Lipoprotein changes in relation to body mass index in Native American adolescents

In view of their known high incidence of noninsulin dependent diabetes (NIDDM), we sought to determine whether Native American (Plains Indian) children and adolescents show evidence of risk factors for both NIDDM and cardiovascular disease. Children and adolescents between the ages of 4 and 19 y were recruited, and field days were organized for data collection, which included height, weight [to compute body mass index (BMI)], waist and hip circumference, family histories, quantum of Native American ancestry, and blood sampling for fasting lipids, apolipoproteins, insulin, and glucose. BMI increased with age in boys and girls and tended to be higher than in Caucasian children. The difference was significant in 5-9-y-old (p < 0.05) and 10-14-y-old (p < 0.05) boys and 10-14-y-old girls (p < 0.001). Ten- to 14-y-old girls in the highest quartile for BMI had higher triglyceride levels (p < 0.05) and lower HDL cholesterol (p < 0.001) when compared with those in the lower quartiles. In contrast, 15-19 y olds in the highest quartile for BMI had higher cholesterol, LDL cholesterol, and apolipoprotein B (p < 0.001). The mean fasting insulin levels were not related to BMI. The data suggest that, within this Plains Indian population, obesity associated with elevated lipid levels tends to begin at an early age in Native American children. Insulin levels do not appear to be related to BMI, a putative index of adiposity, in this population of children known to be prone to NIDDM in adult life.

Triglyceride enriched lipoprotein particles correlate with the severity of coronary artery disease

A group of 100 male normotensive, non-obese, non-diabetic subjects who had undergone coronary angiography were studied to determine relationship between the severity of coronary artery disease (CAD) and plasma lipids, apolipoproteins and lipoprotein particles defined by their apolipoprotein composition. CAD was found in 84 and no measurable lesions were found in 26 subjects. The severity of CAD was determined on the basis of size and number of lesions and expressed in terms of a global CAD score. Low density lipoprotein (LDL)-cholesterol showed a tendency to be higher in CAD patients than in CAD-free subjects (216 vs. 205 mg/dl, P = 0.07). HDL-cholesterol showed a tendency towards lower values in CAD patients compared to CAD-free subjects 35 vs. 41 mg/dl, P = 0.07). In univariate analysis the severity of CAD correlated with (i) complex, apolipoprotein (apo) B containing particles (Lp-B-complex, r = 0.31, P = 0.005), (ii) HDL-cholesterol (r = -0.30, P = 0.005), (iii) apoC-III in heparin precipitate (r = 0.30, P = 0.005) and (iv) plasma triglycerides (r = 0.25, P = 0.02), all of which are related to triglyceride-rich lipoproteins. A comparison between the two subspecies of complex lipoprotein particles revealed that those containing apolipoproteins B, C-III and E (Lp-B:C:E complex) were more closely associated with CAD score (r = 0.27, P = 0.01) than those containing apolipoproteins A-II, B, C, D and E (Lp-A-II:B-complex). LDL-cholesterol also correlated with the global CAD score (r = 0.23, P = 0.03). In multiple regression analysis only HDL-cholesterol (P = 0.003), apoC-III-ratio (P = 0.007), Lp-B-complex (P = 0.02) and Lp-B:C:E-complex (P = 0.04) showed significant correlation with CAD score. The results of this study demonstrate that some of the triglyceride rich lipoprotein particles represent a risk factor for CAD and support the clinical usefulness of specific assays capable of distinguishing lipoprotein particles on the basis of apolipoprotein composition.

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.

Plasma lipoprotein abnormalities in heterozygotes for familial lecithin:cholesterol acyltransferase deficiency

Measurement of plasma lecithin:cholesterol acyltransferase (LCAT) activity was used to segregate unaffected family members (n = 8) from heterozygotes (n = 8) and homozygotes (n = 2) in a large LCAT-deficient kindred. The activity was absent in the homozygotes and was decreased to 50% of normal in the heterozygotes. Endogenous cholesterol esterification rate measurements did not differentiate the heterozygotes from the unaffected family members or normal subjects. The heterozygotes had significantly higher fasting plasma triglycerides, apo B, and lower HDL-cholesterol and apo AI than the unaffected family members. The HDL of the heterozygotes had the same mass of free cholesterol and triglyceride, but the mass of cholesteryl ester was reduced by 47%. The differences were not related to abnormal postheparin lipolytic activities. However, cholesteryl ester transfer activity in the lipoprotein-free (d greater than 1.21 bottom) fraction of plasma was significantly (P less than .05) decreased in the heterozygotes when compared to unaffected members. We conclude that the low LCAT activity is the likely cause of the qualitative and quantitative differences in the plasma lipoproteins of the heterozygotes in this family with LCAT deficiency. However, the low HDL and apo A-I levels are not associated with either a family or personal history of premature atherosclerosis.

Quantification of two different types of apolipoprotein A-I containing lipoprotein particles in plasma by enzyme-linked differential-antibody immunosorbent assay

We describe a method for measuring apolipoprotein A-I (ApoA-I) associated and unassociated with apolipoprotein A-II (ApoA-II) in plasma. To directly determine associated ApoA-I, we coated microtiter plates with antibody to ApoA-II, blocked the nonspecific binding sites, and incubated the plate with plasma, immobilizing the lipoprotein particles containing both ApoA-II and ApoA-I. The unbound constituents of plasma were washed away, peroxidase-labeled antibody to ApoA-I was added, the plate rewashed, peroxidase substrate added, and the resulting color measured. ApoA-I unassociated with ApoA-II was evaluated by subtracting the concentration of associated ApoA-I from the total ApoA-I concentration. The method is specific, rapid, and precise. Within- and between-assay CVs were 5.6 and 9.8%, respectively. Analytical recovery of ApoA-I was 94%. The average normolipidemic concentration of ApoA-I associated with ApoA-II in 50 women was 790 mg/L; in 50 men, it was 788 mg/L. The corresponding values for unassociated ApoA-I were 644, 577 mg/L. Both lipoprotein forms of ApoA-I were detected in all major density classes, but were most abundant in high-density lipoproteins. The technique is applicable to measurement of any two apolipoproteins that occur in both associated and unassociated forms in plasma.

Quantification of two different types of apolipoprotein A-I containing lipoprotein particles in plasma by enzyme-linked differential-antibody immunosorbent assay

We describe a method for measuring apolipoprotein A-I (ApoA-I) associated and unassociated with apolipoprotein A-II (ApoA-II) in plasma. To directly determine associated ApoA-I, we coated microtiter plates with antibody to ApoA-II, blocked the nonspecific binding sites, and incubated the plate with plasma, immobilizing the lipoprotein particles containing both ApoA-II and ApoA-I. The unbound constituents of plasma were washed away, peroxidase-labeled antibody to ApoA-I was added, the plate rewashed, peroxidase substrate added, and the resulting color measured. ApoA-I unassociated with ApoA-II was evaluated by subtracting the concentration of associated ApoA-I from the total ApoA-I concentration. The method is specific, rapid, and precise. Within- and between-assay CVs were 5.6 and 9.8%, respectively. Analytical recovery of ApoA-I was 94%. The average normolipidemic concentration of ApoA-I associated with ApoA-II in 50 women was 790 mg/L; in 50 men, it was 788 mg/L. The corresponding values for unassociated ApoA-I were 644, 577 mg/L. Both lipoprotein forms of ApoA-I were detected in all major density classes, but were most abundant in high-density lipoproteins. The technique is applicable to measurement of any two apolipoproteins that occur in both associated and unassociated forms in plasma.