Table 1.

Selected Breath Compounds Relevant for Diabetes Mellitus

Compound	Possible Source/Relevance for Diabetes and Metabolism
Aerosolized glucose	Elevated in EBC during experimental hyperglycemia[104]
Aromatic compounds (ethylbenzene, o/m/p- xylene, toluene)	Partly metabolized by hepatic enzymes (cytochrome P450 system); rapid-onset hyperglycemia likely suppresses hepatic metabolism of the gases[16, 80]
Alkyl nitrates (2-, 3-pentyl nitrate, methyl nitrate)	By-product of the interaction of oxidative radicals and NO[105] Methyl nitrate correlated with plasma glucose in diabetic patients[106]
Carbon dioxide	Direct oxidative by-product of energy substrates
Carbon monoxide	Marker of oxidative stress (that can be caused by hyperglycemia)[107] Difference in the 13CO excretion were found between diabetic and healthy subjects following a labeled oral glucose tolerance test[108]
Ethane and pentane	Oxidation of ω3 and ω6 fatty acids[91]
Ethanol and methanol	Bacterial fermentation of glucose in intestines and subsequent movement into the portal circulation[79, 109]
Ketones (acetone, 2-pentanone)	Increases in diabetic ketoacidosis, fasting, and high-fat/ketogenic diets[9, 79, 82, 101] Suppressed with insulin-mediated suppression of lipolysis[83, 110] Acetone correlates with blood glucose and hemoglobin A1c in T1DM [98] but not in T2DM patients[99, 100]; exhaled at ~1/330 of plasma acetone concentrations [98]; follows a diurnal pattern [98]; elevated in men [100]
Isoprene	Cholesterol synthesis (from acetyl-CoA via the melavonic acid pathway) [81]
Propane	generated by n-4 fatty acid (18:3) peroxidation[111] or protein oxidation of branched-chain amino acids or production by colonic bacteria[24]
Propionic and butanoic acids	Elevated in EBC following sucrose ingestion[88]