Food for Mood: Relevance of Nutritional Omega-3 Fatty Acids for Depression and Anxiety

Abstract

The central nervous system (CNS) has the highest concentration of lipids in the organism after adipose tissue. Among these lipids, the brain is particularly enriched with polyunsaturated fatty acids (PUFAs) represented by the omega-6 (ω6) and omega-3 (ω3) series. These PUFAs include arachidonic acid (AA) and docosahexaenoic acid (DHA), respectively. PUFAs have received substantial attention as being relevant to many brain diseases, including anxiety and depression. This review addresses an important question in the area of nutritional neuroscience regarding the importance of ω3 PUFAs in the prevention and/or treatment of neuropsychiatric diseases, mainly depression and anxiety. In particular, it focuses on clinical and experimental data linking dietary intake of ω3 PUFAs and depression or anxiety. In particular, we will discuss recent experimental data highlighting how ω3 PUFAs can modulate neurobiological processes involved in the pathophysiology of anxiety and depression. Potential mechanisms involved in the neuroprotective and corrective activity of ω3 PUFAs in the brain are discussed, in particular the sensing activity of free fatty acid receptors and the activity of the PUFAs-derived endocannabinoid system and the hypothalamic-pituitary-adrenal axis.

Keywords: DHA; HPA axis; anxiety; depression; endocannabinoids; mood disorders; nutrient sensing; omega-3 fatty acid.

FIGURE 1

Long-chain PUFAs synthesis. Essential fatty acids precursors of n-6 and n-3 PUFAs are provided by food. Once in the livers, they are metabolized into long-chain PUFAs using a series of desaturations and elongation machinery. The newly synthetized long-chain n-6 PUFAs are AA (20:4n-6) and DPA (22:5n-6) and the long-chain n-3 PUFAs are DHA (22:6n-3) and DPA (22:5n-3).

FIGURE 2

PUFAs are key actors in the regulation of endocannabinoid system. Endocannabinoids are signaling lipids produced from membrane long-chain fatty acid in response to neuronal activity that bind the G-protein-coupled receptor (GPCR) CB1R. The two principal eCBs, AEA and 2-AG, are AA-derived metabolites while DHEA derived from the DHA. eCBs are released into the synaptic cleft and then bind the CB1R on the presynaptic neuron. Activation of CB1R inhibits adenylyl cyclase (AC) activity leading to a subsequent reduction in the cyclic adenosine monophosphate (cAMP) cascade, augmentation of potassium channels, and inhibition of subsequent calcium influx via calcium channels. Consequently, the activation of the CB1R inhibits the release of both excitatory (glutamate) and inhibitory (GABA) neurotransmitters from the presynaptic neuron and decreases synaptic plasticity. The stimulation of CB1R by CB agonists (THC, WIN55,212-2, and CP-55940) or eCBs also activate MAPK signaling pathway. Both eCB-dependent plasticity and CB1R-dependent signaling pathway in brain areas involved in mood-regulation are altered in mice that chronically fed an omega-3 deficient diet.