Effect of fish oil on atherosclerosis and lipoprotein metabolism

Mussel oil is superior to fish oil in preventing atherosclerosis of ApoE-/- mice

Objectives

The present study aimed to explore the preventive effect of mussel oil (MO) on atherosclerosis and the potential mechanism in apolipoprotein E-null (ApoE-/-) mice.

Methods

ApoE-/- mice were fed with a high-fat and high-cholesterol chow and given corn oil (CO), fish oil (FO), MO, or aspirin (ASP, dissolved in CO) by gavage for 12  weeks. The total n-3 polyunsaturated fatty acids (PUFAs) in MO (51.01%) and FO (46.82%) were comparable (mainly C22:6n-3 and C20:5n-3). Wild-type mice were fed with a normal chow and given equivalent CO as health control (CON).

Results

Compared with the CON group, obvious atherosclerotic plaque appeared at aorta and aortic sinus in the CO group. Compared with the CO group, MO but not FO had a significantly smaller atherosclerotic plaque area in the aorta. The aortic atherosclerotic plaque area was comparable in the MO, CON, and ASP groups. The MO group had a significantly smaller atherosclerotic plaque area, lower lipid deposition, lower contents of smooth muscle cell (SMC), and slightly lower contents of macrophage at the aortic sinus than the FO group. Serum concentrations of IL-1β, NF-κB, and VCAM-1 were comparable in the MO and FO groups and were significantly lower than the CO group. Compared with the CO group, the MO group but not FO group had significantly lower aortic protein levels of p65NF-κB, p38MAPK, and VCAM-1. The aortic protein levels of p-p65NF-κB and p-p38MAPK were significantly lower in the MO group than the FO group.

Conclusion

In conclusion, MO is more potent than FO in preventing atherosclerosis, and the possible mechanism may be by downregulating p38MAPK/NF-κB signaling pathway, decreasing VCAM-1 and macrophage, and inhibiting proliferation and migration of SMC.

Dietary fatty acid quality affects systemic parameters and promotes prostatitis and pre-neoplastic lesions

Environmental and nutritional factors, including fatty acids (FA), are associated with prostatitis, benign prostate hyperplasia and prostate cancer. We hypothesized that different FA in normolipidic diets (7%) affect prostate physiology, increasing the susceptibility to prostate disorders. Thus, we fed male C57/BL6 mice with normolipidic diets based on linseed oil, soybean oil or lard (varying saturated and unsaturated FA contents and ω-3/ω-6 ratios) for 12 or 32 weeks after weaning and examined structural and functional parameters of the ventral prostate (VP) in the systemic metabolic context. Mongolian gerbils were included because they present a metabolic detour for low water consumption (i.e., oxidize FA to produce metabolic water). A linseed oil-based diet (LO, 67.4% PUFAs, ω-3/ω-6 = 3.70) resulted in a thermogenic profile, while a soybean oil-based diet (SO, 52.7% PUFAs, ω-3/ω-6 = 0.11) increased body growth and adiposity. Mice fed lard (PF, 13.1% PUFA, ω-3/ω-6 = 0.07) depicted a biphasic growth, resulting in decreased adiposity in adulthood. SO and PF resulted in hepatic steatosis and steatohepatitis, respectively. PF and SO increased prostate epithelial volume, and lard resulted in epithelial hyperplasia. Animals in the LO group had smaller prostates with predominant atrophic epithelia and inflammatory loci. Inflammatory cells were frequent in the VP of PF mice (predominantly stromal) and LO mice (predominantly luminal). RNAseq after 12 weeks revealed good predictors of a later-onset inflammation. The transcriptome unveiled ontologies related to ER stress after 32 weeks on PF diets. In conclusion, different FA qualities result in different metabolic phenotypes and differentially impact prostate size, epithelial volume, inflammation and gene expression.

Effects of n-3 fatty acid supplements on cardiometabolic profiles in hypertensive patients with abdominal obesity in Inner Mongolia: a randomized controlled trial

Daily supplementation with n-3 fatty acid (FA) has been believed to be an adjunct or alternative to drug treatments to reduce blood pressure (BP) and triglyceride (TG) levels in western patients with high risk of cardiovascular disease.

Primary prevention of atherosclerosis by pretreatment of low-density lipoprotein receptor knockout mice with sesame oil and its aqueous components

Pharmacological intervention using statins and PCSK9 inhibitors have become first-line therapy in the prevention of hypercholesterolemia and atherosclerosis. Currently, no agent is available for the primary prevention of atherosclerosis. However, there is an emerging hypothesis that atherosclerosis could be driven by inflammation. In this study, we tested whether pretreatment with an aqueous extract from sesame oil (SOAE), which showed potent anti-inflammatory properties without hypocholesterolemic actions, would prevent subsequent atherosclerosis development in a mouse model. RAW 264.7 macrophages and female low-density lipoprotein receptor knockout (LDLR^−/−) mice were used for in vitro and in vivo studies, respectively. Plasma lipids, cytokines and atherosclerotic lesions were quantified at the end of the study. RNA was extracted from the liver and aortic tissues and used for gene analysis. Pre-treatment of SOAE prevented Ox-LDL uptake by RAW macrophages and further inflammation in vitro. SOAE pre-treatment significantly reduced atherosclerotic lesions and pro-inflammatory gene expressions in LDLR^−/− mice as compared to control mice. No significant change in plasma cholesterol levels was observed. A significant reduction in plasma levels of TNF-α, IL-6, MCP-1 and VCAM1 was observed in the SOAE pre-treated animals. This is the first study that demonstrates that pre-treatment with anti-inflammatory agents, could delay/decrease atherosclerosis.

Sesame Oil and an Aqueous Extract Derived from Sesame Oil Enhance Regression of Preexisting Atherosclerotic Lesions in Low-Density Lipoprotein Receptor Knockout Mice

Diet and exercise are recommended both as a prophylactic and as a therapeutic approach for patients with established coronary artery disease. We previously reported that sesame oil (SESO) and its aqueous extract (SOAE) showed antiatherosclerotic and anti-inflammatory properties. We also observed that genes involved in reverse cholesterol transport (RCT) might be activated. In this study, we tested whether post-treatment with SESO or SOAE would reduce preexisting atherosclerosis by enhancing RCT. Female low-density lipoprotein receptor knockout (LDL-R^-/-) mice were fed an atherogenic diet for 3 months, followed by post-treatment with either control or SESO or SOAE for 1 month. Plasma lipids and atherosclerotic lesions were quantified at the end of the study. RNA was extracted from the aortic tissues and used for real-time polymerase chain reaction analysis. SESO and SOAE post-treatment significantly reduced atherosclerotic lesions in LDL-R^-/- mice compared to controls. No significant change in plasma cholesterol, triglyceride, or LDL cholesterol levels was observed. Aortic gene analysis showed that the SESO/SOAE post-treatment reduced inflammatory gene expression and induced genes involved in cholesterol metabolism and RCT. This is the first study that demonstrates that post-treatment with SESO and SOAE could be an effective treatment for preexisting atherosclerosis and inflammation. The study also may suggest that reducing inflammation might be conducive to an accelerated regression of lesions.

In vivo activation of leukocyte GPR120/FFAR4 by PUFAs has minimal impact on atherosclerosis in LDL receptor knockout mice

G protein-coupled receptor (GPR)120/FFA receptor (FFAR)4 (GPR120/FFAR4) activation by n-3 PUFAs attenuates inflammation, but its impact on atherosclerosis is unknown. We determined whether in vivo activation of leukocyte GPR120/FFAR4 by n-3 versus n-6 PUFAs is atheroprotective. Leukocyte GPR120/FFAR4 WT or KO mice in the LDL receptor KO background were generated by bone marrow transplantation. Mice were fed one of the four atherogenic diets containing 0.2% cholesterol and 10% calories as palm oil (PO) + 10% calories as: 1) PO, 2) fish oil (FO; 20:5 n-3 and 22:6 n-3 enriched), 3) echium oil (EO; 18:4 n-3 enriched), or 4) borage oil (BO; 18:3 n-6 enriched) for 16 weeks. Compared with PO, mice fed BO, EO, and FO had significantly reduced plasma cholesterol, TG, VLDL cholesterol, hepatic neutral lipid, and atherosclerosis that were equivalent for WT and KO mice. In BO-, EO-, and FO-fed mice, but not PO-fed mice, lack of leukocyte GPR120/FFAR4 resulted in neutrophilia, pro-inflammatory Ly6C^hi monocytosis, increased aortic root monocyte recruitment, and increased hepatic inflammatory gene expression. In conclusion, leukocyte GPR120 expression has minimal effects on dietary PUFA-induced plasma lipid/lipoprotein reduction and atheroprotection, and there is no distinction between n-3 versus n-6 PUFAs in activating anti-inflammatory effects of leukocyte GPR120/FFAR4 in vivo.

Water-Soluble Components of Sesame Oil Reduce Inflammation and Atherosclerosis

Atherosclerosis, a major form of cardiovascular disease, is now recognized as a chronic inflammatory disease. Nonpharmacological means of treating chronic diseases have gained attention recently. We previously reported that sesame oil aqueous extract (SOAE) has anti-inflammatory properties, both in vitro and in vivo. In this study, we have investigated the antiatherosclerotic properties of SOAE, and the mechanisms, through genes and inflammatory markers, by which SOAE might modulate atherosclerosis. Low-density lipoprotein receptor (LDL-R) knockout female mice were fed with either a high-fat (HF) diet or an HF diet supplemented with SOAE. Plasma lipids and atherosclerotic lesions were quantified after 3 months of feeding. Plasma samples were used for global cytokine array. RNA was extracted from both liver tissue and the aorta, and used for gene analysis. The high-fat diet supplemented with SOAE significantly reduced atherosclerotic lesions, plasma cholesterol, and LDL cholesterol levels in LDL-R(-/-) mice. Plasma inflammatory cytokines were reduced in the SOAE diet-fed animals, but not significantly, demonstrating potential anti-inflammatory properties of SOAE. Gene analysis showed the HF diet supplemented with SOAE reduced gene expression involved in inflammation and induced genes involved in cholesterol metabolism and reverse cholesterol transport, an anti-inflammatory process. Our studies suggest that a SOAE-enriched diet could be an effective nonpharmacological treatment for atherosclerosis by controlling inflammation and regulating lipid metabolism.

n-3 Polyunsaturated Fatty Acid Supplementation Has No Effect on Postprandial Triglyceride-Rich Lipoprotein Kinetics in Men with Type 2 Diabetes

Dietary n-3 polyunsaturated fatty acids (PUFAs) have been proposed to modulate plasma lipids, lipoprotein metabolism, and inflammatory state and to reduce triglyceride (TG) concentrations. The present double-blind, randomized, placebo-controlled, crossover study investigated the effects of n-3 PUFA supplementation at 3 g/d for 8 weeks on the intravascular kinetics of intestinally derived apolipoprotein (apo) B-48-containing lipoproteins in 10 men with type 2 diabetes. In vivo kinetics of the TG-rich lipoprotein (TRL) apoB-48 and VLDL apoB-100 were assessed using a primed-constant infusion of L-[5,5,5-D3] leucine for 12 hours in a fed state. Compared with the placebo, n-3 PUFA supplementation significantly reduced fasting TG concentrations by -9.7% (P = 0.05) but also significantly increased plasma levels of cholesterol (C) (+6.0%, P = 0.05), LDL-C (+12.2%, P = 0.04), and HDL-C (+8.4, P = 0.007). n-3 PUFA supplementation had no significant impact on postprandial TRL apoB-48 and VLDL apoB-100 levels or on the production or catabolic rates of these lipoproteins. These data indicate that 8-week supplementation with n-3 PUFAs in men with type 2 diabetes has no beneficial effect on TRL apoB-48 and VLDL apoB-100 levels or kinetics.

Anti-atherosclerotic and anti-inflammatory actions of sesame oil

Atherosclerosis, a major form of cardiovascular disease, has now been recognized as a chronic inflammatory disease. Nonpharmacological means of treating chronic diseases have gained attention recently. We previously reported that sesame oil has anti-atherosclerotic properties. In this study, we have determined the mechanisms by which sesame oil might modulate atherosclerosis by identifying genes and inflammatory markers. Low-density lipoprotein receptor knockout (LDLR(-/-)) female mice were fed with either an atherogenic diet or an atherogenic diet reformulated with sesame oil (sesame oil diet). Plasma lipids and atherosclerotic lesions were quantified after 3 months of feeding. Plasma samples were used for cytokine analysis. RNA was extracted from the liver tissue and used for global gene arrays. The sesame oil diet significantly reduced atherosclerotic lesions, plasma cholesterol, triglyceride, and LDL cholesterol levels in LDLR(-/-) mice. Plasma inflammatory cytokines, such as MCP-1, RANTES, IL-1α, IL-6, and CXCL-16, were significantly reduced, demonstrating an anti-inflammatory property of sesame oil. Gene array analysis showed that sesame oil induced many genes, including ABCA1, ABCA2, APOE, LCAT, and CYP7A1, which are involved in cholesterol metabolism and reverse cholesterol transport. In conclusion, our studies suggest that a sesame oil-enriched diet could be an effective nonpharmacological treatment for atherosclerosis by controlling inflammation and regulating lipid metabolism.

Dietary interventions (plant sterols, stanols, omega-3 fatty acids, soy protein and dietary fibers) for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolaemia (FH). However, a consensus has yet to be reached on the most appropriate dietary treatment. Plant sterols are commonly used in FH although patients may know them by other names like phytosterols or stanols.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register, which is compiled from electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (updated with each new issue of The Cochrane Library), quarterly searches of MEDLINE and the prospective handsearching of one journal - Journal of Inherited Metabolic Disease. Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 22 August 2013. We also searched PubMed to 05 February 2012.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and risk of bias and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the 2014 update of the review, 15 trials have been included, with a total of 453 participants across seven comparison groups. The included trials had either a low or unclear risk of bias for most of the parameters used for risk assessment. Only short-term outcomes could be assessed due to the short duration of follow up in the included trials. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included trials. No significant differences were noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found for the following comparisons and outcomes: for the comparison between plant sterols and cholesterol-lowering diet (in favour of plant sterols), total cholesterol levels, mean difference 0.30 mmol/l (95% confidence interval 0.12 to 0.48); decreased serum LDL cholesterol, mean difference -0.60 mmol/l (95% CI -0.89 to -0.31). Fasting serum HDL cholesterol levels were elevated, mean difference -0.04 mmol/l (95% CI -0.11 to 0.03) and serum triglyceride concentration was reduced, mean difference -0.03 mmol/l (95% CI -0.15 to -0.09), although these changes were not statistically significant. Similarly, guar gum when given as an add on therapy to bezafibrate reduced total cholesterol and LDL levels as compared to bezafibrate alone.

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, for the primary outcomes: evidence and incidence of ischaemic heart disease, number of deaths and age at death,due to the lack of data on these. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein, dietary fibers to a cholesterol-lowering diet.

Omega-3 fatty acids ameliorate atherosclerosis by favorably altering monocyte subsets and limiting monocyte recruitment to aortic lesions

OBJECTIVE

Fish oil, containing omega-3 fatty acids, attenuates atherosclerosis. We hypothesized that omega-3 fatty acid-enriched oils are atheroprotective through alteration of monocyte subsets and their trafficking into atherosclerotic lesions.

METHODS AND RESULTS

Low-density lipoprotein receptor knockout and apolipoprotein E(-/-) mice were fed diets containing 10% (calories) palm oil and 0.2% cholesterol, supplemented with an additional 10% palm oil, echium oil (containing 18:4 n-3), or fish oil. Compared with palm oil-fed low-density lipoprotein receptor knockout mice, echium oil and fish oil significantly reduced plasma cholesterol, splenic Ly6C(hi) monocytosis by ≈50%, atherosclerosis by 40% to 70%, monocyte trafficking into the aortic root by ≈50%, and atherosclerotic lesion macrophage content by 30% to 44%. In contrast, atherosclerosis and monocyte trafficking into the artery wall was not altered by omega-3 fatty acids in apolipoprotein E(-/-) mice; however, Ly6C(hi) splenic monocytes positively correlated with aortic root intimal area across all diet groups. In apolipoprotein E(-/-) mice, fish oil reduced the percentage of blood Ly6C(hi) monocytes, despite an average 2-fold higher plasma cholesterol relative to palm oil.

CONCLUSIONS

The presence of splenic Ly6C(hi) monocytes parallels the appearance of atherosclerotic disease in both low-density lipoprotein receptor knockout and apolipoprotein E(-/-) mice. Furthermore, omega-3 fatty acids favorably alter monocyte subsets independently from effects on plasma cholesterol and reduce monocyte recruitment into atherosclerotic lesions.

A double-blind randomized study comparing the efficacy and safety of a composite vs a conventional intravenous fat emulsion in postsurgical gastrointestinal tumor patients

BACKGROUND

Composite intravenous fat emulsion, a fat emulsion composed of soybean oil, medium-chain triglycerides (MCT), olive oil, and fish oil, was evaluated for metabolic efficacy, immune modulation, clinical efficacy, safety, and tolerance in surgical gastrointestinal (GI) tumor patients.

METHODS

In a prospective, randomized, double-blind study, 40 patients were randomized after elective digestive surgery to receive isonitrogenous, isoenergetic parenteral nutrition for 5 days postoperatively with either composite 20% IVFE (composed of soybean, MCT, olive, and fish oils) or a conventional long-chain triglyceride (LCT)/MCT 20% IVFE (LCT/MCT IVFE); IVFE was dosed at 1-2 g/kg body weight. Safety and efficacy parameters were assessed on operation day (day 0) and at the end of study (day 6). Adverse events were documented daily and clinical outcomes were recorded and compared between the groups.

RESULTS

Metabolic parameters, laboratory parameters, proinflammatory cytokine levels, adverse events, and clinical outcomes did not differ between the 2 groups, with the exception that postoperative low-density lipoprotein levels decreased significantly in the composite IVFE group (93.2 ± 24.3 vs 110.5 ± 26.4 mg/dL, P = .038).

CONCLUSIONS

composite IVFE was comparable with conventional LCT/MCT IVFE in efficacy, safety, tolerance, and clinical outcomes in surgical GI tumor patients.

ATP-binding cassette transporter A1 and HDL metabolism: effects of fatty acids

Ample evidence indicates that dietary fatty acids alter the plasma levels of high-density lipoprotein cholesterol (HDL-C). However, the mechanisms underlying the effects of fatty acids still remain elusive. Recent advances in our understanding of ATP-binding cassette transporter A1 (ABCA1) function and regulation have provided a valuable insight into the mechanisms by which fatty acids may affect plasma HDL-C levels. ABCA1 mediates the assembly of phospholipids and free cholesterol with apolipoprotein A-I, which is a critical step for HDL biogenesis. Studies have shown that unsaturated fatty acids, but not saturated fatty acids, repress the expression of ABCA1 in vitro. Although information on mechanisms for the fatty-acid-mediated regulation of ABCA1 expression is still limited and controversial, recent evidence suggests that unsaturated fatty acids inhibit the expression of ABCA1 at the transcriptional and posttranscriptional levels. The transcriptional repression of ABCA1 expression by unsaturated fatty acids is likely liver X receptor dependent. Evidence also suggests that histone deacetylation may play a role in the repression. Posttranscriptionally, unsaturated fatty acids may facilitate ABCA1 protein degradation, which may involve phosphorylation of ABCA1 by protein kinases. Further studies are warranted to better understand the role of dietary fatty acids in HDL metabolism and their effects on cardiovascular health.

A modified sesamol derivative inhibits progression of atherosclerosis

OBJECTIVE

Sesamol, a phenolic component of lignans, has been previously shown to reduce lipopolysaccharide-induced oxidative stress and upregulate phosphatidylinositol 3-kinase/Akt/endothelial nitric oxide synthase pathways. In the present study, we synthesized a modified form of sesamol (INV-403) to enhance its properties and assessed its effects on atherosclerosis.

METHODS AND RESULTS

Watanabe heritable hyperlipidemic rabbits were fed with high-cholesterol chow for 6 weeks and then randomized to receive high-cholesterol diet either alone or combined with INV-403 (20 mg/kg per day) for 12 weeks. Serial MRI analysis demonstrated that INV-403 rapidly reduced atherosclerotic plaques (within 6 weeks), with confirmatory morphological analysis at 12 weeks posttreatment revealing reduced atherosclerosis paralleled by reduction in lipid and inflammatory cell content. Consistent with its effect on atherosclerosis, INV-403 improved vascular function (decreased constriction to angiotensin II and increased relaxation to acetylcholine), reduced systemic and plaque oxidative stress, and inhibited nuclear factor-κB activation via effects on nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) phosphorylation with coordinate reduction in key endothelial adhesion molecules. In vitro experiments in cultured endothelial cells revealed effects of INV-403 in reducing IκBα phosphorylation via inhibition of IκB kinase 2 (IKK2).

CONCLUSIONS

INV-403 is a novel modified lignan derivative that potently inhibits atherosclerosis progression via its effects on IKK2 and nuclear factor-κB signaling.

Dietary n-3 LCPUFA from fish oil but not alpha-linolenic acid-derived LCPUFA confers atheroprotection in mice

The atheroprotective potential of n-3 alpha-linolenic acid (ALA) has not yet been fully determined, even in murine models of atherosclerosis. We tested whether ALA-derived, n-3 long chain polyunsaturated fatty acids (LCPUFA) could offer atheroprotection in a dose-dependent manner. Apolipoprotein B (ApoB)100/100LDLr-/- mice were fed with diets containing two levels of ALA from flaxseed oil for 16 weeks. Fish oil- and cis-monounsaturated-fat-enriched diets were used as positive and negative controls, respectively. The mice fed cis-monounsaturated fat and ALA-enriched diets exhibited equivalent plasma total cholesterol (TPC) and LDL-cholesterol (LDL-c) levels; only mice fed the fish-oil diet had lower TPC and LDL-c concentrations. Plasma LDL-CE fatty acid composition analysis showed that ALA-enriched diets lowered the percentage of atherogenic cholesteryl oleate compared with cis-monounsaturated-fat diet (44% versus 55.6%) but not as efficiently as the fish-oil diet (32.4%). Although both ALA and fish-oil diets equally enriched hepatic phospholipids with eicosapentaenoic acid (EPA) and ALA-enriched diets lowered hepatic cholesteryl ester (CE) levels compared with cis-monounsaturated-fat diet, only fish oil strongly protected from atherosclerosis. These outcomes indicate that dietary n-3 LCPUFA from fish oil and n-3 LCPUFA (mostly EPA) synthesized endogenously from ALA were not equally atheroprotective in these mice.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolemia. However, a consensus has yet to be reached on the most appropriate dietary treatment.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register.Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 09 October 2009.We also searched PubMed till 01 June 2008.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and methodological quality and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the present update, four new trials have been added making eleven trials with a total of 331 participants eligible for inclusion. Only short-term outcomes could be assessed due to the short duration of follow up in the included studies. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included studies. No significant difference was noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found only for the following comparison and outcome: total cholesterol levels for the comparison between plant sterols and cholesterol-lowering diet, mean difference 0.70 (95% confidence interval 0.19 to 1.21).

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein to a cholesterol-lowering diet.

Influence of cholesterol and fish oil dietary intake on nitric oxide-induced apoptosis in vascular smooth muscle cells

Apoptosis of vascular smooth muscle cells (SMC) is critically involved in the progression of atherosclerosis. We previously reported that dietary cholesterol intake induces changes in SMC at molecular and gene expression levels. The objectives of the present study were to investigate the differential response to nitric oxide of vascular SMC obtained from chicks after cholesterol and fish oil dietary intake and to examine effects on the main pro-apoptotic and anti-apoptotic genes. Dietary cholesterol intake reduced the Bcl-2/Bax (anti-apoptotic/pro-apoptotic) protein ratio in SMC, making them more susceptible to apoptosis. When cholesterol was withdrawn and replaced with a fish oil-enriched diet, the Bcl-xl/Bax protein ratio significantly increased, reversing the changes induced by cholesterol. The decrease in c-myc gene expression after apoptotic stimuli and the increase in Bcl-xl/Bax ratio indicate that fish oil has a protective role against apoptosis in SMC. Nitroprussiate-like nitric oxide donors exerted an intensive action on vascular SMC cultures. However, SMC-C (isolated from animals fed with control diet) and SMC-Ch (isolated from animals fed with cholesterol-enriched diet) responded differently to nitric oxide, especially in their bcl-2 and bcl-xl gene expression. SMC isolated from animals fed with cholesterol-enriched and then fish oil-enriched diet (SMC-Ch-FO cultures) showed an intermediate apoptosis level (Bcl-2/Bax ratio) between SMC-C and SMC-Ch, induction of c-myc expression and elevated p53 expression. These findings indicate that fish oil protects SMC against apoptosis.

When does atherosclerosis become irreversible? Chronological change from an early to an advanced atherosclerotic lesion observed by angioscopy

Quite a large number of studies on atherosclerosis have been published to date. However, no report on the development and irreversibility of lesions has been published so far. The authors conducted the following experiments to examine in vivo lesions under direct vision. Atherosclerotic lesions were created in 11 Japanese macaques, and progress of the lesions was observed under changing feeding conditions. The efficacy of cholesterol-lowering therapy was also evaluated and the mechanism by which eicosapentaenoic acid (EPA) suppresses atherosclerosis was examined. The results of this long-term study were as follows: (1) Early lesions of atherosclerosis (fatty streaks) developed in the aortic wall owing to cholesterol loading disappeared when the serum concentration of total cholesterol was reduced. (2) Atheromas first developed at the orifices of major branches of the aorta. And even though serum cholesterol was reduced, the lesions gradually spread to nearby areas. (3) After atheromas developed, advancement of the lesions slowed, as assessed by angioscopy, when EPA was administered while cholesterol loading was continued. Thus, early lesions of atherosclerosis are reversible and cholesterol-lowering therapy is an effective treatment; however, since advanced lesions seem to be irreversible, cholesterol-lowering therapy may not be effective for such lesions. The results of angioscopic examination showed that EPA slowed the progression of atheromatous lesions, and probably suppression of the proliferation of smooth muscle cells is the mechanism of such effect.

Evidence for altered positional specificity of LCAT in vivo: studies with docosahexaenoic acid feeding in humans

The percentage of saturated cholesteryl esters (CEs) synthesized by human LCAT is several times higher than expected from the sn-2 acyl composition of plasma phosphatidylcholine (PC), whereas the synthesis of 20:4 CE and 22:6 CE is much lower than expected. To explain these discrepancies, we proposed that LCAT transfers some saturated fatty acids from the sn-1 position of PC species that contain 20:4 or 22:6 at sn-2. The present studies provide in vivo evidence for this hypothesis. We determined the composition and synthesis of CE species in plasma of volunteers before and after a 6 week dietary supplementation with docosahexaenoic acid (22:6; DHA). In addition to an increase in the DHA content of all plasma lipids, there was a significant (+12%; P <0.005) increase of 16:0 CE, although there was no increase in 16:0 at sn-2 of PC. The increase of DHA in CE was much lower than its increase at sn-2 of PC. Ex vivo synthesis of CE species in plasma showed a significant (+24%; P <0.005) increase in the synthesis of 16:0 CE after DHA supplementation, which correlated positively with the increase of 22:6, but not of 16:0, at sn-2 of PC. These results show that the positional specificity of human LCAT is altered when the concentration of 16:0-22:6 PC is increased by DHA supplementation.

A fish oil diet produces different degrees of suppression of apoB and triglyceride secretion in human apoB transgenic mouse strains

Human apolipoprotein B (apoB) transgenic (HuBTg) mouse strains were used to assess genetic effects on the response to fish oil (FO), a source of n-3 fatty acids. A congenic HuBTg strain of the C57BL/6 (B6) background and six F1 HuBTg strains were fed a FO for 2 weeks. Different responses of plasma lipid levels to FO were observed among these strains. In particular, plasma apoB levels changed minimally in FO-fed male B6 HuBTg mice, but increased markedly ( approximately 40%) in FO-fed male FVB/NJ (FVB) x B6 F1 HuBTg mice. These strain differences were determined mainly by hepatic apoB secretion rates and were likely regulated by posttranscriptional mechanisms. In addition, plasma triglyceride (TG) levels were reduced (14%) in FO-fed B6 mice, but not in FVB x B6 mice. These strain differences were determined mainly by TG secretion rates, but were not due to differences in hepatic lipogenesis. Hepatic mRNA levels of acyl-CoA oxidase, reflective of peroxisomal beta-oxidation rate, were increased in FO-fed B6 but not in FVB x B6 mice, which could account for the difference in TG secretion rates. In summary, differential effects of FO on plasma apoB and TG levels in B6 and FVB x B6 HuBTg mice were associated with strain differences in hepatic apoB and TG secretion and in peroxisomal beta-oxidation.

Dietary alpha-linolenic acid lowers postprandial lipid levels with increase of eicosapentaenoic and docosahexaenoic acid contents in rat hepatic membrane

This study was designed to examine the effects of dietary n-3 and n-6 polyunsaturated fatty acids (PUFA) on postprandial lipid levels and fatty acid composition of hepatic membranes. Male Sprague-Dawley rats were trained for a 3-h feeding protocol and fed one of five semipurified diets: one fat-free diet or one of four diets supplemented with 10% (by weight) each of corn oil, beef tallow, perilla oil, and fish oil. Two separate experiments were performed, 4-wk long-term and 4-d short-term feeding models, to compare the effects of feeding periods. Postprandial plasma lipid was affected by dietary fats. Triacylglycerol (TG) and total cholesterol levels were decreased in rats fed perilla oil and fish oil diets compared with corn oil and beef tallow diets. Hepatic TG and total cholesterol levels were also reduced by fish oil and perilla oil diets. Fatty acid composition of hepatic microsomal fraction reflected dietary fatty acids and their metabolic conversion. The major fatty acids of rats fed the beef tallow diet were palmitic, stearic, and oleic. Similarly, linoleic acid (LA) and arachidonic acid in the corn oil group, alpha-linolenic acid (ALA) and eicosapentaenoic acid (EPA) in the perilla oil group, and palmitic acid and docosahexaenoic acid (DHA) in the fish oil group were detected in high proportions. Both long- and short-term feeding experiments showed similar results. In addition, microsomal DHA content was negatively correlated with plasma lipid levels. Hepatic lipid levels were also negatively correlated with EPA and DHA contents. These results suggest that n-3 ALA has more of a hypolipidemic effect than n-6 LA and that the hypolipidemic effect of n-3 PUFA may be partly related to the increase of EPA and DHA in hepatic membrane.

Markedly elevated lipid transfer inhibitor protein in hypercholesterolemic subjects is mitigated by plasma triglyceride levels

Lipid transfer inhibitor protein (LTIP, apolipoprotein F) regulates the interaction of cholesteryl ester transfer protein (CETP) with lipoproteins and is postulated to enhance the ability of CETP to stimulate reverse cholesterol transport. The factors that regulate LTIP levels and control its biosynthesis are unknown. Here, we demonstrate that plasma LTIP is dramatically increased (3-fold) in hypercholesterolemic subjects with normal to mildly elevated plasma triglyceride (TG) levels compared with control subjects. LTIP in these subjects is not correlated with the extent of hypercholesterolemia or with low density lipoprotein (LDL), high density lipoprotein, or CETP levels. However, unlike CETP, LTIP levels correlate negatively with plasma TG levels. This association does not appear to reflect decreased LTIP synthesis, inasmuch as conditions that stimulate TG synthesis and secretion (200 micromol/L oleate) do not reduce LTIP secretion by SW872 or Caco-2 cells. In contrast, native or acetyl LDL stimulates LTIP secretion 2-fold. Importantly, although plasma LTIP typically resides on LDL, up to 25% of LTIP is bound to very low density lipoprotein when this lipoprotein is enriched in cholesteryl esters, as occurs in hypercholesterolemia. In summary, LTIP levels are markedly elevated by hypercholesterolemia; however, plasma TG levels attenuate this response. We hypothesize that this arises from an increased association of LTIP with very low density lipoprotein, leading to a more rapid clearance of the inhibitor from circulation.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

Familial hypercholesterolaemia is an inherited disorder characterised by a raised blood cholesterol, the presence of xanthomatosis and premature ischaemic heart disease. The aim of treatment is the reduction of blood LDL cholesterol concentrations in order to reduce the risk of ischaemic heart disease. Current treatment is based on a cholesterol lowering diet alone or in combination with drug therapy. Many of the drugs found to be effective in treating adults with this disease are not licensed for use in children, therefore diet is the main treatment of children with familial hypercholesterolaemia. In addition to the cholesterol-lowering diet, several other dietary interventions have been suggested and consensus has yet to be reached on the most appropriate dietary treatment for children and adults with familial hypercholesterolaemia.

OBJECTIVES

To examine the evidence that in children and adults with familial hypercholesterolaemia, a cholesterol lowering diet is more effective at lowering cholesterol and reducing incidence of ischaemic heart disease than no intervention or than other dietary interventions.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Trials Register, a specialist trials register which comprises references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Additional studies were identified from handsearching the Journal of Inherited Metabolic Disease (from inception, 1978 to 2000) and from the reference lists of identified studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs), both published and unpublished, where a cholesterol lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention. Trials which include patients with familial hypercholesterolaemia alongside patients with non-familial hypercholesterolaemia were only included if the group of familial patients was well defined and the results for these patients were available.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the trial eligibility and methodological quality and one reviewer extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

Only short term outcomes could be assessed in this review due to the length of the five eligible studies. Compliance to treatment, quality of life, mortality and evidence of ischaemic or atheromatous disease were not assessed in the studies identified. No differences were found between the cholesterol-lowering diet and all other diets for all of the short term outcomes assessed.

REVIEWER'S CONCLUSIONS

No conclusions can be made about the effectiveness of the cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. A large, parallel, randomised controlled trial is needed to investigate the effectiveness of the cholesterol-lowering diet and other dietary interventions for FH. It is also possible that data from trials including subjects with both familial and non-familial hypercholesterolaemia could alter the results of future updates of this review and until further evidence is available current dietary treatment of FH should continue to be observed and monitored with care.

Fish oil reduces cholesterol and arachidonic acid levels in plasma and lipoproteins from hypercholesterolemic chicks

The value of fish oil for prevention and/or treatment of human atherosclerosis has not been fully established. This study shows that replacement of saturated fat in young chick diet with menhaden oil produced a significant reversion of the hypercholesterolemia previously induced by coconut oil feeding. Fish oil also produced a clear decrease of plasma triacylglycerol levels. Coconut oil increased the percentages of 12:0 and 14:0 fatty acids, while menhaden oil increased those of 20:5 n-3 and 22:6 n-3. Percentages of 20:4 n-6, 18:2 n-6 and 18:1 n-9 significantly decreased by fish oil addition to the diet. Total cholesterol, phospholipid and protein contents of high and low density lipoproteins increased by coconut oil feeding. When coconut oil was replaced by menhaden oil, total cholesterol was significantly reduced in high, low and very low density lipoproteins. All chemical components of VLDL were decreased by menhaden oil feeding. Our results show a strong hypocholesterolemic effect of menhaden oil when this fat was supplemented to hypercholesterolemic chicks. The clear decrease found in arachidonic acid content of chick plasma and lipoproteins may contribute to the beneficial effects of fish oil consumption by lowering the production of its derived eicosanoids.

Dietary monounsaturated fatty acids promote aortic atherosclerosis in LDL receptor-null, human ApoB100-overexpressing transgenic mice

In mice with genetically engineered high levels of plasma low density lipoprotein (LDL), we tested the hypothesis that an increase in the dietary content of monounsaturated fatty acids but not of polyunsaturated fatty acids would promote atherosclerosis. The mouse model used was an LDL receptor-null, human apoB100-overexpressing strain. Six experimental groups of 19 to 38 mice of both sexes were established when the animals had reached 8 weeks of age. For the next 16 weeks, individual groups were fed either a commercial diet or prepared diets including fat as 10% of energy, with 5 different fatty acid enrichment patterns including the following: saturated (sat), cis and trans monounsaturated (mono), and n-3 and n-6 polyunsaturated (poly). Highly significant differences (ANOVA, P<0. 0001) in LDL cholesterol (in mg/dL) were found, with the rank order at 16 weeks being trans mono (mean, 1390)>sat (922)=cis mono (869)=n-6 poly (868)>n-3 poly (652)>commercial diet (526). Significant elevations in very low density lipoprotein cholesterol were also found in the trans and cis mono and sat groups, and triacylglycerol concentrations were also elevated in all groups. High density lipoprotein cholesterol concentrations were consistently low (20 to 50 mg/dL) in all groups. Highly significant differences (ANOVA, P<0.0001) in atherosclerosis, quantified by measurement of aortic cholesteryl ester concentration (mg/g protein) among dietary fatty acid groups were found, with the order being trans mono (mean, 50.4)>sat (35.6)=cis mono (34.6)>n-6 poly (18. 3)=n-3 poly (9.7)=commercial diet (7.8). Therefore, in this mouse model of hypercholesterolemia, dietary cis or trans monounsaturated fat did not protect against atherosclerosis development, whereas aortic atherosclerosis in either of the polyunsaturated fat groups was significantly less than in the saturated fat group.

The effects of cholesterol uptake from high-density lipoprotein subfractions on biliary sterol secretion in rats with essential fatty-acid deficiency

High-density lipoprotein (HDL) participates in the transfer of cholesterol to the liver, in which it is subsequently excreted into bile as bile acid and cholesterol. In this study, the effect of essential fatty-acid (EFA) deficiency on cholesterol contribution from HDL subfractions to bile was investigated. Rats that were rendered EFA-deficient over 4 weeks displayed changes in their plasma HDL subfractions and liver tissue fatty acids. Plasma linoleic (18:2n6), linolenic (18:3n3,) and arachidonic (20:4n6) acids decreased, whereas palmitoleic (16:1n7) and eicosatrienoic (20:3n9) acids increased. EFA deficiency was confirmed by an elevation of the 20:3(n-9)/20:4(n-6) index. To examine the hepatic handling of lipoprotein-derived cholesterol, HDL2 and HDL3 from donor rats were isolated, labeled with [14C]-cholesterol, and injected iv into EFA-deficient and normal rats with a bile fistula. In HDL subfractions from control rats, no significant variations were noted in the specific activity of cholesterol output in both groups of EFA recipient rats; however, the output of biliary bile acids was significantly decreased in EFA-deficient rats following the administration of labeled HDL3. In HDL2 and HDL3 originating from EFA-deficient rats, a decrease in the specific activity of both biliary cholesterol and bile acid output was recorded in EFA-deficient rats. Concomitant with the defective HDL2- and HDL3-[14C] cholesterol translocation into bile of EFA-deficient rats, increased hepatic very-low-density lipoprotein (VLDL)-[14C] cholesterol secretion was observed in vivo. HDL2 and HDL3 particles, derived from EFA-deficient rats, had an altered composition including a depletion in apo A-I and an enrichment in apo E isoforms, which are the the two major HDL apolipoproteins involved in the delivery of cholesterol to the liver. Taken together, these results show that normal EFA status is necessary for efficient HDL-cholesterol processing by the liver.

Effect of dietary omega-3 eicosapentaenoic acid supplements on cholesteryl ester transfer from HDL in cholesterol-fed rabbits

We investigated the reactivities of cholesteryl ester transfer protein (CETP) in Japanese white rabbits fed either a low-cholesterol diet containing 0.1% cholesterol (Control group) or a diet containing 0.1% cholesterol plus 17.5% omega-3 eicosapentaenoic acid (omega-3 20:5, EPA) of 4.5% (w/w) total lipid (EPA group) for 6 weeks. The plasma total and LDL cholesterol levels and aortic cholesterol content were all significantly higher in the EPA group than in the control group. The aortic cholesterol content significantly correlated with LDL cholesterol (r = 0.81). HDL cholesterol levels tended to be lower in the EPA group compared with control group, which was not statistically significant. The plasma VLDL cholesterol levels did not differ significantly between the groups. In addition, no significant differences were observed in the plasma CETP activity or lecithin:cholesterol acyltransferase (LCAT) activity between the groups. However, the cholesteryl ester (CE) mass transfer from fractionated HDL in the EPA group to excess VLDL and/or LDL as acceptors by purified CETP increased significantly compared with the control group, even if the acceptors were fractionated from either the EPA or the control group. Fatty acid analyses of CE showed that the omega-3 18:3, 20:4 or omega-3 20:5 fatty acid acyl groups in CE of HDL were significantly more transferred to apo B-containing lipoproteins compared with the 14:0,16:0, 18:0, 18:1 or 18:2 fatty acid acyl groups in CE of HDL during the incubation period. The amount of CE in HDL containing omega-3 18:3 and omega-3 20:5 fatty acid acyl groups was greater, while the amount of CE containing 18:2 fatty acid acyl groups was smaller in the EPA group than in the control group. These results show that although CETP itself did not change, the transfer of CE in HDL to apo B-containing lipoproteins by CETP increased in the rabbits fed a diet containing EPA as the HDL is modified by the diet, which may partly explain why atherogenicity was thus found to progress in the rabbits fed a cholesterol plus EPA diet.

Eicosapentaenoic acid, but not docosahexaenoic acid, increases mitochondrial fatty acid oxidation and upregulates 2,4-dienoyl-CoA reductase gene expression in rats

The aim of the present study was to investigate whether eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) was responsible for the triglyceride-lowering effect of fish oil. In rats fed a single dose of EPA as ethyl ester (EPA-EE), the plasma concentration of triglycerides was decreased at 8 h after acute administration. This was accompanied by an increased hepatic fatty acid oxidation and mitochondrial 2,4-dienoyl-CoA reductase activity. The steady-state level of 2,4-dienoyl-CoA reductase mRNA increased in parallel with the enzyme activity. An increased hepatic long-chain acyl-CoA content, but a reduced amount of hepatic malonyl-CoA, was obtained at 8 h after acute EPA-EE treatment. On EPA-EE supplementation, both EPA (20:5n-3) and docosapentaenoic acid (DPA, 22:5n-3) increased in the liver, whereas the hepatic DHA (22:6n-3) concentration was unchanged. On DHA-EE supplementation retroconversion to EPA occurred. No statistically significant differences were found, however, for mitochondrial enzyme activities, malonyl-CoA, long-chain acyl-CoA, plasma lipid levels, and the amount of cellular fatty acids between DHA-EE treated rats and their controls at any time point studied. In cultured rat hepatocytes, the oxidation of [1-14C]palmitic acid was reduced by DHA, whereas it was stimulated by EPA. In the in vivo studies, the activities of phosphatidate phosphohydrolase and acetyl-CoA carboxylase were unaffected after acute EPA-EE and DHA-EE administration, but the fatty acyl-CoA oxidase, the rate-limiting enzyme in peroxisomal fatty acid oxidation, was increased after feeding these n-3 fatty acids. The hypocholesterolemic properties of EPA-EE may be due to decreased 3-hydroxy-3-methylglutaryl-CoA reductase activity. Furthermore, replacement of the ordinary fatty acids, i.e., the monoenes (16:1n-7, 18:1n-7, and 18:1n-9) with EPA and some conversion to DPA concomitant with increased fatty acid oxidation is probably the mechanism leading to changed fatty acid composition. In contrast, DHA does not stimulate fatty acid oxidation and, consequently, no such displacement mechanism operates. In conclusion, we have obtained evidence that EPA, and not DHA, is the fatty acid primarily responsible for the triglyceride-lowering effect of fish oil in rats.

Metabolism of linoleic and alpha-linolenic acids in cultured cardiomyocytes: effect of different N-6 and N-3 fatty acid supplementation

The metabolites of linoleic (LA) and alpha-linolenic (ALA) acids are involved in coronary heart disease. Both n-6 and n-3 essential fatty acids (EFAs) are likely to be important in prevention of atherosclerosis since the common risk factors are associated with their reduced 6-desaturation. We previously demonstrated the ability of heart tissue to desaturate LA. In this study we examined the ability of cultured cardiomyocytes to metabolize both LA and ALA in vivo, in the absence and in the presence of gamma linolenic acid (GLA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) alone or combined together. In control conditions, about 25% or LA and about 90% of ALA were converted in PUFAs. GLA supplementation had no influence on LA conversion to more unsaturated fatty acids, while the addition of n-3 fatty acids, alone or combined together, significantly decreased the formation of interconversion products from LA. Using the combination of n-6 and n-3 PUFAs, GLA seemed to counterbalance partially the inhibitory effect of EPA and DHA on LA desaturation/elongation. The conversion of ALA to more unsaturated metabolites was greatly affected by GLA supplementation. Each supplemented fatty acid was incorporated to a significant extent into cardiomyocyte lipids, as revealed by gas chromatographic analysis. The n-6/n-3 fatty acid ratio was greatly influenced by the different supplementations; the ratio in GLA+EPA+DHA supplemented cardiomyocytes was the most similar to that recorded in control cardiomyocytes. Since important risk factors for coronary disease may be associated with reduced 6-desaturation of the parent EFAs, administration of n-6 or n-3 EFA metabolites alone could cause undesirable effects. Since they appear to have different and synergistic roles, only combined treatment with both n-6 and n-3 metabolites is likely to achieve optimum results.

Abnormal membrane concentrations of 20 and 22-carbon essential fatty acids: a common link between risk factors and coronary and peripheral vascular disease?

Although elevated levels of cholesterol are associated with increased risks of coronary and peripheral vascular disease, the association frequently fails to provide a causative explanation at the individual level. New hypotheses are required which, whether or not they are correct, will provide new lines of research. It is proposed here that the causes of vascular disease are abnormal membrane phospholipid concentrations of the 20-carbon and 22-carbon essential fatty acids (EFAs) of the n-6 and n-3 series. These levels become abnormal with ageing, with stress and in response to smoking, high cholesterol levels and high saturated fat intakes. They are also abnormal in patients with diabetes and hypertension. The effects of these EFAs and their metabolites include lowering of triglycerides, elevation of high-density lipoprotein (HDL)-cholesterol, reduction of blood pressure, vasodilatation, reduction of fibrinogen levels and inhibition of platelet aggregation and of cardiac arrhythmias. Prospective studies have shown that abnormal levels of these fatty acids are predictive of future coronary death. Controlled trials of treatment have demonstrated that provision of the fatty acids reduces both coronary and total mortality. Further experimental and clinical investigations of the roles of appropriate membrane concentrations of these fatty acids are justified.

Omega-3 fatty acids in smooth muscle cell phospholipids increase membrane cholesterol efflux

The aim of our work was to determine whether fatty acid modifications in smooth muscle cell phospholipids affect cholesterol efflux and desorption. [3H]Cholesterol was used to label cholesterol pools in the whole cell or selectively in the plasma membrane. Cells were incubated for 12 h in order to increase oleate, linoleate, arachidonate, eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in phospholipids. Cholesterol efflux was monitored using native or tetranitromethane modified high-density lipoprotein3 (HDL3). When all cholesterol pools were labeled, the efflux from cells treated with different fatty acids were not different. Plasma membrane cholesterol efflux remained unchanged after oleate, linoleate or arachidonate treatments, but was markedly increased after EPA and DHA enrichment, both with native HDL3 and with tetranitromethane-high-density lipoprotein. These results suggest that the positive effects of n-3 fatty acid consumption on the atherosclerotic process could be linked in part to an increase in plasma membrane cholesterol efflux from vascular smooth muscle cells.

The effects of n-3 fatty acids on plasma lipids and lipoproteins and other cardiovascular risk factors in patients with hyperlipidemia

This review discusses the effects of dietary n-3 fatty acids on the plasma concentrations and metabolism of lipoproteins with a particular focus on work in human subjects. The influence of dietary n-3 fatty acids on the concentrations of plasma lipoproteins are affected by the amount of n-3 fatty acids as well as by the lipoprotein phenotype in the patients under investigation. On the basis of the observed changes in lipoproteins, dietary n-3 fatty acids exert the greatest effects on the concentrations of triglyceride-rich lipoproteins; their therapeutic potential is greatest in patients with hypertriglyceridemia. In addition to their effects on plasma lipoproteins, dietary n-3 fatty acids have been reported to exert potentially favorable effects on blood pressure, platelet function and viscosity. These effects may justify the use of supplements of dietary n-3 fatty acids in selected patients with hypertriglyceridemia to reduce the risk of atherosclerosis; however, the benefits of such therapy remain to be demonstrated.

The effects of long-term administration of 3-thia fatty acid, a peroxisome proliferator, to Morris 7800 C1 hepatoma cells

Morris 7800 C1 hepatoma cells were grown in the presence of 80 microM tetradecylthioacetic acid (TTA), a peroxisome proliferator, for 1 year (long-term-treated cells). The growth of the Morris 7800 C1 hepatoma cells was inhibited in cells treated with TTA for up to 8 days. Treatment of the cells with TTA for 1 year did not reduce growth further. The growth inhibition was easily reversed by insulin (0.4 microM). Peroxisomal acyl-CoA oxidase (ACO) (EC 1.3.99.3) activity was increased 5.5 times in cells treated with TTA for 3 days. In the cells treated with TTA for 1 year the ACO activity was increased only two times. A similar ACO mRNA half-life (two times the control) was found in cells treated with TTA for 1 year and for 3 days. This implies a loss of effect of TTA on the transcription rate of the ACO gene in long-term-treated cells.

Dietary n-3 polyunsaturated fatty acids prevent the development of atherosclerotic lesions in mice. Modulation of macrophage secretory activities

We examined the effects of dietary n-3 polyunsaturated and saturated fatty acids on the development of the atherogenic process in mice and on the macrophage ability to secrete several effector molecules that may be involved in the atherogenic process. The secretion of inflammatory proteins such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) and the production of lipoprotein lipase (LPL), nitrogen oxide (NO2), and prostaglandin E2 (PGE2) were evaluated in peritoneal macrophages isolated from atherosclerosis-susceptible C57BL/6J mice. The mice were assigned at random to three experimental groups: the first group was fed a semi-defined control diet (control diet); the second group was maintained on the control diet supplemented with 10% menhaden oil (menhaden diet); and the third group received the control diet supplemented with 10% palm oil plus 2% cholesterol (saturated fat diet). Macrophages derived from mice fed the menhaden diet showed a suppression of their basal TNF-alpha mRNA expression and production. They also presented a dramatically decreased ability to express TNF-alpha and IL-1 beta mRNAs in response to exposure to lipopolysaccharide (LPS) compared with the macrophages from the control group. LPL mRNA and protein expression were downregulated after 6 and 15 weeks of menhaden-diet feeding. Significantly higher NO2 production in response to interferon gamma was found, both after 6 and 15 weeks of diet feeding, in the menhaden group compared with the control group. In addition, prostaglandin production and macrophage tumoricidal activity in response to LPS were decreased in this group compared with the control group. Macrophages derived from the saturated fat group did not show any significant alterations in TNF-alpha, LPL, NO2, or PGE2 secretion compared with controls. Interestingly, we observed a progressive increase of the LPS-induced IL-1 beta gene expression and secretion among macrophages harvested from mice receiving the dietary supplement of saturated fatty acids. At 6 and 15 weeks histologic examination of the atherosclerotic lesions did not reveal any important lesions in the control and menhaden groups, whereas a gradual development of fatty streaks was observed in the menhaden experimental diets for 10 additional weeks resulted in a major development of lesions in the control group, whereas only slight lesions were observed in the menhaden group.(ABSTRACT TRUNCATED AT 400 WORDS)

Ethyl all-cis-5,8,11,14,17-icosapentaenoate modifies the biochemical properties of rat very low-density lipoprotein

The biochemical properties of serum very low-density lipoprotein (VLDL) were investigated in rats given highly purified all-cis-5,8,11,14,17-icosapentaenoate (EPA), an ethyl-ester derivative (EPA-E). The elution time (gel filtration) of VLDL from EPA-E-treated serum was increased significantly compared with that of the control. EPA-E-treated VLDL isolated by ultracentrifugation exhibited a marked decrease in triglyceride content with a relative increase in cholesterol. In treated VLDL, a significant increase in the ratio of apo E/apo C was observed. There was a remarkable increase in the content of EPA in all the fractions of phospholipids, cholesteryl esters and triglycerides after EPA-E treatment, resulting in n-3 polyunsaturated fatty acid-rich VLDL. EPA-E also reduced the incorporation of [14C]oleate into triglycerides in hepatic microsomes and the rate of hepatic triglyceride secretion. Moreover, lipoprotein lipase activity in heparin-injected plasma was increased in rats given EPA-E without there being an effect on hepatic triglyceride lipase activity. These findings indicate that EPA-E exerts an inhibitory effect on hepatic triglyceride synthesis/secretion and a stimulatory effect on triglyceride degradation, resulting in a reduction in particle size and an increase in the ratio of apo E/apo C. Triglyceride-poor and EPA-rich VLDL may rapidly be converted into the density of intermediate low-density lipoprotein and low-density lipoprotein and/or may be absorbed into the liver rapidly.