Overview
Abstract
Erectile dysfunction (ED) is a common complication of diabetes, with a prevalence ranging from 15 to 55%. The basis underlying diabetesassociated ED is multifactorial, involving changes in peripheral nerve activity and alterations in endothelial cell function. Due to the complexity of this pathology, the development of experimental models has been crucial in evaluating and translating fundamental results into clinical diabetes-associated ED. The concept of hard-to-treat patients, such as men with diabetes, is now fully accepted due to the complex mechanisms involved. In these men, the response to common oral treatments with phosphodiesterase type 5 inhibitors (PDE5Is) is far from desired, and maximal doses of the drugs are often needed. In addition, diabetes is commonly associated with other co-morbidities, such as hypertension, hypercholesterolaemia and obesity, clusters of the metabolic syndrome (MetS). ED is considered an early warning sentinel for coronary artery disease, just as endothelial dysfunction is seen as a major risk factor for ED. Testosterone deficiency syndrome, a very common syndrome in diabetes and MetS, has been shown to be an independent determinant of endothelial dysfunction, thus contributing to vascular pathology, including ED. This syndrome should be identified among patients, and therapeutic intervention may be required. PDE5Is may improve erectile function with or without the help of other second- or third-line treatments.Other strategies to maximise the response to PDE5Is include risk factor modification and daily dosing of the drugs, instead of on-demand treatment. However, better understanding of the fundamental molecular mechanisms underlying diabetes-associated ED is essential to improving and developing more effective therapies.
Keywords
Diabetes, erectile dysfunction, endothelial dysfunction, phosphodiesterase type 5 inhibitors, penile nitric oxide release test (PNORT)
Disclosure: The authors have no conflicts of interest to declare.
Received: 5 May 2009 Accepted: 13 July 2009
Correspondence:Pedro Vendeira, Department of Urology, S João Central Hospital, EPE, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal. E: vendeira@med.up.pt
Background and Animal Studies
Background and Animal Studies
Diabetes is an increasing disease worldwide, and it is estimated that the number of cases will rise to 300 million globally by 2025. Erectile dysfunction (ED) is a common complication of diabetes and is responsible for a decreased quality of life in diabetic men, who have a three-fold higher risk of ED development compared with healthy individuals. ED may also be the initial presentation of diabetes in 12% of patients subsequently diagnosed with this pathology. In individuals with diabetes, ED occurs at an earlier age, is more severe and increases with disease duration, being approximately 15% at 30 years of age and rising to 55% at 60 years of age. In individuals with diabetes, ED has been associated with the underlying neuropathic condition. However, it seems that as a result of their location, cavernosal vascular endothelial cells (ECs) are the primordial organ affected by this disease. In fact, metabolic derangements induced by hyperglycaemia and increased oxidative stress disable penile EC functional response in order to maintain homeostasis, impairing the endothelium regulatory role on the modulation of vascular- and smooth-muscle (SM) contractile tone, which is crucial for normal erectile functionality. This loss of endothelial ability to vasodilate in response to local and systemic changes is referred to as endothelial dysfunction and recognised as a key feature of diabetes-associated ED. Ageing may also affect the structural and functional properties of ECs and SM, leading to vascular dysfunctions.
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