Biochemistry

nervous system, and the released norepinephrine, the same as adrenaline, increases the rate of lipolysis in fatty tissue. In addition, adrenaline through the system of appropriate enzymes contributes to the formation of the active form of lipase. The operation of glucagon and thyroxine is similar to the effects of epinephrine and norepinephrine (catecholamines): they stimulate lipolysis. Growth hormone (STH), which is formed in the anterior lobe of the pituitary, affects lipid metabolism. With a lack of this hormone increases the deposition of fat in the body, pituitary obesity develops. During increased production of it lipolysis and the content of fatty acids in the blood plasma increases. Insulin has the opposite effect to adrenaline and glucagon: it reduces the formation of active lipase in cells, enhances lipogenesis, promotes the conversion of carbohydrates into fats, and inhibits the oxidation of higher fatty acids in tissues. Table 10.1 - Effect of some factors on the mobilization of fatty acids from fatty tissue Factor Character of influence Estimated mechanism of action Catecholamines, glucagon, thyroxin, glucocorticoids Strengthening Activation of adenylate cyclase STH, ACTH (hormones pituitary gland) » Strengthening the synthesis of adenylate cyclase and hormone-sensitive lipase Stress, physical activity, fasting, cooling » Stimulation of catecholamine secretion and inhibition of insulin secretion Prostaglandins Inhibition The weakening of the action of catecholamines on adenylate cyclase, inhibition of adenylate cyclase Insulin » Deceleration of the release of fatty acids as a result of the activation of glycolysis in adipose tissue; phosphodiesterase c-AMP activation Sex hormones also have a pronounced effect on fat metabolism: when they are deficient, synthesisincreases and inhibition of fat breakdown occurs, which is one of the reasons for the increase in body weight in older people who have an age- related decline in the function of the sex glands. 205