El metabolismo del colesterol

RESUMO

Lipids are essential elements for human beings, and undertake several functions such as cell membrane constitution, energy sources, body fatty tissiue and constitution of several hormones such as sexual hormones and glucocorticoids. Fatty tissue are responsible of body shape, and help to regulate body temperature. Cholesterol is the main sterol found in the tissues of mammals, however excessive tissue cholesterol can be deleterious to human beings. Many studies have shown the direct relationship between cholesterol levels and morbidity and mortality of coronary heart disease in high risk groups. Cholesterol levels corresponding to the superior 10 percent of the distribution are clearly pathologic, and levels between percentile 75 and 90 represent moderate risk of atherosclerosis. The liver plays a preponderant role in the regulation of cholesterol metabolism in human beings, and has the capability of uptake, synthesis and secretion of this important substance. A summary of its metabolism begins with dietary absorption of fatty acids and cholesterol at the level of the small bowel, and transportation as chylomicrons to the circulation through the thoracic duct. Triglycerides are extracted from chylomicrons through the action of lipoprotein lipase (LPL) and fatty acids are stored in the adipose tissue or oxidated by muscles for energy. Chylomicron remanents are rapidly cleared by the hepatocyte through specific membrane receptors, and in the cell digested by lysosomes releasing cholesterol, in order to be stored or utilized in lipoprotein synthesis...