Ethyl EPA and ethyl DHA cause similar and differential changes in plasma lipid concentrations and lipid metabolism in subjects with low-grade chronic inflammation

Abstract

Background:

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been shown to similarly lower plasma TG concentrations but differentially regulate plasma LDL-C and HDL-C concentrations.

Objective:

The aim of this study was to evaluate the common and differential effects of these ω−3 fatty acids on plasma lipids and lipoproteins and to assess the metabolic mechanisms of the effects.

Methods:

In a randomized, double-blind, crossover study, we assessed the effect of 10-week supplementation with 3 g/d pure EPA and pure DHA (both as ethyl ester, ≥97% purity) on plasma lipid and lipoprotein concentrations and activities of lipoprotein lipase (LPL), cholesteryl ester transfer protein (CETP) and lecithin:cholesterol acyl transferase (LCAT) in 21 older (>50 y) men and postmenopausal women with some characteristics of metabolic syndrome and low-grade chronic inflammation.

Results:

Both EPA and DHA lowered plasma TG concentrations and increased LDL-C/apoB and HDL-C/apoA-I ratios, but only DHA increased LDL-C concentrations. The reductions in plasma TG were inversely associated with the changes in LPL activity after both EPA and DHA supplementation. EPA lowered CETP, while DHA lowered LCAT activity. EPA and DHA worked differently in men and women, with DHA increasing LPL activity and LDL-C concentrations in women, but not in men.

Conclusions:

EPA and DHA exerted similar effects on plasma TG, but differences were observed in LDL-C concentrations and activities of some enzymes involved in lipoprotein metabolism. It was also noted that EPA and DHA worked differently in men and women, supporting sex-specific variations in lipoprotein metabolism.

Introduction

Elevated plasma concentrations of triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) are established risk factors for cardiovascular disease (CVD),^{1, 2} the main cause of morbidity and mortality in the U.S.³ Mendelian randomization studies and clinical trials support a causative role of TG and LDL-C in the pathophysiology of CVD.^{4, 5} Elevations in TG and LDL-C concentrations are prevalent in the U.S. population, especially in older individuals with metabolic syndrome.^{6, 7} The characteristic plasma lipid abnormalities observed in metabolic syndrome are usually associated with alterations in enzymes mediating lipoprotein metabolism. Decreased lipoprotein lipase (LPL) activity, which leads to slower very low-density lipoprotein (VLDL) TG hydrolysis and higher plasma TG levels, is commonly observed in dyslipidemia, obesity, and metabolic syndrome.⁸ Hypertriglyceridemia is also associated with higher activity of cholesteryl ester transfer protein (CETP), which exchanges TG for cholesteryl ester between VLDL, HDL and LDL.^{9 10} This leads to an increase in TG content of LDL, which are further metabolized by LPL to form more atherogenic small dense LDL, and to TG-enriched HDL, which are more rapidly cleared from circulation.

The TG-lowering effect of high dose (2–4 g/d) supplementation with the ω−3 fatty acids eicosapentaenoic acid (EPA, 20:5 ω−3) and docosahexaenoic acid (DHA, 22:6 ω−3) is well established.¹¹ However, a putative downside is an increase in plasma LDL-C concentrations by DHA, albeit not observed with EPA.¹² Significant heart-protective effects of high-dose EPA have been reported in the large-scale clinical trials JELIS¹³ and REDUCE-IT¹⁴, but mixed results have been observed in studies using combinations of EPA and DHA.¹⁵ While several mechanisms may account for the differences in results among clinical trials, there is a need to examine the shared and differential effects of EPA and DHA on plasma lipid and lipoprotein metabolism.

The mechanisms by which EPA and DHA differentially affect plasma lipids and the factors affecting lipoprotein metabolism are not well understood. Moreover, despite the well-known sex differences in lipid metabolism and CVD risk, possibly due to sex hormones,¹⁶ there is little information on the sex-specific effects of ω−3 fatty acids on plasma lipid metabolism.

Therefore, the objective of this study was to compare the effects of high-dose EPA and DHA supplementation on plasma lipid profiles and the activities of the major factors involved in lipoprotein metabolism in individuals displaying some characteristics of metabolic syndrome. We also assessed whether EPA and DHA supplementation influences lipoprotein metabolism differently in women and men.

Methods

Study participants

The study design and participants’ characteristics have been previously described.¹⁷ Briefly, individuals with characteristics of metabolic syndrome and low-grade chronic inflammation were enrolled into the study. Inclusion criteria were: 1) age 50–75 years and, if women, postmenopausal; 2) chronic inflammation, defined as serum high sensitivity C-reactive protein (hs-CRP) concentrations ≥2 𝜇g/mL; 3) fasting plasma TG concentrations between 90 and 500 mg/dL; and 4) presence of at least one of the criteria of metabolic syndrome, such as abdominal obesity (waist circumference ≥102 cm in men and ≥89 cm in women), hypertension (blood pressure ≥130/80 mmHg or use of antihypertensive medications), or fasting blood glucose concentrations between 100 and 125 mg/dL. Participants were excluded if they were allergic to fish; usually consumed fish more than 2 times/week; had taken supplements containing fish oil or EPA/DHA during the prior 6 months; regularly used anti-inflammatory medications or were under anticoagulant therapy; had other diseases that might affect their metabolic status such as kidney or liver diseases; were smokers; or were drinking more than 7 drinks/week.

Study design

The study had a double-blind, randomized, crossover design¹⁷ and consisted of a 4-week lead-in phase during which participants took 3 g/d of a control supplement (high-oleic acid sunflower oil; J. Edwards Internationals, Inc., MA), followed by randomization to 3 g/d of either EPA or DHA for 10 weeks, and then a 10-week washout after which participants were crossed over to the other supplement. The end of the lead-in phase was considered baseline. Supplements were provided in 750 mg capsules and participants were instructed to take two capsules in the morning and two capsules in the evening with meals. EPA and DHA were provided as fatty acid ethyl esters and the purity was ≥ 97% (Prevention Pharmaceuticals Inc., CT). The control, EPA and DHA capsules were identical in appearance. Compliance was assessed by the number of returned capsules at the end of each phase and was greater than 80% in all participants. Study participants met with a registered dietician at the beginning of the study and at the end of each phase of the study to receive instructions on how to follow a low-saturated fat diet (25–35% of calories as total fat, <7% as saturated fat, and <200 mg/d cholesterol) throughout the study. Participants were also instructed to maintain the same lifestyle and physical exercise and not to consume more than two fish meals or supplements containing ω−3 fatty acids during the study. The study protocol was approved by the Tufts University Institutional Review Board and all participants gave written consent. The study is registered at ClinicalTrial.gov (NCT02670382). LDL-C was one of the primary outcomes of the study, and it had been determined that 20 participants were needed to achieve 80% power using a two-sided 0.05 significance to detect a significant difference of 6 mg/dL between EPA and DHA.¹⁸ Twenty-four participants were enrolled into the study and three dropped out during the lead-in phase due to family or health reasons unrelated to the study. Therefore, 21 participants, 9 men and 12 women, completed the study.

Biochemical analyses

Twelve-hour fasting blood samples were collected in EDTA tubes (Becton Dickinson; NJ) at the screening visit and on two consecutive days at the end of the lead-in phase (baseline) and the EPA and DHA supplementation phases. Blood was quickly cooled at 4°C and centrifuged (1000 g for 15 min at 4°C), and plasma was separated and stored at −80°C until analysis. EPA and DHA in plasma phospholipids were assessed by gas chromatography and expressed as a relative proportion (mol %) of the total phospholipid fatty acids.¹⁹ Plasma concentrations of total cholesterol (TC), TG, and HDL-C were determined using standard enzymatic methods with reagents from Roche Diagnostics (Indianapolis, IN).²⁰ Plasma LDL-C concentrations were calculated using the Friedewald formula (LDL-C = TC – TG/5 – HDL-C).²¹ Non-HDL-C was calculated as the difference between TC and HDL-C. Plasma apolipoprotein B (apoB) and apolipoprotein A-I (apoA-I) concentrations were measured by immunoturbidimetric assays (Wako Diagnostics; Richmond, VA).²⁰ The values from the two consecutive days at the end of each phase were averaged.

CETP, LCAT and LPL activities

CETP and lecithin:cholesterol acyltransferase (LCAT) activities were assessed in plasma as previously described.^22–24 This assay measures CETP and LCAT activities as a function of time by assessing TC and free cholesterol (FC) in total plasma and in apoB-depleted plasma at two time points [time 0 (initial) and after 3 h of incubation at 37°C (time 3)]. LCAT activity is determined as the total decrease of plasma FC as a function of time. The activity of CETP, which transfers cholesteryl ester (CE) from HDL to VLDL, is calculated as the difference between the rate of total FC change in plasma – i.e. LCAT activity – and the net increase of CE in HDL. CETP activity was calculated using the following equation:

$$CETPactivity=\left[totalF{C}_{t\mathit{0}}-totalF{C}_{t\mathit{3}}\right]-\left[\left(HDL-T{C}_{t\mathit{3}}-HDL-F{C}_{t\mathit{3}}\right)-\left(HDL-T{C}_{t\mathit{0}}-HDL-F{C}_{t\mathit{0}}\right)\right]$$

All inter-assay CVs were <5%.

Post-heparin LPL activity was measured using a commercially available assay kit (Kamiya, Seattle, WA) in plasma samples collected 20 minutes after an intravenous administration of heparin (50 U/kg body weight) performed on the second blood draw day at the end of each phase. The kit utilizes a fluorogenic TG analog which produces fluorescence upon its hydrolysis by LPL at the sn-1 position. Fluorescence was measured at excitation wavelength 485 nm and emission wavelength 525 nm in a Biotek instrument.

Statistical analyses

Analyses were performed in R version 4.0.0 (R core team, 2020). Before analysis, variables were assessed for normal distribution using the Shapiro-Wilk test. Variables normally distributed are shown as mean ± standard deviation (SD) and those not normally distributed as median (interquartile range: quartile 1 – quartile 3). Before analyses, non-normally distributed variables were subjected to log transformation. Differences from baseline after EPA and DHA supplementation were compared by linear mixed models using the lmer function of the lme4 package. The models accounted for a random effect of subjects and fixed effects of treatment, period, and sequence. Baseline values were included in the models as covariates. The changes from baseline within each supplementation were determined using the lsmeansLT function from the lmerTest package, which allows for comparisons of least square means between baseline and each supplemental phase in the linear mixed models. Correlation analyses were performed by Spearman rank test. A P value ≤0.05 was considered statistically significant.

Results

The screening visit characteristics of the 21 participants who completed the study are shown in Table 1. Participants had low-grade chronic inflammation and were on average overweight or obese. There were no differences in screening characteristics between men and women, except for a significantly lower diastolic blood pressure and a trend for higher TG concentrations in women than in men.

Table 1.

Characteristics of subjects at screening visit

	All subjects (N=21)	Women (N=12)	Men (N=9)
Age (y)	61 ± 6	64 ± 6	59 ± 5
Weight (kg)	93 ± 20	85 ± 20	103 ± 17
BMI (kg/m2)	32.2 ± 6.6	32.2 ± 7.5	32.2 ± 5.8
Waist circumference (cm)	104 ± 15	100 ± 15	111 ± 11
SBP (mmHg)	130 ± 16	128 ± 19	132 ± 10
DBP (mmHg)	79 ± 12	73 ± 11	87 ± 8*
hs-CRP (μg/mL)	4.6 (3.7–7.4)	4.5 (3.7–7.0)	4.7 (4.2–7.4)
Fasting glucose (mg/dL)	100 ± 10	99 ± 10	101 ± 11
Fasting TG (mg/dL)	132 (117–172)	142 (117–185)	122 (102–133)

Values are reported as mean ± SD or median (Q1-Q3).

^*P <0.05, women versus men.

BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; TG, triglyceride; hs-CRP, high sensitivity C reactive protein

To convert to S.I. units: TG (mg/dl) × 0.01129

The plasma phospholipid content of EPA, expressed as median (25^th −75^th percentile) mol%, was 0.72 (0.57–0.94) at baseline and increased to 5.34 (4.75–7.51) and 1.55 (1.16–2.02) after EPA and DHA supplementation, respectively. Plasma phospholipid DHA content was 2.80 (2.58–3.22) mol% at baseline and 3.08 (2.50–3.59) and 7.66 (6.68–8.06) after EPA and DHA supplementation, respectively. Relative to baseline, EPA supplementation led to a significant reduction in plasma TG concentration without changes in apoB concentration, resulting in a significant reduction in the TG/apoB ratio (Table 2). Plasma TC, LDL-C, non-HDL-C, HDL-C and apoA-I concentrations were not affected by EPA, but the LDL-C/apoB and HDL-C/apoA-I ratios were modestly but significantly increased. Similarly to EPA, DHA supplementation significantly lowered plasma TG concentration and the TG/apoB ratio and increased the LDL-C/apoB and HDL-C/apoA-I ratios, and the increase in the latter was significantly greater than that observed after EPA supplementation (Table 2). However, DHA significantly increased LDL-C. EPA and DHA caused reductions in TG concentrations and TG/apoB ratios in both women and men (Supplementary Table 1). Unexpectedly, EPA supplementation increased LDL-C concentrations in men while DHA increased LDL-C and apoB concentrations in women.

Table 2.

Lipid and lipoprotein values at baseline and after EPA and DHA supplementation (N=21)

	Baseline	After EPA	ΔEPA 1	After DHA	ΔDHA 1	P 2
TC (mg/dL)	207 ± 35	208 ± 34	0 ± 15	212 ± 40	5 ± 20	0.19
TG (mg/dL)	141 ± 48	112 ± 32	−28 ± 29***	109 ± 38	−31 ± 38***	0.57
LDL-C (mg/dL)	130 ± 26	136 ± 26	5 ± 12	140 ± 32	10 ± 17**	0.17
HDL-C (mg/dL)	49 ± 11	49 ± 11	1 ± 4	50 ± 14	1 ± 6	0.71
Non-HDL-C (mg/dL)	158 ± 29	158 ± 28	−0.2 ± 14	162 ± 33	4 ± 20	0.26
Apo B (mg/dL)	109 ± 19	110 ± 18	2 ± 9	112 ± 22	3 ± 13	0.38
Apo A-I (mg/dL)	141 ± 22	139 ± 21	−2 ± 10	137 ± 23	−4 ± 13	0.47
TC/HDL-C	4.36 ± 0.79	4.33 ± 0.82	−0.03 ± 0.37	4.44 ± 1.11	0.04 ± 0.69	0.77
TG/apo B	1.29 ± 0.36	1.03 ± 0.27	−0.26 ± 0.22***	0.99 ± 0.32	−0.29 ± 0.25***	0.49
LDL-C/apo B	1.20 ± 0.10	1.23 ± 0.10	0.03 ± 0.05*	1.25 ± 0.09	0.05 ± 0.06***	0.10
HDL-C/apo A-I	0.34 ± 0.03	0.35 ± 0.04	0.01 ± 0.02*	0.36 ± 0.04	0.02 ± 0.02****	0.006

Values are reported as unadjusted mean ± SD

¹Change (Δ) after EPA or after DHA, relative to baseline. Comparison to baseline was assessed using a linear mixed-effects model.

^*P ≤0.05

^**P <0.01

^***P <0.001

²P value, comparison between ΔEPA and ΔDHA

TC, total cholesterol; TG, triglycerides; LDL-C, low-density lipoprotein cholesterol, HDL-C, high-density lipoprotein cholesterol; apo, apolipoprotein

To convert to S.I. units: TG (mg/dl) × 0.01129; C (mg/dL) x 0.02586

To better understand the mechanisms of the effects of EPA and DHA on plasma lipids, we measured the activities of LPL, CETP and LCAT, the major modulators of lipoprotein metabolism. Overall, EPA reduced CETP activity while DHA reduced LCAT activity (Table 3). EPA and DHA affected LPL, CETP and LCAT activity in a gender-specific manner. DHA increased LPL activity, EPA decreased CETP activity, and both decreased LCAT activity only in women (Supplementary Table 2).

Table 3.

Enzyme activities at baseline and after EPA and DHA supplementation (N=21)

	Baseline	After EPA	ΔEPA 1	After DHA	ΔDHA 1	P 2
LPL (mU/mL)	103.2 ± 36.2	106.6 ± 30.9	3.3 ± 25.1	109.4 ± 24.5	6.1 ± 18.3	0.59
CETP (nmol/mL/hr)	10.4 ± 4.7	8.7 ± 2.6	−1.6 ± 4.9*	9.7 ± 4.1	−0.7 ± 6.1	0.40
LCAT (nmol/mL/hr)	22.3 ± 4.4	21.1 ± 4.2	−1.2 ± 4.6	20.6 ± 3.5	−1.8 ± 4.9*	0.51

Values are reported as unadjusted mean ± SD

¹Change (Δ) after EPA or after DHA, relative to baseline. Comparison to baseline was assessed using a linear mixed-effects model.

^*P ≤0.05

²P value, comparison between ΔEPA and ΔDHA

LPL, lipoprotein lipase; CETP, cholesteryl ester transfer protein; LCAT, lecithin:cholesterol acyl transferase

The reduction in plasma TG concentrations after EPA and DHA supplementation was negatively correlated with baseline TG concentrations (ρ= −0.72, P <0.0001 and ρ= −0.67, P <0.001, respectively) (Figure 1). The EPA- and DHA-related TG reductions were also correlated with increases in LPL activities (ρ= −0.42, P =0.05 and ρ= −0.46, P <0.05, respectively) and with decreases in LCAT activities (ρ= 0.45, P <0.05 and ρ= 0.54, P <0.02, respectively) (Table 4). In addition, TG changes were negatively associated with changes in the LDL-C/apoB (ρ= −0.67 and ρ= −0.63, respectively; both P <0.01) and HDL-C/apoA-I (ρ= −0.53, P <0.05 and ρ= −0.61, P < 0.01, respectively) ratios. The EPA-mediated changes in LDL-C concentration were positively correlated with the change in LCAT activities. The associations between TG and LDL-C concentrations and LPL, CETP, and LCAT activities were driven by effects in men (Supplementary Table 3).

Figure 1.

Association between baseline TG concentrations and change in TG concentrations after EPA (ρ= −0.72, P <0.0001) and DHA (ρ= −0.67, P <0.001) supplementation, respectively.

Table 4.

Correlations between changes (Δ) in lipid concentrations and changes in enzyme activities following EPA and DHA supplementation (N=21)

	ΔLPL	ΔCETP	ΔLCAT
EPA
ΔTG	-0.42*	0.12	0.45*
ΔLDL-C	0.08	0.39	0.65**
DHA
ΔTG	-0.46*	0.50**	0.54**
ΔLDL-C	0.09	0.32	0.22

Spearman rank test.

^*P ≤0.05

^**P <0.02

LPL, lipoprotein lipase; CETP, cholesteryl ester transfer protein; LCAT, lecithin:cholesterol acyl transferase; TG, triglycerides; LDL-C, low-density lipoprotein cholesterol

Discussion

In our study, the head-to-head comparison of high-dose EPA and DHA supplementation shows both common and differential effects on plasma lipid and lipoprotein concentrations and on major factors mediating lipoprotein metabolism in individuals with chronic low-grade inflammation and characteristics of metabolic syndrome.

Effects of EPA and DHA on plasma TG

EPA and DHA were equally effective in lowering plasma TG concentration, approximately −20% and −22%, respectively. There was a trend toward greater TG reductions in women, possibly due to their higher baseline concentrations. It has been suggested that the TG lowering by EPA and DHA is the result of a combined inhibitory effect on hepatic TG synthesis and VLDL secretion and an enhanced TG hydrolysis and VLDL clearance by LPL in plasma.²⁵ In a stable isotope kinetic study conducted in moderately dyslipidemic subjects, we have previously reported that consumption of a high-fish diet (8 servings/week, 1.23 g/d EPA+DHA) caused a significant reduction in the production rate and an increase in the fractional catabolic clearance of apoB in TG-rich lipoproteins.²⁶ Similar findings have been reported in other studies where EPA+DHA were supplemented.²⁷ Our finding that TG reductions were greater in participants with higher baseline TG and in those who experienced larger increases in LPL activity highlights the major role of VLDL-TG hydrolysis in the reduction of TG by ω−3 fatty acid supplementation. A systematic review of clinical trials assessing the differential effects of EPA and DHA on cardiometabolic risk factors reported similar reductions in TG concentration by both EPA and DHA, with only two studies reporting a modestly greater TG reduction with DHA than EPA.^{12, 28} Though there is no consistent agreement among studies, it has been suggested that DHA causes a greater increase in LPL activity than EPA.²⁹ This may be mediated by greater reductions in the synthesis of apoC-III, a potent inhibitor of LPL, by DHA than EPA through differential regulation of hepatic transcription factors regulating its expression.³⁰ Indeed, we found that LPL activity was significantly elevated by DHA but not EPA in women.

In addition, we assessed the associations between changes in TG concentrations and CETP and LCAT activities after EPA and DHA supplementation. We observed a significant reduction in CETP activity after EPA with only a trend after DHA supplementation, and this reduction was mostly observed in women. It is known that CETP activity is regulated by its substrate, VLDL, availability.³¹ We have found that the reduction in CETP activity was significantly associated with the reduction in TG concentrations, but only after DHA supplementation.

The change in LCAT activity was positively associated with the change in TG after both EPA and DHA supplementation. Previously, it was reported that subjects with metabolic syndrome have increased LCAT activity.³² Moreover, a longitudinal study reported that changes in LCAT activity were significantly associated with changes in TG and in LDL particle size.³³ While these studies are in agreement with our finding of an association between changes in LCAT activity and changes in TG concentration after EPA and DHA, little is known about the potential mechanism linking LCAT to TG metabolism.

Effects of EPA and DHA on LDL-C

Some, but not all, clinical trials of supplementation with DHA or fish oil containing both DHA and EPA have reported an increase in plasma LDL-C concentrations.^{34, 35} Similar findings have also been reported in hamsters, an animal model of lipoprotein metabolism similar to humans.³⁶ Consistent with these previous findings, DHA, but not EPA, increased plasma LDL-C concentration when all subjects were included in our analyses. However, when men and women were analyzed separately, we found that EPA and DHA affected LDL-C differently: EPA increased LDL-C in men, and DHA increased LDL-C in women. While this is different from a study by Allaire et al.²⁸ where a significant increase in LDL-C was noted after DHA in men but not women, our finding is consistent with another study.³⁷ The significant increase in LDL-C in women but not in men after DHA supplementation may be explained by a greater activation of LPL and reduction in TG in women: higher LPL activity may lead to greater hydrolysis of TG in VLDL, resulting in greater conversion to LDL and the formation of larger, more buoyant LDL particles.³⁰ Clinical trials have shown that CETP inhibitors reduce LDL-C concentrations:³⁸ we observed reduced CETP activity only after EPA supplementation, which may have in part blunted the LDL-C increase after EPA. Again, the lowering effect of EPA on CETP activity was more pronounced in women than in men, possibly due to a greater reduction in TG concentrations in women. We also found that the EPA-mediated changes in LDL-C concentrations were strongly associated with the changes in LCAT activity. However, the interrelation between TG, LDL-C and LCAT activity is less clear. In addition, increased LDL-C/apo B ratio by both EPA and DHA indicates more cholesterol-rich and buoyant LDL particles formed after supplementation. At this time, it is not known whether the ω−3 fatty acid-mediated increase in LDL-C carries an increased risk of CVD.

Effect of EPA and DHA on HDL-C

Some studies have reported an increase in HDL-C concentrations after DHA supplementation.^{34, 37} We found no significant effects of EPA and DHA on HDL-C or apo A-I concentrations but observed a significant increase in the HDL-C/apoA-I ratio. It is noteworthy that DHA increased the ratio to a greater degree than EPA. The changes in the HDL-C/apoA-I ratio were significantly and inversely associated with the changes in plasma TG after both EPA and DHA supplementation, supporting the well-established inverse association between TG and HDL composition and the contribution of LPL-mediated VLDL hydrolysis.^{39, 40} Notably, after DHA supplementation, the HDL/apoA-I increases were correlated with the reductions in LCAT activity (ρ = −0.62, P <0.01). This is in line with some studies showing that high-fish diets reduce LCAT activity⁴¹ and our own previous data showing reduction of the expression and secretion of LCAT in hepatic cells after ω−3 fatty acid supplementation,⁴² despite no effect reported from a few other studies.³⁶

Limitations of our study include the small sample size and the slightly different baseline plasma TG concentrations between women and men, which may limit the interpretation of our results. Multiple endpoints were tested, and results have been presented uncorrected for multiple comparison. However, our study has several strengths: the randomized, double-blind, and crossover design suitable for a well-controlled head-to-head comparison; the use of highly pure (>97%) EPA and DHA supplements; and the careful follow-up of the study participants, which resulted in high compliance. In addition, our study subjects had characteristics of metabolic syndrome and chronic inflammation, the ideal target population for ω−3 fatty acid supplementation.

Conclusions

In summary, supplementation with 3 g/d pure EPA and pure DHA ethyl esters showed both shared and differential effects on plasma lipid and on lipoprotein metabolism in older individuals with low-grade chronic inflammation. Changes in LPL, CETP and LCAT activities following EPA and DHA supplementation were variably associated with changes in TG and lipoprotein concentrations. Further investigations are warranted based on our findings of differential sex effects of EPA and DHA on plasma lipids and lipoprotein metabolism.