Is there a need of new RAAS blockers in diabetic hypertension?

Dr. Dominik N. Müller

First World Congress on Controversies in Obesity, Diabetes

and Hypertension

Berlin

October 2006

Ang-(1-7)

ACE2

Ang IVAT4 AT1-7

Prorenin

Renin receptor

Sequence: RILLKKMPSV

Ang I

ACE, chymase

Renin

Angiotensinogen

Ang IIAT1, AT2

Renin-Angiotensin System

1 Phillips MI. Tissue renin-angiotensin systems. In: Izzo JL Jr, Black HR, eds. Hypertension Primer: The Essentials of High Blood Pressure. 3rd ed.

Philadelphia, Pa; Lippincott Williams & Wilkins; 2003:21-23. 2 Strain WD et al. JRAAS. 2002;3:243-246. 3 Dzau VJ. Hypertension. 2001;37;1047-1052.

4 Faloia E et al. J Endocrinol Invest. 2002;25:309-314. 5 Vega GL. Minerva Endocrinol. 2004;29:47-54. 6 Arakawa K et al. Hypertension. 2000; 36:638-641. 7

Frustaci A et al. Circ Res. 2000;87:1123-1132. 8 Danser AH et al. Circulation. 1997;96:220-226. 9 Hokimoto S et al. Circulation. 1996;94:1513-1518. 10

Hollenberg NK et al. Kidney Int. 2003;63:172-178. 11 Mezzano S et al. Kidney Int Suppl. 2003;86;S64-S70.

12 Mezzano SA et al. Kidney Int. 2003;64:S39-S45. 13 Leung PS. J Pancreas. 2003;4:89-91.

Blood Vessels3

↑ with atherosclerosis

Kidney10-12

↑ in diabetes, membranous nephropathy

Adrenal Glands

Pancreas13

↑ in nephropathy

Pituitary Gland

Brain

Eye2

↑ in diabetesHeart7-9

↑ in diabetes, post-MI, failing ventricle

Aorta6

↑ with atherosclerosis

Adipose Tissue4,5

↑ in obesity, hypertensionAng II levels are much higher in

tissue than in plasma

Tissue RAS leads to damage in many organs

especially in patients with metabolic disorders

Endothelialdysfunction

Target-organdamage

Maladaptive remodelling

Diabetes,hypertension,

insulin resistance

Endothelial dysfunction

Vascular diseaseConstriction, inflammation,hypertrophy, hyperplasia,

atherogenesis, thrombosis

Tissue injuryMI, stroke, glomerularischaemia

Pathologicremodelling

LVH, LV dilation, glomerulosclerosis

Target-organdysfunction

HF, nephropathy

End-stageorgan failure

Death

Dzau VJ. Hypertension. 2001; 37: 1047-1052. Dzau V et al. Am Heart J. 1991; 121: 1244-1263. Anderson S. In: Izzo JL Jr,

Black HR, eds. Hypertension Primer: The Essentials of High Blood Pressure. 3rd ed. Philadelphia, Pa:

Lippincott Williams & Wilkins; 2003: 205-208.

The Cardiovascular ContinuumDevelopment and Progression of CV Disease

*Association strongest in white men.†Risk status: high, ≥2 risk factors (smoking, cholesterol, LVH); moderate, 1 risk factor; low, no risk factors.PRA, plasma renin activity.

Alderman MH et al. Am J Hypertens. 1997; 10: 1-8.

MI rate/1000person-

years

0

5

10

15

20

25

30

35

40

Risk Status†

LowModerateHighLow

Normal

High

Plasma Renin Activity

For every 2-unit increasein PRA, there is an overall

25% increase in MI incidence*

PRA Predicts the Incidence of MIInterrelation Between PRA and CV Risk Factors

Renin inhibition

Current Renin System blockers & diuretics raise

plasma renin activity (PRA)*

Feedback Loop

• Glomerular

vasoconstriction

• Inflammation

• Fibrosis

Kidney

• Hypertrophy

• Fibrosis

• Vasoconstriction

Heart

• Vasoconstriction

Brain

• Hyperplasia hypertrophy

• Inflammation

• Oxidation

• Fibrosis

Vessels

AT1 Receptor

ACE

ReninAng I

Angiotensinogen

Ang II

ACEIs

Non ACE pathways

Plasma

Renin

Activity

ARBs

*Increased peptide levels have not been shown to overcome the BP lowering effect of these agents

Renin inhibition acts at the Renin System’s point

of activation and neutralizes the PRA rise

Feedback Loop

• Glomerular

vasoconstriction

• Inflammation

• Fibrosis

Kidney

• Hypertrophy

• Fibrosis

• Vasoconstriction

Heart

• Vasoconstriction

Brain

• Hyperplasia hypertrophy

• Inflammation

• Oxidation

• Fibrosis

Vessels

AT1 Receptor

ACE

ReninAng I

Angiotensinogen

Ang II

ACEIs

ARBs

Renin inhibitor

Plasma

Renin

Activity

Angiotensinogen

Aliskiren binds to the active site of renin

Aliskiren binds to

a pocket in the

renin molecule,

blocking

cleavage of

angiotensinogen

to angiotensin I

Renin

Aliskiren

Adapted from Wood JM, et al. 2003

Renin inhibition

Experimental studies

Systo

lic B

loo

d P

ressu

re

( m

m H

g )

SD

RI

Triple

dTGR

5 6 7 8

Age (weeks)

0100

125

150

175

200

225

*****

***

##

24-h

ou

r A

lbu

min

uri

a (

mg

/ d

)

6 7 8

Age (weeks)

0

5

10

15

20

25

30

**

***###

SD

RI

TripledTGR

Renin inhibition vs. anti-hypertensive treatment

Hypertension 2000;35:587-94

Circ Res 2005; 97:716-24

Albuminuria

Aliskiren provides renoprotective effects in a rat

model of hypertensive diabetic nephropathy

Feldman D, et al. 2005

180

60

140

100

200

160

120

80

Treatment starts

Urinary albumin (mg/24h)

Days60500–4 10 20 30 40

Vehicle

10 mg/kg/d

30 mg/kg/d

Aliskiren

70

Aliskiren preclinical data

Summary

Aliskiren demonstrates organ protective effects in animal models

– renoprotection comparable with ACEIs and ARBs

– LVH reductions comparable with ARBs

– suppresses markers of renal damage in diabetic nephropathy

– atherogenesis prevention

Aliskiren clinical data

Aliskiren is under evaluation in clinical studies for the treatment of hypertension. To date, no clinical trials have assessed the effect of aliskiren on morbidity and mortality

Aliskiren compared with ramipril and combination therapy in patients with diabetes and hypertension – Study design

Single-blind

Washout

2 weeks 2–4 weeks 4 weeks

Placebo

Aliskiren 150 mg Aliskiren 300 mg

Ramipril 5 mg Ramipril 10 mg

Aliskiren 150 mg +ramipril 5 mg

Aliskiren 300 mg +ramipril 10 mg

4 weeks

n=282

n=278

n=277

Uresin Y, et al. 2006 (Study 2307)

Aliskiren/ramipril combination provides significantly greater reductions in BP than component monotherapies

Mean change from baseline in BP (mmHg)

Aliskiren/

ramipril

combination

Ramipril

mono

Aliskiren

mono

−18

−6

0

−14

DBP SBP

−8

−10

−12

−16

Aliskiren/

ramipril

combination

Ramipril

mono

Aliskiren

mono

*p<0.05 for superiority vs ramipril monotherapy; †p<0.05 for superiority vs aliskiren monotherapy;‡p<0.05 for non-inferiority for aliskiren monotherapy vs ramipril monotherapyError bars indicate standard error from the mean Uresin Y, et al. 2006 (Study 2307)

−20 *

n=274n=279n=275 n=274n=279n=275

−12.8

−10.7 −11.3

−16.6

−12.0

−14.7*

‡

†

* ‡

Aliskiren in combination with valsartan

Study design (2101)

Double-blind 4-period crossover study in healthy male subjects with mild salt depletion

Aliskiren 300 mgsingle dose

Valsartan 160 mgsingle dose

Aliskiren 150 mg/valsartan 80 mg

single dose

Placebosingle dose

14-day washout14-day washout 14-day washout14-day washout 14-day washout14-day washout

Azizi M, et al. 2004

0

5

4

3

2

1

Aliskiren neutralizes ARB-induced increase in PRA

PlaceboAliskiren300 mg

Valsartan160 mg

Aliskiren +Valsartan150/80 mg

PRA at 24 hours after dosing (ng/mL/h)

0.83

4.4

2.1 2.0

*p<0.05 vs aliskiren 150 mg/valsartan 80 mg†p<0.05 vs aliskiren 300 mg‡p<0.05 vs valsartan 160 mgn=12 Azizi M, et al. 2004

*

* †

† ‡

Aliskiren neutralizes ARB-induced rises in Ang II

Aliskiren 150 mg +

Valsartan 80 mg

Valsartan 160 mg

Aliskiren 300 mg

Placebo

Plasma Ang II (pg/mL)

0

80

40

20

60

Time (hours)

480 12 246

***

† ‡† ‡

†*

†*

†*‡*

Azizi M, et al. 2004

*p<0.05 vs aliskiren 150 mg/valsartan 80 mg†p<0.05 vs aliskiren 300 mg‡p<0.05 vs valsartan 160 mgn=12

Aliskiren significantly decreases

urinary aldosterone excretion in healthy volunteers

Urinary aldosterone excretion (µg/24h)

2

10

4

6

8

0Placebo Aliskiren

40 mgAliskiren

80 mgAliskiren 160 mg

Aliskiren 640 mg

Enalapril20 mg

**

*

Pretreatment (Day 1)

Day 8

*p<0.05 vs pretreatment (Day 1) Nussberger J, et al. 2002

Aliskiren demonstrates persistence of

effect after discontinuation

Placebo (n=165)

Aliskiren 150 mg (n=172)

Aliskiren 300 mg (n=169)

Aliskiren 600 mg (n=166)

0

−20

−5

−10

−15

∆ SeDBP (mmHg)

Drug discontinuation

100 1 2 3 4 5 6 7 8 9

Week

Herron J, et al. 2006 (Study 2308)

40

0

−20

−80

−100

−60

−40

20

Suppression of PRA is maintained following

discontinuation of aliskiren treatment

Herron J, et al. 2006 (Study 2308)

Change from baseline in PRA(%)

Week100 8

Placebo (n=66)

Aliskiren 150 mg (n=66)

Aliskiren 300 mg (n=66)

Aliskiren 600 mg (n=66)

Double-blind treatment

Treatment-free

withdrawal

• Aliskiren provides long-term suppression of PRA

• Aliskiren effectively reduces PRA from baseline as monotherapy, and blocks the rise in PRA seen during treatment with other antihypertensives such as ARB

• Aliskiren monotherapy provides dose-dependent reductions in DBP and SBP

• Additional BP lowering when combined with other antihypertensives

• Sustained 24-hour BP control with prolonged effect after discontinuation

Aliskiren in hypertension

Clinical summary

Increased peptide levels have not been shown to overcome the BP lowering effect of these agents

Prorenin and the (Pro)renin Receptor:

Functional Significance

Origin of Prorenin

• a significant % of plasma prorenin is of extrarenal origin, whereas renin is of renal origin only

• prorenin-renin conversion appears to occur exclusively in the kidney

Expression of prorenin

Kidneys Adrenal glands

Reproductive

system:

� Testes

� Ovaries

� Placenta

Eye

Low levelsHigh levels

0 1000 2000 3000

time after nephrectomy (minutes)

0

50

100

renin

prorenin

Ang I

% o

f to

tal le

ve

l at t=

0

(Pro)Renin Disappearance after Bilateral Nephrectomycomparison with Ang I

ReninRenin––Prorenin Prorenin RelationshipRelationship

Derkx FHM et al. Clin Exp Hypertens 1988; A10: 1213-1226.

ProreninProrenin as a as a

marker of marker of

microvascularmicrovascular

complications complications

in diabetesin diabetes

LuetscherLuetscher et al., et al.,

NEJM 1985NEJM 1985

patient with microvascular

complications

Diabetes: increased prorenin levels are associated

with the development of retinopathy

• Prorenin levels were significantly (p≤0.01) higher in diabetic patients with

retinopathy compared with those without retinopathy 1-3

– Prorenin levels may be correlated with the degree of retinopathy 4

1 Franken et al. 1990; 2 Wilson et al. 1990; 3 Yokata et al. 2005; 4 Davies et al. 1999.**p<0.01

500

200

400

0

300

100

Prorenin concentration (mU/L)

No

retinopathy

n=64n=99

Proliferative

retinopathy

**

n=60

Background

retinopathy

**

300

100

200

0

150

50

250

Prorenin concentration (mU/L)

Diabetes: prorenin levels are increased in diabetic

patients with microalbuminuria (MA)

• Prorenin is elevated in patients with diabetes compared with non-diabetic siblings 1

– Prorenin can constitute up to 95% of total renin in these patients 2

• Prorenin levels are significantly elevated in diabetes patients withmicroalbuminuria (p<0.0001) compared with those without microalbuminuria 1-4

1 Deinum et al. 1999a; 2 Deinum et al. 1999b;3 Daneman et al. 1994; Chiarelli et al. 2001.

No diabetes

n=39 n=50

Diabetes Diabetes

−MA

n=25 n=25

Diabetes

+MA

p<0.001 p<0.0001

Diabetes: elevated levels of prorenin may predict the

development of nephropathy

• Increase in prorenin levels precedes the development of nephropathy in patients

with diabetes 1,2

– Prorenin may identify diabetes patients at risk of developing nephropathy

1 Chiarelli et al. 2001; 2 Deinum et al. 1999.*p<0.05

100

150

200

250

350

300

400

450

Prorenin mU/l

−5

Time (years)

420−4 −3 −2 −1 31

Developed nephropathy

(n=10)

No nephropathy

(n=87)

Onset of microalbuminuria

* * *

** *

**

New (Pro)renin receptor

Prorenin

Prosegment

Handle region

Active

renin

Angiotensinogen

pocket

Nonproteolyticactivation

Proteolytic

cleavage

Cellmembrane

(Pro)reninreceptor

1 Suzuki et al. 2003; 2 Nguyen et al. 2002;3 Methot et al. 1999.

Receptor-bound prorenin is enzymatically

active

handle

gate

N-terminushuman prorenin model

Human prorenin: two crucial regions T7PFKR10P (gate)

and I11PFLKR15P (handle) for non-proteolytic activation

Renin - LPTDTASFORILLKKMPSVREILEERGVDMTRISAEWGEFIKK - Proenin

Handleregion

Prorenin prosegment

NH2-RILLKKMPSV-COOHHRP

Decoy decapeptide

Sequence of the prosegment seves as blocker

J Clin Invest 2004;114:1128-35

Role of the Renin Receptor Blockade on Diabetic Nephropathy (Ichihara et al.)

WT mice

Role of the Renin Receptor Blockade in Diabetic Nephropathy

WT mice AT1 receptor KO mice

Role of the Renin Receptor Blockade in Diabetic Nephropathy

Human Renin-induced TGF-ββββmRNA Expression

Huang Y. et al. Kidney Int. 2006;69:105-13

Ang II-independentdose-dependent

Renin-induced PAI-1 is mediated via TGF-ββββ

PAI-1 mRNA anti-TGF-ββββ ab

Huang Y. et al. Kidney Int. 2006;69:105-13

Fibronectin and Collagen I

Renin-induced TGF-ββββ is mediated via the Renin Receptor

Huang Y. et al. Kidney Int. 2006;69:105-13

siRNA againstRenin Receptor

TGF-ββββ mRNA

Signaling Pathway

renin

receptor

MEK 1/2

ERK1/2

PD98059

Cellular effects?

PLZF? Th. Unger (Charite,Berlin, Germany, GRC 2006)

HRP?

NOT via EGFR

p38, JNK?

?

prorenin

• (Pro)Renin receptor is most likely expressed in all cell types.

• (Pro)Renin induces ERK 1/2 phosphorylation independent of Ang II.

• Renin signaling depends on MEK-1/2 kinase, not on EGF receptor.

In mesangial cells, TGF-ββββ is involved leading to PAI-1, collagen and fibronectin expression.

• Location is on the surface of the cells, but also intracellular

(endosomes??, lysosomes?? or ER??). Where does signaling take place?

• Affymetrix genes expression and signaling in (pro)renin receptor-

deficient cells might help us to elucidate the function of the renin receptor.

Summary

Open Questions

Does renin and prorenin activate the same signaling pathways?

Is renin and prorenin signaling cell type-specific? Where does it exist (all cells)?

Why is the time course different from other known ERK 1/2 activators (e.g. Ang II)?

Are other MAP kinases (JNK or p38) involved?

Does homodimerization affect signaling?

Does renin signaling regulate its own receptor?

Does a soluble truncated renin receptor exist?

We still have to elucidate whether the major function of the renin receptor is related to cardiovascular disease and whether the blockade of the renin receptor would ameliorate diabetic nephropathy.

Perspectives

C. BurckleM. Bader

INSERM U36

C. BurckleG. Nguyen

S. Feldt

I. MazakM. Wellner

F. C. LuftErasmus MC Rotterdam

W. BatenburgJ. Danser

Collaborators

Aliskiren suppresses key markers of renal damage in a rat model of hypertensive diabetic nephropathy

• Urinary excretion and glomerular gene expression of TGF-β

are elevated in diabetes

– TGF-β is an important mediator of renal damage

• Aliskiren suppressed glomerular gene expression of TGF-β

in a rat model of hypertensive diabetic neuropathy

– Aliskiren showed a trend towards reducing urinary TGF-β excretion compared with vehicle

• Aliskiren showed a trend towards reducing renal collagen III

and IV expression compared with vehicle

Feldman D, et al. 2005

Control Nx

Angiotensin II

0

10

20

fmol/g

Control Nx0

20

40

60

fmol

Ang I/

min/g

Nx, nephrectomy.Danser AHJ et al. Hypertension. 1994;24:37-48.

Cardiac Ang II Depends on Renal Renin

Renin