Do all trans-C18:1 intakes during pregnancy jeopardise polyunsaturated fatty acid status in new-borns? Focus on a trans-vaccenic acid (trans-C18:1 n-7) supplementation in the rat
Résumé
Trans-octadecenoic acids (trans-C18:1) intakes during pregnancy were previously shown to threaten polyunsaturated fatty acid (PUFAs) status in new-borns. However, a distinction should be made between trans-C18:1 positional isomers regarding their impact on human health. If industrial trans fatty acids are known to be harmful, less is known about dairy trans fatty acids such as trans-vaccenic acid (trans-C18:1 n-7, TVA). Studying one isomer at a time remains indeed a technical issue in terms of both purity and elevated amount. Overcoming such a challenge, this study aimed at focusing only on TVA, studying the impact of its supplementation during pregnancy on PUFAs status in new-borns. We first chemically synthesised cis-vaccenic acid (cis-C18:1 n-7, CVA), then isomerised it to yield TVA. Liquid Chromatography Flash, an innovative means, enabled the separation between TVA and CVA, according to a 95%-purity. Second, pregnant Sprague-Dawley (day 14) were used and fed with either a TVA-supplemented diet (2% of total energy), or a CVA-supplemented diet (2% of total energy, control) for three weeks. The linoleic acid/α-linolenic acid ratio was settled at 5 in both diets. Regarding pups, their diet relied exclusively on maternal milk for two weeks. Fatty acid composition of plasma, red blood cells, muscle, adipose tissue, liver and brain of pups was assessed by GC-MS. Data analysis relied on both univariate statistics and a recently developed multiblock procedure that modelled lipid metabolism and interaction between tissues. First, chemical synthesis of TVA was successful, yielding high amounts of pure TVA almost without any other trans-C18:1 isomer. Second, TVA was incorporated in all tissues analysed in the pups fed the TVA diet, including the brain (0.19% of total fatty acids). Compared to control, univariate analyses only revealed a significant decrease in C22:4 n-6 in the brain of pups fed the TVA diet; otherwise, non-significant decreases in arachidonic acid and DHA were found in these pups. In key tissues such as plasma and red blood cells, non-significant increases in both n-6 and n-3 PUFAs in the TVA group were highlighted. The multi-block procedure unravelled a discrimination between both groups, but consistently with univariate outcomes, PUFAs played a weak role in this separation. This study focused on one accurate trans-C18:1 isomer, namely TVA. Its supplementation during pregnancy may not jeopardise PUFAs status in new-borns, but other studies are needed to both draw accurate conclusions and understand the physiological impacts of TVA. As the current consumption of partially hydrogenated oil decreases in developed countries, dairy trans fatty acids will account for a larger part of trans fatty intakes in the forthcoming period. Their impact on human health in general should be properly assessed. Our study underline that solutions do exist to obtain one very pure isomer in high amounts. Our outcomes call for more studies about the relationship between dairy trans fatty acids intakes during pregnancy and PUFAs' status of new-borns.