Conversion ratios of n-3 fatty acids between plasma and erythrocytes: a systematic review and meta-regression

Changes in the Fatty Acid Profile in Erythrocytes in High-Level Endurance Runners during a Sports Season

Fatty acids (FAs) are an essential component of the erythrocyte membrane, and nutrition and physical exercise are two variables that affect their structure and function. The aim of this study was to evaluate the erythrocyte profile in a group of high-level endurance runners, as well as the changes in different FAs, throughout a sports season in relation to the training performed. A total of 21 high-level male endurance runners (23 ± 4 years; height: 1.76 ± 0.05) were evaluated at four different times throughout a sports season. The athletes had at least 5 years of previous experience and participated in national and international competitions. The determination of the different FAs was carried out by gas chromatography. The runners exhibited low concentrations of docosahexaenoic acid (DHA) and omega-3 index (IND ω-3), as well as high values of stearic acid (SA), palmitic acid (PA), and arachidonic acid (AA), compared to the values of reference throughout the study. In conclusion, training modifies the erythrocyte FA profile in high-level endurance runners, reducing the concentrations of polyunsaturated fatty acids (PUFAs) such as DHA and AA and increasing the concentrations of saturated fatty acids (SFAs) such as SA and the PA. High-level endurance runners should pay special attention to the intake of PUFAs ω-3 in their diet or consider supplementation during training periods to avoid deficiency.

ω-3 Polyunsaturated Fatty Acid Status Testing in Humans: A Narrative Review of Commercially Available Options

There is an increasing body of evidence supporting a link between low intakes of ω-3 long-chain polyunsaturated fatty acids (LCPUFA) and numerous diseases and health conditions. However, few people are achieving the levels of fish/seafood or eicosapentaenoic acid and docosahexaenoic acid intake recommended in national and international guidelines. Knowledge of a person's ω-3 LCPUFA status will benefit the interpretation of research results and could be expected to lead to an increased effort to increase intake. Dietary intake survey methods are often used as a surrogate for measuring ω-3 PUFA tissue status and its impact on health and functional outcomes. However, because individuals vary widely in their ability to digest and absorb ω-3 PUFA, analytical testing of biological samples is desirable to accurately evaluate ω-3 PUFA status. Adipose tissue is the reference biospecimen for measuring tissue fatty acids, but less-invasive methods, such as measurements in whole blood or its components (e.g., plasma, serum, red blood cell membranes) or breast milk are often used. Numerous commercial laboratories provide fatty acid testing of blood and breast milk samples by different methods and present their results in a variety of reports such as a full fatty acid profile, ω-3 and ω-6 fatty acid profiles, fatty acid ratios, as well as the Omega-3 Index, the Holman Omega-3 Test, OmegaScore, and OmegaCheck, among others. This narrative review provides information about the different ways to measure ω-3 LCPUFA status (including both dietary assessments and selected commercially available analytical tests of blood and breast milk samples) and discusses evidence linking increased ω-3 LCPUFA intake or status to improved health, focusing on cardiovascular, neurological, pregnancy, and eye health, in support of recommendations to increase ω-3 LCPUFA intake and testing.

Omega-3 Blood Levels and Stroke Risk: A Pooled and Harmonized Analysis of 183 291 Participants From 29 Prospective Studies

BACKGROUND

The effect of marine omega-3 PUFAs on risk of stroke remains unclear.

METHODS

We investigated the associations between circulating and tissue omega-3 PUFA levels and incident stroke (total, ischemic, and hemorrhagic) in 29 international prospective cohorts. Each site conducted a de novo individual-level analysis using a prespecified analytical protocol with defined exposures, covariates, analytical methods, and outcomes; the harmonized data from the studies were then centrally pooled. Multivariable-adjusted HRs and 95% CIs across omega-3 PUFA quintiles were computed for each stroke outcome.

RESULTS

Among 183 291 study participants, there were 10 561 total strokes, 8220 ischemic strokes, and 1142 hemorrhagic strokes recorded over a median of 14.3 years follow-up. For eicosapentaenoic acid, comparing quintile 5 (Q5, highest) with quintile 1 (Q1, lowest), total stroke incidence was 17% lower (HR, 0.83 [CI, 0.76-0.91]; P<0.0001), and ischemic stroke was 18% lower (HR, 0.82 [CI, 0.74-0.91]; P<0.0001). For docosahexaenoic acid, comparing Q5 with Q1, there was a 12% lower incidence of total stroke (HR, 0.88 [CI, 0.81-0.96]; P=0.0001) and a 14% lower incidence of ischemic stroke (HR, 0.86 [CI, 0.78-0.95]; P=0.0001). Neither eicosapentaenoic acid nor docosahexaenoic acid was associated with a risk for hemorrhagic stroke. These associations were not modified by either baseline history of AF or prevalent CVD.

CONCLUSIONS

Higher omega-3 PUFA levels are associated with lower risks of total and ischemic stroke but have no association with hemorrhagic stroke.

Differential effects of high dose omega-3 fatty acids on metabolism and inflammation in patients with obesity: eicosapentaenoic and docosahexaenoic acid supplementation

Background

Obesity is complicated by low-grade chronic inflammation characterised by increases in inflammatory proteins and cells in peripheral blood. It has been known that omega-3 fatty acids (FA) like eicosapentaenoic (EPA) and docosahexaenoic (DHA) could modulate the inflammatory process and improve metabolic markers.

Objective

This study aimed to determine the effect of high-dose omega-3 FA on metabolic and inflammatory markers among patients with obesity and healthy volunteers.

Methods

This prospective study included 12 women with obesity (body mass index [BMI] ≥ 35.0 kg/m²) and 12 healthy women (BMI < 24.0 kg/m²) who were supplemented with a dose of 4.8 g/day (3.2 g EPA plus 1.6 g DHA) for 3 months followed by no treatment for 1 month. Plasma metabolic and inflammatory markers and levels of mRNA transcripts of CD4⁺ T lymphocyte subsets were determined monthly.

Results

None of the participants exhibited changes in weight or body composition after study completion. EPA and DHA supplementation improved metabolic (insulin, Homeostatic Model Assessment of Insulin Resistance [HOMA-IR], triglyceride [TG]/ high-density lipoprotein [HDL] ratio, TG, and arachidonic acid [AA]/EPA ratio) and tumor necrosis factor-alpha (TNF-α). Moreover, the levels of mRNA transcripts of T CD4⁺ lymphocyte subsets (TBX21, IFNG, GATA-3, interleukin [IL]-4, FOXP3, IL-10 IL-6, and TNF-α), were down-regulated during the intervention phase. After 1 month without supplementation, only insulin, HOMA-IR and the mRNA transcripts remained low, whereas all other markers returned to their levels before supplementation.

Conclusion

Supplementation with high-dose omega-3 FAs could modulate metabolism and inflammation in patients with obesity without weight loss or changes in body composition. However, these modulatory effects were ephemeral and with clear differential effects: short-duration on metabolism and long-lasting on inflammation.

Derivation of the Omega-3 Index from EPA and DHA Analysis of Dried Blood Spots from Dogs and Cats

The Omega-3 Index (O3I) is the red blood cell (RBC) eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) content expressed as a percentage of total RBC fatty acids. Although a validated biomarker of omega-3 status in humans, little is known about the O3I status of dogs and cats; species in which omega-3 fatty acids have known health benefits. The purpose of this study was to develop equations to predict the O3I in these species from a dried blood spot (DBS) analysis. Random blood samples from 33 dogs and 10 cats were obtained from a community veterinary clinic. DBS and RBC samples were analyzed for fatty acid composition. For both species, the R2 between the DBS EPA + DHA value and the O3I was >0.96 (p < 0.001). The O3I was roughly 75% lower in dogs and cats than in humans. We conclude that the O3I can be estimated from a DBS sample, and the convenience of DBS collection should facilitate omega-3 research in these companion animals.

Eicosapentaenoic Acid Ameliorates Cardiac Fibrosis and Tissue Inflammation in Spontaneously Hypertensive Rats

Hypertension affects 1 in 3 adults in the United States and leads to left ventricular (LV) concentric hypertrophy, interstitial fibrosis, and increased stiffness. The treatment of cardiac fibrosis remains challenging and empiric. Eicosapentaenoic acid (EPA) is an omega-3 polyunsaturated fatty acid that is highly effective in reducing cardiovascular events in patients and cardiac fibrosis and hypertrophy in animals when administered before pressure overload by promoting the increase of anti-inflammatory M1 macrophages. In this study, we investigated whether EPA mitigates the exacerbation of cardiac remodeling and fibrosis induced by established hypertension, a situation that closely recapitulates a clinical scenario. Twelve-week-old spontaneously hypertensive rats were randomized to eat an EPA-enriched or control diet for 20 weeks. We report that rats eating the EPA-enriched diet exhibited a reduction of interstitial cardiac fibrosis and ameliorated LV diastolic dysfunction despite the continuous increase in blood pressure. However, we found that EPA did not have an impact on cardiac hypertrophy. Interestingly, the EPA diet increased mRNA expression of M2 macrophage marker Mrc1 and interleukin-10 in cardiac tissue. These findings indicated that the antifibrotic effects of EPA are mediated in part by phenotypic polarization of macrophages toward anti-inflammatory M2 macrophages and increases of the anti-inflammatory cytokine, interleukin-10. In summary, EPA prevents the exacerbation of cardiac fibrosis and LV diastolic dysfunction during sustained pressure overload. EPA could represent a novel treatment strategy for hypertensive cardiomyopathy.

Serum Fatty Acid Profiles Are Associated with Disease Activity in Early Rheumatoid Arthritis: Results from the ESPOIR Cohort

Background: Long-chain omega-3 and omega-6 fatty acids (n-3, n-6 FAs) may modulate inflammation and affect the risk of developing rheumatoid arthritis (RA). However, whether n-3/n-6 FA status affects RA after disease onset is unknown. This study aimed to assess whether FA profiles are independently associated with disease activity in a large prospective cohort of patients with early RA. Methods: Baseline serum FAs were quantified in 669 patients in the ESPOIR cohort. Principal component analysis identified three serum FA patterns that were rich in n-7–9, n-3 and n-6 FAs (patterns ω7–9, ω3 and ω6), respectively. The association of pattern tertiles with baseline variables and 6-month disease activity was tested using multivariable logistic regression. Results: Pattern ω3 was associated with low baseline and pattern ω6 with high baseline C-reactive protein level and disease activity. Both patterns ω3 and ω6 were associated with reduced odds of active disease after 6 months of follow-up (pattern ω3: odds ratio, tertile three vs. one, 0.49 [95% CI 0.25 to 0.97] and pattern ω6: 0.51 [0.28 to 0.95]; p = 0.04 and 0.03, respectively). Conclusions: In a cohort of early RA patients, a serum lipid profile rich in n-3 FAs was independently associated with persistently reduced disease activity between baseline and 6-month follow-up. An n-6 FA profile was also associated with lower 6-month disease activity.

Effects of marine-derived and plant-derived omega-3 polyunsaturated fatty acids on erythrocyte fatty acid composition in type 2 diabetic patients

Background

Dietary fatty acids intake affects the composition of erythrocyte fatty acids, which is strongly correlated with glycolipid metabolism disorders. This study aimed at investigating the different effects of marine-derived and plant-derived omega-3 polyunsaturated fatty acid (n-3 PUFA) on the fatty acids of erythrocytes and glycolipid metabolism in patients with type 2 diabetes mellitus (T2DM).

Methods

The randomized double-blinded trial that was performed on 180 T2DM patients. The participants were randomly assigned to three groups for the six-month intervention. The participants were randomly assigned to three groups for the six-month intervention. The fish oil (FO) group was administered with FO at a dose of 3 g/day containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the perilla oil (PO) group was administered with PO at a dose of 3 g/day containing α-linolenic (ALA), the linseed and fish oil (LFO) group was administered with mixed linseed and fish oil at a dose of 3 g/day containing EPA, DHA and ALA. Demographic information were collected and anthropometric indices, glucose and lipid metabolism indexes, erythrocyte fatty acid composition were measured. Statistical analyses were performed using two-way ANOVA.

Results

A total of 150 patients finished the trial, with 52 of them in the FO group, 50 in the PO group and 48 in the LFO group. There were significant effects of time × treatment interaction on fast blood glucose (FBG), insulin, HOMA-IR and C-peptide, TC and triglyceride (TG) levels (P < 0.001). Glucose and C-peptide in PO and LFO groups decreased significantly and serum TG in FO group significantly decreased (P < 0.001) after the intervention. Erythrocyte C22: 5 n-6, ALA, DPA, n-6/n-3 PUFA, AA/EPA levels in the PO group were significantly higher than FO and LFO groups, while EPA, total n-3 PUFA and Omega-3 index were significantly higher in the FO and LFO groups compared to PO group.

Conclusion

Supplementation with perilla oil decreased FBG while fish oil supplementation decreased the TG level. Marine-based and plant-based n-3 PUFAs exhibit different effects on fatty acid compositions of erythrocytes and regulated glycolipid metabolism.

Trial registration

This trial was recorded under Chinese Clinical Trial Registry Center (NO: ChiCTR-IOR-16008435) on May 28 2016.

Beyond Nutrient Deficiency-Opportunities to Improve Nutritional Status and Promote Health Modernizing DRIs and Supplementation Recommendations

The US Dietary Guidelines for Americans (DGA) provide dietary recommendations to meet nutrient needs, promote health, and prevent disease. Despite 40 years of DGA, the prevalence of under-consumed nutrients continues in the US and globally, although dietary supplement use can help to fill shortfalls. Nutrient recommendations are based on Dietary Reference Intakes (DRIs) to meet the nutrient requirements for nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group and many need to be updated using current evidence. There is an opportunity to modernize vitamin and mineral intake recommendations based on biomarker or surrogate endpoint levels needed to 'prevent deficiency' with DRIs based on ranges of biomarker or surrogate endpoints levels that support normal cell/organ/tissue function in healthy individuals, and to establish DRIs for bioactive compounds. We recommend vitamin K and Mg DRIs be updated and DRIs be established for lutein and eicosapentaenoic and docosahexaenoic acid (EPA + DHA). With increasing interest in personalized (or precision) nutrition, we propose greater research investment in validating biomarkers and metabolic health measures and the development and use of inexpensive diagnostic devices. Data generated from such approaches will help elucidate optimal nutrient status, provide objective evaluations of an individual's nutritional status, and serve to provide personalized nutrition guidance.

Polyunsaturated fatty acids as predictors of future suicide attempt

Polyunsaturated fatty acids (PUFAs) and cholesterol are lipids implicated in suicide risk. We prospectively studied plasma glycerophospholipid PUFAs and cholesterol as putative predictors of suicide attempts. In a multicenter cohort study, we enrolled 123 patients admitted to the emergency department (ED) for suicidal ideation or suicide attempt. Clinical assessments were performed, with follow-up telephone evaluations 6, 12, 18, and 24 months later. Blood samples were obtained in the ED and assayed for PUFAs. Using survival analysis, suicide events were not predicted by eicosapentaenoic acid (EPA, HR: -0.83, 95%CI: 0.39-1.76, p = 0.621) or docosahexaenoic acid (DHA, HR: -0.60, 95%CI: 0.19-1.86, p = 0.371). However, higher arachidonic acid (AA) was a trend for a protective factor (HR=0.30, 95%CI: 0.08-1.08, p = 0.065) in the entire trans-diagnostic sample. This protective effect was significant in all participants with a prior suicide attempt history (n = 85; HR=0.16, 95%CI: 0.04-0.67, p = 0.012), and in the subgroup of attempters with major depressive disorder (MDD; n = 55, HR=0.15, 95%CI:0.03-0.76, p = 0.002). Total LDL- and HDL-cholesterol did not predict subsequent suicide events. AA, but not DHA or EPA, positively correlated with baseline depression severity in MDD patients (r = 0.3, p = 0.006). Contrary to our hypothesis that low n-3 PUFA levels would create risk, we found that while higher AA was associated with greater depression severity at baseline, low AA unexpectedly predicted subsequent suicide attempts, the more so in higher-risk patients. Although surprising, this result agrees with a minority of reports concerning n-6 PUFAs and may represent complex interactions with sample characteristics.

Survey of the erythrocyte EPA+DHA levels in the heart attack/stroke belt

BACKGROUND

The Omega-3 Index (O3I; erythrocyte EPA+DHA as a percent of total fatty acids) is inversely related to risk for cardiovascular disease (CVD). The cardioprotective target O3I is 8%-12%. O3I levels in American regions with high CVD risk are poorly characterized.

PURPOSE

To determine the O3I in individuals participating in a Seafood Nutrition Partnership (SNP) survey in seven US cities in the CVD "belt."

METHODS

Fingerstick blood samples were analyzed for the O3I.

RESULTS

The SNP cohort (n = 2177) had a mean (SD) O3I of 4.42% (1.12%). Only 1.2% were in the desirable range, whereas 42% had an undesirable (<4%) O3I. The mean (SD) O3I in a subset of 772 SNP subjects who were matched for age and sex with the Framingham study was 4.6% (1.2%) compared 5.3% (1.6%) in the Framingham cohort (p < 0.0001).

CONCLUSIONS

Individuals in the CVD "belt" had relatively low O3I levels. Since in other settings, a low O3I is associated with increased risk for CVD, this may be one factor contributing to the higher risk for CVD in this region of the US.

Erythrocyte long-chain omega-3 fatty acid levels are inversely associated with mortality and with incident cardiovascular disease: The Framingham Heart Study

BACKGROUND

The extent to which omega-3 fatty acid status is related to risk for death from any cause and for incident cardiovascular disease (CVD) remains controversial.

OBJECTIVE

To examine these associations in the Framingham Heart Study.

DESIGN

Prospective and observational.

SETTING

Framingham Heart Study Offspring cohort.

MEASUREMENTS

The exposure marker was red blood cell levels of eicosapentaenoic and docosahexaenoic acids (the Omega-3 Index) measured at baseline. Outcomes included mortality (total, CVD, cancer, and other) and total CVD events in participants free of CVD at baseline. Follow-up was for a median of 7.3 years. Cox proportional hazards models were adjusted for 18 variables (demographic, clinical status, therapeutic, and CVD risk factors).

RESULTS

Among the 2500 participants (mean age 66 years, 54% women), there were 350 deaths (58 from CVD, 146 from cancer, 128 from other known causes, and 18 from unknown causes). There were 245 CVD events. In multivariable-adjusted analyses, a higher Omega-3 Index was associated with significantly lower risks (P-values for trends across quintiles) for total mortality (P = .02), for non-CVD and non-cancer mortality (P = .009), and for total CVD events (P = .008). Those in the highest (>6.8%) compared to those in the lowest Omega-3 Index quintiles (<4.2%) had a 34% lower risk for death from any cause and 39% lower risk for incident CVD. These associations were generally stronger for docosahexaenoic acid than for eicosapentaenoic acid. When total cholesterol was compared with the Omega-3 Index in the same models, the latter was significantly related with these outcomes, but the former was not.

LIMITATIONS

Relatively short follow-up time and one-time exposure assessment.

CONCLUSIONS

A higher Omega-3 Index was associated with reduced risk of both CVD and all-cause mortality.

Blood Fatty Acid Profiles: New Biomarkers for Cardiometabolic Disease Risk

PURPOSE OF REVIEW

Fatty acid (FA) profiles in different blood compartments are reflections of both diet and metabolism, and some FA levels are related to disease risk.

RECENT FINDINGS

Perhaps the most studied FA-disease relationship is between long-chain omega-3 polyunsaturated fatty acids [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] and cardiovascular disease (CVD). Despite null results from recent large omega-3 FA supplementation trials, new research continues to support past studies showing that blood levels of EPA + DHA are inversely related to risk for total mortality and fatal CVD events. But blood levels of other FAs may also be useful markers of risk for a variety of diseases. The essential omega-6 FA linoleic acid is inversely associated with risk for developing type 2 diabetes (T2D), whereas risk for T2D is directly related to biomarkers of de novo lipogenesis (palmitic and palmitoleic acids). Levels of industrially produced trans FAs have been linked to higher risk for CVD. Thus, blood levels of several individual FAs are emerging as modifiable biomarkers for risk of major chronic diseases.