Abnormal polyunsaturated fatty acid patterns of serum lipids in Reye's syndrome

Analysis of gene-expression profiles by oligonucleotide microarray in children with influenza

In order to clarify the mechanism of the host response to influenza virus, gene-expression profiles of peripheral blood obtained from paediatric patients with influenza were investigated by oligonucleotide microarray. In the acute phase of influenza, 200 genes were upregulated and 20 genes were downregulated compared with their expression in the convalescent phase. Interferon-regulated genes, such as interferon-induced protein with tetratricopeptide repeats 2 (IFIT2) and vipirin, were strongly upregulated in the acute phase. Gene ontology analysis showed that immune response genes were highly overrepresented among the upregulated genes. Gene-expression profiles of influenza patients with and without febrile convulsion were also studied. In patients with febrile convulsion, 22 genes were upregulated and five were downregulated compared with their expression in patients without febrile convulsion. These results should help to clarify the pathogenesis of influenza and its neurological complications.

Aspirin induces short-chain free fatty acid accumulation in rats

Aspirin is used for the prophylaxis of infarction. A low dose of aspirin is effective for the prophylaxis of myocardial infarction, whereas a higher dose is necessary for that of stroke. Salicylic acid, the in vivo metabolite of aspirin, inhibits the beta-oxidation of short-chain fatty acids. Accordingly, drinking water containing 400, 800, or 1200 mg/l aspirin was given to each of eight rats for 30 days to determine the serum short-chain fatty acid levels. Analysis of variance and a post-hoc Fisher's protected least significant differences test revealed significantly increased levels (P < 0.05) of monocarboxylic acids, n-hexanoate, n-octanoate, n-decanoate, n-dodecanoate, and dicarboxylic acids, adipate (C6,) and suberate (C8): 78.7 +/- 36.2, 61.1 +/- 30.6, 215 +/- 151, 47.5 +/- 24.0, 3.64 +/- 2.09 and 1.71 +/- 1.45 micromol/l in the 800 mg/l aspirin group compared to 23.8 +/- 12.3, 20.1 +/- 9.0, 24.3 +/- 12.1, 6.3 +/- 5.6, 0.56 +/- 0.50 and 0.44 +/- 0.25 micromol/l in the control group, respectively. These levels were also increased in the 400 or 1200 mg/l aspirin groups but less so. These findings may help us to understand the aspirin toxicity in Reye's syndrome.

Reye's and Reye-like syndromes, drug-related diseases? (causative agents, etiology, pathogenesis, and therapeutic approaches)

In the literature the separation between RS and RLS is confusing and makes it difficult to plan an appropriate preventive action or to develop new therapeutic approaches. We suggest that the generalized damage and encephalopathy seen in both RS and RLS may be due to a wide variety of causative agents that contribute to a common derangement, principally involving mitochondrial oxidative pathway. Fasting status and infections increase the catabolism and the subsequent flux of metabolites from peripheral tissues to the liver (FA and amino acids); cytokines (TNF, IL-1, and IL-6), in particular, mediate this effect during infection and experimental endotoxemia. Some drugs and other toxic compounds induce functional and morphological liver mitochondrial derangement. Oxidative metabolism is impaired, with subsequent stimulation of alternative pathways of oxidation, following production of unusual toxic acyl CoAs and dicarboxylic acids. Toxic compounds accumulate in the liver, deranging its functions and causing energy depletion, and are also released in the circulation from which they reach other tissues, including the brain. Neurons and astrocytes in the brain may be affected differently: Neurons suffer from the lack of energy and the effect of toxic compounds arriving from the bloodstream, and astrocytes may be directly affected by the beta-oxidation derangement. Very important may be genetic predisposition, which, by making the patient more sensitive to a particular causative agent, may facilitate the onset of RS and RLS. The therapeutic approach is, presently, mainly symptomatic, directed as it is to counteracting each alteration shown, depending by the clinical gravity. Other pharmacological approaches are only studied experimentally, like carnitine supplementation and PGE2 administration, or theoretically envisaged, like monoclonal antibody therapy directed at LPS or at pro-inflammatory cytokines or treatment with interferon-alpha.

Serum fatty acid profiles in cystic fibrosis patients and their parents

Fatty acid compositions of the major serum lipid classes from 43 cystic fibrosis (CF) homozygotes (CF patients), 36 obligate heterozygotes (parents of CF patients) and 34 controls were determined by capillary gas chromatography. Fatty acid compositions of the homozygote CF patients were skewed in the direction of relative essential fatty acid deficiency in comparison with the controls. Less pronounced, but similar deviations from normal, were observed in the heterozygotes. Homozygotes with normal fatty acid compositions and heterozygotes with considerably disturbed fatty acid profiles were found.

Astrocyte volume regulation and ATP and phosphocreatine concentrations after exposure to salicylate, ammonium, and fatty acids

Cellular volume regulation following swelling in hypo-osmotic phosphate-buffered saline (PBS) and ATP and phosphocreatine concentrations of cells incubated in iso-osmotic or hypo-osmotic PBS were measured in primary cultured rat cerebral astrocytes exposed for 30 min to NH4Cl, salicylate, hexanoate, octanoate, and/or dodecanoate. These compounds have been implicated in the pathogenesis of cerebral edema in Reye's Syndrome. NH4Cl (0.10 - 10 mM) had no effect on astrocyte volume regulation or ATP concentration. Salicylate significantly reduced ATP concentrations at 3.0 mM and 10 mM but had no effect on volume regulation. Hexanoate (10 mM and 30 mM) decreased astrocyte ATP content by over 80% while octanoate (10 mM) reduced ATP content by more than 50%. Concentrations of these fatty acids at or below 3.0 mM had no effect on ATP content. Volume regulation was inhibited by 3.0 mM hexanoate and 3.0 mM octanoate but not lower concentrations. Dodecanoate (0.1-3.0 mM) decreased cellular ATP content by 33-51% in iso-osmotic PBS solutions. Phosphocreatine content was reduced by exposure to salicylate or octanoate at concentrations which had no effect on ATP content. These results indicate that astrocyte energy metabolism and volume regulation may be compromised by agents associated with cerebral edema in Reye's Syndrome. Analysis of the dose-dependence of these effects suggests that inhibition of astrocyte energy metabolism is not sufficient to affect volume regulation.

Deficiency of essential fatty acids and membrane fluidity during pregnancy and lactation

In a group of 19 normal pregnant women, plasma lipids were extracted, phospholipids were isolated, and the fatty acid (FA) compositions were measured by capillary gas chromatography. Blood samples were taken at 36 wk, at labor, and at 6 wk postpartum. The FA profiles showed deficiencies of omega 6 and omega 3 FA (omega indicating the length of the terminal saturated chain), the latter more severe, at all three times. Mean melting point (MMP) was calculated for each sample as an index of "fluidity" based upon all FA present. MMP varied linearly with total polyunsaturated FA and with double bond index, current measures of "fluidity" and essential FA status. MMP was elevated 9-11 degrees C in plasma phospholipids of women during pregnancy and labor and postpartum. Lactating mothers showed less recovery from the deficiencies than did the nonlactating mothers, but neither approached normal at 6 wk. The changes seen in phospholipid profiles suggest a significant transfer of omega 3 and omega 6 polyunsaturated FA from the mother to the fetus. These FA are essential for normal fetal growth and development; their relative deficiency in maternal circulation suggests that dietary supplementation may be indicated.

Mitochondrial changes and carnitine status in fasting rats

To elucidate mitochondrial morphology and related pathophysiology in the fasting state, liver mitochondrial area, plasma levels of carnitine and non-esterified fatty acids were measured in fed (N = 30) and fasted for 5 days (N = 28) rats. The rats were divided into three groups according to body weight: 100 g-group (aged 5 weeks), 200 g-group (aged 7-8 weeks), 400 g-group (aged 15-16 weeks). Electron microscopy of the liver revealed mitochondrial enlargement in fasted rats. There were significant differences in mitochondrial area measured by digitizer, between fasted groups with 100 g and 200 g body weights and the compatible fed groups. The grade of mitochondrial swelling was inversely proportional to the body weight (i.e. the age). The fasting induced decreased plasma levels of free carnitine and increased plasma levels of acylcarnitine. Plasma free carnitine levels in all fed rats appeared to be directly correlated to the body weight. The above mitochondrial swelling and abnormal carnitine status are hallmarks of Reye's syndrome (RS). These changes are not specific to RS but might be attributable to fasting.

The effects of salicylate on ketogenesis, gluconeogenesis and urea production in rat liver perfusion

In order to elucidate the relation between the hepatotoxicity of salicylate (SA) and the pathogenesis of Reye's syndrome (RS), urea production, gluconeogenesis and ketogenesis were investigated in isolated perfused rat livers in the presence of salicylate (SA) and oleate. Although urea formation from 0.5 mM NH4Cl, 2 mM ornithine and 0.3 mM oleate was not inhibited by infusion of SA, 3 mM SA caused a 26% decrease of ketogenesis, 85% decrease of 3-hydroxybutyrate/acetoacetate ratio (30HB/AcAc) and 45% increase of oxygen consumption. Glucose production from 2 mM pyruvate in the presence of 0.3 mM oleate decreased by 33% after administration of 3 mM SA, and 30HB/AcAc ratio also decreased by 33%. The decrement of gluconeogenesis and that of the 30HB/AcAc ratio were very close. These results suggested that ATP production was maintained but that the intra-mitochondrial redox state was changed to a more oxidized state after SA administration in perfused rat livers. This change in redox state could be responsible for the decrease of gluconeogenesis. Metabolic characteristics found in RS were not obtained by infusion of 3 mM SA and 0.3 mM oleate in rat livers. Therefore, some other factors in addition to SA seem necessary to establish an animal model of RS.

Animal model of margosa oil ingestion with Reye-like syndrome. Pathogenesis of microvesicular fatty liver

The aetiology and pathogenesis of Reye's syndrome (RS) are incompletely understood. A number of environmental toxins and biological agents, including viruses, have been postulated to cause RS, either acting alone or synergistically. Most investigations have suggested that the primary insult is in the liver mitochondria, leading to a complex biochemical catastrophe, with death from encephalopathy. Margosa oil (MO), a long-chain fatty acid compound, has been shown to cause a Reye-like syndrome with death from hepatoencephalopathy, in children in Malaysia and India. The present time-course study performed in MO-administered mice showed the development of hepatic lesions with many features of RS. MO acts rapidly, within 30 min, on the nuclei of hepatocytes inducing mitoses and binucleated cells. This is followed by mitochondrial injury, with swelling, rarefaction of matrix, loss of dense bodies, pleomorphism, and loss of ribosomes starting at 60 min. There is loss of liver glycogen, and proliferation and hypertrophy of the endoplasmic reticulum (ER), followed by the presence of lipid droplets in the hyaloplasm, and globules within dilated cisterns of the ER. Additional fatty acids from lipolysis of body adipocytes, and fat globules from intestinal MO ingestion further aggravate the liver fatty change. There is evidence of fat globule ingestion by endocytosis into hepatocytes at the level of the sinusoids. The development of microvesicular liver steatosis and glycogen depletion due to involvement of liver cell organelles occur rapidly as in RS.

Biochemical relationships between Reye's and Reye's-like metabolic and toxicological syndromes

Reye's syndrome is a hepatic encephalopathy with fatty infiltration of the liver and is due to mitochondrial dysfunction. Knowledge of the mechanisms causing Reye's syndrome has been gained from the study of Reye's syndrome-like diseases, including inborn errors of mitochondrial energy production, viral disease and toxicological injury. Entry of fatty acids into mitochondria or beta-oxidation itself may be impaired. Toxins such as hypoglycin, pentanoate, valproate, salicylate, and their metabolites inhibit beta-oxidation pathways and can produce Reye's syndrome-like presentations. Biochemical manifestations of the diverse causes of Reye's syndrome-like disorders are similar and include: hypoglycaemia due to impaired gluconeogenesis, accumulation of fatty acids, fatty acyl CoAs, and acyl carnitines with depletion of free CoA and carnitine. Accumulated products may further injure mitochondria and exacerbate impaired beta-oxidation, uncouple oxidative phosphorylation or increase mitochondrial permeability. Mitochondrial swelling and steatosis of hepatic cells are the histological result. With the advances of biochemical techniques for the study of organic acid excretion patterns, serum fatty acid patterns and identification of enzymatic deficiencies in cells from patients with Reye's syndrome-like presentations, it is clear that Reye's syndrome is, in part, a collection of various inborn errors and toxicological states. Circumstances such as viral disease, prolonged fasting and drugs may precipitate clinical expression of these deficiencies as Reye's syndrome. As work progresses, further causes of Reye's syndrome will be identified.

Deficiencies of polyunsaturated fatty acids and replacement by nonessential fatty acids in plasma lipids in multiple sclerosis

Fatty acid compositions of plasma phospholipids, cholesteryl esters, triacylglycerols, and nonesterified fatty acids of 14 clinically proven and graded cases of multiple sclerosis were determined by capillary gas chromatography and compared with the values obtained for 100 normal, healthy subjects. In phospholipids, linoleic acid (18:2 omega 6; 18 carbon atoms, 2 double bonds, 6 carbon atoms beyond last double bond) was normal and 18:3 omega 6 was increased, but all subsequent omega 6 acids were subnormal (P less than 0.001), indicating impairment of chain elongation. All omega 3 acids were subnormal. The paucity of polyunsaturated fatty acids was compensated mass-wise by an increase in saturated acids. Disproportionate increases in short-chain, saturated, and monounsaturated acids, decreases in long-chain homologs, and increases of branched and odd-chain acids were observed. Loss of polyunsaturated fatty acids and replacement by nonessential acids lowered mean chain length and raised mean melting point significantly, suggesting that lowered membrane fluidity was only partially compensated by endogenous synthesis of lower-melting, nonessential acids. This phenomenon was not observed in cholesteryl esters or triacylglycerols. Nonesterified fatty acids showed significant changes in pattern of possible autacoid precursors. The abnormal profile of fatty acids in multiple sclerosis has features in common with profiles of other syndromes involving viral infections.

Application of trace metal analysis to basic problems in neurobiology studies of patients with Reye's syndrome

Reye's syndrome (Rs) is an acute illness in children manifested by encephalopathy and fatty degeneration of the liver. The syndrome may be secondary to injury of mitochondria following a toxic insult in a susceptible individual with a viral illness. Since the response to infection often involves a change in trace metals, we investigated the metal status of patients with Rs. Decreased levels of serum and liver selenium (Se) and copper (Cu) were demonstrated via PIXE analysis, in addition to an increase in serum iron (Fe) and zinc (Zn). In a subsequent study using a rat animal model of Rs, the hepatotoxin 4-pentenoic acid (4-PA) produced similar changes in serum and liver trace metals. Serum and liver Se levels were also significantly depleted in rats exposed to another toxin, valproic acid (VPA). Aspirin, known to complex metals, may also be associated with Rs. Rats chronically exposed to aspirin had decreased serum Se, Fe, and Zn compared to controls. Selenium was also decreased in liver, as was Cu. Atomic absorption spectrophotometric analysis of serum and liver Cu for mice exposed to aspirin and influenza A virus were also studied. In liver, Cu was significantly decreased in mice on Cu-deficient diets but, not in control mice exposed to virus, or aspirin and virus. For the Se-deficient animals, liver Cu was not different from controls, but there was an increase in tissue Cu for Se-sufficient mice exposed to virus and aspirin; Cu levels were decreased in sera of this latter group. Serum Cu was increased in Cu-sufficient mice exposed to virus and aspirin. The above data are of biologic and toxicologic interest because of metalloenzyme localization in the mitochondrial matrix, the cellular compartment showing the greatest degree of pathologic change in Rs. In particular, Se-dependent gluthathione peroxidase is a major deterent of peroxidative damage of lipid membranes. The accumulated evidence suggests that alteration of trace metals, e.g., decrease in Se, may promote peroxidation of mitochondrial membranes in patients with Rs.

Hepatic lipid abnormalities in a chemical/viral mouse model for Reye's syndrome

We have examined hepatic lipid profiles in a mouse model for Reye's Syndrome (RS) in which young animals are exposed to nontoxic doses of an industrial pesticide emulsifier and subsequently are infected with sublethal doses of mouse-adapted human Influenza B (Lee) virus (FluB). The purpose of this study was to determine whether liver lipid content was altered in the mice, the time course of any changes, and whether lipid changes were consistent with liver pathology. Neonatal mice exposed dermally to the emulsifier, Toximul MP8 (Tox), had significantly elevated levels of hepatic cholesterol, with otherwise normal lipid composition. Subsequent inoculation of the mice with FluB significantly increased mortality rate. The combined Tox + FluB treatment had several significant effects on liver lipids, including a transient increase in phospholipid (PL) content, a reduction in neutral glycerides and persistently high cholesterol levels. Abnormalities in fatty acid profiles included an apparent elevation in medium chain fatty acids and increased ratios of PL arachidonic to docosahexaenoic acids. Histologically, there was no evidence of fat accumulation in the liver; however, hepatic mitochondria had severe structural abnormalities characteristic of RS. These studies demonstrate that chemical-dependent enhancement of viral virulence is associated with significant alterations of hepatic lipids. We believe that these abnormalities are related to mitochondrial structural damage in RS despite the absence of hepatic steatosis.

Reye's syndrome: current concepts

Despite greater than 23 years of study, an incomplete understanding of the etiology, epidemiology and pathogenesis of Reye's syndrome persists. Better understanding of the disease has been hampered by the lack of a good animal model on which hypotheses of its pathogenesis could be tested. Human studies indicate that a primary mitochondrial injury may lead to complex metabolic disturbances that produce the observed pathophysiology. Specific directions regarding avenues for future research should pursue two lines: a good animal model still needs to be developed in which the biochemical and morphologic alterations identified in Reye's syndrome are duplicated. This model should include an antecedent viral illness but may not require aspirin exposure as an essential ingredient. With the identification of a satisfactory model, specific questions about the roles of environmental toxins or medications may be answered. Study of noncomatose cases of Reye's syndrome should continue. The specific emphasis should be to delineate what factors (NH3, free fatty acids and dicarboxylic acids) may be implicated in the pathogenesis of the CNS disease with the hopes of devising strategies for more effective treatment of encephalopathy and its attendant morbidity and mortality.

Studies of the regulation of basal adenylate cyclase activity by membrane polyunsaturated fatty acids in cultured neuroblastoma

The role of membrane polyunsaturated fatty acids (PUFAs) in the regulation of basal adenylate cyclase activity was examined in intact N1E-115 neuroblastoma cells. Addition of linoleic acid (50 microM) to the culture medium for 48 h resulted in a significant increase in phospholipid PUFA content and in a two- to fivefold increase in basal accumulation of cyclic AMP (cAMP). Both phenomena were reversed on removal of linoleate from the medium. PUFA enrichment stimulated cell proliferation by approximately 20% without altering the relative proportion of cellular protein. The supplemented cells synthesized significantly larger amounts of prostaglandin (PG) E and D than did the controls; however, blockade of PG synthesis by indomethacin or ibuprofen did not alter cAMP formation. Supplemented cells contained higher levels of malondialdehyde (MDA) than did controls, and MDA formation was reduced by coculture with alpha-tocopherol; however, its inclusion in the medium did not affect cAMP accumulation. Linoleate-supplemented cells responded to cyclase-activating agonists to the same extent as did control cells. Responses to inhibitory agonists (e.g., isoproterenol and carbamylcholine) were altered, but not to a sufficient extent to account for the PUFA-dependent increases in basal adenylate cyclase activity.

Serum lipid abnormalities in a chemical/viral mouse model for Reye's syndrome

Neonatal mice given nontoxic dermal applications of an industrial surfactant, Toximul MP8 (Tox), and subsequently infected with sublethal doses of mouse-adapted human Influenza B (Lee) virus (FluB) develop many of the biochemical features of Reye's Syndrome (RS). To determine whether these also include abnormal circulating lipid, we examined serum lipid profiles in the mouse model throughout the treatment course using Iatroscan-TH10. Following 10 days of exposure to surfactant, serum phospholipid and cholesterol levels were significantly reduced relative to control animals. These reductions were transient; however, four days following virus administration, significant differences in serum lipid were again evident. These abnormalities coincided and correlated with increased animal mortality. Animals that received combined Tox + virus treatment had significant decreases in serum total lipids relative to control animals, a reflection of a reduction in all lipid classes, including phospholipid, cholesterol, neutral glycerides (triglycerides plus diglycerides) and free fatty acids. Phospholipid (specifically phosphatidylcholine and lysophosphatidylcholine) and free fatty acid levels in the Tox + virus group were also significantly lower than those in animals that received virus alone. This study has demonstrated that suckling mice given chemical/viral treatment have the serum hypopanlipidemia but not the freefattyacidemia that are characteristic of RS.

Control of polyunsaturated acids in tissue lipids

Since the discovery in 1929 that certain polyunsaturated fatty acids (PUFA) are essential for life and health, intense investigation has revealed the multiplicity of members in each of several families of PUFA, no two of which are equivalent. The quantified nutrient requirements for the essential dietary precursors of the two dominant families of PUFA have been estimated, and the general functions of these families are slowly becoming known. The PUFA are essential components of structural membrane lipids. The functions of the individual members are not yet differentiated, except as they act as precursors of synthesis of unique octadecanoid, eicosanoid, and docosanoid products of oxidation that have potent biological properties. The PUFA occur in animals and higher plants as ubiquitous and essential components of structural lipid that are in a dynamic equilibrium with the pool of dietary acyl groups. Many human diseases have been found to involve unique essential fatty acid (EFA) deficiencies or distortions of the normal equilibrium pattern. The equilibrium is influenced by the level of dietary intake or precursors, by the presence of competing essential and nonessential acyl groups, by nonoptimum intake of other essential nutrients, by hormonal effects, by drug therapy, and by other effects upon physiological condition. With the many variables already known to modulate or control the equilibrium, it should be possible with more precise understanding of each variable to shift abnormal equilibria in the direction of normalcy. This perhaps will be the next area of intensive investigation in this field of nutrition and metabolism.

Reye syndrome

Reye syndrome has emerged as the quintessential example of an acute metabolic encephalopathy with an annual incidence ranging from 0.3 to 6.0 cases per 100,000 children. The general management has become standardized, and the mortality has declined to approximately 10 per cent. The role of aspirin in the etiopathogenesis remains controversial.

Abnormal polyunsaturated fatty acid patterns of serum lipids in alcoholism and cirrhosis: arachidonic acid deficiency in cirrhosis

Patterns of polyunsaturated fatty acids of serum phospholipids were measured for groups of alcoholics without cirrhosis, alcoholics with cirrhosis, cirrhotics without alcoholism, and a control population. Alcoholics without cirrhosis showed increased polyunsaturated fatty acids derived from linoleic and linolenic acids, but in cirrhotics these products were decreased. Alcoholism accentuated the abnormal polyunsaturated fatty acid pattern of cirrhosis. In alcohol abuse without cirrhosis, the level of 20:3 omega 9 (20 acyl carbon atoms:3 double bonds, omega, 9 carbon atoms beyond last double bond) was significantly increased, despite adequate levels of linoleic and arachidonic acids. Liver involvement appears necessary for development of deficiencies of polyunsaturated fatty acids in serum phospholipids, of which arachidonic acid deficiency is of the largest magnitude.

Reye syndrome

Reye syndrome has emerged as the quintessential example of an acute metabolic encephalopathy. The clinical presentation is quite stereotyped in most instances permitting rapid, accurate diagnosis and early therapeutic intervention. Intoxications and certain inborn metabolic errors may mimic Reye syndrome. All patients with a recurrent episode should be investigated thoroughly for evidence of a metabolic disorder associated with an enzyme deficiency. Notable in this regard are inborn errors affecting organic acid, ammonia, and carbohydrate metabolism. The mitochondrial disturbance in Reye syndrome is well documented but the pathophysiologic sequence linking the antecedent viral illness to the mitochondrial injury remains obscure. Recent identification of a spontaneous Reye-like illness in mice that is associated with a coronavirus infection may provide an opportunity to investigate this initial phase of the pathophysiologic sequence. The primary cerebral insult presumably derives from insufficient substrate availability and results in massive cytotoxic cerebral edema. Treatment revolves around the continuous infusion of hypertonic glucose and intermittent infusion of hypertonic mannitol. Management is designed to attenuate or avoid the various compounding metabolic insults during this critical period when the child is metabolically crippled. In 1963, the disorder was considered to be rare and almost irreversibly fatal. Today, the disorder is recognized to be more common, and the outcome is very satisfactory in 85 to 90 per cent of the cases. The role of aspirin remains very controversial. A number of studies suggest an association between this potential mitochondrial toxin and Reye syndrome, but a causal relationship has not been established. Until better understood, it seems advisable to avoid use of aspirin in children exhibiting symptoms suggestive of Reye syndrome.

Development of encephalopathic features similar to Reye syndrome in rabbits

The progression of neurological abnormalities through four or five clinically distinguishable levels of deepening coma and the development of a fatty liver are the hallmarks of Reye syndrome. A number of animal models have been described that result in fatty liver formation with minimal, static, or catastrophic neurological changes. In this study, we attempted to produce neurological features in rabbits that reflected a rostral-caudal progression of abnormalities that could be categorized into clinically distinguishable levels reminiscent of Reye syndrome. This was accomplished by the intracisternal administration of 0.5-25 mg of 11,14-icosadienoic acid (20:2 omega 6) suspended in a mixture of rabbit serum and isotonic saline solution. A reproducible, dose-titratable spectrum of at least four levels of deepening coma could be produced at will. Increases in serum glutamate-oxaloacetate transaminase and creatine kinase and changes in serum glucose resulted 1-2 hr after the neurological abnormalities were evoked. Other unsaturated fatty acids produced similar responses. Those tested included 18:1 omega 9, 18:2 omega 6, 18:3 omega 3, 20:3 omega 6, 20:4 omega 6, and 22:4 omega 6 fatty acids. Saturated fatty acids, including 6:0, 8:0, 16:0, 18:0, and 20:0, failed to elicit these effects. The abnormalities were sustained for 30-120 min after a single dose. Full recovery was observed in some animals that had not reached the fourth level of our grading system for coma. Pretreatment of the rabbits with aspirin modulated the neurological abnormalities. Twenty micrograms of bee venom melittin, which activates endogenous phospholipase A2, administered intracisternally into rabbits also produced signs of level 3 (our grading system) coma for several hours. These findings suggest a possible role for polyunsaturated fatty acids in the development of Reye syndrome and offer a means of producing the neurological components of that syndrome in a laboratory animal.

Identification of long chain dicarboxylic acids in the serum of two patients with Reye's syndrome

Sera from two patients with Reye's Syndrome were analysed by computerized capillary gas chromatography--mass spectrometry profiling techniques. The most striking abnormalities were the accumulation of long chain dicarboxylic acids. Four saturated dicarboxylic acids (dodecanedioic, tetradecanedioic, hexadecanedioic, and octadecanedioic), and six unsaturated long chain dicarboxylic acids (dodecenedioic, tetradecenedioic, tetradecadienedioic, hexadecenedioic, octadecadienedioic, and octadecenedioic) were identified. The C16 and C13 dicarboxylic acids have never been reported for Reye's Syndrome or any other dicarboxylic acidemias. The data might reflect marked increase of extramitochondrial omega-oxidation of long chain fatty acids or impaired metabolism of omega-dicarboxylic acids formed in Reye's patients.

Induction of brain edema following intracerebral injection of arachidonic acid

The effects of polyunsaturated fatty acids on brain edema formation have been studied in rats. Intracerebral injection of polyunsaturated fatty acids (PUFAs), including linolenic acid (18:3) and arachidonic acid (20:4), caused significant increases in cerebral water and sodium content concomitant with decreases in potassium content and Na+- and K+- dependent adenosine triphosphatase activity. There was gross and microscopic evidence of edema. Saturated fatty acids and monounsaturated fatty acid were not effective in inducing brain edema. The [125I]-bovine serum albumin spaces increased twofold and threefold at 24 hours with 18:3 and 20:4, respectively, indicating vasogenic edema with increased permeability of brain endothelial cells. Staining of the brain was observed five minutes after injection of Evans blue dye followed by arachidonic acid perfusion. A major decrease in brain potassium content was evidence of concurrent cellular (cytotoxic) edema as well. The induction of brain edema by arachidonic acid was dose dependent and maximal between 24 and 48 hours after perfusion. Dexamethasone (10 mg/kg) was effective in ameliorating the brain edema, whereas a cyclooxygenase inhibitor, indomethacin (10 mg/kg), was not. These data indicate that arachidonic acid and other PUFAs have the ability to induce vasogenic and cellular brain edema and further support the hypothesis that the degradation of phospholipids and accumulation of PUFAs, particularly arachidonic acid, initiate the development of brain edema in various disease states.

Perturbation of the metabolism of essential fatty acids by dietary partially hydrogenated vegetable oil

Rats were fed purified diets containing (i) partially hydrogenated soybean oil as source of isomeric octadecenoic acids, (ii) hydrogenated coconut oil as source of saturated fatty acids, and (iii) a low level of corn oil as low-fat control. All diets contained 18% of the linoleate requirement. Rat liver and heart phospholipids were analyzed by gas/liquid chromatography for fatty acids, and liver, microsomes were assayed for desaturase (acyl-CoA, hydrogen-donor: oxidoreductase, EC 1.14.99.5) activities. Products of desaturation reactions measured analytically provided more information with greater statistical significance than did the enzymatic assays. Rats fed isomeric octadecenoic acids showed more severe essential fatty acid deficiency than did saturated-fat and control groups. The suppression of linoleate metabolites was largely due to decreased delta 5 and delta 6 desaturase activities. At several levels of linoleate, the deficiency was more severe at the higher level of isomeric octadecenoic acids. Increasing the intake of linoleate to 7.5% of calories did not suppress deposition of isomeric unsaturated acids in tissue lipids.