Effect of dietary Lorenzo's oil and docosahexaenoic acid treatment for Zellweger syndrome

The Key Role of Peroxisomes in Follicular Growth, Oocyte Maturation, Ovulation, and Steroid Biosynthesis

The absence of peroxisomes can cause disease in the human reproductive system, including the ovaries. The available peroxisomal gene-knockout female mouse models, which exhibit pathological changes in the ovary and reduced fertility, are listed in this review. Our review article provides the first systematic presentation of peroxisomal regulation and its possible functions in the ovary. Our immunofluorescence results reveal that peroxisomes are present in all cell types in the ovary; however, peroxisomes exhibit different numerical abundances and strong heterogeneity in their protein composition among distinct ovarian cell types. The peroxisomal compartment is strongly altered during follicular development and during oocyte maturation, which suggests that peroxisomes play protective roles in oocytes against oxidative stress and lipotoxicity during ovulation and in the survival of oocytes before conception. In addition, the peroxisomal compartment is involved in steroid synthesis, and peroxisomal dysfunction leads to disorder in the sexual hormone production process. However, an understanding of the cellular and molecular mechanisms underlying these physiological and pathological processes is lacking. To date, no effective treatment for peroxisome-related disease has been developed, and only supportive methods are available. Thus, further investigation is needed to resolve peroxisome deficiency in the ovary and eventually promote female fertility.

Diagnostic challenges and disease management in patients with a mild Zellweger spectrum disorder phenotype

Peroxisome Biogenesis Disorders-Zellweger spectrum disorder (PBD-ZSD) is a rare, autosomal recessive peroxisome biogenesis disorder that presents with variable symptoms. In patients with PBD-ZSD, pathogenic variants in the PEX family of genes disrupt normal peroxisomal function, impairing α- and β-oxidation of very-long-chain fatty acids and synthesis of bile acids, resulting in increased levels of toxic bile acid intermediates and multisystem organ damage. The spectrum of severity in PBD-ZSD is variable, with some patients dying in the first year of life, while others live into adulthood. Symptoms of mild PBD-ZSD include various combinations of developmental delay, craniofacial dysmorphic features, visual impairment, sensorineural hearing loss, liver disease, and adrenal insufficiency. Disease progression in mild PBD-ZSD is generally slow, and may include extended periods of stability in some cases. The presence and extent to which symptoms occur in mild PBD-ZSD represents a diagnostic challenge that can cause delays in diagnosis with potential significant implications related to disease monitoring and treatment. There is some support for the pharmacologic therapies of Lorenzo's oil, docosohexanoic acid, and batyl alcohol in altering symptoms; however, systematic long-term studies are lacking. Cholic acid (CA) therapy has demonstrated treatment efficacy in patients with PBD-ZSD, including decreased toxic bile acid intermediates, transaminase levels, and liver inflammation, with improvement in growth parameters. However, these responses are most apparent in patients diagnosed and treated at a young age. Advanced liver disease may limit the efficacy of CA, underscoring the need to diagnose and treat these patients before significant liver damage and other related complications occur. Here we discuss the signs and symptoms of PBD-ZSD in patients with mild disease, standard diagnostic tools, factors affecting disease management, and available pharmacological interventions.

Docosahexaenoic Acid Attenuates Mitochondrial Alterations and Oxidative Stress Leading to Cell Death Induced by Very Long-Chain Fatty Acids in a Mouse Oligodendrocyte Model

In the case of neurodegenerative pathologies, the therapeutic arsenal available is often directed towards the consequences of the disease. The purpose of this study is, therefore, to evaluate the ability of docosahexaenoic acid (DHA), a molecule present in certain foods and considered to have health benefits, to inhibit the cytotoxic effects of very long-chain fatty acids (C24:0, C26:0), which can contribute to the development of some neurodegenerative diseases. The effect of DHA (50 µM) on very long-chain fatty acid-induced toxicity was studied by several complementary methods: phase contrast microscopy to evaluate cell viability and morphology, the MTT test to monitor the impact on mitochondrial function, propidium iodide staining to study plasma membrane integrity, and DHE staining to measure oxidative stress. A Western blot assay was used to assess autophagy through modification of LC3 protein. The various experiments were carried out on the cellular model of 158N murine oligodendrocytes. In 158N cells, our data establish that DHA is able to inhibit all tested cytotoxic effects induced by very long-chain fatty acids.

Dietary rescue of lipotoxicity-induced mitochondrial damage in Peroxin19 mutants

Mutations in peroxin (PEX) genes lead to loss of peroxisomes, resulting in the formation of peroxisomal biogenesis disorders (PBDs) and early lethality. Studying PBDs and their animal models has greatly contributed to our current knowledge about peroxisomal functions. Very-long-chain fatty acid (VLCFA) accumulation has long been suggested as a major disease-mediating factor, although the exact pathological consequences are unclear. Here, we show that a Drosophila Pex19 mutant is lethal due to a deficit in medium-chain fatty acids (MCFAs). Increased lipolysis mediated by Lipase 3 (Lip3) leads to accumulation of free fatty acids and lipotoxicity. Administration of MCFAs prevents lipolysis and decreases the free fatty acid load. This drastically increases the survival rate of Pex19 mutants without reducing VLCFA accumulation. We identified a mediator of MCFA-induced lipolysis repression, the ceramide synthase Schlank, which reacts to MCFA supplementation by increasing its repressive action on lip3. This shifts our understanding of the key defects in peroxisome-deficient cells away from elevated VLCFA levels toward elevated lipolysis and shows that loss of this important organelle can be compensated by a dietary adjustment.

Peroxisomes are organelles that contain several enzymes and fatty acids required for many metabolic tasks in the cell, and upon peroxisome loss, their educts accumulate. One example is the accumulation of very-long-chain fatty acids (VLCFAs) with a chain length of more than 20 carbons. These fatty acids cannot be oxidized in mitochondria but are exclusively degraded in peroxisomes. Lowering increased VLCFA levels is sometimes attempted as a treatment option for human disorders with peroxisomal dysfunction, although its effectiveness remains unclear. Here, we have analyzed this process in Drosophila melanogaster and found that peroxisomal loss results not only in VLCFA accumulation but also in a reduction of medium-chain fatty acids (MCFAs). We could show that this is due to a state of high lipolysis and increased mitochondrial activity. By supplementation with MCFAs from coconut oil, we were able to rescue mitochondrial damage and lethality observed in peroxisome-deficient flies. We found that this process is mediated by the ceramide synthase Schlank, which acts as a transcription factor and shuttles between nuclear membrane and endoplasmic reticulum (ER) in response to MCFA availability. We conclude that peroxisome loss triggers the accumulation of free fatty acids and mitochondrial damage in flies and that these effects can be rescued by a diet rich in MCFAs.

Peroxisomal biogenesis is genetically and biochemically linked to carbohydrate metabolism in Drosophila and mouse

Peroxisome biogenesis disorders (PBD) are a group of multi-system human diseases due to mutations in the PEX genes that are responsible for peroxisome assembly and function. These disorders lead to global defects in peroxisomal function and result in severe brain, liver, bone and kidney disease. In order to study their pathogenesis we undertook a systematic genetic and biochemical study of Drosophila pex16 and pex2 mutants. These mutants are short-lived with defects in locomotion and activity. Moreover these mutants exhibit severe morphologic and functional peroxisomal defects. Using metabolomics we uncovered defects in multiple biochemical pathways including defects outside the canonical specialized lipid pathways performed by peroxisomal enzymes. These included unanticipated changes in metabolites in glycolysis, glycogen metabolism, and the pentose phosphate pathway, carbohydrate metabolic pathways that do not utilize known peroxisomal enzymes. In addition, mutant flies are starvation sensitive and are very sensitive to glucose deprivation exhibiting dramatic shortening of lifespan and hyperactivity on low-sugar food. We use bioinformatic transcriptional profiling to examine gene co-regulation between peroxisomal genes and other metabolic pathways and we observe that the expression of peroxisomal and carbohydrate pathway genes in flies and mouse are tightly correlated. Indeed key steps in carbohydrate metabolism were found to be strongly co-regulated with peroxisomal genes in flies and mice. Moreover mice lacking peroxisomes exhibit defective carbohydrate metabolism at the same key steps in carbohydrate breakdown. Our data indicate an unexpected link between these two metabolic processes and suggest metabolism of carbohydrates could be a new therapeutic target for patients with PBD.

Zellweger spectrum disorders: clinical overview and management approach

Zellweger spectrum disorders (ZSDs) represent the major subgroup within the peroxisomal biogenesis disorders caused by defects in PEX genes. The Zellweger spectrum is a clinical and biochemical continuum which can roughly be divided into three clinical phenotypes. Patients can present in the neonatal period with severe symptoms or later in life during adolescence or adulthood with only minor features. A defect of functional peroxisomes results in several metabolic abnormalities, which in most cases can be detected in blood and urine. There is currently no curative therapy, but supportive care is available. This review focuses on the management of patients with a ZSD and provides recommendations for supportive therapeutic options for all those involved in the care for ZSD patients.

Child neurology: Zellweger syndrome

Zellweger syndrome (ZS) is a severe manifestation of disease within the spectrum of peroxisome biogenesis disorders that includes neonatal adrenoleukodystrophy, infantile Refsum disease, and rhizomelic chondroplasia punctata. Patients with ZS present in the neonatal period with a characteristic phenotype of distinctive facial stigmata, pronounced hypotonia, poor feeding, hepatic dysfunction, and often seizures and boney abnormalities. In patients with ZS, a mutation in one of the PEX genes coding for a peroxin (a peroxisome assembly protein) creates functionally incompetent organelles causing an accumulation of very long chain fatty acids (VLCFA), among other complications. Despite an absence of treatment options, prompt diagnosis of ZS is important for providing appropriate symptomatic care, definitive genetic testing, and counseling regarding family planning.