Effects of age, sex, fasting and surgery on the excretion of neuraminyllactose and neuraminyl-N-acetyllactosamine in rat urine

Metabolism of sialic acids from exogenously administered sialyllactose and mucin in mouse and rat

A mixture of N-acetyl-[4,5,6,7,8,9-14C]neuraminosyl-alpha (2-3(6]-galactosyl-beta (1-4-glucose[( 14C]sialyl-lactose) and N-acetylneuraminosyl-alpha (2-3(6]-galactosyl-beta(1-4)-glucit-1-[3H]ol(sialyl-[3H]lactitol) as well as porcine submandibular gland mucin labeled with N-acetyl- and N-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 [14C]sialyl-lactose/sialyl-[3H]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 14C-radioactivity as free N-acetyl-[4,5,6,7,8,9-14C]neuraminic acid and 60% of this radioactivity in the form of non-anionic compounds including expired 14CO2 within 24 h. The 14C-radioactivity derived from the [14C]sialyl-lactose/sialyl-[3H]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 3H-labeled sialic acids were isolated from liver. Sialyl-alpha (2-3)-[3H]lactitol was injected intravenously 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 resorbed. This is followed either by excretion as free sialic acid or by metabolization at variable degrees, which apparently depends on the compound fed and on the retention time in the digestive tract.

Relationship between urinary sialylated saccharides, serum amyloid A protein, and C-reactive protein in rheumatoid arthritis and systemic lupus erythematosus

The urinary excretion of sialic-acid-containing oligosaccharides, total sialic acid, serum amyloid A protein (SAA), and C-reactive protein (CRP) has been studied in 48 patients with rheumatoid arthritis (RA) and in 17 patients with systemic lupus erythematosus (SLE). Linear regression analysis revealed a close positive correlation between serum SAA and CRP levels in both RA (r = 0.71, p less than 0.001) and SLE (r = 0.86, p less than 0.001). The urinary excretion of sialyl lactose showed a positive correlation with the serum levels of SAA and CRP in RA (r = 0.45 and r = 0.45, respectively, p less than 0.01) but not in SLE (r = 0.05 and r = 0.10 respectively). Changes in serum total sialic acid levels paralleled those in CRP and SAA in RA as well as in SLE. Patients with very active RA had higher urinary sialyl oligosaccharide excretion (p less than 0.001), higher CRP levels (p less than 0.01), and higher SAA levels ( p less than 0.05) than those with moderately active disease.

Urinary excretion of sialic acid-containing saccharides in systemic lupus erythematosus

Urinary sialic acid-containing trisaccharides, total sialic acid, and serum sialic acid were studied in 17 patients with systemic lupus erythematosus (SLE) and in 15 healthy controls. The urinary excretion of sialyllactose, measured by a gas chromatographic method, was significantly greater in patients with SLE (37.4 +/- 21.4 mg/24 hours, SD) than in the control subjects (13.7 +/- 3.8 mg/24 hours, p less than 0.001). The mean excretion of sialyl-N-acetyllactosamine (16.6 +/- 8.5 mg/24 hours) and total sialic acid (82.5 +/- 29.4 mg/24 hours) was also greater in the SLE group than in the controls (8.7 +/- 2.8 and 58.0 +/- 16.0 mg/24 hours, respectively; p less than 0.01). Serum levels of sialic acid were correspondingly higher in the SLE patients (84.4 +/- 20.4 mg/100 ml) than in the controls (63.7 +/- 6.5 mg/100 ml, p less than 0.001). Urinary excretion of sialyl-lactose correlated positively with clinical disease activity (p less than 0.001) and with anti-DNA antibody levels (p less than 0.05). On the average, patients with moderate or severe disease excreted three times more sialyl-lactose than did those with mild or inactive disease. Our results suggest that the excretion of sialyl-oligosaccharides reflects disease activity in SLE.

Urinary sialyloligosaccharide excretion as an indicator of disease activity in rheumatoid arthritis

Urinary trisaccharides containing sialic acid, urinary total sialic acid, and serum sialic acid were studied in 51 patients with rheumatoid arthritis (RA). The urinary excretion of sialyllactose and sialyl-N-acetyllactosamine was measured by quantitative gas chromatography. The output of sialyllactose was significantly greater in patients with RA (31.9 +/- 17.3 mg/24, SD) than in control subjects (15.9 +/- 5.4, P less than 0.001). The RA patients also had higher mean levels of urinary sialyl-N-acetyllactosamine (P less than 0.05), total urinary sialic acid (P less than 0.001), and serum sialic acid (P less than 0.001). Urinary excretion of sialyllactose was considerably higher in patients with active and aggressive RA and moderately higher in patients with moderate disease activity. Excretion in those with mild or almost inactive RA did not differ significantly from that in the controls. Linear regression analysis revealed a strong positive correlation between urinary sialyllactose levels and clinical disease activity (P less than 0.001), as well as between excretion of sialyllactose and sialyl-N-acetyllactosamine in RA. These results suggest that the urinary content of trisaccharides containing sialic acid is an indicator of disease activity of RA.

Increased excretion of two sialic acid-containing trisaccharides in the urine of patients with rheumatoid arthritis

The urinary excretion of sialic acid-containing trisaccharides in patients with active rheumatoid arthritis was studied. Sialyl-lactose and sialyl-N-acetyllactosamine were identified and their excretion patterns studied by thin layer and gas chromatography. The urinary output of sialyl-lactose was greater in patients with active rheumatoid arthritis (48.2 +/- 6.1 mg/24 h, SEM, n = 6) than in healthy subjects (19.8 +/- 3.7 mg/24 h, SEM, n = 5; P less than 0.01). The excretion of sialyl-N-acetyllactosamine was also higher in the rheumatoid group (18.5 +/- 2.1 mg/24 h, SEM, n = 6) than in the controls (11.1 +/- 1.2 mg/24 h, SEM, n = 5; P less than 0.05). The qualitative excretion patterns of the sialyl-oligosaccharide fraction were similar for the two groups as judged from the thin layer chromatograms. Correlating the results with the clinical state of the patients with rheumatoid arthritis suggests that the urinary level of the sialyl-oligosaccharides reflects the activity of the disease. A proposed mechanism for the increased excretion of sialic acid-containing trisaccharides in rheumatoid arthritis is presented.

Excretion of neuraminic acid-containing trisaccharides in the urine during pregnancy

The excretion of neuraminic acid-containing trisaccharides in the urine during the course of normal pregnancy was studied. Neuraminyl-lactose and neuraminyl-galactosyl-(l led to 4)-N-acetylglucosamine were identified, and their excretion patterns were analyzed by thin-layer and gas chromatography. A progressive increase in the outputs of these acidic oligosaccharides was observed during the course of pregnancy in all cases studied. Neuraminyl-lactose excretion increased threefold, from 13.7 +/- 1.75 to 37.1 +/- 2.56 mg/24 h, and neuraminyl-galactosyl-N-acetylglucosamine twofold, from 8.4 +/- 1.27 to 15.3 +/- 2.21 mg/24 h (Mean +/- S.E.).