J. Arenas

Cerebrospinal fluid levels of alpha-tocopherol (vitamin E) in Alzheimer's disease

SummaryWe compared CSF and serum levels, and the CSF/serum ratio of alpha-tocopherol (vitamin E), measured by HPLC, in 44 apparently well-nourished patients with Alzheimers disease (AD) and 37 matched controls. CSF and serum vitamin E levels were correlated, both in AD patients and in controls. The mean CSF and serum vitamin E levels were significantly lower in AD patients, and the CSF/serum ratio of AD patients did not differ significantly between the 2 study groups. CSF vitamin E levels did not correlate with age, age at onset, duration of the disease and score of the Minimental State Examination in the AD group. Weight and body mass index were significantly lower in AD patients than in controls. These results suggest that low CSF and serum vitamin E concentrations in AD patients could be related with a deficiency of dietary intake of vitamin E.

Neurotransmitter amino acids in cerebrospinal fluid of patients with Alzheimer's disease

Summary. We measured the CSF and plasma levels of glutamate, glutamine, aspartate (only in plasma), asparagine, glutamine, glycine and GABA in 37 patients with Alzheimers disease and in 32 matched controls. We used an ion-exchange chromatography method. When compared to controls, AD patients had higher CSF glutamate and glycine levels, higher plasma levels of aspartate and glycine, and lower plasma levels of asparagine and GABA. When expressed relative to CSF proteins, CSF levels of glutamate and glycine remained higher, and CSF asparagine levels were lower in AD patients than in controls. The CSF levels of the amino acids measured were not correlated with the clinical features of AD with the exception of plasma GABA levels with duration of the disease. Our results might suggest a possible pathogenetic role of neurotransmitter amino acids in AD.

Leigh syndrome associated with the T9176C mutation in the ATPase 6 gene of mitochondrial DNA

A child with clinical and neuroradiologic evidence of Leigh syndrome (LS) had the T-to-C transition at nt 9176 in the ATPase 6 gene of mtDNA. The mutation was homoplasmic in muscle and maternally inherited. The probands mother had ataxia and harbored 93% of mutant genomes in blood, whereas three clinically unaffected maternal relatives had varying degrees of heteroplasmy in blood. These data confirm the association of the T9176C mutation with LS and extend the clinical heterogeneity of mutations in the ATPase 6 gene.

Single large-scale mitochondrial DNA deletion in a patient with mitochondrial myopathy associated with multiple symmetric lipomatosis

In a nonalcoholic woman with multiple symmetric lipomatosis (MSL), muscle histochemistry showed ragged-red fibers and cytochrome c oxidase negative fibers. Southern blot analysis revealed a single deletion of mitochondrial DNA (mtDNA). We suggest that MSL is an uncommon manifestation of the wide clinical spectrum of mitochondrial disorders, in particular of those associated with single mtDNA deletions. NEUROLOGY 1996;47: 1012-1014

A double mutation (A8296G and G8363A) in the mitochondrial DNA tRNALys gene associated with myoclonus epilepsy with ragged-red fibers

Objective: To define potential pathogenic mitochondrial DNA (mtDNA) point mutations in a patient with myoclonus epilepsy with ragged-red fibers (MERRF) syndrome. Background: MERRF syndrome is typically associated with point mutations in the mtDNA tRNALys gene. Methods: We performed morphologic, biochemical, and genetic analysis of muscle samples from the patient and four relatives. Molecular genetic studies included sequencing, PCR, and restriction enzyme analysis on whole muscle, blood, and single muscle fibers. Results: Muscle biopsy showed cytochrome c oxidase (COX), negative ragged-red fibers (RRF), and a defect of complex I of the mitochondrial respiratory chain. We found an A8296G transition and a G8363A mutation in the mtDNA tRNALys gene. The A8296G was almost homoplasmic in muscle and blood from the propositus and his oligosymptomatic maternal relatives. The G8363A mutation was heteroplasmic and more abundant in muscle than in blood, and its proportion correlated with clinical severity. Single muscle fiber analysis showed significantly higher levels of G8363A genomes in COX-negative than in normal fibers, and almost homoplasmic levels of mutant A8296G mtDNA in both COX-negative and normal fibers. The two mutations affect highly conserved nucleotides and were not found in controls. Conclusions: The G8363A mutation is pathogenic; the co-ocurrence of the A8296G mutation is of unclear significance and is likely to be a rare polymorphism.

Mitochondrial dysfunction associated with a mutation in the Notch3 gene in a CADASIL family

Background: Cerebral autosomal arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by recurrent subcortical ischemic strokes and dementia caused by mutations in the Notch3 gene. In Drosophila melanogaster, Notch signaling has a pleiotropic effect, affecting most tissues of the organism during development. Objective: To characterize a potential mitochondrial dysfunction associated with mutations in the Notch3 gene. Methods: Biochemical, histochemical, molecular, and genetic analyses were performed on muscle biopsy specimens and fibroblasts obtained from patients of a Spanish family with CADASIL. Additional biochemical and molecular analyses of the N55e11 mutant of D. melanogaster were performed. Results: In muscle biopsy specimens, a significant decrease was found in the activity of complex I (NADH [reduced form of nicotinamide adenine dinucleotide] dehydrogenase), and in one patient, histochemical analysis showed the presence of ragged-red fibers with abnormal cytochrome c oxidase staining. Reduced fibroblast activity of complex V (ATP synthase) was found. Supporting data on patients with CADASIL, it was found that the mutation N55e11 in Drosophila decreases the activity of mitochondrial respiratory complexes I and V. Conclusions: Mitochondrial respiratory chain activity responds, directly or indirectly, to the Notch signaling pathway. Mitochondrial dysfunction in patients with CADASIL may be an epiphenomenon, but results of this study suggest that the pathophysiology of the disease could include a defect in oxidative phosphorylation.

Splicing mosaic of the myophosphorylase gene due to a silent mutation in McArdle disease

The authors report the molecular findings in a patient with McArdle disease who harbored a silent polymorphism (K608K) in the myophosphorylase gene. cDNA studies demonstrated that this polymorphism leads to a severe mosaic alteration in mRNA splicing, including exon skipping, activation of cryptic splice-sites, and exon-intron reorganizations. These findings suggest that, in patients with McArdle disease in whom no pathogenic mutation has been found, any a priori silent polymorphism should be re-evaluated as a putative splicing mutation.

Serum levels of coenzyme Q10 in patients with Parkinson's disease

Summary. We compared serum levels of coenzyme Q10 and the coenzyme Q10/cholesterol ratio in 33 patients with Parkinsons disease (PD) and 31 matched controls. The mean serum coenzyme Q10 levels did not differ significantly between the 2 study groups. Coenzyme Q10 levels were not correlated with age, age at onset, duration of the disease, scores of the Unified Parkinson Disease Rating Scale (UPDRS) or the Hoehn and Yahr staging in the PD group. The coenzyme Q10/cholesterol ratio had a significant correlation (although low) with duration of the disease (r = −0.46), total UPDRS score (r = −0.39), motor examination of the UPDRS (r = 0.45). These values were not influenced significantly by therapy with levodopa or dopamine agonists. The normality of serum coenzyme Q10 and coenzyme Q10/cholesterol ratio suggest that these values are not related with the risk for PD.

Cerebrospinal fluid nitrate levels in patients with Parkinson's disease

It has been suggested that nitric oxide could be implicated in the neuronal degeneration of substantia nigra compacta in patients with Parkinsons disease. Recently, it has been reported decreased CSF nitrate levels (oxidation product that provides an indirect estimation of nitric oxide) in Parkinsons disease patients, assessed with a colorimetric method. We studied the CSF and plasma levels of nitrate with a kinetic cadmium‐reduction method in 31 Parkinsons disease patients and 38 matched controls. The CSF and plasma nitrate levels were not correlated either in patient or in the control group, and they did not differ significantly between the two study groups. They were not influenced significantly by antiparkinsonian drugs in patients, although there was a trend for CSF nitrate levels to be higher in patients treated with levodopa or with dopamine agonists. CSF and plasma nitrate levels did not correlate with age at onset, duration, scores of the unified Parkinsons disease rating scales and Hoehn & Yahr staging in the patients group. These data suggest that CSF and plasma levels of nitrate are apparently unrelated with the risk for PD.

Respiratory‐chain enzyme activities in isolated mitochondria of lymphocytes from untreated Parkinson's disease patients

We studied respiratory-chain enzyme activities in lymphocyte mitochondria from 36 untreated Parkin-sons disease (PD) patients and in 30 age- and sex-matched healthy controls. The respiratory-chain enzyme activities did not differ significantly between patients and controls. Moreover, no patient showed respiratory-chain enzyme levels below normal range. Values for activities of complexes in the PD group did not correlate with age at onset, duration, scores of the Unified Parkinsons Disease Rating scales, or Hoehn and Yahr staging. These results suggest that the presence of defects of respiratory-chain complexes could depend on methodologic aspects, and that determinations of respiratory-chain enzymes in cell homogenates are not generally appropriate for evaluating abnormal mitochondrial dysfunction, especially when the amount of the specific enzyme is relatively low, as is the case of blood cells. In addition, the method of measuring complex I activity is critical for evaluating the results. In conclusion, our finding of normal mitochondrial function in lymphocyte mitochondria suggests that this tissue cannot be used to develop a diagnostic test for PD.