Diabetes exacerbates the functional deficiency of NO/cGMP pathway associated with erectile dysfunction in human corpus cavernosum and penile arteries.
BACKGROUND
Diabetic men with erectile dysfunction (ED) are less responsive to therapy with type 5 phosphodiesterase (PDE5) inhibitors. Although an impairment of the nitric oxide (NO)/cyclic guanosin-monophosphate (cGMP) pathway has been shown in diabetic ED vs. non-diabetic ED, the functionality of NO/cGMP pathway in non-diabetic and diabetic ED patients with respect to non-ED patients has not been established.


OBJECTIVE
The aim of this study is to evaluate the function of NO/cGMP signalling in human erectile tissues from ED patients exploring the added impact of diabetes.


METHODS
Corpus cavernosum strips (human corpus cavernosum [HCC]) and penile resistance arteries (HPRA) were collected from penile specimens from organ donors (OD) and from diabetic and non-diabetic men with ED undergoing penile prosthesis implantation.


METHODS
Relaxations to acetylcholine, electrical field stimulation, sodium nitroprusside, and sildenafil were evaluated in phenylephrine-contracted HCC and norepinephrine-contracted HPRA. cGMP content in HCC was also determined.


RESULTS
The impairment of endothelium-dependent relaxation in HCC and HPRA from ED patients was exacerbated by diabetes (E(max) 76.1, 62.9, and 49.3% in HCC and 73.1, 59.8, and 46.0% in HPRA from OD, non-diabetic and diabetic ED, respectively). Hypertension, hypercholesterolemia, or aging did not exert a further impairment of endothelial relaxation among ED patients. Diabetes also causes a further impairment of neurogenic relaxation in HCC and HPRA. The basal and stimulated content of cGMP in HCC was significantly decreased in patients with ED, but specially reduced in diabetic patients. Diabetes clearly impaired PDE5 inhibitor-induced vasodilation of HPRA from ED patients.


CONCLUSIONS
ED is related to impaired vasodilation, reduced relaxant capacity, and diminished cGMP content in penile tissue. These alterations are more severe in diabetes and accompany reduced relaxant efficacy of PDE5 inhibition. Thus, an exacerbated reduction of nitric oxide/cGMP signaling could be responsible for ED in diabetic men and would explain their reduced response to treatment.
Angulo
Javier
J
Departamento de Investigación, Hospital Ramón y Cajal, Madrid, Spain. jangulo@ibercom.com
González-Corrochano
Rocío
R
Cuevas
Pedro
P
Fernández
Argentina
A
La Fuente
José M
JM
Rolo
Francisco
F
Allona
Antonio
A
Sáenz de Tejada
Iñigo
I
D000328:Adult; D006152:Cyclic GMP / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003925:Diabetic Angiopathies / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000503:physiopathology; D006801:Humans; D018783:Impotence, Vasculogenic / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D009569:Nitric Oxide / Q000502:physiology*; D019935:Penile Implantation; D010413:Penis / Q000098:blood supply*; D058986:Phosphodiesterase 5 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D058986:Phosphodiesterase 5 Inhibitors; D010726:Phosphodiesterase Inhibitors; D009569:Nitric Oxide; D006152:Cyclic GMP