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Effects of diabetes on nitric oxide synthase and growth factor genes and protein expression in an animal model
A I El-Sakka1, C S Lin, R M Chui
1Department of Urology, University of California, School of Medicine, San Francisco 94143-0738, USA.
Abstract:
Erectile dysfunction occurs frequently in humans with diabetes mellitus; the molecular basis of this phenomenon is not known. We investigated the effects of diabetes on penile erection, nitric oxide synthase and growth factors expression in an animal model. Forty male rats were divided into two groups: the experimental group (n = 30) received intraperitoneal injection of Streptozotocin (STZ) dissolved in citrate buffer to induce diabetes; ten age-matched control rats received injection of citrate buffer vehicle only. Before euthanization at eight weeks, erectile function was assessed by electrostimulation of the cavernous nerves. NADPH diaphorase staining was used to identify NOS and immunostaining technique was used to identify nNOS in the penile nerve fibers. RT-PCR was used to identify mRNA expression of nNOS, eNOS, iNOS, ER-beta, ER-alpha, NGF, IGF-I, TGF-beta 1, and AR. Western blot was used to identify nNOS, IGF-I, NGF, and TFG-beta protein expressions. In the diabetic group, there was: (1) a significant decrease in NOS containing nerve fibers in the dorsal and intracavernosal nerves; (2) a significant lower maximal intracavernosal pressure. RT-PCR showed down-regulation of nNOS (large form), iNOS and ER-beta mRNA expression, Immunoblot showed down-regulation of nNOS protein expression and nNOS immunostaining showed less positive staining in the dorsal and intracavernous nerves in the diabetic group. These molecular changes may provide the basis for further studies to explore the association between diabetes and impotence.
Insights
Diabetes impairs erectile function by reducing nitric oxide synthase (NOS) and nerve fiber expression in rats. These findings suggest molecular mechanisms underlying diabetic-induced impotence.
Area of Science:
- Urology
- Endocrinology
- Molecular Biology
Background:
- Erectile dysfunction (ED) is a common complication in men with diabetes mellitus.
- The underlying molecular mechanisms connecting diabetes and ED remain largely unknown.
- This study investigates the impact of diabetes on penile erectile function and related molecular markers in an animal model.
Purpose of the Study:
- To investigate the effects of diabetes on penile erection.
- To examine the expression of nitric oxide synthase (NOS) and growth factors in the penis of diabetic rats.
- To elucidate the molecular basis of erectile dysfunction in diabetes.
Main Methods:
- Diabetes was induced in male rats using Streptozotocin (STZ).
- Erectile function was assessed via cavernous nerve electrostimulation.
- Penile tissues were analyzed for NOS and growth factor expression using NADPH diaphorase staining, immunostaining, RT-PCR, and Western blot.
Main Results:
- Diabetic rats exhibited significantly decreased maximal intracavernosal pressure and reduced NOS-containing nerve fibers.
- Down-regulation of nNOS (large form), iNOS, and ER-beta mRNA was observed in diabetic rats.
- Reduced nNOS protein expression and immunostaining confirmed decreased nNOS in penile nerves of diabetic rats.
Conclusions:
- Diabetes significantly impairs erectile function in rats.
- Molecular changes, including reduced NOS and altered growth factor expression, contribute to diabetic ED.
- These findings provide a basis for understanding the link between diabetes and impotence and for future research.