1) The document discusses insulin signaling and VLDL overproduction in insulin resistance. It notes that insulin signaling activates the PI3-kinase pathway leading to Akt phosphorylation and VLDL assembly. 2) Data is presented showing impaired hepatic tyrosine phosphorylation of the insulin receptor, IRS-1, and IRS-2 in fructose-fed hamsters compared to controls. This provides evidence of reduced insulin signaling. 3) Additional data demonstrates reduced PI3-kinase activity, reduced Akt phosphorylation, and enhanced PTP-1B mass and activity in fructose-fed hamsters, suggesting disrupted insulin signaling.

1. CytosolCytosol
HepatocyteHepatocyte
ApoB
DegradationDegradation
5'
3'
ApoB mRNAApoB mRNA
TranslationTranslation
ERMembraneERMembrane
Insulin
IRS1/IRS2
IR
InsulinSignalingPathway
InsulinSignalingPathway
Plasm
a
Plasm
a
VLDLVLDL
Insulin Signaling & VLDL OverproductionInsulin Signaling & VLDL Overproduction
in Insulin Resistancein Insulin Resistance
PI3-Kinase
VLDL AssemblyVLDL Assembly
PIP3/Phosphorylation CascadePIP3/Phosphorylation Cascade
Akt/PKBAkt/PKB
PTP-1BPTP-1B
3'

2. D
InsulinReceptorproteinMass
(scanningunits/mgproteinx10-3
)
Control Fructose-fed
Control Fructose-fed
0
50
100
150
200
250
IRS-1ProteinMass
(scanningunits/mgproteinx10-3
)
Control Fructose-fed
Control Fructose-fed
0
40
80
120
E F Control Fructose-fed
0
20
40
60
80
100
120
Control Fructose-fed
IRS-2Mass(percentofcontrol)
C
PhosphorylatedIRS-2
(relativetobasallevelofcontrol)
0
20
40
60
80
100
120
140
160
180
_
+
_
+
Insulin
+ + + +Insulin _ _ _ _
Control Fructose-fed
Control
Fructose-fed
Impaired Hepatic Tyrosine Phosphorylation of
Insulin Receptor, IRS-1, and IRS-2
in Fructose-Fed Hamsters
A
PhosphorylatedInsulinReceptorMass
(scanningunits/mgproteinx10-3
)
Control Fructose-fed
0
100
200
300
400
500
600
_
+
_
+
Insulin
+ + + +Insulin _ _ _ _
*
B
_
+
_
+
Insulin
PhosphorylatedIRS-1
(scanningunits/mgproteinx10-3
)
Control Fructose-fed
0
20
40
60
80
100
120
Control
Fructose-fed
+ + + +Insulin _ _ _ _
P= 0.04
P= 0.009
P= 0.02
P= 0.03
P= 0.029
*
*

3. B
0
50
100
150
200
PTP-1BMass
(percentofcontrol)
Control Fructose-fed
Control Fructose-fed
C
0
100
200
300
PTP-1BActivity
(percentofcontrol)
Control Fructose-fed
A
0
20
40
60
80
100
120
PI3-KinaseActivity
(percentofcontrol)
Control Fructose-fed
* **
***
D
+ + + +Insulin
0
20
40
60
80
100
120
140
Insulin-InducedAktSerine
Phosphorylation(%ofcontrol)
Control Fructose-fed
Insulin
_
+ _
+
E
Insulin
Insulin-InducedAktThreonine
Phosphorylation(%ofcontrol)
Control Fructose-fed
0
20
40
60
80
100
120
_
+
_
+
+ + + +
Insulin
F Control Fructose-fed
20
40
60
80
100
120
140
160
AktProteinMass
(percentofcontrol)
0
Control Fructose-fed
****
***
*
Evidence for Reduced PI-3 Kinase
Activity, Reduced Akt Phosphorylation,
& Enhanced PTP-1B Mass & Activity

4. 0
20
40
60
80
100
120
0 20 40 60 80
Vanadate (µM)
RecoveredCellularApoB
(relativetountreated)
B
0
20
40
60
80
100
120
0 20 40 60 80
Vanadate (µM)
RecoveredLabeledMediaApoB
(relativetountreated)
C
Vanadate (µM)
RecoveredTotalApoB
(relativetountreated)
0
20
40
60
80
100
120
0 20 40 60 80
D
Vanadate (µM) 0 10 40 80
IR-pY
0
100
200
300
400
500
600
0 20 40 60 80
Vanadate (µM)
InsulinReceptorPhosphorylation
(relativetountreated)
A
0 10 20 40 80Vanadate (µM)
Cellular ApoB
Secreted ApoB
E
Inhibition of Cellular Phosphatase Activity with Vanadate
Enhances Insulin Signaling and Reduces ApoB Secretion
IR-IR-ppYY
Cellular ApoBCellular ApoB
ApoB StabilityApoB Stability
ApoB SecretionApoB Secretion