This presentation explains metabolism of lipoproteins (Chylomicron, VLDL, LDL, HDL) in very simple way. The presentation contains lots of animation to explain metabolism of individual lipoproteins.

2. Transport of lipids

3. Transport of Lipids in the Blood
Fat absorbed from the diet & fat synthesized by the
liver must be transported between the various tissues
& organs for utilization & storage.
“
”
Since lipids are insoluble in water, these are
transported in the form of lipoprotein.
“
”

4. Logic behind
the structural design of lipoproteins
Serum

5. Lipoprotein
Lipo-
proteins
Triglycerides
Phosholipids
Cholesterol
Proteins

6. Structure of Lipoprotein
Cholesterol Ester
Triacylglycerol
Phospholipid
Free Cholesterol
Apoprotein

8. Classification of Lipoproteins
• Lp can be classified based on….
– Density
– Electrophoresis

9. Classification of Lipoproteins

10.  Formed in the intestinal mucosal cells
 Rich in TG
 Contain apo-B-48
 Apo-E
 Apo-C
 apo-A
 Transport of
dietary lipids

11. 90%
2%
3%
5%
Chylomicron
Triglycerides
Protein
Phospholipids
Cholesterol

12. • Synthesized in the liver
 Rich in TG
• Contain…
– apo-B-100,
– C-II and
– apo-E
 Transport of
endogenous lipids

13. 60% 5%
15%
20%
Very Low Density lipoproteins (VLDL) Triglycerides
Protein
Phospholipids
Cholesterol

14.  Synthesized from VLDL in circulation
 Rich in cholesterol
 Contain apoB-100
 Transport of cholesterol
to peripheral tissues

15. 8%
20%22%
50%
Low Density lipoproteins (LDL) Triglycerides
Protein
Phospholipids
Cholesterol

16. • Synthesized in the liver and intestine
• Contain
– Apo-A-I[Major]
– Apo-C
– Apo-E
 Transport of cholesterol
from peripheral tissues to
Liver.

17. 5%
40%
30%
25%
High Density lipoproteins (HDL)
Triglycerides
Protein
Phospholipids
Cholesterol

18. Diagrammatic representation of lipoprotein with inc
reasing densities
Density 
% Protein 
Diameter 

21. Apoproteins

29. chylomicron
Chylomicron
remnant
Apo C-ll
Apo E
Apo C-ll
Dietary Lipids
HDL
Capillaries
Glycerol
Liver
Lipoprotein
lipase
GIT
Muscle
Adipose tissue
Fat
Fatty acids
Metabolism of
Chylomicrons
Nascent
chylomicron

30. VLDL
Apo C-ll
Apo E
Apo C-ll &
Apo E
HDL
Capillaries
Glycerol
Liver
Lipoprotein
lipase
Muscle
Adipose tissue
Fat
Fatty acids
Metabolism of
VLDL
IDLLDL
Muscle
Nascent
VLDL

31. Metabolism of
LDL
Regulated pathway

32. Regulated pathway

36. Macrophage Foam cell
Antioxidants Free radicals+-
LDL
Oxidized
LDL

37. Unregulated pathway
Metabolism of
LDL

39. Lipoprotein (a) - “a little rascal”
• Lp(a) is very strongly associated with myocardial
infarction (MI)
• And is sometimes called the “little rascal”.
• Lp(a), when present, is attached to apo-B-100 by
a disulfide bond.
• Lp(a) is associated with heart attacks at the age
of 30 or 40 years.
“Indians have a higher level of Lp(a) than Western
populations”.

40. Lipoprotein (a), “a little rascal”.

41. GIT
Nascent
HDL
Muscle
Adipose tissue
Fat
HDL3
HDL2
VLDL
Chole
Chole
LCAT
CCE
Metabolism of
HDL
LCAT
C, CE
Bile acids &
cholesterol
(in bile)
Chole

42. LCAT
Lecithin-Cholesterol acyl transferase
[LCAT]
• a plasma enzyme, synthesized in the liver
• LCAT activity is associated with apo A1 of HDL
• It allows trapping of cholesterol in HDL
• It is responsible for the reverse cholesterol
transport.

43. AshokKatta
Cholesterol ester transfer protein [CETP]

44. HDL and Reverse Cholesterol Transport

45. Diagnostic importance of lipoproteins
Plasma lipid profile

47. Hyperlipoproteinemia
• Elevation in one or more of the lipoprotein fractions
constitutes hyperlipoproteinemias.
• These disorders may be either…
– Primary Hyperlipoproteinemia or
– Secondary Hyperlipoproteinemia.
• Frederickson’s classification of hyperliporoteinemias
based on the electrophoretic patterns of plasma
lipoproteins—is widely accepted to understand these
disorders.

48. Primary Hyperlipoproteinemia

49. Hypolipoproteinemia
• In hypolipoproteinemia concentration of one
or more lipoproteins in plasma is decreased.
– Abetalipoproteinemia
– Familial alpha-lipoprotein deficiency

50. Abetalipoproteinemia
• an autosomal recessive defect
• a genetic defect in the synthesis of apo B.
• The synthesis of lipoproteins that contain apo B 
(chylomicron and VLDL).
• As a result, LDL is totally absent in circulation.
• Both apo B-48 and B-100 are affected because
they are inherited from the same gene.
• Fat malabsorption occurs.
• Absorption of fat soluble vitamins is severely
impaired.
• Resulting in degenerative changes in retina which
may lead to blindness.

51. Familial alpha-lipoprotein deficiency
(Tangier disease)
• Due to an inability to synthesize apo A.
• Apo A is the major apolipoprotein of HDL.
• This results in  level of HDL in plasma and
• Impair reverse transport of cholesterol.
• This leads to the accumulation of cholesterol
esters in tissue.

52. ….