Dietary Ethanolamine Plasmalogen from Ascidian Alleviates Chronic Hepatic Injury in Mice Treated with Continuous Acetaminophen

Background: Ethanolamine plasmalogen (PlsEtn) is a subclass of ethanolamine glycerophospholipids (EtnGpls) and is abundantly found in some marine invertebrates, including ascidian Halocynthia roretzi. PlsEtn is reported to exhibit physiological and nutritional hepatic functions; however, the effects of dietary PlsEtn on continuous acetaminophen (APAP)-induced hepatic injury, including oxidative stress and impaired lipid metabolism, remain unclear. Herein, we investigated the dietary effects of PlsEtn from ascidian on chronic hepatic injury in APAP-treated mice. Methods: Five-week-old male ICR mice were divided into four groups (n = 12), which were treated with the respective experimental diet for two weeks and then the respective APAP-containing diet for five weeks. The results obtained after administering the PlsEtn-rich diet were compared with those obtained after the administration of a phosphatidylethanolamine (PtdEtn)-rich diet, a major subclass of hepatic EtnGpls. Results: The PlsEtn-rich diet effectively suppressed the APAP-induced decrease in body and liver weights of mice; however, this suppressive effect was not observed in mice fed a PtdEtn-rich diet. APAP administration decreased the total fatty acid content in the liver, whereas a PlsEtn-rich diet alleviated this decrease and increased the hepatic content of docosahexaenoic acid (DHA), which exhibits various hepatic functions. Moreover, dietary EtnGpl rich in PlsEtn or PtdEtn suppressed APAP-induced lipid oxidation in the liver. The protein expression results revealed that dietary EtnGpls reduced the expression of certain apoptosis-related proteins in the livers of APAP-administered mice compared to that in the APAP group. This reduction was particularly more effective in mice fed the PlsEtn-rich diet than in those on the PtdEtn-rich diet. Conclusions: Dietary EtnGpls, particularly PlsEtn, alleviated the hepatic cellular stress caused by continuous APAP consumption. These beneficial effects may depend on the subclass and may be related to DHA metabolism in the liver. The results of this study contribute to the understanding of the role of PlsEtn in maintaining liver health.