Functional Abnormality of Lipoprotein Lipase in Type V Hyperlipoproteinemia

Studies were designed to explore the relationship between functional abnormalities of lipoprotein lipase (LpL) and type V hyperlipoproteinemia in two cases. Patient A was a 34-year-old woman with a plasma triglyceride (TG) level of 6, 200mg/dl during pregnancy and who suffered from acute pancreatitis. Patient B was a 14-year-old girl with a plasma triglyceride (TG) level of 2, 200mg/dl and who also suffered from acute pancreatitis. LpL was purified from Postheparin plasma using heparin-Sepharose and phenyl-Sepharose. The LpL from both patients had hydrolyzing activities toward the water soluble substrate, tributyrin.The hydrolyzing activities toward Triton X-100 emulsified triolein and chylomicron-triolein by 1U Esterase of normal LpL were 97.5n moles/h and 39.0n moles/h, respectively, whereas those by 1U Esterase of patient A's LpL were 95.5n moles/h and 14.5n moles/h, respectively. And 1U Esterase of patient B's LpL had almost no hydrolyzing activities toward Triton X-100 emulsified triolein and chylomicron-triolein. These results suggest that patient A has abnormal LpL which cannot recognize chylomicron, and that patient B has abnormal LpL which cannot recognize long chain fatty acid esters.