What biological signaling pathways are fatty acids involved?

Fatty acids are involved in various pathways such the cytosolic FASI pathway and the mitochondrial FASII pathway. The cytosolic FASI pathway is catalyzed via fatty acid synthase, which catalyzes all the steps in fatty acid synthesis. The mitochondrial fatty acid synthesis pathway involves the use of a separate protein carrying out each catalytic step. This pathway is able to synthesize fatty acids with acyl chains of at least 14 carbons (myristic acid) in mammalian cells and can synthesize at least 16 carbons long (palmitic acid) in other species. 

Fatty acids also act as secondary messengers and modulators especially of signals induced at the cell membrane level. For example, fatty acids have a significant role in the generation of eicosanoids. Eicosanoids are composed of 20-carbon polyunsaturated fatty acids which help form molecules involved in chemotaxis, growth factors, and platelet aggregation. Eicosanoids are formed through different enzyme pathways (e.g. lipoxygenase, cyclooxygenase, cytochrome P450). Fatty acids also are able to modulate intestinal cholesterol absorption in animals, a process which is regulated by transporter proteins (e.g. NPCL1). As an example, omega 3 and omega 6 are polyunsaturated fats that are able to induce anti-inflammatory effects in the body. They function to increase the uptake of circulating lDL by the liver and reduce leukocyte activation, and blood pressure.