Molecular Pathways for Muscle and Adipose Tissue Are Altered between Beef Steers Classed as Choice or Standard

Area of Science:

• Animal Science
• Genomics
• Food Science

Background:

• Beef eating quality is influenced by intramuscular and subcutaneous fat levels.
• Variations in fat content affect beef acceptability, uniformity, and tenderness.
• Understanding gene expression differences is crucial for optimizing beef quality targets.

Purpose of the Study:

• To investigate gene expression differences in muscle and adipose tissue related to varying fat endpoints in beef carcasses.
• To determine if subcutaneous fat can serve as a reliable indicator for intramuscular fat (marbling) gene expression.
• To identify genes involved in metabolism and intercellular signaling that impact beef quality.

Main Methods:

• Collected longissimus thoracis muscle and adipose tissue samples from beef carcasses at harvest.
• Extracted RNA and performed RNA sequencing (RNAseq) for gene expression analysis.
• Utilized edgeR for differential gene expression analysis with adjusted p-values (Benjamini-Hochberg), setting thresholds at p<0.005 and log2(fold change)>1.

Main Results:

• Subcutaneous adipose tissue gene expression showed no significant differences compared to intermuscular fat depots.
• Comparing Standard and Choice USDA quality grades, 15 genes were downregulated and 20 upregulated in muscle tissue.
• Adipose tissue showed more significant gene expression changes (49 downregulated, 113 upregulated) between Standard and Choice grades, primarily related to fat and energy metabolism.

Conclusions:

• Subcutaneous fat gene expression can adequately represent fat tissue changes and may be a suitable surrogate for evaluating fat tissue transcriptomics.
• Muscle tissue exhibits less variation in gene expression compared to adipose tissue across different quality grades.
• While subcutaneous fat reflects overall fat metabolism, its utility as a direct surrogate for muscle marbling requires further investigation.