Modification of milk formula to enhance accretion of long‐chain n−6 and n−3 polyunsaturated fatty acids in artificially reared infant rats

Abstract

Artificially reared infant rats were used to determine the effects of long-chain polyunsaturated fatty acid (LCPUFA) supplementation on blood and tissue concentrations of arachidonic acid (AA) and docosahexaenoic acid (DHA). Beginning at 7 d of age, infant rats were fed for 10 d with rat milk formulas supplemented with AA at 0, 0.5 and 1.0%, or supplemented with DHA at 0, 0.5 and 1.0% of total fatty acid. The supplementation of AA increased accretion of the fatty acid in tissue and blood phospholipids with a maximum increase of 9% in brain, 15% in liver, 25% in erythrocytes, and 43% in plasma above the values of unsupplemented infant rats. Rat milk formula containing 1.0% of AA had no added benefits over that containing 0.5% of AA. The supplementation of DHA increased phospholipid DHA by a maximum of 24% in brain, 87% in liver, 54% in erythrocytes, and 360% in plasma above the unsupplemented control. The increase in tissue and blood DHA was concentration-dependent on formula fatty acid. Brain phosphatidylcholine and phosphatidylethanolamine were similarly enriched with AA and DHA by supplementation of the corresponding fatty acids. In general the observed increase of AA was accompanied by a decrease in 16:0, 18:1 n-9, and/or 18:2n-6, whereas the increased DHA was associated with a reduction of 18:1n-9, 18:2n-6, and/or 20:4n-6. Clearly, infant rats were more responsive to DHA than AA supplementation, suggesting a great potential of dietary manipulation to alter tissue DHA concentrations. However, the supplementation of DHA significantly decreased tissue and blood AA/DHA ratios (wt%/wt%), whereas there was little or no change in the ratio by AA supplementation. Although the physiological implications of the levels of AA and DHA, and AA/DHA ratios achieved under the present experimental conditions are not readily known, the findings suggest that artificial rearing could provide a suitable model to investigate LCPUFA requirements using various sources of AA and DHA in rats.

Lowering dietary n-6 polyunsaturated fatty acids

“…Seven studies were identified that measured brain concentrations of ARA and DHA following feeding of different levels of ARA during early life [33,34,[56][57][58][59][60] (Table 2a).…”

“…Five studies reported lower levels of brain ARA in the groups fed lower levels of dietary ARA [56][57][58][59][60], whereas two studies detected no difference between the low and high groups [33,34]. Both studies that found no difference introduced rat dams to the diets at postnatal day (PND) 2 and measured the fatty acid composition of the pup brains at PND 15.…”

“…The five studies with an effect were generally longer, with three lasting at least 3 weeks. Three of the seven studies reported higher levels of brain DHA in the groups fed lower levels of ARA [57][58][59], whereas the remaining four had no effect. All three studies that found an effect of dietary ARA on brain DHA also reported significant changes in brain ARA.…”

Brain Docosahexaenoic Acid Status and Learning in Young Rats Submitted to Dietary Long-Chain Polyunsaturated Fatty Acid Deficiency and Supplementation Limited to Lactation

“…This dietary n-3 FA deficiency profile consists of decreased levels of DHA and increased levels of 22:4 n-6 and 22:5 n-6 and the maintenance of the total n-3 plus n-6 FA in membrane phospholipids (10). Contrariwise, the FA profile of dietary DHA supplementation over a previous n-3 deficiency had also been described in different tissues (11)(12)(13). DHA deficiency is related to learning disturbances in humans (14) and rats (15), and, on the contrary, DHA supplementation is related to learning improvement in some animal models (16).…”

Long-Chain Polyunsaturated Fatty Acids in Rat Maternal Milk, Offspring Brain and Peripheral Tissues in Essential Fatty Acid Deficiency

“…Maternal diet has an important influence on FA composition of milk (3) and, consequently, on FA profiles of plasma and red blood cells (RBC) of infants (4,5). Maternal diet has an important influence on FA composition of milk (3) and, consequently, on FA profiles of plasma and red blood cells (RBC) of infants (4,5).…”