Mitochondrial mistranslation is modulated by metabolic stress

Changes in the rate and fidelity of mitochondrial protein synthesis impact the metabolic and physiological roles of mitochondria. Here we explored how environmental stress in the form of a high-fat diet modulates mitochondrial translation using mutant mice with error-prone (Mrps12ep/ep) or hyper-accurate (Mrps12ha/ha) mitochondrial ribosomes. Intriguingly, although both mutations are metabolically beneficial in reducing body weight, decreasing circulating insulin and increasing glucose tolerance during a high-fat diet, they manifest divergent (either deleterious or beneficial) outcomes in a tissue-specific manner. In two distinct organ types that are commonly affected by metabolic disease, the heart and the liver, Mrps12ep/ep mice were protected against heart defects but sensitive towards lipid accumulation in the liver, activating genes involved in steroid and amino acid metabolism. In contrast, enhanced translational accuracy in Mrps12ha/ha mice protected the liver from a high-fat diet through activation of liver proliferation programs, but enhanced the development of severe hypertrophic cardiomyopathy. While these findings reflect the complex transcriptional and cell signalling responses that differ between post-mitotic (heart) and highly proliferative (liver) tissues, they also suggest that trade-offs between the rate and fidelity of mitochondrial protein synthesis dictate tissue-specific outcomes toward commonly encountered stressful environmental conditions. Overall design: Total RNA differential gene expression of Mrps12ep/ep and Mrps12ha/ha in mouse heart and liver tissue, relative to Mrps12+/+, in triplicate (biological & technical)