Modelling Duchenne muscular dystrophy in vitro with newly generated, blood cell-derived induced pluripotent stem cell line ORIONi003-A

Here, we present newly derived in vitro model for modeling Duchenne muscular dystrophy. Our new cell line was derived by reprogramming of peripheral blood mononuclear cells (isolated from blood from pediatric patient) with Sendai virus encoding Yamanaka factors. Derived iPS cells are capable to differentiate in vitro into three germ layers as verified by immunocytochemistry. When differentiated in special medium, our iPSc formed spontaneously beating cardiomyocytes. As cardiomyopathy is the main clinical complication in patients with Duchenne muscular dystrophy, the cell line bearing the dystrophin gene mutation might be of interest to the research community.

Influence of different spectra of NOTCH3 variants on the clinical phenotype of CADASIL - experience from Slovakia

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary vascular disorder causing ischaemic attacks and strokes in middle-aged adults. Though the clinical spectrum includes some typical symptoms, recognition of the disease, especially at an earlier stage, is very difficult because of the highly variable manifestation and incomplete clinical picture. Characteristic brain MRI findings and the presence of pathogenic variants in the NOTCH3 gene are fundamental for CADASIL diagnosis. In this paper, we provide the first comprehensive report on CADASIL patients from Slovakia. Altogether, we identified 23 different pathogenic variants in 35 unrelated families. In our cohort of patients with clinical suspicion of CADASIL, we found a causal genetic defect and confirmed the diagnosis in 10.2% of cases. We present the case reports with up-to-date unpublished NOTCH3 variants and describe their phenotype-genotype correlation: p.(Cys65Phe), p.(Pro86Leu/Ser502Phe), p.(Arg156*), p.(Cys408Arg), p.(Tyr423Cys), p.(Asp1720His), and p.(Asp1893Thrfs*13). The most frequently described location for pathogenic variants was in exon 4, whereas the most common single variant was p.Arg1076Cys in exon 20. Based on the results of our study, we propose a re-evaluation of the criteria for the selection of patients suitable for NOTCH3 gene analysis. We hereby state that the currently used protocol of a high score requirement is not ideal for assessing molecular analysis, and it will be desirable to be less strict in criteria for genetic testing.

Transthyretin-related familial amyloid polyneuropathy (ATTR-FAP) in Poland - genetic and clinical presentation

BACKGROUND

Transthyretin-related familial amyloid polyneuropathy (ATTR-FAP) is a rare, progressive, hereditary, highly disabling multisystem disorder. ATTR-FAP phenotypes differ according to the type of TTR mutation, geographic region and other as yet unidentified factors. The aim of this study was to establish the clinical and genetic characteristics of Polish patients.

METHODS AND PATIENTS

Clinical data and necessary examinations were collected from patients diagnosed with ATTR-FAP at the Department of Neurology of Medical University of Warsaw between 1970 and 2019.

RESULTS

16 patients from eight unrelated families with five different TTR mutations were identified. The family with Val71Ala TTR mutation presented with early onset severe progressive polyneuropathy, with marked visual symptoms in a few patients. The next family with Ile73Val TTR mutation developed symptoms in middle age, and presented with mixed neuropathic and cardiologic phenotype. Four unrelated families were found to have the Phe33Leu TTR mutation with mixed neuropathic and cardiologic phenotype and late onset of symptoms. Other TTR mutations identified were: Val30Met and Asp38Val, both with late onset sensory, motor and autonomic neuropathy.

CONCLUSION

Polish ATTR-FAP cases presented with heterogeneity typical for non-endemic areas. Phe33Leu TTR mutation was the most common, found in four unrelated families.

Distribution of the most common polymorphisms in TYMS gene in Slavic population of central Europe

Thymidylate synthetase (TS) plays a critical role in the de novo synthesis of dTMP inside the cell. Therefore, TS is a suitable target for cytotoxic drugs such as fluoropyrimidines. Drug efficacy and toxicity depend on the intracellular level of TS, which is significantly influenced by the polymorphisms in the 5'UTR (TSER - rs45445694, TSER*3G>C - rs2853542) and 3'UTR (1494del TTAAAG - rs151264360) of TYMS gene. Polymorphic variants of TYMS gene affect TS activity via gene expression and transcript stability. Patients who undergo fluoropyrimidine therapy may benefit from genetic testing prior to the administration of chemotherapy. At the 5' terminus of TYMS, there is a polymorphic region represented by a variable number of 28bp long tandem repeats (2-9 tandems) with the G or C nucleotide variant (SNP G>C). The 3'end of TYMS gene may decrease the stability of mRNA in the case of 6 base deletion (1494del6, D). In our study, we have focused on testing of TYMS gene polymorphisms, determination of TYMS variant frequencies in Western Slavic population and comparison of Slovak population with other populations.We performed identification of 5'UTR (rs45445694 - TSER*2 or TSER*3; rs2853542 - TSER*3G>C; TSER*3+ins6) and 3'UTR (rs151264360/1494del6/D) polymorphic regions of TYMS gene among 96 volunteers by PCR-RFLP and fragment analysis. Slovak frequencies of selected polymorphisms were established as follows: the frequency of TSER*2, TSER*3, TSER*3G>C, 1494del6/D and I to be 41%, 59%, 34%, 37.5% and 62.5% respectively. The high resolution of the capillary electrophoresis technique allowed among TSER*3 group identification of a subgroup of four individuals with rare 6bp insertion in 3R allele, id est 2.1% TSER*3+ins6 allele frequency. In our study, we have revealed individuals with rare G>C substitution in the first 28bp tandem repeat of TSER*2 promoter enhancer region (rs183205964) as well, the overall frequency of this polymorphic allele in Slovak population was 2.1%. Our results proved that Slovak population is in Hardy-Weinberg equilibrium and proportion of TYMS polymorphisms is in accordance with other published data.

Inhibitors in Severe Hemophilia A: 25-Year Experience in Slovakia

We present 25-year experience with inhibitors in previously untreated patients (PUPs) with severe hemophilia A in Slovakia, where safe factor VIII (FVIII) concentrates have been used since 1990. A prospective study focused on inhibitor incidence in PUPs was established in 1997. Out of a total 61 PUPs born between January 1997 and October 2015, 59 were eligible for evaluation; 50 and 9 were treated with > 20 exposure days (ED) of plasma-derived FVIII (pdFVIII) and recombinant FVIII (rFVIII) products, respectively. In the entire group 13/59 (22%) PUPs developed inhibitors; i.e. 7/50 (14%) and 6/9 (67%) treated with pdFVIII and rFVIII, respectively. Univariate analysis of inhibitor risk factors in patient groups with and without inhibitors showed the rFVIII and serious/recurrent infections within the first 50 EDs to be associated with inhibitor development (OR of 12.3 [95% CI 2.48–60.83; p = 0.002] and 5.0; [95% CI 1.16–21.9; p = 0.03), respectively]). Also, in multivariate Cox regression analysis, peak treatment ≥ 5 EDs reached statistical significance. The hazard ratio (HR) was 7.15 (95% CI 1.65–31.36) p = 0.0086 for rFVIII and 4.38 (95% CI 1.02–18.67) p = 0.046 for intensive treatment. Between 1993 and 2015, 21 immune tolerance inductions (ITIs) in 19 inhibitor patients were performed in the two largest hemophilia centers in Slovakia. In all but one ITI courses pdFVIII containing von Willebrand factor (FVIII/VWF) was used with preferred use of high-dose ITI (HD ITI) in high responders (HRs). Complete or partial success was achieved in 17/19 (89.5%) patients. Evaluating only the patients who already completed ITI, the success rate was even higher (15/16; 94%), including 7/7 low responders and 8/9 HR. Conclusion: Our national prospective study comprising entire group of PUPs with severe hemophilia A showed higher incidence of inhibitors in patients treated with rFVIII and those with intensive therapy within first 50 EDs. However, our experience is limited to small numbers of patients; thus, our results must be interpreted cautiously. High success rate of the ITI in our inhibitor patients has been achieved with FVIII/VWF concentrates and preferred use of HD ITI in HR patients.

Molecular diagnosis of spinal and bulbar muscular atrophy in Slovakia

OBJECTIVES

Molecular-genetic analysis is a determining step in setting the diagnosis of spinal and bulbar muscular atrophy (SBMA). We present the first nation-wide study and experience with this disease and its diagnosis in Slovakia. The study is enriched by comparison of genetic findings from Slovak patients to patients from other countries.

METHODS

Molecular-genetic analysis was performed for patients suspected of SBMA. Data of patients with confirmed diagnosis were statistically evaluated. In addition, the detection rate and the prevalence of the disease for Slovakia were estimated.

RESULTS

In 40 patients with confirmed diagnosis of SBMA, average values were observed at 44.7 CAG repeats and 52.5 years at the time of molecular-genetic diagnosis. The detection rate represents approximately 23% and an estimated prevalence is of 1 : 41,700.

CONCLUSION

Concerning the population of Slovakia with 5,420,000 inhabitants, we document a relatively large cohort of SBMA patients. This is obvious when comparing similar studies from other countries, while this is the only study representing the Central Europe. Our findings prove that molecular-genetic analyses for the detection of this neuromuscular disorder show high efficiency. This fact underlines the necessity of such testing and may serve as a guide for clinicians from other countries in setting the right diagnosis for these patients (Tab. 1, Fig. 2, Ref. 29).

Late onset form of Pompe disease

BACKGROUND

Pompe disease is an autosomal recessive disorder of glycogen metabolism caused by deficiency in lysosomal enzyme α-glucosidase.

OBJECTIVES

We present first two patients from Slovakia with confirmed Pompe disease.

METHODS

Activity of α-glucosidase was measured using 4-methylumbelliferyl-α-D-glucopyranoside with the presence of acarbose, inhibitor that eliminates isoenzyme interference of maltase-glucoamylase. This methodical approach is substantial for determination of lysosomal enzyme deficiency. Using molecular genetic methods, PCR-RFLP and direct sequencing of coding region α-glucosidase gene (GAA) we have identified causal mutations in our patients.

RESULTS

Late-onset type of disease was confirmed by measuring α-glucosidase activity in leukocytes isolated from blood. The presence of common Caucasian mutation c.-32-13T>G was proved by genetic testing in the first patient in homozygous state. Second patient was a compound heterozygote, with mutation c.-32-13T>G on one allele and mutation A486P on the second allele.

CONCLUSION

We present a diagnostic algorithm for diagnosing the Pompe disease in patients of European origin. Enzyme replacement therapy has been used as a treatment option for improving the quality of life of patients. Early diagnosis and treatment of Pompe disease are considered to be critical for maximum efficacy of enzyme replacement therapy (Tab. 1, Fig. 3, Ref. 20).

Improvement of molecular-genetic diagnostics of the most common skeletal dysplasias

achondroplasia (ACH) and hypochondroplasia (HCH) into the routine practice.

BACKGROUND

Both disorders are usually caused by de novo gain-of-function type mutations in FGFR3 gene encoding the fibroblast growth factor receptor 3, which plays an important role in the metabolism of connective tissues. More than 99% of ACH cases are caused by the glycine-to-arginine substitution at codon 380 and about 70% of HCH cases result from the asparagine-to-lysine/-serine/-threonine substitutions at codon 540 in the consequence of the four different possible nucleotide changes occurred at the same codon.

METHODS

Exons 10 and 13 of the FGFR3 gene were analysed by PCR-RFLP and sequencing analysis. The exon 13 sequencing was necessary for mutation type specification.

RESULTS

We confirmed the diagnosis of ACH due to 1138G→A transition in 7 patients and we identified 1620C→A transversion responsible for HCH in 2 patients.

CONCLUSION

Due to serious limitations in recently used methods, we had to modify the molecular-genetic diagnostics approach. We developed the reliable diagnostics and made it available for achondroplasia and hypochondroplasia suspected patients (Tab. 1, Ref. 5, Ref. 17).

Frequencies of polymorphisms in CYP2C9 and VKORC1 genes influencing warfarin metabolism in Slovak population: implication for clinical practice

OBJECTIVES

The study was aimed at establishing an effective molecular-genetic method for detecting polymorphisms in genes CYP2C9 and VKORC1, which affect the pharmacogenetics of warfarin, and at determining their prevalence in Slovak population.

BACKGROUND

Warfarin, derivative of coumarin, belongs to the most commonly prescribed oral anticoagulants with narrow therapeutic index. An insufficient dose of warfarin can result in failure to produce the antithrombotic effect, whereas an overdose increases the risk of bleeding. It was proven that genetic variability in two genes, CYP2C9 a VKORC1, has a significant influence on the individual's response to the dosage of warfarin.

METHODS

In a control group of 112 randomly selected individuals, we tested the frequency of selected single nucleotide polymorphisms including CYP2C9*2 (430C>T), CYP2C9*3 (1075A>C), VKORC1*2 (1173C>T) by allele-specific Real-Time PCR and VKORC1*2 (-1639G>A) by using PCR-RFLP.

RESULTS

Due to the combination of frequent alleles CYP2C9*2, CYP2C9*3 and VKORC1*2 in Slovak population we determine that 25% of population need a standard 5-mg daily dose of warfarin, while 44%, 23%, and 8% need 4 mg, 3 mg and 2 mg of warfarin per day.

CONCLUSION

Slovak population is in Hardy-Weinberg equilibrium and frequencies of SNPs were in accordance with other published results in European populations (Tab. 5. Fig. 3, Ref. 51).

[The role of cholesterol in embryogenesis and the Smith-Lemli-Opitzov syndrom]

The role of cholesterol in cell biology has been known for years. The sight of cholesteol biological function has changed after the discovery that the genetic disorder Smith-Lemli-Opitz syndrome is caused by a defect in cholesterol biosynthetic pathway. Cholesterol has an important role in regulation and modification of Hedgehog proteins, what links cholesterol to early embryonic development. Hedgehog proteins comprise a family of secreted signaling molecules that are essential for embryonic patterning and morphogenesis. The deficit of cholesterol during embryogenesis causes severe abnormalities in SLOS because of disrupt autoprocessing of hedgehog proteins. SLOS is an autosomal recessive disorder of sterol metabolism. The underlying pathogenetic basis for SLOS has been shown to be a deficiency of 7-dehydrocholesterol reductase, which catalyzes the last step in cholesterol biosynthesis. Reduced enzyme activity leads to a deficit of cholesterol and accumulation of precursor sterols. The human 7-dehydrocholesterol reductase gene (DHCR7) is localized on chromosome 11q 12-13.

Adult onset cerebral form of X-linked adrenoleukodystrophy with dementia of frontal lobe type with new L160P mutation in ABCD1 gene

BACKGROUND

X-linked adrenoleukodystrophy is a genetically determined disorder that causes varying degrees of malfunction of the adrenal cortex and central nervous system and is characterized by abnormally high levels of very long chain fatty acid in tissues and body fluids. The gene ABCD1, responsible for X-ALD, has been mapped on chromosome Xq28. More than 500 different mutations have been reported but no correlation between genotype and phenotype has been found.

OBJECTIVES

To investigate the occurrence of known or new mutations in the ABCD1 gene in patients with clinically and biochemical proven adrenoleukodystrophy.

PATIENT AND METHODS

A 37-year-old patient with history of one-year progression of personality and behavioral changes such as, fluctuation of apathy and euphoria, perseveration, bizarre affect, and general disengagement, preliminarily assessed as adrenoleukodystrophy has undergone a clinical, biochemical and genetic examination in order to confirm the diagnosis and discover a possible mutation.

RESULTS

The clinical examination has shown signs of the severe prefrontal syndrome, and a neurological examination disclosed deliberation signs and a spastic quadruparesis predominantly on the lower extremities. MRIs showed confluent hyperintensive lesions in T2 and FLAIR images in both hemispheres with severe progression over 6 to 12 months. Clinical findings referred to adrenoleukodystrophy, consecutively performed genetic analyses showed missense mutation at the codon 479 (T>C) in exon 1 of ABCD 1 gene, predicting the substitution L160P in ALD protein. The same mutation has also been found in patient's mother.

CONCLUSION

We examined a patient with progressive development of early onset frontal lobe type dementia and upper motor neuron signs in which neuroimaging methods and biochemical tests refer to adrenoleukodystrophy. Genetic tests revealed a new mutation at position L160P in ALD protein.

Adrenoleukodystrophy--a new mutation identified

INTRODUCTION

X-linked adrenoleukodystrophy from the group of peroxisomal disorders presents with an extensive spectrum of phenotypes. The mutation affects the ABCD1 gene encoding a peroxisomal membrane protein. So far, its detailed function has not been clarified. However, it plays an essential role in the ethiopathogenesis of X-linked adrenoleukodystrophy. Its defect causes accumulation of the very long chain fatty acids in the tissues of the central and peripheral nervous system, adrenal glands and in the body fluids.

PURPOSE

To review the clinical presentations and diagnostic issues in X-adrenoleukodystrophy diagnosed in the one affected family.

METHODS

A case report. Measurement of very long chain fatty acids. Molecular analysis of the adrenoleukodystrophy gene.

RESULTS

A new "unique" mutation in the initiation codon in the first'exon of ABCD1 gene was identified. We present a phenotype description of a patient with this mutation.

CONCLUSIONS

X-linked adrenoleukodystrophy is a disease with the incidence rate approximately 1:16,800. Detection of new mutations contributes to better understanding of this rare disease and makes the diagnostic more available and precise. The importance of an adequate diagnosis is justified not only by a different therapeutic approach, but also by the need of prenatal diagnostics and the need of genetic counselling in the affected families. As demonstrated in our case, it is necessary to consider this diagnosis also in the adult age, e.g. within the differential diagnosis of spastic paraparesis (Tab. 1, Fig. 4, Ref 23). Full Text (Free, PDF) www.bmrj.sk.

[Peroxisomal hereditary metabolic disorders]

Metabolic function of peroxisomes includes oxidation of wide spectrum of substances in the presence of oxygen. Hydrogen peroxide formed at the same time is either degraded by catalase or further utilized in peroxidative reactions. From the view of cellular pathology, the most important becomes alpha and beta-oxidation of carboxylic acids, particularly beta-oxidation of long-chain carboxylic acids, which undergoes selectively in peroxisomes. Mutations of peroxisomal genes result in serious metabolic disorders. At present about twenty hereditary peroxisomal diseases has been described. One group of them includes generalized forms (impairment of peroxisome biogenesis); diseases of other group result from isolated defects of individual peroxisomal enzymes. Combined incidence of peroxisomal hereditary disorders in the Western Europe is estimated to be 1:10,000. Beside the X-linked adrenoleukodystrophy, all others have the autosomal-recessive type of heredity. In phenotypic manifestation of generalized forms, as in the Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease, rhizomelic chondrodysplasia punctata, an impairment of the central nervous system, liver, and kidney dominate. Most of the patients die within one year, survival period longer than three years becomes exceptional. X-adrenoleukodystrophy, pseudoneonatal adrenoleukodystrophy, trifunctional enzyme deficiency, Refsum disease, primary hyperoxaluria, acatalasemia result from the deficiency of a single enzyme. The most frequent peroxiosomal hereditary disease, the X-adrenoleukodystrophy, has several clinical phenotypes, which most frequently manifest already in infants. The disease has also a clinically less serious form, which manifest only in adults--the adrenomyeloneuropathy. For the postnatal but also for the prenatal diagnostics, methods of biochemistry, molecular genetics, morphology, and immunocytochemistry are necessary.

[Peroxisomes--characteristics, biogenesis and regulation of peroxisomal genes]

Peroxisomes represent cell organelles present in both unicellular eukaryotes and most of the animal and plant cells. Peroxisomes contain about 50 enzymes with high variability in spectrum and quantity, depending on nutritional conditions and presence of some xenobiotics (peroxisome proliferations). New peroxisomes are formed after the protein intake by splitting of the existing peroxisomes or de novo. Biogenesis of peroxisomes requires cytosolic proteins, membrane transporting proteins, and the typical groups of amino acids in polypeptide chains, which have the character of topogenic signal--PTS (peroxisomal targeting signal). PTS signal is based on the terminal tripeptide, formed usually by amino acids serine, lysine and leucine (SKL tripeptide--PTS1) or by the N-terminal PTS2 with amino acid sequence Arg-Leu/Ile-XXXXX-Gln/His-Leu (X is any amino acid). Biogenesis of peroxisomes requires also special membrane proteins--peroxins, which are coded by PEX genes. These proteins act as homo- or heterodimes, they belong to ATP transports, and determine efficacy of the peroxisome biogenesis. Nuclear gene expression is regulated by nuclear receptors activated by peroxisome proliferators (PPAR-proxisome proliferators activated receptors). C-domain of the receptor binds to the specific region of the promotors of peroxisome genes (PPREs-Peroxisomal proliferator response elements), often with tandem arrangement of sequences TGACCT. Polyunsaturated fatty acids represent the effective natural regulator of the peroxisomal gene expression.

[Peroxisomal hereditary diseases]

Nearly two tens of diseases are known to be caused by impairment of several metabolic functions of peroxisomes, or by deficiency in individual peroxisomal enzymes. With the exception of X-bound adrenoleukodystrophy, all diseases are based on autosomally recessive type of inheritance and a majority of them are characteristic by specific neurologic symptoms. The group of diseases in which patients develop a generalised loss of peroxisomal functions includes: Zellweger's cerebro-hepato-renal syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, hyperpipecolic acidaemia. Other diseases, such as rhizomelic chondrodysplasia punctata and Zellweger-like syndrome are accompanied by a deficiency in several enzymatic activities. X-bound adrenoleukodystrophy, pseudo-Zellweger's syndrome, hyperoxaluria 1, adult form of Refsum's disease and acatalasaemia are peroxisomal diseases with a deficiency of a single enzyme. In clinically most severe diseases (generalised loss of peroxisomal functions), the impairment of peroxisomal biogenesis is caused assumedly due to the defect in some of the peroxisomal membrane proteins. The biochemical findings are brought about by insufficiency in such metabolic functions as oxidation of fatty acids with very long chains, oxidation of the phytanic and pipecolic acids, synthesis of cholesterol, bile salts and plasmalogenes. Rhizomelic chondrodysplasia punctata and Zellweger's syndrome are more moderate forms which are dominantly biochemically manifestant by an impairment in the synthesis of plasmalogenes. Among the diseases characterised by a deficiency in individual peroxisomal enzymes, most frequent is the X-bound andrenoleukodystrophy which has several clinical phenotypes manifestant in childhood, as well as a clinically less severe form manifestant in adulthood-adrenomyeloneuropathy. The diagnosis of peroxisomal diseases is performed by use of a wide range of methods (morphological, biochemical, immunochemical and molecular genetic examinations) which enable both postnatal and prenatal diagnostics. (Tab. 1, Ref. 104.)

The role of peroxisomes in intermediary metabolism

The dominant position among oxidoreduction processes in peroxisomes is ascribed to catalase, a number of aerobic oxidases, and Cu,Zn-superoxide dismutase. The peroxidase reaction of catalase requires substrates for hydrogen donation, other than H2O2, e.g. alcohols, aldehydes, formic acid. The peroxisomes contain an alternative system of beta-oxidation of higher carboxylic acids which in some types of plant cells is functionally very closely associated with the glyoxylate cycle. Regarding the role of peroxisomes in the metabolism of carboxylic acids, a very important finding has taken place, namely that besides acyl-CoA synthetase which is specific for long chains, the peroxisomes contain still another enzyme which allows the synthesis of CoA esters of fatty acids with very long chains. It is assumed that the entry of acyl-CoA esters or fatty acids into the perxisomes is performed by means of pores in membranes or acyl-carnitine transferases. Peroxisomes oxidize a very wide scale of substrates and contain several types of acyl-CoA oxidases: palmitoyl-CoA oxidase, pristanoyl-CoA oxidase, trihydroxy-coprostanoyl-CoA oxidase. The second and third reactions of peroxisomal beta-oxidation are catalyzed by the so-called three-functional enzyme, the activities of which are identical to those of 2-enoyl-CoA hydratase, beta-hydroxyacyl-CoA dihydrogenase and enoyl-CoA isomerase. The peroxisomes sufficiently oxidize dicarboxylic acids with a higher number of carbons beginning with the adipic acid. The peroxisomal system of beta-oxidation is utilized in metabolism of prostaglandins, pristanic acid-being the product of phytanic acid alpha-oxidation, and cholesterol. Several enzymatic activities needed for the synthesis of cholesterol partially take place in peroxisomes. The peroxisomes represent a decisive compartment for the initial phases of synthesis of plasmalogens. They contain the following enzymes: NAD(+)-glycerol-P-dehydrogenase, dihydroxyacetone-3-P-acyl-transferase, alkyl-dihydroxyacetone-P synthetase and acyl/alkyl-dihydroxyacetone-P reductase. The metabolism of amino acids takes place under the effect of peroxisomal enzymes--oxidase of diamino acids, D-aspartate oxidase, oxidase of L-pipecolic acid and alanine-glyoxylate aminotransferase. Only a few published sources consider it obvious that liver peroxisomes participate in degradation of spermine and spermidine. Polyamine oxidase oxidizes spermine resulting in the origin of spermidine and 3-aminopropionaldehyde, and spermidine is oxidized to putrescine and 3-aminopropionaldehyde. Peroxisomes in many phylogenetically lower animal species enable the break down of purine bases to urea and glyoxylic acid. In phylogenetically higher primates and in man, the activities of urate oxidase in peroxisomes are absent. (Fig. 14, Ref. 166).

Properties and biogenesis of peroxisomes

Many species of monocellular eukaryots as well as the majority of animal cell and plant tissues show the presence of peroxisomes or microperoxisomes. Their size, shape and internal organization may differ in various cellular types significantly. Typical components of animal cell peroxisomes are the membrane, matrix, low density compartment enriched in lipids, and the compartment containing D-amino acid oxidase. The group of four enzymes (catalase, D-amino acid oxidase, L-alpha-OH-acid oxidase) the location of which had been originally discovered in peroxisomes of hepatocytes of rodents was later widened by approximately forty further enzymes. It is though probable that evolution brought along a reduction and loss of various metabolic functions of peroxisomes and a decrease in the number of enzymes. Peroxisomes are characterized by high variability of the enzymatic content in dependence on the nutritional conditions and the effect of xenobiotics. Fasting, diabetes mellitus, high-lipid diet, peroxisome proliferators induce several peroxisomal enzymes, especially fatty acids beta-oxidation. The mechanism of the impact of heterogeneous substances on the gene transcription has been clarified recently. Substances as fibrates, retinoic acid, polyunsaturated fatty acids activate specific types of receptors-PPAR (peroxisome proliferators activated receptors) belonging to the superfamily of receptors activated by steroid hormones, thyroid hormones, and D-vitamins. A simultaneous induction of several peroxisomal enzymes can be achieved by the linkage between PPAR and specific areas of promotors of particular genes. Such areas-PPREs (peroxisomal proliferator response elements) with five repeated TGA(A/C/T)CT hexanucleotide sequences separated by one nucleotide were discovered in several peroxisomal genes. It is assumed that the stimulation of transcription can be achieved by the linkage between homodimers, and heterodimers of nuclear receptors on these DNA sections. The majority of peroxisomal proteins is synthesised in the cytoplasm, namely on polysomes being in matured forms. Unimpaired biogenesis of peroxisomes requires membrane transport proteins and presence of signal in polypeptide chain of imported proteins (PTS-peroxisomal targeting signal). The function of PTS in many peroxisomal proteins is fulfilled by the C-terminal tripeptide which is composed of amino acids, namely serine, lysine, and leucine (SKL-tripeptide), respectively by a tripeptide with a very similar composition in amino acids. Aside from this signal, still another signal exists, which is located at the N-end of peroxisomal proteins. The role of membrane proteins 70, 35, 256, 22, 15 kDa, is being discussed in relationship to the functions and diseases caused by impaired biogenesis of peroxisomes. (Fig. 4, Ref. 128.)

Antimutagenic properties of fresh-water blue-green algae

The antimutagenic properties of whole fresh-water blue-green algae Aphanisomenon flos-aquae, marketed under the commercial name "Alpha Sun" were tested using the Ames test. Simultaneous addition of both algae and Nitrovin (a mutagen) to the test medium did not reduce the mutagenic activity. On the other hand, addition of freeze-dried blue-green algae to the test medium 2-24 h before the application of mutagen reduced its mutagenic activity.

Cetaben is an exceptional type of peroxisome proliferator

1. Cetaben in contrast to fibrates affect differently peroxisomal constituents. 2. Changes in large scale of liver non-peroxisomal parameters were compared after 10 days administration of equal doses (200 mg/kg/day) of cetaben and clofibric acid to male Wistar rats. 3. Clofibric acid treatment increased markedly the activities of FAD-glycerol-3-P dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, cytochrome-c oxidase, malic enzyme, NAD-glycerol-3-P dehydrogenase, ethoxycoumarin deethylase, p-nitroanisole demethylase and amounts of cytochrome P-450 and b5. 4. However no analogical changes were observed after cetaben treatment in the livers of experimental animals. 5. Both drugs increased the activities of alanine-glyoxylate aminotransferase-1 and acetylcarnitine transferase--enzymes with proven mitochondrial and peroxisomal location. 6. Cetaben contrary to clofibric acid does not increase solubilization of peroxisomal enzymes. 7. Enhanced acetylcarnitine transferase and alanine-glyoxylate aminotransferase-1 activities were distributed in mitochondria as well as in peroxisomes after clofibric acid treatment, however, only peroxisomes were enriched after cetaben administration. 8. The results obtained suggest that cetaben represents an exceptional type of peroxisome proliferator, specifically affecting peroxisomes, without having a negative influence on the processes of peroxisome biogenesis.

Cetaben and fibrates both influence the activities of peroxisomal enzymes in different ways

The effects of cetaben and clofibric acid were compared on the activities of peroxisomal enzymes in the liver and kidney of male Wistar rats. Cetaben at 200 mg/kg body wt increased the activities of all of the enzymes in the liver that were studied two to eight times, whereas the changes induced by the same dose of clofibric acid increased some of the enzymes and decreased others. In the kidney, cetaben increased the activities of all investigated peroxisomal enzymes, while clofibric acid only increased the activity of palmitoyl-CoA oxidase. The data obtained in the dose-response study of cetaben revealed a significant rise in the activities of peroxisomal enzymes in both the liver and kidney at doses of 50-100 mg/kg body wt administered over 10 days, but the maximal effect was observed at 250 mg/kg. Palmitoyl-CoA oxidase and D-amino acid oxidase respond most markedly to cetaben. Cetaben could represent an atypical peroxisomal proliferator, since it increased the activities of all peroxisomal enzymes investigated. The fact that the individual components localized in the peroxisomes do not change markedly could be of importance with respect to the function and physical properties of peroxisomes.