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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