AJCN EB Program 2010 Early Registration
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jacobson, T. A
Right arrow Search for Related Content
PubMed
Right arrow Articles by Jacobson, T. A
Agricola
Right arrow Articles by Jacobson, T. A
American Journal of Clinical Nutrition, Vol. 87, No. 6, 1981S-1990S, June 2008
© 2008 American Society for Nutrition

Beyond Cholesterol: Prevention and Treatment of Coronary Heart Disease with n–3 Fatty Acids

Role of n–3 fatty acids in the treatment of hypertriglyceridemia and cardiovascular disease1,2,3

Terry A Jacobson

1 From the Office of Health Promotion and Disease Prevention, the Department of Medicine, Emory University, Atlanta, GA

2 Presented at the symposium "Beyond Cholesterol: Prevention and Treatment of Coronary Heart Disease with n–3 Fatty Acids," held in New York, NY, June 9, 2007.

3 Address reprint requests and correspondence to TA Jacobson, Emory University Faculty Office Building, 49 Jesse Hill Jr Drive SE, Atlanta, GA 30303. E-mail: tjaco02{at}emory.edu.

ABSTRACT

n–3 Fatty acids (FAs) when used in doses of 3–4 g/d eicosapentaenoic acid and docosahexaenoic acid have profound effects on triacylglycerol (TG) concentrations. The mechanism for their TG reduction relates to their favorable effects on reducing hepatic production and secretion of VLDL and VLDL apolipoprotein B particles, along with favorable effects on plasma lipolytic activity through lipoprotein lipase–mediated clearance, as well as stimulation of β-oxidation of other FAs in the liver. Their hypotriglyceridemic properties are related to both the dose of n–3 FAs used and the baseline TG concentrations of the population. In patients with TG concentrations >500 mg/dL, 4 g n–3 FAs have been shown to reduce TGs by 45%, VLDL by 42%, and non-HDL by 10.2%. A recent pooled meta-analysis with multiple doses of n–3 FAs ranging from 0.8 to 5.4 g revealed changes in TGs of –27 mg/dL (95% CI: –33, –20), in HDL of +1.6 mg/dL (95% CI: + 0.8, +2.3), and in LDL cholesterol of +6 mg/dL (95% CI: + 3, +8). The clinical uses of n–3 FAs include treatment of severe and moderate hypertriglyceridemia, use in statin-treated patients with elevated TG concentrations or non–HDL cholesterol (mixed hyperlipidemia), and use in the secondary and primary prevention of cardiovascular disease. Existing large-scale clinical trials such as the GISSI-Prevenzione Study and JELIS with low doses of n–3 FAs (1–2 g) show clinical benefit in reducing coronary heart disease without substantial changes in concentrations of TGs or other lipids. Future clinical trials need to determine whether the TG-lowering doses of n–3 FAs (3-4 g/d) result in additional risk reduction.

HISTORICAL PERSPECTIVE

One of the earliest observations made by Bang and Dyerberg in the 1970s (1-3) was that Greenland Inuits had lower rates of heart disease than Danes despite a diet high in fats and cholesterol. It was also noted that Inuits consumed high amounts of long chain n–3 fatty acids (i.e.- 5–10 g) and had lower intakes of n–6 fatty acids.

Major differences in lipids characterized by low concentrations of triacylglycerols (TGs) and higher concentrations of HDL cholesterol were noted in the Inuits compared with the Danes (4). It was hypothesized that the high concentrations of n–3 fatty acids (FAs) found in fish might have potent hypolipidemic effects, particularly that of lowering TG and VLDL cholesterol concentrations. In the early 1980s it was confirmed that the active compounds in fish responsible for the potent hypotriglyceridemic effects were the long-chain polyunsaturated n–3 FAs, eicosapentaenoic acid (EPA, C20:5n–3) and docosahexaenoic acid (DHA, C22:6n–3) (5).

n–3 FAs AND TG CONCENTRATIONS: DOSE RESPONSE

Early controlled feeding studies used supraphysiologic doses of n–3 FAs (20–25 g) to lower TG concentrations. In healthy volunteers TG reductions of 33% were seen (6) versus 65% reductions in patients with severe combined dyslipidemia (7). The dose often used in these early studies was 100 mL of salmon oil plus 2 salmon steaks per day. Further studies followed to determine a more reasonable and practical n–3 FA dose for clinical usage. These studies suggested that the determinants of TG reduction were based on both the total n–3 FA dosage as well as on the baseline TG concentration.

Several meta-analyses have been conducted to determine the degree of TG reductions seen with n–3 FAs. In a meta-analysis of 72 placebo-controlled trials, Harris (8) determined that average triacylglycerol reductions with fixed doses of 3–4 g EPA and DHA were between 25% and 35%, with greater reductions seen in those with high TG concentrations of >500 mg/dL (Figure 1Go). It was also shown that at higher TG concentrations there were small increases in LDL of 5–10% and increases in HDL cholesterol of 1–3%.


Figure 1
View larger version (13K):
[in this window]
[in a new window]

  		FIGURE 1.. Meta-analysis of 72 placebo-controlled studies examining the effects of n–3 fatty acid (FA) supplementation on serum lipids and lipoproteins. EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; TG, triacylglycerol. Adapted from Harris (8).

 
A more recent meta-analysis by Balk et al (9) pooled the results of 21 trials involving about 8000 patients taking different doses of n–3 FAs ranging from 0.8 to 5.4 g. Across the widely varying study designs and n–3 FA doses, there was a net change in TGs of –27 mg/dL (95% CI: –33, –20), in HDL of +1.6 mg/dL (95% CI: + 0.8, +2.3), and in LDL cholesterol of +6 mg/dL (95% CI: + 3, +8). The changes in triacylglycerols, HDL, and LDL cholesterol were highly significant (P < 0.001). There was no significant effect on total cholesterol. There were independent associations between the degree of TG reduction with both the fish oil dose and the baseline TG concentration (10). Across the studies, each increase in fish oil dose of 1 g/d was associated with a decrease in TGs of {approx}8 mg/dL. For each mean increase in baseline TGs of 100 mg/dL, there was a decrease in TGs of an additional 16 mg/dL. Fish oil dose and baseline TG concentrations interacted with each other, so that those with both high baseline TGs (ie, >294 mg/dL) had greater TG reduction (–19 mg/dL compared with –8 mg/dL) per additional 1 g fish oil.

Several studies suggested that clinically significant TG reductions do not occur until the n–3 FA dose exceeds 2 g/d, generally in the range of 3–4 g/d. The practical implication of this finding is that to obtain clinically significant TG reductions consumption of 12–15 tablets of standard n–3 FA dietary supplements (i.e., 300–400 mg EPA or DHA per tablet) would be required. Because of the high pill burden, a prescription with superconcentrated n–3 FAs containing 900 mg/dL EPA and DHA was designed to lower TG concentrations and also to ensure the quality, purity, consistency, and safety (mercury free) of n–3 FA therapy. The prescription n–3 FA (Lovaza; Reliant Pharmaceuticals, Liberty Corner, NJ) was approved by the Food and Drug Administration in 2004 for the treatment of very high TG concentrations (>500 mg/dL) at a dose of 4 g/d. As with nonprescription n–3 FA therapy, doses at ≥3 g are required to lower TGs in patients with TG concentrations between 200 and 499 mg/dL (Figure 2Go) (11). A caveat of these dose-response studies with n–3 FAs is that it is unlikely that a diet rich in daily fish intake is likely to significantly reduce TG concentrations. However, there are clearly other cardiovascular benefits of fish consumption that occur at lower intakes, on the average of 250–500 mg/d EPA and DHA (12).


Figure 2
View larger version (8K):
[in this window]
[in a new window]

  		FIGURE 2.. Dose response with 4 g eicosapentaenoic acid and docosahexaenoic acid (Lovaza) in patients with triacylglycerol (TG) concentrations between 177 and 442 mg/dL at baseline after 8 wk of treatment. Courtesy of Reliant Pharmaceuticals, Liberty Corner, NJ (11).

 
n–3 FA EFFECTS ON LIPOPROTEIN SUBCLASSES

Chylomicrons and postprandial lipid changes
Several studies suggested that n–3 FAs reduce postprandial excursion of TG concentrations after a fatty meal (13-15). This effect seems to occur only after a few weeks of pre-feeding with n–3 FAs. One study showed a reduction by 31% in TG excursion with given test meals (16). Of major interest is the fact that a dose as low as 1 g/d has been shown to reduce postprandial hyperlipemia (17, 18). It still remains to be determined whether reducing postprandial lipemia reduces coronary heart disease (CHD) risk.

LDL cholesterol
Unlike n–6 FAs that can reduce LDL cholesterol, n–3 FAs can increase LDL concentrations particularly in patients with severe hypertriglyceridemia. A pooled analysis of 2 studies with 4 g prescription n–3 FAs in severe hypertriglyceridemia (TG concentration >500 mg/dL) showed not only a 45% reduction in TGs from a baseline of 816 mg/dL, but a 45% increase in LDL cholesterol from a baseline of 89 mg/dL (Figure 3Go) (19, 20). This modest rise in LDL cholesterol has also been seen in studies in patients with severe hypertriglyceridemia receiving gemfibrozil and fenofibrate (21). The rise in LDL probably reflects more of an increase in LDL particle size rather than an increase in LDL particle number. This theory is supported by significant reductions in non–HDL cholesterol by 13.8% and modest reductions in apolipoprotein (apo) B (Figure 3Go). Most of the available data suggest that n–3 FAs increase LDL particle size by decreasing small dense LDL (pattern B) and increasing the concentrations of the larger LDL cholesterol (pattern A) (22, 23). The major driver in shifting from the smaller, more dense LDL to the larger LDL particle is the TG concentration achieved as opposed to the percentage of TG reduction. Concentrations of TGs <150 mg/dL are associated with the greatest degree of conversion from LDL subclass pattern B to A.


Figure 3
View larger version (9K):
[in this window]
[in a new window]

  		FIGURE 3.. Effects of 4 g/d n–3 fatty acid (FA) ethyl esters (Lovaza; n = 41) and placebo (corn oil; n = 41) on serum triacylglycerol (TG) concentrations in patients with severe hypertriglyceridemia. Combined data from 2 studies (19, 20). P values compare the change in the placebo versus that in the n–3 group. BL, baseline; C, CHOL, cholesterol.

 
In studies with n–3 FAs in the treatment of mild to moderate hypertriglyceridemia (TG concentration of 200–499 mg/dL), the rise in LDL cholesterol was insignificant compared with the reductions in VLDL and TGs. In addition, in patients receiving statins whose TG concentrations remained in the 200–499 mg/dL range, LDL increases with n–3 FAs are blunted in the majority of patients (24, 25). In one study combining 40 mg/d simvastatin with 4 g prescription n–3 FA, the percentage of increase in LDL was 0.7 mg/dL compared with a 2.8 mg/dL reduction in the placebo group (P = NS) (26). More importantly, in the n–3 FA group there was a 7.9% reduction in non–HDL cholesterol and a net apo B reduction of 2.3% (Figure 4Go).


Figure 4
View larger version (15K):
[in this window]
[in a new window]

  		FIGURE 4.. Effects of 8 wk of treatment with n–3 fatty acid (FA) ethyl esters (Lovaza; 4, 1-g capsules/d; n = 123) and placebo (corn oil; n = 133) on serum lipid and lipoprotein concentrations in patients with triacylglycerol (TG) concentration of 200–499 mg/dL while receiving stable treatment with simvastatin (40 mg/d) (26). Values are median percent changes from baseline, and P values compare the change in the placebo group with those in the n–3 group. Apo, apolipoprotein.

 
HDL cholesterol
Generally n–3 FAs have only a small HDL-raising effect in patients with hypertriglyceridemia. The effect may not be as dependent on the dose of n–3 FA used as it is with TG reductions. The meta-analysis by Balk et al (9) indicated small HDL increases of 1.6 mg/dL in mixed populations with use of multiple n–3 FA doses. The meta-analysis by Harris (8) indicated increases by 3–5% in both normolipidemic patients and patients with high TG concentrations.

In patients with very high TG concentrations of >500 mg/dL, a pooled analysis with 4 g/d suggested increases in HDL of 13% (Figure 4Go) (27). Few data exist for raising low concentrations of HDL <40 mg/dL. Most of the HDL increases are of the HDL2-cholesterol subfraction (22). A kinetic study with use of 4 g n–3 FAs in viscerally obese men with mild to moderate hypertriglyceridemia revealed both slowed production and slowed clearance of apo A-I, resulting in little net change in HDL cholesterol (28).

MECHANISTIC STUDIES OF n–3 FAs ON LIPOPROTEIN METABOLISM

Several theories have been proposed to explain the mechanism of action of n–3 FAs in reducing TG concentrations in humans. Many of the explanations have been derived from rodent experiments. Three potential mechanisms of TG lowering are summarized in Table 1Go and Figure 5Go. Of the postulated mechanisms, the strongest evidence is for reduced hepatic lipogenesis or, more specifically, reduced hepatic production and secretion of VLDL TGs.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Potential mechanisms of triglyceride reduction with n-3 fatty acids (FAs)

 

Figure 5
View larger version (25K):
[in this window]
[in a new window]

  		FIGURE 5.. Mechanisms by which n–3 fatty acids (FAs) reduce triacylglycerol (TG) synthesis in the liver and increase VLDL clearance in the peripheral circulation. n–3 FAs inhibit 2 key enzymes [diacylglycerol acyl transferase (DGAT), phosphatidic acid phosphohydrolase (PA)] involved in hepatic TG biosynthesis in the liver and result in decrease hepatic VLDL secretion. In addition, increased peroxisomal B-oxidation of fatty acids results in decreased availability of FAs for TG synthesis. Finally, there is increased plasma lipolytic activity in the peripheral circulation through lipoprotein lipase (LPL), resulting in conversion of VLDL to larger less dense LDL particles. Apo, apolipoprotein; IDL, intermediate-density lipoprotein; CE, cholesterol ester.

 
Reduced hepatic lipogenesis
Several studies show direct inhibition of diacylglycerol acetyl-transferase and phosphatidic acid phosphohydrolase, 2 key enzymes involved in TG synthesis in the liver (Figure 6Go) (29). This effect is under the control of the nuclear transcription factor, sterol receptor element binding protein-1c, the main genetic switch controlling hepatic lipogenesis (30). n–3 FA therapy reduces sterol receptor element binding protein-1c activity, resulting in diminished hepatic TG production and reduced VLDL assembly and secretion (31). Elegant pharmacokinetic data from Chan et al (32) suggest that n–3 FAs, when given at 4 g/d, in obese, moderately hypertriglyceridemic men, affect mainly the hepatic production of VLDL apo B, but without a change in the pool size of LDL apo B. In addition, no change in the fractional catabolic rate of VLDL apo B was demonstrated. The data of Chan also illustrate that the rise in LDL seen with fish oil results directly from the conversion of VLDL particles into LDL particles. Thus, n–3 FAs result in fewer VLDL particles secreted from the liver into the peripheral circulation and the VLDL particles secreted are rapidly converted to LDL particles.


Figure 6
View larger version (19K):
[in this window]
[in a new window]

  		FIGURE 6.. Potential biochemical mechanisms by which n–3 fatty acids (FAs) influence hepatic triacylglycerol (TG) metabolism. Feeding n–3 FA to rats has been shown to inhibit (–) lipogenesis and the activities of diacylglycerol (DAG) acyl transferase (DGAT), phosphatidic acid (PA) phosphohydrolase (PAP), and hormone-sensitive lipase; and to stimulate (+) β-oxidation, phospholipid synthesis, and apolipoprotein (Apo)-B degradation. The result is a reduced rate of secretion of VLDL TG. The extent to which decreases in serum nonesterified fatty acids (NEFA) are responsible for the reduction in TG levels is not known. Reprinted with permission from reference 29.

 
Recent data suggest that fish oils, through their peroxidation and subsequent oxidative stress, increase apo B degradation (33). Perioxidation products of n–3 FAs increase post–endoplasmic reticulum presecretory proteolysis, leading to decreased secretion of larger VLDL and hence lower concentrations of their catabolic products such as small, dense LDL particles. Thus, antioxidants given with n–3 FAs might blunt their effects on apo B degradation and restore VLDL secretion. This theory may explain in part why antioxidants have been shown in some clinical trials to moderately increase apo B concentrations.

Stimulation of FA oxidation
n–3 FAs also appear to increase the β-oxidation of other FAs in the liver (29). The processes of TG biosynthesis compete with the processes of in vivo FA oxidation for the use of FAs as substrates. This increased rate of FA oxidation occurs primarily in the mitochondria but may also occur in peroxisomes. n–3 FAs also affect the nuclear transcription factor, peroxisome proliferation–activated receptor (PPAR)-{alpha}, responsible for fatty acid oxidation in the peroxisomes, microsomes, and mitochondria (30, 31). Activation of PPAR-{alpha} has also been associated with reductions in apo CIII and induction of lipoprotein lipase (LPL) activity. Although PPAR-{alpha} activation would seem to be an important mechanism of action for TG reduction, n–3 FAs are only weak PPAR agonists (34). In addition, in PPAR-{alpha} knockout mice, n–3 FAs still show significant TG reduction (35). However, metabolites of n–3 FA such as eicosanoids or oxidized FAs derived from EPA have several orders of magnitude higher affinity for the PPAR-{alpha} receptor than the parent molecule (34).

LPL-mediated clearance
n–3 FAs may also increase plasma lipolytic activity (ie, LPL) and thus TG clearance rates. The lipolytic activity of non–heparin-stimulated plasma is enhanced by n–3 FAs (36, 37). However, most studies with postheparin plasma show no effect of n–3 FAs (38). One exception is the study of Khan et al (39), which showed increased LPL concentrations and increased LPL gene expression in adipose tissue. Although kinetic studies fail to show an increase in VLDL clearance with n–3 FAs (32), VLDL particles rich in n–3 are more susceptible to in vitro lipase-mediated conversion to LDL than controls (29, 40, 41).

CLINICAL TRIALS AND n–3 FAs: MAJOR CARDIOVASCULAR OUTCOMES

Although many trials have contributed to our current knowledge base about n–3 FAs, several recent trials (42) stand out as significant in influencing current evidence-based treatment guidelines. Of note, the 2 most important cardiovascular outcome trials [Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI)-Prevenzione Study and the Japan EPA Lipid Intervention Study (JELIS)] used n–3 FAs doses in the range of 0.8–1.8 g. These doses would not be considered sufficient to lower TG concentrations or to improve other lipid parameters.

GISSI-Prevenzione Study
In the GISSI-Prevenzione Study (43, 44) 1 g EPA/DHA from fish oil was used in patients who had had a myocardial infarction (MI) in the prior 3 mo. In brief, 11 234 Italian patients with recent MI (<3 mo) were randomly assigned to 0.85 g/d EPA and DHA for 3.5 y and had a significant reduction of 21% in total mortality and a 45% reduction in sudden death by study end (Table 2Go, Figure 7Go). Analysis of secondary endpoints revealed a 21% reduction in relative risk of total mortality as early as 3 mo after treatment initiation, an effect attributable largely to the reduction in sudden death (44). The primary combined endpoint of death, nonfatal MI, and nonfatal stroke was significantly reduced by 15% (95% CI: 2–26%) with n–3 FA treatment. There was an insignificant change in the relative risk of nonfatal MI (0.86; 95% CI: 0.70–1.18) and nonfatal stroke (1.22: 95% CI: 0.75–1.97). During the trial, the changes in lipids were fairly minimal as expected, owing to the low dose of n–3 FAs used. Thus the mechanism of benefit appears to be independent of lipid changes (Figure 8Go). Because of the rapid time course in the reduction of CHD and total mortality, it was hypothesized that at these n–3 FA doses the primary mechanism of benefit was from their antiarrhythmic effects, resulting in a large reduction in sudden death. However, this was a post hoc finding and needs to be confirmed prospectively. Although the GISSI-Prevenzione Study was a landmark trial owing to its sheer number of post-MI patients (n = 11 234), it did have a few methodologic weaknesses, including the use of a usual care control group instead of a placebo control group and an open-label design.


View this table:
[in this window]
[in a new window]

  		TABLE 2. GISSI-Prevenzione Trial: primary and secondary endpoint results1

 

Figure 7
View larger version (9K):
[in this window]
[in a new window]

  		FIGURE 7.. GISSI-Prevenzione Study. Effects of n–3 fatty acid (FA) ethyl esters (Lovaza; 1 g/d, providing 850 mg eicosapentaenoic acid plus docosahexaenoic acid) versus usual care on total mortality. Early effect within 90 d. Reprinted with permission from reference 44.

 

Figure 8
View larger version (18K):
[in this window]
[in a new window]

  		FIGURE 8.. GISSI-Prevenzione Study. Lipid changes during the study. EPA, eicosapentaenoic acid. Reprinted with permission from reference 44.

 
JELIS
Another important major n–3 FA trial was JELIS. JELIS tested the hypothesis that the addition of 1.8 g/d highly purified EPA to statin therapy can reduce the incidence of major cardiovascular events in Japanese patients with hypercholesterolemia (45). In JELIS, 14 981 primary prevention patients and 3664 secondary prevention patients were randomly assigned in a prospective open-label, blinded endpoint study with a 4.6-y follow-up. Of note, all patients were given low-dose statin therapy and continued to consume a diet rich in omega-3 FAs. At the end of 54 mo, the incidence of major coronary events was reduced 19% (95% CI: 5–31%; P = 0.011), including the composite endpoint of nonfatal MI, coronary artery disease death, unstable angina, and revascularization procedures (Figure 9Go). The incidences of unstable angina and nonfatal coronary events were significantly reduced by 14% (P = 0.014) and 19% (P = 0.015), respectively, but the incidences of sudden death and coronary death were unchanged (Table 3Go). Although there was a small difference in TG concentrations between the 2 groups at the end of the treatment period of {approx}5% (P < 0.001), the results appeared to be independent of lipid mechanisms. In JELIS, the trends in the reduction of the incidence of unstable angina and nonfatal coronary events suggest that important plaque-stabilizing properties may also be involved with n–3 FA therapy. The benefits of therapy appeared to be related most to the underlying risk of the population. When the primary prevention population in JELIS was compared with the secondary prevention population, the number needed to treat to prevent one event over 4.6 y was 333 versus 50 in secondary prevention patients (46). Thus, although there was benefit in primary prevention patients, many more patients would need to be treated to prevent one event. Thus, the benefits of n–3 FA therapy in a low-risk population consuming high amounts of n–3 may be quite small. In interpreting JELIS, it is important to realize that the benefit seen was in addition to the benefit from statin therapy in a population already consuming high amounts of n–3 FAs. The absence of a reduction in CHD death and total mortality in JELIS is supported by the theory that there may be a threshold of benefit in a population already consuming large amounts of n–3 FAs (12).


Figure 9
View larger version (10K):
[in this window]
[in a new window]

  		FIGURE 9.. Major coronary event rates in the Japan EPA Lipid Intervention Study (JELIS). Hypercholesterolemic patients on statin therapy were randomized to usual care with or without 1.8 g of EPA and followed for a mean of 4.6 y. Kaplan-Meier estimates for the control and EPA groups are shown for all 18 645 patients. From Yokoyama et al (45).

 

View this table:
[in this window]
[in a new window]

  		TABLE 3. JELIS and major cardiac events in Japanese patients treated with statin and 1800 mg EPA1,2

 
CLINICAL APPLICATIONS OF n–3 FA THERAPY

Hypertriglyceridemia—TG concentration >500 mg/dL
The major indication in the United States for prescription n–3 FAs is their use in patients with severe hypertriglyceridemia of >500 mg/dL. These patients are at increased risk of pancreatitis and CHD. As noted earlier, the dosage usually required to obtain significant TG reduction is generally >2 g/d, and for most patients the full dose of 4 g/d is required. Although other TG-lowering therapies such as niacin or fibrates can also be used in patients with hypertriglyceridemia, n–3 FAs have particular advantages in that they have very few known drug interactions and need no additional laboratory monitoring. They are generally free of cytochrome P450 interactions and thus are unlikely to affect other medications metabolized by the cytochrome P450 system including statins. Occasionally, abnormalities in liver function tests occur, but these generally are reversible and transient. The degree of TG reduction depends on both the baseline TG concentration and the dose of EPA/DHA used. Although prolongation of bleeding time was reported in prior n–3 FA studies, no evidence of clinically important bleeding has been reported in pooled data or in patients undergoing coronary artery bypass or coronary angioplasty (47). Most n–3 FA studies were done in patients using other antiplatelet or anticlotting agents, including aspirin. Few data, however, are available in the poststent era for patients taking both aspirin and clopidogrel.

The efficacy of n–3 FAs in lowering TGs in patients with TG concentrations >500 mg is a 45% reduction in TG, a non-HDL reduction of 13.8%, an HDL elevation of 9.1%, and an elevation in LDL of 45% (Figure 3Go). The LDL elevation accompanying n–3 FA therapy reflects a conversion of large TGs to the larger pattern A LDL particles. In some cases pattern B or more dense LDL particles may be reduced particularly with larger TG reductions. Of note, the rise in LDL and the shift toward large-density pattern A particles depends on the TG concentration achieved. Achievement of lower TG concentrations is often associated with even greater improvements in LDL particle size. n–3 FAs may also be used safely with other TG-lowering therapies including fibrates, niacin, and statins.

Hypertriglyceridemia—TG concentration >200–499 mg/dL
Although currently prescription n–3 FAs are not Food and Drug Administration–approved for patients with TG concentrations between 200 and 499 mg/dL, their use in this population represents an alternative treatment modality to existing drugs that lower TG concentrations including fibrates, niacin, and statins. Their efficacy in lowering TGs is {approx}25–30% in patients with TG concentrations between 200 and 499 mg/dL. When they are used at 4 g in this population, there are generally insignificant changes in LDL, HDL, and non–HDL cholesterol. According to the National Cholesterol Education Program III guidelines, Non–HDL cholesterol represents the secondary target of treatment in patients with TG concentrations of > 200 mg/dL (48).

Combination therapy with other lipid-lowering drugs
Clinically, one of the most important uses of prescription n–3 FAs will be in combination with other lipid-lowering drugs. Frequently, many patients with elevated TG concentrations of >500 mg/dL will require combinations of lipid-lowering drugs including fibrates, niacin, statins, and n–3 FAs. n–3 FAs are particularly attractive in combination therapy because of their lack of side effects and lack of drug interactions.

Mixed hyperlipidemia (elevated LDL and TG concentrations)—combination n–3 FAs and statins
Because statins have the best evidence base for CHD risk reduction in patients with LDL elevations, they are currently the most prescribed lipid-lowering medication. However, many statin-treated patients, even at National Cholesterol Education Program LDL goal, may still have uncontrolled TG concentrations, elevated non–HDL cholesterol concentrations, or low concentrations of HDL. These other lipid abnormalities still contribute to residual CHD risk and are important additional targets of therapy. Recent data suggest that patients receiving statins whose TG concentrations remain between 200 and 499 mg/dL will have further TG and non-HDL concentration reductions with prescription n–3 FAs (Figure 4Go). A recent trial combining 4 g prescription n–3 FAs with 40 mg simvastatin showed placebo-corrected median reductions in TGs by 23.2%, non–HDL cholesterol by 6.8%, and apo B by 2.3%. In this study called the Combination of Prescription n–3 with Simvastatin Study (COMBOS) (26), there were also small placebo-corrected increases in HDL by 4.6% and LDL by 3.5%. Overall, the combination was well tolerated, with significant improvements in TG and non–HDL cholesterol concentrations over use of simvastatin alone.

CLINICAL APPLICATIONS OF n–3 FA THERAPY: BEYOND TG REDUCTIONS

CHD prevention: secondary prevention
One of the major recommendations for the use of n–3 FA is in secondary prevention. These recommendations go beyond the effects of n–3 FAs on concentrations of TGs or other lipids. Several national recommendations exist for the usage of n–3 FAs in secondary prevention. The American Heart Association (AHA) first recommended n–3 FAs in cardiovascular prevention in their Nutrition Advisory Committee's Recommendation on Fish Oils and n–3 Fatty Acids in Cardiovascular Disease (Table 4Go). Their recommendation was that patients with documented CHD consume about 1 g of EPA and DHA/d, preferably from oily fish or through EPA and DHA supplementation from fish oils (49). This recommendation was reaffirmed in the 2006 AHA/ACC Guidelines for Secondary Prevention for patients with coronary and other atherosclerotic vascular diseases (50). The 2006 AHA/ACC guidelines for secondary prevention recommended that patients increase consumption of n–3 FAs in the form of fish or in capsule form (1g/d) for CHD risk reduction. These recommendations are based on the outcomes of the GISSI-Prevenzione Study.


View this table:
[in this window]
[in a new window]

  		TABLE 4. AHA recommendations for n–3 FA intake1,2

 
CHD prevention: primary prevention
The current AHA recommendation for n–3 FAs in primary prevention is to consume a variety of preferably oily fish at least twice a week or oils and foods rich in {alpha}-linolenic acid (flaxseed, canola, or soybean oils or flaxseed and walnuts). Of note, {alpha}-linolenic acid has little effect on TG concentrations even at high doses. For patients who do not eat fish, 1 g/d EPA/DHA from fish oil can be considered or plant-based n–3 FA sources (flaxseed, walnuts, soybean oil, and canola oil). Patients who try to get 1 g/d EPA/DHA from fish oil supplements will often require 3–4 capsules because most dietary fish oil supplements only contain 300 mg EPA/DHA.

As discussed previously, this low dose of 1 g/d does not have significant effects on TG or other lipid concentrations. However, the JELIS trial supports the idea that low doses of n–3 FAs (<2 g/d) may reduce CHD risk in primary prevention patients even when combined with statin therapy.

CONCLUSIONS

n–3 FAs, when used in doses of 3–4 g/d EPA and DHA, have profound effects on TG concentrations. The mechanism for their TG reduction relates to their favorable effects on reducing hepatic production and secretion of VLDL and VLDL apo B particles, along with favorable effects on plasma lipolytic activity through LPL-mediated clearance, as well as stimulation of β-oxidation of other FAs in the liver. Their hypotriglyceridemic properties are related to both the dose of n–3 FAs used and the baseline TG concentrations of the population. The clinical uses of n–3 FA include the treatment of severe and moderate hypertriglyceridemia, use in statin-treated patients with elevated TGs or non–HDL cholesterol (mixed hyperlipidemia), and use in the secondary and primary prevention of CVD. Existing large-scale clinical trials such as the GISSI-Prevenzione Study and JELIS with low doses of n–3 FAs (1–2 g) show clinical benefit in reducing CHD without substantial changes in TGs or other lipids. Future clinical trials need to determine whether the TG-lowering doses of n–3 FAs (3-4 g/d) result in additional risk reduction.

ACKNOWLEDGMENTS

I thank Richard Deckelbaum, MD, and Sharon Akabas PhD of the Institute of Human Nutrition at Columbia University (New York, NY) for organizing the symposium.

The author takes full responsibility for manuscript preparation. The author has served as a consultant to Reliant Pharmaceuticals and other manufacturers of lipid-lowering therapies and reports no other personal or financial conflict of interest.

REFERENCES

  1. Dyerberg J, Bang HO, Stoffersen E, Moncada S, Vane JR. Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis? Lancet 1978;2:117–9.[Medline]
  2. Bang HO, Dyerberg J. Lipid metabolism and ischemic heart disease in Greenland Eskimos. Adv Nutr Res 1980;3:1–22.[Medline]
  3. Dyerberg J. Linolenate-derived polyunsaturated fatty acids and prevention of atherosclerosis. Nutr Rev 1986;44:125–34.[Medline]
  4. Dyerberg J, Bang HO, Hjorne N. Fatty acid composition of the plasma lipids in Greenland Eskimos. Am J Clin Nutr 1975;28:958–66.[Abstract/Free Full Text]
  5. Bronsgeest-Schoute HC, van Gent CM, Luten JB, Ruiter A. The effect of various intakes of {omega}-3 fatty acids on the blood lipid composition in healthy human subjects. Am J Clin Nutr 1981;34:1752–7.[Abstract/Free Full Text]
  6. Harris WS, Connor WE, McMurry MP. The comparative reductions of the plasma lipids and lipoproteins by dietary polyunsaturated fats: salmon oil versus vegetable oils. Metabolism 1983;32:179–84.[Medline]
  7. Phillipson BE, Rothrock DW, Connor WE, Harris WS, Illingworth DR. Reduction of plasma lipids, lipoproteins and apoproteins by dietary fish oils in patients with hypertriglyceridemia. N Engl J Med 1985;312:1210–6.[Abstract]
  8. Harris WS. n–3 fatty acids and serum lipoproteins: human studies. Am J Clin Nutr 1997;65(suppl):1645S–54S.
  9. Balk EM, Lichtenstein AH, Chung M, Kupelnick B, Chew P, Lau J. Effects of {omega}-3 fatty acids on serum markers of cardiovascular disease risk: a systematic review. Atherosclerosis 2006;189:19–30.[Medline]
  10. Balk E, Chung M, Lichtenstein A, et al. Effects of {omega}-3 fatty acids on cardiovascular risk factors and intermediate markers of cardiovascular disease. Evidence Report/Technology Assessment No. 93 (Prepared by Tufts-New England Medical Center Evidence-based Practice Center under Contract No. 290-02-0022). Rockville, MD: Agency for Healthcare Research and Quality, 2004. [AHRQ Publication No. 04-E010-2.]
  11. Reliant Pharmaceuticals, Liberty Corners, NJ. Data on file.
  12. Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA 2006;296:1885–99.[Abstract/Free Full Text]
  13. Harris WS, Connor WE, Alam N, Illingworth DR. Reduction of postprandial triglyceridemia in humans by dietary {omega}-3 fatty acids. J Lipid Res 1988;29:1451–60.[Abstract]
  14. Westphal S, Orth M, Ambrosch A, Osmundsen K, Luley C. Postprandial chylomicrons and VLDLs in severe hypertriacylglycerolemia are lowered more effectively than are chylomicron remnants after treatment with n–3 fatty acids. Am J Clin Nutr 2000;71:914–20.[Abstract/Free Full Text]
  15. Weintraub MS, Zechner R, Brown A, Eisenberg S, Breslow JL. Dietary polyunsaturated fats of the w-6 and w-3 series reduce postprandial lipoprotein levels. J Clin Invest 1988;82:1884–1893.[Medline]
  16. Harris WS, Muzio F. Fish oil reduces postprandial triglyceride concentrations without accelerating lipid emulsion removal rates. Am J Clin Nutr 1993;58:68–74.[Abstract/Free Full Text]
  17. Roche HM, Gibney MJ. Postprandial triacylglycerolaemia: the effect of low-fat dietary treatment with and without fish oil supplementation. Eur J Clin Nutr 1996;50:617–24.[Medline]
  18. Agren JJ, Hanninen O, Julkunen A, et al. Fish diet, fish oil and docosahexaenoic acid rich oil lower fasting and postprandial plasma lipid levels. Eur J Clin Nutr 1996;50:765–71.[Medline]
  19. Harris WS, Ginsberg HN, Arunakul N, et al. Safety and efficacy of Omacor in severe hypertriglyceridemia. J Cardiovasc Risk 1997;4:385–92.[Medline]
  20. Pownall HJ, Brauchi D, Kilinc C, et al. Correlation of serum triglyceride and its reduction by w-3 fatty acids with lipid transfer activity and the neutral lipid compositions of high-density and low-density lipoproteins. Atherosclerosis 1999;143:285–97.[Medline]
  21. Goldberg AC, Schonfeld G, Feldman EB, et al. Fenofibrate for the treatment of type IV and V hyperlipoproteinemias: a double-blind, placebo-controlled multicenter US study. Clin Ther 1989;11:69–83.[Medline]
  22. Calabresi L, Donati D, Pazzucconi F, Sirtori CR, Franceschini G. Omacor in familial combined hyperlipidemia: effects on lipids and low density lipoprotein subclasses. Atherosclerosis 2000;148:387–96.[Medline]
  23. Minihane AM, Khan S, Leigh-Firbank EC, et al. ApoE polymorphism and fish oil supplementation in subjects with an atherogenic lipoprotein phenotype. Arterioscler Thromb Vasc Biol 2000;20:1990–7.[Abstract/Free Full Text]
  24. Hoskins M, Jacobson TA. Combination use of statins and {omega}-3 fatty acids: an emerging therapy for combined hyperlipidemia. Future Lipidol 2006;1:579–91.
  25. Durrington PN, Bhatnagar D, Mackness MI, et al. An {omega}-3 polyunsaturated fatty acid concentrate administered for one year decreased triglycerides in simvastatin treated patients with coronary heart disease and persisting hypertriglyceridemia. Heart 2001;85:544–8.[Abstract/Free Full Text]
  26. Davidson MH, Stein EA, Bays HE, et al. Efficacy and tolerability of adding prescription {omega}-3 fatty acids 4 g/d to simvastatin 40 mg/d in hypertriglyceridemic patients: an 8-week, randomized, double-blind, placebo-controlled study. Clin Ther 2007;29:1354–67.[Medline]
  27. Lovaza® (omega 3 acid ethyl esters capsules) package insert. Liberty Corners, NJ: Reliant Pharmaceuticals, 2007.
  28. Chan DC, Watts GF, Nguyen MN, Barrett PH. Factorial study of the effect of n–3 fatty acid supplementation and atorvastatin on the kinetics of HDL apolipoproteins A-I and A-II in men with abdominal obesity. Am J Clin Nutr 2006;84:37–43.[Abstract/Free Full Text]
  29. Harris WS, Bulchandani D. Why do {omega}-3 fatty acids lower serum triglycerides? Curr Opin Lipidol 2006;17:387–93.[Medline]
  30. Nakamura MT, Cheon Y, Li Y, Nara TY. Mechanisms of regulation of gene expression by fatty acids. Lipids 2004;39:1077–83.[Medline]
  31. Davidson MH: Mechanisms for the hypotriglyceridemic effect of marine omega-3 fatty acids. Am J Cardiol 2006;98:27i–33i.[Medline]
  32. Chan DC, Watts GF, Barrett PHR, Beilin LJ, Redgrave TG, Mori TA. Regulatory effects of HMG CoA reductase inhibitor and fish oils on apolipoprotein B-100 kinetics in insulin-resistant obese male subjects with dyslipidemia. Diabetes 2002;51:2377–86.[Abstract/Free Full Text]
  33. Pan M, Cederbaum AI, Zhang Y-L, Ginsberg HN, Williams KJ, Fisher EA. Lipid peroxidation and oxidant stress regulate hepatic apolipoprotein B degradation and VLDL production. J Clin Invest 2004;113:1277–87.[Medline]
  34. Krey G, Braissant O, L'Horset F, et al. Fatty acids, eicosanoids, and hypolipidemic agents identified as ligands of peroxisome proliferator-activated receptors by coactivator-dependent receptor ligand assay. Mol Endocrinol 1997;11:779–91.[Abstract/Free Full Text]
  35. Clarke SD, Turini M, Jump DB, Abraham S, Reedy M. Polyunsaturated fatty acid inhibition of fatty acid synthase transcription is independent of PPAR activation. Z Ernahrungswiss 1998;37(suppl 1):14–20.[Medline]
  36. Park Y, Harris WS. Omega-3 fatty acid supplementation accelerates chylomicron triglyceride clearance. J Lipid Res 2002;44:455–63.[Medline]
  37. Harris WS, Lu G, Rambjor GS, et al. Influence of n–3 fatty acid supplementation on the endogenous activities of plasma lipases. Am J Clin Nutr 1997;66:254–60.[Abstract/Free Full Text]
  38. Nozaki S, Garg A, Vega GL, Grundy SM. Postheparin lipolytic activity and plasma lipoprotein response to {omega}-3 polyunsaturated fatty acids in patients with primary hypertriglyceridemia. Am J Clin Nutr 1991;53:638–42.[Abstract/Free Full Text]
  39. Khan S, Minihane AM, Talmud PJ, et al. Dietary long-chain n–3 PUFAs increase LPL gene expression in adipose tissue of subjects with an atherogenic lipoprotein phenotype. J Lipid Res 2002;43:979–85.[Abstract/Free Full Text]
  40. Park Y, Jones PG, Harris WS. Triacylglycerol-rich lipoprotein margination: a potential surrogate for whole-body lipoprotein lipase activity and effects of eicosapentaenoic and docosahexaenoic acids. Am J Clin Nutr 2004;80:45–50.[Abstract/Free Full Text]
  41. Lu G, Windsor SL, Harris WS. Omega-3 fatty acids alter lipoprotein subfraction distributions and the in vitro conversion of very low density lipoproteins to low density lipoproteins. J Nutr Biochem 1999;10:151–8.[Medline]
  42. Jacobson TA: Secondary prevention of coronary artery disease with omega-3 fatty acids. Am J Cardiol 2006, 98:61i–70i.[Medline]
  43. GISSI-Prevenzione Investigators. Dietary supplementation with n–3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet 1999;354:447–55.[Medline]
  44. Marchioli R, Barzi F, Bomba E, et al. Early protection against sudden death by n–3 polyunsaturated fatty acids after myocardial infarction: time-course analysis of the results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI)-Prevenzione. Circulation 2002;105:1897–903.[Abstract/Free Full Text]
  45. Yokoyama M, Origasa H, Matsuzaki M, et al. Effects of eicosapentaenoic acid on major coronary events in hypercholesterolaemic patients (JELIS): a randomised open-label, blinded endpoint analysis. Lancet 2007;369:1090–8.[Medline]
  46. Jacobson TA. Beyond lipids: the role of omega-3 fatty acids from fish oil in the prevention of coronary heart disease. Curr Atherosclerosis Reports 2007;9:145–53.
  47. Harris WS. Expert opinion: omega-3 fatty acids and bleeding—cause for concern? Am J Cardiol 2007;99:S44–6.[Medline]
  48. Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 285:2486-97.
  49. Kris-Etherton PM, Harris WS, Appel LJ. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation 2002;106:2747–57.[Free Full Text]
  50. Smith SC Jr, Allen J, Blair SN, et al. AHA/ACC guidelines for secondary prevention for patients with coronary and other atherosclerotic vascular disease: 2006 update: endorsed by the National Heart, Lung, and Blood Institute. Circulation 2006;113:2363–72.[Free Full Text]



This article has been cited by other articles:


Home page
 Cardiovasc ResHome page
M. K. Duda, K. M. O'Shea, and W. C. Stanley
{omega}-3 polyunsaturated fatty acid supplementation for the treatment of heart failure: mechanisms and clinical potential
Cardiovasc Res, October 1, 2009; 84(1): 33 - 41.
[Abstract] [Full Text] [PDF]

Home page
 J. Nutr.Home page
H. E. C. Hanwell, C. D. Kay, J. W. Lampe, B. J. Holub, and A. M. Duncan
Acute Fish Oil and Soy Isoflavone Supplementation Increase Postprandial Serum (n-3) Polyunsaturated Fatty Acids and Isoflavones but Do Not Affect Triacylglycerols or Biomarkers of Oxidative Stress in Overweight and Obese Hypertriglyceridemic Men
J. Nutr., June 1, 2009; 139(6): 1128 - 1134.
[Abstract] [Full Text] [PDF]

Home page
 J. Nutr.Home page
S. Egert, F. Kannenberg, V. Somoza, H. F. Erbersdobler, and U. Wahrburg
Dietary {alpha}-Linolenic Acid, EPA, and DHA Have Differential Effects on LDL Fatty Acid Composition but Similar Effects on Serum Lipid Profiles in Normolipidemic Humans
J. Nutr., May 1, 2009; 139(5): 861 - 868.
[Abstract] [Full Text] [PDF]

Home page
 Rheumatology (Oxford)Home page
C. Hill, T. K. Gill, S. Appleton, L. G. Cleland, A. W. Taylor, and R. J. Adams
The use of fish oil in the community: results of a population-based study
Rheumatology, April 1, 2009; 48(4): 441 - 442.
[Full Text] [PDF]

Home page
 Am. J. Clin. Nutr.Home page
R. J Deckelbaum, A. Leaf, D. Mozaffarian, T. A Jacobson, W. S Harris, and S. R Akabas
Conclusions and recommendations from the symposium, Beyond Cholesterol: Prevention and Treatment of Coronary Heart Disease with n-3 Fatty Acids
Am. J. Clinical Nutrition, June 1, 2008; 87(6): 2010S - 2012S.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jacobson, T. A
Right arrow Search for Related Content
PubMed
Right arrow Articles by Jacobson, T. A
Agricola
Right arrow Articles by Jacobson, T. A

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS