Effect of feed supplementation with docosahexaenoic acid in regio- and enantiopure triacylglycerols on gut metabolome and microbiota in rats

Docosahexaenoic acid [22:6(n-3), DHA] plays an important role in human physiology including gut health. This research aimed to investigate the impact of positional distribution of DHA in dietary triacylglycerols (TAG) on gut metabolomic profile and microbiota. In the 4-week feeding trial, the Sprague-Dawley rats were fed on an n-3 deficient feed supplemented with TAG containing DHA at the sn-1, 2, or 3 position and palmitic acid at the remaining positions. Three groups receiving standard n-3 adequate feed, n-3 deficient feed, or n-3 deficient feed supplemented with tripalmitin were included as controls. The gut metabolome was studied using LC–MS-based non-targeted metabolomics, and microbiota profiles were investigated by 16S rRNA sequencing. Compared to the n-3 adequate diet, four-week feeding on the n-3 deficient diet affected the fecal pyrimidine metabolism, steroid biosynthesis, and arginine and proline metabolism. Feeding with DHA-containing TAGs, especially TAG with DHA at sn-3 position, increased the level of N5-Carboxy aminoimidazole ribonucleotide related to purine biosynthesis and dimethylbenzimidazole involved in vitamin B2 biosynthesis. N-3 deficient diet lowered the abundance of the genus Alistipes and the species Bacteroides massiliensis in the gut microbiota. Compared to the n-3 deficient groups, feeding with DHA-containing TAGs decreased the abundance of species Prevotella sp. CAG: 1031, and feeding with sn-2 DHA resulted in an increase in the abundance of Bacteroides fragilis and a decrease in the abundance of Faecalibacterium sp. CAP 74. This is the first study showing that dietary DHA from different positions of TAG may affect gut metabolites and microbiota differently.