Triglyceride

Metabolism

Jack Blazyk3/1/04

Triglyceride Metabolism

Triglyceride = Triacylglycerol = Depot Fat

CH2 — CH — CH2

l l lO O O

C=Ol l l

C=O C=Ol l lR R’ R’’

Ester

Glycerol backbone

FattyAcid

Triglyceride Metabolism

• Lipogenesis occurs mainly in liver, adipose and intestinal epithelial cells

• Lipolysis occurs in adipose cells

• Regulation via insulin and glucagon signals

Lipogenesis

R-COOH

R-C-S-CoA

O

=

CoA-SH + ATP

AMP + PPi

Acyl-CoASynthase

Activation

Lipogenesis

CH2 — C — CH2

l l lOH O O P

l

DHAP

Glycerol 3-PDehydrogenase

NADH + H+

NAD+

NADH + H+

NAD+

CH2 — CH — CH2

l lOH OH

lO P

Glycerol 3-P

Lipogenesis

Glycerol

CH2 — CH — CH2

l lOH OH

lO P

Glycerol 3-P

CH2 — CH — CH2

l lOH OH

lOH

GlycerolKinase

ATP

ADP

Liverand kidney

Lipogenesis

CH2 — CH — CH2

l lOH OH

lO P

Glycerol 3-P

AcylTransferases

2 Acyl-CoA

2 CoA

CH2 — CH — CH2

l lO O

C=Ol l

C=Ol lR R’

lO P

PhosphatidicAcid

Lipogenesis

CH2 — CH — CH2

l lO O

C=Ol l

C=Ol lR R’

lO P

Phosphatidic Acid

Phosphohydrolase

PiH2O

CH2 — CH — CH2

l lO O

C=Ol l

C=Ol lR R’

lOH

1,2-Diacylglycerol

Lipogenesis

CH2 — CH — CH2

l lO O

C=Ol l

C=Ol lR R’

lOH

Acyltransferase

CoAAcyl-CoA

1,2-Diacylglycerol Triacylglycerol

CH2 — CH — CH2

l l lO O O

C=Ol l l

C=O C=Ol l lR R’ R’’

Lipogenesis

• Intestinal epithelial cells

Export via chylomicrons

• Liver

Export via VLDL

• Adipose

Storage in cytoplasm

Marks’ Basic Medical Biochemistry: A Clinical Approach (Williams & Wilkins, 1996)

Lipolysis

Triacylglycerol

CH2 — CH — CH2

l l lO O O

C=Ol l l

C=O C=Ol l lR R’ R’’

Adipose Cells

Triglyceride Lipase(Hormone-Sensitive Lipase)

H20

CH2 — CH — CH2

l lO O

C=Ol l

C=Ol lR R’

lOH

1,2-Diacylglycerol

+ R’’-COOH

Free Fatty Acid

Lipolysis

CH2 — CH — CH2

l lO O

C=Ol l

C=Ol lR R’

lOH

1,2-Diacylglycerol

Diglyceride Lipase

H20

+ R-COOH

Free Fatty Acid

2-Monoacylglycerol

CH2 — CH — CH2

l lOH O

lC=OlR’

lOH

Adipose Cells

Lipolysis

Monoglyceride Lipase

H20

2-Monoacylglycerol

CH2 — CH — CH2

l lOH O

lC=OlR’

lOH

Adipose Cells

+ R’-COOH

Free Fatty Acid

CH2 — CH — CH2

l lOH OH

lOH

Glycerol

FFA are transported via albumin

Regulation of Lipolysis

ATP

ADP

Pi

H2OProtein Kinase ALipase Phosphatase

Triglyceride Lipase - OH

Triglyceride Lipase - P

ACTIVE

INACTIVE

Activated by insulin Activated by glucagon

Regulation of Lipolysis

• Activators Glucagon Epinephrine ACTH TSH Growth hormone Glucocorticoids Thyroid hormones

• Inhibitors Insulin Free fatty acids

To see this presentation on the web go to

Click on My TeachingThen click on Triglyceride Metabolism

http://www.oucom.ohiou.edu/dbms-blazyk