Mendelian Randomization Shows a Causal Effect of Low Vitamin D on Non-infectious Uveitis and Scleritis Risk

Prunella vulgaris polyphenols alleviate liver injury-uveitis comorbidity by regulating acylcarnitine via the S100A9-PP2A-AMPK pathway

BACKGROUND

Liver injury and uveitis pose severe threats to human health. Owing to the close relationship of physiology and pathology between the liver and the eyes, cases in which both conditions occur simultaneously are not uncommon in clinical settings, significantly complicating treatment. However, no suitable comorbid animal model has been reported, and research on the pathological mechanisms of this comorbidity is lacking. Prunella vulgaris L., a well-known traditional Chinese medicine renowned for its liver-clearing and eye-brightening properties. Prunella vulgaris polyphenols (PVPs) hold promise for improving liver injury and uveitis. However, research exploring their dual therapeutic effects within a single organism remains lacking, leaving the key active components and mechanisms of action largely uninvestigated.

PURPOSE

This exploratory study aimed to establish a rat model of liver injury combined with uveitis and investigated its pathological mechanisms, evaluating the therapeutic efficacy of PVPs in alleviating liver injury combined with uveitis in rats. Additionally, it explored the mechanism of action and identified key active ingredients of PVPs, offering potential new directions for the development of clinical therapeutic drugs.

METHODS

A rat model of liver injury with uveitis was established through intraperitoneal d-GalN/LPS injection. Metabolomics and proteomics were applied to investigate pathological mechanisms, followed by validation using acylcarnitine and S100A9 inhibitors. PVPs were administered to evaluate therapeutic effects and explore mechanisms involved in alleviating liver injury and uveitis. Network pharmacology combined with molecular docking identified critical active components in PVPs. Subsequent animal experiments verified the efficacy of the representative component in improving liver injury and uveitis.

RESULTS

d-GalN/LPS (150 mg/kg : 1 mg/kg) induced significant liver injury and uveitis in rats. Metabolomics analysis pointed to acylcarnitine as a key metabolite, and its inhibition reduced inflammation. Proteomics analysis implicated S100A9 in inflammation and immunity. Then, we intervened with S100A9 inhibitors in the model rats. The results suggested that the pathological mechanism of liver injury and uveitis caused by d-GalN/LPS involved the upregulation of S100A9 expression, an increase in PP2A activity, the inhibition of AMPK phosphorylation, and the downregulation of CPT1A, leading to the accumulation of acylcarnitine and promoting the inflammatory response in the liver and retina. Further, experiments involving PVPs demonstrated dose-dependent improvements in liver injury and uveitis caused by d-GalN/LPS. The underlying mechanism of action involved suppression of S100A9 expression, reduction of PP2A activity, activation of AMPK, upregulation of CPT1A, and subsequent reduction in acylcarnitine accumulation in both the liver and retina. This mechanism effectively alleviated the inflammatory effects induced by d-GalN/LPS. Network pharmacology and molecular docking analyses pinpointed several key active components of PVPs-namely, rosmarinic acid, salviaflaside, esculetin, 2-hydroxycinnamic acid, 3,4-dihydroxybenzaldehyde, and 7,8-dihydroxycoumarin-that play significant roles in mitigating liver injury and uveitis. Follow-up experiments using the representative active component rosmarinic acid in rats confirmed its efficacy in improving symptoms of d-GalN/LPS-induced liver injury and uveitis, further validating the therapeutic potential of these key active components.

CONCLUSIONS

This study successfully established a rat model of liver injury combined with uveitis and confirmed the efficacy of PVPs in alleviating this condition. Furthermore, it determined that the underlying mechanism involves regulation of the S100A9-PP2A-AMPK pathway, with rosmarinic acid identified as a key active compound. These findings provide a basis for clinical studies on liver-eye comorbidities and offer critical evidence for further research and drug development of PVPs in liver-clearing and eye-brightening.

Vitamin D Supplementation and Remission from Chronic Anterior Uveitis

PURPOSE

Chronic anterior uveitis (CAU) often requires suppressive therapy, which has potential side effects including cataract, ocular hypertension, and increased risk of infection. No remittive therapy is currently available; however, several studies have demonstrated an association between low 25-hydroxy Vitamin D (25OHD) levels and either uveitis incidence or uveitis disease activity. This study investigates the potential of Vitamin D supplementation as a remittive treatment for CAU.

METHODS

We conducted a retrospective analysis using data from the Systemic Immunosuppressive Therapy for Eye Disease (SITE) cohort study, which included patients with ocular inflammatory disease seen at U.S. tertiary centers between 1979 and 2010. Vitamin D supplementation data was analyzed for patients with CAU. Eyes were considered in remission if they remained quiet for at least 90 days off all anti-inflammatory treatment for eye disease.

RESULTS

Among 2688 patients who never used Vitamin D, the cumulative adjusted CAU remission incidence was 13.5% at the 16-month follow-up. In contrast, among 75 patients who used Vitamin D for a duration of ≤1 year, the cumulative adjusted CAU remission incidence was 28% at 16 months. The use of Vitamin D was associated with a crude hazard ratio for remission of 2.14 [95% confidence interval (CI) 1.23-3.71, p = 0.0071], and an adjusted hazard ratio for remission of 2.43 [95% CI: 1.36-4.33, p = 0.0027].

CONCLUSION

In the SITE Cohort, Vitamin D supplementation is associated with a significantly increased incidence of remission. Vitamin D supplementation should be explored in a prospective trial as the next step of evaluation.

Vitamin D levels and risk of ocular disorders: insights from bidirectional and multivariable Mendelian randomization analysis

Purpose

This study aimed to assess the causal relationships between vitamin D levels and ocular disorders.

Methods

Independent genetic variables were obtained from genome-wide association studies (GWAS) and publicly available databases. The summary statistics for 25-hydroxyvitamin D (25(OH)D) were obtained from two large-scale GWAS studies, with sample sizes of 324,105 and 417,580 European individuals. The genetic variants of myopia, primary open angle glaucoma (POAG), anterior iridocyclitis, senile cataract, diabetic retinopathy (DR), retinal vein occlusion (RVO), wet age-related macular degeneration (WAMD) and optic neuritis were extracted from the latest release of FinnGen consortium, which contains genome data from Finnish participants. Subsequently, Mendelian randomization (MR) analyses were conducted to obtain effect estimates. Additionally, we performed multivariable MR analysis and mediation analysis to validate the results.

Results

In the discovery dataset, genetically predicted vitamin D concentration was found to be causally associated with an increased risk of WAMD, (odd ratio (OR) = 1.35, 95% confidence interval (CI) = 1.09-1.67, P IVW = 0.005). However, no causal effects of genetically predisposed vitamin D levels on the risk of most types of ocular disorders were observed. Reverse MR revealed no causal relationships between the ocular diseases and vitamin D concentrations. The MR analyses of the validation dataset yielded consistent results. Additionally, the causal effect of vitamin D levels on the risk of WAMD remained significant after adjusting for potential confounders in the multivariable MR analysis (OR = 1.86, 95% CI = 1.26-2.73, P IVW = 0.002).

Conclusion

Our MR analysis results provide robust evidence of a causal relationship between genetically predicted 25(OH)D levels and an increased risk of WAMD in European population. These findings offer important insights into the management and control of ocular disorders.

Vitamin D and human health: evidence from Mendelian randomization studies

We summarized the current evidence on vitamin D and major health outcomes from Mendelian randomization (MR) studies. PubMed and Embase were searched for original MR studies on vitamin D in relation to any health outcome from inception to September 1, 2022. Nonlinear MR findings were excluded due to concerns about the validity of the statistical methods used. A meta-analysis was preformed to synthesize study-specific estimates after excluding overlapping samples, where applicable. The methodological quality of the included studies was evaluated according to the STROBE-MR checklist. A total of 133 MR publications were eligible for inclusion in the analyses. The causal association between vitamin D status and 275 individual outcomes was examined. Linear MR analyses showed genetically high 25-hydroxyvitamin D (25(OH)D) concentrations were associated with reduced risk of multiple sclerosis incidence and relapse, non-infectious uveitis and scleritis, psoriasis, femur fracture, leg fracture, amyotrophic lateral sclerosis, anorexia nervosa, delirium, heart failure, ovarian cancer, non-alcoholic fatty liver disease, dyslipidemia, and bacterial pneumonia, but increased risk of Behçet's disease, Graves' disease, kidney stone disease, fracture of radium/ulna, basal cell carcinoma, and overall cataracts. Stratified analyses showed that the inverse association between genetically predisposed 25(OH)D concentrations and multiple sclerosis risk was significant and consistent regardless of the genetic instruments GIs selected. However, the associations with most of the other outcomes were only pronounced when using genetic variants not limited to those in the vitamin D pathway as GIs. The methodological quality of the included MR studies was substantially heterogeneous. Current evidence from linear MR studies strongly supports a causal role of vitamin D in the development of multiple sclerosis. Suggestive support for a number of other health conditions could help prioritize conditions where vitamin D may be beneficial or harmful.

Vitamin D deficiency and non-infectious uveitis: A systematic review and Meta-analysis

BACKGROUND

Vitamin D plays a critical role in immunomodulation, and its deficiency is implicated in the pathogenesis of several autoimmune diseases. Nevertheless, its relationship with non-infectious uveitis (NIU), an inflammatory ocular disorder, remains inconclusive.

METHODS

A systematic search was conducted in three databases from database inception until May 8, 2023, to investigate the potential relationship between vitamin D deficiency and NIU. We included observational studies reporting the measurement of vitamin D levels in patients with NIU and healthy controls without restriction of language or date of publication. Three pairs of authors independently screened the title and abstracts for potential eligibility and then in full text. A third author resolved disagreements. Three pairs of independent reviewers abstracted the data from the fully reviewed records and evaluated the risk of bias. We followed The MOOSE and PRISMA guidelines. Random effects meta-analyses were used for primary analysis. Studies not included in the meta-analysis were summarized descriptively. This review was registered in PROSPERO: CRD42022308105.

FINDINGS

Of 933 records screened, 11 studies were included, and five were meta-analyzed, encompassing 354 cases and 5728 controls (mean participant age ranging from 7.1 to 58.9 years). Patients with vitamin D deficiency exhibited an Odds Ratio of 2.04 (95% CI = 1.55-2.68, P < 0.00001) for developing NIU compared to controls. Overall, potential sources of bias were low across most studies.

INTERPRETATION

Our findings suggest that vitamin D may play an essential role in the pathophysiology of NIU. While the included studies demonstrated generally low potential bias, additional rigorous prospective studies are necessary to confirm these findings and further elucidate the underlying mechanisms involved. Vitamin D supplementation could represent a possible therapeutic strategy for preventing or managing NIU if substantiated. Clinicians should consider screening for and addressing vitamin D deficiency in patients with or at risk for NIU.

Insights into the liver-eyes connections, from epidemiological, mechanical studies to clinical translation

Maintenance of internal homeostasis is a sophisticated process, during which almost all organs get involved. Liver plays a central role in metabolism and involves in endocrine, immunity, detoxification and storage, and therefore it communicates with distant organs through such mechanisms to regulate pathophysiological processes. Dysfunctional liver is often accompanied by pathological phenotypes of distant organs, including the eyes. Many reviews have focused on crosstalk between the liver and gut, the liver and brain, the liver and heart, the liver and kidney, but with no attention paid to the liver and eyes. In this review, we summarized intimate connections between the liver and the eyes from three aspects. Epidemiologically, we suggest liver-related, potential, protective and risk factors for typical eye disease as well as eye indicators connected with liver status. For molecular mechanism aspect, we elaborate their inter-organ crosstalk from metabolism (glucose, lipid, proteins, vitamin, and mineral), detoxification (ammonia and bilirubin), and immunity (complement and inflammation regulation) aspect. In clinical application part, we emphasize the latest advances in utilizing the liver-eye axis in disease diagnosis and therapy, involving artificial intelligence-deep learning-based novel diagnostic tools for detecting liver disease and adeno-associated viral vector-based gene therapy method for curing blinding eye disease. We aim to focus on and provide novel insights into liver and eyes communications and help resolve existed clinically significant issues.