Tissue Lipoprotein Lipase in Normal Individuals and in Individuals with Exogenous Hypertriglyceridemia and the Relationship of this Enzyme to Assimilation of Fat *

Lipoprotein lipase activity (LLA) was measured in the adipose tissue of six healthy subjects and five members of a family in whom the trait for familial exogenous hypertriglyceridemia was segregating. The lipase activity measured was characteristic of lipoprotein lipase: increased by feeding, dependent on the presence of serum, and inhibited by sodium chloride and protamine sulfate. When compared with lipase activity in healthy individuals, LLA was grossly deficient in two siblings with postabsorptive chylomicronemia and was intermediate in both parents and one sibling, who had normal postabsorptive triglycerides. These findings are compatible with autosomal recessive inheritance. The hormone-sensitive lipolytic enzyme responsible for mobilization of free fatty acids from adipose storage was normal in the hyperlipemic subjects. After a 104-g fat meal, the serum triglyceride increased more in subjects heterozygotic for LLA deficiency than in the healthy subjects, and there was a relatively greater increase in chylomicrons and very low density lipoproteins in the affected individuals. These observations demonstrate the physiologic importance of lipoprotein lipase in removal of these lipoprotein groups and further clarify the differences between endogenous and exogenous hypertriglyceridemia.