The Emerging Role of Gut Microbiota in Age-Related Macular Degeneration

Association of Age-Related Macular Degeneration with Cholelithiasis

Purpose

Dysregulated lipid metabolism likely contributes to the pathogenesis of age-related macular degeneration (AMD). There is an overlap in risk factors between AMD and diseases of lipid metabolism, such as cholelithiasis, suggesting that an association between these diseases could provide insight into AMD pathogenesis. This study sought to determine if there is an association between cholelithiasis and AMD.

Design

A cohort study was conducted using patients in the Optum deidentified Clinformatics Data Mart database from January 1, 2000, to June 30, 2022.

Participants

Patients over the age of 55 with ≥2 years of data and no prior history of AMD were included. The exposed cohort included patients who had a history of cholelithiasis, cholecystitis, or cholecystectomy. The control cohort included patients with gastroesophageal reflux disease (GERD), matched for age ±3 years, sex, race, and year of index date.

Methods

Propensity scores were created using multivariable logistic regression and applied to inverse probability of treatment weighting (IPTW). Cox proportional hazard regression modeling with IPTW was used to compare progression to AMD in each cohort.

Main Outcome Measures

Progression to AMD for patients with cholelithiasis, cholecystitis, or a history of cholecystectomy.

Results

A total of 332 536 patients with cholelithiasis and 776 591 matched GERD controls were analyzed. After IPTW, the mean age (±standard deviation) was 66.6 ± 9.4 years in the cholelithiasis cohort and 67.5 (±10.3) years in the GERD cohort. Women comprised 58% of the cholelithiasis cohort and 57% of the GERD cohort. In the cholelithiasis cohort, 3511.7 (1.14%) were diagnosed with AMD, compared with 23 367.1 (2.92%) in the GERD cohort and corresponding to a significantly decreased hazard of AMD (adjusted hazard ratio [aHR] = 0.72, 95% confidence interval [CI]: 0.69-0.75, P < 0.0001). In the subanalysis, before IPTW weighting, AMD developed in 3809 of 275 897 (1.4%) patients with only cholelithiasis (aHR = 0.76, 95% CI: 0.73-0.80, P < 0.0001), 335 of 47 166 (0.71%) patients with cholecystitis (aHR = 0.54, 95% CI: 0.47-0.61, P < 0.0001), and 114 of 9473 (1.20%) patients who underwent cholecystectomy (aHR = 0.50, 95% CI: 0.41-0.63, P < 0.0001).

Conclusions

Cholelithiasis was associated with a 28% hazard reduction in AMD. More severe gallbladder disease conferred greater protection.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Features that distinguish age-related macular degeneration from aging

Age-related macular degeneration (AMD) is a complex, multifactorial retinal degenerative disease that is influenced by both genetic and environmental factors. However, the strongest risk factor for AMD is advanced age. Several physiological processes are observed in aging tissues including a low level of chronic inflammation (inflammaging), changed lipid and energy metabolism, and senescence. Nevertheless, whereas everyone ages, only a subset of the population develops AMD. The purpose of this review is to delineate the differences on a cellular and molecular level between natural aging changes and those observed in AMD. We provide a unique perspective on how genetic and environmental components modulate aging in the eye, as well as the specific role of the aging RPE and retina in the pathogenesis of AMD. Topics discussed include the mechanism of aging and its relation to the mechanism of AMD, current animal models that can be used to recapitulate some aspects of the pathology, and potential interventions that shift the balance towards healthy aging and therefore attenuate, prevent or delay the initiation of the disease.

Preparation and characterization of multilayered microcapsules of Lactobacillus rhamnosus encapsulated with sodium alginate, hyaluronic acid and carrageenan and their protective effects on the retina

To improve the activity of probiotics during oral delivery and to investigate the protective effects on the retina. In this study, multilayer microcapsules encapsulating Lactobacillus rhamnosus YBT20 (YBT20) were prepared using sodium alginate, carrageenan and hyaluronic acid. Then it was characterized by determining the encapsulation rate, particle size distribution and zeta potential, and the results showed that the encapsulation rate of YBT20 by microcapsules was 68.51 % ~ 93.73 %, and the particle size distribution was between 100 and 1000 nm. Meanwhile, the storage stability and antioxidant properties of YBT20 were increased by 38.09 % and 37.01 %, respectively. Furthermore, the in vitro digestion simulation showed that the microcapsules could effectively improve the cell viability of YBT20 in saliva, gastric juice and intestinal juice, and the maximum release rate of YBT20 was 82.0 %. Lastly, the protective effect of microcapsule preparation on retinal damage induced by high-fat diet and blue light was evaluated in SD female rats. The results showed that microcapsule preparation can improve the oxidative damage of retinal pigment epithelium (RPE) in rats, and inhibit IL-6, IL-8, IL-1β and TNF-α. This study provides valuable theoretical information for effective delivery of probiotics and retinal protection.

Periodontal Disease and Age-Related Maculopathy: A Case Report

Age-related macular degeneration (AMD) is a leading cause of significant vision impairment in individuals aged 50 and older, primarily impacting central vision. This study seeks to investigate potential associations between periodontal disease and age-related maculopathy in the analyzed clinical case. A male subject of 66 years old, with age-related degenerative maculopathy and severe periodontal disease, was evaluated and treated. After an initial phase of non-surgical causal periodontal therapy, the periodontal indices were re-evaluated. In addition, the extraction of hopeless teeth replaced by dental implants was performed. A retinal topography was used to assess possible regression of the pathology, and proper anti-VEGF therapy was administered. The results showed a regression of periodontal disease and an improvement of the degenerative maculopathy. These preliminary results, even if encouraging, should be supported by larger prospective trials.

Fecal Microbial Profiles and Short-Chain Fatty Acid/Bile Acid Metabolomics in Patients With Age-Related Macular Degeneration: A Pilot Study

Purpose

Age-related macular degeneration (AMD) is a multifactorial disease, and studies have implicated the role of gut microbiota in its pathogenesis. However, characterization of microbiome dysbiosis and associated microbial-derived metabolomic profiles across AMD stages remains unknown. In this pilot study, we explored how gut microbiome composition and gut-derived metabolites differ in AMD.

Methods

Our pilot study analyzed fasted stool samples that were collected from 22 patients at a tertiary academic center. Subjects were classified as control, intermediate AMD, or advanced AMD based on clinical presentation. 16S rRNA amplicon sequencing and standard chromatography-mass spectrometry methods were used to identify bacterial taxonomy composition and abundance of short-chain fatty acids (SCFAs) and bile acids (BAs), respectively. Genetic testing was used to investigate the frequency of 14 high-risk single nucleotide polymorphisms (SNPs) associated with AMD in the AMD cohort.

Results

Forty-three differentially abundant genera were present among the control, intermediate, and advanced groups. Taxa with known roles in immunologic pathways, such as Desulfovibrionales (q = 0.10) and Terrisporobacter (q = 1.16e-03), were in greater abundance in advanced AMD patients compared to intermediate. Advanced AMD patients had decreased abundance of 12 SCFAs, including acetate (P = 0.002), butyrate (P = 0.04), and propionate (P = 0.01), along with 12 BAs, including taurocholic acid (P = 0.02) and tauroursodeoxycholic acid (P = 0.04). Frequencies of high-risk SNPs were not significantly different between the intermediate and advanced AMD groups.

Conclusions

This pilot study identifies distinct gut microbiome compositions and metabolomic profiles associated with AMD and its stages, providing preliminary evidence of a potential link between gut microbiota and AMD pathogenesis. To validate these findings and elucidate the underlying mechanisms, future research with larger cohorts and more comprehensive sampling is strongly recommended.

Short-Chain Fatty Acids and the Gut-Retina Connection: A Systematic Review

The interplay between gut microbiota and retinal health, known as the gut--retina axis, has gained increasing attention in recent years. Short-chain fatty acids (SCFAs), metabolites produced by gut microbiota, have been identified as key mediators of gut-retina communication. This systematic review explores the role of SCFAs in retinal health and their potential impact on the development and progression of retinal diseases, such as diabetic retinopathy (DR), age-related macular degeneration (AMD), and glaucoma. A literature search was conducted across multiple databases, including PubMed, Google Scholar, and Science Direct, to identify studies published between 2014 and December 2024. Studies were included if they investigated the effects of SCFAs on retinal structure, function, or disease pathogenesis in animal models or human subjects. The review included 10 original articles spanning both preclinical and clinical studies. Evidence suggests that SCFAs play a crucial role in maintaining retinal homeostasis through anti-inflammatory and neuroprotective mechanisms. Dysbiosis of the gut microbiota, leading to altered SCFA production, was associated with increased retinal inflammation, oxidative stress, and vascular dysfunction. Furthermore, reduced SCFA levels were linked to the progression of retinal diseases, such as diabetic retinopathy and age-related macular degeneration. Modulation of gut microbiota and SCFA levels through dietary interventions or probiotics may represent a novel therapeutic strategy for preventing or managing retinal diseases. Further research is needed to elucidate the precise molecular mechanisms underlying SCFA-mediated retinal protection and to evaluate the efficacy of targeted therapies in clinical settings.

Luteoloside mitigates premature age-related macular degeneration by suppressing p53-p21-Rb1 axis: Insights from transcriptomic analysis, serum metabolomics and gut microbiota analysis

Transcriptomics of dry age-related macular degeneration (AMD) patients with premature aging revealed the upregulated pathways involved in glycerolipid metabolism, tyrosine metabolism, and pentose and glucuronate interconversion. To investigate natural strategies for modulating these implicated pathways, we examined the impact and underlying mechanism of luteoloside on premature AMD using a stress-induced premature senescence (SIPS)-associated AMD animal model in middle-aged mice that mimicked the dysregulated pathways observed in dry AMD patients with premature aging. Luteoloside supplementation resulted in a significant reduction in serum levels of the pro-inflammatory cytokine IL-1β and lipofuscin, along with increased serum activity of the antioxidant enzyme superoxide dismutase (SOD) and elevated levels of pigment epithelium-derived factor (PEDF), and preserved retinal thickness and structure in AMD mice. Furthermore, luteoloside supplementation effectively reversed the abnormal serum levels of metabolites, particularly by reducing harmful lysophosphatidylcholine (LysoPC) and increasing beneficial 4-guanidinobutanoic acid. In addition to its impact on metabolites, luteoloside modulated the composition of gut microbiota, promoting the enrichment of beneficial bacterial populations, including Lactobacillus, while reducing the abundance of harmful bacterial populations, including Bacteroides. Overall, our findings highlight the potential of luteoloside supplementation in regulating the dysregulated intestinal microbiota and metabolites in premature AMD, thereby reducing ocular levels of senescence-associated secretory phenotype (SASP) factors through the suppression of the p53-p21-retinoblastoma protein 1 (Rb1) axis.

The Relationship Between Gut Microbiome and Ophthalmologic Diseases: A Comprehensive Review

The gut microbiome has been studied in recent years due to its association with various pathological pathways involved in different diseases, caused by its structure, function, and diversity alteration. The knowledge of this mechanism has generated interest in the investigation of its relationship with ophthalmologic diseases. Recent studies infer the existence of a gut-eye microbiota axis, influenced by the intestinal barrier, the blood-retina barrier, and the immune privilege of the eye. A common denominator among ophthalmologic diseases that have been related to this axis is inflammation, which is perpetuated by dysbiosis, causing an alteration of the intestinal barrier leading to increased permeability and, in turn, the release of components such as lipopolysaccharides (LPS), trimethylamine oxide (TMAO), and bacterial translocation. Some theories explain that depending on how the microbiome is composed, a different type of T cells will be activated, while others say that some bacteria can pre-activate T cells that mimic ocular structures and intestinal permeability that allow leakage of metabolites into the circulation. In addition, therapies such as probiotics, diet, and fecal microbiota transplantation (FMT) have been shown to favor the presence of a balanced population of microorganisms that limit inflammation and, in turn, generate a beneficial effect in these eye pathologies. This review aims to analyze how the intestinal microbiome influences various ocular pathologies based on microbial composition and pathological mechanisms, which may provide a better understanding of the diseases and their therapeutic potential.

Janus Kinase Inhibitor Therapy and Risk of Age-Related Macular Degeneration in Autoimmune Disease

Importance

The involvement of chronic inflammation in the pathogenesis of age-related macular degeneration (AMD) opens therapeutic possibilities to AMD management.

Objective

To determine whether Janus kinase inhibitors (JAKis) are associated with a reduced risk of AMD development in patients with autoimmune diseases.

Design, Setting, and Participants

This retrospective observational cohort study used administrative claims data from Merative MarketScan research databases (Commercial and Medicare Supplemental) and Optum Clinformatics Data Mart databases between January 1, 2010, and January 31, 2022. Patients with autoimmune diseases satisfying study eligibility criteria and who received JAKi treatment (9126 in MarketScan and 5667 in Optum) were propensity score matched (1:1) to identical numbers of study-eligible patients who received non-JAKi-based immunotherapy.

Exposure

Treatment duration of 6 months or longer.

Main Outcomes and Measures

Incidence rates of AMD (exudative and nonexudative) over the first 6 to 18 months of treatment were determined, and bayesian Poisson regression models were used to estimate incidence rate ratios, 95% CIs, and posterior probabilities of AMD.

Results

After matching, female sex represented the majority of the patient population in both MarketScan and Optum (14 019/18 252 [76.6%] and 8563/3364 [75.2%], respectively in the JAKi patient population). More than 60% of the patient population was older than 55 years of age in both cohorts. Over the specified treatment period, a 49% relative reduction in incidence of AMD was observed among patients who received JAKi therapy (10/9126 events; adjusted incidence rate ratio [AIRR], 0.51; 95% CI, 0.19-0.90) vs those who received non-JAKi therapy (43/9126 events; AIRR, 1 [reference]) in MarketScan, and a 73% relative reduction in incidence of AMD was observed among patients who received JAKi therapy (3/5667 events; AIRR, 0.27; 95% CI, 0.03-0.74) vs those who received non-JAKi therapy (21/5667 events; AIRR, 1 [reference]) in Optum. The absolute percentage reductions were 0.36% (MarketScan) and 0.32% (Optum), favoring patients who received JAKi therapy. Posterior probabilities of the adjusted risk being less than unity were 97.6% (MarketScan) and 98.9% (Optum) for those who received JAKi therapy vs those who received non-JAKi therapy in MarketScan and Optum, respectively.

Conclusions and Relevance

JAKi use may be associated with a reduced risk of incident AMD in US adults with major autoimmune diseases. The absolute percentage reduction is consistent with a potential role for JAKi in this population. Future studies with long-term follow-up are recommended to investigate the association between JAKi use and incident AMD in other disease indications. Investigation into the role of systemic inflammation and JAK-signal transducers and activators of transcription signaling in AMD may improve understanding of the pathophysiology of AMD and lead to new treatment options.

Potential application of traditional Chinese medicine in age-related macular degeneration-focusing on mitophagy

Retinal pigment epithelial cell and neuroretinal damage in age-related macular degeneration (AMD) can lead to serious visual impairments and blindness. Studies have shown that mitophagy, a highly specialized cellular degradation system, is implicated in the pathogenesis of AMD. Mitophagy selectively eliminates impaired or non-functioning mitochondria via several pathways, such as the phosphatase and tensin homolog-induced kinase 1/Parkin, BCL2-interacting protein 3 and NIP3-like protein X, FUN14 domain-containing 1, and AMP-activated protein kinase pathways. This has a major impact on the maintenance of mitochondrial homeostasis. Therefore, the regulation of mitophagy could be a promising therapeutic strategy for AMD. Traditional Chinese medicine (TCM) uses natural products that could potentially prevent and treat various diseases, such as AMD. This review aims to summarize recent findings on mitophagy regulation pathways and the latest progress in AMD treatment targeting mitophagy, emphasizing methods involving TCM.

Unveiling the gut-eye axis: how microbial metabolites influence ocular health and disease

The intricate interplay between the gut microbiota and ocular health has surpassed conventional medical beliefs, fundamentally reshaping our understanding of organ interconnectivity. This review investigates into the intricate relationship between gut microbiota-derived metabolites and their consequential impact on ocular health and disease pathogenesis. By examining the role of specific metabolites, such as short-chain fatty acids (SCFAs) like butyrate and bile acids (BAs), herein we elucidate their significant contributions to ocular pathologies, thought-provoking the traditional belief of organ sterility, particularly in the field of ophthalmology. Highlighting the dynamic nature of the gut microbiota and its profound influence on ocular health, this review underlines the necessity of comprehending the complex workings of the gut-eye axis, an emerging field of science ready for further exploration and scrutiny. While acknowledging the therapeutic promise in manipulating the gut microbiome and its metabolites, the available literature advocates for a targeted, precise approach. Instead of broad interventions, it emphasizes the potential of exploiting specific microbiome-related metabolites as a focused strategy. This targeted approach compared to a precision tool rather than a broad-spectrum solution, aims to explore the therapeutic applications of microbiome-related metabolites in the context of various retinal diseases. By proposing a nuanced strategy targeted at specific microbial metabolites, this review suggests that addressing specific deficiencies or imbalances through microbiome-related metabolites might yield expedited and pronounced outcomes in systemic health, extending to the eye. This focused strategy holds the potential in bypassing the irregularity associated with manipulating microbes themselves, paving a more efficient pathway toward desired outcomes in optimizing gut health and its implications for retinal diseases.

Role of traditional Chinese medicine in age-related macular degeneration: exploring the gut microbiota's influence

The pathogenesis of age-related macular degeneration (AMD), a degenerative retinopathy, remains unclear. Administration of anti-vascular endothelial growth factor agents, antioxidants, fundus lasers, photodynamic therapy, and transpupillary warming has proven effective in alleviating symptoms; however, these interventions cannot prevent or reverse AMD. Increasing evidence suggests that AMD risk is linked to changes in the composition, abundance, and diversity of the gut microbiota (GM). Activation of multiple signaling pathways by GM metabolites, including lipopolysaccharides, oxysterols, short-chain fatty acids (SCFAs), and bile acids (BAs), influences retinal physiology. Traditional Chinese medicine (TCM), known for its multi-component and multi-target advantages, can help treat AMD by altering GM composition and regulating the levels of certain substances, such as lipopolysaccharides, reducing oxysterols, and increasing SCFA and BA contents. This review explores the correlation between GM and AMD and interventions for the two to provide new perspectives on treating AMD with TCM.