An endogenous regulator of inflammation, resolvin E1, modulates osteoclast differentiation and bone resorption

Background and purpose: The inflammation-resolving lipid mediator resolvin E1 (RvE1) effectively stops inflammation-induced bone loss in vivo in experimental periodontitis. It was of interest to determine whether RvE1 has direct actions on osteoclast (OC) development and bone resorption. Experimental approach: Primary OC cultures derived from mouse bone marrow were treated with RvE1 and analysed for OC differentiation, cell survival and bone substrate resorption. Receptor binding was measured using radiolabelled RvE1. Nuclear factor (NF)-kappa B activation and Akt phosphorylation were determined with western blotting. Lipid mediator production was assessed with liquid chromatography tandem mass spectrometry. Key results: OC growth and resorption pit formation were markedly decreased in the presence of RvE1. OC differentiation was inhibited by RvE1 as demonstrated by decreased number of multinuclear OC, a delay in the time course of OC development and attenuation of receptor activator of NF-kappa B ligand-induced nuclear translocation of the p50 subunit of NF-kappa B. OC survival and apoptosis were not altered by RvE1. Messenger RNA for both receptors of RvE1, ChemR23 and BLT(1) is expressed in OC cultures. Leukotriene B(4) (LTB(4)) competed with [(3)H] RvE1 binding on OC cell membrane preparations, and the LTB(4) antagonist U75302 prevented RvE1 inhibition of OC growth, indicating that BLT(1) mediates RvE1 actions on OC. Primary OC synthesized the RvE1 precursor 18R-hydroxy-eicosapentaenoic acid and LTB(4). Co-incubation of OC with peripheral blood neutrophils resulted in transcellular RvE1 biosynthesis. Conclusions and implications: These results indicate that RvE1 inhibits OC growth and bone resorption by interfering with OC differentiation. The bone-sparing actions of RvE1 are in addition to inflammation resolution, a direct action in bone remodelling.

Anti-inflammatory effect of parenteral fish oil lipid emulsion on human activated mononuclear leukocytes

Background & aim: To compare the effect of fish oil-based (FO) lipid emulsions (LE) for parenteral administration with standard LE and a new FO containing LE composed of four different oils on the antigen presentation and inflammatory variables. Methods: Phytohemagglutinin (PHA) activated human mononuclear leukocytes were cultured with different LE - Control: without LE; SO: soybean oil; SO/FO: soybean and FO (4:1); MCT/SO: medium chain triglycerides and SO (1:1); MCT/SO/FO: MCT/SO and FO (4:1) and SMOF: a new LE containing FO. Cytokine production was evaluated by ELISA, the expression of antigen-presenting and co-stimulatory surface molecules were analyzed by flow cytometry and lymphocyte proliferation was assessed by H(3)-Thymidine incorporation, after tetanus toxoid-induced activation. Results: All LE decreased the HLA-DR and increased CD28 and CD152 expression on monocytes/macrophages and lymphocytes surface (p < 0.05). SO/FO and MCT/SO/FO decreased lymphocyte proliferation (p<0.05). All LE decreased IL-2 product ion, but this effect was enhanced with MCT/SO/FO and SMOF (p < 0.05). MCT/SOTO decreased IL-6 and increased IL-10, whereas SO had the opposite effect (p < 0.05). Conclusion: FO LE inhibited lymphocyte proliferation and had an anti-inflammatory effect. These effects seem to be enhanced when FO is mixed with MCT/SO. SMOF had a neutral impact on lymphocyte proliferation and IL-6 and IL-10 production.

Effect of crude oil extracts from trout offal as a replacement for fish oil in the diets of the Australian native fish Murray cod Maccullochella peelii peelii

The efficacy of trout oil (TO), extracted from trout offal from the aquaculture industry, was evaluated in juvenile Murray cod Maccullochella peelii peelii (25.4-0.81 g) diets in an experiment conducted over 60 days at 23.7-0.8 °C. Five isonitrogenous (48% protein), isolipidic (16%) and isoenergetic (21.8 kJ gm1) diets, in which the fish oil fraction was replaced in increments of 25% (0-100%), were used. The best growth and feed efficiency was observed in fish fed diets containing 50-75% TO. The relationship of specific growth rate (SGR), food conversion ratio (FCR) and protein efficiency ratio (PER) to the amount of TO in the diets was described in each case by second-order polynomial equations (P<0.05), which were: SGR=-0.44TO2+0.52TO+1.23 (r2=0.90, P<0.05); FCR=0.53TO2-0.64TO+1.21 (r2=0.95, P<0.05); and PER=-0.73TO2+0.90TO+1.54 (r2=0.90, P<0.05). Significant differences in carcass and muscle proximate compositions were noted among the different dietary treatments. Less lipid was found in muscle than in carcass. The fatty acids found in highest amounts in Murray cod, irrespective of the dietary treatment, were palmitic acid (16:0), oleic acid (18:1n-9), linoleic acid (18:2n-6) and eicosapentaenoic acid (20:5n-3). The fatty acid composition of the muscle reflected that of the diets. Both the n-6 fatty acid content and the n-3 to n-6 ratio were significantly (P<0.05) related to growth parameters, the relationships being as follows. Percentage of n-6 in diet (X) to SGR and FCR: SGR=-0.12X2+3.96X-32.51 (r2=0.96) and FCR=0.13X2-4.47X+39.39 (r2=0.98); and n-3:n-6 ratio (Z) to SGR, FCR, PER: SGR=-2.02Z2+5.01Z-1.74 (r2=0.88), FCR=2.31Z2-5.70Z+4.54 (r2=0.93) and PER=-3.12Z2-7.56Z+2.80 (r2=0.88) respectively. It is evident from this study that TO could be used effectively in Murray cod diets, and that an n-3:n-6 ratio of 1.2 results in the best growth performance in Murray cod.

Lipid characterisation and distribution in the fillet of the farmed Australian native fish, Murray cod (Maccullochella peelii peelii)

The objective of this study was to determine the distribution pattern of lipids and fatty acids in different tissues of farmed Murray cod (Maccullochella peelii peelii).

Differences in lipid content were found amongst different portions of the fillet, being lowest in the dorsal/cranial portion (P1) and highest in the more ventral/caudal portion (P8) (P < 0.05). The latter also recorded the highest amount of monounsaturated fatty acid (MUFA) and the lowest in polyunsaturated fatty acids (PUFA), arachidonic acid, 20:4n − 6 (ArA), docosahexaenoic acid, 22:6n − 3, (DHA) and the n3/n6 ratio. In general, lipid content in the different fillet portions was inversely correlated to PUFA and directly to MUFA. Contents of saturated fatty acids (SFA) and eicosapentaenoic acid, 20:5n − 3 (EPA) did not show any discernible trends in the different fillet portions, while significant differences in contents of DHA and ArA were observed. This study shows that lipid deposition in Murray cod varies markedly and that different fatty acids are deposited differently throughout the fillet.

Low dose supplementation with two different marine oils does not reduce pro-inflammatory eicosanoids and cytokines in vivo

In view of the reported potential anti-inflammatory activity of the New Zealand green lipped mussel (NZGLM), we aimed to compare the effect of low dose marine oil supplementation, from mussels and fish, in reducing blood markers of inflammation. Thirty apparently healthy males and females were recruited from the general public in Melbourne, Australia to participate in a double blind, randomised, parallel intervention study. Subjects were consuming approximately 73 mg of omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) daily in their background diet prior to the commencement of the intervention. Subjects were randomly assigned to consume either 2 mL/day of the NZGLM oil preparation (mixed with olive oil and dl-alpha-tocopherol) or fish oil preparation (also mixed with olive oil and dl-alpha-tocopherol) for six weeks. Two mL of the oils contained 241 mg and 181 mg of n-3 LCPUFA, respectively. Neutrophil phospholipid fatty acids, serum thromboxane B2 (TXB2), stimulated monocyte production of prostaglandin E2 (PGE2), interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNFalpha) were measured. During the intervention, the total intakes of n-3 LCPUFA from the background diet and the supplements were 199 mg/d and 173 mg/day for the NZGLM and FO groups, respectively. Following six weeks of supplementation, both groups showed a small, but significant increase in neutrophil phospholipid proportion of eicosapentaenoic acid. The NZGLM group also showed a significant increase in docosahexaenoic acid levels. There were no significant changes with time or treatment for TXB2, PGE2, IL-1 beta or TNFalpha. This study showed that low dose supplementation with n-3 LCPUFA from two different marine oil preparations showed no difference in inflammatory markers in this group of healthy individuals. Further studies are warranted including dose response trials and studies in populations with inflammatory conditions.

Lipid characterisation of different tissues and fillet portions of intensively farmed Murray Cod Maccullochella peelii peelii

Although many studies have focused on the lipid and fatty acids composition of farmed fish, no many have investigated their deposition pattern in different portions of the fillet. Previous studies, mainly on salmonids, have shown that lipids distribution varies greatly depending on the species, portion and type of muscle, but nevertheless, there is not accurate description of its deposition pattern in many fish, in particular in warm water, freshwater carnivorous species. Murray cod is the largest Australian native freshwater carnivorous fish and supports a small but well established and fast growing industry. The objective of this study was therefore to determine if there was any difference in lipid and fatty acid in different tissues such as muscle, liver and perivisceral fat and in different portions of the fillet of farmed Murray cod.

Three size fish (small, medium and large), all fed the same commercial diet, were selected from a commercial intensive farm. The left fillet of each fish was sectioned into nine portions, according to muscle lines and main anatomical features. The nine portions as well as whole right fillet, liver and perivisceral fat were analysed for proximate and fatty acid composition (Table 1).

Differences in lipid content were found amongst different portions of the fillet, with the dorsal/cranial portion (P1) recording the lowest and the more ventral/caudal portion (P8) recording the highest (P<0.05) value. The latter also recorded the highest amount of monounsaturated fatty acid (MUFA) and the lowest of polyunsaturated fatty acids (PUFA), arachidonic acid, 20:4n-6 (ArA), docosahexaenoic acid, 22:6n-3, (DHA) and n3/n6 ratio. In general, lipid content in the different fillet portions was inversely correlated to PUFA and directly to MUFA. Saturated fatty acid (SFA) and eicosapentaenoic acid, 20:5n-3 (EPA) did not show any discernible trend and were similar throughout, while significant differences of DHA and ArA content were observed. This study shows that lipid deposition in Murray cod varies remarkably and that different fatty acids are deposited at different rates. The results of this study show how different adjacent portions can be and therefore attention need to be paid when conducting chemical, nutritional and sensorial analyses on Murray cod.

Inhibition of platelet aggregation by omega-3 polyunsaturated fatty acids is gender specific — redefining platelet response to fish oils

Existence of gender differences in cardiovascular disease (CVD) following long-chain omega-3 polyunsaturated fatty acid (LCn-3 PUFA) supplementation have suggested that sex hormones play a role in cardio-protection. The objective of this study was to determine gender specific responses in the efficacy of LCn-3 PUFA to inhibit platelet aggregation in vitro. Blood was analyzed for collagen-induced platelet aggregation following pre-incubation with LCn-3 PUFA in healthy adults (n=42). Eicosapentaenoic acid (EPA) was significantly more effective in reducing platelet aggregation compared with docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). When grouped by gender, this differential pattern was followed in males only. In females, DHA, DPA and EPA were all equally effective. Between group analyses (LCn-3 PUFA vs. gender) showed that both DHA and DPA were significantly less effective in males compared with females. EPA was equally effective in reducing platelet aggregation in both groups. These findings show that significant gender differences exist in platelet aggregation in response to various LCn-3 PUFA treatments.

Effects of alternate phases of fish oil and vegetable oil-based diets in Murray cod

Fish oil (FO)- and canola oil (CO)-based diets were regularly alternated in a daily cycle (amCO: alternation of CO in the morning and FO in the afternoon, and pmCO: alternation of FO in the morning and CO in the afternoon) or in a series of weekly cycles (2W: alternation of 2 weeks on CO and 2 weeks on FO, 4W: alternation of 4 weeks on CO and 4 weeks on FO), over a 16-week period in juvenile Murray cod (Maccullochella peelii peelii). No significant differences were observed between any of the treatments in relation to the final weight. However, fish subjected to the 2W schedule were larger (P>0.05) than all other treatments (37.2 ± 0.30 vs. 34.3 ± 0.58 in the control treatment). Fish receiving the 2W treatment had a significantly lower total net disappearance of eicosapentaenoic acid 20:5n-3 (EPA) and docosahexaenoic acid 22:6n-3 (62.1% and 24.0% respectively) compared with the control treatment (fish continuously fed a blend of 50% FO and 50% CO). Likewise, Murray cod receiving the amCO daily schedule had a significantly lower total net disappearance of EPA in comparison with the CD and pmCO treatments. These data point towards the existence of cyclical mechanisms relative to fatty acid utilization/retention.

Biometric, nutritional and sensory characteristic modifications in farmed Murray cod (Maccullochella peelii peelii) during the purging process

Intensively farmed, market-size Murray cod (~ 600 g), were purged (transferred into a clean water system and starved) and sampled at three day intervals for a total of 18 days (D0, D3, D6, D9, D12, D15 and D18). Purged fish lost from 6% (D3) to 14% (D18) body weight, and the weight loss was highly correlated to the number of days of purging/starvation. Condition factor and Hepatosomatic Index decreased significantly (P < 0.05) only after 18 days of purging compared to the control (D0). Fillet lipid content (%) did not vary during the trial. Eicosapentaenoic acid (EPA: 20:5 n−3) decreased and docosapentaenoic acid (DPA: 22:5 n−3) increased (P < 0.05) during the trial, while docosahexaenoic acid (DHA: 22:6 n−3) did not show any significant variation. Purging contributed positively to the improvement of the volatile flavour compound composition, with a significant (P < 0.05) reduction in total volatile aldehydes and an increase in total volatile hydrocarbons. Since no major differences were found between samples during the last stages of the purging process (D12, D15 and D 18), it is possible to conclude that, under these experimental conditions, 12 days is the minimum duration to obtain an improvement in the volatile compound profile of intensively farmed Murray cod whilst keeping body weight loss to a minimum.

Fish oil replacement in starter, grow-out, and finishing feeds for farmed aquatic animals

As aquaculture production continues to grow, there will be an increased use of lipid resources (oils and fats) alternative to fish oil for feed production. The potential for the use of these alternatives varies depending on the feeds in which they are included according to the production phase of the animals to which they are being fed. In starter feeds, where rapid growth, high survival, and normal development are critical priorities, there will remain a need for the use of lipid resources high in omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). Fish in this starter phase have a critical requirement for the n-3 LC-PUFA docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), and fish oils remain the only cost-effective source of these nutrients in the volumes required. However, the greatest demand for lipids is in those diets for the grow-out phase. Most studies on alternative lipid use with animals in this part of the production phase show positive outcomes, in that there are few studies where all the added fish oil cannot be replaced. There are some species, however, where potential replacement levels are suggested to be more conservative, and a general substitution level in this production phase of 75% has been suggested. One of the key effects noted across the grow-out phase is that all alternatives affect the flesh fatty acid characteristics by reducing the level of n-3 LC-PUFA. This issue has provoked the concept of finisher diets, whereby a high n-3 LC-PUFA content diet is fed in order to restore the desired meat fatty acid profiles. Studies examining this concept have found that the tissue triacylglycerol fatty acids were greatly modified and responded in a simple dilution process to the added oil fatty acid composition, whereas the fatty acids of tissue phospholipids were less influenced by dietary fatty acid makeup.

Oxidation and stability of food grade fish oil : role of antioxidants

Oxidation of lipids containing unsaturated fatty acids is a common and complicated phenomenon. Volatile compounds generated during the oxidation of fish oil contribute to the unfavourable flavours and odours of the oil and the food products containing them. Although the initial mechanism of the oxidation seems simple, the mechanism and product mix become much more complicated and unpredictable during its progress, depending upon factors including the nature of the substrate and its environment. Oxidation of unsaturated fatty acids such as oleic, linoleic, and α-linolenic, predominantly from vegetable oils, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish or microbial oil, produce several types of flavour volatiles that affect the sensory properties of these oils. Antioxidants are commonly used to retard the oxidation and improve the quality of food-grade oils. This chapter will discuss mechanisms of lipid oxidation and methods to control lipid oxidation, including the use of antioxidants.

A short-term n-3 DPA supplementation study in humans

Purpose Despite the detailed knowledge of the absorption and incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into plasma lipids and red blood cells (RBC) in humans, very little is known about docosapentaenoic acid (DPA, 22:5 n-3). The aim of this study was to investigate the uptake and incorporation of pure DPA and EPA into human plasma and RBC lipids.

Methods Ten female participants received 8 g of pure DPA or pure EPA in randomized crossover double-blinded manner over a 7-day period. The placebo treatment was olive oil. Blood samples were collected at days zero, four and seven, following which the plasma and RBC were separated and used for the analysis of fatty acids.

Results Supplementation with DPA significantly increased the proportions of DPA in the plasma phospholipids (PL) (by twofold) and triacylglycerol (TAG) fractions (by 2.3-fold, day 4). DPA supplementation also significantly increased the proportions of EPA in TAG (by 3.1-fold, day 4) and cholesterol ester (CE) fractions (by 2.0-fold, day 7) and of DHA in TAG fraction (by 3.1-fold, day 4). DPA proportions in RBC PL did not change following supplementation. Supplementation with EPA significantly increased the proportion of EPA in the plasma CE and PL fractions, (both by 2.7-fold, day 4 and day 7) and in the RBC PL (by 1.9-fold, day 4 and day 7). EPA supplementation did not alter the proportions of DPA or DHA in any lipid fraction. These results showed that within day 4 of supplementation, DPA and EPA demonstrated different and specific incorporation patterns.

Conclusion The results of this short-term study suggest that DPA may act as a reservoir of the major long-chain n-3 fatty acids (LC n-3 PUFA) in humans.

Jumping on the omega-3 bandwagon : distinguishing the role of long-chain and short-chain omega-3 fatty acids

Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) are almost unanimously recognized for their health benefits, while only limited evidence of any health benefit is currently available specifically for the main precursor of these fatty acids, namely α-linolenic acid (ALA, 18:3n-3). However, both the n-3 LC-PUFA and the short-chain C18 PUFA (i.e., ALA) are commonly referred to as “omega-3” fatty acids, and it is difficult for consumers to recognize this difference. A current gap of many food labelling legislations worldwide allow products containing only ALA and without n-3 LC-PUFA to be marketed as “omega-3 source” and this misleading information can negatively impact the ability of consumers to choose more healthy diets. Within the context of the documented nutritional and health promoting roles of omega-3 fatty acids, we briefly review the different metabolic fates of dietary ALA and n-3 LC-PUFA. We also review food sources rich in n-3 LC-PUFA, some characteristics of LC-PUFA and current industry and regulatory trends. A further objective is to present a case for regulatory bodies to clearly distinguish food products containing only ALA from foods containing n-3 LC-PUFA. Such information, when available, would then avoid misleading information and empower consumers to make a more informed choice in their food purchasing behavior.