Effects of timing, sex, and age on site-specific gastrointestinal permeability testing in children and adults

Abstract

Objectives: Measurement of gastrointestinal (GI) permeability is commonly used in research and often used clinically. Despite its utility, little is known about sugar excretion timeframes or the potential effects of age and sex on GI permeability testing. We seek to determine the timeframes of sugar excretion and the potential effects of age and sex on urinary recovery of the sugars.

Subjects and methods: Healthy adults (n = 17) and children (n = 15) fasted 4 hours after the evening meal and then ingested a solution of sucrose, lactulose, mannitol, and sucralose. Urine was collected at 30, 60, and 90 minutes after ingestion and then each time the subjects voided during the next 24 hours. Each urine void was collected separately.

Results: Median age for the adults was 47.5 years (range 21-57 years) and for children 10 years (range 5-17 years). There were no differences between children and adults in mean percent dose of sugar recovered. The time of peak urinary recovery of the sugars was generally similar between children and adults. Sucrose urinary recovery declined with age (P = 0.008; r2 = 0.19) unrelated to sex. Lactulose and sucralose urinary recovery declined with age in females (P = 0.05, r2 = 0.24 and P = 0.011, r2 = 0.41; respectively) but not in males.

Conclusions: Overall, sugar urinary recovery is comparable in children and adults. Specific sugar urinary recovery may change as a function of age and/or sex. These results need to be taken into account when planning and interpreting gastrointestinal permeability studies.

Figures

Figure 1

Percent urinary recovery of sucrose (top left), lactulose (top right), mannitol (bottom left), and sucralose (bottom right) at each time point (mean ± SEM)

Figure 2

Cumulative urinary recovery of sucrose, lactulose, mannitol, and sucralose normalized to 100% (mean ± SEM)

Figure 3

Sugar ratios at each time point (mean ± sem). Sucrose/lactulose (top left), lactulose/mannitol (top right), and sucralose/lactulose (bottom left)

Figure 4

Sucrose permeability vs. age. Sucrose permeability (percent urinary recovery) declined as a function of age. The data are log transformed.

Figure 5

Lactulose permeability and lactulose/mannitol ratio vs. age. Lactulose permeability (percent urinary recovery) and the lactulose/mannitol ratio declined with age in females but not in males.

Figure 6

Sucralose permeability vs. age. Sucralose permeability (percent urinary recovery) declined with age in females but not in males.