Correlation between glycated lipoproteins and fructosamine level in serum.

The correlation between the level of fructosamine and glycated proteins, including glycated lipoproteins, in serum from diabetic and nondiabetic subjects was studied. Assay of glycated proteins in serum was performed using an agarose gel film electrophoresis with nitroblue tetrazolium coloration. Glycated albumin correlated well with the fructosamine level in the diabetics (r = 0.83-0.92, p less than 0.01) but showed no correlation with the nondiabetics (r = 0.25-0.26). Also, a high correlation between the glycated beta-lipoprotein and fructosamine levels was observed in diabetic patients with hyperglycemia and in nondiabetic subjects with a high risk of atherogenesis (atherogenic index, low-density lipoprotein-cholesterol/high-density lipoprotein-cholesterol greater than 2.8) (r = 0.51-0.66, p less than 0.01). Nondiabetics with a high level of beta-lipoprotein, which is well known to cause high atherogenesity, showed a high level of glycated beta-lipoprotein similar to that in the diabetic groups with hyperglycemia; therefore, the high level of glycated beta-lipoprotein seems to be attributable not only to the hyperglycemia-accelerated glycation of beta-lipoprotein but also to an increase in the level of beta-lipoprotein in serum. Consequently, the present results show that the fructosamine level in serum reflects not only the glycation of albumin but also that of lipoproteins which are known to increase in diabetes mellitus.

Glycation of human serum albumin in long-term incubation with low and high concentrations of glucose.

Glycated albumin levels of incubation mixtures with high (25.8 mM) and low (8.2 mM) concentrations of glucose when measured by the nitroblue tetrazolium (NBT) reducing method, showed similar values at day 20-25. But when tested by thiobarbituric acid (TBA) colorimetry, the levels with high concentrations of glucose were about twice that with low concentration of glucose.

Agarose gel electrophoresis with nitroblue tetrazolium coloration for determination of glycated lipoproteins in serum from diabetics.

We describe a simple method for determining glycated lipoproteins (glc LPs) in serum by agarose gel film electrophoresis, with color development with nitroblue tetrazolium. The resulting blue bands on the film were measured densitometrically at 545 nm to quantify alpha-, pre beta-, and beta-glc LPs. Each glc LP concentration (mmol/L) was calculated from the resulting percentage multiplied by the value for serum fructosamine. Only glc beta-LP was significantly correlated with the atherogenic index: low-density LP-cholesterol/high-density LP-cholesterol (r = 0.545, P less than 0.01). The concentration of glc beta-LP in sera from diabetics was 2.2-fold higher (0.84 mmol/L) than that (0.38 mmol/L) in normal individuals. Diabetic patients with complications had higher concentrations of glc beta-LP, with large individual variations, than did patients without complications, the greatest concentration (1.02 mmol/L) being found in patients with diabetic retinopathy and (or) nephropathy. The concentration of glc beta-LP (glc LDL) in serum seems to depend on the extent and duration of hyperglycemia; it may also be a useful diagnostic indicator of diabetic atherogenesis, microangiopathy (e.g., retinopathy or nephropathy), and other complications.