Refsum Disease Research Articles

Phytanic acid – a tetramethyl‐branched fatty acid in food

AbstractPhytanic acid is a tetramethyl‐branched isoprenoid fatty acid. Its presence in food is linked with chlorophyll, which contains its precursor, i. e. the alcohol side‐chain phytol. The bioconversion of phytol into phytanic acid is effective particularly in the rumen and in the marine environment. Thus, milk, other dairy products and meat from ruminants as well as fish contain the highest concentrations of phytanic acid in the range of ˜100–500 mg/100 g lipids. Phytanic acid has been proposed as a marker for organic milk because its abundance can be linked to the amount of chlorophyll present in the cows' diet. Phytanic acid is also involved in a very rare but dramatic disease, and persons suffering from the so‐called Refsum syndrome have to restrict themselves to a diet with low levels of phytanic acid.

P07.15 The Role of Advanced Neuroimaging in Infantile Refsum Disease

P07.15 The Role of Advanced Neuroimaging in Infantile Refsum Disease

Phytanic acid and pristanic acid, branched-chain fatty acids associated with Refsum disease and other inherited peroxisomal disorders, mediate intracellular Ca 2+ signaling through activation of free fatty acid receptor GPR40

The accumulation of the two branched-chain fatty acids phytanic acid and pristanic acid is known to play an important role in several diseases with peroxisomal impairment, like Refsum disease, Zellweger syndrome and α-methylacyl-CoA racemase deficiency. Recent studies elucidated that the toxic activity of phytanic acid and pristanic acid is mediated by multiple mitochondrial dysfunctions, generation of reactive oxygen species and Ca 2+ deregulation via the InsP 3–Ca 2+ signaling pathway in glial cells. However, the exact signaling mechanism through which both fatty acids mediate toxicity is still under debate. Here, we studied the ability of phytanic acid and pristanic acid to activate the free fatty acid receptor GPR40, a G-protein-coupled receptor, which was described to be involved in the Ca 2+ signaling of fatty acids. We treated HEK 293 cells expressing the GPR40 receptor with phytanic acid or pristanic acid. This resulted in a significant increase in the intracellular Ca 2+ level, similar to the effect seen after treatment with the synthetic GPR40 agonist GW9508. Furthermore, we demonstrate that the GPR40 activation might be due to an interaction of the carboxylate moiety of fatty acids with the receptor. Our findings indicate that the phytanic acid- and pristanic acid-mediated Ca 2+ deregulation can involve the activation of GPR40. Therefore, we suppose that activation of GPR40 might be part of the signaling cascade of the toxicity of phytanic and pristanic acids.

Fatty acid omega‐oxidation as a rescue pathway for fatty acid oxidation disorders in humans

Fatty acids (FAs) can be degraded via different mechanisms including α-, β- and ω-oxidation. In humans, a range of different genetic diseases has been identified in which either mitochondrial FA β-oxidation, peroxisomal FA β-oxidation or FA α-oxidation is impaired. Treatment options for most of these disorders are limited. This has prompted us to study FA ω-oxidation as a rescue pathway for these disorders, based on the notion that if the ω-oxidation of specific FAs could be upregulated one could reduce the accumulation of these FAs and the subsequent detrimental effects in the different groups of disorders. In this minireview, we describe our current state of knowledge in this area with special emphasis on Refsum disease and X-linked adrenoleukodystrophy.

Refsum's Disease—Use of the Intestinal Lipase Inhibitor, Orlistat, as a Novel Therapeutic Approach to a Complex Disorder

Refsum's Disease is an inherited metabolic disorder in which a metabolite of branched chain fatty acids accumulates due to lack of appropriate oxidative enzymes. Patients have elevated plasma phytanic acid levels and high concentrations of phytanic acid in a variety of tissues leading to progressive tissue damage. Besides retinal degeneration or retinal dystrophy associated with adult onset retinitis pigmentosa, additional symptoms include chronic polyneuropathy, cerebellar ataxia, sensorineural hearing loss, anosmia, ichthyosis, as well as skeletal, cardiac, hepatic, and renal abnormalities. Current management includes avoidance of dietary sources of branched chain fatty acids and regular plasmapheresis to prevent accumulation of these compounds to ameliorate progressive neurological deficits. Two brothers with Refsum's disease who experienced progressive symptoms despite optimal diet and plasmapheresis were commenced on a novel therapy. We report the effect of the intestinal lipase inhibitor, Orlistat, which led to significant reduction (P-value <0.001 on 2-sample unpaired t-test) of mean preplasmapheresis phytanic acid levels with retardation of the progression of most of their dermatological and neurological symptoms.

In vitro evidence that phytanic acid compromises Na +,K +-ATPase activity and the electron flow through the respiratory chain in brain cortex from young rats

Phytanic acid (Phyt) tissue concentrations are increased in Refsum disease and other peroxisomal disorders characterized by neurologic damage and brain abnormalities. The present work investigated the in vitro effects of Phyt, at concentrations found in these peroxisomal disorders, on important parameters of energy metabolism in brain cortex of young rats. The parameters analyzed were CO 2 production from labeled acetate and glucose, the activities of the citric acid cycle enzymes citrate synthase, aconitase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate dehydrogenase, fumarase and malate dehydrogenase, as well as of the respiratory chain complexes I–IV, creatine kinase and Na +,K +-ATPase. Our results show that Phyt did not alter citric acid cycle enzyme activities, or CO 2 production from acetate, reflecting no impairment of the functionality of the citric acid cycle. In contrast, respiratory chain activities were reduced at complexes I, II, I–III, II–III and IV. Membrane synaptical Na +,K +-ATPase activity was also reduced by Phyt, with no alteration of creatine kinase activity. Considering the importance of the electron flow through the respiratory chain for brain energy metabolism (oxidative phosphorylation) and of Na +,K +-ATPase activity for maintaining membrane potential necessary for neurotransmission, the data indicate that Phyt impairs brain bioenergetics at the level of energy formation, as well as neurotransmission. It is presumed that Phyt-induced impairment of these important systems may be involved at least in part in the neurological damage found in patients affected by disorders in which brain Phyt concentrations are increased.

Neurochemical evidence that phytanic acid induces oxidative damage and reduces the antioxidant defenses in cerebellum and cerebral cortex of rats

Aims In the present work we investigated the in vitro effects of phytanic acid (Phyt), that accumulates in Refsum disease and other peroxisomal diseases, on important parameters of oxidative stress in cerebellum and cerebral cortex from young rats. Main methods The parameters thiobarbituric acid-reactive substances levels (TBA-RS; lipid peroxidation), carbonyl formation and sulfhydryl oxidation (protein oxidative damage) and the concentrations of the most important nonenzymatic antioxidant defense reduced glutathione (GSH) were determined. Key findings It was observed that Phyt significantly increased TBA-RS levels in both cerebral structures. This effect was prevented by the antioxidants α-tocopherol and melatonin, suggesting the involvement of free radicals. Phyt also provoked protein oxidative damage in both cerebellum and cerebral cortex, as determined by increased carbonyl content and sulfhydryl oxidation. Furthermore, Phyt significantly diminished the concentrations of GSH, while melatonin and α-tocopherol treatment totally blocked this effect. We also verified that Phyt does not behave as a direct acting oxidant, since Phyt did not oxidize commercial solutions of GSH and reduced cytochrome c to Phyt in a free cell medium. Significance Our data indicate that oxidative stress is elicited in vitro by Phyt, a mechanism that may contribute at least in part to the pathophysiology of Refsum disease and other peroxisomal disorders where Phyt is accumulated.

The effectiveness of long-term dietary therapy in the treatment of adult Refsum disease

ObjectiveTo evaluate the long-term effectiveness of dietary therapy with regular dietetic reinforcement for adult Refsum disease.MethodsRetrospective case note analysis of records of plasma phytanic acid and hospital admission of 13...

Diet in dermatology: Revisited

Diet has an important role to play in many skin disorders, and dermatologists are frequently faced with the difficulty of separating myth from fact when it comes to dietary advice for their patients. Patients in India are often anxious about what foods to consume, and what to avoid, in the hope that, no matter how impractical or difficult this may be, following this dictum will cure their disease. There are certain disorders where one or more components in food are central to the pathogenesis, e.g. dermatitis herpetiformis, wherein dietary restrictions constitute the cornerstone of treatment. A brief list, although not comprehensive, of other disorders where diet may have a role to play includes atopic dermatitis, acne vulgaris, psoriasis vulgaris, pemphigus, urticaria, pruritus, allergic contact dermatitis, fish odor syndrome, toxic oil syndrome, fixed drug eruption, genetic and metabolic disorders (phenylketonuria, tyrosinemia, homocystinuria, galactosemia, Refsum's disease, G6PD deficiency, xanthomas, gout and porphyria), nutritional deficiency disorders (kwashiorkar, marasmus, phrynoderma, pellagra, scurvy, acrodermatitis enteropathica, carotenemia and lycopenemia) and miscellaneous disorders such as vitiligo, aphthous ulcers, cutaneous vasculitis and telogen effluvium. From a practical point of view, it will be useful for the dermatologist to keep some dietary information handy to deal with the occasional patient who does not seem to respond in spite of the best, scientific and evidence-based therapy.

Zellweger syndrome with unusual findings: non‐immune hydrops fetalis, dermal erythropoiesis and hypoplastic toe nails

The peroxisomal biogenesis disorders (PBDs) comprise the Zellweger spectrum disorders (i.e., Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease) and rhizomelic chondrodysplasia punctata. Peroxisomal biogenesis disorders can be caused by mutations in any of 13 currently known PEX genes, which encode peroxins involved in peroxisomal protein import and/or assembly of the organelle. We report here on a Turkish patient who presented with unusual clinical findings, that included non-immune hydrops, dermal erythropoiesis and hypoplastic toenails, as well as common dysmorphic features of Zellweger syndrome. The patient has also pulmonary hypoplasia, which has been reported in only a few patients with Zellweger syndrome. A peroxisomal biogenesis disorder was confirmed by enzyme analysis and abnormal very long-chain fatty acid (VLCFA) profiles in plasma and fibroblast and immunofluorescence microscopy studies. Subsequent molecular genetic analysis revealed a homozygous c.856C>T mutation (R268X) in the PEX3 gene, which made this patient the third to have a defect in this gene. In contrast to those of the two previously reported patients, the cells of this patient still contained peroxisomal membrane structures (ghosts), seen by immunofluorescence microscopy analysis. The case presented here and the two previously reported cases point out that a PEX3 gene defect may present with fairly heterogeneous clinical findings. This case also raises a possibility that hydrops fetalis may be associated with a PEX3 gene defect and that peroxisomal disorders can be considered in the etiology of hydrops fetalis as well as other cell organelle disorders when one is considering yet undiscovered complementation groups in peroxisomal disorders.

Bile acids: the role of peroxisomes

It is well established that peroxisomes play a crucial role in de novo bile acid synthesis. Studies in patients with a peroxisomal disorder have been indispensable for the elucidation of the precise role of peroxisomes. Several peroxisomal disorders are associated with distinct bile acid abnormalities and each disorder has a characteristic pattern of abnormal bile acids that accumulate, which is often used for diagnostic purposes. The patients have also been important for determining the pathophysiological consequences of defects in bile acid biosynthesis. In this review, we will discuss all the peroxisomal steps involved in bile acid synthesis and the bile acid abnormalities in patients with peroxisomal disorders. We will show the results of bile acid measurements in several tissues from patients, including brain, and we will discuss the toxicity and the pathological effects of the abnormal bile acids.

Dystrophia Helsinglandica: a new type of hereditary corneal recurrent erosions with late subepithelial fibrosis

To describe the phenotype of an autosomal-dominant corneal dystrophy with an early onset of recurrent corneal erosions and development of subepithelial fibrosis in the cornea, and also to exclude genetic linkage to known corneal dystrophies with autosomal-dominant inheritance and clinical resemblance. We describe the medical history and clinical findings in individuals from a seven-generation family with recurrent corneal erosions. A total of 43 individuals were evaluated by ophthalmological examination. Genomic DNA was prepared from peripheral blood and polymorphic microsatellite markers were analysed to study haplotypes surrounding genes causing corneal dystrophies with similar phenotypes. Erosive symptoms usually lasted for between 1 and 10 days. By the age of 7 almost all of the affected individuals suffered from recurrent corneal erosions. The attacks generally declined in frequency and intensity from the late 20s, but all examined individuals had developed subepithelial fibrosis by the age of 37. The fibrosis generally started in the mid periphery and was followed in some family members by central fibrosis and the development of gelatinous superficial elevations. Only a marginal reduction of visual acuity was seen in a few individuals. The affected individuals did not share haplotypes for genetic microsatellite markers surrounding genes that are known to cause autosomal-dominant corneal dystrophies. We describe a new type of autosomal-dominant corneal disorder with recurrent corneal erosions and subepithelial fibrosis not significantly affecting visual acuity.

The influence of the branched-chain fatty acids pristanic acid and Refsum disease-associated phytanic acid on mitochondrial functions and calcium regulation of hippocampal neurons, astrocytes, and oligodendrocytes

Pristanic acid and phytanic acid are branched-chain fatty acids, which play an important role in diseases with peroxisomal impairment, like Refsum disease (MIM 266500), Zellwegers syndrome and α-methylacyl-CoA racemase deficiency (MIM 604489). Several studies revealed that the toxic activity of phytanic acid is mediated by multiple mitochondrial dysfunctions. However, the action of pristanic acid on brain cells is still completely unknown. Here, we exposed astrocytes, oligodendrocytes and neurons in mixed culture to pristanic acid and phytanic acid to analyse cellular consequences. Pristanic acid exerts a strong cytotoxic activity on brain cells, displayed by dramatic Ca 2+ deregulation, in situ mitochondrial depolarization and cell death. Interestingly, pristanic acid strongly induced generation of reactive oxygen species (ROS), whereas phytanic acid exerts weaker effects on ROS production. In conclusion, pristanic acid as well as phytanic acid induced a complex array of toxic activities with mitochondrial dysfunction and Ca 2+ deregulation.

Peroxisomes, Refsum's disease and the alpha- and omega-oxidation of phytanic acid

Peroxisomes, Refsum's disease and the alpha- and omega-oxidation of phytanic acid

Entwicklung diagnosespezifischer Gruppen in der Pro Retina

The formation, development and external impact of the following eight disease-specific patient groups with rare forms of retinal degeneration (RRD) within the patient organization Pro Retina are described: Gyrate Atrophy, Bardet-Biedl Syndrome (BBS), Adult Refsum's Disease, Usher Syndrome, Rod-Cone Dystrophy, Leber's Congenital Amaurosis, Choroideremia and Stargardt Disease/juvenile macular degeneration. Within the project sponsored by the German Ministry of Health (BMG) approaches of patient self-help for an adequate organization and interaction with the professional medical care system were supported, analyzed and documented. In syndromic RRD a relatively high proportion of patients are organized in patient groups (Refsum's disease 25%, BBS 14%, Usher Syndrome 8%). Patients with syndromic RRD are more highly motivated to contribute to self-help work than patients with non-syndromic RRD. At the same time, these patients are more dependent on the support from their relatives and on technical aids. The following tendencies in the development of RRD groups were observed: increasing focus on one patient organization (PRO RETINA Deutschland, Self-Help Organisation of People with Retinal Degenerations) all RRD groups in Pro Retina grew; RRD groups became increasingly independent within Pro Retina; external activities of the groups showed considerable increase. Stable work relationships with scientific and medical care institutions have been established. The example of RRD demonstrates how rare and isolated patients receive basic coping support by self-help groups, how they deal with resources in a collective way and how they can interact with the medical care system.

Ataxias with Autosomal, X-Chromosomal or Maternal Inheritance

Heredoataxias are a group of genetic disorders with a cerebellar syndrome as the leading clinical manifestation. The current classification distinguishes heredoataxias according to the trait of inheritance into autosomal dominant, autosomal recessive, X-linked, and maternally inherited heredoataxias. The autosomal dominant heredoataxias are separated into spinocerebellar ataxias (SCA1-8, 10-15, 17-23, 25-30, and dentato-rubro-pallido-luysian atrophy), episodic ataxias (EA1-7), and autosomal dominant mitochondrial heredoataxias (Leigh syndrome, MIRAS, ADOAD, and AD-CPEO). The autosomal recessive ataxias are separated into Friedreich ataxia, ataxia due to vitamin E deficiency, ataxia due to Abeta-lipoproteinemia, Refsum disease, late-onset Tay-Sachs disease, cerebrotendineous xanthomatosis, spinocerebellar ataxia with axonal neuropathy, ataxia telangiectasia, ataxia telangiectasia-like disorder, ataxia with oculomotor apraxia 1 and 2, spastic ataxia of Charlevoix-Saguenay, Cayman ataxia, Marinesco-Sjögren syndrome, and autosomal recessive mitochondrial ataxias (AR-CPEO, SANDO, SCAE, AHS, IOSCA, MEMSA, LBSL CoQ-deficiency, PDC-deficiency). Only two of the heredoataxias, fragile X/tremor/ataxia syndrome, and XLSA/A are transmitted via an X-linked trait. Maternally inherited heredoataxias are due to point mutations in genes encoding for tRNAs, rRNAs, respiratory chain subunits or single large scale deletions/duplications of the mitochondrial DNA and include MELAS, MERRF, KSS, PS, MILS, NARP, and non-syndromic mitochondrial disorders. Treatment of heredoataxias is symptomatic and supportive and may have a beneficial effect in single patients. **Please see page 424 for abbreviation list.

RNA interference of long-chain acyl-CoA synthetase 6 suppresses the neurite outgrowth of mouse neuroblastoma NB41A3 cells

Lipogenesis is crucial during neuronal development. Abnormal lipid metabolism causes neurological disorders such as Refsum disease and contributes to tumor formation. Long-chain acyl-CoA synthetase (Acsl) ligates coenzyme A to fatty acids, thereby activating the lipid metabolism pathway. Here, we designed a specific small interference RNA (siRNA) against mouse Acsl6, pU6-487i and pU6-586i, and investigated the function of Acsl6 in neuron differentiation. Expression of mAcsl6 mRNA and protein was markedly decreased by pU6-487i and pU6-586i in NB41A3 mouse neuroblastoma cells. We established two stable cell lines, NB41A3-487 and NB41A3-586, which expressed mAcsl6 siRNA. Knockdown of the mAcsl6 gene inhibited the proliferation of NB41A3 cells; in NB41A3-586 cells neurite outgrowth was suppressed, while in NB41A3-487 cells it was almost absent. In addition, pU6-487i was more effective than pU6-586i in the reduction of cell proliferation and neurite outgrowth. The decline noted in the growth curves as well as the neurite outgrowth resulting from mAcsl6 knockdown indicate that the mAcsl6 gene plays a pivotal role in neuron development.

Decompensation of Refsum Disease Caused by Ibuprofen Intake

Case Report A 33-year-old white female, had a history of progressive loss of vision and hearing since the age of 20, cardiomyopathy, cardiac arrhythmias, gastroparesis, urge incontinence, decreased bone mass, bilateral hip replacement, multiple surgical interventions on the right ankle, and one surgical intervention on the right knee. At the age of 27, she was diagnosed with Refsum disease by associating the shortening of the 4 th metatarsals bilaterally and the retinitis pigmentosa, along with a high phytanic acid level. She was started on the appropriate diet consisting of restrictions on green vegetables, meats from ruminating animals, and dairy products. Since the age of 30, the patient was hospitalized four times at another facility for acute decompensation of her disease. During each hospitalization, she underwent five sessions of plasmapheresis. During her last hospitalization, her phytanic level was 105.5umol/L (reference range : ≤ 9.88). It decreased to zero after the completion of four sessions of plasmapheresis. She took ibuprofen 800 mg by mouth every eight hours during her hospital stay at the other facility. The patient presented to the emergency department at our facility for acute exacerbation of her disease, including retroorbital headaches, chest pain, nausea, vomiting, diarrhea, urinary incontinence, diffuse muscle aches, and weakness that had increased in intensity over two weeks. A detailed history revealed that she was compliant with her diet, but had a chronic ibuprofen intake for recurrent tension headaches. She was never told that ibuprofen is contraindicated in Refsum disease. The patient improved significantly after five sessions of plasmapheresis and discontinuation of ibuprofen.

Heredopathia Atactica Polyneuritiformis. (Phytanic acid storage disease. Refsum's disease). Effect of dietary treatment on retinal and cochlear changes.

Heredopathia Atactica Polyneuritiformis. (Phytanic acid storage disease. Refsum's disease). Effect of dietary treatment on retinal and cochlear changes.

Heredopathia atactica polyneuritiformis: Refsum's disease

Seven patients with Heredopathia Atactica Polyneuritiformis are described. There were 3 groups of clinical characteristics: first, congenital abnormalities such as skeletal deformities, unrelated to phytanic acid levels; second, signs and symptoms such as retinitis pigmentosa which come on slowly and are not directly related to the plasma phytanic acid level; third, lesions such as the neuropathy, rash and cardiac arrhythmias which can change quickly and are linked to the plasma phytanic acid level. Exacerbations of the signs in the third group are precipitated by a low calorie intake and mobilisation of phytanic acid from the adipose tissue. Poor vision is due not only to retinitis but also to small pupils which fail to dilate in the dark. The use of plasma exchange is discussed. With good dietary supervision it is possible to produce a considerable clinical recovery for the neuropathy.