Abstract 2845 Insect UDP-Glycosyltransferases: From Detoxification to Olfaction and Comparative Genomics

The Ndufs4-/-mouse is a model of the mitochondrial disease Leigh syndrome (LS).Mutations in the human homolog NDUFS4 cause LS with reduced ATP synthesis by oxidative phosphorylation.The Ndufs4-/-mouse exhibits brainstem and olfactory bulb degeneration and typically dies due to respiratory failure attributed to brainstem pathology.We recently showed that these mice have decreased activity of the a-ketoglutarate (AKG) dehydrogenase complex-, with subsequent reduced succinyl CoA production and substrate level phosphorylation.We speculated that defective AKG dehydrogenase activity would increase the concentration of AKG, but the levels of this metabolite were only marginally elevated.AKG can be converted to L-2-hydroxyglutarate (L-2-HG) by the promiscuous activity of lactate dehydrogenase (LDH) or malate dehydrogenases (MDH1 and 2), especially if a metabolic acidosis is present, as established in the Ndufs4-/-mice.We employed DATAN derivatization of the hydroxyl groups of the 2-HG enantiomers, L-lactate and L-malate to quantify these metabolites by LC-MS/MS.Lactate and malate levels were increased in the brainstem of the Ndufs4-/-mouse, but L-2-HG levels were reduced, while the levels of D-2-HG were unchanged.In the olfactory bulb we also quantified an increase in lactate and malate levels but L-2-HG levels were unchanged, and surprisingly the levels of D-2-HG were reduced.Finally, we found the levels of the two 2-HG enantiomers reduced in the serum of the Ndufs4-/-mouse.A metabolic challenge with LPS (1mg/kg, 20 h) did not change the levels of D-2-HG, but increased L-2-HG levels in the olfactory bulb, whereas no effect was detected in Ndufs4+/+ mice.Quantitative measurement of the mitochondrial proteome indicated increased abundance of L-2-HG dehydrogenase in the brainstem, suggesting that 2-HG enantiomers may not accumulate in the Ndufs4-/-mouse, instead regenerating AKG in a FAD+dependent process.The data indicate unexpected regionspecific alterations in the enantiomers of 2-HG in the Ndufs4-/-mouse brain, despite the presence of a metabolic acidosis.