High glucose, unsaturated and saturated fatty acids differentially regulate expression of ATP-binding cassette transporters ABCA1 and ABCG1 in human macrophages

Abstract

The ATP-binding cassette transporters ABCA1 and ABCG1 are highly expressed in macrophage-derived foam cells and promote reverse cholesterol efflux via biogenesis of high-density lipoproteins. The aim of this study was to analyze the direct effects of bioactive factors related to the metabolic syndrome on macrophage transcript levels of all 47 human ABC transporters. Using in vitro M-CSF predifferentiated macrophages and TaqMan low density arrays we could show that linoleic acid, palmitic acid, and high glucose levels have a major impact on ABCA1 and ABCG1 expression but do not strongly affect most other human ABC transporters. In Western blot experiments we demonstrate that ABCA1 and ABCG1 protein levels are synchronously suppressed by high glucose levels and the w6-unsaturated fatty acid linoleic acid. We conclude that metabolites associated with the metabolic syndrome enhance the formation of atherosclerotic lesions by diminishing the reverse cholesterol transport function of ABCA1 and ABCG1.

Figure 1

ABCA1 and ABCG1 mRNA levels in human monocyte-derived macrophages as determined by Taqman real-time qRT-PCR. (A) Time kinetic experiments with normal human blood donor macrophages incubated in the presence of M-CSF for the indicated time points. (B) mRNA levels of ABCA1 and ABCG1 after 4 days predifferentiation and further 24 h incubation in the presence of insulin (Ins), palmitic acid (PA), linoleic acid (LA), 9-cis-retinoic acid (RA) and T0901317 (T0). (C) mRNA levels of ABCA1 and ABCG1 of 5 day differentiated macrophages and macrophage cells predifferentiated for 4 days after further incubation in the presence of high-dose glucose (Glc) for 24 h (4 d + 24 h Glc) and 72 h (4 d + 72 h Glc), respectively. Data are presented as mean ± s.e.m of three independent stimulations. Significance was calculated using Student's t-test, ^*P < 0.05.

Figure 2

ABCA1 and ABCG1 protein levels in human monocyte-derived macrophages determined by Western blot analysis. (A) Time kinetic experiments with normal human blood donor macrophages incubated in the presence of M-CSF for the indicated time points. (B) Protein levels of ABCA1 and ABCG1 in 4 days predifferentiated macrophages after incubation in the presence of glucose (Glc), insulin (Ins), palmitic acid (PA), linoleic acid (LA), 9-cis-retinoic acid (RA) and T0901317 (T0) for 24 h. (C) Protein levels of ABCA1 and ABCG1 in 7 d and 9 d control incubated macrophages or cells after incubation in the presence of high-dose glucose for 72 (4 d + 72 h Glc) and 120 h (4 days + 120 h Glc), respectively.