Plasma apolipoprotein C-III levels in children with type I diabetes

The serum concentrations of apolipoproteins C-III, B, and A-I were determined in children with type I diabetes mellitus to establish whether they correlated with the level of glycosylated hemoglobin (Hb A1) and to determine whether these values differ between diabetic children and a population of normal children. Triglyceride (TG), total cholesterol (TC), and apolipoprotein (Apo) levels were studied in 95 children with type I diabetes; 51 of the children were attending a diabetes clinic and 44 were attending a diabetes summer camp. The level of Hb A1 correlated with Apo C-III (P less than .001) and TC (P less than .001) values in the clinic group, but not with Apo A-I or TG levels in either group. The Apo C-III level was higher in both groups of diabetic children (8.0 +/- 0.5 and 9.5 +/- 0.4 mg/dl) (P less than .01) than in normal subjects (6.1 +/- 0.2 mg/dl). We conclude that the Apo C-III level tends to be higher in diabetics than in normal subjects, even in the normotriglyceridemic camp group. The Apo C-III level correlated with both the TC level and Hb A1, suggesting that Apo C-III determinations in type I diabetic patients may permit early identification of atherosclerotic risk.

The magnitude of metabolically induced changes in the density of human low-density lipoproteins

Radiolabelled low-density lipoproteins (LDL), obtained from a patient with heterozygous, familial hypercholesterolaemia and from a normal subject, were injected into the patient and two normal subjects. Two approaches were made to evaluate the kinetics of metabolism of these LDL: (1) by serial measurements of radioactivity in serum, urine and the whole body; (2) by observing the density of the labelled LDL from serum using density-gradient ultracentrifugation. No significant change was seen in the model density of the LDL in either the patient or the normal subjects, but there were changes in the skewness of the radioactivity peaks. This contrasts with previously published findings in the guinea pig, in which LDL radioactivity gradually accumulated in the densest particles. The guinea pig findings suggested that lipoproteins in the LDL region are structurally modified during their intravascular circulation. The present study indicates that modification leading to changes in density does not occur to any significant degree in the human, whose LDL represent the end product of intravascular metabolism of apolipoprotein B-containing lipoproteins.