Egg Phosphatidylcholine Decreases the Lymphatic Absorption of Cholesterol in Rats

Abstract

This study was conducted to determine the effects of phosphatidylcholine (PC) from different sources on intestinal absorption of cholesterol. Male Sprague-Dawley rats were fed an AIN-93G diet containing soybean oil for 4 wk. Each rat with lymph cannula was infused via a duodenal catheter at 3.0 mL/h for 8 h with a lipid emulsion [in micromol: 451.8 triolein, 27.8 kBq 14C-cholesterol (CH), 20.7 CH, 3.6 alpha-tocopherol, and 100 PC in 24 mL PBS, pH 6.6]. The PC in the lipid emulsion was egg PC (EPC), hydrogenated egg PC (HPC), or soy PC (SPC). The EPC in the lipid emulsion markedly lowered the lymphatic absorption of 14C-CH (24.7 +/- 2.5% dose) compared with SPC (34.9 +/- 1.2%) and a lipid emulsion containing no PC (NPC) (30.8 +/- 2.0%). The HPC further lowered the absorption of 14C-CH to 21.1 +/- 1.4% dose. The outputs of phospholipid were unaffected by the source of PC infused (EPC, 32.2 +/- 1.7; HPC, 31.8 +/- 1.6; and SPC, 32.9 +/- 1.8 micromol/8 h). Compared with NPC (595.0 +/- 59.5 micromol), the total output of fatty acids over 8 h was increased significantly by SPC (685.4 +/- 55.8 micromol), but decreased by HPC (467.7 +/- 28.4 micromol). The total lymphatic output of oleic acid (18:1), the major fatty acid infused in the form of triolein, did not differ among the NPC (448.0 +/- 58.2 micromol/8 h), SPC (457.9 +/- 52.3 micromol/8 h) and EPC (412.9 +/- 20.8 micromol/8 h) groups, but was significantly lower in the HPC group (262.0 +/- 24.1 micromol/8 h). The findings provide the first evidence that EPC markedly lowers the lymphatic absorption of cholesterol under in vivo conditions. The inhibitory effect of EPC appears to be due to the higher degree of saturation of its acyl groups relative to SPC, suggesting that the intestinal absorption of egg cholesterol may be reduced by the presence of PC in egg yolk.