Differential Expression of Genes in Fatty Acid Metabolism and Inflammation Pathways in Pectoralis Major of Broilers with Woody Breast Myopathy.

Abstract

Increased fat content and inflammation are observed in woody breast (WB) muscles, suggesting dysregulation of fatty acids and inflammation in WB conditions. This study evaluated the gene expression related to fatty acid metabolism and inflammation responses in WB muscle. In total, 112 Ross × Ross 708 broiler chickens were raised following the commercial husbandry recommendations in a floor-pen chicken house. On day 41, the WB condition of each bird was assessed through palpation, and the birds were then categorized into normal and WB phenotypes. Next, 10 birds were euthanatized, five of which exhibited normal breast conditions (normal group) and five of which exhibited WB conditions (woody group), and breast muscle was sampled. RNA was extracted and reverse transcribed. The first-strand complementary DNA (cDNA) was analyzed using the real-time RT² Profiler PCR Array, targeting 84 genes associated with chicken fatty acid metabolism and five housekeeping genes. Additionally, this cDNA was subjected to real-time quantitative PCR for 10 inflammatory genes, utilizing the chicken 18S rRNA gene as housekeeping control. Fold changes were calculated using the difference in cycle threshold (ΔΔCt) method and were compared using the Student t-test with a significance level set at P ≤ 0.05. Eight of the 84 examined genes related to lipid metabolism showed differential expression (P ≤ 0.05) between normal breast and WB samples. Specifically, three genes were upregulated (P ≤ 0.05) in WB samples: acetyl-coenzyme A acetyltransferase 2, alcohol dehydrogenase 6, and glycerol kinase. In contrast, five genes were downregulated (P ≤ 0.05) in WB samples: acyl-coenzyme A (CoA) dehydrogenase, acyl-CoA synthetase medium-chain family member 4, glycerol-3-phosphate dehydrogenase 2, 5'-AMP-activated protein kinase subunit beta-2, and 5'-AMP-activated protein kinase subunit gamma-3, where AMP is adenosine monophosphate. Compared to the normal group, the expression levels of Toll-like receptor 2A, Toll-like receptor 4, interferon-γ, interleukin-1β, and interleukin-6 in the WB group were significantly increased (P ≤ 0.05). In conclusion, gene expression in WB muscle indicated upregulation of lipid biosynthesis, downregulation of fatty acid catabolism, and an activated inflammation response. This study revealed significant gene expression changes in fatty acid metabolism and inflammatory responses as key factors in the development of WB in broilers.