Search Results (20)

Myopia is increasingly recognized as an inflammatory ocular disease. Vitamin D₃ is a potential modulator of the gut–eye axis, but its role in inflammation-induced myopia remains unclear. This study investigated whether vitamin D₃ supplementation attenuates myopia progression by regulating retinal inflammation, gut microbiota composition, and microbiota-derived metabolites in a TGF-β2–induced myopia model. Three-week-old Brown Norway rats received weekly periocular TGF-β2 injections with or without daily oral vitamin D₃, and myopia development was evaluated on days 1 and 21 by axial length and refractive error. Cecal contents were analyzed for α- and β-diversity and taxonomic differences, and day-21 serum underwent untargeted metabolomic profiling of microbiota-derived metabolites, including bile acids and imidazole derivatives; Spearman correlation linked microbial or metabolic alterations with myopia progression. TGF-β2 induced axial elongation, myopic refractive shifts, and upregulated retinal pro-inflammatory cytokines (p-NFκB, IL-1β, TNF-α), while vitamin D₃ supplementation markedly attenuated myopia progression and retinal inflammation. Cecal α-diversity did not differ among control, vitamin D₃, TGF-β2, and TGF-β2+vitamin D₃ groups, but vitamin D₃ significantly reshaped β-diversity and reduced the Firmicutes/Bacteroidota ratio. Distinct metabolite profiles were observed, with the vitamin D₃ group showing reduced hyodeoxycholic acid and elevated imidazole derivatives (imidazolepropionic and methylimidazoleacetic acids). Vitamin D₃ supplementation attenuated myopia progression by reducing retinal inflammation and concurrently reshaping the gut microbiome and its metabolites compared to the control and myopic groups. These results underscore the potential of vitamin D₃ to modulate the gut–retina axis as a nutritional approach for mitigating myopia development. Full article

Retinopathy of prematurity (ROP) is a leading cause of childhood blindness characterized by disrupted physiologic vascularization followed by pathologic neovascularization, classically organized around the insulin-like growth factor-1 (IGF-1)–vascular endothelial growth factor (VEGF) axis in the retina. Increasing evidence suggests that early-life gut dysbiosis may act as an upstream modifier of this biphasic process. In this review, we synthesize human cohort studies, multi-omics analyses, and experimental animal models examining associations between the neonatal gut microbiome and ROP. Preterm infants who develop severe ROP demonstrate enrichment of facultative anaerobes and reduced acquisition of obligate anaerobes, alongside altered predicted metabolic capacity. Microbiome-derived metabolites, including short-chain fatty acids, bile acid derivatives, and lipid mediators, have been shown in experimental systems to influence systemic IGF-1 production, hypoxia-inducible factor-1α stabilization, and VEGF signaling. Rodent oxygen-induced retinopathy models offer a translation framework to assess the functional link between microbial perturbation and retinal angiogenic responses. Collectively, these findings support a conceptual microbiome–IGF-1–VEGF–retina axis in which early intestinal dysbiosis may modulate inflammatory tone, metabolic signaling, and retinal vascular development. Although current evidence remains largely associative, integrating microbiome profiling with mechanistic and longitudinal studies may clarify potential causal pathways and identify novel biomarkers or preventive strategies for severe ROP. Full article

Chronic exposure to short-wavelength blue light induces oxidative stress, inflammation, and apoptosis in retinal tissues, contributing to vision loss. This study investigated the protective effects of Lactobacillus reuteri Y7, a human-derived probiotic, against blue light–induced retinal damage in mice. Male C57BL/6 mice were exposed to 400 lux blue light for 35 days and received either low- or high-dose Y7, lutein, or no intervention. Retinal morphology, inflammatory gene expression, gut barrier integrity, and gut microbiota composition were assessed. Low-dose Y7 promoted microbial diversity and enrichment of short-chain fatty acid–producing taxa, while high-dose Y7 favored enrichment of Akkermansia, Parasutterella, and Bacteroides, enhancing mucosal barrier function and metabolic regulation. Both doses attenuated retinal inflammation, preserved retinal layers, and improved gut barrier integrity, with high-dose Y7 matching or exceeding lutein’s protective effects. Mechanistic insights suggest a gut–retina axis whereby microbial metabolites modulate oxidative stress, inflammation, and vascular homeostasis. These findings highlight L. reuteri Y7 as a potential non-invasive strategy for retinal degeneration prevention, with efficacy comparable to dietary antioxidants. Future studies should explore long-term safety, metabolite-mediated mechanisms, and comparative efficacy with other antioxidants. Full article

Background: Blue light-induced retinal photodamage represents a growing public health concern globally. Lactic acid bacteria and their bioactive metabolites represent a promising therapeutic strategy for mitigating such damage. Methods: This study evaluated the protective efficacy of Limosilactobacillus fermentum IOB802 and Lactobacillus plantarum subsp. plantarum IOB602 against blue light-induced retinal injury using both in vitro and in vivo models. Results: In ARPE-19 cells exposed to blue light, treatment with postbiotics from IOB802 and IOB602 significantly restored cell viability (p < 0.05), enhanced antioxidant enzyme activities (GSH-Px, SOD, and CAT, p < 0.05), and reduced inflammatory cytokine levels (IL-6, IL-1β, TNF-α, and VEGF, p < 0.05). Subsequent validation in a murine blue light-induced retinal damage model demonstrated that IOB802 notably preserved retinal architecture, upregulated antioxidant defenses, and promoted the expression of tight junction proteins. Mechanistically, IOB802 suppressed inflammation by inhibiting the phosphorylation of the IκBα/NF-κB pathway. Through 16S rDNA sequencing and short-chain fatty acid (SCFA) profiling, IOB802 was further shown to restore gut microbial diversity, increase beneficial bacteria, including Lachnospiraceae, Rikenellaceae, and Bacteroidaceae (p < 0.05), and elevate concentrations of key SCFAs (butyrate, acetate, and propionate; p < 0.05), underscoring the role of the gut–retina axis in mediating retinal protection. Conclusions: In summary, IOB802 and its postbiotics alleviate blue light-induced retinopathy through antioxidative, anti-inflammatory, and microbiota-modulating mechanisms, offering novel insights into microbiome-based interventions for retinal diseases. Full article

Diabetic retinopathy (DR) is a progressive, multifactorial complication of diabetes and one of the major global causes of visual impairment. Its pathogenesis involves chronic hyperglycaemia-induced oxidative stress, inflammation, mitochondrial dysfunction, neurodegeneration, and pathological angiogenesis, as well as emerging systemic contributors such as gut microbiota dysregulation. While current treatments, including anti-vascular endothelial growth factor (anti-VEGF) agents, corticosteroids, and laser photocoagulation, have shown clinical efficacy, they are largely limited to advanced stages of DR, require repeated invasive procedures, and do not adequately address early neurovascular and metabolic abnormalities. Resveratrol (RSV), a naturally occurring polyphenol, has emerged as a promising candidate due to its potent antioxidant, anti-inflammatory, neuroprotective, and anti-angiogenic properties. This review provides a comprehensive analysis of the molecular mechanisms by which RSV exerts protective effects in DR, including modulation of oxidative stress pathways, suppression of inflammatory cytokines, enhancement of mitochondrial function, promotion of autophagy, and inhibition of pathological neovascularisation. Despite its promising pharmacological profile, the clinical application of RSV is limited by poor aqueous solubility, rapid systemic metabolism, and low ocular bioavailability. Various routes of administration, including intravitreal injection, topical instillation, and oral and sublingual delivery, have been investigated to enhance its therapeutic potential. Recent advances in drug delivery systems, including nanoformulations, liposomal carriers, and sustained-release intravitreal implants, offer potential strategies to address these challenges. This review also explores RSV’s role in combination therapies, its potential as a disease-modifying agent in early-stage DR, and the relevance of personalised medicine approaches guided by metabolic and genetic factors. Overall, the review highlights the therapeutic potential and the key translational challenges in positioning RSV as a multi-targeted treatment strategy for DR. Full article

Recent findings highlight that Reelin, a glycoprotein involved in neural development, synaptic plasticity, and neuroinflammation, plays some specific roles in neurodegenerative disorders associated with aging, such as age-related macular degeneration (AMD) and Alzheimer’s disease (AD). Reelin modulates synaptic function and guarantees homeostasis in neuronal-associated organs/tissues (brain and retina). The expression of Reelin is dysregulated in these neurological disorders, showing common pathways depending on chronic neurogenic inflammation and/or dysregulation of the extracellular matrix in which Reelin plays outstanding roles. Recently, the relationship between AMD and AD has gained increasing attention as they share many common risk factors (aging, genetic/epigenetic background, smoking, and malnutrition) and histopathological lesions, supporting certain pathophysiological crosstalk between these two diseases, especially regarding neuroinflammation, oxidative stress, and vascular complications. Outside the nervous system, Reelin is largely produced at the gastrointestinal epithelial level, in close association with innervated regions. The expression of Reelin receptors inside the gut suggests interesting aspects in the field of the gut–brain–eye axis, as dysregulation of the intestinal microbiota has been frequently described in neurodegenerative and behavioral disorders (AD, autism, and anxiety and/or depression), most probably linked to inflammatory, neurogenic mediators, including Reelin. Herein we examined previous and recent findings on Reelin and neurodegenerative disorders, offering findings on Reelin’s potential relation with the gut–brain and gut–brain–eye axes and providing novel attractive hypotheses on the gut–brain–eye link through neuromodulator and microbiota interplay. Neurodegenerative disorders will represent the ground for a future starting point for linking the common neurodegenerative biomarkers (β-amyloid and tau) and the new proteins probably engaged in counteracting neurodegeneration and synaptic loss. Full article

The gut microbiota represents a rich and adaptive microbial network inhabiting the gastrointestinal tract, performing key functions in nutrient processing, immune response modulation, intestinal wall protection, and microbial defense. Its composition remains highly personalized and responsive to external influences, including lifestyle patterns, physical activity, body composition, and nutritional intake. The interactions of the gut microbiota with bodily systems are conventionally interpreted as broad systemic impacts on organ balance. Yet, emerging research—exemplified by the gut microbiota–brain axis—suggests the potential existence of more targeted and direct communication mechanisms. Dysbiosis, characterized by microbial ecosystem disturbance, generates multiple metabolic compounds capable of entering systemic circulation and reaching distant tissues, notably including ocular structures. This microbial imbalance has been associated with both systemic and localized conditions linked to eye disorders. Accumulating scientific evidence now supports the concept of a gut–retina axis, underscoring the significant role of microbiota disruption in generating various retinal pathologies. This review comprehensively investigates gut microbiota composition, functional dynamics, and dysbiosis-induced alterations, with specific focus on retinal interactions in age-related macular degeneration, diabetic retinopathy, glaucoma, and retinal artery occlusion. Moreover, the review explores microbiota-targeted therapeutic strategies, including precision nutritional interventions and microbial transplantation, as potential modulators of retinal disease progression. Full article

Background/Objectives: Neuroinflammation, a hallmark of Alzheimer’s disease (AD), is characterized by elevated levels of inflammatory signaling molecules, including cytokines and eicosanoids, as well as increased microglial reactivity, and is augmented by gut microbiota dysbiosis via the gut–brain axis. We conducted a pilot experiment to elucidate the anti-inflammatory effects of dietary omega-3 polyunsaturated fatty acid (ω-3 PUFA) eicosapentaenoic acid (EPA) on the gut microbiota and neuroinflammation. Methods: Female APP/PS1 mice (TG) and non-transgenic littermates (WT), 13–14 months old, were fed a diet supplemented with 0.3% EPA or control chow for 3 weeks. The gut microbiota composition, hippocampal and plasma eicosanoids levels, platelet activation, and microglial phagocytosis, as well as the brain and retinal genes and protein expression, were analyzed. Results: EPA supplementation decreased the percentage of Bacteroidetes and increased bacteria of the phylum Firmicutes in APP/PS1 and WT mice. Inflammatory lipid mediators were elevated in the hippocampus of the TG mice, accompanied by a reduction in the endocannabinoid docosahexaenoyl ethanolamide (DHEA). Dietary EPA did not affect hippocampal lipid mediators, but reduced the levels of arachidonic-derived 5-HETE and N-arachidonoylethanolamine (AEA) in WT plasma. Moreover, EPA supplementation decreased major histocompatibility complex class II (MHCII) gene expression in the retina in both genotypes, and MHCII+ cells in the hippocampus of TG mice. Conclusions: This pilot study showed that short-term EPA supplementation shaped the gut microbiota by increasing butyrate-producing bacteria of the Firmicutes phylum and decreasing Gram-negative LPS-producing bacteria of the Bacteroidetes phylum, and downregulated the inflammatory microglial marker MHCII in two distinct regions of the central nervous system (CNS). Further investigation is needed to determine whether EPA-mediated effects on the microbiome and microglial MHCII have beneficial long-term effects on AD pathology and cognition. Full article

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. Full article

Background/Objectives: Despite substantial research, the causal relationships between gut microbiota (GM) and age-related macular degeneration (AMD) remain unclear. We aimed to explore these causal associations using Mendelian randomization (MR) and elucidate the potential mechanisms mediated by blood metabolites. Methods: We utilized the 211 GM dataset (n = 18,340) provided by the MiBioGen consortium. AMD outcome data were sourced from the MRC Integrated Epidemiology Unit (IEU) OpenGWAS Project. We performed bidirectional MR, two mediation analyses, and two-step MR to assess the causal links between GM and different stages of AMD (early, dry, and wet). Results: Our findings indicate that the Bacteroidales S24.7 group and genus Dorea are associated with an increased risk of early AMD, while Ruminococcaceae UCG011 and Parasutterella are linked to a higher risk of dry AMD. Conversely, Lachnospiraceae UCG004 and Anaerotruncus are protective against dry AMD. In the case of wet AMD, Intestinimonas and Sellimonas increase risk, whereas Anaerotruncus and Rikenellaceae RC9 reduce it. Additionally, various blood metabolites were implicated: valine, arabinose, creatine, lysine, alanine, and apolipoprotein A1 were associated with early AMD; glutamine and hyodeoxycholate—with a reduced risk of dry AMD; and androsterone sulfate, epiandrosterone sulfate, and lipopolysaccharide—with a reduced risk of wet AMD. Notably, the association between family Oxalobacteraceae and early AMD was mediated by valine, accounting for 19.1% of the association. Conclusions: This study establishes causal links between specific gut microbiota and AMD, mediated by blood metabolites, thereby enhancing our understanding of the gut–retina axis in AMD pathophysiology. Full article

Background/Objectives: Age-related macular degeneration (AMD) is a leading cause of visual impairment in the elderly and is characterized by a multifactorial etiology. Emerging evidence points to the potential involvement of the gut–retina axis in AMD pathogenesis, prompting exploration into novel therapeutic strategies. This study aims to investigate the effects of some micronutrients (such as lutein and zeaxanthin) and saffron (as a supplement)—known for their anti-inflammatory properties—on ophthalmological and microbial parameters in neovascular AMD (nAMD) patients. Methods: Thirty naive nAMD patients were randomized to receive daily micronutrient supplementation alongside anti-VEGF (vascular endothelial growth factor) therapy, or anti-VEGF treatment alone, over a 6-month period, with comparisons made to a healthy control (HC) group (N = 15). Ophthalmological assessments, biochemical measurements, and stool samples were obtained before and after treatment. Gut microbiota (GM) characterization was performed using 16S rRNA sequencing, while short-chain fatty acids (SCFAs), medium-chain fatty acids (MCFAs), and long-chain fatty acids (LCFAs) were analyzed with a gas chromatography–mass spectrometry protocol. Results: Compared to HC, nAMD patients exhibited reduced GM alpha diversity, altered taxonomic composition, and decreased total SCFA levels, in addition to elevated levels of proinflammatory octanoic and nonanoic acids. Micronutrient supplementation was associated with improved visual acuity relative to the group treated with anti-VEGF alone, along with a decrease in the total amount of MCFAs, which are metabolites known to have adverse ocular effects. Conclusions: In conclusion, despite certain limitations—such as the limited sample size and the low taxonomic resolution of 16S rRNA sequencing—this study highlights compositional and functional imbalances in the GM of nAMD patients and demonstrates that micronutrient supplementation may help restore the gut–retina axis. These findings suggest the therapeutic potential of micronutrients in enhancing ocular outcomes for nAMD patients, underscoring the complex interaction between GM and ocular health. Full article

The relationship between gut microbiota and glaucoma has garnered significant interest, with emerging evidence suggesting that gut dysbiosis, inflammation, and immune mechanisms may contribute to glaucoma pathogenesis. Understanding these interactions through the gut–retina axis offers new insights into disease progression and potential therapeutic options. This study combines bibliometric analysis and literature review to evaluate research trends and key research areas related to gut microbiota’s role in glaucoma. Our data were collected from the Web of Science Core Collection (WoSCC) and included the English original articles and reviews published between 1 January 2008, and 6 August 2024. Visual and statistical analyses were conducted using VOSviewer and CiteSpace. The analyses comprised 810 citations from leading journals, representing contributions from 23 countries/regions, 111 institutions, 40 journals, and 321 authors. Among the countries and regions involved, the USA and China were the leading contributors, publishing the most articles and being major research hubs. The Experimental Eye Research and Investigative Ophthalmology & Visual Science were the top journals in citation and co-citations that produced high-quality publications. The top 10 highly cited articles were published in high-ranking, top-quartile journals. The frequently occurring keywords were “glaucoma”, “microbiota”, “gut microbiota”, “inflammation”, “gut–retina axis”, and “probiotics”. Our study highlights the growing interest in the association between gut microbiota and glaucoma. It summarizes the possible ways gut microbiota dysbiosis, systemic and neuroinflammation, and autoimmune mechanisms contribute to glaucomatous pathogenesis. Future research should focus on mechanistic studies to elucidate the pathways linking gut microbiota to glaucoma development and progression. Full article

The human retina is a complex anatomical structure that has no regenerative capacity. The pathogenesis of most retinopathies can be attributed to inflammation, with the activation of the inflammasome protein platform, and to the impact of oxidative stress on the regulation of apoptosis and autophagy/mitophagy in retinal cells. In recent years, new therapeutic approaches to treat retinopathies have been investigated. Experimental data suggest that the secretome of mesenchymal cells could reduce oxidative stress, autophagy, and the apoptosis of retinal cells, and in turn, the secretome of the latter could induce changes in mesenchymal cells. Other studies have evidenced that noncoding (nc)RNAs might be new targets for retinopathy treatment and novel disease biomarkers since a correlation has been found between ncRNA levels and retinopathies. A new field to explore is the interaction observed between the ocular and intestinal microbiota; indeed, recent findings have shown that the alteration of gut microbiota seems to be linked to ocular diseases, suggesting a gut–eye axis. To explore new therapeutical strategies for retinopathies, it is important to use proper models that can mimic the complexity of the retina. In this context, retinal organoids represent a good model for the study of the pathophysiology of the retina. Full article

The objective of this study was to examine the correlation between gut microbiota and both age-related macular degeneration (AMD) and glaucoma. Mendelian randomization studies were conducted utilizing the data sourced from the genome-wide association study (GWAS) database for the gut microbiome, AMD, and glaucoma. Single nucleotide polymorphism (SNP) estimates were summarized through five Mendelian randomization (MR) methods. We utilized Cochran’s Q statistic to evaluate the heterogeneity of the instrumental variables (IVs). Additionally, we employed a “leave-one-out” approach to verify the stability of our findings. Inverse variance weighted (IVW) suggests that Eubacterium (oxidoreducens group) and Parabacteroides had a protective effect on AMD. Both weighted median and IVW suggest that Lachnospiraceae (NK4A136 group) and Ruminococcaceae (UCG009) had a protective effect on AMD. However, both weighted median and IVW suggest that Dorea had a risk effect on AMD. Similarly, The IVW of Eubacterium (ventriosum group) showed a risk effect on AMD. The weighted median of Eubacterium (nodatum group), Lachnospiraceae (NC2004 group), and Roseburia had a risk effect on glaucoma. IVW suggested that Ruminococcaceae (UCG004) had a risk effect on glaucoma. Reverse MR analysis found a causal link between Eubacterium (nodatum group) and glaucoma. No causal relationships were found between AMD or glaucoma and the other mentioned bacterial groups. No significant heterogeneity or evidence of horizontal pleiotropy was detected. This study found that certain gut bacteria had protective effects on AMD, while others may be risk factors for AMD or glaucoma. Likewise, reverse MR found that glaucoma led to an increased abundance of certain gut bacteria. Further trials are needed to clarify the specific mechanisms involved. Full article

Diabetic retinopathy is one of the major causes of blindness today, despite important achievements in diagnosis and therapy. The involvement of a gut–retina axis is thought to be a possible risk factor for several chronic eye disease, such as glaucoma, age-related macular degeneration, uveitis, and, recently, diabetic retinopathy. Dysbiosis may cause endothelial disfunction and alter retinal metabolism. This review analyzes the evidence regarding changes in gut microbiota in patients with DR compared with diabetics and healthy controls (HCs). A systematic review was performed on PubMed, Web of Science, and Google Scholar for the following terms: “gut microbiota” OR “gut microbiome” AND “diabetic retinopathy”. Ultimately, 9 articles published between 2020 and 2022 presenting comparative data on a total of 228 T2DM patients with DR, 220 patients with T2DM, and 118 HCs were analyzed. All of the studies found a distinctive microbial beta diversity in DR vs. T2DM and HC, characterized by an altered Firmicutes/Bacteroidetes ratio, a decrease in butyrate producers, and an increase in LPS-expressing and pro-inflammatory species in the Bacteroidetes and Proteobacteria phyla. The probiotic species Bifidobacterium and Lactobacillus were decreased when compared with T2DM. Gut microbiota influence retinal health in multiple ways and may represent a future therapeutic target in DR. Full article