In vivo itaconate tracing reveals degradation pathway and turnover kinetics

Abstract Itaconate is an immunomodulatory metabolite that alters mitochondrial metabolism and immune cell function. This organic acid is endogenously synthesized via tricarboxylic acid (TCA) metabolism downstream of TLR signaling. Itaconate-based treatment strategies are being explored to mitigate numerous inflammatory conditions. However, little is known about the turnover rate of itaconate in circulation, the kinetics of its degradation, and the broader consequences on metabolism. By combining mass spectrometry and in vivo 13 C itaconate tracing, we demonstrate that itaconate is rapidly eliminated from plasma, excreted via urine, and fuels TCA cycle metabolism specifically in the liver and kidneys. These studies further revealed that itaconate is converted into acetyl-CoA, mesaconate, and citramalate in mitochondria. Itaconate administration also influenced branched-chain amino acid metabolism and succinate levels, indicating a functional impact on succinate dehydrogenase (SDH) and methylmalonyl-CoA mutase (MUT) activity. Our findings uncovered a previously unknown aspect of the itaconate metabolism, highlighting its rapid catabolism in vivo that contrasts findings in cultured cells.