Transgenic mice expressing human phospholipid transfer protein have increased HDL/non-HDL cholesterol ratio

Abstract

The role of plasma phospholipid transfer protein (PLTP) in lipoprotein metabolism is poorly understood. In vitro studies suggest that PLTP influences HDL size and composition and transfers phospholipids among lipoproteins. To provide an in vivo model for studies of PLTP physiology, transgenic mice that express human PLTP were generated. Human PLTP transcripts were detected in total RNA from adipose tissue, lung, heart, and spleen of the two distinct lines (A and C) of transgenic mice. Despite minimal expression of human PLTP in the liver of these transgenic mice and similar plasma phospholipid transfer activity in transgenic and non-transgenic mice (19.1±3.1 vs 18.9±2.7 μmol/ml/h), differences in lipoprotein levels were observed between transgenic and control mice receiving the same chow diet. Male transgenic mice of line C had significantly higher HDL cholesterol than control mice (76.4±4.6 vs 71.9±7.0 mg/dl, p<0.05) and the male transgenic mice of lines A and C had a significantly lower non-HDL cholesterol (15.1±4.1 and 15.6 ±4.7 vs 20.9±5.5 mg/dl,P<0.01 andP<0.02) and a significantly higher HDL cholesterol/non-HDL cholesterol ratio than the control mice (5.3±1.3 and 5.5±2.2 vs 3.9 ±1.9 mg/dl,P<0.01 andP<0.02). Female mice from transgenic line C had higher HDL cholesterol than control mice (64.6±4.8 vs 57.4±5.1 mg/dl,P<0.01) while female mice from line A tended to have higher HDL cholesterol/non-HDL cholesterol ratio than control mice (5.5±3.7 vs 3.8±1.4). These observations suggest that expression of PLTP in peripheral tissues play an important role in lipoprotein metabolism. Expression of human PLTP produced a more favorable lipoprotein profile and thus, enhanced expression of PLTP could potentially retard atherosclerosis.