Intestinal Absorption and Remodeling of Odd-Numbered Plasmalogens Derived from Selenomonas ruminantium in Rats

Plasmalogens are ether phospholipids that play crucial roles in antioxidation and membrane integrity. While plasmalogens in mammals typically have even-numbered hydrocarbon chains, certain anaerobic bacteria, such as Selenomonas ruminantium, can synthesize plasmalogens with even or odd-numbered chains depending on carbon source in the medium. The intestinal absorption and metabolic fate of the odd-numbered plasmalogens in mammals remain unclear. This study investigates the absorption characteristics of bacterial plasmalogens containing odd-numbered hydrocarbon chains in rats. Lipid extracts from S. ruminantium cultured in the medium containing lactate as a sole carbon source, which are rich in odd-numbered ethanolamine plasmalogens (PlsEtn), were administered either into the duodenum or orally. Lymph and plasma samples were analyzed using UPLC-MS/MS. After duodenal administration, the levels of odd-numbered PlsEtn species (e.g., p15:0, p15:1, p17:0 and p17:1) in lymph increased significantly, indicating their intestinal absorption. Notably, species containing polyunsaturated fatty acids such as 20:4 or 22:6 at the sn-2 position appeared, suggesting partial remodeling during absorption. Similarly, orally administered bacterial plasmalogens significantly increased the plasma levels of PlsEtn and PlsCho with odd-numbered hydrocarbon chains, with remodeled species incorporating 20:4 or 22:6. The increase rate of odd-numbered plasmalogens in plasma was greater than that of even-numbered species derived from porcine brain lipids, implying slower metabolic degradation and prolonged circulation. These results are the first evidence that microbially derived plasmalogens with odd-numbered hydrocarbon chains are absorbed and remodeled in the mammalian intestine while maintaining their unique sn-1 structure and undergoing selective acyl modification at sn-2. This study provides the potential that the chemical diversity of plasmalogens influences their physiological roles and potential therapeutic functions.