Absorption of Dietary Fats

Fats or lipids are water-insoluble and tend to coalesce into droplets in water, 

Emulsification breaks lipid droplets into smaller-sized structures, which increases their overall surface area. 

This process involves mixing (peristalsis) in the duodenum with bile salts, which act like detergents to dissipate lipid droplets. 

The increased contact area between water and lipids facilitates interaction with d estive enzymes. 

Dietary lipids are processed by several pancreatic lipases, whose actions facilitate uptake by intestinal epithelial cells (enterocytes). 

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Bde salts, cholesterol, phosphoHpids, and other minor components are secreted by the Hver. Bile salts serve three significant physiological functions. The hydrophilic carboxylate group, which is attached via an alkyl chain to the hydrophobic steroid skeleton, allows the bile salts to form water-soluble micelles with cholesterol and phosphoHpids in the bile. These micelles assist in the solvation of cholesterol. By solvating cholesterol, bile salts contribute to the homeostatic regulation of the amount of cholesterol in the whole body. Bile salts are also necessary for the intestinal absorption of dietary fats and fat-soluble vitamins (24—26). 

Factors negatively affecting absorption of dietary fat may also be expected to negatively affect absorption of calcium. In the normal, healthy adult, dietary fat absorption is very efficient. However, such factors as level of dietary fat, fatty acid chain length, degree of fatty acid saturatedness, or triglyceride structure may have a measurable effect on calcium absorption under some circumstances. 

Orlistat is a pancreatic lipase inhibitor used in conjunction with a hypocaloric diet to reduce the absorption of dietary fat in obese patients. Orlistat is administered twice daily immediately before, during or up to 1 hour after each meal. If the meal contains no fat there is no need to take Orlistat. 

Pharmacology Orlistat is a reversible lipase inhibitor for obesity management that acts by inhibiting the absorption of dietary fats. It exerts its therapeutic activity in the lumen of the stomach and small intestine. 

FIGURE 5.7 Absorption of dietary fat-soluble substances via the lipid route affected by insufficiently emulsified and micellised lipids. 

Individuals who have had surgical resection of portions of the intestine, eg, due to treatment of Crohn s disease, may also have impaired absorption of dietary fats. 

Mecfianism of Action A gastric and pancreatic lipase inhibitor that inhibits absorption of dietary fats by inactivating gastric and pancreatic enzymes. Therapeutic Effect Resulting caloric deficit may positively affect weight control. 

Weight loss aids Orlistat, 60 mg with each meal containing fat (not to exceed 180 mg/d) Alii Approved for weight loss in overweight adults > 18 years of age when used in combination with a reduced-calorie, low-fat diet and exercise program. Orlistat is a nonsystemically absorbed inhibitor of gastrointestinal lipase that blocks the absorption of dietary fat. OTC formulation is a half-strength version of the prescription product (Xenical). 

Decreases absorption of dietary fat and cholesterol Increases fecal loss of cholesterol... 

CCK stimulates the gall bladder to contract, thereby discharging the bile salts stored inside through the bile duct to enter the duodenmn. Bile salts are required for digestion and efficient absorption of dietary fats. Bile salts also are required for the efficient absorption of the fat-soluble vitamins. 

Absorption of dietary fat is a remarkably efficient process, so that in normal health, fecal fat is largely (if not entirely) derived from endogenous rather than dietary sources. Adequate dietary fat intake is therefore essential to minimize false-negative results. The BSG guidehnes recommend a diet containing at least 70 g fat for 6 days. In the UK only a minority of laboratories try to control (20%) or retrospectively assess (8%) fat intake. Patients with steatorrhea may reduce their fat intake to control their diarrhea and despite laboratory instructions may not increase their dietary fat... 

Cholesterol is synthesized from acetyl-CoA in a multistep pathway that occurs primarily in the liver. Small amounts of cholesterol are used to synthesize biologically powerful steroid hormones. Cholesterol is degraded primarily by conversion to the bile salts, which facilitate the emulsification and absorption of dietary fat. 

The intestinal assembly of CM is essential for the absorption of dietary fat and fat-soluble vitamins. Intestinal enterocytes rapidly and efficiently absorb fatty acids released from emulsification and hydrolysis of dietary fat, and re-synthesize TG to form a heterogeneous population of lipoproteins referred to as CM. Available evidence suggests that the intestine tightly regulates its intracellular handling of newly synthesized TG and its output of TG into CM. Intestinally derived lipoproteins have a range of sizes that include LDL-sized CM (CMl l),... 

It was demonstrated that the anti-obesity effects of oolong tea in high-fat diet-treated mice might be partly due to the inhibitory actions of the saponin fraction in oolong tea on pancreatic lipase activity. In this study, tea saponin prevented the high-fat diet-induced increases in body and parametrial adipose tissue weights by inhibiting the intestinal absorption of dietary fat via inhibition of pancreatic lipase activity, Fig. (5). 

Summarizing all these results, the reduction of fat storage and the antihyperlipidaemic action of chondroitin sulfate might be due to the inhibition of small intestinal absorption of dietary fat through the... 

A. Octreotide may inhibit the absorption of dietary fats and cyclosporine. 

Orlistat inhibits pancreatic lipase and prevents the absorption of dietary fat and lipophilic molecules such as ciclosporin. Absorption of ciclosporin from the oil suspension formulation (Sandimmun) is more dependent on the lipid absorption stage and thus may be more affected by orlistat than the microemulsion form (Neorat) ... 

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