Review

1
Review

• Diabetes Type 1 and Type 2
• Lipolysis more on this Today!
• Malonyl CoA as a regulatory molecule
• Progressive nature of Type 2 DM
• Patch Clamp
• Ectopic fat
• Insulin resistance in liver and pancreas

2
Seminar

• The influence of growth hormone on adipose tissue
• Dr. Darlene Berryman
• Assistant Professor
• Dept. of Food and Nutrition
• Ohio University
• Friday, Feb. 27.
• 4-5pm
• 252 Campbell Hall

3
Mobilization of stored TAGb-Oxidation

• Stipanuk 318-330

4
Beta Oxidation

• Major process of fatty acid oxidation
• Removal of 2C units
• Major source of ATP for heart and sm
• Fasting, sustained exercise, stress and
  neonatal-suckling
• Mitochondrial and peroxisomal

5
Last Time
Plasma
Chylomicron VLDL
FA G3P
TG
Glycerol FA
TG
LPL
adipocytes
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1. Mobilize Triacylglycerol
7
TG Mobilization
Other tissues (muscle)
HSL
FFA
FFA-albumin
TG
Rapid reesterification in fed state
G3P
Triglyceride droplet
Glucose
Adipocyte
blood
8
Hormone-Sensitive Lipase

• Broad substrate specificity
• TG, cholesterol, retinyl, and steroid esters
• 3 isoforms 84-130 kDa
• Acutely regulated by phosphorylation

HSL
TG
9
Activation of HSL
hormone
b-AR
a-AR
Plasma Membrane
AC
Gi
Gs
GDP
GTP
cAMP
ATP
()
PKA
()
TG Store
Perilipin
P
Perilipin
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Perilipin
NEFA-albumin
NEFA
P
DG
MGL
TG
MG
glycerol
Lipid droplet
11
Fed state Inhibition of HSL via Insulin
Plasma Membrane
PKA
cAMP
PKB
PDE
amp
12
Fed state Inhibition of HSL via Insulin
glucose
Plasma Membrane
glucose
G 3-P
rapid resterification
NEFA
TG
13
HSL Regulation

• Fed State

Glucose
Insulin
TG synthesis
HSL
Fasted Exercise State -
Glucose
Insulin
Glucagon/Hormones (epinephrine)
HSL
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b-Oxidation

• High in muscle and liver in fasted state
• Proportional to concentration of FA in plasma
• Fatty acid oxidation increases during exercise
  (to a point)
• Plasma fatty acids may not change but increased
  blood flow

15
Compare and Contrast
Synthesis Beta-Oxidation
Location cytosol
mitochondria Acyl carrier
ACP CoASH Carbon units C2 C2 Substrate/Prod
uct Malonyl-CoA/ Acetyl-CoA
Acetyl CoA Redox cofactors
NADPH NAD, FAD Enzymes
multifunctional Separate
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Beta Oxidation

1. Uptake of fatty acids by cell
2. Fatty acid binding protein
3. Fatty acid activation
4. Entry into mitochondria
5. Oxidation

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1. Cellular uptake of fatty acids

• Bound or unbound FA taken up by cell?
• Diffusion or by mediated transport?
• Does not appear to be rate-limiting

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2. FABP

• Transfer FA to site of utilization
• Conflicting data
• box varies but FABP concentrations do not?
• Perhaps important in heart

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3. Activation of FA to FA-CoA

• Acyl-CoA synthetase
• subcellular localization different FA-CoA pools
• Channeling of FA-CoA to esterification or
  b-oxidation

FA-CoA
b-Ox
Phospholipid
TG
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4. Entry into Mitochondria
Cytosol
CoA
FA CoA
CPT I
Outer membrane
carnitine
Mitochondria
FA-carnitine
CP Translocase
Inner membrane
CPT II
CoA
FA CoA
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Regulation
Fed State
ACC
Acetyl CoA
Malonyl CoA
(-)
CoA
FA CoA
CPT I
Outer membrane
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Defects in Fatty Acid Transport into Mitochondria
for Oxidation
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a
b
g
palmitate
FAD
oxidize
Acyl-CoA dehydrogenase
FADH2
Enoyl-CoA hydratase
H20
hydrate
3-hydroxyacyl CoA dehydrogenase
NAD
oxidize
NADH
3-ketoacyl-CoA thiolase
CoA
cleave

24
a
b
g
FAD
FADH2
High ATP/ADP? High NAD/NADH? Low
Acetyl-CoA/CoASH?
H20
NAD
NADH
CoA

25
Oxidation of Unsaturated and Odd Chain Fatty Acids
Unsaturated
Odd Chain
B12
PEP
glucose
Propionyl CoA
Succinyl CoA
26
Energy Yield from b-Ox of Palmitate
Palmitoyl CoA 7 CoASH 7 FAD 7 NAD 7 H20
8 acetyl CoA 7 FADH2 7 NADH 7 H
FADH2 2 ATP X 7 14 ATP NADH 3
ATP X 7 21 ATP Acetyl CoA 12 ATP X
8 96 ATP
131 ATP
- 2 ATP (activation of FA)
129 ATP
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Peroxisomal b-Ox

• Organelles present in almost all eukaroytic cells
• Contain many genes involved in lipid metabolism
  (specifically b-ox)
• Oxidize very long chain fatty acids (gt20c)
• About 10 of all b-ox occurs in peroxisome
• Regulated by the peroxisome proliferator-activated
  receptor a (PPAR)
• PPAR d and PPAR g

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PPARa

• Nuclear hormone receptor
• VLCFA are ligands for this receptor

VLCFA
membrane
RXR
PPAR
cytosol
CPC
nucleus
Increased transcription of b-ox genes
DNA
PPAR Response element
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Ackee Fruit
30
Ackee Fruit

• National Fruit of Jamaica Jamaican Vomiting
  Sickness
• Methylene cyclopropyl acetic acid ? MCAA-CoA
• Suicide inhibitor of several acyl-CoA
  dehydrogenases in b-OX
• Leads to severe hypoglycemia ? can be fatal
• Why?

31
glucose
NADH
?
G3P DH
glyceraldehyde-3-phosphate
1,3 bisphophoglycerate
OAA
Pyruvate Carboxylase Allosterically activated by ?
Acetyl CoA
?
Pyruvate
mitochondria
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lipoproteins
LPL
TCA
FED
Malonyl CoA
Acetyl CoA
Beta oxidation
FA-FABP
FFA
FA CoA
CPT I
FASTED
FFA-albumin
HSL
mitochondria
Fat cells
Cell membrane
33
Ketogenesis
High rate of lipolysis When ? Occurs in liver
mitochondria Production of acetyl CoA
exceeds capacity of TCA cycle Important energy
source during long term fasts (brain)
34
Citric acid cycle
Fatty Acid Oxidation
2 Acetyl CoA
CoA
Acetoacetyl CoA
Acetyl CoA
HMG CoA synthase
CoA
Hydroxymethylglutaryl CoA
HMG CoA Lyase
Acetone
Acetyl CoA Acetoacetate
Cholesterol biosynthesis
3-hydroxybutyrate (80)
35
Ketoacidosis

• 3-hydroxybutyrate and acetoacetate are acids
• Can decrease blood pH
• Diabetes
• Normal prevention mechanisms

36
Normal Regulation of Ketone Body Formation
Liver
Free Fatty Acids
Adipose Tissue
HSL
Insulin
Ketone Bodies
Pancreas