1. Is There a DES That Works Better for Diabetics? by Aloke Finn, MD

2. Aloke Finn, MD DISCLOSURES
Sponsored Research Grant From Boston Scientific

3. Diabetes Mellitus: A Growing Epidemic
Diabetes Mellitus affects over 100 million people worldwide
Over the next 20 years there will be a 42% increase in the number of people with diabetes
By 2050 almost 10% of the US population will have diabetes with the largest percentage increase among those 75 years or older
Vascular disease remains by far the leading cause of mortality in patients with diabetes accounting 80% of deaths in type 2 diabetics
Ischemic heart disease accounts for the majority of these deaths
JAMA. 2001; 286:

4. Diabetes and Drug Eluting Stents
Given the increased risk of restenosis seen in this population, DES have become the standard of care for patients with symptomatic CAD and DM
Little is know about the vascular responses to DES in this population
It remains unknown which DES is superior in terms of intimal suppression and endothelialization in patients with diabetes

5. Clinical Decision Making:
Choosing sirolimus or paclitaxel DES is currently based upon clinical restenosis rates yet these agents are very different in terms of their effects on the arterial wall and on intracellular signaling cascades
Both devices cause a delay in endothelialization and this is the major pathologic substrate underlying late stent thrombosis
A better understanding of the mechanisms of action by which each agent prevents restenosis is necessary to fully realize the benefits of this technology
Appropriate patient selection
Design of future anti-restenotic therapies

6. Mechanism of Action Sirolimus
mTORC1
mTORC2
S6K
Akt
Angiogenesis and Endothelial Regrowth
migration
proliferation
Migration, proliferation, survival
mTOR
PI3K
Growth factors (VEGF, Insulin)
Sirolimus
Endothelial Cell
Sirolimus (SRL) inhibits the mTOR (mammalian target of rapamycin), which plays an important role in connecting extracellular signals with intracellular pathways critical for arterial repair. As a result the potential exists for interaction between diabetic agents which share convergent molecular signaling with mTOR pathways and sirolimus. This may have adverse effects on endothelial regrowth given both Akt and S6K are involved in endothelial cell recovery

7. Mechanism of Action of Paclitaxel
Metaphase
Anaphase
Telophase
Paclitaxel binds to microtubles to prevent mitosis X
Inhibits smooth muscle cell proliferation
Inhibits neointimal hyperplasia
Prevents restenosis
Endothelial regrowth is also inhibited
Prophase G2 M
Cell
Cycle G2 M S G1
The mechanism of action of paclitaxel (Ptx) involves binding to the β subunit of the tubulin heterodimer, promoting tubulin polymerization, cell cycle arrest, and, eventually, inhibition of cell migration and proliferation. Although tubulin cycling is critical for cell division, it is independent of transmission of extra-/intracellular signaling. Thus, in contrast to the effects of SRL on the diverse actions of the mTOR pathway, the action of Ptx may make it independent of these signaling mechanisms

8. Limus versus Ptx: Differential Effects Do Occur in Patients with DM:
Data From SPIRIT IV
P<0.001
P=ns 1 2 3 4 5 6 7
TLF (%)
P interaction=0.02
The effects of PES and SES are significantly different in DM versus no DM
EES
PES
No DM DM
Stone GW TCT 2009.

9. PPAR
Is a ligand-inducible nuclear transcription factor expressed in SMCs and endothelial cells
PPAR agonists are commonly prescribed to type 2 diabetics—Rosiglitazone (Avandia) and Pioglitazone (Actos)--have remarkable effects on insulin sensitivity, and some studies suggest they enhance endothelialization after arterial injury. Moreover, these agents are well known to have effects on the coronary vascular wall in doses normally given to humans
These agents have been reported to have effects on regulators of translational control (S6K)—thus the possibility for convergent signaling with mTOR exists
mTOR itself has also been reported to be involved in control of PPAR mediated gene transcription though this has not been well explored
The potential for drug interaction between PPAR agonists and sirolimus exists and its effect of endothelial regrowth remains unknown

10. Hypothesis
To test our hypothesis that convergence of molecular signaling between oral anti-diabetic medications such as the TZD PPAR agonists and locally eluted SRL can result in significant effects on vascular healing, we examined the effect of the oral PPAR agent rosiglitazone (RSG) in combination with sirolimus-eluting (SES), Ptx-eluting (PES), or bare-metal (BMS) stents on endothelialization in the rabbit iliac model and explored the molecular mechanisms underlying the results

11. Study Protocol SRL stent (3.0 x 18) Paclitaxel stent(3.0 x 16)
Bare Metal stent (3.0 x 18)
Placebo
28 day stent
endothelialization
or 14 day organ
culture/western
blot
SRL (3.0 x 18)
Paclitaxel stent (3.0 x 16)
Bare Metal stent (3.0 x 18)
Rosiglitazone
(3mg/kg/day)

12. Placebo +RSG Placebo +RSG Placebo +RSG *p=0.01 vs. Cypher-Placebo
Bare Metal Stent
Sirolimus-Eluting
Stent
Paclitaxel-Eluting
Stent
Placebo
+RSG
Placebo
+RSG
Placebo
+RSG
Group
Endothelial Strut Coverage (%)
Uncovered Strut Area (mm2)
Cypher-Placebo
42.50±16.33
4.43±0.80
Cypher-Rosiglitazone
18.57±5.89*
5.69±0.27*
Bare Metal-Placebo
87.70±19.29
1.25±1.91
Bare Metal-Rosiglitazone
90.85±15.40
1.03±1.76
Taxus-Placebo
87.37±8.16
1.64±1.13
Taxus-Rosiglitazone
80.53±24.5
2.42±3.11
*p=0.01 vs. Cypher-Placebo
Finn AV et al.
Circ Research

13. 14 Day Organ Culture for VEGF
0.2
0.4
0.6
0.8 1
1.2
SES-Placebo
SES-RSG
Group
Relative VEGF levels (% of control ( placebo))
0.5
1.5 2
2.5
PES-Placebo
PES-RSG
Group Ratio Comparisons
Abs. dif.
95% CI
P value
BMS vs. SES
0.84
0.41,1.58
0.003
PES vs. SES
0.99
0.43,1.55
0.008
BMS vs. PES
0.15
-0.40,0.71
0.55
BMS-Placebo
BMS-RSG
P=0.05
P=0.007 A. B. C. D.

14. A. B. C. D. Rosiglitazone Concentration (uM) DMSO SRL RSG SRL/RSG 1 21 2 3 4 5
p<0.0001
P=0.0007
Fold increase in VEGF Transcript A. B. C.
P=0.002
P=0.001 6 7 8
Ptx
Ptx/RSG
Scr siRNA
PPAR siRNA
P=0.02 D.
Rosiglitazone Concentration (uM)
0.001
0.01
0.1 10 25 50 75
100
P=0.01
P=0.0001
P=0.0002
(N= 4 experiments/group)

15. B A D C DMSO SRL RSG SRL+RSG 4 2 3.5 3 1.5
0.5 1
1.5 2
DMSO
SRL
RSG
SRL+RSG
P=0.001
P=0.01
P=0.002
Relative HO-1 gene transcript A C
Input (negative primer)
Input (positive primer)
IP-PPARγ (negative primer)
IP-PPARγ (positive primer)
2.5 3
3.5 4
Scr shRNA
mTORshRNA
mTOR shRNA
P=0.04
P=0.02 B
P<0.0001
P=0.006
(N= 3 experiments/group)
(N= 4 experiments/group) * D
*p<0.05 versus Scr siRNA DMSO
and siRNA p70s6k DMSO
#p<0.05 versus p70 siRNA RSG
!p=0.09 versus Scr siRNA DMSO
Scr siRNA
p70 siRNA
N= 4 experiments/ group
Relative gene transcript 6 8 10 12 14
VEGF
HO-1
*,#
Akt2 siRNA
*.#
#p<0.05 versus Scr siRNA RSG
!p<0.05 versus Akt2 siRNA DMSO
And Akt2 siRNA RSG
**p<0.05 versus Scr siRNA DMSO
*,! ** !
N= 4 experiments/ group

16. Endothelial Cell PI 3 kinase PDK-1 mTORC2 Akt mTORC1 p70S6K S6 DNA
VEGF Receptor
PI 3 kinase
Endothelial Cell
PDK-1
mTORC2
Akt
Sirolimus
mTORC1
Rosiglitazone
? Downstream
mediator
4EPB1
p70S6K
eIF4E S6
Translation
DNA
Cell
Growth
HIF-1α
VEGF transcription
PPARg-mediated
transcription
Nucleus
VEGF/HO-1

17. Conclusions
mTOR signaling is best known for its role in translational regulation via two downstream effectors, S6K1 and 4E-BP1
In this study we reveal that mTOR also interacts with PPARγ likely through control of transcriptional regulation
This interaction has important consequences for patients receiving sirolimus (and its analogues?) DES who are also taking oral PPAR agents (rosiglitazone and pioglitazone) in that it results in further delay of vascular healing of the vessel wall
Do other commonly used diabetic agents also share convergence with sirolimus/mTOR (i.e. insulin, metformin)and how does this affect healing?

18. Clinical Data
Numerous studies have shown diabetes to be an independent predictor of late stent thrombosis after DES (Iacovou JAMA 2005, Daemen J Lancet 2007)
Meta-analysis of 4 pivotal randomized trials with sirolimus stent (SES) has shown significantly increased cardiac death, Q wave MI, and late stent thrombosis in patients w/ DM treated with SES versus BMS but with significantly reduced TLR (Caixeta A et al. JACC 2009.)
Meta-analysis of 5 randomized trials of paclitaxel eluting stents (PES) demonstrated significantly reduced TLR with no differences in death, MI or stent thrombosis in DM patients treated with PES versus BMS (Kirtane AJ et al. JACC 2008)
Paucity of data exists on the vascular responses to stents in diabetic models despite the routine use of these devices in patients with DM
Long term data from diabetic only randomized trials are lacking
Indeed use of DES in patients with DM is considered “off-label”

19. Conclusion
Mechanisms of action of different DES may have important clinical consequences in patients with DM
Considerable overlap exists between mTOR signaling and many meds used to treat DM but the effect of these interacts remains unknown
Diabetic patients talking TZD in combination with SES may be at risk for delayed stent healing
Further work needs to be done in both clinical and basic realms to improve outcomes in patients with diabetes after PCI

21. A. E C B D F p-Akt Akt p-p70s6k p70s6k Bare Metal Stent
Sirolimus (500 nM)
Rosiglitazone (100 uM) - +
p-Akt
Akt
p-p70s6k
p70s6k
Scr siRNA
PPARγ siRNA
DMSO
RSG
β-Actin
Bare Metal Stent
Sirolimus Stent
RSG
HIF-1α A. E C B
DMSO SRL RSG SRL/RSG
0.5 1
1.5
P=0.002
P<0.0001
P=0.0002
P=0.04
P=0.004
0.2
0.4
0.6
0.8
1.2
P=0.001
DMSO SRL RSG SRL/RSG
Relative Phosphorylation
DMSO
Scr siRNA
PPAR siRNA
RSG 2
2.5 3 D
P=0.02
P=0.03 F
BMS
BMS-RSG
SES
SES-RSG
Group
HIF-1 *
*, #
*,#
*P<0.05 versus BMS
#P<0.05 versus BMS-RSG and SES
(N= 4 arteries/group)
(N=4 experiments/group)
P=0.01
P=0.01