Plasma Sialic Acid Determination

The concentration of plasma sialic acid was estimated using the modified chemical method and the more sensitive enzymatic method in 20 subjects with impaired glucose tolerance and 20 control subjects. The mean sialic acid concentration values of the control subjects and subjects with impaired glucose tolerance using the enzymatic method were 1.747 ± 0.047 and 2.583 ± 0.070 mmole/l and 1.753 ± 0.067 and 2.591 ± 1.02 mmole/l for the chemical method. The intra-assay coefficient of variation for the control subjects and for the subjects with impaired glucose tolerance were 1.963% and 1.583%, respectively, for the enzymatic assay and 2.728% and 2.431%, respectively, for the chemical assay. The inter-assay coefficient of variation for the control subjects and for the subjects with impaired glucose tolerance were 2.686% and 2.723% for the enzymatic assay, and 3.819% and 3.95% for the chemical assay. Since the values do not differ significantly, the chemical assay is a cost effective method that can be used in large epidemiological studies. ponents. The luminal surface of the endothelium is rich in sialoglycated proteins and thus provides an anionic barrier for the receptor mediated uptake of LDL. It has been shown that the removal of sialic acid, as well as glycosaminoglycans, increases the internalization of LDL by 20 fold (Gorog and Pearson, 1984). Thus, desialylation at the endothelium could be an early event in the atherosclerotic process of cardiovascular disease and in NIDDM. Recent evidence suggests that inflammatory processes play a part in the cause of atherosclerotic cardiovascular disease (Ross, 1999) and that the increase in acute phase proteins rich in sialoglycated proteins in serum reflects the atherosclerotic process in the endothelium (Pickup et al, 1997). Thus, an increase in the acute phase proteins may partly explain the elevation of serum sialic acid in Type 2 DM. Since sialic acid is a marker for the early atherosclerotic process and is present in most acute phase proteins, there is a need for a specific assay, which is cost effective, and can be employed in large scale epidemiological studies. In our laboratory, we have modified the periodate resorcinol method (Jourdian et al, 1971) for the measurement of total sialic acid, and compared the values to those obtained with the enzymatic assay (Simpson et al, 1993). SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 1012 Vol 36 No. 4 July 2005 MATERIALS AND METHODS