EFFECTS OF N-3 FATTY-ACIDS ON THE NMR PROFILE OF PLASMA-LIPOPROTEINS

The effects of fish oil supplementation (14.5 g n-3 fatty acids/day) o n plasma lipoprotein particles in healthy volunteers were assessed by high resolution C-13 and H-1 nuclear magnetic resonance (NMR) spectros copy. Resonances not previously observed in the C-13 and H-1 spectra o f plasma and isolated lipoproteins were detected after fish oil ingest ion. The C-13 resonances, centered at 14.3, 127.1, and 131.6 ppm, have been assigned to specific carbon groups ((C) under bar H-3-CH2-CH = C H-, CH3-CH2-CH = (C) under bar H-CH2-, CH3-CH2-(C) under bar H = CH-CH 2-, respectively) in eicosapentaenoic acid (C20:5n-3) and docosahexaen oic (C22:6n-3) DHA. The new lipid resonance observed in the H-1 spectr a of plasma (0.941 ppm) is consistent with the incorporation of these n-3 fatty acids into lipoprotein particles. The presence of increased EPA and DHA in plasma lipids was confirmed by gas-liquid chromatograph y. A marked reduction in the intensity of the methylene signal from ve ry low density lipoproteins (VLDL) was also observed with fish oil. Th is reduction arises from a decrease in plasma triglyceride concentrati on (ca. 18%) and a reduction in the number of VLDL particles. Transver se relaxation studies of isolated VLDL and low density lipoprotein (LD L) showed significant elevation in the T-2 of the -(<C(H)under bar>(2) )(n)- and <C(H)under bar>(3)- signals from non-n-3 fatty acids. The re laxation characteristics and signal intensity of the novel H-1 peak (0 .941 ppm) point to the existence of n-3 enriched microenvironments wit hin lipoprotein particles. These findings suggest that incorporation o f EPA and DHA into VLDL and LDL, after fish oil ingestion, leads to si gnificant alteration in the molecular architecture of lipoprotein part icles.