigs and Duroc × Landrace × Yorkshire pigs (DLY). The results indicated that the relative abundance of Acetic acid butyl ester and 3-Carene flavor compounds characterized by sweet and fruity aroma in JL pork was higher compared with DLY pigs. Lipidomics results showed that 16-carbon and 18-carbon fatty acids are important lipid precursors for the flavor of JL pork. Moreover, two clusters of functional genes correlated with 3-Carene (DCHS2, NRXN1, JAKMIP3, and TRO) and Acetic acid butyl ester (WFIKKN2, CES3, and IYD) were identified. This study enriched the limited understanding of the unique fruity flavor formation in JL pigs, provided a theoretical basis for the breeding of high-quality pig breeds, and the processing of flavorful meat products.