Conversion of dietary polyunsaturated fats between humans and rodents: A review of allometric scaling models.

The purpose of this research was to explore various allometric scaling models for dietary nutrients to improve translational validity between preclinical experimental rodent models and humans, focusing on polyunsaturated fats. Currently, there is no authoritative document that provides standardized guidelines for which dietary designs can be based on to improve translational fidelity between species. This paper reviews the challenges of using a rodent model, the major allometric scaling models, the use of these mathematical models to extrapolate human equivalent doses, and then tests one of these models using data generated in mice, with comparisons of data generated in human clinical trials. Mice were fed diets containing micro- and macronutrient compositions that approximated the US diet based on energy distribution and were then supplemented with increasing levels of various n-3 and n-6 polyunsaturated fatty acids at human equivalent doses. Changes in plasma and erythrocyte fatty acid phospholipid compositions were determined and compared to corresponding data generated in humans. Our findings suggest that basing lipid composition on percent of energy may result in comparable outcomes between mice and humans and that extrapolation of non-energy producing nutrients between species might be done using differences in energy needs (based on food intake).

Similar eicosapentaenoic acid and docosahexaenoic acid plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study.

BACKGROUND: Long-chain n-3 polyunsaturated fatty acids (LC n-3-PUFA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) provide multiple health benefits for heart, brain and eyes. However, consumption of fatty fish, the main source of LC n-3-PUFAs is low in Western countries. Intakes of LC n-3-PUFA can be increased by taking dietary supplements, such as fish oil, algal oil, or krill oil. Recently, conflicting information was published on the relative bioavailability of these omega-3 supplements. A few studies suggested that the phospholipid form (krill) is better absorbed than the fish oil ethyl ester (EE) or triglyceride (TG) forms. Yet studies did not match the doses administered nor the concentrations of DHA and EPA per supplement across such comparisons, leading to questionable conclusions. This study was designed to compare the oral bioavailability of the same dose of both EPA and DHA in fish oil-EE vs. fish oil-TG vs. krill oil in plasma at the end of a four-week supplementation. METHODS: Sixty-six healthy adults (n = 22/arm) were enrolled in a double blind, randomized, three-treatment, multi-dose, parallel study. Subjects were supplemented with a 1.3 g/d dose of EPA + DHA (approximately 816 mg/d EPA + 522 mg/d DHA, regardless of formulation) for 28 consecutive days, as either fish oil-EE, fish oil-TG or krill oil capsules (6 caps/day). Plasma and red blood cell (RBC) samples were collected at baseline (pre-dose on Day 1) and at 4, 8, 12, 48, 72, 336, and 672 h. Total plasma EPA + DHA levels at Week 4 (Hour 672) were measured as the primary endpoint. RESULTS: No significant differences in total plasma EPA + DHA at 672 h were observed between fish oil-EE (mean = 90.9 ± 41 ug/mL), fish oil-TG (mean = 108 ± 40 ug/mL), and krill oil (mean = 118.5 ± 48 ug/mL), p = 0.052 and bioavailability differed by < 24 % between the groups. Additionally, DHA + EPA levels were not significantly different in RBCs among the 3 formulations, p = 0.19, providing comparable omega-3 indexes. CONCLUSIONS: Similar plasma and RBC levels of EPA + DHA were achieved across fish oil and krill oil products when matched for dose, EPA, and DHA concentrations in this four week study, indicating comparable oral bioavailability irrespective of formulation. TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT02427373.

Bioavailability of long-chain n-3 fatty acids from enriched meals and from microencapsulated powder.

BACKGROUND: Despite the potential benefits of long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs), intake is often low because of low consumption of oily seafood. Microencapsulated fish oil powder can improve tolerance and acceptance of LC n-3 PUFAs. Bioavailability is important to achieve efficacy. We investigated the bioavailability of LC n-3 PUFAs from microencapsulated powder in comparison with meals enriched with liquid fish oil. METHODS: Participants (N=99, age⩾50 years) of this 4-week double-blinded dietary intervention were randomized into three groups. Group 1 (n=38) received 1.5 g/d eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as ready-to-eat meals enriched with liquid fish oil; group 2 (n=30) received the same amount of these LC n-3 PUFAs as microencapsulated fish oil powder and regular meals; and group 3 (n=31) was the control group, which received placebo powder and regular meals. Blood samples were taken from fingertips at baseline and at the end point. RESULTS: Seventy-seven subjects (77.8%) completed the study. The amount of EPA in blood doubled in both groups that received LC n-3 PUFAs (P<0.05), but it did not change in the control group. The changes in DHA were less but still significant in both intervention groups. According to multivariate analysis, both intervention groups had higher end-point LC n-3 PUFA concentrations compared with placebo, but differences between intervention groups were not significant. CONCLUSION: Bioavailability of LC n-3 PUFAs in encapsulated powder is very similar to the bioavailability of LC n-3 PUFAs in ready-to-eat meals enriched with liquid fish oil. Thus, encapsulated powder can be considered useful to increase LC n-3 PUFA concentrations in blood.

Papel inmunomodulador de las dietas lipídicas en un modelo murino inmunosuprimido e infectado con Listeria monocytogenes / Immunomodulatory role of dietary lipids in an immunosuppressed mouse model and infected with listeria monocytogenes

Introducción: La capacidad inmunomoduladora de los ácidos grasos de la dieta en situaciones de inmunosupresión puede diferir de acuerdo con el tipo de ácido graso presente. Objetivo: Analizar el efecto de diferentes tipos de dietas lipídicas, en la resistencia de animales inmunosuprimidoso no, frente a una infección experimental con Listeria monocytogenes. Métodos: Ratones Balb/c fueron divididos en cuatro grupos experimentales, según su tratamiento inmunosupresor: control (PBS), Ciclofos famida (CPA), GK 1.5 yRB6-8C5. Cada grupo fue subdividido en cuatro subgrupos según la dieta lipídica utilizada: control con aceite de maíz 5% (BG); aceite de oliva 20% (AO); aceite de pescado20% (AP) y aceite de girasol 20% (AG). Los animales se alimentaron durante un mes antes del tratamiento y posteriormente infectados con L. monocytogenes. Resultados: Mostramos incrementos en el número de bacterias viables en bazo e hígado, y bajos porcentajes de supervivencia en todos los grupos de ratones inmunosuprimidos y también en el grupo PBS alimentado con AP. Además, se observaron incrementos en la linfoproliferación, de bazos de ratones alimentados con AO y tratados con CPA. Discusión: La dieta AP, produce una disminución en la resistencia del hospedador en situaciones de inmunosupresión. Por el contrario, las dietas AO y AG muestran mayor eficacia en la eliminación de L. monocytogenes y mayores ventajas en animales inmunosuprimidos. El tratamiento con RB6-8C5, produce una reducción en la supervivencia de los ratones de los grupos estudiados, lo que induce a establecer que los granulocitos juegan un papel fundamental en el control de la infección (AU)

Introduction: Dietary fatty acids immunomodulatory capacity in immunosuppression conditions may differ according to the type of fatty acid present in the diet. Objective: To analyze the effect of different types of dietary lipids on the immune resistance of immunosuppressed and immunocompetent animals, against experimental infection with a virulent strain of Listeria monocytogenes .Methods: Balb/c mice were divided into four experimental groups, according to their immunosuppressive treatment: control (PBS), cyclophosphamide (CPA), GK1.5 and RB6-8C5. Each group was subdivided into four groups according to the lipid diet used which: control, with corn oil 5% (BG); olive oil 20% (AO); fish oil 20%(AP) and sunflower oil 20% (AG). The animals were fed for a month before treatment and subsequently infected with L. monocytogenes. Results: We show increases in the number of viable bacteria in spleen and liver, and low survival rates in all groups of immunosuppressed mice and also in the PBS group and fed with AP. Furthermore, increases in the lymphocyte proliferation were observed, in the spleen of mice fed with AO and treated with CPA. Discussion: The AP diet produces a significant decrease the host resistance in situations of immunosuppression .On the contrary, the AO and AG diets show major efficiency in the elimination of L. monocytogenes and major immunological advantages in immunosuppressed mice. Treatment with RB6-8C5, produces a reduction in the survival of the mice in all groups studied, which leads us to establish that granulocytes play a key role in the control of infection (AU)

n-3 LC-PUFA deposition efficiency and appetite-regulating hormones are modulated by the dietary lipid source during rainbow trout grow-out and finishing periods.

Largely attributable to concerns surrounding sustainability, the utilisation of omega-3 long-chain polyunsaturated fatty acid-rich (n-3 LC-PUFA) fish oils in aquafeeds for farmed fish species is an increasingly concerning issue. Therefore, strategies to maximise the deposition efficiency of these key health beneficial fatty acids are being investigated. The present study examined the effects of four vegetable-based dietary lipid sources (linseed, olive, palm and sunflower oil) on the deposition efficiency of n-3 LC-PUFA and the circulating blood plasma concentrations of the appetite-regulating hormones, leptin and ghrelin, during the grow-out and finishing phases in rainbow trout culture. Minimal detrimental effects were noted in fish performance; however, major modifications were apparent in tissue fatty acid compositions, which generally reflected that of the diet. These modifications diminished somewhat following the fish oil finishing phase, but longer-lasting effects remained evident. The fatty acid composition of the alternative oils was demonstrated to have a modulatory effect on the deposition efficiency of n-3 LC-PUFA and on the key endocrine hormones involved in appetite regulation, growth and feed intake during both the grow-out and finishing phases. In particular, n-6 PUFA (sunflower oil diet) appeared to 'spare' the catabolism of n-3 LC-PUFA and, as such, resulted in the highest retention of these fatty acids, ultimately highlighting new nutritional approaches to maximise the maintenance of the qualitative benefits of fish oils when they are used in feeds for aquaculture species.

Lower omega-3 index is a marker of increased propensity of hypertensive rat heart to malignant arrhythmias.

Polyunsaturated omega-3 fatty acids (omega-3 PUFA) are important components of cell membrane affecting its function and their deficiency is deleterious to health. We have previously shown that spontaneously hypertensive rats (SHR) are prone to life-threatening arrhythmias that are reduced by omega-3 PUFA intake. Purpose of this study was to explore plasma and red blood cells (RBC) profile of omega-3 and omega-6 PUFA as well as to determine omega-3 index, a risk factor for sudden cardiac death, in aged SHR and the effect of omega-3 PUFA intake. Male and female 12-month-old SHR and age-matched Wistar rats fed with omega-3 PUFA (200 mg/kg BW/day/2 month) were compared with untreated rats. Composition of omega-3 PUFA: alpha linolenic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as well as omega-6 PUFA: linoleic acid and arachidonic acid was analyzed by gas chromatography. Results showed sex- and strain-related differences of basal omega-3 and omega-6 PUFA levels in plasma and RBC as well as in response to omega-3 PUFA intake. Comparing to Wistar rats omega-3 index, expressed as a percentage of EPA+DHA of total fatty acids, was lower in SHR and it increased due to consumption of omega-3 PUFA. Findings support our hypothesis that lower omega-3 index may be also a marker of increased propensity of the hypertensive rat heart to malignant arrhythmias.

Enhanced increase of omega-3 index in response to long-term n-3 fatty acid supplementation from triacylglycerides versus ethyl esters.

BACKGROUND: There is a debate currently about whether different chemical forms of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are absorbed in an identical way. The objective of this study was to investigate the response of the omega-3 index, the percentage of EPA+DHA in red blood cell membranes, to supplementation with two different omega-3 fatty acid (n-3 FA) formulations in humans. DESIGN: The study was conducted as a double-blinded placebo-controlled trial. A total of 150 volunteers was randomly assigned to one of the three groups: (1) fish oil concentrate with EPA+DHA (1.01 g+0.67 g) given as reesterified triacylglycerides (rTAG group); (2) corn oil (placebo group) or (3) fish oil concentrate with EPA+DHA (1.01 g+0.67 g) given as ethyl ester (EE group). Volunteers consumed four gelatine-coated soft capsules daily over a period of six months. The omega-3 index was determined at baseline (t(0)) after three months (t(3)) and at the end of the intervention period (t(6)). RESULTS: The omega-3 index increased significantly in both groups treated with n-3 FAs from baseline to t(3) and t(6) (P<0.001). The omega-3 index increased to a greater extent in the rTAG group than in the EE group (t(3): 186 versus 161% (P<0.001); t(6): 197 versus 171% (P<0.01)). CONCLUSION: A six-month supplementation of identical doses of EPA+DHA led to a faster and higher increase in the omega-3 index when consumed as triacylglycerides than when consumed as ethyl esters.

Olive oil-diet improves the simvastatin effects with respect to sunflower oil-diet in men with increased cardiovascular risk. A preliminary study / Las dietas conteniendo aceite de oliva mejoran los efectos de simvastatina respecto a dietas con aceite de girasol en hombres con riesgo cardiovascular elevado. Estudio preliminar

Background and aims: Concomitant intake of statins together with certain foods may affect their therapeutic effects. The purpose of this preliminary study was to determine the modulating effect of two culinary oils on the hypolipemic effect of statins. Subject and Methods: Twenty-five men with severe hypercholesterolemia and high estimate cardiovascular risk (> 20% according to the Adult Treatment Panel III of USA National Institutes of Health, ATP-III) were enrolled in an observational follow-up study to test lipoprotein profile changes after ix month 20-mg/d Simvastatin treatment. Thirteen volunteers using sunflower oil as the habitual culinary fat, and 12 using olive oil, were selected by non-probabilistic incidental sampling. Volunteers consent in follow their habitual diets and to maintain diet characteristics throughout the study. Diet was evaluated through the study by three 24-h recalls and a food frequency questionnaire. Results: The energy contribution of fat (P = 0.019) and MUFA (P < 0.001) was higher in the olive oil-group while that of PUFA (P = 0.001) and alcohol (P = 0.005) was higher in the sunflower oil-group. TC/HDL-cholesterol and the ATP-III 10-year risk percent decreased more (P < 0.05) in the olive oil group. TC and the TC/HDL-cholesterol and the LDL-cholesterol/HDL-cholesterol ratios and the ATP-III 10-year risk percent decreased significantly more (P < 0.05) in the olive oil-group after BMI, energy and alcohol intakes were adjusted. Conclusion: Data suggest that although Simvastatin is a very effective hypolipemic drug, olive oil-diets in preference to sunflower oil-diets must be consumed in patients with high cardiovascular risk (AU)

Introducción y objetivos: La ingesta de algunos alimentos junto con estatinas puede afectar los efectos terapéuticos del fármaco. Este estudio preliminar pretende determinar el efecto modulador de dos tipos de aceites culinarios sobre los efectos hipolipemiantes de las estatinas. Métodos: Mediante muestreo no probabilístico, 25 hombres con hipercolesterolemia severa y alto riesgo cardiovascular (> 20% según el Panel III para tratamiento de adultos de los Institutos de Salud USA, ATP-III) participaron en el estudio observacional para ver los cambios en el perfil lipoproteico después de seis meses de tratamiento con 20 mg/día de Simvastatina. 13 voluntarios consumían habitualmente aceite de girasol como principal grasa culinaria y 12 aceite de oliva. Todos los sujetos consintieron en mantener sus hábitos alimentarios durante el estudio. Para evaluar la dieta se usaron 3 recuerdos de 24 horas y una frecuencia de consumo. Resultados: El aporte calórico de la grasa (P = 0,019) y de los AGM (P < 0,001) fue mayor en el grupo que consumía aceite de oliva, mientras que el de AGP (P = 0,001) y alcohol (P = 0,005) fue menor. El cociente colesterol/HDL-colesterol y el riesgo cardiovascular disminuyeron más (P<0.05) en los pacientes consumiendo aceite de oliva. Después de ajustar para IMC y para ingesta caló y de alcohol, el colesterol total y los ratios colesterol/HDL-colesterol y LDL-colesterol/HDL-colesterol y el riesgo cardiovascular ATP-III disminuyeron significativamente más (P < 0,05) en el grupo de aceite de oliva. Conclusiones: Los resultados sugieren que aunque Simvastatina es un fármaco hipolipemiante muy efectivo, la inclusión de aceite de oliva, frente a aceite de girasol, mejora dicho efecto en pacientes con alto riesgo cardiovascular (AU)

Enhancement of intragastric acid stability of a fat emulsion meal delays gastric emptying and increases cholecystokinin release and gallbladder contraction.

Preprocessed fatty foods often contain calories added as a fat emulsion stabilized by emulsifiers. Emulsion stability in the acidic gastric environment can readily be manipulated by altering emulsifier chemistry. We tested the hypothesis that it would be possible to control gastric emptying, CCK release, and satiety by varying intragastric fat emulsion stability. Nine healthy volunteers received a test meal on two occasions, comprising a 500-ml 15% oil emulsion with 2.5% of one of two emulsifiers that produced emulsions that were either stable (meal A) or unstable (meal B) in the acid gastric environment. Gastric emptying and gallbladder volume changes were assessed by MRI. CCK plasma levels were measured and satiety scores were recorded. Meal B layered rapidly owing to fat emulsion breakdown. The gastric half-emptying time of the aqueous phase was faster for meal B (72 +/- 13 min) than for meal A (171 +/- 35 min, P < 0.008). Meal A released more CCK than meal B (integrated areas, respectively 1,095 +/- 244 and 531 +/- 111 pmol.min.l(-1), P < 0.02), induced a greater gallbladder contraction (P < 0.02), and decreased postprandial appetite (P < 0.05), although no significant differences were observed in fullness and hunger. We conclude that acid-stable emulsions delayed gastric emptying and increased postprandial CCK levels and gallbladder contraction, whereas acid-instability led to rapid layering of fat in the gastric lumen with accelerated gastric emptying, lower CCK levels, and reduced gallbladder contraction. Manipulation of the acid stability of fat emulsion added to preprocessed foods could maximize satiety signaling and, in turn, help to reduce overconsumption of calories.

Uptake of triacylglycerol-rich lipoproteins of differing triacylglycerol molecular species and unsaponifiable content by liver cells.

The fatty acid composition of dietary oils can modulate the incorporation of triacylglycerol-rich lipoproteins (TRL) into hepatocytes, thus affecting the atherogenicity of these particles. However, nothing is known about the effect of the unsaponifiable fraction of the oils. In the present study, we evaluated the influence of these components on the uptake of TRL by rat primary hepatocytes. TRL were isolated from human serum after the intake of meals enriched in high-oleic sunflower oil (HOSO), virgin olive oil (VOO) or VOO enriched in its own unsaponifiable fraction (EVO). HOSO and HOSO-TRL differed from VOO and EVO and their corresponding TRL in the composition of triacylglycerol molecular species and of the unsaponifiable fraction. Furthermore, the increase in the unsaponifiable fraction of VOO led to changes in the triacylglycerol molecular species in the EVO-TRL. On incubation with hepatocytes, HOSO-TRL were taken up at a faster rate than VOO-TRL or EVO-TRL. In addition, in comparison to VOO-TRL, HOSO-TRL increased the expression of mRNA for the LDL receptor-related protein receptor, which plays an important role in the internalisation of remnant lipoproteins. EVO-TRL also increased LDL receptor-related protein mRNA expression in comparison with VOO-TRL, but this change was not accompanied by a rise in the uptake rate, suggesting that the unsaponifiable fraction of VOO may inhibit LDL receptor-related protein expression or activity post-transcriptionally. In conclusion, TRL from dietary oils with differing triacylglycerol molecular species and unsaponifiable fraction content are taken up by liver cells at different rates, and this may be important in the atherogenicity of these particles.

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.

Relationship between dietary unsaturation and vitamin E in poultry.

Vitamin E requirements are linked to dietary polyunsaturated fatty acids (PUFA) content as a result of the protective effect of vitamin E from lipid peroxidation. On the other hand, it has been suggested that dietary PUFA interfere with vitamin E absorption. A 4 x 4 factorial study was planned to assess the effect of dietary vitamin E inclusion level (0, 100, 200 and 400 mg/kg) and degree of unsaturation (15, 34, 45 and 61 g PUFA/kg) on vitamin E apparent absorption and tissue deposition in poultry. A total of 192 female broiler chickens were used. A digestibility balance was carried out between 19 and 23 days of age to calculate apparent absorption of fat and vitamin E. The livers of 96 animals were obtained at 44 days of age for vitamin E determination. Increasing dietary levels of vitamin E reduced its apparent absorption. The more saturated diet reduced fat and vitamin E apparent absorption while PUFA levels from 34 to 61 g/kg did not modify this parameter but reduced the hepatic vitamin E concentration, suggesting a greater systemic use of this vitamin. These results suggest that PUFA do not limit vitamin E absorption, although they may increase its degradation in the gastrointestinal tract.

Marine lipid-based liposomes increase in vivo FA bioavailability.

Liposomes made from an extract of natural marine lipids and containing a high n-3 PUFA lipid ratio were envisaged as oral route vectors for FA supplements in order to increase PUFA bioavailability. The absorption of FA in thoracic lymph duct-cannulated rats, after intragastric feeding of dietary fats in the form of liposomes or fish oil, was compared. Lipid and FA analyses were also performed on feces. Five mole percent alpha-tocopherol was added to fish oil and incorporated into the liposome membrane. The influence of alpha-tocopherol on FA lymph recovery was also investigated. In vivo, FA absorption in rats was favored by liposomes (98 +/- 1%) compared to fish oil (73 +/- 6%). In the same way, the DHA proportion in lymph was higher after liposome ingestion (78%) than after fish oil ingestion (47%). However, phospholipid (PL) concentration in lymph was not affected by the kind of dietary fat ingested, suggesting a PL regulation due to de novo TAG synthesis. The influence of the intramolecular distribution of n-3 PUFA in dietary lipids (TAG and PL) on the intramolecular FA distribution in TAG of chylomicrons was also investigated. The results obtained showed that the distribution of n-3 PUFA esterified on the sn-2 position of chylomicron TAG depended on the lipid source administered. All these results correlated, at least partly, with in vitro liposome behavior under conditions that mimic those of the gastrointestinal tract. As a whole, this study pointed out that marine PL may constitute an attractive material for the development of liposomes as oral PUFA supplements.

Methodologic challenges in designing clinical studies to measure differences in the bioequivalence of n-3 fatty acids.

Although epidemiologic studies suggest a role for alpha-linolenic acid (ALA) in the prevention of coronary heart disease and certain types of cancer, the findings of clinical studies suggest that ALA is inferior biologically to the n-3 long-chain fatty acids because its bioconversion to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is limited in humans and because the magnitude of its biologic effects is smaller than that of EPA and DHA. This paper reviews several methodologic issues that may confound the findings of clinical studies and complicate our interpretations of them: the ALA and EPA + DHA dietary enrichment levels; the choice of tissue; the choice of lipid species; and the method of reporting fatty acid composition. Although the ALA enrichment levels used in most clinical studies can be achieved by consuming ground flaxseed, flaxseed oil, canola oil and other ALA-rich plants as part of a typical dietary pattern, the EPA + DHA enrichment levels are not practical and can only be obtained from fish oil supplements. The lack of consistency in the choice of lipids species and the reporting of data makes it difficult to compare outcomes across studies. The choice of tissue (blood) for analysis is a limitation that probably cannot be overcome. The use of practical ALA and EPA + DHA dietary enrichment levels and some standardization of clinical study design would allow for greater comparisons of outcomes across studies and ensure a more realistic analysis of how individual n-3 fatty acids differ in their biologic effects in humans.

Effect of dietary conjugated linoleic acid (CLA) on metabolism of isotope-labeled oleic, linoleic, and CLA isomers in women.

The purpose of this study was to investigate the effect of dietary CLA on accretion of 9c-18:1, 9c,12c-18:2, 10t,12c-18:2, and 9c,11t-18:2 and conversion of these FA to their desaturated, elongated, and chain-shortened metabolites. The subjects were six healthy adult women who had consumed normal diets supplemented with 6 g/d of sunflower oil or 3.9 g/d of CLA for 63 d. A mixture of 10t,2c-18:2-d4, 9c,11t-18:2-d6, 9c-18:1-d8, and 9c,12c-18:2-d2, as their ethyl esters, was fed to each subject, and nine blood samples were drawn over a 48-h period. The results show that dietary CLA supplementation had no effect on the metabolism of the deuterium-labeled FA. These metabolic results were consistent with the general lack of a CLA diet effect on a variety of physiological responses previously reported for these women. The 2H-CLA isomers were metabolically different. The relative percent differences between the accumulation of 9c,11t-18:2-d6 and 10t,12c-18:2-d4 in plasma lipid classes ranged from 9 to 73%. The largest differences were a fourfold higher incorporation of 10t,12c-18:2-d4 than 9c,11t-18:2-d6 in 1-acyl PC and a two- to threefold higher incorporation of 9c,11t-18:2-d6 than 10t,12c-18:2-d4 in cholesterol esters. Compared to 9c-18:1-d8 and 9c,12c-18:2-d2, the 10t,12c-18:2-d4 and 9c,11t-18:2-d6 isomers were 20-25% less well absorbed. Relative to 9c-18:1, incorporation of the CLA isomers into 2-acyl PC and cholesterol ester was 39-84% lower and incorporation of 10t,12c-18:2 was 50% higher in 1-acyl PC. This pattern of selective incorporation and discrimination is similar to the pattern generally observed for trans and cis 18:1 positional isomers. Elongated and desaturated CLA metabolites were detected. The concentration of 6c,10t,12c-18:3-d4 in plasma TG was equal to 6.8% of the 10t,12c-18:2-d4 present, and TG was the only lipid fraction that contained a CLA metabolite present at concentrations sufficient for reliable quantification. In conclusion, no effect of dietary CLA was observed, absorption of CLA was less than that of 9c-18:1, CLA positional isomers were metabolically different, and conversion of CLA isomers to desaturated and elongated metabolites was low.

Feeding of red palm oil-supplemented diets to rats may impact positively on vitamin A status.

The impact of feeding of dietary palm oil supplements on plasma vitamin A profile was investigated in animals. Four-week-old Wistar albino rats (n = 8 per group) were maintained for 28 days on standard rat food (4.7% fat by weight) supplemented (10%, 20% and 30% by weight) with red palm oil (RPO) and refined palm olein (REFPO). Plasma beta-carotene and vitamin A concentrations of rats fed RPO-based diets were higher than in rats fed REFPO and control diets. Animals fed 30% RPO-containing diets had lower plasma beta-carotene concentrations than those fed 20% RPO-containing diets. The results suggest that consumption of palm oil in moderate amounts enhances growth of tissues and bioavailability of beta-carotene, which may combat vitamin A deficiency in developing countries, in view of the fact that performed vitamin A in animal products (namely meat, liver, eggs and fatty fish) is out of the reach of economically deprived people.

Dietary long-chain polyunsaturated fatty acids from different sources affect fat and fatty acid excretions in rats.

Several sources of long-chain polyunsaturated fatty acids (LCP) have been evaluated for infant-formula supplementation. These sources differ in their chemical structure [triglyceride (TG) or phospholipid (PL)], arrangement of fatty acids on the TG or PL backbone, fatty acid composition and presence of other lipid components. All of these characteristics influence fat digestion, may affect fat and fatty acid absorption, and hence, LCP bioavailability and metabolism in infancy. The main objective of this work was to establish the influence of different dietary LCP sources on overall fat and LCP absorption in early life. We compared fat and fatty acid excretions at weaning in rats fed control diets or diets supplemented with LCP as TG or PL. Two separate experiments were conducted. In Experiment 1, weanling rats were fed for 3 wk a control diet (C1), a diet with TG from tuna and fungal oils (TF-TG) or a diet with PL from pig brain concentrate (PB-PL). In Experiment 2, weanling rats were fed for 3 wk a control diet (C2), a diet containing egg-TG (EG-TG) or a diet containing egg-PL (EG-PL). Fat, mineral and saturated fatty acid excretions in feces were higher in rats fed PB-PL compared with those fed TF-TG diet. In Experiment 2, groups did not differ in fat and mineral excretions. However, the EG-PL group had lower fecal excretions of saturated fatty acids than the C2 and EG-TG groups. The 16:1(n-7), 18:1(n-9), 18:2(n-6) and 22:6(n-3) levels in feces were higher in the EG-TG group than in the EG-PL group. In summary, total fat and LCP excretions differed among rats fed diets supplemented with LCP from different sources.

Lysophosphatidylcholine as a preferred carrier form of docosahexaenoic acid to the brain.

The metabolic fate of docosahexaenoic acid (DHA) was evaluated from its intake as a nutrient in triglycerides and phosphatidylcholines to its uptake by target tissues, especially the brain. Several approaches were used including the kinetics and tissue distribution of ingested 13C-labeled DHA, the incorporation of radiolabeled DHA injected as its nonesterified form compared to the fatty acid esterified in lysophosphatidylcholine (lysoPC), and the capacity of the two latter forms to cross a reconstituted blood-brain barrier (BBB) consisting of cocultures of brain-capillary endothelial cells and astrocytes. The results obtained allow us to raise the hypothesis that lysoPC may represent a preferred physiological carrier of DHA to the brain.