Dear Colleagues,

Fatty acids (FAs) are especially suitable as tools to examine processes that range from the cellular to organismal levels of organization. Lipids comprise a large group of chemically heterogeneous compounds, the majority of which include esters of FAs as part of their structure. FAs thus represent the “building blocks” of many lipid classes and are the largest constituent of neutral lipids, such as triacylglycerols (TAGs) and wax esters (WEs), that have both energy storage and structural functions. FAs are also part of the polar phospholipids, which are important structural components of cellular membranes. Free FAs (FFAs) can be used directly for energy production through beta-oxidation whilst there are indications that some polyunsaturated fatty acids (PUFAs) have nutritionally stabilizing functions. Essential fatty acids (EFAs) are precursors to eicosanoid signaling molecules such as prostaglandins prostacyclins, thromboxanes and leukotrienes. FA derived metabolites (e.g., oxylipins) may also mediate chemical interactions controlling herbivory patterns and the reproduction of aquatic organisms with implications for the functioning of aquatic food webs.

Studies on FAs and their metabolism are important in several research fields including, biology, microbiology, ecology, physiology, and oncology. Specific FA types and their ratios in the cellular membranes of organisms may be used as biomarkers to aid in the identification of organisms, food web connections, or to study the adaptation of bacterial cells to toxic compounds or environmental conditions. Specialized plasma membrane lipids allow bacteria and archaea to live under extreme conditions, such as those found in abyssal marine trenches or hot vents, where they form the base of the local food web. The ability exhibited by actinomycetes to thrive under conditions fatal to other bacteria is ascribed to the presence of mycolic acids (a group of long-chain FAs) in their unusually robust cell walls. Mycobacterium tuberculosis cells in the human lung enter a dormant state within granulomas where they survive by incorporating FA from the host triacylglycerols into lipid droplets. Alterations in FA metabolism in cancer cells are increasingly recognized and more attention is being devoted to the fact that in these cells, carbon must be diverted from energy production to FA for the biosynthesis of membranes and signaling molecules.

Lipid and FA research has gained considerable applied importance in human nutrition and health as humans are “top predators” that require essential dietary nutrients in their diet, and many signal- and disease-related mechanisms involve lipid components. In humans, PUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) play key roles in heart health, immune and inflammatory responses, visual acuity as well as being major components of the central nervous system. Consumer health trends further contribute to the current interest in lipids as the debate over the benefits and risks of PUFAs, as well as trans-unsaturated and hydrogenated FAs, for human health appear daily in the media.

In this Special Issue, we intend to highlight the relevance of FA studies to answer important questions in different research fields, including the relationship between lipid molecular structure and biochemical function.

Dr. Carla C. C. R. de Carvalho
Dr. Maria José Caramujo
Dr. Craig Frank
Guest Editors

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• free fatty acid (FFA)
• triacylglycerol (TAG)
• wax ester (WE)
• phospholipid (PL)
• monoenoic fatty acid (MUFA)
• polyunsaturated fatty acid (PUFA)
• omega-3 (ω3; n-3) fatty acid
• mycolic acid
• cholesterol ester (CE)