Type I hyperlipoproteinemia caused by lipoprotein lipase defect in lipid-interface recognition was relieved by administration of medium-chain triglyceride.

We have previously reported lipoprotein lipase with a defect of lipid-interface recognition in a patient with type I hyperlipoproteinemia. In this patient, lipoprotein lipase from post-heparin plasma (PHP) hydrolyzed monomeric substrate tributyrin, but scarcely hydrolyzed triolein emulsified with Triton X-100 and that in very-low-density lipoproteins ([VLDL] d < 1.006 g/mL), and did not bind to VLDL. The triglyceride (TG) level of this patient did not decrease to less than 1,000 mg/dL with a low-fat diet (1,400 kcal containing 10 g fat/d). When the patient took 30 g medium-chain TG (MCT) in addition to the 1,400-kcal diet, her serum TG level decreased to 250 mg/dL and her clinical signs improved. The low clearance rate of serum TG with heparin injection improved after intake of MCT. Caproic acid levels were maintained at 1.4% and 2.6% in chylomicrons and VLDL after MCT intake, respectively. The patient's lipoprotein lipase hydrolyzed triolein emulsified with 2% tricaprin at the same rate as that of control lipoprotein lipase. The patient's lipoprotein lipase-catalyzed hydrolyzing rate of triolein in chylomicrons obtained after MCT administration was also enhanced up to 70% of that of control lipoprotein lipase. These findings suggest that hypertriglyceridemia caused by lipoprotein lipase with a defect in lipid-interface recognition could be relieved with the administration of medium-chain TG, and that one of the mechanisms of this effect might be a modification of TG-rich lipoproteins by MCT.