Probucol treatment is associated with an ABCA1-independent mechanism of cholesterol efflux to lipid poor apolipoproteins from foam cell macrophages

Objective Probucol is a cholesterol-lowering agent whose ability to prevent atherosclerosis is currently under study. Herein, we investigate the putative mechanism of probucol by observation of changes in cellular cholesterol efflux and lipid droplet morphology in macrophages. Results The inhibitory activity of probucol was assessed in non-foam or foam cell macrophages expressing ABCA1 generated by treatment with fetal calf serum (FCS) alone or in combination with acetylated LDL, respectively. Probucol inhibited cholesterol efflux to apolipoprotein A-I (apoA-I) by 31.5±0.1% in THP-1 non-foam cells and by 18.5±0.2% in foam cells. In probucol-treated non-foam THP-1 cells, nascent high-density lipoprotein (nHDL) particles with a diameter < 7 nm were generated, while in probucol-treated THP-1 foam cells nHDL particles of > 7 nm in diameter containing cholesterol were produced. Foam cells also displayed a significant accumulation of free cholesterol at the plasma membrane, as measured by percent cholestenone formed. Intracellularly, there was a significant decrease in lipid droplet number and an increase in size in probucol-treated THP-1 foam cells when compared to non-treated cells. Conclusions We report for the first time that probucol is unable to completely inhibit cholesterol efflux in foam cells to the same extent as in non-foam cells. Indeed, functional nHDL is released from foam cells in the presence of probucol. This difference in inhibitory effect could potentially be explained by changes in the plasma membrane pool as well as intracellular cholesterol storage independently of ABCA1

Effect of a PCSK9 Inhibitor and a Statin on Cholesterol Efflux Capacity: a Limitation of Current Cholesterol-Lowering Treatments?

Background: Cellular cholesterol efflux is a key step in reverse cholesterol transport that may impact on atherosclerotic cardiovascular risk. The process may be reliant on the availability of apolipoprotein (apo) B-100 containing lipoproteins to accept cholesterol from high-density lipoprotein. Evolocumab and atorvastatin are known to lower plasma apoB-100-containing lipoproteins which could impact on cholesterol efflux capacity (CEC). Methods: We conducted a 2-by-2 factorial trial of the effects of subcutaneous evolocumab (420mg every 2 weeks) and atorvastatin (80mg daily) for 8 weeks on CEC in 81 healthy, normolipidaemic men. The capacity of whole plasma and apoB-depleted plasma, including ATP binding cassette transporter A1 (ABCA1)-mediated and passive diffusion, to efflux cholesterol was measured. Results: Evolocumab and atorvastatin independently decreased whole plasma CEC (main effect P<0.01 for both). However, there were no significant effects of evolocumab and atorvastatin on apoB-depleted plasma, ABCA1-mediated and passive diffusion-mediated CEC (P>0.05 in all). In the three intervention groups combined, the reduction in whole plasma CEC was significantly correlated with the corresponding reduction in plasma apoB-100 concentration (r =0.339, P<0.01). In the evolocumab monotherapy group, the reduction in whole plasma CEC was also significantly correlated with the corresponding reduction in plasma lipoprotein(a) concentration (r =0.487, P<0.05). Conclusions: In normolipidaemic men, evolocumab and atorvastatin decrease the capacity of whole plasma to efflux cellular cholesterol. These effects may be chiefly owing to a fall in the availability of apoB-100 containing lipoproteins. Reduction in circulating lipoprotein(a) may also contribute to the decrease in whole plasma cholesterol efflux with evolocumab monotherapy

Anti-ApoA-1 IgGs in Familial Hypercholesterolemia Display Paradoxical Associations with Lipid Profile and Promote Foam Cell Formation

Anti-Apolipoprotein A-1 autoantibodies (anti-ApoA-1 IgG) promote atherogenesis via innate immune receptors, and may impair cellular cholesterol homeostasis (CH). We explored the presence of anti-ApoA-1 IgG in children (5-15 years old) with or without familial hypercholesterolemia (FH), analyzing their association with lipid profiles, and studied their in vitro effects on foam cell formation, gene regulation, and their functional impact on cholesterol passive diffusion (PD)

HDL-Mediated Cholesterol Efflux and Plasma Loading Capacities Are Altered in Subjects with Metabolically- but Not Genetically Driven Non-Alcoholic Fatty Liver Disease (NAFLD)

Background. Non-alcoholic fatty liver disease (NAFLD) increases the risk of atherosclerosis but this risk may dier between metabolically- vs. genetically-driven NAFLD. High-density lipoprotein (HDL)-mediated cholesterol efflux (CEC) and plasma loading capacity (CLC) are key factors in atherogenesis. Aims. To test whether CEC and CLC dier between metabolically- vs. genetically-determined NAFLD. Methods: CEC and CLC were measured in 19 patients with metabolic NAFLD and wild-type PNPLA3 genotype (Group M), 10 patients with genetic NAFLD carrying M148M PNPLA3 genotype (Group G), and 10 controls PNPLA3 wild-types and without NAFLD. CEC and CLC were measured ex vivo by isotopic and fluorimetric techniques using cellular models. Results: Compared with Group G, Group M showed reduced total CEC (18.6%; p < 0.001) as well as that mediated by cholesterol transporters (25.3% ABCA1; 16.3% ABCG1; 14.8% aqueous dffusion; all p < 0.04). No difference in CEC was found between Group G and controls. The presence of metabolic syndrome further impaired ABCG1-mediated CEC in Group M. Group M had higher plasma-induced CLC than Group G and controls (p < 0.001). Conclusions: Metabolically-, but not genetically-, driven NAFLD associates with dysfunctional HDL-meditated CEC and abnormal CLC. These data suggest that the mechanisms of anti-atherogenic protection in metabolic NAFLD are impaired

Effects of a dietary intervention with Mediterranean vs lacto-ovo vegetarian diets on HDL function: results from the CARDIVEG study

Background and Aim HDL-cholesterol efflux capacity (CEC) has been shown to be a better cardiovascular (CVD) risk marker than serum HDL concentration. Several foods and nutrients have been shown to improve HDL functions, however no effective dietetic nor pharmacological strategy is available to increase CEC. This study aims to evaluate the possible effect of Mediterranean diet (MD) and lacto-ovo-vegetarian diet (VD) on HDL function in a group of clinically healthy subjects at low-to-moderate CVD risk. Methods and Results Thirty apparently healthy subjects with a low-to-moderate cardiovascular risk profile (21 F; mean age: 51.3 ± 9.7 years) were randomly assigned to a 3-month MD or VD diet and then crossed. Participants on VD showed a reduction in total HDL CEC by 8.99% (p<0.001) as well as a reduction in ABCA1 mediated-CEC by 18.62% (p<0.001) compared to participants on MD. Regarding CEC mediated by aqueous diffusion, no significant changes were observed after treatment with either diet. Finally, a significant positive association between CEC mediated by the ABCA1 transporter and adiponectin was found (r=0.462; p=0.010). Conclusion The results of this study suggest that HDL activity in promoting cholesterol efflux and thereby reducing the concentration of pro-atherogenic lipoproteins was more effective in participants undergoing MD than VD. Based on these findings, the MD could be considered a better therapeutic strategy for cardiovascular prevention than VD

Efficacy of Nutraceutical Combination of Monacolin K, Berberine, and Silymarin on Lipid Profile and PCSK9 Plasma Level in a Cohort of Hypercholesterolemic Patients

The guidelines for the treatment of dyslipidemias include the use of nutraceuticals (NUTs) in association with lifestyle modifications to achieve therapeutic goals. In NUT pill, different substances may be associated; in this study we investigated a combined NUT containing monacolin K (MonK)+KA (1:1), berberine (BBR), and silymarin. The aim of the study was to evaluate low-density lipoprotein cholesterol (LDL-C) reduction in 53 patients suffering from polygenic hypercholesterolemia, characterized by a low/intermediate cardiovascular risk calculated with SCORE algorithm. The effects on lipid profile of 2-month treatment with NUT containing MonK+KA (1:1), BBR, and sylimarin, were compared with Atorvastatin (ATO) 10 mg administrated in a matched control group. Serum proprotein convertase subtilisin/kexin type 9 (PCSK9) levels and the cholesterol loading capacity (CLC) were determined at baseline and at the end of the study in NUT-treated group; variations were assessed. NUT was effective as lipid-lowering agent with a wide interindividual response variability (mean LDL-C from 170.8 +/- 19.9 to 123.8 +/- 20.0 with a change of -47.0 +/- 21.5 mg/dL; P < .001) and the effect was similar to that induced by ATO. The use of NUT significantly modified PCSK9 levels (P < .01) and CLC (P < .001), ultimately suppressing the serum-mediated foam cell generation directly measured on human macrophages. NUT reduces LDL-C levels with an effect similar to what is induced by 10 mg of ATO and ex vivo improves the functional profile of lipoproteins with antiatherogenic action