These results further suggest that smokers have higher concentrations of diacyl-phospholipids and lower concentrations of the plasmalogens, whereas the opposite is seen in former and non-smokers.
The levels of these biomarkers are all up-regulated in smokers compared to those in former and non-smokers, except for three acyl-alkyl-phosphatidylcholines (e.g. plasmalogens).
The first component is dominated by a set of metabolites (Table 1), indicating that these metabolites are primarily responsible for separating smokers from former and non-smokers.
For the 23 potential ND biomarkers, the mean values of current, former and non-smoker groups are clearly distinct (Table 1).
The biomarker levels in current smokers are almost all up regulated compared to those in former and non-smokers, with three acyl-alkyl-phosphatidylcholines (PC ae C40 6, PC ae C36:2 and PC ae C38 2) down regulated.
In KORA study, to characterize the nicotine consumption, the current smoker is defined as 1; sometimes smoker is defined as 2; former and non-smoker are quantified as 3 and 4, respectively.
Interestingly, in a human lung project [33], it was found that the AGPS gene expression is highly increased in former and non-smokers relative to current smokers (Figure S6).
Albeit we are aware that the sample size of current smokers in this pilot study is small, our results are encouraging and we could show that the smokers are distinctly separated from former and non-smokers.
However, the overall fat metabolism is likely not be affected, as the BMI does not vary significantly between the groups of current, former and non-smokers (data not shown).
We investigated the populations at individual and group levels and observed significant changes of two types of metabolites, which are intermediates or end products of glycerophospholipid- and ether lipid-metabolism, in smokers compared to former and non-smokers.
