Galactose oxidation using 13C in healthy and galactosemic children

Galactosemia is an inborn error of galactose metabolism that occurs mainly as theoutcome of galactose-1-phosphate uridyltransferase (GALT) deficiency. The ability toassess galactose oxidation following administration of a galactose-labeled isotope(1-¹³C-galactose) allows the determination of galactose metabolism in apractical manner. We aimed to assess the level of galactose oxidation in both healthyand galactosemic Brazilian children. Twenty-one healthy children and seven childrenwith galactosemia ranging from 1 to 7 years of age were studied. A breath test wasused to quantitate ¹³CO₂ enrichment in exhaled air before andat 30, 60, and 120 min after the oral administration of 7 mg/kg of an aqueoussolution of 1-¹³C-galactose to all children. The molar ratios of¹³CO₂ and ¹²CO₂ were quantified by themass/charge ratio (m/z) of stable isotopes in each air sample by gas-isotope-ratiomass spectrometry. In sick children, the cumulative percentage of ¹³C fromlabeled galactose (CUMPCD) in the exhaled air ranged from 0.03% at 30 min to 1.67% at120 min. In contrast, healthy subjects showed a much broader range in CUMPCD, withvalues from 0.4% at 30 min to 5.58% at 120 min. The study found a significantdifference in galactose oxidation between children with and without galactosemia,demonstrating that the breath test is useful in discriminating children with GALTdeficiencies.