Lipid dietary, solubilization

II Increased extent and possibly rate Large fluid volume in stomach. Solubilization in mixed micelles and dietary lipids... 

Bile acids are sterol derivatives derived from cholesterol that have two major functions. (l) The cholesterol delivered back to the liver by reverse cholesterol transport is converted into bile acids, which are excreted from the body via the intestine. (2) The bile acids secreted into the intestine are required for the solubilization of dietary lipids so that they can be degraded by lipases and absorbed into the intestinal wall (see fig. 18.2). 

The bile acids are usually conjugated to the amino acids, glycine or taurine, as shown for the formation of glycocholate in figure 20.21. It is in this form that the bile acids are secreted via the gallbladder into the intestine where they are critically important for the solubilization of dietary lipids. At pH 7, these acids exist as the sodium salts and are often referred to as bile salts. Of course in the acidic environment of the small intestine, they occur largely in their acidic form. 

Mel nikov, S.M., Seijen ten Hoorn, J.W., and Eijkelenboom, A.P. 2004a. Effect of phytosterols and phytostanols on the solubilization of cholesterol by dietary mixed micelles An in vitro study. Chem. Phys. Lipids 127, 121-141. 

As polar derivatives of cholesterol, bile salts are highly effective detergents because they contain both polar and nonpolar regions. Bile salts are synthesized in the liver, stored and concentrated in the gall bladder, and then released into the small intestine. Bile salts, the major constituent of bile, solubilize dietary lipids (Section 22.1.1). Solubilization increases in the effective surface area of lipids with two consequences more surface area is exposed to the digestive action of lipases and lipids are more readily absorbed by the intestine. Bile salts are also the major breakdown products of cholesterol. 

Bile contains conjugates of cholic acid and cheno-deoxycholic acid, which emulsify dietary fat, facilitate lipolysis, and transport lipid molecules through the unstirred layer of the intestinal mucosa by micellar solubilization. The ability of bile salts to promote lipid... 

Bile salts Cholesterol derivatives with detergent-like properties used to solubilize cholesterol, assist in intestinal absorption of fat-soluble vitamins, and emulsify dietary lipids passing through the intestine to enable fat digestion and absorption by exposing fats to pancreatic lipases. 

The bile salts are syhthesized in the liver, stored ih the gallbladder, and released into the small intestine, where they emulsify dietary lipids and fat-soluble vitamins. This solubilization promotes the absorption of these dietary compounds through the intestinal mucosa. Bile salts are predominantly reabsorbed through the enterohepatic circulation and returned to the liver, where they exert a negative feedback control on 7a-hydroxylase and, thus, regulate any subsequent conversion of cholesterol (4,7). 

The kinetic changes by feeding corn oil supplemented diet with cholesterol are noticeable only after 24 hours (Bloj et al 1973b). When the rats receiving the diet with cholesterol for 11 days were fed the same diet without cholesterol, the kinetic parameters recovered their original values within 4 to 11 days (Bloj et al., 1976a). Values of n=1.6 and lower K 0.5 values were found for the acetylcholinesterase after membrane solubilization irrespective of the kind of dietary lipid used. 

In mammals, carotenoids, freed from foodstuffs by proteolytic digestion of proteins in the stomach and small intestine, are solubilized by conjugated bile salts in the small intestine and are absorbed with other lipids (16,23,24). Dietary... 

Dietary retinyl esters must be hydrolyzed in the lumen of the small intestine before retinol is absorbed, while carotenoids must be absorbed into the intestinal mucosa before being cleaved intracel-lularly. Several enzymes with retinyl ester hydrolase (REH) activity are present in pancreatic juice or on the brush border of duodenal and jujenal enterocytes (Figure 3). Retinol and carotenoids must be solubilized in the lumen in mixed micelles composed of bile acids and products of lipid digestion prior to their uptake into enterocytes. These processes require the release of an adequate amount of bile... 

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