Gastric and Postgastric Processing of ¹³ C Markers Renders the ¹³ C Breath Test an Inappropriate Measurement Method for the Gastric Emptying of Lipid Emulsions in Healthy Adults

Abstract

Breath tests (BTs) present an alternative gastric-emptying (GE) measure. However, their efficacy in the measurement of the GE rate of lipid emulsions (LEs) is unknown. The objective of this work was to investigate the validity of C BTs as a measure of fat GE rate in LEs. The lipophilic C octanoate (OCC) BT marker was investigated for fat GE with the hydrophilicC sodium acetate (ACC) and the triglyceride C trioctanoin (TCC) markers as comparators. Data from 2 randomized studies were combined [50 healthy participants; 25 men, mean ± SD age: 23 ± 2.8 y; mean ± SD body mass index (in kg/m): 22.4 ± 1.7]. Each participant was given either an acid-stable LE (LE1) or an acid-unstable LE (LE4) at each visit. Twenty-three participants underwent simultaneous MRI. The effect of LEs on CO excretion profiles was determined. The BT half-emptying times (BT T) were validated with the MRI half-emptying time of the ingested fat volume (MRI T). The effect of LEs on CO excretion depended on the properties of the C marker. T for OCC was shorter by 98 min for LE1 than for LE4 ( < 0.001). Other markers showed either no LE dependency or a longer T for LE1 than for LE4. No difference in T between OCC and ACC was detected in LE1. In LE4, the T was longer by 154 min ( 0.0001). There was some concordance between MRI T and OCC BT T for LE1 ( = 0.7). No other marker showed any concordance with fat GE. C-Nuclear magnetic resonance in vitro findings were compatible with changes in the kinetics of phase transfer of OCC dependent on its protonation state. The structure of fat present in the stomach affects CO excretion. The chemical properties of the C marker and their gastric and postgastric interaction with fat rendersCO excretion an inappropriate measure of LE emptying in healthy adults. This trial was registered at clinicaltrials.gov as NCT02226029 and NCT02602158.

Indirect vs direct assessment of gastric emptying: A randomized crossover trial comparing C‐isotope breath analysis and MRI

“…Very recent evidence for this effect of gastric lipid content on tracers has been reported by Parker et al . This study used acid stable and unstable stimuli, and compared three differed tracing agents (including acetate and octanoic acid) with MRI measurements to assess whether the distribution of tracing agents was influenced by the food matrix.…”

“…The current study assessed GE over 90 minutes with both BT and MRI, whereas other studies kept collecting breath samples after finishing the MRI measurements . Our MRI measurements showed that at the end of the sampling time not all of the meal had emptied from the stomach.…”

“…The current study assessed GE over 90 minutes with both BT and MRI, whereas other studies kept collecting breath samples after finishing the MRI measurements. 10,11 Our MRI measurements showed that at the end of the sampling time not all of the meal had emptied from the stomach. For research in which relative GE rates between groups are compared, gathering breath samples for 90 minutes can be sensitive enough to measure different emptying rates as these differences occur already quickly after ingestion.…”

“…33 With fat containing foods intragastric lipid layering can occur. 34,35 Intragastric lipid layering is of concern as experimental foods may contain a fat compo- Very recent evidence for this effect of gastric lipid content on tracers has been reported by Parker et al 11 This study used acid stable and unstable stimuli, and compared three differed tracing agents (including acetate and octanoic acid) with MRI measurements to assess whether the distribution of tracing agents was influenced by the food matrix. Their results show that octanoic acid measurements correlate better with fat movement through the stomach than acetate and 13 C trioctanoin measurements, indicating that the chemical properties of the tracer may have influenced GE.…”

“…It was suggested that these differences were caused by dilution by gastric secretions and the composition of the meal . Accordingly, tracer interactions with fat components in a test meal have been shown to affect tracer absorption and subsequent excretion and thus tracer‐based estimates of GE.…”