Neuronal depletion of omega-3 fatty acids induces flax seed dietary self-selection in the rat
Neuronal depletion of omega-3 fatty acids induces flax seed dietary self-selection in the rat
Year: 2009
Authors: Dunlap, S. Heinrichs, S.C.
Publication Name: Brain Research
Publication Details: Volume 1250; 113 – 119.
Abstract:
The impact of essential dietary fatty acid deficiency on self-selection of fatty acid enriched foods is little studied in spite of widespread health promotion claims for fatty acid supplemented diets. Accordingly, the present studies investigated the consequences of consumption over four weeks of omega-3 fatty acid replete and deficient diets on dietary fatty acid self-selection and brain lipid composition in rats. Dietary omega-3 fatty acid deficiency produced correspondingly low levels (50 to 55 % decrease) of omega-3 fatty acids in the forebrain relative to rats consuming an omega-3 fatty acid replete diet. The state of omega-3 fatty acid deficiency generated a robust preference for consumption of an omega-3 fatty acid replete diet. Moreover, omega-3 fatty acid self-selection developed slowly and was not present in rats maintained on laboratory chow diet suggesting that post-ingestive nutritional cues, rather than taste, odor or texture cues, were employed in guiding the preference for the omega-3 fatty acid enriched diet. These results provide evidence for the ability of rats with declining brain levels of omega-3 fatty acids to detect a dietary deficiency of this essential class of lipids and to identify and consume a food source capable of restoring fatty acid repletion. (Author's abstract)
Neurotransmission in the brain relies on dynamic flexibility of ion channels embedded in membranes, and thus neurons composed of membranes deficient in polyunsaturated fatty acids exhibit signaling abnormalities. Dietary polyunsaturated fatty acid deprivation in mice impairs performance in habituation and spatial learning tasks relative to mice maintained on an omega-3 replete diet. Low levels of omega-3 fatty acids has been implicated in susceptibility to psychological stress in human experimental trials. Few studies have explored the consequences of essential brain fatty acid levels on intake of fatty acid-containing foods. This study examined whether animals consuming an omega-3 deficient diet sense the resulting nutritional deficiency and exhibit the appropriate appetitive coping response. The self-selection of omega-3 fatty acid foods requires explicit experimental demonstration in order to bolster the claims assigning important neurodevelopmental and neurobiological functions to polyunsaturated fatty acids. It was therefore hypothesized that rats fed a diet deficient in omega-3 fatty acids would exhibit lower levels of omega-3 fatty acids, and an increased ratio of omega-6 fatty acids to omega-3 fatty acids, in neural tissue than rats fed an omega-3 fatty acid replete diet. It was further hypothesized that chronically deficient rats would develop a preference for a novel, omega-3 replete food relative to a novel, omega-3 deficient food. The results provide evidence for an acquired hunger for omega-3 fatty acids. Here rats maintained on an omega-3 deficient diet learned to select a novel food containing omega-3 fatty acids over repeated exposures to this novel food. It is hypothesized that consumption of small amounts of the omega-3 replete diet exerted a beneficial post-ingestive effect in rats maintained previously on an omega-3 deficient diet and that this perceived nutritional value was the basis for enhanced consumption of the omega-3 replete diet during the third preference test. This preference for omega-3 fatty acid replete diet among omega-3 fatty acid deficient rats was enduring and reproducible since it was also expressed during a fourth dietary preference test conducted over the 24 h period following the third one hour preference test. Omega-3 fatty acid deficient rats exhibited significantly lower levels of eicosapentaenoic acid and docosapentaenoic acid, compared to rats consuming the omega-3 fatty acid replete diet. The present results indicate that fully mature rodents are able to sense nutritional fatty acid deficiencies imposed over four weeks of deficient diet consumption and respond adaptively by expressing a neophilic preference for a fatty acid replete alternative diet in a one-trial learning context, that is without the benefit of experience arising from a prior deficiency/repletion cycle. The neural mechanism for dietary self-selection of omega-3 fatty acids may involve the ratio of omega-3 to omega-6 fatty acids which influences various aspects of serotoninergic and catecholaminergic neurotransmission. Further studies are required in order to elucidate the precise brain mechanisms for detecting and acting upon essential fatty acid deficiency. (Editor's comments)
Neurotransmission in the brain relies on dynamic flexibility of ion channels embedded in membranes, and thus neurons composed of membranes deficient in polyunsaturated fatty acids exhibit signaling abnormalities. Dietary polyunsaturated fatty acid deprivation in mice impairs performance in habituation and spatial learning tasks relative to mice maintained on an omega-3 replete diet. Low levels of omega-3 fatty acids has been implicated in susceptibility to psychological stress in human experimental trials. Few studies have explored the consequences of essential brain fatty acid levels on intake of fatty acid-containing foods. This study examined whether animals consuming an omega-3 deficient diet sense the resulting nutritional deficiency and exhibit the appropriate appetitive coping response. The self-selection of omega-3 fatty acid foods requires explicit experimental demonstration in order to bolster the claims assigning important neurodevelopmental and neurobiological functions to polyunsaturated fatty acids. It was therefore hypothesized that rats fed a diet deficient in omega-3 fatty acids would exhibit lower levels of omega-3 fatty acids, and an increased ratio of omega-6 fatty acids to omega-3 fatty acids, in neural tissue than rats fed an omega-3 fatty acid replete diet. It was further hypothesized that chronically deficient rats would develop a preference for a novel, omega-3 replete food relative to a novel, omega-3 deficient food. The results provide evidence for an acquired hunger for omega-3 fatty acids. Here rats maintained on an omega-3 deficient diet learned to select a novel food containing omega-3 fatty acids over repeated exposures to this novel food. It is hypothesized that consumption of small amounts of the omega-3 replete diet exerted a beneficial post-ingestive effect in rats maintained previously on an omega-3 deficient diet and that this perceived nutritional value was the basis for enhanced consumption of the omega-3 replete diet during the third preference test. This preference for omega-3 fatty acid replete diet among omega-3 fatty acid deficient rats was enduring and reproducible since it was also expressed during a fourth dietary preference test conducted over the 24 h period following the third one hour preference test. Omega-3 fatty acid deficient rats exhibited significantly lower levels of eicosapentaenoic acid and docosapentaenoic acid, compared to rats consuming the omega-3 fatty acid replete diet. The present results indicate that fully mature rodents are able to sense nutritional fatty acid deficiencies imposed over four weeks of deficient diet consumption and respond adaptively by expressing a neophilic preference for a fatty acid replete alternative diet in a one-trial learning context, that is without the benefit of experience arising from a prior deficiency/repletion cycle. The neural mechanism for dietary self-selection of omega-3 fatty acids may involve the ratio of omega-3 to omega-6 fatty acids which influences various aspects of serotoninergic and catecholaminergic neurotransmission. Further studies are required in order to elucidate the precise brain mechanisms for detecting and acting upon essential fatty acid deficiency. (Editor's comments)
