This study aims to test the hypothesis that dietary intake of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) acutely alters plasma lysophosphatidic acid (LPA) levels and autotaxin activity in normal weight and obese subjects.
Lysophosphatidic acid (LPA) is a simple glycerophospholipid that is found at biologically-relevant levels in plasma and has important effects on isolated or cultured blood, vascular and fat cells. The main enzyme responsible for generation of plasma LPA is the secreted lysophospholipase D, autotaxin (ATX). Adipocytes contribute substantially to plasma ATX levels. The investigators have demonstrated rapid production and metabolism of plasma LPA in animals. More recently, the investigators have observed that plasma LPA levels increase in mice fed a high fat ("Western") diet in comparison to levels found in mice fed normal chow. The investigators have also found that diet-induced obesity increased circulating ATX levels in mice. The investigators hypothesize that diet, and in particular dietary phosphatidylcholine (PC), may regulate the autotaxin substrate lysophosphatidylcholine (LPC), from which LPA is derived. Obesity may amplify the response by increasing plasma ATX levels and/or activity. The current study will test whether dietary PC in normal weight and obese subjects acutely alters LPA levels and autotaxin activity.
Study Type
OBSERVATIONAL
Enrollment
44
University of Kentucky Dept of Cardiology
Lexington, Kentucky, United States
Plasma Autotaxin-dependent formation of Lysophosphatidic acid, and Levels of Phosphatidylcholine and its metabolites - Lysophosphatidylcholine, Lysophosphatidic acid, Choline, Trimethylamine and Trimethylamine oxide measured by Tandem Mass Spectrometry
Investigators will use tandem mass spectrometry to measure the most abundant metabolite species. Enzymatic activity of autotaxin involves incubation with the substrate lysophosphatidylcholine and monitoring concentration dependent release of lysophosphatidic acid. Levels of Lysophospholipids Phosphatidylcholine and the products of its metabolism in the blood will be measured. Quantitation will be achieved by stable isotope dilution and by reference to offline calibration curves. By using mass spectrometry and metabolic tracers, studies using a common protocol are effectively multiplexed so data on both endogenous and mass labeled lipids can be obtained from a single individual. Given the sensitivity of these analytical methods (limits of quantitation of approximately 1 fmol), the measurements and the quantities will be reported as concentration in picomoles per liter of plasma volume. A statistical correlation with each group based on BMI will be performed.
Time frame: 8 hours
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