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Gangliosides analysis, Humans, Lipoproteins analysis, Chromatography, Liquid methods, Lipids analysis, and Mass Spectrometry methods

A simple and robust LC-MS-based methodology for the investigation of lipid mixtures is described, and its application to the analysis of human lipoprotein-associated lipids is demonstrated. After an optional initial fractionation on Silica 60, normal-phase HPLC-MS on a YMC PVA-Sil column is used first for class separation, followed by reversed-phase LC-MS or LC-tandem mass spectrometry using an Atlantis dC18 capillary column, and/or nanospray MS, to fully characterize the individual lipids. The methodology is applied here for the analysis of human apolipoprotein B-associated lipids. This approach allows for the determination of even low percentages of lipids of each molecular species and showed clear differences between lipids associated with apolipoprotein B-100-LDL isolated from a normal individual and those associated with a truncated version, apolipoprotein B-67-containing lipoproteins, isolated from a homozygote patient with familial hypobetalipoproteinemia. The methods described should be easily adaptable to most modern MS instrumentation.

Anticholesteremic Agents administration dosage, Anticholesteremic Agents pharmacology, Apolipoproteins E biosynthesis, Atorvastatin, Drug Therapy, Combination, Enzyme Inhibitors pharmacology, Female, Heptanoic Acids administration dosage, Humans, Kinetics, Male, Pyrroles administration dosage, Quinolines pharmacology, Single-Blind Method, Apolipoproteins E metabolism, Cholesterol Ester Transfer Proteins antagonists inhibitors, Lipoproteins, VLDL metabolism, and Quinolines administration dosage

Cholesteryl ester transfer protein (CETP) inhibition leads to changes in lipoprotein metabolism. We studied the effect of the CETP inhibitor torcetrapib on VLDL apolipoprotein E (apoE) metabolism. Subjects, pretreated with atorvastatin (n = 9) or untreated (n = 10), received placebo followed by torcetrapib (4 weeks each). After each treatment, subjects underwent a primed-constant infusion of D(3)-leucine to determine the VLDL apoE production rate (PR) and fractional catabolic rate (FCR). Torcetrapib alone reduced the VLDL apoE pool size (PS) (-28%) by increasing the VLDL apoE FCR (77%) and leaving the VLDL apoE PR unchanged. In subjects pretreated with atorvastatin, torcetrapib increased the VLDL apoE FCR (25%) and PR (21%). This left the VLDL apoE PS unchanged but increased the VLDL apoE content, likely enhancing VLDL clearance and reducing LDL production in this group. Used alone, torcetrapib reduces the VLDL apoE PS by increasing the apoE FCR while leaving the VLDL apoE content unchanged. In contrast, torcetrapib added to atorvastatin treatment increases both the VLDL apoE FCR and PR, leaving the VLDL apoE PS unchanged. Adding torcetrapib to atorvastatin treatment increases the VLDL apoE content, likely leading to decreased conversion of VLDL to LDL, reduced LDL production, and lower levels of circulating VLDL and LDL.

Adult, Aged, Animals, Dietary Fats, Unsaturated blood, Fasting, Fatty Acids, Omega-3 pharmacology, Female, Humans, Kinetics, Male, Middle Aged, Diet, Dietary Fats, Unsaturated analysis, Fishes, Life Style, and Lipoproteins metabolism

The effects of Therapeutic Lifestyle Change (TLC) diets, low and high in dietary fish, on apolipoprotein metabolism were examined. Subjects were provided with a Western diet for 6 weeks, followed by 24 weeks of either of two TLC diets (10/group). Apolipoprotein kinetics were determined in the fed state using stable isotope methods and compartmental modeling at the end of each phase. Only the high-fish diet decreased median triglyceride-rich lipoprotein (TRL) apoB-100 concentration (-23%), production rate (PR, -9%), and direct catabolism (-53%), and increased TRL-to-LDL apoB-100 conversion (+39%) as compared with the baseline diet (all P < 0.05). This diet also decreased TRL apoB-48 concentration (-24%), fractional catabolic rate (FCR, -20%), and PR (-50%) as compared with the baseline diet (all P < 0.05). The high-fish and low-fish diets decreased LDL apoB-100 concentration (-9%, -23%), increased LDL apoB-100 FCR (+44%, +48%), and decreased HDL apoA-I concentration (-15%, -14%) and PR (-11%, -12%) as compared with the baseline diet (all P < 0.05). On the high-fish diet, changes in TRL apoB-100 PR were negatively correlated with changes in plasma eicosapentaenoic and docosahexaenoic acids. In conclusion, the high-fish diet decreased TRL apoB-100 and TRL apoB-48 concentrations chiefly by decreasing their PR. Both diets decreased LDL apoB-100 concentration by increasing LDL apoB-100 FCR and decreased HDL apoA-I concentration by decreasing HDL apoA-I PR.