Lipid metabolism
2016
Lívius Wunderlich
Hydrophobic feature
Energy storage, cell membrane,
some hormones, detergents, vitamins Lipids
Fats and oils
Triglycerides, phospholipides,
steroids, eikosanoids
Fatty acids
palmitic acid stearic acid palmitoleic acid oleic acid
linolic acid linoleic acid
arachidonic acid
Most important fatty acids
Triglycerides, glycerophospholipides
Triglyceride storage
Phospholipide membrane
Phospholipide membrane
Unsaturated phospholipide configuration matters!
Some membrane components
Digestion of lipids
Hydrolase enzymes
Lingual and gastric lipases work in the stomach:
Slow process
Intestinum: bile acids, colipases,
pancreatic lipases activtaed by trypsin Trigliceride-esterases, phospholipases cholesterol-estarases
Resulting:
Free fatty acids, colesterol, monoacyl-glycerols
glycerol phosphatides
Structure of bile acids
Enterohepatic circulation of bile acids
Liver
Primary bile acids
Gall
bladder
Colon
Deconjugation and dehydroxy- lation by bacteria
Secondary bile acids
cca. 9 reabs 0 %
orbed
O R
O
C H2
C H
C H2
O O O
C C C
R1 R2 R3 O
O O
pancreatic lipases cholesterol esterases
cholesterol fatty acids
monoacyl-glicerides
C H2
C H
C H2
OH O OH
R
O H
O O-
O O-
Phospholipases
Absorbtion of digested lipids to epithelial cells
Re-assembling most of them, resulting triglicerides, phospholipides, cholesterin-esters
Non-reassembled fatty acids enter the blood vessels, binding to serum albumin
Re-assembled lipids, free cholesterol and apoproteins form lipoprotein micelles called nascent chylomicrons Nascent chylimicrons enter the lymphatic system, then the blood avoiding vena portae hepatis
Th fate of digested lipids
Y
Y fatty acids LPL
ApoC ApoE
nascent chylomícron
mature chylomicron
chylomicron remnant HDL
adipose tissue striped muscle,
heart muscle
liver intestine
capillary
ApoE receptor
ApoE
ApoC
endocytosis
The chylomicron’s fate
HDL
liver
Y LPL
ApoC
VLDL
capillary
ApoE receptor
endocytosis
VLDL
IDL LDL
ApoE
peripheral tissues
Y Y
ApoB100 receptor
ACAT
endocytosys
The fate of VLDL
fatty acids adipose tissue striped muscle,
heart muscle
chylomicron
liver
intestine
ApoC ApoE
endocytosis
nascent HDL
peripheral tissues
cholesterol
LCAT
VLDL
cholesterol phospholipids ApoC, ApoE, cholesterol-esters
triglicerides
fatty acids
HDL
The roles of HDL
The mobilisation of lipid storages
KoA R C S
O
+ AMP + 2 Pi KoA
S H
R COOH + + ATP + H2O
Activating of fatty acids
Transport to the mitochondrion
β-oxydation
Energy-balance of β-oxydation
ATP production:
Since the energy of 2 ATPs were used for activation:
Fatty acid sythesis: producing malonyl-Coa
This is the engaging step of fatty acid synthesis!
Acetyl-Coa carboxylase
acetyl-Coa
malonyl-Coa
