Metabolic handling of C labelled tripalmitin in healthy controls and patients with cystic fibrosis

Aim—To examine the gastrointestinal handling and metabolic disposal of emulsified [1-C]palmitic acid esterified into a triglyceride in nine healthy children and seven patients with cystic fibrosis on enzyme replacement treatment. Methods—After an overnight fast, each child was given 10 mg/kg body weight [1,1,1-C]tripalmitin with a standardised test meal of low natural C abundance. The total enrichment of C was measured using isotope ratio mass spectrometry in stool collected for a period of up to five days and in breath samples collected over a 24 hour period. Results—The mean proportion of administered C label excreted in stool was 6% (range, 1–12.7%) in healthy children and 24.6% (range, 0–64%) in patients with cystic fibrosis. Healthy children excreted 31.3% of the administered label on their breath (range, 14.2–42.9%). Correcting the excretion of administered C label on the breath for diVerences in digestion and absorption in patients with cystic fibrosis increased the diVerence between individuals from 0–31.3% of administered dose (mean, 17.9%) to 0–49.1% of absorbed dose (mean, 23.2%) and was poorly related to the amount of C label in stool. Conclusion—Measurements of breath 13CO2 do not consistently reflect the gastrointestinal handling of emulsified C labelled tripalmitin because of diVerences in digestion and absorption in cystic fibrosis. Further studies need to examine whether “breath tests” alone can predict with confidence the gastrointestinal handling of other C labelled triglycerides and fatty acids. (Arch Dis Child 1998;79:44–47)