Saturated fat-induced changes in Sf 60–400 particle composition reduces uptake of LDL by HepG2 cells

Kim G Jackson,Vatsala Maitin,David S Leake,Parveen Yaqoob,Christine M Williams

doi:10.1194/jlr.m500382-jlr200

Abstract

The ability of human postprandial triacylglycerol-rich lipoproteins (TRLs), isolated after meals enriched in saturated fatty acids (SFAs), n-6 PUFAs, and MUFAs, to inhibit the uptake of 125I-labeled LDL by the LDL receptor was investigated in HepG2 cells. Addition of TRLs resulted in a dose-dependent inhibition of heparin-releasable binding, cell-associated radioactivity, and degradation products of 125I-labeled LDL (P < 0.001). SFA-rich Svedberg flotation rate (Sf) 60-400 resulted in significantly greater inhibition of cell-associated radioactivity than PUFA-rich particles (P = 0.016) and total uptake of 125I-labeled LDL compared with PUFA- and MUFA-rich particles (P < 0.02). Normalization of the apolipoprotein (apo)E but not apoC-III content of the TRLs removed the effect of meal fatty acid composition, and addition of an anti-apoE antibody reversed the inhibitory effect of TRLs on the total uptake of 125I-labeled LDL. Real time RT-PCR showed that the SFA-rich Sf 60-400 increased the expression of genes involved in hepatic lipid synthesis (P < 0.05) and decreased the expression of the LDL receptor-related protein 1 compared with MUFAs (P = 0.008). In conclusion, these findings suggest an alternative or additional mechanism whereby acute fat ingestion can influence LDL clearance via competitive apoE-dependent effects of TRL on the LDL receptor.

Highlights

The ability of human postprandial triacylglycerolrich lipoproteins (TRLs), isolated after meals enriched in saturated fatty acids (SFAs), n-6 PUFAs, and MUFAs, to inhibit the uptake of 125I-labeled LDL by the LDL receptor was investigated in HepG2 cells
ApoB-48 concentrations in the Svedberg flotation rate (Sf) 60–400 fraction were higher after MUFA than after the SFA and PUFA meals (P, 0.03), with no differences observed in the apoB-100 concentrations between the meals
Because each of the TRL fractions contains a mixture of apoB-48- and apoB-100-containing lipoproteins, the molarity of the apolipoproteins and lipids (TAG and cholesterol) was divided by the molarity of total apoB in each lipoprotein fraction

Summary

Introduction

The ability of human postprandial triacylglycerolrich lipoproteins (TRLs), isolated after meals enriched in saturated fatty acids (SFAs), n-6 PUFAs, and MUFAs, to inhibit the uptake of 125I-labeled LDL by the LDL receptor was investigated in HepG2 cells. PUFA and MUFA-rich TRLs. In contrast, mRNA expression of apoB-100, SREBP1, S1P, HMG-CoA reductase, LDL receptor, MTP, and FAOX showed a tendency to be lower in the presence of PUFA than MUFArich and SFA-rich Sf 20–60 particles (Fig. 5, Table 3).

Results

Conclusion