Measurement of very long-chain fatty acids, phytanic and pristanic acid in plasma and cultured fibroblasts by gas chromatography

Two methods are described, both currently used in our laboratory, for the quantitative analysis of very long-chain fatty acids, phytanic acid and pristanic acid in plasma and cultured fibroblasts by gas-liquid chromatography. The first method is based on the procedure developed by Moser and Moser (1991) and the second is based on the method of Onkenhout and colleagues (1989), which is an application of the original method of Lepage and Roy for plasma and fibroblasts. A survey is given of the concentrations of very long-chain fatty acids, pristanic and phytanic acid in plasma and fibroblasts from control subjects and all patients investigated so far in our laboratory.

Assay of plasmalogens and polyunsaturated fatty acids (PUFA) in erythrocytes and fibroblasts

The direct transesterification method of Lepage and Roy is described as used in our laboratory for the analysis of plasmalogens and polyunsaturated fatty acids in erythrocytes and cultured fibroblasts by gas chromatography. An overview is given of the plasmalogen ratios and docosahexaenoic acid concentrations from controls and patients with different peroxisomal disorders investigated in our laboratory.

Beta-oxidation of fatty acids in cultured human skin fibroblasts devoid of the capacity for oxidative phosphorylation

Prolonged treatment of cultured cells with ethidium bromide results in loss of the capacity for oxidative phosphorylation. Because of the tight coupling between mitochondrial beta-oxidation of fatty acids and the activity of the respiratory chain, such cells may be used to study the contribution of mitochondria and peroxisomes to fatty acid beta-oxidation. To investigate this, human skin fibroblasts were cultured in the presence of ethidium bromide for at least 10 cell generations, resulting in a virtually complete absence of oxidative phosphorylation as demonstrated directly in digitonin-permeabilized fibroblasts. The cells showed a lowered ATP/ADP ratio, most likely as the consequence of the inability to generate ATP via oxidative phosphorylation. The loss of the capacity for oxidative phosphorylation was also reflected in an increased cytosolic NADH/NAD+ ratio: the cells showed a highly elevated lactate/pyruvate ratio in the suspending medium when incubated with glucose. The beta-oxidation of octanoic and palmitic acid was dramatically decreased, suggesting that the beta-oxidation of these fatty acids takes place predominantly (> 90%) in mitochondria, at least in the cells studied. In contrast, the rates of pristanic and cerotic acid beta-oxidation were only slightly decreased, suggesting that this is mainly a peroxisomal process. The reduction of beta-oxidation of cerotic and pristanic acid, 27% and 15%, respectively, is most likely due to a lowered ATP level and an increased NADH/NAD(+)-redoxstate in these cells. We conclude that fibroblasts subjected to prolonged treatment with ethidium bromide can be used as a model system to study the substrate specificity and functional characteristics of the peroxisomal beta-oxidation system.

Altered adrenocortical response under the influence of experimentally increased serum very long chain fatty acids in rats

C 26:0/C 22:0 ratio can be experimentally increased in serum of normal rats by oral administration of hexacosanoic acid (C 26:0) or of thioridazine, an inhibitor of peroxisomal beta-oxidation. This causes a decreased corticosterone response as well as decreased mobilization of cholesterol esters in zona fasciculata interna cells following ACTH administration. Zona fasciculata interna cells and their nuclei are enlarged and contain more Feulgen DNA in thioridazine-fed rats. The similarity of adrenocortical response to inhibition of peroxisomal beta-oxidation and to C 26:0 administration points to raised VLCFA as the common factor which is also operative in many peroxisomal diseases accompanied by adrenocortical function defects.

Studies on the substrate specificity of the inducible and non-inducible acyl-CoA oxidases from rat kidney peroxisomes

We have studied the substrate specificity of the inducible (acyl-CoA oxidase I) and non-inducible (acyl-CoA oxidase II) oxidases in peroxisome-enriched fractions from rat kidney. The two oxidases were separated by means of ion-exchange chromatography and shown to accept a variety of acyl-CoA esters as substrates, including lignoceroyl-CoA, palmitoyl-CoA, lauroyl-CoA, caproyl-CoA, and trimethyltridecanoyl-CoA. Glutaryl-CoA was found to react exclusively with the inducible enzyme, and pristanoyl-CoA exclusively with the non-inducible enzyme. We conclude that under normal non-induced conditions both acyl-CoA oxidase I and II contribute to the oxidation of the various acyl-CoA esters with the exception of pristanoyl-CoA and glutaryl-CoA, although the extent to which each enzyme contributes to the oxidation was found to differ between the various acyl-CoA esters.

Identification and purification of a peroxisomal branched chain fatty acyl-CoA oxidase

Isoprenoid (branched) fatty acids such as pristanic acid can be degraded via beta-oxidation in peroxisomes. We synthesized 2-methylpalmitoyl-CoA as a model substrate in order to study the first step of the peroxisomal beta-oxidation of branched fatty acids, catalyzed by an acyl-CoA oxidase. 2-Methylpalmitoyl-CoA oxidase activity was found in rat liver homogenates. Subcellular fractionation demonstrated that the oxidase was confined to peroxisomes. 2-Methylpalmitoyl-CoA oxidase was also present in kidney and intestine. It was not induced in liver or in the extrahepatic tissues by treatment of rats with peroxisome proliferators or by feeding diets containing excess isoprenoids. The enzyme was partially purified together with palmitoyl-CoA oxidase and trihydroxycoprostanoyl-CoA oxidase by heat treatment and ammonium sulfate fractionation of liver extracts. The partially purified preparation was chromatographed on various columns. 2-Methylpalmitoyl-CoA oxidase could be separated from the inducible (by peroxisome proliferators) palmitoyl-CoA oxidase and from trihydroxycoprostanoyl-CoA oxidase, but it always coeluted with the noninducible palmitoyl-CoA oxidase, recently described by us (Schepers, L., Van Veldhoven, P. P., Casteels, M., Eyssen, H. J., and Mannaerts, G. P. (1990) J. Biol. Chem. 265, 5242-5246). 2-Methylpalmitoyl-CoA oxidase was purified to near homogeneity in three chromatographic steps (anion exchange, hydroxylapatite, and gel filtration). Its apparent molecular mass is approximately 415 kDa, and it consists of identical subunits of approximately 70 kDa. The enzyme oxidized 2-methylpalmitoyl-CoA twice as rapidly as palmitoyl-CoA and pristanoyl-CoA as rapidly as palmitoyl-CoA, so that it can be considered as a branched fatty acyl-CoA oxidase. Since pristanoyl-CoA is one of its naturally occurring substrates we propose to name this enzyme pristanoyl-CoA oxidase.

X-linked recessive chondrodysplasia punctata with XY translocation in a stillborn fetus

A case of X-linked recessive chondrodysplasia punctata (CP) is described. The finding of a reciprocal X-Y translocation involving the region distal to Xp22.3 and the presence of fluorescent Yp11.23 regions confirms the localization of X-linked recessive CP at p22.3. No gross peroxisomal abnormalities were present in the propositus.

Peroxisomal localization of the immunoreactive beta-oxidation enzymes in a neonate with a beta-oxidation defect. Pathological observations in liver, adrenal cortex and kidney

A boy born to healthy, unrelated parents, presented at birth with hypotonia and seizures. Very long chain fatty acids in the plasma were strongly elevated; bile acid intermediates and plasmalogen biosynthesis were normal. Acyl-CoA oxidase activity was normal. The patient died at the age of 3 months. The cerebellum and medulla oblongata showed neuronal migration defects. The specific biochemical basis for the impaired peroxisomal beta-oxidation has not been found. The three immunoreactive peroxisomal beta-oxidation enzymes and catalase were localized in the hepatocellular peroxisomes. Aberrant features of the peroxisomes included: a subpopulation of organelles larger than 1 micron, an amorphous nucleoid in many organelles, and invaginations of the peroxisomal membrane into the matrix. Peroxisomes in the proximal renal tubules also contained the three immunoreactive beta-oxidation enzymes. Regularly spaced trilamellar inclusions were seen in hepatic macrophages; they were much more abundant in adrenocortical macrophages. The inclusions were birefringent and resistant to acetone extraction. Distinct hepatic fibrosis had developed over a period of 2.5 months. We speculate that the impaired beta-oxidation is due to a defect at the level of the peroxisomal carnitine octanoyl or -acetyl transferase, responsible for the export of beta-oxidation products.

Linkage of DNA markers at Xq28 to adrenoleukodystrophy and adrenomyeloneuropathy present within the same family

We present a large kindred that contained patients with either adrenoleukodystrophy (ALD) or adrenomyeloneuropathy (AMN). The pedigree clearly supported the X-linked mode of inheritance of the nonneonatal form of ALD/AMN. Analysis with DNA markers at Xq28 suggested segregation of both ALD and AMN with an identical haplotype. This indicated that nonneonatal ALD and AMN are caused by a mutation in the same gene at Xq28. It showed, furthermore, that phenotypic differences between ALD and AMN are not necessarily the consequence of allelic heterogeneity due to different mutations within the same gene. The maximal lod score for linkage of the ALD/AMN gene and the multiallelic anonymous DNA marker at DXS52 was 3.0 at a recombination fraction of 0.00. This made a prenatal or presymptomatic diagnosis and heterozygote detection by DNA analysis with this marker reliable.

Experimental inhibition of peroxisomal beta-oxidation in rats: influence on brain myelination

Oral administration of thioridazine, an inhibitor of peroxisomal beta-oxidation, to normal rats from weaning till day 60 causes a small increase of the very long chain fatty acid C26 in brain lipids. Myelination in the brain is decreased. In the genu of the corpus callosum the ratio of non-myelinated/myelinated axons is increased. In the commissura anterior the myelin sheaths of the axons are significantly thinner in treated than in control animals. Undernourishment caused by the drug is minimal in this experiment. Area and total DNA of glial nuclei are unaltered in both the genu and the commissura anterior of treated rats. The distribution of chromatin (texture), however, shows small differences in the corpus callosum.

IgA isotyping of antigliadin antibodies. A possible clue for a less invasive diagnosis of coeliac disease

An enzyme-linked immunosorbent assay was used to measure serum antigliadin antibodies (AGA) of IgG and IgA classes. The assay was modified to measure IgA1 and IgA2 subclasses with monoclonal anti-IgA subclass antibodies. Serum IgG- and IgA-AGA levels were elevated in patients with coeliac disease (CD) but an overlap was seen with control sera. IgA-AGA isotyping using monoclonal anti-human IgA1 and IgA2 antibodies increased the sensitivity and specificity of the assay to almost 100%. All patients with active untreated CD and none of the control groups had elevated IgA1-AGA and IgA2-AGA. In order to measure the relative distribution of IgA1-AGA versus IgA2-AGA an IgA1/IgA2 ratio was calculated. In patients with active untreated CD a ratio of 2.8 was found, declining to 2.2 during treatment. A gluten challenge increased the ratio to 3.4. These findings suggest that IgA1-AGA subclass measurements are a useful screening test before small bowel biopsies are performed. This method can also be used to assess the results of a gluten free diet.

Inhibition of peroxisomal beta-oxidation and brain development in rats

Thioridazine, an inhibitor of peroxisomal beta-oxidation, was administered orally to nursing rats during the period of maximal myelination in the pups (8-21 days postnatally). Under the experimental conditions, thioridazine causes accumulation of C24 and C26 fatty acids in pup brain lipids, an effect we consider to be a typical consequence of inhibited peroxisomal beta-oxidation. In the corpus callosum of treated pups, the relationship between axon diameter and myelin sheath thickness is altered compared with matched controls. Thioridazine also induces undernourishment effects in 21 day-old rats. Body and brain weight are severely reduced. Liver peroxisomes show a starvation-type metabolism. Undernourishment is known to influence myelination in developing rat brain. However, known consequences of undernourishment, such as decreased myelin concentration in whole brain, decreased percentage of myelinated fibers, and decreased granule-to-Purkinje cell ratio are not present.

Mannosidosis in a litter of Persian cats

Three kittens in a litter of Persian cats showed, from the age of eight weeks, tremor, ataxia, dysmetria, progressive weakness and emaciation. Cytoplasmic vacuolation was observed in neurons, mesenchymal and epithelial cells of tissues taken post mortem. The alpha-mannosidase activity of brain tissue of one cat tested was 4.8 per cent of control values and the urine of two cats contained large amounts of mannose-rich oligosaccharides.

Short and long term influence of phenothiazines on liver peroxisomal fatty acid oxidation in rodents

Evidence is given that phenothiazines depress hepatic peroxisomal fatty acid oxidation in vivo. After oral administration to rats thioridazine and chlorpromazine inhibit peroxisomal beta-oxidation, evaluated by H2O2 production, during 2 weeks. In mice, this effect could not be demonstrated. However, in both species VLCFA are increased after short and long term drug administration. Electron microscopy reveals the presence of membranous structures in liver cytoplasm or lysosomes. The inhibition by thioridazine of peroxisomal beta-oxidation does not lead to hepatic peroxisome proliferation. The activities of enzymes related to fatty acid breakdown are not increased and liver peroxisomes are microscopically normal.

Inhibition of adenylate cyclase activity of human thyroid membranes by gangliosides

Gangliosides inhibit basal, thyrotropin-induced and fluoride-induced adenylate cyclase activity of human thyroid membranes in physiological conditions. In contrast neutral glycolipids, phospholipids and neuraminic acid containing oligosaccharides show no effect. The efficacy of inhibition is more dependent upon the position of the sialic acid residues than upon their absolute number. In general gangliosides with disialyl groups are more inhibitory than those with single sialyl moieties. The inhibitory effects of the individual gangliosides on the two modes of stimulation are parallel. This parallelism suggests that the inhibitory effect is located at the postreceptor level and that the gangliosides interact directly with the adenylate cyclase system. A possible role of thyroid membrane gangliosides as suppressive cofactors of adenylate cyclase is discussed in relation to recent findings of stimulating anti-ganglioside antibodies in Graves' disease.

Heparan sulfate at the surface of HeLa cells

HeLa cells, labeled with Na235SO4, release into the culture medium 35SO4 bound to plasma membrane vesicles next to 35SO4-glycoproteins and free 35SO4. Plasma membrane vesicles, experimentally produced by treatment with formaldehyde, contain 35SO4 and their surface can be stained with high iron diamine. Scanning of chromatograms of the trypsinate from labeled cells demonstrates radioactivity on the spot of heparan sulfate. It is concluded that HeLa cells synthesize heparan sulfate, which is incorporated at the plasma membrane and released by shedding of small vesicles.

Characterization of two gangliosides from human leukemic polymorphonuclear leukocytes

Eight bands of gangliosides, from human polymorphonuclear leukocytes were demonstrated by thin-layer chromatography. Bands 4 and 5 were isolated and purified in sufficient amounts to allow their biochemical identification by thin-layer chromatography, gas chromatography and sequential action of glycosidases and neuraminidase. The major ganglioside was characterised as N-acetylneuraminylgalactosyl-beta-N-acetylglucosaminyl-beta-galactosyl-beta-glucosylceramide. A second ganglioside was tentatively identified as N-acetylneuraminyl-galactosyl-beta-N-acetylglucosaminyl-beta-(N-acetylneuraminyl)galactosyl-beta-glucosylceramide. Both gangliosides isolated were hydrolysed by neuraminidase. However, treatment of the intact cells with neuraminidase did not alter the ganglioside pattern.