Lipid digestion and absorption

These agents are administered to aid in the digestion of food. The primary digestant preparations contain pancreatic enzymes or bile salts. Pancreatic enzymes such as amylase, trypsin, and lipase are responsible for digestion of carbohydrates, proteins, and lipids, respectively. These enzymes are normally synthesized in the pancreas and secreted into the duodenum via the pancreatic duct. Bile salts are synthesized in the liver, stored in the gallbladder, and released into the duodenum via the common bile duct. Bile salts serve to emulsify lipids in the intestinal tract and are important in lipid digestion and absorption. 

Understand the mechanisms involved in lipid digestion and absorption, including bile salt metabolism. 

This could include retinol, cholecalciferol/ergocalciferol, a-tocopherol, vitamin K from food, all of which are more readily absorbed when they can be part of a normal mixed micelle process that occurs with lipid digestion and absorption... 

Based on data on PAHs, absorption of PAH components of coal tar products after oral exposure may be positively influenced by the presence of oils and fats in the stomach, and bile in the intestines (Agency for Toxic Substances and Disease Registry 1995). Due to relative water insolubility of PAHs, absorption is enhanced by solubilization in an intermediate phase than can be metabolized during the process of lipid digestion and absorption. Excretion after oral exposure may be detected hours to days after exposure. 

Collection of duodenal contents through a duodenal tube after feeding a test meal containing a non-absorbable marker is a commonly used technique for studies of lipid digestion and absorption in man [55]. Using a multilumen tube, Simmonds et al. [56] were able to study in detail in man the absorption kinetics of cholesterol from a micellar solution. 

Cholesterol adds stability to the phospholipid bilayer of membranes. It serves as the precursor of the bile salts, detergent-like compounds that function in the process of lipid digestion and absorption (Fig. VI.3). Cholesterol also serves as the precursor of the steroid hormones, which have many actions, including the regulation of metabolism, growth, and reproduction. 

Lie, O. and Lambertsen, G., 1991a, Lipid digestion and absorption in cod (Gadus morhua) comparing triacylglycerols, wax esters and diacylalkylglycerols, Comp. Biochem. Physiol, 98A, 159. 

Ursodeoxycholic acid (UDCA), cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), and their glyco and tauro-derivatives (Figure 19.7) play an important role in biological systems. Their biological functions are principally associated with lipid digestion and absorption. 

Inhibitors of pancreatic lipase (section 4.3.2) do reduce lipid digestion and absorption, and some have been licensed for pharmaceutical use. The problem with their use is that undigested fat in the gastrointestinal tract can cause discomfort and, if enough is present, foul-smelling fatty diarrhoea (steatorrhoea). 

Also see FATS AND OTHER LIPIDS DIGESTION AND ABSORPTION MODIFIED DIETS MALABSORPTION SYNDROME METABOLISM and OBESITY.)... 

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