PSXI-19 Selenium-specific lipidome in the liver of beef heifers at maternal recognition of pregnancy.

Abstract Multiple selenoproteins have antioxidant capabilities that will effectively scavenge harmful reactive oxygen species to protect cells from oxidative stress and ensure the integrity of cell membranes. Selenium (Se) is an integral component of selenoproteins and an essential trace mineral. However, Se is deficient in the soils and forages of large proportions of the United States, necessitating dietary supplementation in forage-based production systems. We have investigated supplementation with inorganic Se (ISe) versus a 1:1 mixture (MIX) of ISe to organic Se (OSe) and have observed MIX-induced decreases in systemic cholesterol and low-density/ very low-density lipoprotein (LDL/ VLDL) fractions during early gestation (d7 and d17), which occurred concurrently with significantly longer conceptuses at maternal recognition of pregnancy (MRP, d17). Subsequently, we sought to determine the effects of supplementation with MIX versus ISe on the lipidome of hepatic tissue from beef heifers at MRP, for mechanistic insight into form of Se-effects on liver function and its relationship to reported differences in circulating metabolites, the endometrial transcriptome, and development of the conceptus. Angus-cross heifers received no Se for 45 days (Se depletion) followed by ISe alone for 45 days (Se repletion). Heifers then received at least 90 days of supplementation with either ISe or MIX prior to synchronization of estrus and artificial insemination. On d17 of presumed pregnancy, heifers were killed, and their reproductive tracts and conceptuses recovered (n = 6 per treatment). Hepatic samples were collected for untargeted C30 lipidomic analysis. Thermo Scientific LipidSearch software version 5.1.8 was used for lipid identification and sample alignment. Multivariate analysis was performed using MetaboAnalyst6.0. A total of 2306 annotated lipids were identified in positive ion mode and 667 were identified in negative ion mode. The top five types of lipids identified in positive ion mode were triglycerides (20%), phosphatidylcholines (14%), phosphatidylethanolamines (10%), phosphatidic acids (10%), and diglycerides (9%). Alternatively, in negative ion mode, the top five types of lipids were phosphatidylserines (19%), phosphatidylethanolamines (15%), phosphatidylglycerols (12%), lysophosphatidic acids (12%), and fatty acids (9%). At P < 0.05 in positive ion mode, there were 148 affected lipids with 126 being more abundant and 22 being less abundant in MIX compared to ISe. In comparison, in negative ion made, there were 43 affected lipids with 10 greater abundance and 33 of lesser abundance in MIX compared to ISe. Key phosphatidylcholines, phosphatidylserines, phosphatidylethanolamines, and phosphatidylglycerols that primarily compose cell membranes were of greater abundance in the liver of MIX versus ISe. Sphingomyelins however, which contribute to the structure of LDL and VLDL, were less abundant in MIX compared to ISe-supplemented heifers. Overall, it appears that MIX-supplementation contributes to a unique hepatic lipidome ultimately enhancing membrane integrity in the liver, lipid metabolism, and whole animal physiology at MRP.