Excretion of Cholesterol

Cholesterol excretion takes place predominantly through the gastrointesti- 

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The second thing that happens is a very good thing. The liver upregulates its LDL receptor level. In snm, the liver does the two things that it can do to maintain an adequate source of its cholesterol pump up the synthesis (to normal or slightly subnormal rates only) and pnmp np the seqnestration of cholesterol from the blood LDLs. The net effect is that the rate of excretion of cholesterol from the body is increased due to the increase in the nnmber of LDL receptors expressed on hepatic cells without compromising the availability of cholesterol to meet cellular needs. 

Hypolipemic activity. Fiber, administered orally to nine adults with ileostomies at a dose of 13 g/day, increased the excretion of cholesterol " Petroleum ether extract of the fresh fruit, administered to pigs at a concentration of 3.5 g/kg of diet, was inactive "" . Purified green barley extract, in human mononuclear culture of cells isolated from perithelial blood and synovial fluid of patients with rheumatoid arthritis, was active . Leaf essence, administered to atherosclerotic New Zealand White male rabbits at a dose of 1% of diet, produced a decrease of plasma total cholesterol, triacylglycerol, lucigenin-chemilumines-cence, and luminal-chemiluminescence levels. The value of Tj of red blood cell hemolysis and the lag phase of LDL oxidation increased in barley-treated group compared with the control. Ninety percent of the intimal surface of the thoracic aorta was covered with atherosclerotic lesions in the... 

Fenofibrate may increase excretion of cholesterol into bile, leading to cholelithiasis,... 

In summary, the consumption of garlic appears to reduce serum cholesterol in experimental animals in a dose-dependent fashion. This may be due to decreased synthesis or increased excretion of cholesterol through the intestinal tract. It has been reported that garlic consumption increases high-density lipoprotein (HDL) levels, which may help to remove excess cholesterol from arterial tissue. 

Ellegard, L., Andersson, H., and Bosaeus, I. 1997. Inulin and oligofructose do not influence the absorption of cholesterol, or the excretion of cholesterol, Ca, Mg, Zn, Fe, or bile acids but increases energy excretion in ileostomy subjects. Eur. J. Clin. Nutr. 51, 1-5. 

Bile salts (or bile acids) are polar derivatives of cholesterol and constitute the major pathway for the excretion of cholesterol in mammals. In the liver, cholesterol is converted into the activated intermediate cholyl CoA which then reacts either with the amino group of glycine to form glycocholate (Fig. 3a), or with the amino group of taurine (H2N-CH2-CH2-S03", a derivative of cysteine) to form taurocholate (Fig. 3b). After synthesis in the liver, the bile salts glycocholate and taurocholate are stored and concentrated in the gall bladder, before release into the small intestine. Since they contain both polar and nonpolar... 

Diet-induced hypercholesterolemia is useful only for detection of agents interfering with the adsorption, degradation and excretion of cholesterol. Agents interfering with cholesterol biosynthesis are less probable to be detected. 

In chronic cholestasis, xanthelasmas and xanthomas occur as a result of impaired catabolism and reduced excretion of cholesterol. Only when cholesterol levels of >400 mg/dl persist over a period of more than 3 months do these deposits form in the skin. Occasionally, peripheral xanthomatous neuropathy is witnessed. 

The regulation of bile acid metabolism is a major function of the liver. Alterations in bile acid metabolism are usually a reflection of liver dysfunction. Cholesterol homeostasis is in large part maintained by the conversion of cholesterol to bile acids and subsequent regulation of bile add metabolism. Bile acids themselves provide surface-active detergent molecules that facilitate both hepatic excretion of cholesterol and solubilization of lipids for intestinal absorption. Bile acid homeostasis requires normal terminal ileum function to absorb bile adds for recirculation (enterohepatic circulation). Alterations in hepatic bile acid synthesis, intracellular metabolism, excretion, intestinal absorption, or plasma extraction are reflected in derangements in bile add metabolism. 

Nakamura, H. (1966) Effect of y-oryzanol on hepatic cholesterol biosynthesis and fecal excretion of cholesterol metabolites. Radioisotopes, 25, 371-374. 

Increased excretion of cholesterol is thought to be the mechanism for reducing serum cholesterol. Several investigators have reported increased fecal fat (7,19), sterols (7,9,19.26) or bile acids (7,9, 29,30). Kay and Truswell T) reported significant increases in fecal fat excretion, averaging 44% fecal cholesterol. 

A major toxicity of the fibrates is increased risk of gallstone formation, which may be due to enhanced biliary excretion of cholesterol. The answer is (B). 

Dietary pectin affects lipid metabolism, especially that of cholesterol. One of the explanations proposed to explain an action of pectin on cholesterol metabolism is through its ability to bind bile acids and bile salts. However, pectin also has the property of forming a gel in water. This gel lowers the intestinal absorption of cholesterol and thereby decreases liver cholesterol. Recently, evidence has been obtained that the presence of pectin in a cholesterol diet increases the excretion of cholesterol esters. Results from the administration of cholesterol-4-l C in the diet showed that the presence of pectin slows gastric emptying and results in more labeled cholesterol as well as cholesterol esters in all segments of the gut. 

An isolated defect in bile acid production has been found so far only in familial hypercholesterolemia (62), though even in this entity cholesterol catabolism as a whole may be decreased. Essential hypercholesterolemics (11) and hypothyroid patients (11,89) also tend to have a low bile salt elimination, though the excretion of cholesterol as such appears to decrease, too, particularly in the latter condition. In the circumstances in which bile salt elimination is decreased as a result of decreased hepatic function, elimination of cholesterol as such is also reduced (11). Under these conditions, serum cholesterol apparently increases only when the amount of elimination is decreased more than the feedback mechanism(s) are able to suppress synthesis, i.e., when the production exceeds elimination. 

The effects of thyroid hormone on cholesterol metabolism have been studied in bile fistula rats Such preparations exhibit an inverse relationship between serum cholesterol levels and biliary cholesterol concentrations. The level of biliary cholesterol is directly related to thyroid activity, and the biliary excretion of cholesterol increases in the hyperthyroid state and decreases in the hypothyroid state (2,3). 

Recently, there have been two extensive reviews of the role of polyunsaturated fatty acids in the diet. Hoffman and Forster (1981) discussed the influence of dietary linoleic acid on blood pressure regulation-particularly in relation to salt-loaded individuals. In addition, the mechanism of the hypochol-esterolaemic effects of polyunsaturated fatty acids was discussed by Paul et aL (1980). These authors classified the hypocholesterolaemic effect as being due to reduced absorption of cholesterol, redistribution of cholesterol from blood to tissues, reduced cholesterol synthesis and increased excretion of cholesterol or its catabolites. These various factors have all been involved in the hypocholesterolaemic effect but the evidence is equivocal in each case. Other sources of information on dietary polyunsaturated fatty acids are Vergroesen (1975) and Kunau and Holman (1977). 

LDL-C oxidation is unquestionably an important contributor to atherogenesis. However, although the extent to which LDL-C can be oxidized ex vivo has been extensively investigated, its impact in vivo is contentious. The potential inhibition of LDL-C oxidation was tested for six commercial apple juices and the peel, flesh and whole fresh Red Delicious apples. All the tested products inhibited LDL-C oxidation assessed by an in vitro copper catalyzed human LDL-C oxidation system. The inhibition of the test products was 21, 34 and 38% for flesh, whole apple and peel, respectively, and 9—34% for the juices. Apple peel extract rich in quercetin also inhibited LDL-(Z oxidation in vitroP Moreover, apple polyphenols have been shown to increase the excretion of cholesterol oxidation products and protect against peroxidation in rats. ... 

The possible mechanism of action of capsaicinoids is the net effect of decreased cholesterol absorption and increased excretion of cholesterol and bile acids in the feces which may lead to a decrease in plasma LDL-cholesterol concentration by induced expression of hepatic LDL receptors [110]. These authors also have discussed the differences in response between normal and cholesterol-fed animals to possible hypocholesterolemic compounds. It has been demonstrated that dietary capsaicin stimulates hepatic conversion of cholesterol to bile acids through a stimulation of the activity of cholesterol-7a-hydroxylase, an important pathway... 

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