Molecular, clinical and peripheral neuropathy study of Tunisian patients with ataxia with vitamin E deficiency

Ataxia with vitamin E deficiency is an autosomal recessive cerebellar ataxia caused by mutations in the α-tocopherol transfer protein coding gene localized on chromosome 8q, leading to lower levels of serum vitamin E. More than 91 patients diagnosed with ataxia with vitamin E deficiency have been reported worldwide. The majority of cases originated in the Mediterranean region, and the 744delA was the most common mutation among the 22 mutants previously described. We examined the clinical and molecular features of a large cohort of 132 Tunisian patients affected with ataxia with vitamin E deficiency. Of these patients, nerve conduction studies were performed on 45, and nerve biopsy was performed on 13. Serum vitamin E was dramatically reduced for 105 of the patients analysed. Molecular analysis revealed that 91.7% of the patients (n = 121) were homozygous for the 744delA mutation. Three other mutations were detected among the remaining patients (8.3%, n = 11) in the homozygous state. Two were previously reported (400C>T and 205-1G>T), and one was novel (553+1T>A). Age of onset was 13.2 ± 5.9 years, with extremes of 2 and 37 years. All described patients exhibited persistent progressive cerebellar ataxia with generally absent tendon reflexes. Deep sensory disturbances, pyramidal syndrome and skeletal deformities were frequent. Head tremor was present in 40% of the patients. Absence of neuropathy or mild peripheral neuropathy was noted in more than half of the cohort. This is the largest study of the genetic, clinical and peripheral neuropathic characteristics in patients with ataxia and vitamin E deficiency. The 744delA mutation represents the most common pathological mutation in Tunisia and worldwide, likely because of a Mediterranean founder effect. Our study led us to suggest that any patient displaying an autosomal recessive cerebellar ataxia phenotype with absent tendon reflexes and minor nerve abnormalities should first be screened for the 744delA mutation, even in the absence of a serum vitamin E measurement.

Altered lipid metabolism in a Drosophila model of Friedreich's ataxia

Friedreich's ataxia (FRDA) is the most common form of autosomal recessive ataxia caused by a deficit in the mitochondrial protein frataxin. Although demyelination is a common symptom in FRDA patients, no multicellular model has yet been developed to study the involvement of glial cells in FRDA. Using the recently established RNAi lines for targeted suppression of frataxin in Drosophila, we were able to study the effects of general versus glial-specific frataxin downregulation. In particular, we wanted to study the interplay between lowered frataxin content, lipid accumulation and peroxidation and the consequences of these effects on the sensitivity to oxidative stress and fly fitness. Interestingly, ubiquitous frataxin reduction leads to an increase in fatty acids catalyzing an enhancement of lipid peroxidation levels, elevating the intracellular toxic potential. Specific loss of frataxin in glial cells triggers a similar phenotype which can be visualized by accumulating lipid droplets in glial cells. This phenotype is associated with a reduced lifespan, an increased sensitivity to oxidative insult, neurodegenerative effects and a serious impairment of locomotor activity. These symptoms fit very well with our observation of an increase in intracellular toxicity by lipid peroxides. Interestingly, co-expression of a Drosophila apolipoprotein D ortholog (glial lazarillo) has a strong protective effect in our frataxin models, mainly by controlling the level of lipid peroxidation. Our results clearly support a strong involvement of glial cells and lipid peroxidation in the generation of FRDA-like symptoms.

Status of vitamins A and E in schoolchildren in the centre west of Tunisia: a population-based study

OBJECTIVE

The present study was undertaken to assess the status of vitamins A and E (VA and VE, respectively) and their main determinants in Tunisian children.

DESIGN

Cross-sectional population-based study.

SETTING

Kasserine Governorate in the centre west of Tunisia.

SUBJECTS

A total of 7407 children attending the first grade of elementary school were included. VA and VE were assessed by HPLC.

RESULTS

The prevalence of moderate VA deficiency (VAD; <0·70 μmol/l) was 2·3 % and VE deficiency (VED; <6·97 μmol/l) was 5·4 %. Low status in VA (0·70-1·05 μmol/l) and VE (6·97-11·61 μmol/l) was observed in 17 % and 20·2 % of children, respectively. No child exhibited severe VA or VE deficiency (<0·35 and <2·32 μmol/l, respectively). The main predictors of VAD were advanced age (OR = 1·65; 95 % CI 1·13, 2·41; P = 0·05) and sickness within the past 2 weeks (OR = 1·51; 95 % CI 1·09, 2·09; P = 0·01). Predictors of VED were living in the peri-urban region (OR = 1·60; 95 % CI 1·28, 2·01; P < 0·001) and sickness within the past 2 weeks (OR = 0·75; 95 % CI 0·60, 0·94; P = 0·01).

CONCLUSIONS

Moderate VAD and VED were uncommon in Tunisian children. However, low status in VA and/or VE remains frequent. A reinforcement of the national strategies for children's nutrition and health is needed, particularly in disadvantaged regions. Supplementation of VA and VE is not necessary in Tunisia, but food fortification may be beneficial.