Comprehensive (apo)lipoprotein profiling in patients with genetic hypertriglyceridemia using LC-MS and NMR spectroscopy

Abstract

BackgroundMutations in genes encoding lipoprotein lipase (LPL) or its regulators can cause severe hypertriglyceridemia (HTG). Thus far, the effect of genetic HTG on the lipid profile has been mainly determined via conventional techniques. ObjectiveTo show detailed differences in the (apo)lipoprotein profile of patients with genetic HTG by combining LC-MS and NMR techniques. MethodsFasted serum from 7 patients with genetic HTG and 10 normolipidemic controls was used to measure the concentration of a spectrum of apolipoproteins by LC-MS, and to estimate the concentration and size of lipoprotein subclasses and class-specific lipid composition using NMR spectroscopy. ResultsPatients with genetic HTG compared to normolipidemic controls had higher levels of apoB48 (fold change [FC] 11.3, P<0.001), apoC-I (FC 1.5, P<0.001), apoC-II (FC 4.3, P=0.007), apoC-III (FC 3.4, P<0.001), and apoE (FC 4.3, P<0.001), without altered apoB100. In addition, patients with genetic HTG had higher concentrations of TG-rich lipoproteins (i.e., chylomicrons and very low-density lipoproteins [VLDL]; FC 3.0, P<0.001), but lower LDL (FC 0.4, P=0.001), of which medium and small-sized LDL particles appeared even absent. While the correlation coefficient between NMR and enzymatic analysis in normolipidemic controls was high, it was considerably reduced in patients with genetic HTG. ConclusionThe lipoprotein profile of patients with genetic HTG is predominated with large lipoproteins (i.e., chylomicrons, VLDL), explaining high levels of apoC-I, apoC-II, apoC-III and apoE, whereas small atherogenic LDL particles are absent. The presence of chylomicrons in patients with HTG weakens the accuracy of the NMR-based model as it was designed for normolipidemic fasted individuals.