The effect of dietary docosahexaenoic acid on plasma lipoproteins and tissue fatty acid composition in humans

DHA 12-LOX-derived oxylipins regulate platelet activation and thrombus formation through a PKA-dependent signaling pathway

BACKGROUND

The effects of docosahexaenoic acid (DHA) on cardiovascular disease are controversial and a mechanistic understanding of how this omega-3 polyunsaturated fatty acid (ω-3 PUFA) regulates platelet reactivity and the subsequent risk of a thrombotic event is warranted. In platelets, DHA is oxidized by 12-lipoxygenase (12-LOX) producing the oxidized lipids (oxylipins) 11-HDHA and 14-HDHA. We hypothesized that 12-LOX DHA-oxylipins may be involved in the beneficial effects observed in dietary supplemental treatment with ω-3 PUFAs or DHA itself.

OBJECTIVES

To determine the effects of DHA, 11-HDHA, and 14-HDHA on platelet function and thrombus formation, and to elucidate the mechanism by which these ω-3 PUFAs regulate platelet activation.

METHODS AND RESULTS

DHA, 11-HDHA, and 14-HDHA attenuated collagen-induced human platelet aggregation, but only the oxylipins inhibited ⍺IIbβ3 activation and decreased ⍺-granule secretion. Furthermore, treatment of whole blood with DHA and its oxylipins impaired platelet adhesion and accumulation to a collagen-coated surface. Interestingly, thrombus formation was only diminished in mice treated with 11-HDHA or 14-HDHA, and mouse platelet activation was inhibited following acute treatment with these oxylipins or chronic treatment with DHA, suggesting that under physiologic conditions, the effects of DHA are mediated through its oxylipins. Finally, the protective mechanism of DHA oxylipins was shown to be mediated via activation of protein kinase A.

CONCLUSIONS

This study provides the first mechanistic evidence of how DHA and its 12-LOX oxylipins inhibit platelet activity and thrombus formation. These findings support the beneficial effects of DHA as therapeutic intervention in atherothrombotic diseases.

A Randomized Multicenter Phase II Study of Docosahexaenoic Acid in Patients with a History of Breast Cancer, Premalignant Lesions, or Benign Breast Disease

Obesity, a cause of subclinical inflammation, is a risk factor for the development of postmenopausal breast cancer and is associated with poorer cancer outcomes. Docosahexaenoic acid (DHA), an omega-3 fatty acid, possesses anti-inflammatory properties. We hypothesized that treatment with DHA would reduce the expression of proinflammatory genes and aromatase, the rate-limiting enzyme for estrogen biosynthesis, in benign breast tissue of overweight/obese women. A randomized, placebo-controlled, double-blind phase II study of DHA given for 12 weeks to overweight/obese women with a history of stage I-III breast cancer, DCIS/LCIS, Paget's disease, or proliferative benign breast disease was carried out. In this placebo controlled trial, the primary objective was to determine whether DHA (1,000 mg by mouth twice daily) reduced breast tissue levels of TNFα. Secondary objectives included evaluation of the effect of DHA on breast tissue levels of COX-2, IL1β, aromatase, white adipose tissue inflammation, and gene expression by RNA-seq. Red blood cell fatty acid levels were measured to assess compliance. From July 2013 to November 2015, 64 participants were randomized and treated on trial (32 women per arm). Increased levels of omega-3 fatty acids in red blood cells were detected following treatment with DHA (P < 0.001) but not placebo. Treatment with DHA did not alter levels of TNFα (P = 0.71), or other biomarkers including the transcriptome in breast samples. Treatment with DHA was overall well-tolerated. Although compliance was confirmed, we did not observe changes in the levels of prespecified biomarkers in the breast after treatment with DHA when compared with placebo. Cancer Prev Res; 11(4); 203-14. ©2018 AACRSee related editorial by Fabian and Kimler, p. 187.

Preclinical Evaluation of the Short-Term Toxicity of 4-(N)-Docosahexaenoyl 2´, 2´- Difluorodeoxycytidine (DHA-dFdC)

PURPOSE

This study was designed to test the short-term toxicity of DHA-dFdC in a mouse model and its efficacy in a mouse model of leukemia at or below its repeat-dose maximum tolerated dose (RD-MTD).

METHOD

A repeat-dose dose-ranging toxicity study was designed to determine the tolerability of DHA-dFdC when administered to DBA/2 mice by intravenous (i.v.) injection on a repeat-dose schedule (i.e. injections on days 0, 3, 7, 10, and 13). In order to determine the effect of a lethal dose of DHA-dFdC, mice were injected i.v. with three doses of DHA-dFdC at 100 mg/kg on days 0, 3, and 5 (i.e. a lethal-RD). The body weight of mice was recorded two or three times a week. At the end of the study, major organs (i.e. heart, liver, spleen, kidneys, lung, and pancreas) of mice that received the lethal-RD or RD-MTD were weighed, and blood samples were collected for analyses. Finally, DHA-dFdC was i.v. injected into DBA/2 mice with syngeneic L1210 mouse leukemia cells to evaluate its efficacy at or below RD-MTD.

RESULTS

The RD-MTD of DHA-dFdC is 50 mg/kg. At 100 mg/kg, a lethal-RD, DHA-dFdC decreases the weights of mouse spleen and liver and significantly affected certain blood parameters (i.e. white blood cells, lymphocytes, eosinophils, and neutrophil segmented). At or below its RD-MTD, DHA-dFdC significantly prolonged the survival of L1210 leukemia-bearing mice.

CONCLUSION

DHA-dFdC has dose-dependent toxicity, affecting mainly spleen at a lethal-RD. At or below its RD-MTD, DHA-dFdC is effective against leukemia in a mouse model.

Effects of docosahexaenoic acid supplementation on PUFA levels in red blood cells and plasma

INTRODUCTION

Polyunsaturated fatty acids (PUFA) are metabolized in a complex network of elongation, desaturation and beta oxidation.

MATERIAL AND METHODS

The short (1 and 3 wk), and long term (6 and 12 wk) effect of 1076mg/d docosahexaenoic acid (DHA, free of eicosapentaenoic acid (EPA)) on (absolute) PUFA concentrations in plasma and red blood cells (RBC) of 12 healthy men (mean age 25.1±1.5 years) was investigated.

RESULTS

RBC DHA concentrations significantly (p<0.001) increased from 28±1.6µg/mL to 38±2.0µg/mL (wk 1), 52±3.3µg/mL (wk 3), 68±2.6µg/mL (wk 6), and 79±3.5µg/mL (wk 12). Arachidonic acid (AA) concentrations declined in response to DHA treatment, while the effect was more pronounced in plasma (wk 0: 183±9.9µg/mL, wk 12: 139±8.0µg/mL, -24%, p<0.001) compared to RBC (wk 0: 130±3.7µg/mL, wk 12: 108±4.0µg/mL, -16%, p=0.001). Furthermore, an increase of EPA concentrations in plasma (wk 0: 15±1.5µg/mL, wk 1:19±1.6µg/mL, wk 3: 27±2.3µg/mL, wk 6: 23±1.2µg/mL, wk 12: 25±1.7µg/mL, p<0.001) and RBC (wk 0: 4.7±0.33µg/mL, wk 1: 6.7±1.3µg/mL, wk 3: 8.0±0.66µg/mL, wk 6: 6.9±0.44µg/mL, wk 12: 6.7±0.45µg/mL, n.s.) was observed suggesting a retroconversion of DHA to EPA.

CONCLUSION

Based on PUFA concentrations we showed that DHA supplementation results in increased EPA levels, whereas it is not known if this impacts the formation of EPA-derived lipid mediators. Furthermore, shifts in the entire PUFA pattern after supplementation of EPA or DHA should be taken into account when discussing differential physiological effects of EPA and DHA.

A new, microalgal DHA- and EPA-containing oil lowers triacylglycerols in adults with mild-to-moderate hypertriglyceridemia

In this double-blind, parallel trial, 93 healthy adults with hypertriglyceridemia (triacylglycerols [TAG] 150-499 mg/dL) were randomized to receive either a nutritional oil derived from marine algae (DHA-O; 2.4 g/day docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA] in a 2.7:1 ratio), fish oil (FO; 2.0 g/day DHA and EPA in a 0.7:1 ratio), or a corn oil/soy oil control as 4-1g softgel capsules/day with meals for 14 weeks; and were instructed to maintain their habitual diet. Percent changes from baseline for DHA-O, FO, and control, respectively, were TAG (-18.9, -22.9, 3.5; p<0.001 DHA-O and FO vs. control), low-density lipoprotein cholesterol (4.6, 6.8, -0.6; p<0.05 DHA-O and FO vs. control), and high-density lipoprotein cholesterol (4.3, 6.9, 0.6; p<0.05 FO vs. control). This study demonstrated that ingestion of microalgal DHA-O providing 2.4 g/day DHA+EPA lowered TAG levels to a degree that was not different from that of a standard fish oil product, and that was significantly more than for a corn oil/soy oil control.

Effects of supplementing n-3 fatty acid enriched eggs and walnuts on cardiovascular disease risk markers in healthy free-living lacto-ovo-vegetarians: a randomized, crossover, free-living intervention study

Background

Plant and marine n-3 fatty acids (FA) may favorably modify select markers of cardiovascular disease risk. Whether supplementing the habitual diet of lacto-ovo-vegetarians (LOV) with walnuts (containing α-linolenic acid, ALA) and n-3 FA enriched eggs (containing primarily docosahexaenoic acid, DHA and ALA) would have equivalent effects on CVD risk factors is explored in this study.

Methods

In this study, 20 healthy free-living LOVs following their habitual diet were randomly assigned in a crossover design to receive one of three supplements: n-3 FA enriched egg (6/week), walnuts (28.4 g, 6/week) or a standard egg, 6/week (control) for 8 weeks each with 4-wk washout between treatments. Erythrocyte membrane fatty acids, serum lipids and inflammatory markers were measured at the end of each treatment.

Results

Dietary compliance was observed by an expected increase in erythrocyte membrane ALA following the walnut treatment and in DHA following the n-3 FA enriched egg treatment. Walnut treatment lowered serum triacylglycerol, total cholesterol and Apo B (p < 0.05) compared to the standard egg but not the n-3 FA enriched egg treatment. However, walnut treatment significantly reduced total: HDL cholesterol ratio compared to both egg treatments. There were no differences between treatments for any of the inflammatory markers.

Conclusions

For LOV, a direct source of DHA such as n-3 FA enriched eggs seems necessary to increase membrane levels of DHA. However for producing an overall favorable blood lipid profile, daily consumption of a handful of walnuts rich in ALA may be a preferred option for lacto-ovo vegetarian.

Genetic evidence for role of carotenoids in age-related macular degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS)

PURPOSE

We tested variants in genes related to lutein and zeaxanthin status for association with age-related macular degeneration (AMD) in the Carotenoids in Age-Related Eye Disease Study (CAREDS).

METHODS

Of 2005 CAREDS participants, 1663 were graded for AMD from fundus photography and genotyped for 424 single nucleotide polymorphisms (SNPs) from 24 candidate genes for carotenoid status. Of 337 AMD cases 91% had early or intermediate AMD. The SNPs were tested individually for association with AMD using logistic regression. A carotenoid-related genetic risk model was built using backward selection and compared to existing AMD risk factors using the area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 24 variants from five genes (BCMO1, BCO2, NPCL1L1, ABCG8, and FADS2) not previously related to AMD and four genes related to AMD in previous studies (SCARB1, ABCA1, APOE, and ALDH3A2) were associated independently with AMD, after adjusting for age and ancestry. Variants in all genes (not always the identical SNPs) were associated with lutein and zeaxanthin in serum and/or macula, in this or other samples, except for BCO2 and FADS2. A genetic risk score including nine variants significantly (P = 0.002) discriminated between AMD cases and controls beyond age, smoking, CFH Y402H, and ARMS2 A69S. The odds ratio (95% confidence interval) for AMD among women in the highest versus lowest quintile for the risk score was 3.1 (2.0-4.9).

CONCLUSIONS

Variants in genes related to lutein and zeaxanthin status were associated with AMD in CAREDS, adding to the body of evidence supporting a protective role of lutein and zeaxanthin in risk of AMD.

Blood lipids profile in hyperlipidemic children undergoing different dietary long chain polyunsaturated supplementations: a preliminary clinical trial

The aim of this preliminary study was to explore the effect size of different dietary long chain polyunsaturated supplementations on blood lipid profile in children with primary hyperlipidemia. Thirty-six children (8-13 years) were recruited. After an 8-week stabilization period on the Step I diet, they were randomized to additionally receive for a 16-week period one capsule (500 mg) daily of docosahexaenoic acid (DHA) alone or a DHA plus eicosapentaenoic acid (EPA) mixture (45.6% DHA; 41.6% EPA) or wheat germ oil (control). An effect size (as percentage change from baseline) of +8%, -12% and -16% for high-density lipoprotein cholesterol (HDL-C), total cholesterol/HDL-C ratio and triglycerides was observed in children supplemented with DHA, compared to +2%, -8% and -12%, respectively, in children supplemented with DHA plus EPA. This preliminary study suggests powered trials appear feasible and are warranted to evaluate efficacy of n-3 long-chain polyunsaturated fatty acid dietary supplementations on the blood lipid profile of children with primary hyperlipidemia.

Emerging importance of omega-3 fatty acids in the innate immune response: molecular mechanisms and lipidomic strategies for their analysis

The beneficial health properties of dietary omega-3 polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have long been known and their metabolic dysfunction has been linked to a range of diseases including various inflammatory disorders, cardiovascular diseases, and cancer. However, the molecular mechanisms underlying their health benefits have remained unclear. Recent technological advances in lipidomic analytical strategies have resulted in the discovery of a range of bioactive mediators derived from EPA and DHA that possess potent anti-inflammatory and pro-resolving properties and that may be responsible, at least in part, for the beneficial effects observed. These mediators include resolvins, protectins and maresins, as well as EPA derivatives of classical arachidonic acid derived eicosanoids, such as prostaglandin E3 . The aim of this review is to provide an overview of the biosynthetic pathways and biological properties of these omega-3 mediators, with a particular focus on the emerging importance of the counter-regulatory role of omega-3 and -6 fatty acids in the spatial and temporal regulation of the inflammatory response. It will also provide an insight into a range of lipidomic approaches, which are currently available to analyse these fatty acids and their metabolites in biological matrices.

Effects of lutein and docosahexaenoic Acid supplementation on macular pigment optical density in a randomized controlled trial

We studied the macular pigment ocular density (MPOD) in patients with early age macular degeneration (AMD) before and 1 year after nutritional supplementation with lutein and docosahexaenoic acid (DHA). Forty-four patients with AMD were randomly divided into two groups that received placebo (n = 21) or a nutritional supplement (n = 23, 12 mg of lutein and 280 mg of DHA daily). Heterochromatic flicker photometry was used to determine the MPOD. At baseline, the MPOD in AMD patients with placebo was 0.286 ± 0.017 meanwhile in AMD patients with supplementation it was 0.291 ± 0.016. One year later, the mean MPOD had increased by 0.059 in the placebo group and by 0.162 in patients receiving lutein and DHA. This difference between groups was significant (p < 0.05). Lutein and DHA supplementation is effective in increasing the MPOD and may aid in prevention of age related macular degeneration.

Arachidonate 5-lipoxygenase gene variants affect response to fish oil supplementation by healthy African Americans

Arachidonate 5-lipoxygenase (ALOX5) gene variants that are common in people of African ancestry are associated with a differential cardiovascular disease (CVD) risk that may be ameliorated by intake of (n-3) PUFA, such as EPA or DHA. We conducted a double-masked, placebo (PL)-controlled trial of fish oil (FO) supplements to determine if changes in erythrocyte (n-3) PUFA composition, heart rate, blood pressure, and plasma lipid and lipoprotein concentrations are modified by genotype. Participants received 5 g/d FO (2 g EPA, 1 g DHA) or 5 g/d corn/soy oil (PL). A total of 116 healthy adults of African ancestry with selected genotypes (genotypes = "dd," "d5," and "55" with "d" representing the deletion of 1 or 2 Sp1 binding sites in the ALOX5 promoter and "5" indicating the common allele with 5 sites) were enrolled and 98 completed the study. FO caused significant increases (relative to PL) in erythrocyte EPA, DHA, and total (n-3) PUFA and a decrease in the (n-6) PUFA:(n-3) PUFA ratio in the low-CVD risk "d5" and "55" genotypes but not in the high-risk "dd" genotype. Similarly, HDL particle concentration decreased with FO relative to PL in the "d5" and "55" but not "dd" genotypes. The plasma TG concentration decreased significantly with FO relative to PL in the "d5" but not "dd" and "55" genotypes. No changes were seen in LDL particle or cholesterol concentrations, heart rate, or blood pressure. These findings indicate that the efficacy of FO supplements vary by ALOX5 genotype.

A meta-analysis shows that docosahexaenoic acid from algal oil reduces serum triglycerides and increases HDL-cholesterol and LDL-cholesterol in persons without coronary heart disease

Certain algae contain the (n-3) fatty acid DHA, yet the relation between algal oil supplementation and cardiovascular disease risk factors has not been systematically examined. Our objective was to examine the relation between algal oil supplementation and cardiovascular disease risk factors. We conducted a systematic review of randomized controlled trials published between 1996 and 2011 examining the relation between algal oil supplementation and cardiovascular disease risk factors and performed a meta-analysis of the association between algal oil DHA supplementation and changes in the concentrations of TG, LDL-cholesterol (LDL-C), and HDL-cholesterol (HDL-C). We identified 11 randomized controlled trials with 485 healthy participants that evaluated the relation between algal oil DHA supplementation and TG, LDL-C, and HDL-C. The median dose of algal DHA was 1.68 g/d. The pooled estimate for the change in TG concentration was -0.20 mmol/L (95% CI: -0.27 to -0.14), 0.23 mmol/L (95% CI: 0.16-0.30) for LDL-C, and 0.07 mmol/L (95% CI: 0.05-0.10) for HDL-C. DHA supplementation from algal oil, a marine source of (n-3) fatty acids not extracted from fish, may reduce serum TG and increase HDL-C and LDL-C in persons without coronary heart disease.

The relation between the omega-3 index and arachidonic acid is bell shaped: synergistic at low EPA+DHA status and antagonistic at high EPA+DHA status

INTRODUCTION

The relation between docosahexaenoic (DHA) and eicosapentaenoic (EPA) vs. arachidonic acid (AA) seems characterized by both synergism and antagonism.

MATERIALS AND METHODS

Investigate the relation between EPA+DHA and AA in populations with a wide range of EPA+DHA status and across the life cycle. EPA+DHA and AA were determined in erythrocytes (RBC; n=1979), umbilical arteries (UA; n=789) and umbilical veins (UV; n=785).

RESULTS

In all compartments, notably RBC, the relation between EPA+DHA and AA appeared bell-shaped. Populations with low RBC-EPA+DHA (<2g%) exhibited positive relationships; those with high RBC-EPA+DHA (>8g%) negative relationships. Antagonism in UA and UV could not be demonstrated.

CONCLUSION

Both synergism and antagonism might aim at a balance between ω6 and ω3 long-chain polyunsaturated fatty acid (LCP) to maintain homeostasis. Synergism might be a feature of low LCPω3 status. AA becomes suppressed by antagonism from an RBC-EPA+DHA >8g%.

Maternal DHA equilibrium during pregnancy and lactation is reached at an erythrocyte DHA content of 8 g/100 g fatty acids

Low long-chain PUFA (LC-PUFA, or LCP) consumption relates to suboptimal neurodevelopment, coronary artery disease, and [postpartum (PP)] depression. Maternal-to-infant LCP transport during pregnancy and lactation is at the expense of maternal status, a process known as biomagnification. Despite biomagnification, maternal and infant LCP status generally declines during lactation. To assess the 1) turning point of biomagnification [level from which maternal (m)LCP status exceeds infant (i)LCP status]; 2) LCP equilibrium (steady-state-level from which mRBC-LCP stop declining during lactation); 3) corresponding iLCP-status; and 4) the relationship between RBC-DHA and RBC-arachidonic acid (AA), we measured RBC-fatty acids in 193 Tanzanian mother-infant pairs with no, intermediate (2-3 times/wk), and high (4-5 times/wk) freshwater fish consumption at delivery and after 3 mo of exclusive breast-feeding. At 3 mo, mRBC-DHA was lower than the corresponding iRBC-DHA up to a mRBC-DHA of 7.9 g%. mRBC-DHA equilibrium, with equivalent mRBC-DHA at both delivery and at 3 mo PP, occurred at 8.1 g%. This mRBC-DHA equilibrium of 8.1 g% corresponded with an iRBC-DHA of 7.1-7.2 g% at delivery that increased to 8.0 g% at 3 mo. We found between-group differences in mRBC-AA; however, no differences in iRBC-AA were observed at delivery or 3 mo. Relations between RBC-DHA and RBC-AA were bell-shaped. We conclude that, at steady-state LCP intakes during lactation: 1) biomagnification occurs up to 8 g% mRBC-DHA; 2) mRBC-DHA equilibrium is reached at 8 g%; 3) mRBC-DHA equilibrium corresponds with an iRBC-DHA of 7 g% at delivery and 8 g% after 3 mo; 4) unlike RBC-DHA, mRBC-AA and iRBC-AA are independently regulated in these populations; and 5) bell-shaped RBC-DHA vs. RBC-AA-relations might support uniform iRBC-AA. A (maternal) RBC-DHA of 8 g% might be optimal for infant neurodevelopment and adult cardiovascular disease incidence.

The differential effects of EPA and DHA on cardiovascular risk factors

Compelling evidence exists for the cardioprotective benefits resulting from consumption of fatty acids from fish oils, EPA (20:5n-3) and DHA (22:6n-3). EPA and DHA alter membrane fluidity, interact with transcription factors such as PPAR and sterol regulatory element binding protein, and are substrates for enzymes including cyclooxygenase, lipoxygenase and cytochrome P450. As a result, fish oils may improve cardiovascular health by altering lipid metabolism, inducing haemodynamic changes, decreasing arrhythmias, modulating platelet function, improving endothelial function and inhibiting inflammatory pathways. The independent effects of EPA and DHA are poorly understood. While both EPA and DHA decrease TAG levels, only DHA appears to increase HDL and LDL particle size. Evidence to date suggests that DHA is more efficient in decreasing blood pressure, heart rate and platelet aggregation compared to EPA. Fish oil consumption appears to improve arterial compliance and endothelial function; it is not yet clear as to whether differences exist between EPA and DHA in their vascular effects. In contrast, the beneficial effect of fish oils on inflammation and insulin sensitivity observed in vitro and in animal studies has not been confirmed in human subjects. Further investigation to clarify the relative effects of consuming EPA and DHA at a range of doses would enable elaboration of current understanding regarding cardioprotective effects of consuming oily fish and algal sources of long chain n-3 PUFA, and provide clearer evidence for the clinical therapeutic potential of consuming either EPA or DHA-rich oils.

Algal docosahexaenoic acid affects plasma lipoprotein particle size distribution in overweight and obese adults

Fish oils containing both EPA and DHA have been shown to have beneficial cardiovascular effects, but less is known about the independent effects of DHA. This study was designed to examine the effects of DHA on plasma lipid and lipoprotein concentrations and other biomarkers of cardiovascular risk in the absence of weight loss. In this randomized, controlled, double-blind trial, 36 overweight or obese adults were treated with 2 g/d of algal DHA or placebo for 4.5 mo. Markers of cardiovascular risk were assessed before and after treatment. In the DHA-supplemented group, the decrease in mean VLDL particle size (P ≤ 0.001) and increases in mean LDL (P ≤ 0.001) and HDL (P ≤ 0.001) particle sizes were significantly greater than changes in the placebo group. DHA supplementation also increased the concentrations of large LDL (P ≤ 0.001) and large HDL particles (P = 0.001) and decreased the concentrations of small LDL (P = 0.009) and medium HDL particles (P = 0.001). As calculated using NMR-derived data, DHA supplementation reduced VLDL TG (P = 0.009) and total TG concentrations (P = 0.006). Plasma IL-10 increased with DHA supplementation to a greater extent than placebo (P = 0.021), but no other significant changes were observed in glucose metabolism, insulin sensitivity, blood pressure, or markers of inflammation with DHA. In summary, DHA supplementation resulted in potentially beneficial changes in some markers of cardiometabolic risk, whereas other markers were unchanged.

The ins and outs of cholesterol in the vertebrate retina

The vertebrate retina has multiple demands for utilization of cholesterol and must meet those demands either by synthesizing its own supply of cholesterol or by importing cholesterol from extraretinal sources, or both. Unlike the blood-brain barrier, the blood-retina barrier allows uptake of cholesterol from the circulation via a lipoprotein-based/receptor-mediated mechanism. Under normal conditions, cholesterol homeostasis is tightly regulated; also, cholesterol exists in the neural retina overwhelmingly in unesterified form, and sterol intermediates are present in minimal to negligible quantities. However, under certain pathological conditions, either due to an inborn error in cholesterol biosynthesis or as a consequence of exposure to selective inhibitors of enzymes in the cholesterol pathway, the ratio of sterol intermediates to cholesterol in the retina can rise dramatically and persist, in some cases resulting in progressive degeneration that significantly compromises the structure and function of the retina. Although the relative contributions of de novo synthesis versus extraretinal uptake are not yet known, herein we review what is known about these processes and the dynamics of cholesterol in the vertebrate retina and indicate some future avenues of research in this area.

Increased lipid peroxidation and abnormal fatty acid profiles in seminal and blood plasma of normozoospermic males from infertile couples

BACKGROUND

Reactive oxygen species (ROS) are essential for sperm function. However, excessive ROS production can impair sperm function and might be a factor contributing to male infertility.

METHODS

We investigated the levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) as well as lipid peroxidation, as represented by thiobarbituric acid reactive species (TBARS), in blood and seminal plasma of 38 normozoospermic males from infertile couples (NSI-males), compared with that of 17 fertile volunteers (FV-males).

RESULTS

TBARS levels in blood and seminal plasma were higher in NSI-males than in FV-males (P < 0.0002, P < 0.0003, respectively), as were AA levels (P < 0.0003, P < 0.00004, respectively). On the contrary, the blood and seminal plasma levels of DHA were lower in NSI-males than in FV-males (P < 0.02 and P < 0.05, respectively). The AA/DHA ratios in blood and seminal plasma were higher in NSI-males than in FV-males (P < 0.003, P < 0.0007, respectively). Significant correlations between seminal and blood plasma levels of TBARS (P < 0.0001, r = 0.548), AA (P < 0.0001, r = 0.571) and DHA (P < 0.0001, r = 0.506) were found.

CONCLUSIONS

Our data provide new insight into lipid metabolism in male infertility and indicate that systemic oxidative stress resulting in increased lipid peroxidation and an altered fatty acid profile may be, at least in part, responsible for infertility even in normozoospermic males.

Toxicology and safety of DHA

Docosahexaenoic acid (DHA) is a long-chain polyunsaturated fatty acid with activities in both infants and adults. The objective of the current work was to evaluate the published literature concerning the toxicological assessment of DHA-rich oils in animals and the safety profile of DHA consumption in humans. Structured literature searches concerning DHA toxicology and DHA effects on platelet function, lipid levels, oxidative potential, glycemic control, and immune function were conducted. The toxicological profile of DHA derived from single-cell organisms demonstrates that these oils are safe in rats (up to a consumption level of 3290 mg/kg body weight/d) in 90-d toxicology evaluations, as well as in reproductive and developmental toxicology studies. The maximum DHA level in human breast milk exceeds 1% of total fatty acids in high-fish-consuming populations. Consumption of DHA-rich human milk as sole source of nutrition provides approximately 315 mg/d in infants 1-6 months of age, and appears to be a safe level of intake. DHA supplementation studies in adults have employed doses ranging from less than 1 to 7.5 g/d, and have not resulted in any consistent adverse responses in platelet function, lipid levels, in vivo oxidation parameters, glycemic control, or immune function. In conclusion, DHA consumption does not result in consistent adverse events in infants or adults. Safe intake levels may be modeled on DHA intake from human milk in infants, and may be at least as high as the upper doses studied in adults.

Lipid and fatty acid profile of the retina, retinal pigment epithelium/choroid, and the lacrimal gland, and associations with adipose tissue fatty acids in human subjects

Accumulation of lipids within Bruch's membrane (BrM) and between BrM and retinal pigment epithelium (RPE) accounts for one of the biological changes associated with normal aging and may contribute to the development of age-related maculopathies. The origin of these lipids is still being actively investigated. The relative contribution of plasma lipids and lipids coming from the neural retina remains a matter of controversy. Low-density lipoproteins (LDLs) have been reported to significantly participate in the retina's lipid supply, after active remodeling within RPE. Meanwhile, RPE expresses the enzymatic machinery for synthesizing lipoprotein-like particles. The objective of this study was to establish associations between the fatty acid profile of the ocular structures and adipose tissue as a surrogate for the subjects' past dietary intake. Lipids and fatty acids were analyzed from the neural retina, retinal pigment epithelium (RPE)/choroid, the lacrimal gland, and adipose tissue, collected from 27 human donors (19 women, eight men) aged 59-95 years. DHA concentrations in the neural retina were positively associated with the concentrations in cholesteryl esters (CEs) from RPE/choroid and negatively associated with DHA concentrations in phospholipids (PLs) from RPE/choroid. DHA in orbital fat was positively associated with DHA in the lacrimal gland. No significant association was observed in the other ocular structures. Linoleic acid in orbital fat was positively associated with linoleic acid in the lacrimal gland, followed by the neural retina and CEs from RPE/choroid; it was slightly correlated with PLs from RPE/choroid. Other fatty acids that originate exclusively from the diet such as trans fatty acids were detected in orbital fat, the lacrimal gland, PLs, and CEs from RPE/choroid. DHA in the neural retina was poorly associated with its dietary intake, contrary to other fatty acids such as linoleic acid. Within this context, CEs may be important carriers of fatty acids entering the retina. Although epidemiological studies have reported the benefit of DHA in the prevention of age-related macular degeneration, the leading cause of blindness in Western countries, the relevance of supplementing patients with DHA is questioned.

The influence of supplemental lutein and docosahexaenoic acid on serum, lipoproteins, and macular pigmentation

BACKGROUND

Lutein and docosahexaenoic acid (DHA) may protect against age-related macular degeneration (AMD). Lutein is a component of macular pigment. DHA is in the retina.

OBJECTIVE

The objective of this 4-mo study was to determine the effects of lutein (12 mg/d) and DHA (800 mg/d) on their serum concentrations and macular pigment optical density (MPOD).

DESIGN

Forty-nine women (60-80 y) were randomly assigned to placebo, DHA, lutein, or lutein + DHA supplement. Serum was analyzed for lutein and DHA (0, 2, and 4 mo). MPOD was determined (0 and 4 mo) at 0.4, 1.5, 3, and 5 degrees temporal retinal eccentricities. Serum was analyzed for lipoproteins (4 mo).

RESULTS

There was no interaction between lutein and DHA supplementations for serum lutein and MPOD. The lutein supplementation x DHA supplementation x month interaction was significant for serum DHA response (P < 0.05). In the lutein group, serum lutein increased from baseline at 2 and 4 mo (P < 0.001), and MPOD increased at 3.0 degrees (P < 0.01). In the DHA group, serum DHA increased at 2 and 4 mo (P < 0.0001), and MPOD increased at 0.4 degrees (P < 0.05). In the lutein + DHA group, serum lutein and DHA increased at 2 and 4 mo (P < 0.01), and MPOD increased at 0.4, 1.5, and 3 degrees (P = 0.06, 0.08, and 0.09, respectively). Differences from placebo in lipoprotein subfractions were greatest for the lutein + DHA group (4 mo).

CONCLUSIONS

Lutein supplementation increased MPOD eccentrically. DHA resulted in central increases. These results may be due to changes in lipoproteins. Lutein and DHA may aid in prevention of age-related macular degeneration.

Docosahexaenoic acid supplementation decreases remnant-like particle-cholesterol and increases the (n-3) index in hypertriglyceridemic men

Plasma remnant-like particle-cholesterol (RLP-C) and the RBC (n-3) index are novel risk factors for cardiovascular disease. Effects of docosahexaenoic acid (DHA) supplementation on these risk factors in hypertriglyceridemic men have not been studied. We determined effects of DHA supplementation on concentrations of plasma RLP-C, the RBC (n-3) index, and associations between concentrations of plasma RLP-C with those of plasma lipids and fatty acids. Hypertriglyceridemic men aged 39-66 y, participated in a randomized, placebo-controlled, parallel study. They received no supplements for 8 d and then received either 7.5 g/d DHA oil (3 g DHA/d) or olive oil (placebo) for the last 90 d. Fasting blood samples were collected on study d -7, 0 (baseline), 45 (mid-intervention), 84, and 91 (end-intervention). DHA supplementation for 45 d decreased (P < 0.05) fasting RLP-C (36%) and increased plasma eicosapentaenoic acid (EPA):arachidonic acid (AA) (100%) and the RBC (n-3) index (109%). Continued supplementation with DHA between d 45 and 91 further increased the RBC (n-3) index (162%) and plasma EPA:AA (137%) compared with baseline values. RLP-C concentration was positively associated (P < 0.01) with the plasma concentrations of triacylglycerols (Kendall's correlation coefficient or r = 0.46), triacylglycerol:HDL cholesterol (HDL-C) (r = 0.44), total cholesterol:HDL-C (r = 0.26), Apo B (r = 0.22), C III (r = 0.41), and E (r = 0.17), and 18:1(n-9) (r = 0.32); it was negatively associated (P < 0.05) with plasma concentrations of DHA (r = -0.32), EPA (r = -0.25), HDL-C (r = -0.21), LDL cholesterol:Apo B (r = -0.30), and HDL-C:Apo A (r = -0.25). Supplementation with placebo oil did not alter any of the response variables tested. Decreased atherogenic RLP-C and increased cardio-protective (n-3) index may improve cardio-vascular health.

Bioequivalence of Docosahexaenoic acid from different algal oils in capsules and in a DHA-fortified food

Docosahexaenoic acid (DHA), a long-chain omega-3 fatty acid, is important for eye and brain development and ongoing visual, cognitive, and cardiovascular health. Unlike fish-sourced oils, the bioavailability of DHA from vegetarian-sourced (algal) oils has not been formally assessed. We assessed bioequivalence of DHA oils in capsules from two different algal strains versus bioavailability from an algal-DHA-fortified food. Our 28-day randomized, placebo-controlled, parallel group study compared bioavailability of (a) two different algal DHA oils in capsules ("DHASCO-T" and "DHASCO-S") at doses of 200, 600, and 1,000 mg DHA per day (n = 12 per group) and of (b) an algal-DHA-fortified food (n = 12). Bioequivalence was based on changes in plasma phospholipid and erythrocyte DHA levels. Effects on arachidonic acid (ARA), docosapentaenoic acid-n-6 (DPAn-6), and eicosapentaenoic acid (EPA) were also determined. Both DHASCO-T and DHASCO-S capsules produced equivalent DHA levels in plasma phospholipids and erythrocytes. DHA response was dose-dependent and linear over the dose range, plasma phospholipid DHA increased by 1.17, 2.28 and 3.03 g per 100 g fatty acid at 200, 600, and 1,000 mg dose, respectively. Snack bars fortified with DHASCO-S oil also delivered equivalent amounts of DHA on a DHA dose basis. Adverse event monitoring revealed an excellent safety and tolerability profile. Two different algal oil capsule supplements and an algal oil-fortified food represent bioequivalent and safe sources of DHA.

Docosahexaenoic acid supplementation improves fasting and postprandial lipid profiles in hypertriglyceridemic men

BACKGROUND

The effects of docosahexaenoic acid (DHA) on the mean size and concentrations of VLDL, LDL, and HDL subclasses have not been previously studied.

OBJECTIVE

We determined the effects of DHA supplementation on the concentrations of apoproteins; large, medium, and small VLDL, LDL, and HDL particles; and the mean diameters of these particles in fasting and postprandial plasma.

DESIGN

Hypertriglyceridemic men aged 39-66 y (n = 34) participated in a double-blind, randomized, placebo-controlled parallel study. They received no supplements for the first 8 d and received either 7.5 g DHA oil/d (3 g DHA/d) or olive oil (placebo) for the last 90 d. Lipoprotein particle diameters and concentrations were measured by nuclear magnetic resonance spectroscopy.

RESULTS

DHA supplementation for 45 d significantly (P < 0.05) decreased concentrations of fasting triacylglycerol (24%), large VLDL (92%), and intermediate-density lipoproteins (53%) and the mean diameter of VLDL particles (11.1 nm). It elevated concentrations of LDL cholesterol (12.6%), small VLDL particles (133%), and large LDL particles (120%) and the mean diameter of LDL particles (0.6 nm) in fasting plasma. Similar changes were observed for area under the curve for postprandial samples (0-6 h); however, the number of small dense LDL particles decreased significantly (21%), and the change in LDL cholesterol was not significant. Continued supplementation with DHA beyond 45 d caused no further changes; placebo treatment altered none of the responses tested.

CONCLUSION

DHA supplementation may improve cardiovascular health by lowering concentrations of triacylglycerols and small, dense LDL particles.

Circulating triacylglycerol and apoE levels in response to EPA and docosahexaenoic acid supplementation in adult human subjects

High doses ofn–3 PUFA found in fish oils can reduce the circulating concentration of triacylglycerol (TG), which may contribute to the positive impact of these fatty acids on the risk of CVD. The present study aimed to establish the differential impact of EPA and docosahexaenoic (DHA) on plasma lipids and apo in adults. Forty-two normolipidaemic adult subjects completed a double-blind placebo controlled parallel study, receiving an EPA-rich oil (4·8 g EPA/d), DHA-rich oil (4·9 g DHA/d) or olive oil as control, for a period of 4 weeks. No effects of treatment on total cholesterol, LDL-cholesterol or HDL-cholesterol were evident. There was a significant 22 % reduction in TG level relative to the control value following the DHA treatment (P=0·032), with the 15 % decrease in the EPA group failing to reach significance (P=0·258). There were no significant inter-group differences in response to treatment for plasma apoA1, -C3 or -E levels, although a significant 15 % within-group increase in apoE was evident in the EPA (P=0·006) and DHA (P=0·003) groups. In addition, a within-group decrease in the apoA1:HDL-cholesterol ratio was observed in the DHA group, suggesting a positive impact of DHA on HDL particle size. The DHA intervention resulted in a significant increase in the proportion of EPAP=0·000 and DHAP=0·000 in plasma phospholipids, whilst significant increases in EPAP=0·000 and docosapentaenoic acidP=0·002, but not DHAP=0·193, were evident following EPA supplementation (P>0·05). Our present results indicate that DHA may be more efficacious than EPA in improving the plasma lipid profile.

Eicosapentaenoic acid and docosahexaenoic acid from fish oils: differential associations with lipid responses

Fish-oil supplementation can reduce circulating triacylglycerol (TG) levels and cardiovascular risk. This study aimed to assess independent associations between changes in platelet eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and fasting and postprandial (PP) lipoprotein concentrations and LDL oxidation status, following fish-oil intervention. Fifty-five mildly hypertriacylglycerolaemic (TG 1·5–4·0 mmol/l) men completed a double-blind placebo controlled cross over study, where individuals consumed 6 g fish oil (3 g EPA+DHA) or 6 g olive oil (placebo)/d for two 6-week intervention periods, with a 12-week wash-out period in between. Fish-oil intervention resulted in a significant increase in the platelet phospholipid EPA (+491 %,P<0·001) and DHA (+44 %,P<0·001) content and a significant decrease in the arachidonic acid (-10 %,P<0·001) and γ-linolenic acid (-24 %,P<0·001) levels. A 30 % increase inex vivoLDL oxidation (P<0·001) was observed. In addition, fish oil resulted in a significant decrease in fasting and PP TG levels (P<0·001), PP non-esterified fatty acid (NEFA) levels, and in the percentage LDL as LDL-3 (P=0·040), and an increase in LDL-cholesterol (P=0·027). In multivariate analysis, changes in platelet phospholipid DHA emerged as being independently associated with the rise in LDL-cholesterol, accounting for 16 % of the variability in this outcome measure (P=0·030). In contrast, increases in platelet EPA were independently associated with the reductions in fasting (P=0·046) and PP TG (P=0·023), and PP NEFA (P=0·015), explaining 15–20 % and 25 % of the variability in response respectively. Increases in platelet EPA+DHA were independently and positively associated with the increase in LDL oxidation (P=0·011). EPA and DHA may have differential effects on plasma lipids in mildly hypertriacylglycerolaemic men.

Microalgal docosahexaenoic acid decreases plasma triacylglycerol in normolipidaemic vegetarians: a randomised trial

Triacylglycerol (TG) lowering effects ofn−3 long-chain PUFA (n−3 LCPUFA) have been repeatedly demonstrated, but studies investigating the individual effects of EPA or DHA on plasma TG and lipoproteins in man are rare. The effects of a new DHA-rich, almost EPA-free microalgae oil (Ulkeniasp.) on plasma lipids and several safety parameters were investigated in a double-blind, placebo-controlled, parallel design intervention study. Normolipidaemic vegetarians (eighty-seven females, twenty-seven males) consumed daily microalgae oil (0·94g DHA/d) or olive oil (as placebo) for 8 weeks. DHA supplementation decreased plasma TG by 23% from 1·08 (sem 0·07) to 0·83 (sem 0·04) mmol/l (p<0·001). Absolute TG decreases after DHA supplementation were inversely correlated to baseline TG concentrations (r−0·627,p<0·001). Plasma total, LDL and HDL cholesterol increased significantly in the DHA group, resulting in lower TG:HDL cholesterol and unchanged LDL:HDL and total cholesterol:HDL cholesterol ratios. The intake of DHA-rich microalgae oil did not result in any physiologically relevant changes of safety and haemostatic factors. In conclusion, DHA-rich oil from microalgaeUlkeniasp. was well tolerated and can be considered a suitable vegetarian source ofn−3 LCPUFA. Although DHA supplementation improved some CHD risk factors (plasma TG, TG:HDL cholesterol ratio), LDL cholesterol increased. Therefore, the overall effects of this intervention on CHD risk deserve further investigation.

Changes in body fat distribution in relation to parity in American women: a covert form of maternal depletion

Using data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988-1994, we investigated the effect of reproduction on the distribution of body fat in well-nourished American women. While women tend to gain weight and fat with succeeding pregnancies, if age and body mass index are controlled, increasing parity is associated with a decrease in hip and thigh circumferences, suprailiac and thigh skinfolds, and body fat estimated from skinfolds, while waist circumference increases, resulting in a relative decrease in lower-body fat. The mobilization of fat stores in the lower body during late pregnancy and lactation may help to meet the special needs of the developing brain for essential fatty acids and energy during the time of peak growth. When fat is regained after the postpartum period, relatively more is stored in central vs. peripheral depots, resulting in a patterned change in body shape with parity.

Effects of docosahexaenoic acid supplementation on blood lipids, estrogen metabolism, and in vivo oxidative stress in postmenopausal vegetarian women

BACKGROUND

Vegetarians are generally deficient in long-chain n-3 fatty acids. Long-chain n-3 fatty acids have a beneficial effect on plasma lipid levels, and some studies showed that they had breast cancer suppression effect. One of the biomarkers of breast cancer risk is the ratio of urinary 2-hydroxyestrone (2-OHE(1)) to 16alpha-hydroxyestrone (16alpha-OHE(1)).

OBJECTIVE

To investigate the effect of docosahexaenoic acid (DHA, 22:6n-3) supplementation on blood lipids, estrogen metabolism and oxidative stress in vegetarians.

DESIGN

Single-blind, randomized, placebo-controlled trial.

INTERVENTIONS

Twenty-seven postmenopausal vegetarian women were recruited. After a 2-week run-in period with 6 g placebo corn oil, the subjects were subsequently randomized to receive either 6 g corn oil (n=13) or 6 g DHA-rich algae oil (2.14 g of DHA/day) (n=14) for 6 weeks. Two subjects in corn oil group withdrew before completion.

MAIN OUTCOME MEASURES

Plasma lipids, urinary 2-OHE(1) and 16alpha-OHE(1), urinary F(2)-isoprostanes and plasma alpha-tocopherol.

RESULTS

Plasma LDL-DHA and EPA level increased significantly by DHA supplementation. DHA decreased plasma cholesterol (C) levels (P=0.04), but did not influence the levels of plasma TG, LDL-C and HDL-C, alpha-tocopherol, urinary F(2)-isoprostanes, 2-OHE(1), 16alpha-OHE(1) and ratio of 2-OHE(1) to 16alpha-OHE(1) as compared to corn oil.

CONCLUSION

DHA supplementation at a dose of 2.14 g/day for 42 days decreases plasma cholesterol but neither does it show beneficial effects on estrogen metabolism, nor does it induce deleterious effects on the observed in vivo antioxidant or oxidative stress marker in postmenopausal vegetarian women.

SPONSORSHIP

A grant (# DOH89-TD-1062) from Department of Health, Executive Yuan, Taiwan.

Distribution, interconversion, and dose response of n-3 fatty acids in humans

n-3 Fatty acids have important visual, mental, and cardiovascular health benefits throughout the life cycle. Biodistribution, interconversion, and dose response data are reviewed herein to provide a basis for more rational n-3 dose selections. Docosahexaenoic acid (DHA) is the principal n-3 fatty acid in tissues and is particularly abundant in neural and retinal tissue. Limited storage of the n-3 fatty acids in adipose tissue suggests that a continued dietary supply is needed. A large proportion of dietary alpha-linolenic acid (ALA) is oxidized, and because of limited interconversion of n-3 fatty acids in humans, ALA supplementation does not result in appreciable accumulation of long-chain n-3 fatty acids in plasma. Eicosapentaenoic acid (EPA) but not DHA concentrations in plasma increase in response to dietary EPA. Dietary DHA results in a dose-dependent, saturable increase in plasma DHA concentrations and modest increases in EPA concentrations. Plasma DHA concentrations equilibrate in approximately 1 mo and then remain at steady state throughout supplementation. DHA doses of approximately 2 g/d result in a near maximal plasma response. Both dietary DHA and EPA reduce plasma arachidonic acid concentrations. Tissue contents of DHA and EPA also increase in response to supplementation with these fatty acids. Human milk contents of DHA are dependent on diet, and infant DHA concentrations are determined by their dietary intake of this fatty acid. We conclude that the most predictable way to increase a specific long-chain n-3 fatty acid in plasma, tissues, or human milk is to supplement with the fatty acid of interest.

The independent effects of eicosapentaenoic acid and docosahexaenoic acid on cardiovascular risk factors in humans

PURPOSE OF REVIEW

This review details the independent effects of purified eicosapentaenoic acid and docosahexaenoic acid on cardiovascular risk factors in humans. We report data from the recent literature and our own controlled clinical trials which compared the independent effects of these fatty acids in individuals at increased risk of cardiovascular disease, namely overweight hyperlipidaemic men and treated-hypertensive, type 2 diabetic men and women. We discuss the biological effects of these fatty acids and the potential mechanisms through which they may affect cardiovascular disease risk factors.

RECENT FINDINGS

A cardioprotective effect for omega3 fatty acids is supported by prospective studies demonstrating an inverse association between fish intake and coronary heart disease mortality. Data from secondary prevention trials support a reduction in ventricular fibrillation as a primary mechanism for the decreased incidence of myocardial infarction. Clinical trials and experimental studies have shown that omega3 fatty acids have many other potentially important antiatherogenic and antithrombotic effects. Omega-3 fatty acids lower blood pressure and heart rate, improve dyslipidaemia, reduce inflammation, and improve vascular and platelet function. These favourable effects have until recently been primarily attributed to the omega3 fatty acid eicosapentaenoic acid, which is present in large amounts in fish oil. Controlled studies in humans now demonstrate that docosahexaenoic acid, although often present in lower quantities, has equally important anti-arrhythmic, anti-thrombotic and anti-atherogenic effects.

SUMMARY

Available evidence strongly suggests that eicosapentaenoic acid and docosahexaenoic acid have differing haemodynamic and anti-atherogenic properties. The effects of the two fatty acids may also differ depending on the target population.

Phytosterol and phytostanol esters are effectively hydrolysed in the gut and do not affect fat digestion in ileostomy subjects

BACKGROUND

Hydrolysis of phytosterol ester (PSTE) and phytostanol ester (PSTA) during fat digestion is not well characterised under controlled dietary conditions.

AIMS

The main aims of this study were therefore to quantify the PSTE and PSTA hydrolysis after gut passage and to assess whether or not PSTE and PSTA induce fat malabsorption by measuring the fatty acid excretion following PSTE/PSTA consumption.

METHODS

Ileostomy subjects (n = 7) were investigated in a randomised crossover study with one control and two intervention periods, when either 2.5 g of PSTE or PSTA corresponding to 1.5 g free sterol or stanol equivalents were added to a controlled diet. Ileostomy bags were collected and immediately frozen for analysis of nutrients, fatty acids and sterols.

RESULTS

The study showed that 88.4 +/- 5.9% PSTE and 85.7 +/- 6.5% PSTA were hydrolysed following small bowel passage in the ileostomy subjects. The total excretion of fatty acids was similar in all three periods.

CONCLUSIONS

A majority of the 2.5 g PSTE and PSTA was hydrolysed during small bowel passage,which did not affect fat absorption as indicated by similar excretions of fatty acids in all periods. Consumption of increasing amounts of esterified phytosterols and phytostanols from enriched food formats should thereby have no adverse effects in this regard.

Bioavailability and safety of a high dose of docosahexaenoic acid triacylglycerol of algal origin in cystic fibrosis patients: a randomized, controlled study

OBJECTIVE

Several studies have reported omega-3 and omega-6 fatty acid imbalances in patients with cystic fibrosis (CF). Whether these imbalances contribute to or are manifestations of the pathophysiology of CF is unknown. The study objective was to determine bioavailability, tissue accretion, and safety of a large dose of an algal source of docosahexaenoic acid (DHA) triacylglycerol and to observe effects on lung function in patients with CF.

METHODS

Twenty subjects with CF (8 to 20 y of age) were randomly assigned to receive algal oil providing 50 mg of DHA per kilogram per day (1 to 4.2 g of DHA per subject per day) or placebo for 6 mo. Fatty acids, liver enzymes, and lipid soluble antioxidants were measured in blood at baseline and at 1, 3, and 6 mo. Rectal biopsy specimens were collected at baseline and at 3 mo for fatty acid analysis. Lung function, anthropometrics, and adverse experiences were monitored throughout the study.

RESULTS

Compared with placebo, DHA supplementation increased plasma, erythrocyte, and rectal DHA levels four- to five-fold (P < 0.001) with concomitant decreases in blood arachidonic acid levels and the ratio of arachidonic acid to DHA. Supplementation was well tolerated, with no treatment-related changes in liver enzymes, growth, or antioxidant status. DHA supplementation had no detectable effect on lung function during the course of this study.

CONCLUSIONS

Algal DHA triacylglycerol oil is readily absorbed, well tolerated, and increases blood and tissue DHA levels in patients with CF. No adverse developments were associated with this large dose of DHA oil. Larger studies of longer duration are needed to determine whether DHA supplementation results in any clinically significant benefits in patients with CF.

Docosahexaenoic acid reduces in vitro invasion of renal cell carcinoma by elevated levels of tissue inhibitor of metalloproteinase-1

We demonstrate in this study that the n-3 polyunsaturated fatty acids derived from fish oil, namely, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA), can increase levels of tissue inhibitors of metalloproteinase-1 (TIMP-1) in the renal cell carcinoma cell line caki-1 by 26% and 17.42% respectively. The result of this elevation in TIMP-1 levels is a reduction of 48.48% in caki-1 invasion through the basement membrane component matrigel when cells are treated with DHA. By inhibition of 2-series prostaglandin production, a similar increase in TIMP-1 was observed in caki-1 cells. We conclude that the polyunstaurated fatty acid DHA, a component of fish oil, is capable of significantly reducing the invasive profile of renal cell carcinoma, and that this reduction is regulated by levels of 2-series prostaglandin production.

Docosahexaenoic acid-enriched egg consumption induces accretion of arachidonic acid in erythrocytes of elderly patients

Many studies in humans volunteers have shown that dietary docosahexaenoic acid (DHA) supplied as triacylglycerol can increase DHA levels in blood lipids but often strongly decreases those of arachidonic acid (AA). The aim of the present study was to determine the effect of dietary supplementation with egg-yolk powder enriched in DHA, corresponding to the French recommended dietary allowance for DHA, on the blood lipid status of an elderly population. Institutionalised elderly individuals aged between 63 and 93 years consumed an egg product enriched in DHA (150 mg/d) once daily for 9 months. Plasma lipids and the fatty acid composition of erythrocyte membranes were determined every 3 months. The supplementation induced an increase in the PUFA content of plasma and erythrocyte membranes which was +14.5 and +25.3 %, respectively, at 9 months. This effect was mainly due to the level of DHA and, unexpectedly, to that of AA which continuously increased. This increase in AA was the result of an increased dietary intake (+50 mg/d) and very probably of an increased biosynthesis as demonstrated by the behaviour of di-homo-gamma-linolenic acid. The supplementation resulted in a blood PUFA status comparable with that of young healthy controls. The data are consistent with a strong regulatory action of the dietary treatment on the subjects' lipid metabolism.

LDL cholesterol-raising effect of low-dose docosahexaenoic acid in middle-aged men and women

BACKGROUND

Long-chain n-3 polyunsaturated fatty acids have variable effects on LDL cholesterol, and the effects of docosahexaenoic acid (DHA) are uncertain.

OBJECTIVE

The objective of the study was to determine the effect on blood lipids of a daily intake of 0.7 g DHA as triacylglycerol in middle-aged men and women.

DESIGN

Men and women aged 40-65 y (n = 38) underwent a double-blind, randomized, placebo-controlled, crossover trial of treatment with 0.7 g DHA/d for 3 mo.

RESULTS

DHA supplementation increased the DHA concentration in plasma by 76% (P < 0.0001) and the proportion in erythrocyte lipids by 58% (P < 0.0001). Values for serum total cholesterol, LDL cholesterol, and plasma apolipoprotein B concentrations were 4.2% (0.22 mmol/L; P = 0.04), 7.1% (0.23 mmol/L; P = 0.004), and 3.4% (P = 0.03) higher, respectively, with DHA treatment than with placebo. In addition, the LDL cholesterol:apolipoprotein B ratio was 3.1% higher with DHA treatment than with placebo (P = 0.04), which suggested an increase in LDL size. Plasma lathosterol and plant sterol concentrations were unaffected by treatment.

CONCLUSION

A daily intake of approximately 0.7 g DHA increases LDL cholesterol by 7% in middle-aged men and women. It is suggested that DHA down-regulates the expression of the LDL receptor.

Alpha-linolenic acid metabolism in men and women: nutritional and biological implications

PURPOSE OF REVIEW

This review critically evaluates current knowledge of alpha-linolenic acid metabolism in adult humans based on the findings of studies using stable isotope tracers and on increased dietary alpha-linolenic acid intake. The relative roles of alpha-linolenic acid and of longer-chain polyunsaturated fatty acids in cell structure and function are discussed together with an overview of the major metabolic fates of alpha-linolenic acid. The extent of partitioning towards beta-oxidation and carbon recycling in humans is described. The use and limitations of stable isotope tracers to estimate alpha-linolenic acid desaturation and elongation are discussed. A consensus view of the extent of alpha-linolenic acid conversion to longer-chain fatty acids in humans is presented. The extent to which increasing dietary alpha-linolenic acid intake alters the concentrations of longer-chain n-3 fatty acids is described. The biological and nutritional implications of these findings are discussed.

RECENT FINDINGS

Conversion of alpha-linolenic acid to eicosapentaenoic acid is limited in men and further transformation to docosahexaenoic acid is very low. A lower proportion of alpha-linolenic acid is used as a substrate for beta-oxidation in women compared with men, while the fractional conversion to longer-chain fatty acids is greater, possibly due to the regulatory effects of oestrogen.

SUMMARY

Overall, alpha-linolenic acid appears to be a limited source of longer-chain n-3 fatty acids in man and so adequate intakes of preformed n-3 polyunsaturated fatty acids, in particular docosahexaenoic acid, may be important for maintaining optimal tissue function. Capacity to upregulate alpha-linolenic acid transformation in women may be important for meeting the demands of the fetus and neonate for docosahexaenoic acid.

A review of the safety of DHA45-oil

Polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA), are natural constituents of the human diet; however, dietary intakes of these fatty acids are below recommended values. The main dietary source of DHA is fatty fish, with lesser amounts provided by shellfish, marine mammals, and organ meats. The addition to traditional food products of refined oils produced by marine microalgae represents potential sources of supplemental dietary DHA. DHA45-oil is manufactured through a multi-step fermentation and refining process using a non-toxigenic and non-pathogenic marine protist. Comprising approximately 45% DHA, and lesser concentrations of palmitic acid and docosapentaenoic acid, DHA45-oil is intended for use in foods as a dietary source of DHA. The safety of DHA45-oil was evaluated in various genotoxicity and acute, subchronic, and reproductive toxicity studies. DHA45-oil produced negative results in genotoxicity assays and demonstrated a low acute oral toxicity in mice and rats. Dietary administration of DHA45-oil to rats in subchronic and one-generation reproductive studies produced results consistent with those observed in oral studies using high concentrations of omega-3 PUFAs from fish or other microalgal-derived oils. The results of these studies, as well as those of various published metabolic, toxicological, and clinical studies with DHA-containing oils, support the safety of DHA45-oil as a potential dietary source of DHA.

Bread enriched with microencapsulated tuna oil increases plasma docosahexaenoic acid and total omega-3 fatty acids in humans

The aim of this study was to determine the acute and chronic effects of low doses of long chain (LC) n-3 polyunsaturated fatty acids (PUFA) (<100 mg per day) on plasma LC n-3 PUFA levels using a novel delivery form; bread containing microencapsulated tuna oil (MTO). Six omnivores (three men and three women) participated in the acute study, which involved ingesting a prototype MTO bread containing approximately 80 mg of LC n-3 PUFA/four slices. Plasma triacylglycerol fatty acid compositions were measured after an overnight fast and postprandially at 2 and 4 h. In the chronic study, 10 vegetarian subjects (nine men and one woman) consumed MTO bread at six to eight slices/day (comprising 60 mg of LC n-3 PUFA) as the only dietary source of these PUFA for three weeks. Fasting plasma total and phospholipid fatty acid compositions were measured at baseline and endpoint. In the acute study, the proportions of 22:6 n-3 and total n-3 PUFA in plasma triacylglycerol were significantly increased (P < 0.05). In the chronic study, the proportions of 20:5 n-3, 22:5 n-3, 22:6 n-3, total n-3 PUFA in plasma, and 22:6 n-3 and total n-3 PUFA in plasma phospholipid fractions were significantly increased (P < 0.05) at the endpoint compared with the baseline. This study showed that a low dose of LC n-3 PUFA, consumed as MTO-enriched bread, was bioavailable, as measured by an increase in LC n-3 PUFA levels in the plasma of human subjects.

Omega-3 fatty acid supplementation accelerates chylomicron triglyceride clearance

Omega-3 fatty acids (FAs) reduce postprandial triacylglycerol (TG) concentrations. This study was undertaken to determine whether this effect was due to reduced production or increased clearance of chylomicrons. Healthy subjects (n = 33) began with a 4-week, olive oil placebo (4 g/d) run-in period. After a 4-week wash-out period, subjects were randomized to supplementation with 4 g/d of ethyl esters of either safflower oil (SAF), eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA) for 4 weeks. Results for EPA and DHA were similar, and therefore the data were combined into one omega-3 FA group. Omega-3 FA supplementation reduced the postprandial TG and apolipoprotein B (apo B)-48 and apoB-100 concentrations by 16% (P = 0.08), 28% (P < 0.001), and 24% (P < 0.01), respectively. Chylomicron TG half-lives in the fed state were reduced after omega-3 FA treatment (6.0 +/- 0.5 vs. 5.1 +/- 0.4 min; P < 0.05), but not after SAF (6.9 +/- 0.7 vs. 7.1 +/- 0.7 min). Omega-3 FA supplementation decreased chylomicron particle sizes (mean diameter; 293 +/- 44 vs. 175 +/- 25 nm; P < 0.01) and increased preheparin lipoprotein lipase (LPL; 0.6 +/- 0.1 vs. 0.9 +/- 0.1 micromol/h/ml; P < 0.05) activity during the fed state, but had no effect on postheparin LPL or hepatic lipase activities. The results suggest that omega-3 FA supplementation accelerates chylomicron TG clearance by increasing LPL activity, and that EPA and DHA are equally effective.

Dietary effects of arachidonate-rich fungal oil and fish oil on murine hepatic and hippocampal gene expression

BACKGROUND

The functions, actions, and regulation of tissue metabolism affected by the consumption of long chain polyunsaturated fatty acids (LC-PUFA) from fish oil and other sources remain poorly understood; particularly how LC-PUFAs affect transcription of genes involved in regulating metabolism. In the present work, mice were fed diets containing fish oil rich in eicosapentaenoic acid and docosahexaenoic acid, fungal oil rich in arachidonic acid, or the combination of both. Liver and hippocampus tissue were then analyzed through a combined gene expression- and lipid- profiling strategy in order to annotate the molecular functions and targets of dietary LC-PUFA.

RESULTS

Using microarray technology, 329 and 356 dietary regulated transcripts were identified in the liver and hippocampus, respectively. All genes selected as differentially expressed were grouped by expression patterns through a combined k-means/hierarchical clustering approach, and annotated using gene ontology classifications. In the liver, groups of genes were linked to the transcription factors PPARalpha, HNFalpha, and SREBP-1; transcription factors known to control lipid metabolism. The pattern of differentially regulated genes, further supported with quantitative lipid profiling, suggested that the experimental diets increased hepatic beta-oxidation and gluconeogenesis while decreasing fatty acid synthesis. Lastly, novel hippocampal gene changes were identified.

CONCLUSIONS

Examining the broad transcriptional effects of LC-PUFAs confirmed previously identified PUFA-mediated gene expression changes and identified novel gene targets. Gene expression profiling displayed a complex and diverse gene pattern underlying the biological response to dietary LC-PUFAs. The results of the studied dietary changes highlighted broad-spectrum effects on the major eukaryotic lipid metabolism transcription factors. Further focused studies, stemming from such transcriptomic data, will need to dissect the transcription factor signaling pathways to fully explain how fish oils and arachidonic acid achieve their specific effects on health.