Extended indirect calorimetry with isotopic CO2 sensors for prolonged and continuous quantification of exogenous vs. total substrate oxidation in mice

Abstract

Indirect calorimetry (InCa) estimates whole-body energy expenditure and total substrate oxidation based on O 2 consumption and CO 2 production, but does not allow for the quantification of oxidation of exogenous substrates with time. To achieve this, we incorporated 13 CO 2 and 12 CO 2 gas sensors into a commercial InCa system and aimed to demonstrate their performance and added value. As a performance indicator, we showed the discriminative oscillations in 13 CO 2 enrichment associated with food intake in mice fed diets containing naturally low (wheat) vs high (maize) 13 C enrichment. To demonstrate the physiological value, we quantified exogenous vs total carbohydrate and fat oxidation continuously, in real time in mice varying in fat mass. Diet-induced obese mice were fed a single liquid mixed meal containing 13 C-isotopic tracers of glucose or palmitate. Over 13 h, ~70% glucose and ~48% palmitate ingested were oxidised. Exogenous palmitate oxidation depended on body fat mass, which was not the case for exogenous glucose oxidation. We conclude that extending an InCa system with 13 CO 2 and 12 CO 2 sensors provides an accessible and powerful technique for real-time continuous quantification of exogenous and whole-body substrate oxidation in mouse models of human metabolic physiology.

The Effect of Partly Replacing Vegetable Fat with Bovine Milk Fat in Infant Formula on Postprandial Lipid and Energy Metabolism: A Proof‐of‐principle Study in Healthy Young Male Adults

“…[27][28][29] Another explanation might be the oxidation of FAs by intestinal enterocytes directly after uptake. [30,31] Interestingly, the increase in fat oxidation was not seen in mice that were fed labelled fatty acids, [32] rather than providing lipids as TG as is done in this study. So possibly, the initial increase in FA oxidation compared to glucose oxidation may be associated with intestinal handling of TG, but this remains to be tested.…”

In Vivo and In Vitro Quantification of Glucose Kinetics: From Bedside to Bench

“…If one can assume the pool size is similar between groups or constant over the experimental time period, then the simple comparison of FSRs is valid [ 70 , 71 ]. The incorporation model can be applicable to the assessments of the kinetic calculations of various compounds, including the FSR of individual proteins [ 72 , 73 ] and subgroups of proteins (mitochondrial, sarcoplasmic, and mixed muscle protein) [ 74 – 79 ], the substrate oxidation rate [ 6 , 80 – 82 ], the DNA synthesis rate (thus cell division) [ 59 , 60 ], the nitric oxide synthesis rate from its precursor arginine [ 83 – 86 ], and GNG [ 30 , 87 ], the latter of which will be discussed in the following section in detail.…”

“…FSR, fractional synthesis rate. Copyright © 2020 Korean Endocrine Society teins (mitochondrial, sarcoplasmic, and mixed muscle protein) [74][75][76][77][78][79], the substrate oxidation rate [6,[80][81][82], the DNA synthesis rate (thus cell division) [59,60], the nitric oxide synthesis rate from its precursor arginine [83][84][85][86], and GNG [30,87], the latter of which will be discussed in the following section in detail.…”

A Lowly Digestible-Starch Diet after Weaning Enhances Exogenous Glucose Oxidation Rate in Female, but Not in Male, Mice

“…BW and BC were determined directly before and after InCa measurement. The technological extensions of the InCa system and other operational settings and procedures have been described previously [12,13,14].…”