Integrated HS-SPME-GC/MS and RNA sequencing analysis reveals metabolic differences of flavor compounds of muscle tissues with different intramuscular fat contents from Tibetan sheep.

Abstract

Background: A key factor used to evaluate the quality of meat is intramuscular fat (IMF) content, which has a strong association with the flavor of meat. To date, however, the influence of IMF content on the volatile profiles of ovine meat has not been clarified.

Results: We used headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) to study the aroma characteristics of low-IMF (L-IMF) and high-IMF (H-IMF) content in muscle tissue and to identify volatile compounds in L-IMF and H-IMF groups. Thirteen of 557 volatile compounds identified were significantly different between the groups (Odor Activity Values > 1, VIP values > 1), of which aldehydes, ketones, and esters were the predominant volatile compounds. We conducted RNA-seq analysis and found 985 differentially expressed genes (DEGs) in the L-IMF and H-IMF groups. The weighted gene coexpression network analysis (WGCNA) showed that DEGs associated with muscle aroma characteristics were enriched in lipolysis regulation in adipocytes, PPAR signaling, AMPK signaling, arachidonic acid metabolism, and the biosynthesis of unsaturated fatty acids (UFAs). These pathways played a role in regulating energy metabolism and muscle lipid metabolism functions in Tibetan sheep. The combined results of DEGs, WGCNA, and gene-aroma compound interactions revealed ADIPOQ, FABP4, FADS2, GPD2, HSL, LEP, PEPCK and PLIN4 to be potential candidate genes affecting IMF and aroma compounds content.

Conclusion: In this study, we established profiles of the transcriptome and volatile compounds of L-IMF and H-IMF ovine muscle tissues. The findings suggested that HSL, FABP4 and PLIN4, along with the lipolysis regulation in adipocytes and PPAR signaling pathways, contributed to the difference in lipid metabolism within muscle tissues, and biosynthesis of the UFA pathway may influence the production of volatile compound precursors in muscles. These results offer important information about regulating genes that pertain to ovine meat flavor compounds.