The Association of Serum Prolidase Activity and Erectile Dysfunction

Abstract

Prolidase is a cytosolic exopeptidase that cleaves iminodipeptides with carboxy-terminal proline or hydroxyproline and plays a major role in collagen turnover. Collagen is the essential content in atherosclerotic plaque, playing a key role in the stability/ instability and progression of endothelial dysfunction in the pathogenesis of erectile dysfunction (ED). Consequently, in this study we sought to determine serum prolidase activity and markers of oxidative stress, such as lipid hydroperoxide and total free sulfhydryl, in vasculogenic ED. We evaluated 92 patients with vasculogenic ED and 50 control subjects by clinical and laboratory investigations. We measured serum prolidase activity and serum total free sulfhydryl levels spectrophotometrically. Serum lipid hydroperoxide levels were determined with ferrous ion oxidationxylenol orange method. We assessed the association of serum prolidase activity with the presence and severity of vasculogenic ED and clinical characteristics, as well as laboratory parameters. We also assessed the association of serum prolidase activity with the variables according to the vascular status of patients with vasculogenic ED. The comparison included 92 vasculogenic ED patients grouped into 3 categories according to the vascular status of patients with ED-arterial insufficiency (n 5 26), veno-occlusive dysfunction (n 5 37), and mixed-type impotence (n 5 29)-and 50 controls. Receiver-operator characteristics (ROCs) were analyzed to find a cutoff value with the best sensitivity and lowest falsepositive rate. Serum prolidase activity (53.5 6 5.5 U/L vs 45.7 6 4.9 U/L, respectively; P , .001) and serum lipid hydroperoxide levels were significantly increased in patients with vasculogenic ED compared with controls, whereas serum total free sulfhydryl levels were significantly decreased in patients with vasculogenic ED compared with controls (P , .001). The lowest and highest mean serum prolidase activities were detected in control participants and in patients with arterial insufficiency, respectively (analysis of variance P , .001). The overall findings of this study support the predictive accuracy of the serum prolidase activity in our cohort, with a statistically significant ROC value of 0.78. Findings of this study have shown that serum prolidase activity is significantly associated with the presence and severity of vasculogenic ED, and elevated serum prolidase activity might be an independent predictor of ED.

Evaluation of Prolidase Activity, Oxidative Stress, and Antioxidant Enzyme Levels in Testicular and Penile Tissues after Human Chorionic Gonadotropin Treatment in Rats by Predicting Infertility and Erectile Dysfunction

“…Prolidase is a cytosolic enzyme necessary for specific splitting of imidodipeptides with proline or hydroxyproline at their C-terminals, and it has a major role in collagen turnover and cell growth [9, 17]. The relationship between collagen and prolidase activity was observed in a study on fibrotic processes, where an increase in prolidase activity was found to be accompanied by an increase in deposition of tissue collagen [17].…”

“…Prolidase activity has been shown in plasma erythrocytes, leucocytes, and fibroblasts and in organs like the kidney, the brain, the heart, the liver, the small intestines, the stomach, the lung, the spleen, the thymus, and the uterus [19]. While a higher prolidase activity is observed in patients with osteoporosis, osteoarthritis, hypertension, coronary artery disease, and erectile dysfunction [8, 9, 17, 18, 20, 21], a lower level is observed in renal insufficiency because the main source of prolidase is the kidney [19]. The severity of the antioxidant stress is directly correlated with the inhibition of collagen production in which prolidase is the main enzyme [19].…”

“…The severity of the antioxidant stress is directly correlated with the inhibition of collagen production in which prolidase is the main enzyme [19]. Tissue prolidase activity may be an indicator of tissue fibrosis [9]. Fibrosis in the testicular and penile tissues may affect the fertility and erectile capacity.…”

“…Increased levels of prolidase seem to be associated with increased levels of nitric oxide and oxidative stress along with decreased levels of antioxidant [7]. Also studies on vasculogenic erectile dysfunction have detected higher serum levels of prolidase [8, 9]. In this study we aimed to examine the effect of hCG on prolidase activity, oxidative stress, and levels of antioxidant enzyme in the testicles and penile tissue in a rat model.…”

Prolidase

“…High levels of the prolidase activity were detected in both hypertension and erectile dysfunction. An increased collagen deposition in the blood vessels of these patients is leading to the side effects (18,19).…”