Age-Related Changes in O-Acetylation of Sialic Acids Bound to N-Glycans of Male Rat Serum Glycoproteins and Influence of Dietary Intake on Their Changes.

O-Acetylation of sialic acids has been widely found in eukaryotic cells. Such modifications of sialic acids are tissue-specific and seem to be developmentally regulated. In this study, we performed comprehensive analysis of age-related changes in the serum N-glycans of male rats using capillary electrophoresis (CE) and investigated the changes in the O-acetylation of sialic acids bound to N-glycans with aging and different diets. The present method offered sufficient resolution to assess the degree of O-acetylation of the N-glycans and allowed for the determination of the age-related changes in O-acetylation of sialic acids. Using the CE-based method, we found that the relative abundance of disialo-biantennary N-glycans modified with 9-O-acetylated -acetylneuraminic acid (Neu5,9Ac) significantly increased with aging. In addition, the relative abundances of N-glycans with two Neu5,9Ac reversed to those of N-glycans with only Neu5Ac during 12 weeks. Next, we evaluated the influence of high-fat diet and food restriction on age-related changes in O-acetylation. Although the total amount of disialo-biantennary N-glycans increased with aging, age-related O-acetylation of sialic acids was suppressed by a high-fat diet. On the other hand, food restriction enhanced the O-acetylation of sialic acids, and the relative abundance of N-glycans with two Neu5,9Ac residues at 15 weeks of age was higher than that observed in the standard diet group. These findings suggest that the O-acetylation of sialic acids is closely related to changes in energy metabolisms such as glycolysis or fatty acid metabolism.