Scholarly article on topic 'Membrane fatty acid composition of different target populations: Importance of baseline on supplementation'

Membrane fatty acid composition of different target populations: Importance of baseline on supplementation Academic research paper on "Clinical medicine"

CC BY-NC-ND
0
0
Share paper
Academic journal
Clinical Nutrition Experimental
OECD Field of science
Keywords
{"Fatty acid membrane composition" / "Omega 3 index" / EPA / DHA / Cancer / Trauma}

Abstract of research paper on Clinical medicine, author of scientific article — Veronica Silva, Pierre Singer

Summary Omega-3 fatty acids (n-3 FA) supplementation has been widely used regardless the initial FA composition of the studied population. In this work we compared the red blood cell FA (RBC-FA) composition in healthy and different diseased populations at baseline and show how this affects the incorporation of n-3 FA supplementation in ICU-trauma patients. Blood was drawn from Healthy (H, n = 22), Psoriasis (P, n = 13), Cancer(C, n = 81), Geriatric (G, n = 49), Social-phobia (SP, n = 27) and ICU-trauma (T, n = 40) patients before n-3 FA supplementation. For the T group blood was also drawn 8 days after receiving a formula with 4.1 g/L EPA and 5.5 g/L GLA (Oxepa, Abbott). RBC-FA was assessed by gas chromatography and the percentage of each FA was calculated in relation to the total identified FAs. Baseline RBC-FA profile was significantly different between groups (p < 0.0001) with subjects in the healthy group having higher n-3 FA status. H and SP showed the highest content in total n-3 FA (11.89 ± 0.22% H vs 7.45 ± 0.26% T) and EPA (1.61 ± 0.03% H vs 0.41 ± 0.13% P). DHA was higher in C and H than in the other groups (6.15 ± 0.15% C vs 4.32 ± 0.11% T). ARA was highest in C (16.04 ± 0.20% C vs 14.85 ± 0.22% H) and comparable in the rest of the groups. The n-6/n-3 ratio was lowest for H and highest for T (2.75 ± 0.07 vs 4.96 ± 0.13). Moreover, we showed that for the T group, the treatment-associated changes in the n-3 content are dependent on the initial n-3 FA status, since a negative correlation between the baseline omega 3 index (EPA + DHA) and its change after supplementation was found (p = 0.002, r2 = 0.219). We conclude that RBC-FA profile should be evaluated and considered individually for each patient or groups before generalized supplementation schemes, strengthening the concept of personalized medicine.

Academic research paper on topic "Membrane fatty acid composition of different target populations: Importance of baseline on supplementation"

ELSEVIER

Contents lists available at ScienceDirect

Clinical Nutrition Experimental

journal homepage: http:// www.clinicalnutritionexperimental.com

Membrane fatty acid composition of different target populations: Importance of baseline on supplementation

Veronica Silva a' *, Pierre Singer a'b

a Laboratory of Metabolic Research, Felsenstein Medical Research Center, The Sackler School of Medicine, Tel Aviv University, Jabotinsky 39, Petah Tikva 4941492, Israel

b General Intensive Care Department and Institute for Nutrition Research, Rabin Medical Center, Beilinson Hospital, Jabotinsky 39, Petah Tikva 4941492, Israel

ARTICLE INFO

Article history: Received 25 March 2015 Accepted 16 July 2015 Available online 4 August 2015

Keywords:

Fatty acid membrane composition

Omega 3 index

Cancer

Trauma

SUMMARY

Omega-3 fatty acids (n-3 FA) supplementation has been widely used regardless the initial FA composition of the studied population. In this work we compared the red blood cell FA (RBC-FA) composition in healthy and different diseased populations at baseline and show how this affects the incorporation of n-3 FA supplementation in ICU-trauma patients. Blood was drawn from Healthy (H, n = 22), Psoriasis (P, n = 13), Cancer(C, n = 81), Geriatric (G, n = 49), Social-phobia (SP, n = 27) and ICU-trauma (T, n = 40) patients before n-3 FA supplementation. For the T group blood was also drawn 8 days after receiving a formula with 4.1 g/L EPA and 5.5 g/L GLA (Oxepa, Abbott). RBC-FA was assessed by gas chromatography and the percentage of each FA was calculated in relation to the total identified FAs. Baseline RBC-FA profile was significantly different between groups (p < 0.0001) with subjects in the healthy group having higher n-3 FA status. H and SP showed the highest content in total n-3 FA (11.89 ± 0.22% H vs 7.45 ± 0.26% T) and EPA (1.61 ± 0.03% H vs 0.41 ± 0.13% P). DHA was higher in C and H than in the other groups (6.15 ± 0.15% C vs 4.32 ± 0.11% T). ARA was highest in C (16.04 ± 0.20% C vs 14.85 ± 0.22% H) and comparable in the rest of the groups. The n-6/n-3 ratio was lowest for H and highest for T (2.75 ± 0.07 vs 4.96 ± 0.13). Moreover, we showed that for the T group, the treatment-associated changes in the n-3 content are dependent on the initial n-3 FA status, since a negative correlation between the baseline omega 3 index (EPA + DHA) and its change after supplementation was found

* Corresponding author. Laboratory of Metabolic Research, Felsenstein Medical Research Center, Room 106, Beilinson Hospital, Rabin Medical Center, Jabotinsky 39, Petah Tikva 4941492, Israel. Tel.: +972 3 9377292; fax: +972 3 9376181. E-mail addresses: veroasilva@gmail.com (V. Silva), psinger@clalit.org.il (P. Singer).

http://dx.doi.org/10.1016/j.yclnex.2015.07.001

2352-9393/© 2015 The Authors. Published by Elsevier Ltd on behalf of European Society for Clinical Nutrition and Metabolism. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

(p = 0.002, r2 = 0.219). We conclude that RBC-FA profile should be evaluated and considered individually for each patient or groups before generalized supplementation schemes, strengthening the concept of personalized medicine.

© 2015 The Authors. Published by Elsevier Ltd on behalf of European Society for Clinical Nutrition and Metabolism. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

Omega-3 fatty acids (n-3 FAs) are considered essential dietary components with proven beneficial effects on several pathologies [1,2]. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are precursors of numerous bioactive mediators important in anti-inflammatory processes [3], signal transduction [4] and gene expression [5]. These bioactive molecules are consumed in the human diet mainly through fatty fish, but their popularity rose mainly due to their use as a supplement in both health and pathology. The WHO recommends an intake of 0.2—0.5 g/d of EPA and DHA for the prevention of some chronic diseases, however natural intake of this compounds vary among populations and cultures. Research on the effects of n-3 FAs consumption has increased significantly in the past years where the dietary or supplementary intake of n-3 FAs is assessed by following their content in a variety of biological compartments directly reflecting n-3 FA intake [6]. The most common cell population used for this purpose is red blood cells (RBC), which can be easily accessed and respond directly to the dose of n-3 intake [2]. RBC also allow the calculation of the omega 3 index (O31, %EPA + %DHA of total identified FA), which has been used as a biomarker of n-3 intake [7] and as a risk marker for several diseases, mainly cardiovascular [8]. Moreover, it constitutes a useful tool as a first approach when comparing results among publications. 1t was shown that O31 response to n-3 FAs was influenced by initial values and dose of supplementation, and appears to be an important predictor of therapeutic efficacy of n-3 supplementation [9,10]. The basal level, rate and extent of incorporation of n-3 FAs can be influenced by factors such as, concurrent intake of vitamin/minerals and gender [11], age and smoking [12], physical activity and body weight [13], genetics [14] and even the existence of a certain pathology [15—18]. All of which can have an effect on either the normal metabolic functioning or dietary habits, directly influencing the availability of n-3 FAs. The initial status of the membrane's FA composition is not usually taken into consideration when planning supplementation doses and duration, nor is the nature of the target population. Furthermore, it was shown that high doses of dietary n-3 FAs, as well as long-time treatments could be detrimental [1,19]. 1n this sense it is important to characterize the basal FA composition of a certain population before any supplementation plan is applied, in order to understand better the possible outcomes of the study. 1n this work we compared the RBC-FA composition in healthy and different diseased populations at baseline and show how this affects the incorporation of n-3 FA into RBC after supplementation in ICVU-trauma patients.

2. Materials and methods

2.1. Patient groups and blood samples

Blood was drawn from Healthy (group H, n = 22), Psoriasis (group P, n = 13), Cancer (group C, n = 81), Geriatric (group G, n = 49), Social-phobia (group SP, n = 27) and ICU-trauma (group T, n = 40) patients before any n-3 FA supplementation. Group G consisted of patients admitted electively from home to the hospital for hip or knee replacement surgery as part of a different study. Group T further received a formula supplemented with 4.1 g/L EPA and 5.5 g/L GLA (Oxepa, Abbott) upon admission in the 1CU as part of a different study [20]. An extra sample of blood was drawn 8 days after supplementation started, that was used to study the rate of FA incorporation into RBC membranes. Study

protocols were approved by the local institutional review board, and informed consent was obtained for each participant prior to intervention.

2.2. Fatty acid analysis

Whole blood was drawn into EDTA-containing vacutainer tubes. After centrifugation, the plasma and buffy coat were removed. RBC were washed 3 times with 0.9% NaCl and kept under N2 at -70 °C until analysis. Lipid extraction was performed by homogenization of the cells in hexane/isopropanol (3:2 vol/vol) containing 5 mg/dl butylated hydroxytoluene (BHT) as an antioxidant. FAs were converted to methyl esters (FAMEs) by heating with BF3 in methanol, and FAMEs were separated on a HP 5890 Series II Gas Chromatograph containing a flame ionization detector. Helium was used as the carrier gas at 1 mL/min, and nitrogen as the make-up gas at 30 mL/min. A split of 1:30 was used with the following running conditions: initial temperature: 150 °C for 2 min, increasing at a rate of 3 °C/min to 240 °C and kept for 10 min until the end of the run (40 min). Peak areas were integrated and plotted with the aid of the Varian Star Integrator computer package (Varian Star Workstation, 1990, Varian Associates, Inc.). Individual FAMEs were identified by comparing retention times with authentic standards. Values were expressed as percentage of a given FA in respect to total identified fatty acids. The omega 3 index (O31) was calculated by adding together the EPA and DHA percentages for each sample.

The data regarding the RBC-FA composition of groups H, P, C and SP were obtained in previous studies involving these populations and were kindly provided by Dr. Pnina Green for comparison with the other populations studied here. The SP study has been previously published [21].

Statistical analysis was performed by either One Way-ANOVA (OW-ANOVA) + Post-Hoc Tukey's Multiple Comparison Test (MCT) or Pearson's test with the assistance of GraphPad Prism 5.00 software. Results are expressed as Mean ± SEM and significance level was set to p < 0.05.

3. Results

3.1. The RBC-FA composition depends on the nature of the population

The characteristics of the different populations studied regarding sex, age and body mass index (BM1) are presented in Table 1.

Significant differences (p < 0.0001) in the RBC-FA profile between populations were found, the amount of the main n-3 and n-6 FAs and related parameters are summarized in Table 2. Groups H and SP showed the highest content in both EPA alone (Fig. 1; 1.61 ± 0.03% H vs 0.41 ± 0.13% P) and total n-3 FAs (Fig. 2; 11.89 ± 0.23% H vs 7.45 ± 0.16% T). DHA was higher in groups C and H than in the rest of the groups (Fig. 1; 6.15 ± 0.15% C vs 4.32 ± 0.11% T). n-6 arachidonic acid (ARA) was highest in group C (Fig. 1; 16.04 ± 0.20% C vs 14.85 ± 0.22% H) and comparable in the rest of the groups. The n-6/n-3 ratio was lowest for group H and highest for group T (Fig. 2; 2.75 ± 0.07 vs 4.96 ± 0.13).

Table 1

Population characteristics.

Group n Age (years) Sex BMI

Psoriasis 13 NA NA NA

Cancer 81 62.4 - 1.3 36 (F) 44 (M) NA

Trauma 40 46.3 - 2.8 9(F) 31 (M) 25.9 0.6

Geriatric 49 68.9 1.3 37 (F) 12 (M) 30.5 0.8

Social phobia 27 31.7 1.5 14(F) 13 (M) 22.9 0.6

Healthy 22 35.2 - 2.0 14(F) 13 (M) 23.3 0.8

Results are shown as mean ± SEM.

NA: information not available; (F): Females; (M): Males.

Table 2

RBC-FA composition of the different studied populations. Only main FAs and total parameters are presented. Significant differences between groups are identified by superscripts. Percentage (%) of each FA in relation to the total FAs identified is expressed as mean ± SEM.

Parameter Psoriasis (P) Cancer(C) Trauma (T) Geriatric (G) Social phobia (SP) Healthy (H)

16:0 20.86 ± 0.48a'h'1'* 18.87 ± 0.11b'g'h'* 22.33 ± 0.19a'b'c'd 22.18 ± 0.17'e'f'g'1 19.67 ± 0.09c'e'j 19.51 ± 0.16d'f'1

18:0 18.04 ± 0.40adg 16.22 ± 0.12g h i 17.40 ± 0.11b'e'h 17.78 ± 0.20c'f'¡ 15.93 ± 0.10a'b'c 15.79 ± 0.13d'e'f

LA 18:2 n-6 10.07 ± 0.25* 9.57 ± 0.17a'd 10.02 ± 0.20b'1'2 9.07 ± 0.16c'e'1 11.43 ± 0.23a'b'c'z 11.25 ± 0.18d'e'2

ALA 18:3 n-3 0.11 ± 0.011 0.05 ± 0.01a'b'c'# 0.21 ± 0.04a'*'1 0.16 ± 0.01b 0.13 ± 0.01 *'# 0.19 ± 0.01c

ARA 20:4 n-6 13.57 ± 0.65a-1-* 16.04 ± 0.20a'# 14.94 ± 0.22 15.43 ± 0.201 15.41 ± 0.18* 14.85 ± 0.25#

EPA 20:5 n-3 0.38 ± 0.13ae 0.62 ± 0.08b'f 0.81 ± 0.13c'g 0.61 ± 0.04d'h 1.62 ± 0.06a'b'c d 1.61 ± 0.04e'f'g'h

DPA 22:5 n-3 2.29 ± 0.10aei 3.02 ± 0.07b'f'IJ'k 2.42 ± 0.09cgJ 2.48 ± 0.04d'h'k 4.59 ± 0.14a'b'c'd 4.29 ± 0.07e'f'g'h

DPA n-6 22:5 n-6 1.17 ± 0.471'2'*'* 0.65 ± 0.021 0.78 ± 0.10 0.60 ± 0.022 0.67 ± 0.03* 0.58 ± 0.03#

DHA 22:6 n-3 4.66 ± 0.41a'# 6.15 ± 0.15a'b'c'd 4.67 ± 0.18b'* 4.86 ± 0.15c 4.60 ± 0.19d 5.62 ± 0.24*'#

Total n-3 7.56 ± 0.54d-e 9.91 ± 0.22a'b'c'd'z 8.14 ± 0.27a'g 8.19 ± 0.20b'f 11.06 ± 0.22e'f'g'* 11.89 ± 0.25c

Total n-6 29.42 ± 1.08a-b'c'1'* 32.18 ± 0.33'1'2'# 34.02 ± 0.38a'2 33.52 ± 0.26b 33.40 ± 0.32c 32.34 ± 0.35*'#

Total SFA 45.72 ± 1.10a'd'g 40.92 ± 0.22a'b'c 44.31 ± 0.30b'e'h 44.83 ± 0.30c'fi 39.92 ± 0.14d'e'f 39.85 ± 0.11g h l

Total MUFA 17.24 ± 0.32a'1 13.52 ± 0.20a'b'c'd'e 16.30 ± 0.17b 16.67 ± 0.18c'2 15.62 ± 0.21d'1'2 15.93 ± 0.20e

n-6/n-3 4.14 ± 0.33g1 3.40 ± 0.10a'd'* 4.41 ± 0.19a'b'c 4.23 ± 0.12d'e'f 3.06 ± 0.09b'e 2.75 ± 0.08c'f'g'1'*

O3I (EPA + DHA) 5.04 ± 0.52a'1 6.77 ± 0.18d'e'1 5.09 ± 0.25b'd'* 5.48 ± 0.18c e 6.22 ± 0.18* 7.23 ± 0.24a'b'c

LA, linoleic acid; ALA, a-linolenic acid; DPA, docosahexaenoic acid; DPA n-6, docosapentaenoic acid; SFA, saturated FAs; MUFA, medium chain unsaturated FAs. Results are shown as mean ± SEM.

OW-ANOVA + Tukey's MCT,aek: significance level p < 0.001 (***);1_2: significance level p < 0.01 (**); z # significance level p < 0.05 (*).

20- a,1,t

ith ds ^

P C T G SP H

d,h „ ' *» afio

d! £ ih m

• ■ * ru_l-r1 ¿U IX)

8B f* T

15 10 5

^ : ^ <

«•. hi t'lt a; "S if» f« ^

. T ♦

P C T G SP H

0—i-1-1-1-1-1—

P C T G SP H

Fig. 1. Main n-6 and n-3 FAs content in the different populations. The amount (%) of ARA, EPA and DHA was calculated for each population in respect to the total amount of FAs identified. OW-ANOVA + Tukey's MCT. Significant differences among groups were found and are represented in the figures according to significance level: a—h; p < 0.001 (***); 1; p < 0.01 (**); $, #; p < 0.05 (*). The average and SEM for each population are shown in grey lines.

a,b,c,d

a,b,c,d

15- d,e

Total Omega 3

a,g e.f.g* a

X ; bf * b

Total Omega 6

P C T G SP H

45 40 35 30 25 20

a,b,c. tt

: ■ ® ^ ^

P C T G SP H

n-6/n-3 ratio

Omega 3 index

fc o 6

S 4 •= 2

d,e,f T

liLÎÎiß, b-e

c,f,g,

—i-1-1-1-1-1—

P C T G SP H

8 H----1

■A..1..VI..1. S A^ vv Ut

Aa. Tt

3* «§«

P C T G SP H

Fig. 2. Main global parameters of n-6 and n-3 FAs content in the different populations. The total amount of n-3 and n-6

identified FAs was calculated and used to determine the n-6/n-3 ratio. O31 was calculated as %EPA + %DHA for each group. OW-ANOVA + Tukey's MCT. Significant differences among groups were found and are represented in the figures according to significance level: a—g; p < 0.001 (***); 1—2; p < 0.01 (**); #, #; p < 0.05 (*). The average and SEM for each population are shown in grey lines.

a,b,c,d,*

b,d,î

a,d,* A

3.2. The baseline content of n-3 FA determines the extent of incorporation after supplementation

We showed that after group T received a formula supplemented with n-3 FAs for a period of 8 days, the content of EPA increased significantly but no change was observed in DHA levels (Table 3).

The calculated O31 significantly increased from 5.09 ± 0.26% to 6.56 ± 0.24% (p < 0.0001) after 8 days of supplementation (Fig. 3A). Furthermore, a significant negative correlation (p = 0.002) between the baseline O31 and its change after supplementation was found (Fig. 3B).

4. Discussion

1n this comparative study we evaluated the RBC-FA composition of six populations that differed in their nature. Populations analysed included groups of patients with various pathological conditions such as cancer, psoriasis, social phobia, ICU-trauma as well as a group of geriatric patients and healthy volunteers. Omega 3 supplementation has been used in this type of populations for the prevention and/or treatment of their diseases [1,2] with contradictory results for some of them [22]. The source of such contradictions in the literature may be due to the lack of standardized supplementation plans, mainly in terms of dose and duration, but also because of the disregard of the pre-existing amount of n-3 FAs in their cell membranes. Here we showed that the baseline FA composition of RBC varies according to the nature of the population under study. It was already shown how different factors, such as gender, age or lifestyle affect the rate of incorporation of FAs but comparisons between different diseased populations that comprise a valid and already studied target of n-3 supplementation was never performed. In our study the healthy subjects group had the highest omega 3 status, with a total

Table 3

Effect of n-3 supplementation on EPA and DHA levels (% total FAs) in group T.

Fatty acid Baseline Day 8 p value

EPA 0.81 ± 0.13% 2.23 ± 0.16% <0.0001

DHA 4.67 ± 0.18% 4.58 ± 0.12% 0.5483

Results are shown as mean Paired t test.

8------

. > » . . IMS®«:

Baseline

aaä^EAA aaaaaaa aa

ro c ra .c

•« i ••• •

Vft-*—'

— 10

O3I baseline

Fig. 3. O3I response to supplementation. A. Calculated O3I for group T before (baseline) and after an 8-days n-3 supplementation plan. Paired t test, p < 0.0001. The average and SEM are shown in grey lines. Dotted line represents an O3I equivalent to 8%. B. Correlation between baseline and change of O3I (O3IDay8 — O3Ibaseiine) after supplementation. Pearson's test, p = 0.002, r = -0.4677., r2 = 0.2187.

amount of 11.89 ± 0.23% of total identified FAs, almost double of that found for example in ICU-trauma patients, but comparable to that found in social phobia patients. The amount of the main n-3 FAs, EPA and DHA was also variable among the populations. EPA is more than double in the healthy and social phobia groups in comparison to the rest of the groups. In contrast, DHA is highest in the cancer group, followed by the healthy and geriatric groups, all the rest have comparable values. Regarding the n-6 status of the different populations, the psoriasis group is the one with the lowest amount of total n-6 FAs and specifically ARA, all the rest of the groups had comparable amounts. We can infer that the source of such variations among our populations is due to the presence/absence of their specific diseases, more likely than any other factor, but other modifiers weren't evaluated and are not in the scope of this work. It is already known that the dysregulation of FA metabolism is connected to the development and maintenance not only of diseases such as cardiovascular diseases, metabolic and nutritional disease, but also to cancer [23,24] and psoriasis [25] for example. The change in lifestyle and dietary habits associated to age, disease, hospitalization, etc., might also alter the lipid metabolism of a given individual and therefore alter the availability of the different FA in their cell membranes.

In this study we also showed that when one of the populations was supplemented with n-3 FA, the extent of incorporation of the FAs was dependent on the baseline status of each individual. Those with lower baseline O31 values incorporated the n-3 FAs more efficiently than those with higher O31, suggesting that those patients with a worst n-3 status may benefit the most from the supplementation plan. Similar results were obtained by Keenan et al. where they implied the existence of response thresholds in an n-3 supplemented healthy population. They found that the O31 response to n-3 FAs was influenced by initial values and dose, and appears to be an important predictor of therapeutic efficacy of n-3 supplementation. They also found that to maintain levels of O31 in the range for car-dioprotective effects (>8%) a dose of 7 mg/kg/day of n-3 FAs is needed, which is double the amount suggested by different health institutions [9]. If we consider the 8% O31 as a relative threshold in our supplemented population, we can see that only 15% (6/40) of the patients reached such O31 level after supplementation, suggesting that probably our dose or time of supplementation wasn't enough to accomplish such beneficial effects. This was discussed in a recent article describing the clinical results of preemptive administration of EPA and GLA in severe multiple trauma patients. No significant clinical effect was observed [20]. Serini et al. stated the necessity to further study the exact relationships

Fig. 4. Interplay between deficient, normal, supplemented and toxic levels of n-3. Insufficient intakes of n-3 FA or the presence of a pathological condition can cause the loss of these FA and therefore a deficit from the normal levels. Omega 3 intake in this case will replace firstly the lack of FAs and restore its level to normal, further intake will increase n-3 levels above the normal where it will act as a real supplement until the toxicity threshold is reached.

between the actual dosages of FAs ingested, the portion of them that is adsorbed, and the beneficial effects observed, as a strategy to help to definitely establish the levels of intake sufficient to induce a beneficial effect without producing secondary oxidative effects, which are more likely to be observed with high doses and long periods of supplementation (>6 months) [1]. In these sense, when designing a supplementation plan the beneficial effects should be balanced against the potential detrimental effects of n-3 intake. Negative observations associated with very low and high dietary intake of the n-3 FA, EPA and DHA were reported [19].

Considering the contradictory data among publications and the widespread use/prescription of n-3 supplements for health improvement in normal and pathological conditions, it is necessary to validate the biomarkers of n-3 intake among these individuals and associate them with disease risk, prevalence and outcome [1,19]. Whether the amount of n-3 intake is deficient, adequate or excessive should be addressed in particular, and for that it is necessary to know and understand the initial or baseline status of the object in study, either as a whole study population, or ideally, individually for each subject. In a patient that has deficient levels of n-3 FAs, either due to insufficient intake or to the presence of a disease that may induce its decrease; any n-3 intake will be used first to replace this decrease in FAs until "normal" cellular levels are reached. Only after this compensation is accomplished, the supplementation may achieve pharmacological effects. If the subject continues to be supplemented, then the risk threshold of toxicity will be reached and negative effects are more likely to be observed (Fig. 4). The interplay between all these thresholds and their association with health and disease should be further investigated to better design supplementation plans.

5. Conclusion

Baseline RBC-FA profile proved to be different and dependent on the nature of the study population, being the healthy group the one with better n-3 status. Moreover, we showed that for an ICU-trauma patients group, the n-3 supplementation-associated changes are dependent on the initial n-3 FA status. Thus, RBC-FA profile should be evaluated and considered individually for each patient or groups before generalized supplementation schemes, strengthening the concept of personalized medicine.

Conflict of interest

None declared.

Acknowledgements

We would like to thank Dr. Pnina Green for providing valuable data and proofreading assistance. References

[1] Serini S, Fasano E, Piccioni E, Cittadini AR, Calviello G. Dietary n-3 polyunsaturated fatty acids and the paradox of their health benefits and potential harmful effects. Chem Res Toxicol Dec 19 2011;24(12):2093—105.

[2] Silva V, Barazzoni R, Singer P. Biomarkers of fish oil omega-3 polyunsaturated fatty acids intake in humans. Nutr Clin Pract Off Publ Am Soc Parenter Enter Nutr Feb 2014;29(1):63—72.

[3] Calder PC. Omega-3 polyunsaturated fatty acids and inflammatory processes: nutrition or pharmacology? Br J Clin Pharmacol Mar 2013;75(3):645—62.

[4] O'Donnell VB, Murphy RC. New families of bioactive oxidized phospholipids generated by immune cells: identification and signaling actions. Blood Sep 6 2012;120(10):1985—92.

[5] Schroeder F, Petrescu AD, Huang H, Atshaves BP, Mcintosh AL, Martin GG, et al. Role of fatty acid binding proteins and long chain fatty acids in modulating nuclear receptors and gene transcription. Lipids Jan 2008;43(1):1—17.

[6] Browning LM, Walker CG, Mander AP, West AL, Madden J, Gambell JM, et al. Incorporation of eicosapentaenoic and do-cosahexaenoic acids into lipid pools when given as supplements providing doses equivalent to typical intakes of oily fish. Am J Clin Nutr Oct 2012;96(4):748—58.

[7] Freije A. Fatty acid profile of the erythrocyte membranes of healthy Bahraini citizens in comparison with coronary heart disease patients. J Oleo Sci 2009;58(7):379—88.

[8] Harris Ws. The omega-3 index: clinical utility for therapeutic intervention. Curr Cardiol Rep Nov 2010;12(6):503—8.

[9] Keenan AH, Pedersen TL, Fillaus K, Larson MK, Shearer GC, Newman JW. Basal omega-3 fatty acid status affects fatty acid and oxylipin responses to high-dose n3-HUFA in healthy volunteers. J Lipid Res Aug 2012;53(8):1662—9.

[10] Yee LD, Lester JL, Cole RM, Richardson JR, HsuJC, Li Y, et al. Omega-3 fatty acid supplements in women at high risk of breast cancer have dose-dependent effects on breast adipose tissue fatty acid composition. Am J Clin Nutr May 2010;91(5): 1185—94.

[11] Pipingas A, Cockerell R, Grima N, Sinclair A, Stough C, Scholey A, et al. Randomized controlled trial examining the effects of fish oil and multivitamin supplementation on the incorporation of n-3 and n-6 fatty acids into red blood cells. Nutrients May 2014;6(5):1956—70.

[12] Wagner A, Simon C, Morio B, Dallongeville J, Ruidavets JB, Haas B, et al. Omega-3 index levels and associated factors in a middle-aged French population: the MONA LISA-NUT Study. Eur J Clin Nutr 2015;69(4):436—41.

[13] Flock MR, Skulas-Ray AC, Harris WS, Etherton TD, Fleming JA, Kris-Etherton PM. Determinants of erythrocyte omega-3 fatty acid content in response to fish oil supplementation: a dose—response randomized controlled trial. J Am Heart Assoc 2013;2(6):e000513.

[14] Harris WS, Pottala JV, Lacey SM, Vasan RS, Larson MG, Robins SJ. Clinical correlates and heritability of erythrocyte eicosapentaenoic and docosahexaenoic acid content in the Framingham Heart Study. Atherosclerosis Dec 2012;225(2): 425—31.

[15] Elkan AC, Anania C, Gustafsson T, Jogestrand T, Hafstrom 1, Frostegard J. Diet and fatty acid pattern among patients with SLE: associations with disease activity, blood lipids and atherosclerosis. Lupus Nov 2012;21(13):1405—11.

[16] Sertoglu E, Kurt 1, Tapan S, Uyanik M, Serdar MA, Kayadibi H, et al. Comparison of plasma and erythrocyte membrane fatty acid compositions in patients with end-stage renal disease and type 2 diabetes mellitus. Chem Phys Lipids Feb 2014;178: 11 —7.

[17] Astarita G, Jung KM, Berchtold NC, Nguyen VQ, Gillen DL, Head E, et al. Deficient liver biosynthesis of docosahexaenoic acid correlates with cognitive impairment in Alzheimer's disease. PloS One 2010;5(9):e12538.

[18] Petit JM, Guiu B, Duvillard L, Jooste V, Brindisi MC, Athias A, et al. Increased erythrocytes n-3 and n-6 polyunsaturated fatty acids is significantly associated with a lower prevalence of steatosis in patients with type 2 diabetes. Clin Nutr Aug 2012; 31(4):520—5.

[19] Fenton J1, Hord NG, Ghosh S, Gurzell EA. immunomodulation by dietary long chain omega-3 fatty acids and the potential for adverse health outcomes. Prostagl Leukot Essent Fat Acids Nov—Dec 2013;89(6):379—90.

[20] Kagan 1, Cohen J, Stein M, Bendavid 1, Pinsker D, Silva V, et al. Preemptive enteral nutrition enriched with eicosapentaenoic acid, gamma-linolenic acid and antioxidants in severe multiple trauma: a prospective, randomized, double-blind study. 1ntensive Care Med Mar 2015;41(3):460—9.

[21] Green P, Hermesh H, Monselise A, Marom S, Presburger G, Weizman A. Red cell membrane omega-3 fatty acids are decreased in nondepressed patients with social anxiety disorder. Eur Neuropsychopharmacol J Eur Coll Neuro-psychopharmacol Feb 2006;16(2):107—13.

[22] Sanders TA. Protective effects of dietary PUFA against chronic disease: evidence from epidemiological studies and intervention trials. Proc Nutr Soc Feb 2014;73(1):73—9.

[23] Macasek J, Vecka M, Zak A, Urbanek M, Krechler T, Petruzelka L, et al. Plasma fatty acid composition in patients with pancreatic cancer: correlations to clinical parameters. Nutr Cancer 2012;64(7):946—55.

[24] Hashmi S, Wang Y, Suman DS, Parhar RS, Collison K, Conca W, et al. Human cancer: is it linked to dysfunctional lipid metabolism? Biochim Biophys Acta Feb 2015;1850(2):352—64.

[25] Pietrzak A, Michalak-Stoma A, Chodorowska G, Szepietowski JC. Lipid disturbances in psoriasis: an update. Mediat 1nflamm 2010:2010.