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Inflammatory processes are critical components of many illnesses, and dietary n-3 fatty acids have been shown to contribute to a reduction of the inflammatory status, both in in vivo and in vitro studies. The mechanisms underlying the modulation of inflammation are not completely understood, but it is clear that dietary n-3 fatty acids alter the eicosanoid metabolome profile, resulting in increased levels of n-3 fatty acid eicosanoids, whereas eicosanoids from other fatty acids are decreased. Until now, the anti-inflammatory properties of n-3 fatty acids had not been linked to an interaction with endocannabinoids/N-acyl ethanolamides (NAEs) levels before. This thesis describes a series of studies on the link between dietary fatty acids, endocannabinoids/NAEs, and inflammation.
Previous research indicated that dietary fatty acids alter the profile of endocannabinoids/NAEs rather than just affecting single compounds such as arachidonoyl ethanolamide (AEA) and 2-arachidonoyl glycerol (2-AG) as suggested before, and therefore a method based on liquid chromatography coupled to mass spectrometry (LC-MS/MS) to quantify a broad range of endocannabinoids/NAEs was developed. This method was used to demonstrate that n-3 fatty acids are converted to their endocannabinoid derivates by adipocytes in vitro. These n-3 derived NAEs, docosahexaenoyl ethanolamide (DHEA) and eicosapentaenoyl ethanolamide (EPEA), were shown to have anti-inflammatory properties in lipopolysaccharide (LPS)-stimulated adipocytes by reducing interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) excretion. Further studies showed that serum free fatty acid levels and plasma NAE levels are correlated under both fasting and post-prandial conditions in women, and demonstrated that plasma AEA and oleoyl ethanolamide (OEA) correlated with body mass index (BMI).
Considering the complexity of endocannabinoid and eicosanoid metabolism, it is likely that their concentrations are dynamic over time and tissue-specific during inflammation. So far, most studies had focused on limited numbers of endocannabinoids and eicosanoids in restricted numbers of tissues or plasma, and the effect of inflammation on DHEA and EPEA levels had not been studied before. Therefore, an animal study was conducted which investigated in detail the time-dependent effects of i.p. LPS on the levels of lipid derived mediators (endocannabinoids/NAEs and eicosanoids) in plasma, liver, ileum and adipose tissue in mice fed with a diet rich in fish oil. The results demonstrated that both DHEA and EPEA levels were increased after LPS treatment, but also time- and tissue dependent effects were observed. Based on these data, another study was performed which investigated the combined effect of different fish oil diets and inflammation on the profiles of endocannabinoids and eicosanoids using the same multi-compartment targeted lipidomics approach. The data indicated that that dietary n-3 fatty acids and inflammation alter both the endocannabinoid and eicosanoid metabolomes towards higher levels of n-3 derived metabolites at the expense of metabolites derived from other fatty acids. Multivariate data analysis revealed that under normal conditions the diet groups were primarily separated based on decreased levels of other than n-3 derived metabolites. However, during inflammation, the separation was primarily explained by increases in n-3 derived compounds. Finally, additional analyses demonstrated that plasma and erythrocytes contain significant levels of esterified NAEs. The esterified levels were approximately 20-60 fold higher than the free NAE levels, and their profiles resembles the free NAE profiles.
In conclusion, (dietary) n-3 fatty acids increased the levels of DHEA and EPEA, and these metabolites displayed anti-inflammatory properties. Although the n-3 fatty acids are likely to be converted to a variety of other metabolites, the work in this thesis suggests that ‘fish oil-derived’ endocannabinoids are a new link between fish oil and its anti-inflammatory properties. Further research is needed to relate nutrition-based modulation of endocannabinoid profiles to more specific effects on health and disease.
|Qualification||Doctor of Philosophy|
|Award date||24 Apr 2012|
|Place of Publication||S.l.|
|Publication status||Published - 2012|
- omega-3 fatty acids
- polyenoic fatty acids
- fish oils
- antiinflammatory properties
- antiinflammatory agents