Effect of linoleic acid-rich infant formula feeding on brain synaptosomal lipid accretion and enzyme thermotropic behavior in the piglet

The effects of a vegetable oil-based infant formula, virtually devoid of n-6 and n-3 long chain polyenoid fatty acids (LCP) and high in 18:2(n-6) and 18:2(n-6)/18:3(n-3) ratio, on brain synaptosome lipid composition and enzyme thermotropic behavior were studied in neonatal piglets. Term gestation piglets were fed either sow milk (SMF) or formula (FF) from birth for 5, 10, 15, or 25 days. Synaptosomal cholesterol, total lipid phosphorus, and phospholipid class composition did not differ between SMF and FF piglets. Synaptosomal fatty acid composition, however, was influenced by diet. The proportion of n-3 LCP, especially 22:6(n-3), was decreased, while the n-6 LCP, especially 22:4(n-6) and 22:5(n-6), were increased in FF compared to SMF piglets. These diet-related changes were most pronounced in the ethanolamine glycerophospholipid fraction and increased with the duration of feeding. FF thus reversed an apparent developmental increase in the synaptosomal n-3/n-6 LCP ratio. The monoene content, especially 18:1, was also reduced in the synaptosomes of FF compared to SMF pigs. FF had no effect on the activity of synaptosomal acetylcholinesterase. However, higher transition temperatures for this enzyme, indicating decreased membrane fluidity, were found in the FF compared to SMF piglets. The data suggest that exclusive feeding of proprietary formulae, devoid of LCP and high in 18:2(n-6) and/or the 18:2 (n-6)/18:3(n-3) ratio, may compromise normal fatty acid accretion and physical properties of brain synaptosomal membranes.