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 KruskalWallis 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. (Korean J Urol 2009;50:179-185)
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