Dietary Polyunsaturated Fatty Acids Supply Research Articles

Dietary polyunsaturated fatty acid supply improves Daphnia performance at fluctuating temperatures, simulating diel vertical migration

Abstract Diel vertical migration (DVM) is a common predator avoidance strategy of zooplankton. Migration to deeper water layers during the day to escape visually hunting predators is most likely to require physiological adaptations to periodically changing temperatures. Polyunsaturated fatty acids (PUFA) play crucial roles in membrane temperature acclimation. Exposure to cold temperatures typically results in an increase in the relative abundance of PUFA in cell membranes and PUFA requirements of Daphnia increase with decreasing temperatures. To assess the role of dietary PUFA in coping with temperature fluctuations experienced during DVM, we reared Daphnia magna at either constantly warm or fluctuating temperatures, simulating DVM both with and without dietary PUFA supplementation. We show that the well‐known positive effect of dietary eicosapentaenoic acid supplementation on offspring production and population growth rates of D. magna is more pronounced at alternating temperatures than at constantly warm temperatures. Exposure to alternating temperatures caused modification in body PUFA concentrations and, consequently, increased lipid peroxidation. However, detrimental effects of lipid peroxidation were not evident. Our data demonstrate that the capacity to cope with the distinct temperature fluctuations experienced during DVM increases with dietary eicosapentaenoic acid supplementation, suggesting that an adequate dietary PUFA supply is crucial especially for migrating Daphnia populations. A dietary deficiency in long‐chain PUFA may thus severely constrain predator evasion, potentially resulting in increased mortality and cascading effects on lower trophic levels.

Combined effects of dietary polyunsaturated fatty acids and parasite exposure on eicosanoid-related gene expression in an invertebrate model

Eicosanoids derive from essential polyunsaturated fatty acids (PUFA) and play crucial roles in immunity, development, and reproduction. However, potential links between dietary PUFA supply and eicosanoid biosynthesis are poorly understood, especially in invertebrates. Using Daphnia magna and its bacterial parasite Pasteuria ramosa as model system, we studied the expression of genes coding for key enzymes in eicosanoid biosynthesis and of genes related to oogenesis in response to dietary arachidonic acid and eicosapentaenoic acid in parasite-exposed and non-exposed animals. Gene expression related to cyclooxygenase activity was especially responsive to the dietary PUFA supply and parasite challenge, indicating a role for prostanoid eicosanoids in immunity and reproduction. Vitellogenin gene expression was induced upon parasite exposure in all food treatments, suggesting infection-related interference with the host's reproductive system. Our findings highlight the potential of dietary PUFA to modulate the expression of key enzymes involved in eicosanoid biosynthesis and reproduction and thus underpin the idea that the dietary PUFA supply can influence invertebrate immune functions and host-parasite interactions.

A dietary polyunsaturated fatty acid improves consumer performance during challenge with an opportunistic bacterial pathogen.

A dietary deficiency in polyunsaturated fatty acids (PUFAs) and/or sterols can severely constrain growth and reproduction of invertebrate consumers. Single nutrients are potentially assigned to different physiological processes, for example to support defence mechanisms; therefore, lipid requirements of healthy and pathogen-challenged consumers might differ. In an oral exposure experiment, we explored the effects of dietary PUFAs and cholesterol on growth, reproduction and survival of an aquatic key herbivore (Daphnia magna) exposed to an opportunistic pathogen (Pseudomonas sp.). We show that healthy and pathogen-challenged D.magna are strongly albeit differentially affected by the biochemical composition of their food sources. Supplementation of a C20 PUFA-deficient diet with arachidonic acid (ARA) resulted in increased survival and reproduction of pathogen-challenged D.magna. We propose that the observed benefit of consuming an ARA-rich diet during pathogen challenge is conveyed partially via ARA-derived eicosanoids. This study is one of the first to consider the importance of dietary PUFAs in modifying fitness parameters of pathogen-challenged invertebrate hosts. Our results suggest that dietary PUFA supply should receive increased attention in host-microorganisms interactions and invertebrate disease models to better understand and predict disease dynamics in natural populations.

Seasonal changes in the accumulation of polyunsaturated fatty acids in zooplankton

In aquatic food webs, consumers, such as daphnids and copepods, differ regarding their accumulation of polyunsaturated fatty acids (PUFAs). We tested if the accumulation of PUFAs in a seston size fraction containing different consumers and in Daphnia as a separate consumer is subject to seasonal changes in a large deep lake due to changes in the dietary PUFA supply and specific demands of different consumers. We found that the accumulation of arachidonic acid (ARA) in Daphnia increased from early summer to late summer and autumn. However, ARA requirements of Daphnia appeared to be constant throughout the year, because the accumulation of ARA increased when the dietary ARA supply decreased. In the size fraction .140 mm, we found an increased accumulation of docosahexaenoic acid (DHA) during late summer and autumn. These seasonal changes in DHA accumulation were linked to changes in the proportion of copepods in this size fraction, which may have increasingly accumulated DHA for active overwintering. We show that consumer-specific PUFA demands can result in seasonal changes in PUFA accumulation, which may influence the trophic transfer of PUFAs within the food web.

Accumulation of polyunsaturated fatty acids by cladocerans: effects of taxonomy, temperature and food

Summary1. Zooplankton are important in transferring dietary nutrients, including polyunsaturated fatty acids (PUFA), up through aquatic food webs.2. We tested the hypothesis that the taxonomic composition of zooplankton affects the retention and subsequent transfer of PUFA from upwards through the food web. Using laboratory experiments, we investigated dietary PUFA accumulation and bioconversion capacities of six cladoceran species (Ceriodaphnia sp., Daphnia longispina, Daphnia magna, Daphnia pulex, Scapholeberis mucronata and Simocephalus vetulus) fed on two diets (Scenedesmus obliquus and Cryptomonas sp.) that differed in their PUFA profiles. We performed experiments at two different temperatures (14 and 20 °C) to assess the role of temperature in the trophic transfer of PUFA.3. There was little variation in the concentrations of PUFA in these cladocerans which were controlled by dietary PUFA supply. Moreover, as expected, the concentrations of PUFA in all cladoceran species were higher at low temperature.4. However, even if the composition of PUFA in the cladoceran species generally corresponded to that in their diet, preferential accumulation of some PUFA was recorded in all these taxa. When fed on a highly unsaturated fatty acid‐deficient diet, all the cladocerans showed some ability to convert C18‐PUFA into arachidonic acid and eicosapentaenoic acid. Interspecific variation in the ability to accumulate and bioconvert PUFA in cladocerans was more pronounced at low temperature (14 °C) for both diets.5. Our results strongly suggest that in heterogeneous habitats with food partitioning between co‐existing cladocerans, foraging behaviour may affect the transfer of PUFA more strongly than interspecific variation in accumulating and/or bioconverting dietary PUFA.

204 FATTY ACID COMPOSITION OF FOLLICULAR FLUID FROM DAIRY COWS FED TROPICAL FORAGE-BASED DIETS SUPPLEMENTED WITH INCREASING LEVELS OF SOYBEAN OIL

Recent studies have shown that dietary supplementation with sources rich in polyunsaturated fatty acids (PUFA) can improve reproductive perfor-mance of lactating dairy cows. However, no studies have reported the fatty acids composition of follicular fluid (FF) from dairy cows fed high-PUFA diets. This study aimed to evaluate the fatty acids composition of FF from dairy cows fed tropical forage-based diets containing different levels of soybean oil (SO). Four multiparous Holstein-Zebu cows in midlactation (90 ± 25 days in milk) were assigned to 1 of the following dietary treatments (on a dry matter basis): (1) T1 (control) = no SO; (2) T2 = diets containing 1.5% of SO; (3) T3 = diets containing 3.0% of SO; and (4) T4 = diets containing 4.5% of SO. Diets were composed of chopped elephant grass and a concentrate mixture and the forage concentrate ratio was 55 : 45 (dry matter basis). The experimental design was a 4 × 4 Latin square in which each period lasted 21 days. All cows received intravaginal progesterone-releasing devices and follicular waves were synchronized with 0.5 mg of gonadorelin. The FF from dominant follicles was collected by transvaginal ultrasound-guided aspiration on the last day of each period (Day 21) and centrifuged (10000 × g, 1 min) and the supernatant was frozen at -80°C until fatty acid analysis. Extraction and methylation of fatty acids in FF were performed according to the 1-step simplified method described by Masood A et al. (2005 J. Lipid Res. 46, 2299-2305). The fatty acid profile from FF was determined by gas chromatography as described by Cruz-Hernandez C et al. (2007 J. Dairy Sci. 90, 3786-3801). Treatment effects were determined by regression analysis using the REG procedure of SAS (SAS Institute, Cary, NC, USA) and declared significant at P < 0.05. Nearly 30 different fatty acids (70% of the total area) were identified in the FF samples. The most representative fatty acids (% total area) for the 4 dietary treatments (T1, T2, T3, and T4, respectively) were C18 : 2 cis - 9, cis - 12 (19.8, 20.3, 16.1, and 24.2), C18 : 0 (17.7, 16.6, 19.5, and 16.8), C16 : 0 (12.2, 10.7, 11.3, and 17.8), and C18 :1 cis - 9 (6.5, 7.3, 5.5, and 7.7). Inclusion of SO in the diet linearly reduced (P < 0.05) concentrations of C16 : 1 cis - 9 (0.8, 0.7, 0.4, and 0.5) and C20 : 3 (1.2, 1.1, 0.5, and 0.7), but linearly increased (P < 0.05) concentrations of C18 : 1 trans - 11 (0.4, 0.4, 0.6, and 1.4), C18 : 1 cis - 11 (0.4, 0.5, 0.4, and 0.9), and C18 : 1 cis - 12 (0.2, 0.5, 0.5, and 0.7) isomers in FF. The increase in the concentration of C18 : 1 trans - 11 in FF from cows fed higher levels of SO was not accompanied by an increase in the proportion of CLA cis - 9, trans - 11 (0.9, 1.0, 0.7, and 0.9 for T1, T2, T3, and T4, respectively). It suggests the absence or low activity of A9-desaturase enzyme in the follicular environment, unlike that observed in the mammary gland. In general, our results indicate that fatty acid composition of follicular fluid from lactating dairy cows is sensitive to changes in dietary supply of PUFA. Financial support: FAPEMIG (CVZ1815/06).

The effect of dietary polyunsaturated fatty acids (PUFA) on infection with the nematodes Ostertagia ostertagi and Cooperia oncophora in calves

Diet-induced changes in the polyunsaturated fatty acid (PUFA) content of immune cells influences the immune phenotype that develops following infection. The aim of this study was to examine the effect of manipulating dietary PUFA supply on tissue fatty acids composition and immunity to a mixed infection with an abomasal and an intestinal nematode parasite in calves. Calves ( n = 24) were allocated into two treatment groups and fed 25 g/day of either fish oil (n-3 group) or a binary mixture of palm/rapeseed oil (normal group) as a supplement in milk replacer. Within each treatment group eight calves were infected with 2000 L3 Ostertagia ostertagi and Cooperia oncophora, three times per week for 8 weeks, the remaining calves were pair-fed uninfected controls. Faecal egg counts (FEC) were carried out twice weekly. At slaughter, the whole gut was removed intact for worm counts and tissue samples were taken for fatty acid analysis. Samples of abomasum, duodenum and mid-gut were also collected for immunohistological analysis. FEC were not significantly influenced by oil supplement but tended to remain higher in the palm/rapeseed oil-fed group (normal infected). The number of intestinal immature worms was significantly ( p < 0.05) higher in the n-3 group. Mucosal mast cell (MMC) and eosinophil numbers were significantly increased ( p < 0.05) by infection and were significantly lower ( p < 0.05) in the intestinal tissue of the fish oil supplemented and infected group (n-3 infected group). These results suggest that feeding an n-3 PUFA-rich supplement (fish oil) can influence cellular mediators of immunity to nematode infection. This is the first report of the establishment of patency and the subsequent development of immunity to a mixed infection with O. ostertagi and C. oncophora in calves undergoing early rumen development. The trend in the FEC, MMC and eosinophil numbers in the n-3 group suggests that decreasing the dietary n-6/n-3 PUFA ratio may be a worthwhile immunonutritional strategy for potentiating the immune response to nematode parasite infection in the calf.

Effect of dietary conjugated linoleic acids on the distribution of fatty acids in serum lipoprotein fractions and different tissues of growing pigs.

The effect of conjugated linoleic acid (CLA) on blood lipids [total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triacylglycerols (TAG)] and the fatty acid distribution of the lipoprotein fractions, backfat, muscle fat, and liver lipids were examined in an experiment with two groups of 40 pigs [Pietrain x (Landrace x Large White)] each. The 20 female and 20 male castrated pigs of each group were fed with isoenergetic and isonitrogenous diets supplemented with either 20 g/kg rapeseed oil (control) or 20 g/kg CLA-TAG. The CLA preparation contained 54.2% pure CLA consisting of approximately two-thirds cis,trans/trans,cis-isomers and one-third trans,trans-isomers. The fatty acids of lipoproteins, backfat, muscle lipids and liver lipids were analysed by gas chromatograph (GC). CLA supplementation did not significantly influence blood lipids and the LDL to HDL ratio. In the CLA-fed pigs the very low-density lipoprotein (VLDL) contained higher saturated fatty acid (SFA) concentrations at the cost of the monounsaturated fatty acids (MUFA). The percentage of polyunsaturated fatty acids (PUFA) remained unchanged. The highest CLA content was analysed in VLDL (4.00%) followed by LDL (2.78%) and HDL (1.45%). The ratio of cis,cis to trans,trans isomers increased from VLDL over LDL to HDL. The content of SFA, probably in backfat and muscle lipids, increased whereas the part of MUFA decreased as a result of reduced Delta9-desaturase activity. The percentage of PUFA (without CLA) was higher in backfat of the control group in accordance with the dietary PUFA supply. This shift in the fatty acid distribution was not observed in the liver lipids. In all the three tissues analysed, the CLA-fed pigs had a significantly increased CLA content: the highest increase was in the backfat (5.65%), followed by liver lipids (2.41%), and muscle lipids (1.47%). An isomer-specific accumulation was observed for cis,cis-CLA isomers in muscle, and for trans,trans-CLA isomers in backfat. We conclude that CLA supplementation results in a higher SFA content in backfat and muscle lipids but not in liver lipids. There is a discrimination of the trans-10, cis-12 isomer and the trans,trans isomers in the formation of the cell membranes.

FATTY ACIDS, LIPIDS, AND CYTOCHROME P-450 MONOOXYGENASE IN HEPATIC MICROSOMES OF MINKS FED FISH-BASED DIETS AND EXPOSED TO AROCLOR 1242

Minks were fed different fish-based diets and exposed to 1 mg/d of the commercial polychlorinated biphenyl (PCB) mixture Aroclor 1242 for 4 wk (November-December 1995) or 21 wk (July-December 1998). In all the dietary groups, the PCBs increased hepatic phospholipid (PL) content. No significant increase was detected in hepatic triacylglycerols (TGs). In the minks fed the different fish diets, the PCBs caused qualitatively and quantitatively different changes in the microsomal fatty acids. In the minks that were fed a diet rich in fat and low in polyunsaturated fatty acids (PUFAs), the PCBs increased the percentage of oleic acid (18:1 n -9, characteristic of the storage TGs) at the expense of n -3 PUFAs. This seemed to be due to inclusions of TGs in the membrane fragments and partly due to incorporation of TG-derived fatty acids into the membrane PLs. In addition, significant decrease of PUFAs was detected also in the hepatic TGs. The concomitant decrease in the concentrations of hepatic vitamin E suggested that lipid oxidation may also contribute to the decrease of the PUFAs. In the liver of the minks fed a low-fat but PUFA- and vitamin E-rich diet, the fatty acid changes due to the PCBs (the 21-wk exposure) remained small but the cytochrome P-450 system was significantly activated. In the minks fed Baltic herring (rich in organochlorines via the foodweb), the cytosolic glutathione S -transferase (GST) activity, levels of microsomal thiobarbituric acid-reactive substances (TBARS), and hepatic PLs were significantly elevated. In conclusion, in the mink the microsomal fatty acid changes were not directly connected with the ethoxyresorufin O -deethylase (EROD) activity or P-450 expression. Apparently, the PCBs produced definite fatty acid changes only in certain lipid matrices of tissue. In addition, a rich dietary supply of PUFAs and vitamin E may prevent these changes, even in a long-term subchronic exposure.