Reduced expression of ribonucleotide reductase small subunit M2 in muscle and several organs potentially altered tissue health and mitochondria function in woody breast chickens

Authors: SHAKERI, MAJID - Oak Ridge Institute For Science And Education (ORISE); CHOI, JANGHAN - Oak Ridge Institute For Science And Education (ORISE); HARRIS, CAITLIN - Oak Ridge Institute For Science And Education (ORISE); Buhr, Richard - Jeff; Kong, Byungwhi; Zhuang, Hong; Bowker, Brian

Submitted to: American Meat Science Association Conference Reciprocal Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2024
Publication Date: 6/16/2024
Citation: Shakeri, M., Choi, J., Harris, C., Buhr, R.J., Kong, B.C., Zhuang, H., Bowker, B.C. 2024. Reduced expression of ribonucleotide reductase small subunit M2 in muscle and several organs potentially altered tissue health and mitochondria function in woody breast chickens. American Meat Science Association Conference Reciprocal Proceedings. No. 57.

Interpretive Summary:

Technical Abstract: Woody breast is a major meat quality issue in fast growing broiler chickens leading to substantial economic losses due to undesirable breast meat appearance, texture, and functionality. Muscle with the woody breast myopathy exhibits mitochondrial abnormalities and greater oxidative stress. The role of ribonucleotide reductase (RNR), an enzyme involved in DNA synthesis and mitochondria function, and more specifically the RNR subunit M2 (RRM2) has not been explored in myopathic broiler breast meat. The aim of this study was to investigate the role of RRM2 and associated pathways related to mitochondria function and ATP production in severe woody (WB) and normal (N) breast muscles and other potentially related organs. In total 30 birds (15 N and 15 WB) were selected for sampling. Pectoralis major samples and organs (intestine, liver, and spleen) were excised from 8-week-old male broilers immediately postmortem and fixed in liquid nitrogen. Quantitative PCR was performed to determine gene expression using SYBR green, and commercial kits were used for biochemical assays. Data were analyzed using GraphPad Prism software (Version 10.1.1) and t-test analysis. Histology assessment confirmed WB categorization and showed increased fibrosis (P=0.006) in WB samples. Results showed that RRM2 activity (P=0.0002) and RRM2 expression (P=0.05) were reduced in WB compared to N muscle samples. Furthermore, RRM2 expression was reduced in duodenum (P < 0.0001) and liver (P = 0.01), but no significant changes were observed in spleen, ileum, and jejunum. In muscle tissues, expression of genes related to mitochondria function including ATP synthase membrane subunit 6 (essential for normal mitochondrial function, P = 0.03), NADH dehydrogenase 2 (mitochondrial respiratory chain, P = 0.001) and hydroxymethylbilane synthase (impaired oxygen transport and metabolism, P=0.002) were reduced in WB. Muscle samples with the WB myopathy tended to have elevated expression of caveolin 3 (defected membrane integrity, P=0.09), endoglin (increased fibrosis, P=0.06) and secreted protein acidic and rich in cysteine (metabolic dysregulation, P=0.09). Aspartate-aminotransferase-mitochondria activity (P=0.02) pyruvate kinase concentration (P=0.04), DNA damage (P=0.06), creatine kinase concentration (P=0.05) and triglyceride concentration (P=0.002) were increased for WB, while ATPase activity (P=0.01) was decreased in WB muscle tissues. In conclusion, differences in data indicating mitochondria dysfunction and increased DNA damage suggest that RRM2 mediated mitochondrial abnormalities may play an important role in the woody breast myopathy.