Targeted quantification of identified metabolites between
different inflammatory asthma phenotypes and healthy subjects in the
validation set
To validate and determine the expression levels of 40 differentially
expressed metabolites, which were selected to perform targeted
quantification in patients in the validation set. Amongst which, 24
metabolites were significantly differentially expressed between asthma
inflammatory phenotypes (Table 2), with 9 of these metabolites reaching
a significant P value of .001 or less. Histamine expression was
highest but levels of 5-L-glutamyl-L-alanine, nicotinamide,
dihydrothymine, L-leucine, L-phenylalanine, alanyl-leucine,
phenylalanyl-serine, phenylalanylphenylalanine were the lowest in
patients with EA. Expression levels of adenosine 5’-monophosphate,
glyceric acid, taurine, dihydrothymine, L-leucine, tyramine,
L-glutamate, alanyl-leucine, phenylalanyl-serine,
threoninyl-phenylalanine were highest but level of glycerophosphocholine
was lowest in patients with NA. Expression levels of
glycerophosphocholine, cyclohexylamine, heptadecanoic acid, oleic acid
were highest but level of dodecanoic acid was lowest in patients with
PGA (Table 2).
Furthermore, those differentially expressed metabolites were examined by
receiver operating characteristic (ROC) curves to discriminate different
inflammatory asthma phenotypes (Table E4). As a result, taurine,
alanyl-leucine, phenylalanyl-serine and threoninyl-phenylalanine could
be used as a candidate metabolite marker to discriminate between NA and
EA or PGA with the AUC was range from 0.816 to 0.975 (all P< 0.05). However, no single metabolite could satisfactorily
discriminate between EA and PGA as all of the AUC < 0.7.