Postprandial phase time influences uptake of triacylglycerol from postprandial triacylglycerol-rich lipoproteins in THP-1 macrophages

Postprandial triacylglycerol-rich lipoproteins (TRL) can be taken up by macrophages, leading to foam cell formation, probably via receptor-mediated pathways. The present study was performed to investigate whether this process is modulated by the postprandial time point at which they are collected. A meal containing refined olive oil was administered to 9 healthy young men and TRL were isolated from serum at 2, 4 and 6 h postprandially. TRL lipid and apo B compositions were determined by HPLC and SDS-PAGE, respectively. Lipid accumulation in macrophages was determined after incubation of the human cell line THP-1 with the TRL. Gene expression of candidate receptors was measured by real-time PCR. The highest triacylglycerol, apo B48 and B100 concentrations in TRL were observed at 2 h after the intake of the meal. However, the greatest intracellular triacylglycerol accumulation in THP-1 macrophages was found with TRL isolated at 4 h, when their particle size (estimated as the triacylglycerol/apo B ratio) was intermediate. mRNA transcript abundance in macrophages in response to incubation with TRL was down-regulated for the LDL receptor, slightly up-regulated for the VLDL receptor and unchanged for the LDL receptorrelated protein, but no effect of the postprandial time point was found. In contrast, mRNA expression of scavenger receptors SRB1, SRA2 and CD36 was higher with 4 h-TRL. In conclusion, TRL caused massive intracellular triacylglycerol accumulation in THP-1 macrophages, which was greater when cells were incubated with intermediate-size postprandial TRL collected at 4 h and was associated with a significant rise in scavenger receptor mRNA expression. 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21