On the Futile Existence of DHA, None of EPA and the Predominant Role of the Triacylglycerols (TGs) in the Post Mortem Human Brain: An LCMS Study with Evolutionary Implications

Abstract

What is known about the brain is a scanty amount of information despite its importance in human evolution. Here we perform based on a holistic Systems Biology lipidomics approach an attempt describing the brain biochemical lipid composition based on the homogenate of a part (gyrus) of the neocortex of post mortem material of the "Dutch Brain Bank" with LCMS techniques. From evolutionary perception the occurrence of the "fish oils" in blood and/ or brain is interesting and their ability to pass the Blood-Brain Barrier (BBB). Both omega-3 "fish oil" Fatty Acids (FA) Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA). EPA and DHA are found in rather high concentrations respectively 0.277% and 0.258% respectively in blood plasma but not in the brain. EPA is not found in grey or white neocortex matter so probably it cannot pass the BBB while this is the case for DHA giving values of respectively ≈0.00015% while Triacylglycerols (TGs) are the major constituent of the human brain with a mean value of the neocortex of ≈72%. We finally conclude the TGs have played a major role in the process of human brain growth and encephalization during course of evolution. the occurrence of the "fish oils" in blood and/or brain is interesting and their ability to pass the BBB. Based on our observations we open the debate which lipid class-the PUFAs vs. the TGs-have played a major unambiguously role in the process of human brain growth and encephalization. Our initial hypothesis is that the TGs have played a major role in human brain skull expansion or encephalization and that the "fish oil" DHA is a tiny fraction of the FA in the brain and is of minor importance of human encephalization. Material and MethodsWe quantified and qualified the rearrangement and repartitioning of these fat stores in the brain of male post mortem subjects (Control n=8; 73.5 ± 10.5 years; Type-2 diabetes n=8; 77.3 ± 7.2 years) which were obtained from the 'Netherlands Brain Bank' . We quantified 109 lipid compounds based on mass and polarity using LCMS methods as described earlier [5,12]. Briefly, we followed next protocol.Brain-tissue: Human Brain tissue was obtained from the "Netherlands Brain Bank". Causes of death causes are presented in Table 1 [12]. Time of post mortem dissection varied between 4.4 and 24.5 h (Table 1) [12]. The region of post mortem collection of the tissue material was mainly the cortex (Table 1) [12]. Visually, a clear separation could be made between grey and white matter in the cortex. A tissue homogenate of the brain tissue (grey or white; ~10% wet weight/volume) in Phosphate-Buffered Saline (PBS) was made with the Mini-beat Beater.Blood plasma: Blood was centrifuged at 8000 × g for 5 min. The plasma was aliquoted and stored at -80ºC at the "Netherlands Brain Bank" pending analysis LC-MS: Lipids and free fatty acids (FFA) were analyzed with electrospray LC-MS as earlier performed. For blood plasma 10 µl samples were extracted with 300 µl of isopropanol (IPA) containing several internal standards (IS: C17:0 lysopho...