Protein and leucine metabolism in maple syrup urine disease

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · American Journal of Physiology; (USA)

OSTI ID:7043962

Thompson, G N; Bresson, J L; Pacy, P J; Bonnefont, J P; Walter, J H; Leonard, J V; Saudubray, J M; Halliday, D ^[1]

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1. Clinical Research Centre, Harrow (England)

Constant infusions of (13C)leucine and (2H5)phenylalanine were used to trace leucine and protein kinetics, respectively, in seven children with maple syrup urine disease (MSUD) and eleven controls matched for age and dietary protein intake. Despite significant elevations of plasma leucine (mean 351 mumol/l, range 224-477) in MSUD subjects, mean whole body protein synthesis (3.78 +/- 0.42 (SD) g.kg-1. 24 h-1) and catabolism (4.07 +/- 0.46) were similar to control values (3.69 +/- 0.50 and 4.09 +/- 0.50, respectively). The relationship between phenylalanine and leucine fluxes was also similar in MSUD subjects (mean phenylalanine-leucine flux ratio 0.35 +/- 0.07) and previously reported adult controls (0.33 +/- 0.02). Leucine oxidation was undetectable in four of the MSUD subjects and very low in the other three (less than 4 mumol.kg-1.h-1; controls 13-20). These results show that persistent elevation in leucine concentration has no effect on protein synthesis. The marked disturbance in leucine metabolism in MSUD did not alter the relationship between rates of catabolism of protein to phenylalanine and leucine, which provides further support for the validity of the use of a single amino acid to trace whole body protein metabolism. The minimal leucine oxidation in MSUD differs from findings in other inborn metabolic errors and indicates that in patients with classical MSUD there is no significant route of leucine disposal other than through protein synthesis.

• OSTI ID: 7043962
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 258; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550901* -- Pathology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AGE GROUPS
AMINO ACIDS
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHILDREN
DEUTERIUM
DISEASES
EVEN-ODD NUCLEI
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
ISOTOPES
LEUCINE
LIGHT NUCLEI
METABOLISM
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PATHOGENESIS
PHENYLALANINE
PROTEINS
STABLE ISOTOPES
TRACER TECHNIQUES
UROGENITAL SYSTEM DISEASES