PharmacoNutrition Reviewed

Source: Aging Cell (2007), 6: 15-25
Article Type: Original Contribution
Authors: TG Valencak, T Ruf

Image taken from:
http://www.macvillage.de/blog/wp-content/uploads/2006/07/dali_zeit.jpg

Omega-3 fatty acids (n-3) are generally considered as health-beneficial (see also post discussed yesterday). When talking about the lifespan of mammals, however, n-3 fatty acids seem to hamper longevity. The reason for this correlation has been linked to:
• the high susceptibility of polyunsaturated fatty acids (PUFA; n-3, n-6) to oxidation
• the boost in basal metabolic rate (BMC) in the presence of PUFA, e.g. by up-regulating the activity of membrane-associated proteins
These effects have been summarized in the ‘membrane pacemaker theory of aging’: PUFA (up) –> BMR (up) –> longevity (down).

After correcting for body weight and phylogenetic effects, Valencak & Ruf found a clear correlation between the ratio of n3:n6 in muscle and maximum lifespan (MLS), based on the analysis of 42 mammalian species. Noteworthy, MLS was unrelated to docosahexaenoic (DHA, n-3) content, total membrane unsaturation as well as BMR, thus questioning the ‘membrane pacemaker theory of aging’.
Does this mean now that we should avoid consuming PUFAs, particularly n-3?
I would say no, because the current recommendation (see also Simopoulos, 2006) to increase dietary n-3 intake is largely based on the discrepancy in the composition of ingested dietary fat between western societies (n-3:n-6 = 1:15) and our hunting & gathering ancestors (n-3:n-6 = 1:1). Hence, the risk of reducing your (maximum) lifespan by consuming n-3-rich plant and animal foods (which consequently will enhance your n-3:n-6 ratio) is rather small.

Source: Critical Care Medicine (2007), 35: 544-554
Article Type: Original Contribution
Authors: MB Schaefer, J Ott, A Mohr, MH B, A Grosz, N Weissmann, S Ishii, F Grimminger, W Seeger K Mayer

Image taken from: http://doreen.mkbmemorial.com/NF/photos/ICU.JPG

Most intensive care patients are sooner or later affected by the systemic inflammatory response syndrome (SIRS). Hallmark of SIRS is the elevated production of certain eicosanoids possessing strong pro-inflammatory properties. Eicosanoids are derived from its precursor arachidonic acid, an omega-6 (n-6) fatty acid commonly found in biological membranes.
Arachidonic acid (20:4, n-6) in turn can be synthesizes from linoleic acid (18:2, n-6), the main fatty acid found in soy oil-based lipid emulsions, such as Lipoven (Fresenius Kabi, Germany). In contrast, cold water fish are rich in omega-3 fatty acids (especially eicosapentaenoic and docosahexaenoic acid), which are generally considered to show anti-inflammatory activity.
In their recent article, Schaefer et al. compare in a model of murine acute lung injury the inflammatory effect of Lipoven with that of the n-3-rich lipid formulation Omegaven (Fresenius Kabi, Germany). In agreement with previous reports, Lipoven promotes the production of pro-inflammatory biomarkers whereas the application of Omegaven leads to opposite effects. Here it is important to note that the impact of both formulations depends on the experimental design, i.e. the permanent infusion of the mice with the lipid emulsions. The authors point out that it is questionable whether the same effects could be provoked by oral intake of either lipid formulation.
Mechanistically, the article provides an interesting insight in the regulation of inflammation. Platelet-activating factor (PAF)-receptor knock-out mice (-/-) showed an inflammatory response comparable to those of wild type mice. However, neither Lipoven nor Omegaven were able to module the production of inflammatory biomarkers in PAF -/-, suggesting that both PAF and PAF-receptor are important for communicating the molecular signals exerted by n-3- and n-6.
In a nutshell, the administration of lipid emulsions might not only be means to supply the critically ill with enough energy, but also help to modulate the immune system towards pro- or anti-inflammatory response.

Another interesting report on the effect of n-3 in ICU patients can be found on the webpage of the Children’s Hospital Boston.