Influence of arginase polymorphisms and arginase levels/activity on the response to erectile dysfunction therapy with sildenafil.

Arginase 1 (ARG1) and arginase 2 (ARG2) compete with nitric oxide synthases for the substrate l-arginine. Here we aim to assess whether arginase 1 and 2 plasma levels, plasma arginase activity or genetic factors are associated with altered responsiveness to sildenafil. We studied 71 post-prostatectomy erectile dysfunction (ED) patients (PED group) and 72 clinical ED patients (CED). Patients responded to the International Index of Erectile Function questionnaire before and after the treatment. We found positive and negative correlations between plasma levels of arginase 1 and sildenafil responsiveness in the PED and CED groups, respectively. PED group also presented negative correlation between plasma arginase activity and sildenafil responsiveness. Sildenafil poor responders have shown higher plasma arginase activity in PED and higher arginase 1 levels on CED groups. In addition, variant genotypes for the rs2781659, rs2781667 and rs17599586 polymorphisms were associated with reduced arginase activity, as well as the GTTT ARG1 haplotype in CED group.

Endothelial nitric oxide synthase genotypes and haplotypes modify the responses to sildenafil in patients with erectile dysfunction.

Erectile dysfunction (ED) is usually treated with sildenafil. Although genetic polymorphisms in the endothelial nitric oxide synthase (eNOS) gene may impair endogenous NO formation, there is little information about how eNOS polymorphisms and haplotypes affect the responses to sildenafil. We studied 118 patients; 63 patients had ED secondary to radical prostatectomy (PED) and 55 had organic, clinical ED. eNOS genotypes for three eNOS polymorphisms (T(-786)C, rs2070744; a variable number of tandem repeats (VNTR) in intron 4; and Glu298Asp, rs1799983) were determined, and eNOS haplotypes were estimated using PHASE 2.1. The clinical responses to sildenafil were evaluated and the patients were classified as good responders (GR) or poor responders (PR) when their changes in five-item version of International Index for Erectile Function questionnaire were above or below the median value. The TC/CC genotypes and the C allele for the T(-786)C polymorphism were more common in GR, compared with PR patients with PED. However, the 4b4a/4a4a genotypes and the 4a allele for the VNTR polymorphism in intron 4 were more common in GR, compared with PR patients with clinical ED. The C-4a-Glu haplotype was more common in GR than in PR patients with PED. Conversely, the T-4b-Asp haplotype was less common in GR than in PR patients with PED. No other significant differences were found. Our findings show evidence that eNOS polymorphisms affect the responses of PED and clinical ED patients to sildenafil.

VEGF genetic polymorphisms affect the responsiveness to sildenafil in clinical and postoperative erectile dysfunction.

Vascular endothelial growth factor (VEGF) is a cytokine involved in angiogenesis and is closely related to the nitric oxide-cyclic guanosine monophosphate pathway, a target for sildenafil. We investigated for the first time whether three clinically relevant polymorphisms in the VEGF gene are associated with altered responsiveness to sildenafil treatment in postoperative erectile dysfunction (PED) and clinical erectile dysfunction (CED). We determined VEGF genotypes for three polymorphisms in VEGF promoter: -2578C>A (rs699947), -1154G>A (rs1570360) and -634G>C (rs2010963) in 126 patients with erectile dysfunction (ED; 66 patients with PED and 60 patients with CED). The patients were classified as good or poor responders to sildenafil (GR and PR groups, respectively) according to their responses with basis on the changes in five-item version of the International Index for Erectile Function (5-IIEF). We found an association of the -1154AA genotype with PR in both PED and CED patients (P<0.05), whereas the -2578AA and the -2578CA genotypes were associated with PR only in the CED group (P<0.05). The AAG haplotype was more common in PR than in GR patients (38% versus 20%, respectively; P=0.032) in the CED group, thus increasing the risk for a worse response to sildenafil (odds ratio, OR=2.33, 95% confidence interval, CI=1.07-5.09). However, this finding does not resist to Bonferroni's correction (P>0.0125). Our results indicate that VEGF polymorphisms affect the responsiveness of PED and CED patients to sildenafil. These findings may help to improve the therapy of patients with ED.

Circulating matrix metalloproteinases and their endogenous inhibitors in patients with erectile dysfunction.

Erectile dysfunction (ED) may reflect vascular alterations associated with imbalanced matrix metalloproteinases (MMPs) activities. However, no previous study has compared MMPs levels in ED patients with those found in healthy subjects. We measured the circulating MMP-2, MMP-9, TIMP-1 and TIMP-2 levels in ED patients, with or without diabetes mellitus (DM), and in healthy controls. We studied 28 healthy men (control group), 35 men with ED (ED group), and 33 men with ED and DM (ED/DM group). MMP-2, MMP-9, TIMP-1 and TIMP-2 plasma levels were measured by enzyme-linked immunosorbent assay and zymography. We found no differences in MMP-9 levels (P>0.05) among groups. However, while patients in the ED group had similar TIMP-1 levels compared with those found in the control group, we found higher TIMP-1 levels and lower MMP-9/TIMP-1 ratios in the ED/DM group compared with controls (P<0.05). While both groups of patients (ED and ED/DM) had slightly lower MMP-2 levels compared with controls (P<0.05), we found no differences in TIMP-2 levels among the study groups (P>0.05), and no differences in MMP-2/TIMP-2 ratios (P>0.05). We found evidence indicating lack of significant alterations in circulating net MMP-9 and MMP-2 activities in patients with ED, and lower net MMP-9 activity in diabetic patients with ED.