Abstract 5479: PPARgamma Agonist Redirects Macrophage Cholesterol from Fecal Excretion to Adipose Tissue Uptake in Mice
Peroxisome proliferator activated receptor gamma (PPARγ) agonists, used in the treatment of Type 2 diabetes, can raise HDL-C by 15–20%, but their effect on cardiovascular outcomes is controversial. Our aim was to systematically investigate the effects of PPARγ agonists on reverse cholesterol transport (RCT). Male wild type C57BL6/J mice were fed PPARγ agonist GW7845 (20mg/kg/day) or control diet for 2 weeks (n=6 per group). In vivo RCT was assessed by injecting cholesterol loaded and [3H]cholesterol labeled J774 macrophages intraperitoneally and measuring the appearance of [3H]tracer in plasma and feces over 48h. To determine the effect of GW7845 on HDL turnover and HDL derived cholesterol uptake by different tissues, a separate group of mice were injected with HDL labeled with [3H]cholesteryl ether. Blood and feces were collected over 48h, and liver, adipose tissue, muscle, kidney, and adrenal glands harvested at 48h. In vitro cholesterol efflux was assessed in J774 macrophages loaded with acetylated LDL. Cells were treated with LXR agonist (1μM GW3965) as positive control, PPARγ agonist (100nM GW7845) or DMEM-BSA (0.2%) as negative control. ApoA-1, human HDL3 or human serum (2.5%) were used as cholesterol acceptor in the efflux studies. In the macrophage RCT study, PPARγ agonist treatment led to a 56% decrease in macrophage derived 3H-tracer in fecal free sterols (p<0.01). In the in vitro model of macrophage cholesterol efflux, PPARγ agonist significantly (P<0.01) increased cholesterol efflux from macrophages to Apo A-1 and human serum, but had no effect on efflux to HDL3. In the HDL turnover study, there was no change in the [3H]cholesteryl ether-HDL fractional catabolic rate, kidney, muscle or adrenal gland [3H]cholesteryl ether uptake. There was 2.0 fold increase in HDL derived [3H]cholesterol uptake by adipose tissue (p<0.001) with concomitant 22% decrease in HDL derived [3H]cholesterol uptake by the liver (p<0.01) in the PPAR γ agonist treated group. PPARγ agonist treatment decreases the excretion of macrophage derived cholesterol in feces. This effect is not due to inhibition of cholesterol efflux from macrophages, but rather involves a redirection of effluxed cholesterol for uptake by adipose tissue.