ENHANCED LIPOLYSIS IN NORMAL MICE EXPRESSING LIVER-DERIVED HUMAN LIPOPROTEIN-LIPASE AFTER ADENOVIRAL GENE-TRANSFER

The authors previously demonstrated that the gene for human lipoprotei n Lipase (hLPL), an enzyme crucial to the breakdown of triglyceride (T G)-rich dietary fats, corrects the hypertriglyceridemia in lipoprotein lipase (LPL)-deficient knockout mice after adenoviral (Ad)-mediated L PL gene transfer. They have now extended their observations to primary cultured mouse hepatocytes and intact animals of normal LPL genotype, and confirm effective overexpression of hLPL from the liver and a sus tained TG-lowering effect in plasma over 60 days. A typical first-gene ration Ad-vector containing the hLPL cDNA (Ad-LPL) resulted in efficie nt gene transfer into isolated mouse hepatocytes and significant de no vo synthesis of active hLPL protein. In this experiment, 5 x 10(9) vir al particles (5 x 10(7) pfu) of either Ad-LPL or an Ad-LacZ control ve ctor were injected into CD1 mice of normal LPL genotype. Hepatic expre ssion of hLPL was confirmed at Day 7 postinjection by in situ hybridiz ation and direct measurement of LPL in the liver. This correlated with a total LPL activity (human + mouse) in postheparin plasma (PHP) of 1 020.5 standard deviation [SD] 93.6 mU/mL, versus 479.5 SD 129.7 mU/mL (p < 0.001) in Ad-LacZ controls at Day 7. Respective hLPL activity com prised 49% of the total. Significantly raised levels of hLPL protein m ass persisted until Day 60. Corresponding plasma TGs decreased to 39% of Ad-LacZ controls at Day 7, and, despite absent hLPL activity from D ay 28 on, serum TGs remained significantly lower in Ad-LPL mice up to Day 42. Fast phase liquid chromatography analysis showed a dramatic de pletion in TG-rich lipoproteins, mainly very low density Lipoproteins (VLDL) and chylomicron fractions. Therefore, Ad-mediated overexpressio n of hepatic LPL was found to significantly decrease plasma TG levels unrelated to primary LPL deficiency.