Dietary fat composition and age affect synaptosomal and retinal phospholipid fatty acid composition in C57BL/6 mice

The purpose of this study was (i) to determine whether dietary fat-induced differences in neural and retinal membranes occur when dietary fat treatment is implemented in aged animals and (ii) to characterize the effect of long-term differences in dietary fat on neural and retinal membrane composition. For the first objective, young (six-week-old) and old (95-week-old) mice were randomly assigned to beef tallow (TAL) or soybean oil (SBO) diets for eight weeks. For the second objective, young (four-week-old) mice consumed either TAL or SBO diets for 99 weeks. Young and old mice challenged with a change in dietary fat for an eight-week period showed both diet and age effects on neural and retinal phospholipid fatty acid composition (P < 0.05). In addition, significant diet by age interactions were evident. In mice that consumed TAL and SBO diets throughout their life, only retinal phosphatidylethanolamine (PE) 18:2n-6 and neural phosphatidylserine 22:5n-6, PE 18:2n-6 and phosphatidylcholine 18:2n-6 differed between dietary treatments (P < 0.05). Neither the unsaturation index nor the n-6/n-3 ratio was affected by diet. Neural and retinal phospholipid fatty acid composition were responsive to changes in dietary fat even when the treatment was implemented beyond developmental or post-weanling stages. In contrast, when mice consumed TAL or SBO diets throughout their life, fewer differences in phospholipid fatty acid composition were detected, suggesting that the effect of the dietary treatment was mitigated by aging.