Betulin attenuates atherosclerosis in apoE−/− mice by up-regulating ABCA1 and ABCG1

Abstract

Aim: Betulin is a pentacyclic triterpenoid isolated from the bark of yellow and white birch trees with anti-cancer and anti-malaria activities. In this study we examined the effects of betulin on atherosclerosis in apoE -/-mice and the underlying mechanisms. Methods: Murine macrophage RAW264.7 cells and human monocyte-derived THP-1 cells were tested. Foam cell formation was detected with Oil Red O staining. Cholesterol efflux was assessed using [3 H]-cholesterol efflux assay. The expression of ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1) was examined using RT-PCR and Western-blotting. The ABCA1 promoter activity was evaluated using luciferase activity assay. Male apoE -/-mice fed on a high-fat-diet (HFD), and received betulin (20 and 40 mg·kg -1 ·d -1, ig) for 12 weeks. The macrophage content and ABCA1 expression in the aortic sinuses were evaluated with immunofluorescence staining. The hepatic, intestinal and fecal cholesterol were also analyzed in the mice. Results: In RAW264.7 cells, betulin (0.1-2.5 μg/mL) dose-dependently ameliorated oxLDL-induced cholesterol accumulation and enhanced cholesterol efflux. In both RAW264.7 and THP-1 cells, betulin increased the expression of ABCA1 and ABCG1 via suppressing the transcriptional repressors sterol-responsive element-binding proteins (SREBPs) that bound to E-box motifs in ABCA1 promoter, whereas E-box binding site mutation markedly attenuated betulin-induced ABCA1 promoter activity. In HFD-fed apoE -/-mice, betulin administration significantly reduced lesions in en face aortas and aortic sinuses. Furthermore, betulin administration significantly increased ABCA1 expression and suppressed macrophage positive areas in the aortic sinuses. Moreover, betulin administration improved plasma lipid profiles and enhanced fecal cholesterol excretion in the mice. Conclusion: Betulin attenuates atherosclerosis in apoE -/-mice by promoting cholesterol efflux in macrophages.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

“…Betulinic acid was reported to be a potent pharmacological inhibitor of ACAT1 and ACAT2 (Lee et al, 2006), suggesting its potential utility in reduced CE accumulation. Moreover, an in vivo study was done using ApoE -/mice in which increased ABCA1 expression and enhanced fecal cholesterol excretion were observed upon long-term administration of betulin (40 mg/kg), along with suppressed macrophage-positive areas in the aortic sinuses (Gui et al, 2016). Another study confirmed that betulinic acid (50 mg/kg) reduced atherosclerotic lesions and reduced TG, TC, and LDL-C levels in ApoE 2/2 mice (Zhao et al, 2013a).…”

“…One study indicated that betulinic acid may induce cholesterol efflux through blocking the NF-kB-miRNA-33s-ABCA1 signal pathway in LPS-treated macrophages (Zhao et al, 2013a). Consistently, in both RAW264.7 and THP-1 cells, betulin (a betulinic acid derivative) significantly increased ABCA1/ABCG1-mediated cholesterol efflux via suppressing the expression of SREBPs, which bind to E-box motifs in the ABCA1 promoter (Gui et al, 2016).…”

“…Increased ABCA1 expression and enhanced fecal cholesterol excretion, along with suppressed macrophage positive areas in the aorta of ApoE 2/2 mice (Gui et al, 2016). Betulinic acid is a potent pharmacological inhibitor of ACAT1 and ACAT2 (Lee et al, 2006).…”

MicroRNA-124 inhibits macrophage cell apoptosis via targeting p38/MAPK signaling pathway in atherosclerosis development

“…Foam cells were confirmed by oil red O staining according to previous study. Images were taken from at least three randomly fields using IX73 microscopy (Olympus, Japan) [ 35 ].…”

Efficacy of Terpenoid in Attenuating Aortic Atherosclerosis in Apolipoprotein-E Deficient Mice: A Meta-Analysis of Animal Studies

“…Multiple independent groups in a study (e.g., different terpenoid doses) were considered separate datasets. In eleven studies [19, 20, 24, 26, 28, 33, 34, 38–40, 42], multiple groups that tested different terpenoid doses were compared to a single control group. In order to avoid an artificial increase in sample size in the pooled analysis, the number of animals in the control group for each study was divided by the number of comparator groups.…”