DELAYED ADMINISTRATION OF ALT-711, BUT NOT OF AMINOGUANIDINE IMPROVES

ERECTILE FUNCTION IN STREPTOZOTOCIN DIABETIC RATS: CURATIVE VERSUS

PREVENTIVE MEDICINE

Mustafa F. Usta (1,2), Muammer Kendirci (2), Trinity J Bivalacqua (2),

Serap Gur (2), Neale A Foxwell (3), Wayne J.G. Hellstrom (2) , Selim Cellek (3)

Akdeniz University School of Medicine Department of Urology, Section of Andrology Antalya-TURKEY (1)

Tulane University, School of Medicine Department of Urology, Section of Andrology New Orleans, LA-USA (2)

Wolfson Institute for Biomedical Research University College, London-UK (3)

Common Conditions Associated with Erectile Dysfunction

Diabetes 40%

Vascular Disease30%

Spinal Cord Injury8%

Radical Surgery13%

Endocrine Disorders6%

MultipleSclerosis3%

Zonszein. Urol Clin North Am. 1995

Diabetes and Erectile Dysfunction

*Diabetes affects >15 million individuals in the USA, and prevalence of ED reported to be as high as 50 - 75%.

*Causative factors in diabetic ED are the reduction in NOS nerve fibers, disordered endothelial smooth muscle relaxation, and NO bio-availability.

*Animal models of diabetes exhibit ED with significant decreases in eNOS & nNOS protein and NOS-containing nerve fibers in the dorsal and intracavernosal nerves.

El Sakka AI et al., IJIR 1999Vernet D et al., Endocrinology 1995Akingba A & Burnett AL, Mol Urol 2001Bivalacqua TJ et al., BBRC 2001

*Possible relation between elevated levels of AGE in DM and ED

*AGEs are responsible for the impairment of NO-mediated corpus cavernosal smooth muscle relaxation in DM

*The protective effect of Aminoguanidine (selective AGE inhibitor) on erectile function in diabetic rats

Advanced Glycation End Products (AGE) and ED

Seftel A et al, Urology, 1997Cartledge JJ et al, BJU Int, 2001Usta et al, J Urol, 2003Usta et al, BJU Int 2004

*The result of nonenzymatic glycation of proteins commonly encountered in systemic disease (DM, CRF and ageing)

*The reaction occurs between reduced sugars (aldoses and ketoses) and free amino groups of proteins (Amodori product, Maillard reaction)

*One of the most important primer target for Maillard reaction are long lived proteins such:COLLAGEN, LAMININ

*AGEs decrease eNOS expression in the vascular endothelium, causing to decreased NO production

*After inducing diabetes in rats AGEs occur over a period of weeks (3-5 weeks)

What is AGE?

Singh R et al, Diabetologia 2001Vlasara H, Diabetes Metab Res Rev 2001Cellek S et al, Diabetes 2003

Diabetes mellitus

nNOS depletion

in the axons

AGEsaccumulation

Oxidative stress

Caspase-3 activation

Apoptotic cell death

Nitrergic degeneration

serum AGEs

Reversible phase Irreversible phase

NO

Mitochondrial dysfunction

Nitrergic dysfunction

Axonal transport

defect

PO

INT

OF

NO

RE

TU

RN

Cellek S et al., Diabetes 2003

1. Accumulation of AGEs has been linked to diabetes related ED. Inhibitors of AGEs such as AMG prevents ED in diabetic rats ( If administered immediately). We assessed the effect of late administered AMG on erectile function in diabetic rats.

2. Additionally, we investigated whether late administration of a cross-link breaker ALT-711 (alagebrium) can protect against the development of ED in a diabetic rat model.

SPECIFIC AIMS

Harlan Sprague-Dawley rats (18 to 20 weeks old) were divided into 4 groups:

Group-1: Control (n=10)

Group-2: STZ-diabetic rats (n=10) (Free access to water and standard diet)

Group-3: STZ-diabetic rats treated with ALT-711 (3mg/kg i.p. daily)* (n=12)

Group-4: STZ-diabetic rats treated with AMG (AMG added to drinking water 1g/l per day)* (n=11)

*ALT and AMG treatment started 6 weeks after DM induction

STUDY DESIGN

STUDY PROTOCOL

* Blood glucose level was assessed every two weeks throughout the study period (10mmol/l)

* Assessment of erection:Three months after induction of diabetes an in vivo erectile protocol (Intracavernosal pressure and total ICP measurements in response to cavernosal nerve stimulation) was employed

*AGE (serum):ELISA and fluorometry AGE ( penis): Immunofluorescence nNOS (penis): Western Blotting

RESULTS-1

RESULTS-2

RESULTS-3

RESULTS-4

RESULTS-5

RESULTS-6

* STZ induced diabetes caused ED in rats within 12 weeks. However ALT-711 treatment for the last 6 weeks improved erectile function in diabetic rats which was comparable to non-diabetic control group

* Treatment with AMG for the 6 weeks did not reverse erectile function

* ALT-711 treatment normalized the nNOS levels suggesting that AGEs might be interfering with the axonal transport of nNOS. Therefore our results may also suggest a new mechanism by which AGEs may have a detrimental effect on NO production in the autonomic nervous system

*The effect of ALT-711 on arterial compliance has been assessed in a human study. The results of that study clearly demonstrated that ALT-711 improved total arterial compliance in aged humans with vascular stiffness. ALT-711 may provide a novel therapeutic approach in endothelial dysfunction as well as ED, which are commonly seen with diabetes.

CONCLUSIONS