IDIOPATHIC HYPERLIPEMIA: METABOLIC STUDIES IN AN AFFECTED FAMILY*

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Abstract
Alterations in lipid transport in blood plasma were studied in 3 siblings with idiopathic hyperlipemia whose plasma contained abnormal concentrations of very low density lipoproteins which had the chemical and physical characteristics of chylomicrons in normal individuals. The concentration of triglycerides in the blood plasma varied directly with the fat content of the diet, and single fat-rich meals produce marked increases in serum triglyceride concentration which persisted for 48 hr. The blood plasma of these subjects showed little lipoprotein lipase activity in vitro after administration of heparin in doses as high as 1 mg/ kg of body weight. The triglycerides in the very low density lipoproteins in their plasma were hydrolyzed readily by lipoprotein lipase in post-heparin plasma from healthy individuals. Triglycerides contained in the very low density lipoproteins of the plasma of one of the affected siblings were removed much more rapidly from;the circulation of a healthy subject than from that of another sibling. In 2 other subjects with the clinical syndrome of idiopathic hyperlipemia, administration of heparin produced normal levels of lipoprotein lipase activity in their blood plasma. The results of these studies suggest that a genetic deficiency of lipoprotein lipase is responsible for the defective removal of triglycerides from the plasma of the 3 siblings. They also suggest that more than one defect can result in the syndrome of idiopathic hyperlipemia.
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