Potential Role of Ribonucleotide Reductase Enzyme in Mitochondria Function and Woody Breast Condition in Broiler Chickens.

The cellular events leading to the development of the woody breast myopathy in broiler breast muscle are unclear. Affected woody breast muscle exhibits muscle fiber degeneration/regeneration, connective tissue accumulation, and adverse morphological changes in mitochondria. Ribonucleotide reductase (RNR) is an enzyme for the synthesis of dNTP, which is important for mitochondria DNA content (mtDNA). RNR consists of two subunits: . A decrease in is associated with a decrease in mtDNA and mitochondria proteins, leading to impaired ATP production. The objective of this study was to investigate potential RNR differences between woody breast (WB) and normal (N) breast muscle by examining expression and associated pathways. Gene expression and enzyme activities were examined by qPCR and commercial kits. Results showed that expression reduced for WB ( = 0.01) and genes related to mitochondria, including ( = 0.03), ( = 0.001), ( = 0.07), ( = 0.001) and ( = 0.03). Furthermore, and , which are related to mitochondria and ATP synthesis, tended to be reduced in WB. Compared to N, reduced for WB ( = 0.05), which is responsible for glucose transport in cells. Consequently, ( = 0.0001) and ( = 0.008) increased in WB, suggesting increased fatty acid oxidation. Citric synthase activity and the NAD/NADH ratio ( = 0.02) both reduced for WB, while WB increased expression ( = 0.001), which is a possible indicator of high reactive oxygen species levels. In conclusion, a reduction in impaired mitochondria function, potentially ATP synthesis in WB, by increasing fibrosis and the down-regulation of several genes related to mitochondria function.