Real-Time Monitoring of Metabolism during Exercise by Exhaled Breath

Abstract

Continuous monitoring of metabolites in exhaled breath has recently been introduced as an advanced method to allow non-invasive real-time monitoring of metabolite shifts during rest and acute exercise bouts. The purpose of this study was to continuously measure metabolites in exhaled breath samples during a graded cycle ergometry cardiopulmonary exercise test (CPET), using secondary electrospray high resolution mass spectrometry (SESI-HRMS). We also sought to advance the research area of exercise metabolomics by comparing metabolite shifts in exhaled breath samples with recently published data on plasma metabolite shifts during CPET. We measured exhaled metabolites using SESI-HRMS during spiroergometry (ramp protocol) on a bicycle ergometer. Real-time monitoring through gas analysis enabled us to collect high-resolution data on metabolite shifts from rest to voluntary exhaustion. Thirteen subjects participated in this study (7 female). Median age was 30 years and median peak oxygen uptake (VO2max) was 50 mL·/min/kg. Significant changes in metabolites (n = 33) from several metabolic pathways occurred during the incremental exercise bout. Decreases in exhaled breath metabolites were measured in glyoxylate and dicarboxylate, tricarboxylic acid cycle (TCA), and tryptophan metabolic pathways during graded exercise. This exploratory study showed that selected metabolite shifts could be monitored continuously and non-invasively through exhaled breath, using SESI-HRMS. Future studies should focus on the best types of metabolites to monitor from exhaled breath during exercise and related sources and underlying mechanisms.

BreathXplorer: Processing Online Breathomics Data Generated from Direct Analysis Using High-Resolution Mass Spectrometry

“…Participants were instructed to withhold from consuming any food or drink (except water) for at least 1 h prior to the test. , Before breath data collection, participants rinsed their mouths with water. Subsequently, they took a deep breath through the nose and exhaled using a spirometry filter (MicroGardTM, Vyaire Medical, USA) for breath collection.…”

Exercise Metabolome: Insights for Health and Performance

“…Alteration of the urea cycle, which is responsible for ammonia detoxification, was also noted in response to inflammation induced by exercise [ 27 , 42 , 43 ]. Moreover, increased tryptophan degradation and upregulation of the kynurenine/tryptophan metabolic pathway was reported following acute high-intensity endurance exercise interventions [ 44 , 45 ]. While one study—Schenk et al—did not find a statistically significant alteration in kynurenine and tryptophan metabolites, it noted the resting control group showed lower levels of tryptophan degradation three weeks after the intervention than the intervention group [ 46 ].…”

“…Additionally, accelerated fat metabolism was observed in a number of studies, with significant changes across all forms: long-chain, medium-chain, branched-chain, am-ino-FAs (amino-fatty acids), carnitines, ketones, lipid mediators, membrane lipids, and fatty acid esters of hydroxy fatty acids (FAHFAs) [ 2 , 4 , 20 , 27 , 35 , 36 , 42 , 45 , 47 , 48 , 49 ]. Studies also highlighted ketone body accumulation following exercise, suggesting a switch from glycolytic metabolism to ketolytic metabolism during acute endurance exercise [ 2 , 27 , 35 , 45 , 48 ]. The primary ketone bodies acetoacetate and β-hydroxybutyrate increased in response to acute endurance exercise [ 27 , 35 , 45 ] but not to resistance exercise [ 27 ].…”

“…Studies also highlighted ketone body accumulation following exercise, suggesting a switch from glycolytic metabolism to ketolytic metabolism during acute endurance exercise [ 2 , 27 , 35 , 45 , 48 ]. The primary ketone bodies acetoacetate and β-hydroxybutyrate increased in response to acute endurance exercise [ 27 , 35 , 45 ] but not to resistance exercise [ 27 ]. A possible reason for this difference could be the higher caloric expenditure needed for acute endurance exercise, which leads to an energy demand exceeding intracellular supplies, resulting in ketone bodies being delivered from hepatocytes.…”

Breath analysis combined with cardiopulmonary exercise testing and echocardiography for monitoring heart failure patients: the AEOLUS protocol

“…Continuous monitoring of specific metabolites in the breath of nominally healthy volunteers during exercise has been extensively reported in the literature [19][20][21][22][23][24]. Generally, breath composition changes during exercise because of the fast-occurring physiometabolic changes [20].…”