TRIGYCERIDE METABOLISM

1. TRIGLYCERIDE METABOLISM
AND
ADIPOSE TISSUE
Dr. ROOPA R
ASSISTANT PROFESSOR
DEPARTMENT OF BIOCHEMISTRY
GVMCH

2. Specific learning objectives
1.TRIGLYCERIDE SYNTHESIS
2.TRIGLYCERIDE BREAKDOWN
3.TRIGLYCERIDE METABOLISM AND
REGULATION IN ADIPOSE TISSUE
4.FATTY LIVER AND ITS PREVENTION
5.ADIPOSE TISSUE AND DM, OBESITY,
METABOLIC SYNDROME

3. Commonly known as NEUTRAL FAT OR
TRIGLYCERIDES (TGS)
Esters of trihydric alcohol glycerol and fatty acids
TAGs (TRI ACYL GLYCEROLS)
2
1
3

4. Major energy reserves stored in adipose tissue.
Helps in synthesis of compound lipids such as
phospholipids.
TAGs (TRI ACYL GLYCEROLS)
Major Dietary Lipids

5. TRIACYLGLYCEROL SYNTHESIS - LIPOGENESIS
Major sites:
LIVER AND ADIPOSE TISSUE
Minor Sites:
SMALL INTESTINE, MAMMARY GLAND
AND MUSCLE
ACYLATION OF GLYCEROL
OR

6. LIPOGENESIS
Intestine

7. SOURCES OF EACH
COMPONENT
1. FATTY ACIDS
2. GLYCEROL
3. DIHYDROXY ACETONE PHOSPHATE
4. MONO ACYL GLYCEROL

8. TRIACYLGLYCEROL SYNTHESIS
1. PRODUCTION OF GLYCEROL PHOSPHATE
2. ACTIVATION OF FATTY ACID
4. FORMATION OF PHOSPHATIDIC ACID
5. FORMATION OFDAG
6.FORMATION OFTAG
3. FORMATION OF LYSOPHOSPHATIDIC ACID

9. TRIACYLGLYCEROL SYNTHESIS
1. PRODUCTION OF GLYCEROL PHOSPHATE

10. TRIACYLGLYCEROL SYNTHESIS
2

11. TAGSYNTHESIS 3. FORMATION OF LYSOPHOSPHATIDIC ACID

12. 4,5,6.FORMATIONOFPHOSPHATIDICACID,DAGANDTAG

13. (Dependency)
R
TO SUMMARISE:

14. 1.TAG produced in the liver packaged
into very-low density lipoproteins
(VLDL)
2.TAG produced in the adipose tissue is
stored in it.
FATE OF TAG

15. TRIACYLGLYCEROL BREAKDOWN-
LIPOLYSIS

16. Physiologically important lipases
Lipase Site of action Preferred substrate Product(s)
Lingual / acid stable
lipase
Mouth , stomach TAGS with med chain
FAS
FFA+DAG
Pancreatic lipase + co-
lipase
Small intestine TAGS with long chain
FAS
FFA+2MAG
Intestinal lipase with
bile acids
Small intestine TAGS with med chain
FAS
2FFA+glycerol
Phospholipase A2 +
bile acids
Small intestine PLs with unsat. FA on
position 2
Unsat FFA lysolecithin
Lipoprotien lipase
insulin (+)
Capillary walls TAGs in chylomicron
or VLDL
FFA+glycerol
Hormone sensitive
lipase
Adipose cell TAG stored in adipose
cells
FFA+glycerol

17. Only triacylglycerol lipase is
activated by EPINEPHRINE
OR GLUCAGON.
TRIACYLGLYCEROL BREAKDOWN-
LIPOLYSIS

18. FATE OF TRIACYLGLYCEROL IN OTHER
TISSUES
&RBC

19. ROLE OF ADIPOSE
TISSUE IN TAG
METABOLISM

20. Adipos
e
tissue

21. ADIPOSE TISSUE
Unilocular (white) Fat
Multilocular (brown) Fat
Male
greater omentum
(pot belly)
Female
buttocks, thighs
breasts
developing fat- cuddly babies
brown fat of hibernating animals

26. STORAGE OF TAG IN ADIPOSE
TISSUE

27. RELEASE OF TAG FROM ADIPOSE
TISSUE

28. Liver-adipose tissue axis

29. REGULATION OF LIPOGENESIS AND
LIPOLYSIS IN ADIPOSE TISSUE

30. β ADRENERGIC
RECEPTOR
**rate-limiting enzyme
HORMONALREGULATION OF LIPOGENESIS AND
LIPOLYSIS

31. TO SUMMARISE: ROLE OF ADIPOSE TISSUE IN TAG
METABOLISM

32. Adipose
tissue
Adipose tissue is now considered to be more than just a
STORAGE ORGAN FOR TAG
It is considered an ACTIVE ENDOCRINE ORGAN
that secretes a variety of factors that regulate glucose
and fat metabolism
ADIPOKINES
(adipose tissue dervived hormones)

33.  LEPTIN --
 ADIPONECTIN
 RESISTIN-resists insulin action and impairs glucose
homeostasis
 TNF-ALPHA (TUMOR NECROSIS FACTOR)
 IL-6 (INTERLEUKIN-6).

34. Leptin regulates food intake (feeding behavior) and energy
expenditure
A Defect, Decreased Level In Leptin
or its receptor, can lead to
OBESITY.
LEPTIN SUPPLEMENTS leads to
caloric restriction and weight loss

35. INCREASES THE INSULIN SENSITIVITY OF MUSCLE
AND LIVER.
ADIPONECTIN
 Accelerates atherosclerosis.
 Associated with metabolic
syndrome.
Low levels of adiponectin

36. Role of liver in fat metabolism
FATTY LIVER AND LIPOTROPIC FACTORS

37. FATTY LIVER

38. FATTY LIVER
Apo B synthesis
affected
Hepatitis infection

40. FATTY LIVER

41. REQUIRED FOR THE NORMAL
MOBILIZATION OF FAT FROM LIVER.
carnitine synthesis

42. Causes of fatty liver
& DEFICIENCIES
Step1
Step2
Step 3
Step 4

43. HIGH FAT DIET AND UNCONTROLLED DIABETES MELLITUS
Liver function tests
will show
abnormal values.

44. In diabetes,lipolysis is
enhanced and high
FFA level in plasma is
noticed.
Insulin acts through
receptors on the cell
surface ofadipocytes.
These receptors are
decreased, leading to
insulin insensitivity
in diabetes.

45. OBESITY
• Genetics
• Environment
food intake
exercise
• Psychological factors
• Unknown factors

48. METABOLIC
SYNDROME
Obesity
Insulin resistance
Abnormal blood lipid levels
INDIVIDUALS WITH METABOLIC
SYNDROME ARE AT RISK TO DEVELOP
DIABETES MELLITUS AND
CARDIOVASCULAR DISEASE

49. Referenc
eDM Vasudevan, Textbook ofBiochemistry
Lippincott, Textbook ofBiochemistry
Harper’s, Textbook of Biochemistry