Docosahexaenoic acid metabolism and the effect of positional isomers on its bioavailability in triacylglycerols after a long-term feeding trial

Abstract

DHA is a polyunsaturated fatty acid whose endogenous biosynthesis in the body from alpha-linolenic acid is limited making its dietary intake important. The main dietary sources are cold-water fatty fish or food supplements. Globally, the majority of the population does not meet the recommended intake of 250-500 mg per day (EFSA, 2012). Deficiency has been linked to brain and nervous system function and visual acuity. Its effect has also been studied in connection with degenerative brain diseases, lipid metabolism disorders, and cardiovascular diseases. The role of DHA is reflected in its importance as a component of cell membranes, and in the immune system through its interaction with immune-mediator lipids.

In the diet, DHA is usually bound to other lipid molecules, such as triacylglycerols (TAG), which has three binding sites (sn-positions). The study aimed to determine the effect of binding positions on bioavailability and tissue metabolism after a 4-week feeding trial in rats. Between groups, the synthesized TAG (as a dietary source) and the DHA bound to it was at the sn-1, 2, or 3 position of the TAG. The accumulation of DHA in different tissues was examined by determining the total fatty acid composition of the samples by gas chromatography using the flame ionization detector.

The most prominent differences in fatty acid profiles were observed between sn-2 and sn-3 groups in the lungs and in the phospholipid fraction of the kidneys. The results added information in this context about the impact of TAG structure on metabolism.