Biotinidase deficiency: metabolites in CSF

The neurology of biotinidase deficiency

Biotinidase deficiency is an autosomal recessively inherited metabolic disorder in which the enzyme, biotinidase, is defective and the vitamin, biotin, is not recycled. Individuals with biotinidase deficiency, if not treated with biotin, usually exhibit neurological and cutaneous abnormalities. Biotin treatment can ameliorate or prevent symptoms. Biotinidase deficiency meets the major criteria for inclusion in newborn screening programs. With the advent of universal newborn screening for the disorder, the "window-of-opportunity" to characterize the consequences of the untreated disease is essentially gone. To understand the neurology of biotinidase deficiency, we must depend on what is already known about symptomatic individuals with the disorder. Therefore, in this review, the neurological findings of symptomatic individuals with profound biotinidase deficiency have been compiled to catalog the characteristic features of the disorder and the consequences of biotin treatment on these findings. In addition, based on the available evidence, I have speculated on the cause of neurological problems associated with the disorder. Future studies in biotinidase-deficient animals should allow us to demonstrate more definitively if these speculations are correct.

Plasma metabolomic profiles reflective of glucose homeostasis in non-diabetic and type 2 diabetic obese African-American women

Insulin resistance progressing to type 2 diabetes mellitus (T2DM) is marked by a broad perturbation of macronutrient intermediary metabolism. Understanding the biochemical networks that underlie metabolic homeostasis and how they associate with insulin action will help unravel diabetes etiology and should foster discovery of new biomarkers of disease risk and severity. We examined differences in plasma concentrations of >350 metabolites in fasted obese T2DM vs. obese non-diabetic African-American women, and utilized principal components analysis to identify 158 metabolite components that strongly correlated with fasting HbA1c over a broad range of the latter (r = −0.631; p<0.0001). In addition to many unidentified small molecules, specific metabolites that were increased significantly in T2DM subjects included certain amino acids and their derivatives (i.e., leucine, 2-ketoisocaproate, valine, cystine, histidine), 2-hydroxybutanoate, long-chain fatty acids, and carbohydrate derivatives. Leucine and valine concentrations rose with increasing HbA1c, and significantly correlated with plasma acetylcarnitine concentrations. It is hypothesized that this reflects a close link between abnormalities in glucose homeostasis, amino acid catabolism, and efficiency of fuel combustion in the tricarboxylic acid (TCA) cycle. It is speculated that a mechanism for potential TCA cycle inefficiency concurrent with insulin resistance is “anaplerotic stress” emanating from reduced amino acid-derived carbon flux to TCA cycle intermediates, which if coupled to perturbation in cataplerosis would lead to net reduction in TCA cycle capacity relative to fuel delivery.

Biotin-responsive basal ganglia disease maps to 2q36.3 and is due to mutations in SLC19A3

Biotin-responsive basal ganglia disease (BBGD) is a recessive disorder with childhood onset that presents as a subacute encephalopathy, with confusion, dysarthria, and dysphagia, and that progresses to severe cogwheel rigidity, dystonia, quadriparesis, and eventual death, if left untreated. BBGD symptoms disappear within a few days with the administration of high doses of biotin (5-10 mg/kg/d). On brain magnetic resonance imaging examination, patients display central bilateral necrosis in the head of the caudate, with complete or partial involvement of the putamen. All patients diagnosed to date are of Saudi, Syrian, or Yemeni ancestry, and all have consanguineous parents. Using linkage analysis in four families, we mapped the genetic defect near marker D2S2158 in 2q36.3 (LOD=5.9; theta=0.0) to a minimum candidate region (approximately 2 Mb) between D2S2354 and D2S1256, on the basis of complete homozygosity. In this segment, each family displayed one of two different missense mutations that altered the coding sequence of SLC19A3, the gene for a transporter related to the reduced-folate (encoded by SLC19A1) and thiamin (encoded by SLC19A2) transporters.

The clinical spectrum of biotin-treatable encephalopathies in Saudi Arabia

Ten patients with biotin-dependent, chronic progressive encephalopathies were studied retrospectively. In four patients, the underlying disease was either total or partial deficiency of biotinidase. In one patient, the disease was caused by a lack of holocarboxylase synthetase activity. Four patients presented with Leigh encephalopathy. However, a biochemical defect could not always be confirmed. All patients required the administration of large doses of biotin to maintain normal neurologic function.

Neurological manifestations of organic acid disorders

Neurological manifestations are very common and can be the leading and/or presenting feature in organic acid disorders, sometimes in the absence of metabolic derangement. Review of the time course and presentation of neurological disease in organic acid disorders reveals characteristic clinical findings of ataxia, myoclonus, extrapyramidal symptoms, metabolic stroke and megalencephaly. A group of organic acid disorders presents exclusively with neurological symptoms. These include glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type I), succinic semialdehyde dehydrogenase deficiency (4-hydroxybutyric aciduria), mevalonic aciduria, N-acetylaspartic aciduria (Canavan disease) and L-2-hydroxyglutaric aciduria. As a group these "cerebral" organic acid disorders appear to remain often undiagnosed and their true incidence is much less well-known than that of the "classical" organic acid disorders. Unfortunately, stringent guidelines for a clinical preselection of neuropaediatric patients to be investigated for organic acid disorders cannot be provided. Today, screening for neurometabolic disorders should be as comprehensive as possible and include determinations of amino acids, purines and pyrimidines and markers of peroxisomal function in addition to organic acid analysis.

The effects of biotin deficiency on organic acid metabolism: increase in propionyl coenzyme A-related organic acids in biotin-deficient rats

Volatile organic acid levels in plasma and tissues and nonvolatile organic acid levels in urine of biotin-deficient (BD) rats were measured and compared with other factors of biotin deficiency. Biotin levels and the activities of propionyl coenzyme A (CoA) carboxylase (PCC) in the livers of these rats were decreased, respectively, to 22% +/- 3% and 3.6% +/- 0.3% of the average values of pair-fed controls. Plasma concentrations of propionate were higher (15 to 223 micrograms/mL) than those of controls (5 to 7 micrograms/mL), whereas plasma levels of 3-methylcrotonate were only minimally increased as compared with those of controls. Concentrations of these volatile acids in the tissues were similarly increased, although those in brain showed less remarkable increases as compared with levels in other tissues. In the urine of BD rats, large amounts of organic acids derived from propionyl CoA, as well as those from 3-methylcrotonyl CoA, were excreted. Plasma propionate levels were not apparently related to the severity of clinical symptoms, biotin levels, or carboxylase activities, but were related to the amounts of urinary ketone bodies, lactate, and some of the organic acids derived from branched-chain amino acids, including those from propionyl CoA.

Quantitative organic acid analysis in cerebrospinal fluid and plasma: reference values in a pediatric population

Quantitative reference values for the concentrations of organic acids in cerebrospinal fluid (CSF) and plasma, as well as ratios of individual organic acids between CSF and plasma, were determined in twenty-three pairs of samples from pediatric patients. Twenty-six organic acids were present and quantifiable in all or the majority of plasma and CSF specimens (limit of detection 1 mumol/l). There were substantial differences between subgroups of organic acids, best reflected by the ratios of individual acids between CSF and plasma. Metabolites related to fatty acid oxidation were present in CSF in substantially lower amounts than in plasma. Organic acids related to carbohydrate and energy metabolism and to amino acid degradation were present in CSF in equal or slightly lower amounts than in plasma. Finally, some organic acids were found in substantially higher amounts in CSF than in plasma, e.g. glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate. Quantitation of organic acids in CSF and plasma should aid diagnosis and monitoring of treatment of patients with organic acid disorders.

Cerebral metabolic change after treatment in biotinidase deficiency

A 13.5-year-old boy with biotinidase deficiency was studied 8 days before and 5 months after biotin treatment by positron emission tomography (PET) and computerized electroencephalographic topography (CET). With biotin treatment there was a marked improvement in the presenting symptom of loss of visual acuity and a more modest recovery in spastic quadraparesis. By PET scanning, the relative metabolic rate for glucose was more than 2 standard deviations lower in the temporal and occipital cortices than in adult or age-matched controls. With biotin treatment, these values rose to normal limits for both control groups. By CET, normalized EEG equivalent to the relative glucose metabolic rate showed asymmetric slowing in the left temporal and frontal regions before treatment, whereas none of the 32 leads exceeded normal limits of delta, theta, alpha or beta after treatment. These results suggest a strong correlation between clinical, metabolic and electrical measures of brain function as related to biotin treatment in biotinidase deficiency.

Physiology and pathophysiology of organic acids in cerebrospinal fluid

Concentrations of organic acids in cerebrospinal fluid (CSF) appear to be directly dependent upon their rate of production in the brain. There is evidence that the net release of short-chain monocarboxylic acids from the brain is a major route for removing these products of cerebral metabolism. Concentrations of organic acids in blood and CSF are largely independent of each other. Quantitative reference values for the concentrations of organic acids in CSF and plasma as well as ratios of individual organic acids between CSF and plasma were determined in 35 pairs of samples from paediatric patients. Over 25 organic acids were quantifiable in all or in the majority of CSF and/or plasma specimens (limit of detection 1 mumol/L). There were substantial differences in the CSF/plasma ratios between subgroups of organic acids. Metabolites related to fatty-acid oxidation were present in CSF in substantially less amounts than in plasma. Organic acids related to carbohydrate and energy metabolism and to amino acid degradation were present in CSF in the same amounts as or slightly smaller amounts than in plasma. Finally, some organic acids were found in substantially higher amounts in CSF than in plasma, e.g. glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate. Studies of organic acids in CSF and plasma samples are presented from patients with 'cerebral' lactic acidosis, disorders of propionate and methylmalonate metabolism, glutaryl-CoA dehydrogenase deficiency and L-2-hydroxy-glutaric aciduria. It became apparent that derangements of organic acids in the CSF may occur independently of the systemic metabolism. Quantitative organic acid analysis in CSF will yield new information on the pathophysiology in the central nervous system (CNS) of these disorders and may prove necessary for successful monitoring of treatment of organoacidopathies, which present mainly with neurological disease. For example, in glutaryl-CoA dehydrogenase deficiency the urinary excretion of glutarate appears to be an inadequate parameter for monitoring the effect of dietary therapy, without plasma and CSF determinations. In L-2-hydroxyglutaric aciduria the elevation of L-2-hydroxyglutarate was found to be greater in CSF than in plasma. In addition, some other organic acids, glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate, were also elevated in the CSF of the patients out of proportion to normal levels in plasma and urine. High concentrations of an unknown compound, which was tentatively identified as 2,4-dihydroxyglutarate, were found in the CSF of patients with L-2-hydroxyglutaric aciduria.(ABSTRACT TRUNCATED AT 400 WORDS)

Biotin-responsive infantile encephalopathy: EEG-polygraphic study of a case

A case of an infant suffering from progressive lethargy, sparse scalp hair, autistic-like behavior, myoclonias, and drug-resistant generalized seizures is reported. Laboratory investigations revealed, in the absence of metabolic acidosis, an increased urinary excretion of 2-ketoglutaric acid and a small peak of 3-hydroxyisovaleric acid. The serum biotinidase activity was 0.15 nmol min-1 ml-1 (normal range 5.2 +/- 0.9) in the propositus and 0.310 and 0.420 in her father and mother, respectively. The interictal EEG showed multifocal abnormalities; numerous seizures were recorded, with the pattern of true tonic-clonic fits, exceptional in infancy. Also myoclonias, auditory myoclonus, and repetitive startles were documented. Because of dramatic improvement of all symptoms and signs after starting biotin (5 mg twice daily), the authors suggest a therapeutical trial in all drug-resistant infantile seizures.