Investigation of an individual with background levels of exhaled isoprene: a case study

Abstract

Isoprene is one of the most abundant and most frequently evaluated volatile organic compounds in exhaled breath. Recently, several individuals with background levels of exhaled isoprene have been identified. Here, case study data are provided for an individual, identified from a previous study, with this low prevalence phenotype. It is hypothesized that the individual will illustrate low levels of exhaled isoprene at rest and during exercise. At rest, the subject (7.1ppb) shows background (μ=14.2±7.0ppb) levels of exhaled isoprene while the control group illustrates significantly higher quantities (μ=266.2±72.3ppb) via proton transfer reaction mass spectrometry (PTR-MS). The result, background levels of isoprene at rest, is verified by thermal desorption gas chromatography mass spectrometry (TD-GC-MS) collections with the individual showing -3.6ppb exhaled isoprene while the room background contained μ=-4.1±0.1ppb isoprene. As isoprene has been shown previously to increase at the initiation of exercise, exercise bike experiments were performed with the individual identified with low isoprene, yielding low and invariant levels of exhaled isoprene (μ=6.6±0.1ppb) during the exercise while control subjects illustrated an approximate 2.5-fold increase (pre μ=286.3±43.8ppb, exercise μ=573.0±147.8ppb) in exhaled isoprene upon exercise start. Additionally, exhaled breath bag data showed a significant decrease in isoprene (delta post/pre, p=0.0078) of the control group following the exercise regimen. Finally, TD-GC-MS results for exhaled isoprene from the individual’s family (mother, father, sister and maternal grandmother) illustrated that the mother and father exhibited isoprene values (28.5ppb, 77.2ppb) below control samples 95% confidence interval (μ=166.8±43.3ppb) while the individual’s sister (182.0ppb) was within the control range. These data provide evidence for a large dynamic range in exhaled isoprene in this family. Collectively, these results provide additional data surrounding the existence of a small population of individuals with background levels of exhaled isoprene.

Chemical Analysis of Exhaled Vape Emissions: Unraveling the Complexities of Humectant Fragmentation in a Human Trial Study

“…An exception to this is participant 2’s mass spectra for mint and tobacco-flavored trials (Figure S7a,b). These trials had low signal and the dominant peaks were acetone ( m / z 59) and isoprene ( m / z 69), normal baseline substituents of human breath. − Participants 2 and 3 smoked the same vape device and e-liquids, but in comparison to participant 3, participant 2 generated lower intensity mass spectra (Figure S7) for mint and tobacco trials, and mass spectral peaks did not resemble other participant trials. This result reflects the variability in emissions depending on how a participant interacts with their vape device and how personal habits influence VOC mass concentrations…”

A review on isoprene in human breath

“…The parallel increase of breath isoprene with increasing muscle mass with age provides additional support for the hypothesis that isoprene production is related to muscle tissue. Although isoprene is a commonly found endogenous volatile in exhaled breath in high levels, as mentioned previously a few studies have found subjects (approximately 1 in a 1000) whose isoprene levels are deficient or completely absent (below the detection limit) [3,5,6,26,27,34,47,48]. The cause of this lack of production is uncertain.…”

Origin of breath isoprene in humans is revealed via multi-omic investigations

“…Nevertheless, a single rare case was insufficient for detailed down-stream multi-omic analysis to determine the exact source. In a recent case study on one isoprene deficient American adult male and his blood-relatives by Harshman et al 41 and in another study on an isoprene deficient Italian adult female and her blood-relatives by Biagini et al 42 also demonstrated no relation of exhaled isoprene profiles to plasma cholesterol levels. They neither find any isoprene absent rare adult nor investigated the human cholesterol metabolism related gene expressions.…”