ALA is the precursor of EPA and DHA and its dietary availability is limited. Vegetable oils rich in ALA (48–64%) are alternatives for increasing its consumption. The conversion of ALA into EPA and DHA and the ratio (EPA + DHA/ALA) was evaluated in different tissues from male Wistar rats fed ALA –rich oils. Four groups (n = 12/group) were fed for 21 days with oils from: a) corn (CO, 3% ALA); b) soybean (SO, 6% ALA); c) sacha inchi (SIO, 48% ALA) and; d) chia (ChO, 64% ALA). SO, SIO and ChO significantly increased ALA levels (p < 0.05) in the tissues. Only SIO and ChO increased tissue EPA and DHA while reducing n-6/n-3 ratio (p < 0.05). SIO and ChO are suggested as good sources of ALA to increase tissue EPA and DHA.
Polyunsaturated fatty acids (PUFA), are very important for humans especially during pregnancy, breastfeeding and early life (Burlingame
Recent industrialization and commercial availability in Latin America of ancestral oils, such as sacha inchi and chia oil, which have high a content of ALA, open the possibility of providing the population with abundant and inexpensive sources of n-3 PUFA. Sacha inchi oil (42 to 48% ALA) is obtained from the fruit
Male Wistar rats (21 day-old) were obtained from the Bioterium of the Nutrition Department of the Faculty of Medicine, University of Chile. Animals were randomly assigned to one of four groups with free access to the different experimental diets (n = 12 animals/experimental group). Each group was fed with an isocaloric diet, with a macronutrient distribution: 20% protein, 10% fat and 70% carbohydrates, supplemented with micronutrients according to the nutritional requirements of Wistar rats. The total fat in each group was exclusively provided by a vegetable oil according to the following description: corn oil (CO, 3% ALA); soybean oil (SO, 6% ALA); sacha inchi oil (SIO, 48% ALA); chia oil (ChO, 64% ALA). Dietary composition was previously published (González-Mañán
Fatty acid composition of each diet: corn oil (CO), soybean oil (SO), sacha inchi oil (SIO) and chia oil (ChO). Values show the mean of five analyses and are expressed as g FAME per 100 g of diet
Fat content | CO | SO | SIO | ChO |
---|---|---|---|---|
SFA | 1.5 | 1.4 | 0.6 | 0.9 |
MUFA | 2.7 | 2.5 | 1.0 | 0.6 |
Oleic acid | 2.3 | 2.3 | 0.8 | 0.5 |
PUFA | 6.2 | 6.0 | 8.5 | 8.5 |
Total n-6 PUFA | 5.8 | 5.3 | 3.5 | 2.1 |
Linoleic acid | 5.7 | 5.1 | 3.6 | 2.0 |
Total n-3 PUFA | 0.4 | 0.7 | 4.9 | 6.4 |
Alpha linolenic acid | 0.3 | 0.6 | 4.8 | 6.3 |
EPA | n/d | n/d | n/d | n/d |
DHA | n/d | n/d | n/d | n/d |
n6/n-3 PUFA ratio | 14.5 | 0.0 | 0.7 | 0.3 |
Quantitative extraction of total lipids from plasma, hepatic and adipose tissue was carried out according to Bligh and Dyer (Bligh and Dyer,
FAME from plasma, hepatic and adipose tissue total lipids were prepared with methanolic boron trifluoride (12% methanolic solution) according to Morrison and Smith (Morrison and Smith,
FAME were separated and quantified by gas-liquid chromatography using Hewlett-Packard equipment (model 7890A, CA, USA) equipped with a capillary column (Agilent HP-88, 100 m×0.250 mm; I.D. 0.25 µm) and a flame ionization detector (FID). The injector temperature was set at 250 °C and the FID temperature at 300 °C. The oven temperature at injection was initially set at 140 °C and was programmed to increase to 220 °C at a rate of 5 °C·min−1. Hydrogen was used as carrier gas. FAME identification and quantification was achieved using a commercial lipid standard (Nu-Chek Prep Inc. MN, USA.) and C23:0 as internal standard (Nu-Chek Prep Inc. MN, USA.) using the Hewlett-Packard Chemstation Data System.
Statistical analysis was performed with the GraphPad Prism 5.1 software (GraphPad Prism Software, Inc. San Diego, USA). The values shown represent the mean±SEM for the number of separate experiments indicated. The evaluation of normality data distribution was performed using the Shapiro Wilk test. Assessment of the statistical significance of differences between mean values was performed by one-way ANOVA and the Newman-Keuls test. A p < 0.05 was considered significant.
No significant differences, either in the initial or in the final weight or dietary intake of the animals from each group during the 21 days of intervention was observed (not shown). Also, no significant differences in liver weight or in subcutaneous adipose tissue aspect were observed. No mortality was produced during the experimental period.
The composition of the most relevant fatty acids of total plasma lipids are shown in
Most relevant fatty acids obtained from plasma samples of the different experimental groups
Fatty acid | Groups | |||
---|---|---|---|---|
|
||||
CO (a) | SO (b) | SIO (c) | ChO (d) | |
Total SFA | 55.6±5.1 | 52.1±4.7 | 50.4±3.7 | 47.8±5.2 |
Total MUFA | 16.9±2.4 | 16.5±2.5 | 15.2±1.8 | 14.4±1.8 |
Total PUFA | 27.5±3.6d | 31.4±4.3 | 34.4±2.8 | 37.8±4.8a |
Total LCPUFA | 7.84±0.9d | 7.11±0.8 | 11.1±1.4 | 11.6±1.5a |
Total n-6 LCPUFA | 7.31±0.8b,c,d | 3.42±0.5a,d | 4.00±0.6a,d | 1.50±0.08a,b,c |
Total n-3 LCPUFA | 0.30±0.04b,c,d | 3.71±0.6a,c,d | 7.10±1.2a,b,d | 10.1±1.1a,b,c |
18:2, n-6 (LA) | 20.4±3.2c,d | 19.2±2.6c,d | 6.83±0.4a,b | 3.61±0.7a,b |
18:3, n-3 (ALA) | 0.18±0.02b,c,d | 5.31±0.7a,c,d | 16.8±2.6a,b,d | 22.2±3.4a,b,c |
20:4, n-6 (AA) | 7.12±1.9b,c,d | 2.90±0.4a,d | 3.70±0.3a,d | 1.10±0.2a,b,c |
20:5, n-3 (EPA) | 0.16±0.02b,c,d | 2.62±0.3a,c,d | 4.20±0.8a,b,d | 6.12±1.2a,b,c |
22:6, n-3 (DHA) | 0.13±0.03a,c,d | 0.83±0.05a,c,d | 2.21±0.2a,b | 2.71±0.6a,b |
n-6/ n-LCPUFA3 ratio | 24.3±1.4b,c,d | 0.91±0.04a,c,d | 0.60±0.03a,b,d | 0.20±0.02a,b,c |
Values are expressed as g fatty acid per 100 g FAME and represent the mean±SEM for n = 12 rats/experimental group. Values sharing the same letter in each row are not statistically different (p < 0.05). Saturated fatty acids (SFA) correspond to 14:0, 16:0 and 18:0. Monounsaturated fatty acids (MUFA) correspond to 14:1, n-7, 16:1, n-7 and 18:1, n-9. Polyunsaturated fatty acids (PUFA) correspond to 18:2, n-6, 18:3, n-3, 20:4, n-6, 20:5, n-3, 22:5, n-3, and 22:6, n-3; n-6 Long chain polyunsaturated fatty acids (LCPUFA) are 20:4, n-6; n-3 LCPUFA are 20:5, n-3, 22:5, n-3, and 22:6, n-3; n-6/n-3 ratio: 20:4, n-6/ (20:5, n-3 + 22:5, n-3 + 22:6, n-3).
The composition of the most relevant fatty acids of total liver lipids is shown in
Most relevant fatty acids obtained from liver samples of the different experimental groups
Fatty acid | Groups | |||
---|---|---|---|---|
|
||||
CO (a) | SO (b) | SIO (c) | ChO (d) | |
Total SFA | 33.1±2.2 | 33.6±2.1 | 34.2±3.8 | 34.4±2.5 |
Total MUFA | 18.4±1.8 | 19.6±1.4d | 17.7±2.5 | 15.8±1.2b |
Total PUFA | 48.5±4.2 | 46.8±3.5 | 48.1±4.3 | 49.1±3.4 |
Total LCPUFA | 21.4±2.2 | 17.1±2.4d | 21.8±3.2 | 22.4±2.1b |
Total n-6 LCPUFA | 19.6±1.6b,c,d | 9.65±1.1a,d | 6.70±1.4a,b | 2.41±0.4a,b,c |
Total n-3 LCPUFA | 1.80±0.2b,c,d | 7.45±0.5a,c,d | 15.0±1.6a,b,d | 20.0±1.4a,b,c |
18:2, n-6 (LA) | 24.2±4.2c,d | 20.6±2.5c,d | 12.36±1.3a,b,d | 5.04±0.3a,b,c |
18:3, n-3 (ALA) | 0.31±0.05b,c,d | 5.10±0.6a,c,d | 12.4±1.3a,b,d | 17.6±1.6a,b,c |
20:4, n-6 (AA) | 15.8±1.7b,c,d | 7.11±0.4a,c,d | 5.50±2.6a,d | 1.81±0.3a,b,c |
20:5, n-3 (EPA) | 0.26±0.1b,c,d | 3.22±0.5a,c,d | 5.62±0.7a,b,d | 9.02±0.5a,b,c |
22:6, n-3 (DHA) | 1.15±0.2b,c,d | 3.15±0.3a,c,d | 5.91±0.6a,b | 6.22±0.8a,b |
n-6/n-3 LCPUFA ratio | 10.9±1.1b,c,d | 1.30±0.2a,c,d | 0.45±0.1a,b,d | 0.12±0.02a,b,c |
Values are expressed as g fatty acid per 100 g FAME and represent the mean±SEM for n = 12 rats/experimental group. Values sharing the same letter in each row are not statistically different (p < 0.05). Saturated fatty acids (SFA) correspond to 14:0, 16:0 and 18:0. Monounsaturated fatty acids (MUFA) correspond to 14:1, n-7, 16:1, n-7 and 18:1, n-9. Polyunsaturated fatty acids (PUFA) correspond to 18:2, n-6, 18:3, n-3, 20:4, n-6, 20:5, n-3, 22:5, n-3, and 22:6, n-3; n-6 Long chain polyunsaturated fatty acids (LCPUFA) are 20:4, n-6; n-3 LCPUFA are 20:5, n-3, 22:5, n-3, and 22:6, n-3; n-6/n-3 ratio: 20:4, n-6/ (20:5, n-3 + 22:5, n-3 + 22:6, n-3).
The composition of the most relevant fatty acids of total lipids extracted from adipose tissue is shown in
Most relevant fatty acids obtained from adipose tissue samples of the different experimental groups
Fatty acid | Groups | |||
---|---|---|---|---|
|
||||
CO (a) | SO (b) | SIO (c) | ChO (d) | |
Total SFA | 58.1±4.1 | 60.1±3.8 | 57.8±3.4 | 57.1±4.2 |
Total MUFA | 21.3±3.6 | 20.0±2.1 | 19.9±1.8 | 20.0±3.6 |
Total PUFA | 20.6±3.4 | 19.9±1.8 | 22.3±2.4 | 22.9±2.8 |
Total LCPUFA | 6.60±1.4 | 5.80±1.1d | 7.68±1.8 | 9.80±1.5b |
Total n-6 LCPUFA | 5.93±1.1c,d | 4.41±0.5c,d | 2.47±0.3a,b | 1.87±0.5a,b, |
Total n-3 LCPUFA | 0.67±0.02b,c,d | 1.39±0.05a,c,d | 5.21±0.6a,b,d | 7.93±1.1a,b,c |
18:2, n-6 (LA) | 13.6±2.4c,d | 11.4±2.6c,d | 4.71±0.5a,b,d | 1.84±0.4a,b,c |
18:3, n-3 (ALA) | 0.24±0.03b,c,d | 2.73±0.5a,c,d | 8.61±1.1a,b | 10.6±1.6a,b |
20:4, n-6 (AA) | 5.91±1.3 | 4.32±0.7 | 2.46±0.3a,b | 1.81±0.5a,b |
20:5, n-3 (EPA) | 0.01±0.001b,c,d | 0.46±0.1a,c,d | 0.92±0.2a,b,d | 2.88±0.3a,b,c |
22:6, n-3 (DHA) | 0.41±0.03b,c,d | 0.94±0.1a,c,d | 4.22±0.5a,b | 4.74±0.4a,b |
n-6/n-3 LCPUFA ratio | 8.85±1.6b,c,d | 3.17±0.4a,c,d | 0.47±0.1a,b,d | 0.24±0.05a,b,c |
Values are expressed as g fatty acid per 100 g FAME and represent the mean±SEM for n = 12 rats/experimental group. Values sharing the same letter in each row are not statistically different (p < 0.05). Saturated fatty acids (SFA) correspond to 14:0, 16:0 and 18:0. Monounsaturated fatty acids (MUFA) correspond to 14:1, n-7, 16:1, n-7 and 18:1, n-9. Polyunsaturated fatty acids (PUFA) correspond to 18:2, n-6, 18:3, n-3, 20:4, n-6, 20:5, n-3, 22:5, n-3, and 22:6, n-3; n-6 Long chain polyunsaturated fatty acids (LCPUFA) are 20:4, n-6; n-3 LCPUFA are 20:5, n-3, 22:5, n-3, and 22:6, n-3; n-6/n-3 ratio: 20:4, n-6/ (20:5, n-3 + 22:5, n-3 + 22:6, n-3).
The plasma, liver and adipose n-3 LCPUFA (EPA + DHA)/n-3 PUFA (ALA) ratio is shown in
Product/precursor ratio [(EPA + DHA)/ALA] for plasma (A), liver (B) and adipose tissue (C) obtained after CO, SO, SIO and ChO supplementation.
Values sharing the same letter in each row are not statistically different (p < 0.05).
The data presented show that the intake of ALA, when provided in higher amounts by the different vegetable oils, may increase ALA content and n-3 LCPUFA (EPA + DHA) content in the plasma, liver and adipose tissue of animals fed SO, SIO and ChO. The tissue levels of each of the n-3 LCPUFA studied increased with the amount of ALA provided by each of the dietary oils, with sacha inchi oil and chia oil showing higher ALA, EPA and DHA tissue contents when compared to corn oil and soybean oil (
The reduction in the n-6 (AA)/n-3 LCPUFA (EPA + DHA) ratio observed for SIO and ChO (
The product/precursor ratio shown in
Sacha inchi and chia oils have been demonstrated to be very good sources of ALA to be further transformed into EPA and DHA by the liver, transported through the plasma and accumulated in the adipose tissue. Although this accumulative effect remains to be demonstrated in humans, it is interesting to speculate that these vegetable oils, which are now industrially produced in many Latin American countries, should be a good and inexpensive way to supply the population with ALA to be transformed into EPA and DHA. Consumption of sacha inchi and/or chia oils may compensate the very low ingestion of ALA, and also the low ingestion of n-3 LCPUFA (EPA + DHA) from marine origin, as occurs in some countries such as Chile, Colombia, Argentine, the highlands of Peru, the rain forest of Brazil and other regions of South America (Valenzuela
Feeding rats with diets containing higher amounts of ALA, allows for its accretion into different tissues and its conversion to n-3 LCPUFA (EPA and DHA), which are also accreted in the plasma, liver and adipose tissue of the animals. Oils with a high content of ALA, such as sacha inchi and chia oils may be a good alternative for providing n-3 PUFA to be metabolically transformed into n-3 LCPUFA, an efficient and inexpensive way to nutritionally obtain these essential and low available fatty acids.
The authors are grateful to FONDECYT and INNOVA-CORFO for the support of this research. We are also grateful to the Nutrition and Dietetics School, and the Nutrition Department, Faculty of Medicine, University of Chile, to Benexia S.A. which provided chia oil and to Amazonicas Agro-Industry S. A. which provided sacha inchi oil.