1) The document discusses insulin signaling and VLDL overproduction in insulin resistance. It examines how fructose feeding impairs hepatic tyrosine phosphorylation of the insulin receptor, IRS-1, and IRS-2 in hamsters. 2) It also finds evidence for reduced PI3-kinase activity, reduced Akt phosphorylation, and enhanced PTP-1B mass and activity in fructose-fed hamsters. 3) The document shows that inhibition of cellular phosphatase activity with vanadate enhances insulin signaling, increases insulin receptor phosphorylation, reduces cellular and secreted ApoB levels, and stabilizes ApoB, reducing its secretion.

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