Search

We present a relatively mild case of peroxisomal D-bifunctional protein deficiency with inconsistent screening results in plasma for peroxisomal disorders.

Phytanic acid and pristanic acid are branched-chain fatty acids, present at micromolar concentrations in the plasma of healthy individuals. Here we show that both phytanic acid and pristanic acid activate the peroxisome proliferator-activated receptor alpha (PPARalpha) in a concentration-dependent manner. Activation is observed via the ligand-binding domain of PPARalpha as well as via a PPAR response element (PPRE). Via the PPRE significant induction is found with both phytanic acid and pristanic acid at concentrations of 3 and 1 microM, respectively. The trans-activation of PPARdelta and PPARgamma by these two ligands is negligible. Besides PPARalpha, phytanic acid also trans-activates all three retinoic X receptor subtypes in a concentration-dependent manner. In primary human fibroblasts, deficient in phytanic acid alpha-oxidation, trans-activation through PPARalpha by phytanic acid is observed. This clearly demonstrates that phytanic acid itself, and not only its metabolite, pristanic acid, is a true physiological ligand for PPARalpha. Because induction of PPARalpha occurs at ligand concentrations comparable to the levels found for phytanic acid and pristanic acid in human plasma, these fatty acids should be seen as naturally occurring ligands for PPARalpha. These results demonstrate that both pristanic acid and phytanic acid are naturally occurring ligands for PPARalpha, which are present at physiological concentrations.

The branched-chain fatty acid phytanic acid is a constituent of the diet, present in diary products, meat and fish. Degradation of this fatty acid in the human body is preceded by activation to phytanoyl-CoA and starts with one cycle of alpha-oxidation. Intermediates in this pathway are 2-hydroxy-phytanoyl-CoA and pristanal; the product is pristanic acid. After activation, pristanic acid is degraded by peroxisomal beta-oxidation. Several disorders have been described in which phytanic acid accumulates, in some cases in combination with pristanic acid. In classical Refsum disease, the enzyme that converts phytanoyl-CoA into 2-hydroxyphytanoyl-CoA--phytanoyl-CoA hydroxylase--is deficient, resulting in highly elevated levels of phytanic acid in blood and tissues. Also in rhizomelic chondrodysplasia punctata, phytanic acid accumulates, owing to a deficiency in the peroxisomal import of proteins with a peroxisomal targeting sequence type 2. In patients affected with generalized peroxisomal disorders, degradation of both phytanic acid and pristanic acid is impaired owing to absence of functional peroxisomes. In bifunctional protein deficiency, the disturbed oxidation of pristanic acid results in elevated levels of this fatty acid and a secondary elevation of phytanic acid. In addition, several variant peroxisomal disorders with unknown aetiology have been described in which phytanic acid and/or pristanic acid accumulate. This review describes the discovery of phytanic acid and pristanic acid and the initial attempts to elucidate the origins and fates of these fatty acids. The current knowledge on the alpha-oxidation and beta-oxidation of these branched-chain fatty acids is summarized. The disorders in which phytanic acid and/or pristanic acid accumulate are described and some remarks are made on the pathogenic mechanisms of elevated levels of phytanic acid and pristanic acid.

The in vivo oxidation of fatty acids (FA) of different chain length was investigated in three patients with documented mitochondrial FA oxidation disorders: one patient with mild multiple acyl-CoA dehydrogenase deficiency (MADM), one with medium chain acyl-CoA dehydrogenase deficiency (MCAD), and one with carnitine palmitoyltransferase I deficiency (CPT I). Breath tests were performed after oral administration of 1-13C butyric. 1-13C octanoic, and 1-13C palmitic acids. 13C/12C ratio in the expired oxidative end product CO2 was measured. The cumulative 13C elimination was calculated and expressed as a percentage of the administered dose. In the MADM patient the influence of carnitine therapy (or deprivation) on the utilization of 1-13C palmitic acid was also examined. In the MCAD and CPT I patients, the 1-13C butyric, 1-13C octanoic and 1-13C palmitic acids in vivo oxidation were similar to five healthy controls. In the MADM patient, the oxidation of 1-13C butyric and 1-13C octanoic acids were normal, whereas the metabolism of 1-13C palmitic acid ranged from 33% of 66% of controls. In this patient the serum carnitine level decreased from 60 to 27 mumol/l without carnitine supplementation. Clinically there was mild hypotonia. 1-13C palmitic acid oxidation compared to controls was 50%. After 2 further weeks of carnitine deprivation the serum carnitine was 10-15 mumol/l. Clinically he was very hypotonic and had a large liver. 1-13C Palmitic acid oxidation was 33%. After 6 weeks of readministration of carnitine (L-carnitine 100 mg/kg/day p.o.) the serum carnitine was 60 mumol/l and the patient was in good clinical condition. 1-13C palmitic acid oxidation was 66% compared to controls. Our study implies that this simple fatty acid breath test is not of diagnostic use for detection of enzymatic defects in FA oxidation disorders. The carnitine dependent 1-13C palmitic acid oxidation indicates that this test might be of some value in cases with primary or secondary carnitine deficiencies.

Total plasma odd-numbered long-chain fatty acids were analysed in patients with methylmalonic acidaemia (vitamin B12-responsive and unresponsive), combined methylmalonic acidaemia/homocystinuria (CblC), propionic acidaemia (both neonatal-onset and late-onset), biotinidase deficiency and holocarboxylase synthase deficiency, as well as in hospital controls. Total odd-numbered long-chain fatty acids (C15:0, C17:1 and C17:0) were expressed as a percentage of total C12-C20 fatty acids. Control values were 0.72% +/- 0.31% (n = 12). Normalization of the percentage of odd-chain fatty acids occurred in all vitamin-responsive patients, following the institution of vitamin treatment. In general the neonatal-onset propionic acidaemia and B12-unresponsive methylmalonic acidaemia patients had the highest plasma odd-chain fatty acid concentrations, which correlated with the clinical condition but not with the urinary excretion of methylcitrate or methylmalonate. Plasma odd-chain fatty acid concentrations and methylmalonate excretions in CblC patients reacted very well to vitamin B12 treatment, but with no clinical response. Measurement of plasma odd-chain fatty acids is of no value for the monitoring of defects of biotin metabolism.

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 metabolism of the C22 unsaturated fatty acids erucic acid (22:1(n-9)), adrenic acid (22:4(n-6)), docosapentaenoic acid (22:5(n-3)) and docosahexaenoic acid (22:6(n-3)) was studied in cultured fibroblasts from patients with acyl-CoA oxidase deficiency, the Zellweger syndrome, X-linked adrenoleukodystrophy (X-ALD) and normal controls. [3-14C] 22:4 (n-6) and [3-14C] 22:5 (n-3) were shortened (retroconverted) to [1-14C] 20:4 (n-6) and [1-14C] 20:5 (n-3), respectively, in normal and X-ALD fibroblasts. In Zellweger and acyl-CoA oxidase deficient fibroblasts these reactions were deficient. Since the retroconversion is normal in X-ALD fibroblasts peroxisomal very long chain (lignoceryl) CoA ligase is probably not required for the activation of C22 unsaturated fatty acids. The present work with fibroblasts from patients with a specific acyl-CoA oxidase deficiency, previously shown to have a deficient peroxisomal clofibrate-inducible acyl-CoA oxidase, and which accumulate 24:0 and 26:0 fatty acids, supports the view that this enzyme is responsible for the chain-shortening of docosahexaenoic acid (22:6(n-3)), erucic acid (22:1(n-9)), docosapentaenoic acid (22:5(n-3)), and adrenic acid (22:4(n-6)) as well.

The concentration of pristanic acid was measured in plasma from a patient with an isolated peroxisomal very long chain fatty acid (VLCFA) acyl-CoA oxidase deficiency, a defect in peroxisomal beta-oxidation resulting in accumulation of VLCFA in plasma and tissues. Although peroxisomes are believed to be involved in pristanic acid beta-oxidation, the pristanic acid level in the patient's plasma was within the control range. This finding provides evidence for the existence of a pristanyl-CoA oxidase distinct from the specific trihydroxycholestanoyl-CoA and VLCFA acyl-CoA oxidases.

The lack of a validated severity scoring system for individuals with Zellweger spectrum disorders (ZSD) hampers optimal patient care and reliable research. Here, we describe the development of such severity score and its validation in a large, well‐characterized cohort of ZSD individuals. We developed a severity scoring system based on the 14 organs that typically can be affected in ZSD. A standardized and validated method was used to classify additional care needs in individuals with neurodevelopmental disabilities (Capacity Profile [CAP]). Thirty ZSD patients of varying ages were scored by the severity score and the CAP. The median score was 9 (range 6‐19) with a median scoring age of 16.0 years (range 2‐36 years). The ZSD severity score was significantly correlated with all 5 domains of the CAP, most significantly with the sensory domain (r = 0.8971, P = <.0001). No correlation was found between age and severity score. Multiple peroxisomal biochemical parameters were significantly correlated with the severity score. The presently reported severity score for ZSD is a suitable tool to assess phenotypic severity in a ZSD patient at any age. This severity score can be used for objective phenotype descriptions, genotype‐phenotype correlation studies, the identification of prognostic features in ZSD patients and for classification and stratification of patients in clinical trials. [ABSTRACT FROM AUTHOR]

The in vivo oxidation of fatty acids (FA) of different chain length was investigated in three patients with documented mitochondrial FA oxidation disorders: one patient with mild multiple acyl-CoA dehydrogenase deficiency (MADM), one with medium chain acyl-CoA dehydrogenase deficiency (MCAD), and one with carnitine palmitoyltransferase I deficiency (CPT I). Breath tests were performed after oral administration of 1-C butyric, 1-C octanoic, and 1-C palmitic acids. C/C ratio in the expired oxidative end product CO was measured. The cumulative C elimination was calculated and expressed as a percentage of the administered dose. In the MADM patient the influence of carnitine therapy (or deprivation) on the utilization of 1-C palmitic acid was also examined. In the MCAD and CPT I patients, the 1-C butyric, 1-C octanoic and 1-C palmitic acids in vivo oxidation were similar to five healthy controls. In the MADM patient, the oxidation of 1-C butyric and 1-C octanoic acids were normal, whereas the metabolism of 1-C palmitic acid ranged from 33% to 66% of controls. In this patient the serum carnitine level decreased from 60 to 27 μmol/l without carnitine supplementation. Clinically there was mild hypotonia. 1-C palmitic acid oxidation compared to controls was 50%. After 2 further weeks of carnitine deprivation the serum carnitine was 10-15 μmol/l. Clinically he was very hypotonic and had a large liver. 1-C Palmitic acid oxidation was 33%. After 6 weeks of readministration of carnitine ( l-carnitine 100 mg/kg/day p.o.) the serum carnitine was 60 μmol/l and the patient was in good clinical condition. 1-C palmitic acid oxidation was 66% compared to controls. Our study implies that this simple fatty acid breath test is not of diagnostic use for detection of enzymatic defects in FA oxidation disorders. The carnitine dependent 1-C palmitic acid oxidation indicates that this test might be of some value in cases with primary or secondary carnitine deficiencies. [ABSTRACT FROM AUTHOR]