Bile salts digestion

D. In this situation, bile salts from the pancreas could not enter the digestive tract. Therefore, recycling and excretion of bile salts, digestion of fats, and formation of chylomicrons would all decrease. As a consequence, fat in the feces (steatorrhea) would increase. 

Also see BILE BILE SALTS DIGESTION AND ABSORPTION and GALLSTONES.)... 

A significant fraction of the body s cholesterol is used to form bile acids Oxidation m the liver removes a portion of the CsHi7 side chain and additional hydroxyl groups are intro duced at various positions on the steroid nucleus Cholic acid is the most abundant of the bile acids In the form of certain amide derivatives called bile salts, of which sodium tau rocholate is one example bile acids act as emulsifying agents to aid the digestion of fats... 

Entozyme 18/100 Digestive enymes pancreatin/pepsin/bile salts Robins... 

Bile acids, which exist mainly as bile salts, are polar carboxylic acid derivatives of cholesterol that are important in the digestion of food, especially the solubilization of ingested fats. The Na and salts of glycocholic acid and tauro-cholic acid are the principal bile salts (Ligure 25.41). Glycocholate and tauro-cholate are conjugates of cholic acid with glycine and taurine, respectively. 

In general, the sterols perform a structural function, for example as components of the lipid layers of membranes. The Cis, C19 and C21 steroids mainly perform an endocrine function. In other words they are hormones. The bile salts (C24-steroids) fulfil a functional role in digestion in animals. 

Although products of fat digestion, including cholesterol, are absorbed in the first 100 cm of small intestine, the primary and secondary bile acids are absorbed almost exclusively in the ileum, and 98—99% are returned to the liver via the portal circulation. This is known as the enterohepatic circulation (Figure 26—6). However, lithocholic acid, because of its insolubility, is not reabsorbed to any significant extent. Only a small fraction of the bile salts escapes absorption and is therefore eliminated in the feces. Nonetheless, this represents a major pathway for the elimination of cholesterol. Each day the small pool of bile acids (about 3-5 g) is cycled through the intestine six to ten times and an amount of bile acid equivalent to that lost in the feces is synthesized from cholesterol, so that a pool of bile acids of constant size is maintained. This is accomplished by a system of feedback controls. 

In the in vitro digestion method, the compound of interest is transferred from the food matrix to a bile salt micelle suspension that simulates the in vivo digestion process. This in vitro digestion procedure was first developed to estimate iron availability from meals and since then has been modified and applied to studying carotenoid bioaccessibility from various food matrices. This approach assesses the bioaccessibility of the compound from a certain meal before it is presented to and taken up by intestinal cells. 

Different factors inclnding nntrients, bile salts, pH, and microflora present in the gastrointestinal tract dnring the digestion process can affect the bioaccessibility of a compound (Table 3.2.1). The compoimd of interest is generally consiuned together with other nutrients present in the meal and, once the compound and these nutrients are released from the food matrix during the same period, they may interact in the intestinal liunen. 

Bile is produced continuously by the liver bile salts are secreted by the hepatocytes and the water, sodium bicarbonate, and other inorganic salts are added by the cells of the bile ducts within the liver. The bile is then transported by way of the common bile duct to the duodenum. Bile facilitates fat digestion and absorption throughout the length of the small intestine. In the terminal region of the ileum, the final segment of the small intestine, the bile salts are actively reabsorbed into the blood, returned to the liver by way of the hepatic portal system, and resecreted into the bile. This recycling of the bile salts from the small intestine back to the liver is referred to as enterohepatic circulation. 

The return of the bile salts to the liver from the small intestine is the most potent stimulus of bile secretion. In fact, these bile salts may cycle two to five times during each meal. The intestinal hormone secretin, which is released in response to acid in the duodenum, enhances aqueous alkaline secretion by the liver. Secretin has no effect on the secretion of bile salts. During the cephalic phase of digestion, before food even reaches the stomach or intestine, parasympathetic stimulation, by way of the vagus nerve, promotes bile secretion from the liver. 

The pancreatic digestion conditions studied included pH, the method of pH control, and bile salts mixture and concentration. In addition, experiments were run to determine if mineral solubility was affected by enzymatic activity, or only by pH-induced solubility changes. 

Figure 3. Calcium solubility dependence on bile salt preparation and concentration used in in vitro digestion (pH 6.8-6.9). Key ...

The digestion and absorption of fat is considerably more complex than that of carbohydrate or protein because it is insoluble in water, whereas almost aU enzymes catalyse reactions in an aqueous medium. In such media, fat can form small droplets, an emulsion, which is stable in this medium. Formation of an emulsion is aided by the presence of detergents these possess hydrophobic and hydrophilic groups, so that they associate with both the fat and the aqueous phases. Such compounds are known as emulsifying agents and those involved in digestion are mainly the bile salts and phospholipids. 

The products of triacylglycerol digestion, mainly monoacylglycerol and long-chain fatty acids, interact with bile salts to form micelles, which comprise bile salts/ monoacylglycerols/phospholipids and fatty acids. The micelle aids the absorption of monoacylglycerol and fatty... 

Patients suffering from obstruction of the bile duct fail to digest fat, due to a deficiency of bile salts to maintain an effective emulsion of fat. 

Bile salts consist of taurine linked to bile acids. The salts are essential for digestion and absorption of fat and also of fat-soluble vitamins and cholesterol. 

Fats and other lipids are poorly soluble in water. The larger the accessible surface is—i. e., the better the fat is emulsified—the easier it is for enzymes to hydrolyze it (see p. 270). Due to the special properties of milk, milk fats already reach the gastrointestinal tract in emulsified form. Digestion of them therefore already starts in the oral cavity and stomach, where lipases in the saliva and gastric juice are available. Lipids that are less accessible—e.g., from roast pork—are emulsified in the small intestine by bile salts and bile phospholipids. Only then are they capable of being attacked by pancreatic lipase [4] (see p. 270). 

Bile is an important product released by the hepatocytes. It promotes the digestion of fats from food by emulsifying them in the small intestine (see p. 2770). The emulsifying components of bile, apart from phospholipids, mainly consist of bile acids and bile salts (see below). The bile also contains free cholesterol, which is excreted in this way (see p. 312). 

The bile salts are either secreted directly into the duodenum or stored in the gallbladder for use in emulsifying dietary fats during digestion. 

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