Effects of acute and chronic administration of methylmalonic and propionic acids on the in vitro incorporation of 32P into cytoskeletal proteins from cerebral cortex of young rats

Mitochondrial energy metabolism in neurodegeneration associated with methylmalonic acidemia

Methylmalonic acidemia is one of the most prevalent inherited metabolic disorders involving neurological deficits. In vitro experiments, animal model studies and tissue analyses from human patients suggest extensive impairment of mitochondrial energy metabolism in this disease. This review summarizes changes in mitochondrial energy metabolism occurring in methylmalonic acidemia, focusing mainly on the effects of accumulated methylmalonic acid, and gives an overview of the results found in different experimental models. Overall, experiments to date suggest that mitochondrial impairment in this disease occurs through a combination of the inhibition of specific enzymes and transporters, limitation in the availability of substrates for mitochondrial metabolic pathways and oxidative damage.

Methylmalonic and propionic acids increase the in vitro incorporation of 32P into cytoskeletal proteins from cerebral cortex of young rats through NMDA glutamate receptors

In this study we investigated the effects of methylmalonic acid (MMA) and propionic acid (PA) on the phosphorylation of cytoskeletal proteins of cerebral cortex of rats. Slices of tissue were incubated with 32P-orthophosphate in the presence or absence of glutamate, MMA, PA and ionotropic or metabotropic glutamate receptor agonists. The cytoskeletal fraction was isolated and the radioactivity incorporated into the cytoskeletal proteins was measured. Results demonstrated that the acids, glutamate and NMDA increased the phosphorylation of the proteins studied. However, this effect was not observed for non-NMDA ionotropic agonists or metabotropic agonists. Experiments using glutamate receptor antagonists confirmed that MMA and PA at the same concentrations as found in tissues from propionic or methylmalonic acidemic children increase the phosphorylation of cytoskeletal proteins, possibly via NMDA glutamate receptors. Therefore, it is feasible that these findings may be related to the neurological dysfunction characteristic of these disorders.