Parallel findings in age-related macular degeneration and Alzheimer’s disease

Associations between vision impairment and eye diseases with dementia, dementia subtypes and cognitive impairment: An umbrella review

Vision impairment (VI) and eye diseases such as age-related macular degeneration (AMD), diabetic retinopathy (DR), glaucoma and cataract have been reported to be associated with cognitive impairment and dementia, however, to date, very little attempt has been made to collate and synthesizes such literature. Therefore, the aim of this umbrella review is to systematically assesses the credibility and certainty of evidence of associations between vision impairment (VI) and eye diseases with cognitive impairment, dementia and dementia subtypes. We conducted an umbrella review of meta-analyses by screening articles in any language in PubMed, MEDLINE (Ovid), EMBASE, Web of Science, Cochrane CENTRAL and CDSR published from database inception up to May 30, 2024. Quality appraisal of each included original meta-analysis was assessed using A Measurement Tool for Assessing Systematic Reviews 2 (AMSTAR2). The certainty of the evidence was based on statistical significance, study size, heterogeneity, small study effects, prediction intervals (PI), and bias. We followed an a-priori protocol registered with PROSPERO (CRD42024564249). We identified 13 meta-analyses (AMSTAR 2; high accuracy of the findings 1, moderate 10, and low 2) that included 232 original articles based on 99,337,354 participants. Overall, no evidence was highly suggestive or convincing. Suggestive evidence was found for associations between cataract and dementia (equivalent odds ratio [eOR] 1.20, 95 %CI, 1.16-1.25), cataract and Alzheimer's disease (eOR 1.21, 95 %CI, 1.15-1.28), and AMD and Alzheimer's disease (eOR 1.27, 95 %CI, 1.27-1.27). Weak evidence was found for associations between VI and dementia (eOR 1.50, 95 %CI, 1.23-1.84), DR and dementia (eOR 1.33, 95 %CI, 1.17-1.50), cataract and vascular dementia (eOR 1.26, 95 %CI, 1.09-1.45), VI identified by cross-sectional studies and cognitive impairment (eOR 2.37, 95 %CI, 2.31-2.44), and VI identified by objective measures and cognitive impairment (eOR 1.56, 95 %CI, 1.12-2.18). The observed suggestive level of evidence for the relationship between eye disease and dementia (as well as dementia subtypes) suggests that policy and interventions to aid in the prevention and management of eye disease may also aid in the prevention of dementia syndrome. Where the level of evidence is weak, further studies are needed with stronger methodological approaches.

Prostanoid signaling in retinal vascular diseases

The vasculature of the retina is exposed to systemic and local factors that have the capacity to induce several retinal vascular diseases, each of which may lead to vision loss. Prostaglandin signaling has arisen as a potential therapeutic target for several of these diseases due to the diverse manners in which these lipid mediators may affect retinal blood vessel function. Previous reports and clinical practices have investigated cyclooxygenase (COX) inhibition by nonsteroidal anti-inflammatory drugs (NSAIDs) to address retinal diseases with varying degrees of success; however, targeting individual prostanoids or their distinct receptors affords more signaling specificity and poses strong potential for therapeutic development. This review offers a comprehensive view of prostanoid signaling involved in five key retinal vascular diseases: retinopathy of prematurity, diabetic retinopathy, age-related macular degeneration, retinal occlusive diseases, and uveitis. Mechanistic and clinical studies of these lipid mediators provide an outlook for therapeutic development with the potential to reduce vision loss in each of these conditions.

Inflammasome activation aggravates choroidal neovascularization

Inflammasome activation is implicated in diseases of aberrant angiogenesis such as age-related macular degeneration (AMD), though its precise role in choroidal neovascularization (CNV), a characteristic pathology of advanced AMD, is ill-defined. Reports on inhibition of inflammasome constituents on CNV are variable and the precise role of inflammasome in mediating pathological angiogenesis is unclear. Historically, subretinal injection of inflammasome agonists alone has been used to investigate retinal pigmented epithelium (RPE) degeneration, while the laser photocoagulation model has been used to study pathological angiogenesis in a model of CNV. Here, we report that the simultaneous introduction of any of several disease-relevant inflammasome agonists (Alu or B2 RNA, Alu cDNA, or oligomerized amyloid β (1-40)) exacerbates laser-induced CNV. These activities were diminished or abrogated by genetic or pharmacological targeting of inflammasome signaling constituents including P2rx7, Nlrp3, caspase-1, caspase-11, and Myd88, as well as in myeloid-specific caspase-1 knockout mice. Alu RNA treatment induced inflammasome activation in macrophages within the CNV lesion, and increased accumulation of macrophages in an inflammasome-dependent manner. Finally, IL-1β neutralization prevented inflammasome agonist-induced chemotaxis, macrophage trafficking, and angiogenesis. Collectively, these observations support a model wherein inflammasome stimulation promotes and exacerbates CNV and may be a therapeutic target for diseases of angiogenesis such as neovascular AMD.

Hallmarks of aging in age-related macular degeneration and age-related neurological disorders: novel insights into common mechanisms and clinical relevance

Age-related macular degeneration (AMD) and age-related neurological diseases (ANDs), such as Alzheimer's and Parkinson's Diseases, are increasingly prevalent conditions that significantly contribute to global morbidity, disability, and mortality. The retina, as an accessible part of the central nervous system (CNS), provides a unique window to study brain aging and neurodegeneration. By examining the associations between AMD and ANDs, this review aims to highlight novel insights into fundamental mechanisms of aging and their role in neurodegenerative disease progression. This review integrates knowledge from the emerging field of aging research, which identifies common denominators of biological aging, specifically loss of proteostasis, impaired macroautophagy, mitochondrial dysfunction, and inflammation. Finally, we emphasize the clinical relevance of these pathways and the potential for cross-disease therapies that target common aging hallmarks. Identifying these shared pathways could open avenues to develop therapeutic strategies targeting mechanisms common to multiple degenerative diseases, potentially attenuating disease progression and promoting the healthspan.

Genetics in neovascular age-related macular degeneration susceptibility and treatment response to anti-VEGF intravitreal injection: A case series study

BACKGROUND

To identify genotypes associated with neovascular age-related macular degeneration (nAMD) and investigate the associations between genotype variations and anti-vascular endothelial growth factor (VEGF) treatment response.

METHODS

This observational, retrospective, case series study enrolled patients diagnosed with nAMD who received anti-VEGF treatment in National Taiwan University Hospital with at least one-year follow-up between 2012 and 2020. A genome-wide association study (GWAS) was conducted on enrolled patients and controls. Correlations between the genotypes identified from GWAS and the treatment response of functional/anatomical biomarkers, including visual acuity (VA), presence of intraretinal or subretinal fluid (SRF), serous or fibrovascular pigmented epithelium detachment (PED), and disruption of the ellipsoid zone (EZ), were analysed.

RESULTS

In total, 182 patients with nAMD and 1748 controls were enrolled. GWAS revealed 16 single nucleotide polymorphisms (SNPs) as risk loci for nAMD, including seven loci in CFH and ARMS2/HTRA1 and nine novel loci, including rs117517872 and rs79835234(COPB2-DT), rs7525578(RAP1A), rs2123738(LOC105376755), rs1374879(CNTN3), rs3812692(SAR1A), rs117501587(PRKCA), rs9965945(CNDP1), and rs189769231(MATK). Our study revealed rs800292(CFH), rs11200638(HTRA1), and rs2123738(LOC105376755) correlated with poor treatment response in VA (P = 0.005), SRF (P = 0.044), and fibrovascular PED (P = 0.007), respectively. Rs9965945(CNDP1) was correlated with poor response in disruption of EZ (P = 0.046) and serous PED (P = 0.049).

CONCLUSIONS

Among the 16 SNPs found in the GWAS, four loci-CFH, ARMS2/HTRA1, and two novel loci-were correlated with the susceptibility of nAMD and anatomical/functional responses after anti-VEGF treatment.

Genetic and Epigenetic Biomarkers Linking Alzheimer's Disease and Age-Related Macular Degeneration

Alzheimer's disease (AD) represents a prominent neurodegenerative disorder (NDD), accounting for the majority of dementia cases worldwide. In addition to memory deficits, individuals with AD also experience alterations in the visual system. As the retina is an extension of the central nervous system (CNS), the loss in retinal ganglion cells manifests clinically as decreased visual acuity, narrowed visual field, and reduced contrast sensitivity. Among the extensively studied retinal disorders, age-related macular degeneration (AMD) shares numerous aging processes and risk factors with NDDs such as cognitive impairment that occurs in AD. Histopathological investigations have revealed similarities in pathological deposits found in the retina and brain of patients with AD and AMD. Cellular aging processes demonstrate similar associations with organelles and signaling pathways in retinal and brain tissues. Despite these similarities, there are distinct genetic backgrounds underlying these diseases. This review comprehensively explores the genetic similarities and differences between AMD and AD. The purpose of this review is to discuss the parallels and differences between AMD and AD in terms of pathophysiology, genetics, and epigenetics.

Amyloid-beta and tau protein beyond Alzheimer's disease

ABSTRACT

The aggregation of amyloid-beta peptide and tau protein dysregulation are implicated to play key roles in Alzheimer's disease pathogenesis and are considered the main pathological hallmarks of this devastating disease. Physiologically, these two proteins are produced and expressed within the normal human body. However, under pathological conditions, abnormal expression, post-translational modifications, conformational changes, and truncation can make these proteins prone to aggregation, triggering specific disease-related cascades. Recent studies have indicated associations between aberrant behavior of amyloid-beta and tau proteins and various neurological diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as retinal neurodegenerative diseases like Glaucoma and age-related macular degeneration. Additionally, these proteins have been linked to cardiovascular disease, cancer, traumatic brain injury, and diabetes, which are all leading causes of morbidity and mortality. In this comprehensive review, we provide an overview of the connections between amyloid-beta and tau proteins and a spectrum of disorders.

Age-related macular degeneration and neurodegenerative disorders: Shared pathways in complex interactions

Age-related macular degeneration (AMD) is a leading cause of irreversible blindness in the elderly, and neurodegenerative disorders such as Alzheimer disease and Parkinson disease are debilitating conditions that affect millions worldwide. Despite the different clinical manifestations of these diseases, growing evidence suggests that they share common pathways in their pathogenesis including inflammation, oxidative stress, and impaired autophagy. In this review, we explore the complex interactions between AMD and neurodegenerative disorders, focusing on their shared mechanisms and potential therapeutic targets. We also discuss the current opportunities and challenges for developing effective treatments that can target these pathways to prevent or slow down disease progression in AMD. Some of the promising strategies that we explore include modulating the immune response, reducing oxidative stress, enhancing autophagy and lysosomal function, and targeting specific protein aggregates or pathways. Ultimately, a better understanding of the shared pathways between AMD and neurodegenerative disorders may pave the way for novel and more efficacious treatments.

PEDF-derived peptide protects against Amyloid-β toxicity in vitro and prevents retinal dysfunction in rats

Amyloid-beta (Aβ), a family of aggregation-prone and neurotoxic peptides, has been implicated in the pathophysiology of age-related macular degeneration (AMD). We have previously shown that oligomeric and fibrillar species of Aβ42 exerted retinal toxicity in rats, but while the consequences of exposure to amyloid were related to intracellular effects, the mechanism of Aβ42 internalization in the retina is not well characterized. In the brain, the 67 kDa laminin receptor (67LR) participates in Aβ-related neuronal cell death. A short peptide derived from pigment epithelium-derived factor (PEDF), formerly designated PEDF-335, was found to mitigate experimental models of ischemic retinopathy via targeting of 67LR. In the present study, we hypothesized that 67LR mediates the uptake of pathogenic Aβ42 assemblies in the retina, and that targeting of this receptor by PEDF-335 may limit the internalization of Aβ, thereby ameliorating its retinotoxicity. To test this assumption ARPE-19 cells in culture were incubated with PEDF-335 before treatment with fibrillar or oligomeric structures of Aβ42. Immunostaining confirmed that PEDF-335 treatment substantially prevented amyloid internalization into ARPE-19 cells and maintained their viability in the presence of toxic oligomeric and fibrillar Aβ42 entities in vitro. FRET competition assay was performed and confirmed the binding of PEDF-335 to 67LR in RPE-like cells. Wild-type rats were treated with intravitreal PEDF-335 in the experimental eye 2 days prior to administration of retinotoxic Aβ42 oligomers or fibrils to both eyes. Retinal function was assessed by electroretinography through 6 weeks post injection. The ERG responses in rats treated with oligomeric or fibrillar Aβ42 assemblies were near-normal in eyes previously treated with intravitreal PEDF-335, whereas those measured in the control eyes treated with injection of the Aβ42 assemblies alone showed pathologic attenuation of the retinal function through 6 weeks. The retinal presence of 67LR was determined ex vivo by immunostaining and western blotting. Retinal staining demonstrated the constitutional expression of 67LR mainly in the retinal nuclear layers. In the presence of Aβ42, the levels of 67LR were increased, although its retinal distribution remained largely unaltered. In contrast, no apparent differences in the retinal expression level of 67LR were noted following exposure to PEDF-335 alone, and its pattern of localization in the retina remained similarly concentrated primarily in the inner and outer nuclear layers. In summary, we found that PEDF-335 confers protection against Aβ42-mediated retinal toxicity, with significant effects noted in cells as well as in vivo in rats. The effects of PEDF-335 in the retina are potentially mediated via binding to 67LR and by at least partial inhibition of Aβ42 internalization. These results suggest that PEDF-335 may merit further consideration in the development of targeted inhibition of amyloid-related toxicity in the retina. More broadly, our observations provide evidence on the importance of extracellular versus intracellular Aβ42 in the retina and suggest concepts on the molecular mechanism of Aβ retinal pathogenicity.

Shared genetic aetiology of Alzheimer's disease and age-related macular degeneration by APOC1 and APOE genes

Background

Alzheimer's disease (AD) and age-related macular degeneration (AMD) share similar pathological features, suggesting common genetic aetiologies between the two. Investigating gene associations between AD and AMD may provide useful insights into the underlying pathogenesis and inform integrated prevention and treatment for both diseases.

Methods

A stratified quantile-quantile (QQ) plot was constructed to detect the pleiotropy among AD and AMD based on genome-wide association studies data from 17 008 patients with AD and 30 178 patients with AMD. A Bayesian conditional false discovery rate-based (cFDR) method was used to identify pleiotropic genes. UK Biobank was used to verify the pleiotropy analysis. Biological network and enrichment analysis were conducted to explain the biological reason for pleiotropy phenomena. A diagnostic test based on gene expression data was used to predict biomarkers for AD and AMD based on pleiotropic genes and their regulators.

Results

Significant pleiotropy was found between AD and AMD (significant leftward shift on QQ plots). APOC1 and APOE were identified as pleiotropic genes for AD-AMD (cFDR <0.01). Network analysis revealed that APOC1 and APOE occupied borderline positions on the gene co-expression networks. Both APOC1 and APOE genes were enriched on the herpes simplex virus 1 infection pathway. Further, machine learning-based diagnostic tests identified that APOC1, APOE (areas under the curve (AUCs) >0.65) and their upstream regulators, especially ZNF131, ADNP2 and HINFP, could be potential biomarkers for both AD and AMD (AUCs >0.8).

Conclusion

In this study, we confirmed the genetic pleiotropy between AD and AMD and identified APOC1 and APOE as pleiotropic genes. Further, the integration of multiomics data identified ZNF131, ADNP2 and HINFP as novel diagnostic biomarkers for AD and AMD.

Targeting shared pathways in tauopathies and age-related macular degeneration: implications for novel therapies

The intricate parallels in structure and function between the human retina and the central nervous system designate the retina as a prospective avenue for understanding brain-related processes. This review extensively explores the shared physiopathological mechanisms connecting age-related macular degeneration (AMD) and proteinopathies, with a specific focus on tauopathies. The pivotal involvement of oxidative stress and cellular senescence emerges as key drivers of pathogenesis in both conditions. Uncovering these shared elements not only has the potential to enhance our understanding of intricate neurodegenerative diseases but also sets the stage for pioneering therapeutic approaches in AMD.

Alzheimer Disease Treatment With Acetylcholinesterase Inhibitors and Incident Age-Related Macular Degeneration

Importance

Age-related macular degeneration (AMD) is a serious and common ophthalmologic disorder that is hypothesized to result, in part, from inflammatory reactions in the macula. Alzheimer disease (AD) treatment, acetylcholinesterase inhibitors (AChEIs), have anti-inflammatory effects and it remains unclear if they modify the risk of AMD.

Objective

To investigate the association between AChEI medications and the incidence of AMD.

Design, Setting, and Participants

This propensity score-matched retrospective cohort study took place at health care facilities within the US Department of Veterans Affairs (VA) health care system from January 2000 through September 2023. Participants included patients diagnosed with AD between ages 55 and 80 years with no preexisting diagnosis of AMD in the VA database.

Exposure

AChEIs prescription dispensed as pharmacologic treatments for AD.

Main Outcomes and Measure

The first diagnosis of AMD.

Results

A total of 21 823 veterans with AD (mean [SD] age, 72.3 [6.1] years; 21 313 male participants [97.7%] and 510 female participants [2.3%]) were included. Propensity score-matched Cox model reveals each additional year of AChEI treatment was associated with a 6% lower hazard of AMD (hazard ratio, 0.94; 95% CI, (0.89-0.99).

Conclusions and Relevance

This observational study reports a small reduction in the risk of AMD among veterans with AD receiving AChEIs. Randomized clinical trials would be needed to determine if there is a cause-and-effect relationship and further research is required to validate these findings across diverse populations.

Bridging Retinal and Cerebral Neurodegeneration: A Focus on Crosslinks between Alzheimer-Perusini's Disease and Retinal Dystrophies

In the early stages of Alzheimer-Perusini's disease (AD), individuals often experience vision-related issues such as color vision impairment, reduced contrast sensitivity, and visual acuity problems. As the disease progresses, there is a connection with glaucoma and age-related macular degeneration (AMD) leading to retinal cell death. The retina's involvement suggests a link with the hippocampus, where most AD forms start. A thinning of the retinal nerve fiber layer (RNFL) due to the loss of retinal ganglion cells (RGCs) is seen as a potential AD diagnostic marker using electroretinography (ERG) and optical coherence tomography (OCT). Amyloid beta fragments (Aβ), found in the eye's vitreous and aqueous humor, are also present in the cerebrospinal fluid (CSF) and accumulate in the retina. Aβ is known to cause tau hyperphosphorylation, leading to its buildup in various retinal layers. However, diseases like AD are now seen as mixed proteinopathies, with deposits of the prion protein (PrP) and α-synuclein found in affected brains and retinas. Glial cells, especially microglial cells, play a crucial role in these diseases, maintaining immunoproteostasis. Studies have shown similarities between retinal and brain microglia in terms of transcription factor expression and morphotypes. All these findings constitute a good start to achieving better comprehension of neurodegeneration in both the eye and the brain. New insights will be able to bring the scientific community closer to specific disease-modifying therapies.

The Association of Retinal Microvasculature With Gray Matter Changes and Structural Covariance Network: A Voxel-Based Morphometry Study

Purpose

Increasing evidence suggests that retinal microvasculature may reflect global cerebral atrophy. However, little is known about the relation of retinal microvasculature with specific brain regions and brain networks. Therefore, we aimed to unravel the association of retinal microvasculature with gray matter changes and structural covariance network using a voxel-based morphometry (VBM) analysis.

Methods

One hundred and forty-four volunteers without previously known neurological diseases were recruited from West China Hospital, Sichuan University between April 1, 2021, and December 31, 2021. Retinal microvasculature of superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP) were measured by optical coherence tomography angiography using an automatic segmentation. The VBM and structural covariance network analyses were applied to process brain magnetic resonance imaging (MRI) images. The associations of retinal microvasculature with voxel-wise gray matter volumes and structural covariance network were assessed by linear regression models.

Results

In the study, 137 participants (mean age = 59.72 years, 37.2% men) were included for the final analysis. Reduced perfusion in SVP was significantly associated with reduced voxel-wise gray matter volumes of the brain regions including the insula, putamen, occipital, frontal, and temporal lobes, all of which were located in the anterior part of the brain supplied by internal carotid artery, except the occipital lobe. In addition, these regions were also involved in visual processing and cognitive impairment (such as left inferior occipital gyrus, left lingual gyrus, and right parahippocampal gyrus). In regard to the structural covariance, the perfusions in SVP were positively related to the structural covariance of the left lingual gyrus seed with the left middle occipital gyrus, the right middle occipital gyrus, and the left middle frontal gyrus.

Conclusions

Poor perfusion in SVP was correlated with reduced voxel-wise gray matter volumes and structural covariance networks in regions related to visual processing and cognitive impairment. It suggests that retinal microvasculature may offer a window to identify aging related cerebral alterations.

Potential Retinal Biomarkers in Alzheimer's Disease

Alzheimer's disease (AD) represents a major diagnostic challenge, as early detection is crucial for effective intervention. This review examines the diagnostic challenges facing current AD evaluations and explores the emerging field of retinal alterations as early indicators. Recognizing the potential of the retina as a noninvasive window to the brain, we emphasize the importance of identifying retinal biomarkers in the early stages of AD. However, the examination of AD is not without its challenges, as the similarities shared with other retinal diseases introduce complexity in the search for AD-specific markers. In this review, we address the relevance of using the retina for the early diagnosis of AD and the complex challenges associated with the search for AD-specific retinal biomarkers. We provide a comprehensive overview of the current landscape and highlight avenues for progress in AD diagnosis by retinal examination.

Brain-wide genome-wide colocalization study for integrating genetics, transcriptomics and brain morphometry in Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. However, the AD mechanism has not yet been fully elucidated to date, hindering the development of effective therapies. In our work, we perform a brain imaging genomics study to link genetics, single-cell gene expression data, tissue-specific gene expression data, brain imaging-derived volumetric endophenotypes, and disease diagnosis to discover potential underlying neurobiological pathways for AD. To do so, we perform brain-wide genome-wide colocalization analyses to integrate multidimensional imaging genomic biobank data. Specifically, we use (1) the individual-level imputed genotyping data and magnetic resonance imaging (MRI) data from the UK Biobank, (2) the summary statistics of the genome-wide association study (GWAS) from multiple European ancestry cohorts, and (3) the tissue-specific cis-expression quantitative trait loci (cis-eQTL) summary statistics from the GTEx project. We apply a Bayes factor colocalization framework and mediation analysis to these multi-modal imaging genomic data. As a result, we derive the brain regional level GWAS summary statistics for 145 brain regions with 482,831 single nucleotide polymorphisms (SNPs) followed by posthoc functional annotations. Our analysis yields the discovery of a potential AD causal pathway from a systems biology perspective: the SNP chr10:124165615:G>A (rs6585827) mutation upregulates the expression of BTBD16 gene in oligodendrocytes, a specialized glial cells, in the brain cortex, leading to a reduced risk of volumetric loss in the entorhinal cortex, resulting in the protective effect on AD. We substantiate our findings with multiple evidence from existing imaging, genetic and genomic studies in AD literature. Our study connects genetics, molecular and cellular signatures, regional brain morphologic endophenotypes, and AD diagnosis, providing new insights into the mechanistic understanding of the disease. Our findings can provide valuable guidance for subsequent therapeutic target identification and drug discovery in AD.

Frequency of coexistent eye diseases and cognitive impairment or dementia: a systematic review and meta-analysis

OBJECTIVE

We aim to quantify the co-existence of age-related macular degeneration (AMD), glaucoma, or diabetic retinopathy (DR) and cognitive impairment or dementia.

METHOD

MEDLINE, EMBASE, PsycINFO and CINAHL were searched (to June 2020). Observational studies reporting incidence or prevalence of AMD, glaucoma, or DR in people with cognitive impairment or dementia, and of cognitive impairment or dementia among people with AMD, glaucoma, or DR were included.

RESULTS

Fifty-six studies (57 reports) were included but marked by heterogeneities in the diagnostic criteria or definitions of the diseases, study design, and case mix. Few studies reported on the incidence. Evidence was sparse but consistent in individuals with mild cognitive impairment where 7.7% glaucoma prevalence was observed. Prevalence of AMD and DR among people with cognitive impairment ranged from 3.9% to 9.4% and from 11.4% to 70.1%, respectively. Prevalence of AMD and glaucoma among people with dementia ranged from 1.4 to 53% and from 0.2% to 25.9%, respectively. Prevalence of DR among people with dementia was 11%. Prevalence of cognitive impairment in people with AMD, glaucoma, and DR ranged from 8.4% to 52.4%, 12.3% to 90.2%, and 3.9% to 77.8%, respectively, and prevalence of dementia in people with AMD, glaucoma and DR ranged from 9.9% to 62.6%, 2.5% to 3.3% and was 12.5%, respectively.

CONCLUSIONS

Frequency of comorbid eye disease and cognitive impairment or dementia varied considerably. While more population-based estimations of the co-existence are needed, interdisciplinary collaboration might be helpful in the management of these conditions to meet healthcare needs of an ageing population.

TRIAL REGISTRATION

PROSPERO registration: CRD42020189484.

LncRNA NORAD defects deteriorate the formation of age-related macular degeneration

Long noncoding RNAs (lncRNAs) play important roles in the development of age-related macular degeneration (AMD). However, the effect of long non-coding RNA activated by DNA damage (NORAD) on AMD remains unknown. This study aimed to investigate the effect of NORAD on RPE cell senescence and degeneration. Irradiated adult retinal pigment epithelial cell line-19 (ARPE-19) and sodium iodate-treated mice were used as in vitro and in vivo AMD models. Results showed that irradiation-induced AMD characteristics of ARPE-19 and NORAD-knockdown aggravated cell cycle arrest in the G2/M phase, cell apoptosis and cell senescence along with the increased expression of phosphorylated P53 (p-P53) and P21. AMD factors C3, ICAM-1, APP, APOE, and VEGF-A were also increased by NORAD-knockdown. Moreover, NORAD-knockdown increased irradiation-induced reduction of mitochondrial homeostasis factors, (i.e., TFAM and POLG) and mitochondrial respiratory chain complex genes (i.e., ND1 and ND5) along with mitochondrial reactive oxygen species (ROS). We also identified a strong interaction of NORAD and PGC-1α and sirtuin 1 (SIRT1) in ARPE-19; that is, NORAD knockdown increases the acetylation of PGC-1α. In NORAD knockout mice, NORAD-knockout accelerated the sodium iodate-reduced retinal thickness reduction, function impairment and loss of retinal pigment in the fundus. Therefore, NORAD-knockdown accelerates retinal cell senescence, apoptosis, and AMD markers via PGC-1α acetylation, mitochondrial ROS, and the p-P53-P21signaling pathway, in which NORAD-mediated effect on PGC-1α acetylation might occur through the direct interaction with PGC-1α and SIRT1.

The central role of the NLRP3 inflammasome pathway in the pathogenesis of age-related diseases in the eye and the brain

With increasing age, structural changes occur in the eye and brain. Neuronal death, inflammation, vascular disruption, and microglial activation are among many of the pathological changes that can occur during ageing. Furthermore, ageing individuals are at increased risk of developing neurodegenerative diseases in these organs, including Alzheimer's disease (AD), Parkinson's disease (PD), glaucoma and age-related macular degeneration (AMD). Although these diseases pose a significant global public health burden, current treatment options focus on slowing disease progression and symptomatic control rather than targeting underlying causes. Interestingly, recent investigations have proposed an analogous aetiology between age-related diseases in the eye and brain, where a process of chronic low-grade inflammation is implicated. Studies have suggested that patients with AD or PD are also associated with an increased risk of AMD, glaucoma, and cataracts. Moreover, pathognomonic amyloid-β and α-synuclein aggregates, which accumulate in AD and PD, respectively, can be found in ocular parenchyma. In terms of a common molecular pathway that underpins these diseases, the nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) inflammasome is thought to play a vital role in the manifestation of all these diseases. This review summarises the current evidence regarding cellular and molecular changes in the brain and eye with age, similarities between ocular and cerebral age-related diseases, and the role of the NLRP3 inflammasome as a critical mediator of disease propagation in the eye and the brain during ageing.

Retinal inner nuclear layer thickness in the diagnosis of cognitive impairment explored using a C57BL/6J mouse model

Major neurocognitive disorder (NCD) affects over 55 million people worldwide and is characterized by cognitive impairment (CI). This study aimed to develop a non-invasive diagnostic test for CI based upon retinal thickness measurements explored in a mouse model. Discrimination indices and retinal layer thickness of healthy C57BL/6J mice were quantified through a novel object recognition test (NORT) and ocular coherence tomography (OCT), respectively. Based on criteria from the Diagnostic and statistical manual of mental disorders 5th ed. (DSM-V), a diagnostic test was generated by transforming data into rolling monthly averages and categorizing mice into those with and without CI and those with a high or low decline in retinal layer thickness. Only inner nuclear layer thickness had a statistically significant relationship with discrimination indices. Furthermore, our diagnostic test was 85.71% sensitive and 100% specific for diagnosing CI, with a positive predictive value of 100%. These findings have potential clinical implications for the early diagnosis of CI in NCD. However, further investigation in comorbid mice and humans is warranted.

Risk of Subsequent Dementia or Alzheimer Disease Among Patients With Age-Related Macular Degeneration: A Systematic Review and Meta-analysis

PURPOSE

Alzheimer disease (AD), a common form of dementia, shares several clinical and pathologic features with age-related macular degeneration (AMD). Epidemiologic reports on the association of AMD with subsequent dementia or AD are inconsistent.

DESIGN

Systematic review and meta-analysis.

METHODS

The Meta-analysis of Observational Studies in Epidemiology reporting guidelines were applied. The Newcastle-Ottawa Scale was used to evaluate the risk of bias in the included cohort studies that examined the association of AMD with subsequent dementia or AD. We estimated the pooled hazard ratios (HRs) of dementia or AD using random effects model meta-analysis and subgroup analysis on different follow-up periods, AMD subtype, gender, age, study design, and methods to ascertain dementia or AD.

RESULTS

A total of 8 223 581 participants were included in 8 studies published during 2000-2021. The meta-analysis showed that AMD was significantly associated with subsequent dementia (pooled HR 1.22, 95% CI 1.01-1.47) or AD (pooled HR 1.21, 95% CI 1.03-1.43). Our secondary analysis revealed that the association was more noticeable in dry AMD than wet AMD.

CONCLUSIONS

Patients with AMD have higher risks of developing dementia or AD, and therefore identifying related comorbidities and retinal biomarkers is much warranted for older adults with AMD in ophthalmologic practice.

PFKFB3 knockdown attenuates Amyloid β-Induced microglial activation and retinal pigment epithelium disorders in mice

Age-related macular degeneration (AMD) is characterized by progressive accumulation of drusen deposits and retinal pigment epithelium (RPE) disorders. As the main component of drusen, amyloid β (Aβ) plays a critical role in activating microglia and causing neuroinflammation in AMD pathogenesis. However, the role of activated microglia-mediated neuroinflammation in RPE senescence remains unclear. Recent evidence indicates that inflammatory microglia are glycolytic and driven by an increase in 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), an enzyme described as the master regulator of glycolysis. In this study, we mimicked the retinal inflammatory microenvironment of AMD by intravitreal injection of oligomeric Aβ_1-40 in mice, which resulted in activation of microglia and upregulation of PFKFB3. RNA sequencing was performed to evaluate PFKFB3-mediated microglial activation. The effect of microglial activation on RPE disorders was assessed using gene knockout experiments, immunofluorescence, CCK-8 assay, and β-galactosidase staining. Intravitreal Aβ_1-40 injection induced proinflammatory activation of microglia by upregulating PFKFB3 and resulted in RPE disorders, which was verified in heterozygous Pfkfb3-deficient mice (Pfkfb3^+/-) mice, Aβ_1-40-activated microglial cell line BV2, and co-culture of RPE cell line ARPE19. RNA sequencing revealed that PFKFB3 mainly affected innate immune processes during Aβ_1-40-induced retinal inflammation. PFKFB3 knockdown inhibited RPE disorders and rescued the retinal structure and function. Overall, the modulation of PFKFB3-mediated microglial glycolysis and activation is a promising strategy for AMD treatment.

Non-Coding RNAs Regulating Mitochondrial Functions and the Oxidative Stress Response as Putative Targets against Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is an ever-increasing, insidious disease which reduces the quality of life of millions of elderly people around the world. AMD is characterised by damage to the retinal pigment epithelium (RPE) in the macula region of the retina. The origins of this multi-factorial disease are complex and still not fully understood. Oxidative stress and mitochondrial imbalance in the RPE are believed to be important factors in the development of AMD. In this review, the regulation of the mitochondrial function and antioxidant stress response by non-coding RNAs (ncRNAs), newly emerged epigenetic factors, is discussed. These molecules include microRNAs, long non-coding RNAs, and circular non-coding RNAs. They act mainly as mRNA suppressors, controllers of other ncRNAs, or by interacting with proteins. We include here examples of these RNA molecules which affect various mitochondrial processes and antioxidant signaling of the cell. As a future prospect, the possibility to manipulate these ncRNAs to strengthen mitochondrial and antioxidant response functions is discussed. Non-coding RNAs could be used as potential diagnostic markers for AMD, and in the future, also as therapeutic targets, either by suppressing or increasing their expression. In addition to AMD, it is possible that non-coding RNAs could be regulators in other oxidative stress-related degenerative diseases.

Lack of bidirectional association between age-related macular degeneration and Alzheimer's disease: A Mendelian randomization study

INTRODUCTION

Observational studies have reported inconsistent results on the relationship between age-related macular degeneration (AMD) and Alzheimer's disease (AD). Therefore, we aimed to determine whether there is a causal association between AMD and AD.

METHODS

This two-sample bidirectional Mendelian randomization (MR) study evaluated causal associations between advanced AMD and AD using summary data from large genome-wide association studies.

RESULTS

Genetic liability for advanced AMD showed no statistical causal association with AD risk (odds ratio [OR] = 0.999, 95% confidence interval [CI]: 0.955-1.044, P = .948). Reverse MR analysis provided little support for a causal effect of AD on advanced AMD (OR = 0.973, 95%CI: 0.938-1.008, P = .133).

DISCUSSION

This MR study found no evidence to support a bidirectional causality between advanced AMD and AD.

HIGHLIGHTS

We evaluated the bidirectional causal relationship between advanced AMD and AD. Advanced AMD showed no statistical causal association with risk of AD. We found no evidence to support a causal effect of AD on advanced AMD risk. The associations observed in epidemiological studies should not be considered causal.

Altered glucose metabolism in Alzheimer's disease: Role of mitochondrial dysfunction and oxidative stress

Increasing evidence suggests that abnormal cerebral glucose metabolism is largely present in Alzheimer's disease (AD). The brain utilizes glucose as its main energy source and a decline in its metabolism directly reflects on brain function. Weighing on recent evidence, here we systematically assessed the aberrant glucose metabolism associated with amyloid beta and phosphorylated tau accumulation in AD brain. Interlink between insulin signaling and AD highlighted the involvement of the IRS/PI3K/Akt/AMPK signaling, and GLUTs in the disease progression. While shedding light on the mitochondrial dysfunction in the defective glucose metabolism, we further assessed functional consequences of AGEs (advanced glycation end products) accumulation, polyol activation, and other contributing factors including terminal respiration, ROS (reactive oxygen species), mitochondrial permeability, PINK1/parkin defects, lysosome-mitochondrial crosstalk, and autophagy/mitophagy. Combined with the classic plaque and tangle pathologies, glucose hypometabolism with acquired insulin resistance and mitochondrial dysfunction potentiate these factors to exacerbate AD pathology. To this end, we further reviewed AD and DM (diabetes mellitus) crosstalk in disease progression. Taken together, the present work discusses the emerging role of altered glucose metabolism, contributing impact of insulin signaling, and mitochondrial dysfunction in the defective cerebral glucose utilization in AD.

Association of cognitive function with Neurofilament light chain in the aqueous humor of human eye

Objectives

To evaluate the predictive clinical role of neurofilament light chain (NfL), amyloid-β (Aβ), glial fibrillary acidic protein (GFAP), and phosphorylated tau at threonine 181 (p-tau181) proteins in human aqueous humor (AH) and quantify the retinal macular microvascular parameters by optical coherence tomography angiography (OCTA) as early diagnostic markers of Alzheimer's disease (AD).

Methods

This prospective, single-site, cross-sectional, cohort study enrolled 55 participants, including 38 patients with neovascular age-related macular degeneration (nAMD) and 17 individuals with senile cataracts. The single-molecule array platform was used to quantitatively measure the levels of AH NfL, Aβ40, Aβ42, GFAP, and p-tau181 proteins in AH. The mini-mental state examination (MMSE) score was used to assess the global cognitive function. OCTA scan with 6 × 6 mm macular area was used to quantify the retinal thickness and microvascular densities of superficial retinal capillary plexuses and deep retinal capillary plexuses.

Results

NfL, Aβ40, Aβ42, GFAP, and p-tau181 were detected in all AH samples by Simoa platform. Individuals with cataract had higher concentrations of NfL and p-tau181 but lower Aβ40 and Aβ42 and similar GFAP compared to those with nAMD. Lower MMSE scores showed a negative correlation with NfL concentration of AH not only in the nAMD group (p = 0.043), but also in the cataract group (p = 0.032). However, the MMSE scores were not associated with the levels of Aβ40, Aβ42, GFAP, or p-Tau181. Further analysis found that the Aβ40 and Aβ42 concentrations showed a strong positive correlation (p < 0.0001). In addition, the NfL concentration showed a mild positive correlation with that of GFAP in the cataract group (p = 0.021). Although it has not reached statistical significance, there was a correlation between the levels of NfL and Aβ42 in the nAMD group (p = 0.051). Moreover, the macular superficial vessel density values had a negative correlation with the concentration of NfL (p = 0.004) but a positive correlation with MMSE scores (p = 0.045). The macular deep vessel density values were negatively correlated with the concentration of p-tau181 (p = 0.031) and positively correlated with MMSE scores (p = 0.020).

Conclusion

The examination of AD-related biomarkers in human AH and OCTA may improve the ocular-based AD detection methods and contribute to forestalling the progression of preclinical AD.

A deep learning model for detection of Alzheimer's disease based on retinal photographs: a retrospective, multicentre case-control study

BACKGROUND

There is no simple model to screen for Alzheimer's disease, partly because the diagnosis of Alzheimer's disease itself is complex-typically involving expensive and sometimes invasive tests not commonly available outside highly specialised clinical settings. We aimed to develop a deep learning algorithm that could use retinal photographs alone, which is the most common method of non-invasive imaging the retina to detect Alzheimer's disease-dementia.

METHODS

In this retrospective, multicentre case-control study, we trained, validated, and tested a deep learning algorithm to detect Alzheimer's disease-dementia from retinal photographs using retrospectively collected data from 11 studies that recruited patients with Alzheimer's disease-dementia and people without disease from different countries. Our main aim was to develop a bilateral model to detect Alzheimer's disease-dementia from retinal photographs alone. We designed and internally validated the bilateral deep learning model using retinal photographs from six studies. We used the EfficientNet-b2 network as the backbone of the model to extract features from the images. Integrated features from four retinal photographs (optic nerve head-centred and macula-centred fields from both eyes) for each individual were used to develop supervised deep learning models and equip the network with unsupervised domain adaptation technique, to address dataset discrepancy between the different studies. We tested the trained model using five other studies, three of which used PET as a biomarker of significant amyloid β burden (testing the deep learning model between amyloid β positive vs amyloid β negative).

FINDINGS

12 949 retinal photographs from 648 patients with Alzheimer's disease and 3240 people without the disease were used to train, validate, and test the deep learning model. In the internal validation dataset, the deep learning model had 83·6% (SD 2·5) accuracy, 93·2% (SD 2·2) sensitivity, 82·0% (SD 3·1) specificity, and an area under the receiver operating characteristic curve (AUROC) of 0·93 (0·01) for detecting Alzheimer's disease-dementia. In the testing datasets, the bilateral deep learning model had accuracies ranging from 79·6% (SD 15·5) to 92·1% (11·4) and AUROCs ranging from 0·73 (SD 0·24) to 0·91 (0·10). In the datasets with data on PET, the model was able to differentiate between participants who were amyloid β positive and those who were amyloid β negative: accuracies ranged from 80·6 (SD 13·4%) to 89·3 (13·7%) and AUROC ranged from 0·68 (SD 0·24) to 0·86 (0·16). In subgroup analyses, the discriminative performance of the model was improved in patients with eye disease (accuracy 89·6% [SD 12·5%]) versus those without eye disease (71·7% [11·6%]) and patients with diabetes (81·9% [SD 20·3%]) versus those without the disease (72·4% [11·7%]).

INTERPRETATION

A retinal photograph-based deep learning algorithm can detect Alzheimer's disease with good accuracy, showing its potential for screening Alzheimer's disease in a community setting.

FUNDING

BrightFocus Foundation.

Interplay between aging and other factors of the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is a complex eye disease with the retina as the target tissue and aging as per definition the most serious risk factor. However, the retina contains over 60 kinds of cells that form different structures, including the neuroretina and retinal pigment epithelium (RPE) which can age at different rates. Other established or putative AMD risk factors can differentially affect the neuroretina and RPE and can differently interplay with aging of these structures. The occurrence of β-amyloid plaques and increased levels of cholesterol in AMD retinas suggest that AMD may be a syndrome of accelerated brain aging. Therefore, the question about the real meaning of age in AMD is justified. In this review we present and update information on how aging may interplay with some aspects of AMD pathogenesis, such as oxidative stress, amyloid beta formation, circadian rhythm, metabolic aging and cellular senescence. Also, we show how this interplay can be specific for photoreceptors, microglia cells and RPE cells as well as in Bruch's membrane and the choroid. Therefore, the process of aging may differentially affect different retinal structures. As an accurate quantification of biological aging is important for risk stratification and early intervention for age-related diseases, the determination how photoreceptors, microglial and RPE cells age in AMD may be helpful for a precise diagnosis and treatment of this largely untreatable disease.

Retinal Pigment Epithelium-Secreted VEGF-A Induces Alpha-2-Macroglobulin Expression in Endothelial Cells

Alpha-2-macroglobulin (A2M) is a protease inhibitor that regulates extracellular matrix (ECM) stability and turnover. Here, we show that A2M is expressed by endothelial cells (ECs) from human eye choroid. We demonstrate that retinal pigment epithelium (RPE)-conditioned medium induces A2M expression specifically in ECs. Experiments using chemical inhibitors, blocking antibodies, and recombinant proteins revealed a key role of VEGF-A in RPE-mediated A2M induction in ECs. Furthermore, incubation of ECs with RPE-conditioned medium reduces matrix metalloproteinase-2 gelatinase activity of culture supernatants, which is partially restored after A2M knockdown in ECs. We propose that dysfunctional RPE or choroidal blood vessels, as observed in retinal diseases such as age-related macular degeneration, may disrupt the crosstalk mechanism we describe here leading to alterations in the homeostasis of choroidal ECM, Bruch's membrane and visual function.

Neprilysin Inhibitors in Heart Failure: The Science, Mechanism of Action, Clinical Studies, and Unanswered Questions

This article provides a contemporary review and a new perspective on the role of neprilysin inhibition in heart failure (HF) in the context of recent clinical trials and addresses potential mechanisms and unanswered questions in certain HF patient populations. Neprilysin is an endopeptidase that cleaves a variety of peptides such as natriuretic peptides, bradykinin, adrenomedullin, substance P, angiotensin I and II, and endothelin. It has a broad role in cardiovascular, renal, pulmonary, gastrointestinal, endocrine, and neurologic functions. The combined angiotensin receptor and neprilysin inhibitor (ARNi) has been developed with an intent to increase vasodilatory natriuretic peptides and prevent counterregulatory activation of the angiotensin system. ARNi therapy is very effective in reducing the risks of death and hospitalization for HF in patients with HF and New York Heart Association functional class II to III symptoms, but studies failed to show any benefits with ARNi when compared with angiotensin-converting enzyme inhibitors or angiotensin receptor blocker in patients with advanced HF with reduced ejection fraction or in patients following myocardial infarction with left ventricular dysfunction but without HF. These raise the questions about whether the enzymatic breakdown of natriuretic peptides may not be a very effective solution in advanced HF patients when there is downstream blunting of the response to natriuretic peptides or among post-myocardial infarction patients in the absence of HF when there may not be a need for increased natriuretic peptide availability. Furthermore, there is a need for additional studies to determine the long-term effects of ARNi on albuminuria, obesity, glycemic control and lipid profile, blood pressure, and cognitive function in patients with HF.

Differential Epigenetic Status and Responses to Stressors between Retinal Cybrids Cells with African versus European Mitochondrial DNA: Insights into Disease Susceptibilities

Mitochondrial (mt) DNA can be classified into haplogroups, which represent populations with different geographic origins. Individuals of maternal African backgrounds (L haplogroup) are more prone to develop specific diseases compared those with maternal European-H haplogroups. Using a cybrid model, effects of amyloid-β (Amyβ), sub-lethal ultraviolet (UV) radiation, and 5-Aza-2'-deoxycytidine (5-aza-dC), a methylation inhibitor, were investigated. Amyβ treatment decreased cell metabolism and increased levels of reactive oxygen species in European-H and African-L cybrids, but lower mitochondrial membrane potential (ΔΨM) was found only in African-L cybrids. Sub-lethal UV radiation induced higher expression levels of CFH, EFEMP1, BBC3, and BCL2L13 in European-H cybrids compared to African-L cybrids. With respect to epigenetic status, the African-L cybrids had (a) 4.7-fold higher total global methylation levels (p = 0.005); (b) lower expression patterns for DNMT3B; and (c) elevated levels for HIST1H3F. The European-H and African-L cybrids showed different transcription levels for CFH, EFEMP1, CXCL1, CXCL8, USP25, and VEGF after treatment with 5-aza-dC. In conclusion, compared to European-H haplogroup cybrids, the African-L cybrids have different (i) responses to exogenous stressors (Amyβ and UV radiation), (ii) epigenetic status, and (iii) modulation profiles of methylation-mediated downstream complement, inflammation, and angiogenesis genes, commonly associated with various human diseases.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain

BACKGROUND

Altered intestinal microbiota composition in later life is associated with inflammaging, declining tissue function, and increased susceptibility to age-associated chronic diseases, including neurodegenerative dementias. Here, we tested the hypothesis that manipulating the intestinal microbiota influences the development of major comorbidities associated with aging and, in particular, inflammation affecting the brain and retina.

METHODS

Using fecal microbiota transplantation, we exchanged the intestinal microbiota of young (3 months), old (18 months), and aged (24 months) mice. Whole metagenomic shotgun sequencing and metabolomics were used to develop a custom analysis workflow, to analyze the changes in gut microbiota composition and metabolic potential. Effects of age and microbiota transfer on the gut barrier, retina, and brain were assessed using protein assays, immunohistology, and behavioral testing.

RESULTS

We show that microbiota composition profiles and key species enriched in young or aged mice are successfully transferred by FMT between young and aged mice and that FMT modulates resulting metabolic pathway profiles. The transfer of aged donor microbiota into young mice accelerates age-associated central nervous system (CNS) inflammation, retinal inflammation, and cytokine signaling and promotes loss of key functional protein in the eye, effects which are coincident with increased intestinal barrier permeability. Conversely, these detrimental effects can be reversed by the transfer of young donor microbiota.

CONCLUSIONS

These findings demonstrate that the aging gut microbiota drives detrimental changes in the gut-brain and gut-retina axes suggesting that microbial modulation may be of therapeutic benefit in preventing inflammation-related tissue decline in later life. Video abstract.

The Amyloid Precursor Protein Plays Differential Roles in the UVA Resistance and Proliferation of Human Retinal Pigment Epithelial Cells

Background:

Age-related macular degeneration (AMD) can be characterised by degeneration of retinal pigment epithelial (RPE) cells and the accumulation, in retinal drusen deposits, of amyloid beta-peptides proteolytically derived, by secretases, from the amyloid precursor protein (APP). Ultraviolet (UV) light exposure is a risk factor for the development of AMD.

Objectives:

In the current study, we investigated whether APP and/or its proteolysis are linked to the UVA resistance or proliferation of ARPE-19 human RPE cells.

Methods:

Cell viability was determined, following UVA exposure, with prior small interfering RNA-mediated APP depletion or secretase inhibitor treatments. APP levels/proteolysis were analysed by immunoblotting. Cells were also grown in the presence/absence of secretase inhibitors to assess their effects on longer-term culture growth. Finally, the effects of APP proteolytic fragments on ARPE-19 cell proliferation were monitored following co-culture with human embryonic kidney cells stably over-expressing these fragments.

Results:

Endogenous APP was depleted following UVA irradiation and β-secretase, but not α- secretase, and the processing of the protein was reduced. Experimental APP depletion or γ-secretase (but not α- or β-secretase) inhibition ablated the detrimental effect of UVA on cell viability. In contrast, α-secretase, and possibly γ-secretase but not β-secretase activity, appeared to promote the longer-term proliferation of ARPE-19 cells in the absence of UVA irradiation.

Conclusions:

There are clear but differential links between APP expression/proteolysis and the proliferation and UVA resistance of ARPE-19 cells indicating that the protein should be investigated further in relation to the identification of possible drug targets for the treatment of AMD.

Visual Impairment and Risk of Dementia: The UK Biobank Study

PURPOSE

To investigate the relationship between visual impairment (VI) and dementia in the UK Biobank Study.

DESIGN

Prospective cohort study.

METHODS

A total of 117,187 volunteers (aged 40-69 years) deemed free of dementia at baseline were included. Habitual distance visual acuity worse than 0.3 logMAR units in the better-seeing eye was used to define VI. The incident dementia was based on electronically linked hospital inpatient and death records.

RESULTS

During a median follow-up of 5.96 years, the presence of VI was significantly associated with incident dementia (hazard ratio: 1.78; 95% confidence interval: 1.18-2.68; P = .006). There was a clear trend between the severity of VI and risk of dementia (P for trend = .002).

CONCLUSIONS

We found VI was associated with increased risk of dementia, with a progressively greater risk among those with worse visual acuity. Our findings suggested that VI might be a modifiable risk factor for dementia and highlighted the potential value of VI elimination to delay the manifestation of dementia.

Retinal Biomarkers for Alzheimer Disease: The Facts and the Future

ABSTRACT

Alzheimer disease (AD) is a significant cause of morbidity and mortality worldwide, with limited treatment options and considerable diagnostic challenges. Identification and validation of retinal changes that correlate with clinicopathologic features of AD could provide a noninvasive method of screening and monitoring progression of disease, with notable implications for developing new therapies, particularly in its preclinical stages. Retinal biomarkers that have been studied to date include structural changes in neurosensory retinal layers, alterations in vascular architecture and function, and pathologic deposition of proteins within the retina, which have all demonstrated variable correlation with the presence of preclinical or clinical AD. Evolution of specialized retinal imaging modalities and advances in artificial intelligence hold great promise for future study in this burgeoning field. The current status of research in retinal biomarkers, and some of the challenges that will need to be addressed in future work, are reviewed herein.

Absence of an Association between Macular Degeneration and Young-Onset Dementia

A few population-based studies have reported an association between prior age-related macular degeneration and senile dementia. No study has explored a possible link between prior macular degeneration and young-onset dementia (YOD). This case–control study aimed to evaluate the association of YOD with prior macular degeneration diagnosed in the 5-year period before their index date. Data for this retrospective observational study were retrieved from Taiwan’s National Health Insurance (NHI) dataset. A total of 36,577 patients with newly diagnosed YOD from January 2010 to December 2017 were identified as the study cohort, assigning their diagnosis date as their index date. Comparison patients were identified by propensity score-matching (three per case, n = 109,731 controls) from the remaining NHI beneficiaries of the period, their index date being the date of their first ambulatory care claim in the year of diagnosis of their matched YOD case. Chi-square test revealed no significant difference in the prevalence of prior macular degeneration between cases and controls (1.1% vs. 1.0%, p = 0.111). Conditional logistic regression analysis also showed an unadjusted odds ratio (OR) for prior macular degeneration of 1.098 among cases relative to controls (95% CI: 0.9797–1.232). Adjusted analysis confirmed that YOD was not associated with prior macular degeneration, adjusted odds ratio 1.098 (95% CI = 0.979–1.232). We conclude that patients with macular degeneration are not at increased risk for YOD.

Association of neovascular age-related macular degeneration with migraine

Patients with early onset vascular pathology have been reported to manifest neovascular age-related macular degeneration (AMD). While the blood vessels involved in pathogenesis of migraine remains controversial, it is generally accepted that a major contributor is blood vessel pathology. This study aimed to examine the association between migraine and AMD using a nationwide population-based dataset. Retrospective claims data were collected from the Taiwan National Health Insurance Research Database. We identified 20,333 patients diagnosed with neovascular AMD (cases), and we selected 81,332 propensity score-matched controls from the remaining beneficiaries in Taiwan's National Health Insurance system. We used Chi-square tests to explore differences in the prevalence of migraine prior to the index date between cases and controls. We performed multiple logistic regressions to estimate the odds of prior migraine among neovascular AMD patients vs. controls after adjusting for age, sex, monthly income, geographic location, residential urbanization level, hyperlipidemia, diabetes, coronary heart disease, hypertension, and previous cataract surgery. A total of 5184 of sample patients (5.1%) had a migraine claim before the index date; 1215 (6.1%) among cases and 3969 (4.9%) among controls (p < 0.001), with an unadjusted OR of 1.239 (95% CI 1.160~1.324, p < 0.001) for prior migraine among cases relative to controls. Furthermore, the adjusted OR was 1.201 (95% CI 1.123~1.284; p < 0.001) for AMD cases relative to controls. The study offers population-based evidence that persons with migraine have 20% higher risk of subsequently being diagnosed with neovascular AMD.

Novel Possible Protein Targets in Neovascular Age-Related Macular Degeneration: A Pilot Study Experiment

Age-related macular degeneration (AMD) is among the world's leading causes of blindness. In its neovascular form (nAMD), around 25% of patients present further anatomical and visual deterioration due to persistence of neovascular activity, despite gold-standard treatment protocols using intravitreal anti-VEGF medications. Thus, to comprehend, the molecular pathways that drive choroidal neoangiogenesis, associated with the vascular endothelial growth factor (VEGF), are important steps to elucidate the mechanistic events underneath the disease development. This is a pilot study, a prospective, translational experiment, in a real-life context aiming to evaluate the protein profiles of the aqueous humor of 15 patients divided into three groups: group 1, composed of patients with nAMD, who demonstrated a good response to anti-VEGF intravitreal injections during follow-up (good responsive); group 2, composed of patients with anti-VEGF-resistant nAMD, who demonstrated choroidal neovascularization activity during follow-up (poor/non-responsive); and group 3, composed of control patients without systemic diseases or signs of retinopathy. For proteomic characterization of the groups, mass spectrometry (label-free LC-MS/MS) was used. A total of 2,336 proteins were identified, of which 185 were distinctly regulated and allowed the differentiation of the clinical conditions analyzed. Among those, 39 proteins, including some novel ones, were analyzed as potential disease effectors through their pathophysiological implications in lipid metabolism, oxidative stress, complement system, inflammatory pathways, and angiogenesis. So, this study suggests the participation of other promising biomarkers in neovascular AMD, in addition to the known VEGF.

Suppressor of Cytokine Signaling 2 Regulates Retinal Pigment Epithelium Metabolism by Enhancing Autophagy

Retinal pigment epithelium (RPE) serves critical functions in maintaining retinal homeostasis. An important function of RPE is to degrade the photoreceptor outer segment fragments daily to maintain photoreceptor function and longevity throughout life. An impairment of RPE functions such as metabolic regulation leads to the development of age-related macular degeneration (AMD) and inherited retinal degenerative diseases. As substrate recognition subunit of a ubiquitin ligase complex, suppressor of cytokine signaling 2 (SOCS2) specifically binds to the substrates for ubiquitination and negatively regulates growth hormone signaling. Herein, we explore the role of SOCS2 in the metabolic regulation of autophagy in the RPE cells. SOCS2 knockout mice exhibited the irregular morphological deposits between the RPE and Bruch’s membrane. Both in vivo and in vitro experiments showed that RPE cells lacking SOCS2 displayed impaired autophagy, which could be recovered by re-expressing SOCS2. SOCS2 recognizes the ubiquitylated proteins and participates in the formation of autolysosome by binding with autophagy receptors and lysosome-associated membrane protein2 (LAMP-2), thereby regulating the phosphorylation of glycogen synthase kinase 3β (GSK3β) and mammalian target of rapamycin (mTOR) during the autophagy process. Our results imply that SOCS2 participates in ubiquitin-autophagy-lysosomal pathway and enhances autophagy by regulating GSK3β and mTOR. This study provides a potential therapeutic target for AMD.

Therapeutic potential of PGC-1α in age-related macular degeneration (AMD) - the involvement of mitochondrial quality control, autophagy, and antioxidant response

INTRODUCTION

Age-related macular degeneration (AMD) is the leading, cause of sight loss in the elderly in the Western world. Most patients remain still without any treatment options. The targeting of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a transcription co-factor, is a putative therapy against AMD.

AREAS COVERED

The characteristics of AMD and their possible connection with PGC-1α as well as the transcriptional and post-transcriptional control of PGC-1α are discussed. The PGC-1α-driven control of mitochondrial functions, and its involvement in autophagy and antioxidant responses are also examined. Therapeutic possibilities via drugs and epigenetic approaches to enhance PGC-1α expression are discussed. Authors conducted a search of literature mainly from the recent decade from the PubMed database.

EXPERT OPINION

Therapy options in AMD could include PGC-1α activation or stabilization. This could be achieved by a direct elevation of PGC-1α activity, a stabilization or modification of its upstream activators and inhibitors by chemical compounds, like 5-Aminoimidazole-4-carboxamide riboside, metformin, and resveratrol. Furthermore, manipulations with epigenetic modifiers of PGC-1α expression, including miRNAs, e.g. miR-204, are considered. A therapy aimed at PGC-1α up-regulation may be possible in other disorders besides AMD, if they are associated with disturbances in the mitochondria-antioxidant response-autophagy axis.

Nerve Growth Factor-Based Therapy in Alzheimer's Disease and Age-Related Macular Degeneration

Alzheimer's disease (AD) is an age-associated neurodegenerative disease which is the most common cause of dementia among the elderly. Imbalance in nerve growth factor (NGF) signaling, metabolism, and/or defect in NGF transport to the basal forebrain cholinergic neurons occurs in patients affected with AD. According to the cholinergic hypothesis, an early and progressive synaptic and neuronal loss in a vulnerable population of basal forebrain involved in memory and learning processes leads to degeneration of cortical and hippocampal projections followed by cognitive impairment with accumulation of misfolded/aggregated Aβ and tau protein. The neuroprotective and regenerative effects of NGF on cholinergic neurons have been largely demonstrated, both in animal models of AD and in living patients. However, the development of this neurotrophin as a disease-modifying therapy in humans is challenged by both delivery limitations (inability to cross the blood-brain barrier (BBB), poor pharmacokinetic profile) and unwanted side effects (pain and weight loss). Age-related macular degeneration (AMD) is a retinal disease which represents the major cause of blindness in developed countries and shares several clinical and pathological features with AD, including alterations in NGF transduction pathways. Interestingly, nerve fiber layer thinning, degeneration of retinal ganglion cells and changes of vascular parameters, aggregation of Aβ and tau protein, and apoptosis also occur in the retina of both AD and AMD. A protective effect of ocular administration of NGF on both photoreceptor and retinal ganglion cell degeneration has been recently described. Besides, the current knowledge about the detection of essential trace metals associated with AD and AMD and their changes depending on the severity of diseases, either systemic or locally detected, further pave the way for a promising diagnostic approach. This review is aimed at describing the employment of NGF as a common therapeutic approach to AMD and AD and the diagnostic power of detection of essential trace metals associated with both diseases. The multiple approaches employed to allow a sustained release/targeting of NGF to the brain and its neurosensorial ocular extensions will be also discussed, highlighting innovative technologies and future translational prospects.

Retinal Dysfunction in Alzheimer's Disease and Implications for Biomarkers

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that manifests as cognitive deficits and memory decline, especially in old age. Several biomarkers have been developed to monitor AD progression. Given that the retina and brain share some similarities including features related to anatomical composition and neurological functions, the retina is closely associated with the progression of AD. Herein, we review the evidence of retinal dysfunction in AD, particularly at the early stage, together with the underlying molecular mechanisms. Furthermore, we compared the retinal pathologies of AD and other ophthalmological diseases and summarized potential retinal biomarkers measurable by existing technologies for detecting AD, providing insights for the future development of diagnostic tools.

Macrocyclic Immunoproteasome Inhibitors as a Potential Therapy for Alzheimer's Disease

Previously, we reported that immunoproteasome (iP)-targeting linear peptide epoxyketones improve cognitive function in mouse models of Alzheimer's disease (AD) in a manner independent of amyloid β. However, these compounds' clinical prospect for AD is limited due to potential issues, such as poor brain penetration and metabolic instability. Here, we report the development of iP-selective macrocyclic peptide epoxyketones prepared by a ring-closing metathesis reaction between two terminal alkenes attached at the P2 and P3/P4 positions of linear counterparts. We show that a lead macrocyclic compound DB-60 (20) effectively inhibits the catalytic activity of iP in ABCB1-overexpressing cells (IC50: 105 nM) and has metabolic stability superior to its linear counterpart. DB-60 (20) also lowered the serum levels of IL-1α and ameliorated cognitive deficits in Tg2576 mice. The results collectively suggest that macrocyclic peptide epoxyketones have improved CNS drug properties than their linear counterparts and offer promising potential as an AD drug candidate.

Visual Performance and Cortical Atrophy in Vision-Related Brain Regions Differ Between Older Adults with (or at Risk for) Alzheimer's Disease

BACKGROUND

Visual impairment is associated with deficits in cognitive function and risk for cognitive decline and Alzheimer's disease (AD).

OBJECTIVE

The purpose of this study was to characterize the degree of visual impairment and explore the association thereof with cortical atrophy in brain regions associated with visual processing in individuals with (or at risk for) AD.

METHODS

Using the Comprehensive Assessment of Neurodegeneration and Dementia (COMPASS-ND) dataset, we analyzed vision and brain imaging data from three diagnostic groups: individuals with subjective cognitive decline (SCD; N = 35), mild cognitive impairment (MCI; N = 74), and mild AD (N = 30). We used ANCOVAs to determine whether performance on reading acuity and contrast sensitivity tests differed across diagnostic groups. Hierarchical regression analyses were applied to determine whether visual performance predicted gray matter volume for vision-related regions of interest above and beyond group membership.

RESULTS

The AD group performed significantly worse on reading acuity (F(2,138) = 4.12, p <  0.01, ω 2 = 0.04) compared to the SCD group and on contrast sensitivity (F(2,138) = 7.6, p <  0.01, ω 2 = 0.09) compared to the SCD and MCI groups, which did not differ from each other. Visual performance was associated with volume in some vision-related structures beyond clinical diagnosis.

CONCLUSION

Our findings demonstrate poor visual performance in AD and that both group membership and visual performance are predictors of cortical pathology, consistent with the idea that atrophy in visual areas and pathways contributes to the functional vision deficits observed in AD.

Past, present and future role of retinal imaging in neurodegenerative disease

Retinal imaging technology is rapidly advancing and can provide ever-increasing amounts of information about the structure, function and molecular composition of retinal tissue in humans in vivo. Most importantly, this information can be obtained rapidly, non-invasively and in many cases using Food and Drug Administration-approved devices that are commercially available. Technologies such as optical coherence tomography have dramatically changed our understanding of retinal disease and in many cases have significantly improved their clinical management. Since the retina is an extension of the brain and shares a common embryological origin with the central nervous system, there has also been intense interest in leveraging the expanding armamentarium of retinal imaging technology to understand, diagnose and monitor neurological diseases. This is particularly appealing because of the high spatial resolution, relatively low-cost and wide availability of retinal imaging modalities such as fundus photography or OCT compared to brain imaging modalities such as magnetic resonance imaging or positron emission tomography. The purpose of this article is to review and synthesize current research about retinal imaging in neurodegenerative disease by providing examples from the literature and elaborating on limitations, challenges and future directions. We begin by providing a general background of the most relevant retinal imaging modalities to ensure that the reader has a foundation on which to understand the clinical studies that are subsequently discussed. We then review the application and results of retinal imaging methodologies to several prevalent neurodegenerative diseases where extensive work has been done including sporadic late onset Alzheimer's Disease, Parkinson's Disease and Huntington's Disease. We also discuss Autosomal Dominant Alzheimer's Disease and cerebrovascular small vessel disease, where the application of retinal imaging holds promise but data is currently scarce. Although cerebrovascular disease is not generally considered a neurodegenerative process, it is both a confounder and contributor to neurodegenerative disease processes that requires more attention. Finally, we discuss ongoing efforts to overcome the limitations in the field and unmet clinical and scientific needs.

Interactions between Apolipoprotein E Metabolism and Retinal Inflammation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a multifactorial retinal disorder that is a major global cause of severe visual impairment. The development of an effective therapy to treat geographic atrophy, the predominant form of AMD, remains elusive due to the incomplete understanding of its pathogenesis. Central to AMD diagnosis and pathology are the hallmark lipid and proteinaceous deposits, drusen and reticular pseudodrusen, that accumulate in the subretinal pigment epithelium and subretinal spaces, respectively. Age-related changes and environmental stressors, such as smoking and a high-fat diet, are believed to interact with the many genetic risk variants that have been identified in several major biochemical pathways, including lipoprotein metabolism and the complement system. The APOE gene, encoding apolipoprotein E (APOE), is a major genetic risk factor for AMD, with the APOE2 allele conferring increased risk and APOE4 conferring reduced risk, in comparison to the wildtype APOE3. Paradoxically, APOE4 is the main genetic risk factor in Alzheimer’s disease, a disease with features of neuroinflammation and amyloid-beta deposition in common with AMD. The potential interactions of APOE with the complement system and amyloid-beta are discussed here to shed light on their roles in AMD pathogenesis, including in drusen biogenesis, immune cell activation and recruitment, and retinal inflammation.

Single-Nucleotide Polymorphisms Associated with the Senescence-Accelerated Phenotype of OXYS Rats: A Focus on Alzheimer's Disease-Like and Age-Related-Macular-Degeneration-Like Pathologies

Alzheimer's disease (AD) and age-related macular degeneration (AMD) are two complex incurable neurodegenerative disorders the common pathogenesis of which is actively discussed. There are overlapping risk factors and molecular mechanisms of the two diseases; at the same time, there are arguments in favor of the notion that susceptibility to each of these diseases is associated with a distinct genetic background. Here we identified single-nucleotide polymorphisms (SNPs) that are specific for senescence-accelerated OXYS rats, which simulate key characteristics of both sporadic AD and AMD. Transcriptomes of the hippocampus, prefrontal cortex, and retina (data of RNA-Seq) were analyzed. We detected SNPs in genes Rims2, AABR07072639.2, Lemd2, and AABR07045405.1, which thus can express significantly truncated proteins lacking functionally important domains. Additionally, 33 mutations in genes-which are related to various metabolic and signaling pathways-cause nonsynonymous amino acid substitutions presumably leading to disturbances in protein structure or functions. Some of the genes carrying these SNPs are associated with aging, neurodegenerative, and mental diseases. Thus, we revealed the SNPs can lead to abnormalities in protein structure or functions and affect the development of the senescence-accelerated phenotype of OXYS rats. Our data are consistent with the latest results of genome-wide association studies that highlight the importance of multiple pathways for the pathogenesis of AD and AMD. Identified SNPs can serve as promising research objects for further studies on the molecular mechanisms underlying this particular rat model as well as for the prediction of potential biomarkers of AD and AMD.

Co-Prevalence of Alzheimer's Disease and Age-Related Macular Degeneration Established by Histopathologic Diagnosis

BACKGROUND

Previous epidemiologic studies have suggested an association between AMD and AD, and several therapeutic agents are being developed based on this principle. However, prior studies have provided conflicting results due in part to their reliance on clinical diagnoses that are not based on gold-standard histopathology.

OBJECTIVE

To use histopathologic standards for diagnosis in order to determine the co-prevalence of AD among patients with and without AMD.

METHODS

This is a cross-sectional study of 157 autopsy ocular specimens from patients with and without AMD that were greater than 75 years of age at death. Sarks staging was used to document the severity of AMD, and Braak and Braak staging was used to assess the severity of AD in corresponding brain specimens. The prevalence of AD within different severities of AMD was determined using univariable and multivariable logistic regression.

RESULTS

58% of autopsy eyes had AMD. The prevalence of AD was lower in AMD subjects (63%) compared to non-AMD subjects (73%), even when grouped by severity (all p > 0.15). The likelihood of AD was significantly less in AMD subjects, even after adjusting for age and sex in multivariable analysis (OR 0.47, p = 0.049).

CONCLUSION

Histopathologic diagnoses fail to support an increase in prevalence of AD among subjects with AMD, even when disease severity is considered.

MicroRNAs in the regulation of autophagy and their possible use in age-related macular degeneration therapy

Age-related macular degeneration (AMD) is a progressive sight-impairing disease of the elderly. The pathogenic mechanisms of AMD are not well understood although both genetic and many environmental factors have been associated with the development of AMD. One clinical hallmark of AMD is the detrimental aggregation of damaged proteins. Recently, it has been suggested that the weakening of autophagy clearance is an important mechanism in the pathogenesis of AMD. Autophagy is important in the removal of damaged or no longer needed cellular material and its recycling. A considerable number of autophagy-targeting microRNAs (miRNAs), small RNA molecules and epigenetic regulators have been found to be either up- or down-regulated in AMD patients and experimental models. The important role of autophagy-targeting miRNAs is supported by several studies and can open the prospect of the use of these miRNAs in the therapy for AMD.