13C-NMR spectroscopy of human atherosclerotic lesions. Relation between fatty acid saturation, cholesteryl ester content, and luminal obstruction.

Previous investigations have used 13C-nuclear magnetic resonance (NMR) spectroscopy to demonstrate the similarities between lipoproteins and the mobile lipids of atheroma. In this study, we tested the hypothesis that 13C-NMR changes are related to indices of histological severity. We classified 20 human arteries according to their obstruction ratio (OR), defined as the ratio of the plaque area to the area delimited by the external elastic lamina. In group A, OR was < 40%, and in group B, OR was > 40%. We analyzed at 9.4 T the resonances of unsaturated (UFA) and polyunsaturated (PUFA) carbons, the resonances of the carbons 19 and 21 (C19, C21) of cholesteryl esters (CE), the methine carbon peak of fatty acids (CH2)n, the choline peak from phospholipids (PL), and the glycerol peak from triglyceride (TG). The UFA/PUFA, UFA/(CH2)n, and PUFA/(CH2)n ratios are markers of fatty acid saturation. (C19, C21)/(CH2)n, choline/(CH2)n, and glycerol/(CH2)n are indices of CE, PL, and TG content, respectively. UFA/PUFA in group A is 1.15 +/- 0.34 versus 1.63 +/- 0.32 in group B (P = .005). PUFA/(CH2)n is 0.26 +/- 0.10 in group A versus 0.16 +/- 0.04 in group B (P = .049). C19, C21/(CH2)n in group A is 0.32 +/- 0.15 versus 0.63 +/- 0.23 for group B (P = .003). No significant difference was found in UFA/(CH2)n or in the TG or PL ratios. 13C spectral examination of human atherosclerosis demonstrates decreased resonances for polyunsaturated fatty acyl chains and cholesteryl esters with increasing obstruction.