A Pioneer Study of Plasma Lipid Profile Differences in Healthy Individuals, Patients with Chronic Pancreatitis and Pancreatic Cancer in China

3Henan Children’s Hospital,Department of Hematology and Oncology, Zhengzhou, Henan Province, 450053, People’s Republic of China 4Department of Oncology, the Second Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450014, People’s Republic of China 5Department of General, Visceral, and Transplantation Surgery, Ludwig-Maximilians-University Munich, Munich 81377, Germany §Contributed equally

PDAC and CP [5][6][7][8]. Novel metabolic biomarkers for PDAC based on Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR) have been reported [9,10]. However, a consensus regarding these results is yet controversial. In the present study, we analyzed the lipid profile using ultra-performance liquid chromatograph-time of flight mass spectrometry (UPLC-TOF/MS) to investigate the lipid metabolism in healthy individuals (H group), patients with CP (C group), and patients with PDAC (P group). The lipid profiling analysis revealed particular differences in these three groups.

Patient Recruitment Plasma Sample Collection
The present study was approved by the Ethics Committee (1) chronic abdominal pain and or pancreatic calcifications; (2) abdominal pain and morphological features of distortion in duct pancreatograms; (3) exocrine pancreatic insufficiency; (4) histopathological changes, wherein surgical resection was indicated; and (5) one or more than one imaging examinations showing the characteristic morphological changes of CP.
Patients in the C group and healthy individuals in H group were not diagnosed with any cancer, and also, did not present any prior cancer history. The clinic epidemiological characteristics of the participants are summarized in (Table 1).

Extraction of Lipids
Briefly, 100μL plasma was thawed and mixed with 900μL isopropanol (IPA). After vigorously agitating for more than 10 s and sonicating for 10min, the mixture was frozen at -20°C for 1h, followed by centrifugation at 10,000rpm for 10min. The upper layer (800μL) was transferred to a sample vial and analyzed by UPLC-QTOF/MS.

Results
General PCA analysis revealed that dots from the 3 groups localizes in different zones ( Figure 1) indicating different lipid metabolism in the groups analyzed. PCA for comparison of H vs C as well as H vs P clearly demonstrated that lipid element dots were conversely distributed (Figures 2A & 3A). Further, the OPLS-DA found out that in each score plot, dots are localized in diagonal conversely quadrants ( Figures 2B & 3B), presenting the OPLS-DA model efficiently distinguishes the groups tested. Then, VIP was calculated, and compounds with VIP > 1 were screened as deregulated elements contribute to the difference between groups ( Figures 2C & 3C). Finally, these elements were retested by volcano analysis (coefficients vs. VIP spots) ( Fig. 2D and 3D).
Subsequently, totally 669 lipid elements were identified in H, C, and P ( Table 2) with the formula name C57H102O6. There were no elements found to be reduced in P (pink zone) simultaneously elevated in C groups (blue zone). Obviously, compared with H group, PA and TG were elevated and reduced respectively only in C group.          [15]. However, the role of PA in CP needs further investigation. Interestingly, a cross point of C and P groups was identified by two TG elements which are reduced in C group but elevated in P group: chylomicrons [16]. Indeed, Fan et al. reported that VLDL level is higher in PDAC patients and lower in CP patients [10], which is in line with our findings. Also, Ulmer et al. found a statistically significant positive association between the amount of serum TG and the risk of cancers in the colon, respiratory tract, kidney, and skin [17].
However, the specifying of the TG found in this study needs to be done in future. To the best of our knowledge, this is the first study reporting elevation and diminishment of PA and TG in patients with different pancreatic diseases.

Conclusion
Our research revealed the plasma lipid profile in healthy individuals and patients with CP and PDAC. Altered lipid level provides new possibilities of lipid biomarker pool for pancreas disease detection, surveillance and to distinguish CP and PDAC.