Sialic Acids in Human Gastric Aspirates: Detection of 9-O-Lactyl- and 9-O-Acetyl-N-Acetylneuraminic Acids and a Decrease in Total Sialic Acid Concentration with Age

Abstract

1. The total sialic acid content of human gastric aspirates was measured using a colorimetric assay. Care was taken to optimize the assay and to eliminate interference. 2. The sialic acid content of gastric aspirates collected under resting conditions from 77 patients with non-ulcer dyspepsia was found to decrease with age from > 100 micrograms/ml at 25 years and younger to < 20 micrograms/ml above 70 years of age. 3. Analysis of the sialic acids by gas chromatography, mass spectrometry and thin-layer chromatography showed the presence of N-acetylneuraminic acid and two O-acylated derivatives, 9-O-acetyl- and 9-O-lactyl-N-acetylneuraminic acids. These forms were predominantly glycosidically bound. 4. Thin-layer chromatographic analysis of individual aspirate samples showed that the O-acetylated sialic acids were present in all samples, with a maximum of 25% and a minimum of 5% of the total sialic acids.

Metabolism of Sialic Acid by Bifidobacterium breve UCC2003

“…These results suggest that B. bifidum PRL2010 uses its sialidase activity to gain access to the lactose component of this HMO, leaving the sialic acid for B. breve UCC2003 (and others) to forage. These results show that although the sialic acid in the gut is predominantly glycosidically bound (24), a lack of sialidase activity would not necessarily disadvantage the proliferation of a cross-feeding bifidobacterial strain such as B. breve UCC2003 in the infant gut. Similarly, a recent study showed that two pathogens, Salmonella enterica serovar Typhimurium and Clostridium difficile, can scavenge sialic acid released by the sialidase activity of Bacteroides thetaiotaomicron in a gnotobiotic mouse (79).…”

“…Sialic acid also features prominently at the surface-exposed end of human colonic mucin (22), and in healthy adults, approximately 300 g of sialic acid/mg of colonic mucin is present (23). The concentration of sialic acid in gastric juice has been found to decrease with age, with levels of 100 g ml Ϫ1 in young adults Ͻ25 years old compared to less than 20 g ml Ϫ1 in elderly people (24). Representative Clostridium perfringens strains were the first bacteria shown to be capable of utilizing sialic acid as the sole carbon source (25,26).…”

The Adherent Gastric Antral and Duodenal Mucus Gel Layer Thins with Advancing Age in Subjects Infected with <i>Helicobacter pylori</i>

“…Fariniti et al [8] showed that the number of gastric 'mucus-secreting cells' decreases with increasing age, whilst Corfield et al [9] showed a decrease with advancing age in total sialic acid concentration in human gastric juice and speculated that there is a qualitative change in gastric mucus with increasing age. Unfortunately, neither of these studies controlled for the presence or absence of H. pylori.…”

Correlation of gastric mucosal damage with sialic acid profile in rats: effect of hydrochloric acid, pepsin and hypertonic saline

“…In assessing the protective roles of mucus, estimation of luminal mucus in gastric aspirates has been used as an index of secretion. [25][26][27][28][29] However, mucus in gastric aspirates may arise from mechanical or enzymic erosion of the adherent mucus. Since the viscosity of the mucus is dependent on the presence of SIA derived from the mucus glycoprotein, quantitative estimation of the turnover of these substances within a biological system is of great importance.…”