Phosphodiesterase Type 5 Inhibitors in Men With Erectile Dysfunction and the Risk of Alzheimer Disease: A Cohort Study

Uncovering New Therapeutic Targets for Amyotrophic Lateral Sclerosis and Neurological Diseases Using Real-World Data

Although attractive for relevance to real-world scenarios, real-world data (RWD) is typically used for drug repurposing and not therapeutic target discovery. Repurposing studies have identified few effective options in neurological diseases such as the rare disease, amyotrophic lateral sclerosis (ALS), which has no disease-modifying treatments available. We previously reclassified drugs by their simulated effects on proteins downstream of drug targets and observed class-level effects in the EHR, implicating the downstream protein as the source of the effect. Here, we developed a novel ALS-focused network medicine model using data from patient samples, the public domain, and consortia. With this model, we simulated drug effects on ALS and measured class effects on overall survival in retrospective EHR studies. We observed an increased but non-significant risk of death for patients taking drugs with complement system proteins downstream of their targets and experimentally validated drug effects on complement activation. We repeated this for six protein classes, three of which, including multiple chemokine receptors, were associated with a significantly increased risk for death, suggesting that targeting proteins such as CXCR5, CXCR3, chemokine signaling generally, or neuropeptide Y (NPY) could be advantageous therapeutic targets for these patients. We expanded our analysis to the neuroinflammatory condition, myasthenia gravis, and neurodegenerative disease, Parkinson's, and recovered similar effect sizes. We demonstrated the utility of network medicine for testing novel therapeutic effects using RWD and believe this approach may accelerate target discovery in neurological diseases, addressing the critical need for new therapeutic options.

Sildenafil and risk of Alzheimer disease: a systematic review and meta-analysis

BACKGROUND

Alzheimer Disease (AD) affects more than 50 million people worldwide, with 10 million new diagnosis each year. The link between Sildenafil, a Phosphodiesterase-5 (PDE5) inhibitor, and risk of AD has been debated. We conducted the first meta-analysis on the association between Sildenafil use and risk of AD.

METHODS

We searched MEDLINE and Embase from inception to March 11, 2024 to identify cohort, case-control studies comparing the frequency of AD in patients taking Sildenafil with those without. We computed risk ratios (RR) and hazard ratios (HR) with accompanying 95% Confidence Intervals (CIs) for each study, and pooled the results using a random-effects meta-analysis.

RESULTS

Out of 415 studies that were screened initially, 5 studies comprising 885,380 patients were included for analysis. Sildenafil use was associated with a reduced risk of developing AD by two-fold compared to non-use (HR: 0.47, 95% CI: 0.27-0.82, p<0.001). There was a similar association in risk reduction of AD in patients on PDE5 inhibitors compared to non-use (RR: 0.55, 95% CI: 0.38-0.80, p=0.002).

CONCLUSIONS

Our meta-analysis showed that the use of Sildenafil is associated with a reduced risk of developing AD by two-fold. Further randomized control trials to ascertain the effect of Sildenafil on AD pathology would be useful.

Benefits of Tadalafil and Sildenafil on Mortality, Cardiovascular Disease, and Dementia

BACKGROUND

Erectile dysfunction and lower urinary tract symptoms, from benign prostatic hyperplasia and bladder neck obstructions, are prevalent in men and associated with an increased risk of cardiovascular diseases. Phosphodiesterase-5 (PDE-5) inhibitors, such as tadalafil and sildenafil, are used to treat erectile dysfunction and may also offer cardiovascular benefits due to their vasodilatory effects. This study evaluates the impact of these PDE-5 inhibitors on all-cause mortality, cardiovascular disease, and dementia in middle-aged men with erectile dysfunction and lower urinary tract symptoms over a 3 year follow-up period.

METHODS

This longitudinal study analyzed data from 50 million US men using the TriNetX database. Men at least 40 years of age prescribed tadalafil or sildenafil after an erectile dysfunction diagnosis, or tadalafil after lower urinary tract symptom diagnoses, from 2004 to 2021 were included. Three-year outcomes assessed included all-cause mortality, cardiovascular disease, and dementia, comparing men on PDE-5 inhibitors to those not on these medications. Propensity matching was performed for demographics and eight pre-existing conditions.

RESULTS

The final cohort included 509,788 men with erectile dysfunction and 1,075,908 with lower urinary tract symptoms. Tadalafil and sildenafil were associated with significantly reduced risks of all-cause mortality (RR 0.66/0.76), myocardial infarction (0.73/0.83), stroke (0.66/0.78), venous thromboembolism (0.79/0.80), and dementia (0.68/0.75) in erectile dysfunction patients, with tadalafil showing more significant benefits. In lower urinary tract symptom patients, tadalafil was similarly associated with reduced mortality, cardiovascular disease, and dementia.

CONCLUSIONS

In conclusion, tadalafil and sildenafil use in erectile dysfunction patients reduced mortality, cardiovascular disease, and dementia risks, with tadalafil providing more benefits. Tadalafil also conferred similar benefits to patients with lower urinary tract symptoms.

Effect of long and short half-life PDE5 inhibitors on HbA1c levels: a systematic review and meta-analysis

Background

Phosphodiesterase 5 (PDE5) inhibitors, owing to their mechanism of action, have been gaining recognition as a potential case of drug repurposing and combination therapy for diabetes treatment. We aimed to examine the effect of long and short half-life PDE5 inhibitors have on Haemoglobin A1c (HbA1c) levels.

Methods

A systematic review and meta-analysis was conducted of randomised controlled trials (RCTs) in people with elevated HbA1c (>6%) to assess mean difference in HbA1c levels from baseline versus controls after any PDE5 inhibitor intervention of ≥4 weeks, excluding multiple interventions. Cochrane CENTRAL, PMC Medline, ClinicalTrials.gov, and WHO ICTRP were searched without language restrictions up to September 30, 2024. Summary data from published data were extracted. PRISMA and Cochrane guidelines used to extract and assess data using a random-effects meta-analysis. This study is registered with the Research Registry, reviewregistry1733.

Findings

Among 1096 studies identified, in analysis of 13 studies with 1083 baseline patients, long half-life PDE5 inhibitors (tadalafil, PF-00489791) had decreases in HbA1c while short half-life PDE5 inhibitors (sildenafil, avanafil) had no change. Five (38.5%) studies had a low risk of bias, and eight (61.5%) had some concerns. Long half-life inhibitors had significant mean decrease of -0.40% ([-0.66, -0.14], p = 0.002, I2 = 82%, 7.70% baseline HbA1c). Short half-life inhibitors had insignificant mean difference of +0.08% ([-0.16, 0.33], p = 0.51, I2 = 40%, 7.73% baseline HbA1c). In ≥8-week trials with participants with type 2 diabetes (T2D) and mean HbA1c ≥ 6.5%, long half-life inhibitors had significant mean decrease of -0.50% ([-0.83, -0.17], I2 = 88%, p = 0.003); short half-life inhibitors had significant mean increase of +0.36% ([0.03, 0.68], I2 = 3%, p = 0.03).

Interpretation

At the well-controlled HbA1c of the participants, previous literature shows current diabetes treatments have similar HbA1c decreases, so the HbA1c mean difference of long half-life PDE5 inhibitors may indeed be clinically relevant. This suggests future investigation into PDE5 inhibitors as part of combination therapy or as therapy for high HbA1c individuals is needed, especially because of variable risk of biases, homogeneity, and sample sizes in our study.

Funding

None.

E3 ubiquitin ligase CHIP facilitates cAMP and cGMP signalling cross-talk by polyubiquitinating PDE9A

The carboxyl terminus of Hsc70-interacting protein (CHIP) is pivotal for managing misfolded and aggregated proteins via chaperone networks and degradation pathways. In a preclinical rodent model of CHIP-related ataxia, we observed that CHIP mutations lead to increased levels of phosphodiesterase 9A (PDE9A), whose role in this context remains poorly understood. Here, we investigated the molecular mechanisms underlying the role of PDE9A in CHIP-related ataxia and demonstrated that CHIP binds to PDE9A, facilitating its polyubiquitination and autophagic degradation. Conversely, dysfunctional CHIP disrupts this process, resulting in PDE9A accumulation, increased cGMP hydrolysis, and impaired PKG phosphorylation of CHIP at serine 19. This cascade further amplifies PDE9A accumulation, ultimately disrupting mitophagy and triggering neuronal apoptosis. Elevated PKA levels inhibit PDE9A degradation, further exacerbating this neuronal dysfunction. Notably, pharmacological inhibition of PDE9A via Bay 73-6691 or virus-mediated CHIP expression restored the balance of cGMP/cAMP signalling. These interventions protect against cerebellar neuropathologies, particularly Purkinje neuron mitophagy dysfunction. Thus, PDE9A upregulation considerably exacerbates ataxia associated with CHIP mutations, and targeting the interaction between PDE9A and CHIP is an innovative therapeutic strategy for CHIP-related ataxia.

Phosphodiesterase inhibition restores hypoxia-induced cerebrovascular dysfunction subsequent to improved systemic redox homeostasis: A randomized, double-blind, placebo-controlled crossover study

To what extent sildenafil, a selective inhibitor of the type-5 phosphodiesterase modulates systemic redox status and cerebrovascular function during acute exposure to hypoxia remains unknown. To address this, 12 healthy males (aged 24 ± 3 y) participated in a randomized, placebo-controlled crossover study involving exposure to both normoxia and acute (60 min) hypoxia (FiO 2  = 0.14), followed by oral administration of 50 mg sildenafil and placebo (double-blinded). Venous blood was sampled for the ascorbate radical (A•-: electron paramagnetic resonance spectroscopy) and nitric oxide metabolites (NO: ozone-based chemiluminescence). Transcranial Doppler ultrasound was employed to determine middle cerebral artery velocity (MCAv), cerebral delivery of oxygen (CDO 2 ), dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity to hypo/hypercapnia (CVRCO2HYPO/HYPER). Cortical oxyhemoglobin (cO2Hb) and oxygenation index (OI) were assessed using pulsed continuous wave near infra-red spectroscopy. Hypoxia decreased total plasma NO (P = 0.008), CDO 2 (P = <0.001) and cO2Hb (P = 0.005). In hypoxia, sildenafil selectively reduced A•- (P = 0.018) and MCAV (P = 0.018), and increased dCA metrics of low-frequency phase (P = 0.029) and CVRCO2HYPER (P = 0.007) compared to hypoxia-placebo. Collectively, these findings provide evidence for a PDE-5 inhibitory pathway that enhances select aspects of cerebrovascular function in hypoxia subsequent to a systemic improvement in redox homeostasis and independent of altered vascular NO bioavailability.

Hallmarks of aging: middle-aging hypovascularity, tissue perfusion and nitric oxide perspective on healthspan

Aging is a complex process marked by various changes at both cellular and systemic levels, impacting the functioning and lifespan of organisms. Over time, researchers have pinpointed several significant hallmarks of aging that lead to the gradual deterioration of tissue function, regulation, and homeostasis associated with aging in humans. Despite this, the intricate interactions and cumulative effects of these hallmarks are still mostly uncharted territory. Understanding this complex web is a major challenge in Geroscience, yet it is crucial for developing effective strategies that promote healthy aging, reduce medical costs, and ensure the sustainability of health systems. Gaining insights in this area is essential for creating interventions that can slow the aging process, enhance healthspan, and decrease the likelihood of age-related diseases. The integration of knowledge from various fields concerning the middle-aging nitric oxide (NO)-mediated hypovascularity hypoxia hemodynamic hypothesis points to a systems-based approach to the biological hallmarks of aging. Key evidence suggests a systemic connection between the endocrine system (specifically sex hormones), endogenous NO deficiency, and the vascular system, which serves as a network of microvascular structures crucial for tissue perfusion functions at cellular level. These processes also involve oxidative stress and inflammation triggered by hypoxia.

Association between prescription drugs and all-cause mortality risk in the UK population

Although most drugs currently approved are meant to treat specific diseases or symptoms, it has been hypothesized that some might bear a beneficial effect on lifespan in healthy older individuals, outside of their specific disease indication. Such drugs include, among others, metformin, SGLT2 inhibitors and rapamycin. Since 2006, the UK biobank has recorded prescription medication and mortality data for over 500'000 participants, aged between 40 and 70 years old. In this work, we examined the impact of the top 406 prescribed medications on overall mortality rates within the general population of the UK. As expected, most drugs were linked to a shorter lifespan, likely due to the life-limiting nature of the diseases they are prescribed to treat. Importantly, a few drugs were associated with increased lifespans, including notably Sildenafil, Atorvastatin, Naproxen and Estradiol. These retrospective results warrant further investigation in randomized controlled trials.

Phosphodiesterase-5 inhibitors use and the risk of alzheimer's disease: a systematic review and meta-analysis

BACKGROUND

The management of Alzheimer's disease (AD) poses considerable challenges, necessitating the pursuit of innovative therapeutic approaches. Recent research has spotlighted the promising role of phosphodiesterase type 5 inhibitors (PDE5Is) in reducing the prevalence of AD, utilizing their vasodilatory properties to suggest a potential neuroprotective effect. This meta-analysis and systematic review aims to assess the relationship between the use of PDE5Is and the risk of AD.

METHODS

A detailed examination was carried out across several electronic databases till March 2024, including PubMed, Web of Science, Scopus, CENTRAL, and Embase. The focus was on identifying studies that compare the occurrence of AD among PDE5I users vs non-users. Through a random-effects model, pooled hazard ratios (HRs) were calculated, in alignment with guidelines from the Cochrane Handbook for Systematic Reviews and Meta-Analysis and the PRISMA standards.

RESULTS

This analysis included six studies, cumulating a participant count of 8,337,313, involving individuals treated with sildenafil, tadalafil, and vardenafil, against a control group undergoing other or no treatments. The cumulative HR for AD risk among PDE5I users versus the control group was 0.53 (95% CI: 0.32-0.86, p = 0.008), signaling a markedly reduced likelihood of AD development in the PDE5I group. Particularly, sildenafil usage showed a significant risk reduction (HR: 0.46, 95% CI: 0.31-0.70, p < 0.001), while findings for tadalafil and vardenafil were not significant. Test of subgroup differences found no difference between male and female participants in the risk of AD.

CONCLUSIONS

Our findings suggest that the use of PDE5Is is associated with a reduced risk of AD, highlighting its potential as a protective agent against neurodegenerative diseases. Given the very low quality of evidence and the heterogeneity among the included studies, further high-quality research is warranted to confirm these findings and elucidate the underlying mechanisms. Register number PROSPERO 2024: CRD42024522197.

Recent Advances in Therapeutics for the Treatment of Alzheimer's Disease

The most prevalent chronic neurodegenerative illness in the world is Alzheimer's disease (AD). It results in mental symptoms including behavioral abnormalities and cognitive impairment, which have a substantial financial and psychological impact on the relatives of the patients. The review discusses various pathophysiological mechanisms contributing to AD, including amyloid beta, tau protein, inflammation, and other factors, while emphasizing the need for effective disease-modifying therapeutics that alter disease progression rather than merely alleviating symptoms. This review mainly covers medications that are now being studied in clinical trials or recently approved by the FDA that fall under the disease-modifying treatment (DMT) category, which alters the progression of the disease by targeting underlying biological mechanisms rather than merely alleviating symptoms. DMTs focus on improving patient outcomes by slowing cognitive decline, enhancing neuroprotection, and supporting neurogenesis. Additionally, the review covers amyloid-targeting therapies, tau-targeting therapies, neuroprotective therapies, and others. This evaluation specifically looked at studies on FDA-approved novel DMTs in Phase II or III development that were carried out between 2021 and 2024. A thorough review of the US government database identified clinical trials of biologics and small molecule drugs for 14 agents in Phase I, 34 in Phase II, and 11 in Phase III that might be completed by 2028.

Insulin Resistance, a Risk Factor for Alzheimer's Disease: Pathological Mechanisms and a New Proposal for a Preventive Therapeutic Approach

Peripheral insulin resistance (IR) is a well-documented, independent risk factor for the development of type 2 diabetes, cardiovascular disease, cancer and cellular senescence. Recently, the brain has also been identified as an insulin-responsive region, where insulin acts as regulator of the brain metabolism. Despite the clear link between IR and the brain, the exact mechanisms underlying this relationship remain unclear. Therapeutic intervention in patients showing symptoms of neurodegenerative diseases has produced little or no results. It has been demonstrated that insulin resistance plays a significant role in the pathogenesis of neurodegenerative diseases, particularly cognitive decline. Peripheral and brain IR may represent a modifiable state that could be used to prevent major brain disorders. In this review, we will analyse the scientific literature supporting IR as a risk factor for Alzheimer's disease and suggest some therapeutic strategies to provide a new proposal for the prevention of brain IR and its consequences.

Phosphodiesterase-5 Inhibitors and Dementia Risk: Confounding by Indication in Real-World Studies

Pharmacoepidemiologic studies using routinely collected data allow researchers to propose drugs for repurposing trials for dementia prevention or treatment. A recent cohort study reported a 54% lower dementia risk among users of sildenafil compared to users of certain cardiovascular medications. We caution that "confounding by indication" can arise when outcomes are compared between a drug of interest and an inappropriate comparator. Here, we emphasize important considerations in selecting an active comparator. We assess the implications of substantial risk of confounding by indication in pharmacoepidemiologic studies linking phosphodiesterase-5 inhibitors to lower dementia risk.