Metabolism of Sialic Acids from Exogeneously Administered Sialyllactose and Mucin in Mouse and Rat

Abstract

A mixture of-/V-acetyl- [4,5,6,7,8,[9][10][11][12][13][14] C]neuraminosyl-a(2-3(6))-galactosyl-0( 1 -4)-glucose ([ l4 C]sialyl-lactose) and TV-acetylneuraminosyl-a(2-3(6))-galactosyl-|3(l-4)-glucit-l-[ 3 H]ol (sialyl-[ 3 H)lactitol) as well as porcine submandibular gland mucin labeled with TV-acetyland yV-glycoloyl-[9-3 H]neuraminic acid were administered orally to mice. The distribution of the different isotopes was followed in blood, tissues and excretion products of the animals. One half of the [ 14 C]sialyl-lactose/sialyl-[ 3 H]lactitol mixture given orally was excreted unchanged in the urine. The other half was hydrolysed by sialidase and partly metabolized further, followed by the excretion of 30% of the 14 C-radioactivity as free 5,6,7,8,[9][10][11][12][13][14] C]neuraminic acid and 60% of this radioactivity in the form of nonanionic compounds including expired 14 C0 2 within 24 h. The l4 C-radioactivity derived from the [ 14 C]sialyl-lactose/sialyl-[ 3 H]lactitol mixture which remained in the bodies of fasted mice after 24 h was less than 1 %. In the case of well-fed mice, a higher amount of the sialic acid residues was metabolized. The bulk of radioactivity of the mucin was resorbed within 24 h. About 40% of the radioactivity administered was excreted by the urine within 48 h; 30% of this radioactivity represented sialic acid and 70% other anionic and non-anionic metabolic products. 60% of the radioactivity administered remained in the body, and bound 3 H-labeled sialic acids were isolated from liver. Enzymes:jV-Acetylneuraminate lyase, yV-acetylneuraminate pyruvate-lyase (EC 4.1.3.3); Sialidase, acylneuraminyl hydrolase (EC 3.2.1.18). A bbreviations: NeuSAc = yV-Acetyl-D-neuraminic acid; Neu5,9Ac 2 = JV-acetyl-9-0-acetyl-D-neuraminic acid; NeuSGc = yV-glycoloyl-D-neuraminic acid; NeuSAcyl = '-acyl-D-neuraminic acid; NeuSAc-lyase = W-acetylneuraminate lyase; ManNAc = W-acetyl-D-mannosamine; Sialyllactose = Neu5Aca(2-3(6))Gal0(l-4)Glc (mixture of (2-3)-and (2-6)-glycosidically bound NeuSAcJ; sialyllactitol = Neu5Aca(2-3(6))Gal/3(l-4)glucit-l-ol; [ l4 5,6,7,8,[9][10][11][12][13][14] C]Neu5Aca(2-3(6))Gal0(l-4)Glc;( 3 HJsialyl-lactose = [9-3 H]Neu5Aca(2-3(6))Gal/3(l-4)Glc; sialyl-l 3 H]lactitol = Neu5Aa*(2-3(6))Gal0(l-4)glucit-l-| 3 H]ol; [ 14 C]sialyl-lactitol = [4 5,6,7,8,9-14 C]Neu5Aca(2-3(6))Gal0(l-4)glucit-l-ol; [ 3 H]sialyl-lactitol= (9-3 HJNeu5Aca(2-3(6))Gal0(l-4)glucit-l-ol. Copyright © by Walter de Gruyter & Co -Berlin · New York Brought to you by | University of Queensland -UQ Library Authenticated Download Date | 6/24/15 12:27 AM 1458 U. Nöhle and R. Schauer Bd. 365 (l984)Sialyl-a(2-3)-[ 3 H]lactitol was injected intravenous-resorbed. This is followed either by excretion as ly into rats; the substance was rapidly excreted in the urine without decomposition.These studies show that part of the sialic acids bound to oligosaccharides and glycoproteins can be hydrolysed in intestine by sialidase and be free sialic acid or by metabolization at variable degrees, which apparently depends on the compound ...

Involvement of a Non-Human Sialic Acid in Human Cancer

“…Nöhle and Schauer first showed that radioactive free sialic acid fed to mice and rats appeared in urine and was metabolized, as a portion of the radioactivity was recovered as expired CO 2 (63–65). Radioactivity from labeled sialic acids in mucins was also detected in murine tissues after oral gavage (65).…”

The nutritional role of free sialic acid, a human milk monosaccharide, and its application as a functional food ingredient

“…For instance, the exoa-sialidase from Bifidobacterium bifidum that was recently characterized is an enzyme that is located on the outer cell-surface of the bacterium and cleaves sialic acid from glycoconjugates to make the monosaccharide and the resultant oligosaccharides available to the bacterium (Kiyohara et al, 2011). Additionally, Nöhle and Schauer (1984) have shown that half of an orally administered dose of radiolabeled sialyllactose (a conjugated form of sialic acid) is hydrolyzed to free sialic acid by intestinal sialidase in mice and rats Schauer, 1984, Dickson andMesser, 1978). Once released, free sialic acid would remain intact as, unlike its activated nucleotide (CMP-NANA), sialic acid itself has been demonstrated to be stable under conditions similar to those of the gastrointestinal tract (Ruano et al, 1999).…”

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