Endogenous versus exogenous carbohydrate oxidation measured by stable isotopes in pre-pubescent children plus ¹³C abundances in foods consumed three days prior.

ABSTRACT:

Purpose

The purposes of the present study were to (a) examine resting metabolism, substrate utilization, and endogenous versus exogenous carbohydrate (CHO) oxidation before and after 30-g rapidly-digesting carbohydrate (RDC) ingestion using indirect calorimetry and breath test analysis of stable isotope concentrations in pre-pubescent children and (b) report the ¹³C abundances in foods consumed for three days prior.

Methods

Nineteen children (n = 10 boys, n = 9 girls) at Tanner stage I or II participated (mean age ± 95% CI = 9.84 ± 0.77 y) in this study. Food was administered to the children for three days preceding their scheduled breath tests. Breath tests and indirect calorimetry were performed after an 8-h fast before and 60 min following consumption of a 30-g simple RDC drink consisting of maltodextrin and sucrose. Open circuit spirometry and indirect calorimetry monitored resting metabolism and CHO oxidation. Separate breath samples were taken every 15 min. Samples of all foods and breath samples were analyzed for ¹³C and ¹²C abundances with a stable-isotope mass spectrometer.

Results

¹³C in expired breath samples were -23.81 ± 1.64‰ at baseline and increased every 15 min after consumption of the CHO drink (p < 0.001-0.009). Cumulative total, endogenous, and exogenous CHO utilization increased during the post-prandial period (p < 0.001). Endogenous CHO oxidation was consistently greater than exogenous CHO oxidation (p < 0.001-0.002).Blood glucose was elevated from baseline at 30- and 60-min post-prandial (p < 0.001). Insulin did not change over time (p = 0.184).

Conclusions

The foods provided during the 3-day controlled diet effectively minimized ¹³C variation prior to metabolic testing. The ¹³C abundances of foods reported herein should serve as practical recommendations to reduce ¹³C intake before breath tests. While endogenous CHO oxidation remained greater in proportion to exogenous CHO oxidation, these findings suggest that even a relatively small amount of RDC can increase exogenous CHO oxidation and blood glucose in normal-weight children. To further examine shifts in endogenous versus exogenous CHO utilization, we recommend that future studies take steps to minimize ¹³C variation before breath tests and examine changes in substrate metabolism at rest and during exercise in normal weight and overweight pre-pubescent children.

Clinical trial registration number

NCT03185884.

SUBMITTER: Shoemaker ME 

PROVIDER: S-EPMC7424810 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature