Plasma Very-long-chain Fatty Acids Levels Research Articles

Nutritional Counseling and Mediterranean Diet in Adrenoleukodystrophy: A Real-Life Experience

Background/Objectives: Adrenoleukodystrophy (X-ALD) is a metabolic disorder caused by dysfunctional peroxisomal beta-oxidation of very-long-chain fatty acids (VLCFAs). A VLCFA-restricted Mediterranean diet has been proposed for patients and carriers to reduce daily VLCFA intake. Methods: We retrospectively evaluated plasma VLCFAs in a cohort of 36 patients and 20 carriers at baseline and after 1 year of restricted diet. Results: At T1, compliant adult patients had significantly lower C26:0 levels [1.7 (1.2) vs. 2.5 µmol/L (1.7), p < 0.05], C26:0/C22:0 ratio [0.04 (0.02) vs. 0.06 (0.03), p < 0.05], and triglycerides [93 (56.5) vs. 128 mg/dL (109.5), p < 0.05] than non-compliant ones. C26:0 [2.4 (1.7) vs. 1.7 (1.2) µmol/L, p < 0.05], the C26:0/C22:0 ratio [0.06 (0.04) vs. 0.04 (0.02), p < 0.05], and cholesterol [173.5 (68.3) mg/dL vs. 157 (54) mg/dL, p < 0.05] were significantly reduced in compliant adult patients at T1 vs. baseline. As for carriers, the C26:0/C22:0 ratio was lower [0.02 (0.01) vs. 0.04 (0.009), p < 0.05] at T1 in compliant carriers, as compared to non-compliant ones. The C26:0/C22:0 [0.03 (0.02) vs. 0.02 (0.01) p < 0.05] and C24:0/C22:0 [1.0 (0.2) vs. 0.9 (0.3), p < 0.05] ratios were significantly decreased at T1 vs. T0. Conclusions: A VLCFA-restricted diet is effective in reducing plasma VLCFA levels and their ratios and must be strongly encouraged as support to therapy.

Adrénoleucodystrophie liée à l'X

X-linked adrenoleukodystrophy (ALD) is a severe neurodegenerative disorder. ALD is characterized by progressive demyelination within the central and peripheral nervous system, adrenal insufficiency (Addison's disease) and accumulation of very-long-chain fatty acids (VLCFA) in plasma, fibroblasts and tissues. The overall incidence of ALD is 1:17,000 including hemizygotes and heterozygotes who are frequently symptomatic. There are two main ALD phenotypes: 1) a cerebral demyelinating form which affects boys between 5–12 years, but also 35% of adult males; 2) a form that mainly involves the spinal cord (adrenomyeloneuropathy, AMN) in adult males between 20–50 years and 50% of heterozygous women after the age of 40 years. AMN presents with progressive spastic paraparesis. Addison's disease may be the first symptom of ALD in boys and adult males. These patients are at risk to develop cerebral ALD or AMN for life. ALD results from mutations in the ABCD1 gene without correlation between genotype and phenotype. The diagnosis of ALD relies upon the measurement of plasma VLCFA levels that allows the identification of 100% affected males and of 80–95% heterozygous women. Because of these false-negative, it is therefore mandatory to search for a mutation in the ABCD1 gene in all women at risk to be heterozygous for ALD. The ABCD1 gene encodes a peroxisomal transmembrane protein (ALD protein) with the structure of an half ATP-binding cassette transporter. It is possible that ALD protein imports VLCFA or VLCFA-CoA into peroxisomes in which they are degraded by a peroxisomal β-oxidation system. Elongation of VLCFAs is enhanced in fibroblasts from ALD patients and likely contributes to the load of VLCFA in tissues. The underlying mecanisms that lead to cerebral demyelination, axonal degeneration in spinal cord and adrenal insufficiency are unknown. The « toxic » role of VLCFA accumulation remains to be demonstrated. The mecanisms that lead to the inflammatory reaction in cerebral ALD might involve abnormal acylation of gangliosides and phospholipidis by VLCFA that would result in immune reaction of brain macrophages and astrocytes bearing CD1 molecules that recognize lipid antigens. De novo mutation of ABCD1 occurs in less than 8% of ALD patients. The genetic counseling aims to identify: 1) women who are at risk to be heterozygous; 2) neurologically asymptomatic boys. It is only at this stage that allogeneic bone marrow transplantation has clinical benefit; 3) ALD patients who have Addison's disease that can lead to sudden death. Prenatal diagnosis (chorionic villus samples, cultured amniotic fluid cells) relies upon DNA based mutation detection techniques, expression of ALD protein and measurement of VLCFA levels. Allogeneic bone marrow transplantation is the only treatment that provides a permanent cure when the procedure is performed at an early stage of cerebral demyelination, i.e when the patients are asymptomatic despite abnormal brain MRI. Treatment of Addison's disease is mandatory but does not modify the course of neurological symptoms. Dietary therapy failed to halt the neurologic progression in cerebral ALD and AMN. It might have a partial preventive effect in boys treated before 6 years of age.

Novel Insertion 496_497insG Creating a Stop Codon D194X in a Chinese Family with X-Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (XALD, MIM 300100), the commonest inherited peroxisomal disorder, is characterized by central nervous system demyelination, primary adrenal failure and the systemic accumulation of saturated very long chain fatty acids (VLCFAs). The defective gene ABCD1 encodes an ATP-binding cassette (ABC) transport protein named ALDP, which functions as a crucial transporter of VLCFAs into the peroxisomes for β-oxidation. Here, we report a Chinese man with adrenomyeloneuropathy characterized by Addison’s disease and spastic paraparesis. His plasma VLCFA levels, ratios of C24:0/C22:0 and C26:0/C22:0 were all significantly elevated. We performed mutation analysis of the ABCD1 gene in the proband and the family members using direct DNA sequencing and restriction analysis. A novel insertion 496_497insG in exon 1 causing a frame shift and a premature stop codon at amino acid position 194 (D194X) was identified (GenBank accession No. NM_000033). The insertional mutation abolishes an HhaI restriction site. The same mutation was found in his mother and the eldest sister even though their clinical and biochemical abnormalities were milder. Diagnosis of XALD often relies upon the detection of elevated VLCFA levels and ratios of C26:0/C22:0 and C24:0/C22:0 in fasting blood, however, 5–15% of the obligate heterozygotes would give normal values. DNA-based testing thus remains the most reliable tool for heterozygote detection when the disease-causing mutations are known. Using restriction fragment length polymorphism with HhaI, we have devised a rapid method for the identification of the carriers among the proband’s family members and possibly for the screening of the mutations in other XALD patients.

Neonatal cholestasis: A new presentation of X-linked adrenoleukodystrophy

A French-Canadian boy presented with neonatal cholestasis and failure to thrive, bilateral polar cataracts, anemia, thrombocytopenia and hypolonia. Bom at 37 weeks gestational age, he weighed 2450 g (10%ile), with length 46 cm (10%ile) and head circumference 33 cm (50%ile). Jaundice was present at birth. No dysmorphism was noted Transaminases were consistently elevated >2-fold. Liver biopsy showed cholestasis and confirmed the presence of calalase-posilive structures, with normal peroxisomes and mitochondria. HIDA scintigraphy showed mild hepatocellular dysfunction. Other investigations including endoscopy, plasma and urine amino acids, serum copper, alpha-1-antitrypsin levels, erythrocyte galactose-1-phosphate levels, karyotype (46, XY) and TORCH viral studies were non-diagnostic. Brainstem auditory evoked potentials showed mild peripheral hearing loss at 3 weeks of age, and a central loss when repeated at 8 months of age. He developed cachexia, progressive hepatomegaly, splenomegaly, osteopenia, bruxism and opisthotonic posturing, with a progressive motor delay. CT scan revealed cortical atrophy. He died of liver failure at age 12 months after frequent episodes of gastrointestinal bleeding and continued neurological deterioration. Post-mortem, plasma very long-chain fatty acids (VLCFAs) results became available, showing elevation of the C26:C22 ratio. Phytanic acid, assayed on three stored samples was normal in two and 3-fold elevated in one. Other peroxisomal function tests including plasma pipecolic acid and rbc plasmalogen ratios were normal, but C18 DMA levels were somewhat lower than normal. Fibroblast C26:0 and C22 levels were elevated 5-fold, and the C26/C22 ratio, 9-fold. Oxidation of C24:0 was 20% of control values. On immunostaining with antibody to the ALD protein, fibroblasts were CRIM negative. The ALD protein gene contained a previously-unreported mutation, a thymine-to-cytosine transition at nucleotide 1654 in exon 7, predicted to change Ser 552 to Pro in the ATP binding domain. Although the patient's mother had normal plasma VLCFA levels, a subsequent pregnancy showed an elevated C26/C22 ratio in amniocytes and was terminated. A similar patient with biochemically-proven ALD and rapidly-progressive cholestasis was recently reported (Corzo. D. et al., Am J Hum Genet 65, 4 (Suppl.): A1295) demonstrating that the association of mutations in the ALD protein gene and neonatal cholestasis is not spurious, and expanding the phenotypic spectrum of ALD to include neonatal cholestatic jaundice with liver failure.

Etiological diagnosis of primary adrenal insufficiency using an original flowchart of immune and biochemical markers.

Approximately 70-80% of cases of primary adrenal insufficiency are classified as idiopathic. An effective protocol for the etiological diagnosis of primary adrenal insufficiency is needed to ensure correct patient management. With the aim of developing an algorithm for the etiological diagnosis of primary adrenal insufficiency, we studied 56 Italian patients with nonsurgical primary adrenal insufficiency and 24 French patients with X-linked adrenoleukodystrophy (ALD) for serum levels of adrenal cortex, steroid-21-hydroxylase (21OHAb), islet cell (ICA), glutamate decarboxylase (GAD65Ab), IA2/ICA512 (ICA512Ab), thyroid peroxidase (TPOAb) autoantibodies, and plasmatic concentrations of very long chain fatty acids (VLCFA). High levels of 21OH and adrenal cortex antibodies were found in 35/42 (83%) and 17/42 (40%) Italian patients with idiopathic adrenal insufficiency, respectively. Levels of adrenal autoantibodies correlated inversely with disease duration (P < 0.0001). Elevated VLCFA were found in 4/42 (10%) idiopathic patients. A total of 34/35 (97%) idiopathic patients with a disease duration of less than 20 yr was positive for either 21OHSAb or elevated levels of VLCFA. None of 14 patients with posttuberculosis adrenal insufficiency had elevated levels of either adrenal antibodies or VLCFA. ICA, GAD65Ab, ICA512Ab, and TPOAb were found in 6/56 (11%), 8/56 (14%), 4/56 (7%), and 23/56 (41%) patients, respectively. None of 24 French ALD patients with adrenal insufficiency was positive for organ-specific autoantibodies. The measuring of 21OH antibodies and plasma VLCFA levels enabled a correct diagnosis of autoimmune (89%) and ALD (8%) in 97% of patients with idiopathic primary adrenal insufficiency of less than 20 yr of duration. The results of our study have important therapeutic and prognostic implications.

Distinction between peroxisomal bifunctional enzyme and acyl‐CoA oxidase deficiencies

The clinical distinction between patients with a disorder of peroxisome assembly (e.g., Zellweger syndrome) and those with a defect in a peroxisomal fatty acid beta-oxidation enzyme can be difficult. We studied 29 patients suspected of belonging to the latter group. Using complementation analysis, 24 were found to be deficient in enoylcoenzyme A hydratase/3-hydroxyacylcoenzyme A dehydrogenase bifunctional enzyme and 5 were deficient in acyl-CoA oxidase. Elevated plasma very long-chain fatty acids (VLCFA), impaired fibroblast VLCFA beta-oxidation, decreased fibroblast phytanic acid oxidation, normal plasmalogen synthesis, normal plasma L-pipecolic acid level, and normal subcellular catalase distribution were characteristic findings in both disorders. The elevation in plasma VLCFA levels and impairment in fibroblast VLCFA beta-oxidation were more severe in bifunctional-deficient than in oxidase-deficient patients. The clinical course in bifunctional deficiency (profound hypotonia, neonatal seizures, dysmorphic features, age at death approximately 9 months) was more severe than in oxidase deficiency (moderate hypotonia without dysmorphic features, development of a leukodystrophy, age at death approximately 4 yr). Based on these findings, accurate early diagnosis of these deficiencies of peroxisomal beta-oxidation enzymes is possible.

X‐linked adrenoleukodystrophy presenting as neurologically pure familial spastic paraparesis

The familial spastic paraplegias (FSPs) are heterogeneous neurologic disorders that are known to occur clinically as "pure" or "complicated" forms. Although some of the complicated FSPs have been linked to specific metabolic defects, the pure forms of this disorder remain idiopathic and are considered to be primary system degenerations. We report the case of a 28-year-old man who has evidenced a neurologically pure spastic paraparesis since age twenty-five. Consistent with this diagnosis were the findings of magnetic resonance imaging, which revealed atrophy of the thoracic spinal cord without evidence for white matter disease in the cerebrum, cerebellum, or brainstem. His 32-year-old brother has also evidenced progressive spastic paraparesis since age 30, but his case is confounded by a severe head injury at age 24 that caused a skull fracture and a focal demyelinating lesion of the right frontal lobe. Both patients have had hypogonadism, requiring treatment with testosterone, since age 20. Measurement of plasma levels of very long-chain fatty acids (VLCFA) revealed that both brothers had concentrations diagnostic of adrenoleukodystrophy; their mother had plasma VLCFA levels in the heterozygous range. We conclude that neurologically pure FSP can be an early manifestation of adrenoleukodystrophy and that levels of plasma VLCFA should be determined for all cases of FSP in which X-linked inheritance appears tenable. These considerations may have bearing on the ongoing linkage studies for these disorders.

X-LINKED ADRENOLEUKODYSTROPHY (ALD): HORMONAL AND CLINICAL FINDINGS DURING DIETARY ERUCIC-TRIOLEATE THERAPY

X-linked ALD is characterized by primary adrenal insufficiency, demyelination and accumulation of very long chain fatty acids (VLCFA). VLCFA have a toxic effect on adrenocortical cell by increasing cell membrane microviccosity, leading to decreased ability to respond to ACTH (Whitcomb RW et al. J Clin invest 81:185·188, 1988). The regimen of VLCFA restricted diet supplemented with a mixture of oleic and erucic acid (GTEO) determined, for the first time, a normalisation of plasma VLCFA levels in ALD patients. Thus the data suggest that the pathological changes affecting the nervous and endocrine system may be delayed, or even arrested, in these patients. We now report the effects on the clinical course of ALD of this therapeutic approach in 18 patients treated with dietary-GTOE supplementation up to 5 years. There was no effect on the clinical course in patients with childhood and adolescent ALD assessed by neurological, neuropsycological, and neuroadiological (NMI) evaluations. Patients with adrenomyeloneropathy and presymptomic did not exhibit progression of the disease. All but 3 patients had hyposdrenalism. Plasma eldosterone levels were reduced and PRA was increased. Interestingly, normalisation of VLCFA levels in these patients resulted in an increase of aldosterone (M±SD: 112.3±94.6 vs 379.2±12.1 pg/ml, p<0.05) and a reduction of PRA levels form 10.2±7.6 to 5.1±2.8 ng/ml/h, confirming that VLCFA excess has a direct toxic effect on the adrenals whereas other factors are more likely involved in the determination of the pathological changes in the nervous system.