Composition of plasmalogens in serum lipoproteins from patients with non-alcoholic steatohepatitis and their susceptibility to oxidation

Background: Plasmalogens are ether phospholipids (PL) with an alkenyl group including vinyl ether bound at the sn-1 position and a polyunsaturated fatty acid bound at the sn-2 position, and are susceptible to oxidation. To date, there are no reports on the relationship between plasmalogen in serum lipoproteins and non-alceolic steatohepatitis (NASH), caused by multiple factors including oxidative stress. Here, we have investigateu the distribution of plasmalogens in serum lipoproteins isolated from NASH patients and healthy volunteers. Methods: Serum lipoproteins were separated by gel-filtration chromatography, and analyzed for ethanolamine and choline plasmalogens using liquid chromatography-mass spectrometry. Results: Both plasmalogen levels were higher in HDL than in VLDL or LDL. The plasmalogens/PL ratio was significantly lower in NASH than controls, for all lipoprotein fractions. Ethanolamine plasmalogens containing 20:4 and 22:6 at the sn-2 position and choline plasmalogens containing 16:0 at the sn-1 position were predominant in each group. In oxidation test using LDL from healthy serum, both types of plasmalogens were decreased during the early stages of oxidation. Conclusion: Plasmalogens could be a potential biomarker for evaluating the early stages of oxidation in NASH

Novel monoclonal antibody recognizing triglyceride-rich oxidized LDLs associated with severe liver disease and small oxidized LDLs in normal subjects

Background: Triglyceride-rich low-density lipoproteins (TG-rich LDLs) in the plasma of patients with severe liver disease are reported to change macrophages into foam cells in vitro. Methods: Male BALB/c mice were immunized with TG-rich LDLs isolated from the plasma of a patient with severe liver disease. The resulting monoclonal antibody (G11-6) was used in a sandwich enzyme-linked immunosorbent assay (ELISA) in combination with polyclonal anti-apolipoprotein B antibodies. The time course of copper-mediated LDL oxidation was monitored using this ELISA. The results were compared to those of the two commercial ELISAs for oxidized LDL using DLH or ML25, thiobarbituric acid reactive substances (TBARS), and the optical absorbance for the conjugated dienes generated in lipid peroxides. Further, the lipoprotein fractions separated by gel filtration were tested with this ELISA in healthy volunteers (n = 11) and patients (n = 3) with liver disease. Results: G11-6 reacted with oxidized LDLs during only the early phase of copper-oxidation, being distinct from the other monoclonal antibodies and methods. G11-6 was confirmed to react with TG-rich LDLs in patients, while it reacted with small LDL particles in normal controls. Conclusions: The monoclonal antibody G11-6 is useful for detecting oxidized small LDLs in normal controls and oxidized TG-rich LDLs in patients with severe liver disease