Bezafibrate In Vivo Administration Prevents 3-Methylglutaric Acid-Induced Impairment of Redox Status, Mitochondrial Biogenesis, and Neural Injury in Brain of Developing Rats.

3-Methylglutaric acid (MGA) is an organic acid that accumulates in 3-methylglutaconic (MGTA) and 3-hydroxy-3-methylglutaric (HMGA) acidurias. Patients affected by these disorders present with neurological dysfunction that usually appears in the first years of life. In order to elucidate the pathomechanisms underlying the brain injury in these disorders, we evaluated the effects of MGA administration on redox homeostasis, mitochondrial respiratory chain activity, and biogenesis in the cerebral cortex of developing rats. Neural damage markers and signaling pathways involved in cell survival, and death were also measured after MGA administration. Furthermore, since the treatment for MGTA and HMGA is still limited, we tested whether a pre-treatment with the pan-peroxisome proliferator-activated receptor (PPAR) agonist bezafibrate could prevent the alterations caused by MGA. MGA provoked lipid peroxidation, increased heme oxygenase-1 content, and altered the activities of antioxidant enzymes, strongly suggestive of oxidative stress. MGA also impaired mitochondrial function and biogenesis by decreasing the activities of succinate dehydrogenase and various respiratory chain complexes, as well as the nuclear levels of PGC-1α and NT-PGC-1α, and cell content of Sirt1. AMPKα1 was further increased by MGA. Neural cell damage was also observed following the MGA administration, as verified by decreased Akt and synaptophysin content and reduced ERK phosphorylation, and by the increase of active caspase-3 and p38 and Tau phosphorylation. Importantly, bezafibrate prevented MGA-elicited toxic effects towards mitochondrial function, redox homeostasis, and neural cell injury, implying that this compound may be potentially used as an adjunct therapy for MGTA and HMGA and other disorders with mitochondrial dysfunction.

Evidence that 3-hydroxy-3-methylglutaric and 3-methylglutaric acids induce DNA damage in rat striatum.

3-Hydroxy-3-methylglutaryl-CoA lyase (HL) deficiency is a rare autosomal recessive disorderaffecting the final step of leucine degradation and ketogenesis and biochemically characterized by the predominant accumulation of 3-hydroxy-3-methylglutaric (HMG) and 3-methylglutaric (MGA) acids in biological fluids and tissues of affected patients. Considering that previous studies reported that HMG and MGA have pro oxidant properties, the present study evaluated the ex vivo and in vitro effects of HMG and MGA on frequency and index of DNA damage in cerebral cortex and striatum of young rats. The ex vivo effects of both organic acids on 8-hydroxy-2'-deoxyguanosine (OHdG) levels and their in vitro effects on 2',7'-dichlorofluorescin (DCFH) oxidation and glutathione (GSH) concentrations in rat striatum were also determined. We also investigated the ex vivo effects of both organic acids on 8-hydroxy-2'-deoxyguanosine (OHdG) levels in rat striatum. In the ex vivo experiments, DNA damage was determined in striatum homogenates prepared 30 min after a single intrastriatal administration of HMG or MGA. On the other hand, the in vitro evaluation was performed after an incubation of rat cerebral cortex or striatum homogenates or slices in the presence of HMG or MGA during 1 h at 37 °C. We observed that the intrastriatal administration of HMG and MGA increased the frequency and the index of DNA damage, as well as OHdG staining in rat striatum. We also verified that MGA, but not HMG, increased DNA damage frequency and index in vitro in striatum of rats. In contrast, no alterations were verified in vitro in cerebral cortex. Finally, we found that HMG and MGA increased DCFH oxidation and decreased GSH concentrations in rat striatum. Therefore, it may be presumed that DNA damage provoked by HMG and MGA possibly via reactive species generation is involved, at least in part, in the pathophysiology of brain injury, particularly in the striatum of HL-deficient patients.

Dietary secoisolariciresinol diglucoside and its oligomers with 3-hydroxy-3-methyl glutaric acid decrease vitamin E levels in rats.

Secoisolariciresinol diglucoside (SDG) is an important dietary lignan that is found at very high levels in flaxseed (1-4 %, w/w). Flaxseed lignans have received much research interest in recent years because of reported phyto-oestrogenic, anticarcinogenic, and anti-atherogenic effects. Previously, flaxseed feeding has been shown to decrease vitamin E concentrations in rats despite the antioxidant potential of SDG in vitro. Sesamin, a sesame lignan, on the other hand has been shown to increase vitamin E concentrations in rats. The aim of the present study was to investigate the effect of dietary SDG and its oligomers on vitamin E and cholesterol concentrations in rats. SDG was extracted from defatted flaxseed flour with a dioxane-ethanol mixture and purified by silica column chromatography. The major oligomers with 3-hydroxy-3-methyl glutaric acid, containing a high ratio of SDG to p-coumaric and ferulic acid glucosides, were purified from the extracts by reversed-phase liquid chromatography. When fed to rats at 0.1 % in the diet for 27 d, both SDG and its oligomers had no effect on animal performance but caused an increase in liver cholesterol and a 2-fold reduction in the levels of alpha- and gamma-tocopherols in rat plasma and liver. It is notable that a phenolic antioxidant, such as SDG, causes a vitamin E-lowering effect in rats. This cannot be explained at present, but warrants further investigations with respect to the magnitude, mechanism, and significance of the observed effect for human nutrition.