Chronic administration of propionic acid reduces ganglioside N-acetylneuraminic acid concentration in cerebellum of young rats

Reduction of gangliosides, phospholipids and cholesterol content in cerebral cortex of rats caused by chronic hypermethioninemia

Neurological dysfunction is observed in patients with severe hypermethioninemia, whose physiopathology is still poorly understood. In the current study we investigated the effect of chronic administration of methionine on the content and species of gangliosides and phospholipids, as well as on the concentration of cholesterol in rat cerebral cortex. Wistar rats received subcutaneous injections of methionine (1.34-2.68 micromol/g of body weight), twice a day, from the 6th to the 28th day of age and controls received saline. Animals were killed 12h after the last injection. Results showed that methionine administration significantly decreased the total content of lipids in cerebral cortex of rats. We also observed that this amino acid significantly reduced the absolute quantity of the major brain gangliosides (GM1, GD1a, GD1b and GT1b) and phospholipids (sphingomyelin, phosphatidylcholine and phosphatidylethanolamine). We also showed that Na+,K+-ATPase activity and TBARS were changed in cerebral cortex of rats subjected to hypermethioninemia. If confirmed in human beings, these data could suggest that the alteration in lipid composition, Na+,K+-ATPase activity and TBARS caused by methionine might contribute to the neurophysiopathology observed in hypermethioninemic patients.

Ethanolamine and phosphoethanolamine inhibit mitochondrial function in vitro: implications for mitochondrial dysfunction hypothesis in depression and bipolar disorder

BACKGROUND

A growing body of experimental evidence suggests that mitochondrial dysfunction, including alterations in phospholipid metabolism, might be involved in the pathophysiology of affective illnesses, such as depression and bipolar disorder. The purpose of this study was to determine whether the phosphomonoester phosphoethanolamine (PE) and the lipid metabolite choline (Cho), which are known to be altered in depression and bipolar disorder, and/or their precursors/metabolites, might directly affect mitochondrial bioenergetic function in vitro.

METHODS

To this end, rates of oxygen consumption in freshly isolated, intact mitochondria were determined polarographically in the presence and absence of PE, Cho, ethanolamine (Etn), glycerophosphoethanolamine (GPE), and glycerophosphocholine (GPC).

RESULTS

The data demonstrate that PE and Etn inhibit mitochondrial respiratory activity in a dose-dependent manner, whereas Cho, GPC, and GPE have no measurable effect on bioenergetic function.

CONCLUSIONS

This reflects a specific inhibition by Etn and PE on mitochondrial function rather than a more generalized phenomenon induced by similarities in structure between the lipid metabolites. These results also suggest a possible relationship between mitochondrial dysfunction and altered phospholipid metabolism in the brains of patients with depression and bipolar disorder.

Neonatal hypoxia-ischemia reduces ganglioside, phospholipid and cholesterol contents in the rat hippocampus

Hypoxia-ischemia is a common cause of neonatal brain damage producing serious impact on cerebral maturation. This report demonstrates that rats submitted to hypoxia-ischemia present a marked decrease in hippocampal gangliosides, phospholipids and cholesterol contents as from 7 days after the injury. Although chromatographic profiles of the different ganglioside species (GM1, GD1a, GD1b, and GT1b) from the hippocampus of hypoxic-ischemic hippocampi groups (HI) were apparently unaffected, as compared with controls, there were quantitative absolute reductions in HI. The phospholipid patterns were altered in HI as from the 14th to the 30th day after the injury, where phosphatidylcholine (PC) quantities were higher than phosphatidylethanolamine (PE); additionally, the cardiolipin band was detected only in hippocampi of control adult rats. In general, the absolute quantities of phospholipids were lower in HI than in correspondent controls since 7th day after the injury. Considering that reported effects were maintained, we suggest they express a late biochemical response triggered by the neonatal hypoxic-ischemic episode; the consequences would be cell death and a delay on brain development, expressed by a reduction on synaptogenesis and myelinogenesis processes.

Ganglioside alterations in the central nervous system of rats chronically injected with methylmalonic and propionic acids

Neurological dysfunction and structural cerebral abnormalities are commonly found in patients with methylmalonic and propionic acidemia. However, the mechanisms underlying the neuropathology of these disorders are poorly understood. We have previously demonstrated that methylmalonic and propionic acids induce a significant reduction of ganglioside N-acetylneuraminic acid in the brain of rats subjected to chronic administration of these metabolites. In the present study, we investigated the in vivo effects of chronic administration of methylmalonic (MMA) and propionic (PA) acids (from the 6th to the 28th day of life) on the distribution and composition of gangliosides in the cerebellum and cerebral cortex of rats. Control rats were treated with the same volumes of saline. It was first verified that MMA and PA treatment did not modify body, cerebellum, or cortical weight, nor the ganglioside concentration in the cerebral cortex of the animals. In contrast, a significant reduction in total ganglioside content in the cerebellum of approximately 20-30% and 50% of control levels occurred in rats injected with MMA and PA, respectively. Moreover, chronic MMA and PA administration did not interfere with the ganglioside pattern in the cerebral cortex, whereas the distribution of individual gangliosides was altered in the cerebellum of MMA- and PA-treated animals. Rats injected with MMA demonstrated a marked decrease in GM1 and GD3, whereas chronic PA treatment provoked a significant reduction of all ganglioside species, with the exception of an increase in GM2. Since gangliosides are closely related to the dendritic surface and other neural membranes, indirectly reflecting synaptogenesis, these ganglioside abnormalities may be associated with the brain damage found in methylmalonic and propionic acidemias.

Effects of methylmalonic and propionic acids on glutamate uptake by synaptosomes and synaptic vesicles and on glutamate release by synaptosomes from cerebral cortex of rats

Neurological dysfunction is common in patients with methylmalonic and propionic acidemias. However, the mechanisms underlying the neuropathology of these disorders are far from understood. In the present study we investigated the in vitro effects of methylmalonic (MMA) and propionic (PA) acids at various concentrations (1 microM-5 mM) on three parameters of the glutamatergic system, namely the basal and potassium-induced release of L-[3H]glutamate by synaptosomes, Na+-dependent L-[3H]glutamate uptake by synaptosomes and Na+-independent L-[3H]glutamate uptake by synaptic vesicles from cerebral cortex of male adult Wistar rats. The results showed that MMA significantly increased potassium-induced but not basal L-[3H]glutamate release from synaptosomes with no alteration in synaptosomal L-[3H]glutamate uptake. A significant reduction of L-[3H]glutamate incorporation into vesicles caused by MMA was also detected. In contrast, PA had no effect on these parameters. These findings indicate that MMA alters the glutamatergic system. Although additional studies are necessary to evaluate the importance of these observations for the neuropathology of methylmalonic acidemia, it is possible that the effects elicited by MMA may lead to excessive glutamate concentrations at the synaptic cleft, a fact that may explain previous in vivo and in vitro findings associating MMA with excitotoxicity.