# Effects of Workers Exposure to Nanoparticles Studied by NMR Metabolomics
## 3 Results and Discussion
### Analysis of Blood Plasma
Propylene glycol is known to be predominantly of exogenous origin as a part of various vitamins and other dietary supplements. The  
Figure 5: OPLS-DA of healthy controls (blue diamonds) and pre-shift subjects (yellow circles); Acc. 80.7%, Sen. 88.2%, Spe. 73.2% (**a**). OPLS-DA of post-shift subjects (red squares) and healthy controls (blue diamonds); Acc. 86.0%, Sen. 86.4%, Spe. 85.7% (**b**). Both using 58 normalized metabolites from blood plasma samples. increased concentrations of propylene glycol in the post-shift group corresponds to the increased consumption of such supportive products in the morning before the shift. On the other hand, the NPs exposure also induced a depletion of other metabolites in post-shift samples; namely of 3-methyl-2-oxovalerate, 2-oxoisocaproate, 2-hydroxybutyrate, 3-hydroxybutyrate, isobutyrate, isopropanol, mannose, \(O\)-acetylcarnitine and tryptophan (Figure 8). All the changes found in the post-shift group can be attributed to the acute effect of the NPs on workers' health. The long-term effect of the NPs on workers' health can be deduced from the simultaneous changes in the pre- and post-shift group when compared to the control group. The levels of acetone, glutamine and cystine were found to decrease, while the levels of lactate and hypoxanthine increased in both groups when compared to the controls (Figure 9). The changes in levels of lactate and hypoxanthine were found to be more pronounced in the pre-shift group, which indicates involvement of these compounds in several metabolic pathways and mixing of acute and chronic effects. Figure 6: OPLS-DA of pre-shift (yellow circles) and post-shift subjects (red squares); Acc. 75.4%, Sen. 74.0%, Spe. 76.9% (**a**). mPLS analysis of pre-shift (yellow circles) and post-shift subjects (red squares); Acc. 89% (**b**). Both using 58 normalized metabolites from blood plasma samples. Figure 7: Boxplots of metabolites with increased levels in the post-shift samples. Figure 8: Boxplots of metabolites showing a depletion in the post-shift samples. Figure 9: Boxplots of metabolites showing simultaneous changes in the pre- and post-shift group in comparison to the controls. Metabolic pathway analysis was performed in MetaboAnalyst to assess involvement of the statistically significant metabolites in the individual metabolic pathways. The alterations between individual groups found by the pathway analysis are depicted in Figure S8 (Supplementary Materials) and the most affected pathways are summarized in Table S4 (Supplementary Materials). The increased levels of lactate found in the pre-shift group can be partially associated with the metabolism of propylene glycol, which is contained in the food supplements administrated before the shift, as mentioned above. On the other hand, lactate is also involved in several other metabolic pathways, including pyruvate metabolism, according to pathway analysis (Figure S6 in Supplementary Materials) or glucose-alanine metabolism, according to the literature [42]. These pathways play an important role as energy pathways where lactate is usually produced from pyruvate. The highest concentrations of pyruvate were found in the post-shift group, indicating that the energy pathways were affected and the transformation between lactate and pyruvate is impacted by the NPs exposure. Increased levels of lactate have been observed in several studies on the impact of NPs exposure to rats [21; 43; 44]. Additionally, decreased levels of mannose, which can serve as an additional energy source, were observed in the post-shift group [45]. Elevated levels of lactate can lead to metabolic acidosis, similarly to increased levels of glycolate, which were found in the post-shift group. The formation of acid metabolites can induce inhibition of other metabolic pathways [46]. Glycolate is mainly involved in glyoxylate metabolism where it is oxidized to glyoxylate, which is further transformed into glycine [47]. Glyoxylate can be also transformed into oxalate, which is then caught and secreted by the renal tubules.