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Song, Bae, Kim, and Moon: Effects of Metformin on Penile Expression of Nitric Oxide Synthase in OLETF Rats
Original Article
Basic and Translational Research
Korean Journal of Urology

Korean Journal of Urology 2009; 50(2): 179-185.

Published online: 25 February 2009

DOI: https://doi.org/10.4111/kju.2009.50.2.179

Effects of Metformin on Penile Expression of Nitric Oxide Synthase in OLETF Rats

Phil Hyun Song, In Soo Bae1, Yong Woon Kim2, Ki Hak Moon

Department of Urology, College of Medicine, Yeungnam University, Daegu, Korea.

1Hanvit Urology Clinic, Korea.

2Department of Physiology, College of Medicine, Yeungnam University, Daegu, Korea.

Correspondence to: Ki Hak Moon. Department of Urology, Yeungnam University College of Medicine, 317-1, Daemyeongdong, Nam-gu, Daegu 705-717, Korea. TEL: 053-620-3693, FAX: 053-627-5535, khmoon@med.yu.ac.kr

Received 4 September 2008       Accepted 13 October 2008

Copyright © The Korean Urological Association, 2009

Abstract

Purpose

It is well known that metformin, an oral biguanide insulinsensitizing agent, targets AMP-activated protein kinase (AMPK), which activates endothelial nitric oxide synthase (eNOS), which may be associated with erectile dysfunction. The aim of this study was to evaluate whether metformin activates eNOS in the penile tissue of a genetically obese rat model.

Materials and Methods

We measured phospho-eNOS levels and eNOS expression in the penile tissue of Otsuka Long Evans Tokushima Fatty (OLETF) rats after 3 days of treatment with metformin (150 or 300 mg) to evaluate whether metformin activates eNOS in the penile tissue of this genetically obese rat model. Seven-month-old OLETF rats were used, and eNOS expression was analyzed by real-time polymerase chain reaction (PCR). The experimental groups were compared with use of the Kruskal-Wallis or Mann-Whitney test.

Results

Seven-month-old OLETF rats had severe visceral fat deposition and elevated serum leptin concentrations. eNOS expression analyzed by real-time PCR was lower in the penile tissue of OLETF rats than in Long Evans Tokushima Otsuka (LETO) rats. Short-term treatment with metformin did not change visceral fat mass or serum leptin levels. However, metformin treatment increased eNOS mRNA expression in the penile tissue as determined by real-time PCR. The levels of phospho-eNOS and phospho-AMPK (pAMPK) in penile tissue revealed a dose-dependent tendency to increase with metformin treatment; however, there was no statistical difference by Kruskal-Wallis test among the experimental groups. The pAMPK level was dose-dependently elevated in the soleus by metformin treatment. There was no significant change in pSTAT3 by metformin treatment in the soleus.

Conclusions

Metformin activates eNOS mRNA expression in the penile tissue of OLETF rats. Further study on the relation between erectile function and eNOS levels is needed for clinical application.

Keywords: Nitric oxide synthase, AMP-activated protein kinase, Penis

Figures and Tables

Fig. 1
The expression of endothelial nitric oxide synthase (eNOS) of penile tissues in Long Evans Tokushima Otsuka (LETO) and Otsuka Long Evans Tokushima Fatty (OLETF) rats. LETO; n=4, OLETF; n=4, Bars are mean±SEM of four experimental cases. a: p<0.05.
kju-50-179-g001
Fig. 2
Changes in AMP-activated protein kinase (AMPK) and phospho-AMPK (pAMPK) in soleus muscle measured by Western blot in Otsuka Long Evans Tokushima Fatty (OLETF) rats. pSTAT3: phospho-signal transducer and activator of transcription 3, GAPDH: glyceraldehyde-3-phosphate dehydrogenase.
kju-50-179-g002
Fig. 3
Quantitative comparisons of phospho-AMP-activated protein kinase (pAMPK) expression by Western blot of soleus muscle in Otsuka Long Evans Tokushima Fatty (OLETF) rats. Bars are mean±SEM. Values that do not share a common superscript are significantly different at p<0.05. GAPDH: glyceraldehyde-3-phosphate dehydrogenase.
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Fig. 4
Changes in endothelial nitric oxide synthase (eNOS) and AMP-activated protein kinase (AMPK) expression in penile tissue by Western blot in Otsuka Long Evans Tokushima Fatty (OLETF) rats. GAPDH: glyceraldehyde-3-phosphate dehydrogenase.
kju-50-179-g004
Fig. 5
Quantitative comparisons of phospho-AMP-activated protein kinase (pAMPK) (A) and phospho-endothelial nitric oxide synthase (eNOS) (B) expressions by Western blot of penile tissue in Otsuka Long Evans Tokushima Fatty (OLETF) rats. Bars are mean±SEM. GAPDH: glyceraldehyde-3-phosphate dehydrogenase.
kju-50-179-g005
Fig. 6
Changes in endothelial nitric oxide synthase (eNOS) expression by real-time polymerase chain reaction (PCR) in penile tissue. Bars are mean±SEM. Values that do not share a common superscript are significantly different at p<0.05.
kju-50-179-g006
Table 1
Primer sequences used for real-time PCR
kju-50-179-i001

PCR: polymerase chain reaction, eNOS: endothelial nitric oxide synthase, Tm: melting temperature

Table 2
Body weight and total visceral fat mass of the experimental groups
kju-50-179-i002

Values are mean±SEM

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