Lipidomic and Transcriptomic Analysis of the Longissimus Muscle of Luchuan and Duroc Pigs

Abstract

Meat is an essential food, and pork is the largest consumer meat product in China and the world. Intramuscular fat has always been the basis for people to select and judge meat products. Therefore, we selected the Duroc, a western lean pig breed, and the Luchuan, a Chinese obese pig breed, as models, and used the longissimus dorsi muscle for lipidomics testing and transcriptomics sequencing. The purpose of the study was to determine the differences in intramuscular fat between the two breeds and identify the reasons for the differences. We found that the intramuscular fat content of Luchuan pigs was significantly higher than that of Duroc pigs. The triglycerides and diglycerides related to flavor were higher in Luchuan pigs compared to Duroc pigs. This phenotype may be caused by the difference in the expression of key genes in the glycerolipid metabolism signaling pathway.

Keywords: Duroc; Luchuan; intramuscular fat; lipomics; pork.

Figure 1

The difference in IMF content and muscle fiber type between Luchuan and Duroc pigs. (A) Body weight. (B) Muscle triglyceride levels. (C,D) Western blot of type I and II muscle fibers and its quantification. The data are expressed as mean ± SD. ^*P < 0.05, ^**P < 0.01.

Figure 2

Muscle lipid composition and correlation. (A) Lipidomics correlation analysis. (B) Principal component analysis (PCA), and (C) orthogonal partial least squares discriminant analysis (OPLS-DA) of muscle tissue from six Luchuan and Duroc pigs.

Figure 3

Total lipid difference analysis. (A) Overall sample cluster heat map. (B) Correlation analysis for significantly different metabolites (top 50 VIP value). Red represents positive correlation, green represents negative correlation.

Figure 4

Different metabolites related to meat quality and flavor. (A) Top ten upregulated metabolites (P-value). (B) Top ten downregulated metabolites (P-value). (C) The number (in the column) of carbons in the alkyl chain of differential metabolites and their percentages. (D) Saturation of differential metabolites and their percentages. (E) The average number of carbons and saturation in alkyl chains in different metabolites.

Figure 5

Pathways enriched by differential metabolites. (A) KEGG classification. (B) Enrichment of KEGG signaling pathway. Rich factor is the ratio of the number of different metabolites in the corresponding pathway to the total number of metabolites detected and annotated by the pathway. The larger the value, the greater the degree of enrichment. The closer the P-value is to 0, the more significant the enrichment. The size of the dot in the figure represents the number of significantly different metabolites enriched in the corresponding pathway.

Figure 6

Transcriptome analysis. (A) Transcriptome correlation analysis. (B) Gene Ontology (GO) enrichment. (C) KEGG classification. LM, Luchuan muscle; DM, Duroc muscle.

Figure 7

Joint analysis of transcriptome and metabolomics. (A) Enrichment of pathway genes and metabolites (red represents the enriched P-value of differential genes, and green represents the enriched P-value of differential metabolites). (B) Differential genes and differential metabolites of the same group of the KEGG pathway (red represents upregulation, green represents downregulation, and blue represents both upregulation and downregulation). (C) Lipid synthesis related genes. FASN, fatty acid synthase; SREBP1, Sterol-regulatory element binding protein 1. (D) Key genes expression of glycerolipid metabolism pathway. AKR1B1, Aldo-Keto Reductase Family 1 Member B 1. The data are expressed as mean ± SD. *P < 0.05.