The clinical features and the pattern of plasma lipoprotein abnormalities were investigated in six cases of hyperlipoproteinemia which were suspected to be broad β disease.
Plasma samples containing ethylenediamine tetraacetic acid were obtained after an overnight fast. Samples were fractionated by two steps of ultracentrifugation at d=1.006 and 1.019 into four fractions; 1) VLDL or the top fraction obtained by the first centrifugation at d=1.006, 2) the second fraction (density class near 1.006) which was obtained from 1ml portion just beneath the VLDL fraction, 3) LDL1 fraction or the top fraction at the second centrifugation (1.006 <1.019), 4) the last bottom fraction which contained LDL2 and HDL(d >1.019).
Lipoproteins were analyzed on polyacrylamide gel (PAG, 3%, 4mm×5cm) electrophoresis. The lipid composition was also determined for each fraction.
PAG electrophoresis revealed one or more peaks of abnormal lipoproteins with different migration rates for each fraction. Lipoproteins in VLDL fraction had a peak at the position identical to the ordinary VLDL, but the peak was accompanied by long trailing or a group of several small components, which showed a higher migration rate than the ordinary VLDL. Corresponding to the fast migrating part of the VLDL fraction, one or more irregular peaks appeared also in the second fraction. In LDL1 fraction, an abnormal lipoprotein appeared as a single symmetrical peak with a relatively narrow base which showed an intermediate migration rate between VLDL and LDL. In normal subjects, no lipoprotein peaks were found in the second and third (LDL1) fractions. Even LDL2fraction appeared as a group of several peaks in these cases. The result shows that the abnbrmal limroteins in the plasma were distributed through a wide range of density classes.
The ratio of cholesterol to trig1ycerid in VLDL fraction in these cases ranged from 0.20 to 0.62. These values were significantly higher than the control value (=0.20). The ratio became increasingly higher through the second (density near 1.006) and the third (LDL1) fractions toward LDL2. The continuous changes in the density as well as in the lipid composition showed that the abnormal lipoproteins are intermediates between VLDL and LDL.
With an exception of case 6, these cases are diagnosed as the primary form of hyperlipoproteinemia. Although broad β disease is strongly suggested, it must be pointed out that all of the cases showed normal ECG and no one had an evidence of ischemic heart disease nor any kind of xanthomas. Although the ratio of cholesterol to triglyceride in VLDL fraction was increased, a half of our cases were excluded from the definite type III, if the criterion suggested by Hazzard (>0.42) was applied. Applying the criterion introduced by Fredrickson and his associates (VLDL-cholesterol to total triglyceride>0.25), only one of our cases fell under the category of broad disease. Estimation of the lipoprotein lipase activity and the analysis of apoproteins are now going on in our laboratory.
One of these cases (case 3) was defmitely familial. One of his brother and three of his five children had also hyperlipoproteinemia. The patient had a history of acute illness at his age of 50 showing abdominal pain, diarrhea and anemia. Soon after the recovery from the crisis, hyperlipemia was noticed which was enhanced by the intake of alcoholic biverage. When the triglyceride level was markedly increased (2,500 mg/100ml), hyperlipoproteinemia of Type V was suggested by the presence of chylomicron and the increased amount of VLDL on plasma lipoprotein electrophoresis. The intake of low fat diet decreased the plasma concentration of triglyceride to approximately 500mg/100ml, when lipoprotein electrophoresis revealed a pattern of broad βdisease.
