Lipoprotein Lipase with a Defect in Lipid Interface Recognition in a Case with Type V Hyperlipoproteinemia

We investigated the mechanism for expression of lipase activity of functionally abnormal LpL with a defect in lipid interface recognition and the treatment for this patient. The patient was a 14-year-old girl with maximum plasma triglyceride (TG) level of 3, 600mg/dl who had been suffering from recurrent pancreatitis. The patient's LpL was purified from post-heparin plasma by heparin-Sepharose hydrolyzed tributyrin, but not by triolein emulsified with Triton X-100, phosphatidylcholine (PC), or Chylomicrons. Normally, LpL hydrolyzes these substrates. However, the patient's LpL hydrolyzed triolein emulsified with lysophospholipid at a normal rate in the presence of apolipoprotein C-II. Moreover, the patient's LpL hydrolyzed triolein emulsified with medium chain triglyceride, tricaprin. The patient's serum triglyceride level decreased remarkably from 500-750mg/dl to 250-300mg/dl with 7.8-15.6g oral administration of medium chain triglyceride. These results might suggest that this is a case of Type V hyperlipoproteinemia with a defect in lipid interface recognition of LpL. LpL activity might be expressed by modifying the substrate condition.