dig n abs lipids NURSING 2023.pptxdig n abs lipids NURSING 2023.pptx

dig n abs lipids NURSING 2023.pptxdig n abs lipids NURSING 2023.pptx

1. Digestion & Absorption of lipids Dr.Dinesh kumar Ravi M.B.B.S., MD., FID., PGDEM.,FRCEM CONSULTANT EMERGENCY MEDICINE DIABETOLOGIST ASSISTANT PROFESSOR , BIOCHEMISTRY

2. SPECIFIC LEARNING OBJECTIVES At the end of the session , students must be able to : Describe the enzymes involved in the digestion of lipids Describe the absorption of digested lipids Describe the processes involved in digestion and absorption of dietary lipids and also the key features of their metabolism Describe the role of bile acids in the process of emulsification of lipids Explain Disorders associated

3. The major dietary lipids are triacylglycerol, cholesterol & phospholipids & fatty acids The average normal Indian diet contains about 20-30 g of lipids/day DIETARY LIPIDS

4. lingual lipase : LINGUAL LIPASE by Ebner’s glands on dorsum of tongue Optimum pH: 2.5-5 Splits TAG into Fatty acids(FA) and glycerol. Mainly act on short chain triglycerides (milk, butter) The action of lingual lipase is more significant in the newborns More significant in newborns . DIGESTION IN MOUTH

5. Gastric lipase: Gastric lipase is acid stable, with an optimum pH around 5 . 4 It is secreted by chief cells, the secretion is stimulated by gastrin . Upto 3 0 % digestion of triglycerides occurs in stomach Digestion in Stomach: TAG → DAG + FA MAG + FA

6. DIGESTION OF LIPIDS IN SMALL INTESTINE CHOLECYSTOKININ (CCK) STIMULATES GALL BLADDER AND PANCREAS

7. Emulsification of lipids in the small intestine: Emulsification is a prerequisite for digestion of lipids The lipids are dispersed into smaller droplets; surface tension is reduced; and surface area of droplets is increased This process is favoured by: Bile salts (detergent action) Peristalsis (mechanical mixing) Phospholipids

8. Emulsification of lipids

9. Bile salts The bile salts are sodium glycocholate & sodium taurocholate Bile salts are the biological detergents synthesized from cholesterol in the liver They are secreted with bile into the duodenum Bile salts possess steroid nucleus, the side chain is attached to either glycine (glycocholic acid) or taurine (taurocholic acid) Bile salts are the most effective biological emulsifying agents

10. Bile salts cont.. They interact with lipid particles and the aqueous duodenal contents and convert them into smaller particles (emulsified droplets) The bile salts lower surface tension The emulsification increases the surface area of the particles for enhanced activity of enzymes

11. Mixed Micelle Formation Due to detergent action, the bile salts help to form micellar aggregates Micellar formation is essential for the absorption of fat-soluble vitamins such as vitamin A, D, E and K The micelles are aligned at the microvillous surface of the jejunal mucosa Fatty acids, 2-MAG and other digested products passively diffuse into the mucosal cell

12. Long chain fatty acids are absorbed into the intestinal cell wall, they are re-esterified, made into chylomicrons & enter into lymphatics Short chain fatty acids are directly absorbed into blood capillaries Bile acids are reabsorbed into portal vein Absorption of fatty acids

13. CHYLOMICRONS The lipids that are resynthesized in the intestinal cells are hydrophobic in nature They are put together as lipid droplets and surrounded by a thin layer consisting of mostly apolipoproteins (A1 and B-48) & phospholipids This package of lipids enveloped in the layer stabilizes the droplets and increases their solubility These particles are known as chylomicrons

14. Chylomicrons migrate to the plasma membrane of intestinal mucosal cells They are released into the lymphatic vessels by exocytosis The presence of chylomicrons (Greek; chylos-juice) gives the lymph a milky appearance , observed after a lipid-rich meal Chylomicrons enter the large body veins via the thoracic duct Blood from here flows to the heart & then to the peripheral tissues (muscle, adipose tissue) & finally, to the liver

15. Absorption of fat as chylomicrons

16. Size: 0.1–1 µm Average composition TG (84%) Cholesterol(2%) Ester Cholesterol (4%) Phospholipid (8%) Apo lipoproteins (2%) Formation & transport of chylomicrons

17. Transport & utilization of chylomicrons

18. Clinical significance of Chylomicron synthesis & utilization Defective synthesis- Due to deficiency of apo-B 4 8 protein. The triglyceride may accumulate in intestinal cells.

19. Abnormalities in lipid digestion & Absorption: Defective digestion: In steatorrhea, daily excretion of fat in feces is >6 g/day It is due to chronic diseases of pancreas In such cases, unsplit fat is seen in feces Defective absorption: If the absorption alone is defective, most of the fat in feces may be split fat, i.e. fatty acids and monoglycerides Celiac disease

20. Abnormalities in lipid digestion & Absorption cont.. Surgical removal of intestine Obstruction of bile duct: Due to gall stones, tumors of head of pancreas, enlarged lymph glands, etc. The result is deficiency of bile salts. TAGs with short chain and medium chain fatty acids are digested & absorbed properly, they do not require micellerisation for absorption Since milk fat & coconut oil are made up of medium chain fattyacids,they are therapeutically useful in malabsorption syndromes

21. Chyluria: There is an abnormal connection between the urinary tract & lymphatic drainage system of the intestine. Urine appears milky due to lipid droplets .

22. Chylothorax can result from an abnormal connection between the pleural cavity and thoracic duct resulting in accumulation of lymph in pleural cavity giving Milky pleural effusion

23. Thank You