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

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 ¹³ C 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 ¹³ C and ¹² C abundances with a stable-isotope mass spectrometer.
Results: ¹³ C 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 ¹³ C variation prior to metabolic testing. The ¹³ C abundances of foods reported herein should serve as practical recommendations to reduce ¹³ C 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 ¹³ C 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.
Competing Interests: Current disclosures for JTC: From 2001-present, Dr. Cramer’s research has been externally funded by 22 separate project grants from 10.13039/100011947Abbott Nutrition, Nebraska Beef Council, Nebraska Extension, Stepan Lipid Nutrition, Rock Creek Pharmaceuticals, General Nutrition Corporation, Experimental & Applied Sciences, Nutricia, and the University of Nebraska Agriculture Research Division with funds provided by the Hatch Act (Agency: 10.13039/100000199U.S. Department of Agriculture, 10.13039/100005825National Institute for Food and Agriculture: Accession No: 1000080; Project No: NEB-36-078). From 2010 to 2013, Joel was an expert witness or expert consultant in 10 separate legal matters representing defendants Vital Pharmaceuticals, MusclePharm, and Celsius. From 2008 to 2016, Dr. Joel T. Cramer was a paid consultant for either Abbott Nutrition, General Nutrition Center, ErgoGenix/ErgoPharm, and/or Corr-Jensen Labs. From 2018-present, Joel has served as a paid consultant for Regeneron Pharmaceuticals. VAM is an employee and stockholder of Abbott Nutrition. MES, ZMG, BDM, and TJL did not report any potential conflicts of interest.
(© 2020 The Authors.)