UCLA

Lipids are a diverse group of molecules that play critical structural, signaling, and energy storage roles in all cells. Fatty acids are key building blocks for many lipids, and the fatty acid content of a lipid species has important effects on its properties and function. As a result, changes in fatty acid metabolism are an essential part of many normal and pathophysiological processes. However, there remain significant gaps in our knowledge of fatty acids and their metabolism, in part due to challenges in measuring fatty acid pool sizes and fluxes. Herein, we demonstrate how stable isotope labeling of cells followed by modeling of gas chromatography-mass spectrometry data from their fatty acids can begin to address these issues and yield important insights into how fatty acid metabolism affects other aspects of biology. First, we describe a new analytical method optimized for measuring fatty acids and cholesterol from stable isotope-labeled cells. Next, we report a novel mathematical model that allows for measurement of fatty acid elongation, which is particularly useful in analyzing very long chain fatty acids. Finally, we apply our new analytical and modeling approaches to reveal previously unmeasured aspects of cellular fatty acid metabolism and to demonstrate that distinct pro-inflammatory stimuli specifically reprogram fatty acid synthesis and elongation in macrophages. Given the importance of fatty acids and their metabolism both in normal cells and in many diseases, we anticipate that this work will be useful to a wide variety of scientists.