Grayson, C.; Faerman, B.; Koufos, O.; Mailloux, R.

Here, we conducted the first in-depth investigation into sex effects on mitochondrial hydrogen peroxide (mH2O2) generation in hepatic tissue. Female liver mitochondria produce less mH2O2 when oxidizing pyruvate, palmitoyl-carnitine, and succinate when compared to male samples. This difference was attributed to superior coupling between fuel metabolism and oxidative phosphorylation (OxPhos) in female liver mitochondria. Examination of mH2O2 production by individual sites of generation revealed that KGDH was a major source in both male and female liver mitochondria oxidizing pyruvate and malate. Surprisingly, -keto-{beta}-methyl-n-valeric acid (KMV), a site-specific inhibitor for KGDH, nearly abolished mH2O2 generation in both male and female liver mitochondria oxidizing palmitoyl-carnitine. KMV did not interfere with the fatty acid oxidation (FAO) pathway and was specific to KGDH. KMV inhibited mH2O2 production in liver mitochondria from male and female mice oxidizing myristoyl, octanoyl, and butyryl-carnitine. We also supply evidence that KGDH, not complex I or complex III, is the major mH2O2 generator in liver mitochondria. Together, we discovered KGDH is a major mH2O2 source, regardless of sex and during FAO.