Acyl-carnitine esters dehydrogenase deficiency

Quantitation of urinary carnitine esters in a patient with medium-chain acyl-coenzyme A dehydrogenase deficiency effect of metabolic state and L-camitine therapy. 

Fig. 3.2.3 Profiles of acylcarnitines as their butyl esters in plasma (precursor of m/z 85 scan) of a normal control (a) and three patients with elevated Gi-acyl carnitine (m/z 288 peak 4) that represents primarily butyrylcarnitine in a patient with short-chain acyl-CoA dehydrogenase (SCAD) deficiency (b), isobutyrylcarnitine in a patient with isobutyryl-CoA dehydrogenase (IBDH) deficiency (c), and a natural isotope of formiminoglutamate (FIGLU m/z 287 peak 3) in a patient with glutamate formimino-transferase deficiency (d). Peak 1 free carnitine (m/z 218), peak 2 acetylcarnitine (C2 m/z 260). The asterisks represent the internal standards (from left to right) d3-acetylcarnitine (C2 m/z 263), d3-propionylcarnitine (C3 m/z 277), d3-butyrylcarnitine (C4 m/z 291), d3-octanoylcarnitine (C8 m/z 347), d3-dodecanoylcarnitine (Ci, m/z 403), and d3-pal-mitoylcarnitine (Ci6 m/z 459)...

Figure 55-14 Plasma profiles of plasma acylcarnitine butyl-ester derivatives. A, Normal control. B, Propionic acidemia. C, Short-chain acyl-CoA dehydrogenase deficiency. D, Isovaleric acidemia. E, Medium-chain acyl-CoA dehydrogenase deficiency. F, Very long-chain acyl-CoA dehydrogenase deficiency. G, Long-chain L-3-hydroxy acyl-CoA dehydrogenase deficiency.The symbol marks internal standards [ Hjj-acetylcarnitine (m/z 263) [ HaJ-propionylcarnitine (m/z 277) fH ]-butyrylcarnitlne (m/z 295) pHal-octanoylcarnitine (m/z 347) [ Haj-dodecanoylcarnltine (m/z 403) [ Haj-palmitoy I carnitine (m/z 459).

Several diseases are known that result in elevations in tissues and fluids of various esters of carnitine and reduce the availability of free carnitine, which is normally synthesized by humans and is necessary for the transport of long-chain fatty acids into mitochondria for oxidation. In several disorders arising from acyl-CoA dehydrogenase deficiencies, the accumulation of the acyl-CoA substrate frequently sequesters coenzyme A and reduces its availability for other unrelated but important and otherwise competent pathways. Carnitine administration can displace and make available much of the coenzyme A that had been isolated, and stimulate the excretion of the accumulating acidic metabolites now esterified to carnitine. Detection of reduced levels of serum or urinary free carnitine and elevations of esterified carnitine is therefore useful for diagnosis of a variety of metabolic disorders, among them congenital inability to synthesize carnitine. In this disorder, carnitine must be supplied by a carnitine-enriched diet as it is, in effect, a vitamin. 

Figure 7 Fast atom bombardment mass spectra obtained in glycerol matrix for quantitation of free carnitine and carnitine esters in the urines of a patient with medium-chain acyl-CoA dehydrogenase deficiency (A) and a patient with propionic acidaemia (B). The identities and concentrations of the annotated ions are listed in Table 2. The composition of the ions has been confirmed by measurements...

Carnitine and its esters (see [1]) cannot be introduced to the mass spectrometer by gas chromatography, as they incorporate quaternary amine functions and will decompose in the attempt. Fast atom bombardment (FAB) and electrospray ionization (ESI) can use the formal charge on the quaternary amine function to advantage, as carnitine and its esters are very easily desorbed from glycerol on the FAB probe and from aerosol sprays in ESI. Eigure 7A illustrates the use of EAB in the quantitation of carnitine and its esters excreted in the urine of a patient presenting with a severe dicarboxylic aciduria associated with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. 

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