Gastrointestinal handling of [1-13C]palmitic acid in healthy controls and patients with cystic fibrosis

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Abstract
AIM To examine the gastrointestinal handling of [1-13C]palmitic acid given as the free acid by measuring the excretion of 13C label in stool in 16 healthy children and 11 patients with cystic fibrosis on their habitual enzyme replacement treatment. METHODS After an overnight fast, each child ingested 10 mg/kg body weight [1-13C]palmitic acid with a standardised test meal of low natural 13C abundance. A stool sample was collected before the test and all stools were collected thereafter for a period of up to five days. The total enrichment of 13C in stool and the species bearing the13C label was measured using isotope ratio mass spectrometry. RESULTS The proportion of administered13C label excreted in stool was 24.0% (range 10.7–64.9%) in healthy children and only 4.4% (range 1.2–11.6%) in cystic fibrosis patients. The enrichment of 13C in stool was primarily restricted to the species consumed by the subjects (that is as palmitic acid). CONCLUSION There does not appear to be a specific defect in the absorption of [1-13C]palmitic acid in patients with cystic fibrosis. The reasons why cystic fibrosis patients appear to absorb more of this saturated fatty acid than healthy children is not clear and requires further investigation.