Background – Brain tissue contains large quantity of n-3 fatty acids, particularly decosahexaenoic acid (DHA). DHA is derived from its precursor alpha-linolenic acid, a dietary essential n-3 fatty acid, or it can be obtained directly from dietary sources. Dietary deficiency of n-3 fatty acids leads to impairment of spatial learning and memory in experimental animals, and dietary supplementation with DHA appears to improve mental development in human infants. How DHA influences brain memory function is not fully understood although a number of potential mechanisms have been proposed. One of the possible mechanisms is to affect the synthesis of neurotrophic factors in the brain.
Objectives – The present study aimed to investigate the effect of dietary n-3 fatty acid deficiency on brain-derived neurotrophic factor (BDNF) gene expression and spatial learning performance in young rats.
Design – Sprague Dawley rats were fed on an n-3 fatty acid deficient diet for three generations. The rat pups of the third generation were tested for their spatial learning performance using Morris Water Maze at four and ten weeks of age. At the end of the behaviour test, the rat pups were killed and the brain tissue was dissected for measurement of BDNF and its mRNA levels using ELISA and real-time PCR techniques respectively.
Results – Dietary n-3 fatty acid deficiency led to a marked depletion of DHA in the brain tissue. The concentration of BDNF mRNA in the cerebral cortex and the hippocampus was significantly lower in n-3 deficient rat pups than in the control counterparts (P<0.05), although BDNF level in the brain tissue did significantly differ between the control and n-3 deficient animals. In comparison with the control animals, n-3 deficient rats performed significantly poorer in Morris Water Maze task (P<0.05), and the effect was particularly evident at four weeks of age. Conclusion – Dietary n-3 fatty acid deficiency leads to the impairment of spatial learning and memory performance and to a reduction of BDNF gene expression in the brain, the latter is a neurotrophic factor known to be involved in the memory function of the brain.