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Omega-3 FAs EPA and DHA influence membrane fluidity, lipid rafts, and signal transduction. A clinical trial, Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial, demonstrated that high-dose EPA (4 g/d icosapent ethyl) reduced composite cardiovascular events in statin-treated high-risk patients. EPA benefits correlated with on-treatment levels, but similar trials using DHA-containing formulations did not show event reduction. We hypothesized that differences in clinical efficacy of various omega-3 FA preparations could result from differential effects on membrane structure. To test this, we used small-angle X-ray diffraction to compare 1-palmitoyl-2-eicosapentaenoyl-sn-glycero-3-phosphocholine (PL-EPA), 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PL-DHA), and 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PL-AA) in membranes with and without 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol. Electron density profiles (electrons/Å 3 vs. Å) were used to determine membrane structure, including membrane width (d-space). PL-EPA and PL-DHA had similar membrane structures without POPC and/or cholesterol but had contrasting effects in the presence of POPC and cholesterol. PL-EPA increased membrane hydrocarbon core electron density over an area of ±0-10 Å from the center, indicating an extended orientation. PL-DHA increased electron density in the phospholipid head group region, concomitant with disordering in the hydrocarbon core and a similar d-space (58 Å). Adding equimolar amounts of PL-EPA and PL-DHA produced changes that were attenuated compared with their separate effects. PL-AA increased electron density centered ±12 Å from the membrane center. The contrasting effects of PL-EPA, PL-DHA, and PL-AA on membrane structure may contribute to differences observed in the biological activities and clinical actions of various omega-3 FAs., Competing Interests: Conflict of interest S. C. R. S. declares thathehasno conflicts of interest with the contents of this article. R. A. J. and C. C. are employees and stockholders of Amarin Pharma, Inc. D. L. B. discloses the following relationships: Advisory Board: Cardax, CellProthera, Cereno Scientific, Elsevier Practice Update Cardiology, Janssen, Level Ex, Medscape Cardiology, MyoKardia, NirvaMed, Novo Nordisk, PhaseBio, PLx Pharma, Regado Biosciences; Board of Directors: Boston VA Research Institute, Society of Cardiovascular Patient Care, TobeSoft; Chair: Inaugural Chair, American Heart Association Quality Oversight Committee; Data Monitoring Committees: Baim Institute for Clinical Research (formerly Harvard Clinical Research Institute, for the PORTICO trial, funded by St. Jude Medical, now Abbott), Cleveland Clinic (including for the ExCEED trial, funded by Edwards), Contego Medical (Chair, PERFORMANCE 2), Duke Clinical Research Institute, Mayo Clinic, Mount Sinai School of Medicine (for the ENVISAGE trial, funded by Daiichi Sankyo), Population Health Research Institute; Honoraria: American College of Cardiology (Senior Associate Editor, Clinical Trials and News, ACC.org; Chair, ACC Accreditation Oversight Committee), Baim Institute for Clinical Research (formerly Harvard Clinical Research Institute; RE-DUAL PCI clinical trial steering committee funded by Boehringer Ingelheim; AEGIS-II executive committee funded by CSL Behring), Belvoir Publications (Editor in Chief, Harvard Heart Letter), Canadian Medical and Surgical Knowledge Translation Research Group (clinical trial steering committees), Duke Clinical Research Institute (clinical trial steering committees, including for the PRONOUNCE trial, funded by Ferring Pharmaceuticals), HMP Global (Editor in Chief, Journal of Invasive Cardiology), Journal of the American College of Cardiology (guest editor; associate editor), K2P (Co-chair, interdisciplinary curriculum), Level Ex, Medtelligence/ReachMD (CME steering committees), MJH Life Sciences, Population Health Research Institute (for the COMPASS operations committee, publications committee, steering committee, and USA national coleader, funded by Bayer), Slack Publications (Chief Medical Editor, Cardiology Today's Intervention), Society of Cardiovascular Patient Care (Secretary/Treasurer), WebMD (CME steering committees); Other: Clinical Cardiology (Deputy Editor), NCDR-ACTION Registry Steering Committee (Chair), VA CART Research and Publications Committee (Chair); Research Funding: Abbott, Afimmune, Amarin, Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Cardax, CellProthera, Cereno Scientific, Chiesi, CSL Behring, Eisai, Ethicon, Ferring Pharmaceuticals, Forest Laboratories, Fractyl, Garmin, HLS Therapeutics, Idorsia, Ironwood, Ischemix, Janssen, Lexicon, Lilly, Medtronic, MyoKardia, NirvaMed, Novartis, Novo Nordisk, Owkin, Pfizer, PhaseBio, PLx Pharma, Regeneron, Roche, Sanofi, Synaptic, The Medicines Company, 89Bio; Royalties: Elsevier (Editor, Cardiovascular Intervention: A Companion to Braunwald's Heart Disease); Site coinvestigator: Abbott, Biotronik, Boston Scientific, CSI, St. Jude Medical (now Abbott), Philips, Svelte; Trustee: American College of Cardiology; and Unfunded Research: FlowCo, Merck, and Takeda. P. L. is an unpaid consultant to, or involved in clinical trials for Amgen, AstraZeneca, Baim Institute, Beren Therapeutics, Esperion Therapeutics, Genentech, Kancera, Kowa Pharmaceuticals, Medimmune, Merck, Norvo Nordisk, Novartis, Pfizer, Sanofi-Regeneron. P. L. is a member of the scientific advisory board for Amgen, Caristo, Cartesian, Corvidia Therapeutics, CSL Behring, DalCor Pharmaceuticals, Dewpoint, Kowa Pharmaceuticals, Olatec Therapeutics, Medimmune, Novartis, PlaqueTec, and XBiotech, Inc. P. L.: the laboratory has received research funding in the last 2 years from Novartis. P. L. is on the Board of Directors of XBiotech, Inc. P.L. has a financial interest in Xbiotech, a company developing therapeutic human antibodies. The interests of P. L. were reviewed and are managed by Brigham and Women's Hospital and Partners HealthCare in accordance with their conflict-of-interest policies., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Oxidation of small dense low-density lipoprotein (sdLDL) and membranes is causally related to atherosclerosis. The omega-3 fatty acid (FA) eicosapentaenoic acid (EPA, 20:5, ω-3) significantly reduced oxidized LDL in patients with hypertriglyceridemia by unknown mechanisms. We compared EPA effects to related FAs of varying chain length and unsaturation on oxidation of sdLDL and model membranes, and on cholesterol crystal domains. We compared EPA to the FAs: stearic (SA, 18:0), oleic (OA, 18:1, ω-9), linoleic (LA, 18:2, ω-6), alpha-linolenic (ALA, 18:3, ω-3), eicosanoic (EA, 20:0), eicosatrienoic (ETE, 20:3, ω-3), arachidonic (AA, 20:4, ω-6), docosapentaenoic (DPA, 22:5, ω-3), and docosahexaenoic (DHA, 22:6, ω-3)., Methods: Human sdLDL or model membranes of cholesterol and 1,2-Dilinoleoyl-sn-glycero-3-phosphocholine [18:2(cis)PC or DLPC] were preincubated with FAs followed by copper-induced oxidation. Malondialdehyde (MDA) or lipid hydroperoxides (LOOH) levels measured oxidation; small-angle X-ray diffraction assessed cholesterol domain formation., Results: After 40 min, EPA reduced MDA levels 70% compared to vehicle (p < 0.001). Lesser inhibition was observed with DHA, DPA, ETE, and ALA (33%, 34%, 32%, and 16%, respectively; all p < 0.001 versus vehicle). Similar relative FA effects were observed in model membranes where EPA more substantially inhibited cholesterol crystal domain formation., Conclusion: We observed relationships between hydrocarbon length and unsaturation with antioxidant activity and membrane cholesterol domain formation. EPA had the most favorable molecular structure, likely contributing to membrane stability, improved lipoprotein clearance, and reduced inflammation., General Significance: Insight is provided into FA hydrocarbon length and unsaturation relationships with antioxidant activity in lipoproteins and membranes, and cholesterol crystal domains formation., Competing Interests: Declaration of competing interest Dr. Juliano is an employee and stockholder of Amarin Pharma Inc. Dr. Mason has received consulting and research grants from Amarin Pharma Inc. Mr. Sherratt has no competing interests., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Background and Aims: Remnant-like particle cholesterol (RLP-C) is atherogenic and may increase atherosclerotic cardiovascular disease risk. Icosapent ethyl is a high-purity prescription eicosapentaenoic acid ethyl ester (approved as an adjunct to diet to reduce triglyceride [TG] levels in adult patients with TGs ≥500 mg/dL [≥5.65 mmol/L] at 4 g/day). In the MARINE and ANCHOR studies, icosapent ethyl reduced TG and other atherogenic lipid parameter levels without increasing low-density lipoprotein cholesterol (LDL-C) levels. This exploratory analysis evaluated the effects of icosapent ethyl on calculated and directly measured RLP-C., Methods: MARINE (TGs ≥500 and ≤2000 mg/dL [≥5.65 mmol/L and ≤22.6 mmol/L]) and ANCHOR (TGs ≥200 and <500 mg/dL [≥2.26 and <5.65 mmol/L] despite statin-controlled LDL-C) were phase 3, 12-week, double-blind studies that randomized adult patients to icosapent ethyl 4 g/day, 2 g/day, or placebo. This analysis assessed median percent change from baseline to study end in directly measured (immunoseparation assay) RLP-C levels (MARINE, n = 218; ANCHOR, n = 252) and calculated RLP-C levels in the full populations., Results: Icosapent ethyl 4 g/day significantly reduced directly measured RLP-C levels -29.8% (p = 0.004) in MARINE and -25.8% (p = 0.0001) in ANCHOR versus placebo, and also reduced directly measured RLP-C levels to a greater extent in subgroups with higher versus lower baseline TG levels, in patients receiving statins versus no statins (MARINE), and in patients receiving medium/higher-intensity versus lower-intensity statins (ANCHOR). Strong correlations were found between calculated and directly measured RLP-C for baseline, end-of-treatment, and percent change values in ANCHOR and MARINE (0.73-0.92; p < 0.0001 for all)., Conclusions: Icosapent ethyl 4 g/day significantly reduced calculated and directly measured RLP-C levels versus placebo in patients with elevated TG levels from the MARINE and ANCHOR studies., (Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.)

Background: Apolipoprotein C-III (ApoC-III) regulates lipoprotein and triglyceride (TG) metabolism and may have a causal role in cardiovascular disease. In the Multi-Center, Placebo-Controlled, Randomized, Double-Blind, 12-Week Study With an Open-Label Extension (MARINE) and ANCHOR studies, icosapent ethyl, a high-purity prescription eicosapentaenoic acid ethyl ester, reduced TG, and other atherogenic lipid parameters without increasing low-density lipoprotein cholesterol (LDL-C) compared with placebo., Objective: To evaluate the effects of icosapent ethyl on plasma ApoC-III levels in patients from 2 phase 3 studies., Methods: MARINE and ANCHOR were 12-week double-blind studies of icosapent ethyl in adult patients. Patients in MARINE had very high TG levels (≥500 and ≤2000 mg/dL) and patients in ANCHOR had high TG levels (≥200 and <500 mg/dL) despite statin control of LDL-C. This post hoc analysis of MARINE and ANCHOR assessed the median percent change from baseline in plasma ApoC-III levels vs placebo and includes subgroup analyses by statin use/efficacy and median ApoC-III levels., Results: We assessed ApoC-III levels in 148 and 612 patients in the MARINE and ANCHOR studies, respectively. In MARINE, the approved prescription dose of icosapent ethyl (4 g/day) significantly reduced ApoC-III levels by 25.1% (P < .0001) vs placebo. In ANCHOR, icosapent ethyl 4 g/day significantly reduced ApoC-III levels by 19.2% (P < .0001) vs placebo; subanalysis by statin efficacy revealed significant reductions vs placebo in the higher-efficacy and medium-efficacy groups (24.6% and 17.2%, respectively; both P < .0001)., Conclusion: Icosapent ethyl 4 g/day significantly reduced plasma ApoC-III levels in patients with elevated TGs from the MARINE and ANCHOR studies., (Copyright © 2016 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: Icosapent ethyl (IPE) is a high-purity prescription form of eicosapentaenoic acid ethyl ester approved at a dose of 4 g/day as an adjunct to diet to reduce triglyceride (TG) levels in adult patients with severe hypertriglyceridemia (TG ≥ 500 mg/dL)., Objective: In this prespecified exploratory analysis from the ANCHOR study of patients at high cardiovascular risk with TG ≥ 200 and <500 mg/dL despite statin control of low-density lipoprotein cholesterol, we assessed the effects of IPE on lipoprotein particle concentration and size and examined correlations of atherogenic particles with apolipoprotein B (ApoB)., Methods: Nuclear magnetic resonance spectroscopy was used to measure lipoprotein particle concentration and size., Results: Compared with placebo (n = 211), IPE 4 g/day (n = 216) significantly reduced concentrations of: total (12.2%, P = .0002), large (46.4%, P < .0001), and medium (12.1%, P = .0068) very-low-density lipoprotein (VLDL) particles; total (7.7%, P = .0017) and small (13.5%, P < .0001) LDL particles; and total (7.4%, P < .0001) and large (31.0%, P < .0001) high-density lipoprotein particles. Atherogenic lipoprotein particles (total VLDL and total LDL) correlated with ApoB at baseline (R(2) = 0.57) and week 12 (R(2) = 0.65) as did total LDL particle concentration at baseline (R(2) = 0.53) and week 12 (R(2) = 0.59). Compared with placebo, IPE 4 g/day significantly reduced VLDL (7.7%, P < .0001) and high-density lipoprotein (1.2%, P = .0014) particle sizes with a modest but significant increase in LDL particle size (0.5%, P = .0031)., Conclusions: Compared with placebo, treatment with IPE 4 g/day for 12 weeks reduced key atherogenic lipoprotein particle concentrations. At both baseline and end of study, atherogenic lipoprotein concentrations correlated with ApoB., (Copyright © 2015 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

The sterol regulatory element binding-proteins (SREBPs) are transcription factors that regulate the genes of lipid metabolism. Cholesterol and unsaturated fatty acids regulate SREBPs. Giardia lamblia (GL) is an intestinal parasite and one of the earliest derived members within the eukaryotic lineage. GLs exist as trophozoites and cysts. Growth in cholesterol depletion induces transcription of cyst-wall protein (CWP) genes that are upregulated during encystation. The hypothesis was investigated that SREBP-like pathways have a role in cwp gene transcription. Chinese hamster ovary cells were transfected with a cwp-2 promoter reporter construct. Incubation with cholesterol or oleate reduced cwp-2 mediated gene transcription to about half of the control. Incubation in sterol-depleted media, or in the presence of either an inhibitor of intracellular cholesterol movement or inhibitor of cholesterol synthesis, increased gene expression up to 3-fold. Overexpression of SREBPs increased reporter gene activity 2.5-fold. In the absence of functional SREBPs, cwp-2 was not regulated by cholesterol. Footprint analysis of cwp-2 reveals three novel binding sites for mammalian SREBPs with no homologies in other species or humans. The data show that SREBP binds to and can modulate transcription of a regulatory element from an ancient eukaryote and suggest the existence of an SREBP homolog in GL.