2- Hydroxybutyric aciduria

Oast house urine disease (methionine malabsorption syndrome, 2-hydroxybutyric aciduria) Methionine, 2-hydroxybutyric, phenylpyruvic and the branched-chain keto acids especiaUy 2-oxoisovaleric Methionine malabsorption (amino acid-transport defect) (Chapter 16)... 

Gupta, M Greven, R., Jansen, E. E., et al. (2002) Therapeutic intervention in mice deficient for succinate semialdehyde dehydrogenase (gamma-hydroxybutyric aciduria). J. Pharmacol. Exp. Ther. 302,180-187. 

The educational role fulfilled by active participation in EQA is demonstrable. Redistribution of the same sample following a gap of several years indicated a detection rate that improved by 20% for mevalonic aciduria, L-2-hydroxyglutaric aciduria, Canavan disease, 4-hydroxybutyric aciduria and long-chain hyroxy-acyl CoA dehydrogenase deficiency [6]. These results probably reflect the fact that many participants encounter rarer conditions for the first time as a member of an EQA scheme. Stored residual samples from such EQA schemes and unlabelled chromatograms can also be used as a valuable training aid or even a competency test for analysts. 

Figure 20.20 Pathways of branched-chain amino acid metabolism. A, B, C, D, E, and F indicate defects in valinemia, maple syrup urine disease, isovaleric acidemia, /3-hydroxyisovaleric aciduria, a-methyl-j3-hydroxybutyric aciduria, and methylmalonic aciduria, respectively.

Gibson KM. y-Hydroxybutyric aciduria a biochemist s education from a heritabie disorder of GABA metaboiism. J inherit Metab Dis 2005 28 247-265. 

Concentrations of various carboxylic acids in human body fluids reflect some of the major metabolic processes of the body. These metabolites apparently originate from lipid and amino acid metabolism the major metabolic defects are frequently associated with unbalanced concentrations of these acidic substances. One of the most widely occurring conditions of this kind is ketoacidosis in diabetic disease high concentrations of the so-called ketone bodies (3-hydroxybutyric acids, acetoacetic acid and others) are the traditional hallmarks of ketoacidosis. Many additional acidurias were discovered (particularly during the last 15 years) in major part due to the availability of GC and GC/MS techniques. Acidurias are among the serious medical conditions that are usually a result of genetic aberration (enzyme deficiencies), but environmental factors or nutritional deficiency could occasionally be involved. These conditions are characterized by either (a) drastically enhanced excretion of normal metabolic intermediates, or (b) excretion of unusual metabolites that are produced from the accumulated intermediates via alternate biochemical pathways. Many acidemic conditions have now been documented in the literature, and the role of GC in such medical discoveries has been adequately stressed in the recent reviews of Jellum [15] and Tanaka and Hine [373]. 

The concentration and associated ratio of the ketone bodies, aceto-acetate and 3-hydroxybutyrate, may also be helpful [15, 18, 19]. Ketosis and keto-aciduria are observed in certain patients with a mitochondrial disorder. A non-physiological increase of ketone bodies postprandially may be another indicator of a mitochondrial defect (Saudubray et al). Increased 3-hydroxybutyrate/acetoacetate ratio may suggest a defect in the respiratory chain in liver tissue. 

Diagnosis may be made using gas chromatography alone (Gompertz et al, 1974), and this may be illustrated by reference to methylmalonic aciduria. Fig. 9.3 shows the chromatogram of amniotic fluid containing 9 tg of methyl-malonate ml as its methyl ester, obtained by ether extraction. Because of the possible confusion of methylmalonate with 3-hydroxybutyrate, a normal amniotic fluid constituent (Section 8.1), or 2-methyl-3-hydroxybutyrate, depending on the GC column used, these authors advised the use of mass... 

Fig. 10.1 Metabolites in the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease). Extracted using ethyl acetate and separated as their trimethylsilyl-oxime derivatives on a 25 m SE-30 capillary column, using temperature programming from 80°C to 110°C at 0.5°C min and an injection split ratio 1 12 at a temperature of 250°C. The peaks marked R are due to solvent and reagents. Peak identifications are 1, lactic 2, 2-hydroxyisobutyric 3, 2-hydroxybutyric 4, pyruvic 5, 3-hydroxybutyric 6, 2-hydroxyisovaleric 7, 2-oxobutyric 8, 2-methyl-3-hydroxy-isovaleric 10, a and b, 2-oxoisovaleric 11, acetoacetic 12, 2-hydroxyisocaproic 13, 2-hydroxy-3-methyl- -valeric 14, 2-oxo-3-methyl-/i-valeric (14a L- 14b D-) 15, 2-oxoisocaproic acids. The internal standard was malonic acid. (Redrawn with modifications from Jellum etal., 1976)...

Fig. 10.3 Chromatogram of organic acids extracted from the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease), extracted and separated as described in the legend to Fig. 10.2. The chromatogram illustrates the overlapping peaks in the regions occupied by 3-hydroxybutyric, 2-hydroxyisovaleric and 2-oxoisovaleric acids (peak 1) and 2-oxo-3-methyl-valeric, 2-hydroxyisocaprioic and 2-oxoisocaproic acids (peak 2) and phosphate (peak 3). Other peaks of interest are (4) citric, (5) 4-hydroxyphenyl-lactic, (6) 4-hydroxyphenylpyruvic, (7) n-tetracosane (standard) and (8) -hexacosane (standard). (Compare with Fig. 10.4.)...

Gompertz, D., Saudubray, J.M., Charpentier, C., Bartlett, K., Goodey, P.A. and Draffan, G.H. (1974), A defect in L-isoleucine metabolism associated with a-methyl-/S-hydroxybutyric and a-methylacetoacetic aciduria Quantitative in vivo and in vitro studies. Clin. Chim. Acta, 57,269. 

Halvorsen, S., Stokke, O. and Jellum, E. (1979), A varient form of 2-methyl-3-hydroxybutyric and 2-methylacetoacetic aciduria. Acta. Paediatr. Scand., 68,123. 

Fig. 13.2 Chromatogram of organic acids extracted using ethyl acetate from the urine from a patient (S.G.) with 2-oxoadipic aciduria and separated as their trimethylsilyl derivatives on 5 per cent SE-52 on Chromosorb W (AW-DMCS, 100-120 mesh) by temperature programming from 75°C to 220°C at 2°C min with 10 min initial and final isothermal delays. Peak identifications are 1, 3-hydroxybutyrate 2, urea 3, glutarate 4, butenedicarboxylate 5,4-phenylbutyrate (internal standard) 6,2-hydroxyglutarate 7, 2-oxoglutarate 8, 2-hydroxyadipate 9, 2-oxoadipate 10, aconitate. (Redrawn with modifications from Przyrembel et al, 1975)...

Greatly increased lactic aciduria is generally associated with an increased excretion of 2-hydroxy-n-butyric acid (Pettersen et al., 1973 Landaas and Pettersen, 1975) irrespective of the underlying cause of the increased lactate excretion. This acid is thought to arise from 2-oxobutyric acid, a metabolite of methionine, homocystine, cystathionine, serine and threonine, owing to the effect of the changes in NADH/NAD+ ratio in lactic acidosis (Pettersen etaL, 1973). The occurrence of 2-hydroxybutyrate in urine would thus imply an imbalance in cytosolic NADH/NAD and this metabolite may be of value in the further assessment of patients with lactic acidosis. 

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