Serum sialic acid is a risk factor for cardiovascular disease in the general population. Serum total sialic acid concentrations were therefore measured in 20 type 1 diabetic patients and in 20 age- and sex-matched non-diabetic subjects. Serum sialic acid were not significantly different in the type 1 diabetic patients and the normal subjects ( 2.00 ± 0.37 vs. 1.98 ± 0.67 mmol/l ), but was significantly correlated with serum total cholesterol ( r = 0.55, P ) and serum triglyceride concentration ( r = 0.63, P ) in the type 1 diabetic patients. There was no relationship of sialic acid levels to age, duration of diabetes, smoking, body mass index, systolic or diastolic blood pressure, plasma glucose, serum fructosamine, or daily insulin dosage. Six of the type 1 diabetic patients with retinopathy had higher total serum sialic acid concentrations than those patients without retinopathy ( 2.38 ± 0.33 vs. 1.85 ± 0.26 mmol/l , P ) A further study of 16 type 1 and 16 type 2 diabetic patients matched for serum fructosamine and blood glucose concentrations and without tissue complications showed that the serum total sialic acid concentration was significantly higher in the type 2 diabetic patients compared with the type 1 patients ( 2.32 ± 0.41 vs. 1.84 ± 0.24 mmol/l , P ). Although the serum concentrations of the non-sialylated acute phase protein, C-reactive protein, was higher in type 2 than type 1 diabetes, sialylated acute phase protein levels did not explain differences in serum total sialic acid in diabetes. We conclude that the serum sialic acid concentration is elevated in both type 2 diabetes and in patients with diabetic retinopathy, whether the retinopathy occurs in type 1 or type 2 diabetes.
