jats:pThe metabolite 2-hydroxybutyrate (2HB) is produced by skeletal muscle acutely during exercise and persists for several hours in the blood post-exertion. We show here that 2HB directly inhibits branched- chain aminotransferase enzymes, and that this inhibition in turn triggers a SIRT4-dependent shift in the compartmental abundance of protein ADP-ribosylation. The 2HB-induced decrease in nuclear protein ADP-ribosylation leads to a C/EBPβ mediated transcriptional response in the branched-chain amino acid degradation pathway. This response to 2HB exposure leads to an improved oxidative capacity both in vitro and in vivo , with the latter mimicking the effects of exercise training on whole body metabolism. Thus, we show here that 2-HB production by skeletal muscle represents a novel mechanism for the modification of metabolism by exercise. </jats:p>