Biochemical and functional effects of prenatal and postnatal ω3 fatty acid deficiency on retina and brain in rhesus monkeys

Docosahexaenoic acid [22.6ω3; 22:6(4,7,10,13,16,19)] is the major polyunsaturated fatty acid in the photoreceptor membranes of the retina and in cerebral gray matter. It must be obtained either from the diet or by synthesis from other ω3 fatty acids, chiefly α-linolenic acid (18:3ω3). We tested the effect of dietary ω3 fatty acid deprivation during gestation and postnatal development upon the fatty acid composition of the retina and cerebral cortex and upon visual function. Rhesus monkeys (Macaca mulatta) were fed semipurified diets very low in 18:3ω3 throughout pregnancy, and their infants received a similar diet from birth. A control group of females and their infants received a semipurified diet supplying ample 18:3ω3. In near-term fetuses and newborn infants of the deficient group, the 22:6ω3 content of phosphatidylethanolamine was one-half of control values in the retina and one-fourth in cerebral cortex. By 22 months of age, the content of 22:6ω3 in these tissues approximately doubled in control monkeys, but it failed to increase in the deficient group. Low levels of 22:6ω3 in the deficient animals' tissues were accompanied by a compensatory increase in longer-chain ω6 fatty acids, particularly 22:5ω6. Functionally, the deficient animals had subnormal visual acuity at 4-12 weeks of age and prolonged recovery time of the dark-adapted electroretinogram after a saturating flash. Abnormally low levels of 22:6ω3 may produce alterations in the biophysical properties of photoreceptor and neural membranes that may underlie these functional impairments. The results of this study suggest that dietary ω3 fatty acids are essential for normal prenatal and postnatal development of the retina and brain.