Effects of Stearidonic Acid on Serum Triacylglycerol Concentrations in Overweight and Obese Subjects: a Randomized Controlled Trial

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ORIGINAL ARTICLE Effects of stearidonic acid on serum triacylglycerol concentrations in overweight and obese subjects: a randomized controlled trial

DJM Pieters and RP Mensink

BACKGROUND/OBJECTIVES: Eicosapentaenoic acid (EPA), which may reduce the risk for coronary heart disease (CHD), can be synthesized at low rates from α-linolenic acid (ALA). The rate-limiting step for this conversion is the Δ6-desaturation of ALA into stearidonic acid (SDA). Thus providing oils rich in SDA may increase endogenous synthesis of EPA, which may subsequently lower serum triacylglycerol concentrations, an effect frequently observed after EPA supplementation. We therefore studied the effects of Echium oil on serum triacylglycerol concentrations and the omega-3 index, which correlate negatively with the risk for CHD. SUBJECTS/METHODS: A randomized, double-blind, placebo-controlled crossover trial was conducted, in which 36 healthy overweight and slightly obese subjects daily received 10 g of Echium oil (providing 1.2 g of SDA) or a high oleic acid sunflower oil (HOSO) as control for 6 weeks, with a washout period of at least 14 days. Four subjects dropped out. Differences between periods were tested for statistical significance (Po0.05) using a paired t-test. RESULTS: Serum triacylglycerol and other lipid concentrations were not significantly affected by consumption of Echium oil compared with HOSO. Echium oil significantly increased percentage of EPA in red blood cell (RBC) membranes with 0.14 ± 0.25% (mean ± s.d.) compared with HOSO (P = 0.02). No significant effects on docosahexaenoic acid in RBC membranes or on the omega-3 index were found. CONCLUSIONS: In healthy overweight and slightly obese subjects, an increased intake of SDA from Echium oil does not lower serum triacylglycerol concentrations. Despite an increase in the percentage of EPA in RBC membranes, the omega-3 index was not changed. European Journal of Clinical Nutrition (2015) 69, 121–126; doi:10.1038/ejcn.2014.193; published online 17 September 2014

INTRODUCTION hypothesized, as fish-oil fatty acids have frequently been shown to Many lines of evidence suggest that the intake of n-3 long-chain lower serum triacylglycerol concentrations. In a noncontrolled polyunsaturated fatty acids from fish such as eicosapentaenoic study with slightly hypertriglyceridemic subjects, a daily intake of 6 acid (EPA or C20:5n-3) and docosahexaenoic acid (DHA or C22:6n- 15 g of Echium oil also increased plasma EPA concentrations. 3) are cardioprotective.1 Therefore, specific recommendations for Although the amount of SDA in Echium oil is lower than in adequate intakes of these fatty acids have been formulated. In SDA-enriched soybean oil (12% vs 28%), serum triacylglycerol these guidelines, no distinction is made between EPA and DHA. In concentrations were decreased by 21%. One may speculate that one study, however, EPA supplementation was associated with a this is due to the unique fatty acid composition of Echium oil or to 19% reduction in major coronary events,2 supporting dietary some other minor (unknown) component in Echium oil. However, approaches to increase tissue EPA concentrations. Current intakes no control group was included in that study, which may have of EPA and DHA are however below recommended intakes. confounded the results. Therefore, we designed a randomized, Therefore, alternative (plant-based) sources of n-3 polyunsatu- placebo-controlled, double-blind study to compare the effects of fl rated fatty acids may be needed to bridge the gap between Echium oil with those of high oleic sun ower oil (HOSO) on serum triacylglycerol in subjects with an increased body mass index, who guidelines and actual intakes. EPA can be synthesized from 7 α-linolenic acid (ALA, C18:3n-3), the most common vegetable- are at increased risk to develop hypertriglyceridemia. In addition, oil-based n-3 fatty acid. In humans, however, this conversion is effects on the omega-3 index were studied. This index is 3 negatively related to cardiovascular risk, and defined as the extremely low. It has been suggested that the rate-limiting step 8 for this conversion is the Δ6-desaturation of ALA into stearidonic proportion of EPA+DHA in red blood cells (RBCs). acid (SDA, C18:4n-3).4 Thus, providing oils rich in SDA may increase the endogenous synthesis of EPA. SDA levels in vegetable oils are however low, but there are exceptions. An SDA-enriched MATERIALS AND METHODS soya bean oil increased plasma EPA concentrations as compared Study population 5 with a conventional soya bean oil. Serum triacylglycerol Healthy, overweight or slightly obese subjects with a body mass index concentrations did not change, although such an effect can be between 25 and 35 kg/m2 and aged between 18 and 70 years were

Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands. Correspondence: Professor RP Mensink, Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Universiteitssingel 50, Maastricht, NL-6200 MD, The Netherlands. E-mail: [email protected] Received 4 April 2014; revised 17 July 2014; accepted 22 July 2014; published online 17 September 2014 Stearidonic acid and lipid metabolism DJM Pieters and RP Mensink 122 recruited via advertisements in local newspapers, posters in the university Blood sampling and hospital buildings and among subjects who participated in earlier Subjects were asked to fast overnight (from 20.00 hours) and not to studies at the department from July until October 2011. Forty-two subjects perform any strenuous physical exercise or to consume alcohol 1 day were invited for two screening visits. At each visit, fasting blood was before blood sampling. Venous blood was sampled at weeks 0, 3, 5 and 6 sampled for analyses of serum lipids and lipoproteins. In addition, height of both intervention periods in BD Vacutainer tubes (Becton, Dickinson and and body weight were determined. Furthermore, subjects had to complete Company, Franklin Lakes, NJ, USA). Serum was obtained after coagulation medical and general questionnaire. Seventeen men and nineteen women for 30 min at 21 °C and centrifugation at 1300 g at 21 °C for 15 min. EDTA enroled into the study. Inclusion criteria were mean serum triacylglycerol and NaF tubes were placed on ice directly after sampling, plasma was o3.0 mmol/l, stable body weight (weight gain or loss o2 kg in the 9 obtained by centrifugation at 1300 g at 4 °C for 15 min. Serum and plasma previous 3 months), no indications for treatment of hyperlipidemia, no aliquots were snap frozen and stored at − 80 °C until analysis. RBCs were use of medication or a diet known to affect serum lipid or glucose obtained from EDTA blood samples, after removal of the plasma and buffy metabolism, no active cardiovascular disease, no drug or alcohol abuse, no coat, at weeks 0, 5 and 6 of both intervention periods. After the RBCs were use of an investigational product within the previous 30 days and willing to μ fi fi washed twice with a physiological salt solution, 2 l butylated hydro- stop the consumption of vitamin supplements, sh oil capsules, fatty sh xytoluene (0.5 mg/ml methanol) was added per 1 ml RBC as an antioxidant, and products rich in plant stanol or sterol esters 3 weeks before the start of where after cups were capped under a nitrogen flow and stored at − 80 °C the study. This study was conducted according to the guidelines laid down until analysis. in the Declaration of Helsinki and the standards for Good Clinical Practice. All procedures involving human subjects were approved by the Medical Ethical Committee of Maastricht University. Written informed consent was Serum lipids, glucose and insulin obtained from all subjects before the start of the study. The study was All serum samples were analysed for total cholesterol, high-density registered at clinicaltrials.gov as NCT01365078. lipoprotein cholesterol, and triacylglycerol (corrected for free glycerol concentrations) concentrations at the department of Clinical Chemistry, Study design and intervention University Hospital Maastricht (Beckman Coulter Synchron LX20 PRO Clinical Systems, Beckman Coulter Inc., Fullerton, CA, USA). Serum low-density In this randomized, double-blind, placebo-controlled crossover trial, each lipoprotein cholesterol was calculated with the Friedewald formula.11 All NaF subject received Echium oil or HOSO for 6 weeks with a washout period of plasma samples were analysed for free fatty acids (Wako Nefa C test kit; at least 2 weeks between the intervention periods. Subjects were allocated Wako Chemicals, Neuss, Germany) and glucose (hexokinase method; Roche to start with either Echium oil or HOSO according to a preestablished Diagnostic Systems, Hoffmann-La Roche, Basel, Switzerland). Serum insulin randomization scheme. During the Echium oil period, subjects consumed concentrations from weeks 0 and 6 were analysed with a human insulin- fi daily 10 g of Echium oil (BioMega SDA Re ned Echium Oil, Bioriginal specific RIA kit (Linco Research, St Charles, MO, USA). All samples from one Europe Asia b.v. Den Bommel, The Netherlands), providing approximately subject were analysed within the same run. 1.2 g SDA. During the control period, subjects consumed daily 10 g of HOSO. The fatty acid composition of the oils is shown in Table 1. Both oils were provided in sachets containing 5 g of oil, which were letter-coded to Fatty acid analyses in RBCs blind the subjects and the investigators. Subjects consumed one sachet at Total lipids from RBCs were extracted according to the method of Sonja lunch and one at dinner. At each visit, subjects were supplied with a Garcia, using 1,2-dinonadecanoyl phosphatidylcholine (C19:0) as internal number of sachets sufficient till the next visit. Sachets that were not standard. Phospholipids were isolated by thin-layer chromatography (pre- consumed had to be returned and were used to estimate compliance. At coated glass plates, Silica gel 60, 0.5 mm; 20 × 20 cm), and subsequently weeks 0, 3, 5 and 6 of both intervention periods, body weight was hydrolysed and methylated into their corresponding fatty acid methyl fi recorded. In addition, blood pressure was measured four times (Omron M7, esters. For separation and quanti cation of a GC2010 gas chromatography CEMEX Medische Techniek BV, Nieuwegein, The Netherlands) and the last was used (Shimadzu, Duisburg, Germany) equipped with a CP-Sil 88 μ fi three readings were averaged. At the end of both intervention periods, capillary column (50 m × 0.25 mm, 0.20 m lm thickness; Agilent Tech- nologies, Santa Clara, CA, USA), using helium as the carrier gas (injector energy and nutrient intakes of the previous 6 weeks were assessed by a inlet pressure of 130 kPa). The injection and the detector temperature were validated food frequency questionnaire,10 which was checked immediately set at 300 °C. The oven temperature started at 160 °C and increased for by a registered dietician in the presence of the subjects. Subjects recorded 10 min to 190 °C in steps of 5 °C/min. Temperature was kept constant at daily signs of illness, medication used and any deviations from the protocol 190 °C for 15 min and then increased at 5 °C/min to 230 °C, where it was in diaries, which were checked at each visit. All measurements were kept steady for 7 min. performed at the Metabolic Research Unit Maastricht of Maastricht Fatty acid composition of RBC membranes was reported as weight University. percentage of the following 22 selected fatty acids: saturated (14:0, 16:0, 18:0 and 24:0); cis monounsaturated (16:1, 18:1, 20:1 and 24:1); trans (16:1, Table 1. Fatty acid composition of the two experimental oils 18:1 and 18:2); cis n-6 polyunsaturated (18:2, 18:3, 20:2, 20:3, 20:4, 22:4 and 22:5); cis n-3 polyunsaturated (18:3, 20:5, 22:5 and 22:6).12 All samples from HOSO Echium oil one subject were analysed within the same run. The omega-3 index was calculated as the sum of EPA and DHA expressed as a percentage of the Fatty acid %a g/10 g %a g/10 g selected fatty acids.

Saturated fatty acids General health parameters C16:0 Palmitic acid 3.5 0.3 6.7 0.6 C18:0 Stearic acid 3.2 0.3 3.8 0.3 From weeks 0 and 6 of both intervention periods, serum concentrations of markers of liver function (total bilirubin, aspartate aminotransferase, Monounsaturated fatty acids alanine-aminotransferase, alkaline phosphatase, γ-glutamyl transpepti- C18:1(n-9) Oleic acid 84.2 7.6 15.2 1.4 dase) and kidney function (creatinine) were determined at the Department C22:1(n-9) Erucic acid 0.1 o0.1 of Clinical Chemistry, University Hospital Maastricht (Beckman Coulter Synchron LX20 PRO Clinical Systems, Beckman Coulter Inc.). Haemato- Polyunsaturated fatty acids logical parameters in EDTA blood (number of white blood cells, percentage Omega-6 fatty acids of lymphocytes, percentage of monocytes, percentage of granulocytes, C18:2(n-6) Linoleic acid 7.4 0.7 15.5 1.4 number of RBCs, haemoglobin, haematocrit, mean corpuscular volume and C18:3(n-6) γ-Linolenic acid 10.8 1 the number of platelets) were determined at the Department of Omega-3 fatty acids Haematology, University Hospital Maastricht on a Coulter AcT diff (Coulter C18:3(n-3) α-Linolenic acid 32.3 2.9 Corporation, Miami, FL, USA). C18:4(n-3) Stearidonic acid 12.8 1.2 High-sensitive C-reactive protein was measured in all serum samples Abbreviation: HOSO, high oleic acid sunﬂower oil. aValues are expressed as with a highly sensitive immunoturbidimetric assay (Kamiya Biomedical, percentage of total fatty acids. Seattle, WA, USA). All samples from one subject were analysed within the same run.

European Journal of Clinical Nutrition (2015) 121 – 126 © 2015 Macmillan Publishers Limited Stearidonic acid and lipid metabolism DJM Pieters and RP Mensink 123 Statistics protein was slightly increased during the Echium oil period Before the start of the study, it was calculated that with 32 subjects the (P=0.04). Differences in the intake of oleic, linoleic and α-linoleic statistical power to detect a true difference of 0.20 mmol/l in serum acids—due to the fatty acid composition of the experimental triacylglycerol concentrations between the treatments was 80%. The effect oils—were as expected (Table 3). Mean body weights were size of 0.20 mmol/l was derived from the study of Surette et al.6 For the 85.6 ± 12.2 kg at the end of the HOSO period and 85.4 ± 12.0 kg at calculations, a within-subject variability of 0.40 mmol/l in serum triacylgly- the end of the Echium oil period. Compliance, as estimated from cerol concentrations was used. the returned number of sachets, was 96.2% during the HOSO First, values of weeks 5 and 6 were averaged when available. Period and period and 94.4% during the Echium oil period. carryover effects, which were absent indicating that 2 weeks washout was sufficient, were examined as described.13 Differences between the periods Serum triacylglycerol concentrations, the primary end point of were tested for significance using a paired samples t-test. A Po0.05 was the study, were 1.26 ± 0.73 mmol/l after HOSO consumption and considered to be statistically significant. Results are presented as means ± 1.36 ± 0.59 mmol/l after the intake of Echium oil (Table 4). The s.d. Statistical analyses were performed using SPSS version 19.0 for Mac difference of 0.11 ± 0.47 mmol/l did not reach statistical signifi- (SPSS Inc., Chicago, IL, USA). cance (P = 0.21). Also, serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol concentrations and the total to high-density lipoprotein cholesterol RESULTS ratio were comparable between the two intervention periods. Baseline characteristics of the subjects who completed the study Plasma free fatty acids, glucose, insulin and high-sensitive are shown in Table 2. A total of 36 subjects were included. One C-reactive protein concentrations did not also change during man and three women dropped out due to various personal the study. Five subjects had, unrelated to the dietary treatments, reasons, unrelated to the intake of the test products. Analyses on one or more occasion high-sensitive C-reactive protein were performed for the 32 subjects who completed the study. concentrations 410 mg/l. When these subjects were excluded Food intake is shown in Table 3. The proportion of energy from from the analysis, conclusions did not change.

Table 2. Study population characteristics at screening

Men Women All subjects

Mean s.d. Mean s.d. Mean s.d.

Number of subjects 16 16 32 Age (years) 56 14 50 14 51 15 BMI (kg/m2) 28.5 2.4 29.3 3.5 28.9 3 Total cholesterol (mmol/l) 5.92 0.86 5.97 1.02 5.94 0.93 LDL-cholesterol (mmol/l) 3.65 0.71 3.72 0.78 3.69 0.73 HDL-cholesterol (mmol/l) 1.57 0.24 1.75 0.45 1.66 0.37 Triacylglycerol (mmol/l) 1.51 0.7 1.08 0.43 1.3 0.61 Total to HDL-cholesterol ratio 3.85 0.78 3.53 0.72 3.69 0.75 Mean SBP (mm Hg) 142 18 119 14 130 20 Mean DBP (mm Hg) 90 12 80 9 85 12 Abbreviations: BMI, body mass index; DBP, diastolic blood pressure; HDL, high-density lipoprotein; LDL, low-density lipoprotein; SBP, systolic blood pressure.

Table 3. Energy and nutrient intake during the two intervention periods according to the food frequency questionnaires

HOSO Echium oil Change P-value

Mean s.d. Mean s.d. Mean s.d.

Energy MJ/day 9.7 3.1 9.4 2.5 − 0.3 2.8 0.5 Kcal/day 2328 752 2247 602 − 81 667 0.5 Protein (En%) 15.1 4 16.3 3.6 1.3 3.3 0.04 Carbohydrates (En%) 43.9 8.7 41.2 7.7 − 2.7 8.9 0.1 Total fat (En%) 38.5 6.7 39.9 6.8 1.4 8.2 0.35 Saturated fatty acids (En%) 10.8 2.5 11.3 2.1 0.5 1.8 0.1 Monounsaturated fatty acids (En%) 15.2 3.8 13.3 4.5 − 1.9 4.4 0.02 Oleic acid (En%) 13.8 3.7 11.8 4.4 − 2 4.1 0.01 Polyunsaturated fatty acids (En%) 9.1 3.4 9 3.3 − 0.1 3.7 0.84 Linoleic acid (En%) 8 3 10.3 3.3 2.3 3.6 o 0.01 α-Linoleic acid (En%) 0.4 0.1 1.7 0.5 1.3 0.4 o 0.01 α-Linoleic acid (g/day) 0.9 0.4 4 0.5 3 0.5 o 0.01 Trans fatty acids (En%) 1 0.6 1.1 0.8 0.1 0.6 0.26 Alcohol (En%) 2.6 3.9 2.6 4 0 1.2 0.99 Cholesterol (mg/day) 166.3 73.5 181.2 92.4 14.9 71.9 0.25 Fibre (g/day) 26 7.1 25 9.2 − 0.8 6.4 0.51 Abbreviations: En%, energy percentage; HOSO, high oleic sunﬂower oil. P-values for diet effects were calculated by a paired t-test, Po0.05 was considered to be statistically signiﬁcant.

© 2015 Macmillan Publishers Limited European Journal of Clinical Nutrition (2015) 121 – 126 Stearidonic acid and lipid metabolism DJM Pieters and RP Mensink 124 Proportion of the various fatty acids at the start of the first and consumption on markers of liver and kidney function compared second intervention periods did not differ between the groups, with HOSO consumption were observed (data not shown). who started at these time points with, respectively, the HOSO and Echium oil periods (Supplementary Table S1 and S2). Echium oil decreased the proportions of myristic (C14:0) and oleic acid DISCUSSION (C18:1n-9) and increased those of γ-linoleic (C18:3n-6), dihomo- In the present study, a daily intake of 1.2 g SDA from Echium oil for gamma-linoleic (C20:3n-6) and α-linoleic acid (C18:3n-3). More 6 weeks did not change serum triacylglycerol concentrations or interestingly, EPA (C20:5n-3) in RBC membranes increased with the omega-3 index in overweight and slightly obese subjects. 0.14% to 0.60% after the Echium oil period. Also the proportion of Our results contrast the findings of Surette et al.,6 who reported docosapentaenoic acid (22:5n-3) was significantly greater after the a reduction in serum triacylglycerol concentrations of 21% after Echium oil period (P=0.02), whereas there was no difference in consumption of 15 g of Echium oil providing 1.88 g SDA a day for the proportion of DHA (C22:6n-3) after consumption of HOSO and 4 weeks. In that study, subjects were hypertriglyceridemic, which Echium oil (P=0.96). Despite the change in the proportion of EPA, may explain the different findings, as effects of fish oils depend on the omega-3 index was not significantly affected (P=0.68; initial triacylglycerol concentrations.1,14 Although we deliberately Table 5). chose for overweight and slightly obese subjects, who have Systolic blood pressure was 127 ± 17 mm Hg and 129 ± 16 increased serum triacylglycerol concentrations compared with mm Hg (P=0.24), and diastolic blood pressure was 81 ± 9 mm Hg lean subjects,15 levels were not as high as in the study of Surette and 82 ± 2 mm Hg (P=0.39) after the HOSO and Echium oil et al.6 A potential flaw of that study; however, was that no control periods, respectively. Finally, no significant effects of Echium oil group was included. Therefore, another explanation is that

Table 4. Mean concentrations of lipids and lipoproteins, high-sensitive CRP (hsCRP), glucose and insulin at the end of the two intervention periods

HOSO Echium oil Change P-value

Mean s.d. Mean s.d. Mean s.d. 95%CI

Total cholesterol (mmol/l) 5.6 1 5.7 1 0.03 0.39 − 0.18 to 0.11 0.62 LDL-cholesterol (mmol/l) 3.71 0.75 3.66 0.76 − 0.04 0.33 − 0.08 to 0.16 0.46 HDL-cholesterol (mmol/l) 1.33 0.33 1.36 0.37 0.03 0.12 − 0.07 to 0.01 0.18 Total to HDL-cholesterol ratio 4.37 0.97 4.32 1.01 − 0.06 0.44 − 0.1 to 0.21 0.48 Triacylglycerol (mmol/l) 1.26 0.73 1.36 0.59 0.11 0.47 − 0.27 to 0.06 0.21 Free fatty acids (μmol/l) 426 154 442 145 16 153 − 71 to 39 0.57 hsCRP (mg/l) 2.05 1.72 3.55 5.77 1.5 5.25 − 3.39 to 0.39 0.12 Glucose (mmol/l) 5.7 0.69 5.75 0.73 0.05 0.36 − 0.18 to 0.08 0.42 Insulin (mU/l) 17.5 8.2 17 7.1 − 0.4 4.8 − 1.3 to 2.1 0.62 Abbreviations: HDL, high-density lipoprotein; HOSO, high oleic sunﬂower oil; hsCRP, high-sensitive C-reactive protein; LDL, low-density lipoprotein. P-values for oil effects were calculated by a paired t-test.

Table 5. Mean fatty acid composition of red blood cell membranes at the end of the two intervention periods

HOSO Echium oil Change P-value

Mean s.d. Mean s.d. Mean s.d.

Total saturated fatty acids 49.6 4.5 48.7 2.6 − 0.88 4.48 0.35 Palmitic acid C16:0 24.3 2.3 23.9 1.6 − 0.43 2.39 0.39 Stearic acid C18:0 17.8 1.5 17.9 1 0.06 1.17 0.79 Total monounsaturated fatty acids 19.5 1.7 18.8 1.1 − 0.73 1.48 0.03 Oleic acid C18:1n-9 12.5 1.1 12 1.1 − 0.56 0.91 0.01 Total trans fatty acids 0.69 0.3 0.69 0.43 0 0.29 0.97 Trans palmitoleic acid C16:1n-7tr 0.1 0.04 0.09 0.03 − 0.01 0.02 0.17 Trans oleic acid C18:1tr 0.55 0.27 0.55 0.41 0 0.3 1 Trans linoleic acid C18:2n-6tr 0.05 0.04 0.05 0.04 0 0.03 0.72 Total polyunsaturated fatty acids 30.2 4.9 31.8 2.7 1.6 5.3 0.15 Total omega-6 fatty acids 24.5 3.7 25.7 2.1 1.2 3.87 0.14 Linoleic acid C18:2n-6 9 1.2 9 0.9 − 0.01 0.87 0.94 Arachidonic acid C20:4n-6 11.3 2.3 12.1 1.6 0.76 2.38 0.13 Total omega-3 fatty acids 5.7 1.8 6.1 1.3 0.4 1.71 0.26 α-Linolenic acid (ALA) C18:3n-3 0.1 0 0.2 0.1 0.06 0.08 0 Eicosapentaenoic acid (EPA) C20:5n-3 0.5 0.2 0.6 0.3 0.14 0.25 0.02 Docosapentaenoic acid C22:5n-3 2.1 0.4 2.3 0.3 0.22 0.44 0.02 Docosahexaenoic acid (DHA) C22:6n-3 3.1 1.3 3 1 −0.02 1.29 0.96 Omega-3 index 3.5 1.5 3.7 1.2 0.12 1.4 0.68 Abbreviation: HOSO, high oleic sunﬂower oil. Values are means ± s.d. and are expressed as weight percentage of 22 fatty acids identiﬁed.12 P-values for oil effects were calculated by an independent samples t-test.

European Journal of Clinical Nutrition (2015) 121 – 126 © 2015 Macmillan Publishers Limited Stearidonic acid and lipid metabolism DJM Pieters and RP Mensink 125 aspecific drifts with time may have biased results. In fact, our beneficial health effects on the longer term, remains to be results do agree with other placebo-controlled studies looking at investigated. the effect of SDA intake.5,16–19 In these studies, subjects received SDA-enhanced soybean oil for 12 and 14 weeks, providing daily 1.5, 4.2 and 3.7 g SDA,5,16,19 respectively, or SDA provided as ethyl CONFLICT OF INTEREST esters in doses ranging from 0.43 to 5.2 g a day for 12 weeks17 or The authors declare no conflict of interest. 0.75 g and then 1.5 g for a period of 3 weeks each.18 In none of these studies, significant changes in serum triacylglycerol concentrations were observed. It should be noted, however, that ACKNOWLEDGEMENTS none of these studies were specifically designed to examine We would like to thank M Hulsbosch, H Aydeniz and W Sluijsmans for their technical effects on serum triacylglycerol, while subjects were also not support, and N Wystyrk for her dietary assistance. Bioriginal Europe Asia b.v., Den hypertriglyceridemic. Bommel, The Netherlands, funded the study and provided the test products. In the present study, serum total cholesterol, low-density Bioriginal Europe Asia b.v. had no role in the design, analysis or writing of this article. lipoprotein cholesterol, high-density lipoprotein cholesterol concentrations and the total to high-density lipoprotein cholesterol AUTHOR CONTRIBUTION ratio were also comparable between the two intervention periods. These results are in line with other studies.5,6,16,18,19 Krul et al.,17 RPM designed the research; DJMP conducted the research; DJMP and RPM analysed fi fi the data and wrote the paper; RPM had primary responsibility for final content. Both however did nd a signi cant increase in the total to high-density fi lipoprotein cholesterol ratio at the end of treatment relative to authors read and approved the nal manuscript. control in several treatment groups receiving different doses of SDA, but this may have been a chance finding. Mean percentage REFERENCES changes from baseline ranged from − 12% (1.5 g SDA per day) to 1 Roth EM, Harris WS. Fish oil for primary and secondary prevention of coronary 7% (3.0 g SDA/day), compared with − 8% in the control group, 12 – 17 heart disease. Curr Atheroscler Rep 2010; :66 72. with no indication of a pattern related to dosage. 2 Yokoyama M, Origas H, Matsuzaki M, Matsuzawa Y, Saito Y, Ishikawa Y et al. 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Dietary echium oil the HOSO period (8.0 ± 3.0 energy percentage), due to the increases plasma and neutrophil long-chain (n-3) fatty acids and lowers relatively high linoleic acid content in Echium oil. Previous studies serum triacylglycerols in hypertriglyceridemic humans. JNutr2004; 134: – have indicated that linoleic acid lowers the conversion of ALA into 1406 1411. 7 Tirosh A, Shai I, Bitzur R, Kochba I, Tekes-Manova D, Israeli E et al. Changes in EPA,3,20 because these two essential fatty acids compete for the 21 triglyceride levels over time and risk of type 2 diabetes in young men. Diabetes Δ6-desaturase. The Echium oil also contained a relatively high 31 – fi Care 2008; : 2032 2037. amount of ALA, resulting in a signi cantly higher ALA intake 8 Harris WS, Von Schacky C. The Omega-3 Index: a new risk factor for death from during the Echium oil period (1.7 ± 0.5 energy percentage) coronary heart disease? Prev Med 2004; 39:212–220. compared with the HOSO period (0.4 ± 0.1 energy percentage). 9 Netherlands Centraal begeleidingsorgaan voor de intercollegiale toetsing. This was also reflected by changes in the proportion of ALA in RBC Behandeling en preventie van coronaire hartziekten door verlaging van de plasma membranes. Although ALA can be converted to EPA and DHA, the cholesterolconcentratie. Utrecht, 1998. efficiency of this conversion will be lower than that of SDA. A 10 Plat J, Mensink RP. Vegetable oil based versus wood based stanol ester mixtures: meta-regression of six ALA supplementation studies that ranged effects on serum lipids and hemostatic factors in non-hypercholesterolemic 148 – from 2 to 14 g/day however, showed a dose–response increase in subjects. Atherosclerosis 2000; : 101 112. EPA levels without detectable increases in DHA.22 Therefore, it can 11 Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative be speculated that the increase in the proportion of EPA and ultracentrifuge. Clin Chem 1972; 18:499–502. docosapentaenoic acid in RBC membranes in the Echium oil 12 Harris WS, Pottala JV, Vasan RS, Larson MG, Robins SJ. Changes in erythrocyte period was also partly due to the higher ALA intake during this membrane trans and marine fatty acids between 1999 and 2006 in older period. Noteworthy, the Japan EPA lipid intervention study Americans. J Nutr 2012; 147: 1297–1303. suggested that EPA supplementation alone reduced the risks of 13 Pocock SJ. Clinical Trials. A practical approach. John Wiley & Sons: Hoboken, 1983. cardiac events.2 Although it is not known whether results can be 14 Balk EM, Lichtenstein AH, Chung M, Kupelnick B, Chew P, Lau J. Effects of omega- extrapolated to other populations, it does support the notion that 3 fatty acids on serum markers of cardiovascular disease risk: a systematic review. increasing tissue EPA concentrations can have beneficial effects Atherosclerosis 2006; 189:19–30. 15 Sanders TAB, Filippou A, Berry SE, Baumgartner S, Mensink RP. Palmitic acid in the on heart health. fl In summary, our findings suggest that low daily intake of SDA in sn-2 position of triacylglycerols acutely in uences postprandial lipid metabolism. Am J Clin Nutr 2011; 94: 1433–1441. the form of Echium oil, easily achievable through dietary means, 16 Harris WS, Lemke SL, Hansen SN, Goldstein DA, DiRienzo MA, Su H et al. does not lower serum triacylglycerol concentrations or improve Stearidonic Acid-Enriched Soybean Oil Increased the Omega-3 Index, an the omega-3 index, but does raise the proportion of EPA in Emerging Cardiovascular Risk Marker. Lipids 2008; 43: 805–811. RBC phospholipids in non-hypertriglyceridemic overweight and 17 Krul ES, Lemke SL, Mukherjea R, Taylor ML, Goldstein DA, Su H et al. Effects of slightly obese subjects. Whether this latter effect is translated into duration of treatment and dosage of eicosapentaenoic acid and stearidonic acid

© 2015 Macmillan Publishers Limited European Journal of Clinical Nutrition (2015) 121 – 126 Stearidonic acid and lipid metabolism DJM Pieters and RP Mensink 126 on red blood cell eicosapentaenoic acid content. Prostaglandins Leukot Essent 20 Pawlosky RJ, Hibbeln JR, Novotny JA, Salem N Jr. Physiological compartmental Fatty Acids 2012; 86:51–59. analysis of a-linolenic acid metabolism in adult humans. J Lipid Res 2001; 42: 18 James MJ, Ursin VM, Cleland LG. Metabolism of stearidonic acid in human 1257–1265. subjects: comparison with the metabolism of other n-3 fatty acids. Am J Clin Nutr 21 Plourde M, Cunnane SC. Extremely limited synthesis of long chain 2003; 77: 1140–1145. polyunsaturates in adults: implications for their dietary essentiality and use as 19 Lemke SL, Maki KC, Hughes G, Taylor ML, Krul AS, Goldstein DA et al. supplements. Appl Physiol Nutr Metab 2007; 32:619–634. Consumption of stearidonic acid-rich oil in foods increases red blood cell 22 Arterburn LM, Hall EB, Oken H. Distribution, interconversion, and dose response of eicosapentaenoic acid. J Acad Nutr Diet 2013; 113: 1044–1056. n-3 fatty acids in humans. Am J Clin Nutr 2006; 83: 1467S–1476S.

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