Vegetable oils: Classification, quality analysis, nutritional value and lipidomics applications

In 2005, the International Lipid Classification and Nomenclature Committee under the sponsorship of the LIPID MAPS Consortium developed and established a "Comprehensive Classification System for Lipids" based on well-defined chemical and biochemical principles and using an ontology that is extensible, flexible, and scalable. This classification system, which is compatible with contemporary databasing and informatics needs, has now been accepted internationally and widely adopted. In response to considerable attention and requests from lipid researchers from around the globe and in a variety of fields, the comprehensive classification system has undergone significant revisions over the last few years to more fully represent lipid structures from a wider variety of sources and to provide additional levels of detail as necessary. The details of this classification system are reviewed and updated and are presented here, along with revisions to its suggested nomenclature and structure-drawing recommendations for lipids.

Lipids are produced, transported, and recognized by the concerted actions of numerous enzymes, binding proteins, and receptors. A comprehensive analysis of lipid molecules, "lipidomics," in the context of genomics and proteomics is crucial to understanding cellular physiology and pathology; consequently, lipid biology has become a major research target of the postgenomic revolution and systems biology. To facilitate international communication about lipids, a comprehensive classification of lipids with a common platform that is compatible with informatics requirements has been developed to deal with the massive amounts of data that will be generated by our lipid community. As an initial step in this development, we divide lipids into eight categories (fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, prenol lipids, saccharolipids, and polyketides) containing distinct classes and subclasses of molecules, devise a common manner of representing the chemical structures of individual lipids and their derivatives, and provide a 12 digit identifier for each unique lipid molecule. The lipid classification scheme is chemically based and driven by the distinct hydrophobic and hydrophilic elements that compose the lipid. This structured vocabulary will facilitate the systematization of lipid biology and enable the cataloging of lipids and their properties in a way that is compatible with other macromolecular databases.

Lipidomics is a rapidly expanding research field in which multiple techniques are utilized to quantitate the hundreds of chemically distinct lipids in cells and determine the molecular mechanisms through which they facilitate cellular function. Recent developments in electrospray ionization mass spectrometry (ESI/MS) have made possible, for the first time, the precise identification and quantification of alterations in a cell's lipidome after cellular perturbations. This review provides an overview of the essential role of ESI/MS in lipidomics, presents a broad strategy applicable for the generation of lipidomes directly from cellular extracts of biological samples by ESI/MS, and summarizes salient examples of strategies utilized to conquer the lipidome in physiologic signaling as well as pathophysiologically relevant disease states. Because of its unparalleled sensitivity, specificity, and efficiency, ESI/MS has provided a critical bridge to generate highly accurate data that fingerprint cellular lipidomes to facilitate insight into the functional role of subcellular membrane compartments and microdomains in mammalian cells. We believe that ESI/MS-facilitated lipidomics has now opened a critical door that will greatly increase our understanding of human disease.