Effect of large oral doses of vitamin E on the neurological sequelae of patients with abetalipoproteinemia

Diet management in congenital diarrheas and enteropathies - general concepts and disease-specific approach, a narrative review

Congenital diarrheas and enteropathies (CODE) are a group of rare, heterogenous, monogenic disorders that lead to chronic diarrhea in infancy. Definitive treatment is rarely available, and supportive treatment is the mainstay. Nutritional management in the form of either specialized formulas, restrictive diet, or parenteral nutrition support in CODE with poor enteral tolerance is the cornerstone of CODE treatment and long-term growth. The evidence to support the use of specific diet regimens and nutritional approaches in most CODE disorders is limited due to the rarity of these diseases and the scant published clinical experience. The goal of this review was to create a comprehensive guide for nutritional management in CODE, based on the currently available literature, disease mechanism, and the PediCODE group experience. Enteral diet management in CODE can be divided into 3 distinct conceptual frameworks: nutrient elimination, nutrient supplementation, and generalized nutrient restriction. Response to nutrient elimination or supplementation can lead to resolution or significant improvement in the chronic diarrhea of CODE and resumption of normal growth. This pattern can be seen in CODE due to carbohydrate malabsorption, defects in fat absorption, and occasionally in electrolyte transport defects. In contrast, general diet restriction is mainly supportive. However, occasionally it allows parenteral nutrition weaning or reduction over time, mainly in enteroendocrine defects and rarely in epithelial trafficking and polarity defects. Further research is required to better elucidate the role of diet in the treatment of CODE and the appropriate diet management for each disease.

Clinical and biochemical footprints of inherited metabolic disorders. XI. Gastrointestinal symptoms

Inherited metabolic disorders presenting with gastrointestinal (GI) symptoms are characterized by the dysfunction of the esophagus, stomach, small and large intestines, and pancreas. We have summarized associations of signs and symptoms in 339 inherited metabolic diseases presenting with GI symptoms. Feeding difficulties represent the most common abnormality reported for IMDs with GI involvement (37%) followed by intestinal problems (30%), vomiting (22%), stomach and pancreas involvement (8% each), and esophagus involvement (4%). This represents the eleventh of a series of articles attempting to create and maintain a comprehensive list of clinical and metabolic differential diagnoses according to system involvement.

The tocopherol transfer protein TTP mediates Vitamin Vitamin E trafficking between cerebellar astrocytes and neurons

Alpha-tocopherol (vitamin E) is an essential nutrient that functions as a major lipid-soluble antioxidant in humans. The tocopherol transfer protein (TTP) binds α-tocopherol with high affinity and selectivity and regulates whole-body distribution of the vitamin. Heritable mutations in the TTPA gene result in familial vitamin E deficiency, elevated indices of oxidative stress, and progressive neurodegeneration that manifest primarily in spinocerebellar ataxia. Although the essential role of vitamin E in neurological health has been recognized for over 50 years, the mechanisms by which this essential nutrient is transported in the central nervous system are poorly understood. Here we found that, in the murine cerebellum, TTP is selectively expressed in GFAP-positive astrocytes, where it facilitates efflux of vitamin E to neighboring neurons. We also show that induction of oxidative stress enhances the transcription of the TtpA gene in cultured cerebellar astrocytes. Furthermore, secretion of vitamin E from astrocytes is mediated by an ABC-type transporter, and uptake of the vitamin into neurons involves the low-density lipoprotein receptor-related protein 1 (LRP1) receptor. Taken together, our data indicate that TTP-expressing astrocytes control the delivery of vitamin E from astrocytes to neurons, and that this process is homeostatically responsive to oxidative stress. These are the first observations that address the detailed molecular mechanisms of vitamin E transport in the central nervous system, and these results have important implications for understanding the molecular underpinnings of oxidative stress-related neurodegenerative diseases.

Treatment of tardive dyskinesias with vitamin E*

The hypothesis that tardive dyskinesias observed after long-term administration of neuroleptics are due to the formation of free radicals following this medication has prompted studies on the use of vitamin E (α-tocopherol), an antioxidant to treat patients suffering from such side-effects. The present study aimed at reproducing earlier encouraging results in treating 23 patients with vitamin E, using a double-blind crossover design. Inclusion criteria were: duration of tardive dyskinesia for at least 3 months, appearance of the symptoms during neuroleptic treatment or after stopping this kind of medication. The 10 subjects in the first group (Gl) were treated for 14 days with 1 200 mg vitamin E per day and then for 14 days with placebo. For the second group (G2) with 9 subjects, the treatment periods were inversed. The 2 dropouts in each group were not due to experimental problems: there was no complication due to vitamin E intake, or only negligible side-effects. Side-effects were rated on the AIM scale on days 0, 14 and 28. The results of the present study do not confirm earlier reports: there was no significant difference in the therapeutic effect between placebo and vitamin E in any of the groups. However, the fact of taking these symptoms into account in the physician-patient relationship has contributed significantly to a decrease of tardive dyskinesia in both groups, from the beginning until the end of the investigation period, during which both neuroleptic and tranquilizing treatments were kept constant. Further studies should include longer treatment periods with vitamin E or even test the preventive effect of vitamin E in the production of tardive dyskinesia by neuroleptics.

Nutritional neuropathies

Neuropathies associated with nutritional deficiencies are routinely encountered by the practicing neurologist. Although these neuropathies assume different patterns, most are length-dependent, sensory axonopathies. Cobalamin deficiency neuropathy is the exception, often presenting with a non-length-dependent sensory neuropathy. Patients with cobalamin and copper deficiency neuropathy characteristically have concomitant myelopathy, whereas vitamin E deficiency is uniquely associated with a spinocerebellar syndrome. In contrast to those nutrients for which deficiencies produce neuropathies, pyridoxine toxicity results in a non-length-dependent sensory neuronopathy. Deficiencies occur in the context of malnutrition, malabsorption, increased nutrient loss (such as with dialysis), autoimmune conditions such as pernicious anemia, and with certain drugs that inhibit nutrient absorption. When promptly identified, therapeutic nutrient supplementation may result in stabilization or improvement of these neuropathies.

Efficacy of two vitamin E formulations in patients with abetalipoproteinemia and chylomicron retention disease

Abetalipoproteinemia (ABL) and chylomicron retention disease (CMRD) are extremely rare recessive forms of hypobetalipoproteinemia characterized by intestinal lipid malabsorption and severe vitamin E deficiency. Vitamin E is often supplemented in the form of fat-soluble vitamin E acetate, but fat malabsorption considerably limits correction of the deficiency. In this crossover study, we administered two different forms of vitamin E, tocofersolan (a water-soluble derivative of RRR-α-tocopherol) and α-tocopherol acetate, to three patients with ABL and four patients with CMRD. The aims of this study were to evaluate the intestinal absorption characteristics of tocofersolan versus α-tocopherol acetate by measuring the plasma concentrations of α-tocopherol over time after a single oral load and to compare efficacy by evaluating the ability of each formulation to restore vitamin E storage after 4 months of treatment. In patients with ABL, tocofersolan and α-tocopherol acetate bioavailabilities were extremely low (2.8% and 3.1%, respectively). In contrast, bioavailabilities were higher in patients with CMRD (tocofersolan, 24.7%; α-tocopherol acetate, 11.4%). Plasma concentrations of α-tocopherol at 4 months were not significantly different by formulation type in ABL or CMRD. This study provides new insights about vitamin E status in ABL and CMRD and suggests the potential of different formulations as treatment options.

Microsomal triglyceride transfer protein gene mutations in Turkish children: A novel mutation and clinical follow up

Abetalipoproteinemia (ABL; OMIM 200100) is a rare autosomal recessive disease that affects the absorption of dietary fats and fat soluble vitamins. Here, we describe the clinical and genetic characteristics of three patients with ABL. Two patients (patients 1 and 2) who were carriers of the c.398-399delAA mutation (previously known mutation) had developmental delay and hepatic steatosis developed at the age of five in patient 1. Patient 3 was the carrier of a novel mutation (g.10886-10902delAAGgtaagtttgtgttg in intron 3 and c.506A>T exon 5) in microsomal triglyceride transfer protein (MTP) gene and had hepatic steatosis.

Insights from human congenital disorders of intestinal lipid metabolism

The intestine must challenge the profuse daily flux of dietary fat that serves as a vital source of energy and as an essential component of cell membranes. The fat absorption process takes place in a series of orderly and interrelated steps, including the uptake and translocation of lipolytic products from the brush border membrane to the endoplasmic reticulum, lipid esterification, Apo synthesis, and ultimately the packaging of lipid and Apo components into chylomicrons (CMs). Deciphering inherited disorders of intracellular CM elaboration afforded new insight into the key functions of crucial intracellular proteins, such as Apo B, microsomal TG transfer protein, and Sar1b GTPase, the defects of which lead to hypobetalipoproteinemia, abetalipoproteinemia, and CM retention disease, respectively. These "experiments of nature" are characterized by fat malabsorption, steatorrhea, failure to thrive, low plasma levels of TGs and cholesterol, and deficiency of liposoluble vitamins and essential FAs. After summarizing and discussing the functions and regulation of these proteins for reader's comprehension, the current review focuses on their specific roles in malabsorptions and dyslipidemia-related intestinal fat hyperabsorption while dissecting the spectrum of clinical manifestations and managements. The influence of newly discovered proteins (proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 protein) on fat absorption has also been provided. Finally, it is stressed how the overexpression or polymorphism status of the critical intracellular proteins promotes dyslipidemia and cardiometabolic disorders.

[Have centers of rare neurological diseases changed their practices and management of the hereditary cerebellar ataxias?]

The classification and management of hereditary cerebellar ataxias have been considerably changed by advances made in the field of genetics. Given the numerous genes implicated in the disorders, genetic analysis, which alone can confirm the diagnosis, needs to be based on phenotypically precise studies. Diagnostic algorithms including both recessive and dominant forms of ataxia have been proposed. The range of disease effects has been further expanded in the light of evidence of ataxias associated with permutations of the Fragile X gene, and ataxias linked to mutations of the nuclear genes coding for structural proteins of mitochondrial DNA. In the field of therapeutics, several studies are currently ongoing for Friedreich's ataxia.

Abetalipoproteinemia: two case reports and literature review

Abetalipoproteinemia (ABL, OMIM 200100) is a rare, autosomal recessive disorder, characterized by fat malabsorption, acanthocytosis and hypocholesterolemia in infancy. Later in life, deficiency of fat-soluble vitamins is associated with development of atypical retinitis pigmentosa, coagulopathy, posterior column neuropathy and myopathy. ABL results from mutations in the gene encoding the large subunit of microsomal triglyceride transfer protein (MTP; OMIM 157147). To date at least 33 MTP mutations have been identified in 43 ABL patients. We describe the clinical progress of two patients, both currently in the fifth decade of life, who were diagnosed with ABL as children and were treated with high oral doses of fat soluble vitamins, including vitamin E over the last three decades. Treatment appears to have been associated with arrest of the neuropathy and other complications in both patients. Because pharmacologic inhibition of MTP is being developed as a novel approach to reduce plasma cholesterol for prevention of cardiovascular disease, defining the long-term clinical features of patients with a natural deficiency in MTP might provide some insight into the possible effects of such treatments. We review the range of clinical, biochemical and molecular perturbations in ABL.

Autosomal recessive cerebellar ataxias

Autosomal recessive cerebellar ataxias (ARCA) are a heterogeneous group of rare neurological disorders involving both central and peripheral nervous system, and in some case other systems and organs, and characterized by degeneration or abnormal development of cerebellum and spinal cord, autosomal recessive inheritance and, in most cases, early onset occurring before the age of 20 years. This group encompasses a large number of rare diseases, the most frequent in Caucasian population being Friedreich ataxia (estimated prevalence 2–4/100,000), ataxia-telangiectasia (1–2.5/100,000) and early onset cerebellar ataxia with retained tendon reflexes (1/100,000). Other forms ARCA are much less common. Based on clinicogenetic criteria, five main types ARCA can be distinguished: congenital ataxias (developmental disorder), ataxias associated with metabolic disorders, ataxias with a DNA repair defect, degenerative ataxias, and ataxia associated with other features. These diseases are due to mutations in specific genes, some of which have been identified, such as frataxin in Friedreich ataxia, α-tocopherol transfer protein in ataxia with vitamin E deficiency (AVED), aprataxin in ataxia with oculomotor apraxia (AOA1), and senataxin in ataxia with oculomotor apraxia (AOA2). Clinical diagnosis is confirmed by ancillary tests such as neuroimaging (magnetic resonance imaging, scanning), electrophysiological examination, and mutation analysis when the causative gene is identified. Correct clinical and genetic diagnosis is important for appropriate genetic counseling and prognosis and, in some instances, pharmacological treatment. Due to autosomal recessive inheritance, previous familial history of affected individuals is unlikely. For most ARCA there is no specific drug treatment except for coenzyme Q10 deficiency and abetalipoproteinemia.

Intestinal absorption in health and disease: micronutrients

The main theme of this chapter concerns the precise biochemical mechanisms involved in stages up to, and including, gastrointestinal absorption of vitamins and certain selected minerals. Essential data regarding sequential events, immediately following absorption of these micronutrients, are also included. There is reference to water-soluble vitamins that are, in general, either coenzymes in various metabolic reactions or carriers of certain biochemical groupings. In contrast, fat-soluble vitamins frequently function as integral components of cell membranes; they, too, receive ample attention. It is appropriate, nevertheless, to recognize that some minerals required in very small amounts are closely allied biochemically with particular vitamins; these specific associations are apportioned emphasis at relevant places in the text. Although predominant discussion centres on the physiological state, clinical reference is necessarily made to gastrointestinal disorders in which imbalance of vitamins and minerals consequently results in an additional detrimental impact on health.

[Familial hypobetalipoproteinemia]

We present the case of a 5-month-old girl, with consanguineous parents, who was born at 28 weeks of gestation and who showed intermittent signs of abdominal distension accompanied by increased regurgitation and vomiting after food intake. Significant biochemical alterations (reduced levels of triglicerides, cholesterol, and vitamin A and absence of apolipoprotein B and vitamin E) led to the diagnosis of homozygous hypobetalipoproteinemia, which was subsequently confirmed by genetic studies.

Long-term assessment of combined vitamin A and E treatment for the prevention of retinal degeneration in abetalipoproteinaemia and hypobetalipoproteinaemia patients

PURPOSE

To assess the long-term efficacy of combined vitamin A and E treatment in preventing retinal degeneration in patients with abetalipoproteinaemia (ABL) or homozygous hypobetalipoproteinaemia (HBL).

METHODS

Ten patients with ABL and 3 with homozygous HBL who were treated with oral supplements of vitamins A and E were studied. Systemic, ophthalmological and electroretinographic follow-up for a mean of 11.7 years (range 4-20 years) after onset of treatment was evaluated.

RESULTS

Despite vitamin A and E treatment, 7 of 10 patients who began treatment prior to 2 years of age and all 3 patients who began treatment later in life manifested unusual fundoscopic pigmentary changes over time. At the end of follow-up, 11 of 13 patients had subnormal mixed cone-rod electroretinogram amplitudes. Seven of 10 patients for whom perimetry was available had mild to severe constriction of the visual fields.

CONCLUSIONS

Combined oral vitamin A and E supplementation that is initiated prior to 2 years of age can markedly attenuate the severe retinal degeneration that is associated with untreated ABL or homozygous HBL. Yet, fundoscopic and functional retinal changes do occur despite early initiation of vitamin treatment. Therefore, the adequacy of the present treatment protocol for ABL and homozygous HBL should be re-evaluated.

The role of the microsomal triglygeride transfer protein in abetalipoproteinemia

The microsomal triglyceride transfer protein (MTP) is a dimeric lipid transfer protein consisting of protein disulfide isomerase and a unique 97-kDa subunit. In vitro, MTP accelerates the transport of triglyceride, cholesteryl ester, and phospholipid between membranes. It was recently demonstrated that abetalipoproteinemia, a hereditary disease characterized as an inability to produce chylomicrons and very low-density lipoproteins in the intestine and liver, respectively, results from mutations in the gene encoding the 97-kDa subunit of the microsomal triglyceride transfer protein. Downstream effects resulting from this defect include malnutrition, very low plasma cholesterol and triglyceride levels, altered lipid and protein compositions of membranes and lipoprotein particles, and vitamin deficiencies. Unless treated, abetalipoproteinemic subjects develop gastrointestinal, neurological, ophthalmological, and hematological abnormalities.

Isolated vitamin E deficiency

A 22-year-old man presented with progressive gait instability, tremor, and dysarthria since childhood. Electrophysiologic studies revealed a sensorimotor polyneuropathy. Laboratory studies documented vitamin E deficiency; however, no gastrointestinal, hepatic, or lipoprotein disorder could be identified. Vitamin E therapy normalized the serum level, but there was no neurologic improvement. Isolated vitamin E deficiency, in the absence of lipid malabsorption, should be considered in the evaluation of children and adults with ataxia and peripheral neuropathy.

Angioid streaks associated with abetalipoproteinemia

Angioid streaks were observed in two patients with abetalipoproteinemia. The progression of the angioid streaks was minimal over the years that these patients received vitamin A and E supplementation, though in one patient the development of subretinal neovascular membranes within the angioid streaks was the cause of rapid central visual loss. The simultaneous appearance of two rare entities in unrelated individuals strengthens the relationship between these two disorders that has been suggested by previous case studies. The authors propose a common metabolic pathway involving trace element deficiencies that may account for this relationship as well as the association of angioid streaks with other rare disorders such as Paget's disease, hypoparathyroidism, lead poisoning, hyperphosphatemia, and a number of hemoglobinopathies. Their study of these two patients underscores the need for further investigations as to the role of copper, zinc and omega-3 fatty acids in the pathogenesis of retinopathy in abetalipoproteinemia.

Isolated vitamin E deficiency and progressive ataxia

A case of progressive spinocerebellar syndrome due to isolated vitamin E deficiency is reported. Measurement of the vitamin E concentration in serum should be included when investigating all children with unexplained, progressive ataxia, even in the absence of malabsorption. Replacement treatment in patients with a vitamin E deficiency can arrest or improve the associated neurological disorder.

Familial hypobetalipoproteinaemia: a rare presentation to the lipid clinic

OBJECTIVE

To report a case of familial hypobetalipoproteinaemia in a woman who presented after the incidental finding of marked hypocholesterolaemia during laboratory tests.

CLINICAL FEATURES

An asymptomatic 37-year-old Lebanese woman presented to the lipid clinic with a serum total cholesterol concentration of 1.1 mmol/L, high density lipoprotein (HDL) cholesterol of 1.0 mmol/L, and triglycerides of 0.28 mmol/L. No secondary cause for the hypocholesterolaemia was established. INVESTIGATION AND OUTCOME: Her serum apolipoprotein B (apo B) levels were markedly reduced at 0.07 g/L. Except for one daughter (IV-4), all other family members including her husband (her first cousin) had apo B levels about 25% of normal. Daughter IV-4 had undetectable apo B levels. Family studies confirmed an autosomal dominant pattern of inheritance consistent with familial hypobetalipoproteinaemia.

CONCLUSION

Familial hypobetalipoproteinaemia is a rare condition that should be considered in the differential diagnosis of hypocholesterolaemia. Absence of clinical features, autosomal dominant pattern of inheritance, and reduced apo B levels suggest the diagnosis.

Intestinal and hepatic apolipoprotein B gene expression in abetalipoproteinemia

A 20-year-old woman with abetalipoproteinemia underwent orthotopic liver transplantation for cirrhosis, affording access to her liver and small intestine for study. Before transplantation, her plasma apolipoprotein B concentration was less than 1 mg/dL according to enzyme-linked immunosorbent assay, whereas after transplantation her plasma apolipoprotein B concentration was 76 mg/dL (all apolipoprotein B-100). Apolipoprotein B content was reduced in her intestine and liver compared with normal and cirrhotic controls. Cultured hepatocytes from the patient's explanted liver secreted a 1.006 g/mL less than or equal to d less than or equal to 1.063 g/mL lipoprotein rich in apolipoprotein E and a 1.063 g/mL less than or equal to d less than or equal to 1.21 g/mL lipoprotein containing apolipoproteins E and A-I with no immunodetectable apolipoprotein B in the culture medium. Normal hepatocytes secreted very low-density lipoprotein and low-density lipoprotein containing apolipoprotein B-100. Abetalipoproteinemic intestinal apolipoprotein B messenger RNA concentration was 4-5-fold higher than control values. However, the patient's liver apolipoprotein B messenger RNA level was one fifth that of control normal and cirrhotic liver. Analysis of the patient's intestinal and hepatic apolipoprotein B messenger RNA for posttranscriptional stop-codon insertion revealed normally edited transcripts. These results suggest that apolipoprotein B is synthesized as the product of a normally edited messenger RNA transcript, but not secreted, in abetalipoproteinemia.

Liver steatosis in hypobetalipoproteinemia. A case report

A case of hypobetalipoproteinemia is described; a 16-year-old girl had been suffering for nearly 2 years from diffuse abdominal pain. The only clinical features were liver steatosis, slightly increased amino transferases and an incipient polyneuropathy. No sign of malabsorption or gastrointestinal disease was found. She had extremely low levels of cholesterol and triacylglycerol in her serum, slightly decreased serum phospholipids and normal HDL-cholesterol levels. Apolipoprotein B-100 was approx. 8% of normal, whereas B-48 was present at essentially normal levels. Electron microscopy of lipoprotein particles showed normal morphology of LDL. Examination of close relatives showed no abnormalities. Southern blots revealed no major deletions or rearrangements at the genomic level. Although rare, a- and hypobetalipoproteinemia should be considered as possible etiologies in patients with unexplained steatosis in the liver.

Vitamin E and oxidative stress

Oxidative stress can result from or be enhanced by a large variety of conditions, including nutritional imbalance, exposure to chemical and physical agents in the environment, strenuous physical activities, injury, and hereditary disorders. While many enzymes and compounds are involved in protecting cells from the adverse effects of oxidative stress, vitamin E occupies an important and unique position in the overall antioxidant defense. The antioxidant function of vitamin E is closely related to the status of many dietary components. Vitamin E-depleted animals are generally more susceptible to the adverse effects of environmental agents than supplemented animals. Also, vitamin E supplementation is beneficial to certain groups of the population. However, supplementing vitamin E in experimental subjects maintained on a nutritionally adequate diet does not always provide additional protection. Differential metabolic responses in various organs and differences in experimental conditions often contribute in the discrepancies in the literature. The lack of clear evidence for the occurrence of lipid peroxidation or antioxidant function of vitamin E in vivo can be attributed partly to the presence of active pathways for metabolizing hydroperoxides, aldehydes, and other oxidation products. Specific and sensitive techniques for measuring lipid peroxidation products in biological systems are essential for understanding the role of free radical-induced lipid peroxidation in tissue damage and antioxidant function of vitamin E in vivo.

Ocular pathologic features of arteriohepatic dysplasia (Alagille's syndrome)

Arteriohepatic dysplasia (Alagille's syndrome), an autosomal dominant condition involving jaundice caused by a developmental scarcity of intrahepatic bile ducts, has characteristic cardiovascular, skeletal, facial, and ocular features that distinguish it from extrahepatic biliary atresia and an array of other neonatal intrahepatic cholestatic disorders. Two children who died of this syndrome had prominent Schwalbe's rings with attached iris strands characteristic of Axenfeld's syndrome. Additional histologic findings of iris atrophy and stromal nodules, however, made the designation Axenfeld-Reiger's syndrome more appropriate. Pigmentary retinopathy, degeneration of Bruch's membrane, and prominent lipofuscin deposition in the ciliary muscle noted in one of the patients were not regarded as primary changes of Alagille's syndrome, but were believed to be secondary to acquired deficiency of the fat-soluble vitamins A and E. Early recognition of the ocular changes in arteriohepatic dysplasia is helpful in establishing the proper diagnosis to avoid unnecessary abdominal surgery and institute vitamin therapy.

Nutritional management of plasma lipid disorders

Prevention of vascular disease and acute pancreatitis is the goal of hyperlipidemia treatment. The risk of coronary heart disease (CHD) increases with increasing plasma cholesterol levels because low-density lipoprotein (LDL), the major carrier of cholesterol in the plasma, is atherogenic. High-density lipoprotein (HDL), especially the HDL2 subfraction, protects against CHD. Hypertriglyceridemia, although not an independent risk factor for CHD, is generally accompanied by low HDL cholesterol (HDLch), which may predispose to CHD. Reducing plasma LDL and raising HDL levels are thus goals in preventing CHD. Serum LDL levels may be lowered by reducing saturated fat and cholesterol intake; weight loss may decrease LDL but is more effective in lowering plasma triglycerides and raising HDLch. The percent of total calories from polyunsaturated, monounsaturated, and saturated fats should be less than 10%, up to 10-15%, and less than 10%, respectively. High cholesterol intake increases the flux of cholesterol, which may be harmful to arterial walls, but beyond a certain point does not increase plasma cholesterol levels. Some diets change the composition rather than the level of LDL and apoproteins. Weight reduction and maintenance are the most effective dietary measures to lower plasma triglycerides; omega-3 fatty acids (fish oils) have shown promise in reducing triglyceride but not cholesterol levels. Substitution of starch for sugar lowered triglyceride levels toward normal in hypertriglyceridemia patients. Fasting triglyceride levels rise in all individuals fed high-carbohydrate diets, but the high levels persist in hypertriglyceridemia patients. Weight loss, cessation of cigarette smoking, increased physical activity, good control of diabetes, and moderate alcohol use all raise HDLch levels. Vitamin E deficiency causes neurological sequelae in children with severe malabsorption problems due to abetalipoproteinemia or cholestatic liver disease.

Active oxygen in neuromuscular disorders

Although muscle and nerve are reasonably well protected against active oxygen and related free radicals, environmental or inherited malfunctions can overpower their defences. Active oxygen is involved in many neuropathies and myopathies. In every case the damage is caused by agents which exert effects disproportionately greater than the quantities encountered, through a variety of amplification mechanisms. We can categorize these amplification mechanisms as follows: (a) non-replacement of targets (e.g. loss of genetic information, ataxia telangectasia being an hereditary ataxia in which an oxygen mediated chromosomal instability is apparent), (b) non-removal of unwanted materials (e.g. lipofuscin accumulation in brain and heart), (c) redox cycling, usually involving catalysis by trace-metal ions (e.g. some forms of Parkinsonism), (d) non-redox catalysis (e.g. toxicity in cardiac muscle or brain due to vanadium or aluminium respectively), (e) modification of ion transport (e.g. calcium ionophore or acrylamide induce histopathological changes in muscle, similar in some respects to those seen in Duchenne muscular dystrophy), (f) compromised defences (e.g. muscle and nerve become particularly susceptible to free radical damage after loss of the protective actions of vitamin E), and (g) amplification by inflammatory and immune responses (e.g. multiple sclerosis, reperfusion injury to brain and heart, and traumatic injury to nervous tissue). Unfortunately, a variety of therapeutic agents which might be expected to protect against almost every conceivable form of oxygen mediated damage have proved clinically ineffective in most of these disorders. The reasons for this will be explored with an emphasis on common features, differences, mechanisms, and potential therapeutic approaches.

Evoked potential abnormalities in children with chronic cholestasis

To assess the effect of chronic cholestasis and vitamin E deficiency on nervous system function, we did multimodality evoked potential testing of 17 children (mean age = 47 months) who had chronic liver disease. Evoked potential testing was repeated periodically in 11 patients 1 to 33 months after the initial study. Eight children had abnormal delays of the P100 peak of the visual evoked potential, and these children each had significantly higher total serum bile acid levels than did children who had normal visual evoked potentials (p = 0.002). Bilateral brainstem auditory evoked potential abnormalities consistent with conductive hearing losses were initially present in six patients. However, persistent conductive losses were found in four patients, all of whom had arteriohepatic dysplasia. Four children had mildly abnormal somatosensory evoked potentials that were due solely to a mild peripheral neuropathy. Biochemical measures of vitamin E status were not consistently associated with either normal or abnormal visual, brainstem auditory or somatosensory evoked potentials or a combination of evoked potential abnormalities, and an abnormality of one evoked potential type was not associated with an abnormality of any other. A similar lack of relationship between evoked potential results and plasma vitamin A measurement was noted. Following marked improvement in or resolution of cholestasis in four patients, the visual evoked potential became normal, but other evoked potentials did not change. Visual evoked potential improvement was greatest in two patients who underwent orthotopic liver transplantation. This is the first report that demonstrates frequent, potentially reversible visual system abnormalities that are associated with cholestasis and cannot be attributed solely to vitamin E and/or A deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic evidence from two families that the apolipoprotein B gene is not involved in abetalipoproteinemia

Abetalipoproteinemia (ABL) is a recessive disorder in which affected individuals have extremely low or undetectable levels of serum apo B-containing lipoproteins. Using restriction fragment length polymorphisms, we have studied two families, each with two children with classical ABL born of normal parents. In each of these families, the two affected children have inherited different apo B alleles from at least one parent, whereas the siblings would be anticipated to share common alleles if this disorder were due to an apo B gene mutation. This linkage study shows that in these families, the apo B gene is discordant with ABL and therefore the disorder is caused by a defect in another gene, which is important for the normal synthesis or secretion of apo B-containing lipoproteins from both the liver and intestine.

Retinitis pigmentosa

Retinitis pigmentosa is a clinically and genetically heterogeneous group of hereditary disorders in which there is progressive loss of photoreceptor and pigment epithelial function. The prevalence of retinitis pigmentosa is between 1/3000 and 1/5000 making it one of the most common causes of visual impairment in all age groups. The natural history, differential diagnosis, diagnostic clinical and electrophysiologic findings are reviewed. Generalization about the different genetic subtypes of retinitis pigmentosa are reviewed along with the uses of DNA probes for linkage studies. Syndromes in which retinitis pigmentosa is a manifestation are summarized.

[Role of the electrophysiologic examination in the diagnosis of Bassen-Kornzweig syndrome]

An autosomal recessive disorder, abetalipoproteinemia or Bassen-Kornzweig disease, concerning two sisters are described. This disorder, clinically similar to Friedreich ataxia, should be examined by electrophysiological and laboratory procedures because of the possibility of treatment by high doses of vitamin A and E. The routine electrophysiological examination of the two sisters revealed a degenerative spinocerebellar and peripheral nervous process which confirmed the damage of large myelinated fibers, as reported in the literature: neurogenic muscular atrophy of distal muscles, polyphasic motor unit potentials, moderately decrease of lower motor and sensory nerve conduction rates, and reduced amplitude of evoked responses in sensory nerves and muscles. We stress out the diagnostic value of the heterogenous conduction decrease in the distal motor fibers, signs of processes of demyelination or distal regeneration.

Visual and somatosensory evoked potentials in vitamin E deficiency with cystic fibrosis

Patients with cystic fibrosis (CF) and pancreatic malabsorption frequently have vitamin E deficiency. Affected patients may develop spinocerebellar degeneration with dysarthria, ataxia, proximal weakness, proprioceptive loss and areflexia. Of a highly selected group of 10 patients with vitamin E levels below 5 micrograms/ml (normal 5-20 micrograms/ml), 7 had abnormal neurological examinations, predominantly affecting vibration and joint position perception with some severely affected patients manifesting diminished visual acuity, tremor, ataxia and diffuse weakness. Evoked potential studies showed marked abnormalities in 3 patients, demonstrating deficits in the optic pathways and in the cervical cord dorsal column pathways. Evoked potential studies may supplement careful neurological examination in patients with CF before and after supplementation with vitamin E to evaluate their progression and response to treatment.

Homozygous hypobetalipoproteinemia: a disease distinct from abetalipoproproteinemia at the molecular level

apoB DNA, RNA, and protein from two patients with homozygous hypobetalipoproteinemia (HBL) were evaluated and compared with normal individuals. Southern blot analysis with 10 different cDNA probes revealed a normal gene without major insertions, deletions, or rearrangements. Northern and slot blot analyses of total liver mRNA from HBL patients documented a normal size apoB mRNA that was present in greatly reduced quantities. ApoB protein was detected within HBL hepatocytes utilizing immunohistochemical techniques; however, it was markedly reduced in quantity when compared with control samples. No apoB was detectable in the plasma of HBL individuals with an ELISA assay. These data are most consistent with a mutation in the coding portion of the apoB gene in HBL patients, leading to an abnormal apoB protein and apoB mRNA instability. These results are distinct from those previously noted in abetalipoproteinemia, which was characterized by an elevated level of hepatic apoB mRNA and accumulation of intracellular hepatic apoB protein.

Abetalipoproteinaemia in adults: role of vitamin therapy

The retinal and neurological complications of abetalipoproteinaemia may be preventable by replacing vitamins A and E from an early age, but their role in adult presentations is less clear. Two adult females with abetalipoproteinaemia have received 8 and 10 years respectively of replacement therapy with vitamins A, E and linoleic acid. In Case 1, visual function improved objectively on commencing therapy but has subsequently deteriorated and her neuropathy has slowly progressed. The rate of progression of neurological impairment in Case 2 was slowed but not halted by therapy, and her severe visual disturbance was unaffected. Replacement by fat soluble vitamins has only a limited role in the management of abetalipoproteinaemia once irreversible neurological/retinal damage has occurred.

Absence of intestinal synthesis of apolipoprotein B-48 in two cases of abetalipoproteinemia

Previous studies have reported that the absence of chylomicron, very-low-density lipoprotein, and low-density lipoprotein in abetalipoproteinemia is a consequence of apoprotein B (apo B) deficiency. Although the absence of apo B from the intestine has been shown by immunofluorescence, the antiserum used was raised against low-density lipoprotein apo B. Therefore, the precise nature of the underlying defect remains unknown, given that the postulated gene mutation could prevent the synthesis of the molecular form of apo B specific for chylomicrons, apo B-48, or produce an unstable aberrant form of apo B particle. This report concerns 2 girls aged 5.5 and 4.75 with well-documented clinical and biological manifestations of the disease in whom there was no immunologically detectable plasma apo B-48 and apo B-100. Their cultured jejunal explants incubated with [14C]palmitate showed slight decrease in the esterification of triglycerides, phospholipids, and cholesteryl esters. However, only traces of triglycerides and small amounts of cholesteryl esters were found in the culture medium in contrast to phospholipids, which were readily exported. Protein synthesis as assessed by [3H]leucine incorporation by explants was normal and only modestly diminished in the fat chylomicronlike fraction floated from the sonicated explants. However, there was no radioactivity at the electrophoretic position of apo B-100 and apo B-48. Immunologic confirmation of the absence of these two apoproteins was obtained by Western blots. These data confirm the hypothesis that in certain cases of abetalipoproteinemia the intestinal defect results from the lack of synthesis of apo B-48.

Vitamin E deficiency and its clinical significance in adults with primary biliary cirrhosis and other forms of chronic liver disease

The vitamin E status of 146 adults with chronic liver disease was assessed by estimating both their serum vitamin E concentration and the ratio of serum vitamin E to serum cholesterol concentration. Low levels of vitamin E occurred most frequently in patients with primary biliary cirrhosis and other forms of chronic cholestatic liver disease. When a serum vitamin E concentration of 12.3 mumol/l (mean-2 SD of a control population) was taken as the lower limit of normal, 44% of patients with primary biliary cirrhosis and 32% with other chronic cholestatic liver disease had a reduced concentration, indicating a biochemical deficiency of vitamin E. If a vitamin E/total cholesterol ratio of 2.35 mumol/mmol was taken as the lower limit of normal, then 64% and 43% of patients with primary biliary cirrhosis and other chronic cholestatic liver disease, respectively, had a biochemical deficiency of vitamin E. Of the patients with chronic cholestasis and a serum bilirubin concentration greater than 100 mumol/l, 91% had a reduced vitamin E/cholesterol ratio. Twelve patients with primary biliary cirrhosis and severe vitamin E deficiency (serum vitamin E less than 5.0 mumol/l and a vitamin E/cholesterol ratio less than 1.0 mumol/mmol) underwent extensive neurological investigation. Five had a mild mixed sensorimotor peripheral neuropathy, which was not, however, typical of the neurological syndrome associated with vitamin E deficiency. In patients with severe biochemical deficiency of vitamin E (less than 5 mumol/l and less than 1 mumol/mmol total cholesterol), administration of large oral doses of vitamin E only increased serum concentrations to within the normal range in one patient; in the others even weekly parenteral administration over a 3-month period did not correct deficiency. In patients with less severe biochemical deficiency, the serum vitamin E concentration and vitamin E/total cholesterol ratio were restored to normal by oral or intramuscular supplements of the vitamin.

Serum alpha-tocopherol levels after high-dose enteral vitamin E administration in patients with acute respiratory failure

Serum levels of tocopherols were measured in 5 healthy volunteers and in 14 patients with acute respiratory failure before and after onset of high-dose enteral vitamin E administration. The initial alpha-tocopherol levels did not differ between both groups (12.1 +/- 2.7 micrograms/ml in the volunteers and 11.3 +/- 3.5 micrograms/ml in the patients; mean +/- SD). After oral administration of 1 g d,l-alpha-tocopherylacetate per day the serum levels more than doubled within 1 day and reached a plateau between 22 and 30 micrograms/ml after 3 days in the volunteers. In contrast, application of even 3 g vitamin E/day by gastric tube in the patients with respiratory failure caused only a delayed increase of the serum levels with values nearly doubling after 5-10 days (6 patients), or there was no increase at all (8 patients). Serum alpha-tocopherol did not rise in patients without accompanying highmolecular weight formula diet and in patients with prolonged hemodynamic insufficiency and metabolic acidosis. The age of the patients, the fact of severe blood losses, hemodialysis and hemofiltration and the final outcome of death or survival appeared to be without influence on the response to enteral vitamin application. Neither in the volunteers nor in the patients with acute respiratory failure were there any detectable amounts of beta-, gamma- or delta-tocopherol or of alpha-tocopherolquinone or alpha-tocotrienol.

Analysis of the apolipoprotein B gene and messenger ribonucleic acid in abetalipoproteinemia

The apolipoprotein B-100 (apoB-100) gene in leukocytes and the apoB-100 messenger RNA (mRNA) and translated apolipoprotein in the livers from normal and abetalipoproteinemic individuals were evaluated. Four complementary DNA probes for apoB-100 covering the 5', middle, and 3' regions of the apoB-100 mRNA were utilized and Southern blot analysis indicated that the apoB-100 gene is present in abetalipoproteinemia without major insertions or deletions. Polyadenylated hepatic apoB-100 mRNA from two abetalipoproteinemic patients was normal in size, and the concentration of apoB-100 mRNA was increased sixfold compared with control hepatic apoB-100 mRNA levels. ApoB-100 was detected in hepatocytes of abetalipoproteinemic patients by immunohistochemical techniques. These results indicate that the biochemical defect in abetalipoproteinemic patients studied is most consistent with a posttranslational defect in apoB-100 processing or secretion with an up-regulation of the apoB-100 mRNA.

Oral vitamin E supplements can prevent the retinopathy of abetalipoproteinaemia

Six patients with abetalipoproteinaemia are described who received large doses of oral vitamin E for between 12 and 18 years in addition to a low fat diet and supplements of the other fat soluble vitamins. The progressive retinopathy observed in untreated abetalipoproteinaemia was substantially modified and most probably prevented by this therapy. Angioid streaks were noted in one patient. Treatment with vitamin A alone did not prevent or arrest the progression of the retinal lesion.

Vitamin E--its role in neurological function

Studies in patients with abetalipoproteinaemia, other chronic and severe fat malabsorptive states and a selective defect in vitamin E absorption, together with neuropathological studies in the vitamin E deficient human, monkey and rat indicate that vitamin E is important for normal neurological function. Appropriate vitamin E supplementation is, therefore, advisable for all patients with chronic fat malabsorption who have low serum vitamin E concentrations. Serum vitamin E concentrations should also be measured in patients with spinocerebellar disorders, whatever the aetiology.