Human breath isoprene and its relation to blood cholesterol levels: new measurements and modeling

Abstract

Numerous publications have described measurements of breath isoprene in humans, and there has been a hope that breath isoprene analyses could be a noninvasive diagnostic tool to assess blood cholesterol levels or cholesterol synthesis rate. However, significant analytic problems in breath isoprene analysis and variability in isoprene levels with age, exercise, diet, etc., have limited the usefulness of these measurements. Here, we have applied proton transfer reaction-mass spectrometry to this problem, allowing on-line detection of breath isoprene. We show that breath isoprene concentration increases within a few seconds after exercise is started as a result of a rapid increase in heart rate and then reaches a lower steady state when breath rate stabilizes. Additional experiments demonstrated that increases in heart rate associated with standing after reclining or sleeping are associated with increased breath isoprene concentrations. An isoprene gas-exchange model was developed and shows excellent fit to breath isoprene levels measured during exercise. In a preliminary experiment, we demonstrated that atorvastatin therapy leads to a decrease in serum cholesterol and low-density-lipoprotein levels and a parallel decrease in breath isoprene levels. This work suggests that there is constant endogenous production of isoprene during the day and night and reaffirms the possibility that breath isoprene can be a noninvasive marker of cholesterologenesis if care is taken to measure breath isoprene under standard conditions at constant heart rate.

Chlorophyll‐normalized isoprene production in laboratory cultures of marine microalgae and implications for global models

“…No isoprene was detected in any of the blanks, and so no corrections were applied, and all data reported are thus attributed to biological activity. In contrast to many other BVOC, isoprene has a low Henry's constant (k H ) of , 0.286 3 10 23 (mol aq /m 3 aq )/Pa (0.029 M/atm; Karl et al 2001), and is characterized by low water solubility and high volatility. This suggests that the effect of temperature on its solubility is small, and we calculated that the difference in solubility between 21uC and 26uC is below 2.3%.…”

Human exhaled air analytics: biomarkers of diseases

“…Figure 8 shows the concentration-times series for ionic mass m/z = 69 (= m 1 + m H , tentatively identified as isoprene with molecular mass m 1 = 68 u) during one night (Amann et al, 2004, in comparison with the heart rate. Increasing heart rate leads to an increased blood flow and consequently to an increased concentration of exhaled isoprene (Karl et al, 2001) as long as no wash-out phenomenon occurs.…”

Estimations of isoprenoid emission capacity from enclosure studies: measurements, data processing, quality and standardized measurement protocols

“…For example, methylbutenol and several other alcohols and aldehydes can form fragment ions with m/z of 69 + , i.e. with the same m/z as the protonated parent ion for isoprene Karl et al, 2001), and several C6 aldehydes and monoterpenes can form fragments with m/z 81 + Ishizuka et al, 2010). …”