Tomoteru Kishimoto1, Tomoya Kataoka2, Yuka Yamamoto3, Gakuto Asano3, Ayako Fukamoto3, Yuji Hotta3, Yasuhiro Maeda3, Masayuki Takahashi1, Hiro-Omi Kanayama1, Kazunori Kimura4. 1. Department of Urology, Institute of Biomedical Science, Tokushima University Graduate School, Tokushima, Japan. 2. Department of Clinical Pharmaceutics, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan. 3. Department of Hospital Pharmacy, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan. 4. Department of Clinical Pharmaceutics, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan; Department of Hospital Pharmacy, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan. Electronic address: kkimura@med.nagoya-cu.ac.jp.
Abstract
BACKGROUND: High salt intake is a risk factor for hypertension, which can potentially lead to erectile dysfunction (ED); however, the underlying pathological mechanisms remain unclear. AIM: To investigate whether erectile function is directly impaired by high salt intake and whether selective inhibition of mineralocorticoid receptor (MR) could provide protection from ED. METHODS: 6-week-old male Dahl salt-sensitive rats were randomly divided into 3 groups: normal diet (0.3% NaCl; control, n = 8), high-salt diet (8% NaCl; HS, n = 8), and high-salt diet plus eplerenone (HS + EPL, n = 11). HS + EPL rats were orally administered daily doses of EPL (75 mg/kg) for 6 weeks; control and HS rats received purified water on the same schedule. OUTCOMES: At the end of the study period, erectile function was evaluated by measuring intracavernosal pressure and mean arterial pressure after cavernous nerve stimulation. Serum levels of asymmetric dimethylarginine and L-arginine were determined using ultraperformance liquid chromatography-tandem mass spectrometry. Quantitative PCR was used to assess the expression of MR, inflammation, and oxidative stress markers (nicotinamide adenine dinucleotide phosphate oxidase-1/4, p22phox, interleukin-6, and superoxide dismutase-1), and protein arginine N-methyltransferase-1. RESULTS: The intracavernosal pressure/mean arterial pressure ratio was significantly lower, whereas systolic blood pressure, MR expression, serum asymmetric dimethylarginine levels, oxidative stress, and levels of inflammatory biomarkers were significantly higher in HS rats than in control rats (P < .05). EPL administration significantly improved each of these parameters except systolic blood pressure and MR expression. No significant intergroup differences were observed for L-arginine and superoxide dismutase-1 levels. CLINICAL TRANSLATION: Our results provide a rationale for the need of salt restriction and the use of selective MR inhibitors in prophylaxis or treatment of ED in men consuming a high-salt diet. STRENGTHS & LIMITATIONS: We are the first to report that the adverse impact of high salt intake on erectile function is mediated via MR activation, independent of its effect on blood pressure. A major limitation of this study is that responses of salt-resistant rats were not studied. CONCLUSIONS: High salt intake directly impaired erectile function in Dahl salt-sensitive rats, whereas selective MR inhibition ameliorated this effect. Kishimoto T, Kataoka T, Yamamoto Y, et al. High Salt Intake Impairs Erectile Function in Salt-Sensitive Rats Through Mineralocorticoid Receptor Pathway Beyond Its Effect on Blood Pressure. J Sex Med 2020;17:1280-1287.
BACKGROUND: High salt intake is a risk factor for hypertension, which can potentially lead to erectile dysfunction (ED); however, the underlying pathological mechanisms remain unclear. AIM: To investigate whether erectile function is directly impaired by high salt intake and whether selective inhibition of mineralocorticoid receptor (MR) could provide protection from ED. METHODS: 6-week-old male Dahl salt-sensitive rats were randomly divided into 3 groups: normal diet (0.3% NaCl; control, n = 8), high-salt diet (8% NaCl; HS, n = 8), and high-salt diet plus eplerenone (HS + EPL, n = 11). HS + EPLrats were orally administered daily doses of EPL (75 mg/kg) for 6 weeks; control and HS rats received purified water on the same schedule. OUTCOMES: At the end of the study period, erectile function was evaluated by measuring intracavernosal pressure and mean arterial pressure after cavernous nerve stimulation. Serum levels of asymmetric dimethylarginine and L-arginine were determined using ultraperformance liquid chromatography-tandem mass spectrometry. Quantitative PCR was used to assess the expression of MR, inflammation, and oxidative stress markers (nicotinamide adenine dinucleotide phosphate oxidase-1/4, p22phox, interleukin-6, and superoxide dismutase-1), and protein arginine N-methyltransferase-1. RESULTS: The intracavernosal pressure/mean arterial pressure ratio was significantly lower, whereas systolic blood pressure, MR expression, serum asymmetric dimethylarginine levels, oxidative stress, and levels of inflammatory biomarkers were significantly higher in HS rats than in control rats (P < .05). EPL administration significantly improved each of these parameters except systolic blood pressure and MR expression. No significant intergroup differences were observed for L-arginine and superoxide dismutase-1 levels. CLINICAL TRANSLATION: Our results provide a rationale for the need of salt restriction and the use of selective MR inhibitors in prophylaxis or treatment of ED in men consuming a high-salt diet. STRENGTHS & LIMITATIONS: We are the first to report that the adverse impact of high salt intake on erectile function is mediated via MR activation, independent of its effect on blood pressure. A major limitation of this study is that responses of salt-resistant rats were not studied. CONCLUSIONS: High salt intake directly impaired erectile function in Dahl salt-sensitive rats, whereas selective MR inhibition ameliorated this effect. Kishimoto T, Kataoka T, Yamamoto Y, et al. High Salt Intake Impairs Erectile Function in Salt-Sensitive Rats Through Mineralocorticoid Receptor Pathway Beyond Its Effect on Blood Pressure. J Sex Med 2020;17:1280-1287.