Protein Glycosylation and Gut Microbiota Utilization Can Limit the In Vitro and In Vivo Metabolic Cellular Incorporation of Neu5Gc.

Abstract

Red meat intake is reported to be correlated with chronic diseases. A potential causal factor is N-glycolylneuraminic acid (Neu5Gc) which metabolically incorporates into diverse glycoconjugates in humans. This study aims to investigate the impact of exposure to Neu5Gc-rich red meat on healthy cytidine-5'-monophospho-N-acetylneuraminic acid hydroxylase (Cmah) knock-out mice and the underlying mechanisms. CMAH-/- mice are fed Neu5Gc-rich diet for short-term (4 months) and long-term (10 months). Health status and levels of inflammatory cytokines are assessed. Caco-2 cells are used to investigate the intestinal absorption of Neu5Gc-containing glycoprotein, and in vitro fermentation is used to investigate the Neu5Gc utilization by gut microbiota. Neu5Gc-rich diets show neither measurable abnormality in physio-biochemical and inflammatory indexes nor observable alterations of liver tissue in mice. Glycosylation of lactoferrin limits its intestinal epithelial absorption, and the absorption of Neu5Gc attach onto glycoprotein is thus limited. Neu5Gc is also simultaneously utilized by microorganisms under simulated gut conditions. The results indicate that the long-term intake of Neu5Gc-rich red meat has no adverse effect on the health of CMAH-/- mice, which may be related to the limited absorption of Neu5Gc that is regulated by protein glycosylation, and the metabolism of Neu5Gc by gut microorganisms.