Friedreich's ataxia 1976-an overview

Platelet Taurine Uptake in Spinocerebellar Degeneration

The uptake of 14C-laurine was studied in the platelets of 20 ataxic patients and 20 age-matched normal control subjects. No significant differences were found in uptake or kinetics of taurine between the two groups of subjects. If a transport defect in taurine exists in Friedreich's ataxia, it is not present in all tissues. Preliminary indication was obtained in favor of heterogenity of the uptake pattern between ataxic individuals.

Cooperative Study, Phase Two: Statement of the Problems

A short summary of the state of our knowledge at the start of Phase Two of the Quebec Cooperative Study of Friedreich's ataxia is presented. The main questions raised hy the discoveries made in the Phase One Survey are listed and the plan of our current investigations is outlined.

Cardiac Pharmacology and Cardiomyopathy in Friedreich's Ataxia

Friedreich's ataxia is almost always associated with a cardiomyopathy. The cardiomyopathy and its attendant cardiopulmonary sequelae is the usual cause of death in this disease. The author reviews the known pharmacology of the heart, particularly as it applies to hypertrophic cardiomyopathy. The important role played by calcium and the possible role of taurine is stressed. Therapeutic possibilities are mentioned.

Antagonism by Taurine of Morphine Induced Growth Hormone Secretion

The intraperitoneal (IP) or intraventricular (IVT) administration of small amounts of taurine did not modify pentobarbital-induced sleep or pituitary hormone release. However, the drastic increment in plasma GH values induced by morphine administration was completely blocked by the IVT injection of the amino acid. Whether taurine plays a physiological role in the control ofGH secretion is highly speculative.

Plasma Lipids and Lipoproteins in Friedreich's Ataxia and Familial Spastic Ataxia — Evidence for an Abnormal Composition of High Density Lipoproteins

A systematic study of plasma lipids and lipoproteins was carried out in II cases of Friedreich's ataxia and 6 cases of familial spastic ataxia (Charlevoix-Saguenay disease) using II healthy normolipidemic volunteers of comparable age and sex as controls. No differences were noted in the fatty acid profile of the total lipid fraction, in the total cholesterol and phospholipids or in the percentage distribution of the individual phospholipid classes. The triglycerides were significantly higher in Friedreich's ataxia, but remained within the normal range. Although no systematic abnormalities could be detected in the electrophoretic pattern of plasma lipoproteins or in the apolipoprotein profile on polyacrylamide gel electrophoresis, major differences were found in the high density lipoprotein (HDL) fraction. Their total amount was reduced and their composition was abnormal in both neurological diseases. In Friedreich patients, the relative proportion of cholesterol and triglycerides was increased while the relative protein content was greatly reduced. In Charlevoix disease, a similar abnormality was seen except for the excess of triglycerides. The proportion of phospholipids in HDL was the same in the three groups of patients. In addition, the low density lipoprotein (LDL) fraction was slightly reduced in both diseases. This anomaly of the HDL fraction could indicate that the HDL apolipoprotein moiety has a greater affinity for cholesterol and triglycerides in Friedreich's ataxia than its normal counterpart.

Friedreich ataxia: neuropathology revised

Friedreich ataxia is an autosomal recessive disorder that affects children and young adults. The mutation consists of a homozygous guanine-adenine-adenine trinucleotide repeat expansion that causes deficiency of frataxin, a small nuclear genome-encoded mitochondrial protein. Low frataxin levels lead to insufficient biosynthesis of iron-sulfur clusters that are required for mitochondrial electron transport and assembly of functional aconitase, and iron dysmetabolism of the entire cell. This review of the neuropathology of Friedreich ataxia stresses the critical role of hypoplasia and superimposed atrophy of dorsal root ganglia. Progressive destruction of dorsal root ganglia accounts for thinning of dorsal roots, degeneration of dorsal columns, transsynaptic atrophy of nerve cells in Clarke column and dorsal spinocerebellar fibers, atrophy of gracile and cuneate nuclei, and neuropathy of sensory nerves. The lesion of the dentate nucleus consists of progressive and selective atrophy of large glutamatergic neurons and grumose degeneration of corticonuclear synaptic terminals that contain γ-aminobutyric acid (GABA). Small GABA-ergic neurons and their projection fibers in the dentato-olivary tract survive. Atrophy of Betz cells and corticospinal tracts constitute a second intrinsic CNS lesion. In light of the selective vulnerability of organs and tissues to systemic frataxin deficiency, many questions about the pathogenesis of Friedreich ataxia remain.

Hereditary motor and sensory neuropathy associated with cerebellar atrophy (HMSNCA): a new disease

Seven patients with hereditary motor and sensory neuropathy associated with cerebellar atrophy (HMSNCA) are presented. This is the first comprehensive evaluation of what is a unique disorder, half way between the cerebellar atrophies and the hereditary motor and sensory neuropathies. In addition to cerebellar ataxia and peripheral neuropathy, the most frequent features in HMSNCA were nystagmus, dysarthria, mental impairment and tremor. Pyramidal signs or autonomic nerve dysfunction was never revealed. Scoliosis or kyphoscoliosis was not noted. Progression of the disorder was very slow, most of the patients being ambulatory more than 10 years after the onset. Most of the patients had hypoalbuminemia. Half-life periods of serum albumin were normal and decreased synthesis of albumin in the liver was suspected. An autosomal recessive inheritance was strongly suggested, because of healthy consanguineous parents and affected siblings in these families. The segregation ratio was 0.32 +/- 0.10 and was close to the expected ratio of 0.25 in an autosomal recessive inheritance.

Biomechanical analysis of simple jaw movements in Friedreich's ataxia

The jaw movement kinematics in relation to the EMG activity of two antagonistic jaw muscles (the masseter and the digastricus pars anterior) were examined in healthy subjects and patients with Friedreich's disease. Dysarthria and ataxia are the main characteristics of this disease. Jaw movement was monitored with a magnetometer system, and bipolar surface electrodes were used to record EMG activity. Unidirectional opening, unidirectional closing and opening-closing movements of the mandible were performed in a simple reaction time situation. The data were compared with those for normal control subjects. The kinematic and electromyographic characteristics were: (a) prolonged total movement duration resulting from increased acceleration and deceleration durations; (b) decreased maximum velocity, and a secondary peak in the velocity profile; (c) tonic EMG activity in muscles supposedly at rest; (d) prolonged EMG bursts. Premotor reaction time was also increased. These characteristics are similar to those, previously described, of limb movements in subjects with cerebellar dysfunctions and suggest that the alterations of jaw movement in Friedreich's ataxia could be due to a deficit in cerebellar control.

Congestive heart failure and cardiac thrombus as first presentations of Friedreich ataxia

The majority of patients with Friedreich ataxia present with gait ataxia. Congestive heart failure usually is a terminal event. We report a 9-year-old boy who developed congestive heart failure and thrombus formation in the left ventricle at age 5 years and then progressive ataxia as well as other features of Friedreich ataxia; therefore, congestive heart failure and thrombus formation may rarely be the initial findings in Friedreich ataxia.

Quantitative measures of neurological function in chronic neuromuscular diseases and ataxia

Interexaminer and intraexaminer reliability were determined for 30 quantitative measures of neurological function, including sensory threshold, tendon reflexes, maximum isometric strength, and timed tests and coded ratings of functional ability, in patients with Charcot-Marie-Tooth disease (n = 30), idiopathic polyneuropathy (n = 16) and spinocerebellar degeneration (n = 30). Five of 6 sensory and reflex measures had interexaminer reliability greater than 0.80 when the neurologists' examinations were 1 h apart; 2 of 7 achieved this level when the examinations were separated by 1 month. Interexaminer reliability between physical therapists was greater than 0.80 for 19 of 20 measures of strength and functional ability. Intraexaminer reliability coefficients greater than 0.80 were found for 13 of 24 sensory and reflex measures, 28 of 30 isometric strength measures, 24 of 30 timed tests and 5 of 6 coded ratings of functional ability. Electro-oculography, oral diadochokinetic syllable rates, hand and foot accelerometry, and tracings of sine and square waves were examined as quantitative indices of ataxia for patients with spinocerebellar degeneration. Of 11 measures of ataxia, only the oral diadochokinetic syllable rate test had acceptable reliability.

On the neurolinguistic nature of language abnormalities in Huntington's disease

Spontaneous language of 18 patients suffering from Huntington's disease and 15 dysarthric controls suffering from Friedreich's ataxia were investigated. In addition, language functions in various modalities were assessed with the Aachen Aphasia Test (AAT). The Huntington patients exhibited deficits in the syntactical complexity of spontaneous speech and in the Token Test, confrontation naming, and language comprehension subtests of the AAT, which are interpreted as resulting from their dementia. Errors affecting word access mechanisms and production of syntactical structures as such were not encountered.

Friedreich's ataxia: electrophysiologic and histologic findings in patients and relatives

Peripheral nerve conduction velocity and cortical evoked potentials were investigated in 48 patients with Friedreich's disease and in 35 relatives. There were 14 patients and 2 relatives who underwent sural nerve biopsy. In the patients sensory conduction velocity was moderately slowed, whereas sensory responses were markedly reduced. Nerve biopsy showed a severe loss of large myelinated fibers and no demyelination. On teased nerve fiber preparations, most fibers presented uniformly short internodes. No correlation was seen between sensory conduction findings or histologic abnormalities and clinical disability. In patients SSEP changes, which were constant, and VEPs, which were frequently involved, were unrelated to the severity or duration of clinical disability. There were 14 relatives who showed clinical signs of Friedreich's disease. Slightly decreased distal conduction velocity along sensory fibers was observed in more than half of the relatives. Nerve biopsy was noncontributory. In conclusion, we could not determine whether the abnormalities observed in the siblings were an expression of a heterozygotic condition, or whether they were early signs of the disease.

Long latency muscle responses in cerebellar diseases

Long latency reflexes were measured from the hand muscles of 27 patients suffering from different cerebellar diseases (12 diffuse cerebellar atrophies, 7 cerebellar hemispheric infarcts, 8 Friedreich's disease) and from 45 controls after electrical stimulus of the median nerve at the wrist. The M3 response (latency about 70 ms) was increased in about 50% of cerebellar atrophy cases and occasionally (10 of 12 cases) separated from the M2 response (50 ms). M3 was sometimes (3/7) increased and the M2-3 complex was prolonged ipsilaterally in cases of cerebellar infarcts. In the cases of Friedreich's ataxia M2 was always lost uni or bilaterally because of the disturbance of afferent or efferent fibres. The latencies of the spinal reflex M1 and also of M2 were not always increased strongly enough to be clearly separated from the normal values.

Friedreich's ataxia: clinical involvement and evoked potentials

In 15 patients definitely affected by Friedreich's ataxia, precocious SEP abnormalities were constantly recorded independent of the duration of symptoms and the severity of clinical involvement; VEPs were frequently involved, but neither VEP abnormalities, nor visual impairment could be correlated with the severity or duration of Friedreich's ataxia clinical involvement; BAEPs were, to different extents, abnormal. These were completely dissociated from hearing disorders and significantly correlated (P less than 0.001) with Friedreich's ataxia clinical disability. Our observation of increased latency of the VEP P100 component and the early disappearance of BAEP Wave V with persistence of Wave I is in contrast with the hypothesis that changes are related to primary axonal degeneration. For practical purposes SEPs could help in the early diagnosis of Friedreich's ataxia, and BAEPs could be used for the electrophysiological monitoring of its clinical progression.

Plasma cholesteryl sulfate in Friedreich's ataxia

Alteration of membrane fluidity and anomalies of membrane structural proteins have been suspected in Friedreich's ataxia. Plasma lecithin:cholesterol acyltransferase (LCAT) activity is also lowered in this disease, presumably because of a substrate effect. The membrane-stabilizing effect of cholesteryl sulfate (CS) and its inhibitory effect on LCAT activity prompted us to measure this substance in the plasma of Friedreich's ataxia patients as well as in normal subjects and in patients with Charlevoix-Saguenay disease. Plasma cholesteryl sulfate concentrations were significantly higher in Friedreich's ataxia, with levels above the upper limit of normal in nearly half of the cases. This increase was unrelated to age, sex or plasma cholesterol levels, but closely associated with the severity of the disease and thus considered to be secondary. A similar phenomenon (except the association with severity) was observed in Charlevoix-Saguenay ataxia. Levels also tended to be higher in first-degree relatives of Friedreich cases. The significance of these findings is discussed in the light of recent knowledge and experimental data obtained in this laboratory on rats made deficient in essential fatty acids. The highest concentrations of CS observed in Friedreich's ataxia (1097 micrograms/dL, 6 times the normal mean) was only 25% as high as the concentrations reported to inhibit LCAT activity.

Distribution of apolipoprotein E phenotypes in Friedreich's ataxia

Allelic polymorphism at the apolipoprotein E (apo E) gene locus (alleles epsilon 2, epsilon 3, and epsilon 4) is responsible for the existence of 6 discrete electrophoretic phenotypes of plasma apo E. Since the presence of the epsilon 2 allele in the genotype tends to be associated with higher triglyceride levels, a study was undertaken to determine if a higher frequency of this allele could account for the presence of higher plasma triglycerides in subsets of patients with Friedreich's Ataxia. The frequency of the apo E phenotypes was determined in 37 subjects with Friedreich's Ataxia and compared with that of 102 normolipidemic and 102 hyperlipidemic individuals. There was no increased prevalence of the E3/2 phenotype and the epsilon 2 allele in the Friedreich's sample as is found in a hyperlipidemic sample. Furthermore, the epsilon 2 subset did not have significantly higher plasma triglycerides than the non-epsilon 2 subset and the hypothesis was rejected. On the other hand, there was a trend for a decreased frequency of the E4/3 phenotype in the Friedreich's sample relative to the hyperlipidemic group but the difference did not reach statistical significance. The apo E phenotype distribution was also measured in a smaller sample of Charlevoix-Saguenay disease; this led to the discovery of two siblings with the relatively rare E2/2 phenotype and unexpectedly low levels of plasma lipid and lipoprotein concentrations. Plasma apolipoprotein E concentrations in both diseases were within the normal range except for subjects bearing the E2/2 phenotype.

Visual evoked potentials and brain stem auditory potentials in Friedreich's ataxia--a longitudinal study

Six patients with Friedreich's ataxia, 4 males and 2 females, their ages ranging from 13 to 33 years, were studied. The early manifestations started between age 7 and 13 with an evolution time between 6 and 20 years. Serial visual and brain stem auditory evoked potential recordings were made. A progressive increase in latency, reduction in amplitude and in latency inter-ocular difference of P100 were observed. The pattern of the reversal checker-board visual evoked potential was preserved. A disorganized BAEP pattern, a well defined potential I, a very small potential V and a delay in the interpeak latency were constant findings. The assumption is made of a progressive involvement of both visual and central auditory pathways. Pathophysiological mechanisms are discussed.

Neuro-otological abnormalities in Friedreich's ataxia

Ten patients with an accepted diagnosis of Friedreich's ataxia have been examined neuro-otologically, and oculomotor, vestibular and auditory function assessed. Brainstem auditory evoked potentials (BAEPs) were also recorded. A high incidence of various eye movement disorders was noted. Some of these were indicative of cerebellar dysfunction. Reduced vestibular function and impaired hearing were common to most of the patients. BAEPs were also abnormal in the majority; reasons underlying these abnormalities are discussed. Neuro-otologically, the patients did not constitute an homogeneous group. The findings cast doubt upon the accuracy and validity of the currently accepted criteria for the diagnosis and classification of the spinocerebellar degenerations.

Friedreich's ataxia: electrophysiological and histological findings

Electromyography was performed, and motor and sensory nerve conduction velocities were measured in 19 patients definitely affected by Friedreich's ataxia. Biopsy of the sural nerve was also performed in 9 patients. Most patients presented a moderate to severe loss of motor units, a significant increase in mean duration of motor unit potentials, and in the incidence of polyphasic potentials. Short-lasting spontaneous activity was rarely seen. Conduction velocity along the motor and sensory fibres of the median and tibial nerves was moderately slowed, while distal conduction time to muscle was significantly increased and the sensory orthodromically-evoked response markedly reduced. Intraoperative electrophysiological recordings obtained during biopsy of the sural nerve in 4 patients were consistent with the changes conventionally observed in the median, tibial and sural (6 patients) nerves. Quantitative histology revealed a reduced number of total myelinated fibres with a severe loss of large fibres, and a moderate loss of fibres of less than 7 microns in diameter. In teased nerve fibre preparations, the most evident abnormality consisted of fibres with uniformly short internodal length, while signs of remyelination were less prominent. Signs of active axonal degeneration were rarely observed in electron microscopy. Electrophysiological and histological findings were uniformly distributed, and the changes were neither related to the duration nor to the severity of the clinical condition.

Visual evoked potentials in spinocerebellar degenerations

Pattern reversal visual evoked potentials were studied in 21 patients with spinocerebellar ataxias among whom 6 had Friedreich's ataxia, 10 had hereditary spastic ataxia and 5 had spinocerebellar degeneration with slow eye movements (olivopontocerebellar degeneration). The VEP abnormalities found in 4 cases of Friedreich's ataxia and one with spinocerebellar degeneration with slow eye movements, consisted of, bilaterally absent VEP in 3 patients and bilaterally abnormal responses with asymmetry in two. All the patients with spastic ataxia had normal VEP latencies. The N 70 - P 100 amplitudes, in patients with hereditary ataxias were significantly reduced compared to controls (P less than 0.001). The VEP abnormalities correlated best with neuroophthalmic findings, but had no relation to age, sex, inheritance or duration of illness. The VEP findings are probably suggestive of progressive nerve fibre loss in the visual pathways with associated slowing of conduction. The higher incidence of visual pathway involvement in Friedreich's ataxia compared to other hereditary ataxias as reported in recent studies is confirmed.

Quantitative metabolic profiling of alpha-keto acids in Friedreich's ataxia

The plasma distribution of alpha-keto acids was measured in 26 subjects including 8 patients with Friedreich's ataxia, 8 with the recessive spastic ataxia of Charlevoix-Sageunay and 10 healthy volunteers. The groups were matched with regards to age, sex, weight and the study was conducted under standardized dietary intake. The result indicate significant differences in the alpha-keto acids distribution between the groups.

Friedreich's disease 1982: etiologic hypotheses a personal analysis

The author reviews the arguments for and against the four etiologic hypotheses in Friedreich's disease that have been proposed since 1974: the "pyruvate hypothesis", the "lipid-membrane hypothesis", the "energy-defect hypothesis" and finally the "taurine hypothesis". While none of these hypotheses are mutually exclusive, the author shows that all of these mechanisms play some role in the pathophysiology of the symptoms, but that only the "taurine hypothesis" appears to be compatible with all the known facts and the biochemical abnormalities reported. The author proposed that the taurine retention defect (possibly due to a block in the high affinity-low capacity transport of taurine - The TH System) is a primary event in Friedreich's disease. Whether it is the primary genetic event still has to be determined.

Electrophysiological investigation of the auditory system in Friedreich's ataxia

Auditory brainstem responses (ABRs) and cortical auditory evoked responses (AERs) were studied in a series of 16 Friedreich's ataxia patients who varied in age, degree of clinical involvement and duration of the disorder. The ABRs were markedly abnormal in all but the youngest patient, and the abnormalities reflected the severity and duration of the disease. The latencies of the AERs were significantly longer in the Friedreich's ataxia patients compared to normal controls, suggesting cortical as well as peripheral involvement of the auditory system. These data are discussed in terms of the neuropathology of the disorder and the similarities with the other sensory systems in Friedreich's ataxia patients.

Plasma lipoprotein lipase and hepatic lipase activities in Friedreich's ataxia

Plasma triglycerides although within the normal range have been shown to be higher in Friedreich's ataxia than in control subjects. To determine whether this difference could be ascribed to a reduced catabolism of triglyceride-rich lipoproteins, the activities of lipoprotein lipase (LPL) and hepatic triglyceride lipase (HL), released into plasma after an heparin injection, were measured in 13 cases of Friedreich's ataxia and 14 control subjects of comparable signs. LPL was found to be significantly lower in the ataxic patients. Moreover about half of the cases clustered below the normal range for both lipase activities. This subgroup of Friedreich's patients had significantly higher plasma triglycerides than those with normal lipase activities. Further studies are needed to relate these findings to other characteristics of the disease.

A case of Charcot-Marie-Tooth disease mimicking Friedreich's ataxia: is there any association between friedreich's ataxia and Charcot-Marie-Tooth disease?

The authors report a case of Charcot-Marie-Tooth disease that mimicked Friedreich's ataxia and featured impaired tendon reflexes in the limbs, incoordination mimicking cerebellar disease in the extremities, extensor plantar responses on both sides, bilateral foot deformity, imparied position sense in the toes, absent vibratory sense in the distal parts of the legs and minimal distal weakness with wasting. Motor conduction velocity in the upper limbs was substantially reduced. Other cases similar in nature reported in the literature resemble spino-cerebellar degeneration in general, and Friedreich's ataxia, in particular. It is emphasized that the natural history, EMG, motor conduction velocity studies and examination of other affected members of the family permit the correct diagnosis to be made in such cases. It is also emphasized that patients similar to the one reported here may also resemble, and should be differentiated from, cases of familial dorsal column ataxia (Biemond type). Stress is put upon the fact that when Charcot-Marie-Tooth disease mimicks spino-cerebellar degeneration, substantial slowing of motor conduction in the upper limbs is generally sufficient to establish the diagnosis. The relation between Friedreich's ataxia an Charcot-Marie-Tooth disease is reviewed and it is concluded that these two disorders are distinct clinical and pathological entities.

[Differential diagnosis of infratentorial atrophies by computed tomography (author's transl)]

Computed tomographical findings are documented for 140 patients with different cerebellar atrophic or heredodegenerative processes. There are idiopathic cerebellar atrophies, so called alcoholic and paraneoplastic cerebellar atrophies, cerebellar atrophies associated with nutritional deficiency diseases or intake of diphenylhydantoin. Further, there are patients suffering from Friedreich's ataxia. Nonne-Marie's spastic ataxia, olivo-ponto-cerebellar atrophy and various other diseases. With the aid of CT individual patterns of atrophy can be recognized. The method therefore, helps to distinguish the above mentioned diseases from each other and also distinguishes them from inflammatory, cerebrovascular or neoplastic processes.

Cranial computerized tomography in spinocerebellar atrophies

Cranial computerized tomography was carried out in 110 patients with cerebellar ataxia [53 with Friedreich's ataxia, 4 with Marie's spastic ataxia, 51 with cerebellar atrophy, and 2 patients with olivopontocerebellar atrophy). In CT scans, cerebellar atrophies are found to be of various localization and partially of characteristic distribution. CT, therefore, greatly helps to distinguish different types of cerebellar and spinocerebellar atrophies and allows the differentiation of cerebellar atrophies of various origins from other diseases, such as multiple sclerosis.

Hypersensitivity to N-methyl-N'-nitro-N-nitrosoguanidine in fibroblasts from patients with Huntington disease, familial dysautonomia, and other primary neuronal degenerations

Cells from patients with ataxia telangiectasia, a rare autosomal recessive disease characterized by primary neuronal degeneration, are abnormally sensitive to the DNA-damaging chemical N-methyl-N'-nitro-N-nitrosoguanidine. We have conducted experiments to determine whether more common primary neuronal degenerations also have a hypersensitivity to this radiomimetic chemical. Fibroblast strains from 13 control donors and from 13 patients with inherited primary neuronal degenerations were treated in vitro with the chemical, and the strains' sensitivity to the chemical was then determined by measuring their ability to divide and form colonies. Twelve of the 13 patient strains, including the 6 Huntington disease and the 4 familial dysautonomia strains, were abnormally sensitive. This hypersensitivity, which is believed to reflect defective repair of the chemically-induced DNA damage, might provide the basis for presymptomatic and prenatal diagnostic tests for these disorders and for elucidating their pathogenesis.

Friedreich's ataxia. A light- and electron microscopic study of peripheral nerve biopsies

Sural or superficial peroneal nerve biopsies of patients with clinical diagnosis of Friedreich's ataxia were studied. Patients were divided in two groups, typical and abortive forms: loss of fibers accompanied by axonal atrophy and segmental demyelination are the basic changes in both groups, although the decrease in number of myelinated fibers was most severe in typical FA. In the cases with slower progression there is a tendency to form onion bulb complexes.

[Computerized tomography in atrophy of the posterior fossa (author's transl)]

Cranial computerized tomography was carried out in 69 patients with cerebellar ataxia (45 with Friedreich's ataxia, 4 with Marie's spastic ataxia, 14 with cerebellar atrophy, and one patient with olivo-pontocerebellar atrophy). In CT scans cerebellar atrophy is found to be of various localisation and partially of characteristic distribution. CT, therefore, greatly helps to distinguish different types of cerebellar and spino-cerebellar atrophy and also distinguishes separate cerebellar atrophy of various origin from other diseases like multiple sclerosis.

Lecithin: cholesterol acyltransferase activity and fatty acid composition of erythrocyte phospholipids in Friedreich's ataxia

In a study of the fatty acid composition of erythrocyte membrane phospholipids in Friedreich's ataxia, a lower percentage of linoleic acid in phosphatidylcholine was demonstrated. An enzyme involving the exchange of lipids between plasma and erythrocyte membrane, lecithin: cholesteryl acyltransferase (LCAT) was also studied. It was found that the LCAT activity had a trend towards low values. However, crossing-over studies indicated that when the LCAT enzyme of patients was exposed to its own substrate it gave low activity values but that the result reverted to normal when control substrate was used.

Friedreich's ataxia 1980. An overview of the physiopathology

Phase three of the Quebec Cooperative Study of Friedreich's Ataxia was devoted to an understanding of the physiopathology of individual symptoms on the basis of previously discovered biochemical leads. The present paper attempts to pull these results together by presenting, as a hypothesis, a unifying scheme of possible interactions and relationships. The central core of this hypothesis is the demonstration in Friedreich's ataxia of a state of mitochondrial energy deprivation. This is indirectly responsible for such associated and important symptoms as muscle weakness, dying-back neuropathy, scoliosis and hypertrophic cardiomyopathy. Secondarily, and possibly as an independent but linked-event, the entry of glucose into cells and pyruvate oxidation, are slowed down, favoring the development of diabetes. As a consequence, tissue concentrations of glutamic acid and aspartic acid are decreased, particularly in more vulnerable areas such as the cerebellum, brain stem and dorsal root ganglia. This tissue deficiency in putative excitatory neurotransmitters is directly responsible for the symptom of ataxia. This conclusion is reinforced by the correction of the ataxia in experimental animals, by the intraventricular injection of the same amino acids, and not by the injection of other stimulants of motricity. The observed mitochondrial energy deprivation could be the metabolic consequence of major changes in the linoleic acid (18.2) composition of inner mitochondrial membrane phospholipids, such as cardiolipin. Such decreases in membrane 18:2 could be the result of interference with the normal incorporation of this fatty acid to lipoproteins and/or cell membranes. It is at this level that the search for the specific enzyme defect in Friedreich's ataxia is continuing.

Friedreich's ataxia in the south of Italy: a clinical and biochemical survey of 23 patients

We report a clinical and biochemical survey of 23 patients with Friedreich's ataxia from southern Italy. They were studied clinically and by means of a clinical rating scale devised by us (Inherited Ataxias Clinical Rating Scale). Laboratory tests, based on the Quebec Cooperative Study, were also performed on our patients. No major clinical or biochemical differences were found between Italian and Canadian patients. Investigation of CSF monoamine metabolites showed that HVA decreased after probenecid and metoclopramide loading.

[Investigations of peripheral and central somatosensory pathways in peroneal muscular atrophy and Friedreich's heredoataxia (author's transl)]

Twenty-eight patients with peroneal muscular atrophy (PMA) have been investigated. Eighteen of them were affected by the Charcot-Marie-Tooth disease and three by Dejerine-Sottas disease. In these 21 cases the nerve conduction velocity (NCV) was decreased. Four patients presented the neuronal type of PMA, two cases showed sensory neuropathy of the neuronal type with ophthalmoplegia, and one case, PMA with ataxia, i.e., a myatrophic ataxia. In the neuronal type of PMA, including both cases with ophthalmophegia, the amplitudes of the sensory nerve action potentials were decreased, and the NCV was normal to slightly subnormal. In myatrophic ataxia NCV was decreased. In all cases with reduced NCV, the latencies of the spinal-evoked potentials (spinEP) and somatosensory-evoked potentials (ssEP) were prolonged. In the neuronal type of PMA, these latencies were normal. The central latencies (from thoracic and cervical level) were normal in all 28 patients with PMA of different types. Seventeen patients with Friedreich's heredoatazia have been investigated. In all except two cases, NCV was normal. The sensory nerve-action potentials markedly decreased or disappeared in all cases. The peripheral neurographic picture, accordingly, corresponds to that of patients with the neuronal type of PMA. The latencies of spinEP were normal. All patients with Friedreich's heredoatazia, however, showed prolonged latencies of ssEP. Calculating the central latencies as the difference between ssEP and spinEP latencies (cervical and thoracic) confirms that this is due to a slowing of the conduction velocity via the spinobulbar tracts.

Evidence for an altered physical state of membrane proteins in erythrocytes in Friedreich's ataxia

Electron spin resonance, scanning electron microscopic, and SDS-polyacrylamide gel electrophoretic studies of erythrocytes in Friedreich's ataxia have been performed. No alteration in the physical state of membrane lipids, in morphology, or in the staining profile of erythrocytes in Friedreich's ataxia could be demonstrated. An altered conformation and/or organization of proteins in erythrocyte membranes in this disorder was suggested by spin labeling studies (P less than 0.025), favoring the possibility of a generalized membrane abnormality in Friedreich's ataxia. These findings are discussed in relation to other inherited neurological diseases where similar studies have been performed.