Fatty acids exist in the body primarily as triglycerides and phospholipids. Phospholipids make up the bilipid membrane of cells and the membranes of organelles within the cytoplasm. Fatty acids are split from the triglyceride glycerol backbone and broken down into carbon fragments which are then oxidized to provide energy. Usually, just the 16 carbon fatty acids or shorter are metabolized in this fashion.
Fatty acids 16 carbons and longer from the omega-3 and -6 families can undergo the formation of double bonds and chain lengthening to create compounds called eicosanoids. These substances are autacoids, evanescent compounds which exert their effects locally in the microenvironment of the tissues where they are generated.1 Eicosanoids are cyclic oxygenated derivatives of fatty acids consisting of prostaglandins, leukotrienes, thromboxanes, prostacyclines, and lipoxins which are the moderators of life processes at the microcellular and tissue level (Fig. 14). They are intermediate between biochemicals and hormones. Their presence in extremely small nano and pico molar amounts exerts effects which are more powerful by many fold than various potent organ level hormones.
Eicosanoids are regulatory, turning various life processes on and off. For example, eicosanoids can stimulate the clotting mechanism when blood vessels are injured, but they can also stop the clotting Pathway Environmental so it does not proceed to the point where circulation other than at the local site of injury is impaired.
Eicosanoids must exist in precise balances for life to continue without the presence of disease. Since the various eicosanoids are produced from dietary fatty acids, modifying the diet can shift eicosanoid balances. Overconsumption of one kind of fatty acid may overproduce one kind of eicosanoid. Its effect will then become predominant and not be properly balanced by its antagonistic eicosanoid and thus disease may result. For example, the overconsumption of omega-6 fatty acids can create eicosanoids which promote inflammation. If these fatty acids are consumed in excess at the expense of a balancing amount of omega-3 fatty acids, inflammatory diseases such as arthritis, cardiovascular disease, and allergic conditions may result. Balance is the essence of life.
The various metabolic pathways leading to the production of eicosanoids are complex. The pathways begin with the types of fatty acids in the diet. These in turn are converted by enzyme systems into progressively longer and more unsaturated fatty acids until they reach their eicosanoid destination. Figures 15 and 16 outline these synthetic pathways.
Desaturase and elongase enzymes responsible for these conversions vary in functionality from species to species, within the same species, and even within the same individual under differing circumstances. Additionally, it is believed, these enzyme systems can be affected adversely by various toxins and disease states. Thus not only diet, but environmental and genetic factors can influence eicosanoid balances.