Omega-3 fatty acids upregulate adult neurogenesis

Abstract

Omega-3 fatty acids play crucial roles in the development and function of the central nervous system. These components, which must be obtained from dietary sources, have been implicated in a variety of neurodevelopmental and psychiatric disorders. Furthermore, the presence of omega-6 fatty acids may interfere with omega-3 fatty acid metabolism. The present study investigated whether changes in dietary ratios of omega-3:omega-6 fatty acids influence neurogenesis in the lobster (Homarus americanus) brain where, as in many vertebrate species, neurogenesis persists throughout life. The factors that regulate adult neurogenesis are highly conserved among species, and the crustacean brain has been successfully utilized as a model for investigating this process. In this study, lobsters were fed one of three diets that differed in fatty acid content. These animals were subsequently incubated in 5-bromo-2'-deoxyuridine (BrdU) to detect cells in S-phase of the cell cycle. A quantitative analysis of the resulting BrdU-labeled cells in the projection neuron cluster in the brain shows that short-term augmentation of dietary omega-3 relative to omega-6 fatty acids results in significant increases in the numbers of S phase cells, and that the circadian pattern of neurogenesis is also altered. It is proposed that the ratio of omega-3:omega-6 fatty acids may alter neurogenesis via modulatory influences on membrane proteins, cytokines and/or neurotrophins.

Figure 1

The levels of neurogenesis in cluster 10 in the brains of lobsters fed UN, O3 or SP diet. Each histogram represents the mean of BrdU-labeled cell counts. Following a two-way repeated measures ANOVA (P<0.05), Holm-Sidak paired comparisons revealed significant differences in levels of neurogenesis between the UN vs. O3 and SP diets. Statistical similarity is indicated by the same letters (O3 and SP diets).

Figure 2

Mean counts and 95% confidence intervals of BrdU-labeled cells normalized to the average value for dusk within each diet treatment, for the different sampling times over a 24-hour period. There was a significant diet versus time interaction for cell count data, and thus the normalized ranked data were analyzed separately for each diet. Statistical similarity within the UN treatment is denoted by the same letters; there were no significant differences between time periods for the SP data. When lobsters are fed unenriched Artemia, cell proliferation is significantly greater at dusk than at any other time of the day. Cell proliferation between 09:30 and 12:30 averages 50% that of the dusk period, and all 95% confidence intervals are < 60%. When lobsters are fed the Spirulina enriched Artemia diet, cell proliferation during the day is relatively uniform, with only the dawn (05:30–08:30) and pre-dusk (13:30–16:30) time periods averaging 80% that of the dusk period.