The Fats of Life: Essential Fatty Acids in Health and Disease

Glossary

adipose fat or adipose tissue The distribution of fat storage (adipose) cells is genetically determined, with some individuals concentrating the cells almost exclusively in the abdominal area (especially men), some concentrating them in the hips and thighs (especially women), while others tend to distribute the adipose cells throughout the body (both men and women). There is some question about how much turnover (removal and redepositing) of fats occurs in adipose tissue. albumin The most abundant protein in blood plasma, albumin can bind and transport many lipids or lipophilic substances. Fatty acids are transported through the blood on albumin, although this is relatively minor in comparison to the fatty acids bound to triglycerides and phospholipids that are transported by lipoproteins. aldosterone A steroid hormone secreted by the adrenal cortex that regulates sodium levels in the blood by its effect on sodium resorption in the kidney tubules. alveoli Air sacs in the lungs that can become constricted in response to certain leukotrienes formed from arachidonic acid acting on the smooth-muscle cells around the alveoli. androgens Steroid hormones responsible for masculine sex characteristics, such as muscle mass and facial hair. These include testosterone and dehydroepiandrosterone . antioxidants Substances that prevent the oxidation of important biological components. Antioxidants are usually oxidized in the process of protecting other biological components but are then usually recycled or reduced by enzymes to enable repeated cycles of their oxidation. Many natural substances, such as vitamins A, C, and E, as well as phytochemicals (derived from plants) are classified as antioxidants. GLOSSARY 235 GLOSSARY 236 apolipoproteins The protein components of lipoproteins are designated apolipoproteins , where apo- is a prefix used to indicate the protein portion of a proteinaceous molecule that is lacking other components for its complete makeup and ultimate function. There are several apolipoproteins that are components of the various lipoproteins. See appendix D for a more complete description of apolipoproteins and lipoproteins. apoptosis When cells receive damage to critical components, there seem to be signals within the cell for its own demise, or programmed cell death (apoptosis ). This is self-destruction of a cell, which may provide some advantage to the organism as a whole. arachidonic acid One of the most important fatty acids in the body, in terms of its biochemical and physiological effects, is represented symbolically as C20:4, delta-5,8,11,14. It contains twenty carbons and has four carbon-carbon double bonds. It is classified an omega-6 essential fatty acid and metabolized to numerous bioactive eicosanoids and related compounds. asthma An obstructive pulmonary disease that involves constriction of the deeper airways of the lungs, which is triggered by contraction of smooth muscles surrounding airways in response to leukotrienes formed from arachidonic acid. atherosclerosis The accumulation of modified or oxidized low-density lipoprotein (oxidized LDL) in the lining of the arteries between endothelial cells and smooth muscle results in fatty deposits known as stenosis or atherosclerosis. This results in reduced volume in the arteries and is usually accompanied by high blood pressure. The fatty deposits may be encapsulated in fibrous proteins to form plaque. Breakdown of the fibrous cap over these fatty deposits exposes the connective proteins to blood platelets, triggering formation of thromboxane A2 that causes platelet aggregation and initiates a blood clot. autoimmune disease Autoimmune disease results when the immune system forms antibodies against the body’s own tissues or components. This is usually accompanied by inflammation and destruction of the tissue that is causing the immune response. bile The bile salts, cholesterol, lecithin, and waste products such as bilirubin (from breakdown of heme in hemoglobin) form the bile that is stored in the gallbladder. Bile is usually highly concentrated in bile salts before it is secreted into the small intestine (duodenum) after a meal is consumed. Cholesterol may precipitate or condense in the bile to form gallstones. About 75 percent of gallstones are cholesterol aggregates; the other 25 percent are from bilirubin. Consumption of bile salts may help to break down (dissolve) gallstones. GLOSSARY 237 bile acids/bile salts Cholesterol is oxidized in the liver to form cholic acid, deoxycholic acid, and chenodeoxycholic acid, among others. These are collectively known as bile acids. Like all organic acids, they will ionize in the neutral medium of body fluids, forming the corresponding salts that have the -ate ending ( such as cholate and deoxycholate). The bile salts act as detergents in the digestive system, along...