Low density lipoprotein-sialic acids in patients with non-insulin dependent diabetes mellitus

The important function of sialic acids in glycoproteins is to prolong the half life of the glycoproteins in the circulation. In this study, the sialic acid content of plasma low density lipoprotein (LDL)-apoproteins (predominantly B-100 apoprotein, a sialoglycoprotein) was analyzed together with relative electrophoretic mobility of LDL in 46 hypercholesterolemic and normo-cholesterolemic diabetics and non-diabetics. There was a significant positive correlation between the LDL-sialic acid content and LDL mobility either in the non-diabetics (r = 0.534, p less than 0.01) or in the diabetics (r = 0.482, p less than 0.02). Thus, the effect of the LDL-sialic acids upon the LDL electric charge was apparent. However, the LDL-sialic acids in the hypercholesterolemic diabetics were significantly (p less than 0.01) decreased to 9.64 +/- 0.63 micrograms/mg LDL protein (mean +/- S.E.) as compared with that in the normocholesterolemic diabetics (12.85 +/- 0.62 micrograms/mg LDL protein). Since the relatively sialic acid-poor LDL particles are rather accumulated in plasma of diabetic patients, the grade of sialylation of glycoprotein seems to have no role in the interaction with peripheral cells and therefore, the glycoprotein turnover, as far as the LDL apoproteins are concerned.