Inhibition of mammalian mtDNA transcription paradoxically activates liver fatty acid oxidation to reverse diet-induced hepatosteatosis and obesity

The oxidative phosphorylation (OXPHOS) system in mammalian mitochondria plays a key role in harvesting energy from ingested nutrients^{1, 2}. Mitochondrial metabolism is very dynamic and can be reprogrammed to support both catabolic and anabolic reactions, depending on physiological demands or disease states^{3, 4}. Rewiring of mitochondrial metabolism is intricately linked to metabolic diseases^{5, 6}and is also necessary to promote tumour growth^7–11. Here, we demonstrate thatper oraltreatment with an inhibitor of mitochondrial transcription (IMT)¹¹shifts whole animal metabolism towards fatty acid oxidation, which, in turn, leads to rapid normalization of body weight, reversal of hepatosteatosis and restoration of glucose tolerance in mice on high-fat diet. Paradoxically, the IMT treatment causes a severe reduction of OXPHOS capacity concomitant with a marked upregulation of fatty acid oxidation in the liver, as determined by proteomics and non-targeted metabolomics analyses. The IMT treatment leads to a marked reduction of complex I, the main dehydrogenase that feeds electrons into the ubiquinone (Q) pool, whereas the levels of electron transfer flavoprotein dehydrogenase (ETF-DH) and other dehydrogenases connected to the Q pool are increased. This rewiring of metabolism caused by reduced mtDNA expression in the liver provides a novel principle for drug treatment of obesity and obesity-related pathology.