Lipids are a heterogeneous group of organic compounds that contain carbon, hydrogen, oxygen, and sometimes phosphorus and sulfur. They are insoluble in water but soluble in organic solvents. Dietary lipids undergo digestion in the mouth, stomach, and small intestine to be broken down into absorbable forms. In the small intestine, bile salts emulsify lipids and pancreatic lipases hydrolyze triglycerides into fatty acids and monoglycerides. Absorbed lipids are packaged into micelles that enter mucosal cells for re-esterification. Clinical issues related to lipid digestion and absorption include steatorrhea, cystic fibrosis, chyluria, chylothorax, and defects in pancreatic function or bile

1. Digestion and
Absorption
Of
Lipids

2.  Heterogenous group of Organic
compounds,
 Contains C, H, O and some times P
and S
 Esters of Fatty acids with alcohol
 Insoluble in water
 Soluble in organic solvents

3. SOURCES OF
LIPIDS
Endogenous source:
Lipids which are synthesized in body,
Fatty acids, TAG, Cholesterol,
Cholesterol esters, Phospho lipids
Exogenous Sources:
Lipids obtained through diet,
TAG – 90%, Phospholipids, Cholesterol
Cholesterol esters, Free fatty acids,
And Fat soluble vitamins – 10%

4. Exogenous sources
of lipids
Animal source:
Milk, Butter, Ghee,
Meat, Egg yolk, Pork
Vegetable Sources:
Oils from various oil seeds like
Ground nut, Sunflower, Coconut,
Mustered seed, Cotton seed

5. How much is required ?

6. TAG, 90
FFA, 4
PL - 5
cholesterol,
2
TAG Cholesterol Phospholipid FFA
Dietary Lipid contents

7. What is digestion?
Complex lipid food molecules are
converted to simple and absorbable
forms
• Requirements
• Place
• Emulsifiers… Bile,
PL
• Enzymes…….Lipases
• Difficulty
• Hydrophobic
molecules in
hydrophilic
environment
• Solution
• Emulsified,
• increased surface
area,

8. STRUCTURE OF A LIPID

10. Digestion in Mouth
Lingual Lipase
Ebner’s gland
Short chain fatty acids
From TAG of milk
Short chain fatty acids
+ Glycerol
Pediatric group
important
Absorbed directly
into blood stream

11. Digestion in the stomach
Churning of the food
Brings emulsification Tri acyl glyceride having
medium chain FA
hydrolysed
Action of lingual lipase
continued
TAG → MAG + FA
DAG
Important in infants
digestion of milk fat
Less important or not at all in
adult
30% digestion
TAG

12. Digestion in small intestine
Helped by
1. Emulsification
2. Action of lipase

13. LIPID DIGESTION AND ABSORPTION
.

14. ACTION OF ESTERASES
PANCREATIC ESTERASE
FFA
CHOLESTEROL ESTERASES
TAG 2,3-DAG 2-MAG
1-MAG GLYCEROL FFA2-MAG
LIPASE LIPASE
ISOMERASE LIPASE

Action of pancreatic lipase on Tri acyl glycerol
Play major role
Colipase
Bile acids
Olestra and orlistat powrful inhibitor of pancreatic lip

16. ACTION OF PACREATIC LIPASES

17. End product of Triacyl glyceride
digestion
Glycerol,
Mono acyl glycerol,
Di acyl glycerol
and
free fatty acids

18. Digestion of phospholipids
Enzymes --- Phospholipases
Four different types
Pancreatic ---
Phopholipase A2
Product lysophospholipid

19. Phospholipase A1
Phospholipase A2
Phospholipase C Phospholipase D
Action of Phospholipases

20. Action of Esterases
Pancreatic origin
Cholesterol Ester
Cholesterol
Free fatty acid
Cholesterol esterase
Bile acids
+

21. 1. EMULSIFICATION
2. STABLISE THE EMULSION
3. PROVIDES ALKALINE MEDIUM
4. HELPS IN ABSORPTION
5. PRODUCE SURFACTANTS
6. POTENT CHOLERETICS
7. EXCRETES THE WASTE
8. SOLUBLISES THE CHOLESTEROL

23. ABSORPTION THEORIES
LIPOLYTIC THEORY BY
VERZAR
PARTITION THEORY BY
FRAZER
BERGSTROM THEORY

24. Bergstrom

25. ABSORPTION

27. MICELLE

31. CLINICAL ASPECTS
Digestion and absorption of lipids
Steatorrhea
Cystic fibrosis
Chyluria
Chylothorax

32. STEATORRHEA
A clinical condition
Daily excretion of fat in feces is more
than 6 gm per day.
CAUSES:
– Defective digestion of fat
– Defective absorption of fat

33. Defective Digestion - 1
• Bile duct
obstruction
• Gall stone
• Emulsification
defective
• Improper digestion
• Split fat in stool

34. Defective Digestion -
2
• Disease of
pancreas
• Pancreatitis
• Tumor- head of
pancreas
• Partial or complete
Pancreactomy
• Pancreatic juice
block
• No lipase
• Unsplit fat in stool

35. • Normal
• Pancreatic lipase is found in
high concentration in
pancreatic secretions.
• It has high catalytic activity.
• BUT
• Cystic Fibrosis:
• Severe pancreatic lipase
deficiency seen in cystic
fibrosis results in
malabsorption of lipids.
Bacterial infection

36. Causes of steatorrhea
Gastractomy
Pancreactomy
Surgical removal of Small
Cholecystectomy

37. Normal Absorption in small
intestine

38. Coeliac sprue Change in the intestinal
mucosal cell membrane
leads to improper
absorption

40. Prevent Fat Absorption and Obesity
• Olestra:
• Commercial lipid produced by esterification of
natural fatty acids with sucrose instead glycerol.
• 6 to 8 fatty acids are covalently coupled with
sucrose
• They taste like lipid but not hydrolyzed to
absorbable constituents and hence excreted.
• Orlistat:
• Non hydrolysable analog of triacylglycerol.
• Powerful inhibitor of pancreatic lipase.
• Blocks lipid absorption and hence results in lipid
excretion

41. • Chyluria
• Abnormal
connection
between
lymphatics and
urinary tract.
• Milky urine

42. • Chylothrorax
• Abnormal connection
between pleural cavity
and thoracic duct
• Leakage of lipid in pleural
fluid

43. Oral fat tolerance test
Deficiency of lipoprotein lipase in the peripheral tissues