ABSTRACT
Why study fatty acid uptake and why is it so important? To the average lipid biochemist, this of course is a question that will have them rattling off a long list of reasons and then moving over to their soap box to further illuminate the questioner about why granting agencies should care as well. So why is this question so
12.1 Introduction .................................................................................................. 373 12.1.1 Importance of Fatty Acids in Signaling ........................................... 374 12.1.2 Factors Regulating Fatty Acid Uptake and Targeting ...................... 375 12.1.3 Why Concentration Matters ............................................................. 376 12.1.4 Cell Cultures vs. in Vivo ................................................................... 377
12.2 Fatty Acid Uptake in Cultured Cells ............................................................ 378 12.2.1 Cell Incubation with Fatty Acids and Cell Lipid Extraction ............ 378 12.2.2 Pulse Experiments and Why Time Is Important ..............................380
12.3 Fatty Acid Uptake in Tissues ........................................................................ 381 12.3.1 Tracer Preparation, Surgery, and Infusion ........................................ 382 12.3.2 Tissue and Plasma Extraction ........................................................... 383 12.3.3 Assessing β-Oxidation ......................................................................384 12.3.4 Assessing Fatty Acid Uptake and Targeting .....................................384
12.4 Conclusions ................................................................................................... 385 Acknowledgments .................................................................................................. 385 Appendix ................................................................................................................ 386 List of Abbreviations .............................................................................................. 389 References ..............................................................................................................390
important? First, we do not truly comprehend how this process occurs and only now have we begun to appreciate the multiple in uences by which many systems regulate this process. Second, many individuals just squirt some fatty acid into some cells, generally arachidonic acid (ARA, not the commonly seen AA), and sometime later stimulate them with a particular agonist and then measure ARA release. What they do not know may ultimately signi cantly impact their experimental outcomes and lead to more confusion in the literature. Third, concentrations matter. Some people gure that if a little is good, a whole lot more will be better. With fatty acids, this in uences where the fatty acid goes in the cell, to a membrane or to a lipid droplet or, in more metabolic terms, to be used in a phospholipid as a membrane constituent or to be stored in a triacylglycerol (TAG) because the cell cannot gure out what else to do with all of this fatty acid. Fourth, fatty acids have really become important of late as we now know that fatty acids are intimately involved in gene expression (see Chapters 9 and 10). Hence, fatty acids coming into a cell or tissue in uence what genes are turned on, which in turn regulate downstream cellular function. So, in short, there are a lot of reasons to understand the bases for fatty acid uptake and traf cking in cells. Even if you are not a lipid biochemist but a person really interested in looking at lipid-mediated signal transduction, you need to understand some important aspects of fatty acid uptake and hopefully you will nd what follows useful.
