Cytosol

1
Insulin Signaling VLDL Overproduction in
Insulin Resistance
Insulin
IR
Cytosol
PTP-1B
IRS1/IRS2
PI3-Kinase
Akt/PKB
Insulin Signaling Pathway
ApoB mRNA Translation
PIP3/Phosphorylation Cascade
3'
3'
5'
Degradation
ER Membrane
ApoB
Hepatocyte
VLDL Assembly
VLDL
Plasma
2
Impaired Hepatic Tyrosine Phosphorylation of
Insulin Receptor, IRS-1, and IRS-2 in
Fructose-Fed Hamsters
A
C
B
Control Fructose-fed
Control Fructose-fed
Control Fructose-fed
_ _ _ _
Insulin

_ _ _ _
Insulin
_ _ _ _

Insulin

Control
Control
P 0.02
Fructose-fed
180
Fructose-fed
P 0.04
120
600
P 0.03
160
P 0.009
140
100
500
P 0.029
120
80
Phosphorylated IRS-2 (relative to basal level of
control)
400

100
Phosphorylated IRS-1 (scanning units/mg protein
x10-3)
Phosphorylated Insulin Receptor Mass (scanning
units/mg protein x10-3)
60
300
80

60
40
200
40
100
20
20
_
_
_
_
_
_
0
0
0






Insulin
Insulin
Insulin
D
E
F
Control Fructose-fed
Control Fructose-fed
Control Fructose-fed
120
250
120
100
200

80
80
150
IRS-2 Mass (percent of control)
IRS-1 Protein Mass (scanning units/mg protein
x10-3)
60
Insulin Receptor protein Mass (scanning units/
mg protein x10-3)

100
40
40
50
20
0
0
0
Control Fructose-fed
Control Fructose-fed
Fructose-fed
Control
3
Evidence for Reduced PI-3 Kinase Activity,
Reduced Akt Phosphorylation, Enhanced PTP-1B
Mass Activity
B
C
A
Control Fructose-fed
300
120

100


200
200
80
PTP-1B Activity (percent of control)
PI 3-Kinase Activity (percent of control)
150
60
PTP-1B Mass (percent of control)
100
40
100
50
20
0
0
0
Control Fructose-fed
Control Fructose-fed
Control Fructose-fed
F
E
D
Control Fructose-fed
Control Fructose-fed
Control Fructose-fed


Insulin
Insulin


120
140

160
100
120
140
100
120

80
100
Akt Protein Mass (percent of control)
80
Insulin-Induced Akt Serine Phosphorylation ( of
control)

60
80
Insulin-Induced Akt Threonine Phosphorylation (
of control)
60
60
40
40
40
20
20
20
_
_
0
_
0
_

0


Control Fructose-fed

Insulin
Insulin
4
Inhibition of Cellular Phosphatase Activity with
Vanadate Enhances Insulin Signaling and Reduces
ApoB Secretion
A
B
120
IR-pY
Vanadate (?M) 0 10
40 80
100
IR-pY
80
600
Recovered Cellular ApoB (relative to untreated)
500
60
400
40
Insulin Receptor Phosphorylation (relative to
untreated)
300
Cellular ApoB
200
20
100
0
0
0
20
40
60
80
0
20
40
60
80
C
D
Vanadate (?M)
Vanadate (?M)
120
120
100
100
ApoB Secretion
80
80
Recovered Total ApoB (relative to untreated)
Recovered Labeled Media ApoB (relative to
untreated)
60
60
40
40
ApoB Stability
20
20
0
0
0
20
40
60
80
0
20
40
60
80
Vanadate (?M)
Vanadate (?M)