Fatty acids and TxA(2) generation, in the absence of platelet-COX-1 activity

BACKGROUND AND AIMS

Omega-3 fatty acids suppress Thromboxane A(2) (TxA(2)) generation via mechanisms independent to that of aspirin therapy. We sought to evaluate whether baseline omega-3 fatty acid levels influence arachidonic acid proven platelet-cyclooxygenase-1 (COX-1) independent TxA(2) generation (TxA(2) generation despite adequate aspirin use).

METHODS AND RESULTS

Subjects with acute myocardial infarction, stable CVD or at high risk for CVD, on adequate aspirin therapy were included in this study. Adequate aspirin action was defined as complete inhibition of platelet-COX-1 activity as assessed by <10% change in light transmission aggregometry to ≥1 mmol/L arachidonic acid. TxA(2) production was measured via liquid chromatography-tandem mass spectrometry for the stable TxA(2) metabolite 11-dehydro-thromboxane B2 (UTxB2) in urine. The relationship between baseline fatty acids, demographics and UTxB(2) were evaluated. Baseline omega-3 fatty acid levels were not associated with UTxB(2) concentration. However, smoking was associated with UTxB(2) in this study.

CONCLUSION

Baseline omega-3 fatty acid levels do not influence TxA(2) generation in patients with or at high risk for CVD receiving adequate aspirin therapy. The association of smoking and TxA(2) generation, in the absence of platelet COX-1 activity, among aspirin treated patients warrants further study.

Docosahexaenoic acid therapy in peroxisomal diseases: results of a double-blind, randomized trial

OBJECTIVES

Peroxisome assembly disorders are genetic disorders characterized by biochemical abnormalities, including low docosahexaenoic acid (DHA). The objective was to assess whether treatment with DHA supplementation would improve biochemical abnormalities, visual function, and growth in affected individuals.

METHODS

This was a randomized, double-blind, placebo-controlled trial conducted at a single center. Treatment groups received supplements of DHA (100 mg/kg per day). The primary outcome measures were the change from baseline in the visual function and physical growth during the 1 year follow-up period.

RESULTS

Fifty individuals were enrolled and randomized. Two were subsequently excluded from study analysis when it was determined that they had a single enzyme disorder of peroxisomal beta oxidation. Thirty-four returned for follow-up. Nine patients died during the trial of their disorder, and 5 others were lost to follow-up. DHA supplementation was well tolerated. There was no difference in the outcomes between the treated and untreated groups in biochemical function, electroretinogram, or growth. Improvements were seen in both groups in certain individuals.

CONCLUSIONS

DHA supplementation did not improve the visual function or growth of treated individuals with peroxisome assembly disorders.

CLASSIFICATION OF EVIDENCE

This interventional study provides Class II evidence that DHA supplementation did not improve the visual function or growth of treated individuals with peroxisome assembly disorders during an average of 1 year of follow-up in patients aged 1 to 144 months.

A PEX10 defect in a patient with no detectable defect in peroxisome assembly or metabolism in cultured fibroblasts

Zellweger spectrum disorders (ZSD) are diagnosed by biochemical assay in blood, urine and cultured fibroblasts and PEX gene mutation identification. In most cases studies in fibroblasts corroborate results obtained in body fluids. In 1996 Clayton and colleagues described a 10-year old girl with evidence of a peroxisome disorder, based on elevated bile acid metabolites and phytanate. At the time it was not possible to distinguish whether she had a ZSD or a single peroxisomal protein defect. Studies in our laboratory showed that she also had elevated plasma pipecolate, supporting the former diagnosis. Despite the abnormal metabolites detected in blood (phytanate, bile acid intermediates and pipecolate), analysis of multiple peroxisomal pathways in fibroblasts yielded normal results. In addition, she had a milder clinical phenotype than usually associated with ZSD. Since complementation analysis to determine the gene defect was not possible, we screened this patient following the PEX Gene Screen algorithm (PGS). The PGS provides a template for sequencing PEX gene exons independent of complementation analysis. Two mutations in PEX10 were identified, a frameshift mutation inherited from her father and a de novo missense mutation in a conserved functional domain on the other allele. This case highlights that molecular analysis may be essential to the diagnosis of patients at the milder end of the ZSD spectrum. Furthermore, it supports the concept that some tissues are less affected by certain PEX gene defects than brain and liver.

Orthotopic liver transplantation from a living-related donor in an infant with a peroxisome biogenesis defect of the infantile Refsum disease type

Peroxisomal biogenesis defects include a number of severe neurodevelopmental disorders, among which infantile Refsum disease (IRD) occupies the mildest end of the spectrum. Although high docosahexaenoic acid (DHA) and low phytanic acid diets can correct some of the biochemical defects, they have not consistently altered the progressive course of the disease. We carried out orthotopic liver transplantation (OLT) in a mildly symptomatic 6-month-old infant who was a sibling of a severely neurologically impaired older sister. After transplantation the clinical course of this young child appeared much improved by comparison to her older sister. She walked alone at 4 years, had acceptable social interaction and had a noticeable recovery of audition. After transplantation her biochemical parameters were significantly improved: phytanic acid and very long-chain fatty acid (VLCFA) serum concentrations decreased. Abnormal bile acids disappeared from plasma. Although the OLT did not result in a cure of the disorder, the clinical and biochemical results suggest that OLT should be considered in mildly symptomatic patients.

MRI and proton MRSI in women heterozygous for X-linked adrenoleukodystrophy

OBJECTIVE

To utilize neuroimaging procedures to assess the extent of cerebral involvement in female subjects heterozygous for X-linked adrenoleukodystrophy (X-ALD).

METHODS

Brain MRI studies were performed in 76 female subjects heterozygous for X-ALD (mean age 43 years, range 8 to 75 years). Sixty-five had clinical evidence of spinal cord involvement resembling that in males with adrenomyeloneuropathy (AMN), two had clinical evidence of cerebral involvement, and nine showed no neurologic abnormality. Readers blinded to clinical findings further analyzed abnormal MRI studies. In eight women whose MRI results were normal, four-slice long echo time MRS imaging (MRSI) studies were performed and compared to those of eight age-matched controls.

RESULTS

MRI results were normal in 65 subjects and abnormal in 11. In eight of the latter group, the MRI changes were judged to be due to causes other than X-ALD. Lesions were attributed to X-ALD in the remaining three. Two of these patients had lesions that resembled those in male patients with cerebral X-ALD. In one patient with a mild AMN-like syndrome, brain MRI abnormalities were confined to the corticospinal tract. When compared to those of controls, MRSI studies in eight female patients with normal results on brain MRI showed a significant reduction of N-acetylaspartate/creatine and N-acetylaspartate/choline ratios in the internal capsule and corticospinal projection fibers. The N-acetylaspartate/choline ratio was significantly reduced in the parieto-occipital white matter and the choline/creatine ratio was significantly increased in the frontal white matter.

CONCLUSION

Brain involvement demonstrable by MRI is rare in female subjects heterozygous for X-ALD, including those who have clinical evidence of spinal cord involvement. Nevertheless, N-acetylaspartate levels are reduced in the corticospinal projection fibers in female subjects with normal results on MRI, suggesting axonal dysfunction.

Lipid status and long-chain polyunsaturated fatty acid concentrations in adults and adolescents with phenylketonuria on phenylalanine-restricted diet

Blood lipid studies are reported in 25 adults and 2 adolescents with PKU who had been on phenylalanine-restricted diets for a mean period of 22.6 years (range 7-39 years). Measurements included plasma concentrations of phenylalanine, cholesterol, lipoproteins, triglycerides and fatty acid profiles, including the analysis of seven fatty acids in plasma and red blood cells. Lipid screening identified 7 subjects with significantly elevated cholesterol/HDL ratios ranging from 5.6 to 10.3. Triglyceridaemia was documented in 5 of these 7, with concentrations ranging between 0.24 and 4.5 mmol/L (219-402 mg/dl) with a mean of 3.5 mmol/L (310 mg/dl). The fatty acid analyses demonstrated slight but statistically significant reductions in the concentrations of long-chain polyunsaturated fatty acids (LCPUFA), including plasma docosahexaenoic (DHA) and arachidonic acid (AA), and red blood cell DHA concentrations. The pattern resembles that reported previously in children, but alterations in the mean levels are less severe. In six of the adult patients plasma DHA or AA concentrations were less than 50% of controls. Since DHA and AA have important physiological roles, including brain and retinal function, it is recommended that blood lipid concentrations be monitored in all patients with PKU, including adults, and that DHA and AA supplementation be provided, particularly in those patients in whom the blood concentrations of these substances are reduced significantly.

Peroxisomal straight-chain Acyl-CoA oxidase and D-bifunctional protein are essential for the retroconversion step in docosahexaenoic acid synthesis

Docosahexaenoic acid (DHA, C22:6n-3) is essential for normal brain and retinal development. The nature and subcellular location of the terminal steps in DHA biosynthesis have been controversial. Rather than direct Delta4-desaturation of C22:5n-3, it has been proposed that this intermediate is elongated to C24:5n-3, desaturated to C24:6n-3, and "retroconverted" to DHA via peroxisomal beta-oxidation. However, this hypothesis has recently been challenged. The goal of this study was to determine the mechanism and specific enzymes required for the retroconversion step in human skin fibroblasts. Cells from patients with deficiencies of either acyl-CoA oxidase or D-bifunctional protein, the first two enzymes of the peroxisomal straight-chain fatty acid beta-oxidation pathway, exhibited impaired (5-20% of control) conversion of either [1-14C]18:3n-3 or [1-14C]22:5n-3 to DHA as did cells from peroxisome biogenesis disorder patients comprising eight distinct genotypes. In contrast, normal DHA synthesis was observed in cells from patients with rhizomelic chondrodysplasia punctata, Refsum disease, X-linked adrenoleukodystrophy, and deficiency of mitochondrial medium- or very long-chain acyl-CoA dehydrogenase. Acyl-CoA oxidase-deficient cells accumulated 2-5 times more radiolabeled C24:6n-3 than did controls. Our data are consistent with the retroconversion hypothesis and demonstrate that peroxisomal beta-oxidation enzymes acyl-CoA oxidase and D-bifunctional protein are essential for this process in human skin fibroblasts.

Potential environmental and host participants in the early white matter lesion of adreno-leukodystrophy: morphologic evidence for CD8 cytotoxic T cells, cytolysis of oligodendrocytes, and CD1-mediated lipid antigen presentation

The 2 most common forms of X-linked adreno-leukodystrophy (ALD) are the juvenile or childhood cerebral form with inflammatory demyelination and the adult adrenomyeloneuropathy (AMN) involving spinal cord tracts without significant inflammation. Modifier genes or environmental factors may contribute to the phenotypic variability. We performed immunohistochemical, an in situ polymerase chain reaction, and TUNEL analyses to identify several viruses, lymphocyte subpopulations, apoptotic cells, and effector molecules, focusing on morphologically normal white matter, dysmyelinative and acute demyelinative lesions. No distinguishing viral antigens were detected. Most lymphocytes were CD8 cytotoxic T cells (CTLs) with the alpha/beta TCR, and they infiltrated morphologically unaffected white matter. Only a few oligodendrocytes were immunoreactive for caspase-3. MHC class II- and TGF-beta-positive microglia were present. CD44, which can mediate MHC-unrestricted target cell death, was seen on many lymphocytes and white matter elements. CD1 molecules, which play major roles in MHC-unrestricted lipid antigen presentation, were noted. Our data indicate that unconventional CD8 CTLs are operative in the early stages of dysmyelination/demyelination and that cytolysis of oligodendrocytes, rather than apoptosis, appears to be the major mode of oligodendrocytic death. The presentation of lipid antigens may be a key pathogenetic element in ALD and AMN-ALD.

The dorsal root ganglia in adrenomyeloneuropathy: neuronal atrophy and abnormal mitochondria

Adrenomyeloneuropathy (AMN), a disease of spinal cord, brain, adrenal, and testis, mostly affects men with spastic paraparesis or ataxia beginning in their second or third decade. The spinal cord displays bilateral, usually symmetrical, long tract degeneration particularly of the gracile tract in a "dying-back" pattern. The available data strongly indicate that the fundamental lesion in AMN is an axonopathy or neuronopathy. We compared lumbar dorsal root ganglia (DRG) from 3 AMN patients to 6 age-matched controls histologically, morphometrically, immunohistochemically, and ultrastructurally. There was no apparent neuronal loss, necrosis or apoptosis, nor obvious atrophy; nodules of Nageotte were sparse in both groups. The morphometric studies, however, did reveal neuronal atrophy with a decrease in the number of large neurons and a corresponding increase in neurons less than 2,000 microm2, especially in the 1,500-1,999 microm2 range. No consistent immunohistochemical differences were observed, and no specific cell type appeared to be lost. Many mitochondria in the AMN neurons demonstrated lipidic inclusions; this raises the possibility that, in addition to the well-known peroxisomal defect, impaired mitochondrial function may lead to a failure of ATP-dependent axoplasmic transport in AMN spinal tracts with consequent "dying-back" axonal degeneration. The observation that the DRG parent neurons of the degenerate gracile tracts in AMN undergo atrophy and do not display appreciable evidence of cell death, even at autopsy, provides a wide window of opportunity for the development of therapeutic strategies to combat or prevent this myeloneuropathy.

Adrenoleukodystrophy: incidence, new mutation rate, and results of extended family screening

Utilizing the plasma very long chain fatty acid assay, supplemented by mutation analysis and immunofluorescence assay, we determined the number of X-linked adrenoleukodystrophy (X-ALD) hemizygotes from the United States identified each year in the two laboratories that perform most of the assays in this country: the Kennedy Krieger Institute between 1981 and 1998 and the Mayo Clinic Rochester from 1996 to 1998. The minimum frequency of hemizygotes identified in the United States is estimated to be 1:42,000 and that of hemizygotes plus heterozygotes 1:16,800. Our studies involved 616 pedigrees with a total of 12,787 identified at-risk members. Diagnostic assays were performed in 4,169 at-risk persons (33%) and included members of the extended family. Only 5% of male probands and 1.7% of X-ALD hemizygotes were found to have new mutations. The extended family testing led to the identification of 594 hemizygotes and 1,270 heterozygotes. Two hundred fifty of the newly identified hemizygotes were asymptomatic and represent the group in which therapy has the greatest chance of success. Identification of heterozygotes provides the opportunity for disease prevention through genetic counseling. Diagnostic tests should be offered to all at-risk relatives of X-ALD patients and should include members of the extended family.

Neurological and neuropathologic heterogeneity in two brothers with cobalamin C deficiency

Two adult brothers, one documented to have methylmalonic acidemia with homocystinuria, or cobalamin C deficiency, after autopsy, displayed severe but divergent neurological presentations. One exhibited a myelopathy and the other chronic endocrine problems (Schmidt's syndrome) followed by a neuropsychiatric and dementing disorder owing to cerebral perivascular demyelination. The recognition of cobalamin C deficiency has practical implications because it is one of the few inherited diseases of central white matter that is treatable.

Determination of 30 X-linked adrenoleukodystrophy mutations, including 15 not previously described

X-linked Adrenoleukodystrophy (X-ALD) is the most frequent peroxisomal disease. It mainly involves the nervous system white matter, adrenal cortex and testes. Several distinct clinical phenotypes are known. The principal biochemical abnormality is the accumulation of saturated very-long-chain fatty acids (VLCFAs : > C22:0, mainly C26:0), which is due to impaired capacity for beta-oxidation in peroxisomes. Diagnosis is usually based on the VLCFA levels in plasma or cultured skin fibroblasts in both patients and carriers. In 0.1% of affected males, however, the plasma C26:0 level is borderline normal, and 15% of obligate female carriers have normal results. Effective mutation detection in these families is therefore fundamental to unambiguously determine the genetic status of each individual at risk. Of particular concern are female members of kindreds segregating X-ALD mutations, because normal VLCFA levels do not guarantee lack of carrier status. We describe a fast method for detection of X-ALD mutations. The method is based on SSCP analysis of nested PCR fragments followed by sequence-determination reactions. Using this methodology we have found X-ALD mutations in 30 kindreds, including 15 not previously reported.

Peroxisomal ghosts are intracellular structures distinct from lysosomal compartments in Zellweger syndrome: a confocal laser scanning microscopy study

Peroxisome ghosts are aberrant peroxisomal structures found in cultured skin fibroblasts from patients affected by Zellweger Syndrome (ZS), a genetic disorder of peroxisomal assembly. They contain peroxisomal integral membrane proteins (PxIMPs) and they lack most of the matrix enzymes that should be inside the organelle (Santos et al., Science 239 (1988) 1536-1538). Considerable evidence indicates that these ghosts result from genetic defects in the cellular machinery for importing newly-synthesized peroxisomal proteins into the organelle. In contrast to these observations, (Heikoop et al., Eur. J. Cell Biol. 57 (1992) 165-171) report that in Zellweger Syndrome, peroxisomal membranes are located within lysosomes and/or contain lysosomal enzymes. We have undertaken a more detailed and systematic investigation of this matter, employing confocal laser scanning microscopy (CLSM). In fibroblasts derived from ZS patients belonging to different complementation groups, peroxisomes were labeled with antibodies against PxIMPs and lysosomes were labeled with an antibody against a lysosome associated membrane protein (LAMP-2) or with LysoTracker. The results unambiguously demonstrated no appreciable colocalization of PxIMPs and LAMPs (or LysoTracker), indicating that peroxisomal ghosts are distinct subcellular structures, occupying separate subcellular locations.

Pharmacological induction of peroxisomes in peroxisome biogenesis disorders

Inherited aberrant peroxisome assembly results in a group of neurological diseases termed peroxisome biogenesis disorders (PBDs). PBDs include three major clinical phenotypes that represent a continuum of clinical features from the most severe form, Zellweger syndrome (ZS), through neonatal adrenoleukodystrophy (NALD) to the least severe form, infantile Refsum's disease (IRD). Somatic cell complementation studies have identified 13 PBD complementation groups, each representing a defect in a peroxisomal protein (peroxin) involved in peroxisome biogenesis. Most complementation groups include a range of clinical phenotypes. In this study, peroxisome numbers were determined in fibroblasts from 29 PBD (ZS, NALD, and IRD) patients, with various phenotypes from nine complementation groups, using antibodies against either a peroxisomal membrane protein (anti-Pex14p) or peroxisomal matrix proteins (anti-SKL). A correlation between the number of peroxisomes, determined with either antibody, and PBD phenotype was found, suggesting that induction of peroxisome number might have a favorable effect on PBD. After treatment of PBD fibroblasts with sodium 4-phenylbutyrate, a human peroxisome proliferator, there was an approximate twofold increase in peroxisome number. After 4-phenylbutyrate treatment, an increase in transcription of the adrenoleukodystrophy-related gene and the peroxin gene, PEX11alpha, was found in PBD fibroblasts. In NALD and IRD, but not ZS, fibroblasts there was an increase in very-long-chain fatty acid beta-oxidation and plasmalogen concentrations, and a decrease in very-long-chain fatty acid concentrations. These data suggest that pharmacological agents that induce peroxisome proliferation, such as 4-phenylbutyrate, may have therapeutic potential in the treatment of PBD patients with milder phenotypes (NALD and IRD).

Adrenomyeloneuropathy: a neuropathologic review featuring its noninflammatory myelopathy

The neuropathologic features of adrenomyeloneuropathy (AMN) are reviewed by supplementing those few previously published cases with 5 additional cases collected over the years. The endocrine involvement in AMN is briefly presented to serve as a pathogenetic backdrop and to emphasize that most of the lesions in AMN, as in adreno-leukodystrophy (ALD), are noninflammatory in the traditional sense of the word. The myeloneuropathy is emphasized, but the dysmyelinative/inflammatory demyelinative lesions also are presented. The preponderance of available data indicates that the myeloneuropathy of AMN is a central-peripheral distal (dying-back) axonopathy, as was originally proposed. The severity of the myeloneuropathy does not appear to correlate with the duration or severity of endocrine dysfunction. Microglia are the dominant participating cells in the noninflammatory myelopathy. Abnormalities in the ALD gene, which encodes a peroxisomal ABC half-transporter, do not correlate with clinical phenotypes. The relationship of the gene product, ALDP, to the peroxisomal very long chain fatty acid (VLCFA) synthetase, the activity of which is deficient in ALD/AMN, is unclear. An ALD-knockout mouse model has developed axonal degeneration, particularly in spinal cord, and is therefore more reminiscent of AMN than ALD. We continue to postulate that the fundamental defect in the myeloneuropathy of AMN is an axonal or neuronal membrane abnormality perhaps due to the incorporation of VLCFA-gangliosides, which perturbs the membrane's microenvironment and leads to dysfunction and atrophy.

Cerebellar atrophy in chronic rhizomelic chondrodysplasia punctata: a potential role for phytanic acid and calcium in the death of its Purkinje cells

Cerebellar atrophy, consequent to the postdevelopmental degeneration and loss of Purkinje cells and granular neurons, has been identified in three patients with rhizomelic chondrodysplasia punctata (RCDP). Cerebellar atrophy in our two chronic patients was symmetrical, but the vermis and medial portions of both hemispheres, particularly the dorsal lobules, displayed more severe atrophy than the lateral hemispheres. The distal tips of folia showed the greatest neuronal loss. Residual Purkinje cells showed progressive degenerative changes that appeared to be due, in part, to their topography. The precise mode of death of Purkinje cells in RCDP has not been established, but it does not appear to be mediated by entrance into the cell cycle or by ubiquitination; however, alterations in intracellular calcium levels and mitochondria may be involved. Elevated serum/CSF phytanic acid, decreased levels of tissue plasmalogens and increased chronological age are believed to play synergistic pathogenetic roles in this lesion.

Metabolic control of peroxisome abundance

Zellweger syndrome and related disorders represent a group of lethal, genetically heterogeneous diseases. These peroxisome biogenesis disorders (PBDs) are characterized by defective peroxisomal matrix protein import and comprise at least 10 complementation groups. The genes defective in seven of these groups and more than 90% of PBD patients are now known. Here we examine the distribution of peroxisomal membrane proteins in fibroblasts from PBD patients representing the seven complementation groups for which the mutant gene is known. Peroxisomes were detected in all PBD cells, indicating that the ability to form a minimal peroxisomal structure is not blocked in these mutants. We also observed that peroxisome abundance was reduced fivefold in PBD cells that are defective in the PEX1, PEX5, PEX12, PEX6, PEX10, and PEX2 genes. These cell lines all display a defect in the import of proteins with the type-1 peroxisomal targeting signal (PTS1). In contrast, peroxisome abundance was unaffected in cells that are mutated in PEX7 and are defective only in the import of proteins with the type-2 peroxisomal targeting signal. Interestingly, a fivefold reduction in peroxisome abundance was also observed for cells lacking either of two PTS1-targeted peroxisomal beta-oxidation enzymes, acyl-CoA oxidase and 2-enoyl-CoA hydratase/D-3-hydroxyacyl-CoA dehydrogenase. These results indicate that reduced peroxisome abundance in PBD cells may be caused by their inability to import these PTS1-containing enzymes. Furthermore, the fact that peroxisome abundance is influenced by peroxisomal 105-oxidation activities suggests that there may be metabolic control of peroxisome abundance.

Prenatal diagnosis of rhizomelic chondrodysplasia punctata due to isolated alkyldihydroacetonephosphate acyltransferase synthase deficiency

Current practices in prenatal diagnosis of rhizomelic chondrodysplasia punctata (RCDP) are reviewed. A case is presented with a family having one daughter affected with RCDP due to alkyldihydroacetonephosphate acyltransferase synthase (DHAPAT synthase) deficiency, and three subsequent pregnancies. Biochemical test values are presented for the pregnancies and daughter. Post-mortem tests of one fetus of a terminated pregnancy showed that radiologic examination could not make the diagnosis of RCDP. We conclude that biochemical or molecular testing is necessary to accurately diagnose this type of RCDP prenatally.

Peroxisomal very long chain fatty acid beta-oxidation activity is determined by the level of adrenodeukodystrophy protein (ALDP) expression

Impaired peroxisomal beta-oxidation of saturated very long chain fatty acids (VLCFA, >/=C22:0) results in increased VLCFA levels in the tissues and body fluids of patients with disorders of peroxisomal biogenesis (i.e., Zellweger syndrome and neonatal adrenoleukodystrophy) and single peroxisomal protein defects (i.e., X-linked adrenoleukodystrophy (X-ALD) and acyl-CoA oxidase deficiency). We show that SV40T transformation also results in impaired peroxisomal beta-oxidation and VLCFA accumulation despite the presence of abundant peroxisomes. To explore the mechanism responsible for this observation, we have examined expression of key components of peroxisomal VLCFA beta-oxidation. We found that expression of both acyl-CoA oxidase, the rate limiting enzyme of peroxisomal VLCFA beta-oxidation and the adrenoleukodystrophy protein (ALDP), the defective gene product in X-ALD, are reduced after SV40T transformation. Surprisingly, ALDP overexpression by itself restores peroxisomal VLCFA beta-oxidation in SV40T-transformed control and X-ALD cells. These results demonstrate that ALDP is a fundamental component in VLCFA peroxisomal beta-oxidation and may serve as a "gatekeeper" for VLCFA homeostasis.

Plasma and red blood cell fatty acids in peroxisomal disorders

The demonstration of abnormal levels of fatty acids or plasmalogens in plasma or red blood cells is key to the diagnosis of peroxisomal disorders. We report the levels of 62 fatty acids and plasmalogens in patients with X-linked adrenoleukodystrophy (X-ALD), Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD), both at baseline and after dietary interventions. "Lorenzo's Oil" therapy in X-ALD normalizes the levels of saturated very long chain fatty acids in plasma, but leads to reduced levels of omega 6 and other omega 3 fatty acids, and requires monitoring and appropriate dietary supplements. Patients with ZS, NALD and IRD have reduced levels of docosahexaenoic acid (DHA) and arachidonic acid (AA) which can be normalized by the oral administration of microencapsulated DHA and AA.

Plasma very long chain fatty acids in 3,000 peroxisome disease patients and 29,000 controls

The assay of plasma very long chain fatty acids (VLCFAs), developed in our laboratory in 1981, has become the most widely used procedure for the diagnosis of X-linked adrenoleukodystrophy (X-ALD) and other peroxisomal disorders. We present here our 17 years' experience with this assay. Three VLCFA parameters, the level of hexacosanoic acid (C26:0), the ratio of C26:0 to tetracosanoic acid (C24:0), and of C26:0 to docosanoic acid (C22:0), were measured in 1,097 males (hemizygotes) with X-ALD, 1,282 women heterozygous for this disorder, including 379 obligate heterozygotes, 797 patients with other peroxisomal disorders, and 29,600 control subjects. All X-ALD hemizygotes who had not previously received Lorenzo's oil or a diet with a high erucic acid content had increased VLCFA levels, but the application of a discriminant function based on all three measurements is required to avoid the serious consequences of a false-negative result. VLCFA levels are increased at day of birth, thus providing the potential for neonatal mass screening, are identical in the childhood and adult forms, and do not change with age. Eighty-five percent of obligate heterozygotes had abnormally high VLCFA levels, but a normal result does not exclude carrier status. VLCFA levels were increased in all patients homozygous for Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, and in patients with deficiencies of peroxisomal acyl-coenzyme A oxidase, bifunctional enzyme, and 3-oxoacyl-coenzyme A thiolase. In these patients the degree of VLCFA excess correlated with clinical severity.

Developmental delay and growth failure caused by a peroxisomal disorder, dihydroxyacetonephosphate acyltransferase (DHAP-AT) deficiency

We describe a 6 1/2-year-old-girl presenting with a unique phenotype and dihydroxyacetonephosphate acyltransferase (DHAP-AT) deficiency (1.6% of control activity in cultured fibroblasts), a peroxisomal enzyme deficiency which was reported previously to cause rhizomelic chondroplasia punctata (RCDP). Her phenotype is less severe than that seen in classical RCDP, and is notable for short stature, microcataracts, normal limbs, mild hypotonia, and severe mental retardation. Epiphyseal stippling is present. This patient illustrates the variability of peroxisomal disorders whereby a specific defect in peroxisomal plasmalogen synthesis may lead to several phenotypes. Her case also suggests that children presenting with deficient growth, developmental delay, and epiphyseal stippling should be screened carefully for peroxisomal disorders, with measurement of plasmalogens in addition to very long chain fatty acids.

Gene redundancy and pharmacological gene therapy: implications for X-linked adrenoleukodystrophy

As more functional redundancy in mammalian cells is discovered, enhanced expression of genes involved in alternative pathways may become an effective form of gene therapy. X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with impaired very-long-chain fatty acid metabolism. The X-ALD gene encodes a peroxisomal membrane protein (ALDP) that is part of a small family of related peroxisomal membrane proteins. We show that 4-phenylbutyrate treatment of cells from both X-ALD patients and X-ALD knockout mice results in decreased levels of and increased beta-oxidation of very-long-chain fatty acids; increased expression of the peroxisomal protein ALDRP; and induction of peroxisome proliferation. We also demonstrate that ALDP and ALDRP are functionally related, by ALDRP cDNA complementation of X-ALD fibroblasts. Finally, we demonstrate the in vivo efficacy of dietary 4-phenylbutyrate treatment through its production of a substantial reduction of very-long-chain fatty acid levels in the brain and adrenal glands of X-ALD mice.

Adrenoleukodystrophy: increased plasma content of saturated very long chain fatty acids. 1981

With a new method we measured the saturated very long chain fatty acids in the plasma of adrenoleukodystrophy (ALD) hemizygotes, ALD heterozygotes, and controls. ALD hemizygotes showed increased levels of hexacosanoate (C26 fatty acid) which represented 0.081 ± 0.0066% (SEM) of total fatty acids, compared to 0.015 ± 0.0032% in the controls. C25, C24, and C23 fatty acids were also increased, but the C22 and C20 fatty acids were normal. C26 levels were also increased in most ALD heterozygotes, with a mean level 0.057± 0.0063% of total fatty acids. The technique can be used for diagnosis and carrier identification, and in the evaluation of therapy.

Peroxisomal disease cell lines with cellular plasmalogen deficiency have impaired muscarinic cholinergic signal transduction activity and amyloid precursor protein secretion

We tested whether alterations in membrane lipid composition associated with peroxisomal diseases affect muscarinic cholinergic signal transduction activity and amyloid precursor protein (APP) secretion in cultured human skin fibroblasts and Chinese hamster ovary (CHO) mutants. We found that in cell lines from patients with peroxisomal disorders where plasmalogen levels were low, the low-Km GTPase activity was not induced by carbachol, and APP secretion was reduced. This effect on signal transduction activity was not associated with decreased levels of the M1-muscarinic cholinergic receptor or its associated heterotrimeric G-protein. Specifically, this decrease was associated with a plasmalogen deficiency since a CHO cell line with only a deficit in plasmalogens was as severely affected as were generalized peroxisomal disorder cell lines. Thus, plasmalogens appear to be implicated in muscarinic cholinergic signal transduction and secretion of APP. These results provide new insights about the pathophysiology of peroxisomal diseases and may be relevant to Alzheimer's disease where reduced plasmalogen levels have been reported.

Suppression of peroxisomal membrane protein defects by peroxisomal ATP binding cassette (ABC) proteins

X-Linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disorder characterized by reduced peroxisomal very long chain fatty acid (VLCFA) beta-oxidation. The X - ALD gene product (ALDP) is a peroxisomal transmembrane protein with an ATP binding cassette (ABC). ALDP and three other ABC proteins (PMP70, ALDR, P70R) localize to the peroxisomal membrane. The function of this family of peroxisomal membrane proteins is unknown. We used complementation studies to begin analysis of their role in VLCFA beta-oxidation and on the peroxisomal membrane. Expression of either ALDP or PMP70 restores VLCFA beta-oxidation in X-ALD fibroblasts, indicating overlapping functions. Their expression also restores peroxisome biogenesis in cells that are deficient in the peroxisomal membrane protein Pex2p. Thus it is likely that complex protein interactions are involved in the function and biogenesis of peroxisomal membranes that may contribute to disease heterogeneity.

A mouse model for X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with impaired beta-oxidation of very long chain fatty acids (VLCFAs) and reduced function of peroxisomal very long chain fatty acyl-CoA synthetase (VLCS) that leads to severe and progressive neurological disability. The X-ALD gene, identified by positional cloning, encodes a peroxisomal membrane protein (adrenoleukodystrophy protein; ALDP) that belongs to the ATP binding cassette transporter protein superfamily. Mutational analyses and functional studies of the X-ALD gene confirm that it and not VLCS is the gene responsible for X-ALD. Its role in the beta-oxidation of VLCFAs and its effect on the function of VLCS are unclear. The complex pathology of X-ALD and the extreme variability of its clinical phenotypes are also unexplained. To facilitate understanding of X-ALD pathophysiology, we developed an X-ALD mouse model by gene targeting. The X-ALD mouse exhibits reduced beta-oxidation of VLCFAs, resulting in significantly elevated levels of saturated VLCFAs in total lipids from all tissues measured and in cholesterol esters from adrenal glands. Lipid cleft inclusions were observed in adrenocortical cells of X-ALD mice under the electron microscope. No neurological involvement has been detected in X-ALD mice up to 6 months. We conclude that X-ALD mice exhibit biochemical defects equivalent to those found in human X-ALD and thus provide an experimental system for testing therapeutic intervention.

Urinary bile acids and peroxisomal bifunctional enzyme deficiency

The biosynthesis of normal bile acids involves beta-oxidation of the 8-carbon side-chain of cholesterol, in addition to numerous modifications of the sterol nucleus. Because beta-oxidation of the sterol side-chain has been localized to the peroxisome, bile acid analysis has been suggested to be useful in the diagnostic evaluation of individuals suspected of having peroxisomal disorders. Although data from subjects with generalized peroxisomal disorders support this, few data exist regarding the bile acids in individuals having single peroxisomal beta-oxidation enzyme disorders. In this study, we analyzed the urinary bile acids from 12 patients with peroxisomal bifunctional protein deficiency using continuous flow fast atom bombardment mass spectrometry. All 12 patients had abnormal spectra, although their ion profiles and rank order of intensity of ions varied considerably. Ten of 12 individuals had abnormal spectra with presence of taurine-conjugated tetrahydroxycholestenoates, allowing a definite diagnosis of a peroxisomal beta-oxidation defect and a presumptive diagnosis of bifunctional protein deficiency; the other two cases were nondiagnostically abnormal. The strengths and limitations of urinary bile acid analysis for the diagnosis of peroxisomal beta-oxidation disorders are discussed.

Very long-chain fatty acids in diagnosis, pathogenesis, and therapy of peroxisomal disorders

Abnormally high levels of very long-chain fatty acids (VLCFA) are a feature in nine of the fifteen peroxisomal disorders that have been identified so far. Saturated VLCFA accumulate in X-linked adrenoleukodystrophy, appear to disrupt membrane structure, and may play a role in the pathogenesis of a brain inflammatory response. Dietary therapy initiated when patients are still asymptomatic may be of clinical benefit.

Neuronal migration abnormality in peroxisomal bifunctional enzyme defect

Patterns of brain dysgenesis that resemble those in the Zellweger syndrome were demonstrated in a boy with an isolated defect of the peroxisomal bifunctional enzyme. There was bilateral centrosylvian pachygyria and polymicrogyria, diffuse hemispheric hypomyelination with heterotopic neurons, Purkinje cell heterotopias, and simplified convolutions of the dentate nucleus and inferior olive. This association of Zellweger syndrome-like brain dysgenesis with a defect of a single peroxisomal enzyme provides new opportunities for the study of pathogenetic mechanisms in peroxisomal disorders.

Neurodegenerative course in ceramidase deficiency (Farber disease) correlates with the residual lysosomal ceramide turnover in cultured living patient cells

Farber's lipogranulomatosis is an inborn lipid storage disease characterized by tissue accumulation of ceramide due to deficient activity of lysosomal ceramidase. Symptoms include painful swelling of joints, subcutaneous nodules, a hoarse cry, hepatosplenomegaly and nervous system dysfunction of markedly variable degree. In most cases the neural dysfunction rather than the general dystrophy, seems to limit the duration of Farber disease. We examined whether the severity can be shown as a function of ceramide turnover by lysosomal ceramidase. The lysosomal degradation of sphingomyelin-derived ceramide was studied in situ in patient skin fibroblasts and lymphoid cells loaded with LDL-associated radioactive sphingomyelin. We could show for the first time a significant correlation between the ceramide accumulated in situ and the severity of Farber disease. Our method provides an alternative means for determining ceramide degradation by lysosomal ceramidase, but in intact cells. The relatively simple method is at least of the same diagnostic use for Farber disease as the in vitro assay of acid ceramidase using cell homogenates and may also have some prognostic use.

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.

Altered expression of ALDP in X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a neurodegenerative disorder with variable phenotypic expression that is characterized by elevated plasma and tissue levels of very long-chain fatty acids. However, the product of the gene defective in ALD (ALDP) is a membrane transporter of the ATP-binding cassette family of proteins and is not related to enzymes known to activate or oxidize fatty acids. We generated an antibody that specifically recognizes the C-terminal 18 amino acids of ALDP and can detect ALDP by indirect immunofluorescence. To better understand the mechanism by which mutations in ALDP lead to disease, we used this antibody to examine the subcellular distribution and relative abundance of ALDP in skin fibroblasts from normal individuals and ALD patients. Punctate immunoreactive material typical of fibroblast peroxisomes was observed in cells from seven normal controls and eight non-ALD patients. Of 35 ALD patients tested, 17 had the childhood-onset cerebral form of the disease, 13 had the milder adult phenotype adrenomyeloneuropathy, 3 had adrenal insufficiency only, and 2 were affected fetuses. More than two-thirds (69%) of all patients studied showed no punctate immunoreactive material. There was no correlation between the immunofluorescence pattern and clinical phenotype. We determined the mutation in the ALD gene in 15 of these patients. Patients with either a deletion or frameshift mutation lacked ALDP immunoreactivity, as expected. Four of 11 patients with missense mutations were also immunonegative, indicating that these mutations affected the stability or localization of ALDP. In the seven immunopositive patients with missense mutations, correlation of the location and nature of the amino acid substitution may provide new insights into the function of this peroxisomal membrane protein. Furthermore, the study of female relatives of immunonegative ALD probands may aid in the assessment of heterozygote status.

Phenotype of patients with peroxisomal disorders subdivided into sixteen complementation groups

OBJECTIVE

To use the technique of complementation analysis to help define genotype and classify patients with clinical manifestations consistent with those of the disorders of peroxisome assembly, namely the Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP).

STUDY DESIGN

Clinical findings, peroxisomal function, and complementation groups were examined in 173 patients with the clinical manifestations of these disorders.

RESULTS

In 37 patients (21%), peroxisome assembly was intact and isolated deficiencies of one of five peroxisomal enzymes involved in the beta-oxidation of fatty acids or plasmalogen biosynthesis were demonstrated. Ten complementation groups were identified among 93 patients (54%) with impaired peroxisome assembly and one of three phenotypes (ZS, NALD, or IRD) without correlation between complementation group and phenotype. Forty-three patients (25%) had impaired peroxisome assembly associated with the RCDP phenotype and belonged to a single complementation group. Of the 173 patients, 10 had unusually mild clinical manifestations, including survival to the fifth decade or deficits limited to congenital cataracts.

CONCLUSIONS

At least 16 complementation groups, and hence genotypes, are associated with clinical manifestations of disorders of peroxisome assembly. The range of phenotype is wide, and some patients have mild involvement.

Identification of three distinct peroxisomal protein import defects in patients with peroxisome biogenesis disorders

Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, and classical rhizomelic chondrodysplasia punctata are lethal genetic disorders caused by defects in peroxisome biogenesis. We report here a characterization of the peroxisomal matrix protein import capabilities of fibroblasts from 62 of these peroxisome biogenesis disorder patients representing all ten known complementation groups. Using an immunofluorescence microscopy assay, we identified three distinct peroxisomal protein import defects among these patients. Type-1 cells have a specific inability to import proteins containing the PTS1 peroxisomal targeting signal, type-2 cells have a specific defect in import of proteins containing the PTS2 signal, and type-3 cells exhibit a loss of, or reduction in, the import of both PTS1 and PTS2 proteins. Considering that the common cellular phenotype of Zellweger syndrome, neonatal adrenoleukodystrophy and infantile Refsum's disease has been proposed to be a complete defect in peroxisomal matrix protein import, the observation that 85% (40/47) of the type-3 cell lines imported a low but detectable amount of both PTS1 and PTS2 proteins was surprising. Furthermore, different cell lines with the type-3 defect exhibited a broad spectrum of different phenotypes; some showed a complete absence of matrix protein import while others contained 50–100 matrix protein-containing peroxisomes per cell. We also noted certain relationships between the import phenotypes and clinical diagnoses: both type-1 cell lines were from neonatal adrenoleukodystrophy patients, all 13 type-2 cell lines were from classical rhizomelic chondrodysplasia punctata patients, and the type-3 import defect was found in the vast majority of Zellweger syndrome (22/22), neonatal adrenoleukodytrophy (17/19), and infantile Refsum's disease (7/7) patients. Our finding that all type-1 cell lines were from the second complementation group (CG2), all 13 type-2 cell lines were from CG11, and that cells from the eight remaining complementation groups only exhibit the type-3 defect indicates that mutations in particular genes give rise to the different types of peroxisomal protein import defects. This hypothesis is further supported by correlations between certain complementation groups and particular type-3 subphenotypes: all patient cell lines belonging to CG3 and CG10 showed a complete absence of peroxisomal matrix protein import while those from CG6, CG7, and CG8 imported some peroxisomal matrix proteins. However, the fact that cell lines from within particular complementation groups (CG1, CG4) could have different matrix protein import characteristics suggests that allelic heterogeneity also plays an important role in generating different import phenotypes in certain patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Sulfatide and sphingomyelin loading of living cells as tools for the study of ceramide turnover by lysosomal ceramidase--implications for the diagnosis of Farber disease

The ceramide turnover by lysosomal ceramidase in intact, living cells was investigated by loading radiolabeled sulfatide or sphingomyelin in situ on skin fibroblasts and lymphoid cells. The cells originated from normal individuals and from patients with acid ceramidase deficiency (Farber disease). While fibroblasts from individuals with Farber disease exhibited some impairment in the degradation of the ceramide produced by sulfatide hydrolysis, lymphoid cells from individuals with Farber disease metabolized the ceramide as readily as did normal cells, suggesting the existence in lymphoid cells of a non-lysosomal degradation pathway for the sulfatide-derived ceramide. In contrast, sphingomyelin loading in the presence of serum showed a considerably decreased turnover of ceramide in both fibroblasts and lymphoid cells from individuals with Farber disease. Further methodologic variation led to the use of LDL-associated radioactive sphingomyelin; LDL-association promoted the targeting of exogenous sphingomyelin to lysosomes. As a result, an almost complete deficiency of ceramide degradation was found in cells from severely affected patients with Farber disease. Our data with this novel method show that sphingomyelin loading of intact living cells is a simple, alternative means for determining ceramide degradation by lysosomal ceramidase and for diagnosing Farber disease.

Brain, liver, and adipose tissue erucic and very long chain fatty acid levels in adrenoleukodystrophy patients treated with glyceryl trierucate and trioleate oils (Lorenzo's oil)

Brain, liver, and adipose lipids were studied in the postmortem tissues of four adrenoleukodystrophy patients who had been treated with a mixture of glyceryl trioleate and trierucate oils ("Lorenzo's Oil") and compared to 7 untreated ALD patients and 3 controls. The dietary therapy appeared to reduce the levels of saturated very long chain fatty acids in the plasma, adipose tissue and liver; in the brain they were reduced in only one of the four patients. While substantial amounts of erucic acid were present in some of the tissues even 12 months after therapy had been discontinued, the levels in brain did not exceed those in controls at any time. The failure of erucic acid to enter the brain in significant quantity may be a factor in the disappointing results of dietary therapy for adrenoleukodystrophy.

Solvent vapor abuse leukoencephalopathy. Comparison to adrenoleukodystrophy

Chronic organic solvent vapor inhalation can cause permanent damage to the central nervous system. Clinical features and radiologic abnormalities are well known, but pathology has not been definitely established. This study describes the gross, microscopic and ultrastructural changes and fatty acid composition of cholesterol esters in the brain of two chronic paint sniffers as well as the electron microscopic findings from a third, all with permanent neurological impairment. The abnormalities which were the same in all cases consisted of a demyelinating process which grossly manifested itself as brain atrophy and subtle discoloration of the cerebral and cerebellar white matter. Periodic acid-Schiff-positive macrophages in the absence of foamy macrophages were the histological hallmark of this process. Electron microscopy revealed oval membrane-bound cytoplasmic bodies filled with bundles of trilaminar inclusions composed of 3 nm paired dense leaflets separated by a space 3-7 nm wide in macrophages. Biochemical analysis showed an increase of very long chain fatty acids in the white matter cholesterol esters. This study defines the morphologic substrate of solvent vapor abuse leukoencephalopathy. The novel ultrastructural observations in conjunction with biochemical findings provide a link with adrenoleukodystrophy and raise the possibility of similar mechanisms of myelin degradation in both.

Cytosolic compartmentalization of hepatic alanine:glyoxylate aminotransferase in patients with aberrant peroxisomal biogenesis and its effect on oxalate metabolism

Two patients with atypical manifestations of aberrant peroxisomal biogenesis are described. Contrary to previous studies, which had shown that Zellweger syndrome patients usually have normal levels of urinary oxalate excretion, the patients in the present study had evidence of abnormal oxalate metabolism in the form of hyperoxaluria and, in one of the patients, calcium oxalate urolithiasis. Activity of the liver-specific peroxisomal enzyme alanine:-glyoxylate aminotransferase (AGT), which is a major determinant of the level of endogenous oxalate synthesis in humans, was normal in one patient and markedly supranormal in the other. Using the technique of post-embedding protein A-colloidal gold immunoelectron microscopy, AGT was found to be mainly cytosolic in the livers of both patients, with significant amounts also localized in the nuclei. In a small minority of the hepatocytes of one patient, who was homozygous for the more common (major) AGT allele, large numbers of unidentified fibrillar arrays were found in the cytosol, which labelled heavily for immunoreactive AGT. The background cytosolic AGT labelling was markedly reduced in such cells when compared to the majority of cells that did not contain fibrils. In the other patient, who was heterozygous for the major and minor AGT alleles, there appeared to be low levels of mitochondrial AGT labelling. In the light of these data, the possible metabolic function of cytosolic AGT in the livers of panperoxisomal disease patients is discussed.

Neonatal adrenoleukodystrophy presenting as infantile progressive spinal muscular atrophy

Two siblings with neonatal adrenoleukodystrophy are described. The signs and laboratory data documenting infantile progressive spinal muscular atrophy included the initial presentation of 1 sibling with neonatal adrenoleukodystrophy. These patients indicate that neonatal adrenoleukodystrophy should be considered in the differential diagnosis of infantile progressive spinal muscular atrophy.

Fatty alcohol accumulation in the autosomal recessive form of rhizomelic chondrodysplasia punctata

Patients with the autosomal recessive form of rhizomelic chondrodysplasia punctata (AR-RCDP) and other generalized peroxisomal disorders are deficient in the incorporation of fatty alcohol into plasmalogen lipids. To determine whether these patients accumulated fatty alcohol, we measured their plasma fatty alcohol concentrations. Plasma octadecanol levels were elevated in six patients with AR-RCDP but tended to be normal in other generalized peroxisomal disorders such as neonatal adrenoleukodystrophy and Zellweger syndrome. Cultured skin fibroblasts from AR-RCDP patients accumulated six-fold more hexadecanol than normal when cells were incubated in the presence of palmitate but had normal hexadecanol content when palmitate was not present in the culture medium. These cells were profoundly deficient in the incorporation of hexadecanol into ether lipids but oxidized hexadecanol to fatty acid normally. AR-RCDP fibroblasts also showed a two- to seven-fold increase in the rate of hexadecanol synthesis, which was associated with an increase in the activity of acyl-CoA reductase. We conclude that patients with AR-RCDP accumulate fatty alcohol due to its impaired incorporation into ether lipids and a greatly increased rate of fatty alcohol synthesis.

Analysis of peroxisomes in lymphoblasts: Zellweger syndrome and a patient with a deletion in chromosome 7

Lymphoblasts are useful cells for the diagnosis and basic studies of several human genetic disorders. Peroxisomal disorders are usually diagnosed by using fibroblasts or blood samples. Here, we report the characterization of peroxisomes in lymphoblasts. We demonstrated that lymphoblasts from a patient with Zellweger syndrome, the prototypical disorder of peroxisome biogenesis, contained peroxisomal ghosts like those described previously in Zellweger fibroblasts. We also found that lymphoblasts that carry a deletion on chromosome 7 (q11.23q22.1), a region thought to contain one Zellweger syndrome gene, contained normal peroxisomes.

Increased very long chain fatty acids in patients on a ketogenic diet: a cause of diagnostic confusion

We found an elevation of very long chain fatty acids in 13 of 22 plasma samples from patients on a ketogenic diet for the treatment of uncontrolled seizures. Because elevated values of very long chain fatty acids are a biochemical manifestation of peroxisomal dysfunction, this phenomenon might lead to diagnostic confusion. Thus the history and clinical status should be considered when plasma levels of very long chain fatty acids are interpreted.

Complementation analysis of patients with intact peroxisomes and impaired peroxisomal beta-oxidation

Complementation analysis, using peroxisomal beta-oxidation of very long chain fatty acids (VLCFA) as the criterion for complementation, is useful in the study of patients who are suspected of having a single enzyme defect in the peroxisomal beta-oxidation pathway. Laboratory findings for these patients include elevated plasma VLCFA and impaired VLCFA oxidation in fibroblasts. Some of these patients have slightly abnormal phytanic acid oxidation in fibroblasts. In addition, elevated levels of bile acid intermediates have been reported in some cases. Plasmalogen synthesis, pipecolic acid levels, and subcellular distribution of catalase are normal. Using complementation analysis, we show that six patients, who were suspected of having a single enzyme defect in the peroxisomal beta-oxidation pathway, are deficient in peroxisomal bifunctional enzyme [enoyl-CoA hydratase (EC 4.2.1.17)/3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35)] activity. This group of six patients, deficient in bifunctional enzyme activity, may be subdivided into two complementation groups. It would appear that patients in each of these two groups are deficient in only one of the bifunctional enzyme activities.

The Inflammatory Myelinopathy of Adreno-Leukodystrophy

Prominent inflammation in the demyelinative lesion of adreno-leukodystrophy (ALD) has suggested an immune-mediated pathogenetic component. Commercially available antibodies to T cells, B cells, macrophages, class I and II molecules, complement, IgG, IgM, IgA, interleukin-1 (IL-1), intercellular adhesion molecule-1 (ICAM-1) and tumor necrosis factor-alpha (TNF) were applied to paraffin sections of formaldehyde-fixed postmortem samples. Twenty-five primary demyelinative lesions from five juvenile ALD, three adult ALD, and three adrenomyeloneuropathic patients were evaluated with appropriate positive and negative controls. Macrophages and astrocytes were the predominant cells detected at the active edge; T lymphocytes, including T4 and CD45R subsets, were nearly as numerous but usually located around vessels within the lesion. B cells and plasma cells, usually containing IgG, were uncommon. The expression of class II molecules, restricted to one adult, was problematic; class I expression was increased in microvascular and other cells. Degraded myelin was labeled with antibodies to C3d and IL-1; IL-1 and ICAM-1 immunoreactivity was seen on microvessels and astrocytes. Tumor necrosis factor-alpha immunoreactivity was detected in macrophages, but more prominently in astrocytes. These data support a natural immune response in the demyelinative lesion of ALD, consisting predominantly of reactive astrocytes, macrophages, T cells and cytokines. A two-stage pathogenetic theory is discussed. The postulated roles of TNF and reactive astrocytes, in concert with a fundamental myelinolytic biochemical defect, suggest a different pathogenetic mechanism and raise novel therapeutic possibilities.

Phospholipids in X-linked adrenoleukodystrophy white matter: fatty acid abnormalities before the onset of demyelination

Changes in fatty acid composition of complex lipids were analyzed in postmortem white matter from a patient with late onset adrenoleukodystrophy (ALD). The specimen showed three regions with progressive myelin breakdown: morphologically normal white matter; areas with active demyelination and perivascular lymphocyte and macrophage infiltration; and areas with marked gliosis. In the morphologically intact region, cholesterol esters were similar in amount and fatty acid composition to those in control tissue, although marked changes were observed in the actively demyelinating area. Galactolipids in these areas were also similar to those in controls. In contrast, glycerophospholipids were increased in amount and in very long chain fatty acids (VLCFA), which are the hallmark of ALD, at the active edge of the demyelinative lesion and even in the apparently intact sample. Further fractionation of the glycerophospholipids by high performance liquid chromatography showed a significant (up to 39-fold) accumulation of hexacosanoic acid (C26:0) in phosphatidylcholine, but not in other phosphatidyl derivatives. The consistent increases in phosphatidylcholine VLCFA in all samples from the ALD brain, which are postulated to represent progressive stages in the development of the disorder, suggest that phosphatidylcholine may be involved in antigen formation and may underlie an immunological basis for the pathogenesis of ALD.

Peroxisome assembly mutations in humans: structural heterogeneity in Zellweger syndrome

Empty membrane ghosts of peroxisomes were found in fibroblasts from a patient with Zellweger's syndrome, a genetic disease of humans (Santos et al: Science 239:1536-1538, 1988). Import of soluble matrix proteins into the organelle was defective. We have now studied fibroblasts from seven patients representing five complementation groups of the syndrome (defined by complementation for peroxisome enzyme function). We find that empty peroxisome ghosts are present in all seven cell samples. Three patients, representing three complementation groups, give the same membrane pattern by immunofluorescence: few large ghosts. Three other patients, representing two complementation groups, give a second pattern: many large ghosts. The seventh patient's pattern is distinct. Thus, all seven of these patients exhibit Peroxisome IMport (PIM) mutations. Since membrane assembly occurs in these cells, the results indicate that biogenesis of organelle content and membrane proteins proceed by different mechanisms. Growth and division of the empty peroxisomal membrane must occur, but are modified by the mutations (ghost size and abundance vary). Cell fusion and immunofluorescence analyses of peroxisome size and catalase packaging formally demonstrate genetic complementation groups for peroxisome assembly in Zellweger syndrome.

Adrenoleukodystrophy: phenotypic variability and implications for therapy

X-linked adrenoleukodystrophy (ALD) is a relatively common disorder that shows a great deal of phenotypic variability. Approximately half of the patients have the rapidly progressive childhood cerebral form that is associated with an inflammatory response in brain and leads to total disability or death during the first decade. Twenty five per cent or more of the patients have adrenomyeloneuropathy (AMN), a form that progresses slowly, involves the spinal cord mainly, shows little or no inflammatory response, manifests in adulthood, and is compatible with a near-normal life span. The two forms of the disease occur frequently within the same kindreds and nuclear families. Segregation analysis based on 3862 individuals in 89 kindreds points to the existence of an autosomal modifier locus with a likelihood ratio of 20:1. In addition, we present preliminary results of three types of therapy. Two hundred and four patients have received a dietary regimen that combines the administration of oils containing mono-unsaturated fatty acids (oleic and erucic) with the restricted intake of very long-chain fatty acids. This regimen normalizes the levels of satured very long-chain fatty acids in plasma within 4 weeks. It appears to improve peripheral nerve function in patients with AMN, and a large-scale trial is in progress to determine whether it can prevent the onset of neurological involvement in patients who have the biochemical abnormality of ALD but are neurologically intact. We report early results of bone marrow transplantation in 14 patients. There is encouraging but still preliminary evidence that transplantation can arrest the progression of the disease in patients with mild neurological involvement. There is urgent need to develop methods to combat the rapid progression of the cerebral forms of the disease, which so far has resisted therapeutic intervention, including immunosuppression or the administration of immunoglobulin.