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

Transcription

1 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

2 Renin-Angiotensin System Prorenin Angiotensinogen Renin Sequence: RILLKKMPSV AT 1, AT 2 Renin receptor Ang I ACE, chymase Ang II ACE2 AT 4 Ang IV Ang-(1-7) AT 1-7

3 Tissue RAS leads to damage in many organs especially in patients with metabolic disorders Brain Pituitary Gland Eye 2 in diabetes Adrenal Glands Blood Vessels 3 with atherosclerosis Adipose Tissue 4,5 in obesity, hypertension Aorta 6 with atherosclerosis Heart 7-9 in diabetes, post-mi, failing ventricle Kidney in diabetes, membranous nephropathy Pancreas 13 in nephropathy Ang II levels are much higher in tissue than in plasma 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: Strain WD et al. JRAAS. 2002;3: Dzau VJ. Hypertension. 2001;37; Faloia E et al. J Endocrinol Invest. 2002;25: Vega GL. Minerva Endocrinol. 2004;29: Arakawa K et al. Hypertension. 2000; 36: Frustaci A et al. Circ Res. 2000;87: Danser AH et al. Circulation. 1997;96: Hokimoto S et al. Circulation. 1996;94: Hollenberg NK et al. Kidney Int. 2003;63: Mezzano S et al. Kidney Int Suppl. 2003;86;S64-S Mezzano SA et al. Kidney Int. 2003;64:S39-S Leung PS. J Pancreas. 2003;4:89-91.

4 The Cardiovascular Continuum Development and Progression of CV Disease Maladaptive remodelling Endothelial dysfunction Vascular disease Constriction, inflammation, hypertrophy, hyperplasia, atherogenesis, thrombosis Endothelial dysfunction Diabetes, hypertension, insulin resistance Tissue injury MI, stroke, glomerular ischaemia Pathologic remodelling LVH, LV dilation, glomerulosclerosis Target-organ dysfunction HF, nephropathy Target-organ damage End-stage organ failure Death Dzau VJ. Hypertension. 2001; 37: Dzau V et al. Am Heart J. 1991; 121: 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:

5 PRA Predicts the Incidence of MI Interrelation Between PRA and CV Risk Factors MI rate/1000 personyears High Moderate Risk Status Low For every 2-unit increase in PRA, there is an overall 25% increase in MI incidence* Low Normal High Plasma Renin Activity *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.

6 Renin inhibition

7 Current Renin System blockers & diuretics raise plasma renin activity (PRA)* Kidney Angiotensinogen Renin Feedback Loop Plasma Renin Activity Ang I Ang II ARBs AT 1 Receptor ACEIs Non ACE pathways ACE Glomerular vasoconstriction Inflammation Fibrosis Heart Hypertrophy Fibrosis Vasoconstriction Vessels Hyperplasia hypertrophy Inflammation Oxidation Fibrosis Brain *Increased peptide levels have not been shown to overcome the BP lowering effect of these agents Vasoconstriction

8 Renin inhibition acts at the Renin System s point of activation and neutralizes the PRA rise Renin inhibitor Kidney Angiotensinogen Glomerular vasoconstriction Inflammation Fibrosis Renin Ang I Heart Feedback Loop Plasma Renin Activity Ang II ARBs AT 1 Receptor ACEIs ACE Hypertrophy Fibrosis Vasoconstriction Vessels Hyperplasia hypertrophy Inflammation Oxidation Fibrosis Brain Vasoconstriction

9 Aliskiren binds to the active site of renin Renin Aliskiren Angiotensinogen Aliskiren binds to a pocket in the renin molecule, blocking cleavage of angiotensinogen to angiotensin I Adapted from Wood JM, et al. 2003

10 Renin inhibition Experimental studies

11 Renin inhibition vs. anti-hypertensive treatment Systolic Blood Pressure ( mm Hg ) ** ## *** *** dtgr Age (weeks) Triple RI SD 24-hour Albuminuria ( mg / d ) ** dtgr *** ### Age (weeks) Triple RI SD Hypertension 2000;35:587-94

12 Circ Res 2005; 97: Albuminuria

13 Aliskiren provides renoprotective effects in a rat model of hypertensive diabetic nephropathy Urinary albumin (mg/24h) Vehicle Aliskiren 10 mg/kg/d 30 mg/kg/d Days Treatment starts Feldman D, et al. 2005

14 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

15 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

16 Aliskiren compared with ramipril and combination therapy in patients with diabetes and hypertension Study design Aliskiren 150 mg Aliskiren 300 mg n=282 Washout Placebo Ramipril 5 mg Ramipril 10 mg n=278 Single-blind Aliskiren 150 mg + ramipril 5 mg Aliskiren 300 mg + ramipril 10 mg n=277 2 weeks 2 4 weeks 4 weeks 4 weeks Uresin Y, et al (Study 2307)

17 Aliskiren/ramipril combination provides significantly greater reductions in BP than component monotherapies Ramipril mono Aliskiren mono DBP Aliskiren/ ramipril combination Mean change from baseline in BP (mmhg) Ramipril mono Aliskiren mono SBP Aliskiren/ ramipril combination n=275 n=279 n=274 n=275 n=279 n= * * * 16.6 *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 monotherapy Error bars indicate standard error from the mean Uresin Y, et al (Study 2307)

18 Aliskiren in combination with valsartan Study design (2101) Double-blind 4-period crossover study in healthy male subjects with mild salt depletion 14-day washout 14-day washout 14-day washout Aliskiren 300 mg single dose Valsartan 160 mg single dose Aliskiren 150 mg/ valsartan 80 mg single dose Placebo single dose Azizi M, et al. 2004

19 Aliskiren neutralizes ARB-induced increase in PRA PRA at 24 hours after dosing (ng/ml/h) 5 4 * * Aliskiren 300 mg Valsartan 160 mg Aliskiren + Valsartan 150/80 mg Placebo *p<0.05 vs aliskiren 150 mg/valsartan 80 mg p<0.05 vs aliskiren 300 mg p<0.05 vs valsartan 160 mg n=12 Azizi M, et al. 2004

20 Aliskiren neutralizes ARB-induced rises in Ang II Plasma Ang II (pg/ml) 80 * *p<0.05 vs aliskiren 150 mg/valsartan 80 mg p<0.05 vs aliskiren 300 mg p<0.05 vs valsartan 160 mg n=12 0 * Time (hours) * * * 48 * * Placebo Aliskiren 300 mg Valsartan 160 mg Aliskiren 150 mg + Valsartan 80 mg Azizi M, et al. 2004

21 Aliskiren significantly decreases urinary aldosterone excretion in healthy volunteers Urinary aldosterone excretion (µg/24h) 10 Pretreatment (Day 1) Day * * * Placebo Aliskiren 40 mg Aliskiren 80 mg Aliskiren 160 mg Aliskiren 640 mg Enalapril 20 mg *p<0.05 vs pretreatment (Day 1) Nussberger J, et al. 2002

22 Aliskiren demonstrates persistence of effect after discontinuation SeDBP (mmhg) Drug discontinuation Week Aliskiren 300 mg (n=169) Aliskiren 600 mg (n=166) Placebo (n=165) Aliskiren 150 mg (n=172) Herron J, et al (Study 2308)

23 Change from baseline in PRA (%) Suppression of PRA is maintained following discontinuation of aliskiren treatment Week 8 Placebo (n=66) Aliskiren 150 mg (n=66) Double-blind treatment Aliskiren 300 mg (n=66) Aliskiren 600 mg (n=66) Treatment-free withdrawal 10 Herron J, et al (Study 2308)

24 Aliskiren in hypertension Clinical summary 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 Increased peptide levels have not been shown to overcome the BP lowering effect of these agents

25 Prorenin and the (Pro)renin Receptor: Functional Significance

26 Origin of Prorenin a significant % of plasma prorenin is of extrarenal origin, whereas renin is of renal origin only Expression of prorenin High levels Low levels Eye prorenin-renin conversion appears to occur exclusively in the kidney Kidneys Adrenal glands Reproductive system: Testes Ovaries Placenta

27 (Pro)Renin Disappearance after Bilateral Nephrectomy comparison with Ang I 100 % of total level at t=0 50 renin prorenin Ang I time after nephrectomy (minutes)

28 Renin Prorenin Relationship Derkx FHM et al. Clin Exp Hypertens 1988; A10:

29 Prorenin as a marker of microvascular complications in diabetes Luetscher et al., NEJM 1985 patient with microvascular complications

30 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 Prorenin concentration (mu/l) n=99 No retinopathy ** n=60 Background retinopathy ** n=64 Proliferative retinopathy **p< Franken et al. 1990; 2 Wilson et al. 1990; 3 Yokata et al. 2005; 4 Davies et al

31 Diabetes: prorenin levels are increased in diabetic patients with microalbuminuria (MA) Prorenin concentration (mu/l) 300 p< n=39 n=50 0 No diabetes Diabetes Diabetes MA p< n=25 n=25 Diabetes +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 with microalbuminuria (p<0.0001) compared with those without microalbuminuria Deinum et al. 1999a; 2 Deinum et al. 1999b; 3 Daneman et al. 1994; Chiarelli et al

32 Diabetes: elevated levels of prorenin may predict the development of nephropathy Prorenin mu/l * * * Time (years) * * * Onset of microalbuminuria 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 * * 4 Developed nephropathy (n=10) No nephropathy (n=87) *p< Chiarelli et al. 2001; 2 Deinum et al

33 New (Pro)renin receptor

34 Receptor-bound prorenin is enzymatically active Prorenin Handle region Prosegment Cell membrane Proteolytic cleavage Nonproteolytic activation (Pro)renin receptor Angiotensinogen pocket Active renin 1 Suzuki et al. 2003; 2 Nguyen et al. 2002; 3 Methot et al

35 Human prorenin: two crucial regions T 7P FKR 10P (gate) and I 11P FLKR 15P (handle) for non-proteolytic activation handle gate human prorenin model N-terminus

36 Sequence of the prosegment seves as blocker Prorenin prosegment Handle region Renin - LPTDTASFORILLKKMPSVREILEERGVDMTRISAEWGEFIKK - Proenin NH 2 -RILLKKMPSV-COOH HRP Decoy decapeptide

37 Role of the Renin Receptor Blockade on Diabetic Nephropathy (Ichihara et al.) J Clin Invest 2004;114:

38 Role of the Renin Receptor Blockade in Diabetic Nephropathy WT mice

39 Role of the Renin Receptor Blockade in Diabetic Nephropathy WT mice AT1 receptor KO mice

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41 Human Renin-induced TGF-β mrna Expression dose-dependent Ang II-independent Huang Y. et al. Kidney Int. 2006;69:105-13

42 Renin-induced PAI-1 is mediated via TGF-β PAI-1 mrna anti-tgf-β ab Huang Y. et al. Kidney Int. 2006;69: Fibronectin and Collagen I

43 Renin-induced TGF-β is mediated via the Renin Receptor sirna against Renin Receptor TGF-β mrna Huang Y. et al. Kidney Int. 2006;69:105-13

44 Signaling Pathway prorenin renin receptor HRP?? NOT via EGFR PLZF? Th. Unger (Charite, Berlin, Germany, GRC 2006) MEK 1/2 PD98059 p38, JNK? ERK1/2 Cellular effects?

45 Summary (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-β 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 receptordeficient cells might help us to elucidate the function of the renin receptor.

46 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?

47 Perspectives 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.

48 Collaborators S. Feldt I. Mazak M. Wellner F. C. Luft C. Burckle M. Bader INSERM U36 C. Burckle G. Nguyen Erasmus MC Rotterdam W. Batenburg J. Danser

49 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

50 Cardiac Ang II Depends on Renal Renin 20 Angiotensin II 60 Renin fmol/g 10 fmol Ang I/ min/g Control Nx Nx, nephrectomy. Danser AHJ et al. Hypertension. 1994;24: Control Nx