Lack of central nitric oxide triggers erectile dysfunction in diabetes

D-aspartic Acid Supplementation Effects on Body Composition: A Systematic Review of Randomized Clinical Trials on Trained Males

Context: D-Aspartic acid (DAA) is an amino acid found in the brain and reproductive system. Some investigations have reported beneficial effects of DAA on brain function and reproductive system health by increasing testosterone through the hypothalamic-pituitary-gonadal axis. However, its effect on body composition is unknown. Given testosterone's role in muscle growth, this study aimed to evaluate the effect of DAA supplementation on the body composition of trained males. Evidence Acquisition: PubMed, Scopus, Embase, and Web of Science (until 1 August 2021) were searched for this systematic review. Inclusion criteria assumed as clinical trials assessed the effect of DAA on body composition in trained males. After including articles by keywords, the articles were reviewed for meeting the eligibility criteria. Three independent researchers conducted the search and full-text review. Results: Among 134 articles located during the primary search, five articles (47 interventions and 43 controls) were included in the study based on eligibility criteria. All included clinical trials had a low risk of bias. A review of the relevant literature concludes that different doses of DAA (three grams, six grams, 7.12, and 12 grams) in different intervention periods (two weeks, four weeks, and 12 weeks) have no effects on body composition in trained males. Conclusions: DAA supplementation is a low-level booster of testosterone and has no significant effect on the testosterone level in professional male athletes, and cannot alter the body composition.

Effect of low-dose tadalafil once daily on glycemic control in patients with type 2 diabetes and erectile dysfunction: a randomized, double-blind, placebo-controlled pilot study

BACKGROUND

Phosphodiesterase type 5 inhibitors restore nitric oxide signaling, that plays a significant role in erectile function, and appears to counteract insulin resistance in animal and human models. This study was aimed to evaluate the glycemic and metabolic effects of low-dose tadalafil once daily in patients with type 2 diabetes and erectile dysfunction.

METHODS

A 6-month, randomized, double-blind, placebo-controlled pilot trial was conducted. Eligible patients were randomly assigned in a ratio of 2:1 to the tadalafil 5 mg and placebo groups; all patients received either tadalafil or placebo once a day. The primary efficacy endpoint was the absolute change in glycated hemoglobin (HbA1c) levels during the 6-month study period. The secondary efficacy endpoints included metabolic parameters and erectile function.

RESULTS

Of the 68 patients who completed this study, 45 and 23 patients were allocated to the tadalafil and placebo groups, respectively. The mean HbA1c level was significantly different between the groups over the 6-month study period (P = 0.021). After 6 months of treatment, the HbA1c decrement in the tadalafil group was greater than that in the placebo group (- 0.14 ± 0.53% vs. 0.20 ± 0.69%, P = 0.030). The International Index of Erectile Function-5 scores improvement was significantly greater in the tadalafil group than in the placebo group at 6 months (P = 0.003).

CONCLUSION

This prospective pilot study showed that low-dose tadalafil administered once a day was effective in improving glycemic control and erectile function in patients with type 2 diabetes and erectile dysfunction. Trial registration KCT0005666.

Erectile Function and Sexual Behavior: A Review of the Role of Nitric Oxide in the Central Nervous System

Nitric oxide (NO), the neuromodulator/neurotransmitter formed from l-arginine by neuronal, endothelial and inducible NO synthases, is involved in numerous functions across the body, from the control of arterial blood pressure to penile erection, and at central level from energy homeostasis regulation to memory, learning and sexual behavior. The aim of this work is to review earlier studies showing that NO plays a role in erectile function and sexual behavior in the hypothalamus and its paraventricular nucleus and the medial preoptic area, and integrate these findings with those of recent studies on this matter. This revisitation shows that NO influences erectile function and sexual behavior in males and females by acting not only in the paraventricular nucleus and medial preoptic area but also in extrahypothalamic brain areas, often with different mechanisms. Most importantly, since these areas are strictly interconnected with the paraventricular nucleus and medial preoptic area, send to and receive neural projections from the spinal cord, in which sexual communication between brain and genital apparatus takes place, this review reveals that central NO participates in concert with neurotransmitters/neuropeptides to a neural circuit controlling both the consummatory (penile erection, copulation, lordosis) and appetitive components (sexual motivation, arousal, reward) of sexual behavior.

Pathobiology of ischiocavernosus and bulbospongiosus muscles in long-term diabetic male rats and its implication on erectile dysfunction

OBJECTIVE

To analyze pathobiology of ischiocavernosus (IC) and bulbospongiosus (BS) muscles in long-term diabetic male rats and its implication on erectile dysfunction (ED).

METHODS

Male rats were grouped into control and diabetic rats (received single injection of 60 mg/kg bw. of streptozotocin [STZ]). At 120th day, the animals were subjected to various analyses like serum hormone, penile reflex, electromyography of IC and BS muscles, after euthanasia IC and BS muscles were processed for morphological, histology, histometric analysis, immunostaining and immunoblotting synaptophysin, nNOS and NADPH diaphorase histochemistry.

RESULTS

Significant reduction in serum hormone level, penile reflex, reduced action potential or activity in both these muscles and wide range of histological alterations were observed in STZ rats. Muscles showed significant reduction in the diameter, volume and numerical density of the fiber in both muscles of STZ rats. Synaptophysin, nNOS and NADPH diaphorase were significantly reduced in diabetic animal IC and BS.

CONCLUSION

Severe neuromuscular circuitry alteration in IC and BS. Study concludes that degenerative changes in IC and BS may play a major role in ED in diabetic condition. Indicating diabetic-induced postsynaptic neuronal degeneration along with impaired motor action of the muscle and severe muscle degeneration affecting ED.

Aqueous extract of Lespedeza cuneata improves male menopause by increase of nitric oxide and dihydrotestosterone

This study aimed to evaluate the effect of aqueous extract of Lespedeza cuneata (ALC) on men menopause induced erectile dysfunction (ED) and testosterone deficiency syndrome (TDS) in vitro and in vivo. Nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) have been fundamental factors of ED, and free testosterone such as dihydrotestosterone (DHT) has a crucial role in mitigation of TDS. ALC increased the production of NO in a dose-dependent manner in vitro and in vivo. The level of neuronal nitric oxide synthase and cGMP was increased in the ALC group. The level of DHT and 17-beta hydroxysteroid dehydrogenases (17β-HSD) was also increased in the ALC group. There was no significant change of hepatotoxicity, renal toxicity, lipid metabolism, and glucose. These results suggest that ALC enhanced NO, cGMP and free testosterone which could be developed as a health supplement for improving male menopause.

Neuroprotective effects of melatonin on erectile dysfunction in streptozotocin-induced diabetic rats

PURPOSE

To explore the neuroprotective effects and its possible mechanisms of melatonin (MT) on erectile dysfunction in streptozotocin-induced diabetic rats.

METHODS

Twenty-eight Sprague-Dawley rats received intraperitoneal injection of streptozotocin and 8 weeks later, the determined diabetic rats randomly got intraperitoneal injection of phosphate buffer solution (PBS) or MT. Another 12 normal rats received PBS treatment. Four weeks later, intracavernous pressure, mean arterial pressure, pathological changes in penis, and major pelvic ganglion (MPG) were measured. Malondialdehyde, superoxide dismutase, p38 and p-p38 levels in penis were detected.

RESULTS

Diabetic rats showed significant decreases of erectile function accompanied with serious neuropathy in dorsal penile nerve (DPN) and MPG, meanwhile collagen deposition, oxidative stress, and p-p38 levels in penis were elevated. Melatonin treatment partially but significantly improved the erectile function, ameliorated neuropathy in DPN and MPG, and decreased collagen deposition, oxidative stress, and p-p38 levels in diabetic rats.

CONCLUSIONS

Melatonin treatment helps improve erectile function and ameliorate neuropathy and fibrosis in diabetic rats. These may be associated with reductions in oxidative stress, p38MAPK signaling pathway, and neuropathy.

Effects of exercise on sexual function and central mechanism in the streptozotocin-induced diabetic rats

Diabetes mellitus is associated with the impairment of sexual function including desire and orgasmic dysfunction. Sexual dysfunction in the diabetes mellitus is due to a selective defect of the nitric oxide synthase (NOS) within paraventricular nucleus (PVN). c-Fos is an immediate early gene and c-Fos expression represents neuronal activity in response to various stimuli. In the present study, we investigated the effects of treadmill exercise on sexual behaviors and the expressions of NOS and c-Fos in the PVN were evaluated using streptozotocin (STZ)-induced diabetic rats. Diabetes mellitus was induced by intraperitoneal injection of STZ. The rats in the treadmill exercise groups were made to run on a treadmill for 30 min once a day during 4 weeks. Male sexual behaviors were evaluated by recording the number of mounting, intromission, and ejaculation frequency. The present results revealed that treadmill exercise ameliorated sexual dysfunction in the STZ-induced diabetic rats. Treadmill exercise restored the contents of NOS and c-Fos in the PVN. The improving effect of treadmill exercise on sexual function can be considered as the neuronal activating effect of exercise through increasing expressions of NO and c-Fos.

Yawning-Its anatomy, chemistry, role, and pathological considerations

Yawning is a clinical sign of the activity of various supra- and infratentorial brain regions including the putative brainstem motor pattern, hypothalamic paraventricular nucleus, probably the insula and limbic structures that are interconnected via a fiber network. This interaction can be seen in analogy to other cerebral functions arising from a network or zone such as language. Within this network, yawning fulfills its function in a stereotype, reflex-like manner; a phylogenetically old function, preserved across species barriers, with the purpose of arousal, communication, and maybe other functions including respiration. Abnormal yawning with ≥3 yawns/15min without obvious cause arises from lesions of brain areas involved in the yawning zone, its trajectories causing a disconnection syndrome, or from alteration of network activity by physical or metabolic etiologies including medication.

Post-translational regulation of neuronal nitric oxide synthase: implications for sympathoexcitatory states

INTRODUCTION

Nitric oxide (NO) synthesized via neuronal nitric oxide synthase (nNOS) plays a significant role in regulation/modulation of autonomic control of circulation. Various pathological states are associated with diminished nNOS expression and blunted autonomic effects of NO in the central nervous system (CNS) including heart failure, hypertension, diabetes mellitus, chronic renal failure etc. Therefore, elucidation of the molecular mechanism/s involved in dysregulation of nNOS is essential to understand the pathogenesis of increased sympathoexcitation in these diseased states. Areas covered: nNOS is a highly regulated enzyme, being regulated at transcriptional and posttranslational levels via protein-protein interactions and modifications viz. phosphorylation, ubiquitination, and sumoylation. The enzyme activity of nNOS also depends on the optimal concentration of substrate, cofactors and association with regulatory proteins. This review focuses on the posttranslational regulation of nNOS in the context of normal and diseased states within the CNS. Expert opinion: Gaining insight into the mechanism/s involved in the regulation of nNOS would provide novel strategies for manipulating nNOS directed therapeutic modalities in the future, including catalytically active dimer stabilization and protein-protein interactions with intracellular protein effectors. Ultimately, this is expected to provide tools to improve autonomic dysregulation in various diseases such as heart failure, hypertension, and diabetes.

Molecular mechanisms associated with diabetic endothelial-erectile dysfunction

Erectile dysfunction (ED) is a common complication of diabetes, affecting up to 75% of all diabetic men. Although the aetiology of diabetic ED is multifactorial, endothelial dysfunction is recognized as a mainstay in the pathophysiology of the disease. Endothelial dysfunction is induced by the detrimental actions of high glucose levels and increased oxidative stress on endothelial cells that make up the vascular lining. Besides directly injuring the endothelium, diabetes might also hamper vascular repair mechanisms of angiogenesis and vasculogenesis. These states exacerbate and maintain endothelial dysfunction, impairing vasorelaxation events and cavernosal blood perfusion, which are crucial for normal erectile function.

Basic Science Evidence for the Link Between Erectile Dysfunction and Cardiometabolic Dysfunction

INTRODUCTION

Although clinical evidence supports an association between cardiovascular/metabolic diseases (CVMD) and erectile dysfunction (ED), scientific evidence for this link is incompletely elucidated.

AIM

This study aims to provide scientific evidence for the link between CVMD and ED.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current literature on basic scientific support for a mechanistic link between ED and CVMD, and deficiencies in this regard with a critical assessment of current preclinical models of disease.

RESULTS

A link exists between ED and CVMD on several grounds: the endothelium (endothelium-derived nitric oxide and oxidative stress imbalance); smooth muscle (SM) (SM abundance and altered molecular regulation of SM contractility); autonomic innervation (autonomic neuropathy and decreased neuronal-derived nitric oxide); hormones (impaired testosterone release and actions); and metabolics (hyperlipidemia, advanced glycation end product formation).

CONCLUSION

Basic science evidence supports the link between ED and CVMD. The Committee also highlighted gaps in knowledge and provided recommendations for guiding further scientific study defining this risk relationship. This endeavor serves to develop novel strategic directions for therapeutic interventions.

Autonomic neuropathy in experimental models of diabetes mellitus

Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.

Centrally mediated erectile dysfunction in rats with type 1 diabetes: role of angiotensin II and superoxide

INTRODUCTION

Erectile dysfunction is a serious complication of diabetes mellitus. Apart from the peripheral actions, central mechanisms are also responsible for penile erection.

AIM

This study aims to determine the contribution of angiotensin (ANG) II in the dysfunction of central N-methyl-D-aspartic acid (NMDA)- and nitric oxide (NO)-induced erectile responses in streptozotocin-induced type 1 diabetic (T1D) rats.

METHODS

Three weeks after streptozotocin injections, rats were randomly treated with the angiotensin-converting enzyme inhibitor-enalapril, or the ANG II type 1 receptor blocker, losartan, or the superoxide dismutase mimetic, tempol, or vehicle via chronic intracerebroventricular infusion by osmotic mini-pump for 2 weeks.

MAIN OUTCOME MEASURE

Central NMDA receptor stimulation or the administration of the NO donor, sodium nitroprusside (SNP)-induced penile erectile responses and concurrent behavioral responses were monitored in conscious rats.

RESULTS

Two weeks of enalapril, losartan, or tempol treatment significantly improved the erectile responses to central microinjection of both NMDA and SNP in the paraventricular nucleus (PVN) of conscious T1D rats (NMDA responses-T1D+enalapril: 1.7 ± 0.6, T1D+losartan: 2.0 ± 0.3, T1D+tempol: 2.0 ± 0.6 vs. T1D+vehicle: 0.6 ± 0.3 penile erections/rat in the first 20 minutes, P < 0.05; SNP responses-T1D+enalapril: 0.9 ± 0.3, T1D+losartan: 1.3 ± 0.3, T1D+tempol: 1.4 ± 0.4 vs. T1D+vehicle: 0.4 ± 0.2 penile erections/rat in the first 20 minutes, P < 0.05). Concurrent behavioral responses including yawning and stretching, induced by central NMDA and SNP microinjections, were also significantly increased in T1D rats after enalapril, losartan, or tempol treatments. Neuronal NO synthase expression within the PVN was also significantly increased, and superoxide production was reduced in T1D rats after these treatments.

CONCLUSIONS

These data strongly support the contention that enhanced ANG II mechanism/s within the PVN of T1D rats contributes to the dysfunction of central NMDA-induced erectile responses in T1D rats via stimulation of superoxide.

Noncontact erection is enhanced by Ginkgo biloba treatment in rats: role of neuronal NOS in the paraventricular nucleus and sacral spinal cord

RATIONALE

Nitric oxide (NO) is an important messenger mediating erection in the central nervous system (CNS). Paraventricular nucleus (PVN) neurons can be activated by NO and project the signals to the sacral spinal cord, which is involved in regulation of erection. Ginkgo biloba extract (EGb 761) facilitates noncontact erection (NCE) in rats; however, it is not clear whether EGb 761 increased NCE is associated with NO.

OBJECTIVE

The present study was designed to investigate the effects of neuronal nitric oxide synthase (nNOS) on NCE in rats following EGb 761 treatment.

METHODS

Adult Long-Evans male rats were treated with 50 mg/kg of EGb 761 or distilled water for 14 days. The NCE test was performed after 14 days of EGb 761 treatment and the NCE frequency was recorded. Approximately 14 h following the NCE behavioral tests, animals were sacrificed, and nNOS activity in the PVN and S6-L1 spinal cord was measured by immunohistochemistry and western blotting, respectively.

RESULTS

Treatment with 50 mg/kg of EGb 761 for 14 days increased the NCE numbers compared to either the controls treated with distilled water on the same day or the same group on day 0. Also, EGb 761 treatment enhanced nNOS-immunoreactive cell numbers in the PVN. Furthermore, western blot analysis showed that EGb 761-treated animals displayed higher levels of nNOS expression in the S1 spinal cord than controls.

CONCLUSION

Our results suggest that enhanced NCE in male rats administrated with EGb 761 may be related to the central nNOS activity in the PVN and the spinal cord.

Exercise training improves the defective centrally mediated erectile responses in rats with type I diabetes

INTRODUCTION

Erectile dysfunction is a serious and common complication of diabetes mellitus. Apart from the peripheral actions, central mechanisms are also responsible for the penile erection.

AIM

The goal of the present study was to determine the impact of exercise training (ExT) on the centrally mediated erectile dysfunction in streptozotocin (STZ)-induced type I diabetic (T1D) rats.

METHODS

Male Sprague-Dawley rats were injected with STZ to induce diabetes mellitus. Three weeks after STZ or vehicle injections, rats were assigned to either ExT (treadmill running for 3-4 weeks) or sedentary groups to produce four experimental groups: control + sedentary, T1D + sedentary, control + ExT, and T1D + ExT.

MAIN OUTCOME MEASURE

After 3-4 weeks ExT, central N-methyl-D-aspartic acid (NMDA) or sodium nitroprusside (SNP)-induced penile erectile responses were measured. Neuronal nitric oxide synthase (nNOS) expression in the paraventricular nucleus (PVN) of the hypothalamus was measured by using histochemistry, real time polymerase chain reaction (PCR) and Western blot approaches.

RESULTS

In rats with T1D, ExT significantly improved the blunted erectile response, and the intracavernous pressure changes to NMDA (50 ng) microinjection within the PVN (T1D + ExT: 3.0 ± 0.6 penile erection/rat; T1D + sedentary: 0.5 ± 0.3 penile erection/rat within 20 minutes, P < 0.05). ExT improved erectile dysfunction induced by central administration of exogenous nitric oxide (NO) donor, SNP in T1D rats. Other behavior responses including yawning and stretching, induced by central NMDA and SNP microinjection were also significantly increased in T1D rats after ExT. Furthermore, we found that ExT restored the nNOS mRNA and protein expression in the PVN in T1D rats.

CONCLUSIONS

These results suggest that ExT may have beneficial effects on the erectile dysfunction in diabetes through improvement of NO bioavailability within the PVN. Thus, ExT may be used as therapeutic modality to up-regulate nNOS within the PVN and improve the central component of the erectile dysfunction in diabetes mellitus.

Chronic administration of sildenafil modified the impaired VEGF system and improved the erectile function in rats with diabetic erectile dysfunction

INTRODUCTION

Men frequently develop diabetic erectile dysfunction (DMED), as a result of endothelial dysfunction. DMED patients often have reduced efficacy with phosphodiesterase type 5 inhibitors therapy.

AIM

To determine whether chronic sildenafil administration can modify the impaired vascular endothelial growth factor (VEGF) system and improve the erectile function in rats with diabetic erectile dysfunction.

METHODS

A group of Sprague Dawley rats (n = 30) with DMED were induced by intraperitoneal injection of streptozotocin (40 mg/kg) and screened by subcutaneous injection of Apomorphine (100 mg/kg). They were then exposed to either vehicle or sildenafil (prescribed in our hospital, 5 mg/kg and 10 mg/kg, respectively) for 10 weeks. An additional nondiabetic and age-matched control group (n = 10) was also allocated and given the routine diet for the same period. Assessments were performed to both groups at 36 hours after the last dose of sildenafil. Penile intracavernous pressure (ICP), mean arterial pressure (MAP), penile tissue morphology, immunohistologic analysis, and Western blot analysis of VEGF, VEGFR1, and eNOS were determined.

MAIN OUTCOME MEASURE

Functional, morphological, and proteomical changes on penile structures by the chronic Sildenafil (5 mg/kg and 10 mg/kg, respectively) administration were determined.

RESULTS

A significant increase of ICP, ICP/MAP ratio, and area under the curve were observed in the both groups treated by sildenafil (5 mg/kg and 10 mg/kg, respectively), compared with the DMED rats without receiving Sildenafil. Immunohistochemical staining of their penile tissue showed a decrease in VEGF, VEGFR1, and eNOS staining in the controlled group compared with an improvement in the chronic sildenafil administration group. Western blot analysis demonstrated exactly the same results.

CONCLUSION

We demonstrated that daily sildenafil administration can restore the impaired VEGF system in the penis of DMED rats and progressively improve both erectile function and endothelial function, suggesting a potential general mechanism of improved signaling through the VEGF/eNOS signaling cascade.

Effect of Mucuna pruriens (Linn.) on sexual behavior and sperm parameters in streptozotocin-induced diabetic male rat

INTRODUCTION

Sexual dysfunction is one of the major secondary complications in the diabetic. Mucuna pruriens, a leguminous plant identified for its antidiabetic, aphrodisiac, and improving fertility properties, has been the choice of Indian traditional medicine.

AIM

Objective of the present study was to analyze the efficacy of M. pruriens on male sexual behavior and sperm parameters in long-term hyperglycemic male rats.

METHODS

Male albino rats were divided as group I control, group II diabetes induced (streptozotocin [STZ] 60 mg/kg of body weight (b.w.) in 0.1 M citrate buffer), group III diabetic rats administered with 200 mg/kg b.w. of ethanolic extract of M. pruriens seed, group IV diabetic rats administered with 5 mg/kg b.w. of sildenafil citrate (SC), group V administered with 200 mg/kg b.w. of extract, and group VI administered with 5 mg/kg b.w. of SC. M. pruriens and SC were administered in single oral dosage per day for a period of 60 days. The animals were subjected to mating behavior analyses, libido, test of potency, and epididymal sperms were analyzed.

MAIN OUTCOME MEASURE

The mating behavior, libido, test of potency, along with epididymal sperms were studied.

RESULTS

The study showed significant reduction in sexual behavior and sperm parameters in group II. Daily sperm production (DSP) and levels of follicular stimulating hormone, luteinizing hormone, and testosterone were significantly reduced in group II, whereas the animals with diabetes administered with seed extract of M. pruriens (group III) showed significant improvement in sexual behavior, libido and potency, sperm parameters, DSP, and hormonal levels when compared to group II.

CONCLUSION

The present work reveals the potential efficacy of ethanolic seed extract of M. pruriens to improve male sexual behavior with androgenic and antidiabetic effects in the STZ-induced diabetic male rats. This study supports the usage of M. pruriens in the Indian system of medicine as sexual invigorator in diabetic condition and encourages performing similar study in men.

Association of genetic variants of NOS1AP with type 2 diabetes in a Chinese population

AIMS/HYPOTHESIS

Chromosome 1q21-q24 has been shown to be linked to type 2 diabetes. The International Type 2 Diabetes 1q Consortium showed that one of the nominal associations was located in the NOS1AP gene. Although this association was not replicated in additional samples of European descent, it remains unknown whether NOS1AP plays a role in Chinese individuals.

METHODS

In stage 1 analyses, 79 single nucleotide polymorphisms (SNPs) of the NOS1AP gene were successfully genotyped in a group of Shanghai Chinese individuals, comprising 1,691 type 2 diabetes patients and 1,720 control participants. In stage 2 analyses, the SNP showing the strongest association was genotyped in additional Chinese individuals, including 1,663 type 2 diabetes patients and 1,408 control participants.

RESULTS

In stage 1 analyses, 20 SNPs were nominally associated with type 2 diabetes (p < 0.05), with SNP rs12742393 showing the strongest association (OR 1.24 [95% CI 1.11-1.38]; p = 0.0002, empirical p = 0.019). Haplotype analysis also confirmed the association between rs12742393 and type 2 diabetes. In stage 2 analyses, the difference in allele frequency distribution of rs12742393 did not reach statistical significance (p = 0.254). However, the meta-analysis showed a significant association between rs12742393 and type 2 diabetes with an OR of 1.17 (95% CI 1.07-1.26; p = 0.0005).

CONCLUSIONS/INTERPRETATION

Our data suggest that NOS1AP variants may not play a dominant role in susceptibility to type 2 diabetes, but a minor effect cannot be excluded.

Increased expression of the nitric oxide synthase gene and protein in corpus cavernosum by repeated dosing of udenafil in a rat model of chemical diabetogenesis

Erectile dysfunction (ED) is a major complication of diabetes mellitus (DM). This study investigates the relationship between ED and the downregulation of constitutive nitric oxide synthase (cNOS) in the corpus cavernosum (CC) of diabetic rats. It also examines the effects of udenafil, a phosphodiesterase type 5 (PDE5) inhibitor, on ED and cNOS expression levels. After 16 weeks of daily oral treatment with udenafil in diabetic rats, the intracavernous pressure/mean arterial pressure (ICP/MAP) ratio was recorded to measure erectile function, and cNOS expression was measured using reverse transcriptase (RT)-PCR and immunoblots. Although the ICP/MAP ratio and the expression levels of endothelial NOS (eNOS) and neuronal NOS (nNOS) in the CC were markedly decreased in diabetic rats, long-term udenafil treatment improved the erectile function and increased cNOS expression compared with diabetic controls. These findings suggest that ED in DM is closely related to decreased cNOS expression in the CC and that udenafil has the ability to compensate for this pathological change by modulating cNOS expression. Udenafil also has an inhibitory role in cGMP (cyclic guanosine monophosphate) degradation.

Heterogeneous distribution of basal cyclic guanosine monophosphate within distinct neuronal populations in the hypothalamic paraventricular nucleus

The supraoptic (SON) and the paraventricular (PVN) hypothalamic nuclei constitute major neuronal substrates underlying nitric oxide (NO) effects on autonomic and neuroendocrine control. Within these nuclei, constitutively produced NO restrains the firing activity of magnocellular neurosecretory and preautonomic neurons, actions thought to be mediated by a cGMP-dependent enhancement of GABAergic inhibitory transmission. In the present study, we expanded on this knowledge by performing a detailed anatomical characterization of constitutive NO-receptive, cGMP-producing neurons within the PVN. To this end, we combined tract-tracing techniques and immunohistochemistry to visualize cGMP immunoreactivity within functionally, neurochemically, and topographically discrete PVN neuronal populations in Wistar rats. Basal cGMP immunoreactivity was readily observed in the PVN, both in neuronal and vascular profiles. The incidence of cGMP immunoreactivity was significantly higher in magnocellular (69%) compared with preautonomic ( approximately 10%) neuronal populations (P < 0.01). No differences were observed between oxytocin (OT) and vasopressin (VP) magnocellular neurons. In preautonomic neurons, the incidence of cGMP was independent of their subnuclei distribution, innervated target (i.e., intermediolateral cell column, nucleus tractus solitarii, or rostral ventrolateral medulla) or their neurochemical phenotype (i.e., OT or VP). Finally, high levels of cGMP immunoreactivity were observed in GABAergic somata and terminals within the PVN of eGFP-GAD67 transgenic mice. Altogether, these data support a highly heterogeneous distribution of basal cGMP levels within the PVN and further support the notion that constitutive NO actions in the PVN involve intricate cell-cell interactions, as well as heterogeneous signaling modalities.

nNOS-dependent reactivity of cerebral arterioles in Type 1 diabetes

Our goals were to determine whether Type 1 diabetes (T1D) alters neuronal nitric oxide synthase (nNOS)-dependent reactivity of cerebral arterioles and to identify a potential role for oxidative stress in T1D-induced impairment in nNOS-dependent responses of cerebral arterioles. Rats were injected with vehicle (sodium citrate buffer) or streptozotocin (50 mg/kg IP) to induce T1D. Two to three months later, we measured functional responses of cerebral arterioles to nNOS-dependent (NMDA and kainate) and -independent (nitroglycerin) agonists in nondiabetic and diabetic rats before and during inhibition of oxidative stress using tempol (100 microM). In addition, we measured superoxide anion production under basal conditions, during stimulation with NMDA and kainate, and during treatment with tempol. We found that nNOS-dependent, but -independent, vasodilatation was impaired in diabetic compared to nondiabetic rats. In addition, treatment of the cerebral microcirculation with tempol restored impaired nNOS-dependent vasodilatation in diabetic rats toward that observed in nondiabetic rats. Furthermore, the production of superoxide anion (lucigenin chemiluminescence) was increased in parietal cortical tissue of diabetic rats under basal conditions. Application of NMDA and kainate did not increase superoxide anion production in nondiabetic or diabetic rats. However, tempol decreased basal production of superoxide anion in diabetic rats. Our findings suggest that T1D impairs nNOS-dependent dilatation of cerebral arterioles by a mechanism that appears to be related to the formation of superoxide anion.

Daily Administration of Phosphodiesterase Type 5 Inhibitors for Urological and Nonurological Indications

OBJECTIVES

Although the discovery of phosphodiesterases (PDEs) was made soon after the identification of cyclic adenosine monophosphate nearly half a century ago, their true importance in medicine has taken many decades to be realised. The recognition of the important role PDE enzymes play and the impact of altering intracellular cyclic nucleotide levels became significant for most urologists and clinicians in the early 1990s with the discovery of sildenafil, a PDE5 inhibitor (PDE5-I). Once approved around the world, on-demand use of PDE5-Is became the gold standard. Recently, the potential beneficial effects of PDE5-Is on the pulmonary, vascular, and other systems has led to examination of alternative dosing regimens. In this review, we have synthesised the available published peer-reviewed literature to provide a critical contemporary view of evolving indications for PDE5-Is and how alternative dosing regimens may impact on sexual and other functions.

METHODS

MEDLINE search of all peer-reviewed English literature for the period 1990-2007.

RESULTS

The plethora of articles detailing potential uses of PDE5-I in multiple fields of medicine was uncovered. Use of alternative dosing regimens shows great promise across a number of clinical indications, including post-radical retropubic prostatectomy, pulmonary hypertension, endothelial dysfunction, and salvage of on-demand PDE5-I nonresponders.

CONCLUSIONS

Use of PDE5-I on a daily basis may evolve into a major form of drug administration both for men with erectile dysfunction and for those with a myriad of other conditions shown to benefit from this approach.